JP2006170170A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent occurrence of misfire by optimally controlling air/fuel ratio in a proximity of a spark plug even if fuel injection quantity is increased and decreased in an internal combustion engine performing stratified combustion. <P>SOLUTION: This device is provided with an intake valve 36 feeding gas into a cylinder of the internal combustion engine by opening at predetermined timing, a fuel injection valve 30 injecting fuel into the cylinder of the internal combustion engine 10 in compression stroke, a spark plug 42 igniting fuel injected into the cylinder, and a variable mechanism (a pinion gear 30a, a rack 32) varying injection direction of fuel from the fuel injection valve 30 according to fuel injection quantity from the fuel injection valve 30. Since injection direction of fuel is varied according to fuel injection quantity, distance between the spark plug 42 and spray fuel can be adjusted, air fuel ratio around the spark plug can be optimally controlled, occurrence of misfire can be surely prevented. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control device for an internal combustion engine, and is particularly suitable for application to an internal combustion engine that injects fuel directly into the cylinder of the engine.

  By directly injecting fuel into the engine cylinder, a mixture with good ignitability is formed only near the spark plug at the time of ignition, and stratified combustion that enables combustion of a lean mixture as a whole in the cylinder Is known.

  For example, Japanese Patent Laid-Open No. 2001-27170 discloses a technique for changing the direction of spraying in an internal combustion engine that performs stratified combustion by rotating an injection valve that performs fan-shaped spraying according to operating conditions.

Japanese Patent Laid-Open No. 2001-27170 Japanese Patent No. 3532098 JP 2000-205088 A JP 10-339244 A

  However, in an internal combustion engine that performs stratified combustion, if the fuel injection amount is increased or decreased in accordance with a change in load required for the internal combustion engine, the air-fuel ratio around the spark plug changes. For this reason, in operation in a high load region where the fuel injection amount is large, the air-fuel ratio around the spark plug may become over-rich. Further, in an operation in a low load region where the fuel injection amount is small, the air-fuel ratio around the spark plug may be over lean. When the air-fuel ratio around the spark plug becomes overlean or overrich, there is a problem that the ignitability of the air-fuel mixture is lowered and misfire occurs.

  The present invention has been made to solve the above-described problems. In an internal combustion engine that performs stratified combustion, even when the fuel injection amount is increased or decreased, the air-fuel ratio in the vicinity of the spark plug is optimized. The purpose is to control and prevent the occurrence of misfire.

  In order to achieve the above object, a first invention is an intake valve that sends gas into a cylinder of an internal combustion engine by opening at a predetermined timing, and a fuel injection valve that injects fuel into the cylinder of the internal combustion engine in a compression stroke And an ignition plug for igniting the fuel injected into the cylinder, and a variable mechanism for changing the injection direction of the fuel from the fuel injection valve in accordance with the fuel injection amount from the fuel injection valve. It is characterized by.

  In a second aspect based on the first aspect, the variable mechanism injects fuel in the vicinity of the spark plug as the fuel injection amount decreases, and injects the fuel at a position away from the spark plug as the fuel injection amount increases. It is characterized by spraying.

  According to the first invention, since the fuel injection direction is varied according to the fuel injection amount, the distance between the spark plug and the sprayed fuel can be adjusted. Therefore, the air-fuel ratio around the spark plug can be optimally controlled, and the sprayed fuel can be reliably ignited. This makes it possible to reliably prevent the occurrence of misfire.

  According to the second aspect of the invention, the fuel is injected near the spark plug as the fuel injection amount decreases, so that the air-fuel ratio around the spark plug can be prevented from being over lean. Further, as the fuel injection amount increases, fuel is injected toward a position away from the spark plug, so that it is possible to prevent the air-fuel ratio around the spark plug from becoming overrich.

  An embodiment of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

  FIG. 1 is a diagram for explaining a control device for an internal combustion engine according to an embodiment of the present invention and a structure around the control device. An intake passage 12 and an exhaust passage 14 communicate with the internal combustion engine 10. The intake passage 12 includes an air filter 16 at an upstream end. The air filter 16 is assembled with an intake air temperature sensor 18 for detecting the intake air temperature THA (that is, the outside air temperature). An exhaust purification catalyst 31 is disposed in the exhaust passage 14.

  An air flow meter 20 is disposed downstream of the air filter 16. A throttle valve 22 is provided downstream of the air flow meter 20. A throttle sensor 24 that detects the throttle opening degree TA and an idle switch 26 that is turned on when the throttle valve 22 is fully closed are disposed in the vicinity of the throttle valve 22. A surge tank 28 is provided downstream of the throttle valve 22.

  The internal combustion engine 10 is provided with a fuel injection valve 30 that injects fuel into the combustion chamber (inside the cylinder). The internal combustion engine 10 includes an intake valve 36 and an exhaust valve 38. An ignition plug 42 (not shown in FIG. 1) is provided in the cylinder of the internal combustion engine 10 to ignite the fuel sprayed into the combustion chamber. Further, a piston 44 that reciprocates inside the cylinder is provided in the cylinder.

  As shown in FIG. 1, the control device of the present embodiment includes an ECU (Electronic Control Unit) 40. In addition to the various sensors described above, the ECU 40 includes a KCS sensor that detects the occurrence of knocking, a throttle opening, an engine speed, an exhaust temperature, a cooling water temperature, a lubricating oil temperature in order to grasp the operating state of the internal combustion engine 10. Various sensors (not shown) for detecting the catalyst bed temperature and the like are connected. Further, each actuator such as the fuel injection valve 30 described above is connected to the ECU 40.

  In the internal combustion engine 10 of the present embodiment, the fuel injection timing from the fuel injection valve 30 is varied according to the operating state. When the internal combustion engine 10 is operated in the idling to normal rotation range (low load range), fuel is injected in the compression stroke to burn a lean air-fuel mixture (stratified combustion). Further, when the internal combustion engine 10 is operated in a high rotation range (high load range), fuel is injected and combustion is performed in the intake stroke (homogeneous combustion).

  In the operation of stratified combustion, the throttle valve 22 is fully opened regardless of the engine speed and load fluctuations. Therefore, the amount of intake air into the cylinder is constant even when there is a load fluctuation, and the output of the internal combustion engine 10 is controlled only by controlling the fuel injection amount. On the other hand, in the case of homogeneous combustion, the output of the internal combustion engine 10 is controlled by varying the opening of the throttle valve 22 and controlling the fuel injection amount.

  In the internal combustion engine 10 of the present embodiment, the fuel injection valve 30 is rotatable about its central axis as a rotation center. FIG. 2 is a schematic view showing the vicinity of the fuel injection valve 30 in detail. Here, FIG. 2A shows a state in which the vicinity of the fuel injection valve 30 is viewed from above. FIG. 2B shows a state in which the vicinity of the fuel injection valve 30 is viewed from the side.

  As shown in FIGS. 2A and 2B, a pinion gear 30 a is provided on the outer periphery of the fuel injection valve 30. The pinion gear 30a is engaged with a rack 32, and the rack 32 is supported by a member such as a cylinder head in a state where the rack 32 can be moved in the longitudinal direction. When the rack 32 is driven in the longitudinal direction by the power of an actuator (not shown), the pinion gear 30a is rotated, and as a result, the fuel injection valve 30 is rotated.

  FIG. 3 is a schematic diagram showing a state in which the combustion chamber in the cylinder of the internal combustion engine 10 is viewed from the piston 44 side, and shows a state immediately after fuel is injected from the fuel injection valve 30 during stratified combustion. As shown in FIG. 3, two intake valves 36 and two exhaust valves 38 are arranged in the combustion chamber. The fuel injection valve 30 is disposed substantially at the center of the combustion chamber. A spark plug 42 is disposed at a position separated from the fuel injection valve 30 by a predetermined distance.

  FIG. 3A shows a case where the internal combustion engine 10 is operated in a relatively low load region. FIG. 3 (B) shows a case where the internal combustion engine 10 is operated in a higher load region than in the case of FIG. 3 (A). As described above, in the stratified charge combustion operation, the intake air amount is substantially constant regardless of the load fluctuation, and the output is controlled by increasing or decreasing the fuel injection amount. Therefore, compared with FIG. ) More fuel is injected from the fuel injection valve 30. Therefore, the air-fuel ratio in the cylinder becomes richer as the load increases, and the air-fuel ratio in the cylinder becomes richer in FIG. 3B than in FIG. 3A.

  The fuel injection valve 30 is a multi-hole injector having six injection ports, and fuel is injected from the fuel injection valve 30 in six directions as shown in FIG. In this embodiment, the rotational position of the fuel injection valve 30 is varied by varying the position of the rack 32 in accordance with the fuel injection amount. Thereby, the angular position of the injection port of the fuel injection valve 30 is changed, and the fuel injection direction is varied.

  As shown in FIG. 3A, when the fuel injection amount is relatively small and the air-fuel ratio in the cylinder is relatively lean, the fuel injected in one of the six directions is spark plug. The angular position of the fuel injection valve 30 is set so as to go to 42.

  As a result, even when the fuel injection amount is small, a large amount of fuel can be sent to the spark plug 42 side, and the air-fuel ratio in the vicinity of the spark plug 42 can be prevented from being over lean. Therefore, it is possible to prevent misfire from occurring when the fuel injection amount is small.

  On the other hand, when the fuel injection amount from the fuel injection valve 30 is large as shown in FIG. 3B and the air-fuel ratio in the cylinder becomes relatively rich, the rack 32 is driven from the case of FIG. The angular position of the fuel injection valve 30 is changed. Then, as shown in FIG. 3B, the angular position of the fuel injection valve 30 is set so that the fuel injected from the injection port of the fuel injection valve 30 does not go directly to the spark plug 42. That is, as shown in FIG. 3B, the angular position of the fuel injection valve 30 is set so that the position of the ignition plug 42 is in the middle between two adjacent fuel injection directions.

  Thereby, compared with the case where fuel is directly injected toward the spark plug 42, the amount of fuel sent to the vicinity of the spark plug 42 can be reduced, and the air-fuel ratio around the spark plug 42 is set to an appropriate value. be able to. Therefore, even when the fuel injection amount is large, it is possible to prevent the air-fuel ratio in the vicinity of the spark plug 42 from becoming over-rich, and it is possible to suppress the occurrence of misfire.

  As described above, in the present embodiment, during stratified combustion, the fuel injection valve 30 is rotated in accordance with the change in load, and the air-fuel ratio around the spark plug 42 is controlled to be appropriate. Even in such a case, the air-fuel ratio around the spark plug 42 can be made appropriate. Therefore, the range in which stratified combustion is established with respect to load fluctuations can be widened.

  In the present embodiment, the fuel injection direction is varied by rotating the entire fuel injection valve 30. However, only the injection port of the fuel injection valve 30 may be rotated. Further, the fuel injection direction may be other than six directions.

  As described above, according to the present embodiment, the fuel injection direction from the fuel injection valve 30 is made variable according to the fuel injection amount, so that the air-fuel ratio around the spark plug 42 can always be optimized. It becomes possible. Therefore, the injected fuel can be reliably ignited without the air-fuel ratio around the spark plug 42 becoming overrich or overlean. As a result, it is possible to reliably suppress the occurrence of misfire.

It is a figure for demonstrating the structure of the control apparatus of the internal combustion engine which concerns on one Embodiment of this invention, and its periphery. It is a schematic diagram which shows the vicinity of a fuel injection valve in detail. It is a schematic diagram which shows the state which looked at the combustion chamber of the internal combustion engine from the piston side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 30 Fuel injection valve 30a Pinion gear 32 Rack 36 Intake valve 42 Spark plug

Claims (2)

An intake valve that sends gas into the cylinder of the internal combustion engine by opening at a predetermined timing;
A fuel injection valve for injecting fuel into the cylinder of the internal combustion engine in the compression stroke;
A spark plug for igniting the fuel injected into the cylinder;
A variable mechanism that varies a fuel injection direction from the fuel injection valve in accordance with a fuel injection amount from the fuel injection valve;
A control apparatus for an internal combustion engine, comprising:   2. The variable mechanism according to claim 1, wherein the variable mechanism injects fuel in the vicinity of the spark plug as the fuel injection amount decreases, and injects the fuel at a position away from the spark plug as the fuel injection amount increases. Control device for internal combustion engine.

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