JP2008038711A - Control device of cylinder injection type spark ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suitably provide the jet effect, by preventing generation of an inverse tumble flow, when strengthening a tumble flow by injected fuel. <P>SOLUTION: An ECU 1 controls an internal combustion engine 50 for generating the tumble flow T in a cylinder and strengthening the tumble flow T by the fuel injected toward the exhaust side from a fuel injection valve 21 arranged in the supper substantial center of a combustion chamber 57 in the vicinity of a bottom dead center of an intake stroke, and has an injection finish control means for finishing fuel injection in the vicinity of the bottom dead center of the intake stroke, and an injection prohibiting means for prohibiting the fuel injection at a crank angle of a predetermined range corresponding to a half of the intake stroke when a range of the crank angle corresponding to an injection period of the fuel injection reaches up to the half of the intake stroke from the vicinity of the bottom dead center of the intake stroke, and also has a fuel injection means for injecting a part of the fuel before the predetermined range when the injection prohibiting means prohibits the fuel injection. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an in-cylinder injection spark ignition internal combustion engine.

  A tumble flow is generated in the cylinder of an in-cylinder injection spark ignition internal combustion engine, and the tumble flow is moderately strengthened with fuel injected near the bottom dead center of the intake stroke during homogeneous combustion. Can be maintained. As a result, the turbulence of the air-fuel mixture can be increased at the ignition timing, so that the combustion speed of the air-fuel mixture can be improved moderately and good homogeneous combustion can be obtained. As a technique for enhancing the in-cylinder intake flow during homogeneous combustion, for example, Patent Document 1 discloses an in-cylinder direct injection internal combustion engine intake control device that controls an intake flow control valve provided in an intake passage to strengthen intake flow. Proposed. Patent Document 2 proposes a technique for improving the homogeneity of the air-fuel mixture by dividing and injecting fuel into the first half and the second half of the intake stroke.

JP 2005-180247 A JP-A-10-159619

  By the way, in the above-described in-cylinder spark ignition internal combustion engine, for example, when the rotational speed becomes high with the injection amount being constant, the crank angle range corresponding to the injection period is from the vicinity of the intake stroke bottom dead center to the intake stroke top dead center. It will spread towards. For example, when the injection amount increases with the rotation speed being constant, the range of the crank angle corresponding to the injection period similarly extends from the vicinity of the intake stroke bottom dead center toward the intake stroke top dead center. . As a result, when the injection period reaches the middle of the intake stroke, the following problems occur depending on the fuel injection method. FIG. 5 is a diagram schematically showing a state when fuel is injected in the middle of the intake stroke. This in-cylinder injection spark-ignition internal combustion engine has a fuel injection valve in the approximate center above the combustion chamber, and is directed toward the vicinity of the outer peripheral portion on the exhaust side of the piston located at the bottom dead center from the fuel injection valve. It is intended to enhance the tumble flow with the injected fuel. In such an in-cylinder spark ignition internal combustion engine, when the injection period reaches the middle of the intake stroke, the injected fuel collides with the piston as shown in FIG. Since the fuel that collided with the piston swirls so as to wind up after the collision, a reverse tumble flow that swirls in a direction opposite to the tumble flow to be strengthened by the injected fuel is also formed. The reverse tumble flow is then formed and acts to weaken the tumble flow strengthened by the fuel injection. Therefore, when the reverse tumble flow is formed, the jet effect by the fuel injection cannot be sufficiently obtained. End up.

  Therefore, the present invention has been made in view of the above problems, and in-cylinder injection that can suitably obtain a jet effect by preventing the occurrence of a reverse tumble flow when the tumble flow is strengthened with the injected fuel. An object of the present invention is to provide a control device for an internal spark ignition internal combustion engine.

  In order to solve the above-mentioned problems, the present invention generates a tumble flow in a cylinder and sends the tumble flow from the fuel injection valve disposed in the upper center of the combustion chamber in the vicinity of the bottom dead center of the intake stroke to the exhaust side. A control device for an in-cylinder injection spark ignition internal combustion engine for controlling an in-cylinder injection spark ignition internal combustion engine that is reinforced with fuel injected toward the end, and an injection end control means for ending the fuel injection near the bottom dead center of the intake stroke And an injection prohibiting means for prohibiting fuel injection in the middle of the intake stroke when the injection period of the fuel injection extends from near the bottom dead center of the intake stroke to the middle of the intake stroke. According to the present invention, the jet effect can be suitably obtained by prohibiting fuel injection in the middle of the intake stroke in which a reverse tumble flow is formed.

  The present invention may further include a fuel injection unit that injects a part of the fuel before the middle of the intake stroke when the injection prohibiting unit prohibits fuel injection. Here, instead of prohibiting fuel injection in the middle of the intake stroke, if the required amount of fuel is injected before the middle of the intake stroke, the in-cylinder space becomes considerably narrow, so the injected fuel collides with the piston. However, there is no risk of forming a reverse tumble flow. Thus, according to the present invention, it is possible to suitably obtain the jet effect while ensuring the injection amount.

  ADVANTAGE OF THE INVENTION According to this invention, the control apparatus of the cylinder injection type spark ignition internal combustion engine which can acquire a jet effect suitably by preventing generation | occurrence | production of a reverse tumble flow in strengthening a tumble flow with the injected fuel can be provided. .

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram schematically showing a control device for a direct injection spark ignition internal combustion engine according to the present embodiment realized by an ECU (Electronic Control Unit) 1 together with an internal combustion engine system 100. . The internal combustion engine system 100 includes an intake system 10, a fuel injection system 20, and an internal combustion engine 50. The intake system 10 is configured to introduce air into the internal combustion engine 50, and includes an air cleaner 11 for filtering intake air, an air flow meter 12 for measuring the amount of air, a throttle valve 13 for adjusting the flow rate of intake air, For temporarily storing the intake tank 15, the intake manifold 15 for distributing the intake air to the cylinders of the internal combustion engine 50, the intake pipe appropriately disposed therebetween, and the like.

  The fuel injection system 20 is configured to supply and inject fuel, and includes a fuel injection valve 21, a fuel injection pump 22, a fuel tank 23, and the like. The fuel injection valve 21 is a structure for injecting fuel, and is opened at an appropriate injection timing to inject fuel under the control of the ECU 1. The fuel injection amount is adjusted by the length of the valve opening period until the fuel injection valve 21 is closed under the control of the ECU 1. The fuel injection pump 22 is configured to pressurize the fuel and generate an injection pressure, and adjusts the injection pressure to an appropriate injection pressure under the control of the ECU 1.

  FIG. 2 is a diagram schematically showing a main part of the internal combustion engine 50. The internal combustion engine 50 includes a cylinder block 51, a cylinder head 52, a piston 53, a spark plug 54, an intake valve 55, and an exhaust valve 56. The internal combustion engine 50 shown in this embodiment is an in-line four-cylinder in-cylinder spark ignition internal combustion engine. However, the internal combustion engine 50 may have other appropriate cylinder arrangement structure and the number of cylinders. In FIG. 2, the main part of the internal combustion engine 50 is shown with respect to the cylinder 51a as a representative of each cylinder, but in this embodiment, the other cylinders have the same structure. The cylinder block 51 is formed with a substantially cylindrical cylinder 51a. A piston 53 is accommodated in the cylinder 51a. A cavity 53 a for guiding the tumble flow T is formed on the top surface of the piston 53. A cylinder head 52 is fixed to the upper surface of the cylinder block 51.

  The combustion chamber 57 is formed as a space surrounded by the cylinder block 51, the cylinder head 52, and the piston 53. In addition to an intake port 52a for guiding intake air to the combustion chamber 57, the cylinder head 52 is formed with an exhaust port 52b for exhausting the combusted gas from the combustion chamber 57, and opens and closes the intake and exhaust ports 52a and 52b. For this purpose, intake and exhaust valves 55 and 56 are provided. The internal combustion engine 50 may have an intake / exhaust valve structure including an appropriate number of intake / exhaust valves 55 and 56 per cylinder. The spark plug 54 is disposed in the cylinder head 52 with an electrode protruding substantially in the center above the combustion chamber 57. The fuel injection valve 21 is also disposed in the cylinder head 52 with a fuel injection hole projecting into the combustion chamber 57 from a position adjacent to the spark plug 54 at approximately the center above the combustion chamber 57. The injection direction of the fuel injection valve 21 is a direction toward the vicinity of the outer peripheral portion on the exhaust side of the piston 51 located at the bottom dead center.

  An air flow control valve 58 for generating a tumble flow T in the combustion chamber 57 is disposed in the intake port 52a. The airflow control valve 58 is configured to generate a tumble flow T in the combustion chamber 57 by causing the intake air to drift in the intake port 52 a under the control of the ECU 1. However, the tumble flow generating means for generating the tumble flow T in the combustion chamber 57 is not limited to the air flow control valve 58, and for example, the shape of the intake port 52a formed so that the tumble flow T can be generated in the cylinder. There may be other appropriate means capable of generating the tumble flow T in the cylinder. The tumble flow T is a forward tumble flow that turns in the cylinder so as to rise on the intake valve 55 side in the combustion chamber 57. In the present embodiment, under the control of the ECU 1, the fuel injection valve 21 injects fuel so that the fuel injection ends at the bottom dead center of the intake stroke during homogeneous combustion, so that the fuel is injected near the bottom dead center of the intake stroke. Is done. The fuel injected near the bottom dead center of the intake stroke moderately strengthens the tumble flow T, and the enhanced tumble flow T is maintained until the ignition timing. As a result, the turbulence of the air-fuel mixture increases at the ignition timing and the combustion speed is improved moderately, so that good homogeneous combustion can be obtained.

  The air flow control valve 58 is opened at an opening degree such as half-open or full-open to increase intake during homogeneous combustion, and it is difficult to obtain a sufficiently strong tumble flow T only by the shape of the intake port 52a. However, there is generally room for improvement in the mixing characteristics of the air-fuel mixture and the flame propagation characteristics during homogeneous combustion. In addition, the internal combustion engine 50 is provided with various sensors such as a crank angle sensor 71 for generating an output pulse proportional to the rotational speed Ne and a water temperature sensor 72 for detecting the water temperature of the internal combustion engine 50.

  The ECU 1 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output circuit, and the like (not shown). The ECU 1 is mainly configured to control the internal combustion engine 50. In the present embodiment, in addition to the fuel injection valve 21 and the fuel injection pump 22, an ignition plug 54 (more specifically, an igniter not shown) and an airflow control valve 58 are provided. (More specifically, an actuator for the airflow control valve 58 (not shown)) is also controlled. In addition to the fuel injection valve 21 and the like, various control objects are connected to the ECU 1 via a drive circuit (not shown). The ECU 1 is connected to various sensors such as an air flow meter 12, a crank angle sensor 71, a water temperature sensor 72, and an accelerator sensor 73 for detecting the amount of depression (accelerator opening) of an accelerator pedal (not shown). Has been.

  The ROM is configured to store a program in which various processes executed by the CPU are described. In this embodiment, the ROM is used for controlling the fuel injection valve 21 for controlling the fuel injection valve 21 in addition to the program for controlling the internal combustion engine 50. Also stores programs. The fuel injection valve control program may be configured as a part of the internal combustion engine 50 control program. The fuel injection valve control program includes an injection amount control program for controlling the fuel injection amount, an injection pressure control program for controlling the fuel injection pressure, and an injection for controlling the fuel injection timing. And a timing control program. In this embodiment, the fuel injection valve control program further includes an injection end control program for ending fuel injection in the vicinity of the intake stroke bottom dead center, and a fuel injection period from the vicinity of the intake stroke bottom dead center to the middle of the intake stroke. The injection prohibition program for prohibiting fuel injection in the middle of the intake stroke when it reaches the range, and the injection timing for injecting part of the fuel before the mid-intake stroke when prohibiting fuel injection It is characterized by having a program for specific control. Note that the injection end control program, the injection prohibition program, and the injection timing specifying control program may be configured as a part of another program.

  In this embodiment, the injection end control program is specifically created so as to end the fuel injection at the bottom dead center of the intake stroke. Further, in the injection prohibition program, when the compression process top dead center is set to 0 degree and the intake stroke top dead center is set to 360 degrees, the crank angle range corresponding to the mid intake stroke is specifically 300 degrees to 260 degrees. The predetermined range is set. In addition, the injection timing specifying control program specifically divides and splits the fuel for injection at a crank angle larger than the crank angle corresponding to the end of the mid-intake stroke (260 degrees in this embodiment). The fuel injection timing is changed to before the mid-intake stroke, and the divided fuel injection is completed at the beginning of the mid-intake stroke (the corresponding crank angle is 300 degrees in this embodiment). At the same time, the injection timing specifying control program is created so that the fuel injection timing for the remaining part of the division is at the end of the middle of the intake stroke. In the present embodiment, various detection means, determination means, control means, and the like are realized by a CPU, a ROM, a RAM (hereinafter simply referred to as a CPU, etc.), and a program for controlling the internal combustion engine 50. And the injection end control program, the injection end control means is realized by the CPU and the injection prohibition program, and the fuel injection means is realized by the CPU and the injection timing specifying control program.

  Next, the process performed by the ECU 1 in controlling the fuel injection to prevent the formation of the reverse tumble flow and to obtain the jet effect suitably will be described in detail with reference to the flowchart shown in FIG. The ECU 1 controls the internal combustion engine 50 by repeatedly executing the processing shown in the flowchart based on various programs such as the above-described internal combustion engine 50 control program stored in the ROM and the fuel injection valve control program. To do. The CPU calculates an injection amount commensurate with the required air-fuel ratio, and executes a process of calculating an injection timing corresponding to the injection amount (step 11). In this embodiment, since the fuel injection ends at the bottom dead center of the intake stroke, the injection timing is calculated according to the injection amount corresponding to the required air-fuel ratio. Subsequently, the CPU executes a process of determining whether or not the crank angle corresponding to the injection timing is larger than 260 degrees (step 12). If the determination is negative, the process returns to step 11 because no special processing is required in this flowchart.

  On the other hand, if the determination in step 12 is affirmative, the CPU executes a process for prohibiting fuel injection in the middle of the intake stroke (step 13). In prohibiting fuel injection, specifically, in this step, the fuel for the amount of fuel that was to be injected at a crank angle larger than the crank angle corresponding to the end of the intake stroke (in this case, 260 degrees) is divided and divided. A process of calculating the fuel injection timing so that the fuel injection is completed at the start of the middle of the intake stroke (here, the corresponding crank angle is 300 degrees) is executed. The crank angle corresponding to the fuel injection timing for the remaining part of the division is 260 degrees.

  FIG. 4 is a diagram schematically showing the state of fuel injection when the injection prohibition process is performed in this step, together with the state of fuel injection when the injection prohibition process is not performed. When the injection amount is constant, the injection period increases from the intake stroke bottom dead center toward the intake stroke top dead center as the rotational speed Ne increases. As a result, when the crank angle range corresponding to the injection period reaches 260 degrees, the injection prohibition process is performed in step 13, thereby prohibiting fuel injection in a predetermined range from 260 degrees to 300 degrees. The At the same time, the injection timing of the fuel to be injected at a crank angle larger than 260 degrees is divided and changed so that the fuel injection ends at 300 degrees. Further, when the rotational speed Ne is constant, the crank angle range corresponding to the injection period increases from the intake stroke bottom dead center toward the intake stroke top dead center as the injection amount increases instead of the rotational speed Ne. In this case, the injection prohibiting process is performed in the same manner as in the case where the injection amount is constant. The rotational speed Ne and the injection amount may change simultaneously.

  Subsequently, the CPU executes a process for controlling the fuel injection valve 21 so as to perform fuel injection according to the injection timing divided and changed in step 13 (step 14). Thereby, it is prevented that a reverse tumble flow is formed, and a jet effect can be suitably obtained. In addition, when performing the injection prohibition process, the fuel injection timing is changed so that the injection is completed at 300 degrees at the same time as the crank angle greater than 260 degrees is injected, so fuel injection is prohibited in the middle of the intake stroke Even so, the injection amount can be secured. As described above, it is possible to realize the ECU 1 that can appropriately obtain the jet effect by preventing the occurrence of the reverse tumble flow when the tumble flow T is strengthened with the injected fuel.

  The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.

1 is a diagram schematically showing an ECU 1 together with an internal combustion engine system 100. FIG. FIG. 2 is a diagram schematically showing a main part of an internal combustion engine 50. It is a figure which shows the process performed by ECU1 with a flowchart. It is a figure which shows typically the mode of fuel injection when an injection prohibition process is performed with the mode of fuel injection when an injection prohibition process is not performed. It is a figure which shows typically a mode when fuel is injected in the middle of an intake stroke.

Explanation of symbols

1 ECU
DESCRIPTION OF SYMBOLS 10 Intake system 20 Fuel injection system 21 Fuel injection valve 50 Internal combustion engine 100 Internal combustion engine system

Claims (2)

In-cylinder injection type that generates a tumble flow in the cylinder and reinforces the tumble flow with fuel injected toward the exhaust side from a fuel injection valve disposed in the upper center of the combustion chamber near the bottom dead center of the intake stroke A control device for a direct injection spark ignition internal combustion engine for controlling a spark ignition internal combustion engine,
An injection end control means for ending fuel injection in the vicinity of the intake stroke bottom dead center, and prohibiting fuel injection in the middle of the intake stroke when the injection period of the fuel injection extends from near the intake stroke bottom dead center to mid intake stroke An in-cylinder injection spark ignition internal combustion engine control device comprising: The in-cylinder spark ignition internal combustion engine according to claim 1, further comprising fuel injection means for injecting a part of fuel before the middle of the intake stroke when the injection prohibiting means prohibits fuel injection. Engine control device.

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