JP4240084B2 - In-cylinder injection spark ignition internal combustion engine control device - Google Patents

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, when the output is improved by the vaporization latent heat effect in the high load operation region, it is important to inject the fuel when the air enters the cylinder most. The injection timing approaches the intake stroke top dead center from the vicinity of the intake stroke bottom dead center as the rotational speed of the internal combustion engine increases. On the other hand, in this case, since the piston position at the time of fuel injection approaches the top dead center, the in-cylinder space at the time of fuel injection becomes narrow. However, since the tumble flow does not rotate well when the in-cylinder space is narrow, it is difficult to enhance the tumble flow even if fuel is injected in this state. That is, in this case, the vaporization latent heat effect can be obtained, but there remains room for improvement in the homogeneity and combustion speed of the air-fuel mixture.

  Therefore, the present invention has been made in view of the above problems, and by dividing the fuel injection in strengthening the tumble flow with the injected fuel, the vaporization latent heat effect and the homogeneity of the air-fuel mixture in the high load operation region Or it aims at providing the control apparatus of the cylinder injection type spark ignition internal combustion engine which can make a combustion speed compatible.

In order to solve the above-described problems, the present invention controls a cylinder injection spark ignition internal combustion engine that generates a tumble flow in a cylinder and enhances the tumble flow with fuel injected near the bottom dead center of the intake stroke. A control device for an in-cylinder injection spark ignition internal combustion engine, wherein the in-cylinder injection spark ignition internal combustion engine is charged with air flowing into the cylinder when the rotation speed is higher than a predetermined rotation speed in a high load operation region. The fuel cell system includes an injection timing control unit that performs the first fuel injection at the time when the efficiency becomes maximum and performs the second fuel injection that is completed at the bottom dead center of the intake stroke. According to the present invention, the first fuel injection can improve the output due to the latent heat effect of vaporization, and the second fuel injection can enhance the tumble flow, which further improves the homogeneity of the air-fuel mixture and the combustion speed. Can be planned.

In the present invention, the injection timing control means may advance the first fuel injection as the rotational speed increases. Here, since the timing at which the charging efficiency of the air flowing into the cylinder becomes maximum differs depending on the rotational speed of the internal combustion engine even in the same high-load operation region, specifically, the first fuel injection is advanced as in the present invention. By making the angle, the first fuel injection can be performed at the time when the charging efficiency of the air flowing into the cylinder is maximized .

  Furthermore, the present invention further provides a fuel injection system in which the crank angle range corresponding to the fuel injection period of the second fuel injection is substantially constant with respect to changes in the operating state of the direct injection spark ignition internal combustion engine. You may provide the injection quantity control means which controls the injection quantity. Here, in order to improve the combustion speed, it is necessary to maintain the tumble flow until the ignition timing, so a certain amount of injection is required. On the other hand, to improve the homogeneity of the air-fuel mixture, the tumble flow needs to be strengthened so much. Therefore, if the fuel injection is the minimum necessary, the effect can be sufficiently obtained. The present invention pays attention to such a point, and according to the present invention, the homogeneity of the air-fuel mixture is particularly improved by the second fuel injection, and the second fuel injection is made the minimum necessary fuel injection. Thus, sufficient vaporization latent heat effect can be obtained by the first fuel injection.

  According to the present invention, by dividing the fuel injection to enhance the tumble flow with the injected fuel, it is possible to achieve both the latent heat effect of vaporization and the homogeneity of the air-fuel mixture or the combustion speed in the high load operation region. A control device for an in-cylinder injection spark ignition internal combustion engine 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 the fuel injection hole protruding into the combustion chamber 57 from a position adjacent to the spark plug 54 above the combustion chamber 57. The arrangement of the fuel injection valve 21 is not limited to this. For example, the cylinder head with the fuel injection hole projecting into the combustion chamber 57 from the intake port 52a side (portion A shown in FIG. 2) above the combustion chamber 57. 52 may be provided. A plurality of fuel injection valves 21 may be provided per cylinder.

  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 this embodiment, the fuel injection valve 21 injects fuel near the bottom dead center of the intake stroke at the time of homogeneous combustion except when the rotational speed Ne is higher than the predetermined rotational speed α in the high load operation region under the control of the ECU 1. . The injected fuel moderately strengthens the tumble flow T, and the strengthened 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 the present embodiment, in particular, when the rotational speed Ne is higher than the predetermined rotational speed α in the high load operation region, the program for controlling the injection timing controls the first fuel at the time when the charging efficiency of the air flowing into the cylinder becomes maximum. The injection timing control program for performing the injection and performing the second fuel injection in the vicinity of the bottom dead center of the intake stroke, and the injection amount control program are the second fuel injection And an injection amount specifying control program for controlling the fuel injection amount so that the range of the crank angle corresponding to the fuel injection period becomes substantially constant with respect to a change in the operating state of the internal combustion engine 50. It has the feature in being made.

In the first fuel injection, the injection timing is set to a timing at which the charging efficiency of the air flowing into the cylinder becomes maximum at a predetermined rotation speed α, and this injection timing is injected with respect to the change in the rotation speed Ne. The time from the timing to the closing timing of the intake valve 55 is set to be substantially constant. As a result, the injection timing is advanced as the rotational speed Ne increases, and the first fuel injection is started at the time when the charging efficiency of the air flowing into the cylinder is maximized. The output of the engine 50 can be improved. Further, the injection timing of the first fuel injection is set to be in the middle of the intake stroke during WOT (Wide Open Throttle). The setting of the injection timing is not limited to this. For example, map data showing the relationship between the rotational speed Ne and the injection timing of the first fuel injection is provided, and the first is based on the detected rotational speed Ne and this map data. One fuel injection may be started when the air enters the cylinder most.

  In contrast, in the second fuel injection, the injection timing is set in the vicinity of the intake stroke bottom dead center, and further, the fuel injection is set to be completed at the intake stroke bottom dead center. In the second fuel injection, the range of the crank angle corresponding to the fuel injection period is set so that the range of the crank angle becomes substantially constant with respect to the change in the operating state of the internal combustion engine 50. Thereby, the minimum fuel injection required for improving the homogeneity of the air-fuel mixture can be performed near the bottom dead center of the intake stroke regardless of the rotational speed Ne. In the second fuel injection, the injection amount corresponding to the predetermined crank angle range is always ensured in this way, whereas in the first fuel injection, the injection amount is the injection amount of the second fuel injection. Accordingly, the injection amount required to make the air-fuel ratio appropriate is adjusted. 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. The injection timing control means is realized by the injection timing specifying control program, and the injection amount control means is realized by the CPU and the injection amount specifying control program.

  Next, the process performed by the ECU 1 in controlling the fuel injection to achieve both the vaporization latent heat effect and the homogeneity of the air-fuel mixture in the high load operation region 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 executes a process of determining whether or not the operating state of the internal combustion engine 50 is in the high load operation region (step 11). In the present embodiment, the rotational speed Ne detected based on the output signal of the crank angle sensor 71, the load factor KL detected based on the output signal of the accelerator sensor 73, and the operating range defined by the rotational speed Ne and the load factor KL. Based on the map data, the operating state of the internal combustion engine 50 is determined.

  FIG. 4 is a diagram schematically showing map data of the operation region. In this embodiment, the operation area is divided into a high load operation area and other areas according to the rotational speed Ne and the load factor KL in this map data. However, the operation region is not limited to this, and the operation region may be further divided into a plurality of regions. The operating region is not limited to the rotational speed Ne and the load factor KL, and may be set according to an appropriate operating state of the internal combustion engine 50.

  If a negative determination is made in step 11, the process returns to step 11 because no special processing is required in this flowchart. On the other hand, if the determination in step 11 is affirmative, the CPU executes a process of determining whether or not the rotational speed Ne is higher than a predetermined rotational speed α (step 12). The predetermined rotational speed α is set to 1,600 rpm, for example. If a negative determination is made in step 12, the process returns to step 11 because no special processing is required in this flowchart. On the other hand, if an affirmative determination is made in step 12, the CPU executes a process of changing the injection control so that the fuel is injected divided into the first fuel injection and the second fuel injection (step 13). FIG. 5 is a diagram schematically showing the state of fuel injection when the injection control is not changed and when the injection control is not changed in the high-load high-rotation operation region. When the injection control is not changed, it can be seen that the injection timing approaches the intake stroke top dead center from the vicinity of the intake stroke bottom dead center as shown in FIG. In this case, the output of the internal combustion engine 50 can be improved by the vaporization latent heat effect, but the tumble flow T cannot be appropriately strengthened by fuel injection. On the other hand, when the injection control is changed in this step, as shown in FIG. 5B, the first fuel injection is performed in the middle of the intake stroke, and the second fuel injection is dead in the intake stroke. Performed near the point.

  Therefore, the CPU executes a process for controlling the fuel injection valve 21 to perform the first injection and the second injection in accordance with these injection timings (step 14), so that the latent heat effect of vaporization and the mixture are changed. Both homogeneity can be achieved. In the present embodiment, the second fuel injection is performed to improve the homogeneity of the air-fuel mixture, but the second fuel injection may be performed to improve the combustion speed. Specifically, for example, when the rotational speed Ne is relatively low even in the high load operation region, the combustion speed is improved by changing the injection period of the second fuel injection longer than in the present embodiment as a countermeasure against knocking. May be. However, in this case, since a considerable injection amount is required in the second fuel injection, the latent heat effect of vaporization is lower than that in the case where both the homogeneity of the air-fuel mixture is achieved. As described above, by dividing the fuel injection in strengthening the tumble flow T with the injected fuel, the ECU 1 that can achieve both the vaporization latent heat effect and the homogeneity of the air-fuel mixture or the combustion speed in the high load operation region. It is feasible.

  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 map data of a driving | operation area | region. It is a figure which shows typically the mode of fuel injection about the case where it changes when it does not change injection control.

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 (3)

A control device for a cylinder injection spark ignition internal combustion engine that controls a cylinder injection spark ignition internal combustion engine that generates a tumble flow in a cylinder and that reinforces the tumble flow with fuel injected near the bottom dead center of an intake stroke. There,
When the rotational speed of the in-cylinder injection spark ignition internal combustion engine is higher than a predetermined rotational speed in the high load operation region, the first fuel injection is performed at the time when the charging efficiency of the air flowing into the cylinder becomes maximum. An in-cylinder injection spark ignition internal combustion engine control device comprising injection timing control means for performing second fuel injection that completes injection at an intake stroke bottom dead center. 2. The control apparatus for a direct injection spark ignition internal combustion engine according to claim 1, wherein the injection timing control means advances the first fuel injection as the rotational speed increases. Further, the fuel injection amount is controlled so that the crank angle range corresponding to the fuel injection period of the second fuel injection becomes substantially constant with respect to a change in the operating state of the direct injection spark ignition internal combustion engine. The control apparatus for an in-cylinder spark ignition internal combustion engine according to claim 1, further comprising an injection amount control means.

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