JP4400516B2 - In-cylinder injection internal combustion engine control device - Google Patents

Description

  The present invention relates to a fuel injection control device for an internal combustion engine that performs fuel injection by setting a fuel injection timing in a stroke period selected from an intake stroke and a compression stroke for each cylinder of a direct injection internal combustion engine. About.

  Conventionally, when the internal combustion engine is at a low load, such as during idling, fuel is injected into the cylinder during the compression stroke to perform stratified combustion, and during high load, the fuel is injected into the cylinder during the intake stroke. Thus, there is a cylinder injection type internal combustion engine that achieves both low fuel consumption and high output.

  In such an internal combustion engine, fuel is injected during the compression stroke in order to warm up the catalyst so that the catalyst reaches the activation temperature early when it is cold. By stratifying the air-fuel mixture and burning it for a long time, the exhaust gas temperature is raised and the early activation of the catalyst is promoted. Thus, after the fuel is injected in the compression stroke and the catalyst is warmed up, the fuel injection timing is changed so that the fuel is injected in the intake stroke. When the fuel injection timing is changed from the compression stroke to the intake stroke, the fuel injection amount is reduced for a while. This compensates for the vaporization of the fuel adhering to the piston top surface during fuel injection in the compression stroke, and maintains the mixture in the combustion chamber at an appropriate fuel concentration (so as not to become too rich). It is.

  In such a direct injection internal combustion engine, when the fuel injection timing is changed from the compression stroke to the intake stroke, the intake stroke injection immediately after the change of the fuel injection timing particularly generates black smoke in the exhaust. Easy state. JP 2004-176590 A (Patent Document 1) is a compression method in view of the fact that the increase in the amount of adhesion to the piston top surface cannot be suppressed by reducing the fuel injection amount as described above, and black smoke is not suppressed. Disclosed is a fuel injection control device for a direct injection internal combustion engine that effectively suppresses the generation of black smoke when the fuel injection timing is changed from a stroke to an intake stroke. This control device is a fuel injection control device that performs fuel injection by setting a fuel injection timing in a stroke period selected from an intake stroke and a compression stroke for each cylinder of a direct injection internal combustion engine. When changing the fuel injection timing from the compression stroke to the intake stroke, there is provided an injection timing retarding means for temporarily retarding the fuel injection timing in the intake stroke immediately after the change between the strokes.

According to this fuel injection control device for a direct injection internal combustion engine, when fuel injection is executed during the compression stroke, fuel accumulation occurs on the piston top surface without post-combustion. When the fuel injection timing is changed from the compression stroke to the intake stroke by the injection timing retarding means, the fuel injection timing in the intake stroke immediately after the change between the strokes is temporarily retarded. Due to the retard of the injection timing, in the intake stroke injection, the fuel injection is executed in a state where the piston top surface is sufficiently separated from the fuel injection valve. For this reason, at the start of the intake stroke injection, a large amount of fuel is not added to the fuel adhering to the piston top surface accumulated at the time of the compression stroke injection, and the amount of fuel combusted in the afterburning state by homogeneous combustion is reduced. Can do. This effectively suppresses black smoke generation when the fuel injection timing is changed from the compression stroke to the intake stroke.
JP 2004-176590 A

  During rapid catalyst warm-up (stratified combustion by compression stroke injection) in a cylinder injection internal combustion engine as described above, for example, when the accelerator pedal is depressed, the rapid catalyst warm-up is temporarily interrupted, and intake stroke injection is performed. It may be changed to homogeneous combustion. If rapid catalyst warm-up is required after changing to this homogeneous combustion, the fuel injection timing is changed from the intake stroke to the compression stroke. This indicates that the fuel injection timing is changed contrary to the above-described Patent Document 1. Even in such a case, it is conceivable to correct the fuel injection amount in consideration of the amount of fuel adhering to the piston. However, if the fuel cut is executed during the intake stroke injection, the piston operates and intake / exhaust is performed even during the fuel cut, so that the amount of fuel adhering to the piston changes. If the amount of fuel adhering to the piston changes, an appropriate mixture cannot be formed even if the fuel injection amount is corrected when the fuel injection timing is changed from the intake stroke to the compression stroke. May become a mixture. That is, the air-fuel ratio of the air-fuel mixture may deviate from the target value when the fuel injection timing is changed from the intake stroke to the compression stroke across the fuel cut. Such a problem cannot be solved by the fuel injection control device disclosed in Patent Document 1.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to change the fuel injection timing from the intake stroke to the compression stroke with a fuel cut in a direct injection internal combustion engine. It is an object of the present invention to provide a control device for a direct injection internal combustion engine that does not cause the air-fuel ratio of the air-fuel mixture to deviate from the target value, and particularly does not become lean.

  A control device according to a first aspect of the present invention controls a direct injection internal combustion engine that can switch between intake stroke injection for injecting fuel in an intake stroke and compression stroke injection for injecting fuel in a compression stroke during engine operation. The control device executes a fuel cut after the intake stroke injection is performed, and a detection means for detecting a switch request to the compression stroke injection either during the fuel cut or immediately after the fuel cut is detected. And a control means for controlling the internal combustion engine so as to switch to the compression stroke injection after executing the intake stroke injection until a predetermined condition is satisfied with respect to the state of the combustion chamber of the internal combustion engine.

  According to the first invention, when the fuel injection timing is switched from the intake stroke to the compression stroke across the fuel cut, the state in the combustion chamber of the internal combustion engine, particularly before changing from the intake stroke injection to the compression stroke injection, The intake stroke injection is extended until the state of the amount of fuel adhering to the piston is stabilized so as not to be affected by the fuel cut. In this way, even when the injection fuel amount is corrected to decrease when switching to compression stroke injection, the fuel corresponding to the decrease correction amount adheres to the piston and the fuel is vaporized in the combustion chamber. Even if the fuel injection amount is corrected as usual immediately after the intake stroke injection is changed to the compression stroke injection, the air-fuel ratio of the mixture does not deviate from the target value. As a result, in the direct injection internal combustion engine, even when the fuel injection timing is changed from the intake stroke to the compression stroke across the fuel cut, the air-fuel ratio of the mixture does not deviate from the target value. In addition, it is possible to provide a control device for a direct injection internal combustion engine that does not become particularly lean.

  In the control device according to the second invention, in addition to the configuration of the first invention, the predetermined condition is a condition determined with respect to time.

  According to the second aspect of the present invention, since the intake stroke injection is continued (extended) for a predetermined time after the fuel is cut after the fuel is injected in the intake stroke, the influence of the fuel cut is restored to the state in the combustion chamber. Desired wet state. Even if the fuel injection amount is corrected as usual immediately after the intake stroke injection is changed to the compression stroke injection across the fuel cut, the air-fuel ratio of the mixture does not deviate from the target value.

  In the control device according to the third aspect of the invention, in addition to the configuration of the second aspect of the invention, the predetermined condition is that the time until the amount of attached fuel in the combustion chamber reaches a desired state elapses. .

  According to the third aspect of the present invention, the intake stroke injection is continued (extended) for a predetermined time after the fuel is cut after the fuel is injected in the intake stroke, so that the influence of the fuel cut is restored to the state in the combustion chamber. Desired wet state.

  In the control device according to the fourth invention, in addition to the configuration of the first invention, the predetermined condition is a condition determined for the number of times of fuel injection.

  According to the fourth aspect of the invention, after the fuel is cut in the intake stroke and then the fuel cut is performed, the intake stroke injection is continued (extended) for a predetermined number of injections or more. To the desired wet state. Even if the fuel injection amount is corrected as usual immediately after the intake stroke injection is changed to the compression stroke injection across the fuel cut, the air-fuel ratio of the mixture does not deviate from the target value.

  In the control device according to the fifth aspect of the invention, in addition to the configuration of the fourth aspect of the invention, the predetermined condition is that the number of times of fuel injection elapses until the amount of attached fuel in the combustion chamber reaches a desired state. It is.

  According to the fifth aspect of the present invention, since the intake stroke injection is continued (extended) after the fuel cut is performed after the fuel is injected in the intake stroke, the influence of the fuel cut is restored to the state in the combustion chamber. To the desired wet state.

  In the control device according to the sixth invention, in addition to the configuration of any one of the first to fifth inventions, the compression stroke injection is performed when warming up the catalyst for purifying the exhaust gas of the internal combustion engine. .

  According to the sixth aspect of the invention, fuel is injected in the compression stroke for warming up the catalyst so that the catalyst reaches the activation temperature early when cold. In this way, the exhaust gas temperature can be increased by stratifying the air-fuel mixture and combusting for a long time, and early activation of the catalyst can be promoted.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

FIG. 1 shows an overall configuration diagram of a direct injection engine controlled by the control device of the present invention.
The engine body 10 has a cylinder head 110 covered over a cylinder block 100, and a piston 120 is slidably held in a cylinder 100A formed in the cylinder block 100. The reciprocating motion of the piston 120 in the cylinder 100A is converted into the rotational motion of the crankshaft 130 and transmitted to a transmission or the like. The crankshaft 130 is connected to the starter 30 via the flywheel 140 when the engine is started.

  A combustion chamber 1000 is formed above the piston 120 with the cylinder block 100 and the cylinder head 110 as chamber walls. In the combustion chamber 1000, a mixture of fuel and air is burned, and the piston 120 moves up and down by the explosive force. Move it. The air-fuel mixture is ignited by a spark plug 150 provided through the cylinder head 110 and protruding into the combustion chamber 1000.

  Supply of air constituting the air-fuel mixture is performed by an intake passage 1010 formed in the intake pipe connected to the cylinder head 110 and the cylinder head 110. Further, exhaust from the combustion chamber 1000 is performed by an exhaust passage 1020. The cylinder head 110 is provided with an intake valve 160 for switching communication between the intake passage 1010 and the combustion chamber 1000 and an exhaust valve 170 for switching communication between the exhaust passage 1020 and the combustion chamber 1000. ing.

  A flap-like throttle valve 190 is provided in the intake pipe, and the air flow in the intake passage 1010 is adjusted according to the opening.

  The fuel constituting the air-fuel mixture is supplied by an electromagnetic injector 210. The injector 210 is provided through the cylinder head 110 and injects fuel into the combustion chamber 1000 from the tip nozzle portion.

  The fuel supplied to the injector 210 is supplied by boosting the fuel sucked from the fuel tank 250 in two stages by the low pressure pump 240 and the high pressure pump 230. The high-pressure pump 230 is driven by power transmitted from the crankshaft 130 of the engine body 10 via a belt or the like. On the other hand, the low-pressure pump 240 is electrically driven, and the fuel is also supplied from the low-pressure pump 240 to the injector 210 at the time of starting.

Further, an engine control computer (hereinafter referred to as an engine ECU (Electronic ECU)) that controls each part of the engine such as the spark plug 150, the throttle valve 190, the injector 210, and the like.
Control Unit) 60) is provided. The engine ECU 60 has a general configuration including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like, and the ignition plug 150 is installed on the basis of detection signals from various sensors. Actuate, output a control signal to the throttle valve 190 to adjust the opening of the throttle valve 190 (throttle opening), energize the injector 210 by the control signal, and open the nozzle of the injector 210 at a predetermined timing for a predetermined time. .

  The engine ECU 60 includes a combustion stabilization control circuit. The combustion stabilization control circuit detects the misfire state of the engine 10 based on the engine speed signal from the crank angle sensor 520 of the engine 10, and stabilizes the combustion of the engine 10 in the misfire state. Thus, the engine 10 is controlled. As will be described later, this combustion stabilization control circuit is realized by software for controlling each part of the engine in the engine ECU 60.

  Sensors input to the engine ECU 60 include a mass flow meter 510 that measures the flow rate of air flowing through the intake passage 1010, a crank angle sensor 520, an A / F sensor 530, and a cooling water temperature sensor that detects an engine cooling water temperature representative of the engine temperature. Etc. Further, when the driver operates the key at the time of starting, the ignition (IG) on signal and the starter on signal are input to the engine ECU 60, and when the driver depresses the accelerator pedal 420, the depression amount is input. It has become.

  The engine ECU 60 controls the combustion injection amount based on the intake air amount detected by the mass flow meter 510 or the like. At this time, the engine ECU 60 controls the injection amount and the injection timing according to the engine speed and the engine load so as to achieve an optimal combustion state based on signals from the sensors. In the engine main body 10, in order to inject fuel directly into the cylinder, injection timing control and injection amount control are performed simultaneously. Further, the engine ECU 60 performs ignition timing control so as to achieve an optimal ignition timing based on signals (including a knocking sensor and the like) detected by the crank angle sensor 520, the cam position sensor, and the like. Such control realizes both high output and low emission of the engine body 10.

  The engine ECU 60 that is the control device according to the present embodiment does not cause the air-fuel ratio of the air-fuel mixture to deviate from the target value when the fuel injection timing is changed from the intake stroke to the compression stroke with the fuel cut interposed therebetween. As described above (in particular, so as not to become lean), control is performed to extend the fuel injection in the intake stroke before changing the fuel injection timing in the compression stroke.

  With reference to FIG. 2, a control structure of a program executed by engine ECU 60 according to the present embodiment will be described. This program is a program for rapid catalyst warm-up control.

  In step (hereinafter step is abbreviated as S) 100, engine ECU 60 executes catalyst rapid warm-up control. At this time, the injector 210 injects fuel in the compression stroke. Further, the ignition timing of the spark plug 150 is retarded, and the temperature of the catalyst provided in the exhaust passage 1020 is rapidly increased so that the mixture is stratified and combusted for a long time (also combusted in the exhaust stroke). To activate the catalyst.

In S110, engine ECU 60 determines whether or not rapid catalyst warm-up has been completed. At this time, for example, when the integrated intake air amount from the start of catalyst rapid warm-up exceeds a predetermined air amount, engine ECU 60 determines that catalyst rapid warm-up has ended. The engine ECU 60 may determine that the rapid catalyst warm-up has ended based on a temperature detected by a temperature sensor provided in the exhaust passage 1020 in the vicinity of the catalyst. When the rapid catalyst warm-up is completed (YES in S110), this process ends. If not (NO in S110), the process proceeds to S120. In S120, engine ECU 60 determines whether or not an interruption request for rapid catalyst warm-up control has been detected during rapid catalyst warm-up control. . For example, when the accelerator pedal 420 is depressed by the driver, a request for interrupting the rapid catalyst warm-up control is generated. If a request for interrupting rapid catalyst warm-up control is detected (YES in S120), the process proceeds to S130. If not (NO in S120), the process returns to S100, and the rapid catalyst warm-up control is continued.

  In S130, engine ECU 60 performs normal control. At this time, the injector 210 injects fuel in the intake stroke to form a homogeneous mixture in the combustion chamber 1000.

  In S140, engine ECU 60 determines whether or not a request for resuming catalyst rapid warm-up control has been detected during normal control. For example, when the accelerator pedal 420 that has been stepped on by the driver is returned to an idle state, if the integrated intake air amount from the start of rapid catalyst warm-up does not exceed a predetermined air amount, the catalyst rapid A restart request for warm-up control is generated. If a request for resuming catalyst rapid warm-up control is detected (YES in S140), the process proceeds to S150. If not (NO in S140), the process returns to S130, and normal control is continued.

  In S150, engine ECU 60 determines whether or not the catalyst rapid warm-up control can be restarted when a request for restart of catalyst rapid warm-up control is generated. For example, the determination is made based on the conditions for resuming the rapid catalyst warm-up control stored in engine ECU 60 and the operating state of the engine. If it is determined that the rapid catalyst warm-up control can be resumed (YES in S150), the process proceeds to S160. If not (NO in S150), the process returns to S130, and normal control is continued.

  In S160, engine ECU 60 determines whether or not a fuel cut is in progress. If it is determined that a fuel cut is in progress (YES in S160), the process returns to S130, and normal control is continued. If not (NO in S160), the process proceeds to S170.

  In S170, engine ECU 60 determines whether or not the number of fuel injections from injector 210 is within 100 after returning from the fuel cut. If the number of fuel injections from injector 210 is still within 100 after returning from the fuel cut (YES in S170), the process returns to S130, and normal control is continued. If not (NO in S170), the process returns to S100, and the rapid catalyst warm-up control is resumed. Note that, after returning from the fuel cut, the number of times of fuel injection from the injector 210 is determined to be 100 times, but the present invention is not limited to this 100 times, and is reduced during the fuel cut by the intake stroke injection. What is necessary is just the number of times until the fuel adhering amount of the piston is stabilized to the original state.

  An operation when the engine controlled by engine ECU 60 according to the present embodiment is executing the rapid catalyst warm-up control based on the above-described structure and flowchart will be described.

  When the engine is started and the engine is cold, rapid catalyst warm-up control is executed (S100). At this time, the injector 210 injects fuel in the compression stroke to form a stratified mixture in the combustion chamber 1000, and the ignition timing by the spark plug 210 is retarded, so that hot exhaust gas is discharged into the exhaust passage 1020. The catalyst is warmed. Such catalyst rapid warm-up control is continued until the intake air amount integrated from the start of the catalyst rapid warm-up control becomes a predetermined air amount.

  In such a case, when the driver steps on accelerator pedal 420, a request to interrupt catalyst rapid warm-up control is detected (YES in S120). The fuel injection timing from the injector 210 is changed to the intake stroke, a homogeneous mixture is formed in the combustion chamber 1000, and homogeneous combustion is performed (S130).

  When the driver returns the accelerator pedal 420, if the intake air amount accumulated from the start of the catalyst rapid warm-up control has not reached the predetermined air amount, a request for restarting the catalyst rapid warm-up control is detected. (YES at S140). The catalyst rapid warm-up control can be restarted (YES at S150), not during fuel cut (NO at S160), and the number of fuel injections from injector 210 after returning from fuel cut is within 100 times (YES in S170), normal control is continued. In other words, the intake stroke injection is not changed to the compression stroke injection until the fuel adhering amount of the piston decreased during the fuel cut is stabilized (YES in S170).

  When the intake stroke injection is continuously performed and the number of fuel injections from the injector 210 after returning from the fuel cut exceeds 100 (NO in S170), the amount of fuel adhering to the piston decreased during the fuel cut. Since it is stabilized as before (NO in S170), the intake stroke injection is changed to the compression stroke injection. The fuel injection amount is corrected when the intake stroke injection is changed to the compression stroke injection, but the amount of fuel adhering to the piston is restored to the extent that it is not affected by the fuel cut. The air-fuel ratio of the air-fuel mixture when changed to the compression stroke injection does not deviate from the target value.

  As described above, according to the engine ECU according to the present embodiment, when the fuel injection timing is changed from the intake stroke to the compression stroke across the fuel cut, before changing from the intake stroke injection to the compression stroke injection. In addition, the intake stroke injection is extended until the fuel adhesion amount of the piston is stabilized so as not to be affected by the fuel cut. Thereafter, even when the injection fuel amount is corrected to decrease when the compression stroke injection is changed, the fuel corresponding to the decrease correction amount adheres to the piston and the fuel is vaporized in the combustion chamber. Even after the injection is changed to the compression stroke injection, the air-fuel ratio of the air-fuel mixture does not deviate from the target value.

  In the above-described embodiment, the change to the compression stroke injection is permitted based on the number of fuel injections from the injector after returning from the fuel cut. However, the present invention is limited to such a number. Is not to be done. For example, the change to the compression stroke injection may be permitted based on the time (period) in which the fuel is injected from the injector after returning from the fuel cut instead of the number of times.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is an overall configuration diagram of an engine controlled by an engine control device according to an embodiment of the present invention. It is a flowchart which shows the control structure of the program performed by engine ECU which is an engine control apparatus which concerns on embodiment of this invention.

Explanation of symbols

  10 engine body, 30 starter, 60 engine ECU, 150 spark plug, 160 intake valve, 170 exhaust valve, 190 throttle valve, 210 injector, 520 crank angle sensor, 1000 combustion chamber, 1010 intake passage, 1020 exhaust passage.

Claims (3)

A control device for a direct injection internal combustion engine capable of switching between an intake stroke injection for injecting fuel in an intake stroke and a compression stroke injection for injecting fuel in a compression stroke during engine operation,
Detecting means for detecting a switching request to the compression stroke injection, either during the fuel cut or immediately after the fuel cut, after performing the intake stroke injection;
When the switching request is detected, the internal combustion engine is controlled to perform the intake stroke injection until a predetermined condition is satisfied with respect to the state of the combustion chamber of the internal combustion engine, and then switch to the compression stroke injection. and a control means for viewing including,
The control device for a direct injection internal combustion engine, wherein the predetermined condition is a condition that is determined with respect to time, and that a time until the amount of attached fuel in the combustion chamber reaches a desired state elapses . A control device for a direct injection internal combustion engine capable of switching between an intake stroke injection for injecting fuel in an intake stroke and a compression stroke injection for injecting fuel in a compression stroke during engine operation,
Detecting means for detecting a switching request to the compression stroke injection, either during the fuel cut or immediately after the fuel cut, after performing the intake stroke injection;
When the switching request is detected, the internal combustion engine is controlled to perform the intake stroke injection until a predetermined condition is satisfied with respect to the state of the combustion chamber of the internal combustion engine, and then switch to the compression stroke injection. and a control means for viewing including,
The predetermined condition is a control of the cylinder injection internal combustion engine, which is a condition that the number of times of fuel injection elapses until the amount of attached fuel in the combustion chamber reaches a desired state, which is determined with respect to the number of times of fuel injection. apparatus. The control apparatus for a direct injection internal combustion engine according to claim 1 or 2 , wherein the compression stroke injection is performed when a catalyst for purifying exhaust gas of the internal combustion engine is warmed up.

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