JP2008223543A - Multifuel internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make the mixing property of alcohol mixing fuel with high concentration of alcohol and suction air satisfactory. <P>SOLUTION: The multifuel internal combustion engine is provided with a fuel injection means (fuel injection valve 56) for directly injecting the alcohol mixing fuel comprising a plurality of kinds of fuels having different fuel properties containing at least alcohol fuel into a combustion chamber CC; and an air stream adjustment means 27 for varying the flowing state of the suction air in the combustion chamber CC. An air stream control means (electronic control device 1) for performing control of the air stream adjustment means 27 such that the gas flowing in the combustion chamber CC becomes larger than the present state when the alcohol concentration of the alcohol mixing fuel is a predetermined concentration or higher is provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a multi-fuel internal combustion engine that can be operated by directly supplying an alcohol mixed fuel having an arbitrary alcohol concentration into a combustion chamber.

  In recent years, in the automobile industry, various efforts have been made to cope with changes in the environment surrounding automobiles. For example, in the field of internal combustion engines, efforts have been made on so-called multi-fuel internal combustion engines that use a plurality of types of fuels having different fuel properties and compensate for each of the disadvantages. A vehicle equipped with this type of multi-fuel internal combustion engine is generally called a flexible fuel vehicle (FFV). As an example, gasoline fuel and alcohol fuel such as ethanol are matched to the required performance. Known to improve environmental performance such as fossil fuel consumption control, such as gasoline fuel, which is operated alone or in a mixed manner, and continues to be limited in terms of emissions performance and reserves. ing.

  For example, the following Patent Document 1 discloses a multi-fuel internal combustion engine that is operated using an alcohol mixed fuel composed of gasoline fuel and alcohol fuel. This multi-fuel internal combustion engine of Patent Document 1 is a swirl control valve when the alcohol concentration of the alcohol-mixed fuel is equal to or higher than a set value in order to realize a good lean fuel operation even at any mixing ratio of gasoline fuel and alcohol fuel. And the swirl control is performed so that the swirl control valve is closed when the alcohol concentration is smaller than the set value.

JP-A-2-305335

  However, in a multi-fuel internal combustion engine that can be operated with an alcohol mixed fuel of any alcohol concentration directly injected into the combustion chamber, the energy density decreases as the alcohol concentration increases, so the injection period is prolonged. And the expansion stroke (that is, combustion) starts before the alcohol-mixed fuel and the intake air are sufficiently mixed, which may worsen the combustion state. That is, in this type of in-cylinder direct injection type multi-fuel internal combustion engine, fuel injection and mixing of alcohol mixed fuel and intake air must be performed in a short time. Prolonged injection period of the mixed fuel deteriorates the mixing property of the alcohol mixed fuel and the intake air, so that there is a possibility that appropriate combustion is not performed. Therefore, in this multi-fuel internal combustion engine, there is a possibility that the emission performance deteriorates and the output performance deteriorates due to an increase in HC (hydrocarbon) and unburned HC (unburned hydrocarbon) in the exhaust gas.

  Accordingly, an object of the present invention is to provide a multi-fuel internal combustion engine that improves the disadvantages of the conventional example and can improve the mixing property of the alcohol mixed fuel and the intake air when the alcohol concentration is high.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a fuel injection means for directly injecting into the combustion chamber an alcohol-mixed fuel comprising a plurality of types of fuels containing at least alcohol fuel and having different fuel properties; In a multi-fuel internal combustion engine equipped with an air flow adjusting means for varying the flow state of the intake air, the air flow adjusting means so that the gas flow in the combustion chamber becomes larger than the current state when the alcohol concentration of the alcohol-mixed fuel exceeds a predetermined concentration Airflow control means for controlling the above is provided.

  In the multifuel internal combustion engine according to the first aspect, when the injection period of the alcohol mixed fuel is long and the miscibility with the intake air is deteriorated, the alcohol mixed fuel and the intake air are well mixed by the gas flow promotion. Will fit.

  In order to achieve the above object, according to a second aspect of the present invention, in the multifuel internal combustion engine according to the first aspect, the alcohol concentration of the alcohol-mixed fuel is not less than a predetermined concentration, the engine speed is low, and the engine The airflow control means is configured to control the airflow adjustment means so that the gas flow in the combustion chamber is larger than the current state when the load is high.

  The multi-fuel internal combustion engine according to claim 2 promotes the gas flow at the time of high load when the injection period of the alcohol-mixed fuel having a high alcohol concentration is particularly long and at the time of low rotation where the gas flow in the combustion chamber is particularly small. As a result, the mixing property of the alcohol mixed fuel and the intake air at that time is improved.

  The multi-fuel internal combustion engine according to the present invention can improve the mixing property of the alcohol-mixed fuel and the intake air, so that the good combustion is performed by igniting this. Therefore, in this multi-fuel internal combustion engine, the generation of HC and unburned HC in the combustion gas can be suppressed more than before due to the improvement of the mixing property, so that the emission performance can be prevented from deteriorating. Further, in this multi-fuel internal combustion engine, the combustion efficiency becomes better than the conventional one due to the improvement of the mixing property, so that it is possible to prevent the output performance from being lowered.

  Embodiments of a multi-fuel internal combustion engine according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the embodiments.

  A multifuel internal combustion engine according to a first embodiment of the present invention will be described with reference to FIGS. The multi-fuel internal combustion engine of the first embodiment is an internal combustion engine that is operated using alcohol mixed fuel in one fuel tank containing alcohol fuel, and is an electronic control unit (ECU) 1 shown in FIG. Thus, various control operations such as combustion control are executed. The alcohol mixed fuel is a mixed fuel of an alcohol fuel and at least one fuel having different fuel properties. The electronic control unit 1 includes a CPU (Central Processing Unit) (not shown), a ROM (Read Only Memory) that stores a predetermined control program in advance, and a RAM (Random Access) that temporarily stores the calculation result of the CPU. Memory) and a backup RAM for storing information prepared in advance.

  First, the configuration of the multi-fuel internal combustion engine exemplified here will be described with reference to FIG. Although only one cylinder is shown in FIG. 1, the present invention is not limited to this, and can be applied to a multi-cylinder multifuel internal combustion engine. In the first embodiment, description will be made assuming that a plurality of cylinders are provided.

  The multifuel internal combustion engine is provided with a cylinder head 11, a cylinder block 12, and a piston 13 that form a combustion chamber CC. Here, the cylinder head 11 and the cylinder block 12 are fastened with bolts or the like via the head gasket 14 shown in FIG. 1, and the recess 11a on the lower surface of the cylinder head 11 and the cylinder bore 12a of the cylinder block 12 formed thereby. The piston 13 is disposed so as to be capable of reciprocating in the space. And the combustion chamber CC mentioned above is comprised by the space enclosed by the wall surface of the recessed part 11a of the cylinder head 11, the wall surface of the cylinder bore 12a, and the top surface 13a of the piston 13. FIG.

  The multifuel internal combustion engine of the first embodiment sends air and alcohol mixed fuel to the combustion chamber CC according to operating conditions such as engine speed and engine load, and executes combustion control according to the operating conditions. The air is sucked from the outside through the intake passage 21 and the intake port 11b of the cylinder head 11 shown in FIG. On the other hand, the alcohol mixed fuel is supplied using the fuel supply device 50 shown in FIG.

  First, the air supply path will be described.

  On the intake passage 21 of the first embodiment, there are provided an air cleaner 22 for removing foreign matters such as dust contained in air introduced from the outside, and an intake air amount detection means 23 for detecting the amount of intake air from the outside. It has been. As the intake air amount detection means 23, an air amount detection sensor such as an air flow meter that directly detects the intake air amount, an intake pipe pressure sensor that detects the pressure in the intake passage 21 (ie, intake pressure), and the like are conceivable. When the latter intake pipe pressure sensor is used, the intake air amount is obtained indirectly from the intake pressure and the engine speed. In this multifuel internal combustion engine, the detection signal of the intake air amount detection means 23 is sent to the electronic control unit 1, and the electronic control unit 1 calculates the intake air amount, the engine load, and the like based on the detection signal. The engine speed can be grasped from the detection signal of the crank angle sensor 16 that detects the rotation angle of the crankshaft 15.

  A throttle valve 24 for adjusting the amount of intake air into the combustion chamber CC and a throttle valve actuator 25 for opening and closing the throttle valve 24 are provided downstream of the intake air amount detection means 23 on the intake passage 21. And are provided. The electronic control unit 1 according to the first embodiment controls the throttle valve actuator 25 according to the operating condition, and controls the throttle valve 24 so that the valve opening degree (in other words, the intake air amount) according to the operating condition is obtained. Adjust the valve opening angle. For example, the throttle valve 24 is adjusted so that the intake air amount necessary for achieving the air-fuel ratio corresponding to the operating conditions is sucked into the combustion chamber CC. The multifuel internal combustion engine is provided with a throttle opening sensor 26 that detects the valve opening of the throttle valve 24 and transmits the detection signal to the electronic control unit 1.

  On the other hand, one end of the intake port 11b opens to the combustion chamber CC, and an intake valve 31 that opens and closes the opening is disposed in the opening portion. The number of openings may be one or more, and an intake valve 31 is provided for each opening. Therefore, in this multi-fuel internal combustion engine, air is sucked into the combustion chamber CC from the intake port 11b by opening the intake valve 31 and closed in the combustion chamber CC by closing the intake valve 31. Inflow of air to is blocked.

  Here, as the intake valve 31, for example, there is a valve that is driven to open and close in accordance with the rotation of an intake camshaft (not shown) and the elastic force of an elastic member (string spring). In this type of intake valve 31, by interposing a power transmission mechanism such as a chain or a sprocket between the intake side camshaft and the crankshaft 15, the intake side camshaft is interlocked with the rotation of the crankshaft 15, Open / close drive is performed at a preset opening / closing timing. In the multifuel internal combustion engine of the first embodiment, the intake valve 31 that is opened and closed in synchronization with the rotation of the crankshaft 15 is applied.

  However, this multi-fuel internal combustion engine may be provided with a variable valve mechanism such as a so-called variable valve timing & lift mechanism that can change the opening / closing timing and lift amount of the intake valve 31. The opening / closing timing and the lift amount can be changed to suitable ones according to the operating conditions. Furthermore, in this multi-fuel internal combustion engine, a so-called electromagnetically driven valve that opens and closes the intake valve 31 using electromagnetic force may be used in order to obtain the same effect as the variable valve mechanism.

  Further, the intake port 11b is provided with an air flow adjusting means 27 for varying the flow state of the gas (intake air) in the combustion chamber CC according to operating conditions (engine speed and engine load). The airflow adjusting means 27 exemplified here narrows the flow path of the intake port 11b by operating the valve body at a desired valve closing angle between the fully open position and the fully closed position, thereby increasing the flow velocity of the intake air. As a typical example, a swirl control valve that generates a swirl flow and a tumble control valve that generates a tumble flow are known. The air flow adjusting means 27 is operated in accordance with the movement of the air flow adjusting valve actuator 28 that is driven and controlled according to the operating conditions by the air flow control means of the electronic control unit 1.

  Here, the amount of intake air into the combustion chamber CC decreases as the valve closing angle of the valve body of the airflow adjusting means 27 increases, that is, as the flow path of the intake port 11b is reduced. Therefore, when the flow path of the intake port 11b is excessively restricted, there is a possibility that the intake air amount is insufficient and an appropriate combustion state corresponding to the operating condition cannot be maintained. Specifically, there is a possibility that combustion on the richer side than the original may occur, so there is a possibility that the emission amount of HC and unburned HC increases and the emission performance is deteriorated. In addition, there is a possibility that desired combustion may not be performed due to a decrease in filling efficiency in the combustion chamber CC, which may lead to a decrease in output performance. For this reason, here, the valve closing angle of the valve body corresponding to the operating condition that does not cause such inconvenience is determined as the maximum valve closing angle during normal airflow control.

  Next, the fuel supply device 50 will be described.

  The fuel supply device 50 guides alcohol fuel and at least one fuel having different fuel properties to the combustion chamber CC. The first embodiment is for supplying an alcohol mixed fuel composed of an alcohol fuel and a hydrocarbon fuel (gasoline fuel) stored in a mixed state in one fuel tank 41, and the alcohol mixed fuel is supplied to the combustion chamber CC. An example of a fuel supply device 50 configured to be directly injected into the fuel is illustrated.

  Specifically, the fuel supply device 50 sucks alcohol mixed fuel from the fuel tank 41 and sends it to the fuel passage 51, and pressurizes the alcohol mixed fuel in the fuel passage 51 and pressurizes it to the high pressure fuel passage 53. The high pressure fuel pump 54, the delivery passage 55 for distributing the alcohol mixed fuel in the high pressure fuel passage 53 to the respective cylinders, and the alcohol mixed fuel supplied from the delivery passage 55 are injected into the respective combustion chambers CC. A cylinder fuel injection valve (fuel injection means) 56.

  The fuel supply device 50 controls the electronic control device 1 to drive and control the high-pressure fuel pump 54 and the fuel injection valve 56 in accordance with the operating conditions, whereby the fuel injection amount, fuel injection timing, and fuel injection corresponding to the operating conditions are controlled. An alcohol mixed fuel is injected under fuel injection conditions such as a period. For example, the electronic control unit 1 causes the alcohol-mixed fuel to be pumped from the high-pressure fuel pump 54 and causes the fuel injection valve 56 to perform injection under the fuel injection conditions corresponding to the operating conditions.

  The alcohol mixed fuel supplied to the combustion chamber CC in this way is mixed with the air described above in the combustion chamber CC, and is combusted by the ignition operation of the spark plug 61 at the ignition timing according to the operating conditions. The in-cylinder gas (combustion gas) after the combustion is discharged from the combustion chamber CC to the exhaust port 11c shown in FIG. 1 and discharged to the atmosphere through the exhaust passage 81.

  An exhaust valve 71 that opens and closes an opening between the exhaust port 11c and the combustion chamber CC is disposed. The number of openings may be one or more, and the exhaust valve 71 described above is provided for each opening. Accordingly, in this multi-fuel internal combustion engine, the combustion gas is discharged from the combustion chamber CC to the exhaust port 11c by opening the exhaust valve 71, and the combustion gas exhaust port is closed by closing the exhaust valve 71. The discharge to 11c is blocked. Here, as the exhaust valve 71, as in the intake valve 31 described above, a valve with a power transmission mechanism, a valve with a variable valve mechanism such as a so-called variable valve timing & lift mechanism, or a so-called electromagnetically driven valve is used. Can be applied.

An exhaust purification device 82 is disposed on the exhaust passage 81 to purify harmful components in the exhaust gas. Here, as the exhaust purification device 82, harmful HC (hydrocarbon), unburned HC (unburned hydrocarbon), CO (carbon monoxide) and NOx (nitrogen oxide) in the exhaust gas are harmless H _2. Prepare a three-way catalyst for reduction or oxidation to O (water), CO ₂ (carbon dioxide), or N ₂ (nitrogen).

  In the first embodiment, as described above, since alcohol fuel and gasoline fuel are stored in a mixed state in one fuel tank 41, alcohol fuel and gasoline are not controlled unless the respective fuel supply amounts are accurately controlled. The fuel mixing ratio of the fuel changes, and the alcohol concentration of the alcohol mixed fuel changes. In general, it is difficult to cause the refueling operator to execute the control, and one fuel may not be available. Therefore, the multifuel internal combustion engine of the first embodiment has any fuel mixing ratio (that is, It is configured so that it can be operated at any alcohol concentration.

  On the other hand, when the alcohol concentration of the alcohol mixed fuel is high, the injection period must be lengthened as described above, so that the mixing property of the alcohol mixed fuel and the intake air is deteriorated, and the combustion state in the combustion chamber CC is deteriorated. It can get worse. For example, in this multi-fuel internal combustion engine, it becomes difficult to completely burn alcohol mixed fuel as its mixing property deteriorates, so that the generation amount of HC and unburned HC in the combustion gas is increased, and all of them are reduced. The exhaust purification device 82 cannot completely purify, and the emission performance is deteriorated. Further, in this multi-fuel internal combustion engine, the combustion efficiency is lowered as the mixing property is deteriorated, so that the output performance is lowered.

  Here, the combustion state usually worsens as the alcohol concentration increases. However, the deterioration of the combustion state does not necessarily cause a serious deterioration in the emission performance or a decrease in the output performance, but the emission performance is not deteriorated until the alcohol concentration becomes a predetermined concentration (for example, 70%) or more. In general, the deterioration of the combustion state is caused so as to cause the above.

  For this reason, in the first embodiment, it is configured so that the mixing property of the alcohol mixed fuel and the intake air is improved when the alcohol concentration is increased to a predetermined concentration (for example, 70%) or more. The combustion state at that time will be improved. For example, here, the air flow control means of the electronic control device 1 is configured to move the air flow adjusting means 27 described above in the valve closing direction from the current state in such a case, thereby increasing the flow rate of the intake air and increasing the flow rate of the intake air. The flow of the intake air in the CC is promoted more than the current state. That is, when the alcohol concentration of the alcohol mixed fuel is high, the flow of the intake port 11b is made narrower than the current state to increase the flow of intake air in the combustion chamber CC, and the intake air and the injected alcohol mixed fuel are Make it easy to mix. Here, air flow control at the time of high alcohol concentration is performed in this way to promote gas flow in the combustion chamber CC, thereby improving the mixing property of the alcohol mixed fuel and the intake air to improve the combustion state.

  The alcohol concentration is detected by an alcohol concentration detection means (for example, a capacitive alcohol concentration sensor) 57 provided in the fuel tank 41 or the fuel supply device 50. Here, the alcohol concentration detection means 57 is disposed on the fuel passage 51 of the fuel supply device 50. The alcohol concentration may be calculated from the learned value of the exhaust gas A / F (air-fuel ratio) instead of the detected value of the alcohol concentration detecting means 57. The A / F of the exhaust gas is acquired from an A / F sensor 83 provided on the exhaust passage 81, for example.

  Here, the air flow control at the time of high alcohol concentration does not always have to be performed because the alcohol concentration is a predetermined concentration (for example, 70%) or more. In other words, depending on the current valve closing angle of the air flow adjusting means 27 required for normal air flow control, the valve closing angle is set to the maximum closing time during normal air flow control by executing the air flow control at high alcohol concentration. There is a possibility of increasing beyond the valve angle. In this case, as described above, the combustion state may be deteriorated due to insufficient intake air amount, while the gas flow in the combustion chamber CC may be increased to improve the combustion state. For this reason, the improvement of the combustion state due to the gas flow may surpass the deterioration of the combustion state due to insufficient intake air amount, and vice versa. It is better not to execute airflow control during concentration.

  Therefore, in the first embodiment, the airflow control at the time of high alcohol concentration is executed with emphasis on the operating condition in which the effect of improving the combustion state by the gas flow appears. Here, the alcohol concentration of the alcohol-mixed fuel is equal to or higher than a predetermined concentration, the injection period of the alcohol-mixed fuel is particularly high, and the gas flow in the combustion chamber CC is particularly low during low rotation. In the case of the operating conditions (region for airflow enhancement at the time of high alcohol concentration shown in FIG. 2), the valve closing angle of the airflow adjusting means 27 is made larger than the current state.

  Specifically, in the multifuel internal combustion engine of the first embodiment, the air flow control means of the electronic control unit 1 detects the alcohol concentration of the alcohol mixed fuel from the alcohol concentration detection means 57 as shown in the flowchart of FIG. ST1).

  Then, the air flow control means determines whether or not the alcohol concentration is equal to or higher than a predetermined concentration (here, 70%) (step ST2). If the alcohol concentration is equal to or higher than the predetermined concentration, the current operating condition (engine speed and engine speed) is determined. It is determined whether or not (engine load) corresponds to the above-described airflow enhancement target region at the time of high alcohol concentration (step ST3).

  When it is determined in step ST3 that the airflow control means corresponds to the airflow enhancement target region, the airflow control means 27 operates the airflow adjustment means 27 in the valve closing direction from the current state (step ST4). For example, the airflow adjusting means 27 here adjusts the valve closing angle to a desired angle. For this reason, here, the air flow adjusting means 27 is operated to a valve closing angle corresponding to the current operating conditions (engine speed and engine load) and / or alcohol concentration. The valve closing angle is an angle when the effect of improving the combustion state due to the promotion of gas flow exceeds the deterioration of the combustion state due to insufficient intake air amount, and the operating conditions (engine speed and engine load) or / and alcohol The airflow control means is set using map data having the density as a parameter.

  Thereby, in the combustion chamber CC, the gas flow becomes large, and the intake air and the alcohol mixed fuel injected from the fuel injection valve 56 are well mixed. Therefore, by igniting this air-fuel mixture from the spark plug 61, Good combustion will be performed. Therefore, in this multi-fuel internal combustion engine, the generation of HC and unburned HC in the combustion gas can be suppressed by improving the mixing property of the alcohol mixed fuel and the intake air as compared with the conventional one. Can be prevented. Further, in this multi-fuel internal combustion engine, the combustion efficiency becomes better than the conventional one due to the improvement of the mixing property, so that it is possible to prevent the output performance from being lowered.

  Note that the airflow control means of the first embodiment enhances the airflow when the alcohol concentration is determined to be lower than the predetermined concentration in step ST2 or even when the alcohol concentration is equal to or higher than the predetermined concentration in step ST3. When it is determined that the target area does not fall, normal airflow control corresponding to the operation condition is executed (step ST5).

  As described above, in the multifuel internal combustion engine of the first embodiment, the alcohol concentration of the alcohol-mixed fuel is equal to or higher than the predetermined concentration, and the operating condition is in the airflow enhancement target region (that is, the low rotation, high load region). When applicable, the gas flow in the combustion chamber CC is made larger than the current state, and the mixing property of the alcohol-mixed fuel and the intake air is improved to improve the combustion state. For this reason, according to the multifuel internal combustion engine, it is possible to suppress the deterioration of the emission performance and the decrease of the output performance at such time.

  Next, a second embodiment of the multifuel internal combustion engine according to the present invention will be described with reference to FIG.

  The multi-fuel internal combustion engine of the first embodiment described above is operated with an alcohol mixed fuel composed of alcohol fuel and hydrocarbon fuel (gasoline fuel) stored in a mixed state in one fuel tank 41 in advance. Therefore, in the multi-fuel internal combustion engine of the first embodiment, the operation is performed using the alcohol mixed fuel having the fixed fuel mixing ratio until at least one of the fuels is replenished.

  However, the fuel mixing ratio is preferably set to be variable to an arbitrary value in accordance with the operating conditions, rather than being fixed to one value, in order to obtain good emission performance and output performance.

  On the other hand, when the multi-fuel internal combustion engine is configured so that the fuel mixture ratio can be changed according to the operating conditions, the engine may be operated with an alcohol-mixed fuel having a high alcohol concentration depending on the operating conditions. For this reason, in such a case, the mixing property of the alcohol-mixed fuel and the intake air described in the first embodiment is deteriorated, which deteriorates the combustion state in the combustion chamber CC and deteriorates the emission performance and the output performance. May lead to a decrease in

  Therefore, the second embodiment is configured so that the mixing property is improved in the multifuel internal combustion engine capable of changing the fuel mixing ratio as in the first embodiment. That is, the multifuel internal combustion engine of the second embodiment is obtained by replacing the fuel supply device 50 with the fuel supply device 150 shown in FIG. 4 in the multifuel internal combustion engine of the first embodiment, and otherwise the first embodiment. It is constructed in the same way as

  The fuel supply device 150 according to the second embodiment mixes at least a plurality of types of fuels having different fuel properties including alcohol fuel at a fuel mixing ratio according to operating conditions, and the alcohol mixed fuel is supplied to the combustion chamber of each cylinder. And directly inject. In the second embodiment, the alcohol fuel stored in the first fuel tank 141A and the gasoline fuel stored in the second fuel tank 141B are mixed at a fuel mixing ratio according to the operating conditions.

  Specifically, the fuel supply device 150 includes a first feed pump 152A that sucks alcohol fuel from the first fuel tank 141A and sends it to the first fuel passage 151A, and a second fuel pump that sucks gasoline fuel from the second fuel tank 141B. The second feed pump 152B sent to the fuel passage 151B, the fuel mixing means 158 for mixing the alcohol fuel and the gasoline fuel respectively sent from the first and second fuel passages 151A and 151B, and the fuel mixing means 158 A high-pressure fuel pump 54 that pumps the alcohol-mixed fuel produced in step 3 from the third fuel passage 159 to the high-pressure fuel passage 53, a delivery passage 55 that distributes the alcohol-mixed fuel in the high-pressure fuel passage 53 for each cylinder, and The alcohol mixed fuel supplied from the delivery passage 55 is fed into each combustion chamber CC. Comprising a fuel injection valve 56 for injecting, the. That is, the fuel supply device 150 according to the second embodiment is obtained by changing the configuration upstream of the high-pressure fuel pump 54 in the fuel supply device 50 according to the first embodiment. The alcohol concentration detection means 57 of the second embodiment is disposed on the third fuel passage 159 as shown in FIG.

  In the fuel supply device 150, the first feed pump 152A, the second feed pump 152B, and the fuel mixing means 158 are driven and controlled by the supply fuel control means (fuel content ratio control means) of the electronic control device 1, thereby The fuel mixing means 158 is configured to generate an alcohol mixed fuel having a predetermined fuel mixing ratio according to the operating conditions. For example, the fuel supply device 150 adjusts the fuel mixing ratio of the alcohol-mixed fuel by adjusting the discharge amount of the first feed pump 152A and the second feed pump 152B to the supply fuel control means of the electronic control device 1. Alternatively, the fuel mixing ratio of the alcohol mixed fuel may be adjusted by increasing or decreasing the mixing ratio of the alcohol fuel and the gasoline fuel in the fuel mixing means 158 according to the instruction of the supplied fuel control means.

  In the second embodiment, the alcohol concentration of the alcohol mixed fuel mixed in this way is equal to or higher than a predetermined concentration, and the air flow enhancement target region (that is, the operation condition is the same as in the first embodiment when the alcohol concentration is high, i.e., If it corresponds to the low rotation and high load region), the air flow control at the time of high alcohol concentration is executed as in the first embodiment.

  Thereby, also in the multi-fuel internal combustion engine of the second embodiment, the gas flow in the combustion chamber CC becomes larger than the current state, the mixing property of the alcohol mixed fuel and the intake air is improved, and the combustion state is improved. For this reason, according to this multi-fuel internal combustion engine, when the alcohol concentration of the alcohol-mixed fuel is equal to or higher than the predetermined concentration and the operating condition corresponds to the airflow enhancement target region, the emission performance deteriorates and the output performance decreases. It becomes possible to suppress the decrease.

  By the way, although the airflow adjusting means 27 of each of the first and second embodiments described above is illustrated as being capable of adjusting the valve closing angle to a desired angle, the airflow adjusting means 27 is only in two states, a fully open state and a fully closed state. If the angle can only be selected, the airflow control means 27 may be fully closed to improve the combustion state in the above-described airflow enhancement target region at a high alcohol concentration.

  As described above, the multifuel internal combustion engine according to the present invention is useful as a technique for improving the mixing property of the alcohol-mixed fuel and the intake air when the alcohol concentration is high.

It is a figure shown about the structure of Example 1 of the multi-fuel internal combustion engine which concerns on this invention. It is a figure explaining the airflow reinforcement | strengthening object area | region at the time of alcohol high concentration in Example 1. FIG. 3 is a flowchart illustrating an airflow control operation of the multifuel internal combustion engine of the first embodiment. It is a figure shown about the structure of Example 2 of the multi-fuel internal combustion engine which concerns on this invention.

Explanation of symbols

1 Electronic control unit (ECU)
11b Intake port 16 Crank angle sensor 21 Intake passage 23 Intake air amount detection means 27 Airflow adjustment means 28 Airflow adjustment valve actuator 41 Fuel tank 50, 150 Fuel supply device 56 Fuel injection valve 57 Alcohol concentration detection means 83 A / F sensor 141A First 1 fuel tank 141B 2nd fuel tank 158 Fuel mixing means CC combustion chamber

Claims (2)

A fuel injection means for directly injecting into the combustion chamber an alcohol-mixed fuel comprising a plurality of types of fuels containing at least alcohol fuel and having different fuel properties; and an airflow adjusting means for varying the flow state of the intake air in the combustion chamber. In the multi-fuel internal combustion engine provided,
A multi-fuel internal combustion engine provided with an air flow control means for controlling the air flow adjusting means so that the gas flow in the combustion chamber becomes larger than the current state when the alcohol concentration of the alcohol mixed fuel is a predetermined concentration or more. .   The air flow control means is configured to increase the gas flow in the combustion chamber when the alcohol concentration of the alcohol mixed fuel is equal to or higher than a predetermined concentration, the engine speed is low, and the engine load is high. 2. A multi-fuel internal combustion engine according to claim 1, wherein the adjusting means is controlled.

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