JP2006316655A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress vibration of an engine in which fuel is directly injected into a cylinder. <P>SOLUTION: ECU which is a control device executes a program including a step S106 stopping a high pressure fuel pump of a fuel pump pressurizing fuel supplied to an injector directly injecting fuel into the cylinder and the high pressure fuel pump pressurizing fuel pressurized by the fuel pump if a cylinder of which fluctuation quantity of engine rotation speed is large exists (Yes in S104) when an engine is under idling condition (Yes in S102). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine provided with an in-cylinder injector that injects fuel into a cylinder.

  Conventionally, there has been proposed a technique capable of suppressing vibration due to deterioration in exhaust cleanliness and rotational fluctuation during idling. An internal combustion engine combustion control apparatus described in Japanese Patent Laid-Open No. 2-64252 (Patent Document 1) includes an operation state detection unit that detects an operation state of an engine having a plurality of cylinder groups each composed of a pair of cylinders before and after combustion. A crank angle detector that outputs a signal capable of determining a cylinder in the combustion stroke and a signal corresponding to a predetermined unit crank angle, an idle detector that detects an idle state of the engine, a crank angle detector, and an idle detector Based on the output of the engine, when the engine is in an idle state, a speed change amount calculation unit that calculates a change amount of the engine rotation speed for each combustion of each cylinder, and a pair of cylinders based on the change amount of the rotation speed Rotate between a pair of cylinders by correcting the injection amount for one cylinder to the increase side and the injection amount for the other cylinder to the decrease side to balance the change in rotational speed between them. A correction amount calculation unit for calculating a correction amount for correcting the injection amount for one cylinder group to the increase side and the injection amount for the other cylinder group to the decrease side so as to balance the change amount of the degree, and an engine operating state The basic injection amount is calculated based on the calculation result, and when the engine is in an idle state, the basic injection amount is corrected according to the correction amount, the fuel injection amount for each cylinder is calculated, and the output of the injection amount calculation unit And a fuel supply unit for supplying fuel based on the above.

According to the combustion control apparatus for an internal combustion engine described in this publication, when the engine is in an idle state, the amount of change in the rotational speed of the engine is calculated by the speed change amount calculation unit for each combustion of each cylinder. Based on this calculation result, one is set on the injection amount increasing side and the other on the injection amount decreasing side so that the change in rotational speed is balanced between each pair of cylinders before and after combustion, and further between a pair of cylinder groups. A correction amount to be corrected is determined. Thus, the fuel injection amount control is performed so that the correction amount approaches zero as a whole. Therefore, control is performed so that the combustion state of all cylinders does not deviate from the target operating point. As a result, it is possible to suppress vibrations due to deterioration in exhaust cleanliness and fluctuations in the idle speed.
Japanese Patent Laid-Open No. 2-64252 (Patent No. 2510250)

  However, Japanese Patent Laid-Open No. 2-64252 does not consider an internal combustion engine provided with an in-cylinder injector that directly injects fuel into the cylinder. Therefore, there is a problem that there is room for further improvement in order to suppress such vibration in the internal combustion engine.

  The present invention has been made to solve the above-described problems, and an object of the present invention is an internal combustion engine capable of suppressing vibration of the internal combustion engine in an internal combustion engine in which fuel is directly injected into a cylinder. It is to provide a control device.

  Another object of the present invention is to provide a control device for an internal combustion engine that can suppress deterioration of exhaust emission performance.

  A control apparatus for an internal combustion engine according to a first aspect controls an internal combustion engine provided with a fuel injection means for injecting fuel into a cylinder. The control device includes an internal combustion engine for detecting a combustion state in the cylinder and an internal combustion engine so as to lower an injection pressure from the fuel injection unit when the fluctuation amount of the combustion state is larger than a predetermined fluctuation amount. Pressure control means for controlling the pressure.

  According to the first invention, when the fluctuation amount of the combustion state is larger than the predetermined fluctuation amount, the injection pressure from the fuel injection means is lowered. For example, a first pressurizing unit for pressurizing the fuel supplied to the fuel injection unit and a second pressurizing unit for further pressurizing the fuel pressurized by the first pressurizing unit The fuel pressurization by the second pressurizing means is stopped, and the injection pressure is lowered. Thereby, the vibration accompanying the action | operation of a 2nd pressurization means can be suppressed. Therefore, in the internal combustion engine in which the fuel is directly injected into the cylinder, it is possible to provide a control device for the internal combustion engine that can suppress the vibration of the internal combustion engine.

  In the control apparatus for an internal combustion engine according to the second invention, in addition to the configuration of the first invention, the internal combustion engine includes a first pressurizing means for pressurizing the fuel supplied to the fuel injection means, And a second pressurizing unit for further pressurizing the fuel pressurized by the one pressurizing unit. The pressure control means includes means for controlling the internal combustion engine to stop the pressurization of the fuel by the second pressurization means.

  According to the second invention, when the variation amount of the combustion state is larger than the predetermined variation amount, the pressurization of the fuel by the second pressurizing means is stopped. Thereby, the vibration accompanying the action | operation of a 2nd pressurization means can be suppressed. Therefore, in an internal combustion engine in which fuel is directly injected into the cylinder, vibration of the internal combustion engine can be suppressed.

  In the control device for an internal combustion engine according to the third invention, in addition to the configuration of the first or second invention, the internal combustion engine is provided with a plurality of cylinders and a catalyst for purifying exhaust gas discharged from the internal combustion engine. . The detection means includes means for detecting the combustion state in each cylinder. The control device includes first air-fuel ratio control means for controlling the internal combustion engine so that the air-fuel ratio in the cylinder in which the fluctuation amount of the combustion state is larger than a predetermined fluctuation amount is small, and exhaust gas guided to the catalyst. And a second air-fuel ratio control means for controlling the internal combustion engine so that the air-fuel ratio of the engine becomes a predetermined air-fuel ratio.

  According to the third aspect of the invention, in the internal combustion engine, since the fluctuation amount of the combustion state is minimized at the air-fuel ratio smaller than the stoichiometric air-fuel ratio, in the cylinder in which the fluctuation amount of the combustion state is larger than the predetermined fluctuation amount. The air-fuel ratio is reduced. Thereby, the rotation speed of an internal combustion engine can be stabilized and the vibration of an internal combustion engine can be suppressed. Further, since the range of the air-fuel ratio at which the catalyst can efficiently purify the exhaust is limited, the air-fuel ratio of the exhaust led to the catalyst is set to a predetermined air-fuel ratio (for example, the theoretical air-fuel ratio). Thereby, exhaust gas can be purified by the catalyst. Therefore, it is possible to provide a control device for an internal combustion engine that can suppress the deterioration of exhaust emission performance accompanying the correction of the air-fuel ratio in order to suppress the vibration of the internal combustion engine.

  In the control apparatus for an internal combustion engine according to the fourth aspect of the invention, in addition to the configuration of the third aspect of the invention, the fuel injection means is provided corresponding to each cylinder. The first air-fuel ratio control means includes means for controlling the fuel injection means so that the fuel injection amount of the fuel injection means in the cylinder in which the fluctuation amount of the combustion state is larger than the predetermined fluctuation amount. .

  According to the fourth invention, the fuel injection amount of the fuel injection means in the cylinder in which the fluctuation amount of the combustion state is larger than the predetermined fluctuation amount is increased. Thereby, the air-fuel ratio in the cylinder in which the fluctuation amount of the combustion state is larger than the predetermined fluctuation amount can be reduced, the rotational speed of the internal combustion engine can be stabilized, and the vibration of the internal combustion engine can be suppressed.

  In the control apparatus for an internal combustion engine according to the fifth invention, in addition to the configuration of the third invention, the first air-fuel ratio control means sucks into the cylinder in which the fluctuation amount of the combustion state is larger than the predetermined fluctuation amount. Means are included for controlling the internal combustion engine such that the amount of air being reduced is reduced.

  According to the fifth aspect of the present invention, the amount of air taken into the cylinder in which the fluctuation amount of the combustion state is larger than the predetermined fluctuation amount is reduced. Thereby, the air-fuel ratio in the cylinder in which the fluctuation amount of the combustion state is larger than the predetermined fluctuation amount can be reduced, the rotational speed of the internal combustion engine can be stabilized, and the vibration of the internal combustion engine can be suppressed.

  In the control apparatus for an internal combustion engine according to the sixth aspect of the invention, in addition to the configuration of any one of the third to fifth aspects, the second air-fuel ratio control means is configured so that the fluctuation amount of the combustion state is greater than a predetermined fluctuation amount. Means for controlling the internal combustion engine to increase the air-fuel ratio in the smaller cylinder.

  According to the sixth aspect of the invention, the air-fuel ratio in the cylinder in which the fluctuation amount of the combustion state is smaller than the predetermined fluctuation amount is increased. As a result, the air-fuel ratio in the exhaust gas in which the exhaust gas discharged from the cylinder with the large fluctuation amount of the combustion state and the exhaust gas discharged from the cylinder with the small fluctuation amount of the combustion state is mixed, that is, the change in the air-fuel ratio in the entire internal combustion engine. The amount can be suppressed. Therefore, the air-fuel ratio of the exhaust gas purified by the catalyst can be set to a predetermined air-fuel ratio (for example, the theoretical air-fuel ratio). As a result, it is possible to suppress the deterioration of the exhaust emission performance accompanying the correction of the air-fuel ratio in order to suppress the vibration of the internal combustion engine.

  In the control apparatus for an internal combustion engine according to the seventh aspect of the invention, in addition to the configuration of any one of the first to sixth aspects, the detection means includes the number of revolutions of the internal combustion engine, vibration of the internal combustion engine, and pressure in the cylinder. Means for detecting a combustion condition in the cylinder based on at least one of them.

  According to the seventh invention, the combustion state in the cylinder can be detected appropriately from at least one of the rotational speed of the internal combustion engine, the vibration of the internal combustion engine, and the pressure in the cylinder.

  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.

  With reference to FIG. 1, the engine of the vehicle carrying the control apparatus which concerns on the 1st Embodiment of this invention is demonstrated. The control device according to the present embodiment is realized, for example, by a program executed by an ECU (Electronic Control Unit) 200 shown in FIG.

  Air is drawn into the engine 100 from the air cleaner 102. The intake air amount is adjusted by the throttle valve 104. The throttle valve 104 is an electrically controlled throttle valve that is driven by a motor.

  Air is mixed with fuel in the cylinder 106 (combustion chamber). Fuel is directly injected into the cylinder 106 from the injector 108. That is, the injection hole of the injector 108 is provided in the cylinder 106. The fuel is injected from the intake side (the side where air is introduced) of the cylinder 106.

  Fuel is injected during the intake stroke. Note that the timing of fuel injection is not limited to the intake stroke. In this embodiment, the engine 100 is described as a direct injection engine in which the injection hole of the injector 108 is provided in the cylinder 106. However, in addition to the direct injection injector 108, a port injection injector is provided. May be.

  The air-fuel mixture in the cylinder 106 is ignited by the spark plug 110 and burns. The air-fuel mixture after combustion, that is, the exhaust gas is purified by the three-way catalyst 112 and then discharged outside the vehicle. The piston 114 is pushed down by the combustion of the air-fuel mixture, and the crankshaft 116 rotates.

  An intake valve 118 and an exhaust valve 120 are provided at the top of the cylinder 106. The amount and timing of air introduced into the cylinder 106 are controlled by an intake valve 118, and the amount and timing of exhaust gas discharged from the cylinder 106 are controlled by an exhaust valve 120. The intake valve 118 is driven by a cam 122, and the exhaust valve 120 is driven by a cam 124.

  The fuel supplied to the injector 108 is stored in the fuel tank 126. The fuel stored in the fuel tank 126 is pressurized by the fuel pump 128, further pressurized by the high-pressure fuel pump 130, and supplied to the injector 108.

  In the high-pressure fuel pump 130, the amount of pressurization is changed according to the timing at which an electromagnetic spill valve (not shown) is closed. In addition, about the fuel pump 128 and the high pressure fuel pump 130, what is necessary is just to use a known general technique, Therefore The detailed description is not repeated here.

  The ECU 200 controls the throttle opening, ignition timing, fuel injection timing, fuel injection amount, intake / exhaust valve opening / closing timing, etc. so that the engine 100 is in a desired operating state. The ECU 200 receives signals representing the cam position from the cam angle sensor 300, and signals representing the rotation speed (engine rotation speed) of the crankshaft 116 and the rotation angle of the crankshaft 116 from the crank angle sensor 302 to the engine. A signal representing the intensity of 100 vibrations is input.

  ECU 200 controls engine 100 based on signals input from these sensors, a map and a program stored in a memory (not shown). In the present embodiment, ECU 200 detects the combustion state of the air-fuel mixture based on the engine speed, and corrects the air-fuel ratio when the fluctuation amount of the combustion state, that is, the fluctuation amount of the engine speed at the time of ignition is large.

  Hereinafter, the relationship between the variation amount of the engine speed (the variation amount of the fuel state in the cylinder) and the air-fuel ratio will be described. As shown in FIG. 2, the fluctuation amount is minimized at a position where the air-fuel ratio is smaller (rich) than the stoichiometric air-fuel ratio. On the other hand, the amount of fluctuation increases as the air-fuel ratio becomes smaller (lean) than the stoichiometric air-fuel ratio.

  Hereinafter, the relationship of the amount of fluctuation of the engine speed with respect to the fuel injection timing and the injection pressure will be described. As shown in FIG. 3, the fluctuation amount of the engine speed is less affected by the injection pressure and is more affected by the injection timing. That is, if the injection timing is set to the top dead center side, the combustion fluctuation can be reduced even if the injection pressure is low.

  With reference to FIG. 4, a control structure of a program executed by ECU 200 that is the control device according to the present embodiment will be described.

  In step (hereinafter, step is abbreviated as S) 100, ECU 200 reads engine information (engine speed, water temperature, intake air amount, etc.).

  In S102, ECU 200 determines whether engine 100 is in an idle state or not. As a method for determining whether or not the vehicle is in the idle state, a well-known general technique may be used. Therefore, detailed description thereof will not be repeated here. If it is in an idle state (YES in S102), the process proceeds to S104. Otherwise (NO in S102), this process ends.

  In S104, ECU 200 determines whether or not there is a cylinder having a large fluctuation amount of the engine speed. ECU 200 determines that the fluctuation amount of the engine speed is large when the average increase rate or average increase rate of the engine speed after ignition during idling is larger than a predetermined value. At this time, since the cylinder at the ignition timing can be identified from the crank angle, it is possible to determine whether or not the fluctuation amount of the engine speed is large for the desired cylinder. If there is a cylinder with a large variation in engine speed (YES in S104), the process proceeds to S106. Otherwise (NO in S104), this process ends.

  In S106, ECU 200 stops high-pressure fuel pump 130. Instead of stopping the high-pressure fuel pump 130, for example, by delaying the closing timing of an electromagnetic spill valve (not shown) of the high-pressure fuel pump 130 and reducing the pressurization amount in the high-pressure fuel pump 130, the injection The pressure may be lowered. It is desirable that the fuel injection timing be on the top dead center side (the top dead center side with respect to a predetermined crank angle) from the viewpoint of suppressing the fluctuation amount of the engine speed.

  In S108, ECU 200 decreases the air-fuel ratio of the cylinder having a large fluctuation amount of the engine speed. The ECU 200 reduces the air-fuel ratio by increasing the fuel injection amount to the cylinder with a large engine speed fluctuation amount or reducing the air amount sucked into the cylinder with the large engine speed fluctuation amount. .

  In S110, ECU 200 determines that the air-fuel ratio of the exhaust gas purified by the three-way catalyst 112 becomes the stoichiometric air-fuel ratio, which is different from the cylinder with a large engine speed variation (the engine speed variation is small). Cylinder) air / fuel ratio is increased. That is, the air-fuel ratio of the exhaust gas mixed with the exhaust gas discharged from the cylinder with a large engine speed fluctuation amount and the exhaust gas discharged from the cylinder with a small engine speed fluctuation amount becomes the stoichiometric air-fuel ratio. The fuel ratio is increased. The ECU 200 increases the air-fuel ratio by reducing the fuel injection amount to the cylinder with a small fluctuation amount of the engine speed or increasing the amount of air sucked into the cylinder with a small fluctuation amount of the engine speed. . It should be noted that the air-fuel ratio of the cylinder with a small amount of fluctuation in the combustion state is increased so that the air-fuel ratio is different from the stoichiometric air-fuel ratio and the three-way catalyst 112 can efficiently purify the exhaust gas. Also good.

  An operation of ECU 200 that is the control device for the internal combustion engine according to the present embodiment based on the above-described structure and flowchart will be described.

  During operation of engine 100, engine information (engine speed, water temperature, intake air amount, etc.) is read (S100), and it is determined whether engine 100 is in an idle state (S102). If engine 100 is in an idle state (YES in S102), it is determined whether or not there is a cylinder with a large fluctuation amount of the engine speed (S104).

  If there is a cylinder with a large fluctuation amount of the engine speed (YES in S104), high-pressure fuel pump 130 is stopped (S106), and the injection pressure is reduced to the feed pressure (discharge pressure from fuel pump 128). Thereby, the operation sound of the high pressure fuel pump 130 can be suppressed. Moreover, the vibration accompanying the action | operation of the high pressure fuel pump 130 can be suppressed.

  In a state where the high-pressure fuel pump 130 is stopped, the air-fuel ratio of the cylinder with the large fluctuation amount of the engine speed is reduced (S108), and the air-fuel ratio of the cylinder with the small fluctuation amount of the engine speed is increased (S110). As a result, as shown in FIG. 5, the fluctuation amount in the cylinder with the large fluctuation amount of the engine speed is reduced, and the fluctuation amount in the cylinder with the small fluctuation amount of the engine rotation speed is increased. Therefore, the average value of the fluctuation amount of the engine speed is reduced, and vibration of engine 100 during idling is suppressed.

  At this time, the air-fuel ratio in each cylinder is corrected so that the air-fuel ratio of the exhaust gas purified by the three-way catalyst 112 becomes the stoichiometric air-fuel ratio. Therefore, the exhaust can be appropriately purified by the three-way catalyst 112. As a result, it is possible to suppress the deterioration of the exhaust emission performance accompanying the correction of the air-fuel ratio.

  As described above, according to the ECU that is the control device for the internal combustion engine according to the present embodiment, the high-pressure fuel pump is stopped when there is a cylinder with a large fluctuation amount of the engine speed when the engine is idle. Thereby, the vibration accompanying the action | operation of a high pressure fuel pump can be suppressed. In addition, the air-fuel ratio of the cylinder having a large fluctuation amount of the engine speed is reduced, and the air-fuel ratio of the cylinder having a small fluctuation amount of the engine speed is increased. Thereby, the average value of the fluctuation amount of the engine speed can be reduced, and the vibration of the engine during idling can be suppressed. At this time, the air-fuel ratio in each cylinder is corrected so that the air-fuel ratio of the exhaust gas purified by the catalyst becomes the stoichiometric air-fuel ratio. Therefore, the exhaust gas can be appropriately purified by the catalyst. As a result, it is possible to suppress the deterioration of the exhaust emission performance accompanying the correction to the air-fuel ratio.

  In the present embodiment, the variation amount of the combustion state is detected from the variation amount of the engine speed, but instead of the engine speed, the combustion is performed using the vibration of the engine 100 detected by the knock sensor 304. You may make it detect the fluctuation amount of a state. In this case, of the vibration of engine 100 after ignition, when the increase width or increase rate of the vibration intensity (amplitude) in a predetermined frequency band is larger than a predetermined value, the fluctuation amount of vibration, that is, combustion You may make it discriminate | determine that there exists a cylinder with the large amount of state fluctuations.

  Further, a sensor for detecting the pressure in the cylinder 106 may be provided, and the fluctuating force of the combustion state may be detected using the pressure in the cylinder 106 instead of the engine speed. In this case, when the pressure increase range or rate after ignition is larger than a predetermined value, it may be determined that there is a cylinder having a large pressure fluctuation amount, that is, a combustion state fluctuation amount.

  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.

It is a schematic block diagram which shows the engine of the vehicle carrying the control apparatus which concerns on the form of this invention. It is a figure which shows the relationship between the variation | change_quantity of an engine speed, and an air fuel ratio. It is a figure which shows the relationship of the variation | change_quantity of the engine speed with respect to injection timing and injection pressure. It is a flowchart which shows the control structure of the program which ECU which is a control apparatus which concerns on embodiment of this invention performs. It is a figure which shows the fluctuation amount of the engine speed before and behind correct | amending an air fuel ratio.

Explanation of symbols

  100 engine, 102 air cleaner, 104 throttle valve, 106 cylinder, 108 injector, 110 spark plug, 112 three-way catalyst, 114 piston, 116 crankshaft, 118 intake valve, 120 exhaust valve, 122,124 cam, 300 cam angle sensor, 302 Crank angle sensor, 304 Knock sensor.

Claims (7)

A control device for an internal combustion engine comprising fuel injection means for injecting fuel into a cylinder,
Detecting means for detecting a combustion state in the cylinder;
Control of the internal combustion engine, including pressure control means for controlling the internal combustion engine so as to lower the injection pressure from the fuel injection means when the fluctuation amount of the combustion state is larger than a predetermined fluctuation amount apparatus. The internal combustion engine includes a first pressurizing unit for pressurizing the fuel supplied to the fuel injection unit, and a second pressurizing unit for further pressurizing the fuel pressurized by the first pressurizing unit. Pressurizing means,
2. The control apparatus for an internal combustion engine according to claim 1, wherein the pressure control means includes means for controlling the internal combustion engine so as to stop pressurization of fuel by the second pressurization means. The internal combustion engine is provided with a plurality of cylinders and a catalyst for purifying exhaust exhausted from the internal combustion engine,
The detection means includes means for detecting a combustion state in each cylinder,
The control device includes:
First air-fuel ratio control means for controlling the internal combustion engine so that an air-fuel ratio in a cylinder in which the fluctuation amount of the combustion state is larger than the predetermined fluctuation amount is reduced;
3. The internal combustion engine according to claim 1, further comprising second air-fuel ratio control means for controlling the internal combustion engine such that an air-fuel ratio of the exhaust led to the catalyst becomes a predetermined air-fuel ratio. Engine control device. The fuel injection means is provided corresponding to each cylinder,
The first air-fuel ratio control means controls the fuel injection means so that the fuel injection amount of the fuel injection means in the cylinder in which the fluctuation amount of the combustion state is larger than the predetermined fluctuation amount is increased. The control device for an internal combustion engine according to claim 3, comprising means.   The first air-fuel ratio control means includes means for controlling the internal combustion engine such that the amount of air taken into a cylinder in which the fluctuation amount of the combustion state is larger than the predetermined fluctuation amount is reduced. The control device for an internal combustion engine according to claim 3.   The second air-fuel ratio control means includes means for controlling the internal combustion engine so as to increase the air-fuel ratio in a cylinder in which the fluctuation amount of the combustion state is smaller than the predetermined fluctuation amount. The control apparatus for an internal combustion engine according to any one of 3 to 5.   The detection means includes means for detecting a combustion state in the cylinder based on at least one of a rotational speed of the internal combustion engine, vibration of the internal combustion engine, and pressure in the cylinder. Item 7. The control device for an internal combustion engine according to any one of Items 1 to 6.

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