JPH10121950A - Exhaust emission control device for cylinder direct injection type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent fuel from mixing with lubricating oil by injection fuel even at an expansion stroke or an exhaust stroke while injecting fuel from fuel injection means at an intake stroke or a compression stroke, and controlling an injection range of a second injection fuel for prevent fuel from arriving to a wall surface in a cylinder. SOLUTION: In the case where an injector 1 is driving-controlled, a timing signal for showing a start timing of fuel injection (main injection) is outputted from an injection timing means 29. A start timing of the main injection is set to, for example, near a top dead center of compression. A timing signal for showing a start timing of fuel injection (auxiliary injection) is outputted from an injection timing means 30. The start timing of auxiliary injection is set at a final period of an expansion stroke or an initial period of an exhaust stroke. A total auxiliary injection rate is decided by an injection control means 32, and then, injection pressure is controlled by an injection range control means 31 when the total auxiliary injection rate is injected. Fuel is thus controlled so as to prevent fuel from arriving to a wall surface of a cylinder 2.

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 apparatus for a diesel engine employing a direct injection type in a cylinder.

[0002]

2. Description of the Related Art In recent years, the emission concentration of CO, HC, NOX and the like contained in exhaust gas discharged from a diesel engine has been regulated. In particular, in a diesel engine, since combustion is performed in an excess air region, the average air-fuel ratio of the air-fuel mixture formed in the combustion chamber is in a lean state, and it is difficult to purify NOX by the three-way catalyst.

For this reason, in a diesel engine, a lean NOX catalyst having an ability to absorb NOX in exhaust gas when the air-fuel ratio of the exhaust gas is lean is provided in the exhaust system. However, since the NOX absorption capacity of the lean NOX catalyst is limited, NOX is released from the lean NOX catalyst before the NOX absorption capacity of the lean NOX catalyst is saturated.
It is necessary to purify the released NOX.

As such a system, Japanese Utility Model Laid-Open No. 3-6
An exhaust gas purification system for a diesel engine described in Japanese Patent No. 8516 is known. In an exhaust purification system for a diesel engine, in a diesel engine having a lean NOx catalyst in an exhaust system, fuel is injected into a cylinder at an early stage of an exhaust stroke to increase the concentration of unburned HC in exhaust gas.

[0005] In this case, exhaust gas having a high HC concentration flows through the lean NOX catalyst, and as a result, the oxygen concentration in the exhaust gas flowing through the lean NOX catalyst decreases, and NOX is released from the lean NOX catalyst. At the same time, the released NOX is reduced and purified by HC in the exhaust gas.

[0006]

However, in the above-mentioned prior art, the fuel injected in the exhaust stroke sometimes adheres to the inner wall of the cylinder and mixes with the lubricating oil of the internal combustion engine.
When fuel is mixed into the lubricating oil, the viscosity of the lubricating oil decreases, and the lubricating function decreases.

[0007] The present invention has been made in view of the above problems, and prevents fuel from adhering to a wall surface in a cylinder.
It is an object of the present invention to provide an exhaust gas purification apparatus for a direct injection type internal combustion engine that can purify NOx of a lean NOx catalyst without mixing fuel into lubricating oil.

[0008]

The present invention employs the following means in order to solve the above-mentioned problems. That is,
An exhaust gas purification device for a direct injection type internal combustion engine according to the present invention is an exhaust gas purification device for a direct injection type internal combustion engine equipped with a lean NOX catalyst in an exhaust system, and includes a fuel injection unit for injecting fuel into a cylinder. First injection timing means for injecting fuel from the fuel injection means in an intake stroke or a compression stroke, second injection timing means for injecting fuel from the fuel injection means in an expansion stroke or an exhaust stroke, and Injection range control means for controlling the means so that the injection range of the fuel injected by the second injection timing means does not reach the wall surface in the cylinder.

In the exhaust purification system for a direct injection type internal combustion engine according to the present invention, when the internal combustion engine is in an intake stroke or a compression stroke, the first injection timing means injects fuel from the fuel injection means. This fuel injection is a fuel injection for the purpose of combustion, and the injected fuel burns together with the air compressed in the cylinder.

Next, when the internal combustion engine is in the expansion stroke or the exhaust stroke, the second injection timing means injects fuel from the fuel injection means. This fuel injection has a lean NO
This is fuel injection for releasing NOX absorbed by the X catalyst, and the fuel injected by this fuel injection is discharged together with the burned gas in the cylinder. Then, the burned gas discharged together with the fuel becomes exhaust gas and flows to the lean NOx catalyst of the exhaust system.

When fuel is injected at the second injection timing, the injection range control means controls the fuel injection means so that the injection range of the fuel injected from the fuel injection means does not reach the inner wall surface of the cylinder. I do.

The control of the fuel injection range is performed, for example, by injecting a predetermined amount of fuel to be injected at a time by the second injection timing means into a plurality of injections of a specific amount in a plurality of times. Is adjusted to reduce the injection range.

As a result, when fuel is injected from the fuel injection means in the expansion stroke or the exhaust stroke, the fuel does not adhere to the inner wall surface of the cylinder. Further, as another example, the fuel injection means has a first injection unit for injecting fuel along the axial direction of the cylinder, and a second injection unit for uniformly injecting fuel into the cylinder. , The injection range control means,
When the fuel is injected by the first injection timing means, the fuel is injected from the second injection portion of the fuel injection means. When the fuel is injected by the second injection timing means, the fuel is injected. By injecting the fuel from the first injection unit of the means, the fuel may be prevented from adhering to the wall surface in the cylinder.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an exhaust gas purification apparatus for a direct injection type internal combustion engine according to the present invention will be described with reference to the drawings.

FIG. 1 is a view for explaining the principle of an exhaust gas purifying apparatus for a direct injection type internal combustion engine according to the present invention. FIG.
As shown in FIG. 1, the exhaust gas purifying apparatus for a direct injection type internal combustion engine includes an injector 1 as a fuel injection unit, a first injection timing unit 29, and a second injection timing unit 3.
0, an injection control means 32, and an injection range control means 31.

Hereinafter, each component will be sequentially described. <Injector> The injector 1 includes an injector body 101 having a plurality of injection holes 100 at the tip, a needle valve 102 movably housed in the injector body 101, and an electromagnetic valve 103 for opening and closing the needle valve 102. Have. This injector 1
Is mounted so that the tip of the injector body 101 is located in the cylinder 2 of the diesel engine,
From 00, fuel is directly injected into the cylinder 2.

The injector body 101 has an injection hole 1
00, the small holes 124.
Communication hole 104, liquid storage chamber 105, valve through hole 106
It has a spring chamber 107, a valve piston chamber 108, a pressure control chamber 109, and an electromagnetic valve chamber 110.

Further, the injector body 101 has a fuel intake port 111 which is connected to a pressure control chamber 109 via an electromagnetic valve chamber 110 and a liquid reservoir chamber via a fuel passage 112. It communicates with 105.

The communication hole 104 is provided in the small hole 1.
The valve seat 113 has an inner diameter larger than 24 and a boundary surface with the small hole 124. The needle valve 102
Communication hole 104, liquid storage chamber 105, valve through hole 106
-The interior is extended over the valve piston chamber 108, and the small holes 12
A valve shaft 114 which comes into contact with and separates from the valve seat 113 on the fourth side and has a fixed clearance between itself and the inner wall surface in the communication hole 104;
A valve main portion 115 which is located in the valve through hole 106 and is slidably inserted into the valve through hole 106 in a liquid-tight manner, and is slidably fitted into the spring chamber 107 connected to the valve main portion 115. A spring seat 116, a connection shaft 117 connected to the spring seat 116 and extending to the valve piston chamber 108, a piston 118 connected to the connection shaft 117 and housed in the valve piston chamber 108 in a liquid-tight and slidable manner. And

Then, the spring seat 1 is placed in the spring chamber 107.
A coil spring 119 that abuts the needle valve 16 and biases the needle valve 102 toward the distal end is provided. The urging force of the coil spring 119 causes the normal valve shaft 1
14 is in a state of being seated on the valve seat 113.

Next, the solenoid valve 103 is installed in the solenoid valve chamber 110.
The solenoid valve 103 includes a rod 120 that can move forward and backward along the axial direction, and a valve body 121 that is connected to the tip of the rod 120 and is located in the pressure control chamber 109.

The valve body 121 is separated from or seated on a valve seat 122 formed between the pressure control chamber 109 and the electromagnetic valve chamber 110. Here, when drive power is not applied from the injection range control means 31 to the solenoid valve 103, the solenoid valve 10
Rod 1 by a spring (not shown) built in
20 is advanced. As a result, the valve body 121 is
2 and the fuel supply pressure is applied to the pressure control chamber 109.

When the driving power from the injection range control means 31 is applied, the solenoid valve 103 causes the rod 120 to retreat, whereby the valve body 121 is seated on the valve seat 122,
The fuel supply pressure to the pressure control chamber 109 is shut off.

Here, when the diesel engine is in a stopped state, no fuel is supplied to the fuel intake port 111 of the injector 1, so that the needle valve 102 is driven by the urging force of the coil spring 119 so that the distal end 12
3 is seated on the valve seat 113 and the small hole 124 (injection hole 100)
Close.

When the diesel engine is in operation, fuel is supplied to the injector 1. At this time, if the injector 1 is not at the fuel injection timing, no drive power is applied from the injection range control means 31 to the solenoid valve 103.

In this case, the solenoid valve 103 advances the rod 120 by a spring (not shown), and the valve body 121 is moved to the valve seat 1.
Since the pressure control chamber 109 and the electromagnetic valve chamber 110 communicate with each other, the fuel supply pressure applied to the fuel inlet 111 is applied to the pressure control chamber 109 via the electromagnetic valve chamber 110. Then, the fuel supply pressure applied to the pressure control chamber 109 pushes the piston 118 of the needle valve 102.

Further, the fuel applied to the fuel inlet 111 further passes through the fuel passage 112 and the liquid accumulating chamber 10.
5 is applied. Here, the combined force of the force applied to the piston 118 by the fuel supply pressure applied to the pressure control chamber 109 and the force for urging the spring seat 116 by the coil spring 119 is determined by the fuel supply pressure applied to the liquid storage chamber 105. The pressure is set to be equal to or greater than the force applied to the valve main portion 115 of the needle valve 102. As a result, the distal end portion 123 of the needle valve 102 closes the small hole 124 (injection hole 100).

On the other hand, when the injector 1 is at the fuel injection timing, the injection range control means 31
The driving power is applied to the valve 3, whereby the solenoid valve 103 retreats the rod 120, and the valve body 121 is seated on the valve seat 122.

At this time, the application of the fuel supply pressure to the pressure control chamber 109 is cut off, and the volume of the pressure control chamber 109 increases by the retreat of the rod 120. It decreases with increase.

Here, the force applied to the piston 118 of the needle valve 102 and the coil spring 119 correspond to the spring seat 1.
Since the resultant force with the force for urging the valve 16 is set smaller than the force applied to the valve main portion 115 by the fuel supply pressure applied to the liquid storage chamber 105, the needle valve 102 is opposed to the coil spring 119. Regress.

As a result, the distal end 123 of the needle valve 102 is separated from the valve seat 113, whereby the communication hole 104 and the small hole 124 communicate with each other, and the communication hole 104
Is applied to the small hole 124. And the small hole 124
Is injected from the injection hole 100 into the cylinder 2.

The driving control of the injector 1 described above is performed by the first injection timing means 29, the second injection timing means 30, the injection control means 32, and the injection range control means 31. I do.

<First Injection Timing Means> The first injection timing means 29 outputs a timing signal indicating the start timing of fuel injection for combustion (hereinafter, referred to as main injection).

The start timing of the main injection is determined by the position of the crankshaft of the diesel engine, and is, for example, near the compression top dead center. <Second Injection Timing Means> The second injection timing means 30 is activated at regular intervals. The activated second injection timing means 30 starts fuel injection (hereinafter, referred to as sub-injection) for purifying a lean NOx catalyst attached to the exhaust system of the diesel engine based on the position of the crankshaft. A timing signal indicating a time is output.

The above-mentioned fixed period is determined by the lean N after the release of NOx.
This is a period shorter than the time required for the OX catalyst to be saturated. Incidentally, the start timing of the sub-injection is determined by the position of the crankshaft of the diesel engine.
Even when the sub-injection is performed when the reactivity between the NOx absorbed by the OX catalyst and the fuel (HC) is poor, the release and reduction of the NOX absorbed by the lean NOX catalyst are not sufficiently performed. Therefore, when the reactivity between NOx and fuel (HC) is high, that is, when the temperature of the burned gas in the cylinder 2 is high, the sub-injection must be performed. When fuel is injected into high-temperature burned gas, the fuel (HC) is broken down into small molecules and some of the fuel (HC) becomes radicals, which activates the fuel and shows strong reactivity to NOx. It is.

The time when the temperature of the burned gas is high is the expansion stroke after the main injection is completed and the fuel (air-fuel mixture) injected by the main injection is burned. When the sub-injection is performed immediately after the main injection is completed, the fuel molecules undergo a dehydrogenation reaction due to thermal decomposition to generate a black smoke (soot) precursor, and the black smoke (soot) precursor aggregates and coalesces. Produces black smoke (soot).

Therefore, it is preferable that the timing signal indicating the start timing of the sub-injection is output at the latter stage of the expansion stroke or at the beginning of the exhaust stroke, that is, near the bottom dead center of the expansion stroke or the exhaust stroke, which satisfies the above condition. .

<Injection control means> The injection control means 32 controls the injector 1 based on the timing signal from the first injection timing means 29 and the timing signal from the second injection timing means 30. First, the control of the main injection will be described.

When the timing signal is input from the first injection timing means 29, the injection control means 32
Determine the amount of fuel required for main injection. The amount of fuel required for the main injection (main injection amount Imain) is determined in advance by experiment on the relationship between the intake air amount Q of the diesel engine, the engine speed N, and the main injection amount Imain, and the intake air amount Q and the engine speed Nmain are obtained. As a function of

In this case, the injection control means 32 substitutes the intake air amount Q and the engine speed N at the time when the timing signal is inputted from the first injection timing means 29 into the above function, thereby obtaining the main injection. Determine the quantity Imain.

Then, the injection control means 32 calculates the injection time (main injection time tmain) required to satisfy the obtained main injection amount Imain, and supplies the electromagnetic valve 103 of the injector 1 for the calculated main injection time tmain. Apply drive power. Next, the control of the sub injection will be described.

When the timing signal is input from the second injection timing means 30, the injection control means 32
The amount of fuel required for sub-injection (total sub-injection amount Isub) is determined. The total sub-injection amount Isub is calculated based on the temperature of the exhaust gas flowing into the lean NOX catalyst (inlet gas temperature Tin), the temperature of the exhaust gas flowing out of the lean NOX catalyst (outgoing gas temperature Tout),
The relationship between the intake air amount Q of the diesel engine and the total sub-injection amount Isub is obtained by an experiment in advance, and is expressed as a function of the inlet gas temperature Tin, the outlet gas temperature Tout, and the intake air amount Q.

In this case, the injection control means 32 substitutes the input gas temperature Tin, the output gas temperature Tout, and the intake air amount Q at the time when the timing signal is input from the second injection timing means 30 into the function. As a result, the total sub-injection amount I
Find sub.

<Injection Range Control Unit> When the total sub-injection amount Isub is determined by the injection control unit 32, the control of the sub-injection is transferred to the injection range control unit 31.

The injection range control means 31 calculates the total sub-injection amount Isu
When b is injected from the injector 1, the injection pressure is controlled so that the fuel does not reach the wall surface of the cylinder 2. This is because the reach of the fuel injected from the injector 1 becomes wider in accordance with the injection pressure of the injector 1.

That is, the injection pressure Pa (hereinafter, referred to as the sub-injection pressure Pa) when the injected fuel reaches the wall surface of the cylinder 2 is previously determined by an experiment, and the sub-injection pressure is set at an injection pressure less than the sub-injection pressure Pa. I do. In the present embodiment, the injection pressure (injection range) is controlled using the characteristics of the injector 1.

As already explained, the injector 1
It operates based on the force relationship between the pressure in the pressure control chamber 109, the urging force of the coil spring 119, and the pressure in the liquid pool chamber 105 applied to the needle valve 102, so that the small hole 124 is opened due to mechanical operation delay. It takes some time from the start of drilling to the full opening.

Therefore, in a period t1 from the start of the opening of the small holes 124 to the full opening thereof, the injection pressure of the fuel injected from the injection holes 100 increases according to the degree of opening of the small holes 124.

For example, when performing the fuel injection for the injection time t3, the driving power is normally supplied to the solenoid valve 103 during the injection time t3. At this time, during the period t1 (t1 <t3) from the start of the supply of the driving power to the solenoid valve 103, the mechanical operation of the injector 1 (the opening operation of the small hole 124) is spent, so the injection from the injector 1 is performed. As shown in FIG. 2 (a), the injection pressure of the fuel
24, depending on the degree of opening.

When the period t1 has elapsed from the start of the supply of the driving power to the solenoid valve 103, the small hole 124 is fully opened, the fuel injection pressure reaches the maximum value Pmax, and thereafter maintains the maximum value Pmax.

Here, focusing on a period t1 from the start of the injection (at the start of the supply of the driving power to the solenoid valve 103) until the injection pressure reaches the maximum value Pmax, the possible value of the injection pressure during this period t1 is as follows. 0 to Pmax.

The maximum value Pmax is a value assuming main injection, and the range in which fuel injected at the maximum value Pmax reaches (first injection range A) is, as shown in FIG. It extends to two walls. Therefore, when the injection pressure is in the period t
The value (0 to Pmax) that can be taken between 1 is the sub-injection pressure Pa
Will be included.

In the present embodiment, the time required from the start of the injection to the time when the injection pressure reaches the sub-injection pressure Pa (reference sub-injection time tsub = t2) is determined in advance, and the injection range control means 31 uses this reference sub-injection time. The injection (reference sub-injection) shorter than the injection time t2 is performed.

However, since the reference sub-injection time t2 is extremely short, the fuel amount (reference sub-injection amount isub) injected by the injector 1 during a period shorter than the reference sub-injection time t2 is small. For this reason, it is difficult to satisfy the total sub-injection amount Isub by one reference sub-injection.

Therefore, in the present embodiment, the total sub-injection amount Isub is supplemented by repeating the reference sub-injection a plurality of times. Here, a method of determining the number of sub injections will be described.

First, the injection range control means 31 calculates a reference sub-injection amount isub to be injected by the injector 1 during the reference sub-injection time t2. Subsequently, the injection range control means 31
Is obtained by dividing the previously calculated total sub-injection amount Isub by the reference sub-injection amount isub to obtain the number of reference sub-injections Ninj and the remaining fuel amount
Ask for ub. The surplus fuel amount i'sub is determined by the injection time t4
Is converted to

Then, as shown in FIG. 2B, the injection range control means 31 repeats the operation of supplying drive power to the solenoid valve 103 of the injector 1 Ninj times during a period shorter than the reference sub-injection time t2, Further, during time t4, the solenoid valve 103
The operation of supplying the driving power to is performed.

As a result, as shown in FIG. 1, the range in which the fuel injected by the sub-injection (the fuel injected by the reference sub-injection) reaches (the second injection range B) extends to the wall surface of the cylinder 2. Would not be as good.

The first injection timing means 2
9, second injection timing means 30, injection control means 3
2. The injection range control means 31 is a means that is conceptually realized on a microcomputer for controlling the engine. Therefore, from a different viewpoint, the first and second injection timing units or the fuel injection range control may be considered to be included in the injection control unit. <Embodiment> An embodiment in which the above-described principle is applied to a diesel engine will be described below with reference to FIGS.

FIG. 3 is a diagram showing a configuration of a diesel engine to which the above principle is applied. This diesel engine is 4
A cylinder diesel engine body 200 is provided.

The injector 1 is attached to each cylinder of the diesel engine main body 200. Each of these injectors 1 communicates with a common rail chamber 3 via a communication passage 4, and the common rail chamber 3 is connected to a fuel pump 26 via a fuel passage 24.

The fuel pump 26 sucks up the fuel in the fuel tank 25, pressurizes the sucked-up fuel and sends it to the fuel passage 24, and the fuel sent to the fuel passage 24 is provided in the middle of the fuel passage 24. Pressure regulator 28
The pressure is adjusted to a predetermined pressure and supplied to the common rail chamber 3.

A common rail pressure sensor 5 for detecting the pressure Pc of the fuel stored in the common rail chamber 3 is attached to the common rail chamber 3, and a signal output from the common rail pressure sensor 5 is input to the ECU 23. It has become.

The diesel engine body 200
Are connected to the turbine housing 7a of the turbocharger 7 through an exhaust manifold (exhaust manifold branch) 6, and are connected to a surge tank 14 through an intake branch 13.

The turbine housing 7 a of the turbocharger 7 is connected to a lean NOx catalyst 9 via a first exhaust pipe 8. This lean NOx catalyst 9
Is, for example, alumina as a carrier, potassium K, sodium Na, alkali metal such as cesium Cs, barium Ba, alkaline earth such as calcium Ca on the carrier,
In this configuration, at least one selected from rare earth elements such as lanthanum La and yttrium Y and a noble metal such as platinum Pt are supported.

Here, the ratio of the air supplied to the combustion chamber in each cylinder of the diesel engine main body 200 and the first exhaust pipe 8 upstream of the lean NOX catalyst 9 to the fuel (hydrocarbon: HC) is determined as lean NOX. When referred to as the air-fuel ratio of the exhaust gas flowing into the catalyst 9, the lean NOX
The catalyst 9 absorbs NOX in the exhaust gas when the air-fuel ratio of the exhaust gas flowing into the lean NOX catalyst 9 is lean, and absorbs the NOX when the oxygen concentration in the flowing exhaust gas decreases.
It has the effect of releasing X.

If the exhaust system connecting the diesel engine body 200 and the lean NOX catalyst 9 is not provided with a mechanism for supplying fuel (HC) or air to the exhaust gas flowing through the exhaust system, the lean NOX catalyst 9
The air-fuel ratio of the exhaust gas flowing into the cylinder matches the average air-fuel ratio of the air-fuel mixture formed in the combustion chamber in each cylinder of the diesel engine main body 200.

In this case, the lean NOX catalyst 9 absorbs NOX in the exhaust gas if the average air-fuel ratio of the mixture formed in each combustion chamber is lean, and the mixture formed in each combustion chamber. When the average oxygen concentration in the inside decreases, the absorbed NOX is released.

The lean NOx catalyst 9 constructed as described above
Gas temperature sensor 1 for detecting the temperature of the exhaust gas flowing into the lean NOx catalyst 9 (input gas temperature Tin)
An outlet gas temperature sensor 12 for detecting the temperature of the exhaust gas flowing out of the lean NOX catalyst 9 (outlet temperature Tout) is attached to the outlet of the lean NOX catalyst 9. The signals (Tin, Tout) output from the sensors 11 and 12 are input to the ECU 23.

The outlet side of the lean NOX catalyst 9 is connected to the second
The exhaust gas flowing out of the lean NOX catalyst 9 flows through the exhaust pipe 10 to the muffler through an exhaust pipe 10.

The surge tank 14 connected to the diesel engine main body 200 via the intake branch pipe 13 has a first
Is connected to an intercooler 16 via an intake pipe 15 and to the exhaust manifold 6 via a recirculation passage 20 for exhaust gas recirculation (EGR). In the middle of the return passage 20, the return passage 2
An EGR valve 21 that opens and closes 0 is attached.

The intercooler 16 is connected to a compressor housing 7b of the turbocharger 7 via a second intake pipe 17, and the compressor housing 7b is connected to an air flow meter (AFM) 19 via a third intake pipe 18. Is linked to

The air flow meter (AFM) 19
An electric signal indicating the amount of air taken in from the air intake 27 is output, and the output electric signal is input to the ECU 23.

Further, the diesel engine body 20
At 0, a crank angle sensor 22 that outputs an electric signal every time a crankshaft (not shown) rotates by a predetermined angle is attached, and the electric signal output from the crank angle sensor 22 is input to the ECU 23. .

Based on signals from the air flow meter (AFM) 19, the incoming gas temperature sensor 11, the outgoing gas temperature sensor 12, the common rail pressure sensor 5, and the crank angle sensor 22, the ECU 23 performs the first Injection timing means, second injection timing means, injection control means,
In addition, an injection range control unit is realized. (Internal Configuration of ECU 23) The ECU 23 is formed of a digital computer, and is connected to a ROM (Read Only Memory) 23b and RA by a bidirectional bus 23e.
M (Ramdom Access Memory) 23c, CPU (Central
Processing Unit) 23a, output port 23d, and
It has an input port 23k.

Further, an A / D converter 23f is connected to the input port 23k, and four drive circuits 23g, 23h, 23i and 23j are connected to the output port 23d. The ROM 23b stores an application program to be executed by the CPU 23a, a first control map for main injection, a second control map for main injection, a first control map for sub-injection, and a control map for sub-injection. A second control map and a third control map for sub-injection are stored.

The first control map for main injection is a map showing the relationship between the intake air amount Q of the diesel engine body 200, the engine speed N, and the main injection amount Imain. When N is specified, the main injection amount Imain
Is to be determined.

The second control map for the main injection is a map showing the relationship between the common rail pressure Pc, the main injection amount Imain, and the main injection time tmain. When the common rail pressure Pc and the main injection amount Imain are specified. , The main injection time tmain is determined.

The first control map for sub-injection includes the intake air amount Q of the diesel engine body 200 and the input gas temperature T
FIG. 4 is a map showing a relationship between in, an outgassing temperature Tout, and a total sub-injection amount Isub. When the intake air amount Q, the input gas temperature Tin, and the outgassing temperature Tout are specified, the total sub-injection amount Isub is determined. It has become so.

The second control map for sub-injection is a map showing the relationship between the common rail pressure Pc and the reference sub-injection time tsub. When the common rail pressure Pc is specified, the reference sub-injection time t2 is determined. It has become.

The third control map for sub-injection includes a common rail pressure Pc, a reference sub-injection time tsub, and a reference sub-injection amount isub.
Is a map showing the relationship between the reference sub injection amount is and the reference sub injection amount is determined when the common rail pressure Pc and the reference sub injection time tsub are determined.
ub is to be determined.

The CPU 23a operates according to the application program in the ROM 23b,
A control signal for the injector 1 is output with reference to the control map 3b.

The RAM 23c stores an intake air amount Q detected by an air flow meter (AFM) 19, an input gas temperature Tin detected by the input gas temperature sensor 11, and an output gas temperature Tou detected by the output gas temperature sensor 12.
t, a common rail pressure Pc detected by the common rail pressure sensor 5, a crank position signal from the crank angle sensor 22, a calculation result of the CPU 23a, and the like.
The calculation result of the CPU 23a is, for example, an engine speed N calculated based on a crank position signal of the crank angle sensor 22. The data stored in the RAM 23c is updated when an electric signal from the crank angle sensor 22 is input.

The input port 23k is connected to the air flow meter (AFM) 1 through an A / D converter 23f.
9, connected to the incoming gas temperature sensor 11 and the outgoing gas temperature sensor 12. In this case, the air flow meter (AFM) 1
9, analog electric signals from the input gas temperature sensor 11 and the output gas temperature sensor 12 are converted into digital electric signals by the A / D converter 23f, and are converted into the input electric ports 23k.
Is input to

The input port 23k is connected to the common rail pressure sensor 5 and the crank angle sensor 22.
Input digital electric signal from.

The four drive circuits 23g, 23h, 23i and 23j connected to the output port 23d are respectively connected one-to-one with the injectors 1 mounted on the respective cylinders of the diesel engine main body 200.
Drive power is supplied to each injector 1 according to a control signal from 23a. <Operation of Embodiment> The operation of the present embodiment will be described below.

The CPU 23a of the ECU 23 executes a fuel injection processing routine shown in FIG. 5 every time an electric signal is input from the crank angle sensor 22. In the fuel injection processing routine, the CPU 23a refers to the crank position signal stored in the RAM 23c to determine the cylinder at the fuel injection timing, that is, the cylinder whose crankshaft position is near the top dead center of the compression stroke ( S501).

Subsequently, the CPU 23a reads the intake air amount Q, the engine speed N and the common rail pressure Pc stored in the RAM 23c (S502). And the CPU 23a
Accesses the first control map for main injection in the ROM 23b and reads the main injection amount Imain corresponding to the intake air amount Q and the engine speed N read in S502 (S
503).

Next, the CPU 23a accesses the second control map for main injection, and determines the main injection pressure corresponding to the common rail pressure Pc read in S502 and the main injection amount Imain read in S503. The time tmain is read (S504).

The CPU 23a operates the drive circuit 23 corresponding to the injector 1 of the cylinder determined in S501.
The main injection time tmain is given to g, 23h, 23i and 23j. At this time, the drive circuit 23 supplies drive power to the injector 1 during the main injection time tmain (S50).
5). Thus, the injector 1 continues to inject fuel during the main injection time tmain.

The injection range of the fuel injected from the injector 1 is, as shown in FIG.
And spread evenly in the combustion chamber. Next, CPU2
3a determines whether or not a certain period has elapsed since the previous sub-injection process was completed (S506).

If it is determined in S506 that the predetermined period has elapsed, the CPU 23a executes a sub-injection process (S507). On the other hand, if it is determined in S506 that the predetermined period has not elapsed, the CPU 23a ends the fuel injection processing routine.

Here, the sub-injection processing shown in S507 will be described with reference to FIG. FIG. 6 shows the CPU 23a
Is a sub-injection processing routine executed by the subroutine. CPU
23a accesses the RAM 23c to find the incoming gas temperature T
In, the outgassing temperature Tout, and the intake air amount Q are read (S601).

Then, the CPU 23a accesses the first control map for sub-injection stored in the ROM 23b, and corresponds to the input gas temperature Tin, the output gas temperature Tout and the intake air amount Q read out in S601. Total sub injection amount Isub
Is read (S602).

The CPU 23a accesses the RAM 23c and reads out the common rail pressure Pc (S60).
3). Subsequently, the CPU 23a accesses the second control map for sub-injection stored in the ROM 23b, and reads out the reference sub-injection time tsub corresponding to the common rail pressure Pc read out in S603 (S604).

Further, the CPU 23a accesses the third control map for sub-injection stored in the ROM 23b, and reads the common rail pressure Pc read out in S603 and the reference sub-injection time tsub read out in S604. Is read out (S605).

Subsequently, the CPU 23a divides the total sub-injection amount Isub read out in S602 by the reference sub-injection amount isub read out in S605 to obtain the number Ninj of reference sub-injections and the remainder The fuel amount i'sub is calculated (S6
06).

The remaining fuel amount i′sub is determined by the injection time t′sub
(S607). Here, the CPU 23a
Referring to the crank position signal stored in the RAM 23c, the cylinder whose crankshaft position is near the bottom dead center of the expansion stroke or the exhaust stroke is determined (S60).
8).

The CPU 23a operates the drive circuit 23 corresponding to the injector 1 of the cylinder determined in S608.
After the reference sub-injection time tsub is repeatedly given Ninj times to g, 23h, 23i, and 23j, the injection time t′sub
(S609). In this case, the driving circuits 23g, 2g
3h, 23i, and 23j supply the driving power to the injector 1 for the injection time t'sub after repeating the operation of supplying the driving power to the injector 1 for the reference sub-injection time tsub Ninj times.

As a result, the injector 1 repeats the operation of injecting the fuel for the reference sub-injection time tsub Ninj times, and then injects the fuel for the injection time t'sub.

The injection range of the fuel injected from the injector 1 during the reference sub injection time tsub does not reach the wall surface 2a of the cylinder 2 as shown in FIG. further,
Since the injection time t'sub is shorter than the reference sub-injection time tsub, during the injection time t'sub, the injector 1
The injection range of the fuel injected from the cylinder 2 is the wall surface 2a of the cylinder 2.
It does not even extend to. According to the embodiment described above, when the sub-injection for purifying the lean NOx catalyst 9 is performed, it is possible to suppress the fuel injected by the sub-injection from adhering to the wall surface 2a of the cylinder 2. As a result, it is possible to prevent fuel from being mixed into the lubricating oil of the diesel engine main body 200 and suppress a decrease in the viscosity of the lubricating oil. << Other Embodiments >> Another embodiment of the exhaust gas purifying apparatus for a direct injection type internal combustion engine according to the present invention will be described with reference to FIGS. Here, only the configuration different from the above-described embodiment will be described, and the description of the same configuration as the above-described embodiment will be omitted.

FIG. 9 is a sectional view of the tip of the injector 1, FIG. 10 is a perspective view of the tip of the needle valve 102, and FIG. 11 is a perspective view of the tip of the injector body 101.

At the tip of the injector body 101, a through hole 100a penetrating the injector body 101 along the axial direction is formed. The injector body 101 is provided with a distal small outer diameter hole 100b and a proximal large outer diameter hole 10b that are sequentially arranged on the proximal side following the through hole 100a.
0c ・ A valve through hole 106 is provided. Here, since the inner diameter of the proximal-side large outer diameter hole 100c is smaller than the inner diameter of the valve through-hole 106, the valve seat 150 is formed by the step between the proximal-side large outer diameter hole 100c and the valve through-hole 106. You.

Injection holes 100 penetrating the injector body 101 are formed at a plurality of locations along the circumferential direction of the small outer diameter hole 100b on the distal end side. Further, the base end side large outer diameter hole 100 c communicates with the fuel intake port 111 via a fuel passage 112.

In response, the needle valve 10
Reference numeral 2 denotes a valve distal end 125 which is slidably inserted into the through hole 100a in a liquid-tight manner, and following the valve distal end 125, the distal-side small outer diameter hole 100b and the proximal-side large outer diameter hole 1
00c and at the tip side small outer diameter hole 100
valve shaft 114 inserted in a liquid-tight and slidable manner
And a valve main portion 115 that is slidably and liquid-tightly inserted into the valve through hole 106 following the valve shaft 114.

Further, at a plurality of locations along the circumferential direction of the valve shaft 114, fuel intake ports 114a penetrating the valve shaft 114 are formed. This fuel intake 114
a communicates with a fuel injection port 125a formed along the axial direction from the tip of the valve tip 125, so that the fuel supplied to the fuel intake port 114a is injected from the fuel injection port 125a. . The injector 1 configured as described above is in a state where the normal valve main portion 115 is seated on the valve seat 150 by the urging force of the coil spring 119 described in the above embodiment. At this time, a part of the valve shaft 114 is located in the distal-side small outer diameter hole 100b, and the fuel intake port 114a is located in the distal-side small outer diameter hole 1
00b is closed by the inner wall surface. Also,
The space between the proximal-side large outer diameter hole 100c and the injection hole 100 is blocked by the distal-side small outer diameter hole 100b and the valve shaft 114.

As a result, the fuel supplied to the base end side large outer diameter hole 100c is not applied to the fuel intake port 114a and the injection hole 100, and the injector 1 does not inject the fuel.

Next, the force applied to the valve main portion 115 by the fuel supply pressure applied to the large-diameter portion 100c on the proximal end side of the needle valve 102 against the urging force of the coil spring 119 is applied.
Is regressed. In the regression process, first, FIG.
As shown in FIG.
a is located in the proximal-side large outer diameter hole 100c, and a part of the valve shaft 114 is located in the distal-side small outer diameter hole 100b. At this time, the base end side large outer diameter hole 100c communicates with the fuel intake port 114a, and the base end side large outer diameter hole 1c
00c and the injection hole 100 are shut off. Then, the fuel supplied from the fuel passage 112 to the base end side large outer diameter hole 100c flows into the fuel intake port 114a, and is injected from the fuel injection port 125a in the axial direction.

As a result, the injector 1 injects fuel only from the fuel injection port 125a. In this state, the entire valve shaft 114 retreats to the inside of the proximal-side large outside diameter hole 100c, and the proximal-side large outside diameter hole 100c and the distal side small outside diameter hole 1
Continue until 00b is communicated.

The fuel thus injected does not reach the wall surface 2a of the cylinder 2 because it spreads in the cylinder 2 in the axial direction. From this point, the fuel injection port 125a is
It can be said that this is the first injection unit according to the present invention.

Subsequently, when the entire valve shaft 114 retreats into the large-diameter hole 100c on the proximal side, as shown in FIG.
The proximal-side large outer diameter hole 100c communicates with the distal-side small outer diameter hole 100b, and the fuel supplied to the proximal-side large outer diameter hole 100c flows into the distal-side small outer diameter hole 100b. Then, the fuel that has flowed into the front-end-side small outer diameter hole 100b is injected outside the injector 1 through the injection hole 100.

The fuel injected from the injection hole 100 in this way spreads uniformly in the cylinder 2 and reaches the wall surface of the cylinder 2. From this point, the injection hole 100 can be said to be the second injection portion of the present invention.

In the case of performing the sub-injection using the injector 1 described above, after the needle valve 102 starts to retreat (after the power supply to the solenoid valve 103 is started), the proximal large-diameter hole 100c and the distal end The time t required for the communication with the small outer diameter hole 100b (time required for the entire valve shaft 114 to retreat into the large outer diameter hole 100c on the proximal end) is determined, and this time t is determined by the above-described embodiment. May be used instead of the reference sub-injection time tsub described in the above.

[0114]

According to the exhaust gas purifying apparatus for a direct injection type internal combustion engine of the present invention, when the fuel injection for purifying the NOX absorbed by the lean NOX catalyst is performed, the injection range of the injected fuel is determined. Does not reach the inner wall of the cylinder, so that the fuel does not adhere to the wall.

Therefore, according to the present invention, the injected fuel does not mix with the lubricating oil of the internal combustion engine, and the viscosity of the lubricating oil can be prevented from lowering.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of an exhaust gas purification apparatus for a direct injection type internal combustion engine according to the present invention.

FIG. 2 is a timing chart showing fuel injection characteristics of an injector.

FIG. 3 is a diagram showing a configuration of a diesel engine to which an exhaust purification device for a direct injection type internal combustion engine is applied.

FIG. 4 is a diagram showing an internal configuration of an ECU 23.

FIG. 5 is a flowchart showing a fuel injection processing routine executed by a CPU 23a.

FIG. 6 is a flowchart showing a sub-injection processing routine executed by a CPU 23a.

FIG. 7 is a diagram showing a state of fuel injection by main injection.

FIG. 8 is a diagram showing a state of fuel injection by sub-injection.

FIG. 9 is a sectional view of a tip portion of an injector 1 according to another embodiment.

FIG. 10 shows a needle valve 102 according to another embodiment.
Perspective view of the tip

FIG. 11 shows an injector body 1 according to another embodiment.
01 perspective view

FIG. 12 is a sectional view showing the injector 1 at the time of sub injection.

FIG. 13 is a sectional view showing the injector 1 at the time of main injection.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Injector 101 ... Injector body 100 ... Injection hole 100a ... Through-hole 100b ... Tip-side small outer diameter hole 100c ... Base end-side large outer diameter hole 125 ... Valve tip part 125a・ Fuel injection port 2 ・ ・ ・ Cylinder 2a ・ ・ ・ Wall surface 5 ・ ・ ・ Common rail pressure sensor 11 ・ ・ ・ Inlet gas temperature sensor 12 ・ ・ ・ Outlet gas temperature sensor 19 ・ ・ ・ Air flow meter (AFM) 22 ・ ・ ・Crank angle sensor 23 ECU 23a CPU 23b ROM 23c RAM 23g Drive circuit 23h Drive circuit 23i Drive circuit 23j Drive circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 41/40 ZAB F02D 41/40 ZABD F02M 45/08 ZAB F02M 45/08 ZABB 61/14 310 61/14 310Z 61/18 360 61/18 360J

Claims (3)

[Claims] 1. An exhaust purification system for a direct injection type internal combustion engine having a lean NOX catalyst in an exhaust system, comprising: a fuel injection unit for injecting fuel into a cylinder; and a fuel injection unit for performing an intake stroke or a compression stroke. A first injection timing means for injecting fuel, a second injection timing means for injecting fuel from the fuel injection means in an expansion stroke or an exhaust stroke, and a second injection timing for controlling the fuel injection means. An injection range control means for preventing an injection range of the fuel injected by the means from reaching a wall surface in the cylinder. 2. The injection range control means injects a predetermined amount of fuel to be injected at a time by the second injection timing means in a plurality of times by a specified amount. Exhaust purification system for in-cylinder direct injection internal combustion engine. 3. The fuel injection unit has a first injection unit that injects fuel along an axial direction of the cylinder, and a second injection unit that injects fuel uniformly into the cylinder. When the fuel is injected by the first injection timing means, the injection range control means causes fuel to be injected from the second injection part of the fuel injection means, and the fuel is injected by the second injection timing means. The exhaust gas purifying apparatus for a direct injection type internal combustion engine according to claim 1, wherein when the fuel injection is performed, fuel is injected from the first injection unit of the fuel injection means.