JPH0323337A - Trouble diagnosing device for suction control device - Google Patents

Abstract

PURPOSE:To effect given coping with a situation through diagnosis of the trouble of a suction control device by a method wherein a pressure in an intake air passage on the downstream of a suction control valve is detected, and it is decided that a trouble occurs when a difference between a maximum and a minimum value exceeds a given value. CONSTITUTION:A constant pressure control device A controls a suction control valve 12 so that a pressure in an intake air passage 2 on the downstream of the suction control valve 12 is adjusted to a specified value. In this case, a pressure in the intake air passage 2 on the downstream of the suction control valve 12 is detected by a means B. Based on the detecting result of the means B, a fluctuation in a pressure containing the maximum and the minimum value of a pressure during a given period is detected by a means C. Based on the detecting result of the means C, it is decided by a means D that a trouble occurs when a difference between a maximum and a minimum value exceeds a given value. This constitution diagnoses the trouble of the suction control device and performs given coping with the trouble.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a failure diagnosis device for an intake control device.

[Conventional technology]

In order to reduce NOx while preventing the generation of smoke in a diesel engine, it is necessary to recirculate an optimum amount of exhaust gas into the engine intake passage depending on the engine operating state. Therefore, exhaust gas is recirculated between the engine exhaust passage and the engine intake passage! I (under J2J, referred to as EGR) An intake control valve is arranged in the intake passage upstream of the opening of the EGR passage with respect to the intake passage, and the pressure in the intake passage downstream of the intake control valve is A diesel engine is known that is equipped with a constant pressure control device that responds to the intake control valve so that the pressure becomes a predetermined constant pressure.
See Publication No. 2-4663 or Publication of Japanese Utility Model Application No. 55-100052>. In this diesel engine, a constant pressure acts on the opening of the EGR passage relative to the intake passage, so the EGR
The amount of exhaust gas recirculated from the passage to the intake passage can be easily controlled to the optimum amount according to the operating condition of the engine.

[Problem to be solved by the invention]

However, in such a diesel engine, if the passage for transmitting the pressure in the intake passage to the constant pressure control device becomes clogged with carbon etc., there will be a delay in transmitting pressure fluctuations in the intake passage to the constant pressure control device. Even when the pressure decreases, the intake control valve does not easily rotate in the opening direction, and after a while, the intake control valve begins to rotate in the opening direction. When the intake control valve rotates in the opening direction, the pressure in the intake passage increases, but because there is a delay in transmitting pressure fluctuations to the constant pressure control device, the intake control valve rotates in the closing direction after a while. Change direction. Therefore, the intake control valve repeatedly opens and closes, and the amount of intake air increases and decreases repeatedly, resulting in a problem that the engine output fluctuates. In such a case, it is preferable to be able to determine that there is an abnormality in the constant pressure control device.

[Means to solve the problem]

In order to solve the above problems, according to the present invention, the intake control valve 12 is arranged in the intake passage 2 as shown in the configuration diagram of the invention in FIG. In an internal combustion engine equipped with a constant pressure control device A that controls the intake control valve l2 so that the pressure becomes a predetermined constant pressure in response to the pressure of the intake passage 2 downstream of the intake control valve 12,
pressure detection means B for detecting the pressure of , and pressure fluctuation detection means C for determining the maximum and minimum values of this pressure within a predetermined period based on the detection results of the pressure detection means B;
The pressure fluctuation detection means D determines that a failure has occurred when the difference between the maximum value and the minimum value exceeds a predetermined difference based on the detection result of the pressure fluctuation detection means C.

[For production]

It is detected that the pressure, which should originally be kept constant, has fluctuated, and based on this, it is determined that some kind of problem has occurred.

〔Example〕

Referring to FIG. 2, 1 is a diesel engine body, 2 is an intake passage, 3 is an exhaust passage, and 4 is a negative pressure bomb driven by the engine. The intake passage 2 and the exhaust passage 3 are connected to each other by an EGR passage 5, and the EGR passage 5 is connected to the intake passage 2.
An EGR valve 7 is disposed in the opening 6 of. EGR valve 7 is E
It has a valve body 8 that controls the opening and closing of the opening 6 of the GR passage 5, a diaphragm 9 connected to the valve body 8, and a negative pressure chamber 10 defined by the diaphragm 9, and this negative pressure chamber 10 is connected to the atmosphere. It is connected to the negative pressure bomb 4 via an electromagnetic switching valve Vl that can communicate with the negative pressure bomb 4.

On the other hand, the intake passage 2 upstream of the opening 6 of the EGR passage 5
An intake control valve l2 driven by an actuator 1l is disposed therein. This actuator 11 includes a pair of diaphragms 13 and 14, and these diaphragms 13.
a first negative pressure chamber l5 and a second negative pressure chamber 16 defined by the first negative pressure chamber l5, a stopper 17 arranged in the first negative pressure chamber l5 to restrict movement of the diaphragm 14, and a stopper 17 that restricts movement of the diaphragm 14;
A stopper 18 is fixed to the diaphragm 4 to restrict movement of the diaphragm 13. Diaphragm 13 is connected to intake control valve 12 via control rod 19 .

The first negative pressure chamber 15 is connected to the modulator 20 via an electromagnetic switching valve V2 that can communicate with the atmosphere and an electromagnetic switching valve V3 that can communicate with the negative pressure pump 4, and the second negative pressure chamber l6 is connected to the electromagnetic switching valve V5. It is connected to the negative pressure bomb 4 via. The modulator 20 has an atmospheric pressure chamber 22 and a constant pressure chamber 23 formed on both sides of a diaphragm 21, and the constant pressure chamber 23 is connected to a negative pressure conduit 2.
4 into the intake passage 2 downstream of the intake control well 12. On the other hand, a valve port 25 that is controlled to open and close by the diaphragm 21 is open in the atmospheric pressure chamber 22, and this valve port 25 is connected to the lth negative pressure chamber 15 of the actuator 11 via the electromagnetic switching valves V3 and V2. and on the other hand to the negative pressure pump 4 via a throttle 26 . Further, an electromagnetic switching valve V4 for selectively connecting the negative pressure conduit 24 or the negative pressure chamber lO of the EGR valve 7 to the absolute pressure sensor 27 is provided, and each electromagnetic switching valve Vl, V2, V3, V4 . V5 is controlled by the output signal of electronic control unit 30.

The electronic control unit 30 consists of a digital computer with ROMs interconnected by a bidirectional bus 3l.
(read only memory) 32, RAM (random access memory) 33, CPU (microprocessor) 3
4. It is equipped with an input boat 35 and an output boat 36.

A backup RAM 38 is connected to the CPIJ 34 via a bidirectional bus 37. The absolute pressure sensor 27 generates an output voltage proportional to the pressure guided by the absolute pressure sensor 27, and this output voltage is inputted to the manual power port 35 via the AD converter 39. The load sensor 40 generates an output voltage proportional to the amount of depression of the accelerator pedal 41, that is, the engine load, and this output voltage is input to the input port 35 via the AD converter 42. Also connected to input port 35 is a rotational speed sensor 43 that generates an output signal representative of engine rotational speed. The output port 36 is connected to each electromagnetic switching valve Vl, V2, V3, V4, V51 via the corresponding drive circuit 44.
:Connected.

Next, while referring to Figures 2 and 3, constant pressure control and E
GR control will be explained.

First, constant pressure control will be explained. The electromagnetic switching valve V5 shown in FIG. 2 is normally turned off, and at this time the second negative pressure chamber 16 of the actuator 11 is opened to the atmosphere. When the second negative pressure chamber l6 is opened to the atmosphere, the diaphragm 1
4 moves toward the first negative pressure chamber l5 and is held in contact with the stopper 17. At this time, the movement of the diaphragm 13 is regulated by the stopper 18, and the intake control valve 12
The valve can only be closed to the half-open position shown in FIG.

The area where constant pressure control is performed is curve a and curve C in Figure 3.
This region is determined by the engine speed N and the engine load L. This area is pre-installed in ROM 32.
Therefore, when it is determined from the engine speed N and the engine load L that the engine operating state has reached an operating state that requires constant pressure control, the electromagnetic switching valve V2. V3 are both turned off, the first negative pressure chamber l5 of the actuator 11 is connected to the modulator 20, and constant pressure control is started. The pressure in the constant pressure chamber 23 of the modulator 20 is equal to the pressure in the intake passage 2 downstream of the intake control valve 12, and the pressure in the constant pressure chamber 23, that is, the pressure in the intake passage 2, is lower than the predetermined set pressure. When the temperature decreases, the diaphragm 21 opens the valve port 25. When the valve port 25 is opened, the air is supplied into the first negative pressure chamber l5 of the actuator 11, so the intake control valve I2 is rotated in the valve opening direction.

When the intake control valve 12 is rotated in the opening direction, the pressure in the intake passage 2 downstream of the intake control valve 12 increases, and when this pressure exceeds a predetermined set value, the diaphragm 21 closes the valve boat 25. do. At this time, since the negative pressure from the negative pressure pump 4 is applied to the first negative pressure chamber 15, the intake control valve 12 is rotated in the valve closing direction. In this way, the pressure in the intake passage 2 downstream of the intake control valve 12, in fact the negative pressure, is maintained at a predetermined set pressure. Therefore, it can be seen that the actuator 1l and the modulator 20 constitute a constant pressure control device. During low-speed, low-load operation of the engine, the amount of intake air decreases, so the opening degree of the intake control valve 12 becomes considerably small in order to maintain the pressure in the intake passage 2 at the set pressure. However, the intake control valve l2 can only be closed to the half-open state shown in FIG.
It is maintained in the half-open state shown in the figure. This situation occurs in the hatched area d of FIG.

In the region above curve a in FIG. 3, the electromagnetic switching valve v2 is turned on and the first negative pressure chamber 15 is opened to the atmosphere, thereby fully opening the intake control valve 12. In this way, high output can be obtained by fully opening the intake control valve 12 during high engine load operation.

In the region below the curve C in FIG. 3, the electromagnetic switching valve v3 is turned on and the first negative pressure chamber l5 is connected to the negative pressure pump 4,
As a result, the intake control valve l2 is maintained in the half-open state shown in FIG. In this way, by half-opening the intake control valve 12 during low-load engine operation, the generation of intake noise can be suppressed.

When stopping the engine, use the solenoid switching valve V3. Both V5 are turned on, and both the first negative pressure chamber l5 and the second negative pressure chamber 16 are connected to the negative pressure bomb 4, thereby completely closing the intake control valve 12. By fully closing the intake control valve 12 when the engine is stopped, the engine can be stopped smoothly.

Next, EGR control will be explained. EGR control is performed in the region between curve b and curve C in FIG. 3. This EGR
The control may be performed by feedback control or oven lube control.

When EGR feedback control is performed, the electromagnetic switching valve V4 is turned off and the negative pressure applied to the negative pressure chamber 10 of the EGR valve 7 is guided to the absolute pressure sensor 27. The negative pressure in lO, in fact the absolute pressure PI, is detected.

The target negative pressure P0 in the negative pressure chamber IO is stored in advance in the ROW 32 in the form of a map as a function of the engine speed N and the load L, and during feedback control, the negative pressure is adjusted based on the output signal of the absolute pressure sensor 27. Negative pressure PI in chamber IO is target negative pressure P
. The duty ratio of the control pulse of the electromagnetic switching valve V1 is controlled so that.

Further, the target negative pressure P when the negative pressure PI in the negative pressure chamber 10 is maintained at the target negative pressure Pa. and target duty ratio DT
The relationship between the
Stored within 3g.

On the other hand, the target negative pressure P in the negative pressure chamber 10. Oven loop control is performed when the target negative pressure Pa in the negative pressure chamber 10 is kept constant, and the target negative pressure P0 stored in the backup RAM 38
A target duty ratio DT is determined based on the target negative pressure Po from the relationship between the target duty ratio DT and the target duty ratio DT, and the electromagnetic switching valve V1 is duty-controlled in accordance with this target duty ratio.

Therefore, at this time, the output signal of the absolute pressure sensor 27 is not used.

Next, feedback control and open loop control of EGR will first be explained with reference to FIGS. 6 and 7.

FIG. 6 shows a routine for performing EGR control, and this routine is executed by interrupts at fixed time intervals.

Referring to FIG. 6, first, in step 50, E
It is determined whether the supply of GR gas is stopped.

When the negative pressure chamber 10 of the EGR valve 7 is opened to the atmosphere by the switching action of the electromagnetic switching valve V1, the supply of EGR gas is stopped, and in this case, the process proceeds to step 51.

In step 51, it is determined whether the solenoid switching valve V4 is off or not.
That is, it is determined whether the atmospheric pressure in the negative pressure chamber IO is being guided to the absolute pressure sensor 27 or not. When the electromagnetic switching valve v4 is off, the process proceeds to step 52, where the absolute pressure PI in the negative pressure chamber 10 detected by the absolute pressure sensor 27 is set as PA. Therefore, this PA represents atmospheric pressure.

On the other hand, if EGR gas is being supplied, step 5
Proceeding from step 0 to step 53, the target negative pressure P in the pressure chamber 10 is determined based on standard atmospheric pressure. is calculated. This target negative pressure P. As described above, is stored in advance in the ROM 32 as a function of the engine speed N and the engine load L. Next, in step 54, it is determined whether the target negative pressure P0 has been constant for a certain period of time, for example, 1 second. If the target negative pressure Po remains constant for a certain period of time, the process proceeds to step 55, where it is determined whether the feedback completion flag is set. When the process proceeds to step 55 for the first time after the target negative pressure P0 becomes constant for a certain period of time, the process proceeds to step 56 because the feedback completion flag has been reset.

In step 56, a feedback flag is set;
The oven lube flag is then reset in step 57. When the feedback flag is set in step 56, feedback control shown in FIG. 7 is started.

First, the feedback control routine shown in FIG. 7 will be explained. This routine is also executed by interrupts at regular intervals.

Referring to FIG. 7, first, in step 70, it is determined whether or not a feedback flag is set. If the feedback flag is set, the process proceeds to step 71, where atmospheric pressure FA and absolute pressure sensor 27 are detected.
Pressure PI in the negative pressure chamber 10 of the EGR valve 7 detected by
The differential pressure ΔP is calculated. That is, the negative pressure ΔP in the negative pressure chamber IO is calculated based on the current atmospheric pressure. Next, in step 72, the target negative pressure P is set. It is determined whether or not ΔP+S (S is a constant value and is larger than S<ΔP). That is, the current negative pressure ΔP in the negative pressure chamber 10 is the target negative pressure P. It is determined whether or not it is smaller than . When Pa>ΔP+S, the process proceeds to step 73, where the minimum duty ratio DTI and maximum duty ratio DT2 are increased by a constant value ΔD.

Next, referring to FIG. 4, these minimum duty ratios DTI
and the maximum duty ratio DT2 will be explained. FIG. 4 shows the relationship between the target negative pressure Po and the target decourage ratio DT, and these relationships are indicated by a straight line L. That is,
Basically, when the target negative pressure P0 becomes a certain negative pressure Po+, the target duty ratio DT corresponding to this POI
．． Therefore, if the electromagnetic switching valve V1 is subjected to duty control, the actual negative pressure ΔP in the negative pressure chamber 10 becomes the target negative pressure P. , matches. Note that as the target duty ratio DT increases, the time during which the negative pressure chamber 10 is in communication with the negative pressure pump 4 becomes longer, so the target negative pressure P0 also increases. However, if the atmospheric pressure changes from the standard atmospheric pressure or changes over time, the target negative pressure P is set as the target duty ratio DT. Even if the target duty ratio D To corresponding to , is used, the actual negative pressure ΔP in the negative pressure chamber IO will deviate from the target negative pressure Pot. Therefore, in order to eliminate such deviation, learning control is performed on the minimum duty ratio DTI and the maximum duty ratio DT2. That is, as mentioned above, step 7
2, the actual negative pressure ΔP in the negative pressure chamber 10 becomes the target negative pressure P.
When it is smaller than 0, the minimum duty ratio DTI and the maximum duty ratio DT2 are set to ΔD in step 73.
Thus, the target negative pressure P is increased at this time. The relationship between the target duty ratio DT and the target duty ratio DT is expressed by the straight line M in FIG.
Shifts to the right as shown in . Next, in step 74, the target duty ratio DT is calculated from the target negative pressure Pa based on the relationship shown in FIG. At this time, as mentioned above, since the curve showing the relationship between the target negative pressure P0 and the target duty ratio DT is shifted to the right from L to M, the target duty ratio DT becomes larger, and thus the actual inside the negative pressure chamber lO The negative pressure ΔP increases. By repeating this process, a curve in which the actual negative pressure ΔP in the negative pressure chamber 10 becomes the target negative pressure Po is finally determined. Therefore, from now on, if the target duty ratio DT is calculated according to this curve, the actual negative pressure ΔP in the negative pressure chamber 1B will be maintained at the target negative pressure P0. Note that in reality, only the values of the minimum duty ratio DTI and maximum duty ratio DT2 are stored in the backup RAM 38.
The target duty ratio DT between the minimum duty ratio DTI and the maximum duty ratio DT2 is determined by interpolation calculation.

P in step 72 of FIG. If it is determined that Pa<ΔP+3, the process advances to step 75 and Pa<ΔP−S.
It is determined whether or not the actual negative pressure ΔP in the negative pressure chamber 1O is larger than the target negative pressure P0. Pa<
When ΔP-S, the process proceeds to step 76, where the minimum duty ratio DTI and the maximum decoupling ratio DT2 are set to a constant value Δ.
D is decreased by D, so that it is now shifted to the left with respect to curve L, as shown by curve N in FIG.

Next, in step 74, the target duty ratio DT is calculated based on this curve L.

On the other hand, when it is determined in step 75 that Pa≧ΔP−S, that is, when the actual negative pressure ΔP in the negative pressure chamber 10 is approximately equal to the target negative pressure P0, the process proceeds to step 77 and the feedback completion flag is set.

Returning to FIG. 6 again, once the feedback completion flag is set, the process proceeds from step 55 to step 59, where the feedback flag is reset, and then in step 60, the open lube flag is set. Next, in step 61, the target negative pressure P is determined based on the relationship shown in FIG.
. The target duty ratio DT is calculated from. Therefore, at this time, the target duty ratio DT is the absolute pressure sensor 27.
It is not controlled using the output signal of the oven, so it is oven loop control. Whether or not oven loop control is being performed can be determined from the oven loop flag.

On the other hand, when the engine speed N or the engine load L changes and the target negative pressure P0 changes, the process proceeds from step 54 to step 58, where the feedback completion flag is reset, and then the process proceeds to step 59. Therefore, open loop control is performed at this time as well.

In FIG. 2, if the negative pressure conduit 24 becomes clogged with carbon or the like, there will be a delay in transmitting the pressure fluctuations in the intake passage 2 to the modulator 20, and even if the pressure in the intake passage 2 decreases, the intake control valve 12 will be closed. It does not rotate in the direction to open the valve, but after a while it begins to rotate in the direction to open the valve. When the intake control valve l2 rotates in the opening direction, the pressure in the intake passage 2 increases, but since there is a delay in transmitting the pressure fluctuation to the modulator 20, the intake control valve 12 rotates in the closing direction after a while. Change the direction of movement. Therefore, the intake control valve l2 repeatedly opens and closes, and the pressure within the intake passage 2 repeatedly moves up and down. When the intake control valve 12 repeats opening and closing operations in this way, the engine and its output fluctuate.

By the way, when such an abnormality occurs, it must first be determined that such an abnormality is occurring. Therefore, attention is paid to the fact that when such an abnormality occurs, the pressure within the intake passage 2 fluctuates, and when this pressure fluctuation becomes large, it is determined that there is an abnormality in the negative pressure conduit 24.

By the way, when determining whether or not there is an abnormality in this way, it is necessary to detect the pressure inside the intake passage 2, and in order to detect this pressure, the absolute pressure sensor 27 for EGR control is used. If you want to use it, you have to select a time when the absolute pressure sensor 27 is not being used for EGR control.

Further, in order to detect such an abnormality, it is necessary to perform constant pressure control. Therefore, such abnormality detection is performed in the area of curve a and curve b in Fig. 3, that is, EGR.
This is done in an area where the supply of EGR is stopped and constant pressure control is being performed, or in an area where EGR oven lube control is being performed and constant pressure control is being performed. Furthermore, if such an abnormality occurs, the intake control valve 1
2 is forcibly opened fully to prevent the engine output from fluctuating.

Further, for example, if an abnormality occurs in the modulator 20, the pressure downstream of the intake control well 12 may become excessively large or excessively small relative to a predetermined set pressure while constant pressure control is being performed.

In this case, especially if the pressure downstream of the intake control well 12 becomes too small, that is, if the opening degree of the intake control valve 12 becomes too small, the amount of intake air will decrease and the EGR rate will increase, resulting in poor combustion. Therefore, the intake control valve 12
For example, it is determined whether there is an abnormality in the modulator 20 by determining whether or not the downstream pressure has significantly deviated from the set value. Furthermore, when such an abnormality occurs, the intake control valve 12 is forcibly opened fully to prevent combustion from deteriorating.

Further, for example, if an abnormality occurs in the actuator 11 and the stopper 18 of the intake control valve l2 cannot maintain the normal half-open position, and as a result, the intake control valve l2 is closed too much, the intake air amount decreases and the EGR rate increases. As a result, combustion worsens.

Therefore, it is determined whether or not there is an abnormality in the actuator 1l by determining whether or not the intake control valve 12 is held at the normal half-open position by the stopper l8. Furthermore, when such an abnormality occurs, the intake control valve 12 is forcibly opened fully to prevent combustion from deteriorating.

Next, a failure diagnosis routine for the intake control device will be explained with reference to FIGS. 8 to 10. This routine is executed by interrupts at regular intervals.

Referring to Figures 8 and 9, first step 1
At step 00, it is determined whether or not the electromagnetic switching valve V2 is off, and if it is off, the process proceeds to step 101, where it is determined whether or not the electromagnetic switching valve V3 is off. When both the electromagnetic switching valves V2 and V3 are off, the first negative pressure chamber 15 of the actuator 11 is connected to the modulator 20 as described above, so that constant pressure control is performed. In this case, the process advances to step 102. On the other hand, the solenoid switching valve V2. V3
When either one is on, constant pressure control is not being performed, and in this case, the process proceeds to step 103, where the electromagnetic switching valve V4 is turned off, and the negative pressure in the negative pressure chamber 10 of the EGR valve 7 is detected by the absolute pressure sensor. Let yourself be guided by 27. Then in step 104, N, C, MAX, Ml
Reset ~ and complete the processing routine.

In step 102, the engine speed N is set to a predetermined value, for example 900r. p. It is determined whether or not it is lower than m. N≧9oor. p. m, the process proceeds to step 105 where the engine speed N is set to a predetermined value, for example 1500r, p.m. It is determined whether or not it is higher than m.

N>150Or. p. When m, the constant pressure control area is outside the hatched area d in FIG. 3, that is, the opening degree of the throttle valve l2 is in a constant pressure control area larger than the half-open position in FIG. Therefore, at this time, the pressure in the intake passage 2 downstream of the intake control valve 12 is controlled to a predetermined set pressure. N>150Or. p. When m, the process proceeds to step 106, and N f- 150Or, p,
When it is m, the process proceeds to step 103. Step 106
Then, it is determined whether or not EGR control is stopped, and if it is stopped, the process advances to step 107. On the other hand, E
When GR control is being performed, the process proceeds to step 108, where it is determined whether EGR control is in oven loop control. If the oven lube control is not being performed, the process proceeds to step 103, and if the oven lube control is being performed, the process proceeds to step 107. Therefore, the process proceeds to step 107 because the EGR control is stopped, or even if the EGR control is performed, oven lube control is performed, and the intake control valve 12 is not subject to opening restriction by the stopper 18 and is maintained at a constant pressure. This is when control is in place.

In step 107, it is determined whether the absolute value of the difference ΔN between the engine rotation speed N in the previous processing cycle and the engine rotation speed N in the current processing cycle is smaller than a predetermined constant value ΔNo.

When ΔN1≧ΔN0, the process proceeds to step 103.

On the other hand, when 1ΔNl<ΔNo, that is, when the engine speed N is stable, the process proceeds to step 109, where the electromagnetic switching valve V4 is turned on and the pressure inside the intake passage 2 is measured by the absolute pressure sensor 27.
lead to. Next, in step 110, the count value C becomes =
Fixed value C. It is determined whether or not it is larger than . When C<Co, the process proceeds to step 111, where the count value C is incremented by 1, and the process proceeds to step 112. In step 112, it is determined whether the absolute pressure P in the intake passage 2 detected by the absolute pressure sensor 27 is smaller than the minimum value MIN, and if P<MIN, the process proceeds to step 113 where the absolute value P is set to MIN. , proceed to step 114.

In step 114, it is determined whether the absolute pressure P is larger than the maximum value MAX, and if P>MAX, the process proceeds to step 115, where the absolute pressure P is set to MAX.

From step 110 to step 115, C=C. , that is, it is repeated for a certain period of time.Therefore, the maximum value of the absolute pressure P within this certain period of time is taken as MAX, and the minimum value is M.
It is considered IN.

When C 2 Co is reached, the process proceeds to step 116 where the count value C is reset, and then in step 117 it is determined whether the minimum value MIN is smaller than the constant value (A - α), that is, the minimum value MIN is the set value for constant pressure control. It is determined whether or not it is extremely small. When MIN≧8−α, the process proceeds to step 118, where it is determined whether the maximum value MAX is larger than a constant value (B+β), that is, whether the maximum value MAX is extremely large with respect to the set value of the constant pressure control. It is determined. Minimum value MI
If N or the maximum value MAX is extremely deviated from the set value, the process proceeds to step 119 and, for example, the modulator 2
A flag F2 is set indicating that 0 is faulty. On the other hand, if the minimum value MIN and maximum value MΔX do not deviate much from the set values, step 1
Proceed to step 20 to reset flag F2, and step 121
Proceed to.

In step 121, it is determined whether the minimum value MIN is larger than a constant value A, and if MIN>A, step 1
Proceed to step 22. In step 122, it is determined whether the maximum value MΔX is smaller than a constant value B, and if MAX<B, the process proceeds to step 123. Therefore, the process proceeds to step 123 when the minimum value MIN and maximum value MAX are between A and B. In step 123, it is determined whether the value obtained by subtracting the minimum value MIN from the maximum value MAX is larger than a constant value D, that is, whether the fluctuation width of the absolute pressure P in the intake passage 2 during constant pressure control is greater than or equal to D. be done. MAX-MIN>
When D, the process proceeds to step 124 and the count value N becomes 1.
is incremented by 1, and then proceeds to step 125. In step 125, the count value N is a constant value N.

In other words, it is determined whether MAX-MIN has exceeded D more than N0 times during the failure diagnosis, and if N≧No, the process proceeds to step 126 to determine if the negative pressure conduit 24 is clogged. A flag F1 is set to indicate that this is occurring.

On the other hand, in step 102, N<90Qr. p. If it is determined that the condition is m, the process proceeds to the actuator failure diagnosis process shown in FIG. N<90Or. p. At point m, the current is in the hatched region d in FIG. 3, and therefore, constant pressure control is being performed, but the intake control valve l2 is held in a half-open state by the stopper l8.

Referring to FIG. 10, in step 127, it is determined whether or not EGR control is being performed. If EGR control is being performed, the process proceeds to step 128, where it is determined whether EGR is oven loop control. If it is not open loop control, the process proceeds to step 129, where the electromagnetic switching valve V4 is turned off, and the negative pressure in the negative pressure chamber 10 of the EGR valve 7 is guided to the absolute pressure sensor 27. On the other hand, when oven lube control is being performed, the process proceeds to step 130, where the electromagnetic switching valve V4 is turned on, and the pressure within the intake passage 2 is guided to the absolute pressure sensor 27. The process then proceeds to step 131.

In step 131, it is determined whether the backup RAM 38 is abnormal. That is, backup RAM
Some bits in 38 are used to determine whether the backup RAM 38 is abnormal, and for example, all of these bits are set to "1". If all these bits are "1", it is determined that the backup RAM 38 is normal, and if any of the bits becomes "0" for some reason, it is determined that an abnormality has occurred in the backup RAM 3g. When the process proceeds to step 131 for the first time, these bits are all "0", so it is determined that the backup RAM 38 is abnormal, and the process proceeds to step 132. In step 132, the absolute pressure P in the intake passage 2 detected by the absolute pressure sensor 27 is divided by the correction coefficient K, and the division result P/K is set as PL. That is, when there is no abnormality and the engine speed N is determined, the absolute pressure P in the intake passage 2 at that time is determined.
is almost decided. Therefore, for example, N = 80Or. 11.
The absolute pressure when 1l1 is P. Then, the absolute pressure at any rotation speed is K - P. This correction coefficient K is expressed as shown in FIG. Therefore, P/K, that is, PL, is the absolute pressure P at a given engine speed N.
=80Or. p. It shows the value converted to absolute pressure at m. At the time of the operation inspection before factory shipment, the constant pressure control device is operating normally, and at this time the process proceeds from step 131 to step 132, so PL is the N-80Or. when the constant pressure control device is operating normally. p. The absolute pressure inside the intake passage 2 at m is shown. This PL is stored in backup RAM 38. Then step 133
Then, all the backup RAM abnormality determination bits are set to "1". If an abnormality occurs in the backup RAM 38 and even one of these bits becomes "0", the process proceeds to step 132 to update the PL, but as long as all of these bits are "1", the process proceeds to step 134. Step 1
34, it is determined whether P/K calculated based on the current absolute pressure P is larger than the value obtained by subtracting the expected change over time r from PL (PL-T).The actuator 1l operates normally. If the intake control valve l2 is maintained in a half-open state by the stopper 18, P/K > P L-γ, and the process proceeds to step 135, where the flag F3 indicating that the actuator 11 is abnormal is reset. ,
If an abnormality occurs in the actuator 11 and the holding action of the intake control valve 12 by the stop valve l8 is not performed normally, and as a result, the intake control valve 12 is closed too much, the absolute pressure in the intake passage 2 becomes small, so that P/KiPL-γ becomes. In this case, the process advances to step 136 and flag F3 is set.

On the other hand, if EGR control is not performed, step 1
The process advances from step 27 to step 137, where the same processing as in open-lube control is performed. That is, in step 137, the electromagnetic switching valve V4 is turned on, and when it is determined in step 138 that there is an abnormality in the backup RAM 38, the process proceeds to step 139, where P/K is set to PM. In this case, since EGR gas is being supplied, this P
M is slightly different from PL. Next, in step 140, all backup RAM abnormality determination bits are set to "1". If the backup RAM 38 is not abnormal, the process proceeds to step 141, where it is determined whether P/K is larger than the value obtained by subtracting the expected change over time δ from PM (PM-δ). If P/K>PM-δ, the process advances to step 135 and flag F3 is reset; if P/KKPM-δ, 1
The program proceeds to step 36, where flag F3 is set.

FIG. 11 shows a processing routine when an abnormality occurs, and this routine is executed by interrupts at fixed time intervals.

Referring to FIG. 11, first, in step 200, it is determined whether the flag Fl is set.

If flag Fl is not set, step 20
1, it is determined whether flag F2 is set. If flag F2 is not set, the process proceeds to step 202, where it is determined whether flag F3 is set. If flag F3 is not set, the processing cycle is completed.

On the other hand, if the flag Fl is set, the process proceeds to step 203, where the x1 lamp is turned on, and then step 206
If the flag F2 is set, the process proceeds to step 204, where the X2 lamp is turned on, and then the process proceeds to step 20.
Proceed to step 6, and if flag F3 is set, proceed to step 205, turn on the X3 lamp, and then proceed to step 2
Proceed to 06. In step 206, the electromagnetic switching valve V2 is turned on, the first negative pressure chamber l5 of the actuator 11 is opened to the atmosphere, and the intake control valve 12 is fully opened.

FIG. 12 shows another embodiment of the portion 300 surrounded by chain lines in FIG.

In this example, N = 80Or. p. It is determined whether or not there is an abnormality in the modulator 20 based on whether the value P/K converted to absolute pressure at m is within a certain range. That is, first, in step 301, it is determined whether or not there is an abnormality in the backup RAM 38, and the backup I? If there is an abnormality in the AM 38, the process advances to step 302 and P/K is set to PN. Next, in step 303, all backup RAM abnormality determination bits are set to "1". If there is no abnormality in the backup RAM 38, the process proceeds to step 304, where the value P/K obtained by dividing the current absolute pressure P in the intake passage 2 by the correction coefficient K (Fig. 5) is the value obtained by adding a constant value ε to PN. It is determined whether or not it is smaller than (PN+ε). When P/K<PN+ε, the process proceeds to step 305, where P/K is changed from PN to a constant value ε.
It is determined whether or not the value is larger than the value obtained by subtracting the value (PN-ε). When P/K>(PN-E), the process advances to step 120 in FIG. On the other hand, when P/K≧PN+ε, or P/K! ．． When PN-ε, it is determined that there is an abnormality in the modulator 20, and the process proceeds to step 306, where flag F2 is set.

[Effects of the Invention] By detecting that the pressure, which should originally be kept constant, has fluctuated, it is possible to determine that some kind of problem has occurred.

[Brief explanation of drawings]

Figure 1 is a structural diagram of the invention, Figure 2 is an overall diagram of the diesel engine, Figure 3 is a diagram showing the constant pressure control region and EGR region, and Figure 4 shows the relationship between target negative pressure and target duty ratio. Figure 5 is a diagram showing correction coefficients, Figure 6 is a flowchart for performing EGR control, Figure 7 is a flowchart for performing feedback control, Figures 8 to I
FIG. 11 is a flowchart for performing fault diagnosis, FIG. 11 is a flowchart for abnormality processing, and FIG. 12 is a flowchart for another embodiment. 2...Intake passage, 3...Exhaust passage, 5.
...EGR passage, 1l...actuator, 20...modulator, Vi. V2, V3, V4 7... EGR valve, 12... Intake control valve, 27... Absolute pressure sensor, V5... Solenoid switching valve.

Claims (1)

[Claims] An intake control valve is arranged in an intake passage, and a constant pressure control device is provided that controls the intake control valve in response to the pressure in the intake passage downstream of the intake control valve so that the pressure becomes a predetermined constant pressure. An internal combustion engine equipped with a pressure detection means for detecting pressure in an intake passage downstream of an intake control valve, and a maximum value and a minimum value of the pressure within a predetermined period based on the detection result of the pressure detection means. A pressure fluctuation detection means is provided, and a determination means is provided for determining that a failure has occurred when the difference between the maximum value and the minimum value exceeds a predetermined difference based on the detection result of the pressure fluctuation detection means. A failure diagnosis device for intake control equipment.