JP4900257B2 - Fuel injection device - Google Patents

Description

  The present invention relates to a fuel injection device for an engine.

  In an engine that performs spark ignition using a spark plug, the required voltage for the spark plug increases when the engine is in a high load state, and misfire is likely to occur. The required voltage of the spark plug increases as the in-cylinder pressure increases. In recent years, in-cylinder pressure tends to increase, for example, in order to improve the performance of the engine, a high compression ratio is achieved and it is sometimes combined with a supercharger. The in-cylinder pressure increases as the ignition timing approaches the top dead center (TDC). For this reason, in a high load state in which knocking countermeasures and ignition retardation control are performed, the in-cylinder pressure rapidly increases, and as a result, the required voltage also increases. In particular, since the direct injection engine has good knock resistance, it is easy to achieve a high compression ratio and is also compatible with the supercharger. Thus, the direct injection engine with a high compression ratio and combined with the supercharger is operated with a high in-cylinder pressure, and misfire is likely to occur.

  Recently, so-called FFV (Flexible-fuel vehicle) and bi-fuel engines have been developed, and gasoline and non-gasoline fuel, for example, alcohol fuel, may be used as fuel for the same engine. Alcohol fuel is more easily vaporized than gasoline, so that liquid components hardly remain in the cylinder, and the required voltage of the spark plug is increased.

  For such a situation, Patent Document 1 proposes a spark plug that can reduce the required voltage.

Japanese Patent Laid-Open No. 9-97667

In the proposal of Patent Document 1, it becomes easy to cause discharge from the surface of the center electrode, and the discharge voltage can be reduced. Therefore, the actual discharge voltage is reduced as compared with the conventional spark plug.
However, the discharge voltage exhibits a characteristic that it increases as the ambient pressure increases. For this reason, if the in-cylinder pressure further increases due to the influence of the fuel used, the high compression ratio, the combination with the supercharger, etc., the spark plug proposed in Patent Document 1 may not be able to cope with it. There is. Further, if the discharge voltage becomes higher as the ambient pressure increases, there is a risk of causing an ignition system failure.

  Therefore, an object of the present invention is to provide a fuel injection device capable of forming an atmosphere for reducing the required voltage of a spark plug in an engine in which the in-cylinder pressure becomes high.

A fuel injection device according to the present invention that solves such a problem corresponds to a fuel injection means, a required voltage prediction means that predicts a voltage required for discharge of a spark plug, and a required voltage predicted by the required voltage prediction means. Injection control means for determining injection parameters of fuel injection performed by the fuel injection means . With such a configuration, the atmosphere in the cylinder can be easily ignited, and the required voltage of the spark plug can be reduced. As a result, misfires and ignition system failures can be suppressed. Here, the fuel injection means includes an injector that performs fuel injection. This includes a configuration that includes both a port injector and a direct injector. It is also assumed that the fuel injection means is used in combination with an FFV or bi-fuel engine. The required voltage predicting means predicts the required voltage with reference to various factors that may affect the required voltage of the spark plug. For example, the required voltage can be predicted from the air amount and the ignition timing. Further, for example, the required voltage can be predicted with reference to the ethanol concentration. Furthermore, the required voltage can be predicted from the injection ratio of gasoline and ethanol fuel.

  The injection specifications include the fuel injection timing, more specifically, the distinction between injection in the compression stroke and injection in the intake stroke, the ratio between the injection amount in the compression stroke and the injection amount in the intake stroke, and the like. Further, the injection specifications include the injection ratio between gasoline and non-gasoline fuel (for example, ethanol fuel), the injectors used (the distinction between port injectors and direct injectors), and the like.

  In such a fuel injection device, the injection control means can be configured to perform compression stroke injection in accordance with the predicted required voltage. If fuel injection is performed in the compression stroke, liquid fuel tends to remain around the spark plug at the time of ignition. As a result, ignition by the spark plug is facilitated, the required voltage is reduced, and misfire can be suppressed.

The injection control means may be configured to change the ratio between the injection amount in the compression stroke and the injection amount in the intake stroke according to the predicted required voltage . For example, the higher the engine load and the closer the ignition timing is to top dead center, the higher the injection ratio in the compression stroke. That is, the ratio of the injection amount in the compression stroke is increased as the predicted required voltage is higher .

It is also assumed that the fuel injection means constituting the fuel injection device of the present invention is used in combination with the FFV as described above. Therefore, when the fuel injection device combined with FFV is used, the required voltage predicting means can be configured to predict the required voltage based on the concentration of the highly volatile fuel mixed with the fuel . Various combinations of fuels used in the FFV are assumed, but the required voltage of the spark plug increases as the volatile fuel is used. For example, when gasoline and ethanol fuel are mixed and used, the highly volatile fuel is ethanol fuel, and the required voltage can be predicted based on the concentration of the ethanol fuel. If the predicted required voltage is high, measures such as increasing the fuel injection amount in the compression stroke are taken.

In addition, when the fuel injection means has a metering means for low volatile fuel and high volatile fuel, the injection control means can reduce the ratio of the low volatile fuel as the predicted required voltage is higher. The metering means may be controlled so as to increase . For example, when gasoline is used as the low volatile fuel and ethanol fuel is used as the highly volatile fuel, the required voltage can be lowered by increasing the gasoline ratio. It is more effective to control the metering means so as to increase the ratio of low-volatile fuel (for example, gasoline) in the compression stroke injection as the predicted required voltage is higher .

As described above, the fuel injection means constituting the fuel injection device of the present invention may include a port injection injector and a direct injection injector. In such a configuration, the injection control means uses the predicted required voltage. The higher the is, the higher the ratio of injection from the direct injection injector . When the fuel injected from the port injector reaches the inside of the cylinder, it atomizes and acts in the direction of increasing the in-cylinder pressure. On the other hand, since a direct injection injector directly injects fuel into a cylinder, the injected fuel is easy to maintain a droplet state in the cylinder, and acts in a direction to reduce a required voltage. For this reason, if the ratio which injects from a direct injection injector is raised, the required voltage of a spark plug can be reduced.

  Further, when the port injection injector and the direct injection injector are provided, the required voltage of the spark plug can be obtained by injecting high volatile fuel from the port injection injector and injecting low volatile fuel from the direct injection injector. It is effective for reduction.

  According to the fuel injection device of the present invention, when the required voltage of the spark plug is high, the fuel injection parameters are changed to control the atmosphere around the spark plug, so that the required voltage is reduced and misfire is suppressed. And failure of the ignition system can be suppressed.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. Note that the present invention controls factors that affect changes in the required voltage in accordance with the predicted required voltage of the spark plug, thereby reducing the actual required voltage. Table 1 summarizes the required voltage of the spark plug and countermeasures for reducing the required voltage. First, when injection in the compression stroke and injection in the intake stroke can be performed, the ratio of injection in the compression stroke is increased as the required voltage of the spark plug is higher. The fuel injected in the compression stroke gathers around the spark plug, and since the time from fuel injection to ignition is short, the fuel is likely to exist in a droplet state, reducing the required voltage of the spark plug. I can do it. When gasoline that is low volatile fuel and ethanol fuel that is high volatile fuel are used, the gasoline injection ratio is increased as the required voltage of the spark plug is higher. Gasoline is less likely to vaporize than ethanol fuel, tends to exist in the form of droplets around the spark plug, and can reduce the required voltage of the spark plug. When the port injection injector and the direct injection are provided, the ratio of injection from the direct injection injector is increased as the required voltage of the spark plug is higher. The fuel directly injected into the cylinder from the direct injection injector tends to exist in the form of droplets around the spark plug, and the required voltage of the spark plug can be reduced. These measures can be appropriately combined to reduce the required voltage of the spark plug. In the following embodiments, typical configurations will be described.

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing a schematic configuration of a main part of an engine 1 incorporating a fuel injection device 100 of the present invention. The engine 1 includes a single fuel tank 2. Moreover, the direct injection injector 3 which comprises the fuel-injection means in this invention is provided. The engine 1 includes an air flow meter 5 in the intake pipe 4 and an O ₂ sensor 7 in the exhaust pipe 6. Further, a crank angle sensor 8 for measuring the crank angle is provided. The air flow meter 5, the O ₂ sensor 7, and the crank angle sensor 8 are electrically connected to an ECU (Electronic control unit) 9. The ECU 9 is electrically connected to the spark plug 10 and issues an ignition command. The ECU 9 corresponds to the injection control device in the present invention, is electrically connected to the direct injection injector 3, and determines the injection specifications of the fuel injection device 100. The injection specifications include the ratio between the injection amount in the compression stroke injection and the injection amount in the intake stroke injection. The ECU 9 also functions as a required voltage predicting unit. The engine 1 of this embodiment includes a variable valve phase mechanism (not shown).

  The engine 1 uses gasoline as a fuel, but can also be an FFV using a mixed fuel with ethanol, which is a highly volatile fuel.

  The fuel injection control of the fuel injection device 100 configured as described above will be described with reference to the flowchart shown in FIG.

  The ECU 9 determines the injection specifications and issues a fuel injection command to the direct injection injector 3 based on the determined injection specifications. The ECU 9 performs a calculation for predicting the required voltage Pe for the spark plug 9 in step S1. Specifically, data on the air amount is acquired from the air flow meter 5. Moreover, the data regarding the ignition timing of the spark plug 10 is acquired. The ECU 9 separately calculates the ignition timing of the spark plug 10 based on the operating state of the engine 1, and refers to the calculated data. The required voltage Pe is predicted in consideration of the data regarding the air amount, the data regarding the ignition timing, and the data regarding the crank angle acquired from the crank angle sensor 8.

  In step S2, it is determined whether or not the required voltage Pe predicted in step S1 is larger than a preset threshold value Pt. If YES is determined in step S2, the process proceeds to step S3. In step S3, the ECU 9 calculates a ratio between the injection amount in the compression stroke injection and the injection amount in the intake stroke according to the required voltage Pe predicted in step S1, and performs the compression stroke injection according to the ratio. The larger the predicted required voltage Pe, the higher the ratio of the injection amount in the compression stroke. By performing the compression stroke injection, the fuel can be easily present in the droplet state around the spark plug 10, the actual required voltage of the spark plug 10 can be reduced, and misfire can be suppressed. For this reason, it is effective to increase the ratio of the injection amount in the compression stroke as the predicted required voltage Pe increases. In addition, when performing the compression stroke injection, an effect of collecting fuel in a droplet state around the spark plug 10 is expected due to the influence of the in-cylinder airflow during compression. After the process of step S3, the process performed by the ECU 9 is a return. If NO is determined in step S2, the control is returned without performing the process of step S3. The processes in steps S1 to S3 as described above are performed for each fuel injection.

When the fuel in the fuel tank 2 is an FFV in which a mixture of gasoline and ethanol fuel is used, the concentration value of the ethanol fuel is taken into consideration in the prediction calculation of the required voltage Pe in step S1. When the concentration of ethanol fuel is high, the in-cylinder pressure is usually high and the required voltage Pe is high. Therefore, when the concentration of ethanol fuel is high, the ratio of the injection amount in the compression stroke injection becomes high. The concentration of the ethanol fuel is grasped by processing measurement data obtained from the O ₂ sensor 7, but a configuration in which a dedicated ethanol concentration measurement sensor is attached can also be used.

  Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 3 is an explanatory view showing a schematic configuration of a main part of the engine 50 incorporating the fuel injection device 100 of the present invention. The engine 1 of the first embodiment is different from the engine 50 of the second embodiment in the following points. In other words, the engine 50 of the second embodiment differs from the engine 1 of the first embodiment in that it includes a port injection injector 11 in addition to the direct injection injector 3. The port injector 11 is electrically connected to the ECU 9. The hardware configuration itself of the fuel injection device 100 is the same as that in the first embodiment, but in the second embodiment, the injection ratio of the direct injection injector 3 and the port injection injector 11 is included in the injection specifications. Hereinafter, fuel injection control of the fuel injection device 100 will be described with reference to the flowchart shown in FIG. In the second embodiment, the ratio between the injection amount in the compression stroke injection and the injection amount in the intake stroke can be included in the injection specifications. However, for convenience of explanation, in the second embodiment, the direct injection injector 3 and the port injection are used. Only the ratio of the injection with the injector 11 will be described.

  The ECU 9 determines the injection specifications and issues a fuel injection command to the direct injection injector 3 and the port injection injector 11 based on the determined injection specifications. In step S11, the ECU 9 performs a calculation for predicting the required voltage Pe for the spark plug 9. Specifically, data on the air amount is acquired from the air flow meter 5. Moreover, the data regarding the ignition timing of the spark plug 10 is acquired. The ECU 9 separately calculates the ignition timing of the spark plug 10 based on the operating state of the engine 50, and refers to the calculated data. The required voltage Pe is predicted in consideration of the data regarding the air amount, the data regarding the ignition timing, and the data regarding the crank angle acquired from the crank angle sensor 8. The process in step S11 is the same as step S1 in the first embodiment. Further, when the engine 50 is FFV compatible, the required voltage Pe is predicted in consideration of the ethanol concentration of the fuel as in the case of the first embodiment.

  In step S12, it is determined whether or not the required voltage Pe predicted in step S11 is larger than a preset threshold value Pt. If YES is determined in step S12, the process proceeds to step S13. In step S13, the ECU 9 calculates a ratio between the injection amount from the direct injection injector 3 and the injection amount from the port injector 11 according to the required voltage Pe predicted in step S11, and performs injection according to the ratio. To do. The larger the predicted required voltage Pe is, the higher the ratio of the injection amount from the direct injection injector 3 is. By performing the injection from the direct injection injector 3, the fuel can easily exist in the droplet state around the spark plug 10, the actual required voltage of the spark plug 10 can be reduced, and misfire can be suppressed. For this reason, it is more effective to increase the ratio of the injection amount from the direct injection injector 3 as the predicted required voltage Pe is larger. After the process of step S13, the process performed by the ECU 9 is a return. If NO is determined in step S12, the control is returned without performing the process of step S13. The process of step S11-step S13 which was demonstrated above is performed for every fuel injection. In addition to controlling the ratio between the injection amount from the direct injection injector 3 and the injection amount from the port injection injector 11, the ratio between the injection amount in the compression stroke injection and the injection amount in the intake stroke can be controlled. .

  Next, Embodiment 3 of the present invention will be described with reference to FIGS. FIG. 5 is an explanatory view showing a schematic configuration of a main part of the engine 60 incorporating the fuel injection device 100 of the present invention. The engine 1 of the first embodiment differs from the engine 60 of the third embodiment in the following points. That is, the engine 60 of the third embodiment includes the second fuel tank 12 in addition to the fuel tank 2. Further, a fuel line for supplying fuel from the fuel tank 2 to the direct injection injector 3 and a fuel line for supplying fuel from the fuel tank 12 to the direct injection injector 3 are joined, and the metering means according to the present invention is formed at this joining point. A metering valve 13 corresponding to is attached. Gasoline is stored in the fuel tank 2 as a low-volatile fuel, and ethanol fuel is stored in the fuel tank 12 as a high-volatile fuel. The metering valve 13 is electrically connected to the ECU 9, and the mixing ratio of gasoline and ethanol fuel can be adjusted by the opening degree. This adjustment of the mixing ratio is included in the injection specifications. Hereinafter, the fuel injection control of the fuel injection device 100 will be described with reference to the flowchart shown in FIG. In the third embodiment, the ratio between the injection amount in the compression stroke injection and the injection amount in the intake stroke can be included in the injection specifications. However, for convenience of explanation, in the third embodiment, the ratio of gasoline to ethanol fuel is used. Only will be described.

  The ECU 9 determines the injection specifications and issues a fuel injection command to the direct injection injector 3 based on the determined injection specifications. In step S21, the ECU 9 performs a calculation for predicting the required voltage Pe for the spark plug 9. Specifically, data on the air amount is acquired from the air flow meter 5. Further, data regarding the ignition timing of the spark plug 10 is acquired. The ECU 9 separately calculates the ignition timing of the spark plug 10 based on the operating state of the engine 60, and refers to the calculated data. The required voltage Pe is predicted in consideration of the data regarding the air amount, the data regarding ignition, and the data regarding the crank angle acquired from the crank angle sensor 8. The process in step S21 is the same as step S1 in the first embodiment.

  In step S22, it is determined whether or not the required voltage Pe predicted in step S21 is larger than a preset threshold value Pt. If YES is determined in this step S22, the process proceeds to step S23. In step S23, the ECU 9 calculates the ratio of the injection amount of gasoline and ethanol fuel according to the required voltage Pe predicted in step S21, and controls the metering valve 13 according to the ratio. The larger the predicted required voltage Pe, the higher the ratio of gasoline injection amount. Since gasoline is less liable to vaporize than ethanol fuel, it is easy for the fuel to be present in the form of droplets around the spark plug 10, reducing the actual required voltage of the spark plug 10 and suppressing misfire. For this reason, it is more effective to increase the ratio of the gasoline injection amount as the predicted required voltage Pe is larger. After the process of step S23, the process performed by the ECU 9 is a return. When it is determined NO in step S22, the control is returned without performing the process of step S23. The processes in steps S21 to S23 as described above are performed for each fuel injection. In addition to controlling the ratio between the gasoline injection amount and the ethanol fuel injection amount, it is also possible to control the ratio between the injection amount in the compression stroke injection and the injection amount in the intake stroke.

  Next, a fourth embodiment of the present invention will be described with reference to FIGS. FIG. 7 is an explanatory view showing a schematic configuration of a main part of an engine 70 incorporating the fuel injection device 100 of the present invention. The engine 1 of the first embodiment differs from the engine 70 of the fourth embodiment in the following points. That is, the engine 70 of the fourth embodiment includes a second fuel tank 12 in addition to the fuel tank 2. Further, the engine 70 of the fourth embodiment is different from the engine 1 of the first embodiment in that a port injection injector 11 is provided in addition to the direct injection injector 3. The port injector 11 is electrically connected to the ECU 9. Gasoline is stored in the fuel tank 2 as a low-volatile fuel, and ethanol fuel is stored in the fuel tank 12 as a high-volatile fuel. A fuel line to which fuel is supplied from the fuel tank 2 is connected to the direct injection injector 3. A fuel line to which fuel is supplied from the fuel tank 12 is connected to the port injector 11. The ECU 9 controls the gasoline injection amount and the ethanol fuel injection amount. Here, since gasoline is injected from the direct injection injector 3 and ethanol fuel is injected from the port injection injector 11, the ECU 9 has a ratio between the injection amount from the direct injection injector 3 and the injection amount from the port injection injector 11. Will also control. These are included in the injection specifications. Hereinafter, the fuel injection control of the fuel injection device 100 will be described with reference to the flowchart shown in FIG. In the fourth embodiment, the ratio between the injection amount in the compression stroke injection and the injection amount in the intake stroke can be included in the injection specifications. However, for convenience of explanation, in the fourth embodiment, the ratio between gasoline and ethanol fuel is used. Only will be described.

  The ECU 9 determines the injection specifications and issues a fuel injection command to the direct injection injector 3 and the port injection injector 11 based on the determined injection specifications. In step S31, the ECU 9 performs a calculation for predicting the required voltage Pe for the spark plug 9. Specifically, data on the air amount is acquired from the air flow meter 5. Moreover, the data regarding the ignition timing of the spark plug 10 is acquired. The ECU 9 separately calculates the ignition timing of the spark plug 10 based on the operating state of the engine 70, and refers to the calculated data. The required voltage Pe is predicted in consideration of the data regarding the air amount, the data regarding ignition, and the data regarding the crank angle acquired from the crank angle sensor 8. The process in step S31 is the same as step S1 in the first embodiment.

  In step S32, it is determined whether or not the required voltage Pe predicted in step S31 is larger than a preset threshold value Pt. If YES is determined in this step S32, the process proceeds to step S33. In step S33, the ECU 9 calculates the ratio of the injection amount of gasoline and ethanol fuel according to the required voltage Pe predicted in step S31, and issues an injection command according to the ratio to the direct injection injector 3 and the port injection injector 11. Depart. The larger the predicted required voltage Pe, the higher the gasoline injection amount, that is, the ratio of the injection amount from the direct injection injector 3. Since gasoline is less liable to vaporize than ethanol fuel, it is easy for the fuel to be present in the form of droplets around the spark plug 10, reducing the actual required voltage of the spark plug 10 and suppressing misfire. For this reason, it is more effective to increase the ratio of the gasoline injection amount as the predicted required voltage Pe is larger. Moreover, since gasoline is injected from the direct injection injector 3, this also contributes to lowering the actual required voltage of the spark plug 10. After the process of step S33, the process performed by the ECU 9 is a return. If NO is determined in step S32, the control is returned without performing the process of step S33. The processes in steps S31 to S33 as described above are performed for each fuel injection. In addition to controlling the ratio between the gasoline injection amount and the ethanol fuel injection amount, it is also possible to control the ratio between the injection amount in the compression stroke injection and the injection amount in the intake stroke.

  The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited thereto. Various modifications of these embodiments are within the scope of the present invention. It is apparent from the above description that various other embodiments are possible within the scope. When the required voltage of the spark plug is high and there is a risk of misfire, it is only necessary to perform fuel injection so that fuel in a droplet state can exist around the spark plug at the time of ignition.

It is explanatory drawing which showed schematic structure of the principal part of the engine incorporating the fuel-injection apparatus of Example 1. FIG. It is a flowchart which shows an example of control of the fuel injection apparatus of Example 1. It is explanatory drawing which showed schematic structure of the principal part of the engine incorporating the fuel-injection apparatus of Example 4. FIG. It is a flowchart which shows an example of control of the fuel-injection apparatus of Example 2. It is explanatory drawing which showed schematic structure of the principal part of the engine incorporating the fuel-injection apparatus of Example 3. FIG. It is a flowchart which shows an example of control of the fuel-injection apparatus of Example 3. It is explanatory drawing which showed schematic structure of the principal part of the engine incorporating the fuel-injection apparatus of Example 4. FIG. It is a flowchart which shows an example of control of the fuel-injection apparatus of Example 4.

Explanation of symbols

1,50,60,70 engine 2, 12 fuel tank 3 direct injector 4 intake pipe 5 flow meter 6 an exhaust pipe 7 O ₂ sensor 8 crank angle sensor 9 ECU
DESCRIPTION OF SYMBOLS 10 Spark plug 11 Port injection injector 100 Fuel injection apparatus

Claims (7)

Fuel injection means;
A required voltage predicting means for predicting a voltage required for discharging the spark plug;
Injection control means for determining injection parameters of fuel injection performed by the fuel injection means according to the required voltage predicted by the required voltage prediction means, and performing compression stroke injection according to the predicted required voltage ;
With
The fuel injection apparatus characterized in that the injection control means changes a ratio between an injection amount in a compression stroke and an injection amount in an intake stroke according to a predicted required voltage . The fuel injection device according to claim 1, wherein
The fuel injection device characterized in that the injection control means increases the ratio of the injection amount in the compression stroke as the predicted required voltage is higher. The fuel injection device according to claim 1 or 2,
The required voltage predicting means predicts the required voltage based on the concentration of the highly volatile fuel mixed with the fuel. The fuel injection device according to any one of claims 1 to 3,
The fuel injection means includes metering means for low volatile fuel and high volatile fuel,
The fuel injection device, wherein the injection control means controls the metering means so as to increase the ratio of low-volatile fuel as the predicted required voltage is higher. The fuel injection device according to any one of claims 1 to 3,
The fuel injection means includes metering means for low volatile fuel and high volatile fuel,
The injection control means performs compression stroke injection and intake stroke injection, and controls the metering means to increase the ratio of low-volatile fuel in the compression stroke injection as the predicted required voltage is higher. Fuel injector. The fuel injection device according to any one of claims 1 to 5,
The fuel injection means includes a port injection injector and a direct injection injector,
The fuel injection device characterized in that the injection control means increases the ratio of injection from the direct injection injector as the predicted required voltage is higher. The fuel injection device according to claim 6, wherein
A fuel injection device characterized by injecting highly volatile fuel from the port injector and injecting low volatile fuel from the direct injector.

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