JP2008169747A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology performing VIGOM injection while inhibiting bore flashing when VIGOM injection is performed together with main injection in a control device for an internal combustion engine. <P>SOLUTION: Main injection is performed near a compression top dead center by a first fuel injection valve 6 injecting fuel in a cylinder 2 and VIGOM injection is performed near top dead center of exhaust stroke or intake stroke by a second fuel injection valve 12 injecting fuel in the cylinder 2 from an exhaust gas passage 10 outside of the cylinder 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine.

  In a conventional internal combustion engine, a fuel injection valve that injects fuel in a cylinder performs main injection near the compression top dead center, and injects fuel into the cylinder near the top dead center of the exhaust stroke or the intake stroke. (So-called big rubber injection) is performed. As a result, the unburned hydrocarbons in the cylinders are increased and the mixture containing the unburned hydrocarbons is compressed, so that the fuel injection timing can be delayed and the exhaust gas discharged from the internal combustion engine can be delayed. The temperature can be relatively high.

And the technique which raises the cylinder internal pressure in the timing when this big rubber injection is performed, suppresses the momentum of the spray by big rubber injection, and suppresses the damage given to a piston is disclosed (for example, refer to patent documents 1).
JP 2005-163548 A JP 2006-22788 A

  However, when the big rubber injection is performed by the fuel injection means for injecting the fuel in the cylinder, even if the cylinder internal pressure is increased as in Patent Document 1, the momentum of the spray of the fuel injected at a high pressure is still strong, The fuel that diffuses after injection tends to adhere to the cylinder inner wall surface in the liquid state. For this reason, the fuel may wash away the oil on the inner wall surface of the cylinder and the oil film may be cut (so-called bore flushing).

  An object of the present invention is to provide a technique for performing big rubber injection while suppressing bore flushing when performing main rubber injection and big rubber injection in a control device for an internal combustion engine.

In the present invention, the following configuration is adopted. That is,
First fuel injection means for injecting fuel in the cylinder;
Second fuel injection means for injecting fuel into the cylinder from an exhaust passage outside the cylinder;
Fuel injection control means for performing main injection in the vicinity of compression top dead center by the first fuel injection means and performing sub-injection in the vicinity of top dead center of the exhaust stroke or intake stroke by the second fuel injection means. This is a control device for an internal combustion engine.

  Big rubber injection is a sub-injection into the cylinder near the top dead center of the exhaust stroke or intake stroke. The big rubber injection mainly increases the unburned hydrocarbon in the cylinder and compresses the air-fuel mixture containing the unburned hydrocarbon so that the fuel injection timing can be delayed. This is performed for the purpose of increasing the temperature of the exhaust gas exhausted from the exhaust system and increasing the temperature of the exhaust gas purification device provided in the exhaust system. When raising the temperature of the exhaust purification device, particles collected in the particulate filter as the exhaust purification device or during the temperature rise control of the sulfur poisoning recovery control of the NOx storage reduction catalyst as the exhaust purification device An example of the temperature increase control in the PM regeneration process control for removing the particulate matter (PM) can be given.

  In the present invention, this big rubber injection is not performed by the first fuel injection means for injecting fuel in the cylinder, but by the second fuel injection means for injecting fuel into the cylinder from the exhaust passage outside the cylinder.

  According to the present invention, since the fuel is injected into the cylinder from the second fuel injection means arranged in the exhaust passage outside the cylinder, the distance until the fuel reaches the cylinder is larger than when the fuel is injected in the cylinder. It becomes longer and the momentum of fuel spray reaching the cylinder is weakened. Further, high-temperature exhaust exists in the exhaust passage, and fuel is injected into the exhaust, so that atomization of fuel is promoted. For this reason, the fuel that has reached the inside of the cylinder floats in a weakly atomized state and easily mixes with the air in the cylinder.

  Therefore, the fuel injected with the rubber according to the present invention is not liable to adhere to the cylinder inner wall surface in a liquid state, and bore flushing can be suppressed. Therefore, according to the present invention, when performing the main injection and the big rubber injection, the big rubber injection can be performed while suppressing bore flushing.

A variable valve timing mechanism for changing the valve timing of the exhaust valve;
A valve that opens the exhaust valve by the variable valve timing mechanism when the fuel injection control means performs sub-injection into the cylinder near the top dead center of the exhaust stroke or the intake stroke by the second fuel injection means. Timing control means;
It is good to have.

  Here, since the second fuel injection means is disposed in the exhaust passage outside the cylinder, fuel cannot be injected into the cylinder if the exhaust valve is closed. According to the present invention, when the big rubber injection is performed by the second fuel injection means, the exhaust valve is opened by the variable valve timing mechanism. For this reason, the fuel injected from the second fuel injection means disposed in the exhaust passage outside the cylinder can reach the cylinder through the exhaust valve in the valve open state. Thereby, big rubber injection is enabled from the 2nd fuel injection means.

  According to the present invention, in the control device for an internal combustion engine, when performing the main rubber injection and the big rubber injection, the big rubber injection can be performed while suppressing the bore flushing.

  Specific examples of the present invention will be described below.

<Example 1>
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the control device for an internal combustion engine according to the present embodiment is applied and an intake system / exhaust system thereof.

  An internal combustion engine 1 shown in FIG. 1 is a diesel engine for driving a vehicle. A piston 3 is slidably provided in the cylinder 2 of the internal combustion engine 1. An intake port 4 and an exhaust port 5 are connected to the combustion chamber in the upper part of the cylinder 2.

  Further, the cylinder 2 is provided with a first fuel injection valve 6 that directly injects fuel into a combustion chamber in the cylinder 2. The first fuel injection valve 6 corresponds to the first fuel injection means of the present invention.

  The opening of the intake port 4 to the combustion chamber is opened and closed by the intake valve 7, and the opening of the exhaust port 5 to the combustion chamber is opened and closed by the exhaust valve 8. The intake port 4 is connected to the intake passage 9, and the exhaust port 5 is connected to the exhaust passage 10.

  An intake throttle valve 11 is disposed in the intake passage 9 to adjust the amount of external intake air (hereinafter referred to as fresh air) introduced into the cylinder 2.

  The most upstream exhaust passage 10 is provided with a second fuel injection valve 12 that injects fuel from the exhaust passage 10 outside the cylinder 2 into the combustion chamber in the cylinder 2. This second fuel injection valve 12 corresponds to the second fuel injection means of the present invention.

  Further, a particulate filter (hereinafter referred to as a filter) 13 is provided in the exhaust passage 10 downstream of the portion where the second fuel injection valve 12 is disposed. The filter 13 may carry an NOx storage reduction catalyst (hereinafter referred to as NOx catalyst). The filter 13 collects PM in the exhaust gas. Further, when the NOx catalyst is supported, when the oxygen concentration of the exhaust gas flowing into the NOx catalyst is high, the NOx in the exhaust gas is occluded, while the oxygen concentration of the exhaust gas flowing into the NOx catalyst is lowered. Sometimes the stored NOx is released. At the time of the release, if a reducing component such as unburned hydrocarbon or carbon monoxide is present in the exhaust gas, the NOx released from the NOx catalyst is reduced.

  The internal combustion engine 1 configured as described above is provided with an ECU 14 that is an electronic control unit. An accelerator opening sensor 15 and a crank position sensor 16 are electrically connected to the ECU 14. The accelerator opening sensor 15 detects the accelerator opening of a vehicle on which the internal combustion engine 1 is mounted. The crank position sensor 16 detects the crank angle of the crankshaft of the internal combustion engine 1. These output values are input to the ECU 14. The ECU 14 estimates the engine load of the internal combustion engine 1 based on the detection value of the accelerator opening sensor 15 and calculates the engine speed of the internal combustion engine 1 based on the detection value of the crank position sensor 16.

  Further, the ECU 14 is electrically connected to the first fuel injection valve 6, the second fuel injection valve 12, and the intake throttle valve 11. These are controlled by the ECU 14.

  In this embodiment, a variable valve timing mechanism (hereinafter referred to as VVT) 17 is used. The VVT 17 can change the relative rotation phase between the exhaust side camshaft 18 that opens and closes the exhaust valve 8 and the exhaust side pulley 19 attached to the exhaust side camshaft 18, and according to a command from the ECU 14. The relative rotation phase between the exhaust camshaft 18 and the exhaust pulley 19 is controlled. The exhaust pulley 19 is rotationally driven by the driving force of the crankshaft of the internal combustion engine 1. Thereby, the exhaust side camshaft 18 is rotationally driven, and the opening / closing operation of the exhaust valve 8 is performed. The exhaust valve 8 can be maintained in an open state by using the VVT 17 and retarding the valve timing (valve closing timing) of the exhaust valve 8.

  Then, the ECU 14 performs fuel injection control based on the operating state of the internal combustion engine 1 that is grasped from the detection signals of various sensors. In the fuel injection control, parameters such as the fuel injection amount, the injection timing, and the injection pattern are set with respect to the implementation of fuel injection into the cylinder 2 through the first and second fuel injection valves 6 and 12, and based on the set parameters. Thus, the opening / closing operation of the first and second fuel injection valves 6 and 12 is executed.

  The ECU 14 repeatedly performs such fuel injection control every predetermined time during the operation of the internal combustion engine 1. The fuel injection amount and injection timing are basically based on the engine load derived from the detected value of the accelerator opening sensor 15 and the engine speed derived from the detected value of the crank position sensor 16 and refer to a preset map. And decide. In addition to obtaining the engine output by performing fuel injection near the compression top dead center as the main injection, the fuel injection pattern includes sub injection near the top dead center of the exhaust stroke or the intake stroke in addition to the main injection. May be carried out as a big rubber injection.

This big rubber injection is performed for the purpose of raising the temperature of the filter 13 provided in the exhaust system. The case of increasing the temperature of the filter 13 is, for example, at the time of temperature increase control of the sulfur poisoning recovery control of the NOx catalyst or at the time of temperature increase control of the PM regeneration processing control for removing PM collected by the filter 13. is there.

  Here, the sulfur poisoning recovery control will be described. The fuel of the internal combustion engine 1 usually contains a sulfur component. In addition to NOx, the exhaust contains a sulfur component originating from the sulfur component in the fuel (SOx (sulfur oxide), S, etc.). Is also present. The sulfur component present in the exhaust is absorbed by the NOx catalyst with higher efficiency than NOx, and the oxygen concentration in the exhaust sufficient to release NOx stored in the NOx catalyst is below a predetermined value. Even under conditions, it is not easily released from the NOx catalyst. For this reason, as the engine operation continues, sulfur components in the exhaust gradually accumulate on the NOx catalyst, resulting in sulfur poisoning. Therefore, as a measure for recovering sulfur poisoning, control (sulfur poisoning recovery control) is performed in which the temperature of the NOx catalyst is raised and the air-fuel ratio of the exhaust is made richer than the stoichiometric air-fuel ratio or slightly richer.

  The PM regeneration process control will be described. The filter 13 is provided in the exhaust passage 10 of the internal combustion engine 1 and collects PM contained in the exhaust gas. However, since the amount of PM that can be collected by the filter 13 is limited, It is necessary to appropriately remove the collected PM. Therefore, as a method for removing the PM collected in the filter 13, the temperature of the filter 13 is raised to a temperature range where the PM can be oxidized while the inside of the filter 13 is in an oxidizing atmosphere, whereby the PM is oxidized and removed. ing.

  By the way, conventionally, the rubber injection is performed by a fuel injection valve that injects fuel in the cylinder 2 like the first fuel injection valve 6. In this case, even if the internal pressure of the cylinder 2 is increased, the momentum of the spray of the fuel injected at a high pressure is still strong, and the fuel diffused after the injection is liable to adhere to the inner wall surface of the cylinder 2 in the liquid state. For this reason, the fuel may wash off the oil on the inner wall surface of the cylinder 2 and the oil film may be cut (so-called bore flushing).

  Therefore, in the present embodiment, the second rubber injection is not performed by the first fuel injection valve 6 that injects the fuel in the cylinder 2 but the fuel is injected from the exhaust passage 10 outside the cylinder 2 into the combustion chamber in the cylinder 2. The fuel injection valve 12 is used.

  As described above, since the fuel is injected from the exhaust passage 10 outside the cylinder 2 into the combustion chamber in the cylinder 2 using the second fuel injection valve 12, the second fuel injection valve 12 is the most upstream of the exhaust passage 10. As shown in FIG. 1, the fuel injection direction is arranged in the cylinder 2 (in a direction reverse to the exhaust flow direction).

  Here, the injection timing of the main injection and the big rubber injection in the case of the present embodiment will be described with reference to FIG. (A) shows a four-stroke cycle of an intake stroke, a compression stroke, an expansion stroke (explosion stroke), and an exhaust stroke in the internal combustion engine 1, (b) shows a valve open state of the intake valve 7 and the exhaust valve 8, (c) ) Indicates the injection timing of main injection and big rubber injection.

  The injection timing of the big rubber injection performed by the second fuel injection valve 12 is near the top dead center of the exhaust stroke or the intake stroke. In particular, in this embodiment, after the exhaust top dead center, the fuel is also sucked into the cylinder 2 from the exhaust passage 10 by the suction force when fresh air in the intake passage 9 is sucked into the cylinder 2 in the intake stroke. A corner rubber is injected.

After this exhaust top dead center, the exhaust valve 8 is normally closed, and even if fuel is injected from the second fuel injection valve 12, the fuel does not reach the cylinder 2, and the outside of the cylinder 2 Fuel is only sprayed to the exhaust valve 8 and the exhaust port 5 in the closed state. Therefore, in this embodiment, the valve closing timing of the exhaust valve 8 is retarded using the VVT 17. For this reason, in this embodiment, the exhaust valve 8 is still maintained in the open state at the timing at which the big rubber injection is performed after the exhaust top dead center. As a result, the fuel injected from the second fuel injection valve 12 disposed in the exhaust passage 10 outside the cylinder 2 can reach the cylinder 2 through the exhaust valve 8 in the opened state.

  In this embodiment, the timing of performing the rubber injection after the exhaust top dead center is set so that the fuel is sucked into the cylinder 2 more efficiently. However, in the present invention, the normal exhaust valve 8 is used without using the VVT 17. The rubber injection may be performed from the second fuel injection valve 12 while the valve is open.

  The injection timing of the main injection performed by the first fuel injection valve 6 is near the compression top dead center. In particular, in the present embodiment, the fuel by the big rubber injection evaporates in the subsequent stroke and becomes easily ignited, and the combustion is stabilized. Therefore, the main injection is performed at a retarded angle after the compression top dead center. As a result, the exhaust energy increases, and the exhaust gas whose temperature rises accordingly is discharged into the exhaust passage 10 and reaches the filter 13, whereby the temperature of the filter 13 can be raised.

  According to the present embodiment described above, fuel is injected into the combustion chamber in the cylinder 2 from the second fuel injection valve 12 disposed in the exhaust passage 10 outside the cylinder 2 as big rubber injection. The distance until the fuel reaches the cylinder 2 becomes longer than the case where the fuel is sprayed, and the momentum of the fuel spray reaching the cylinder 2 is weakened. Further, high-temperature exhaust exists in the exhaust passage 10, and fuel is injected into the exhaust, so that fuel atomization is promoted. For this reason, the fuel that has reached the inside of the cylinder 2 floats in the atomized state with a low momentum, and easily mixes with the air in the cylinder 2.

  Therefore, the fuel injected with the big rubber according to the present embodiment is difficult to adhere to the inner wall surface of the cylinder 2 in a liquid state, and bore flushing can be suppressed. Therefore, according to the present embodiment, when performing the main injection and the big rubber injection, the big rubber injection can be performed while suppressing bore flushing.

  In addition, since bore flushing can be suppressed, there is no need to limit the fuel injection amount of the big rubber injection because of fear of the occurrence of bore flushing.

  FIG. 3 is a flowchart showing a control routine of main injection and big rubber injection that is executed every predetermined time through the ECU 14.

  When the process shifts to this routine, the ECU 14 first determines in step S101 whether or not the temperature raising control of the exhaust system is necessary. When it is determined that the temperature raising control is necessary, the process proceeds to step S102, and when it is determined that the temperature increase control is not necessary, this routine is once ended.

  In step S102, the ECU 14 determines whether or not the operating state of the internal combustion engine 1 is in the low / medium load range. When the engine operating state is in a high load range, if big rubber injection is performed in addition to main injection, the air-fuel ratio of the air-fuel mixture supplied to engine combustion becomes rich and smoke is generated. Is concerned. In view of this, when the engine is operating such that smoke does not occur, that is, when the engine is operating in a low / medium load range, main injection and big rubber injection are performed.

  When it is determined that the operating state of the internal combustion engine is in the low / medium load region, the process proceeds to step S103, and when it is determined that the operating state of the internal combustion engine is not in the low / medium load region, this routine is temporarily performed. finish.

In step S103, the ECU 14 performs main injection and big rubber injection. Specifically, main injection is performed after the compression top dead center by the first fuel injection valve 6, and big rubber injection is performed after the exhaust top dead center by the second fuel injection valve 12. Further, when the big rubber injection is performed by the second fuel injection valve 12, the valve closing timing of the exhaust valve 8 is delayed so that the exhaust valve 8 is opened by the VVT 17. Thereafter, this routine is temporarily terminated.

  The ECU 14 that executes this step corresponds to the fuel injection control means and the valve timing control means of the present invention.

  The main injection and the big rubber injection are controlled by the routine described above.

  In the present embodiment, the second fuel injection valve 12 injects fuel into the cylinder 2 when the exhaust valve 8 is in an open state in order to perform big rubber injection. However, fuel is injected when the exhaust valve 8 is closed, and the injected fuel is injected into the exhaust valve 8 and the exhaust port 5 outside the cylinder 2 to add fuel to the exhaust. Also good. The addition of fuel to the exhaust is performed in order to make the air-fuel ratio of the exhaust rich at a stoichiometric air-fuel ratio or slightly richer in so-called NOx reduction treatment control or sulfur poisoning recovery control.

  Further, in the present embodiment, the second fuel injection valve 12 is arranged in the exhaust gas passage 10 at the most upstream portion. However, according to the present invention, the exhaust port 5 is also part of the exhaust gas passage outside the cylinder 2. Assuming that the second fuel injection valve 12 is disposed in the exhaust port 5 may be used.

  The control device for an internal combustion engine according to the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the gist of the present invention.

1 is a diagram illustrating an internal combustion engine and an intake system / exhaust system thereof according to Embodiment 1. FIG. It is a figure for demonstrating the injection timing of the main injection which concerns on Example 1, and a big rubber injection. 3 is a flowchart illustrating a control routine for main injection and big rubber injection according to the first embodiment.

Explanation of symbols

1 Internal combustion engine 2 Cylinder 3 Piston 4 Intake port 5 Exhaust port 6 First fuel injection valve 7 Intake valve 8 Exhaust valve 9 Intake passage 10 Exhaust passage 11 Intake throttle valve 12 Second fuel injection valve 13 Filter 14 ECU
15 Accelerator opening sensor 16 Crank position sensor 17 VVT
18 Exhaust side camshaft 19 Exhaust side pulley

Claims (2)

First fuel injection means for injecting fuel in the cylinder;
Second fuel injection means for injecting fuel into the cylinder from an exhaust passage outside the cylinder;
Fuel injection control means for performing main injection in the vicinity of compression top dead center by the first fuel injection means and performing sub-injection in the vicinity of top dead center of the exhaust stroke or intake stroke by the second fuel injection means. A control device for an internal combustion engine. A variable valve timing mechanism for changing the valve timing of the exhaust valve;
Valve timing control means for opening the exhaust valve by the variable valve timing mechanism when the fuel injection control means performs sub-injection near the top dead center of the exhaust stroke or the intake stroke by the second fuel injection means; ,
The control apparatus for an internal combustion engine according to claim 1, further comprising:

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