JP2015129470A - Internal combustion engine controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure appropriate determination in relation to execution of the injection of a gas fuel and eventually suppress problems such as deterioration in exhaust gas emission and degradation in drivability.SOLUTION: A gas fuel is injected into an engine 10 from each first injection valve 21. A control unit 80 sets a requested quantity of fuel injection by each first injection valve 21 on the basis of an engine operating state, and controls the first injection valve 21 to inject the gas fuel on the basis of the requested quantity. Furthermore, the control unit 80 determines whether each first injection valve 21 is in a state of being able to inject the gas fuel by as much as the requested quantity for the engine operating state at present time, and executes restriction over the fuel injection by the first injection valve 21 if determining that the first fuel injection 21 is not in the state of being able to inject the gas fuel by as much as the requested quantity. On the other hand, the control unit 80 determines the composition of the gas fuel supplied to each first injection valve 21, and variably sets a criterion for determining whether the first fuel injection valve 21 is able to inject the gas fuel by as much as the requested quantity.

Description

  The present invention relates to a control device for an internal combustion engine.

  When gaseous fuel such as natural gas (CNG) is used, the amount of fuel required for combustion differs from that when liquid fuel is used, and various techniques have been proposed in consideration of the difference in the amount of fuel. For example, in the technique described in Patent Document 1, in the system that calculates the injection amount of the gaseous fuel based on the injection amount of the liquid fuel, the injection amount of the gaseous fuel is corrected according to the composition change of the gaseous fuel. As a result, even when the composition of the gaseous fuel is changed, stable gaseous fuel injection can be realized, and it is possible to prevent the emission performance from being lowered and the malfunction detection of the air-fuel ratio sensor to be prevented.

JP 2013-130156 A

  However, when a gaseous fuel such as natural gas (CNG) is used, it is conceivable that the fuel composition varies widely, and due to the variation in the fuel composition, the amount of fuel required for each combustion varies. In this case, when the amount of inert gas components (impurities) in the gaseous fuel increases, the amount of fuel required for each combustion increases, and during high speed / high load operation where a large amount of fuel must be injected in a short time. The air-fuel ratio becomes unintentionally lean. Therefore, there is a concern that inconveniences such as deterioration of exhaust emission and drivability will occur.

  SUMMARY OF THE INVENTION The main object of the present invention is to provide a control device for an internal combustion engine that makes it possible to make an appropriate judgment regarding the implementation of gaseous fuel injection, and thereby suppress inconveniences such as deterioration of exhaust emission and drivability. To do.

  Hereinafter, means for solving the above-described problems and the effects thereof will be described.

  The control apparatus for an internal combustion engine according to the present invention includes a pressure adjusting means (43) for adjusting the pressure of the gaseous fuel supplied from the fuel tank (42) to a predetermined pressure, and a pressure adjustment by the pressure adjusting means in the internal combustion engine (10). And a fuel injection system including a gaseous fuel injection valve (21) for injecting the subsequent gaseous fuel, and setting a required amount of fuel injection by the gaseous fuel injection valve based on an operating state of the internal combustion engine, The gaseous fuel injection valve performs fuel injection based on the required amount. And about the driving | running state of the said internal combustion engine each time, the driving | running state determination means which determines whether it is a state which can implement the fuel injection for the said required amount by the said gaseous fuel injection valve, and the said driving | running state determination means, An injection limiting means for limiting the fuel injection by the gaseous fuel injection valve when it is determined that the fuel injection for the required amount by the gaseous fuel injection valve cannot be performed. Based on the composition determination means for determining the composition of the gaseous fuel supplied to the valve and the fuel composition determined by the composition determination means, the operating state determination means determines whether or not the required amount of fuel injection can be performed. And setting means for variably setting the determination criterion.

  When using gaseous fuel made of natural gas, etc., the volume of fuel required for combustion is larger than that of liquid fuel, so that a desired amount of fuel can be injected at a predetermined time in the combustion cycle, for example, in a high-load operation state. Otherwise, exhaust emissions will deteriorate due to an unintended shortage of fuel. For this reason, for example, in a high-load operation state, it is conceivable to limit fuel injection so that an unintended fuel shortage does not occur.

  On the other hand, in the case of gaseous fuel, it is assumed that the composition will vary greatly, and in the case of containing a lot of inert components (impurities), in anticipation that the required fuel amount will increase, set the injection restriction area with a margin It can be considered. However, when gas fuel with few inert components (impurities) is actually used, it is conceivable that injection restriction is unnecessary. In such a case, excessive injection restriction (originally unnecessary restriction) is considered. ) Is concerned that there may be inconveniences such as a decrease in drivability.

  In this regard, in the above configuration, the determination criterion for determining whether or not the fuel injection for the required amount by the gaseous fuel injection valve can be performed is variably set based on the fuel composition. The gas fuel can be properly restricted while complying with the fuel composition. For example, in the case of gaseous fuel with a small amount of inert components, the range in which gaseous fuel injection can be performed without restriction is expanded, and conversely, in the case of a gaseous fuel with many inert components, gaseous fuel injection can be performed without limitation. It becomes possible to narrow the region. As a result, it is possible to make an appropriate determination regarding the implementation of the injection of the gaseous fuel, and to suppress inconveniences such as deterioration of exhaust emission and drivability.

The schematic block diagram which shows the whole engine control system. The figure which shows an injection restricted area | region and a non-restricted area | region. The figure which shows the relationship between an air fuel ratio correction coefficient and the amount of inert gas. The flowchart which shows the control procedure of the fuel injection of gaseous fuel. The flowchart which shows the control procedure of the fuel injection of gaseous fuel in 2nd Embodiment.

(First embodiment)
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings. This embodiment is embodied as a fuel injection system for a so-called bi-fuel type on-vehicle multi-cylinder engine that uses compressed natural gas (CNG) that is gaseous fuel and gasoline that is liquid fuel as fuel for engine combustion. . An overall schematic diagram of this system is shown in FIG.

  An engine 10 shown in FIG. 1 is an inline three-cylinder spark ignition engine, and an intake system 11 and an exhaust system 12 are connected to an intake port and an exhaust port, respectively. The intake system 11 has an intake manifold 13 and an intake pipe 14. The intake manifold 13 has a plurality of (for the number of cylinders of the engine 10) branch pipe portions 13a connected to the intake port of the engine 10, and a collective portion 13b connected to the intake pipe 14 on the upstream side. ing. The intake pipe 14 is provided with a throttle valve 15 as air amount adjusting means. The throttle valve 15 is configured as an electronically controlled throttle valve whose opening degree is adjusted by a throttle actuator 15a such as a DC motor. The opening degree of the throttle valve 15 (throttle opening degree) is detected by a throttle opening degree sensor 15b built in the throttle actuator 15a. An intake valve is provided in the intake port of the engine 10, and an air-fuel mixture is introduced into the cylinder 24 (inside the cylinder) by opening the intake valve.

  The exhaust system 12 has an exhaust manifold 16 and an exhaust pipe 17. The exhaust manifold 16 has a plurality of (for the number of cylinders of the engine 10) branch pipe portions 16a connected to the exhaust port of the engine 10 and a collecting portion 16b connected to the exhaust pipe 17 on the downstream side. ing. The exhaust port of the engine 10 is provided with an exhaust valve. Exhaust gas after combustion of the engine 10 is discharged from the cylinders 24 of the engine 10 to the exhaust pipe 17 by opening the exhaust valve. The exhaust pipe 17 is provided with an exhaust sensor for detecting exhaust components and a catalyst 19 for purifying the exhaust. As the exhaust sensor, an air-fuel ratio sensor 18 that detects the air-fuel ratio from the oxygen concentration in the exhaust is provided.

  The engine 10 is provided with a variable valve operating device 26 that variably adjusts the opening / closing timing of an intake valve (not shown). By this variable valve operating device 26, the opening timing and closing timing of the intake valve are advanced. It can be changed to the side or retard side. The configuration of the variable valve device 26 is well known and will not be described here. For example, it may be provided with a hydraulically or electrically driven phase adjusting mechanism.

  Further, the engine 10 of this embodiment is an engine with a supercharger, and supercharging of intake air is performed by a turbocharger 31 as a supercharger. The turbocharger 31 has an intake air compressor 32 provided in the intake pipe 14 and an exhaust turbine 33 provided in the exhaust pipe 17, and these are connected so as to be integrally rotatable by a rotating shaft (not shown). A bypass passage 34 is provided between an upstream portion and a downstream portion of the exhaust pipe 17 with the exhaust turbine 33 interposed therebetween, and an electric waste gate valve 35 is provided in the bypass passage 34.

  A spark plug 20 is provided in each cylinder 24 of the engine 10. A high voltage is applied to the ignition plug 20 at a desired ignition timing through an ignition device 20a including an ignition coil. By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 20, and the fuel introduced into the cylinder 24 (combustion chamber) is ignited and used for combustion.

  Further, the present system is a fuel injection means for injecting and supplying fuel to the engine 10, a first injection valve 21 for injecting gaseous fuel (CNG fuel), and a second injection valve 22 for injecting liquid fuel (gasoline). And have. Among these injection valves 21 and 22, the first injection valve 21 is a port injection type that injects fuel into the branch pipe portion 13 a of the intake manifold 13, and the second injection valve 22 is a fuel in the cylinder 24 of the engine 10. It is a direct injection type that injects directly. Each of the injection valves 21 and 22 is an open / close type control valve in which the valve body is lifted from the closed position to the open position by electrically driving the electromagnetic drive unit. Each valve is driven to open by a valve opening drive signal. Each of these injection valves 21 and 22 is opened by energization, closed by energization interruption, and injects an amount of fuel (gaseous fuel, liquid fuel) according to the energization time.

  Here, the gaseous fuel supply part 40 which supplies gaseous fuel with respect to the 1st injection valve 21, and the liquid fuel supply part 70 which supplies liquid fuel with respect to the 2nd injection valve 22 are demonstrated. In the gaseous fuel supply unit 40, a gas tank 42 is connected to the first injection valve 21 via a gas pipe 41. In the middle of the gas pipe 41, a regulator 43 is provided as pressure adjusting means for adjusting the pressure of the gaseous fuel supplied to the first injection valve 21 to reduce the pressure. The regulator 43 is configured so that gaseous fuel in a high pressure state (for example, a maximum of 20 MPa) stored in the gas tank 42 is a predetermined set pressure (for example, in a range of 0.2 to 1.0 MPa) that is an injection pressure of the first injection valve 21. The pressure is adjusted to be constant. The gaseous fuel after the decompression adjustment is supplied to the first injection valve 21 through the gas pipe 41.

  The gas pipe 41 further includes a tank main stop valve 44 disposed near the fuel outlet of the gas tank 42, and a shut-off valve disposed downstream of the tank main stop valve 44 and near the fuel inlet of the regulator 43. 45 is provided. These valves 44 and 45 allow and block the flow of gaseous fuel in the gas pipe 41. Both the tank main stop valve 44 and the shut-off valve 45 are electromagnetic on-off valves, and are normally closed types in which the flow of gaseous fuel is blocked when not energized and the flow of gaseous fuel is allowed when energized. In the gas pipe 41, pressure sensors 46a and 46b for detecting the fuel pressure and temperature sensors 47a and 47b for detecting the fuel temperature are provided on the upstream side and the downstream side of the regulator 43, respectively.

  In the liquid fuel supply unit 70, a fuel tank 72 is connected to the second injection valve 22 via a fuel pipe 71. The fuel pipe 71 is provided with a fuel pump 73 that feeds the liquid fuel in the fuel tank 72 to the second injection valve 22.

  In addition, this system is provided with a starter 25 as a starting device that applies initial rotation to the engine 10 when the engine is started.

  The control unit 80 includes a CPU 81, a ROM 82, a RAM 83, a backup RAM 84, an interface 85, and a bidirectional bus 86. The CPU 81, ROM 82, RAM 83, backup RAM 84, and interface 85 are connected to each other by a bidirectional bus 86.

  The CPU 81 executes a routine (program) for controlling the operation of each unit in this system. The ROM 82 stores in advance various data such as a routine executed by the CPU 81, maps (including tables, relational expressions, etc. in addition to maps) and parameters referred to when the routine is executed. The RAM 83 temporarily stores data as necessary when the CPU 81 executes a routine. The backup RAM 84 appropriately stores data under the control of the CPU 81 in a state where the power is turned on, and retains the stored data even after the power is shut off.

  The interface 85 includes the throttle opening sensor 15b, the air-fuel ratio sensor 18, the pressure sensors 46a and 46b, the temperature sensors 47a and 47b, and other sensors (crank angle sensor, cam angle sensor, air flow sensor) provided in this system. Meter, cooling water temperature sensor, vehicle speed sensor, accelerator sensor, and the like), and outputs (detection signals) from these sensors to the CPU 81. The interface 85 is electrically connected to driving units such as the throttle actuator 15a, the ignition device 20a, the injection valves 21 and 22, the variable valve device 26, the waste gate valve 35, the tank main stop valve 44, and the shutoff valve 45. The drive unit is driven by outputting a drive signal sent from the CPU 81 to the drive unit. That is, the control unit 80 acquires the operating state of the engine 10 based on the output signals of the above-described sensors, and implements the above-described driving unit control based on the acquired operating state.

  Specifically, for example, a target air amount of the engine 10 is calculated based on an accelerator operation amount detected by an accelerator sensor, an engine rotation speed detected by a crank angle sensor, and the like, and based on the calculated value, the throttle actuator 15a Control the drive. Further, the fuel injection amount (requested amount) is calculated based on the engine rotational speed and the intake air amount (engine load) detected by the air flow meter, and the injection valves 21 and 22 are driven based on the calculated value. Control. Further, the optimal ignition timing is calculated based on the engine rotation speed, the intake air amount, and the like, and the drive of the ignition device 20a is controlled so that ignition is performed at the optimal ignition timing. Further, the target valve opening timing (or target valve closing timing) of the intake valve is calculated based on the engine speed, the intake air amount, and the like, and the drive of the variable valve device 26 is controlled based on the calculated value.

  The control unit 80 has a function of switching between the gas fuel mode and the liquid fuel mode. In the gas fuel mode, the control unit 80 performs the injection of the gas fuel by the first injection valve 21. The liquid fuel is injected by the two injection valves 22. Switching between these modes may be performed according to the remaining amount of fuel in the tank, an input signal from a fuel selection switch (not shown), or the like. Specifically, when the remaining amount of gaseous fuel in the gas tank 42 falls below a predetermined value or when the use of liquid fuel is selected by the fuel selection switch, the liquid fuel is injected by the second injection valve 22. The engine 10 is combusted. Further, when the remaining amount of liquid fuel in the fuel tank 72 falls below a predetermined value, or when the use of gaseous fuel is selected by the fuel selection switch, the engine 10 is injected by gaseous fuel from the first injection valve 21. Carry out combustion.

  By the way, when using gaseous fuel such as CNG, the amount of fuel required for combustion is larger than that of liquid fuel, so that a desired amount of fuel cannot be injected at a predetermined time in the combustion cycle, for example, in a high-load operation state. As a result, unintended fuel shortage will lead to deterioration of exhaust emissions. For this reason, for example, in high-load operation, it is conceivable to limit the injection of gaseous fuel so that an unintended fuel shortage does not occur. For example, in region A where the engine speed is high and the load is high in FIG. 2, there is a concern that a lean deviation of the air-fuel ratio may occur due to the fact that a desired amount of fuel cannot be injected.

  On the other hand, in the case of CNG, it is assumed that the composition varies greatly. That is, there are areas where the mined natural gas is used as fuel without being refined, and the fuel composition varies greatly depending on the mining area. In particular, when a lot of inert gas such as nitrogen and carbon dioxide is mixed in the fuel, the volume of fuel that must be injected per the same amount of air increases. In some regions, the inert gas may occupy 20% or more of the total, and the required injection amount increases in proportion to the inert gas ratio. Therefore, it is conceivable that the injection restriction region (region A in FIG. 2) is set with a margin in anticipation of an increase in the required fuel amount when a large amount of inert gas (impurities) is contained. However, in reality, it is considered that there may be wasteful injection restrictions when using gaseous fuel with a small amount of inert gas. In such cases, excessive injection restrictions (restrictions that are essentially unnecessary) are implemented. Therefore, there is a concern about inconveniences such as a decrease in drivability.

  Therefore, in the present embodiment, a criterion for determining whether or not the fuel injection for the required amount by the first injection valve 21 can be performed (the boundary between the injection limited region A and the non-restricted region B in FIG. 2). Line) is variably set based on the fuel composition so that the restriction of the gaseous fuel can be appropriately performed while corresponding to the fuel composition of each time. Specifically, as shown in FIG. 2, in the case of gaseous fuel with a lot of inert gas, a determination is made to narrow the region where the required amount of fuel can be injected (non-restricted region B where the injection of gaseous fuel is not restricted). In the case of gaseous fuel with less inert gas by shifting the standard to a lower rotation / low load side, the judgment criterion is increased to expand the area where the required amount of fuel can be injected (unlimited area B). Shift to rotation / high load side.

  FIG. 4 is a flowchart showing a processing procedure related to gaseous fuel injection control, and this processing is repeatedly performed by the CPU 81 of the control unit 80 in a predetermined cycle when in the gaseous fuel mode.

  In FIG. 4, in step S <b> 11, it is determined whether learning of the gaseous fuel composition is completed. The fuel composition learning method may be arbitrary, but in this embodiment, the fuel composition learning is performed based on the fuel correction amount under the gaseous fuel mode. Briefly, when the air-fuel ratio feedback control is performed, the air-fuel ratio correction coefficient FAF required to make the actual air-fuel ratio coincide with the target air-fuel ratio is calculated, and the fuel composition is calculated based on the air-fuel ratio correction coefficient FAF. To implement. In this case, as the amount of the inert gas mixed in the gaseous fuel increases, the fuel amount to be increased by the correction increases with respect to the basic injection amount calculated based on the engine speed and the engine load, and the air-fuel ratio correction coefficient FAF is Larger value. Whether the fuel amount is increased or decreased by the correction (whether FAF> 1 or FAF <1) is determined according to the reference fuel composition (reference composition which is a premise of the basic injection amount), If the amount of inert gas mixed in with respect to the reference composition is large, the fuel amount is increased by correction (FAF> 1). Conversely, if the amount of mixed inert gas is small with respect to the reference composition, the correction is performed. This reduces the amount of fuel (FAF <1).

  In the present embodiment, for example, using the relationship shown in FIG. 3, the amount of inert gas as a parameter of the fuel composition is calculated based on the air-fuel ratio correction coefficient FAF. The inert gas amount calculated in this way is sequentially stored in the backup memory as a learning value. For example, the learning of the fuel composition may be performed every time the vehicle is operated (once per trip) or every time fuel gas is replenished.

  When step S11 is YES, it progresses to step S12, and the setting of the injection restricted area | region A and the non-restricted area | region B is implemented based on the inert gas amount (result of fuel composition learning) in gaseous fuel. Step S12 corresponds to “setting means”. In this case, as the amount of the inert gas increases, the injection restriction region A is expanded, that is, the region where fuel injection by the first injection valve 21 is restricted is expanded. More specifically, in FIG. 2, the range (setting range) in which the determination criterion is changed is La to Lc, and the amount of the inert gas is greater than the predetermined amount K when the determination criterion is “L1”. For example, the criterion is shifted from L1 to La, and if the amount of inert gas is less than the predetermined amount K, the criterion is shifted from L1 to Lc. Note that the determination criterion is desirably changed in small increments according to the amount of inert gas. For example, the criterion is appropriately changed to Lb or the like between L1 to La according to the amount of inert gas.

  If NO in step S11, the process proceeds to step S13, and the injection restriction area A and the non-restriction area B are set so that the non-restriction area B is the smallest. In this case, the non-restricted region B is minimized by setting the determination criterion to “La”.

  Thereafter, in step S14, the required operating condition of the engine 10 is calculated from the current vehicle and the operating state of the engine 10. Specifically, the engine operating state (rotation speed, load) to be realized is calculated based on the accelerator operation amount, the transmission gear ratio, the electric load driving amount, and the like.

  Thereafter, in step S15, it is determined whether or not the required operation condition calculated in step S14 is in the non-restricted region B set in steps S12 and S13. If it is in the non-restricted region B, the process proceeds to step S16 and normal control is performed. At this time, normal control is performed for each of these without limiting the operation of the engine 10 and others. If it is not in the non-restricted area B (that is, if it is in the injection restricted area A), the process proceeds to step S17 and operation restriction is performed on the engine 10 and others. Step S15 corresponds to “driving state determination means”, and step S17 corresponds to “injection restriction means”.

Specifically, the following configuration may be considered for the operation restriction. That is, when the required operating condition is in the injection restriction region A, it is necessary to reduce the fuel injection amount of the gaseous fuel with respect to the original fuel injection amount. In this embodiment, the intake air amount of the engine 10 The fuel injection amount of the gaseous fuel is reduced by reducing. Further, the following (1) to (3) are specifically considered as means for reducing the intake air amount.
(1) The throttle valve 15 is controlled to reduce the opening.
(2) The drive of the variable valve device 26 is controlled so that the closing timing of the intake valve is kept away from the intake bottom dead center. That is, the closing timing of the intake valve is advanced or retarded with respect to the intake bottom dead center. If the variable valve device 26 can change the lift amount of the intake valve, the lift amount is limited.
(3) By adjusting the opening degree of the wastegate valve 35 of the turbocharger 31, the supercharging pressure is limited to a lower pressure side.

  When the required operation condition is in the injection restriction region A, the operation restriction is performed as described above, so that the fuel injection amount is suppressed from leaning against the intention, and as a result, the exhaust emission deteriorates. The inconvenience of doing is suppressed.

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  Based on the fuel composition, a determination criterion (a boundary line between the injection restriction region A and the non-restriction region B) for determining whether or not fuel injection for the required amount by the first injection valve 21 can be performed is performed. Since it is set to be variable, it is possible to appropriately limit the gaseous fuel while corresponding to the fuel composition of each time. As a result, it is possible to make an appropriate judgment regarding the implementation of the injection of the gaseous fuel, and to suppress inconveniences such as deterioration of exhaust emission and drivability.

  When the amount of the inert gas in the gaseous fuel is large, the non-restricted region B (unrestricted operation region) is made narrower than when it is small. Accordingly, when the amount of the inert gas is large, the fuel injection can be appropriately performed in consideration of the increase in the volume of the fuel injection.

  Before the composition learning of the gaseous fuel is completed, the non-restricted region B (unrestricted operation region) is set to the narrowest region (for example, a region using La in FIG. 2 as a criterion) among the changeable ranges. I made it. Accordingly, it is possible to suppress the deterioration of exhaust emission due to the lean deviation of the air-fuel ratio even when the fuel composition is unlearned while considering that there is a composition variation in the gaseous fuel.

  When it is determined that the fuel injection for the required amount by the first injection valve 21 cannot be performed, the fuel injection of the first injection valve 21 is limited by limiting the intake air amount. In this case, by implementing the restriction on the intake air amount and the restriction on the injection of the gaseous fuel, it is possible to suppress the air-fuel ratio shift and thus to suppress the deterioration of the exhaust emission.

(Second Embodiment)
In the present embodiment, as a difference from the first embodiment, the remaining amount of fuel in the gas tank 42 is determined, and the determination criterion is variably set based on the remaining amount of fuel.

  FIG. 5 is a flowchart showing a processing procedure relating to the injection control of gaseous fuel in the present embodiment, and this processing is performed in place of the above-described FIG. 5 is obtained by changing a part of FIG. 4, and steps S11 to S13 in FIG. 4 are changed to steps S21 to S24.

  In FIG. 5, in step S <b> 21, the remaining fuel amount in the gas tank 42 is determined. This remaining fuel amount is obtained from, for example, the detection value of the pressure sensor 46a provided on the upstream side of the regulator 43, or from the detection value of the tank internal pressure sensor when the gas tank 42 is provided with a tank internal pressure sensor. Good.

  In a succeeding step S22, it is determined whether or not fuel composition learning (calculation of the amount of inert gas in the gaseous fuel) is completed. This process is the same as step S11 in FIG. If step S22 is YES, the process proceeds to step S23, and the injection restriction area A and the non-restriction area B are set based on the amount of inert gas in the gaseous fuel and the remaining amount of fuel.

  In this case, when setting the injection restricted area A and the non-restricted area B shown in FIG. 2, the areas A and B are set based on the remaining amount of fuel in addition to the amount of inert gas. Specifically, in addition to expanding the injection restriction area A when the amount of inert gas is large and narrowing the injection restriction area A when the amount of inert gas is small, the remaining amount of fuel becomes smaller than a predetermined value Th. In this case, the areas A and B are set based on the remaining fuel amount (remaining remaining fuel amount). At this time, when the remaining amount of fuel becomes less than Th, the injection restriction region A may be expanded as the remaining amount decreases. The predetermined value Th is preferably determined based on whether or not the pressure adjustment at the set pressure is possible in the regulator 43, and the remaining amount of fuel is reduced to such an extent that the pressure adjustment at the set pressure is impossible. Is a determination value for determining.

  If step S22 is NO, the process proceeds to step S24, and the minimum setting of the non-restricted region B is performed while taking into account the remaining amount of fuel. That is, when the remaining amount of fuel is small, it is considered that it becomes difficult to perform fuel injection for the required amount. Therefore, the non-restricted region B is narrowed as the remaining amount of fuel decreases.

  Step S14 and subsequent steps are as described in FIG. Briefly, the required operating condition of the engine 10 is calculated, and it is determined whether or not the required operating condition is in the unrestricted region B (steps S14 and S15). If it is not in the non-restricted region B, normal control is performed, and if it is not in the non-restricted region B, the operation is restricted for the engine 10 and others (steps S16 and S17).

  In short, when the remaining amount of fuel in the gas tank 42 decreases, the tank internal pressure decreases, making it difficult for the regulator 43 to adjust the fuel pressure to a predetermined pressure (that is, the fuel pressure is equal to or lower than the predetermined pressure). . In this case, since the fuel injection rate decreases as the remaining amount of fuel decreases, the determination of whether or not the fuel injection for the required amount by the first injection valve 21 can be performed is affected, and the determination is appropriate. If this is not done, the remaining gaseous fuel may not be used properly. For example, there is a concern that the determination that the vehicle can no longer travel is made prematurely.

  In this respect, since the determination criterion is set based on the remaining amount of fuel in addition to the fuel composition, it is determined that the remaining gas fuel is properly used and the vehicle cannot be traveled prematurely. Such inconvenience can be suppressed. In addition, the fuel in the gas tank 42 can be properly used until the remaining amount becomes small, which can contribute to the extension of the travel distance of the vehicle.

(Other embodiments)
You may change the said embodiment as follows, for example.

  When the required operating condition is in the injection restriction region A and the injection restriction of the gaseous fuel is performed, the following processing is performed instead of reducing the intake air amount of the engine 10 as described above. You may do it. That is, when the injection restriction of the gaseous fuel is performed, in addition to the injection of the gaseous fuel by the first injection valve 21, the injection of the liquid fuel by the second injection valve 22 may be performed (gas & liquid Dual injection). Specifically, in step S17 of FIG. 4 and FIG. 5, the required amount as the fuel injection amount is injected by the first injection valve 21 by the amount that can be injected by the first injection valve 21, and the remaining shortage is changed to the first amount. The two injection valves 22 are used for injection.

  In this configuration as well, it is possible to suppress the deterioration of exhaust emission due to the air-fuel ratio shift and further suppress the decrease in drivability. Moreover, the operation | movement using gaseous fuel can be continued as much as possible by using liquid fuel according to a shortage, continuing gaseous fuel use.

  Alternatively, when the injection restriction of the gaseous fuel is performed, the liquid fuel may be injected by the second injection valve 22 instead of the injection of the gaseous fuel by the first injection valve 21 (gaseous fuel injection). Switch to liquid fuel injection). Specifically, in step S <b> 17 of FIGS. 4 and 5, the fuel injection of the first injection valve 21 is stopped, and the required amount as the fuel injection amount is injected by the second injection valve 22.

  In this configuration as well, it is possible to suppress the deterioration of exhaust emission due to the air-fuel ratio shift and further suppress the decrease in drivability. Moreover, even if it is a case where gaseous fuel with much inert gas amount is used by switching to liquid fuel automatically, it can suppress impairing the driving | running | working performance of a vehicle.

  In the above embodiment, the present invention is embodied in a bi-fuel engine that uses gaseous fuel (CNG) and liquid fuel (gasoline) as combustion fuel. However, this is changed to a gas that uses only gaseous fuel. It is also possible to embody the present invention with an engine.

  In the above embodiment, the CNG fuel is used as the gaseous fuel, but other gaseous fuels that are gas in the standard state can also be used. For example, a fuel mainly composed of methane, ethane, propane, butane, hydrogen, etc. It is good also as a structure to use. Further, the liquid fuel is not limited to gasoline fuel, and for example, light oil or the like may be used.

  DESCRIPTION OF SYMBOLS 10 ... Engine (internal combustion engine), 21 ... 1st injection valve (gaseous fuel injection valve), 42 ... Gas tank (fuel tank), 43 ... Regulator (pressure adjustment means), 80 ... Control part (operation state determination means, injection restriction) Means, composition determination means, setting means).

Claims (6)

Pressure adjusting means (43) for adjusting the pressure of the gaseous fuel supplied from the fuel tank (42) to a predetermined pressure, and gaseous fuel injection for injecting gaseous fuel after pressure adjustment by the pressure adjusting means in the internal combustion engine (10) The fuel injection system is provided with a valve (21), sets a required amount of fuel injection by the gaseous fuel injection valve based on the operating state of the internal combustion engine, and the gaseous fuel injection valve based on the required amount A control device for an internal combustion engine that performs the fuel injection of
About the operating state of the internal combustion engine each time, an operating state determination means for determining whether or not fuel injection for the required amount by the gaseous fuel injection valve can be performed;
An injection limiting unit for limiting the fuel injection by the gaseous fuel injection valve when the operation state determining unit determines that the fuel injection for the required amount by the gaseous fuel injection valve is not possible;
While comprising
Composition determining means for determining the composition of the gaseous fuel supplied to the gaseous fuel injection valve;
Setting means for variably setting a determination criterion for determining whether or not the required amount of fuel injection can be performed in the operating state determination means based on the fuel composition determined by the composition determination means;
A control device for an internal combustion engine, comprising: The composition determination means calculates the amount of inert gas contained in the gaseous fuel as the composition determination of the gaseous fuel,
The setting means performs the determination by narrowing an unrestricted operation region in which the required amount of fuel can be injected by the gaseous fuel injection valve when the amount of the inert gas is large, compared to when the amount is small. The control apparatus for an internal combustion engine according to claim 1, wherein the reference is set. The operating state determination means defines an unrestricted operating region in which fuel injection for the required amount by the gaseous fuel injection valve can be performed, and whether the operating state of the internal combustion engine is in the unrestricted operating region. Based on whether or not to determine whether or not the fuel injection for the required amount by the gaseous fuel injection valve can be carried out,
The means for setting the unrestricted operation region in the narrowest region of the set range in the state where the composition determination is completed before the composition determination of the gaseous fuel by the composition determination unit is completed. The control apparatus of the internal combustion engine described in 1. A remaining amount determining means for determining the remaining amount of fuel in the fuel tank;
4. The control device for an internal combustion engine according to claim 1, wherein the setting unit variably sets the determination criterion based on the fuel remaining amount determined by the remaining amount determining unit. 5.   The injection restricting means restricts the amount of air taken into the internal combustion engine when the operating state determining means determines that the fuel injection for the required amount by the gaseous fuel injection valve is not possible. 5. The control device for an internal combustion engine according to claim 1, wherein the fuel injection is restricted by the gaseous fuel injection valve. Applied to a fuel injection system comprising a liquid fuel injection valve (22) for injecting liquid fuel;
When the fuel injection restriction by the gaseous fuel injection valve is performed by the injection restriction means, in addition to or in place of the fuel injection by the gaseous fuel injection valve, the fuel injection by the liquid fuel injection valve is performed. The control device for an internal combustion engine according to any one of claims 1 to 5, further comprising means for performing the operation.

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