JP2008075566A - Multi-fuel internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate the deviation in a fuel remaining ratio between a plurality of fuels. <P>SOLUTION: The multi-fuel internal combustion engine is operated by changing fuel characteristic of fuel in the combustion chamber CC to become suitable for either a premixed spark ignition flame diffusive combustion mode, or compression self-ignition diffusive combustion mode by individually supplying or mixing and supplying a first fuel F1 having the high evaporability and low ignitability and a second fuel F2 having the high ignitability and low evaporability so as to be a prescribed fuel content in a combustion chamber CC. The engine is provided with a fuel remaining ratio adjusting means (an electronic control unit 1) for reducing a fuel supply ratio of the first fuel F1 and expanding a compression self-ignition diffusive combustion area besides curtailing a premixed spark ignition flame diffusive combustion area when a fuel remaining ratio of the first fuel F1 to the second fuel F2 is smaller than a specified value and on the other hand for raising the fuel supply ratio of the first fuel F1 and curtailing a compression self-ignition diffusive combustion area besides expanding the premixed spark ignition flame diffusive combustion area when the fuel remaining ratio is larger than the specified value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a multi-fuel internal combustion engine that is operated by introducing at least one of at least two types of fuels having different properties into a combustion chamber or guiding a mixed fuel composed of the at least two types of fuel into the combustion chamber.

  Conventionally, so-called multi-fuel internal combustion engines that are operated using a plurality of types of fuels having different properties are known. For example, Patent Document 1 below discloses a multi-fuel internal combustion engine that is operated by supplying a mixed fuel of gasoline and light oil stored in separate fuel tanks to a combustion chamber. This multifuel internal combustion engine increases the mixing ratio of light oil with high ignitability at the time of engine start, and realizes diffusion combustion operation at the time of engine start using the highly ignitable mixed fuel generated thereby.

  Patent Document 2 below discloses a multi-fuel internal combustion engine that can be operated using a fuel selected by a driver from various types of fuel such as gasoline, light oil, and ethanol. Further, Patent Document 2 also describes a multi-fuel internal combustion engine that is operated in a spark ignition mode when the engine load is lighter than a predetermined load, and that is operated in a diffusion combustion mode when the engine load is high. Each operation mode is switched in accordance with the type of fuel used (ignitability).

  The following Patent Document 3 discloses a multi-fuel internal combustion engine that is operated using a high-octane fuel and a low-octane fuel that can be individually injected, and in this multi-fuel internal combustion engine, the remaining fuel remains. If there is an imbalance in the quantity, the supply ratio of the fuel with the larger remaining quantity is increased so that each fuel is consumed at the same time.

JP-A-9-68061 JP 2004-245126 A JP 2005-155469 A

  However, in the multifuel internal combustion engine disclosed in Patent Documents 1 and 2, when the frequency of use of a specific fuel increases and a large difference occurs in the remaining amount of each fuel, the optimum operation cannot be performed thereafter. There is a possibility that. For example, if the operation in the operation mode depending on the specific property of the specific fuel is continued, the specific fuel is consumed up, and thereafter the operation in the operation mode cannot be performed. There is a risk that. And when it falls into such a situation, it is limited to operation in another operation mode with the remaining other fuel in all operating conditions, so sometimes the engine performance typified by emission performance and output performance etc. May be exacerbated.

  Therefore, an object of the present invention is to provide a multi-fuel internal combustion engine that can improve the disadvantages of the conventional example and can eliminate the deviation of the remaining fuel ratio among a plurality of fuels.

  In order to achieve the above object, according to the first aspect of the present invention, separately stored first fuel having high evaporability and low ignitability and second fuel having high ignitability and low evaporability are contained in the combustion chamber. The fuel characteristics of the fuel in the combustion chamber composed of the first fuel and the second fuel are supplied at least in a premixed spark ignition flame propagation combustion mode or compression auto-ignition diffusion. In a multi-fuel internal combustion engine operated by changing the combustion mode to a mode suitable for the selected combustion mode, when the fuel remaining ratio of the first fuel to the second fuel becomes smaller than a predetermined value, the combustion chamber The fuel supply ratio of the first fuel to the total fuel supply amount required for the fuel is reduced, and the premixed spark ignition flame propagation combustion region is reduced and the compression self-ignition diffusion combustion region is expanded, while the second fuel is supplied When the fuel remaining ratio of the first fuel becomes larger than a predetermined ratio, the fuel supply ratio of the first fuel to the required total fuel supply amount into the combustion chamber is increased, and the premixed spark ignition flame propagation combustion region is set. Fuel remaining ratio adjusting means for expanding and reducing the compression auto-ignition diffusion combustion region is provided.

  In order to achieve the above object, according to the second aspect of the present invention, the separately stored first fuel having high knock resistance and low ignitability and second fuel having high ignitability and low knock resistance are provided. The fuel characteristics of the fuel in the combustion chamber consisting of the first fuel and the second fuel are supplied at least in the premixed spark ignition flame propagation combustion mode or When the remaining fuel ratio of the first fuel to the second fuel becomes smaller than a predetermined value in the multi-fuel internal combustion engine operated by changing the compression auto-ignition diffusion combustion mode to a mode suitable for the selected combustion mode In addition, the fuel supply ratio of the first fuel to the required total fuel supply amount into the combustion chamber is reduced, and the premixed spark ignition flame propagation combustion region is reduced and the compression auto-ignition diffusion combustion region is expanded, When the fuel remaining ratio of the first fuel to the two fuels exceeds a predetermined value, the fuel supply ratio of the first fuel to the required total fuel supply amount into the combustion chamber is increased, and the premixed spark ignition flame propagation Fuel remaining ratio adjusting means for expanding the combustion region and reducing the compression auto-ignition diffusion combustion region is provided.

  In the multifuel internal combustion engine according to claims 1 and 2, the first fuel is used when the remaining ratio of the first fuel is lower than the predetermined ratio with respect to the remaining ratio of the second fuel. The frequency of selection of the premixed spark ignition flame propagation combustion mode suitable for operation is reduced, and the fuel supply ratio of the first fuel is reduced regardless of which combustion mode is selected. For this reason, in the multifuel internal combustion engine in this case, the consumption amount of the first fuel is reduced, while the consumption amount of the second fuel is increased, so that the fuel remaining ratio approaches a predetermined state. Further, when the remaining ratio of the second fuel is lower than a predetermined ratio with respect to the remaining ratio of the first fuel, the compression auto-ignition diffusion combustion mode suitable for the operation using the second fuel is performed. While the selection frequency is lower than that during normal operation, the fuel supply ratio of the second fuel is reduced regardless of which combustion mode is selected. For this reason, in the multifuel internal combustion engine in this case, the consumption amount of the second fuel is reduced, while the consumption amount of the first fuel is increased, so that the remaining fuel ratio approaches a predetermined state.

  Even if the remaining fuel ratio between the first fuel and the second fuel deviates from a predetermined ratio (for example, a ratio at which optimum engine performance can be exhibited), the multifuel internal combustion engine according to the present invention has the fuel. The deviation can be eliminated by bringing the remaining ratio close to a predetermined ratio. For this reason, according to this multi-fuel internal combustion engine, it is possible to continuously perform the optimum operation capable of exhibiting the most suitable engine performance in this engine.

  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 first embodiment of a multi-fuel internal combustion engine according to the present invention will be described with reference to FIGS. This multi-fuel internal combustion engine is an internal combustion engine that is operated by introducing at least one of at least two types of fuels having different properties into the combustion chamber or by introducing a mixed fuel composed of the at least two types of fuel into the combustion chamber. It is. In the first embodiment, the latter multi-fuel internal combustion engine will be described as an example.

  In this multifuel internal combustion engine, various control operations such as combustion control are executed by an electronic control unit (ECU) 1 shown in FIG. The electronic control unit 1 includes a CPU (Central Processing Unit) (not shown), a ROM (Read Only Memory) that stores a predetermined control program and the like, and a RAM (Random Access Memory) that temporarily stores the calculation result of the CPU. , 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 fuel into the combustion chamber CC according to the operating conditions such as the engine speed and engine load and the combustion mode, 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 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, an air cleaner 22 that removes foreign matters such as dust contained in air introduced from the outside, and an air flow meter 23 that detects the amount of intake air from the outside are provided. . In this multi-fuel internal combustion engine, the detection signal of the air flow meter 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.

  A throttle valve 24 that adjusts the amount of intake air into the combustion chamber CC and a throttle valve actuator 25 that opens and closes the throttle valve 24 are disposed downstream of the air flow meter 23 on the intake passage 21. Is provided. The electronic control device 1 according to the first embodiment controls the throttle valve actuator 25 according to the operating conditions and the combustion mode so that the valve opening degree (in other words, the intake air amount) according to the operating conditions is obtained. The valve opening angle of the throttle valve 24 is adjusted. For example, the throttle valve 24 is adjusted so that the intake air amount necessary for achieving an air-fuel ratio corresponding to the operating conditions and the combustion mode 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.

  Further, one end of the intake port 11b opens to the combustion chamber CC, and an intake valve 31 for opening and closing the opening is disposed at 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 and the combustion mode. 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.

  Next, the fuel supply device 50 will be described. The fuel supply device 50 guides a plurality of types of fuel having different properties to the combustion chamber CC. In the first embodiment, two types of fuels having different properties (a first fuel F1 stored in the first fuel tank 41A and a second fuel F2 stored in the second fuel tank 41B) are preliminarily stored in a predetermined fuel. An example is shown in which the mixture is mixed at a mixing ratio and the mixed fuel is directly injected into the combustion chamber CC. Therefore, in this type of fuel supply apparatus 50, the fuel mixing ratio is the fuel content ratio of each fuel in the combustion chamber CC.

  Specifically, the fuel supply device 50 includes a first feed pump 52A that sucks up the first fuel F1 from the first fuel tank 41A and sends it to the first fuel passage 51A, and a second fuel F2 from the second fuel tank 41B. Fuel mixing for mixing the second feed pump 52B sucked up and sent to the second fuel passage 51B, and the first and second fuels F1 and F2 sent from the first and second fuel passages 51A and 51B, respectively. Means 53, a high-pressure fuel pump 55 for pressurizing and feeding the mixed fuel produced by the fuel mixing means 53 to the high-pressure fuel passage 54, and a delivery passage for distributing the mixed fuel in the high-pressure fuel passage 54 to the respective cylinders 56 and a fuel injection valve 57 for each cylinder for injecting the mixed fuel supplied from the delivery passage 56 into the combustion chamber CC.

  In the fuel supply device 50, the first feed pump 52A, the second feed pump 52B, and the fuel mixing means 53 are driven and controlled by the fuel mixing control means of the electronic control unit 1, thereby mixing at a predetermined fuel mixing ratio. The fuel is mixed by the fuel mixing means 53. For example, the fuel supply device 50 adjusts the fuel mixing ratio of the mixed fuel by adjusting the discharge amounts of the first feed pump 52A and the second feed pump 52B to the fuel mixing control means of the electronic control device 1. Alternatively, the fuel mixing ratio of the mixed fuel may be adjusted by increasing or decreasing the mixing ratio of the first and second fuels F1 and F2 in the fuel mixing means 53 in accordance with the instruction of the fuel mixing control means. Here, the fuel mixing ratio in the fuel mixing means 53 of the first embodiment is a variation value that varies depending on the operating conditions, the combustion mode, and the like.

  In addition, the fuel supply device 50 causes the high-pressure fuel pump 55 and the fuel injection valve 57 to be driven and controlled by the fuel injection control means of the electronic control unit 1, so that a desired fuel injection amount, fuel injection timing, and fuel injection period can be obtained. The generated mixed fuel is configured to be injected under fuel injection conditions such as the above. For example, the fuel injection control means of the electronic control unit 1 pumps the mixed fuel from the high-pressure fuel pump 55 and causes the fuel injection valve 57 to perform injection under fuel injection conditions corresponding to operating conditions, combustion modes, and the like.

  The mixed fuel supplied to the combustion chamber CC in this way is combusted by the ignition operation in the ignition mode corresponding to the combustion mode in combination with the air described above. The in-cylinder gas (combustion gas) after the combustion is discharged from the combustion chamber CC to the exhaust port 11c shown in FIG. Here, an exhaust valve 61 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 61 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 61, and the combustion gas exhaust port is closed by closing the exhaust valve 61. The discharge to 11c is blocked.

  Here, as the exhaust valve 61, 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 can be used. Can be applied.

  By the way, in an internal combustion engine, combustion modes are generally divided into a diffusion combustion mode and a flame propagation combustion mode, and a compression auto-ignition mode and a premixed spark ignition mode are prepared as ignition modes corresponding to the combustion modes. Hereinafter, they are collectively referred to as a combustion mode, and are respectively referred to as a compression autoignition diffusion combustion mode and a premixed spark ignition flame propagation combustion mode.

  First, the compression self-ignition diffusion combustion mode is a method in which a part of fuel is self-ignited by injecting high-pressure fuel into high-temperature compressed air formed in the combustion chamber CC in the compression stroke, and the fuel and air Is a combustion mode in which combustion proceeds while diffusing and mixing. Here, since the compressed air in the combustion chamber CC and the fuel are difficult to be mixed instantaneously, immediately after the start of fuel injection, the air-fuel ratio varies in some places. On the other hand, it is generally preferable to use a fuel having excellent ignitability as described below when performing diffusion combustion, and such a fuel with good ignitability does not have to wait for the entire injection amount to be injected. It will ignite by itself at the air fuel ratio suitable for combustion. For this reason, in this compression self-ignition diffusion combustion mode, the fuel of the air-fuel ratio part suitable for combustion self-ignites first, and the flame formed thereby gradually advances the combustion while entraining the remaining fuel and air. Let

  In order to operate in this compressed self-ignition diffusion combustion mode, a fuel with good ignitability whose ignition point is lower than the compression heat of compressed air is usually required. For example, light oil or dimethyl ether can be considered as the fuel with good ignitability. Further, in recent years, GTL (Gas To Liquids) fuel has attracted attention as an alternative fuel for light oil, and this GTL fuel is easily produced in a desired property. For this reason, the GTL fuel produced | generated in order to improve ignitability can also be used for fuel with good ignitability. Such fuel with good ignitability not only enables compression auto-ignition diffusion combustion, but also reduces the generation amount of nitrogen oxides (NOx) when operating in the compression auto-ignition diffusion combustion mode, Noise and vibration during combustion can be suppressed.

  On the other hand, in the premixed spark ignition flame propagation combustion mode, the premixed gas in the combustion chamber CC in which fuel and air are mixed in advance is given a spark by spark ignition, and combustion is performed while propagating the flame around the fire type. It is a combustion form that advances the. In this premixed spark ignition flame propagation combustion mode, homogeneous combustion for igniting a homogeneously mixed premixed gas or a highly concentrated premixed gas is formed around the ignition means, and further, a lean mixture is formed around the premixed spark ignition flame propagation combustion mode. It includes a combustion mode such as stratified combustion in which a premixed gas is formed and ignition is performed on the rich premixed gas.

  As a fuel suitable for the premixed spark ignition flame propagation combustion mode, a highly evaporative fuel represented by gasoline is generally considered. As such highly evaporable fuel, in addition to gasoline, GTL fuel produced as a highly evaporable property, dimethyl ether, and the like are known. Here, since highly evaporable fuel is easily mixed with air, the excessively concentrated region of fuel during compression auto-ignition diffusion combustion is reduced, and particulate matter (PM), smoke, NOx, unburned hydrocarbon ( Contributes to suppression of unburned HC).

  The multi-fuel internal combustion engine of the first embodiment is configured to enable operation in at least both combustion modes. Accordingly, the multifuel internal combustion engine of the first embodiment is provided with the spark plug 71 shown in FIG. 1 for spark ignition of the premixed gas in order to enable operation in the premixed spark ignition flame propagation combustion mode. To do. The spark plug 71 executes spark ignition when the ignition timing according to the operating condition in the premixed spark ignition flame propagation combustion mode is reached in accordance with the instruction of the electronic control unit 1.

  Further, in the first embodiment, as the first fuel F1 in the first fuel tank 41A, a highly evaporable and low ignitable fuel (hereinafter referred to as “highly evaporable fuel” in the first embodiment) is stored. Then, as the second fuel F2 in the second fuel tank 41B, fuel with high ignitability and low evaporability (hereinafter referred to as “highly ignitable fuel” in the first embodiment) is stored. For example, gasoline is stored as the first fuel F1, and light oil is stored as the second fuel F2.

  In addition, the electronic control device 1 of the first embodiment is provided with combustion mode setting means for setting the combustion mode. The combustion mode setting means exemplified here uses the combustion mode map data as shown in FIG. 2 with the operating conditions (engine speed Ne and engine load Kl) as parameters, and the optimal combustion mode according to the operating conditions. To select. For example, this combustion mode map data can be operated in the compression auto-ignition diffusion combustion mode when operating conditions such as medium / high load / low rotation, high load / high rotation, etc., and low load / low rotation, low medium load / high rotation, etc. This is set in advance based on experiments and simulations so as to operate in the premixed spark ignition flame propagation combustion mode under the above operating conditions. The engine speed Ne can be grasped from the detection signal of the crank angle sensor 16 shown in FIG. The crank angle sensor 16 is a sensor that detects the rotation angle of the crankshaft 15. On the other hand, the engine load Kl can be grasped from the detection signal of the air flow meter 23 described above.

  For example, when the compression auto-ignition diffusion combustion mode is selected, the content ratio of the second fuel (highly ignitable fuel) F2 alone or the second fuel (highly ignitable fuel) F2 in the combustion chamber CC is set to the first The fuel (highly evaporable fuel) F1 is made higher than the content ratio, and the fuel is changed to a highly ignitable fuel suitable for the operating conditions at that time. On the other hand, when the premixed spark ignition flame propagation combustion mode is selected, the content ratio of the first fuel (highly evaporative fuel) F1 alone or the first fuel (highly evaporative fuel) F1 in the combustion chamber CC is determined. It is made higher than the content ratio of the second fuel (highly ignitable fuel) F2, and is changed to a highly evaporable fuel suitable for the operating conditions at that time.

  Thus, which combustion mode this combustion mode setting means selects depends on the operating conditions (engine speed Ne and engine load Kl) of the multifuel internal combustion engine. For this reason, for example, it is rare that the respective combustion modes are continuously selected at an equivalent ratio, and one combustion mode may be frequently used for the other, so that the first fuel in the first fuel tank 41A is used. F1 and the second fuel F2 in the second fuel tank 41B are not necessarily consumed evenly, and the fuel in one of the fuel containers decreases first.

  Therefore, in this multi-fuel internal combustion engine, when any specific fuel is exhausted, it is necessary to operate in a combustion mode suitable for other fuels until the specific fuel is replenished. The engine performance (output performance, emission performance, fuel consumption performance, etc.) is unavoidable. Here, in order to avoid this, it is sufficient to replenish the specific fuel before it runs out, but it is necessary to replenish a specific fuel even though a large amount of other fuel remains. It is not preferable because it only deteriorates the convenience for the user.

  Therefore, in the first embodiment, while monitoring the remaining amounts of the respective fuels (the first fuel F1 and the second fuel F2), when the variation in the remaining amount between these exceeds a predetermined state, this is detected. A fuel residual ratio adjusting means to be eliminated is provided in the electronic control unit 1.

  The fuel remaining ratio adjusting means of the first embodiment compares the fuel remaining ratio (V1 / V2) of the first fuel (highly evaporable fuel) F1 with the predetermined value with respect to the second fuel (highly ignitable fuel) F2. In accordance with the comparison result, the amount of fuel that is determined to be relatively small in the remaining amount is reduced in the combustion chamber CC and the combustion region in the combustion mode depending on the fuel is reduced. Thus, the fuel remaining ratio (V1 / V2) is brought close to the predetermined value Ra.

  Here, “V1” is the remaining amount of the first fuel (highly evaporative fuel) F1, and is detected by using the remaining fuel amount detecting means 42A such as a remaining amount meter disposed in the first fuel tank 41A. “V2” is the remaining amount of the second fuel (highly ignitable fuel) F2, and is detected by using the remaining fuel amount detecting means 42B such as a remaining amount meter disposed in the second fuel tank 41B.

Further, the predetermined value here means that the optimum engine performance (output performance, emission performance, fuel consumption performance, etc.) is maintained at the boundary between the premixed spark ignition flame propagation combustion region and the compression auto-ignition diffusion combustion region. This is a value unique to the engine in accordance with the optimum usage ratio of the first fuel F1 and the second fuel F2 that can be normally operated. Here, the optimum usage ratio Ra of the first fuel F1 to the second fuel F2 is used. . For example, the boundary at the time of normal operation is expressed by an engine load function expression Kl _sp-si {= Kl (Ra, Ne)} that varies depending on the optimum usage ratio Ra and the engine speed Ne as shown in FIG. Can be determined. Here, if the boundary portion belongs to the premixed spark ignition flame propagation combustion region, the optimum use ratio Ra is set to an optimum ratio for the premixed spark ignition flame propagation combustion mode operation, and the boundary portion is compressed. If it belongs to the self-ignition diffusion combustion region, an optimum ratio is set for the compression auto-ignition diffusion combustion mode operation. The normal operation refers to an operating state in which the most suitable engine performance can be exhibited in this engine.

  Specifically, an example of the operation of the multifuel internal combustion engine of the first embodiment will be described based on the flowchart of FIG.

  First, in the electronic control unit 1 of the first embodiment, the first fuel (highly evaporable fuel) F1 and the second fuel (highly ignitable fuel) F2 detected from the respective remaining fuel amount detecting means 42A and 42B. Respective remaining amounts V1 and V2 are input (step ST5).

  Then, the fuel remaining ratio adjusting means of the electronic control unit 1 obtains the fuel remaining ratio (V1 / V2) of the first fuel F1 with respect to the second fuel F2 from the remaining amounts V1 and V2, and obtains the predetermined value ( It is compared with the optimum usage ratio Ra) of the first fuel F1 to the second fuel F2 (step ST10).

  Here, when the remaining fuel ratio (V1 / V2) is smaller than the optimum usage ratio Ra, that is, the remaining ratio of the first fuel (highly evaporable fuel) F1 is the second fuel (highly ignitable fuel) F2. If the fuel remaining ratio is lower than the predetermined ratio, the fuel remaining ratio adjusting means reduces the premixed spark ignition flame propagation combustion region of the combustion mode map data shown in FIG. Further, the fuel supply ratio with respect to the total required fuel supply amount of the first fuel (highly evaporative fuel) F1 into the combustion chamber CC is reduced (in other words, the second fuel which is a highly ignitable fuel). The fuel supply ratio with respect to the total required fuel supply amount of F2 into the combustion chamber CC is increased) (step ST20).

  Here, the boundary is moved in a direction to reduce the premixed spark ignition flame propagation combustion region. The amount of movement is set to a value that can maintain the engine performance (output performance, emission performance, fuel consumption performance, etc.) in a good state even if the premixed spark ignition flame propagation combustion region is reduced. For example, the movement amount may be a fixed value set in advance, or may be a variable value that can be increased or decreased according to the difference between the remaining fuel ratio (V1 / V2) and the optimum usage ratio Ra. Further, the amount of movement may be set to a different value for each engine speed Ne.

  The required total fuel supply amount into the combustion chamber CC is the sum of the supply amounts of all fuels introduced into the combustion chamber CC, and is determined by the air-fuel ratio and the intake air amount. For example, during normal operation, the first fuel F1 and the second fuel are adjusted so that the required total fuel supply amount is obtained according to the fuel content ratio of the first fuel F1 and the second fuel F2 in the combustion chamber according to the combustion mode and the operating conditions. F2 is supplied at each supply amount. The fuel content ratio during normal operation (the fuel supply ratio of the first fuel F1 and the fuel supply ratio of the second fuel F2) is set in advance according to the combustion mode and operating conditions. For this reason, in step ST20 here, the fuel supply ratio of the first fuel F1 with respect to the required total fuel supply amount into the combustion chamber CC is lowered from the set value during normal operation. The reduction amount is set to a value that can maintain the engine performance (output performance, emission performance, fuel consumption performance, etc.) in a good state even if the fuel supply ratio of the first fuel F1 is reduced. For example, the amount of decrease may be a fixed value set in advance, or may be a variable value that can be increased or decreased according to the difference between the remaining fuel ratio (V1 / V2) and the optimum usage ratio Ra. Further, the amount of decrease may be varied according to the operating conditions (engine speed Ne and engine load Kl).

  On the other hand, when the remaining fuel ratio (V1 / V2) is larger than the optimum usage ratio Ra in step ST10, that is, the remaining ratio of the second fuel (highly ignitable fuel) F2 is the first fuel (highly evaporable). When the remaining ratio of the fuel (F1) is lower than a predetermined ratio, the fuel remaining ratio adjusting means reduces the compression self-ignition diffusion combustion area of the combustion mode map data shown in FIG. 2 and propagates the premixed spark ignition flame. The combustion region is expanded (step ST25), and the fuel supply ratio with respect to the total required fuel supply amount of the first fuel (highly evaporative fuel) F1 into the combustion chamber CC is increased (in other words, it is a highly ignitable fuel). The fuel supply ratio with respect to the total required fuel supply amount of the second fuel F2 into the combustion chamber CC is reduced) (step ST30).

  Here, regarding the amount of movement of the boundary between the premixed spark ignition flame propagation combustion region and the compression auto-ignition diffusion combustion region, even if the compression auto-ignition diffusion combustion region is reduced, engine performance (output performance, emission performance, fuel consumption performance, etc.) Is set to a value that can maintain a good state. For example, the amount of movement may be a fixed value set in advance as in the case of reducing the premixed spark ignition flame propagation combustion region, and the remaining fuel ratio (V1 / V2) and the optimum usage ratio It may be a variable value that can be increased or decreased according to the difference in Ra. Further, the amount of movement may be set to a different value for each engine speed Ne.

  Further, regarding the amount of decrease in the fuel supply ratio of the second fuel F2 here, the engine performance (output performance, emission performance, fuel consumption performance, etc.) should be kept in a good state even if the compression auto-ignition diffusion combustion region is reduced. Set to a possible value. For example, the amount of decrease may be a fixed value set in advance as in the case of reducing the fuel supply ratio of the first fuel F1, and the remaining fuel ratio (V1 / V2) and the optimum usage ratio It may be a variable value that can be increased or decreased according to the difference in Ra. Further, the amount of decrease may be varied according to the operating conditions (engine speed Ne and engine load Kl).

  Subsequently, the engine speed Ne and the engine load Kl detected based on the detection signal of the crank angle sensor 16 and the detection signal of the air flow meter 23 are input to the electronic control unit 1 of the first embodiment (step ST35). The electronic control unit 1 collates the engine speed Ne and the engine load Kl with the combustion mode map data of FIG. 2, and the combustion region corresponding to the operating condition (the engine speed Ne and the engine load Kl) is the diffusion combustion region. It is determined whether or not (specifically, compression auto-ignition diffusion combustion region) (step ST40).

  The electronic control unit 1 selects and operates the compression auto-ignition diffusion combustion mode if it is a diffusion combustion region (step ST45), and selects the premixed spark ignition flame propagation combustion mode if it is not a diffusion combustion region. Operate (step ST50). In steps ST45 and ST50, the first fuel F1 and the second fuel F2 are injected so that the fuel content ratio reflects the set value of the fuel supply ratio in step ST20 or step ST30.

  Thereby, in this multi-fuel internal combustion engine, when an affirmative determination is made in step ST10 above (that is, the remaining fuel ratio (V1 / V2) is smaller than the optimum usage ratio Ra, the first fuel (highly evaporative fuel)) When the remaining ratio of F1 is lower than the predetermined ratio with respect to the remaining ratio of the second fuel (highly ignitable fuel) F2,} the same operating conditions as in normal operation (engine speed Ne and engine load Kl) The frequency of selection of the premixed spark ignition flame propagation combustion mode that is suitable for operation using the first fuel (highly evaporative fuel) F1 is reduced as compared with the normal operation, and in any combustion mode. Regardless of the existence, the fuel supply ratio of the first fuel (highly evaporative fuel) F1 decreases. Therefore, in the multi-fuel internal combustion engine in this case, the consumption amount of the first fuel (highly evaporative fuel) F1 is reduced, while the consumption amount of the second fuel (highly ignitable fuel) F2 is increased. The remaining ratio (V1 / V2) approaches the optimum usage ratio Ra. Further, in the multi-fuel internal combustion engine in this case, the engine performance (output performance, emission performance, fuel consumption performance, etc.) can be maintained in a good state even if such a change in the combustion region and the fuel supply ratio is performed. it can.

  On the other hand, in this multi-fuel internal combustion engine, when a negative determination is made in step ST10 {that is, the remaining fuel ratio (V1 / V2) is larger than the optimum usage ratio Ra, the second fuel (highly ignitable fuel) F2 When the remaining ratio is lower than a predetermined ratio with respect to the remaining ratio of the first fuel (highly evaporative fuel) F1} under the same operating conditions (engine speed Ne and engine load Kl) as in normal operation. Even during operation, the frequency of selection of the compression auto-ignition diffusion combustion mode suitable for operation using the second fuel (highly ignitable fuel) F2 is reduced compared with that during normal operation, and which combustion mode is selected. Regardless, the fuel supply ratio of the second fuel (highly ignitable fuel) F2 decreases. For this reason, in the multi-fuel internal combustion engine in this case, the consumption amount of the second fuel (highly ignitable fuel) F2 is reduced, while the consumption amount of the first fuel (highly evaporative fuel) F1 is increased. The remaining ratio (V1 / V2) approaches the optimum usage ratio Ra. Further, even in the multi-fuel internal combustion engine in this case, the engine performance (output performance, emission performance, fuel consumption performance, etc.) can be maintained in a good state without being affected by changes in the combustion region and the fuel supply ratio.

  Thus, in the multi-fuel internal combustion engine of the first embodiment, the fuel remaining ratio of the first fuel F1 to the second fuel F2 while maintaining the engine performance (output performance, emission performance, fuel consumption performance, etc.) in a good state. (V1 / V2) can be brought close to the optimum usage ratio Ra of the first fuel F1 to the second fuel F2. Therefore, according to this multi-fuel internal combustion engine, the normal operation can be performed again without deteriorating the engine performance, and the optimum operation capable of exhibiting the most suitable engine performance can be performed in this engine. It can be done continuously.

  Here, the first fuel that can be normally operated while maintaining the optimum engine performance at the boundary portion between the premixed spark ignition flame propagation combustion region and the compression auto-ignition diffusion combustion region, and is fully filled. The optimal use ratio Ra described above may be set so that the tank 41A and the second fuel tank 41B are emptied at substantially the same time. According to this, in addition to the above-described effects, the first fuel F1 and the second fuel F2 can be used up at substantially the same time, so the replenishment frequency is reduced and the convenience for the user is increased.

  By the way, in the above-described example, it is described that the fuel can surely self-ignite in the compressed air when the compressed self-ignition diffusion combustion mode is selected. For example, the operating conditions and the fuel itself in the combustion chamber CC If the ignitability of the fuel is poor due to low ignitability, the fuel may not be self-ignited in compressed air, or even if it can self-ignite, it may misfire. For this reason, in such a case, it is preferable to perform compression auto-ignition diffusion combustion (spark-assisted compression auto-ignition diffusion combustion) by assisting ignition with the spark plug 71. For example, a multi-fuel internal combustion engine that also operates in the spark-assist compression auto-ignition diffusion combustion mode selects the combustion mode using the combustion mode map data shown in FIG.

In the combustion mode map data of FIG. 4, the boundary between the premixed spark ignition flame propagation combustion region and the spark assisted compression self-ignition diffusion combustion region is expressed by a function equation Kl _sp-si {= Kl (Ra, Ne)}. The boundary between the compression auto-ignition diffusion combustion region and the spark-assisted compression auto-ignition diffusion combustion region depends on the optimum usage ratio R _si of the first fuel F1 to the second fuel F2 and the engine speed Ne at the boundary portion. It can be determined by the function expression Kl _Si {= Kl (R _Si , Ne)} of the fluctuating engine load.

Here, the engine load Kl _Si is a representation of the lower engine load which can be self-ignited by the fuel in the combustion chamber CC of the fuel content ratio corresponding to optimum use ratio R _si. Hereinafter, the engine load Kl _Si is referred to as "self-ignitable limit load Kl _Si".

The optimum usage ratio R _si maintained optimum engine performance (output performance, emission performance, fuel consumption performance, etc.) at the boundary between the compression auto-ignition diffusion combustion region and the spark-assisted compression auto-ignition diffusion combustion region. It is a value unique to the engine in accordance with the optimum use ratio of the first fuel F1 and the second fuel F2 that can be operated normally. For this optimum usage ratio R _si , if the boundary portion belongs to the premixed spark ignition flame propagation combustion region, an optimum ratio is set for the premixed spark ignition flame propagation combustion mode operation, and the boundary portion is compressed by the compression auto If it belongs to the ignition diffusion combustion region, an optimum ratio is set for the compression auto-ignition diffusion combustion mode operation.

  Hereinafter, an example of the operation of the multi-fuel internal combustion engine having the spark-assisted compression auto-ignition diffusion combustion mode will be described with reference to the flowchart of FIG.

  First, also in the electronic control unit 1 here, the remaining amounts V1 and V2 of the first fuel (highly evaporable fuel) F1 and the second fuel (highly ignitable fuel) F2 are inputted (step ST5). The fuel remaining ratio adjusting means compares the fuel remaining ratio (V1 / V2) of the first fuel F1 with respect to the second fuel F2 with a predetermined value (the optimum usage ratio Ra of the first fuel F1 with respect to the second fuel F2) ( Step ST10).

  When the remaining fuel ratio (V1 / V2) is smaller than the optimum usage ratio Ra, the remaining fuel ratio adjusting means reduces the premixed spark ignition flame propagation combustion region of the combustion mode map data shown in FIG. The compression auto-ignition diffusion combustion region is expanded (step ST15), and the fuel supply ratio with respect to the total required fuel supply amount of the first fuel (highly evaporative fuel) F1 into the combustion chamber CC is lowered (in other words, high The fuel supply ratio with respect to the total required fuel supply amount of the second fuel F2 as the ignitable fuel into the combustion chamber CC is increased) (step ST20).

  Regarding the expansion of the compression auto-ignition diffusion combustion region here, only the spark-assisted compression auto-ignition diffusion combustion region may be expanded, and the compression auto-ignition diffusion combustion region may be expanded together with the spark-assist compression auto-ignition diffusion combustion region. Also good. Regarding the amount of movement of the boundary and the amount of decrease in the fuel supply ratio of the first fuel F1 in this case, the engine performance (output performance, emission performance, fuel consumption performance, etc.) can be maintained in a good state even if the combustion region is changed. It is set in the same manner as described above so as to be a possible value.

  On the other hand, when the remaining fuel ratio (V1 / V2) is larger than the optimum usage ratio Ra in step ST10, the remaining fuel ratio adjusting means reduces the compression auto-ignition diffusion combustion region of the combustion mode map data shown in FIG. At the same time, the premixed spark ignition flame propagation combustion region is expanded (step ST25), and the fuel supply ratio with respect to the total required fuel supply amount of the first fuel (highly evaporative fuel) F1 into the combustion chamber CC is increased (in other words, in other words). In other words, the fuel supply ratio of the second fuel F2, which is a highly ignitable fuel, to the required total fuel supply amount into the combustion chamber CC is reduced) (step ST30).

  Regarding the compression auto-ignition diffusion combustion region reduction here, only the spark-assisted compression auto-ignition diffusion combustion region may be reduced, and the compression auto-ignition diffusion combustion region together with the spark-assist compression auto-ignition diffusion combustion region may be reduced. Also good. For example, the amount of movement of the boundary in this case is the same as described above so that the engine performance (output performance, emission performance, fuel consumption performance, etc.) can be maintained in a good state even if the combustion region is changed. Set. In addition, the amount of decrease in the fuel supply ratio of the second fuel F2 here is a value that can maintain the engine performance (output performance, emission performance, fuel consumption performance, etc.) in a good state even if the combustion region is changed. Set in the same way as above.

  Subsequently, the engine speed Ne and the engine load Kl are input to the electronic control device 1 of the first embodiment in the same manner as described above (step ST35), and the electronic control device 1 receives the engine speed Ne and the engine load Kl. 4 is compared with the combustion mode map data shown in FIG. 4, and the combustion region corresponding to the operating conditions (engine speed Ne and engine load Kl) is the diffusion combustion region (specifically, the compression auto-ignition diffusion combustion region and the spark-assisted compression self-compression). It is determined whether or not it is an ignition diffusion combustion region) (step ST40).

Then, the electronic control unit 1 calculates the self-ignitable limit load Kl _Si in the diffusion combustion region by using the above-mentioned function formula (step ST41), and the engine load Kl input in step ST35 is self-ignited. It is determined whether it is smaller than the possible limit load Kl _Si (step ST42).

Here, the case the engine load Kl is lower than the self-ignition can limit load Kl _Si is is not good ignitability to the fuel in the combustion chamber CC because the lower the engine load Kl, represents that Therefore, the electronic control unit 1 in this case selects and operates the spark assist compression self-ignition diffusion combustion mode (step ST43).

On the other hand, the case where the engine load Kl is equal to or greater than the self-ignitable limit load Kl _Si indicates that the engine load Kl is sufficiently high and the ignitability of the fuel in the combustion chamber CC is good. Therefore, the electronic control unit 1 in this case selects and operates the compression auto-ignition diffusion combustion mode (step ST45).

  When it is determined in step ST40 that the region is not the diffusion combustion region, the electronic control unit 1 selects and operates the premixed spark ignition flame propagation combustion mode (step ST50).

  As a result, in this multi-fuel internal combustion engine as well, the remaining fuel ratio of the first fuel F1 to the second fuel F2 while maintaining the engine performance (output performance, emission performance, fuel consumption performance, etc.) in a good state. (V1 / V2) can be brought close to the optimum usage ratio Ra of the first fuel F1 to the second fuel F2. Therefore, even in this multi-fuel internal combustion engine, normal operation can be performed again without deteriorating engine performance, and optimum operation capable of exhibiting the most suitable engine performance is continued in this engine. Can be done.

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

  In the above-described first embodiment, the multi-fuel internal combustion engine operated using the highly evaporative fuel and the highly ignitable fuel has been exemplified. However, regarding the technique for adjusting the residual fuel ratio according to the multi-fuel internal combustion engine of the first embodiment, FIG. The present invention can also be applied to a multi-fuel internal combustion engine that uses a plurality of types of fuels having different properties.

  For example, the second embodiment is a multi-fuel internal combustion engine of the first embodiment described above. As the first fuel F1 in the first fuel tank 41A, a fuel having high knock resistance and low ignitability (hereinafter referred to as the second embodiment). Is stored as a "high knock resistance fuel"), and the second fuel F2 in the second fuel tank 41B has a high ignitability and low knock resistance (hereinafter referred to as "high ignitability" in the second embodiment). An example of a multi-fuel internal combustion engine storing “fuel”) is illustrated. As the high knock resistance fuel, gasoline, alcohol fuel, GTL fuel generated as a high knock resistance property, and the like are known. Here, gasoline is stored as the first fuel F1. As the highly ignitable fuel, the same light oil as in Example 1 is known. Here, the light oil is stored as the second fuel F2.

  Therefore, also in the multifuel internal combustion engine of the second embodiment, the premixed spark ignition flame propagation combustion mode suitable for the high knock resistance fuel and the compression self-ignition diffusion combustion mode suitable for the high ignition fuel are provided. For example, the combustion mode is selected using the combustion mode map data similar to that shown in FIG. 2, and the premixed spark ignition flame propagation combustion region and the compression auto-ignition diffusion combustion of the combustion mode map data are further prepared. The boundary of the region is changed according to the fuel remaining ratio (V1 / V2) of the first fuel F1 to the second fuel F2. Here, for convenience, the combustion mode is set using FIG. 2, and therefore “Ra” shown in FIG. 2 is read as “Rb”. The “Rb” is an engine-specific value that represents the optimum usage ratio of the first fuel (high knock resistance fuel) F1 to the second fuel (high ignition resistance) F2 similar to the optimum usage ratio Ra of the first embodiment. These are set separately for each fuel.

  Hereinafter, an example of the operation of the multi-fuel internal combustion engine of the second embodiment that is operated using the fuel having such two kinds of fuel characteristics will be described with reference to the flowchart of FIG.

  First, in the electronic control unit 1 according to the second embodiment, the remaining amounts V1 of the first fuel (high knock resistance fuel) F1 and the second fuel (high ignition resistance) F2 as in the first embodiment. V2 is input (step ST55).

  Then, the fuel remaining ratio adjusting means of the electronic control unit 1 obtains the fuel remaining ratio (V1 / V2) of the first fuel F1 with respect to the second fuel F2 from the remaining amounts V1 and V2, and obtains the predetermined value ( It is compared with the optimum usage ratio Rb) of the first fuel F1 to the second fuel F2 (step ST60).

  Here, when the remaining fuel ratio (V1 / V2) is smaller than the optimum usage ratio Rb, that is, the remaining ratio of the first fuel (high knock resistance fuel) F1 is the second fuel (high ignitability fuel). When the remaining ratio of F2 is lower than a predetermined ratio, the fuel remaining ratio adjusting means reduces the premixed spark ignition flame propagation combustion area of the combustion mode map data shown in FIG. (Step ST65), and further, the fuel supply ratio with respect to the total required fuel supply amount of the first fuel (high knock resistance fuel) F1 into the combustion chamber CC is reduced (in other words, the first fuel that is a highly ignitable fuel). The fuel supply ratio with respect to the total required fuel supply amount of the fuel F2 into the combustion chamber CC is increased) (step ST70).

  Here, the boundary is moved in the direction of reducing the premixed spark ignition flame propagation combustion region suitable for combustion using the first fuel (high knock resistance fuel) F1. The amount of movement is set in the same manner as in the first embodiment so that the engine performance (output performance, emission performance, fuel consumption performance, etc.) can be maintained in a good state even if the combustion region is changed.

  Further, the amount of reduction is set in the same manner as in the first embodiment so that the engine performance (output performance, emission performance, fuel consumption performance, etc.) can be maintained in a good state even if the combustion region is changed. To do.

  On the other hand, when the remaining fuel ratio (V1 / V2) is larger than the optimum usage ratio Rb in step ST60, that is, the remaining ratio of the second fuel (highly ignitable fuel) F2 is the first fuel (high knock resistance). When the fuel remaining ratio F1 is lower than the predetermined ratio, the fuel remaining ratio adjusting means reduces the compression auto-ignition diffusion combustion region of the combustion mode map data shown in FIG. 2 and premixed spark ignition flame. The propagation combustion region is expanded (step ST75), and the fuel supply ratio with respect to the total required fuel supply amount of the first fuel (high knock resistance fuel) F1 into the combustion chamber CC is increased (in other words, high ignitability). The fuel supply ratio with respect to the total required fuel supply amount of the second fuel F2 as the fuel into the combustion chamber CC is reduced) (step ST80).

  Here, regarding the amount of movement of the boundary between the premixed spark ignition flame propagation combustion region and the compression auto-ignition diffusion combustion region, even if the compression auto-ignition diffusion combustion region is reduced, engine performance (output performance, emission performance, fuel consumption performance, etc.) Is set in the same manner as in Example 1 so that the value can be maintained in a good state. In addition, the amount of decrease in the fuel supply ratio of the second fuel F2 here is a value that can maintain the engine performance (output performance, emission performance, fuel consumption performance, etc.) in a good state even if the combustion region is changed. In the same manner as in Example 1, the setting is made.

  Subsequently, the engine speed Ne and the engine load Kl are input to the electronic control unit 1 of the second embodiment (step ST85), and the electronic control unit 1 sets the engine speed Ne and the engine load Kl in FIG. The combustion mode map data is collated, and it is determined whether or not the combustion region corresponding to the operating conditions (engine speed Ne and engine load Kl) is a diffusion combustion region (specifically, a compression autoignition diffusion combustion region) ( Step ST90).

  Then, the electronic control unit 1 selects and operates the compression auto-ignition diffusion combustion mode if it is the diffusion combustion region (step ST95), and selects the premixed spark ignition flame propagation combustion mode if it is not the diffusion combustion region. Operate (step ST100).

  Thus, in this multi-fuel internal combustion engine, when an affirmative determination is made in step ST60 {that is, the remaining fuel ratio (V1 / V2) is smaller than the optimum usage ratio Rb, the first fuel (high knock resistance fuel) ) When the remaining ratio of F1 is lower than the predetermined ratio with respect to the remaining ratio of the second fuel (highly ignitable fuel) F2,} the same operating conditions as in normal operation (engine speed Ne and engine load Kl) ), The frequency of selection of the premixed spark ignition flame propagation combustion mode suitable for operation using the first fuel (high knock resistance fuel) F1 is reduced as compared with the normal operation, and any combustion is performed. Regardless of the mode, the fuel supply ratio of the first fuel (high knock resistance fuel) F1 decreases. For this reason, in the multi-fuel internal combustion engine in this case, the consumption of the first fuel (high knock resistance fuel) F1 is reduced, while the consumption of the second fuel (high ignitability fuel) F2 is increased. The fuel remaining ratio (V1 / V2) approaches the optimum usage ratio Rb. Further, in this multi-fuel internal combustion engine, the engine performance (output performance, emission performance, fuel consumption performance, etc.) can be maintained in a good state even if such a change in the combustion region and the fuel supply ratio is performed.

  On the other hand, in this multi-fuel internal combustion engine, when a negative determination is made in step ST60 {that is, the remaining fuel ratio (V1 / V2) is larger than the optimum usage ratio Rb, the second fuel (highly ignitable fuel) F2 When the remaining ratio of the fuel is lower than a predetermined ratio with respect to the remaining ratio of the first fuel (high knock resistance fuel) F1}, the same operating conditions as in normal operation (engine speed Ne and engine load Kl) The frequency of selection of the compression auto-ignition diffusion combustion mode suitable for operation using the second fuel (highly ignitable fuel) F2 is reduced as compared with the normal operation, and which combustion mode is selected. Regardless of this, the fuel supply ratio of the second fuel (highly ignitable fuel) F2 decreases. For this reason, in the multi-fuel internal combustion engine in this case, the consumption amount of the second fuel (highly ignitable fuel) F2 is reduced, while the consumption amount of the first fuel (highly evaporative fuel) F1 is increased. The remaining ratio (V1 / V2) approaches the optimum usage ratio Ra. Further, even in the multifuel internal combustion engine in this case, the engine performance (output performance, emission performance, fuel consumption performance, etc.) can be maintained in a good state.

  As described above, in the multifuel internal combustion engine of the second embodiment, as in the multifuel internal combustion engine of the first embodiment, the engine performance (output performance, emission performance, fuel consumption performance, etc.) is maintained in a good state. The fuel remaining ratio (V1 / V2) of the first fuel F1 to the second fuel F2 can be brought close to the optimum usage ratio Ra of the first fuel F1 to the second fuel F2. Therefore, according to this multi-fuel internal combustion engine, the normal operation can be performed again without deteriorating the engine performance, and the optimum operation capable of exhibiting the most suitable engine performance can be performed in this engine. It can be done continuously.

  By the way, also in the multifuel internal combustion engine of the second embodiment, it is preferable to perform spark-assisted compression self-ignition diffusion combustion depending on the ignitability with respect to the fuel in the combustion chamber CC. Combustion mode map data to which the ignition diffusion combustion mode is added may be used. Here, for convenience, the combustion mode is set using FIG. 4, and therefore, “Ra” shown in FIG. 4 is read as “Rb”.

  For example, as shown in the flowchart of FIG. 7, first, in the electronic control unit 1 of the multi-fuel internal combustion engine in this case, the first fuel (high knock resistance fuel) F1 and the second fuel (high ignition quality fuel) F2 are used. Respective remaining amounts V1 and V2 are input (step ST55), and the fuel remaining ratio (V1 / V2) of the first fuel F1 with respect to the second fuel F2 and a predetermined value (for the second fuel F2) by the fuel remaining ratio adjusting means. The optimum usage ratio Rb) of the first fuel F1 is compared (step ST60).

  When the remaining fuel ratio (V1 / V2) is smaller than the optimum usage ratio Ra, the remaining fuel ratio adjusting means reduces the premixed spark ignition flame propagation combustion region of the combustion mode map data shown in FIG. The compression auto-ignition diffusion combustion region is expanded (step ST65), and the fuel supply ratio with respect to the total required fuel supply amount of the first fuel (high knock resistance fuel) F1 into the combustion chamber CC is reduced (in other words, The fuel supply ratio with respect to the total required fuel supply amount of the second fuel F2, which is a highly ignitable fuel, into the combustion chamber CC is increased) (step ST70).

  Regarding the expansion of the compression auto-ignition diffusion combustion region here, as in the first embodiment, only the spark-assisted compression auto-ignition diffusion combustion region may be expanded, and the compression auto-ignition diffusion together with the spark-assist compression auto-ignition diffusion combustion region. The combustion area may also be enlarged. Regarding the amount of movement of the boundary and the amount of decrease in the fuel supply ratio of the first fuel F1 in this case, the engine performance (output performance, emission performance, fuel consumption performance, etc.) can be maintained in a good state even if the combustion region is changed. It is set in the same manner as described above so as to be a possible value.

  On the other hand, when the remaining fuel ratio (V1 / V2) is larger than the optimum usage ratio Rb in step ST60, the remaining fuel ratio adjusting means reduces the compression auto-ignition diffusion combustion region of the combustion mode map data shown in FIG. At the same time, the premixed spark ignition flame propagation combustion region is expanded (step ST75), and the fuel supply ratio with respect to the total required fuel supply amount of the first fuel (high knock resistance fuel) F1 into the combustion chamber CC is increased (in other words, Then, the fuel supply ratio of the second fuel F2, which is a highly ignitable fuel, to the required total fuel supply amount into the combustion chamber CC is reduced) (step ST80).

  As for the compression auto-ignition diffusion combustion region reduction here, as in the first embodiment, only the spark-assisted compression auto-ignition diffusion combustion region may be reduced, and the compression auto-ignition diffusion together with the spark-assist compression auto-ignition diffusion combustion region. The combustion area may also be reduced. Regarding the amount of movement of the boundary and the amount of decrease in the fuel supply ratio of the second fuel F2 in this case, the engine performance (output performance, emission performance, fuel consumption performance, etc.) can be maintained in a good state even if the combustion region is changed. It is set in the same manner as described above so as to be a possible value.

  Subsequently, the engine speed Ne and the engine load Kl are input to the electronic control device 1 of the first embodiment in the same manner as described above (step ST85), and the electronic control device 1 receives the engine speed Ne and the engine load Kl. 4 is compared with the combustion mode map data shown in FIG. 4, and the combustion region corresponding to the operating conditions (engine speed Ne and engine load Kl) is determined to be a diffusion combustion region (specifically, a compression auto-ignition diffusion combustion region and a spark-assisted compression It is determined whether or not it is an ignition diffusion combustion region) (step ST90).

Then, the electronic control unit 1 calculates the self-ignitable limit load Kl _Si in the diffusion combustion region using the same function formula as that in the first embodiment (step ST91), and the engine load input in the step ST85. Kl is less determines whether than the self-ignition can limit load Kl _Si (step ST92).

Here, the electronic control unit 1 when the engine load Kl is lower than the self-ignition can limit load Kl _Si, it is operated to select a spark-assisted compression ignition diffusion combustion mode (step ST93), the engine load Kl is equal to or greater than the self-ignitable limit load Kl _Si, it is operated to select the compressed self-ignition diffusive combustion mode (step ST95).

  If it is determined in step ST90 that the region is not the diffusion combustion region, the electronic control unit 1 selects and operates the premixed spark ignition flame propagation combustion mode (step ST100).

  As a result, in this multi-fuel internal combustion engine as well, the remaining fuel ratio of the first fuel F1 to the second fuel F2 while maintaining the engine performance (output performance, emission performance, fuel consumption performance, etc.) in a good state. (V1 / V2) can be brought close to the optimum usage ratio Rb of the first fuel F1 with respect to the second fuel F2. Therefore, even in this multi-fuel internal combustion engine, normal operation can be performed again without deteriorating engine performance, and optimum operation capable of exhibiting the most suitable engine performance is continued in this engine. Can be done.

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

  In the first and second embodiments described above, a so-called in-cylinder direct injection type multi-fuel internal combustion engine that directly injects the mixed fuel of the first fuel F1 and the second fuel F2 into the combustion chamber CC is illustrated. The fuel residual ratio adjusting technique 2 according to the multi-fuel internal combustion engine can be applied to a multi-fuel internal combustion engine having another configuration.

  For example, the technology replaces the fuel supply device 50 with the fuel supply device 150 shown in FIG. 8 in the multifuel internal combustion engine of the first and second embodiments, and mixes the mixed fuel of the first fuel F1 and the second fuel F2 with the combustion chamber CC. The present invention may be applied to a multi-fuel internal combustion engine configured to inject not only into the intake port 11b but also in this case, the same effects as those of the multi-fuel internal combustion engines of the first and second embodiments can be obtained.

  Here, the fuel supply device 150 shown in FIG. 8 discharges the mixed fuel generated by the fuel mixing means 53 to the fuel passage 154 in addition to the various components of the fuel supply device 50 in the first and second embodiments. A fuel pump 155, a delivery passage 156 that distributes the mixed fuel in the fuel passage 154 to each cylinder, and a fuel injection in each cylinder that injects the mixed fuel supplied from the delivery passage 156 into the intake port 11b of each cylinder And a valve 157. In the multi-fuel internal combustion engine in this case, for example, when operating in the compression auto-ignition diffusion combustion mode, the fuel injection valve 57 is driven and controlled to inject the mixed fuel into the combustion chamber CC, and the premixed spark ignition flame propagation When operating in the combustion mode, the fuel injection valve 157 is driven to inject the mixed fuel into the intake port 11b.

  Further, the technology replaces the fuel supply device 50 with the fuel supply device 250 shown in FIG. 9 in the multifuel internal combustion engine of the first and second embodiments, and uses the first fuel F1 and the second fuel without using the fuel mixing means 53. The present invention may be applied to a multi-fuel internal combustion engine configured to inject F2 individually, and in this case as well, the same effects as those of the multi-fuel internal combustion engines of the first and second embodiments can be obtained.

  Here, the fuel supply device 250 shown in FIG. 9 includes a first fuel supply means that directly injects the first fuel F1 (highly ignitable fuel) into the combustion chamber CC, and a second fuel F2 ( Second fuel supply means for injecting highly evaporative fuel and high knock resistance). The first fuel supply means sucks up the first fuel F1 from the first fuel tank 41A and sends it to the first fuel passage 251A, and the first fuel F1 in the first fuel passage 251A as the high-pressure fuel. A high pressure fuel pump 255A for pumping to the passage 254A, a first delivery passage 256A for distributing the first fuel F1 in the high pressure fuel passage 254A to the respective cylinders, and a first fuel F1 supplied from the first delivery passage 256A And a fuel injection valve 257A for each cylinder that injects into the combustion chamber CC. On the other hand, the second fuel supply means sucks the second fuel F2 from the second fuel tank 41B and sends it to the second fuel passage 251B, and the second fuel F2 in the second fuel passage 251B, respectively. A second delivery passage 256B that distributes to the cylinders, and a fuel injection valve 257B for each cylinder that injects the second fuel F2 supplied from the second delivery passage 256B into the intake port 11b. In the multi-fuel internal combustion engine in this case, for example, when operating in the compression auto-ignition diffusion combustion mode or the spark assist compression auto-ignition diffusion combustion mode, only the fuel injection valve 257A or both of the fuel injection valves 257A and 257B are driven and controlled. Then, the fuel is led into the combustion chamber CC, and when operating in the premixed spark ignition flame propagation combustion mode, only the fuel injection valve 257B or both of the fuel injection valves 257A and 257B are driven and controlled to enter the combustion chamber CC. Lead.

  In each of the above-described first to third embodiments, the multi-fuel internal combustion engine operated with two types of fuels has been illustrated. However, regarding the residual fuel ratio adjustment technique according to each of the multi-fuel internal combustion engines of the first to third embodiments. May be applied to multi-fuel internal combustion engines that are operated using more types of fuel.

  As described above, the multi-fuel internal combustion engine according to the present invention is useful for a technique for eliminating the deviation of the remaining fuel ratio between a plurality of fuels.

It is a figure shown about the structure of Example 1, 2 of the multi-fuel internal combustion engine which concerns on this invention. It is a figure which shows an example of the combustion mode map data which has a premixed spark ignition flame propagation combustion area | region and a compression auto-ignition diffusion combustion area | region. 3 is a flowchart for explaining the operation of the multifuel internal combustion engine of the first embodiment. It is a figure which shows an example of the combustion mode map data which has a premixed spark ignition flame propagation combustion area | region, a compression auto-ignition diffusion combustion area | region, and a spark assist compression auto-ignition diffusion combustion area | region. 6 is a flowchart for explaining the operation of a modified example of the multifuel internal combustion engine of the first embodiment. 6 is a flowchart for explaining the operation of the multifuel internal combustion engine of the second embodiment. 6 is a flowchart for explaining the operation of a modified example of the multifuel internal combustion engine of the second embodiment. It is a figure shown about the structure of Example 3 of the multi-fuel internal combustion engine which concerns on this invention. It is a figure shown about the structure of the modification of Example 3 of the multi-fuel internal combustion engine which concerns on this invention.

Explanation of symbols

1 Electronic control unit 41A First fuel tank 41B Second fuel tank 42A, 42B Fuel remaining amount detection means CC Combustion chamber F1 First fuel F2 Second fuel V1 First fuel remaining amount V2 Second fuel remaining amount V1 / V2 Fuel remaining ratio

Claims (2)

A separately stored first fuel with high evaporability and low ignitability and a second fuel with high ignitability and low evaporability are supplied individually or mixed so as to have a predetermined fuel content ratio in the combustion chamber. The fuel characteristics of the fuel in the combustion chamber composed of the first fuel and the second fuel are at least suitable for the combustion mode selected from the premixed spark ignition flame propagation combustion mode or the compression auto-ignition diffusion combustion mode. In a multi-fuel internal combustion engine that is operated by changing,
When the fuel remaining ratio of the first fuel to the second fuel becomes smaller than a predetermined value, the fuel supply ratio of the first fuel to the required total fuel supply amount into the combustion chamber is reduced and When the mixed spark ignition flame propagation combustion region is reduced and the compression auto-ignition diffusion combustion region is expanded, the fuel remaining ratio of the first fuel to the second fuel becomes larger than a predetermined value. Fuel remaining ratio adjusting means for increasing the fuel supply ratio of the first fuel to the required total fuel supply amount, expanding the premixed spark ignition flame propagation combustion region, and reducing the compression self-ignition diffusion combustion region is provided. A multi-fuel internal combustion engine characterized by that. A separately stored first fuel having high knock resistance and low ignition resistance and a second fuel having high ignition resistance and low ignition resistance are individually or mixed so as to have a predetermined fuel content ratio in the combustion chamber. The fuel characteristics of the fuel in the combustion chamber comprising the first fuel and the second fuel are suitable for at least a combustion mode selected from a premixed spark ignition flame propagation combustion mode or a compression auto-ignition diffusion combustion mode In the multi-fuel internal combustion engine operated by changing to
When the fuel remaining ratio of the first fuel to the second fuel becomes smaller than a predetermined value, the fuel supply ratio of the first fuel to the required total fuel supply amount into the combustion chamber is reduced and When the mixed spark ignition flame propagation combustion region is reduced and the compression auto-ignition diffusion combustion region is expanded, the fuel remaining ratio of the first fuel to the second fuel becomes larger than a predetermined value. Fuel remaining ratio adjusting means for increasing the fuel supply ratio of the first fuel to the required total fuel supply amount, expanding the premixed spark ignition flame propagation combustion region, and reducing the compression self-ignition diffusion combustion region is provided. A multi-fuel internal combustion engine characterized by that.

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