JP2569546B2 - Exhaust gas recirculation control device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation control device for an internal combustion engine, and more particularly, to an exhaust gas of an internal combustion engine that improves control of an exhaust gas recirculation amount during a transition of the internal combustion engine. The present invention relates to a recirculation control device.

[Related Art] In order to reduce the NOx component in exhaust gas of an internal combustion engine, exhaust gas recirculation for circulating exhaust gas to the intake air of the internal combustion engine is performed. In the exhaust gas recirculation control device that controls the circulation of exhaust gas,
A recirculation amount control valve for controlling the flow rate of exhaust gas is provided in a recirculation passage communicating the exhaust passage and the intake passage, and an opening degree of the valve is controlled to control an exhaust gas recirculation amount. The recirculation amount control valve starts control based on the pressure of the exhaust passage, and controls the recirculation amount of the exhaust gas by adjusting the opening degree of the recirculation passage based on the negative pressure introduced into the negative pressure chamber.

The negative pressure introduced into the negative pressure chamber of the recirculation amount control valve is generated as an arbitrary pressure by negative pressure generating means for diluting the negative pressure of the negative pressure portion of the intake passage (for example, the portion where the throttle valve is disposed) with the atmosphere. Is done. Conventionally, the negative pressure generating means shuts off communication with the atmosphere when the pressure in the exhaust passage becomes equal to or higher than a predetermined value.After that, the pressure in the negative pressure portion of the intake passage is set as a signal negative pressure to the negative pressure chamber of the recirculation amount control valve. However, various types of exhaust gas recirculation control devices that use an electromagnetic valve as the negative pressure generation means and attempt to optimally control the amount of exhaust gas recirculation have been proposed, since they cannot sufficiently respond to changes in the operating state of the internal combustion engine. Have been.

For example, according to the "exhaust gas recirculation control device" of Japanese Patent Application Laid-Open No. 55-78150, the opening degree of a solenoid valve communicating with the negative pressure section of the intake passage and the atmosphere is adjusted, and the recirculation amount control valve is controlled. A configuration is disclosed in which the introduced negative pressure is controlled according to the operating state of the internal combustion engine. Further, Japanese Patent Application Laid-Open No. Sho 58-2459, "EGR
The control device uses an electromagnetic valve that communicates with the negative pressure portion of the intake passage and the atmosphere, and constantly controls the duty of the time that is communicated with the atmosphere side and the time that is communicated with the negative pressure portion, thereby controlling the amount of exhaust gas recirculation. Further, there is disclosed a configuration for correcting a delay time of a control system during a transition of the internal combustion engine.

[Problems to be Solved by the Invention] However, such an exhaust gas recirculation control device for an internal combustion engine has the following problems, and further improvement has been desired.

(1) Negative pressure generating means for controlling a recirculation amount control valve for adjusting the recirculation amount of exhaust gas is communicated with a negative pressure portion of the intake passage and the atmosphere, and a negative signal to the recirculation amount control valve is generated by the negative pressure and the atmospheric pressure. When the pressure is generated, air flows into the suction passage from the atmosphere through the negative pressure generating means. Therefore, conventionally, a restrictor such as an orifice is provided in a passage from the negative pressure generating means to the intake passage so that an amount of air that causes a significant error in the intake air amount of the internal combustion engine does not flow through the negative pressure generating means. Have been. For this reason, there has been a problem that the response of the signal negative pressure is reduced by the throttle. That is, even if the operation of the solenoid valve is controlled based on the operating state of the internal combustion engine, the change in the signal negative pressure is buffered by the throttle.
As a result, the problem that the exhaust gas recirculation amount does not follow and the NOx and the like in the exhaust gas may increase is caused.

(2) In the case where the signal negative pressure is controlled by the opening degree of the solenoid valve or the like, the solenoid valve must be continuously energized during the control of the exhaust gas recirculation, so that the solenoid valve is required to have high durability. There was a problem. Further, if the solenoid valve fails, control of exhaust gas recirculation cannot be performed at all, so that in such a case, a problem that emission is deteriorated is caused. Furthermore, if the amount of exhaust gas recirculation is controlled by the opening of the solenoid valve, it is necessary to use a solenoid valve having good linearity flow rate characteristics, which requires time and labor for adjustment and maintenance, and also increases the cost. there were.

An exhaust gas recirculation control device for an internal combustion engine according to the present invention has been made to solve the above problems and to control exhaust gas recirculation with a simple configuration in a reliable and responsive manner.

Configuration of the Invention The configuration of the present invention that achieves the above object will be described below.

[Means for Solving the Problems] As shown in FIG. 1, the present invention restricts the flow of air from the negative pressure portion M3 to the negative pressure portion M3 of the intake passage M2 of the internal combustion engine M1. A negative pressure generating means M5 communicating with the throttle M4 and diluting the negative pressure with the atmosphere to generate a signal negative pressure, and an exhaust gas recirculation path M7 communicating the exhaust passage M6 and the intake passage M2 of the internal combustion engine M1. And a recirculation amount control valve M9 for controlling the flow rate of the exhaust gas recirculated to the intake passage M2 by controlling the pressure of the negative pressure chamber M8 to which the signal negative pressure generated by the negative pressure generating means M5 is led. In the exhaust gas recirculation control device for an internal combustion engine, a communication path M10 that communicates a negative pressure section M3 of the intake path M2 with a negative pressure chamber M8 of the recirculation amount control valve M9 is provided.
And a transient state detecting means for detecting a transient state caused by a transition of the throttle valve of the internal combustion engine M1 from fully closed to non-fully closed.
M12, when the transient state detecting means M12 determines that the internal combustion engine M1 is in the transient state, after setting the negative pressure introduction valve M11 to a predetermined open state, Negative pressure introduction valve control means M13 that gradually controls in the valve closing direction
And characterized in that:

[Operation] The exhaust gas recirculation control device for an internal combustion engine according to the present invention having the above-described configuration uses the signal negative pressure generated by the negative pressure generating means M5 connected to the negative pressure portion M3 of the intake passage M2 via the throttle M4. It is led to the negative pressure chamber M8 of the reflux amount control valve M9, and by this signal negative pressure,
A recirculation amount of exhaust gas from the exhaust passage M6 to the intake passage M2 is controlled by a recirculation amount control valve M9 provided in the exhaust gas recirculation passage M7. Moreover, in the present invention, when the transient state detecting means M12 detects a transient state caused by the transition of the throttle valve of the internal combustion engine M1 from the fully closed state to the non-fully closed state, the negative pressure introducing valve control means M13 performs the following operation. It is provided in a communication passage M10 that communicates the negative pressure portion M3 of the intake passage M2 and the negative pressure chamber M8 of the recirculation amount control valve M9.)
The open / close state of the communication path M10 is adjusted by controlling the negative pressure introduction valve M11. Therefore, due to the presence of the throttle M4 (internal combustion engine
The response delay of the signal negative pressure during the transition is eliminated by the transition of the throttle valve of M1 from fully closed to non-fully closed. Controlled.

That is, instead of gradually opening the recirculation amount control valve M9 and gradually exhausting as in the conventional case (due to the shift of the throttle valve of the internal combustion engine M1 from fully closed to non-fully closed).
Since the negative pressure is immediately introduced via the negative pressure introduction valve M11 in response to the signal at the time of the transition, the recirculation of the exhaust gas increases quickly. As a result, it is possible to preferably solve the problem of the increase in NOx in the exhaust, which has conventionally occurred during the period in which the increase in the exhaust gas recirculation amount is delayed.

Further, when controlling the exhaust gas recirculation amount in this way, when it is determined that the exhaust gas recirculation amount is set to the predetermined value, the exhaust gas recirculation amount is set to a predetermined value at a stretch when it is determined that the engine is in a transient state. Not only that valve M11 was provided,
The responsiveness is also excellent in that the negative pressure introduction valve M11 is immediately controlled to a predetermined value as in the present invention.

Further, after the exhaust gas recirculation amount is set to a predetermined value, the exhaust gas recirculation amount is gradually reduced in the valve closing direction to reduce the exhaust gas recirculation amount, that is, a change that converges to a steady state as soon as the transient state elapses. Accordingly, the exhaust gas recirculation amount changes gradually, so that a shock such as an operation state due to a sudden change in the exhaust gas recirculation amount is reduced.

In addition, the control of the recirculation amount control valve M9 does not need to be performed based on the lift sensor that detects the valve lift amount of the recirculation amount control valve M9, and simply transmits a predetermined signal to the negative pressure introduction valve M11. Thus, the lift sensor can be omitted, and there is no need for a complicated calculation process of performing feedback control of the recirculation amount control valve M9 according to the output of the lift sensor.

Embodiment In order to further clarify the configuration and operation of the present invention described above, a preferred embodiment of an exhaust gas recirculation control device for an internal combustion engine according to the present invention will be described below. FIG. 2 is a schematic configuration diagram of the exhaust gas recirculation control device for the internal combustion engine.

As shown in the figure, the intake system of the internal combustion engine 1 includes, from the upstream, an air cleaner 3, an air flow meter 5 for detecting an intake air amount, a throttle valve 7, which is provided in an intake pipe 6 and opens and closes in conjunction with an accelerator pedal. And a surge tank 9 for absorbing the pulsation of the air. Fuel is injected from a fuel injection valve (not shown) into the air flowing through the intake system, and the air-fuel mixture is drawn into the internal combustion engine 1 and ignited by an electric spark formed in a spark plug (not shown). . The exhaust gas after explosion combustion in the internal combustion engine 1 is exhaust pipe 12
Is discharged through.

A part of the exhaust is supplied to the surge tank 9 via the flow control valve 15.
Reflux. The recirculation amount control valve 15 is a valve body that opens and closes between an exhaust chamber 19 provided with a throttle 16 and communicated with the exhaust pipe 12 by a recirculation passage 17a and a recirculation passage 17b communicating with the exhaust chamber 19 and the surge tank 9. 20 and a diaphragm 30 for driving the valve element 20 by a balance between the pressure of the negative pressure chamber 25 and the compression spring 27. Further, the exhaust pipe 19 of the recirculation amount control valve 15 is
It communicates with the pressure chamber 37 of the negative pressure control valve 35 via 32,
On the other hand, the negative pressure chamber 25 is connected to the negative pressure introduction valve 40 through the communication passage 39,
The pressure chamber 43 opened to the atmosphere of the negative pressure control valve 35 and the intake pipe 6
Is communicated with the downstream of the throttle valve 7. Incidentally, the negative pressure introduction valve 40 is connected to the surge tank 9. In the passage from the negative pressure chamber 25 to the intake pipe 6, a throttle 44 for limiting the flow rate is provided.

The negative pressure control valve 35 includes a diaphragm 46 having a valve seat 45 at the center and separating the two pressure chambers 37 and 43.
And a spring 48 for urging the pressure chamber 37 toward the pressure chamber 37 side.

The recirculation amount control valve 15 and the negative pressure control valve 35 having the above configurations operate as follows when the negative pressure introduction valve 40 is closed.

(1) In the idle state, the exhaust pressure of the exhaust pipe 12 is low, and the pressure of the pressure chamber 39 of the negative pressure control valve 35 is also low. Therefore, the diaphragm 46 is moved downward in FIG. 2 by the bias of the spring 48, and the communication path 39 is opened to the atmosphere. As a result, the pressure (signal negative pressure) in the communication passage 39 is maintained at substantially the atmospheric pressure due to the presence of the throttle 44 provided in the passage to the intake pipe 6. Accordingly, the pressure in the negative pressure chamber 25 of the recirculation amount control valve 15 also becomes substantially the atmospheric pressure, the diaphragm 30 is pushed down by the compression spring 27, and the valve body 20 is seated on the valve seat. That is, the communication between the recirculation paths 17a and 17b is completely shut off, and the exhaust gas is not recirculated.

(2) When the throttle valve 7 is opened from this idle state, the intake air amount of the internal combustion engine 1 increases, and the exhaust pipe 12
, The pressure in the pressure chamber 37 of the negative pressure control valve 35 also increases. As a result, the diaphragm 46
The valve seat 45 on the diaphragm moves against the bias of the spring 48 and seats on the open end 39a of the communication path 39. Therefore, the negative pressure of the intake pipe 6 is introduced into the communication path 39, and the pressure of the negative pressure chamber 25 of the recirculation amount control valve 15 also gradually decreases. When the force acting on the diaphragm 30 due to the pressure difference between the two sides of the diaphragm 30 exceeds the urging force of the compression spring 27, the diaphragm 30 moves toward the negative pressure chamber 25, and the valve body 20 also moves. That is, the return passages 17a and 17b are communicated, and the exhaust gas from the exhaust pipe 12 returns to the surge tank 9.

In the present embodiment, in addition to these operations, the recirculation amount control valve
Control is performed to correct the pressure of the negative pressure chamber 25 by the opening and closing operation of the negative pressure introduction valve 40. The negative pressure introduction valve 40 is controlled by a vehicle-mounted electronic control device 50. This electronic control unit
50 is a well-known CPU 51, storage unit 52, timer 53, input / output port 54
The input / output port 54 has an air flow meter 5, a throttle valve 7
A throttle sensor 56 for detecting the opening of the engine, a water temperature sensor 57 for detecting the cooling water temperature of the internal combustion engine 1, a rotational speed sensor 59 for detecting the rotational speed N of the internal combustion engine 1, and the like are connected.

The electronic control device 50 starts its operation when the ignition switch is turned on. The electronic control unit 50 executes the negative pressure introduction valve control interrupt routine shown in FIG. 3 every 4 msec due to the interruption signal from the timer 53. In a control routine different from such an interruption routine, a process of reading output signals of the air flow meter 5, the throttle sensor 56, the water temperature sensor 58, the rotation speed sensor 59, and the like via the input / output port 54 is performed. The air amount Q, the throttle opening θ, the cooling water temperature Thw, and the rotation speed N are read in advance.

When the interrupt routine shown in FIG. 3 is started, first, it is determined whether or not the throttle valve 7 is in a fully closed state (step S1).
100) In the case of the fully closed state, the value 1 is set to the flag F (step 105). In this case, it is determined that there is no need to perform exhaust gas recirculation, and processing for turning off the negative pressure introducing valve 40, that is, closing the valve (step 110), exits to "NEXT", and ends the present control routine once. .

When the accelerator is depressed and the throttle valve 7 is operated from the fully closed state to the open direction, the determination in step 100 becomes "NO", and the processing proceeds to step 115 and below, and first, the value of the flag F is determined ( Step 115). If this interrupt routine is started immediately after the throttle valve 7 is not fully closed, the value of the flag F is 1, and in this case, the value of the flag F is reset to 0 ( Step 120), a process of setting an initial value to the valve opening time DTon of the negative pressure introduction valve 40 is performed (step 125). That is, when the throttle valve 7 is opened from the fully closed state, it is determined that the internal combustion engine 1 is in the transient state, and the control of the negative pressure introducing valve 40 is started. The initial value of the valve opening time DTon of the negative pressure introducing valve 40 is, as shown in FIG.
Is set as a larger value as the rotation speed N is lower. The valve opening time DTon is determined as the number of activations of the interrupt routine in the duty control with 48 msec as one cycle. That is, if the duty is 100%, the valve opening time DTon is a value of 12 (48 msec = 12 × 4 mse
In c), if the duty is 50%, a value of 6 is set. If the rotational speed N of the internal combustion engine 1 is, for example, 1200 [rpm], the initial value of the valve opening time DTon is set to the value 7 according to the map of FIG. This map shows the electronic control unit 50
Is stored in the storage unit 52.

After the setting of the initial value of the valve opening time DTon is completed, the variable C48 for counting the time is cleared (step 130), and the process of setting the initial value of the valve opening time DTon of the negative pressure introducing valve 40 is ended.

Subsequently, a process of incrementing the value of the variable C48 by 1 is performed (step 135), and it is determined whether or not the value of the variable C48 is equal to or longer than the valve opening time DTon (step 14).
0). The value of the variable C48 is incremented each time this interrupt routine is executed every 4 msec (step 13).
5) If the valve opening time DTon is 7, the initial value is set to 7
Until the turning interruption routine is started, the determination in step 140 is “NO”. In this case, it is determined whether the cooling water temperature Thw of the internal combustion engine 1 is higher than 50 [° C.] and lower than 90 [° C.] (step 145). If the temperature is less than 50 [° C], it is warming up and exhaust recirculation is not performed.
If it is [° C.] or more, it is determined that overheating has occurred and that exhaust gas recirculation is not performed. Accordingly, the process proceeds to step 110 described above. After performing the process of closing the negative pressure introduction valve 40, the process exits to “NEXT” and temporarily ends the control routine. On the other hand, if the cooling water temperature Thw is within this temperature range, it is determined that the exhaust gas recirculation is to be performed, and the negative pressure introducing valve 40 is turned on so that the exhaust gas recirculation in the transient state of the internal combustion engine 1 is started without delay. (The valve open state) (step 150), and then the process exits to "NEXT" to temporarily end the control routine.

As a result of the opening of the negative pressure introducing valve 40, the negative pressure of the surge tank 9 is immediately introduced into the negative pressure chamber 25 of the recirculation amount control valve 15, the recirculation amount control valve 15 is opened, and the intake pipe 12 The recirculation of exhaust gas to the system surge tank 9 is started immediately.

Next, when this control routine is started, until the throttle valve 7 is fully closed, the determinations in steps 100 and 115 are both “NO”, and the process proceeds to step 160 where the value of the variable C48 is 12 or less. Is determined. Until this interrupt routine is executed 12 times, the process directly proceeds to step 135 and thereafter, and executes the processing described above. Therefore,
When the value of the variable C48 is less than the valve opening time DTon, the negative pressure introduction valve 40 is maintained in the ON state, and when the value becomes longer than the valve opening time DTon, the negative pressure introduction valve 40 is closed. . On the other hand, the variable C4
If the value of 8 becomes 12 or more, it is determined that one cycle has been completed, and a process of updating the valve opening time DTon is performed (step
165). The update of the valve opening time DTon is performed by subtracting the attenuation value DTsb from the valve opening time DTon (DTon ← DTon−
DTsb). Here, the damping value DTsb may be determined as a function of the rotational speed of the internal combustion engine 1 as shown in FIG. 5, or may be determined as a function of the intake air amount Q as shown in FIG. You may. Further, the ternary map may be determined based on both the engine speed N and the intake air amount Q. These maps are prepared in advance in the storage unit 52 of the electronic control unit 50.

After updating the value of the valve opening time DTon, the value of the variable C48 is cleared to zero (Step 170), and then the process proceeds to the above-described Step 135 and subsequent steps. As a result, the updated valve opening time DT
By turning on, the duty control of the negative pressure introducing valve 40 with 48 msec as one cycle is executed.

According to the exhaust gas recirculation control device for an internal combustion engine of the present embodiment described above, when the throttle valve 7 of the internal combustion engine 1 is controlled to open from the fully closed state (i.e., idle state), As illustrated in Fig. 7, time
During the period from T1 to T2, the negative pressure introduction valve 40 is controlled to open with a duty determined by the valve opening time DTon. Therefore, when the amount of intake air of the internal combustion engine 1 increases and the exhaust pressure increases, and the negative pressure control valve 35 cuts off the communication with the atmosphere, the negative pressure of the intake pipe 6 is conventionally gradually introduced through the throttle 44 conventionally. Reflux control valve 15
Opened slowly, and the exhaust gas recirculated gradually as shown by the broken line B in FIG. 7, whereas in the present embodiment,
The negative pressure is immediately introduced through the negative pressure introducing valve 40, and the recirculation of the exhaust gas rapidly increases as shown by the solid line J in FIG.
As a result, according to the exhaust gas recirculation control device of the present embodiment, when the negative pressure of the internal combustion engine 1 suddenly increases, the exhaust gas recirculation is promptly performed, and the increase in the exhaust gas recirculation amount is conventionally delayed. The problem of an increase in NOx in exhaust gas that occurred during the period I in FIG. 7 can be solved. Also, when controlling the exhaust gas recirculation amount in this way, the valve opening time DTon is set to the initial value at a stretch when it is determined that the exhaust gas is in a transient state.
The responsiveness is excellent not only in that the negative pressure introducing valve 40 is simply provided, but also in that the negative pressure introducing valve 40 is immediately controlled to the initial value as in the present embodiment. Furthermore, since the valve opening time DTon is gradually reduced after being set to the initial value, a shock such as an operation state due to a sudden change in the exhaust gas recirculation amount can be reduced.
In addition, the control of the recirculation amount control valve 15 does not need to be performed based on a lift sensor that detects the valve lift amount of the recirculation amount control valve 15, and simply sends a predetermined signal to the negative pressure introduction valve 40. In this case, there is an advantage that the lift sensor can be omitted, and a complicated calculation process of performing feedback control of the recirculation amount control valve 15 according to the output of the lift sensor is not required. Moreover, the exhaust gas recirculation control device of this embodiment is different from the above-described device in that the negative pressure introduction valve 40
And the existing device can be effectively used. Further, since the negative pressure introduction valve 40 is controlled only in a transient state, the power consumption is small, and a high durability can be obtained with a simple structure. Also, even if the negative pressure introduction valve
Exhaust gas recirculation is performed even if a disconnection failure occurs in 40, so that the exhaust gas recirculation amount control valve 15 of the present embodiment is more secure in terms of system safety compared to a case where a proportionally controllable solenoid valve is used. The configuration has advantages. In addition, since high-precision characteristics such as linearity are not required, the configuration and adjustment can be simplified, which can contribute to cost reduction.

In addition, according to the exhaust gas recirculation control device of the present embodiment,
The inside diameter of the throttle 44 provided at the portion of the intake pipe 6 where the negative pressure is introduced can be made sufficiently small, and the amount of air directly flowing from the atmosphere via the negative pressure control valve 35 can be made sufficiently small. Therefore, the measurement of the intake air amount by the air flow meter 5 can be performed with high accuracy, and the influence on other controls (such as air-fuel ratio control) of the internal combustion engine 1 can be reduced.

As shown in FIG. 8, in the exhaust gas recirculation control device according to the present embodiment, the auxiliary flow rate control valve 190 may be provided in the recirculation passage 17a. In this case, the auxiliary flow control valve
Since the opening of the valve body 192 of the 190 changes according to the negative pressure in the surge tank 9 communicated via the communication passage 193, the exhaust gas recirculation amount can be changed according to the negative pressure of the internal combustion engine 1,
The exhaust gas recirculation control can be performed more precisely, together with the improvement of the transient response by the negative pressure introduction valve 40. FIG. 9 is a graph showing the exhaust gas recirculation rate with respect to the load of the internal combustion engine 1 in this embodiment. The exhaust gas recirculation rate is
The ratio of the exhaust gas recirculation flow rate to the total intake air amount of the internal combustion engine 1 is a value expressed as a percentage.

As a second modified example, as shown in FIG. 10, a so-called advance port 19 for introducing a negative pressure when the throttle valve 7 is opened to a predetermined opening degree is provided near the throttle valve 7.
5, a configuration is adopted in which the exhaust gas is recirculated in two stages by using the negative pressure generated at the port 195, and the negative pressure introduction valve 40 is controlled at the same time. Also in this case, the exhaust gas recirculation control can be performed precisely as in the example of FIG. FIG. 11 is a graph showing the exhaust gas recirculation rate in this case.

Further, as a third modified example, as shown in FIG. 12, a negative control valve 35 is provided with a sub-control valve for adjusting the pressure of the pressure chamber 43 thereof.
It can also be considered as a configuration provided with 200. In this case, the flow rate of air flowing from the atmosphere side into the pressure chamber 43 of the negative pressure control valve 35 changes according to the negative pressure of the intake system, and as a result, the exhaust gas recirculation amount can be controlled. The exhaust gas recirculation rate at this time is almost the same as that shown in FIG.

Although the embodiments of the present invention have been described above, the present invention is not limited to such embodiments at all. For example,
A range that does not deviate from the paper according to the present invention, such as a configuration that detects a transient state by not only a change from the fully closed throttle valve but also by acceleration or a configuration that detects a transient state of the internal combustion engine by a change in intake pipe negative pressure. Of course, the present invention can be implemented in various modes.

Effects of the Invention As described in detail above, according to the exhaust gas recirculation control device for an internal combustion engine of the present invention, the delay of the exhaust gas recirculation in a transient state of the internal combustion engine is improved by a simple configuration, and the generation of NOx and the like is reduced. This is an extremely excellent effect that the exhaust gas can be prevented and the exhaust gas can be always purified appropriately. Moreover, according to the exhaust gas recirculation control device for an internal combustion engine of the present invention, compared with the control of the exhaust gas recirculation amount by a proportional solenoid valve, the durability is excellent and the exhaust gas recirculation can be ensured. Have. In the case of controlling the exhaust gas recirculation amount, if it is determined that the exhaust gas recirculation amount is in a transitional state, the exhaust gas recirculation amount is set to a predetermined valve opening state (ie, the exhaust gas recirculation amount is set to a predetermined value). Not only that, the response is excellent in that the negative pressure introduction valve is controlled in that way. Furthermore, after the exhaust gas recirculation amount is set to a predetermined value, the exhaust gas recirculation amount is gradually reduced, that is, the exhaust gas recirculation amount is gradually reduced in accordance with a change to a steady state as the transient state elapses. Is changed, it is possible to reduce a shock such as an operation state due to a sudden change in the exhaust gas recirculation amount. In addition, the control of the reflux control valve is
Since it is not necessary to perform the determination based on the lift sensor that detects the valve lift amount of the recirculation amount control valve, it is only necessary to output a predetermined signal to the negative pressure introduction valve.
There is an advantage that the lift sensor can be omitted, and a complicated calculation process of feedback-controlling the recirculation amount control valve according to the output of the lift sensor is not required. Further, there is no control delay in the feedback control.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a basic configuration of the present invention, FIG. 2 is a schematic configuration diagram of an exhaust gas recirculation control device for an internal combustion engine as one embodiment of the present invention, and FIG. 4 is a flowchart showing a negative pressure introduction valve control interrupt routine executed by the apparatus every 4 msec. FIG. 4 is a graph for determining an initial value of the valve opening time DTon. FIGS. 5 and 6 are attenuation values of the valve opening time DTon. FIG. 7 is a timing chart showing an example of control in the embodiment, FIG. 8 is a schematic configuration diagram showing a first modification of the embodiment, and FIG. 9 is an exhaust gas recirculation rate in that case. FIG. 10 shows the second example of the embodiment.
FIG. 11 is a graph showing the exhaust gas recirculation rate in the same case, and FIG. 12 is a schematic diagram showing a third modification of the embodiment. 1 Internal combustion engine 6 Intake pipe 7 Throttle valve 9 Surge tank 12 Exhaust pipe 15 Flow control valve 17a, 17b Recirculation passage 19 Exhaust chamber 20 Valve body 25 … Negative pressure chamber 35 …… Negative pressure control valve 37 …… Pressure chamber 40 …… Negative pressure introduction valve 44 …… Throttle

Claims (1)

(57) [Claims] 1. A negative pressure section in an intake passage of an internal combustion engine is communicated with a negative pressure section through a throttle that restricts a flow of air from the negative pressure section, and the negative pressure is diluted with the atmosphere to generate a signal negative pressure. Negative pressure generating means, provided in an exhaust gas recirculation passage communicating the exhaust passage and the intake passage of the internal combustion engine, the flow rate of the exhaust gas recirculated to the intake passage,
A recirculation amount control valve controlled by a pressure of a negative pressure chamber into which a signal negative pressure generated by the negative pressure generation means is guided.The negative pressure section of the intake passage, A negative pressure introduction valve that is provided in a communication path communicating with the negative pressure chamber of the recirculation amount control valve and opens and closes the communication path; and a transient state caused by the throttle valve of the internal combustion engine shifting from fully closed to non-fully closed. A transient state detecting means for detecting when the internal combustion engine is in the transient state, the negative pressure introducing valve is set to a predetermined open state. And a negative pressure introduction valve control means for gradually controlling the valve in a valve closing direction after the exhaust gas is recirculated.