JPH0631571B2 - Exhaust gas recirculation control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust gas recirculation control device for recirculating a part of exhaust gas of an internal combustion engine to an intake pipe of the internal combustion engine, and more specifically to the exhaust gas recirculation control device. The present invention relates to a self-diagnosis device for a control device.

[Prior Art] Conventionally, this type of exhaust gas recirculation control device (hereinafter referred to as EGR) has been widely used in an internal combustion engine as a means for reducing nitrogen oxides (NOx) in the exhaust gas (Japanese Patent Laid-Open Publication No. Sho. 59-192838).

By the way, when a malfunction occurs in the EGR due to malfunction of the EGR valve or blockage of the EGR pipe, NOX is apt to increase remarkably. However, the failure of EGR has little influence on the driving performance itself, so that the driver does not notice the abnormality,
May emit a large amount of NOx and pollute the atmosphere.

As means for solving this, for example, JP-A-56-6
As described in Japanese Patent No. 0912, there is known one that corrects a detection value from a sensor by a learning control or the like according to a predetermined setting pattern and notifies an abnormality when the correction value becomes a predetermined value or more. ing.

[Problems to be Solved by the Invention] However, in order to apply the above-mentioned conventional technique to EGR, it is necessary to detect an operating state of EGR, for example, a flow rate sensor must be provided in the EGR pipe, so that the configuration becomes complicated. There is a problem.

[Means for Solving the Problems] The present invention made to solve the above problems is, as shown in FIG. 1, a recirculation pipe for recirculating exhaust gas of an internal combustion engine to an intake pipe, and a recirculation pipe. An opening / closing means for opening / closing, a first control means for opening / closing the opening / closing means according to an operating state of the internal combustion engine, an operating state detecting means for detecting an operating state of the internal combustion engine, and the opening / closing by the first controlling means. When the means are open. Second control means for temporarily closing and controlling the opening / closing means, and storage means for separately storing the detection values from the operating state detecting means before and after the opening / closing means is closed by the second control means, When receiving both detection values from the storage means, determining means for determining whether the difference between the two detection values is within a predetermined range, and when the determination means determines that the difference is within the predetermined range, The gist is an exhaust gas recirculation control device including an alarm means for issuing an alarm.

[Operation] In the present invention thus configured, the first control means controls the opening / closing in accordance with the operating state of the internal combustion engine of the opening / closing means. For example, when the opening / closing means is controlled to be opened, the recirculation pipe is opened, and the exhaust gas of the internal combustion engine is recirculated to the intake pipe (EGR-ON).

Next, the second control means temporarily controls the opening / closing means to be closed while the opening / closing means is being opened by the first control means. Then, the recirculation of the exhaust gas is stopped (EG
R-OFF). Further, at this time, the storage means separately stores the detection values from the operating state detection means before and after the opening / closing means is closed by the second control means.

Here, when EGR is turned from ON to OFF, the operating state of the internal combustion engine changes accordingly. For example, as illustrated in FIG. 2, when EGR is switched from ON to OFF, the intake pipe pressure decreases, and with this pressure decrease, the basic fuel injection time is shortened and the air-fuel ratio changes from rich to lean. To do.

However, if an abnormality occurs in the EGR, such as clogging of the return pipe, changes in these operating states due to the switching of the EGR become small. Therefore, in the present invention,
The determination means determines whether or not the difference between the two detection values stored in the storage means is within a predetermined range. When it is determined that the difference is within the predetermined range, the alarm means issues an alarm. Therefore, the driver can immediately detect the EGR abnormality.

Further, in the present invention, when EGR is ON, EG is temporarily
R is turned off, and the presence or absence of abnormality is determined based on the change in the operating state at this time. Then, since the change in the operating state at this time reflects only the change caused by the switching of the EGR, the present invention makes it possible to judge the EGR abnormality extremely accurately.

Further, in the present invention, it is not necessary to newly install a sensor in the recirculation pipe (EGR pipe) or the like, and the configuration of the exhaust gas recirculation control device as a whole is simplified.

Here, the operating state detecting means may be any as long as it detects the operating state of the internal combustion engine that changes depending on the presence or absence of exhaust gas recirculated through the recirculation pipe, for example, intake pipe pressure,
An example is one that detects the fuel injection amount, the air-fuel ratio, the engine speed, or the like obtained by using the intake pipe pressure as one parameter. Further, this operating state may be the same as or different from the operating state referred to when the first control means controls the opening / closing means. On the other hand, as the storage means, various storage means such as an analog type memory using a capacitor or the like can be applied in addition to the digital memory. Further, as the warning means, any means can be used as long as it informs the driver of the abnormality of the EGR, and various means such as character display and sound warning can be applied in addition to the lamp display.

[Embodiment] FIG. 3 is a schematic configuration diagram of an internal combustion engine and its control system to which an embodiment of the present invention is applied.

Reference numeral 1 is a cylinder of a 6-cylinder internal combustion engine, 2 is an intake pipe pressure sensor for detecting the intake air pressure in an intake manifold 3 connected to the cylinder 1, and is composed of a semiconductor pressure sensor. Reference numeral 4 is an electromagnetically-operated fuel injection valve provided near each cylinder intake port of the intake manifold 3, and 6 is a distributor. The rotor of the distributor 6 is rotationally driven at a rotational speed that is half the engine rotational speed, and a rotation sensor 7 that outputs a signal indicating the engine rotational speed and the fuel injection timing and a cylinder discrimination signal is provided inside.
Reference numeral 9 is a throttle valve, 10 is a throttle position sensor for detecting the opening of the throttle valve 9, 11 is a thermistor-type water temperature sensor for detecting the cooling water temperature of the engine, 1
An intake air temperature sensor 2 detects the intake air temperature. Thirteen
Is the intake manifold 3 and the exhaust manifold 16
A vacuum servo type exhaust gas recirculation control valve (hereinafter referred to as EGR) connected between the exhaust gas circulation passages 17 and
The control conduit 18 for controlling the EGR valve 13 is connected between the diaphragm chamber of the EGR valve 13 and the inlet of the surge tank 19, and the EGR valve 13
A modulator 14 that determines the valve opening of the solenoid valve and a solenoid valve 15 that switches whether exhaust gas recirculation is performed or not are installed in the control line 18. The solenoid valve 15 is an electronic control circuit 8
Is connected to the output port 107 (see FIG. 4) of the surge tank 19 and operates, for example, so that the atmospheric pressure is communicated to the modulator 14 at the time of cold, idle, and high load, while the throttle at the inlet of the surge tank 19 at the time of performing exhaust gas recirculation. An actuation signal is received to apply a negative pressure near the valve 9 to the modulator 14. Reference numeral 30 is a warning lamp for warning the abnormality of EGR.

FIG. 4 shows a block diagram of an electronic control circuit 8 for controlling the fuel injection amount of the internal combustion engine to control the air-fuel ratio and various sensors. The electronic control circuit 8 is mainly composed of a microcomputer.

The control circuit 8 takes in each detection signal from the intake pipe pressure sensor 2, the rotation sensor 7, the throttle position sensor 10, the water temperature sensor 11, and the intake temperature sensor 12, and calculates the fuel injection amount based on these detection data, Fuel injection valve 4
The air-fuel ratio control is performed by controlling the valve opening time of. Reference numeral 100 denotes an MPU (microprocessor unit) that executes arithmetic processing according to a predetermined program, 101 denotes an interrupt control unit that outputs an interrupt signal to the MPU 100, and 102 counts a rotation angle signal from the rotation sensor 7 to calculate an engine rotation speed. A counter unit 104 that selectively inputs the detection signals (analog signals) from the intake pipe pressure sensor 2, the water temperature sensor 11, the intake temperature sensor 12, and the throttle position sensor 10 and converts them into digital signals.
It is a conversion unit. Reference numeral 105 denotes a ROM, which is a read-only memory in which programs and map data used for calculation are stored in advance, and 106, a RAM, which is a writable and readable nonvolatile memory, and retains the stored contents even after the key switch is turned off. Reference numeral 107 denotes an output port connected to the solenoid valve 15, reference numeral 108 denotes an output counter unit for outputting a fuel injection amount (time) control signal including a register, and the MPU 100
The fuel injection amount data sent from the controller is input, the duty ratio of the control pulse signal for controlling the valve opening time of the fuel injection valve 4 is determined based on this data, and the injection amount control signal is output. The control signal output from the output counter unit 108 is applied to the fuel injection valve 4 for each cylinder via the power amplifier 110. In the control circuit 8,
MPU 100, interrupt control unit 101, input counter unit 102, A / D converter 104, ROM 105, RAM 1
06, the output counter unit 108 is the common bus 11
1, and necessary data is transferred according to a command from the MPU 100.

Next, the operation will be described.

When the internal combustion engine is started, an EGR operation map stored in the ROM 105 in the control circuit 8, that is, a map using the intake pipe pressure and the engine speed as parameters (not shown)
Based on the above, the MPU 100 determines whether or not the current intake pipe pressure and the detected value of the engine speed are within the EGR operating range. When it is determined to be in the operating region, the solenoid valve 15 is excited to apply a negative pressure near the throttle valve 9 at the inlet of the surge tank 19 to the modulator 14, and the EGR valve 13
The exhaust gas is recirculated to the intake manifold 3 by opening the valve.

The self-diagnosis by EGR that performs such an operation is executed as an interrupt process of the flowchart shown in FIG. As an interrupt condition, for example, it is set only once after 30 minutes have passed since the engine was started. This is to reduce the number of interruptions of EGR operation due to frequent self-diagnosis.

In the flowchart of FIG. 5, first, step 20
At 0, it is judged whether or not it is in the EGR operation region, and when it is judged that it is in the operation region, the next step 205,
Then, it proceeds to step 210. These steps 20
5 and 210, the deviation ΔNE of the engine speed NE per predetermined time and the deviation ΔTA of the throttle opening TA per predetermined time are obtained. Next, at step 215, the deviation ΔNE of the engine speed and the deviation ΔTA of the throttle opening are equal to or less than predetermined values α and β (ΔNE ≦
It is determined whether α, ΔTA ≦ β). this is,
This is to prevent this from being erroneously recognized as a detection value in these states if the subsequent processing is executed when the system is not in the steady operation state, that is, at the time of starting, acceleration, or deceleration. In this step 215, both are "YES".
In this case, that is, when it is determined that the engine is in the steady operation state, the routine proceeds to step 220, where the pressure of the intake pipe pressure sensor 2 when the EGR is ON is detected and stored in the RAM 106. At this time, the average of the detected values PON for about 3 seconds is calculated in order to prevent misjudgment against a sudden pressure change. Next, step 225 is executed to energize the solenoid valve 15, close the EGR valve 13, and stop the recirculation of exhaust gas. Then, in step 230, the pressure of the intake pipe pressure sensor 2 when the EGR is OFF is detected, and this is detected as R
It is stored in the AM 106. Also in this case, the above step 220
Similarly to, the average of the detected values POFF of about 3 seconds is adopted.

In the next step 235, the above steps 220, 23
Calculate the pressure difference ΔP between the detected value PON and POFF obtained in 0,
At the next step 240, it is determined whether or not ΔP ≧ γ. Then, when ΔP is equal to or larger than the predetermined value γ, it is determined that the EGR is normal, the process proceeds to step 245, and E
If the GR is reactivated and ΔP is equal to or less than the predetermined value γ, it is determined that the EGR is abnormal, and step 25
The process proceeds to 0, the warning lamp 30 is turned on, and abnormal information is stored in the RAM for self-diagnosis. The warning by the above warning lamp 30 notifies the driver of the abnormality of EGR,
It is possible to take measures for trouble repair.

That is, when the EGR is turned on and when it is turned off, the intake pipe pressure should differ by a predetermined value or more by the amount of the recirculated gas recirculated to the intake manifold 3. If there is no difference, it is determined to be abnormal, and the operation is performed. The person is informed of this.

In the above embodiment, the exhaust gas circulation path 17 serves as a recirculation pipe, the EGR valve 13 serves as an opening / closing means, the intake pipe pressure sensor 2 serves as an operating state detecting means, the RAM 106 serves as a storing means, and the warning lamp 30 serves as an alerting means. , Respectively.
Further, among the above-described processing, step 200 and the opening / closing processing of the EGR valve 13 corresponding thereto are performed by the first control means, steps 220 and 230 are performed by the operating state detection means, step 225 is performed by the second control means, and step 235 and step are performed. Reference numeral 240 is a determination means, and step 250 is a warning means.

Next, another embodiment will be described with reference to the flowchart of FIG. In the flowchart of FIG. 6,
The determination of whether or not the vehicle is in a steady operation state is made by detecting the intake pipe pressures PON and POFF a predetermined number of times and using the deviation thereof. That is, EG in step 300
After determining the R operation region, in steps 305 to 315, the intake pipe pressures PON and P depending on when the EGR is ON and OFF.
OFF is detected respectively, and these processes are performed in step 320.
Is repeated a predetermined number of times. Then, when it is repeated a predetermined number of times, in step 325, the intake pipe pressure PON
1 Calculate the average value and deviation of PONn.

Then, it is judged whether or not the calculated deviation is within a predetermined value (step 330), and when it is within the predetermined value, the process proceeds to the next step 333. That is, if it is determined in step 333 that the intake pipe pressure PON is within the predetermined range, it indicates that the intake pipe pressure PON fluctuates little. Therefore, it is determined that the engine is in the steady operation state, and the process proceeds to step 333. Step 3
In 33, the average value OFF of POFF1 ... POFFn when EGR is OFF is calculated, and then in step 335,
Pressure difference ΔP at mean value of intake pipe pressure ON and OFF
(= ON-OFF) is calculated. For this pressure difference ΔP, determination of ΔP ≧ γ (γ: positive number) is executed in step 340, and if “YES”, it means that the EGR is determined to be normal (step 345), and EGR is determined. O
N operation is performed to restore EGR. On the other hand, in the case of "NO", the warning lamp 30 is turned on to inform the driver of the EGR abnormality, and the information is stored in the RAM (step 350).

In the above embodiment, the variation value of the intake pipe pressure is used for the EGR abnormality determination. However, the present invention is not limited to this, and the intake fuel pressure may be determined by the basic fuel injection amount as one parameter. In addition to the detected value from the air-fuel ratio sensor, EG
Even if the operating state detection value that fluctuates depending on whether R is ON or OFF is applied, the same effect as that of the above-described embodiment can be obtained.

[Effects of the Invention] As described in detail above, in the exhaust gas recirculation control device of the present invention, when EGR is ON, EGR is temporarily switched to OFF, and whether or not there is an abnormality based on the change in the operating state at this time. Is judged and an alarm is given. Then, since the change in the operating state at this time reflects only the change caused by the switching of the EGR, the present invention is extremely accurate.
The abnormality of GR can be determined.

Further, in the present invention, it is not necessary to newly install a sensor in the recirculation pipe (EGR pipe) or the like, and the configuration of the entire exhaust gas recirculation control device can be simplified.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a graph explaining the operation of the present invention, FIG. 3 is a schematic configuration diagram showing an embodiment of the present invention, and FIG. A block diagram, FIG. 5 is a flowchart of the same embodiment, and FIG. 6 is a flowchart of another embodiment. 3 ... Intake manifold 2 ... Intake pipe pressure sensor, 8 ... Electronic control circuit 13 ... Exhaust gas recirculation control valve 15 ... Solenoid valve, 17 ... Exhaust gas circulation path 30 ... Warning lamp, 106 ... ... RAM

Claims (1)

[Claims] 1. A recirculation pipe for recirculating exhaust gas of an internal combustion engine to an intake pipe, an opening / closing means for opening / closing the recirculation pipe, and a first control means for controlling opening / closing of the opening / closing means in accordance with an operating state of the internal combustion engine. An operating state detection means for detecting an operating state of the internal combustion engine; and a second control means for temporarily closing the opening / closing means when the opening / closing means is opened by the first control means, A storage means for separately storing the detection values from the operating state detection means before and after the second control means closes the opening / closing means, and a difference between the detection values received from the storage means. An exhaust gas recirculation control device comprising: a determination means for determining whether or not is within a predetermined range; and an alarm means for issuing an alarm when the determination means determines within the predetermined range. .