JPH08296481A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PURPOSE: To provide main injection and additional injection during exhaust stroke by reciprocating the plunger of a fuel injection pump by the identical number as the number of cylinders. CONSTITUTION: The fuel pressurized by a plunger 46 is discharged in order to respective fuel outflow ports 71a, 71b, 71c, 71d through a fuel discharge passage 69 and a main injection fuel discharge port 70a in a plunger 46, and the discharged fuel is injected from a corresponding Fuel injection valve. In the plunger 46, a sub injection fuel discharge port 70b is formed at an angular interval a little larger than 90 degree from the sub injection fuel discharge port 70b. The fuel discharged from the sub injection fuel discharge port 70b at the time of main injection is supplied to the inside of the combustion chamber of the cylinder under an exhaust stroke.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification device for an internal combustion engine.

[0002]

Absorbs NO _x when the air-fuel ratio is lean of the Related Art inflowing exhaust gas, engine exhaust to _the NO _x absorbent to release the NO _x absorbed to decrease the oxygen concentration in the exhaust gas flowing placed in the passage, typically absorbs NO _x discharged from the engine to _the NO _x absorbent, N from _the NO _x absorbent
When O _x should be released, additional fuel is supplied into the combustion chamber during the explosion stroke or exhaust stroke to reduce the oxygen concentration in the exhaust gas flowing into the NO _x absorbent, thereby reducing the NO _x.
Diesel engine which is adapted to release NO _x from the absorbent are known (see Japanese Patent Laid-Open No. 6-212961).

This diesel engine is provided with a plunger that can be reciprocated while rotating in the plunger insertion hole, and the same number of fuel outflow ports as the number of cylinders are opened at equal angular intervals on the inner peripheral surface of the plunger insertion hole. In addition, each fuel outflow port is connected to the fuel injection valve of each cylinder, and a fuel discharge passage for sequentially communicating the pressurization chamber filled with fuel and pressurized by the plunger with each fuel outflow port is provided in the plunger. formed, and the fuel injection pump is used to pressurized fuel equipped with a spill valve for spilling from the pressure chamber of the pressurizing chamber, NO _x from _the NO _x absorbent
When the fuel is to be released, the spill valve is controlled to inject additional fuel during the explosion stroke.

That is, in this fuel injection pump, when the internal combustion engine is a four-cylinder internal combustion engine, the plunger is reciprocated eight times, that is, twice the number of cylinders in one cycle, and is formed in the plunger. The fuel discharge passage is connected to the fuel outflow port for each cylinder twice at the main injection and the explosion stroke at a time interval, and the main injection quantity in each cylinder and the additional injection quantity in the subsequent explosion stroke are spilled. It is controlled by a valve.

[0005]

However, when the plunger is reciprocated twice as many times as the number of cylinders in one cycle in this way, it is possible to take sufficient time for sucking fuel into the pressurizing chamber at high engine speed. As a result, it becomes impossible to operate the engine at high rotation speed.

[0006]

In order to solve the above problems, according to the present invention, there is provided a plunger that can reciprocate while rotating in a plunger insertion hole, and the same number of fuel outflow ports as the number of cylinders are provided in the plunger. Each fuel outlet port is connected to the fuel injection valve of each cylinder, and the pressurization chamber filled with fuel and pressurized by the plunger is connected to each fuel on the inner peripheral surface of the insertion hole at equal angular intervals. A fuel discharge passage for sequentially communicating with the outflow port is formed in the plunger, and a spill valve for overflowing the pressurized fuel in the pressurizing chamber from the pressurizing chamber is provided, and NO _x is provided in the engine exhaust passage.
In the internal combustion engine in which the processing device is arranged and the fuel is additionally injected from the fuel injection valve during the exhaust stroke according to the condition determined by the NO _x processing device, the plunger reciprocates as many times as the number of cylinders in one cycle. The fuel discharge passage is formed so as to be able to simultaneously communicate with the fuel outflow port of the cylinder to be main-injected and the fuel outflow port of the cylinder in the exhaust stroke, and the fuel injection action to the cylinder in the exhaust stroke is controlled by the spill valve. It is set according to the closing period.

[0007]

The spill valve closing period is set so that fuel can be injected when the fuel discharge passage communicates with both the fuel outflow port of the cylinder to be main-injected and the fuel outflow port of the cylinder in the exhaust stroke. While the main injection and additional injection during the exhaust stroke are performed, the fuel discharge passage communicates with the fuel outflow port of the cylinder to be main injected, but communicates with the fuel outflow port of the cylinder in the exhaust stroke. When the closing period of the spill valve is set so that the fuel can be injected when there is no fuel injection, only the main injection is performed, and no additional injection is performed in the exhaust stroke.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, 1 is a 4-stroke diesel engine main body, 2 is a combustion chamber, 3 is a fuel injection valve for injecting fuel into each combustion chamber 2, and 4 is an engine-driven fuel injection pump. Show each. The fuel discharged from the fuel injection pump 4 is supplied to each fuel injection valve 3, and when the fuel pressure supplied to each fuel injection valve 3 exceeds the valve opening pressure, the fuel is injected from each fuel injection valve 3. . Further, each combustion chamber 2 is connected to a surge tank 6 via a corresponding intake branch pipe 5, and the surge tank 6 is connected to an air cleaner 8 via an intake duct 7. On the other hand, each combustion chamber 2 has a built-in NO _x selective reduction catalyst 11 via an exhaust manifold 9 and an exhaust pipe 10.
It is connected to the O _x processor 12.

The electronic control unit 20 is composed of a digital computer, and has a ROM (read only memory) 22, a RAM (random access memory) 23, a CPU (microprocessor) 24, and an input port 25 which are mutually connected by a bidirectional bus 21. And an output port 26. A crank angle sensor 27 for detecting the crank angle of the engine is connected to the input port 25, and the current crank angle and engine speed are obtained from the output pulse of the crank angle sensor 27. The accelerator pedal 28 is connected to a load sensor 29 that generates an output voltage proportional to the depression amount of the accelerator pedal 28, and the output voltage of the load sensor 29 is A
It is input to the input port 25 via the D converter 30.

FIG. 2 shows the structure of the fuel injection pump 4. As shown in FIG. 2, the housing 40 of the fuel injection pump 4
A drive shaft 42, which projects into the fuel chamber 41 and is rotationally driven by a crankshaft (not shown) of the engine at a speed half that of the crankshaft, is arranged therein. A fuel pump 43 is integrally formed in the housing 40. To facilitate understanding of the structure of the fuel pump 43, FIG. 2 shows the fuel pump 43 rotated by 90 degrees. The drive shaft 42 has a rotor 4 of a fuel pump 43.
4 and a timing gear 45 arranged in the fuel chamber 41
And a coupling 47 for driving the plunger 46.
And are fixed.

A plunger insertion hole 4 is provided in the housing 40.
8 is formed, and the right end portion of the plunger 46 is inserted into the plunger insertion hole 48. On the other hand, a disc-shaped cam plate 50 having a cam surface 49 and a coupling 47 are fixed to the left end portion of the plunger 46. As described above, since the plunger 46 and the drive shaft 42 are connected to each other via the coupling 47, when the drive shaft 42 rotates, the plunger 46 is rotated accordingly.
The coupling 47 connects the drive shaft 42 and the plunger 46 so that the plunger 46 can move in the axial direction. Therefore, the plunger 46 can move in the axial direction while rotating. A roller ring 51 is arranged in the fuel chamber 41 so as to surround the coupling 47, and the roller ring 51 can rotate around the axis of the plunger 46. The roller ring 51 has a lever 52 extending downward.
A cam roller 53, which comes into contact with the cam surface 49 and rolls on the cam surface 49, is rotatably mounted on the top. A timer cylinder 55 having a timer piston 54 is provided below the roller ring 51, and the lower end of the lever 52 engages with the timer piston 54. Note that, in order to facilitate understanding of the operation of the timer piston 54, the timer cylinder 55 is shown rotated by 90 degrees in FIG. It is possible. Thus, the timer piston 5
When 4 moves, the roller ring 50 is rotated accordingly.

A high pressure chamber 56 and a low pressure chamber 57 separated by a timer piston 54 are formed in the timer cylinder 55, and the high pressure chamber 56 is always in communication with the fuel chamber 41.
On the other hand, the low pressure chamber 57 is connected to a fuel inlet 59 via a fuel inflow passage 58, and the fuel inlet 59 is connected to a fuel tank (not shown). In the low pressure chamber 57, a compression spring 60 that urges the timer piston 54 toward the high pressure chamber 56.
Is inserted into the low pressure chamber 57, and the timer piston 54
A timer position sensor 62 whose output voltage is changed depending on the position of the core 61 fixed to the timer piston 54 is arranged to detect the position. The timer position sensor 62 comprises a differential transformer,
Is output to the input port 25 of the electronic control unit 20 via the AD converter 30 (FIG. 1). Low pressure chamber 5
7 and the high pressure chamber 56 are connected to each other via a fuel escape passage 63, and the drive circuit 3 is provided in the fuel escape passage 63.
The pressure regulating valve 64 connected to the output port 25 of the electronic control unit 20 via 1 (FIG. 1) is inserted. The pressure regulating valve 64 is controlled to be opened and closed by an output control signal of the electronic control unit 20, and thereby the rotational position of the roller ring 50 is controlled.

On the cam surface 49 of the cam plate 50, four convex portions, which are the same in number as the number of cylinders, are formed, and the cam surface 49 is constantly pressed against the cam roller 53 by the spring force of the return spring 65. When the drive shaft 42 rotates, the plunger 46 is moved in the axial direction when the convex portion of the cam surface 49 engages with the cam roller 53. Therefore, when the drive shaft 46 makes one rotation, the plunger 46 reciprocates four times. That is, as described above, since the drive shaft 46 is rotated at a rotation speed half that of the crankshaft, the plunger 46 reciprocates four times during one cycle including the intake stroke, compression stroke, explosion stroke and exhaust stroke. Will be done. The pressurizing chamber 66 defined by the right end surface of the plunger 46 is connected to the fuel chamber 41 via the fuel overflow passage 67, and the drive circuit 31 (FIG. 1) is inserted into the fuel overflow passage 67. A spill valve 68 connected to the output port 26 is arranged.

On the other hand, as shown in FIGS. 2 and 3, a fuel discharge passage 69 is formed in the plunger 46 so as to extend in the plunger 46 from the pressurizing chamber 66 in the axial direction of the plunger 46. A pair of fuel discharge ports extending in the radial direction of the plunger 46 from the innermost portion of the fuel discharge passage 69, that is, a main injection fuel discharge port 70a and a sub-injection fuel discharge port 70b are formed in the cylinder 46. In the embodiment shown in FIGS. 2 and 3, the sub-injection fuel discharge port 70b is arranged at an angular interval slightly larger than 90 degrees in the direction opposite to the rotation direction R of the plunger 46 with respect to the main injection fuel discharge port 70a. Furthermore, the sub-injection fuel discharge port 70b has a smaller cross-sectional area than the main-injection fuel discharge port 70a. On the other hand, the plunger insertion hole 4
On the inner peripheral surface of 8, there are four fuel outflow ports 71a, 71b, 71 which can communicate with the respective fuel discharge ports 70a, 70b.
c, 71d are formed 90 degrees apart from each other, and these fuel outflow ports 71a, 71b, 71c, 71d are formed.
Are connected to the respective fuel injection valves 3 via the corresponding check valves 72.

As described above, the main injection fuel discharge port 70
a and the sub-injection fuel discharge port 70b are separated from each other by an angle slightly larger than 90 degrees,
Therefore, as shown in FIG. 3B, the main injection fuel discharge port 70a and the sub-injection fuel discharge port 70b can simultaneously communicate with the fuel outflow ports 71a, 71b, 71c, 71d.

The NO _x selective reduction type catalyst 11 shown in FIG.
Is a hydrocarbon H in the presence of excess oxygen in the exhaust gas.
The presence of C serves to selectively reduce NO _x .
As the NO _x selective reduction catalyst 11, various catalysts such as a Cu-zeolite catalyst in which copper Cu is supported on zeolite and a catalyst in which platinum Pt or cobalt Co is supported on zeolite are known. In this NO _x selective reduction catalyst 11, hydrocarbons HC and oxygen O ₂ are generated in the pores of the zeolite.
There active species formed by the reaction, metal supported on a zeolite, such as copper the active species on Cu and NO _x react NO _x is made to reducing (NO _x + active species → N
₂ + CO + CO ₂ ).

In order to reduce NO _x by the NO _x selective reduction catalyst 11, it is necessary that a large amount of oxygen O ₂ and hydrocarbon HC be present in the exhaust gas as described above. In this regard, since the internal combustion engine shown in FIG. 1 is a diesel engine, the exhaust gas always contains a large amount of oxygen. However the amount of hydrocarbons HC in the exhaust gas is not sufficient, therefore in order to satisfactorily reduce NO _x by _the NO _x selective reduction catalyst 11 becomes necessary to supply additional hydrocarbon HC. By the way, when the engine is operated at a low load with a small fuel injection amount, NO _x is hardly generated, and at this time, the exhaust gas temperature is low, so that the NO _x selective reduction catalyst 11 does not reach the activation temperature. Therefore, at this time, it is not necessary to additionally supply the hydrocarbon HC, and if the hydrocarbon HC is additionally supplied at this time, the hydrocarbon HC adheres to the inside of the pores of the zeolite in a gum shape, thereby deteriorating the catalytic function. Cause On the other hand, a large amount of NO _x is generated during engine high load operation with a large amount of fuel injection,
At this time, since the exhaust gas temperature is high, the NO _x selective reduction catalyst 11 exceeds the activation temperature. Therefore, at this time, N
It is necessary to supply additional hydrocarbon HC to reduce O _x . Therefore, in the embodiment according to the present invention, the additional supply of the hydrocarbon HC is stopped during the engine low load operation, and the additional hydrocarbon HC is supplied only during the engine medium high load operation. Next, a method for controlling the additional supply of the hydrocarbon HC will be described with reference to FIGS. 2 to 5.

In FIG. 4, the horizontal axis represents the crank angle, and the vertical axis represents the depression amount of the accelerator pedal 28, that is, the engine load L and the change in the injection period QT when the engine load L changes. In FIG. 4, θS indicates the injection start timing, and θE indicates the injection completion timing. Also, FIG.
Section X indicates the crank angle range in which the main injection fuel discharge port 70a communicates with the corresponding fuel outflow ports 71a, 71b, 71c, 71d, and section Y indicates the fuel outflow corresponding to the sub-injection fuel discharge port 70b. Port 71
The crank angle range communicating with a, 71b, 71c, and 71d is shown. As can be seen from FIG. 4, the section X covers a relatively wide range from before the compression top dead center TDC to after the compression top dead center TDC, while the section Y is relatively narrow after the compression top dead center TDC. It is within the range. The section Y is located within the section X as shown in FIG.

As shown in FIG. 4, the injection completion timing θE changes according to the engine load L, and when the engine load L is relatively low, the injection completion timing θE is the crank angle before the section Y. As the engine load L increases, the crank angle is within the section Y. The injection completion timing θE is controlled by the spill valve 68. On the other hand, the injection start timing θS
Also changes according to the engine load, and the injection start timing θS is controlled by the timer piston 54.

Next, the operation of the fuel injection pump 4 when the engine load L is relatively low will be described. When the plunger 46 moves to the left in FIG. 2, the fuel in the fuel chamber 41 is supplied into the pressurizing chamber 66 via the fuel supply passage 73. Then, the spill valve 68 is turned on shortly before the plunger 46 starts moving to the right in FIG.
7 is shut off, and thus the plunger 46 starts moving to the right in FIG. 2, the fuel in the pressurizing chamber 66 is pressurized by the plunger 46. Next, when the main injection fuel discharge port 70a communicates with the fuel outflow port 71c as shown in FIG. 5A, for example, the pressurized fuel in the pressurizing chamber 66 causes the fuel discharge passage 69, the main injection fuel discharge port 70a and the fuel outflow. It is supplied to the fuel injection valve 3 of the cylinder connected to the fuel outflow port 71c via the port 71c. Next, when the fuel pressure supplied to the fuel injection valve 3 exceeds the valve opening pressure, fuel injection from the fuel injection valve 3 is started.

Next, when the crank angle reaches the injection completion timing θE shown in FIG. 4, the spill valve 68 is turned off and the spill valve 68 is opened. Pressurization chamber 66 when spill valve 68 opens
The pressurized fuel therein is caused to overflow into the fuel chamber 41 through the fuel overflow passage 67, and thus the fuel pressure in the pressurized chamber 66 decreases, so that the main injection is stopped. The crank angle at this time is before the section Y in FIG. 4, and the position of the plunger 46 at this time is shown in FIG. 5 (A). FIG.
And as can be seen from FIG. 5, when the spill valve 68 is opened, the sub-injection fuel discharge port 70b is not yet in communication with the fuel outflow port 71b, and therefore the fuel outflow port 71b
No additional fuel is injected from the fuel injector 3 connected to b. That is, at this time, only the main injection is performed.

On the other hand, when the engine load L increases, the spill valve 6
When the injection completion timing θE when 8 is turned off is in the section Y, and therefore the spill valve 68 is turned off and main injection is being performed, as shown in FIG. 5B, the sub-injection fuel discharge port 70b. Communicate with the fuel outflow port 71b. Therefore, at this time, the pressurized fuel in the pressurizing chamber 66 is injected from the fuel injection valve 3 connected to the fuel outflow port 71b. The cylinder having the fuel injection valve 3 connected to the fuel outflow port 71b is ahead of the cylinder in which the main injection is performed by 180 degrees in crank angle, and therefore, the fuel injection valve connected to the fuel outflow port 71b. The cylinder having 3 is at about the bottom dead center during the exhaust stroke at this time. Therefore, when the engine load L is relatively high, additional fuel is supplied into the combustion chamber 2 near the bottom dead center during the exhaust stroke.

FIG. 6 shows a time chart of injection control. It should be noted that FIG. 6A shows the engine at low load operation, and FIG. 6B shows the engine at medium and high load operation. As shown in FIG. 6 (A), the spill valve 68 is off before the compression top dead center TDC during engine low load operation, so only main injection is performed, and during engine medium / high load operation, FIG. 6 (B).
As shown in (4), the spill valve 68 is turned off after a while after the compression top dead center TDC, so that in addition to main injection, sub injection,
That is, the additional fuel is injected into the cylinder during the exhaust stroke. As can be seen from FIGS. 6 (A) and 6 (B), when the engine load increases, the timer piston 54 causes the plunger 4 to move.
The rising of the lift of No. 6 is advanced, and thus the injection start timing θS is advanced.

FIG. 7 shows an injection control routine. Referring to FIG. 7, in step 100, the fuel injection amount Q is calculated from the depression amount of the accelerator pedal 28, that is, the engine load L and the engine speed, and then in step 101, the injection completion timing θE, that is, the spill valve, is calculated based on the engine load L. The valve opening timing of 68 is calculated. Next, at step 102, the injection start timing θS is calculated from the fuel injection amount Q and the injection completion timing θE. Next, at step 103, the injection start timing is θS.
The pressure regulating valve 64 is controlled so that

When an additional fuel, that is, an additional hydrocarbon HC is supplied into the combustion chamber near the bottom dead center during the exhaust stroke, the hydrocarbon HC is contacted with the hot burned gas and activated. The reactivity is enhanced. Next, the hydrocarbon HC having the increased reactivity flows into the NO _x selective reduction catalyst 11, and thus the NO _x in the exhaust gas is favorably reduced.

8 to 10 show NO_xThe processing device 12 is N
O_xNO instead of selective reduction catalyst_xBuilt-in absorbent 11
It shows the case. This NO_xAbsorbent 11 is an example
For example, alumina is used as a carrier, and potassium
Alkali gold such as K, sodium Na, cesium Cs
Alkaline earth such as genus, barium Ba, calcium Ca
From rare earths like lanthanum, lanthanum La, yttrium Y
At least one selected and a precious metal such as platinum Pt
It is carried. Engine combustion chamber 2 and NO_xAbsorbent 11
Air and fuel (carbonized water supplied to the upstream exhaust passage)
Ratio) to NO_xAir-fuel ratio of exhaust gas flowing into the absorbent 11
This is NO_xThe absorbent 11 is the air-fuel of the inflowing exhaust gas
NO when the ratio is lean_xAbsorbed in the exhaust gas
NO absorbed when the oxygen concentration of_xReleases NO
_xIt absorbs and releases. Note that NO _xAbsorbent 11 upstream
No fuel (hydrocarbons) or air is supplied to the exhaust passage
If not, the air-fuel ratio of the inflowing exhaust gas is not formed in the combustion chamber 2.
Corresponding to the average air-fuel ratio of the mixture
NO_xThe absorbent 11 is a mixture of the air-fuel mixture formed in the combustion chamber 2.
NO when the air-fuel ratio is lean_xAbsorbs the combustion chamber 2
If the oxygen concentration in the air-fuel mixture formed in the
NO_xWill be released.

If the above-mentioned NO _x absorbent 11 is arranged in the engine exhaust passage, this NO _x absorbent 11 actually performs the action of absorbing and releasing NO _x , but the detailed mechanism of this action of absorbing and releasing is not clear. There is also. 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 the case where platinum Pt and barium Ba are supported on the carrier as an example, but the same mechanism can be obtained by using other noble metals, alkali metals, alkaline earths and rare earths.

That is, when the inflowing exhaust gas is lean, the oxygen concentration in the inflowing exhaust gas is considerably high.
As shown in (A), the oxygen O ₂ is O ₂ ⁻ or O _2.
It adheres to the surface of platinum Pt in the form of ^2- . On the other hand, NO in the inflowing exhaust gas reacts with O ₂ ⁻ or O ^{2 −} on the surface of platinum Pt to become NO ₂ (2NO + O ₂ → 2NO ₂ ). Next, a part of the generated NO ₂ is absorbed on the platinum Pt while being absorbed in the absorbent and combined with barium oxide BaO to be absorbed in the form of nitrate ion NO ₃ ⁻ as shown in FIG. 8 (A). Diffuses in the agent. In this way, NO _x is absorbed in the NO _x absorbent 11.

The oxygen concentration in the inflowing exhaust gas is generated NO ₂ on the surface of as high as platinum Pt, as long as NO ₂ of absorption of NO _x capacity of the absorbent is not saturated is absorbed in the absorbent and nitrate ions NO ₃ ^- Is generated. In contrast the reaction with the amount of NO ₂ oxygen concentration is lowered in the inflowing exhaust gas is lowered backward (NO ₃ ^- → NO ₂₎ proceeds to, thus nitrate ions to the absorber NO ₃ ^- Are released from the absorbent in the form of NO ₂ . Namely, when the oxygen concentration in the inflowing exhaust gas is released NO _x from the NO _x absorbent 11 when lowered.

On the other hand, the hydrocarbons in the burnt gas in the combustion chamber 2
HC is supplied and the air-fuel ratio of the inflowing exhaust gas becomes rich
At this time, the HC contained in the exhaust gas is the acid on the platinum Pt.
Element O ₂ ^-Or O^2-It reacts with and is oxidized. Also,
When the air-fuel ratio of the inflowing exhaust gas becomes rich, inflowing exhaust gas
NO from the absorbent due to extremely low oxygen concentration₂But
Released, this NO₂Is H as shown in FIG.
It reacts with C and is reduced. In this way platinum P
NO on the surface of t₂No longer exists and next from the absorbent
Next to NO₂Is released. Therefore, the inflow of exhaust gas is empty
If the fuel ratio is made rich, NO in a short time_xAbsorbent 11
To NO_xWill be released.

That is, when the air-fuel ratio of the inflowing exhaust gas is made rich, first, HC immediately reacts with O ₂ ⁻ or O ^{2 −} on platinum Pt to be oxidized, and then O on platinum Pt is oxidized.
₂ ^- or O ^2- when is any remaining still HC be consumed NO _x discharged from the NO _x and engine released from the absorbent by the HC is made to reduction. Therefore, if the air-fuel ratio of the inflowing exhaust gas is made rich, NO in a short time
_The NO _x absorbed in the _x absorbent 11 is released, and the released NO _x is reduced, so that N is released into the atmosphere.
It will be possible to prevent the emission of O _x .

In a diesel engine, combustion is usually carried out in the presence of excess air, so the average air-fuel ratio of the air-fuel mixture formed in the combustion chamber 2 is lean, and therefore the NO _x contained in the exhaust gas at this time. Will be absorbed by the NO _x absorbent 11. On the other hand, there is a limit to the absorption of NO _x capacity of the NO _x absorbent 11, therefore absorption of NO _x capacity of the NO _x absorbent 11 needs to release the NO _x from the NO _x absorbent 11 before saturation. Therefore, in this embodiment, every time a certain period of time elapses, hydrocarbons HC are supplied into the combustion chamber 2 near the bottom dead center in the exhaust stroke to make the air-fuel ratio of the inflowing exhaust gas rich, whereby the NO _x absorbent 11 is removed. It is designed to release NO _x . Incidentally, NO _x released from the time _the NO _x absorbent 11 as described above is caused to reduction by HC.

In FIG. 9, as in FIG. 4, the horizontal axis represents the crank angle and the vertical axis represents the depression amount of the accelerator pedal 28, that is, the engine load L, and the injection period QT when the engine load L changes.
Shows the change. In FIG. 9 as well, θS indicates the injection start timing, and θE indicates the injection completion timing. Also in FIG. 9, in the section X, the fuel outflow ports 71a, 71b, 7 corresponding to the main injection fuel discharge port 70a.
1c and 71d are in communication with the crank angle range, and section Y represents the crank angle range in which the sub-injection fuel discharge port 70b is in communication with the corresponding fuel outflow ports 71a, 71b, 71c and 71d. .

FIG. 9A shows a normal operation. This
At the time of, regardless of the engine load L, the injection completion timing θE
Is defined before the compression top dead center TDC. That is, the clan
The spill valve 68 should be opened before the corner angle reaches the section Y.
Therefore, at this time, additional hydrocarbon HC is supplied.
The salary is stopped. On the other hand, FIG. 9B shows NO. _x
Absorbent 11 to NO_xIndicates when to release.
At this time, the injection completion timing θE is entirely at the compression top dead center T
Delayed until after DC, and thus the spill valve 68 opens.
The fuel injection port to which the sub-injection fuel discharge port 70b corresponds
Connected to the doors 71a, 71b, 71c, 71d.
It Therefore, at this time, the smell near the bottom dead center during the exhaust stroke
The additional hydrocarbon HC is supplied into the combustion chamber 2. What
At this time, the amount of additional hydrocarbon HC is in the combustion chamber 2.
The average air-fuel ratio is set to be rich.

FIG. 10 shows an injection control routine. Figure 10
Referring to, in step 200, the accelerator pedal 2
Depression amount of 8, i.e. the fuel injection amount Q is calculated from the engine load L and the engine speed, and then whether _the NO _x releasing condition from _the NO _x absorbent 11 at step 201 is satisfied or not. When the NO _x releasing condition is not satisfied, that is, N
When it is estimated that the O _x absorbent 11 has a sufficient absorption capacity, the routine proceeds to step 202, where the injection completion timing θE shown in FIG.
The valve opening timing of is calculated. Then step 203
Then, the injection start timing θS is calculated from the fuel injection amount Q and the injection completion timing θE. Next, at step 204, the pressure regulating valve 64 is controlled so that the injection start timing becomes θS. At this time, only the main injection is performed.

On the other hand, from the NO _x absorbent 11 to the NO _x
When the condition for releasing is satisfied, the process proceeds to step 205 only for a certain period. At step 205, the engine load L
9B, the injection completion timing θE, that is, the valve opening timing of the spill valve 68 is calculated. Next, at step 206, the injection start timing θS is calculated from the fuel injection amount Q and the injection completion timing θE, then at step 204, the pressure regulating valve 64 is controlled so that the injection start timing becomes θS. At this time, in addition to the main injection, additional hydrocarbon HC is supplied near the bottom dead center in the exhaust stroke, so that the average air-fuel ratio in the combustion chamber 2 becomes rich. As a result, NO _x
The action of releasing NO _x from the absorbent 11 is performed.

[0037]

EFFECTS OF THE INVENTION Since the plunger can be reciprocated as many times as the number of cylinders in one cycle, sufficient time can be taken for sucking the fuel even when the engine is rotating at high speed. It becomes possible to rotate the engine at high speed.

[Brief description of drawings]

FIG. 1 is an overall view of a 4-stroke diesel engine.

FIG. 2 is a side sectional view of a fuel injection pump.

FIG. 3 is a view showing a relationship between a plunger and a fuel discharge port, and FIG. 3A is a perspective view schematically showing the plunger;
(B) is a cross-sectional view of the plunger.

FIG. 4 is a diagram showing a fuel injection timing.

FIG. 5 is a sectional view of the plunger.

FIG. 6 is a time chart showing fuel injection control.

FIG. 7 is a flowchart for performing injection control.

FIG. 8 is a diagram for explaining the action of absorbing and releasing NO _x .

FIG. 9 is a diagram showing a fuel injection timing.

FIG. 10 is a flowchart for performing injection control.

[Explanation of symbols]

 3 ... Fuel injection valve 4 ... Fuel injection pump 46 ... Plunger 66 ... Pressurization chamber 69 ... Fuel discharge passage 70a ... Main injection fuel discharge port 70b ... Sub-injection fuel discharge port 71a, 71b, 71c, 71d ... Fuel outflow port

Claims (1)

[Claims] 1. A plunger is provided which is reciprocated while rotating in a plunger insertion hole, and the same number of fuel outflow ports as the number of cylinders are opened at equal angular intervals on the inner peripheral surface of the plunger insertion hole. The fuel outflow port is connected to the fuel injection valve of each cylinder, and a fuel discharge passage is formed in the plunger for sequentially communicating the pressurization chamber filled with fuel and pressurized by the plunger with each fuel outflow port, A spill valve is provided for overflowing the pressurized fuel in the pressurizing chamber from the pressurizing chamber, a NO _x processing device is arranged in the engine exhaust passage, and the exhaust stroke from the fuel injection valve is performed according to the conditions determined by the NO _x processing device. In an internal combustion engine in which fuel is additionally injected into the plunger, the plunger is reciprocated the same number of times as the number of cylinders in one cycle,
The fuel discharge passage is formed so as to be able to simultaneously communicate with the fuel outflow port of the cylinder to be main-injected and the fuel outflow port of the cylinder in the exhaust stroke, and the fuel injection action to the cylinder in the exhaust stroke is the closing period of the spill valve. Purification device for internal combustion engine determined according to