JP2007255374A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve stable combustion and drivability, by well restraining knocking of a spray guide direct injection engine capable of stratified lean combustion operation. <P>SOLUTION: This control device controls a cylinder injection type internal combustion engine 1 capable of the stratified lean combustion operation, by directly igniting fuel 17 injected by pointing to a spark plug 12 from a fuel injection valve 13, and has a knock detecting means 23 detecting the knocking of the internal combustion engine, and simultaneously equally changes the target fuel injection timing of the fuel injection valve 13 and the target ignition timing of the spark plug 12 to the injection timing delay side by a control means 20, when detecting the knocking by the knock detecting means, in the stratified lean combustion operation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  An in-cylinder injection type gasoline engine capable of stratified dilute combustion operation has been put into practical use. In such an in-cylinder gasoline engine, a recess is generally formed on the upper surface of the piston, and a fuel injection valve is arranged so that fuel can be injected toward the recess on the upper surface of the piston. The spark plug is disposed so that the tip of the spark plug is located at the top.

  As a result, the fuel injected into the combustion chamber has a relatively rich air-fuel ratio around the spark plug, and forms a super lean atmosphere at a location away from the spark plug, thereby causing a layered lean state in the combustion chamber. In this state, the ignition plug is ignited, so that the combustion chamber as a whole can be stably operated even when the air-fuel ratio is lean.

  On the other hand, in addition to the above-described general in-cylinder injection type engine, an in-cylinder injection type gasoline engine (hereinafter referred to as “spray guide direct injection engine”) called a spray guide system has been developed. This spray guide direct injection engine is an in-cylinder injection type gasoline engine that can form a layered lean state in a combustion chamber by directly injecting fuel toward a spark plug provided on the upper surface of the combustion chamber. For example, the technique is disclosed in Patent Document 1.

Japanese Patent Laid-Open No. 10-54246

However, as described above, the spray guide direct-injection engine is greatly different in technical idea from a general port injection type engine and a general in-cylinder injection type engine. Even if this control is executed, it is difficult to operate in a stable state. That is, in the spray guide direct injection engine, since the fuel spray injected from the fuel injection valve toward the ignition plug is ignited until it passes through after reaching the ignition plug, when knocking occurs, Even if only the ignition timing is changed as in the prior art, it is difficult to eliminate it well.
An object of the present invention is to provide a control device for an internal combustion engine that can satisfactorily suppress knocking of a spray-guided direct injection engine capable of stratified lean combustion operation and improve stable combustion and drivability.

  In order to achieve the above object, the invention of claim 1 controls a direct injection internal combustion engine capable of performing a stratified lean combustion operation by directly igniting fuel injected from a fuel injection valve toward a spark plug. In the control device for an internal combustion engine, the knock detection means for detecting knocking of the internal combustion engine, and the target fuel injection timing of the fuel injection valve and the spark plug when the knock detection means detects knocking during the stratified lean combustion operation. And a control means for simultaneously changing the target ignition timing equally.

  In the invention of claim 2, when knock detection is detected by the knock detection means, the target fuel injection timing and the target ignition timing are simultaneously retarded equally and the fuel injection device and the ignition plug are controlled by the control means, respectively. It is characterized by.

  The invention of claim 3 has a knock strength deriving means for deriving a knocking strength based on the knocking information detected by the knock detecting means, and the target fuel injection timing increases as the knocking strength derived by the knock strength deriving means increases. The control means controls the fuel injection device and the spark plug by increasing the delay angle with respect to the target ignition timing.

  According to a fourth aspect of the present invention, when the stratified lean combustion operation is not being performed, as the knocking strength derived by the knocking strength deriving unit increases, only the target ignition timing is retarded and the spark plug is controlled by the control unit. It is a feature.

  According to the present invention, the target fuel injection timing of the fuel injection valve and the target ignition timing of the spark plug are simultaneously changed when knocking is detected by the knock detection means so that the fuel injection valve is directed to the spark plug. In-cylinder injection type internal combustion engine (so-called spray guide direct injection engine) capable of stratified lean combustion operation by igniting the igniter plug in a state where the fuel injected in the stratified lean state exists in the vicinity of the igniter plug Knocking can be easily suppressed, and stable combustion and drivability can be improved.

  According to the present invention, when knocking occurs in the spray guide direct injection engine, the fuel injection is performed according to the target fuel injection timing and the target ignition timing obtained by delaying equally from the reference fuel injection timing and the reference ignition timing, respectively. Since the valve and the spark plug are controlled, knocking of the spray guide direct injection engine can be reliably suppressed, and stable combustion and drivability can be further improved.

  According to the present invention, as the knocking strength derived by the knocking strength deriving means increases, the delay angle with respect to the target fuel injection timing and the target ignition timing is increased to control the fuel injection device and the spark plug. The knocking of the spray guide direct injection engine can be suppressed, and stable combustion and drivability can be improved.

  According to the present invention, the target ignition timing increases as the knocking strength derived by the knocking strength deriving means increases when not in the stratified lean combustion operation in which the fuel injected from the fuel injection valve toward the spark plug is directly ignited. Since the spark plug is controlled by retarding only the ignition plug, the occurrence of knocking in the stratified lean combustion operation and other operations can be suppressed, and stable combustion and drivability can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. An internal combustion engine 1 shown in FIG. 1 is a spray guide type in-cylinder injection gasoline engine (hereinafter referred to as “spray guide direct injection engine 1”). The combustion chamber 7 of the spray guide direct injection engine 1 includes a cylindrical cylinder 3 formed in the cylinder block 2, a top surface of a piston 5 that is slidably inserted into the cylinder 3, and a cylinder block. 3 is formed so as to be surrounded by the lower surface of the cylinder head 6 mounted on the upper portion of the cylinder 3.

  The cylinder head 6 is provided with an intake valve 9 for opening and closing an intake port 8 connected to the combustion chamber 7 and an exhaust valve 11 for opening and closing an exhaust port 10, and between the intake port 8 and the exhaust port 10, the combustion chamber is provided. 7 is provided with a spark plug 12 so that the electrode portion 12a protrudes. Below the intake port 8, a fuel injection valve 13 that injects fuel (gasoline) toward the electrode portion 12 a of the spark plug 12 is provided. The fuel injection valve 13 is connected to the inside of the fuel tank 15 via the fuel pipe 14. Fuel is stored in the fuel tank 15, pumped up by a pressure pump (not shown), pressurized by a high-pressure pump 16, and supplied to the fuel injection valve 13. The fuel injection valve 13 is an electronic type in which fuel is injected by driving an electromagnetic actuator (not shown).

  The spray guide direct injection engine 1 includes an engine control unit (hereinafter referred to as “ECU”) 20 serving as a control means for generally controlling the operation thereof. The ECU 20 is configured by a known computer having a CPU, a ROM, a RAM, a timer, and an interface. On the input side of the ECU 20, an engine rotation detecting means 21 for detecting the engine speed Ne, an accelerator opening sensor 22 for detecting an accelerator opening θ which is an opening of an accelerator pedal (not shown), and a spray guide direct injection engine. Knock detecting means 23 for detecting one knocking is electrically connected. A spark plug 12 and a fuel injection valve 13 are electrically connected to the output side of the ECU 20. As the knock detection means 23, a known type of type that detects knocking from the vibration state of the cylinder block or a type that detects knocking state from the pressure state in the combustion chamber 7 is used.

  The ECU 20 includes an operation region determination unit 201 that determines a stratified lean combustion operation region from the engine speed Ne and the accelerator opening θ, a knock determination unit 202 that determines a knock state from a signal detected by the knock detection unit 23, an engine Information detected by the knock detection means 23 and the fuel injection / ignition timing calculation unit 203 that calculates the target fuel injection timing of the fuel injection valve 13 and the target ignition timing of the spark plug 12 from the rotational speed Ne and the accelerator opening θ. Knock strength deriving means 204 for deriving the knocking strength based on this is provided.

  For example, the operation region determination unit 201 includes a map in which the vertical axis shown in FIG. 2 represents the accelerator opening θ as load information, and the horizontal axis represents the engine speed Ne. The reference fuel injection timing and the reference ignition timing calculated by the fuel injection / ignition timing calculation unit 203 are referred to as “matching points” indicated by reference numeral P1 in FIG. 3, and the matching point P1 is a stable combustion region during the stratified lean combustion operation. It is set to become. In the spray guide operation region, the ECU 20 drives the fuel injection valve 13 near the top dead center during the compression stroke to execute the compression stroke injection. In the normal operation region, the ECU 20 drives the fuel injection valve 13 in the intake stroke to perform intake air. Perform stroke injection.

  The knock strength derivation means 204 is configured from the map shown in FIG. 4 in which the target fuel injection timing calculated by the fuel injection / ignition timing calculation unit 203 and the delay angle with respect to the target ignition timing increase as the knock strength increases. Yes. A knock determination value for determining whether or not knocking is set in the ROM of the ECU 20 in advance.

  The ECU 20 sets a target ignition timing to be ignited by the spark plug 12 calculated by the fuel injection / ignition timing control unit 203 and a target fuel injection timing at which fuel is injected by the fuel injection valve 13, and ignites at that timing. The plug 12 and the fuel injection valve 13 are driven. When the spray guide direct injection engine 1 is in the stratified lean combustion operation and knocking is detected by the knock detection means 23, the ECU 20 simultaneously changes the target fuel injection timing and the target ignition timing equally. Specifically, the same amount is retarded, and the retarded values are set as the new target fuel injection timing and target ignition timing, and the spark plug 12 and the fuel injection valve 13 are controlled to be driven. The ECU 20 controls the spark plug 12 and the fuel injection valve 13 respectively by increasing the delay angle with respect to the target fuel injection timing and the target ignition timing as the knocking strength derived by the knock strength deriving means 204 increases. Such retardation control between the target ignition timing and the target fuel injection timing is repeatedly executed every unit time (for example, 0.1 second). That is, the timing at which the fuel is actually injected by the fuel injection valve 13 and the timing at which the fuel is actually ignited by the spark plug 12 can be delayed.

  Control in the control apparatus for an internal combustion engine having such a configuration will be described with reference to the flowchart shown in FIG. When the spray guide direct injection engine 1 is started, the ECU 20 takes in various information from the sensor as shown in step S1 of FIG. This includes the engine speed Ne, the accelerator opening θ, and the knocking signal.

  In step S2, the target ignition timing and the target fuel injection timing are calculated from a map (not shown) from the engine speed Ne and the accelerator opening θ, a matching point P1 is obtained, and the matching point P1 obtained here is used as the target fuel injection timing. And set as the target ignition timing.

  In step S3, the signal from the knock detection means 23 is compared with a preset knock determination value. If the detection signal exceeds the knock determination value, it is determined that knocking has occurred, and the process proceeds to step S4. If the signal does not exceed the knock determination value, it is determined that knocking has not occurred and this control is terminated.

  In step S4, the knocking strength is calculated from the difference between the detection signal of the knock detection means 23 and the knock determination value, and the retarded degree is derived based on the retard map shown in FIG. In this case, the retard angle increases as the retard angle increases, and decreases as the retard angle decreases.

  In step S5, it is determined whether it is a spray guide combustion area using the map shown in FIG. If the values based on the engine speed Ne and the accelerator opening θ are located in the spray guide combustion region, the process proceeds to step S6. In step S6, the target ignition timing and the target fuel injection timing are changed so as to be retarded by an amount corresponding to the knocking intensity. That is, as shown in FIG. 3 (matching point P1), it is moved to the retard side. Then, the spark plug 12 and the fuel injection valve 13 are driven at the target ignition timing and the target fuel injection timing changed in step S7.

  On the other hand, if it is not the spray guide combustion region in step S5 (normal combustion region), the process proceeds to step S8. In step S8, since it is not spray guide combustion, the target fuel injection timing is not changed, and only the target ignition timing is changed so as to be retarded by an amount corresponding to the knocking intensity as in the known knocking suppression control. Then, the spark plug 12 and the fuel injection valve 13 are driven at the target ignition timing and the normal target fuel injection timing changed in step S9.

  The spray-guided direct-injection engine 1 has a narrower stable combustion region than a general port injection type engine and a general in-cylinder injection type engine, and therefore has a strong correlation between the ignition timing and the fuel injection timing. Therefore, it is difficult to control knocking. This point will be described with reference to FIG. If the accelerator opening θ is the same and the load on the engine is constant, such as travel conditions and load weight, the engine speed Ne should not fluctuate theoretically. However, actually, the engine speed Ne slightly varies, and the amount of variation correlates with the ignition timing and the fuel injection timing. This point is the same whether it is the spray guide direct injection engine 1 or a general engine such as a port injection type.

  However, in the case of the spray guide direct injection engine 1, the correlation thereof is stronger than that of a general port injection type engine or the like, and the rotational speed Ne of the spray guide direct injection engine 1 is indicated by a hatched area in FIG. The relationship between the ignition timing at which the fuel is relatively stable and the fuel injection timing is approximately 1: 1. This is because the spray guide direct injection engine 1 sprays gasoline as fuel directly on the spark plug 12 and ignites the sprayed fuel.

  3 are reference target ignition timing and target fuel injection timing, that is, the above-described matching points. If the ignition timing and the fuel injection timing are retarded simultaneously and at the same rate from this matching point, knocking of the spray guide direct injection engine 1 is suppressed and rotational stability is improved.

  In this way, the target fuel injection timing of the fuel injection valve 13 and the target ignition timing of the spark plug 12 are simultaneously changed equally when the knock detection means 23 detects knocking, so that the fuel injection valve 13 to the spark plug 12 The spark plug 12 can be ignited in a state in which the fuel spray 17 injected in the direction of is present in the vicinity of the spark plug. Thereby, the vibration by knocking of the spray guide direct injection engine 1 can be easily suppressed, and stable combustion and drivability can be improved.

  As described above, according to the present embodiment, when knocking occurs in the spray guide direct injection engine 1, the target fuel injection timing and the target ignition obtained by equally retarding the reference fuel injection timing and the reference ignition timing, respectively. Since the fuel injection valve 13 and the ignition plug 12 are controlled according to the timing, vibration due to knocking of the spray guide direct injection engine 1 can be reliably suppressed, and more stable combustion and drivability can be improved.

  Further, as the knocking strength derived by the knocking strength deriving means 204 increases, the delay angle with respect to the target fuel injection timing and the target ignition timing (matching point) is increased to control the fuel injection device and the spark plug. Further, by suppressing knocking of the spray guide direct injection engine 1, more stable combustion and improved drivability can be achieved. When the stratified lean combustion operation is not being performed, the spark plug 12 is retarded by retarding only the target ignition timing as the knocking strength derived by the knock strength derivation means 204 increases. The occurrence of knocking during operation can be suppressed, and stable combustion and drivability can be improved.

  In the above embodiment, the fuel injection valve 13 is disposed on the side of the combustion chamber 7, but the present invention is not limited to this, and can be applied to a type in which the fuel injection valve is disposed in the center of the combustion chamber. .

1 is a diagram showing a schematic configuration of a spray guide type cylinder injection type internal combustion engine and a control device thereof according to an embodiment of the present invention. FIG. It is a map used for determination of a combustion area. It is a figure which shows the characteristic of the stable combustion area | region of a spray guide direct injection engine. It is a retardation map which shows an example of a knock intensity | strength derivation means. It is a flowchart which shows one form of the control for knocking suppression concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 In-cylinder injection type internal combustion engine 12 Spark plug 13 Fuel injection valve 17 Fuel injected 20 Control means 23 Knock detection means 204 Knock strength derivation means

Claims (4)

In a control apparatus for an internal combustion engine that controls a direct injection internal combustion engine capable of performing a stratified lean combustion operation by directly igniting fuel injected from a fuel injection valve toward an ignition plug,
Knock detecting means for detecting knocking of the internal combustion engine;
Control means for simultaneously changing the target fuel injection timing of the fuel injection valve and the target ignition timing of the spark plug equally when the knock detection is detected by the knock detection means during the stratified lean combustion operation. A control device for an internal combustion engine. The control apparatus for an internal combustion engine according to claim 1,
The control means controls the fuel injection device and the spark plug by respectively retarding the target fuel injection timing and the target ignition timing equally when knocking is detected by the knock detection means. A control device for an internal combustion engine. The control apparatus for an internal combustion engine according to claim 2,
Knock strength derivation means for deriving knock strength based on the knocking information detected by the knock detection means;
The control means controls the fuel injection device and the spark plug, respectively, by increasing the delay angle with respect to the target fuel injection timing and the target ignition timing as the knocking intensity derived by the knock intensity deriving means increases. A control device for an internal combustion engine. The control apparatus for an internal combustion engine according to claim 3,
The first-stage control means controls the spark plug by retarding only the target ignition timing as the knocking intensity derived by the knock intensity deriving means increases when the stratified lean combustion operation is not being performed. A control device for an internal combustion engine.

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