JPH079225B2 - 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 control thereof. The present invention relates to a device self-diagnosis device.

[Prior Art and its Problems] 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 for reducing nitrogen oxides (NO _x ) in exhaust gas. ing.

By the way, when an EGR failure occurs due to a malfunction of an ERG valve or a blockage of an EGR pipe, NO _x tends to increase remarkably. However, since the failure of the EGR has little influence on the driving performance itself, the driver may not notice abnormally and a large amount of NO _x may be emitted to pollute the atmosphere.

As a countermeasure against this, conventionally, as a means for detecting a failure of the EGR, there is a means for providing a flow rate sensor or the like in the pipe of the EGR, as described in JP-A-56-60912. However, the above-mentioned conventional techniques have the problems that a flow rate sensor is required, the configuration is complicated, and the cost is increased.

To solve this, EGR is turned off from ON during steady operation.
When the change amount of the intake pipe pressure at the time of switching to is determined, the change amount of the pressure is determined to be abnormal when the change amount is equal to or less than a predetermined value, and the result is warned. I have already proposed it in the issue.

However, if the above steady operation does not continue for a predetermined period of time or longer, it is not possible to make an abnormality determination, and when the air conditioner, brake, etc. are operating, the pressure changes due to factors other than EGR operation, resulting in erroneous detection. It could happen.

The present invention has been made to solve the problems of the prior art and the prior application of the applicant of the present application, and has a simple structure and exhaust gas recirculation with a self-diagnosis function without erroneous detection. An object is to provide a control device.

[Means for Solving the Problems] The present invention made to solve the above problems and achieve the above object, as shown in FIG. 1, recirculates exhaust gas of an internal combustion engine A to an intake pipe B. Reflux tube C
An opening / closing means D for opening / closing the return pipe C, a control means E for opening / closing the opening / closing means D, an intake state detecting means for detecting an intake state of the intake pipe B of the internal combustion engine A, for example, an intake pipe pressure. Pressure detecting means F for detecting
When the opening / closing means D is being closed by the control of the control means E, and when the opening / closing means D is being opened before and after the closing operation, the intake pipe pressure from the pressure detecting means F is separately provided. A storage unit G for storing, a determination unit H for determining whether or not the deviation is within a predetermined range based on the three intake states stored in the storage unit G, and a determination unit H within the predetermined range. An exhaust gas control device including alarm means I for issuing an alarm when it is determined that

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

The warning means I is means for informing the driver of the EGR abnormality, and includes a character display and a sound display in addition to the lamp display.

As a preferable mode of the determining means H, a function of making an abnormality determination is provided when the deviation between the average value of the intake pipe pressure during the opening operation and the detected intake pipe pressure value during the closing operation is within a predetermined range.

Further, as another preferable mode of the determining means, a function of performing abnormality determination is provided when both intake pipe pressures in the opening operation are within a predetermined range.

[Operation] First, the control means E determines whether the operating range of the EGR, that is, the opening / closing normal operation range of the opening / closing D based on a map determined by parameters such as the engine speed of the internal combustion engine and the intake pipe negative pressure. It is determined whether or not.

Then, when the EGR opening operation condition is satisfied and EGR is turned on, the intake pipe pressure when it is turned on is detected, then EGR is turned off, the intake pipe pressure at this time is detected, and EGR is turned on again. Turn on to detect intake pipe pressure.

Then, the three intake pipe pressures are stored in the storage means G and then determined by the determination means H. If the determination means H determines that these intake pipe pressures are within a predetermined deviation, the determination means H determines that the abnormality occurs, and the alarm means I reports the abnormality.

As a preferred embodiment of the present invention, for example, as shown in FIG. 2, the EGR is turned on when the operating range of the EGR is reached (at time t.
1) Furthermore, when the operating condition is stable and the self-diagnosis condition is satisfied, the EGR is turned off after reading the intake pipe pressure P _ON1 when the EGR is turned on (time point t2). Then, when the time until the intake pipe pressure stabilizes (for example, 500 ms) has elapsed, the pressure P _OFF2 when the EGR is OFF is detected, and the EGR is turned ON again (time point t3). And likewise for a predetermined time (eg 500m
s) When the time elapses, the EGR is turned on again to obtain the intake pipe pressure P _ON2 at this time (time point t4). Then, an average of the P _ON1 and P _ON2. When the deviation between this average value and the intake pipe pressure when OFF is less than or equal to a predetermined value, it is determined to be abnormal.

As another preferred embodiment of the present invention, in addition to the self-diagnosis processing of FIG. 3, as shown in FIG. 3, the intake pipe pressures P _ON1 and P ON when the EGR is ON before and after the EGR is OFF _ON2 is detected,
When there is a predetermined deviation between the two, it is determined that the operating conditions have changed, and the EGR self-diagnosis at this time is stopped.

[Effects of the Invention] As described above, according to the present invention, ON in EGR is performed.
Since the EGR self-diagnosis is performed based on the detected intake condition of the intake pipe from time → OFF → ON, it is necessary to install a flow sensor etc. in the return pipe as in the prior art. Since it does not exist, the configuration can be simplified.

Further, since the intake pipe states at two points when EGR is ON and one point when EGR is OFF are used, accurate self-diagnosis of EGR can be performed.

[Embodiment] FIG. 4 is a schematic configuration diagram of an internal combustion engine and its control system to which an embodiment of the present invention is applied.

In FIG. 4, 1 is one cylinder of a 6-cylinder internal combustion engine, 2 is an intake pipe pressure sensor for detecting the pressure in the intake manifold 3 connected to the cylinder 1, and is composed of a semiconductor type pressure sensor. It 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 this distributor 6 is
It is driven to rotate at two rotation speeds, and a rotation sensor 7 that outputs a signal indicating the engine rotation speed and fuel injection timing and a cylinder discrimination signal is provided inside. Reference numeral 9 is a slot valve, 10 is a throttle position sensor, 11 is a thermistor type water temperature sensor for detecting the cooling water temperature of the engine, and 12 is an intake air temperature sensor for detecting the intake air temperature. 13 is an exhaust gas circulation path connected between the intake manifold 3 and the exhaust manifold 16.
It is a vacuum servo type exhaust gas recirculation control valve (hereinafter referred to as EGR valve) mounted on 17, and the control conduit 18 for controlling the EGR valve 13 is the diaphragm chamber of the EGR valve 13 and the inlet of the surge tank 19. A modulator 14 for determining the valve opening degree of the EGR valve 13 and a solenoid valve 15 for switching whether or not exhaust gas recirculation is connected are arranged in the control line 8 between the two. The solenoid valve 15 is connected to the output port 107 (FIG. 5) of the electronic control circuit 8 and operates so that atmospheric pressure is communicated to the modulator 14 during cold, idle, and high load, while the exhaust gas recirculation is performed. Occasionally, an operation signal is received so as to apply a negative pressure near the throttle valve 9 at the inlet of the surge tank 19 to the modulator 14. 30 is
This is a warning lamp that warns of an EGR abnormality.

FIG. 5 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 each sensor, and is mainly composed of the electronic control circuit 8 and 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, the intake temperature sensor 12, and calculates the fuel injection amount based on these detection data, Air-fuel ratio control is performed by controlling the valve opening time of the fuel injection valve 4. 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. Counter part, 104
Is the intake pipe pressure sensor 2, the water temperature sensor 11, the intake temperature sensor 12
It is an A / D conversion unit that selectively inputs the detection signal (analog signal) from and converts it to a digital signal. 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. . 107 is an output port connected to the solenoid valve 15, 108 is an output counter section for outputting a fuel injection amount (time) control signal including a register, and the MPU100
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 transmitted through the power amplifier 110 to the fuel injection valve 4 for each cylinder.
Applied to. In the control circuit 8, the MPU1
00 and the interrupt counter unit 108 are respectively connected to the common bus 111, and necessary data is transferred according to a command from the MPU 100.

The operation of the EGR with the above configuration is executed by the flowchart of FIG. 6 stored in the ROM 105 in the control circuit 8.
The flow chart is started when the internal combustion engine is started. First, in step 200, it is determined whether or not the operating condition of step EGR is satisfied. That is, EGR
Of the intake pipe pressure Pm, engine speed Ne, water temperature Tw, etc. on the MPU100 based on a map (not shown) using the intake pipe pressure, engine speed and water temperature as parameters. It is determined whether or not it is in the operating region of. If the conditions are satisfied here, EGR O
Judge N, OFF, and if it is OFF, EGR in the next step 220.
It is determined whether or not the operating condition of is satisfied for the first time, and when it is the first time, the EGR self-diagnosis permission flag F _PER is set (step 230). After setting the flag F _PER , the EGR is turned on, that is, 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 to open the EGR valve 13. Thus, the exhaust gas is recirculated to the intake manifold 3.

On the other hand, when it is determined in step 200 that the EGR is not in the operating range, the EGR is turned off, that is, the solenoid valve 15 is deenergized to stop the exhaust gas recirculation (step 250).

Then, as the interrupt processing of the above-mentioned flowchart, the flowchart of FIG. 7 is activated at every predetermined time (for example, 4 ms). First, in step 300, the self-diagnosis permission flag F _PER is determined, and if the flag F _PER is 0 (reset), this processing is terminated, while the flag F is 1
If it is (set), it is determined in steps 305, 310 and 315 whether or not the operating state is such that self-diagnosis can be determined. That is, the engine speed Ne is within the predetermined speed range (N1 <Ne
<N2) or the intake pipe pressure Pm is within the specified pressure range (P1 <
It is determined whether Pm <P2) and whether the atmospheric pressure P _A is a predetermined value P ₂ or more.

Here, the operation state is determined in order to add a stricter condition than the EGR region to perform accurate self-diagnosis and to set a release condition for a change in the operation state.

Next, in step 320, the graph F _FAIL showing that the self-diagnosis is being executed is 1 (set), or
It is determined whether it is 0 (reset). here,
Since this processing is the first processing, the case of proceeding to step 325 will be described. In this step 325, after the flag F _FAIL under self-diagnosis is set, in the next step 330, the intake pipe pressure Pm is read from the pressure sensor 2 and stored. Next, after the EGR is turned off (step 335), the counter C _DLY is reset (step 340), and then this processing is temporarily terminated.

Then, in the iterative process, the determination of the self-diagnosis flag F _FAIL is performed in step 320. Here, since the flag F _FAIL has already been set, the process proceeds to step 400. In this step 400, it is determined whether or not the EGR is ON, but since the EGR is switched to OFF in the above step 335, the process proceeds to step 405, and it is determined whether or not the counter C _DLY has passed the predetermined time T1. If it is determined that the time has not elapsed, the counter C _DLY is incremented (step 410), and if the predetermined time has elapsed, the counter C _DLY is cleared (step 415). Then, the intake pipe pressure P _OFF when the EGR is turned _off is detected (step 420), and the EGR is _turned on again (step 42).
5), this process is finished once.

Then, through repeated processing, the EGR is determined by the judgment in step 400.
Since it is turned on, the routine proceeds to step 500, where it is judged whether or not a predetermined time T _{2 has} passed since the EGR was turned on. If not, the counter C _DLY is counted up (step 505) and the predetermined time is passed. When the time has elapsed, the counter C _DLY is cleared (step 510). And at this time the EGR is turned on
The intake pipe pressure P _ON2 at the time of is detected (515).

Next, at step 520, the deviation ΔP is calculated from the three intake pipe pressures read at steps 330, 420 and 515 based on the following equation.

In the next step 525, it is determined that the EGR is abnormal when the deviation ΔP is within the predetermined value α, and in step 530, a flag F _EGR indicating the abnormality is set. By setting the flag F _EGR , the warning lamp 30 is turned on to notify the driver of the EGR abnormality, and the information is stored in the RAM 106 so that it can be used for inspection or the like.

Further, the self-diagnosis permission flag F _{PER of the} EGR and the flag F _FAIL indicating that the self-diagnosis is in progress are reset, and this processing is ended (steps 535, 540).

In addition, in steps 305 to 315, when the operating condition is out of the range, the process proceeds to step 600, the flag F _FAIL indicating that the self-diagnosis is being performed is determined, and the flag F _FAIL is 1 For example, EGR is turned on and F _FAIL is reset (steps 605 and 610). As a result, even if the self-diagnosis processing once started goes out of the range of the operating state, it is possible to execute it again from the beginning.

Also, steps 220 and 230 of the flowchart of FIG. 6 and step steps 300 and 535 of the flowchart of FIG.
As a result, the self-diagnosis permission flag F _PER is judged, and the EGR self-diagnosis is executed only once after the EGR control condition is controlled first.
Since it is not necessary to turn N and OFF, it is possible to reduce the influence on driving performance and emissions. In the present embodiment, it is performed only once, but it may be performed three to five times to the extent that the driving performance and the emission are not deteriorated in order to improve the detection accuracy.

FIG. 8 is a modified example in which steps 700 and 705 are added to the embodiment of FIG. 7, and the intake pipe pressure when the EGR is turned on in step 700.
It calculates the difference △ P _M of P _ON1, P _ON2, these in the case of more than the predetermined range beta, is processed so as to interrupt the determination (step 705). As a result, since the self-diagnosis process is once canceled for a large change in the operating state and the process is performed again when the operating state becomes stable, accurate self-diagnosis of the EGR becomes possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIGS. 2 and 3 are graphs for explaining the operation of the present invention, and FIG. 4 is a configuration diagram showing the periphery of an engine according to an embodiment of the present invention. 5
FIG. 6 is a block diagram of the engine surrounding the same embodiment, FIG. 6 is a flow chart for judging the EGR operation of the same embodiment, FIG. 7 is a flow chart for processing the EGR self-diagnosis of the same embodiment, and FIG. 6 is a flowchart for processing an EGR self-diagnosis according to the embodiment of A ... Internal combustion engine, B ... Intake pipe C ... Reflux pipe D ... Opening / closing means, E ... Control means F ... Pressure detecting means G ... Storage means, H ... Judging means I ... Warning means

Front page continuation (72) Inventor Toshio Kondo 1-chome, Showa-cho, Kariya city, Aichi Nihon Denso Co., Ltd. (56) References JP 62-51747 (JP, A) JP 62-51746 ( JP, A)

Claims (4)

[Claims] 1. A recirculation pipe for recirculating exhaust gas of an internal combustion engine to an intake pipe, a control device for controlling opening / closing of the opening / closing device, a control device for controlling opening / closing of the opening / closing device, and an intake state of the intake pipe of the internal combustion engine. The intake state detected by the intake state detecting means and the intake state from the intake state detecting means during the closing operation of the opening / closing means under the control of the control means and during the opening operation before and after the closing operation. And a determination means for determining whether the deviation is within a predetermined range based on the three intake states stored in the storage means, and a determination means for determining within the predetermined range. An exhaust gas recirculation control device comprising: alarm means for issuing an alarm when it is determined to be present. 2. The exhaust gas recirculation control device according to claim 1, wherein the intake state detecting means comprises pressure detecting means for detecting the pressure of the intake pipe. 3. The determining means has a function of making the above determination when the deviation between the average value of the intake pipe pressure during the opening operation and the intake pipe pressure during the closing operation is within a predetermined range. The exhaust gas recirculation control device according to claim 2. 4. The exhaust gas according to claim 2 or 3, wherein the determining means has a function of performing an abnormality determination when the pressures of both intake pipes during the opening operation are within a predetermined range. Reflux control device.