JP2001164968A - Exhaust emission control device for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable reduction and purifying of trapped nitrogen oxides while suppressing torque fluctuation within a wide range in a device equipped with a nitrogen oxides trapping catalyst on an exhaust passage for trapping the nitrogen oxides in exhaust gas when HC density in the exhaust gas flowing thereinto is small, and discharging the trapped nitrogen oxides when the HC density is high for discharging and reducing nitrogen oxides. SOLUTION: An exhaust gas recirculation ratio and swirl are set high in a specified operation condition, that is, in an MK area (S3). An ignition timing is set after TDC (S8), and low temperature premix combustion (MK combustion) is carried out. A generation amount of nitrogen oxides is thus reduced. A trapping amount of the nitrogen oxides in a nitrogen oxide trapping catalyst is sensed. When the amount reaches a specified value or higher, the ignition timing is so shifted as to be before TDC with high swirl and high exhaust gas recirculation ratio (S4 to S7). Combustion is changed over to premix combustion with early ignition, for increasing HC density, discharging the nitrogen oxides from the nitrogen oxides trapping catalyst, and attaining reduction and purifying.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for purifying exhaust gas of a diesel engine.

[0002]

2. Description of the Related Art Diesel engines are operated in a lean state with an A / F (air-fuel ratio) of 20 or more in all operating ranges, and the exhaust gas is in an oxygen atmosphere. HC, SOF in exhaust gas
A catalyst that oxidizes only the catalyst is used.

In such a diesel engine,
To reduce NOx in exhaust gas, see Japanese Patent Application Laid-Open No. 8-21892.
As shown in Japanese Patent Publication No. 0, NOx absorption absorbs NOx in the exhaust gas when the exhaust air-fuel ratio flowing into the exhaust passage is lean, and releases the absorbed NOx when the oxygen concentration of the flowing exhaust gas decreases. A material is arranged, and when NOx is to be released from the NOx absorbent, the A / F is switched to rich (rich spike) to reduce and purify the NOx absorbed by the absorbent.

In this case, the enrichment is performed by greatly increasing the fuel injection amount and lowering the excess air ratio. However, when the fuel injection amount is increased in diffusion combustion, which is a general combustion mode of a diesel engine, the fuel injection amount is increased. Since most of the increased fuel does not burn and a large amount of smoke is generated, the amount of fuel injected into the combustion chamber before the start of combustion is increased, so that premixed combustion of injected fuel and air can be achieved. The amount of fuel contributing is increased relative to the amount of fuel contributing to diffusion combustion generated in the combustion chamber by the injected fuel, and the effect of premixed combustion on the operability of combustion in the combustion chamber is within an allowable range. This is performed under the internal load condition, that is, in the low load region. In other words, enrichment is enabled by utilizing premixed combustion by early injection in a low load region.

[0005]

However, performing a rich spike in a low load range involves a significant deterioration in fuel efficiency and torque fluctuation, and may cause a deterioration in drivability.
Also, if rich spikes are not performed because the torque fluctuation is large in a medium load to high load region where the NOx emission is large, the NOx absorption amount of the NOx absorbent immediately reaches saturation, and the low spikes at which the rich spikes can be generated. There is a problem that NOx cannot be purified until the load region is reached.

On the other hand, there is a combustion system disclosed in Japanese Patent Application Laid-Open No. 8-86251. This means that under certain operating conditions,
Combustion temperature lowering means for lowering the combustion temperature of the engine;
Equipped with ignition delay increasing means for extending the ignition delay period of the injected fuel, and swirl generating means for generating swirl in the combustion chamber, performing premixed combustion at a relatively low temperature and simultaneously reducing NOx and smoke. Since the combustion speed can be suppressed, the combustion noise is also reduced. Hereinafter, such a combustion method is referred to as MK (Modulated Kinetic) combustion.

As concrete measures for realizing the MK combustion, (1) large EGR, (2) optimization of fuel injection timing, and (3) generation of high swirl are performed. (1) Mass EGR In premixed combustion, combustion is performed at a stretch, so combustion temperature increases, NOx increases, and combustion noise also increases.
By performing a large amount of EGR, the combustion after ignition is performed slowly, the rise in combustion temperature after ignition is suppressed, and the combustion noise and NOx are reduced. Further, by increasing the ignition delay period by a large amount of EGR, sufficient time for fuel vaporization can be obtained, and premix combustion can be performed.

(2) Optimization of Fuel Injection Timing Conventionally, fuel injection which was started considerably before the compression top dead center TDC is started after TDC (delaying the injection timing), so that compressed air is compressed. Enters the expansion process, and the combustion is performed after the pressure starts to decrease, so that the combustion start pressure can be kept low. Further, by injecting at this time, even if the fuel is injected, the fuel does not ignite immediately, so that a sufficient time for vaporizing the fuel can be taken and premix combustion can be performed.

(3) Generation of high swirl High (strong) swirl is generated in the combustion chamber by a swirl control valve or the like, and mixing and combustion of fuel and air are performed in a stable manner.

The present invention has been made in view of the above situation,
Assuming K combustion, when the NOx trap material is provided in the exhaust passage, the torque fluctuation can be suppressed in a wider area (low load to medium load area) only by changing the fuel injection timing.
An object of the present invention is to enable regeneration of a NOx trap material (reduction and purification of trapped NOx).

[0011]

Accordingly, as shown in FIG. 1, the present invention provides an operating condition detecting means for detecting an operating condition of an engine, and a combustion device for lowering the combustion temperature of the engine under a predetermined operating condition. Temperature decreasing means, ignition delay increasing means for increasing the ignition delay period of the injected fuel under the predetermined operating conditions, swirl generating means for generating swirl in the combustion chamber under the predetermined operating conditions, and an exhaust passage of the engine. A NOx trap material installed when the HC concentration in the inflowing exhaust gas is low and traps NOx in the exhaust gas when the HC concentration is high, and releases the trapped NOx when the HC concentration is high. NOx release condition detecting means for detecting a NOx release condition for releasing NOx from the NOx trap material, on the assumption that At Ox release condition, the fuel injection timing is advanced, and the fuel injection timing changing means for premixed combustion of early injection, the provided, constituting a device for purifying exhaust gas of diesel engines.

According to a second aspect of the present invention, the fuel injection timing changing means advances the fuel injection timing from after compression top dead center to before compression top dead center. In the invention according to claim 3, the NOx release condition detecting means includes the NOx release condition detecting means.
NOx trap amount detecting means for detecting the NOx trap amount of the x trap material, and detecting when the NOx trap amount of the NOx trap material is equal to or more than a predetermined value under the predetermined operating conditions as a NOx release condition. It is characterized by.

According to a fourth aspect of the present invention, the NOx releasing condition detecting means has a time measuring means, and sets the NOx releasing condition periodically at predetermined time intervals under the predetermined operating conditions. And

The invention according to claim 5 has a NOx trap material for releasing and reducing trapped NOx when the HC concentration is high, and a trap material temperature detecting means for detecting the temperature of the NOx trap material. The fuel injection timing changing means may advance the fuel injection timing only when the temperature of the NOx trapping material is within a predetermined temperature range.

The invention according to claim 6 is characterized in that the fuel injection timing changing means gradually changes the fuel injection timing when changing the fuel injection timing.

[0016]

According to the present invention, HC is discharged from the engine by switching from MK combustion by the combustion temperature lowering means, the ignition delay increasing means and the swirl generating means to premixed combustion by early injection. The concentration is greatly increased, and the NOx trapped in the NOx trapping material can be released by the HC concentration fluctuation.

Further, since MK combustion is used as a basis, the amount of NOx released from the engine is significantly reduced as compared with conventional normal combustion. Therefore, when the NOx trap material is saturated NOx
The interval at which the trap amount is reached can be extended, the frequency of HC concentration fluctuations caused by premixed combustion by early injection can be reduced, and deterioration of fuel efficiency and the like can be suppressed.

Further, in order to realize the premixed combustion by the early injection, it is necessary to increase the ignition delay period and to form a uniform premixed gas. The ignition delay period is extended by the EGR, and the premixed fuel is increased by the high swirl. Is possible with the formation of
Basically, it is possible to cope with high EGR and high swirl performed by MK combustion. Therefore, it is possible to switch from the MK combustion to the premixed combustion by the early injection only by changing the fuel injection timing, and it is possible to change the HC with almost no change in the A / F.
Since the concentration can be changed, there is almost no deterioration in drivability.

The MK region for MK combustion extends over a wide range from low load to medium load, and the area where NOx can be purified with a small torque shock is wide.
x Easy to purify.

According to the second aspect of the invention, the fuel injection timing is advanced from after compression top dead center to before compression top dead center, so that MK combustion (premixed combustion by fuel injection after compression top dead center) is performed. ) Can be reliably switched to premixed combustion by early injection (fuel injection before compression top dead center).

According to the third aspect of the present invention, the NOx trapping amount of the NOx trapping material is detected, and when the NOx trapping amount is equal to or more than a predetermined value, the mode is switched to premix combustion by early injection to reduce
In order to reduce and purify x, the NOx trap material can be surely regenerated before the NOx trap material reaches a saturated state.

According to the present invention, trapping, desorption, and purification of NOx are reliably performed since the mode is switched to premix combustion by early injection periodically at predetermined time intervals.
The performance of the Ox trap material can be maximized.

According to the fifth aspect of the invention, the early injection is performed only when the temperature of the NOx trapping material is within the predetermined temperature range, that is, within the predetermined temperature range in which the performance of reducing trapped NOx is high. , It is possible to improve the NOx reduction performance.

According to the invention of claim 6, when the fuel injection timing is changed, the fuel injection timing is gradually changed,
Torque shock can be further reduced.

[0025]

Embodiments of the present invention will be described below. FIG. 2 is a system diagram of a diesel engine showing an embodiment of the present invention.

Each cylinder of the diesel engine (engine main body) 1 is provided with a direct injection type fuel injection valve 2. Each fuel injection valve 2 is supplied with high-pressure fuel from a common common rail (fuel pressure accumulation pipe) 3. Common rail 3
Is supplied from the supply pump 4 driven by the engine. By using such a common rail type fuel injection device, it is possible to inject high-pressure fuel into the cylinder at any time.

An intake passage to the engine 1 is constituted by an intake pipe 5 and an intake manifold 6, and an exhaust passage from the engine 1 is constituted by an exhaust manifold 7 and an exhaust pipe 8.

A turbocharger 9, more specifically, an intake compressor 9b driven by an exhaust turbine 9a on the exhaust passage (exhaust pipe 8) side is interposed in the intake passage (intake pipe 5). The turbocharger 9 has a variable nozzle mechanism on the exhaust turbine 9a side, and can control the turbocharging pressure to an arbitrary boost pressure by adjusting the nozzle opening.

A part of the exhaust gas (EGR gas) from the exhaust passage (exhaust pipe 8) to the intake passage (intake manifold 6).
An EGR passage 10 is provided to recirculate the EG.
An EGR control valve 11 is interposed in the R passage 10.

Although not shown in FIG. 2, the intake manifold 6 or the intake port is provided with a swirl generating means. As the swirl generating means, a swirl control valve having a notch in a part of the butterfly valve may be used. Here, a variable swirl device 45 of a rotary blade type as shown in FIGS. 3 and 4 is provided. The swirl in the cylinder can be set arbitrarily.

The variable swirl device 45 is located near a spiral path 46b of a so-called helical intake port 46 (formed of a substantially linear intake path 46a and a spiral path 46b around the intake valve axis). A rotating blade 47 rotatably provided, a link mechanism 48 connected to the rotating blade 47, a negative pressure actuator 49 for driving the link mechanism 48, and a negative pressure operating chamber 50 of the negative pressure actuator 49. The swirl ratio can be adjusted at the rotational position of the rotary blade 47 by including a negative pressure adjusting valve 51 for controlling a negative pressure. For example, when the rotating blade 47 reaches the position shown in FIG. 4A, the swirl ratio becomes high, and when it reaches the position shown in FIG. 4B, the swirl ratio becomes low. This rotary blade system has a quick response and enables swirl control over a wide range.
Therefore, it is suitable for reducing HC which reacts sensitively to the swirl ratio.

Exhaust turbine 9a in the exhaust passage (exhaust pipe 8)
Downstream, a NOx trap catalyst 12 having the function of a NOx trap material is disposed. As the NOx trap catalyst 12, the present applicant has disclosed in Japanese Patent Application No. 10-319689.
There are, for example, potassium, sodium, lithium, alkali metals consisting of cesium, barium, magnesium, calcium, alkaline earth metals consisting of strontium, lanthanum, cerium, praseodymium, neodymium, from samarium A catalyst comprising at least one selected from the group consisting of rare earths, transition metals composed of manganese, iron, nickel and cobalt, zirconium and yttrium, and at least one selected from platinum, palladium, rhodium and iridium, in a lean region (A / When F> 18) and the HC concentration at the catalyst inlet fluctuates, the trapped NOx can be released and reduced and purified.

That is, as shown in FIG. 5, when the atmosphere is in a lean state where the atmosphere contains a small amount of HC and CO as reducing agents, NOx is trapped in the trapping material in a state of NO ₃ . When the atmosphere contains a large amount of HC and CO as reducing agents, NO ₃ is released from the trapping material and reduced to N ₂ .

Therefore, as shown in FIG.
By changing the C concentration (HC concentration at the engine outlet),
NOx trapping and emission reduction occur. The lower graph in FIG. 6 shows that the HC concentration at the engine outlet is small (section T
FIG. 6 shows a case where the value is changed from 1) to large (section T2).
The upper graph shows the change in NOx concentration at the outlet of the exhaust pipe, with the horizontal axis (time axis) corresponding to the lower graph.

According to FIG. 6, the NOx trap amount is large in the section T1 due to the low HC concentration. When the HC concentration becomes high in the section T2, NOx trapped in the section T1 is released (section T2A). The amount of release here is smaller than the amount of NOx trapped in the previous section (T1, T1 and T2B when viewed periodically), and the difference is the NOx purification amount. When the release is completed, NOx is trapped again, but the NOx trap amount in the section T2B where the HC concentration is high is smaller than that in the section T1.

Further, as shown in Table 1, the NOx reduction rate in the sections T1 and T2 according to the atmospheric oxygen concentration in the release reduction process, the HC concentration variation type NOx trap catalyst 12
The effect is further exhibited in a region where F> 18 (oxygen concentration is 10% or more).

[0037]

[Table 1] Here, the operations of the fuel injection valve 2, the EGR control valve 11, and the variable swirl device 45 (the negative pressure adjusting valve 51) of the common rail fuel injection system are controlled by a signal from an engine control unit (hereinafter referred to as ECU) 13.

The ECU 13 receives signals from an engine speed sensor, an accelerator opening sensor and the like, as well as a temperature sensor 14 for detecting the exhaust gas temperature at the inlet of the NOx trap catalyst 12 as a trap material temperature detecting means.

The control by the ECU 13 will be described with reference to the flowchart of FIG. 7 which is the first embodiment. In step 1 (referred to as S1 in the figure, the same applies hereinafter),
The operating conditions are read from the engine speed and the accelerator opening (torque). This part corresponds to operating condition detecting means.

In step 2, the operating conditions are determined, that is, whether or not the engine is in the MK range (low load to medium load range) for MK combustion shown in FIG. In the case of the MK region, the process proceeds to step 3 to set a high EGR rate (EGR rate of 30% or more) and a high swirl. Unless a predetermined condition is satisfied, the process proceeds to step 8 to increase the injection timing. The injection timing is set after the dead center TDC (for example, 4 ° ATDC), and the premix combustion (MK combustion) after the injection timing TDC is performed.

Here, the portion for setting the high EGR rate corresponds to the combustion temperature lowering means, and the portion for setting the high EGR rate and the portion for setting the injection timing after TDC correspond to the ignition delay increasing means. Corresponds to the swirl generating means.

Premixed combustion (MK) whose injection timing is after TDC
If combustion is realized, NOx emission is suppressed in a wide operating range (MK range) of low to medium loads as shown in FIG. In FIG. 9, in the MK region, there is an interval between the equal NOx emission lines, and it can be seen that the increase in the NOx emission is also gradual.

Further, since low-temperature premixed combustion is realized by high EGR, high swirl, and injection timing retard, as shown particularly in the case of IT = 4 ° ATDC in FIG. 10, NOx is greatly reduced without deterioration of smoke. It becomes possible to reduce to. As a result, in the MK region, the amount of NOx emission can be greatly reduced as compared with the conventional diesel engine.

In step 4, the NOx trap catalyst 12
The amount of NOx trapping to is determined. The determination is made by reading the NOx emission amount discharged from the engine from the map of the NOx emission amount with respect to the engine speed and the torque shown in FIG.
Then, the amount of NOx trapping to No. 2 is calculated and compared with a predetermined value. This part corresponds to NOx release condition detecting means (NOx trap amount detecting means).

If the result of the NOx trap amount determination is that NOx trap amount ≧ predetermined value (when the NOx trap amount has reached near saturation), the routine proceeds to step 7. In step 7, the injection timing is changed for a predetermined time before TDC (for example, during the intake stroke). That is, the injection timing is switched to the premixed combustion by the early injection with the injection timing before TDC. This part corresponds to the fuel injection timing changing means. Here, in order to achieve premixed combustion by early injection, injection is performed earlier (for example, 100 ° before top dead center) than 15 to 5 ° before top dead center, which is a conventional non-MK combustion injection timing. There is a need.

The premixed combustion (MK
By switching the injection timing from combustion to premixed combustion by early injection before TDC (early premixed combustion), the HC concentration in the exhaust gas increases as shown in FIG. This allows
NOx is released from the NOx trap catalyst 12 and reduced and purified.

In order to realize early premix combustion,
(1) It is necessary to increase the ignition delay period, and (2) it is necessary to form a uniform premixed gas. In this embodiment, (1) the ignition delay period is extended by EGR, and (2) the premixed gas is increased by high swirl. Since formation is possible, basically, high swirl and high EGR performed in MK combustion can be used. Therefore, the swirl variable device 45 maintains the high swirl as in the case of the MK combustion, and also introduces the EGR gas by the EGR control valve 11 for combustion at a low temperature. , MK combustion → early premix combustion, and the HC concentration can be changed with little change in A / F, so that there is almost no deterioration in drivability.

When switching between MK combustion and early premix combustion, as shown in FIG. 11, the injection timing is gradually changed, and more specifically, the injection amount (MK combustion) for MK combustion is changed.
It is preferable to gradually change the ratio between the injection amount for the early premixed combustion (early injection amount) and the injection amount for the early premixed combustion so as to avoid a sudden change in the combustion state and to prevent the occurrence of torque shock.

In FIG. 11, curve A represents the ratio of the amount of premixed fuel forming fuel (early injection amount) injected earlier than TDC (for example, during the intake stroke) relative to the total fuel injection amount, and similarly curve B Indicates the ratio of the amount of fuel (MK injection amount) injected at the injection timing during MK combustion to the total fuel injection amount. The horizontal axis indicates the elapsed time from the transition from MK combustion to early premix combustion, and the period indicated by T indicates the MK combustion.
The period from combustion to the early premix combustion is completely shown.

Referring to FIG. 11, in this embodiment, during normal operation, the entire amount (100%) of fuel is injected after TDC, and during switching to early premixed combustion, the fuel after TDC during period T is switched. The injection amount is gradually reduced to zero at the end of the period T (curve B). Further, the amount of fuel injected early is zero during normal operation, and is increased from 0 to 100% during the period T during switching to early premixed combustion. That is, during the transition period T from the MK combustion to the early premix combustion, both the early injection and the injection after the TDC for the MK combustion are performed. As described above, instead of rapidly switching from MK combustion to early premix combustion, a certain transition period T is provided, and switching from MK combustion to early premix combustion gradually proceeds within this period T. Accordingly, occurrence of torque shock due to switching from MK combustion to early premix combustion is prevented.

Although FIG. 11 shows only the transition from MK combustion to early premix combustion, a transition period is similarly provided when returning from early premix combustion to MK combustion.
If the switching of the combustion is performed gradually, the occurrence of the torque shock accompanying the switching between the MK combustion and the early premix combustion is completely prevented.

Next, a second embodiment of the present invention will be described. FIG. 12 is a control flowchart according to the second embodiment of the present invention. Performance of reducing trapped NOx (NOx
By switching to premixed combustion by early injection in a predetermined temperature range where the conversion rate is high, NOx reduction performance can be improved.

Therefore, the catalyst activation temperature range as shown in FIG. 13 (T1 to T2 exhaust temperature conditions, for example, 200 to 400 ° C.)
Only to switch to early premix combustion. Therefore, FIG.
In the flow of (1), step 6 is added to the flow of FIG.

That is, if it is determined in step 4 that the NOx trap amount is equal to or larger than the predetermined value, the process proceeds to step 6. In step 6, it is determined whether or not the exhaust temperature (trap material temperature, catalyst temperature) at the inlet of the NOx trap catalyst 12 detected by the temperature sensor 14 is within the active temperature range T1 to T2 in which the reduction activity of the catalyst is high as shown in FIG. Is determined. This portion corresponds to the trap material temperature detecting means.

As a result, when the temperature is within the activation temperature range, NO
Since the reduction purification of x is possible, proceed to Step 7
The injection timing is changed before TDC to switch to early premix combustion. On the other hand, when the catalyst is not active outside the activation temperature range, the effect cannot be obtained even if the HC concentration fluctuates due to the early premixed combustion. Leave MK burning.

Next, a third embodiment of the present invention will be described. FIG. 14 is a control flowchart according to the third embodiment of the present invention. By causing the HC concentration to fluctuate periodically in the active region of the catalyst, trapping, desorption, and purification of NOx are reliably performed, and the performance of the catalyst can be maximized.

Therefore, by periodically switching from MK combustion to early premix combustion at predetermined time intervals, trapped NOx is reliably purified. For this reason, in the flow of FIG. 14, step 5 is provided instead of step 4 in the flow of FIG.

That is, the process proceeds to step 5 in the MK area. In step 5, it is determined whether or not the cycle is the NOx release cycle every predetermined time. Specifically, the injection timing is M
The continuation time of K combustion is measured, and when this time becomes a predetermined time or more, the NOx release cycle is set. This part is NO
It corresponds to x release condition detecting means (time measuring means).

Then, in the case of the NOx release cycle, the process proceeds to step 6, and if it is within the activation temperature range, step 7 is performed.
To change the injection timing to before TDC, and switch to early premix combustion.

As described above, by periodically switching between MK combustion and early premix combustion, NOx trapped in the NOx trap catalyst 12 can be constantly desorbed and purified.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a configuration of the present invention.

FIG. 2 is a system diagram of a diesel engine showing an embodiment of the present invention.

FIG. 3 is a configuration diagram of a variable swirl device.

FIG. 4 is a perspective view showing a state of swirl generation by the variable swirl device.

FIG. 5 is a diagram showing a NOx trap / release / reduction mechanism of a NOx trap catalyst.

FIG. 6 is a diagram showing the NOx trapping / release / reduction action due to HC concentration fluctuation.

FIG. 7 is a control flowchart of the first embodiment.

FIG. 8 is a diagram showing an MK region.

FIG. 9 is a diagram showing an engine NOx emission map.

FIG. 10 is a graph showing the amounts of NOx and smoke generated.

FIG. 11 is a diagram showing an injection amount ratio at the time of switching between MK combustion and early premix combustion.

FIG. 12 is a control flowchart of a second embodiment.

FIG. 13 is a diagram showing an activation temperature range of the NOx trap catalyst.

FIG. 14 is a control flowchart of the third embodiment.

[Explanation of symbols]

 Reference Signs List 1 diesel engine 2 fuel injection valve 3 common rail 4 supply pump 5 intake pipe 6 intake manifold 7 exhaust manifold 8 exhaust pipe 9 turbocharger 10 EGR passage 11 EGR control valve 12 NOx trap catalyst (NOx trap material) 13 ECU 14 temperature sensor 45 variable Swirl device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F01N 3/28 301 F02B 23/00 S 4D048 F02B 23/00 31/00 321E 31/00 321 321F 331A 331 F02D 41/02 380G F02D 41/02 380 45/00 314Z 45/00 314 F02F 1/42 F F02F 1/42 B01D 53/36 101A 101B F-term (reference) 3G023 AA02 AA04 AA05 AA18 AB05 AC04 AD05 AD06 AE05 AF03 AG03 3024 AA09 DA02 DA04 DA25 3G084 AA01 BA08 BA13 BA15 BA20 BA21 DA02 DA10 DA25 DA27 EA04 EA11 EC02 FA10 FA27 FA28 FA33 3G091 AA02 AA10 AA11 AA18 AB05 AB08 BA14 BA32 BA33 CA13 CA18 CB02 CB03 CB08 DA01 FC02 DA03 DA02 GB03W GB04W GB05W GB06W GB07W HA01 HA18 HA36 HB03 HB05 HB06 3G3 01 HA02 HA11 HA13 HA17 JA02 JA25 JB09 LA05 MA11 MA19 NA08 NB02 NB15 NE03 NE08 NE11 PD01Z PD11Z PE01Z PF03Z 4D048 AA06 AB02 AB03 BA01Y BA02Y BA08Y BA14Y BA15X BA15Y BA18Y BA19Y BA28Y BA30X BA30 DABAY DA33

Claims (6)

[Claims] An operating condition detecting means for detecting an operating condition of an engine, a combustion temperature lowering means for lowering a combustion temperature of the engine under a predetermined operating condition, and an ignition delay period of the injected fuel under the predetermined operating condition Means for increasing the ignition delay, swirl generating means for generating swirl in the combustion chamber under the above-mentioned predetermined operating conditions, and installed in the exhaust passage of the engine. N
A NOx trap material for trapping Ox and releasing the trapped NOx when the HC concentration is high, assuming that the predetermined operating condition is satisfied.
NOx release condition detecting means for detecting a NOx release condition for releasing NOx from the x trap material; and advancing the fuel injection timing under the NOx release condition;
An exhaust gas purification device for a diesel engine, comprising: fuel injection timing changing means for performing premixed combustion of early injection. 2. The exhaust gas purifying apparatus for a diesel engine according to claim 1, wherein said fuel injection timing changing means advances the fuel injection timing from after compression top dead center to before compression top dead center. 3. The NOx release condition detecting means includes:
NOx trap amount detecting means for detecting the NOx trap amount of the x trap material, and detecting when the NOx trap amount of the NOx trap material is equal to or more than a predetermined value under the predetermined operating conditions as a NOx release condition. The exhaust gas purification device for a diesel engine according to claim 1 or 2, wherein: 4. The NOx releasing condition detecting means includes a time measuring means, and sets the NOx releasing condition periodically at predetermined time intervals under the predetermined operating conditions. The exhaust purification device for a diesel engine according to claim 2. 5. The trapped NOx when the HC concentration is high.
A NOx trapping material that releases and reduces the temperature of the NOx trapping material, and a trapping material temperature detecting unit that detects the temperature of the NOx trapping material. The fuel injection timing changing unit sets the temperature of the NOx trapping material within a predetermined temperature range. The exhaust gas purifying apparatus for a diesel engine according to any one of claims 1 to 4, wherein the fuel injection timing is advanced only at a certain time. 6. The diesel engine according to claim 1, wherein the fuel injection timing changing means gradually changes the fuel injection timing when changing the fuel injection timing. Exhaust purification equipment.