JP2007291887A - Cylinder direct injection gasoline engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylinder direct injection gasoline engine which inhibits generation of smoke and drop of engine output due to adhesion of fuel on an intake valve in homogeneous combustion. <P>SOLUTION: The cylinder direct injection gasoline engine provided with an injector 8 injecting fuel directly to an inside of a cylinder, is provided with an injection timing change correction means changing and correcting injection timing of fuel spray to avoid interference of the intake valve 3 opened to a predetermined lift with fuel spray injected from the injector 8. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an in-cylinder direct injection gasoline engine.

  2. Description of the Related Art An in-cylinder direct injection gasoline engine is known that directly injects fuel into a cylinder to minimize the fuel injection amount and prevent deterioration of the fuel consumption rate. In such an in-cylinder direct injection gasoline engine, it is intended to perform homogeneous combustion by forming a homogeneous mixture in the cylinder by fuel injection in the intake stroke (see, for example, Patent Document 1).

  By the way, in general, in a direct injection gasoline engine, in order to promote atomization of the injected fuel, the fuel injection valve injects the fuel in a divergent shape. As a result, the fuel injected from the fuel injection valve may collide with the intake valve that is lifted (opened) in the intake stroke. When the injected fuel collides with the intake valve in this way, a part of the fuel adheres to the intake valve, and particularly when the temperature of the intake valve is low, the attached fuel does not evaporate completely during the intake stroke, thereby entering the cylinder. As a result, the required amount of fuel is not supplied and the engine output decreases.

  Therefore, as a technique for avoiding such fuel adhesion to the intake valve, Patent Document 2 discloses that the central axis of the fuel spray from the fuel injection valve is directed obliquely downward and the fan-shaped fuel spray that expands forward is shown. It is disclosed that injection is performed such that the central plane in the thickness direction substantially coincides with a vertical plane passing between two intake valves.

  Patent Document 3 discloses a technique in which the injection timing is changed according to the temperature of the internal combustion engine, for example, when the temperature is low, the injection timing is delayed to suppress the formation of the wall film on the cold piston head. ing.

JP 2000-345847 A JP 2004-218603 A JP-T-2004-507658

  By the way, in a direct injection gasoline engine, in order to improve the homogeneity of the air-fuel mixture at the time of homogeneous combustion in which fuel is injected in the intake stroke where the intake valve is lifted, the fuel is aimed above the combustion chamber. It is desired to be injected.

  However, if the fuel is injected toward the upper side of the combustion chamber, as described above, collision or interference with the intake valve occurs, resulting in a decrease in engine output due to part of fuel adhering to the intake valve. In particular, when fuel adheres to the umbrella combustion chamber side of the intake valve, it becomes steamed and smoke is likely to be generated.

  Accordingly, an object of the present invention is to provide an in-cylinder direct injection gasoline engine that can suppress a reduction in engine output and the occurrence of smoke due to fuel adhering to an intake valve during homogeneous combustion.

  An in-cylinder direct injection gasoline engine according to an aspect of the present invention is an in-cylinder direct injection gasoline engine provided with a fuel injection device that directly injects fuel into a cylinder, and an intake valve that is opened to a predetermined lift amount. In order to avoid interference with the fuel spray injected from the fuel injection device, there is provided an injection period change correcting means for changing and correcting the injection period of the fuel spray.

  Here, the injection period change correcting means is configured such that an injection period of the fuel spray from the fuel injection device overlaps with a predetermined valve opening period in which a lift amount of the intake valve exceeds a predetermined value, and an injection end timing is the predetermined valve opening. When it is predicted that it is later than the start timing of the period, it is preferable to change and correct the injection period of the fuel spray so as to perform divided injection before and after the predetermined valve opening period.

  Further, the injection period change correcting means includes an injection period of the fuel spray from the fuel injection device overlapping a predetermined valve opening period in which a lift amount of the intake valve exceeds a predetermined value, and an injection start timing is the predetermined valve opening period. When it is predicted that the fuel injection timing is later than the start timing, it is preferable that the fuel spray injection period is changed and corrected so that the fuel injection is performed after the predetermined valve opening period.

  According to one aspect of the present invention, the injection period change correcting means for changing and correcting the fuel spray injection period causes interference between the intake valve opened to a predetermined lift amount and the fuel spray injected from the fuel injection device. Since it can be avoided, fuel does not adhere to the intake valve, and the reduction in engine output and the occurrence of smoke are suppressed.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a direct injection gasoline engine according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic longitudinal sectional view showing an embodiment of an in-cylinder direct injection gasoline engine 10. In the figure, 1 is an intake port and 2 is an exhaust port. The intake port 1 passes through a poppet type intake valve 3 having an umbrella part 3A that opens and closes the opening 1A, and the exhaust port 2 passes through a poppet type exhaust valve 4 that has an umbrella part 4A that opens and closes the opening 2A. Each leading into the cylinder. Reference numeral 5 denotes a piston, and reference numeral 6 denotes an ignition plug that protrudes from the cylinder upper wall to the combustion chamber 7 in the vicinity of the center of the cylinder upper portion. Reference numeral 8 denotes an injector as a fuel injection device disposed on the intake port 1 side around the upper part of the cylinder.

  In the in-cylinder direct injection gasoline engine 10 according to the present embodiment, as shown in FIG. 2, the injector 8 is arranged in the direction of the center line of the combustion chamber 7 between the intake ports 1 and 1 formed in parallel. Has been. The injector 8 is a slit nozzle injector that injects a fan-shaped fuel spray having a widening shape and a relatively thin thickness.

  Since the fuel injected from the injector 8 is reliably supplied into the cylinder, it is sufficient that the necessary minimum amount of fuel is injected from the injector 8, and deterioration of the fuel consumption rate can be prevented. In-cylinder direct injection gasoline engine 10 in this embodiment performs homogeneous stratification combustion by injecting fuel from injector 8 in the intake stroke to form a homogeneous mixture in the cylinder and injecting fuel in the latter half of the compression stroke. carry out. In order to promote the vaporization of the injected fuel during the homogeneous combustion, the injector 8 aims at the upper side of the combustion chamber and injects into a fan shape that expands and is thin.

  Further, the engine 10 includes a crank angle sensor (not shown) for detecting the rotational speed of the engine 10 (hereinafter referred to as a rotational speed sensor), an accelerator opening sensor for detecting a required load (accelerator opening), Various sensors such as an air flow meter for measuring the amount of intake air and a water temperature sensor for detecting the cooling water temperature of the engine 10 are provided. The outputs of these various sensors are sent to an electronic control unit (not shown) constituted by a microcomputer or the like.

  An electronic control unit (hereinafter referred to as ECU) controls a fuel injection amount, a fuel injection timing, an ignition timing, and the like according to output values sent from the various sensors described above. The basic control values used for controlling the fuel injection amount, the fuel injection timing, the ignition timing, etc. are, for example, the engine load represented by the intake air amount on the vertical axis, and the engine on the horizontal axis. In the basic map representing the operating state of the engine 10 taking the rotational speed, the optimum value obtained experimentally according to the required characteristics of the engine 10 is set as the control value, and these basic maps are stored in the electronic control unit. Stored in ROM.

  Therefore, one mode of control according to the embodiment of the present invention will be described with reference to the flowchart shown in FIG. This control routine is executed, for example, every predetermined crank angle. That is, when the control is started, in step S301, the intake air amount Ga representing the engine load and the engine speed n by the rotational speed sensor detected by the air flow meter are read as parameters representing the engine operating state. Then, the process proceeds to the next step S302, where a fuel injection time tau, which is a predetermined fuel injection amount, is acquired from the basic map based on the intake air amount Ga and the engine speed n, and in the next step S303, the fuel injection time tau is also injected from the basic map. The start time s0 is acquired.

  Next, in step S304, based on the engine speed n and the fuel injection time tau acquired in the above step, a fuel injection period x (= f (n, tau)) is calculated as a function of these. Then, the process proceeds to step S305, and the fuel injection end timing e0 (= s0−x) is obtained using the calculated fuel injection period x and fuel injection start timing s0.

  The fuel injection period x is represented by a crank angle (deg). In the following description, the “period” is represented by a crank angle. The “time” is represented by a crank angle (degBTDC) before the top dead center with the top dead center (TDC) as a reference (0 deg). Therefore, the crank angle (deg) indicating the fuel injection start timing s0 and the fuel injection end timing e0 shown in FIG. 4 described later is relatively larger on the left side.

  Here, in order to facilitate understanding of the following description, the fuel spray injected from the injector 8 collides with the umbrella portion 3A of the intake valve 3 with reference to the intake valve lift curve Lc in FIG. In particular, a description will be given of a situation in which fuel easily adheres to the umbrella combustion chamber side, that is, a start timing a1 and an end timing a2 of the so-called interference between the fuel spray and the intake valve 3. Assuming that the intake valve 3 starts to open near the top dead center (TDC), the period during which the lift amount exceeds a predetermined value Ls on the way to the maximum lift (for example, 10 mm) is the above fuel spray. It becomes the interference period It with the intake valve. Therefore, the intersections of the intake valve lift curve Lc and the predetermined lift amount value Ls in FIG. 4 become the interference start timing a1 and end timing a2, respectively. In an engine having a variable valve timing mechanism for an intake valve, the start timing a1 and end timing a2 of this interference and the interference period It between them are changed with respect to TDC.

  The values of the start timing a1 and the end timing a2 of these interferences are obtained by experiment or calculation in association with the opening / closing timing of the intake valve 3 by the variable valve timing mechanism of the intake valve, mapped and stored in the ROM of the electronic control unit. These are stored, and these are obtained in the next step S306 of the flowchart of FIG.

  In the next step S307, it is determined whether or not the fuel injection start timing s0 acquired in step S303 is greater (earlier) than the above-described interference start timing a1. If the determination is affirmative, that is, “yes”, the process proceeds to step S308. If the determination is negative, that is, “no”, the process proceeds to step S311, and the fuel spray injection period is changed and corrected as described later.

  On the other hand, in step S307, when the fuel injection start timing s0 is determined to be greater (early) than the interference start timing a1, in step S308, whether the fuel injection end timing e0 is greater than (earlier) the interference start timing a1. It is determined whether or not. In step S308, if the determination is affirmative, that is, "yes", the process proceeds to step S309, and the fuel spray injection period is not changed and corrected as described later. On the other hand, if negative, ie, “no”, the process proceeds to step S310, and the fuel spray injection period is changed and corrected as described later.

  Here, the determination made in the above-described steps S307 and S308 and the contents set as correction correction of the fuel spray injection period in steps S311, S309 and S310 based on the determination results are shown in the time chart of FIG. This will be described more specifically with reference to FIG. In FIG. 4, in relation to the intake valve lift curve Lc described above, the injection start timing (s0, s1), the injection end timing (e0, e1, e2) of the fuel spray injected from the injector 8 and the injection periods thereof. (x) is shown separately before and after correction. Here, before the correction, the provisional injection start timing s0, the injection end timing e0, and the injection period x, which are the targets of the determinations made in the above-described steps S307 and S308 and are simply obtained based on the operating state, After the correction, the first or second injection start timing s1 or s2, which is set in steps S311, S309 and S310 and actually executed in the engine after the correction is corrected, is determined as a result of the determination. The injection end timing e1 or e2 and the injection period x are shown.

  Here, in the flowchart of FIG. 3, m is a symbol indicating whether or not the injection from the injector 8 is divided in order to avoid interference, in other words, in order to facilitate understanding, in other words, a symbol indicating the presence or absence of divided injection. Yes, m = 1 when the divided injection is performed, and m = 0 when the divided injection is not performed.

  Therefore, in the above determination, the fuel injection start timing s0 acquired in step S303 is greater than the interference start timing a1 (step S307: “yes”), and the fuel injection end timing e0 obtained in step S305 is the start of interference. In step S309, which proceeds when the time is greater than time a1 (step S308: “yes”), the fuel spray injection period x does not overlap the spray-intake valve interference period It, and therefore the fuel spray injection period is not corrected. That is, m = 0 without split injection is set, and the temporary injection start timing s0, the injection end timing e0, and the injection period x are respectively the first injection start timing s1 that is actually executed in the engine as it is. The first injection end timing e1 and the injection period x are set (see * 1 in FIGS. 3 and 4).

  Further, if the fuel injection start timing s0 acquired in step S303 is greater than the interference start timing a1 (step S307: “yes”), the fuel injection end timing e0 obtained in step S305 is the interference in the determination in step S308 described above. In step S310 that proceeds when the start time is less (slow) than the start time a1, since the fuel spray injection period x overlaps the spray-intake valve interference period It, m = 1 and split injection is performed. Then, the first injection start timing s1 and the first injection end timing e1 that are actually executed in the engine are set to the temporary injection start timing s0 and the interference start timing a1, respectively (s1 = s0, e1). = 2), the second injection start timing s2 is set to the interference end timing a2 (s2 = a2), and the second injection end timing e2 is set to e2 = a2- (a1-e0) ( (See * 2 in FIGS. 3 and 4). In FIG. 4, the fuel injection end timing e0 is predicted to be during the interference period It as * 2 (1), and the fuel injection end timing e0 is predicted to be after the interference period It as * 2 (2). However, as shown in step S310 of FIG. 3, the second injection start timing s2 and the injection end timing e2 are set in order to avoid the interference period It.

  Further, in step S311, which proceeds when the fuel injection start timing s0 acquired in step S303 is not greater than the interference start timing a1 (step S307: “no”), the fuel spray injection period x is an interference between the spray and the intake valve. Since it overlaps the period It, the fuel spray injection period is changed and corrected. In this case, m = 0 without split injection is set, and the temporary injection start timing s0, the injection end timing e0, and the injection period x are respectively the first injection start timing actually executed in the engine. Interference end timing a2 is set as s1, e1 = a2-x as the first injection end timing e1, and the injection period x (see * 3 in FIGS. 3 and 4).

  As apparent from the above description, according to the present embodiment, the fan-shaped fuel spray injected from the injector 8 in the intake stroke is injected while avoiding the interference period It in which the intake valve 3 exceeds the predetermined lift amount. Therefore, it does not collide with the intake valve 3 and is atomized into the cylinder and spreads, and a homogeneous mixture using all of the injected fuel is formed in the cylinder. As a result, fuel adhesion to the intake valve 3 can be avoided, the occurrence of smoke can be suppressed, and the intended engine output can be generated.

1 is a schematic longitudinal sectional view showing an embodiment of an in-cylinder direct injection gasoline engine according to the present invention. FIG. 2 is a bottom view of the cylinder of the direct injection gasoline engine in FIG. 1 as viewed from the combustion chamber side. It is a flowchart which shows an example of the fuel injection control of the direct injection gasoline engine by this invention. It is a time chart which shows the injection timing and period before and behind correction | amendment of the result of fuel injection control with the intake valve lift curve Lc.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Intake port 2 Exhaust port 3 Intake valve 4 Exhaust valve 5 Piston 6 Spark plug 7 Combustion chamber 8 Injector (fuel injection device)

Claims (3)

In-cylinder direct injection gasoline engine equipped with a fuel injection device that directly injects fuel into the cylinder,
In order to avoid interference between the intake valve opened to a predetermined lift amount and the fuel spray injected from the fuel injection device, an injection period change correcting means for changing and correcting the injection period of the fuel spray is provided. In-cylinder direct injection gasoline engine.   The injection period change correcting means includes an injection period of the fuel spray from the fuel injection device overlapping a predetermined valve opening period in which a lift amount of the intake valve exceeds a predetermined value, and an injection end timing is the start of the predetermined valve opening period. 2. The direct injection gasoline engine according to claim 1, wherein when it is predicted that the fuel injection timing is later than the predetermined time, the injection period of the fuel spray is changed and corrected so as to perform divided injection before and after the predetermined valve opening period. . The injection period change correcting means includes an injection period of the fuel spray from the fuel injection device overlapping a predetermined valve opening period in which a lift amount of the intake valve exceeds a predetermined value, and an injection start timing is the start of the predetermined valve opening period. The in-cylinder direct injection gasoline engine according to claim 1, wherein when it is predicted that the fuel injection is later than the timing, the injection period of the fuel spray is changed and corrected so as to be injected after the predetermined valve opening period.

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