JPH03233164A - Maintenance device of intake control unit - Google Patents

Abstract

PURPOSE:To prevent foreign matter from accumulating in a passage by additionally providing an air introducing pipe, having a selector valve, in the pressure detecting passage, opened at more downstream side of an intake control valve related to an intake passage, and introducing air to the pressure detecting passage at the time of stopping an internal combustion engine. CONSTITUTION:An engine is stopped by placing an intake control valve 12 in a fully closed condition and cutting off intake air and further fuel. Since a negative pressure is generated in the downstream of the fully closed intake control valve 12 while the engine is continued to rotate by inertia, when an electromagnetic selector valve V5 is opened being selected from off to on, air is advanced by a large differential pressure from an air intake port 46 of an air cleaner or the like to pass through a pressure detecting passage 24 from an air introducing pipe 47 and the electromagnetic selector valve V5, and a large amount of air is jetted at a high speed to an intake passage 2 in the downstream of the intake control valve 12. As a result, carbon or the like of adhering to a wall surface of the pressure detecting passage 24 is blown and removed by a strong air stream. Accordingly, the pressure in the intake passage is transmitted to an intake control unit always in good responsiveness to prevent generation of hunting or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates primarily to a maintenance device for automatically preventing clogging of a pressure detection passage in an intake control device for an internal combustion engine.

[Conventional technology]

For example, in a diesel engine, in order to reduce NO while preventing the occurrence of smoke, etc., it is necessary to recirculate an optimum amount of exhaust gas into the engine intake passage depending on the operating state of the engine. Therefore, the engine exhaust passage and the engine intake passage are connected through an exhaust gas recirculation (hereinafter referred to as EGR) passage, and an intake control valve is arranged in the intake passage upstream of the opening of the EGR passage with respect to the intake passage. A diesel engine is known which is equipped with a constant pressure control device that controls the intake control valve in response to the pressure in the intake passage downstream of the intake control valve so that this pressure becomes a predetermined constant pressure (for example, 6
2-4663 or Japanese Utility Model Application Publication No. 55100052). In this diesel engine, the E for the intake passage is
Since a constant pressure acts on the opening of the GR passage, the amount of exhaust gas recirculated from the EGR passage to the intake passage can be easily controlled to the optimum amount according to the operating state of the engine.

Also, in spark ignition engines, for example, JP-A-60-2
As seen in Publication No. 16048, the suction negative pressure downstream of the throttle valve provided in the intake passage of the engine is detected,
Many devices are known for controlling engine combustion.

All of these devices have a pressure detection passage (negative pressure extraction passage) that opens into the intake passage downstream of the intake control valve (or throttle valve), and the passage allows the pressure in the intake passage to be detected by a control device or a pressure sensor. It usually leads to etc.

[Problem to be solved by the invention]

The pressure detection passage that opens downstream of the intake control valve in the intake passage of the internal combustion engine contains exhaust gas that is recirculated from the EGR passage that also opens in the intake passage, and a portion of the blow-by gas that flows into the upstream side of the constant pressure control device. invades and their residue (
(carbon, oil, etc.) accumulates at the opening of the pressure detection passage and inside the passage, reducing the passage area of the pressure detection portion, thereby deteriorating pressure detection responsiveness. For example, in the above-mentioned constant pressure control in a diesel engine, the pressure downstream of the intake control valve is controlled to a constant pressure under any conditions, so the pressure downstream of the intake control valve must be transmitted to the constant pressure control device in a responsive manner. However, if carbon, oil, etc. accumulate on the pressure detection part, the responsiveness will deteriorate, causing hunting of the intake control valve during transient periods. Therefore, unless measures are taken to prevent deposits, normal constant pressure control cannot be performed for a long period of time.

Additionally, in order to prevent carbon etc. from accumulating on this pressure detection part, it is possible to change the shape of the detection part or attach a protective member, but in general, if such palliative means are used, the pressure detection The responsiveness of the pressure control device often deteriorates, making it difficult to operate the constant pressure control device normally over a long period of time.

The problem to be solved by the present invention is to actively prevent foreign matter from accumulating in a pressure detection passage in an intake control device of an internal combustion engine, and to enable the intake control device to operate without trouble for a long period of time. It is said that

[Means to solve the problem]

As a means for solving the above-mentioned problems, the present invention provides an intake control valve that is provided in an intake passage and becomes fully closed when the engine stops, and an intake control valve that is opened downstream of the intake control valve with respect to the intake passage. In the intake control device for an internal combustion engine, the combustion state is controlled by the pressure of the intake passage downstream of the intake control valve, which is taken out through the pressure detection passage, and a switching valve is provided in the pressure detection passage. The pressure detection passage is configured to be provided with an air introduction pipe having an air intake pipe, and to operate the switching valve when the internal combustion engine is stopped to introduce air into the pressure detection passage, thereby preventing clogging of the pressure detection passage. a maintenance device for an intake control device; an intake control valve provided in an intake passage; and a pressure detection passage opening downstream of the intake control valve with respect to the intake passage; In an intake control device for an internal combustion engine that controls a combustion state based on the pressure taken out from the intake passage downstream of the intake control valve, an air introduction pipe having a switching valve is attached to the pressure detection passage;
By operating the switching valve and introducing air into the pressure detection passage when the pressure in the intake passage downstream of the intake control valve becomes negative pressure below a predetermined value in a stable operating state of the internal combustion engine, There is provided a maintenance device for an intake control device, characterized in that the pressure detection passage is configured to prevent clogging.

[For production]

In the first invention, when the engine is operated to stop, the intake control valve provided in the intake passage is fully opened, but after that, the engine rotates for a short time mainly due to inertia and then stops. During this time, the engine acts like a vacuum pump, so the pressure in the intake passage downstream of the intake control valve becomes quite negative. Therefore, at the same time as the engine stop operation,
A switching valve of an air introduction pipe attached to the pressure detection passage is operated to introduce air into the pressure detection passage, and a high-speed air flow is formed in the pressure detection passage by the negative pressure of the intake passage. This air flow blows away and cleans carbon and other foreign matter that is about to accumulate in the pressure detection passage or in the vicinity of its opening in the intake passage.

In the second invention, when the pressure downstream of the intake control valve in the intake passage decreases to negative pressure below a predetermined value in a stable operating state such as an idling state of the engine, the switching valve of the air intake pipe is activated, air is introduced into the pressure detection passage, and carbon and other foreign matter are blown away and cleaned as in the case of the first invention, and the air is sucked into the combustion chamber of the engine.

In this way, the pressure sensing passage is always kept in good condition, free of flow resistance due to deposits, in each case, and the transmission of pressure in the intake pipe is rapid, thereby reducing the responsiveness of the operating equipment. It is prevented from doing so. Furthermore, the operation of this maintenance device is automatically performed each time the engine is stopped or the negative pressure in the intake passage increases, and does not require manual operation.

〔Example〕

FIG. 1 shows, as an embodiment of the present invention, a diesel engine having a constant pressure control device in the intake passage.
An intake control valve 12 is arranged therein, and a constant pressure control device A is provided for controlling the intake control valve 12 so that the pressure in the intake passage 2 downstream of the intake control valve 12 becomes a predetermined constant pressure. The passage 24 for detecting the pressure in the intake passage 2 downstream of the intake control valve 12 is equipped with a maintenance device B that introduces fresh air from the pressure detection passage 24 into the intake passage 2 when the engine is stopped. Next, the configuration of an embodiment of the present invention will be described in detail with reference to FIG. In the figure, 1 is a diesel engine main body, 2 is an intake passage, 3 is an exhaust passage, and 4 is an engine-driven negative pressure pump. The intake passage 2 and the exhaust passage 3 are connected to each other by an EGR passage 5, and an EGR valve 7 is disposed at an opening 6 of the EGR passage 5 with respect to the intake passage 2. The EGR valve 7 includes a valve body 8 that controls opening and closing of the opening 6 of the EGR passage 5, and a diaphragm 9 connected to the valve body 8.
and a negative pressure chamber 10 defined by a diaphragm 9, and this negative pressure chamber 10 has an electromagnetic switching valve V1 that can communicate with the atmosphere.
It is connected to the negative pressure pump 4 via.

On the other hand, the intake passage 2 upstream of the opening 6 of the EGR passage 5
An intake control valve 12 driven by an actuator 11 is disposed therein. This actuator 11 includes a pair of diaphragms 13 and 14, and these diaphragms 13.
a first negative pressure chamber 15 and a second negative pressure chamber 16 defined by
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 16 is connected to the electromagnetic switching valve V4. It is connected to the negative pressure pump 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 the intake passage 2 downstream of the intake control valve 12 via a pressure detection passage 24.

On the other hand, a valve port 25 whose opening/closing is controlled by the diaphragm 21 is open in the atmospheric pressure chamber 22, and this valve port 25 is connected to one side of the electromagnetic switching valve V3. It is connected to the first negative pressure chamber 15 of the actuator 11 via V2, and on the other hand to the negative pressure pump 4 via the throttle 26.

The negative pressure of the negative pressure pump 4 and atmospheric pressure are selectively introduced into the negative pressure chamber 10 of the EGR valve 7 by a solenoid switching valve Vl. An absolute pressure sensor 27 for detection is provided in a conduit leading to the negative pressure chamber 10. Furthermore, an electromagnetic switching valve v5 for selectively introducing atmospheric air is provided in the middle of the pressure detection passage 24. Reference numeral 46 indicates an air intake port of an air cleaner or the like, and 47 indicates an air introduction pipe provided with an electromagnetic switching valve V5.

These electromagnetic switching valves Vl, V2. V3. V4 and V5 are all controlled by the output signal of the electronic control unit 30. The electronic control unit 30 consists of a digital computer, and includes a ROM (II-only memory) 32, a RAM (random access memory) 33, a CP[I (microprocessor) 34, a human power boat 35 and Output port 36
Equipped with. A backup RAM 3B is connected to the CPLI 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 input to the human 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 sent to the AD converter 42.
The water is man-powered by a human-powered boat 35 via the . Also connected to the human power 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. V
4. VS2. :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 V4 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 16 is opened to the atmosphere, the diaphragm 1
4 moves toward the first negative pressure chamber 15 and is held in contact with the stopper 17.

At this time, the movement of the diaphragm 13 is restricted by the stopper 18, and the intake control valve 12 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. This area is pre-installed in ROM 32.
Therefore, when it is determined from the engine speed N and the engine load that the operating state of the engine has reached the operating state that requires constant pressure control, the electromagnetic switching valve V2. V3 are both turned off, the first negative pressure chamber 15 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 atmosphere is supplied into the first negative pressure chamber 15 of the actuator 11, so the diaphragm 13 is pushed upward and moved, and the intake control valve 12 is rotated in the 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 the set value set in the reserved window, the diaphragm 21 of the modulator 20 closes the valve. Boat 25 is closed. At this time, since the negative pressure from the negative pressure pump 4 is applied to the first negative pressure chamber 15 of the actuator 11, the diaphragm 13 is pushed downward and moves, and 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, the actuator 11 and 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 12 can only be closed to the half-open state shown in FIG. 2, and therefore, even if constant pressure control is performed during engine low-speed, low-load operation, the intake control valve 12 is in the half-open state shown in FIG. will be maintained. This situation occurs in the hatched area d in 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 curve C in FIG. 3, the electromagnetic switching valve V3 is turned on and the first negative pressure chamber 15 is connected to the negative pressure pump 4,
As a result, the intake control valve 12 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. V4 are both turned on, and both the first negative pressure chamber 15 and the second negative pressure chamber 16 are connected to the negative pressure pump 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 a region between curves C and C in FIG. This EGR
Control may be performed by feedback control or open loop control.

When feedback control of EGR is performed, the electromagnetic switching valve V1 is controlled by the decoupage ratio, and the negative pressure applied to the negative pressure chamber 10 of the EGR valve 7 is guided to the absolute pressure sensor 27.
Therefore, at this time, the absolute pressure sensor 27 detects the negative pressure in the negative pressure chamber 10, in fact, the absolute pressure PI. Target negative pressure P in the negative pressure chamber 10. is stored in advance in the ROM 32 in the form of a map as a function of engine speed N and load, and during feedback control, the negative pressure PI in the negative pressure chamber 10 is set to the target negative value based on the output signal of the absolute pressure sensor 27. The duty ratio of the control pulse of the electromagnetic switching valve V1 is controlled so that the pressure becomes P0.

Further, the target negative pressure P0 and the target duty ratio DT when the negative pressure PI in the negative pressure chamber 10 is maintained at the target negative pressure Po
The relationship between the
38.

On the other hand, the target negative pressure P in the negative pressure chamber 10. Open loop control is performed when the target negative pressure P0 in the negative pressure chamber 10 is kept constant, and when the target negative pressure P0 in the negative pressure chamber 10 is kept constant.

Target negative pressure P from the relationship between and target duty ratio DT. A target duty ratio DT is determined based on the target duty ratio, and the electromagnetic switching valve V1 is subjected to density control 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.

If EGR control is not to be performed, the process advances to step 51.

In step 51, whether or not the electromagnetic switching valve V1 is off,
That is, it is determined whether the atmospheric pressure in the negative pressure chamber 10 is being guided by the absolute pressure sensor 27 or not. When the electromagnetic switching valve V1 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
The process proceeds from step 0 to step 53, where the target negative pressure P0 in the pressure chamber 10 is calculated based on standard atmospheric pressure.

This target negative pressure P. As described above, is stored in the ROM 32 in advance as a function of the engine speed N and the engine load. Next, in step 54, it is determined whether the target negative pressure Pa has been constant for a certain period of time, for example, one second. Target negative pressure P. If is constant for a certain period of time, step 5
Proceeding to step 5, it is determined whether the feedback completion flag is set. Target negative pressure P. When the process proceeds to step 55 for the first time after becoming constant for a certain period of time, the feedback completion flag has been reset, so the process proceeds to step 56. A feedback flag is set in step 56 and then an open loop flag is 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 PA 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 10 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). In other words, it is determined whether the current negative pressure ΔP in the negative pressure chamber 10 is smaller than the target negative pressure P0. When Po > ΔP + S”
Second, the process proceeds to step 73, where the minimum duty ratio DTI and the maximum duty ratio DT2 are increased by a constant value ΔD.

Next, referring to FIG. 4, these minimum deniity ratios DTI
and the maximum duty ratio DT2 will be explained. Figure 4 shows the target negative pressure P. and target duty ratio DT, and these relationships are shown as a straight line. That is,
Basically, target negative pressure P.

Negative pressure P. 1, the target duty ratio DT corresponding to this Pot, and the solenoid switching valve V
1, the actual negative pressure ΔP in the negative pressure chamber 10 becomes the target negative pressure P. Matches 1. Note that as the target duty ratio DT increases, the time that 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. Target duty ratio DT corresponding to 1
Even if 0 is used, the actual negative pressure ΔP in the negative pressure chamber 10 is the target negative pressure P. It deviates from 1. Therefore, in order to eliminate such deviations, the minimum duty ratio DTI and the minimum duty ratio DT2 are controlled by learning.

That is, as described above, in step 72, the negative pressure chamber 10
The actual negative pressure ΔP within is the target negative pressure P. When it is smaller than , the minimum duty ratio DTI and the maximum duty ratio DT2 are increased by ΔD in step 73,
Thus, the target negative pressure P at this time. and target duty ratio D
The relationship between T is shifted to the right as shown by straight line M in FIG. Next, in step 74, a target duty ratio DT is calculated from the target negative pressure Po 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 large, and thus the inside of the negative pressure chamber 10 The actual negative pressure ΔP increases. By repeating this process, a curve is finally determined in which the actual negative pressure ΔP in the negative pressure chamber 10 becomes the target negative pressure Po. 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 10 will be maintained at the target negative pressure P0. In fact, only the minimum duty ratio DTI and the maximum duty ratio DT2 are stored in the backup RAM 38, and the target duty ratio DT between the maximum duty ratio DT1 and the maximum duty ratio DT2 is calculated by interpolation. Determined by calculation.

When it is determined in step 72 of FIG. 7 that PoxΔP+S, the process advances to step 75 and the process returns to step P.

<Whether or not ΔP-3, that is, the actual negative pressure ΔP in the negative pressure chamber 10 is the target negative pressure P. It is determined whether or not it is larger than . When Pa<ΔP-3, the process proceeds to step 76, where the minimum duty ratio DT1 and the maximum duty ratio DT2 are decreased by a constant value ΔD. and shift to the left. Next, in step 74, a target duty ratio DT is calculated based on this curve.

Meanwhile, in step 75, P. When it is determined that 2ΔP-3, 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, when the feedback completion flag is set, the process proceeds from step 55 to step 59, where the feedback flag is reset, and then, at step 60, the open loop 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.
The control is not performed using the output signal of the controller, so it is open loop control. Whether or not open loop control is being performed can be determined from the open loop flag.

On the other hand, the engine speed N or engine load changes and the target negative pressure P is reached. When the value 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, when the pressure detection passage 24 begins to be clogged with carbon, etc., there is a delay in transmitting 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 does not rotate in the valve opening direction quickly, but starts to rotate in the valve opening direction after a while. Intake control valve 1
2 rotates in the valve opening direction, the pressure in the intake passage 2 increases, but since there is a delay in transmitting pressure fluctuations to the modulator 20, the intake control valve 12 rotates in the valve closing direction after a while. change. Therefore, the intake control valve 12 repeatedly opens and closes, and the pressure within the intake passage 2 repeatedly moves up and down, resulting in a hunting state. When the intake control valve 12 repeats opening and closing operations in this manner, the engine output fluctuates.

By the way, as a method of detecting such an abnormality, the negative pressure downstream of the intake control valve 12 is detected, and when the negative pressure exceeds a certain value during fluctuation, it is determined that there is an abnormality, and the carbon in the negative pressure passage 24 is detected. There is a method to remove the above, but in this embodiment, as mentioned above, since the air introduction pipe 47 for introducing air and the electromagnetic switching valve V5 are provided in the middle of the pressure detection passage 24, each time the engine is stopped, Carbon etc. can be automatically removed.

Its operation will be explained below with reference to diagrams (a) to (f) in FIG.

At the time t1 when the engine is stopped, as shown in FIG. 5(a), the IG double signal, which is the engine stop signal, is turned off, and at the same time, the signal from the electronic control unit 30 is activated as shown in FIG. 5(a).
b) Turning the electromagnetic switching valve V3 from off to on (with the electromagnetic switching valve V2 remaining off), and switching the electromagnetic switching valve V4
By turning on from off as shown in FIG. 5(C), negative pressure is introduced into both the first negative pressure chamber 15 and the second negative pressure chamber 16 of the actuator 11.
moves downward to fully open the intake control valve 12, cutting off intake air and cutting off fuel (not shown), thereby stopping the engine as shown in FIG. 5(f). At this time, while the engine 1 continues to rotate due to inertia, the pressure downstream of the intake control valve 12, which is fully open, is
As shown in Figure (e), the maximum negative pressure is about -600 mmHg, so when the electromagnetic switching valve v5 is switched from OFF to ON and opened as shown in Figure 5 (D), the air is released due to the large pressure difference. A large amount of air enters from an air intake port 46 of an air cleaner or the like, passes through the pressure detection passage 24 from the air introduction pipe 47 and the electromagnetic switching valve V5, and is blown out at high speed to the intake passage 2 downstream of the intake control valve 12. As a result, carbon and the like adhering to the wall surface of the pressure detection passage 24 are blown away and removed by the strong air current. Then, at the time t2 when a predetermined time has passed
In the electromagnetic switching valve V3. V4. V5 is turned from on to off, control by the electronic control unit 30 is stopped, and the operation of the maintenance device B is completed.

In the embodiment described above, the EGR valve 7 is disposed in the intake passage downstream of the intake control valve 12, and the intake control valve 12 is a diesel engine 1 equipped with a constant pressure control device A that maintains the downstream pressure at a constant pressure.
The case where the maintenance device B of the present invention is applied to is shown, but the maintenance device B according to the present invention is disclosed in, for example, the above-mentioned Japanese Patent Laid-Open No. 60-21
It is also possible to apply the present invention to a device that controls the combustion state of the engine using fluctuating intake pressure in a spark ignition engine as described in Japanese Patent No. 6048, a general diesel engine, and the like.

This type of control device generally has a pressure detection passage (usually called a negative pressure extraction passage) for combustion control downstream of the intake control valve (for example, the throttle valve in a spark ignition engine), and the EGR If blow-by gas flows into the intake passage, there is a risk that foreign matter such as carbon may clog the negative pressure outlet passage. Therefore, an air introduction pipe 47 having an electromagnetic switching valve V5 is attached to the negative pressure take-off passage in the same way as the pressure detection passage 24 shown in the above-described embodiment. If the maintenance device B is configured so that the valve V5 introduces the air from the air introduction pipe 47 into the negative pressure takeout passage when the can be cleaned.

That is, since the throttle valve is normally fully closed when the engine is stopped, the pressure in the intake passage downstream of the throttle valve becomes a high negative pressure when the engine is stopped, similar to the intake control valve in the above embodiment.

Therefore, the switching valve V5 of the air introduction pipe 47 is switched in response to an engine stop signal to introduce air into the negative pressure take-out pipe to blow out and clean the foreign matter such as carbon that is clogging the pipe.

When operating maintenance device B while the engine is running, a sensor that can detect negative pressure downstream of the throttle valve in the intake passage is installed, and the signal is manually input to the electronic control unit. When the high negative pressure in the intake passage remains stable for a certain period of time, such as when a vehicle descends a long downhill slope with engine braking, switching valve V5 of maintenance device B is switched and air is diverted to the negative pressure extraction passage. It is better to allow it to flow in.

In any of these embodiments, what must be newly added to the conventional internal combustion engine as a maintenance device B is the air introduction pipe 4.
7 and the switching valve V5, and the device that controls the switching valve V5 is an electronic control unit 30 normally used in this type of engine.
There is also the advantage that the cost required for equipment can be relatively low because it can be used for a variety of purposes.

〔Effect of the invention〕

According to the present invention, the pressure detection passage that opens downstream of the intake control valve in the intake passage is automatically maintained when the engine is stopped or when the negative pressure in the intake passage continues to exceed a certain level. When the device is activated, the switching valve is switched and air is sent into the pressure detection passage, which is then ejected into the negative pressure intake passage, which naturally cleans the pressure detection passage.
The pressure in the intake passage is always transmitted to the intake control device with good responsiveness, and troubles such as hunting do not occur.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing a schematic configuration of an embodiment in which the present invention is applied to a diesel engine having a constant pressure control device, FIG. 2 is an overall configuration diagram showing the embodiment in more detail, and FIG. 3 is a conceptual diagram showing the embodiment. FIG. 4 is a diagram showing the constant pressure control region and EGR region in the operation of the system, FIG. 4 is a diagram showing the relationship between target negative pressure and target duty ratio, and FIG. 5 is a timing chart showing the operating state of the maintenance device. FIG. 6 is a flowchart for performing the same <EGR control, and FIG. 7 is a flowchart when branching from a part of FIG. 6 to perform feedback control. 2... Intake passage, 5... EGR passage, lO... Negative pressure chamber, 12... Intake control valve, 24... Pressure detection passage, 4... Negative pressure pump, 7... EGR valve, 11... Actuator, 20... Modulator, 27... Absolute pressure sensor, 30... Electronic control unit, 45... IG double signal 46... Air intake port, 47... Air introduction pipe, ■1 to V5...Solenoid switching valve, B...Maintenance device.

Claims (1)

[Claims] 1. An intake control valve that is provided in the intake passage and is fully closed when the engine stops, and a pressure detection passage that opens downstream of the intake control valve with respect to the intake passage. We are equipped with
In the intake control device for an internal combustion engine, the combustion state is controlled by the pressure in the intake passage downstream of the intake control valve, which is taken out through the pressure detection passage. A maintenance device for an intake control device, characterized in that the switching valve is operated when the engine is stopped to introduce air into the pressure detection passage, thereby preventing clogging of the pressure detection passage. 2. An intake control valve provided in an intake passage, and a pressure detection passage opening downstream of the intake control valve with respect to the intake passage, the pressure detection passage being taken out through the pressure detection passage. In the intake control device for an internal combustion engine, the combustion state is controlled by the pressure in the intake passage, an air introduction pipe having a switching valve is attached to the pressure detection passage, and when the internal combustion engine is in a stable operating state, the intake control valve is The switching valve is actuated to introduce air into the pressure detection passage when the pressure in the intake passage becomes a negative pressure below a predetermined value, thereby preventing clogging of the pressure detection passage. A maintenance device for an air intake control device, characterized by: