JPH06200739A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce the consumption of a reducing agent without causing a speed reducing shock at the time of regeneration of an NOx absorbent disposed at the exhaust passage of a diesel engine. CONSTITUTION:An Nox absorbent 15 is disposed at the exhaust pipe 3 of a diesel engine 1, and a reducing agent is supplied from a reducing agent feeder 11 to perform the regeneration of the Nox absorbent 15. The intake pipe 2 of the diesel engine 1 is provided with an intake shutter valve 6, and the intake air quantity is throttled at the regenerating operation time of the NOx absorbent so as to reduce the exhaust flow flowing into the Nox absorbent, thereby reducing the consumption of the reducing agent. The intake shutter valve 6 is controlled in such a way that the throttle quantity is larger in the case of braking operation being performed than the case of no braking operation being performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine, and more particularly to N in exhaust gas of a diesel engine.
The O _X on the Effective removable exhaust gas purification device.

[0002]

BACKGROUND OF THE INVENTION engine exhaust passage, the exhaust air-fuel ratio is absorbed NO _X when the lean, the oxygen concentration in the exhaust gas arranged _the NO _X absorbent to release the NO _X absorbed and reduced, the exhaust air-fuel ratio the NO _X in the exhaust gas in a lean state with is absorbed in the NO _X absorbent to release the NO _X which the exhaust air-fuel ratio was absorbed in the rich or stoichiometric air-fuel ratio at every predetermined period of time has elapsed from _the NO _X absorbent, purifies exhaust A purification device has already been proposed by the applicant of the present application. (See Japanese Patent Application No. 3-281907).

In this exhaust emission control device, the operating air-fuel ratio of the engine (the air-fuel ratio of combustion in the combustion chamber) is switched between lean and rich (or stoichiometric air-fuel ratio) so that N
The above-mentioned NO _X absorption and release action of the O _X absorbent is controlled. On the other hand, when the above NO _x absorbent is used in an engine such as a diesel engine that is always operated at a lean air-fuel ratio and the operating air-fuel ratio of the engine cannot be freely switched to lean and rich, instead of switching the operating air-fuel ratio to the rich, and introducing a reducing agent to the NO _X absorbent during the operation, together with lowering the atmospheric oxygen concentration of the NO _X absorbent to consume oxygen in the exhaust, released from _the NO _X absorbent It is necessary to reduce the generated NO _x . Further, when performing the above-mentioned NO _X release and reduction purification operation (hereinafter referred to as “regeneration”) while the exhaust gas is flowing through the NO _X absorbent, the amount of the reducing agent for consuming oxygen in the exhaust gas is extremely low. larger for the, in these cases, for example, an intake shutter valve or exhaust shutter valve in the engine intake passage and an exhaust passage provided by means such as closing the shutter valve during an engine braking, the NO _X absorbent The flow rate of the inflowing exhaust gas is reduced to reduce the amount of reducing agent consumed during regeneration of the NO _x absorbent.

[0004]

As described above, NO _X
When performing the regeneration by introducing the reducing agent while the exhaust gas is flowing to the absorbent, the smaller the amount of the exhaust gas flowing into the NO _x absorbent during the regeneration operation, the more necessary it is to consume the oxygen in the exhaust gas. The amount of reducing agent can be reduced. Therefore, in order to reduce the consumption of the reducing agent, it is desirable to increase the closing amount (throttle amount) of the shutter valve as much as possible during the regeneration operation of the NO _x absorbent. However, if the intake shutter valve or the exhaust shutter valve is set to an excessively large amount during engine braking, deceleration torque more than expected by the driver will be generated during engine braking, and the deceleration shock will increase and the driving sensation will increase. It causes problems that get worse. When reducing the exhaust flow rate by using the intake shutter valve, if the throttle amount of the intake shutter valve is large, the negative pressure of the intake manifold will increase, which will increase the cylinder negative pressure in the intake stroke and increase the cylinder negative pressure. Due to the pressure, the lubricating oil enters between the piston ring and the cylinder wall into the combustion chamber, which causes a problem of increasing the lubricating oil consumption.

In view of the above problems, the present invention makes it possible to reduce the consumption of the reducing agent by using the shutter valve without deteriorating the driving feeling during regeneration of the NO _X absorbent and increasing the consumption of the lubricating oil. The present invention relates to an exhaust emission control device for an internal combustion engine.

[0006]

According to Means for Solving the Problems] The present invention, in an exhaust passage of a diesel engine for a vehicle, when the air-fuel ratio of the inflowing exhaust absorbs NO _X when the lean, the oxygen concentration of the inflowing exhaust drops the _the NO _X absorbent to release the absorbed NO _X is arranged, to absorb NO _X in the exhaust gas to the _the NO _X absorbent, the exhaust by introducing a reducing agent into the _the NO _X absorbent at a predetermined operating conditions in the exhaust purification system of an internal combustion engine to reduce and purify the released NO _X with the release of NO _X absorbed from _the NO _X absorbent to reduce the oxygen concentration, said closed to the predetermined opening degree at the time of the reducing agent introducing NO _X throttle valve means for reducing the flow rate of exhaust gas flowing into the absorbent, means for detecting the presence or absence of the brake operation of the vehicle driver when introducing the reducing agent, and the brake operation detected when the brake operation is detected If not Compared to an exhaust purification system of an internal combustion engine, characterized in that a control means for reducing the opening degree of the throttle valve means.

[0007]

When the driver does not perform the brake operation during the NO _X absorbent regeneration operation, the throttle valve means is closed to a predetermined opening to reduce the exhaust flow rate flowing into the NO _X absorbent. When the driver is operating the brake, the throttle valve means is throttled more than when the driver is not operating the brake, thereby further reducing the flow rate of exhaust gas. When the brake operation is not performed, the throttle of the throttle valve is relatively small even when the NO _x absorbent is regenerated, and a large deceleration torque shock and an increase in lubricating oil consumption do not occur. When the driver is operating the brake, the throttle valve means is throttled more than in the normal regeneration operation, and the exhaust flow rate is further reduced, so that the reducing agent consumption is reduced. When the driver is operating the brake, the driver needs a large deceleration torque.Therefore, a deceleration shock due to an increase in the throttle amount of the throttle valve is expected to some extent, and the driver's feeling deteriorates. Absent.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing the configuration of an embodiment of an exhaust gas purification apparatus for an internal combustion engine of the present invention. In FIG. 1, 1
Is a diesel engine, 2 is an engine intake pipe, and 3 is an engine exhaust pipe. NO _x absorbent 15 in the exhaust pipe 3
Is connected to the casing, and the exhaust pipe 3 upstream of the NO _x absorbent 15 is provided with a reducing agent supply device described later. Further, in this embodiment, N is set at the time of reproduction operation.
In order to reduce the flow rate of exhaust flowing into the O _x absorbent 15,
A shutter valve 6 is provided in the intake pipe 2 of the engine. As will be described later, the shutter valve 6 is kept fully open during normal operation of the engine and does not generate intake resistance, but is closed to a predetermined opening when the NO _X absorbent 15 is regenerated, and the intake pipe 2 is throttled to intake the engine. The amount of air, that is, the flow rate of exhaust gas flowing into the NO _X absorbent 15 is reduced.

The reducing agent supply device 11 includes a NO _x absorbent 15
Is provided with an injection valve 11a for injecting a reducing agent into the exhaust pipe 3 on the upstream side of the engine, and the engine control unit (ECU) 10 described later
The exhaust pipe 3 is supplied with a predetermined flow rate of reducing agent according to the input signal from
Inject into. Any reducing agent may be used as long as it generates a reducing component such as hydrocarbon or carbon monoxide in the exhaust gas, and a reducing gas such as carbon monoxide or hydrogen, or a carbonization of liquid or gas such as propane, propylene or butane. Liquid fuels such as hydrogen, gasoline, light oil, and kerosene can be used.

Reference numeral 10 in the drawing denotes an electronic control unit (ECU) of the engine 1. ECU10 is CPU, RA
An M, a ROM, an input port, and an output port are connected to each other by a bidirectional bus. The digital computer is configured to perform basic control such as fuel injection amount control of the engine, and in this embodiment, injection of the reducing agent injection valve 11a. The control and open / close control of the intake shutter valve 6 are performed. For these controls, a brake switch 12 for detecting a driver's operation of a brake pedal is provided at an input port of the ECU 10.
In addition to inputting signals from the sensors, signals such as engine speed, accelerator opening, and exhaust temperature are input from sensors not shown.

The NO _x absorbent 15 uses, for example, alumina as a carrier, and potassium K, sodium Na, etc. are provided on the carrier.
, Lithium Li, alkali metals such as cesium Cs, alkaline earths such as barium Ba and calcium Ca, rare earths such as lanthanum La and yttrium Y, and a noble metal such as platinum Pt. Has been done. This _the NO _X absorbent 15 absorbs NO _X in the case the air-fuel ratio of the exhaust gas flowing is lean, the oxygen concentration is carried out to absorbing and releasing action of the NO _X that releases NO _X when lowered.

Incidentally, the above-mentioned exhaust air-fuel ratio means here N
The exhaust passage on the upstream side of the O _X absorbent 15 and the engine combustion chamber,
It means the ratio of the total amount of air and the total amount of fuel supplied to the intake passage and the like. Accordingly, exhaust air-fuel ratio when the fuel or reducing agent or air is not supplied to the upstream side exhaust passage of the NO _X absorbent 15 becomes equal to the operating air-fuel ratio of the engine (air-fuel ratio in the combustion in the engine combustion chamber).

In this embodiment, since the diesel engine is used, the exhaust air-fuel ratio during normal operation is lean, and the NO _X absorbent 15 absorbs NO _{X in} the exhaust.
Further, when the reducing agent is introduced into the exhaust gas and the oxygen concentration is lowered by the operation described later, the NO _x absorbent 15 releases the absorbed reducing agent. There are some points where the detailed mechanism of this absorption / release action is not clear. However, it is considered that this absorbing / releasing action is performed by the mechanism shown in FIG. Next, this mechanism will be described by taking as an example the case where platinum Pt and barium Ba are supported on a carrier, but the same mechanism can be obtained by using other noble metals, alkali metals, alkaline earths and rare earths.

That is, the inflow exhaust becomes considerably lean.
And the oxygen concentration in the exhaust gas increased significantly, as shown in Figure 2 (A).
As these oxygen O₂Is O₂ ^-Or O^2-In the form of
It adheres to the surface of platinum Pt. On the other hand, the NO in the exhaust gas is
This O on the surface of platinum Pt₂ ^-Or O^2-Reacts with N
O₂Becomes (2NO + O₂→ 2 NO₂ ). Then generated
NO₂Part of the inside of the absorbent while being oxidized on platinum Pt
2 while being absorbed by and bound to barium oxide BaO.
As shown in (A), nitrate ion NO₃ ^-Absorbent in the form of
Diffuse in. NO in this way_XIs NO_XAbsorbent 1
Absorbed within 5.

Therefore, NO ₂ is produced on the surface of platinum Pt as long as the oxygen concentration in the inflowing exhaust gas is high, and NO ₂ is absorbed in the absorbent and nitrate ion NO ₃ unless the NO _X absorption capacity of the absorbent is saturated. ^- is generated. In contrast the oxygen concentration decreases and the amount of NO ₂ is reduced by reaction backward in the inflowing exhaust gas (NO ₃ ^- → NO ₂₎ proceeds to thus of the absorbent and nitrate ions NO ₃ ^- is NO ₂ Is released from the absorbent in the form of. Namely, when the oxygen concentration in the inflowing exhaust gas is released NO _X from _the NO _X absorbent 15 when lowered.

On the other hand, if reducing components such as HC and CO are present in the inflowing exhaust gas, these components are oxygen O ₂ on platinum Pt.
^- or it is reacted with oxide and O ^2-, lowering the oxygen concentration in the exhaust to consume oxygen in the exhaust. Further, the NO released from the NO _X absorbent 15 due to the decrease in the oxygen concentration in the exhaust gas.
₂ is reduced by reacting with HC and CO as shown in Fig. 2 (B). When NO ₂ is no longer present on the surface of platinum Pt in this manner, NO ₂ is released from the absorbent one after another. Accordingly HC in the inflowing exhaust gas, NO _X from _the NO _X absorbent 15 in a short time when the CO component is present is released,
Will be reduced.

That is, HC and CO in the inflowing exhaust gas first react with O ₂ ⁻ or O ²⁻ on platinum Pt immediately to be oxidized, and then O ₂ ⁻ or O ²⁻ on platinum Pt are consumed. the HC, NO _X discharged from the released NO _X and the engine from the absorbent by CO is reduced even yet HC, any remaining CO is. Therefore, while the engine is operating, NO
_X emissions, the amount of reduction (regeneration) reducing agent to be supplied to _the NO _X absorbent in order to perform the required to reduce sufficiently the oxygen concentration in the exhaust gas by the oxygen consumption by oxidation on the platinum Pt This is the sum of the amount and the amount required to reduce the total NO _x released from the NO _x absorbent 15. However, in diesel engines, the air-fuel ratio of the exhaust is always lean, so
_The NO _X absorbent 15 release of the NO _X while flowing exhaust, and if you try to reducing the amount of reducing agent to consume the oxygen in the exhaust gas becomes very large. Therefore, in this embodiment, when the NO _x absorbent 15 is regenerated, the intake shutter valve 6 provided in the intake pipe 2 is closed to reduce the flow rate of the exhaust gas flowing into the NO _x absorbent 15 to reduce oxygen consumption in the exhaust gas. It reduces the amount of reducing agent used.

FIG. 3 shows the structure of the intake shutter valve 6 used in this embodiment. The intake shutter valve 6 of this embodiment includes a main valve 61 and a sub valve 6.
2 and. That is, in this embodiment, the intake pipe 2 of the engine 1 is divided into the main intake passage 21 and the sub intake passage 22, and the main valve 61 is provided in the main intake passage 21.
However, the sub valves 62 are arranged in the sub intake passages 22, respectively.

The main valve 61 operates in conjunction with the accelerator pedal, and is fully closed to close the main intake passage 21 when the driver is not operating the accelerator pedal (not stepping on it). Further, the sub-valve 62 is provided with a negative pressure actuator 63. The negative pressure actuator 63 includes two diaphragms 63a and 63b connected to the sub-valve 62 via a link 64c, and working chambers 64a and 64b formed on one side of the diaphragms 63a and 63b. Pressure switching valve (VSV1, V
The negative pressure from a negative pressure source such as a vacuum pump (not shown) and the atmospheric pressure can be selectively supplied via SV2). The VSV1 and VSV2 are, for example, solenoid-operated three-way valves, and switch between the supply of negative pressure and the supply of atmospheric pressure to the working chambers 64a and 64b, respectively, according to the signal from the ECU 10 described above.

VSV1 and VSV2 are operating chambers 64a and 64 of the actuator 63 during normal operation (when the solenoid is destaticizing).
b to communicate with the atmosphere, and the diaphragms 63a, 6a
Since 4b is pressed by the spring 64d to assume the position shown in FIG. 3A, the sub valve 62 is held fully open. When the VSV1 solenoid is energized by a signal from the ECU 10, negative pressure is supplied only to the working chamber 64a of the actuator 63, and the diaphragms 63a and 63b move to the right to take the positions shown in FIG. 3 (B). Therefore, the sub valve 62 is held half open. Further, when the VSV2 solenoid is energized by a signal from the ECU 10, a negative pressure is also supplied to the working chamber 64b, so that the diaphragms 63a and 63b.
Moves further to the right to take the position shown in FIG. 3C, and the sub-valve 62 is held fully closed.

In the present embodiment, as described above, the main valve 61 of the intake shutter valve 6 is always fully closed to block the main intake passage when the driver is not operating the accelerator, that is, at the time of engine braking. It is designed to increase resistance and increase the effectiveness of engine braking. On the other hand, the sub-valve 62 does not operate only by the engine brake, but closes only when the NO _x absorbent 15 regeneration condition is satisfied. Further, during operation, the opening degree of the sub valve 62 is controlled in two steps depending on whether or not the driver operates the brake pedal.

FIG. 4 is a flow chart showing a regenerating operation of the NO _X absorbent 15. This routine is executed by the ECU 10 at regular intervals. When the routine starts in FIG. 4, at step 401, it is judged if the condition for executing the regeneration of the NO _X absorbent is satisfied. Where NO
_The conditions for executing the regeneration of the _X absorbent are (1) the driver does not operate the accelerator, and the engine speed is equal to or higher than a predetermined value (that is, the engine is in a brake state), (2) the engine it exhaust temperature is equal to or greater than a predetermined value, only the step 403 if (3) the NO _X absorption of the NO _X absorbent is equal to or greater than a predetermined value, a is the above conditions are satisfied for all 413 Playback operation is performed. The NO _x absorbent is regenerated only during engine deceleration (condition (1) above). During regeneration, it is necessary to close the intake shutter valve to reduce the intake air amount as described later, so regeneration is performed during normal operation. This is because torque shock will occur and the drivability will deteriorate. Further, the reason why the exhaust gas temperature is equal to or higher than the predetermined value (the above-mentioned condition (2)) is that the NO _X absorbent must reach the activation temperature at which the NO _X release and the reducing action are activated. Further, when the NO _X absorption of the NO _X absorbent that is equal to or higher than a predetermined value (the condition (3)) required to reproduce execution conditions are you doing truly reproduced avoiding frequent regeneration operations This is because only the reproduction operation is performed.

[0023] Incidentally, NO _X absorption of the NO _X absorbent, separately by a routine executed by the ECU 10, for example, advance the engine load emissions of the NO _X from the engine per unit time (accelerator opening) and the engine rotational It is stored in the ROM of the ECU 10 as a function of the number, etc., and NO _{x is} calculated by the above function from the accelerator opening and the rotational speed at regular intervals.
Calculated emissions, this is determined by integrating the multiplied by the constant factor as NO _X absorption of _the NO _X absorbent in said predetermined time.

When the NO _x absorbent regeneration execution condition is not satisfied in step 401, steps 417 to 420
Is executed, the counter C is reset (step 417), both VSV1 and VSV2 are communicated with the atmosphere, and the sub valve 62 is held fully open (FIG. 3 (A)).
At the same time (step 419), the injection valve 11a of the reducing agent supply device 11 is closed and the supply of the reducing agent is stopped (step 420).

If the NO _X absorbent regeneration execution condition is satisfied at step 401, the routine proceeds to step 403, where the counter C is incremented by one. The counter C is a counter indicating the time when the reproducing operation is continuously executed. Next, at step 405, it is judged from the signal from the brake switch 12 whether or not the driver is performing the brake operation. If the brake operation is not performed, step 407 is executed and only the negative pressure switching valve VSV1 is energized. It As a result, the sub valve 62 is shown in FIG.
Close the valve until it is half open. For this reason, the intake air amount is throttled compared to the normal engine braking state, but since the throttle amount is small, a deceleration shock does not occur and the lubricating oil consumption amount does not increase due to a rise in the negative pressure of the intake manifold. Further, in step 409, the reducing agent in an amount corresponding to the half-open state of the sub valve 62 is supplied from the injection valve 11a to the NO _X absorbent 15, and the NO _X absorbent is regenerated.

If it is determined in step 405 that the driver is operating the brake, the process proceeds from step 405 to step 411, and the negative pressure switching valves VSV1 and VSV are selected.
Both 2 are energized. As a result, the sub valve 62 is fully closed as shown in FIG. 3C, and the intake air amount is further reduced. Further, in step 413, the reducing agent supply device 1
The reducing agent supply amount from the injection valve 11a of No. 1 is the sub valve 62.
Is reduced corresponding to the fully closed state of.

Step 415 shows the judgment of the end time of the reproduction operation. The reproduction operation ends after a predetermined time has elapsed from the start. In step 415, when reproduction is started (step 40
It is judged from the value of the counter C whether or not a predetermined time has passed from 1). If C is equal to or _larger than the predetermined value C ₀ , it is judged that the reproducing operation is completed, steps 417 to 420 are executed, and the routine is ended. To do.

FIG. 5 shows the sub valve 6 according to the above routine.
5A and 5B are timing charts showing changes in the opening of the vehicle. FIG. 5A shows a change in vehicle speed, FIG. 5B shows a signal output from the brake switch 12, and FIGS. 5C and 5D show a main valve 61. , The change in the opening degree of the sub valve 62 is shown with respect to time (horizontal axis). In FIG. 5, section I shows a normal engine braking operation. In this section, the NO _x absorbent regeneration execution condition (FIG. 4, step 401) is not satisfied,
The main valve 61 is fully closed (FIG. 5 (C)), while the sub valve 62 is kept fully open (FIG. 5 (D)). Section II shows a case where the regeneration execution condition of the NO _X absorbent is satisfied during engine braking. Since the brake operation is not performed in this section (FIG. 5 (B)), the sub valve 62 is in a half-open state at the same time when the engine braking is started (FIG. 3 (B)).
Is closed until. As described above, in this state, the decrease in the intake air amount is not so large, so a deceleration shock that deteriorates the driving sensation and an increase in the intake manifold negative pressure that increases the lubricating oil consumption do not occur.

Next, section III shows the case where the driver operates the brakes in the state of section II. In this case, since the sub-valve 62 is fully closed, the intake air amount is greatly reduced and a deceleration shock occurs. However, since the driver is operating the brake and fully anticipates deceleration, this deceleration shock is generated. Will not worsen the driving sensation. Further, if the sub-valve 62 remains fully open before the sub-valve 62 is fully closed, the rise in intake manifold negative pressure when the sub-valve is fully closed is moderated, so that the consumption of lubricating oil is significantly increased. Is prevented.

FIG. 6 shows changes in the intake manifold negative pressure in the sections II and III. The solid line in Fig. 6 shows the case where the sub-valve 62 is fully closed after being held in the half-open state (section II).
(Section III), and the dotted line in FIG. 6 shows the case where the sub-valve 62 is fully closed immediately without being held in the half-opened state. As can be seen from Fig. 6, when the sub-valve is kept fully open for a certain period of time and then fully closed (solid line), the maximum negative pressure rise in the intake manifold becomes smaller than when the sub-valve is fully closed from the beginning, and the lubrication It does not reach the level at which oil consumption will increase significantly. Depending on the operating conditions, N
It is possible that the driver performs a braking operation at the same time when engine braking is started due to a sudden deceleration during regeneration of the O _X absorbent. In this case, however, the driver is requesting a rapid deceleration. Since driving safety is prioritized over oil consumption, there is no problem even if the sub-valve is fully closed at the same time as the brake operation.

Further, section IV in FIG. 5 shows the case where the brake operation is released in the state of section III. In this case, the sub-valve 62 is returned to the half-opened state, so that it is possible to prevent a problem that the engine torque suddenly increases and the driving feeling is deteriorated when the sub-valve is fully opened after the engine brake is released. Incidentally, when the reproduction of the NO _X absorbent is completed during braking operation the sub-valve 62 will be moving to the fully open state from the fully closed state, there is a possibility of causing a torque shock, the duration of braking is NO _X probability reproduction operation is completed in _the nO _X absorbent in short order during the braking operation compared to the playback time of the absorbent is relatively small, does not become a practical problem.

As described above, according to this embodiment, when the intake shutter valve 6 is closed and the intake air amount of the engine is reduced to reduce the flow rate of exhaust gas flowing into the NO _X absorbent, the driver's brake operation is performed. By changing the opening degree of the shutter valve 6 depending on the presence or absence of the above, it is possible to reduce the reducing agent consumption while preventing the deterioration of the driving feeling and the increase of the lubricating oil consumption due to the deceleration shock.

In the above embodiment, the negative pressure switching valve VS is used.
Since the diameters of V1 and VSV2 are set sufficiently large, the sub-valve 62 moves to the half-open or fully-closed position almost at the same time as the switching operation of VSV1 and VSV2.
By narrowing the diameter of VSV2 appropriately, the working chamber 64a,
It is also possible to change the closing speed of the sub-valve 62 by changing the decreasing speed of the pressure in 64b.

FIG. 7 is a view similar to FIG. 5D showing the case where the closing speed of the sub-valve 62 is changed. The section a in FIG. 7 shows a state in which only VSV1 is energized. In this case, since the pressure of only the working chamber 64a of the actuator 63 gradually decreases through VSV1, the sub-valve 62 closes at a relatively moderate speed. Speak. Also,
Section b in FIG. 7 shows the case where VSV2 is further energized from this state. In this state, in addition to the working chamber 64a, the working chamber 6
Since the pressure of 4b also decreases, the diaphragms 63a, 63
The force acting on b is increased, and the closing speed of the sub valve 62 is increased. In addition, VSV1 is shown by a dotted line in section b in FIG.
The figure shows the case where only the energized state continues, and the sub-valve 62 shifts to the half-open state at a relatively slow speed. By adjusting the closing speed of the sub-valve 62 in this way, it is possible to mitigate a deceleration shock when the sub-valve 62 is fully closed and a sudden increase in negative pressure of the intake manifold.

Further, in the above embodiment, the NO _x absorbent 1
The case where the intake shutter valve 6 is provided in the intake pipe 2 of the engine 1 as a means for reducing the exhaust flow rate flowing into the absorbent during the regeneration operation of No. 5 has been described, but instead of providing the intake shutter valve as a means for reducing the exhaust flow rate. As shown in FIG. 8, the exhaust shutter valve 7 may be provided in the exhaust pipe 3 upstream of the injection valve 11a of the NO _x absorbent 15 and the reducing agent supply device 11. Also in this case, the exhaust shutter valve 7 is held half-opened or fully-closed in accordance with the regeneration execution condition of the NO _x absorbent and the driver's braking operation as in the case of the sub-valve 62 of the intake shutter valve 6. The same effect as can be obtained. Further, when the exhaust shutter valve 7 is used, the problem of increase in lubricating oil consumption due to increase in intake manifold negative pressure, unlike the case of the intake shutter valve, does not occur even in the case of sudden deceleration.

[0036]

As described above, the exhaust gas purifying apparatus of the present invention is regenerated without deteriorating the driving feeling and increasing the consumption of lubricating oil due to the deceleration shock during the regeneration operation of the NO _X absorbent. It is possible to reduce the amount of reducing agent consumed during operation.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an embodiment of the present invention.

FIG. 2 is a diagram illustrating the NO _X absorption and release action of a NO _X absorbent.

FIG. 3 is a diagram showing a configuration of an intake shutter valve of the embodiment shown in FIG.

FIG. 4 is a flowchart showing a regeneration operation of the NO _X absorbent.

5 is a timing diagram illustrating the flowchart of FIG.

FIG. 6 is a diagram illustrating a change in intake manifold negative pressure.

FIG. 7 is a view similar to FIG. 5D when the closing speed of the shutter valve is changed.

FIG. 8 is a diagram illustrating another embodiment of the present invention.

[Explanation of symbols]

1 ... Diesel engine 2 ... Engine intake pipe 3 ... Engine exhaust pipe 6 ... Intake shutter valve 7 ... Exhaust shutter valve 10 ... Electronic control unit 11 ... Reductant supply device 11a ... Reductant injection valve 12 ... Brake switch 15 ... NO _X absorption Agent 61 ... Main valve 62 ... Sub valve 63 ... Negative pressure actuator

Claims (1)

[Claims] In an exhaust passage of 1. A diesel engine for a vehicle, the air-fuel ratio of the inflowing exhaust absorbs NO _X when the lean, the oxygen concentration of the inflow exhaust gas is absorbed when the reduced NO
Place _the NO _X absorbent to release the _X, to absorb NO _X in the exhaust gas to the _the NO _X absorbent, the NO in a predetermined operating conditions
In the exhaust purification system of an internal combustion engine to reduce and purify the released NO _X with by introducing a reducing agent to release NO _X absorbed from _the NO _X absorbent to reduce the oxygen concentration in the exhaust to the _X absorbent, the reducing agent a throttle valve means for reducing the flow rate of exhaust gas flowing into the _the NO _X absorbent and closed to the predetermined opening degree at the time of introduction, and means for detecting the presence or absence of braking operation of the vehicle driver when the reducing agent introduction, the brake operation And a control means for reducing the opening degree of the throttle valve means as compared with the case where the brake operation is not detected.