JPH10317950A - Fuel injection control device of direct injection type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always supply a proper quantity of reductant by interposing upper stream side catalyst purifying exhaust gas by reductant on an exhaust passage on the upper stream side of a confluent part where the exhaust passage of two cylinder groups meet, and computing the quantity of reductant to be supplied to this catalyst based on engine speed and intake air pressure. SOLUTION: During operation of an internal combustion engine 1, a CPU 42 computes the exhaust gas volume passing through NOx catalyst 10a on the upper stream side based on supercharging pressure detected by a pressure sensor 72 and engine speed obtained from the output of a crank angle sensor. The higher the supercharging pressure is, the larger the gas volume is, and the higher the engine speed, the larger the volume. Next, an HC quantity to be supplied to the NOx catalyst 10a on the upper stream side is computed based on the exhaust gas volume. Further, based on the difference of the detected temperature of the respective NOx catalyst 10a, 10b on the upper stream and the downstream, the HC quantity for NOx cleaning to be injected by sub-injection is corrected. Namely when the upper stream side temperature is higher than the downstream side temperature in the NOx catalyst, the HC quantity for NOx cleaning is corrected so as to be restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel injection control device for a direct injection type internal combustion engine.

[0002]

2. Description of the Related Art A plurality of cylinders are divided into two cylinder groups, and exhaust passages connected to these cylinder groups are joined together.
2. Description of the Related Art There is known an internal combustion engine in which exhaust gas discharged from one cylinder group is introduced into intake air to reduce the amount of nitrogen oxides (hereinafter, NO _x ) generated in the engine. Also,
2. Description of the Related Art In the above-mentioned internal combustion engine, there is known an internal combustion engine provided with an NO _X catalyst for purifying NO _X exhausted from the engine in an exhaust passage on an upstream side of an intake for taking exhaust gas to be introduced into intake air. The NO _X catalyst catalyzes hydrocarbons (hereinafter, HC) in a state where the oxygen concentration in the exhaust gas is extremely high because the air-fuel ratio of the air-fuel mixture burned in the engine is much higher than the stoichiometric air-fuel ratio. adsorbed on the surface to produce an active species, to purify NO _X by reacting an active species and NO _X in the HC. Supplies for HC in the exhaust gas after the engine combustion in an internal combustion engine equipped with this NO _X catalyst is hardly included, the NO _X purifying HC separately as a reducing agent to the engine driving HC to the NO _X catalyst . However, when the engine driving HC supply amount or more purifying HC consumed in the NO _X catalyst when separately supplying purifying HC in the NO _X catalyst, HC passes through the NO _X catalyst in air Will be released to Therefore, it is necessary to control the HC amount that can be consumed in the NO _X catalyst is supplied to the NO _X catalyst. For example generally proportional to and the amount of intake air to the amount the intake air amount of the NO _X produced in the JP-A 6-117225 at engine and the engine speed by utilizing the fact that generally proportional to the engine speed and engine load The amount of NO _X generated in the engine is estimated based on the engine load, and the amount of HC for purification is calculated based on the amount of NO _X. However, when the amount of exhaust gas per unit time passing through the NO _X catalyst is large, that is, when the catalyst passing speed of the exhaust gas passing through the NO _X catalyst is high, HC is adsorbed on the catalyst surface to become an active species, and NO _X The time that can be secured to react with is shortened. Therefore, even if the amount of purification HC calculated based on the amount of NO _X generated in the engine is supplied, the supplied HC becomes N
It is discharged to the atmosphere without being consumed in the _OX catalyst. Therefore, the internal combustion engine is configured to estimate the amount of exhaust gas per unit time passing through the NO _X catalyst from the amount of intake air supplied to the engine and calculate the amount of HC to be supplied to the NO _X catalyst based on the amount of exhaust gas. Agencies are known.

[0003]

However, the exhaust gas discharged from the one group of cylinders is introduced into the intake air, and NO gas is provided upstream of the exhaust gas inlet of the exhaust passage connected to the one group of cylinders. _In an internal combustion engine provided with an _X catalyst, since the exhaust gas passing through the NO _X catalyst contains exhaust gas introduced from an exhaust passage connected to the one cylinder group, it is determined based on the intake air amount. It can not be calculated amount of exhaust gas passing through the nO _X catalyst. Therefore, an object of the present invention is to provide a catalyst for purifying exhaust gas discharged from some cylinders, and to consume a part of the exhaust gas passing through the catalyst into the intake air in the internal combustion engine in which the catalyst can be consumed. It is to supply an appropriate amount of a reducing agent for purification, that is, HC, to the catalyst.

[0004]

According to a first aspect of the present invention, a plurality of cylinders are divided into two cylinder groups, and a junction where an exhaust passage connected to the cylinder groups merges. An upstream catalyst for purifying exhaust gas with a reducing agent is provided in an exhaust passage on the upstream side, and a downstream catalyst for purifying exhaust gas with a reducing agent is provided in an exhaust passage on the downstream side of the junction. In an in-cylinder direct injection internal combustion engine in which an exhaust circulation pipe for introducing exhaust gas into intake air is connected to an exhaust passage between the junction, the amount of reducing agent to be supplied to the upstream catalyst is determined. There is provided a reducing agent amount calculating means for calculating based on the engine speed and the intake air pressure.

According to a second aspect of the present invention, in the first aspect, a turbine wheel of a supercharger is provided in an exhaust passage between the junction and the downstream catalyst. This reduces the exhaust gas temperature as the exhaust gas passes through the turbine wheel.

According to a third aspect of the present invention, in the first aspect, the reducing agent amount calculating means determines the amount of the reducing agent to be supplied to the upstream catalyst by the temperature of the upstream catalyst. Is corrected based on

According to a fourth aspect of the present invention, in the first aspect, the reducing agent amount calculating means determines the amount of the reducing agent to be supplied to the downstream catalyst based on the amount of intake air. calculate.

According to a fifth aspect of the present invention, in the fourth aspect, the reducing agent amount calculating means determines the amount of the reducing agent to be supplied to the downstream side catalyst by the temperature of the downstream side catalyst. Is corrected based on

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration of a direct injection type diesel internal combustion engine of the present embodiment. In FIG. 1, 1 is an engine body, # 1 to # 4 are first cylinders, second cylinders,
The third and fourth cylinders, 6a to 6d, are a first fuel injection valve, a second fuel injection valve, a third fuel injection valve, and a fourth fuel injection valve for injecting fuel into each cylinder. Each cylinder ♯1
The intake pipe 9 is connected to # 4 via an intake manifold 66. A pressure sensor 72 for detecting a pressure inside the intake manifold 66 is attached to the intake manifold 66. A first exhaust branch pipe 8a, a second exhaust branch pipe 8b, a third exhaust branch pipe 8c, and a fourth exhaust branch pipe 8d are respectively connected to the cylinders # 1 to # 4.

The second exhaust branch pipe 8b, the third exhaust branch pipe 8c, and the fourth exhaust branch pipe 8d are joined at the upstream junction 11 and connected to the common upstream exhaust pipe 7. That is, a cylinder group is formed by the second cylinder # 2, the third cylinder # 3, and the fourth cylinder # 4. Further, the first exhaust branch pipe 8a and the upstream exhaust pipe 7 are joined at the downstream junction 12 and connected to a common downstream exhaust pipe 64.

[0011] _the NO _X selective reducing catalyst on the upstream side exhaust pipe 7 as the lean NO _X catalyst (hereinafter, upstream NO _X catalyst) 10
a is arranged. The upstream end portion of the upstream-side NO _X catalyst 10a upstream temperature sensor 70a for measuring the temperature of the upstream end portion is arranged. Further, the downstream end portion of the upstream-side NO _X catalyst 10a downstream temperature sensor 71a for measuring the temperature of the downstream end portion is disposed. On the other hand, the downstream exhaust pipe 6
The 4 NO _X selective reducing catalyst (hereinafter, downstream NO _X catalyst) as the lean NO _X catalyst 10b is disposed. Downstream side N
O _X is the upstream end portion of the catalyst 10a upstream temperature sensor 70b for measuring the temperature of the upstream end portion is arranged. Further, the downstream end portion of the downstream NO _X catalyst 10a downstream temperature sensor 71b for measuring the temperature of the downstream end portion is disposed. It should be noted that the NO _X catalyst adsorbs HC on the catalyst surface in a state where the oxygen concentration in the exhaust gas is extremely high because the air-fuel ratio of the air-fuel mixture burned by the engine is much higher than the stoichiometric air-fuel ratio, and Generates active species and this HC
Purifying NO _X by reacting an active species and NO _X in. Further, the NO _X catalyst exhibits a higher NO _X purification rate than a predetermined purification rate in a predetermined temperature range (hereinafter, appropriate temperature range). According to the present embodiment, since two NO _X catalysts can be arranged for one engine, a high NO _X purification rate can be obtained.

An exhaust circulation pipe 65 for introducing exhaust gas into intake air is connected to the upstream exhaust pipe 7 downstream of the upstream NO _X catalyst 10a and upstream of the downstream junction 12. . The other end of the exhaust circulation pipe 65 is connected to an intake manifold 66. The NO _X amount generated in the cylinder decreases as the combustion temperature in the cylinder decreases. In addition, inert gas such as moisture and carbon dioxide contained in the exhaust gas has a function of lowering the combustion temperature in the cylinder. Therefore, by introducing the exhaust gas into the intake air, the NO _X amount generated in the cylinder is reduced. An exhaust circulation control valve 67 for controlling the amount of exhaust gas to be introduced into the intake air is attached to the exhaust circulation pipe 65. Exhaust circulation control valve 6
7 is connected to a suction pump 69 and the atmosphere via a three-way valve 68. When the exhaust circulation control valve 67 is connected to the suction pump 69 by the three-way valve 68, a negative pressure is applied to the exhaust circulation control valve 67 and the exhaust circulation control valve 67 is opened. On the other hand, the exhaust circulation control valve 67 is
When the exhaust gas circulation control valve 67 is communicated with the atmosphere by the atmospheric pressure, the atmospheric pressure is applied to the exhaust gas circulation control valve 67 and the valve is closed.

Further, the internal combustion engine of the present embodiment
NO on the downstream side of the part 12 _XUpstream of the catalyst 10b
Exhaust turbine turbine disposed in the downstream exhaust pipe 64
The intake-side turbine wheel disposed in the wheels 62 and the intake pipe 9
A supercharger 63 having an eel 61 is provided. Exhaust side
The turbine wheel 62 and the intake-side turbine wheel 61
Are connected to each other by one shaft 60. Exhaust gas
The exhaust-side turbine wheel 62 is rotated by the
And the intake-side turbine wheel through the shaft 60
61 is rotated. This increases the intake air volume
As a result, the engine output is improved. Further in this embodiment
According to the description, the downstream merging portion 12 where all the exhaust gas merges
Since the exhaust turbine wheel 62 is located downstream,
Exhaust gas passing through the air-side turbine wheel 62
In many cases, a very high supercharging effect can be obtained. Note that the intake side
Intake air at the intake pipe 9 on the upstream side of the bin wheel 61
Air flow meter 2 for detecting
You.

Further, as will be described later, NO _X injected in the second cylinder # 2, the third cylinder # 3, and the fourth cylinder # 4.
HC for purification to be consumed in the upstream NO _X catalyst 10a, the exhaust gas containing HC does not reach the exhaust circulation pipe 65. Further, since the exhaust-side turbine wheel 62 is disposed downstream of the downstream-side merging portion 12, the first cylinder #
Exhaust gas containing injected NO _X purifying HC in 1 is made to reach the downstream NO _X catalyst 10b without flowing into the upstream-side exhaust pipe 7. Thus the upstream side exhaust pipe 7 on the upstream side of the downstream-side merging portion 12 a downstream side of the exhaust circulation pipe 65 according to this embodiment the upstream NO _X catalyst 10a
, Exhaust gas not containing HC can be introduced into the intake air. Therefore, the exhaust circulation pipe 65 is prevented from being blocked by the HC. In addition, it supplies the correct amount of HC to the downstream side NO _X catalyst 10b.
Since the exhaust gas still contains no NO _X is introduced into the intake air, it can reduce the amount of NO _X discharged from the engine.

The electronic control unit 40 is composed of a digital computer, and is connected to a CPU (microprocessor) 42, a RAM (random access memory) 43, a ROM (read only memory) 44 and an input via a bidirectional bus 41. A port 45 and an output port 46 are provided. Upstream NO _X catalyst 10a disposed the upstream-side temperature sensor 70a and the downstream temperature sensor 71a and the downstream NO _X disposed catalyst 10b the upstream temperature sensor 7
1a and the downstream temperature sensor 71b are connected to the input port 45 via the corresponding AD converters 47, respectively.
The pressure sensor 72 and the air flow meter 2 are connected to the input port 45 via the corresponding AD converters 48 and 52.
Connected to.

Further, the internal combustion engine of the present embodiment has an engine body 1.
Is provided with a crank angle sensor 16 that generates an output pulse every time a crankshaft (not shown) rotates, for example, 30 degrees. The crank angle sensor 16 is connected to the corresponding AD converter 4
9 and connected to the input port 45. Further, the internal combustion engine of the present embodiment includes an accelerator depression amount sensor 18 that generates an output voltage proportional to the accelerator depression amount D. The accelerator depression amount sensor 18 is connected to the input port 45 via the corresponding AD converter 49. On the other hand, the output port 46
Are connected to the respective fuel injection valves 6 and the three-way valve 68 via the corresponding drive circuit 51.

Next, the operation of the internal combustion engine of this embodiment will be described. In the present embodiment, the main injection is performed immediately after the compression top dead center in each of the cylinders # 1 to # 4, and the fuel for driving, that is, HC is supplied from each of the fuel injection valves 6a to 6d into each of the cylinders # 1 to # 4. Inject. The amount of drive fuel injected into each of the cylinders # 1 to # 4 by the main injection is calculated based on the accelerator pedal depression amount D detected by the accelerator pedal depression sensor 18, and the fuel amount increases as the depression amount D increases. Is increased. After the main injection is executed, a sub-injection is executed separately from the main injection, and the fuel for purification, that is, HC is injected into each of the cylinders # 1 to # 4 from the fuel injection valves 6a to 6d as a reducing agent. .

[0018] The temperature of the upstream-side NO _X catalyst 10a executes the sub injection in the cylinder group when in the appropriate temperature range, when in the out of the proper temperature range stops execution of the sub injection in the cylinder group. Also, run the sub injection in the first cylinder ♯1 when the temperature of the downstream NO _X catalyst 10b is within the appropriate temperature range, when in the out of the proper temperature range stops executing the sub injection in the first cylinder ♯1 I do.

Further, differences in the materials constituting the catalyst, that is, whether the catalyst carries a substance having a high purification rate at a low temperature or a substance having a high purification rate at a high temperature, a difference in heat capacity of the catalyst, the difference in degree of deterioration, but the appropriate temperature range that can purify NO _X in the upstream side NO _X catalyst and the downstream NO _X catalyst are different, the catalyst temperature is the appropriate temperature range for the NO _X catalyst in this case Is determined on the basis of whether or not the sub-injection is performed.

Therefore, for example, even when the temperature of the downstream NO _X catalyst is lower than the temperature of the upstream NO _X catalyst, the sub-injection is executed in the cylinder group and the first cylinder depending on the appropriate temperature range of each NO _X catalyst. At this time, if the sub injection by supplying more than usual HC in the cylinder groups, a part of HC is reformed without being consumed in the upstream NO _X catalyst, HC supplied by the auxiliary injection in the first cylinder upstream They are mixed in HC and the downstream NO _X catalyst modified with side NO _X catalyst. That HC having high activity is reformed downstream NO _X catalyst is supplied. Thus since the catalyst temperature is NO _X purification reaction takes place even at low downstream NO _X catalyst, NO _X purification rate is further improved.

Further, according to the present embodiment, the upstream NO _X
Exhaust gas temperature by NO _X purifying reaction heat in the catalyst 10a rises is cooled deprived of heat when passing through the exhaust side turbine wheel 62. Thus since the high-temperature exhaust gas is prevented from flowing into the downstream NO _X catalyst 10b, to maintain the temperature of the upstream side NO _X catalyst 10a and the downstream-side NO _X catalyst 10b approximately equal to the appropriate temperature range it can.

[0022] Incidentally, for example, the upstream-side NO _X catalyst 10a is disposed very close to the combustion chamber of the engine, the downstream-side NO
_In an internal combustion engine in which the _X catalyst 10b is located very far from the combustion chamber, the temperature of the upstream NO _X catalyst 10a may be higher than the temperature of the downstream NO _X catalyst 10b.

Next, control of the execution timing of the sub-injection in the internal combustion engine of the present embodiment will be described. Note that the following is the NO _X catalyst in the description includes an upstream NO _X catalyst 10a and the downstream-side NO _X catalyst 10b, the first cylinder is the cylinder ♯1
To the fourth cylinder # 4. The temperature of the NO _X catalyst, for example determined by the average of the upstream temperature sensor and the downstream temperature sensor of each NO _X catalyst.

[0024] when the temperature of the NO _X catalyst is lower than the appropriate temperature range to perform the sub injection in the expansion stroke to mid expansion stroke initial in each cylinder. Further, delay the execution timing of the sub injection as the temperature of the NO _X catalyst is increased.
Since the temperature in the cylinder is relatively high from the initial stage of the expansion stroke to the middle stage of the expansion stroke, the ratio of the HC injected by the sub-injection to be reformed to the low boiling point HC is high. Therefore, as the execution timing of the sub-injection is delayed, the proportion of the HC injected by the sub-injection that is reformed to the low boiling point HC decreases, and the high boiling point HC is reduced.
The proportion of HC remaining as it is increases. That is, according to the present embodiment, when the catalyst temperature is at a relatively low temperature within an appropriate temperature range, the NO _X purification operation can be started relatively easily by supplying a low-boiling HC having a high activity to the NO _X catalyst. Therefore, the NO _X purification rate is improved. Further, when HC is injected by sub-injection from the initial stage of the expansion stroke to the middle stage of the expansion stroke, there is a lot of HC which is burned in the cylinder without remaining as a low boiling point HC. In other words, the more the execution timing of the sub-injection is delayed, the less HC is burned. Therefore, according to the present embodiment, the purifying action is started by the low boiling point HC, and after the catalyst temperature is increased, the high boiling point HC is removed.
As a result, the amount of fuel used for the purification operation can be reduced.

Next, the HC injection control for purification according to this embodiment will be described. In the present embodiment, first, based on the supercharging pressure detected by the pressure sensor 72 and the engine speed, the upstream NO
_The amount of exhaust gas passing through the _X catalyst 10a (hereinafter, the amount of exhaust gas passing upstream) is calculated. The upstream side passing exhaust gas amount increases as the supercharging pressure increases, and increases as the engine speed increases. Next, based on the amount of exhaust gas passing through the upstream side,
_The amount of HC to be supplied to the _X catalyst 10a is calculated. Upstream N
O _X catalyst 10a capable HC amount consumed in order to become less the larger the upstream passage exhaust gas amount, the amount of HC to be supplied to the upstream side NO _X catalyst 10a is reduced the more upstream side passage exhaust gas amount.

Also, the air flow meter 2 detects
NO based on the intake air volume _XPass through catalyst 10b
The amount of exhaust gas to be discharged (hereinafter, the amount of exhaust gas passing downstream)
I do. The amount of exhaust gas passing downstream increases as the amount of intake air increases.
It becomes. Next, based on the amount of exhaust gas passing downstream,
NO_XThe amount of HC to be supplied to the catalyst 10b is calculated. downstream
Side NO_XThe amount of HC that can be consumed in the catalyst 10b is on the downstream side.
As the amount of passing exhaust gas increases, the amount decreases, so that the downstream side NO
_XThe amount of HC to be supplied to the catalyst 10b is the amount of exhaust gas passing downstream.
The larger the amount, the less. Note that the pressure sensor 72
Supply to all cylinders based on the detected boost pressure and engine speed
The supplied intake air amount may be calculated.

Therefore, according to the present embodiment, one of the
The exhaust gas discharged from the cylinder group is introduced into the intake air,
An exhaust gas inlet of an exhaust passage connected to one cylinder group,
That is, NO is located upstream of the portion where the exhaust circulation pipe is connected._X
In an internal combustion engine equipped with a catalyst, this NO_XCatalyst smell
The amount of the purifying reducing agent that can be consumed by _X
Supplied to the catalyst.

Further, in the HC injection control for purification of the present embodiment,
Means each NO_XDetected by temperature sensor attached to catalyst
Based on the difference between the upstream and downstream temperatures
NO to be injected by injection_XCorrect the HC amount for purification.
That is, each NO_XThe upstream temperature is the downstream temperature in the catalyst
When the temperature is higher than the
The downstream temperature is expected to rise
When the downstream temperature rises from the appropriate temperature range
N to be injected by sub-injection to prevent departure
O_XReduce the amount of HC for purification. Conversely, upstream temperature is downstream
When the temperature is lower than the side temperature, the downstream temperature will soon be upstream
It is expected that the temperature will decrease following the temperature.
When the temperature decreases following the temperature, the downstream
Inject by sub-injection to prevent falling out of the enclosure
Should be NO_XIncrease the amount of HC for purification. Therefore this implementation
NO according to the form _XDepending on the temperature change in the catalyst,
The amount of purification HC to be injected is controlled by the injection. this
NO_XThe catalyst temperature can be maintained within an appropriate temperature range,
NO_XThe purification rate is further improved.

Next, referring to the flowchart of FIG.
The HC injection control for purification according to the embodiment will be described. First,
In step S310.
Upstream NO based on the supply pressure P and the engine speed N_XCatalyst 1
0a, the amount G of exhaust gas flowing upstream on the upstream side₁ Is calculated
You. Next, proceeding to step S312, the upstream side NO_XCatalyst 1
0a upstream detected by the downstream temperature sensor 71a
NO_XDownstream temperature T of catalyst 10a_d1And step S310
Upstream passing exhaust gas amount G calculated by₁ And based on
Outflow side NO_XBasic HC amount to be supplied to catalyst 10a HC_b1But
Is calculated. Next, the process proceeds to step S314, where the upstream side NO
_XDetected by the upstream temperature sensor 70a of the catalyst 10a
NO upstream_XUpstream temperature T of the catalyst 10a_u1And upstream N
O_XDownstream temperature T of catalyst 10a_d1HC correction based on
Amount HC_k1Is calculated. The HC correction amount HC_k1Is T_U1
<T_d1Takes a positive value when_U1> T_d1When
Takes a negative value. Next, the process proceeds to step S316.
Basic HC amount HC calculated in S312_b1And step S3
HC correction amount HC calculated in 14_k1HC supply based on
Supply HC_f1Is calculated. The HC supply amount HC_f1Is the expression
HC_f1= HC_b1+ HC _k1Is calculated by Next,
Proceeding to step S318, the HC supply amount HC_f1And the fuel injection valve 6
Sub injection time t based on injection pressure_s1Is calculated. Next
In step S320, the sub-injection time t_s1Of the secondary injection
This is executed in the cylinder group.

[0030] Next downstream passage exhaust gas amount G ₂ flowing into the downstream NO _X catalyst 10b based on the output of the air flow meter 2 proceeds to step S322 is calculated. Then downstream NO _X catalyst 10b on the downstream side temperature sensor of the downstream NO _X catalyst 10b detected by 71b downstream temperature T _d2 and the downstream side passage exhaust gas calculated in step S322 the amount G ₂ proceeds to step S324 downstream NO _X based on bets
Basic amount of HC HC _b2 to be supplied to the catalyst 10b is calculated. Then downstream NO _X catalyst 1 proceeds to step S326
0b on the basis of the downstream temperature T _d2 of the upstream temperature T _u2 and the downstream NO _X catalyst 10b of the upstream temperature sensor 70b by the detected downstream NO _X catalyst 10b of HC correction amount HC _k2
Is calculated. Note that the HC correction amount HC _k2 takes a positive value when T _U2 <T _d2 , and takes a negative value when T _U2 > T _d2 . Next, the process proceeds to step S328 and proceeds to step S324.
The HC supply amount HC is calculated based on the basic HC amount HC _b2 calculated at step S326 and the HC correction amount HC _k2 calculated at step S326.
_f2 is calculated. Note that the HC supply amount HC _f2 is _calculated by the formula HC _f2 =
It is calculated by HC _b2 + HC _k2 . Next, step S33
The process proceeds to 0, and the sub injection time _ts2 is calculated based on the HC supply amount _HCf2 and the injection pressure of the fuel injection valve 6. Next, the routine proceeds to step S332, in which the sub-injection for the sub-injection time t _s2 is executed in the first cylinder # 1, and the process ends.

In this embodiment, the cylinders are the first cylinder # 1 and the first cylinder # 1.
Split into two cylinders # 2, third cylinder # 3 and fourth cylinder # 4
However, the third cylinder # 3 and the fourth cylinder # 4_X
NO on the downstream side through the catalyst 10a_XConnected to the catalyst 10b
The first cylinder group # 1 and the second cylinder # 2
Outflow side NO_XNO on the downstream side directly bypassing the catalyst 10a _X
It may be a second cylinder group connected to the catalyst 10b.

Further, the frequency of executing the sub-injection and the amount of HC injected per sub-injection may be controlled according to the catalyst temperature. For example, as shown in FIG. 3, when the catalyst temperature T is in the first temperature range T ₁ executes the sub injection each time the injection timing of the auxiliary injection sequentially arriving. Executing the sub injection at a rate of once a second time injection timing of the sub injection sequentially arriving when the catalyst temperature T is in the second temperature range T _2. Hereinafter, the inside third temperature range T ₃ once every three times, the inside fourth temperature range T ₄ executes once sub injection to four times. Further, simultaneously with the sub-injection execution frequency control, as the frequency of executing the sub-injection decreases, the amount of HC injected per sub-injection increases.

The number of times the sub-injection is stopped at a predetermined number of sub-injection injection timings may be controlled. For example, as shown in FIG.
There when in a first temperature range T ₁ performs sub injection of five times per five times engine cycle, when in the second temperature range T within ₂ performs sub injection four times per five times engine cycle. That is, in the second temperature range T within ₂ stops once the execution of the sub injection. The following sequence, when in a third temperature range T ₃ the execution of the sub injection is stopped twice, fourth temperature range T
When it is within ₄ , the execution of the sub-injection is stopped three times. Further, simultaneously with the sub-injection execution stop frequency control, the amount of HC injected per sub-injection is increased.

When the amount of HC injected per sub-injection is increased, the amount of HC not exposed to the cylinder atmosphere increases. Therefore, the amount of HC burned in the cylinder among the HCs supplied by the sub-injection over the predetermined number of sub-injection injection timings is reduced as compared with the conventional case (see FIG. 5). Therefore, the amount of HC supplied to the NO _X catalyst 10 can be controlled to a desired amount. Furthermore, a smaller amount of HC than before
The be injected into the cylinder, since the amount of HC is burned according to the present embodiment is small, it is possible to supply an appropriate amount of HC amount in the NO _X catalyst.

Although the fuel injection control device applied to a diesel internal combustion engine has been described in the present application, the present invention can also be applied to an in-cylinder direct injection spark ignition type internal combustion engine of a lean burn type. Further, NO _X is absorbed and stored in a state where the oxygen concentration in the exhaust gas is very high,
C can also be the oxygen concentration in the exhaust gas is supplied to apply the present invention the catalyst is reacted with HC to release the NO _X when dropped.

[0036]

According to the first to fifth aspects of the present invention, an upstream catalyst for purifying exhaust gas discharged from some cylinders is provided, and a part of the exhaust gas passing through the upstream catalyst is sucked. In the internal combustion engine introduced into the air, the amount of the reducing agent to be supplied to the upstream catalyst is calculated based on the engine speed and the intake air pressure. The engine speed and the intake air pressure are parameters related to the amount of exhaust gas passing through the upstream catalyst. Therefore, the calculated amount of the reducing agent to be supplied to the upstream catalyst is an amount in consideration of the amount of exhaust gas passing through the upstream catalyst. For this reason, an amount of purifying reducing agent that can be consumed in the upstream catalyst is supplied, and waste of the reducing agent can be reduced.

According to the second aspect of the present invention, the temperature of the exhaust gas raised by the purification reaction in the upstream catalyst is reduced in the turbine wheel.
Excessive increase in the temperature of the downstream catalyst is prevented.

Further, according to the third and fifth aspects, the amount of the reducing agent to be supplied to the catalyst is corrected based on the temperature of the catalyst. Although the purification characteristics of the catalyst vary depending on its temperature, the amount of the reducing agent in accordance with the purification characteristics of the catalyst is supplied to the catalyst by correcting the amount of the reducing agent based on the catalyst temperature. Be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a direct injection type internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a flowchart of HC injection control for purification in an in-cylinder direct injection internal combustion engine according to an embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a catalyst temperature and a sub-injection interval.

FIG. 4 is a diagram showing a relationship between a catalyst temperature and the number of sub injections.

FIG. 5 is a diagram showing the relationship between the in-cylinder temperature and the amount of HC.

[Explanation of symbols]

1 ... engine body 6 a to 6 d ... fuel injection valves 10a ... upstream NO _X catalyst 10b ... downstream NO _X catalyst 63 ... turbocharger 65 ... exhaust circulation pipe 72 ... pressure sensor

──────────────────────────────────────────────────の Continuation of front page (51) Int.Cl. ⁶ Identification code FI F01N 3/24 F01N 3/28 ZAB ZAB 301C 3/28 ZAB 301G 301 F02B 37/02 E H F02B 37/02 F02D 41/02 325A F02M 25/07 580D F02D 41/02 325 B01D 53/36 ZAB F02M 25/07 580 102H (72) Inventor Toshiaki Tanaka 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Yoichi Iwata Aichi 1 Toyota Town, Toyota City, Japan

Claims (5)

[Claims] A plurality of cylinders are divided into two cylinder groups, and an upstream catalyst for purifying exhaust gas with a reducing agent is provided in an exhaust passage upstream of a junction where the exhaust passages connected to the cylinder groups merge. A downstream catalyst for purifying exhaust gas with a reducing agent in an exhaust passage downstream of the junction, and introducing exhaust gas into intake air into an exhaust passage between the upstream catalyst and the junction. Amount of reducing agent to be supplied to the upstream catalyst is calculated based on the engine speed and the intake air pressure in a direct injection type internal combustion engine connected to an exhaust circulation pipe for exhaust gas. A fuel injection control device for a direct injection internal combustion engine, comprising: 2. The fuel injection of a direct injection internal combustion engine according to claim 1, wherein a turbine wheel of a supercharger is provided in an exhaust passage between the junction and the downstream catalyst. Control device. 3. The direct in-cylinder according to claim 1, wherein said reducing agent amount calculating means corrects the amount of reducing agent to be supplied to said upstream catalyst based on the temperature of said upstream catalyst. A fuel injection control device for an injection type internal combustion engine. 4. The direct injection type internal combustion engine according to claim 1, wherein said reducing agent amount calculating means calculates an amount of reducing agent to be supplied to said downstream side catalyst based on an intake air amount. Engine fuel injection control device. 5. The direct in-cylinder according to claim 4, wherein said reducing agent amount calculating means corrects the amount of reducing agent to be supplied to said downstream catalyst based on the temperature of said downstream catalyst. A fuel injection control device for an injection type internal combustion engine.