JPH09133036A - Intake control device for internal combustion engine - Google Patents

Abstract

(57) Abstract: In an internal combustion engine having an intake control valve and a NOx absorption decomposition catalyst, torque shock during purification is reduced, and deterioration of the function due to deterioration of the catalyst is suppressed. SOLUTION: A surge tank 9 downstream of a throttle valve 8
An intake control valve 19 which is opened and closed by an actuator 20 is provided in the intake passage 2 between the injector 4 and the injector 4, and a NOx absorption decomposition catalyst 31 is provided in the exhaust passage 7. When the air-fuel ratio lean state continues for a long time, the electronic control unit (ECU) 41 increases the air-fuel ratio from the lean state up to that point because the amount of absorbed NOx reaches a saturated state, and releases NOx. To do. When increasing the air-fuel ratio, the ECU 41 shortens the opening time of the intake control valve 19. Therefore, even if the fuel injection amount is not increased, the actual air-fuel ratio becomes richer than that until then, and the output is suppressed from suddenly increasing due to the rapid increase of the fuel injection amount. Further, there is no need to perform retard control of the ignition timing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake control device for an internal combustion engine, and more particularly, to an intake control device provided in an intake passage of an internal combustion engine and provided in an exhaust passage separately from a throttle valve. The present invention relates to an intake control device for an internal combustion engine having a NOx absorption decomposition catalyst.

[0002]

2. Description of the Related Art Conventionally, for example, a lean burn engine having an NOx absorption decomposition catalyst in an exhaust passage is known. This NOx absorption / decomposition catalyst means that NO is present in exhaust gas (in an oxidizing atmosphere) with a lean air-fuel ratio
absorb x. On the other hand, during the air-fuel ratio rich or stoichiometric exhaust (in the reducing atmosphere), since unburned gas exists in the exhaust gas, NOx reacts with hydrocarbons in the unburned gas in the exhaust passage. By this reduction reaction, NOx is reduced to nitrogen gas or the like, and as a result, NOx absorbed by the NOx absorption decomposition catalyst is released.

As described above, since the NOx absorption / decomposition catalyst has the above characteristics, the amount of NOx that can be absorbed reaches a saturated state when the lean air-fuel ratio state continues.
After that, it is considered that NOx cannot be absorbed. Therefore, a technique called "rich spike control" in which NOx is forcibly released has been established (see, for example, JP-A-6-58185). In this technique, when the air-fuel ratio is lean, the fuel injection amount is temporarily increased and the air-fuel ratio is made rich before the amount of NOx that can be absorbed reaches the saturation state. Therefore, the NOx absorbed by the NOx absorbing / decomposing catalyst is released, and the catalyst is purified and reused.

[0004]

However, in the above-mentioned technique, the air-fuel ratio, which was in the lean state until then, changes to the rich state (or the stoichiometric state) due to the increase in the fuel injection amount. There was a risk of a sudden increase and a torque shock.

On the other hand, in order to suppress the torque shock, it is conceivable to retard the ignition timing as the fuel injection amount is increased. However, when such retard control is performed, the exhaust gas temperature in the exhaust passage may rise. Therefore, the NOx absorption / decomposition catalyst provided in the exhaust passage may be heated, and the catalyst may be adversely affected such that the deterioration is accelerated.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an intake control valve provided in an intake passage corresponding to each cylinder of an internal combustion engine, separately from the throttle valve. At the same time, in the intake control device of the internal combustion engine having the NOx absorption decomposition catalyst in the exhaust passage, it is needless to say that the function of the NOx absorption decomposition catalyst is effectively exhibited by purifying the NOx absorption decomposition catalyst as necessary. An object of the present invention is to provide an intake control device for an internal combustion engine, which can reduce torque shock during purification and can suppress functional deterioration due to catalyst deterioration and the like.

[0007]

In order to achieve the above object, in the invention described in claim 1, as shown in FIG. 1, the internal combustion engine M1 is driven at a predetermined timing in synchronism with the rotation of the internal combustion engine M1 for combustion. An intake valve M4 that opens and closes an intake passage M3 leading to the chamber M2, a throttle valve M5 provided in the middle of the intake passage M3, and the throttle valve M5.
An intake control valve M6 provided in the intake passage M3, an actuator M7 for opening and closing the intake control valve M6, and an operating state detecting means M8 for detecting an operating state of the internal combustion engine M1. Based on the detection result of the operating state detection means M8, it is provided in the middle of the intake control means M9 for controlling the actuator M7 and the exhaust passage M10 leading to the combustion chamber M2, and absorbs NOx in the exhaust of lean air-fuel ratio. , An intake control device for an internal combustion engine, comprising an NOx absorption decomposition catalyst M11 that releases NOx in an air-fuel ratio rich or stoichiometric exhaust gas, and the amount of NOx absorbed by the NOx absorption decomposition catalyst M11 reaches saturation. Before, NOx is released by the release determination means M12 that determines that the NOx needs to be released, and the release determination means M12. If it is determined that it is necessary to the valve opening time reduction control means for controlling said actuator M7 to shorten the opening time of the intake control valve M6 M
The provision of 13 and 13 is the gist.

According to the above structure, the intake valve M4 is
It is driven at a predetermined timing in synchronization with the rotation of the internal combustion engine M1, and opens and closes the intake passage M3 leading to the combustion chamber M2. Further, by opening and closing the throttle valve M5 provided in the middle of the intake passage M3, basically, the internal combustion engine M1
The amount of intake air supplied to the can be adjusted. Further, on the downstream side of the throttle valve M5, the intake control valve M6 provided in the intake passage M3 is opened / closed by the operation of the actuator M7. By this opening / closing, intake control can be executed separately from the opening / closing of the throttle valve M5. That is, the operating state detecting means M8 detects the operating state of the internal combustion engine M1, and the intake control means M9 controls the actuator M7 based on the detection result.

Further, an exhaust passage M10 leading to the combustion chamber M2.
In the NOx absorption / decomposition catalyst M11 provided in the middle of NOx, NOx is absorbed in the exhaust gas having a lean air-fuel ratio. NO
In the x absorption decomposition catalyst M11, NOx is released in the air-fuel ratio rich or stoichiometric exhaust gas.

Now, the operation at the lean air-fuel ratio is continued,
If the state is maintained as it is, the amount of NOx absorbed by the NOx absorption decomposition catalyst M11 reaches a saturated state. In contrast, in the present invention, the release determination means M12 determines that the NOx needs to be released before the amount of NOx absorbed by the NOx absorption decomposition catalyst M11 reaches saturation. When it is determined by the release determination means M12 that NOx needs to be released, the valve opening time reduction control means M13 controls the actuator M7 and the intake control valve M6.
The valve opening time is shortened.

For this reason, the intake air amount is reduced by shortening the opening time of the intake control valve M6, and even if the fuel injection amount is not increased, the actual air-fuel ratio is up to then (lean state). ) Will be richer than.
Therefore, there will be unburned gas in the exhaust gas,
N that had been absorbed by the NOx absorption decomposition catalyst M11 until then
Ox reacts with hydrocarbons in the unburned gas in the exhaust passage M10. By this reduction reaction, NOx is reduced to nitrogen gas or the like, and as a result, the absorbed NOx is released.

Further, when purifying the NOx absorption decomposition catalyst M11, the actual air-fuel ratio may become rich even if the fuel injection amount is not increased. Therefore, it is possible to prevent the output from rapidly increasing due to the sudden increase in the fuel injection amount. Therefore, since it is not necessary to perform the ignition timing retard control that was considered in the prior art, it is possible to suppress the exhaust temperature from rising.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) A first embodiment in which the intake control device for an internal combustion engine according to the present invention is embodied in a gasoline engine will be described in detail below with reference to FIGS.

FIG. 3 is a schematic configuration diagram showing an intake control device for an engine mounted on a vehicle in this embodiment. As shown in the figure, the engine 1 as an internal combustion engine
The outside air is taken in from the air cleaner 3 through the intake passage 2. Further, the engine 1 takes in the fuel injected from the injector 4 provided for each cylinder in the vicinity of the intake port 2a at the same time as taking in the outside air. Then, a mixture of the taken-in fuel and the outside air is introduced into the combustion chamber 1a through the intake valve 5 provided for each cylinder, and exploded and burned in the combustion chamber 1a to obtain a driving force. Further, the exhaust gas after the explosion and combustion is led out of the combustion chamber 1a via the exhaust valve 6 to the exhaust passage 7 where the exhaust manifold for each cylinder is gathered, and is discharged to the outside.

A throttle valve 8 which is opened / closed in conjunction with the operation of an accelerator pedal (not shown) is provided in the middle of the intake passage 2. And this throttle valve 8
Is opened and closed, the amount of air taken into the intake passage 2 is adjusted. On the downstream side of the throttle valve 8,
A surge tank 9 for smoothing the pulsation of the intake air is provided.

In the middle of the intake passage 2, the bypass intake passage 1 bypassing the throttle valve 8, that is, connecting the upstream side and the downstream side of the throttle valve 8 with each other.
0 is provided. And this bypass intake passage 1
In the middle of 0, a linear solenoid type idle speed control valve (ISCV) 11 for adjusting the flow rate of air flowing through the passage 10 is provided. This I
In the SCV 11, the solenoid 11a is basically duty-controlled when the throttle valve 8 is closed and the engine 1 is in the idle state. The duty ratio is controlled to open and close (drive) the ISCV 11 as appropriate. By this opening and closing, the air flow rate (intake air amount) of the bypass intake passage 10 is adjusted. The adjustment of the intake air amount controls the engine speed NE during idling.

In the intake passage 2, the throttle valve 8
A throttle sensor 22 for detecting the opening degree (throttle opening degree) TA is provided in the vicinity of, and an idle switch 23 for detecting an idle state by "turning on" when the throttle valve 8 is fully closed. It is provided.

Further, the surge tank 9 has the same tank 9
An intake pressure sensor 24 that communicates with the intake air pressure (intake pressure) PiM to detect the intake air pressure (intake pressure) PiM is provided. An intake air temperature sensor 21 is provided in the surge tank 9, and the intake air temperature THA is detected by the intake air temperature sensor 21.

On the other hand, an oxygen sensor 25 for detecting the oxygen concentration OX in the exhaust gas is provided in the middle of the exhaust passage 7. Further, the engine 1 is provided with a water temperature sensor 26 for detecting the temperature (cooling water temperature) THW of the cooling water.

An ignition signal distributed by a distributor 13 is applied to an ignition plug 12 provided for each cylinder of the engine 1. The distributor 13 distributes the high voltage output from the igniter 14 to each of the ignition plugs 12 in synchronization with the crank angle of the engine 1. The ignition timing of each of the ignition plugs 12 is the high voltage output timing from the igniter 14. Is determined by

The distributor 13 is provided with a rotation speed sensor 27 for detecting the rotation speed (engine speed) NE of the engine 1 from the rotation of a rotor (not shown) built in the distributor 13. The distributor 13 is also provided with a crank angle sensor 28 for detecting a change in the crank angle of the engine 1 at a predetermined rate according to the rotation of the rotor.

In addition, a vehicle speed sensor 29 is provided in the automatic transmission 15 which is drivingly connected to the engine 1. The vehicle speed sensor 29 is capable of detecting the vehicle speed (vehicle speed) SPD at that time and outputting a signal indicating the value.

In addition, inside the automatic transmission 15,
A neutral start switch 30 is provided.
The neutral start switch 30 detects that the current shift position ShP is in a neutral range [N range (including P range)]. That is, it is possible to detect whether the current shift position ShP is in the N range or the drive range (D range).

Furthermore, in the present embodiment, a known exhaust gas circulation (EGR) device 16 is provided. The EGR device 16 includes an EGR passage 17 and an EGR valve 18 provided in the passage 17. EG
The R passage 17 is provided so as to connect the intake passage 2 on the downstream side of the throttle valve 8 and the exhaust passage 7. Further, the EGR valve 18 has a valve seat, a valve body, and a step motor (all not shown) built therein. EGR
The opening degree of the valve 18 is changed by the step motor intermittently displacing the valve body with respect to the valve seat. Then, when the EGR valve 18 is opened, a part of the exhaust gas discharged into the exhaust passage 7 flows into the EGR passage 17. The exhaust gas flows into the intake passage 2 via the EGR valve 18. That is, a part of the exhaust gas is generated by the EGR device 1
6 to recirculate into the intake mixture. At this time, EG
The recirculation amount of the exhaust gas is adjusted by adjusting the opening degree of the R valve 18.

In the present embodiment, an intake control valve 19 is provided in the intake passage 2 downstream of the throttle valve 8 between the surge tank 9 and the injector 4 so as to be openable and closable. The intake control valve 19 is provided for each cylinder. Further, the intake control valve 19 can be continuously opened and closed by an actuator 20 (electromagnetic oscillating device, rotary device, etc.) driven by duty control.

Further, in the present embodiment, the exhaust passage 7
A NOx absorption decomposition catalyst 31 is provided midway. The NOx absorption / decomposition catalyst 31 absorbs NOx in the air-fuel ratio lean exhaust gas and releases NOx in the air-fuel ratio rich or stoichiometric exhaust gas. Therefore, NOx
The absorption / decomposition catalyst 31 has a property that the amount of NOx absorbed reaches a saturated state when the air-fuel ratio lean state continues for a long time.

Then, each of the sensors 21, 22, 24 ...
The operating state and the like of the engine 1 are appropriately detected by the engine 29, the idle switch 23, the neutral start switch 30, and the like, and these constitute an operating state detecting means.

Further, each injector 4, the solenoid 11a for the ISCV 11, the igniter 14, the EGR valve 1
8 and the actuator 20 of the intake control valve 19 are electrically connected to an electronic control unit (hereinafter, simply referred to as “ECU”) 41, and their drive timing is controlled by the operation of the ECU 41. The ECU 41 constitutes intake control means, discharge determination means, and valve opening time reduction control means.

The ECU 41 includes the intake air temperature sensor 21, the throttle sensor 22, and the idle switch 2 described above.
3, intake pressure sensor 24, oxygen sensor 25, water temperature sensor 2
6, a rotation speed sensor 27, a crank angle sensor 28, a vehicle speed sensor 29, and a neutral start switch 30 are connected to each other. Therefore, the ECU 41 controls the sensors 21, 22, 24 to 29 and the idle switch 2
3 and the output signal from the neutral start switch 30, etc., the injector 4 and the solenoid 11a.
(ISCV11), igniter 14, EGR valve 18
The actuator 20 (the intake control valve 19) and the like are preferably controlled.

Next, the structure of the ECU 41 will be described with reference to the block diagram of FIG. The ECU 41 includes a central processing unit (CPU) 42, a read-only memory (ROM) 43 in which a predetermined control program, a map, and the like are stored in advance, a CPU 42
A random access memory (RAM) 44 for temporarily storing the calculation results of the above, a backup RAM 45 for storing previously stored data, and the like. The ECU 41
Are the external input circuit 46 and the external output circuit 47
And the like are connected by a bus 48 to constitute a logical operation circuit.

The external input circuit 46 includes the intake air temperature sensor 21, the throttle sensor 22, and the idle switch 2 described above.
3, intake pressure sensor 24, oxygen sensor 25, water temperature sensor 2
6, a rotation speed sensor 27, a crank angle sensor 28, a vehicle speed sensor 29, a neutral start switch 30, and the like are connected to each other. Then, the CPU 42 reads output signals from the sensors 21, 22, 24 to 29, the idle switch 23 and the neutral start switch 30 via the external input circuit 46 as input values. Then, the CPU 42 based on these input values, the injector 4, the solenoid 11a, which is connected to the external output circuit 47,
The igniter 14, the EGR valve 18, the actuator 20 (the intake control valve 19), etc. are suitably controlled. The learning values and flags in this embodiment are stored in the backup RAM 45 described above.

Next, of the processing executed by the ECU 41, the processing contents centering on the opening control of the intake control valve 19 will be described. That is, as described above, the NOx absorption / decomposition catalyst 31 provided in the exhaust passage 7 has a property that the amount of NOx absorbed reaches a saturated state when the air-fuel ratio lean state continues for a long time. . Therefore, in the present embodiment, the following control for releasing NOx is executed before the amount of absorbed NOx reaches the saturation state.

The process for performing the control will be described below with reference to the flowchart of FIG. FIG. 4 is a flowchart showing an “intake control valve control routine” for controlling the intake air control valve 19 executed by the ECU 41 to control the actual air-fuel ratio after the engine 1 is started. It is executed by interruption at the corner.

When the processing shifts to this routine, first, in step 101, the ECU 41 causes the sensors 21
Detection signals (for example, intake pressure PiM, throttle opening TA, intake temperature THA, oxygen concentration OX, cooling water temperature THW, engine speed NE, vehicle speed SPD, shift position ShP, air conditioner operation signal, etc.) and a separate routine Read the flags etc. set in.

Then, in the following step 102,
The lean control flag XFAFL read this time is "1".
Or not. Here, the lean control flag X
FAFL is set in a separate routine, and "1" or "0" is adopted according to the operating state at that time. In other words, if the operating condition at that time does not require the output so much,
The lean control flag XFAFL is set to "1" in order to execute lean control and prioritize improvement of fuel efficiency. On the other hand, when the driving state is such that a high output is requested, the lean control flag XFAFL is set to "0" in order to execute the rich control and give priority to the improvement of the fuel consumption. Then, in step 102, when the lean control flag XFAFL is "0", it is determined that the lean control is not executed at that time. That is, at that time, NOx is not absorbed by the NOx absorption decomposition catalyst 31, and there is no possibility that the amount of NOx absorbed will reach the saturated state, and the routine proceeds to step 107. Then, in step 107, the count value C of the counter is cleared to "0" and the intake control valve 1
The actuator 20 is drive-controlled so that the valve opening timing of No. 9 becomes the normal valve opening timing, and the subsequent processing is once ended.

When the lean control flag XFAFL is "1", lean control is being executed at that time, and it is judged that NOx is absorbed by the NOx absorption decomposition catalyst 31, and the following control is performed. In order to execute, it moves to step 103.

In step 103, the count value C of the counter is incremented by "1". Further, in step 104, it is determined whether or not the count value C of the counter is equal to or greater than a predetermined value (corresponding to a predetermined time) T1 set in advance. Here, predetermined value (predetermined time)
T1 is the NOx absorbed by the NOx absorption decomposition catalyst 31 after the control of the lean air-fuel ratio is started.
Is the time until just before the amount reaches the saturated state, which is a value that is empirically or experimentally determined in advance. Then, if the count value C is equal to or greater than the predetermined value T1, it is assumed that the amount of absorbed NOx may reach the saturated state, and the process proceeds to step 105.

In step 105, the ECU 41
Controls the actuator 20 so as to delay the opening timing of the intake control valve 19. In this way, the intake control valve 1
9 is delayed, the intake control valve 19 is delayed.
The time that is open will be shortened. Then, the intake air amount is temporarily reduced by shortening the opening time of the intake control valve 19. Therefore, the air-fuel ratio is effectively increased, and the NOx absorbed by the NOx absorption / decomposition catalyst 31 until then is released.

Next, in step 106, the count value C is a predetermined value (corresponding to a predetermined time) T2.
It is determined whether or not the above. Here, the predetermined value (predetermined time) T2 is determined based on the period (T2-T1) during which the opening time of the intake control valve 19 is shortened, and the period (T2-T1) is , N that had been absorbed by the NOx absorption decomposition catalyst 31 until then
This is the period necessary for Ox to be sufficiently released by the virtual increase control of the air-fuel ratio. And the count value C
Is greater than or equal to the predetermined value T2, it is determined that the NOx absorbed until then is sufficiently released, and the routine proceeds to step 107. In step 107, the count value C of the counter is cleared to "0", and the actuator 20 is drive-controlled so that the opening timing of the intake control valve 19 becomes the normal opening timing, and the subsequent processing is temporarily terminated. To do.

When the count value C has not reached the predetermined value T2 or more, it is determined that the NOx absorbed by the NOx absorbing / decomposing catalyst 31 has not been fully released, and the routine proceeds to step 101. And transition. Then, the above-described processing is repeated until the count value C becomes equal to or larger than the predetermined value T2 or the control of the air-fuel ratio lean ends (the lean control flag XFAFL becomes “0”).

As described above, in the "intake control valve control routine", the lean control flag XFAFL is "1", that is, the air-fuel ratio lean control is executed, and when it is continued for a predetermined time, , Intake control valve 1
The valve opening time of 9 is shortened by a predetermined period.

As described above, according to the present embodiment, the NOx absorption / decomposition catalyst 31 absorbs NOx in the exhaust gas having a lean air-fuel ratio. In addition, the NOx absorption decomposition catalyst 3
In No. 1, NOx is released in the air-fuel ratio rich or stoichiometric exhaust gas. Now, the operation with lean air-fuel ratio is continued,
If the state is maintained as it is, the amount of NOx absorbed by the NOx absorption decomposition catalyst 31 reaches a saturated state. However, in the present embodiment, it is determined that the NOx needs to be released before the amount of NOx absorbed by the NOx absorption decomposition catalyst 31 reaches saturation (steps 102 to 104). And the ECU
When it is determined by 41 that NOx needs to be released, the actuator 20 is controlled and the valve opening time of the intake control valve 19 is shortened.

For this reason, the intake air amount is reduced by shortening the opening time of the intake control valve 19, and even if the fuel injection amount is not increased, the actual air-fuel ratio is up to that (lean state). ) Will be richer than.
Therefore, there will be unburned gas in the exhaust gas,
NO absorbed up to that time by the NOx absorption decomposition catalyst 31
The x and the hydrocarbon in the unburned gas react in the exhaust passage 7. By this reduction reaction, NOx is reduced to nitrogen gas or the like, and as a result, the absorbed NOx is released.

In purifying the NOx absorption / decomposition catalyst 31, the actual air-fuel ratio may be rich even if the fuel injection amount is not increased. Therefore, it is possible to prevent the output from rapidly increasing due to the sudden increase in the fuel injection amount. Therefore, torque shock can be suppressed. At the same time, the torque shock can be suppressed without performing the ignition timing retard control that has been considered in the prior art, so that the exhaust temperature can be prevented from rising. Therefore, it is possible to prevent the NOx absorption decomposition catalyst 31 from being heated by the rise in the exhaust temperature. As a result, it is possible to prevent the deterioration of the NOx absorption decomposition catalyst 31 from being promoted, and it is possible to extend the life of the catalyst 31.

Further, in this embodiment, since it is not necessary to control the ignition timing retard, it is possible to suppress an increase in the required voltage of the ignition system. Therefore, the consumption of the electrode of the spark plug 12 can be reduced, and the situation where the life of the plug 12 is shortened can be avoided.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. However, since the configuration and the like of the present embodiment are almost the same as those of the above-described first embodiment, the same members and the like are denoted by the same reference numerals and description thereof is omitted. The following description focuses on the differences from the first embodiment.

This embodiment differs from the first embodiment in that the control of the fuel injection amount TAU is also executed in order to suppress the torque shock more reliably. Then, next, the content of the control will be described with reference to the flowchart of FIG.

FIG. 5 shows EC during operation of the engine 1.
It is a flow chart which shows an "intake control valve control routine" performed by U41, and is performed by interruption at a predetermined crank angle.

When the processing shifts to this routine, first in step 201, the ECU 41 causes the sensors 21
The detection signals and flags from 30 to 30 are read. In the following step 202, similarly to the first embodiment, it is determined whether or not the lean control flag XFAFL read this time is "1". Then, in step 202, when the lean control flag XFAFL is "0",
At that time, it is determined that the lean control is not executed, and the process proceeds to step 209. And step 20
At 9, the count value C of the counter is cleared to "0", and the actuator 20 is drive-controlled to set the opening timing of the intake control valve 19 to the normal opening timing, and the subsequent processing is temporarily terminated.

Further, when the lean control flag XFAFL is "1", lean control is being executed at that time, and it is judged that NOx is absorbed by the NOx absorption decomposition catalyst 31, and the following control is performed. In order to execute, it moves to step 203.

In step 203, the count value C of the counter is incremented by "1". In step 204, it is determined whether the count value C of the counter is equal to or larger than the predetermined value T1. And
If the count value C is greater than or equal to the predetermined value T1,
As it is, it is assumed that the amount of NOx absorbed may reach the saturated state, and the routine proceeds to step 205 to control the air-fuel ratio to the stoichiometric state.

In step 205, the ECU 41
When the air-fuel ratio is stoichiometric, the target intake air amount QA that has the same torque as the current state is calculated. This target intake air amount QA
When calculating, for example, a map in which the target intake air amount QA with respect to the engine speed NE and the intake pressure PiM at that time is predetermined is referred to.

Next, at step 206, assuming that the intake air amount becomes the target intake air amount QA calculated this time, the target injection amount T for making the air-fuel ratio stoichiometric.
AU is calculated. Then, the injector 4 is controlled based on the target injection amount TAU to control the fuel injection amount.

Further, in the following step 207, the opening timing of the intake control valve 19 is calculated so that the actual intake air amount becomes the target intake air amount QA calculated this time.
Of course, the valve opening timing calculated here is set to be later than that as described in the first embodiment, and the valve opening time of the intake control valve 19 is shortened as compared with that. Become.

Then, in step 208, the count value C of the counter is the same as in the case of the first embodiment.
It is determined whether or not it is equal to or larger than the predetermined value T2. Then, when the count value C is equal to or greater than the predetermined value T2, it is determined that the NOx absorbed up to that point has been sufficiently released, and the process proceeds to step 209. In step 209, the count value C of the counter is set to "0".
At the same time, the actuator 20 is driven and controlled so that the opening timing of the intake control valve 19 becomes the normal opening timing, and the subsequent processing is temporarily terminated.

When the count value C has not reached the predetermined value T2 or more, it is determined that the NOx absorbed by the NOx absorption / decomposition catalyst 31 has not been fully released, and the routine proceeds to step 201. And transition. Then, the above-described processing is repeated until the count value C becomes equal to or larger than the predetermined value T2 or the control of the air-fuel ratio lean ends (the lean control flag XFAFL becomes “0”).

As described above, in the "intake control valve control routine", the lean control flag XFAFL is "1", that is, the air-fuel ratio lean control is executed, and when it is continued for a predetermined time, , Intake control valve 1
The valve opening time of 9 is shortened by a predetermined period. However, in the present embodiment, the intake control valve 1 is set so that the air-fuel ratio becomes stoichiometric.
The valve opening time of 9 is shortened by a predetermined period. Further, by shortening the opening time of the intake control valve 19, the fuel injection amount is controlled so that torque shock is not generated as much as possible.

As described above, according to the present embodiment, basically the same operational effects as those of the above-described first embodiment are obtained. In addition to the above-described effects, in the present embodiment, when the NOx absorbed by the NOx absorption decomposition catalyst 31 is released, the air-fuel ratio is controlled to be stoichiometric. Further, when the air-fuel ratio is stoichiometric, the target intake air amount QA should be the same as the current torque.
Is set, and the fuel injection amount control is executed based on the target intake air amount QA. Therefore, when performing the control for shortening the valve opening time of the intake control valve 19, there is almost no change in the output, and the occurrence of torque shock can be suppressed more reliably.

The present invention is not limited to the above embodiments, but may be configured as follows, for example. (1) In each of the above-described embodiments, the opening time of the intake control valve 19 is delayed so that the opening time of the intake control valve 19 is shortened. On the other hand, by advancing the closing timing of the intake control valve 19, the intake control valve 19
The control for shortening the valve opening time may be performed.

(2) In each of the above-described embodiments, particularly the second embodiment, the intake control valve 19 is controlled to be shortened so that the lean state is changed to the stoichiometric state. However, as long as the torque shock does not occur so much, it can be embodied in the case where the actual air-fuel ratio temporarily becomes rich.

(3) In each of the above embodiments, the gasoline engine 1 is embodied as the internal combustion engine, but a vehicle equipped with a diesel engine may be embodied.

The technical idea which is not described in the claims of the present invention and which can be understood from the above-mentioned embodiment will be described below together with its effect. (A) In the intake control device for an internal combustion engine according to claim 1, when the air-fuel ratio is substantially rich or stoichiometric by the valve opening time shortening control means, an output substantially equal to that up to that time is obtained. The intake air amount calculating means for calculating the intake air amount, and the fuel injection amount for substantially making the air-fuel ratio rich or stoichiometric, based on the intake air amount calculated by the intake air amount calculating means. An injection amount control control unit that executes fuel injection amount control based on the calculated fuel injection amount; and a valve opening time reduction control unit that is controlled based on the intake air amount calculated by the intake air amount calculation unit. And an opening / closing timing calculation means for calculating the opening / closing timing of the intake control valve.

With this structure, when the intake valve is opened for a shorter period of time, the torque shock can be more reliably suppressed with almost no output fluctuation.

[0064]

As described in detail above, according to the present invention,
In an intake control device for an internal combustion engine, which has an intake control valve provided in an intake passage corresponding to each cylinder of the internal combustion engine and a NOx absorption decomposition catalyst in the exhaust passage, separately from the throttle valve. , NO if necessary
The excellent effect that not only the function of the catalyst can be effectively exhibited by purifying the x-absorption decomposition catalyst, but also the torque shock at the time of purification can be reduced and the functional deterioration due to the deterioration of the catalyst can be suppressed. Play.

[Brief description of the drawings]

FIG. 1 is a conceptual configuration diagram illustrating a basic conceptual configuration of the present invention.

FIG. 2 is a schematic configuration diagram showing an intake control device for an engine according to the first embodiment.

FIG. 3 is a block diagram showing an electrical configuration of an ECU and the like.

FIG. 4 is a flowchart showing an “intake control valve control routine” executed by the ECU.

FIG. 5 is a flowchart showing an “intake control valve control routine” according to the second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine as an internal combustion engine, 1a ... Combustion chamber, 2 ... Intake passage, 5 ... Intake valve, 7 ... Exhaust passage, 8 ... Throttle valve, 19 ... Intake control valve, 20 ... Actuator,
21 ... Intake air temperature sensor which constitutes an operating state detecting means, 22
... Throttle sensor constituting operation state detecting means, 23
... Idle switch that constitutes an operating state detecting means, 24
Intake pressure sensor that constitutes the operating state detecting means, 25 ... Oxygen sensor that constitutes the operating state detecting means, 26 ... Water temperature sensor that constitutes the operating state detecting means, 27 ... Rotation speed sensor that constitutes the operating state detecting means, 28 ... a crank angle sensor that constitutes the operating state detecting means, 29 ... a vehicle speed sensor that constitutes the operating state detecting means, 30 ... a neutral start switch that constitutes the operating state detecting means, 31 ... NOx absorption decomposition catalyst, 41 ... intake control means, An ECU that constitutes a release determination means and a valve opening time reduction control means.

Claims (1)

[Claims] 1. An intake valve which is driven at a predetermined timing in synchronization with rotation of an internal combustion engine to open and close an intake passage communicating with a combustion chamber, a throttle valve provided in the middle of the intake passage, and a throttle valve of the throttle valve. On the downstream side, an intake control valve provided in the intake passage, an actuator for opening and closing the intake control valve, an operating state detecting means for detecting an operating state of the internal combustion engine, and a detection by the operating state detecting means. Based on the results, the intake control means for controlling the actuator and the exhaust passage communicating with the combustion chamber are provided in the middle of the exhaust passage, and absorb NOx in the exhaust air having a lean air-fuel ratio and emit NOx in the exhaust gas having a rich air-fuel ratio or stoichiometry. An intake air control device for an internal combustion engine, comprising an NOx absorption / decomposition catalyst that releases the amount of NOx absorbed by the NOx absorption / decomposition catalyst. A release determination unit that determines that the NOx needs to be released before reaching saturation, and a valve opening time of the intake control valve when the release determination unit determines that the NOx needs to be released. And a valve opening time shortening control means for controlling the actuator so as to shorten the intake air intake control device for an internal combustion engine.