JP2914341B2 - Deposit detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for detecting a deposit in an internal combustion engine.

[0002]

2. Description of the Related Art In an internal combustion engine, when fuel injected from a fuel injection valve contacts a wall surface of about 200 degrees or more, fuel is carbonized and deposits are deposited on the wall surface. Looking at the inside of the intake passage, the temperature of the wall surface is about 200 degrees or more at the back of the bulk of the intake valve, and the temperature of the inner wall of the intake port does not rise as much as the back of the bulk of the intake valve. When fuel is injected, the deposit mainly adheres to the back of the bulk of the intake valve. Further, when lubricating oil leaks from between the intake valve stem and the intake valve stem guide, the lubricating oil reaches the back of the bulk of the intake valve along the intake valve stem, and then carbonizes and deposits on the back of the bulk. Therefore, the deposit adheres to the back surface of the bulk of the intake valve even by the lubricating oil. However, if the deposit adheres to the back of the bulk of the intake valve, the amount of intake air flowing into the engine cylinder decreases because the inflow resistance to the intake air flow increases, and if the deposit adheres to the inner wall surface of the intake passage, The amount of fuel adhering to the inner wall surface of the intake passage increases. If the amount of intake air decreases or the amount of injected fuel increases, the state of combustion changes or the air-fuel ratio fluctuates. To address such problems, the amount of deposit must be reduced as much as possible. It is necessary to detect it accurately.

[0003] Therefore, there is known an internal combustion engine in which an air-fuel ratio sensor is disposed in an engine exhaust passage, and the amount of deposit is estimated from the time when the air-fuel ratio detected by the air-fuel ratio sensor keeps lean during engine acceleration operation. Yes (Japanese Unexamined Patent Publication No.
-128944).

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a deposit detecting apparatus for obtaining a deposit amount by a method completely different from the method for obtaining the deposit amount from the fluctuation of the air-fuel ratio. With the goal.

[0005]

According to a first aspect of the present invention, as shown in the block diagram of the invention of FIG. 1, in an internal combustion engine in which a throttle valve 16 is disposed in an intake passage, the throttle valve 16 has an idling opening degree. Throttle valve 16 is closed when the fuel injection is stopped.
Pressure detecting means 21 for detecting the pressure in the downstream intake passage
And detecting the amount of the deposit adhering mainly to the back surface of the intake valve 6 based on the pressure in the intake passage detected by the pressure detecting means 21 and the engine speed when the pressure is detected by the pressure detecting means. And a deposit detecting means A. That is, the deposit amount is detected from the pressure in the intake passage and the engine speed.

In the second invention, in the first invention,
Computing means for dimensionless by decrementing the deviation between the pressure in the intake passage detected by the pressure detecting means and the atmospheric pressure by the atmospheric pressure is provided. The deposit amount is calculated from the number. By making the deviation dimensionless in this way, the deposit amount can be accurately obtained regardless of the level of the atmospheric pressure.

[0007] In the third invention, in the first invention,
An exhaust gas recirculation device for recirculating exhaust gas is provided in the intake passage, and when the deposit amount is detected by the deposit detection means, the recirculation of the exhaust gas is stopped.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 2, 1 is an engine body, 2 is a piston, 3 is a cylinder head, 4 is a combustion chamber,
Reference numeral 5 denotes an ignition plug, 6 denotes an intake valve, 7 denotes an intake port, 8 denotes an exhaust valve, and 9 denotes an exhaust port. The intake port 7 is connected to the surge tank 11 through the corresponding branch pipe 10, and each branch pipe 10
A fuel injection valve 12 for injecting fuel into the corresponding intake port 7 is attached to the intake port 7. The surge tank 11 is connected to an air cleaner 15 through an intake duct 13 and an air flow meter 14.
, And a throttle valve 16 is arranged in the intake duct 13. On the other hand, each exhaust port 9 has a common exhaust manifold 17.
Linked to An intake duct 13 and an exhaust manifold 17 downstream of the throttle valve 16 are connected to each other via an EGR passage 18. 19 is arranged. In the embodiment shown in FIG. 2, the EGR control valve 19 is driven by a step motor, which is controlled based on an output signal of the electronic control unit 30.

The electronic control unit 30 is composed of a digital computer, and a ROM (read only memory) 32, a RAM (random access memory) 33, and a CPU (microprocessor) 3 interconnected by a bidirectional bus 31.
4. It has an input port 35 and an output port 36. The air flow meter 14 generates an output voltage proportional to the amount of intake air, and this output voltage is supplied to an input port 35 via an AD converter 37.
Is input to A throttle switch 20 that is turned on when the throttle valve 16 is at the idling position is attached to the throttle valve 16, and an output signal of the throttle switch 20 is input to an input port 35. A pressure sensor 21 that generates an output voltage proportional to the absolute pressure in the surge tank 11 is disposed in the surge tank 11, and the output voltage of the pressure sensor 21 is input to an input port 35 via an AD converter 38. An atmospheric pressure sensor that generates an output voltage proportional to the atmospheric pressure
22 and the output voltage of the atmospheric pressure sensor 22
Through the input port 35. 35 input ports
Is connected to a rotation speed sensor 23 that generates an output pulse representing the engine rotation speed. On the other hand, the output port 36 is connected to the drive circuit 40
Is connected to the step motor of the EGR control valve 19 through
It is connected to each fuel injection valve 12 via a corresponding drive circuit 41.

Next, first, a basic control method of the EGR control valve 19 will be described. FIG. 3A shows a target EGR rate.
EGRt is shown, and each number shown in FIG. 3A indicates a target EGR rate expressed as a percentage. FIG.
As can be seen from (A), the target EGR rate EGRt is the engine load Q
/ N (intake air amount Q / engine speed N) and the engine speed N. The target EGR rate EGRt is stored in the ROM 32 in advance in the form of a map as shown in FIG. 3B as a function of the engine load Q / N and the engine speed N.

FIG. 4A shows that the EGR rate is adjusted to a specific target E.
The valve element 19a of the EGR control valve 19 necessary for obtaining the GR rate EGRo
Is shown in FIG. As can be seen from FIG. 4A, the lift amount Lo is determined by the engine load Q / N and the engine speed N.
Is a function of This lift amount Lo is stored in advance in the ROM 32 in the form of a map as shown in FIG. 4B as a function of the engine load Q / N and the engine speed N. In the embodiment shown in FIG. 2, the shape of the valve body 19a is selected such that the opening area of the EGR control valve 19 is proportional to the lift amount L of the valve body 19a. It is proportional to L. In this case, the lift amount L of the valve element 19a required to set the EGR rate to the target EGR rate EGRt is expressed by the following equation.

K = EGRt / EGRo L = K · Lo FIG. 5 shows the relationship between the opening of the EGR control valve 19 and the step position of the step motor of the EGR control valve 19. As can be seen from FIG. 5, when the step position of the step motor is zero, the EGR control valve 19 is fully closed, and when the step position of the step motor is the maximum step position MAX, EG
The R control valve 19 is fully opened. When the engine is running,
A target EGR rate EGRt is calculated from the engine load Q / N and the engine speed N based on the relationship shown in FIG.
Using the relationship shown in (B), the EGR rate is changed to the target EGR rate EGRt.
The amount of lift of the valve element 19a required to make the EGR control valve 19, ie, the target opening of the EGR control valve 19, is calculated.
The step motor of the GR control valve 19 is driven. Thus, the EGR rate becomes the target EGR rate shown in FIG.
Controlled by EGRt.

Next, referring to FIG. 6 and FIG.
A method for detecting the amount of deposit attached to the back of the shank will be described. In FIG. 6A, the throttle valve 16 is closed to the idling opening degree, the fuel injection is stopped, and the EGR control valve 19 is fully closed to stop the EG.
The absolute pressure PM _off in the surge tank 11 when the recirculation of the R gas is stopped is shown. FIG.
In (A), the solid line a indicates the absolute pressure in the surge tank 11 when no deposit adheres to the back of the bulk of the intake valve 6.
Represents PM _off . At this time, the absolute pressure PM _off in the surge tank 11 is a function of only the engine speed N, and the absolute pressure PM _off gradually increases as the engine speed N decreases.

On the other hand, if the deposit adheres to the back of the bulk of the intake valve 6, the suction resistance increases, so that the absolute pressure PM _off in the surge tank 11 increases as shown by the broken line b in FIG. At this time, the amount of intake air supplied into the engine cylinder decreases. When the amount of the deposit attached to the back surface of the bulk of the intake valve 6 increases, the absolute pressure PM _off in the surge tank 11 further increases as shown by a broken line c in FIG. By the way, the absolute pressure PM _off indicated by the solid line a when no deposit is attached is known in advance, and therefore, by detecting the absolute pressure PM _off , it is possible to detect how much the deposit is attached.

As described above, the absolute pressure PM _off indicated by the solid line a
Can be obtained in advance, that is, it can be obtained by an experiment. If this solid line a is obtained based on an experiment performed under a standard atmospheric pressure, for example, even if a deposit adheres, Is not the standard atmospheric pressure, the absolute pressure PM _off deviates from the solid line a. Accordingly, if the absolute pressure PM _off deviates from the solid line a and it is determined that the deviation is based on the adhesion of the deposit, an erroneous determination is made. On the other hand, the absolute pressure for the solid line a
Regarding the shift amount of PM _{off, even if} the amount of deposit is the same, the shift amount becomes smaller as the atmospheric pressure becomes lower. Therefore, if the deposit amount is immediately obtained from this deviation amount, the deposit amount will be erroneously determined. Therefore, in the embodiment according to the present invention, the deposit amount is determined using the dimensionless deviation ΔPM _off of the absolute pressure PM _off and the atmospheric pressure PA shown in the following equation.

ΔPM _off = (PA−PM _off ) / PA Generally speaking, (PA−PM _off ) is not affected by the change in atmospheric pressure, so that there is a shift in (PA−PM _off ). If this is the case, this shift will be based on the adhesion of the deposit, and by dividing this (PA-PM _off ) by PA, the same deposit amount can be obtained regardless of the atmospheric pressure (PA-PM _off ).
_off ) / PA shift amounts are equal. Therefore, the above-mentioned deviation Δ
PM _off will accurately represent the amount of deposit.

FIG. 7A shows the deviation ΔPM _off and the engine speed N.
The relationship is shown. Note that a, a in FIG.
6B and 6C show the same state as a, b and c in FIG. 6A. Therefore, the solid line a shows the case where the deposit is not attached, and the broken line b shows the case where the deposit is attached. The dashed line c indicates the case where the deposit is further attached. As can be seen from FIG. 7A, when the engine speed N is the same, the deposit amount increases as the deviation ΔPM _off decreases. In this way, mainly the intake valve 6
The amount of deposit attached to the back of the shank can be accurately detected.

Next, a method of controlling the EGR rate based on the detected deposit amount will be described. That is, when the deposit amount increases, the inflow direction of the intake air into the engine cylinder changes, and, for example, the swirling flow generated in the engine cylinder weakens.
It is necessary to reduce the GR rate. Therefore, in the embodiment according to the present invention, the target EGR rate EGRt is corrected based on the following equation by introducing the deposit correction coefficient FD.

EGRa = FD · EGRt In the above equation, EGRa is a corrected target EGR rate corrected by deposit adhesion. When no deposit is attached, FD = 1.0, and therefore, the solid line a in FIG. 7A shows a curve where FD = 1.0. This solid line a is obtained in advance by an experiment. On the other hand, if a small amount of deposit adheres, FD = 0.95, for example, in order to lower the EGR rate. Therefore, the broken line b in FIG.
It represents a curve that is 0.95. Similarly, a broken line c in FIG. 7A represents a curve where, for example, FD = 0.9. Therefore, the deposit correction coefficient FD is a function of the deviation ΔPM _off and the engine speed N. The deposit correction coefficient FD is stored in advance in the ROM 32 in the form of a map as shown in FIG. 7B as a function of the deviation ΔPM _off and the engine speed N.
In this way, the larger the amount of deposit, the more EG
Since the R rate is reduced, good combustion can be obtained even when deposits adhere.

Next, even if the EGR control system changes with time using the absolute pressure PM _off detected when the supply of the EGR gas is stopped, the EGR rate is calculated based on the deposit adhering to the back of the bulk of the intake valve 6. A method for maintaining the optimum EGR rate in consideration of the following will be described. FIG. 6B shows a case where the throttle valve 16 is closed to the idling opening degree, the fuel injection is stopped, and the EGR control valve 19 is fully opened to recirculate the EGR gas. The absolute pressure PM _on in the surge tank 11 is shown. 6B, the solid line d represents the absolute pressure PM in the surge tank 11 when no deposit is attached to the back surface of the bulk of the intake valve 6 and the EGR control system does not change with time.
represents _on . At this time, the absolute pressure PM _on in the surge tank 11 is a function of only the engine speed N, and the absolute pressure PM _on gradually increases as the engine speed N decreases.

Next, first, a case where no deposit is attached to the back surface of the bulk portion of the intake valve 6 will be described. In this case, for example, the EGR passage 18 and the EGR control valve 19
If the amount of recirculation of the EGR gas decreases due to deposits on the EGR gas and the EGR rate decreases, the absolute pressure PM _on in the surge tank 11 decreases as indicated by the broken line e in FIG. 6B.
If the EGR rate further decreases, the absolute pressure PM _on in the surge tank 11 further decreases as indicated by a broken line f in FIG. Incidentally, the absolute pressure PM _on indicated by the solid line d can be obtained in advance by an experiment. However, this absolute pressure PM _on is
_{If the off} becomes higher, it becomes higher accordingly, so that the decrease in the EGR rate cannot be detected from the absolute pressure PM _on itself, and the decrease in the EGR rate must be detected from the deviation ΔPM _on between PM _on and PM _off. Must be done.

That is, the chain line a in FIG.
FIG. _6A shows the same PM _off as the solid line a shown in FIG.
As can be seen from (B), if the engine speed N is the same, PM
The deviation ΔPM _on (= PM _on −PM _off ) between _on and PM _{of f} is EGR
The smaller the rate, the smaller. In this case, if the amount of deposit adhering to the back of the bulk of the intake valve 6 increases, FIG.
As shown in (A), the PM _off increases, but the deviation ΔPM
_on does not change. .DELTA.PM _on · PM also the amount of deposit adhering to the bevel portion back of the intake valve 6 since larger the .DELTA.PM _on the PM _off becomes small when the reduction rate is the same more accurately referred to when the EGR rate is increased _off will not change. When the atmospheric pressure decreases, ΔPM _on decreases even if the reduction rate of the EGR rate is the same. Therefore, even if the amount of the deposit adhering to the back surface of the bulk of the intake valve 6 increases or the atmospheric pressure fluctuates, if the rate of decrease in the EGR rate is the same, ΔPM
_on・ PM _off / PA will not change. Therefore, in the embodiment according to the present invention, EGR is performed using the deviation ΔPM _on
The rate of decline is calculated.

ΔPM _on = (PM _on −PM _off ) · PM _off / PA FIG. 8A shows the relationship between the deviation ΔPM _on and the engine speed N. Note that d, e, and f in FIG.
(B) shows the same state as d, e, and f, and therefore, the solid line d shows the case where the EGR rate is maintained at the normal EGR rate, and the broken line e shows the case where the EGR rate is the normal EGR rate. The broken line f indicates a case where the EGR rate is smaller than the normal EGR rate.

Therefore, in the embodiment according to the present invention, when the EGR rate becomes smaller than the normal EGR rate, an EGR rate correction coefficient FE is introduced so that the EGR rate becomes the normal EGR rate, and the target EGR rate is calculated based on the following equation. The rate EGRt is corrected. EGRa = FE · FGRt In this case, when the EGR rate is maintained at the normal EGR rate, FE = 1.0, and therefore, the solid line d in FIG.
Indicates a curve where FE = 1.0. On the other hand, when the EGR rate is lower than the normal EGR rate, FE = 1.05, for example, in order to match the EGR rate with the normal EGR rate. Therefore, a broken line e in FIG. Is represented. Similarly, a broken line f in FIG.
The curve where E = 1.1 is represented. Therefore, the EGR rate correction coefficient FE is a function of the deviation ΔPM _on and the engine speed N.
The EGR rate correction coefficient FE is determined by the deviation ΔPM _on and the engine speed N.
Are stored in the ROM 32 in advance in the form of a map as shown in FIG. Even if the EGR control system changes over time in this manner, the EGR rate is determined based on the optimum EG taking into account the deposit attached to the back of the bulk of the intake valve 6.
The R rate can be controlled accurately.

Next, the flowcharts shown in FIGS. 10 to 15 will be described with reference to the time chart shown in FIG. FIG. 10 shows a cut flag processing routine indicating that the supply of fuel should be stopped, and this routine is repeatedly executed in the main routine.

Referring to FIG. 10, first, at step 50, it is determined whether or not the cut flag is set. When the cut flag is not set, the routine proceeds to step 51, where it is determined whether or not the throttle switch 20 is on, that is, whether or not the throttle valve 16 is at the idling position. When the throttle valve 16 is at the idling position, the routine proceeds to step 52, where it is determined whether or not the engine speed N is higher than a constant value Nh, for example, 2000 rpm. When N ≧ Nh, the routine proceeds to step 53, where the cut flag is set. When the cut flag is set, the operation of fuel injection from the fuel injection valve 12 is stopped in a routine (not shown). The process proceeds to step 53 when the throttle valve 16 is at the idling position and the engine speed N is high, that is, during deceleration operation. Therefore, the fuel supply is stopped during the deceleration operation.

On the other hand, once the cut flag is set, the process proceeds from step 50 to step 54, where the throttle switch
It is determined whether or not 20 is on, that is, whether or not the throttle valve 16 is at the idling position. When the throttle valve 16 is opened, the routine jumps to step 56, where the cut flag is reset, and fuel injection from the fuel injection valve 12 is started. On the other hand, when the throttle valve 16 is maintained at the idling position, the routine proceeds to step 55, where it is determined whether or not the engine speed N has become lower than a fixed value Nl, for example, 1400 rpm. When N ≦ Nl, the routine proceeds to step 56, where the cut flag is reset, and fuel injection is started.

Time To in FIG. 9 indicates the time when the deceleration operation is started. When the deceleration operation is started, the engine speed N gradually decreases as shown in FIG. 9, and the absolute pressure PM in the surge tank 11 rapidly decreases and then gradually increases. As shown in FIG. 9, when the engine speed N at the start of the deceleration operation is higher than Nh, the cut flag is set, and thereafter, when the engine speed N becomes lower than Nl, the cut flag is reset.

FIGS. 11 to 15 show an EGR control routine, which is executed by interruption every predetermined time. Referring to FIG. 11, first, at step 60, it is determined whether or not the cut flag is set. If the cut flag has not been set, the routine proceeds to step 64, where the flags F ₁ , F ₂ and F ₃ are reset, and
Next, at step 65, the count values C ₁ , C ₂ , C ₃
Is set to zero. Next, at step 66, the EGR shown in FIG.
A control routine for the control valve 19 is executed, which will be described later. On the other hand, whether the initiated deceleration operated cut flag is set the flag F ₁ proceeds from step 60 to step 61 has been set or not. When the deceleration operation is started as shown in FIG.
_{Since 1} has been reset, the process proceeds to step 70 in FIG.

In step 70, a control signal for fully closing the EGR control valve 19 is given to the step motor of the EGR control valve 19, whereby the EGR control valve 19 is turned on as shown in FIG.
19 is quickly closed completely. Then the count value C ₁ in step 71 is incremented by 1, then the count value C ₁ in step 72 whether exceeds a predetermined value C ₁₀ is determined. That is, the control waits until the EGR control valve 19 is fully closed and the influence of the recirculation of the EGR gas on the absolute pressure in the surge tank 11 is completely eliminated. When C ₁ ≧ C ₁₀ , the _routine proceeds to step 73, where the absolute pressure PM in the surge tank 11 detected by the pressure sensor 21 is set to PM _off1 . C ₁ ≧ C ₁₀
When, for example, the engine speed N becomes N _{1 in} FIG.
If the deposit adheres to the back of the bulk of the intake valve 6, the absolute pressure PM at this time is, for example, as shown in FIG.
PM _off1 . Next, at step 74 the flag F ₁ is set to complete the processing routine. Flag F ₁ is whether the flag F ₂ proceeds when set at step 61 in FIG. 11 to step 62 is set or not. Since the flag F ₂ is reset in this case the process proceeds to step 80 in FIG. 13.

In step 80, a control signal for fully opening the EGR control valve 19 is given to the step motor of the EGR control valve 19, and as a result, as shown in FIG.
19 is fully opened rapidly. Then the count value C ₂ in step 81 is incremented by 1, then the count value C ₂ in step 82 whether exceeds a predetermined value C ₂₀ is determined. That is, the EGR control valve 19 is fully opened and the EG
Wait until the recirculation amount of the R gas reaches a steady state. C ₂ ≧ C
_When it reaches ₂₀ , the routine proceeds to step 83, where the absolute pressure PM in the surge tank 11 detected by the pressure sensor 21 is set to PM _on, and then to step 84, the engine speed N at this time is N _on
It is said. The engine speed N _on is lower than N ₁ as shown in FIG. 6, and the PM _{on at} this time is, for example, a value indicated by a point in FIG. 6B. Then step 85
In the flag F ₂ is set to complete the processing routine. Whether the flag F ₂ is set a flag F ₃ proceeds from step 62 to step 63 in FIG. 11 has been set or not. Since the flag F ₃ is reset at this time the flow proceeds to step 90 in FIG. 14.

In step 90, the EGR control valve 19 is fully closed.
Control signal is supplied to the EGR control valve 19 step motor.
The EGR control valve as shown in FIG.
19 is completely closed again rapidly. Then at step 91
Is the count value C_Three Is incremented by one, then
In step 92, the count value C_Three Is a constant value C₃₀Has exceeded
It is determined whether or not it is. That is, the EGR control valve 19 is fully closed and
EGR gas recirculation relative to absolute pressure in surge tank 11
Wait until the effects of the effect are completely eliminated. C_Three ≧ C ₃₀become
And proceeds to step 93, where the sensor detected by the pressure sensor 21
The absolute pressure PM in the storage tank 11 is PM_off2It is said. This PM
_off2Is a value shown in FIG. 6, for example. Then in step 94
Is this PM_off2And the atmospheric pressure detected by the atmospheric pressure sensor 23.
Using the pressure PA, the deviation ΔPM_offIs calculated.

ΔPM _off = (PA−PM _off2 ) / PA Next, at step 95, the deviation ΔPM _off and the engine speed N
Then, the deposit correction coefficient FD is calculated based on the map shown in FIG. Next, at step 96, PM _off1 and PM
The average value of _off2 is set to PM _off . This PM _off is a surge tank when the engine speed N is N _on as shown in FIG.
11 can be regarded as the absolute pressure PM. Next, at step 97, the deviation ΔPM _on is calculated based on the following equation.

ΔPM _on = (PM _on −PM _off ) · PM _off / PA Next, at step 98, the EGR rate correction coefficient FE is calculated from the deviation ΔPM _on and the engine speed N _on based on the map shown in FIG. Is calculated. Next, at step 99, the flag F
₃ is set and the processing routine is completed. FIG. 15 shows a routine executed in step 66 of FIG. 11 when fuel injection is being performed.

Referring to FIG. 15, first, step 100 is executed.
From the engine load Q / N and the engine speed N in FIG.
The target EGR rate EGRt is calculated based on the map shown in (B). Next, at step 101, the correction target E is calculated based on the following equation.
The GR rate EGRa is calculated. EGRa = FD ・ FE ・ EGRt Next, at step 102, a specific EGR is obtained from the engine load Q / N and the engine speed N based on the map shown in FIG.
Lift amount L of the valve element 19a of the EGR control valve 19 for obtaining the rate
o is calculated. Next, at step 103, the ratio K (= EGRa / EGRt) between EGRa and EGRt is calculated.
In 04, the valve body of the EGR control valve 19 for multiplying the ratio K by the lift amount Lo to obtain the corrected target EGR rate EGRa
The lift amount L (= K · Lo) of 19a, that is, the target opening of the EGR control valve 19 is calculated. Next, at step 105, the EGR
The step position ST of the step motor required for setting the opening of the control valve 19 to the target opening is calculated, and then in step 106, the step motor is driven so that the step position becomes ST.

[0036]

According to the present invention, it is possible to detect mainly the amount of deposit attached to the back of the bulk of the intake valve.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of the present invention.

FIG. 2 is an overall view of an internal combustion engine.

FIG. 3 is a diagram showing a target EGR rate.

FIG. 4 is a diagram showing a lift amount of a valve body of an EGR control valve.

FIG. 5 is a diagram showing an opening degree of an EGR control valve.

FIG. 6 is a diagram showing an absolute pressure PM in a surge tank.

FIG. 7 is a diagram showing a relationship between a deviation ΔPM _off and a deposit correction coefficient FD.

FIG. 8 is a diagram showing a relationship between a deviation ΔPM _on and an EGR rate correction coefficient FE.

FIG. 9 is a time chart.

FIG. 10 is a flowchart for processing a cut flag.

FIG. 11 is a flowchart for performing EGR control.

FIG. 12 is a flowchart for performing EGR control.

FIG. 13 is a flowchart for performing EGR control.

FIG. 14 is a flowchart for performing EGR control.

FIG. 15 is a flowchart for controlling an EGR control valve.

[Explanation of symbols]

 12 ... fuel injection valve 16 ... throttle valve 18 ... EGR passage 19 ... EGR control valve 21 ... pressure sensor

Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 45/00 312 F02D 45/00 312P 360 360H F02M 25/07 550 F02M 25/07 550L

Claims (3)

(57) [Claims] In an internal combustion engine having a throttle valve disposed in an intake passage, the pressure in the intake passage downstream of the throttle valve when the throttle valve is closed to an idling opening degree and fuel injection is stopped. Detecting means for detecting pressure in the intake passage detected by the pressure detecting means and the engine speed when the pressure is detected by the pressure detecting means. A deposit detecting means for detecting the amount of deposit to be deposited. 2. An arithmetic unit for dimensionlessly calculating the difference between the pressure in the intake passage detected by the pressure detecting unit and the atmospheric pressure by subtracting the deviation from the atmospheric pressure using the atmospheric pressure. 2. The deposit detecting device according to claim 1, wherein a deposit amount is obtained from the calculated deviation and the engine speed. 3. An exhaust gas recirculation device for recirculating exhaust gas in an intake passage, wherein the exhaust gas recirculation operation is stopped when the deposit amount is detected by the deposit detecting means. A deposit detection device as described.