JPS6251746A - Exhaust gas recirculation control device - Google Patents

Abstract

PURPOSE:To aim at simplifying the structure of a self-diagnosing device, by comparing a detected value by an engine operating condition detecting means upon turning on of an EGR with a detected value upon turning off of an EGR so that an EGR is self- diagnosed with no flow-meter sensor etc. being disposed in an exhaust gas recirculation pipe. CONSTITUTION:During operation of an internal combustion engine A, a control means E judges whether a shut-off means D in an exhaust recirculation pipe C is in the opening operation range or not with the use of a map in accordance with parameters such as, for example, an engine rotational speed, vacuum in an intake-air pipe, etc. in order to check whether the EGR is in its actuating range or not, and also judges whether the internal combustion engine A is in its steady state operating condition or not. When it is judged that the shut-off means is in the opening operation range and the engine is in the steady state operating condition, detections values from an operating condition detecting means F as the shut-off means D is opened or closed, are stored in a memory means G. Further, the thus stored detection values are com pared with each other by means of judging means H. If it is judged that the difference between both values is below a predetermined value, an alarm means I is actuated to inform the drivers concerning the abnormal condition of the EGR.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an exhaust gas recirculation control device that recirculates part of the exhaust gas of an internal combustion engine to the intake pipe of the internal combustion engine. 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 internal combustion engines as a means to reduce nitrogen oxides (NOx) in exhaust gas (Japanese Patent Application Laid-Open No. 59-192838).

By the way, when a failure occurs in the EGR due to malfunction of the EGR valve or blockage of the EGR piping, NOx tends to increase significantly. However, EGR failure has little effect on driving performance itself, so the driver may not notice anything abnormal.
It may emit large amounts of NOx and pollute the atmosphere.

As a means to solve this problem, for example, JP-A-56-6
As described in Publication No. 0912, the detected value from the sensor is corrected using a predetermined setting pattern using letter-erasing control, etc., and an abnormality is notified when the corrected value exceeds a predetermined value. It has been known.

[Problems to be Solved by the Invention] However, in order to apply the above-mentioned conventional technology to EGR, it is necessary to install a flow sensor, for example, in the EGR pipe, to detect the operating state of EGR, which makes the configuration complicated. There is a problem.

[Means for Solving the Problems] The present invention, which has been made to achieve the above problems, includes a recirculation pipe C that recirculates exhaust gas from an internal combustion engine A to an intake pipe B, as shown in FIG.
an opening/closing means for opening and closing this reflux pipe C; a control means E for controlling the opening and closing of this opening/closing means; an operating state detection means F for detecting the operating state of the internal combustion engine A; and an opening/closing means by the control means E. When the opening and closing operations are performed, a storage means G separately stores the detected values from the detection means F, and the storage means G stores both side-out values based on both side-out values of this storage means G. A device comprising: a determining means for determining whether the difference is within a predetermined range; and an alarm means I for issuing an alarm when the determining means H determines that the difference is within the predetermined range. It is.

Here, the operating state detection means F refers to a means for detecting changes in characteristics that occur in the internal combustion engine A depending on the presence or absence of exhaust gas recirculated through the recirculation pipe C. This refers to each sensor that measures the fuel injection amount, air-fuel ratio, engine speed, etc. determined as parameters.

The storage means G includes not only a digital memory but also an analog type storage means using a capacitor or the like.

The above-mentioned warning means (2) is a means for informing the driver of an EGR abnormality, and includes a text display, an audible warning, etc. in addition to a lamp display.

[Function] First, the control means E determines whether or not the opening/closing means is in the opening operation range based on the EGR operation range, that is, a map predetermined based on parameters such as the engine speed of the internal combustion engine and the intake pipe negative pressure. A judgment is made. Roughly speaking, it is determined whether or not the engine is in a steady operating state, and when the above-mentioned operating range and steady operating state conditions are satisfied, the following processing is performed. In other words, the opening/closing means is an opening operation, that is,
The detected value from the operating state detection means F is stored in the storage means G in the EGR operating state. On the other hand, when the opening/closing means is closed, the detection value from the detection means F at that time is stored in the storage means G.
to be memorized. Then, the determination means compares both side output values in the storage means G, and when it is determined that the difference is less than a predetermined value, the alarm means (2) is activated to notify the driver of the EGR abnormality.

In other words, as shown in Figure 2, when EGR is normal,
When EGR is turned from ON to OFF, the intake pipe pressure decreases,
This pressure drop manifests itself in a shortening of the calculated basic fuel injection time, a change in the air-fuel ratio from rich to rich, etc. Therefore, if there is no fluctuation greater than the expected predetermined value, it is determined that the EGR is abnormal, and the driver is alerted to this.

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

1 is a cylinder of a six-cylinder internal combustion engine, and 2 is an intake pipe pressure sensor that detects the intake air pressure in an intake manifold 3 connected to the cylinder 1, and is constituted by a semiconductor pressure sensor. 4 is an electromagnetically actuated 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 driven to rotate at 1/2 of the engine rotation speed, and a rotation sensor 7 that outputs a signal indicating the engine rotation speed, fuel injection timing, and a cylinder discrimination signal is disposed inside.

9 is a throttle valve; 10 is a throttle position sensor that detects the opening degree of the throttle valve 9; 11 is a thermistor-type water temperature sensor that detects the engine cooling water temperature;
12 is an intake air temperature sensor that detects the intake air temperature. 1
3 is intake manifold 3 and extreme manifold 1
A vacuum servo type exhaust gas recirculation control valve (hereinafter referred to as E
A control line 18 for controlling the EGR valve 13 is connected between the diaphragm chamber of the EGR valve 13 and the surge tank 19, and a modulator 14 for determining the valve opening degree of the EGR pulp 13. A solenoid valve 15 for switching whether or not to perform exhaust gas recirculation is installed in this control line 18. The N magnetic piece 15 is connected to the output port 107 (FIG. 3) of the electronic control circuit 8, and for example, the modulator 1 is connected to the output port 107 (FIG. 3) of the electronic control circuit 8.
4, and when exhaust gas recirculation is performed, the throttle valve 9 of the surge tank 19 operates.
An actuation signal is received to apply a nearby negative pressure to the modulator 14 . 30 is a warning lamp that warns of EGR abnormality.

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

The control circuit 8 includes an intake pipe pressure sensor 2, a rotation sensor 7, a throttle position sensor 10. Each detection signal from the water temperature sensor 11 and intake temperature sensor 12 is taken in, the fuel injection amount is calculated based on these detection data, and the fuel injection valve 4 is
The air-fuel ratio is controlled by controlling the valve opening time. 100 is an MPLJ that executes arithmetic processing according to a predetermined program.
(Microprocessor unit), 101 is MPLll
an interrupt control unit 102 that outputs an interrupt signal to oo;
104 is a counter unit that counts the rotation angle signal from the rotation sensor 7 and calculates the engine rotation speed, and 104 selectively receives the detection signals (analog signals) from the intake pipe pressure sensor 2, water temperature sensor 11, and intake air temperature sensor This is an A/D converter that inputs the signal and converts it into a digital signal. 105 is a ROM which is a read-only memory in which map data, etc. used for programs and calculations are stored in advance, and 106 is a RAM which is a readable and writable non-volatile memory, and retains the stored contents even after the key switch is turned off. 107 is an output port connected to the electromagnetic valve 15, and 108 is an output counter section including a register for outputting a fuel injection amount (time) control signal. Based on this, a duty ratio of a control pulse signal that controls the opening time of the fuel injection valve 4 is determined, and an injection amount control signal is output. Note that the output counter section 1
A control signal outputted from 08 is applied to the fuel injection valve 4 of each cylinder via a power amplifier 110.

In addition, in the control circuit 8, the MPU 100° interrupt control section 101, input counter section 102, A/D converter 104, ROM 105, RAM 106, and output counter section 10B are each connected to a common bus 111, so that necessary data transfer is possible. This is performed according to a command from the MPU 100.

Next, the operation will be explained.

When the internal combustion engine starts, the EGR operation map stored in the ROM 105 in the control circuit 8, that is, the map whose parameters are intake pipe pressure and engine speed (not shown).
Based on this, the MPU 100 determines whether or not the current intake pipe pressure and engine rotational speed are in the EGR operation range. When it is determined that the operating range is reached, the solenoid valve 15 is excited to apply negative pressure near the throttle valve 9 of the surge tank 19 to the modulator 14, and the EGR valve 13 is activated.
By opening the valve, exhaust gas is recirculated to the intake manifold 3.

Self-diagnosis in the EGR, which performs such operations, is executed as an interrupt process in the flowchart shown in FIG. As an interrupt condition, for example, 3 from the slight start
Set only once after 0 minutes have passed. This is to reduce the number of EGR operation interruptions due to frequent self-diagnosis.

In the flowchart of FIG. 5, first, step 20
At step 205.0, it is determined whether or not it is in the EGR operation region.If it is determined that it is in the EGR operation region, the next step 205.
The process then proceeds to step 210. These steps 205
, 210, the deviation ΔNE of the engine rotational speed NE per predetermined time, , 15 and the deviation ΔTA of the throttle opening TA per predetermined time are determined, respectively. Next, in step 215, the engine speed deviation ΔNE and the throttle opening deviation ΔTA are equal to or less than predetermined values α, β (ΔN
A determination is made as to whether E≦α, ΔTA≦β). This is to prevent if subsequent processing is executed when the engine is not in a steady operating state, that is, during startup, acceleration, or deceleration, it may be mistaken for a detected value in these states. In this step 215, both rYE
In the case of sJ, that is, when the steady operating state is determined, the process proceeds to step 220, where the pressure of the intake pipe pressure sensor 2 when EGR is turned on is detected, and this is stored in the RAM 106. At this time, in order to prevent erroneous recognition due to sudden pressure fluctuations, the average of the detected values PON for about 3 seconds is calculated. Next, step 225 is executed to energize the electromagnetic 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 EGR is OFF is detected, and this is stored in the RAM1.
Stored in 06. In this case, as in step 220 above, the average of the detected values P OFF for about 3 seconds is used.

In the next step 235, the above step 220.23
The pressure difference ΔP between the detected values PON and POFF determined in step 0 is calculated, and in the next step 240, it is determined whether ΔP≧T. Then, if ΔP is greater than or equal to a predetermined value of 1, EG
H is determined to be normal, the process proceeds to step 245, and EGR is reactivated. On the other hand, if ΔP is less than the predetermined value γ, it is determined that EGR is abnormal, and the process proceeds to step 250, where a warning is issued. The lamp 30 is ignited and abnormality information is stored in the RAM for self-diagnosis. The above-mentioned warning lamp 30 notifies the driver of the abnormality of the EGR, and it is possible to take measures to repair the failure.

In other words, when EGR is ON and OFF, there should be a difference in intake pipe pressure equal to or greater than a predetermined value by the amount of recirculated gas returned to the intake manifold 3. If there is no difference, it is determined that there is an abnormality and the operation is stopped. This will be communicated to the public.

Next, another embodiment will be described according to the flowchart of FIG. In the flowchart in Figure 6,
The determination as to whether or not the vehicle is in a steady operating state is made by detecting the intake pipe pressures PON and POFF a predetermined number of times and based on the deviation thereof.

That is, after determining the EGR operating region in step 300, in steps 305 to 315, EGR is turned on and off.
The intake pipe pressures PON and POFF during FF are detected, and these processes are repeated a predetermined number of times based on the determination in step 320. Then, when the process is repeated a predetermined number of times, in step 325, the intake pipe pressure PONI...PO
Calculate the average value and deviation of Nn.

Next, it is determined 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 is within the predetermined range, this indicates that the fluctuation in the intake pipe pressure PON is small, and therefore it is determined that the steady operating state exists, and the process proceeds to step 333. In step 333, P 0FFI when EGR is OFF
...The average value 75 OFF of pOFFn is calculated, and then in step 335, the average value PON of the intake pipe pressure,
Pressure difference ΔP at POFF (= PON-POF
F) is calculated. Regarding this pressure difference ΔP, determination of ΔP≧γ (γ: positive number) is executed in step 340, and if “rYES”, it is determined that EGR is normal (step 345), and EGR ON and E
Restore GR. On the other hand, in the case of rNOJ, the warning lamp 30 is turned on to notify the driver of the EGR abnormality, and the information is stored in the RAM (step 3).
50).

In addition, in the above embodiment, the fluctuation value of the intake pipe pressure is used to determine the EGR abnormality, but the present invention is not limited to this, and the determination can also be made using the basic fuel injection amount with the intake pipe pressure as one parameter. In addition to the detected value from the air-fuel ratio sensor, the EG
Even if a driving state detection value that varies depending on whether R is turned on or off is applied, the same effect as in the above embodiment can be obtained.

[Effects of the Invention] As explained above, according to the present invention, EGR self-diagnosis can be performed by comparing the detected value of the driving state detection means when EGR is ON and OFF. Since there is no need to provide a flow rate sensor or the like in the reflux pipe as in the technique described above, the configuration can be simplified.

In addition, clogging of the reflux tube is also indicated by a decrease in the difference in detected values, so abnormalities can be easily detected in this case as well.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a graph explaining the present invention in detail, FIG. 3 is a schematic configuration diagram showing one embodiment of the present invention, and FIG. 4 is a diagram showing the same embodiment. The block diagram, FIG. 5 is a flowchart of the same embodiment, and FIG. 6 is a flowchart of another embodiment. A... Internal combustion engine B... Intake pipe C... Reflux pipe D... Opening/closing means E... Control means
F... Operating state detection means G... Storage means
Eyes... Judgment means ■... Alarm means

Claims (1)

[Scope of Claims] A recirculation pipe that recirculates exhaust gas from an internal combustion engine to an intake pipe, an opening/closing means for opening and closing this recirculation pipe, a control means for controlling opening/closing of this opening/closing means, and a means for detecting the operating state of the internal combustion engine. an operating state detection means; a storage means for separately storing the detection values from the detection means when the opening/closing means is opened and closed by the control means; and a storage means for separately storing the detection values from the storage means. and determining means for determining whether or not the difference between the detected values is within a predetermined range, and an alarm means for issuing an alarm when the determining means determines that the difference is within the predetermined range. Exhaust gas recirculation control device.