JP2008088955A - Start control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a start control device for an internal combustion engine capable of obtaining a combustion improvement effect by an air flow control valve at the time of engine start and improving startability of the internal combustion engine and reducing emission.
An ECU 1 for controlling the start of an internal combustion engine 50 in which an air flow control valve 58 is disposed in an intake port 52a communicating with a combustion chamber 57. When the internal combustion engine 50 is started, the air flow control valve 58 is Cranking prohibiting means is provided for prohibiting cranking when it is not closed more than a predetermined opening. As a result, depending on the open state of the intake control valve 58 before starting the engine, it is possible to suppress the need to inject extra fuel when starting the engine in order to ensure the appropriateness of the air-fuel ratio. The combustion improvement effect by the airflow control valve 58 can be obtained in the form of optimization.
[Selection] Figure 2

Description

  The present invention relates to an internal combustion engine start control device, and more particularly to an internal combustion engine start control device that controls start of an internal combustion engine in which an airflow control valve is disposed in an intake passage communicating with a combustion chamber.

  In general, an internal combustion engine starts when a starter motor performs cranking based on a starter signal generated when a driver turns on an ignition switch, and fuel is injected and ignited accordingly. However, if the air-fuel ratio at the time of starting the engine is not appropriate, the startability of the internal combustion engine deteriorates or the emission increases. On the other hand, in Patent Document 1, for example, at the time of starting an internal combustion engine provided with control means for prohibiting the operation of the ignition system and the fuel system until the intake throttle valve (corresponding to the throttle valve) is opened to the target opening degree. Control devices have been proposed. According to this start-up control device, it is possible to suppress the air-fuel ratio from becoming rich due to the shortage of the air amount due to the operation delay of the intake throttle valve, and as a result, the startability of the internal combustion engine from being deteriorated.

  On the other hand, when a surge tank is provided in the intake passage downstream of the throttle valve, a large amount of air flows into the combustion chamber on the contrary even if the throttle valve is controlled to the target opening when the engine is started as described above. It becomes easy to do. On the other hand, when an airflow control valve is provided in the intake passage downstream of the surge tank, a small amount of air is circulated through the airflow control valve when the engine is started. It is possible to suppress the inflow of air. However, if so-called deposits mainly composed of solid carbon are deposited on the airflow control valve, even if the airflow control valve has a normal opening, the flow area in the airflow control valve is smaller than the normal flow area. Thus, the amount of air actually supplied into the combustion chamber becomes smaller than the normal amount.

  For this reason, in Patent Document 2, the pressure in the intake passage downstream of the intake control valve (corresponding to the airflow control valve) at the time of engine start is detected, and the next engine start is performed so that the detected pressure matches the target pressure. A start control device for an internal combustion engine that controls the opening of an intake control valve at the time has been proposed. According to this start control device, the amount of air supplied into the combustion chamber when the engine is started can be made a normal amount of air, so that the engine start can be completed with certainty.

Japanese Patent Laid-Open No. 5-240099 JP 2005-54600 A

  In the start-up control device for an internal combustion engine proposed in Patent Document 1, the ignition system and the fuel system are not controlled until the intake throttle valve is controlled to the target opening at the start of the engine, while cranking is not performed. During this time, it continues. Therefore, for example, when the function of the battery is deteriorated, such as in winter, the battery may rise before the internal combustion engine is started. That is, when the function of the battery is deteriorated, the startability of the internal combustion engine may be deteriorated. Further, even in the internal combustion engine start control device proposed in Patent Document 2, when the opening control of the intake control valve is performed together with cranking at the time of engine start, the intake control valve is controlled to the intended opening. During this time, the appropriateness of the air-fuel ratio is not ensured, and the startability may be deteriorated and the emission may be increased during this period.

  Further, Patent Document 2 proposes an internal combustion engine start control device that can reliably complete the engine start by controlling the fuel injection amount instead of controlling the opening of the intake control valve. In this case, since the open state of the intake control valve before starting the engine is not considered, depending on the open state, it becomes necessary to inject extra fuel. That is, with this start control device, although it is possible to improve the startability of the internal combustion engine and reduce emissions, there is a possibility that the combustion control effect of the intake control valve cannot be sufficiently obtained in the form of optimization of the fuel injection amount. is there.

  Accordingly, the present invention has been made in view of the above-described problems, and an internal combustion engine capable of obtaining the combustion improvement effect by the airflow control valve at the time of starting the engine and improving the startability of the internal combustion engine and reducing the emission. An object is to provide a start control device.

  In order to solve the above problems, the present invention provides an internal combustion engine start control device for controlling start of an internal combustion engine in which an airflow control valve is disposed in an intake passage communicating with a combustion chamber. And cranking prohibiting means for prohibiting cranking when the airflow control valve is not closed more than a predetermined opening degree. According to the present invention, cranking is performed after the airflow control valve is closed beyond a predetermined opening, so that when the fuel is injected according to the cranking, the intake control valve is optimized in the form of fuel injection. The combustion improvement effect can be obtained. At the same time, since the appropriateness of the air-fuel ratio is ensured, the startability of the internal combustion engine can be improved and the emission can be reduced. Further, according to the present invention, the cranking is prohibited when the airflow control valve is not closed more than a predetermined opening degree, so that the internal combustion engine cannot be started even when the battery function is deteriorated. In this respect, the startability of the internal combustion engine can be improved.

  The present invention is also an internal combustion engine start control device for controlling start of an internal combustion engine in which an airflow control valve is disposed in an intake passage communicating with a combustion chamber, wherein the airflow control is performed when the internal combustion engine is started. Cranking prohibiting means for prohibiting cranking is provided when the valve is not at the target opening. For example, when the opening degree of the airflow control valve is controlled as in the start control device for an internal combustion engine proposed in Patent Document 2 above, cranking is prohibited when the airflow control valve is not at the target opening degree. Thus, it is possible to obtain the combustion improvement effect by the airflow control valve, improve the startability of the internal combustion engine, and reduce the emission.

  ADVANTAGE OF THE INVENTION According to this invention, while obtaining the combustion improvement effect by an airflow control valve at the time of engine start, the startability improvement of an internal combustion engine and the reduction of emissions 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 an internal combustion engine start control device 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, an exhaust system 20, a fuel injection system 30, 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 the intake air, an air flow meter 12 for measuring the intake air amount, a throttle valve 13 for adjusting the intake air flow rate, And the intake manifold 15 that distributes intake air to the cylinders of the internal combustion engine 50, and intake pipes that are appropriately disposed between them.

  The exhaust system 20 includes an exhaust manifold 21, a three-way catalyst 22, a silencer (not shown), and an intake pipe appropriately disposed between these components. The exhaust manifold 21 is configured to join the exhaust from each cylinder, and the exhaust passage branched according to each cylinder is gathered into one exhaust passage on the downstream side. The three-way catalyst 22 is configured to purify exhaust gas, and performs oxidation of hydrocarbons HC and carbon monoxide CO and reduction of nitrogen oxides NOx. In the exhaust system 20, an A / F sensor 23 for linearly detecting the air-fuel ratio based on the oxygen concentration in the exhaust is upstream of the three-way catalyst 22, and the air-fuel ratio is based on the oxygen concentration in the exhaust from the stoichiometric air-fuel ratio. Also, oxygen sensors 24 for detecting whether the gas is rich or lean are arranged downstream of the three-way catalyst 22 as air-fuel ratio sensors.

  The fuel injection system 30 is configured to supply and inject fuel, and includes a fuel injection valve 31, a fuel injection pump 32, a fuel tank 33, and the like. The fuel injection valve 31 is configured to inject fuel, and is opened at an appropriate injection timing and injects 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 31 is closed under the control of the ECU 1. The fuel injection pump 32 is configured to pressurize the fuel to generate an injection pressure, and adjusts the injection pressure to an appropriate injection pressure under the control of the ECU 1.

  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 the present embodiment is an inline 4-cylinder gasoline engine. However, the internal combustion engine 50 is not particularly limited as long as it is an internal combustion engine capable of implementing the present invention, and may have other appropriate cylinder arrangement structure and number of cylinders. In FIG. 1, the main part of the internal combustion engine 50 is shown with respect to the cylinder 51a as a representative of each cylinder. However, 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 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. The piston 53 is connected to a crankshaft (not shown) via a connecting rod (not shown). A starter motor (not shown) for cranking the internal combustion engine 50 when the engine is started is connected to the crankshaft via a gear.

  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 31 is disposed in the cylinder head 52 with a fuel injection hole protruding into the intake port 52a so as to perform so-called port injection. However, the present invention is not limited to this, and the fuel injection valve 31 may be disposed so that fuel can be directly injected into the cylinder, for example.

  An air flow control valve 58 for generating a tumble flow in the combustion chamber 57 is disposed in the intake port 52a. The airflow control valve 58 is configured to generate a tumble flow 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. The airflow control valve 58 may be disposed in the intake passage formed by the intake manifold 15. Further, the air flow control valve 58 is not limited to the one that generates the tumble flow, and any reverse tumble may be used as long as it can generate a strong swirling air flow in the combustion chamber 57 in a predetermined valve open state and improve the mixing property of the air-fuel mixture. It is also possible to generate an oblique tumble flow formed by combining a flow, a swirl flow, a tumble flow and a swirl flow. In addition, the internal combustion engine 50 detects an opening degree sensor 71 for detecting the opening degree of the airflow control valve 58, a crank angle sensor 72 that generates an output pulse proportional to the rotational speed NE, and a water temperature of the internal combustion engine 50. Various sensors such as a water temperature sensor 73 are provided.

  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 this embodiment, the ECU 1 controls the air flow in addition to the fuel injection valve 31, the fuel injection pump 32, the ignition plug 54 (more specifically, an igniter not shown) and the starter motor. The valve 58 (more specifically, an actuator not shown) is also controlled. In addition to the fuel injection valve 31 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, an opening sensor 71, a crank angle sensor 72, and a water temperature sensor 73. The ECU 1 receives power supply from a battery (not shown) when the engine is started.

  The ROM is configured to store a program in which various processes executed by the CPU are described. In this embodiment, in addition to the program for controlling the internal combustion engine 50, the ROM is used for controlling the fuel injection valve 31. A program or a cranking prohibiting program for prohibiting cranking by prohibiting the starter motor operation when the airflow control valve 58 is not closed at a predetermined opening or less when the internal combustion engine 50 is started is stored. ing. The cranking prohibition program may be configured as a part of the internal combustion engine 50 control program. In this embodiment, various detection means, determination means, control means, etc. are realized by a CPU, a ROM, a RAM (hereinafter simply referred to as a CPU) and a program for controlling the internal combustion engine 50. The cranking prohibition means is realized by the cranking prohibition program.

  Next, the process performed by the ECU 1 when the engine is started will be described in detail with reference to the flowchart shown in FIG. The ECU 1 starts the internal combustion engine 50 by 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 cranking inhibition program. The CPU executes a process of determining whether or not there is a request for starting the internal combustion engine 50 (step 11). In this step, it is determined whether or not there is a start request based on whether or not a starter signal generated when an ignition SW (not shown) is turned on is generated. If the determination is negative, no special process is required in this flowchart, and the process ends. On the other hand, if the determination is affirmative, the CPU executes a process of calculating the opening degree of the airflow control valve 58 based on the output signal of the opening degree sensor 71 (step 12).

  Subsequently, the CPU executes a process of determining whether or not the opening degree of the airflow control valve 58 is sufficiently small (step 13). Specifically, in this step, the CPU executes a process of determining whether or not the airflow control valve 58 is closed more than a predetermined opening. In this embodiment, the opening degree when the airflow control valve 58 is fully closed is set to 0 degree, and the predetermined opening degree is set to 5 degrees. The predetermined opening is not limited to 5 degrees, and may be appropriately set according to the specifications of the internal combustion engine 50 so that the effect of improving combustion by the airflow control valve 58 can be obtained. If a negative determination is made in step 13, the CPU executes a process for prohibiting the starter motor operation (step 14). This prohibits cranking. As the cranking is prohibited, the CPU executes a process for prohibiting fuel injection and ignition (step 15). Further, until the determination in step 13 is affirmative, the CPU repeatedly executes the processes shown in steps 12 to 15. Thereby, cranking can be prohibited when the opening degree of the airflow control valve 58 is not closed more than the predetermined opening degree when the engine is started.

  On the other hand, if an affirmative determination is made in step 13, the CPU executes a process for operating the starter motor (step 16). Accordingly, cranking can be performed efficiently, so that the startability of the internal combustion engine 50 when the battery function is degraded can be improved. Accordingly, the CPU executes a process for permitting fuel injection and ignition (step 17). In this step, since it becomes easy to perform fuel injection with an appropriate fuel injection amount in accordance with the opening degree of the airflow control valve 58, it is possible to easily ensure the appropriateness of the air-fuel ratio. Further, by ensuring the appropriateness of the air-fuel ratio, the startability of the internal combustion engine 50 can be improved and the emission can be reduced at the same time.

  FIG. 3 is a time chart showing a process performed by the ECU 1 when the engine is started. First, when the ignition SW is turned ON at time T1, the opening degree of the airflow control valve 58 gradually decreases from time T1 to time T2. Since cranking is prohibited during this period, the starter motor is OFF. Along with this, fuel injection and ignition are also prohibited. For this reason, the rotational speed NE is also zero. Next, when the airflow control valve 58 is fully closed at time T2, the airflow control valve 58 is closed more than a predetermined opening, so that the starter motor is turned on to operate. Along with this, fuel injection and ignition are also permitted. As a result, combustion starts and the rotational speed NE increases. When the rotational speed NE further reaches a predetermined rotational speed (for example, 400 rpm) at time T3, the starter motor is stopped and the start is completed.

  Next, the required injection amount at the start when the fuel injection amount is adjusted to ensure the appropriateness of the air-fuel ratio will be described in detail with reference to FIG. Case A shown in FIG. 4 shows a required injection amount when cranking is started after the airflow control valve 58 is closed more than a predetermined opening, and fuel injection and ignition are performed. Case B shows a required injection amount when cranking is started immediately after the ignition SW is turned ON, and fuel injection and ignition are performed. Note that the required injection amount corresponding to the first to fourth injections shown on the horizontal axis is different from the required injection amount corresponding to the fifth to eighth injections in order to ensure an appropriate air-fuel ratio. This is because the required injection amount is reduced in accordance with the opening degree change of the airflow control valve 58 toward the closing side.

  In case B, depending on the open state of the airflow control valve 58 before the engine is started, the airflow control valve 58 is not sufficiently closed, so that the combustion chamber 57 is not yet closed until the airflow control valve 58 is closed. A large amount of intake air flows into the. At this time, in order to ensure the appropriateness of the air-fuel ratio by the fuel injection amount, it is necessary to inject extra fuel as much intake air flows. For this reason, in case B, the required injection amount at the time of starting increases accordingly. On the other hand, in case A, it is not necessary to inject extra fuel as in case B, so that the required injection amount can be kept low when ensuring the appropriateness of the air-fuel ratio. That is, the combustion improvement effect of the airflow control valve 58 can be obtained in the form of optimizing the fuel injection amount at the time of starting the engine. Further, since the appropriateness of the air-fuel ratio is ensured, at the same time, the engine startability is improved and the emission is reduced.

  In this embodiment, the cranking prohibition program is created so as to prohibit cranking when the airflow control valve 58 is not closed at a predetermined opening degree when the engine is started. May be created so that cranking is prohibited when the airflow control valve 58 is not at the target opening when the engine is started. Thus, for example, even when the airflow control valve 58 is controlled to a target opening that takes into account the influence of deposits deposited on the airflow control valve 58, the combustion improvement effect can be obtained and the startability of the internal combustion engine 50 can be improved. In addition, emission can be reduced. As described above, it is possible to realize the ECU 1 that can obtain the combustion improvement effect by the airflow control valve 58 at the time of starting the engine and can improve the startability of the internal combustion engine 50 and reduce the emission.

  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. It is a figure which shows the process performed by ECU1 with a flowchart. It is a figure which shows the process performed by ECU1 with a time chart. It is a figure which shows the request | requirement injection quantity at the time of engine starting at the time of adjusting the fuel injection quantity in order to ensure the appropriateness of an air fuel ratio.

Explanation of symbols

1 ECU
DESCRIPTION OF SYMBOLS 10 Intake system 20 Exhaust system 30 Fuel injection system 50 Internal combustion engine 100 Internal combustion engine system

Claims (2)

An internal combustion engine start control device for controlling start of an internal combustion engine in which an airflow control valve is disposed in an intake passage communicating with a combustion chamber,
A startup control device for an internal combustion engine, comprising: cranking prohibiting means for prohibiting cranking when the airflow control valve is not closed more than a predetermined opening when the internal combustion engine is started. An internal combustion engine start control device for controlling start of an internal combustion engine in which an airflow control valve is disposed in an intake passage communicating with a combustion chamber,
A start control device for an internal combustion engine, comprising: cranking prohibiting means for prohibiting cranking when the air flow control valve is not at a target opening when the internal combustion engine is started.

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