WO2014115510A1

WO2014115510A1 - Fuel injection device for internal combustion engine

Info

Publication number: WO2014115510A1
Application number: PCT/JP2014/000172
Authority: WO
Inventors: 優一竹村; 幸敏信田; 和田　実; 溝渕　剛史
Original assignee: 株式会社デンソー
Priority date: 2013-01-25
Filing date: 2014-01-16
Publication date: 2014-07-31
Also published as: JP2014141952A

Abstract

In an engine (10), a gas fuel injection valve (21) is provided for each cylinder group having two cylinders each, said cylinders having a continuous combustion order. A distributor (24) is connected to each gas fuel injection valve (21) for each cylinder group, and a fuel-guiding pipe (23) is connected for each cylinder, to the distributor (24). Gas fuel injected from the gas fuel injection valves (21) is ejected to each intake section in the same cylinder group, via the distributor (24) and the fuel-guiding pipe (23). A control unit (60) calculates the amount of gas fuel required for two cylinders in the same cylinder group, and controls fuel injection by the gas fuel injection valves (21), for each cylinder group and on the basis of the amount required.

Description

Fuel injection device for internal combustion engine

Cross-reference of related applications

This disclosure is based on Japanese Application No. 2013-012088 filed on January 25, 2013, the contents of which are incorporated herein by reference.

The present disclosure relates to a fuel injection device for an internal combustion engine.

Conventionally, an internal combustion engine in which gas fuel such as compressed natural gas (CNG) is combusted has been put into practical use. In addition, in an internal combustion engine, a technique is known in which fuel is supplied to each cylinder using a smaller number of fuel injection valves than the number of cylinders in order to simplify the configuration. For example, in Patent Document 1, three cylinder groups each having a phase shift of 240 ° CA in a 6-cylinder engine are individually coupled by an intake manifold, and fuel injection by a fuel injection valve is performed for each intake manifold.

However, in a configuration that uses a smaller number of fuel injection valves than the number of cylinders, the transient response may be low. In addition, since the fuel of a plurality of cylinders is injected at the same time, there is a difference in mixing characteristics between the fuel and air for each cylinder, which may cause variations in combustion within the cylinder. For example, when using gas fuel, it is difficult for gas fuel to mix with air, and the combustion variation based on the difference in mixing property becomes remarkable.

JP-A-54-152712

An object of the present disclosure is to provide a fuel injection device for an internal combustion engine capable of realizing optimization of combustion in the internal combustion engine while simplifying the configuration.

A fuel injection device for an internal combustion engine according to a first aspect of the present disclosure is applied to an internal combustion engine having an even number of cylinders in which gas fuel is subjected to combustion, and the combustion order is continuous in the internal combustion engine. A gas fuel injection valve that is provided for each cylinder group of two cylinders that injects the gas fuel into the cylinder group, a first end connected to the gas fuel injection valve, and the same cylinder group A second end connected to an intake portion of each cylinder, and a distribution portion for distributing and discharging the gas fuel injected from the gas fuel injection valve to each intake portion of the same cylinder group, and the same cylinder group An injection control unit that calculates a required amount of gas fuel for two cylinders in the engine and controls fuel injection by the gas fuel injection valve for each cylinder group based on the required amount.

In the above configuration, when gas fuel is injected from the gas fuel injection valve, the gas fuel is discharged to the intake portions of the respective cylinders belonging to the same cylinder group via the distribution portion. In the intake stroke of each cylinder, gas fuel flows into the cylinder and is used for combustion. In this case, since one gas fuel injection valve is provided for two cylinders, the configuration can be simplified.

Also, the two cylinders belonging to the same cylinder group have a continuous combustion order, and the intake strokes are continuous in these two cylinders. Therefore, in the configuration in which the gas fuel for two cylinders is collectively injected by the gas fuel injection valve, it is possible to reduce the intake delay that occurs before the cylinder flows after the fuel injection. For example, in a situation where an increase in fuel is required due to acceleration transients, even if the increase in required amount is insufficient in the post-combustion cylinder after the combustion order, the influence of the insufficient amount can be reduced.

In addition, since the intake strokes of two cylinders belonging to the same cylinder group are continuously gathered, the non-intake stroke period (duration) in which both the cylinders do not become the intake stroke becomes long, and the gas fuel injection period is secured. Is easy. In particular, in the case of gas fuel, the volume of the injected fuel is larger than that of the liquid fuel, and the injection period becomes longer, so that the injection period can be easily secured. Furthermore, it is possible to suppress a difference in mixing performance between the gas fuel and the air for the two cylinders belonging to the same cylinder group, thereby suppressing variations in combustion. As described above, it is possible to achieve appropriate combustion in the internal combustion engine while simplifying the configuration.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.
It is the schematic which shows the structure of the fuel injection system of an engine, It is a time chart showing the relationship between the stroke order of each cylinder and the injection timing of gas fuel, In the comparative example is a time chart showing the relationship between the stroke order of each cylinder and the injection timing of gas fuel, It is a flowchart showing a procedure of injection control processing of gas fuel, It is a time chart for explaining injection control of gas fuel more concretely.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

Hereinafter, an embodiment embodying the present disclosure will be described with reference to the drawings. In this embodiment, compressed natural gas (CNG) as a gas fuel and gasoline as a liquid fuel are used as combustion fuels, and a bi-fuel type on-vehicle multi-cylinder engine (multi-cylinder internal combustion engine) corresponding to a multi-cylinder internal combustion engine is used. The fuel injection system is applied to the engine). An overall schematic diagram of the fuel injection system is shown in FIG.

The engine 10 shown in FIG. 1 is an in-line four-cylinder spark ignition engine, and the first cylinder (# 1), the second cylinder (# 2), the third cylinder (# 3), and the fourth cylinder (# 4). An intake system 11 and an exhaust system 12 are connected to an intake port and an exhaust port of the engine 10, respectively. The intake system 11 has an intake manifold 13 and an intake pipe 14. The intake manifold 13 has a plurality of first branch pipe portions 13 a connected to the intake port of the engine 10 and a first main pipe portion 13 b connected to the intake pipe 14 on the upstream side. In this case, the number of the first branch pipe portions 13a is the number of cylinders of the engine 10. The first branch pipe portion 13a corresponds to an intake portion. The intake pipe 14 is provided with a throttle valve 15 as an air amount adjusting unit. The throttle valve 15 is configured as an electronically controlled throttle valve whose opening is adjusted by a throttle actuator 15a such as a DC motor, and the opening of the throttle valve 15 is detected by a throttle opening sensor 15b built in the throttle actuator 15a. Is done. In this case, the opening degree of the throttle valve 15 is the throttle opening degree.

Further, the exhaust system 12 has an exhaust manifold 16 and an exhaust pipe 17. The exhaust manifold 16 has a plurality of second branch pipe portions 16 a connected to the exhaust port of the engine 10 and a second main pipe portion 16 b connected to the exhaust pipe 17 on the downstream side thereof. In this case, the number of the second branch pipe portions 16a is the number of cylinders of the engine 10. The exhaust pipe 17 is provided with an exhaust sensor 18 for detecting exhaust components and a catalyst 19 for purifying exhaust. Specifically, the exhaust sensor 18 may be an air-fuel ratio sensor that detects the air-fuel ratio from the oxygen concentration in the exhaust gas.

Each cylinder of the engine 10 is provided with a spark plug (not shown). A high voltage is applied to the ignition plug at a desired ignition timing through an ignition device 20 including an ignition coil. By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug, and the fuel introduced into the cylinder or the combustion chamber is ignited and burned.

Further, the fuel injection system includes a gas fuel injection valve 21 that injects gas fuel and a liquid fuel injection valve 22 that injects liquid fuel as fuel injection units that inject and supply fuel to the engine 10. . Each of these

injection valves

21 and 22 injects fuel into the first branch pipe portion 13a of the intake manifold 13 in the intake system 11, and the gas fuel is injected into the intake port of each cylinder by the injection of the gas fuel injection valve 21. The liquid fuel is supplied to the intake port of each cylinder by the injection of the liquid fuel injection valve 22.

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, and the valve opening drive input from the control unit 60. Each valve is driven to open by a signal. These

injection valves

21 and 22 are opened by energization and closed by energization interruption. An amount of fuel (gas fuel, liquid fuel) corresponding to the energization time is injected from each of the

injection valves

21 and 22. In this embodiment, a fuel conduit 23 is connected to the distal end side of the gas fuel injection valve 21, and the gas fuel injected from the gas fuel injection valve 21 passes through the fuel conduit 23 to the first of the intake manifold 13. It is discharged to the branch pipe part 13a.

Next, the configuration of the gas fuel supply unit 40 that supplies gas fuel to the gas fuel injection valve 21 and the configuration of the liquid fuel supply unit 50 that supplies liquid fuel to the liquid fuel injection valve 22 will be described.

In the gas fuel supply unit 40, a gas tank 42 is connected to the gas fuel injection valve 21 via a gas pipe 41, and the pressure of the gas fuel supplied to the gas fuel injection valve 21 is in the middle of the gas pipe 41. There is provided a regulator 43 having a pressure adjusting function for adjusting the pressure under pressure. Specifically, the regulator 43 converts the gas fuel stored in the gas tank 42 in a high pressure state (for example, a maximum of 20 MPa) to a predetermined set pressure (for example, 0.2 to 1.0 MPa) that is the injection pressure of the gas fuel injection valve 21. The gas fuel after the pressure reduction adjustment is supplied to the gas fuel injection valve 21 through the gas pipe 41. In the gas piping 41, the upstream side of the regulator 43 is a high-pressure piping portion 41a that forms a high-pressure passage, and the downstream side is a low-pressure piping portion 41b that forms a low-pressure passage.

A gas fuel passage formed by the gas pipe 41 and the like further includes a tank main stop valve 44 corresponding to a tank outlet valve disposed near the fuel outlet of the gas tank 42 and a downstream side of the tank main stop valve 44. And a shutoff valve 45 disposed in the vicinity of the fuel inlet of the regulator 43. The

valves

44, 45 allow and shut off the flow of gas fuel in the gas pipe 41. For example, the tank main stop valve 44 and the shutoff valve 45 are both electromagnetic on-off valves, and are normally closed so that the flow of gas fuel is cut off when not energized and the flow of gas fuel is allowed when energized. Yes.

In the gas pipe 41, a first pressure sensor 46 for detecting the fuel pressure and a first temperature sensor 47 for detecting the fuel temperature are provided in the high pressure pipe 41a, and a first pressure sensor 47 for detecting the fuel pressure is provided in the low pressure pipe 41b. A two-pressure sensor 48 and a second temperature sensor 49 for detecting the fuel temperature are provided.

The shut-off valve 45 and the first pressure sensor 46 can be provided integrally with the regulator 43. In this embodiment, a configuration in which the shut-off valve 45 and the first pressure sensor 46 are provided integrally with the regulator 43 is employed. To do.

In the liquid fuel supply unit 50, a fuel tank 52 is connected to the liquid fuel injection valve 22 via a fuel pipe 51. The fuel pipe 51 is provided with a fuel pump 53 that feeds the liquid fuel in the fuel tank 52 to the liquid fuel injection valve 22.

The control unit 60 includes a CPU 61, a ROM 62, a RAM 63, a backup RAM (BK RAM) 64, an interface 65, and a bidirectional bus 66. The CPU 61, ROM 62, RAM 63, backup RAM 64, and interface 65 are connected to each other by a bidirectional bus 66. The control unit 60 corresponds to an injection control unit or a transient determination unit.

The CPU 61 executes a routine (program) for controlling the operation of each part in the fuel injection system. The ROM 62 stores in advance various types of data such as a routine executed by the CPU 61 and maps, parameters, and the like referred to when the routine is executed. In this case, the map includes a table, a relational expression, and the like. The RAM 63 temporarily stores data as necessary when the CPU 61 executes the routine. The backup RAM 64 appropriately stores data under the control of the CPU 61 in a state where the power is turned on, and retains the stored data even after the power is shut off.

The interface 65 is electrically connected to sensors provided in the fuel injection system, including the throttle opening sensor 15b, the exhaust sensor 18, the

pressure sensors

46 and 48, and the

temperature sensors

47 and 49 described above. In this case, these sensors include a crank angle sensor, an air flow meter, a coolant temperature sensor, a vehicle speed sensor, and the like. An output corresponding to detection signals from these sensors is transmitted to the CPU 61. The interface 65 is electrically connected to driving units such as the throttle actuator 15a, the ignition device 20, the

injection valves

21 and 22, the tank main stop valve 44, the shutoff valve 45, and the like, and drives these driving units. Therefore, the drive signal sent from the CPU 61 is output toward the drive unit. That is, the control unit 60 acquires an operating state based on the output signal of the above-described sensor and controls the above-described driving unit based on this operating state.

By the way, in the configuration in which the gas fuel is supplied to the intake portion by using a smaller number of gas fuel injection valves 21 than the number of cylinders of the engine 10 as in this embodiment, there is a possibility that a response delay may occur in terms of transient response. is there. In other words, when gas fuel for multiple cylinders is injected all at once, if a transient change occurs before the next injection timing arrives, fuel increase according to the transient change cannot be performed immediately, and the response to the transient request is delayed. Sometimes. In this regard, in this embodiment, all the cylinders (# 1 to # 4) of the engine 10 are grouped into two cylinders having consecutive combustion orders (strokes), and the same is applied to the two cylinders. Gas fuel is injected from each gas fuel injection valve 21. This suppresses a delay in response to the transient request.

Specifically, when the combustion order of the engine 10 is # 1 → # 3 → # 4 → # 2, the four cylinders are designated as “# 1 and # 2” and “# 3 and # 2”. 4 ”and the second cylinder group, the fuel injection is performed from one gas fuel injection valve 21 to the first cylinder group, and another gas fuel injection is performed to the second cylinder group. Fuel injection is performed from the valve 21. In this case, as shown in FIG. 1, a distributor 24 is connected to each of the two gas fuel injection valves 21, and a fuel conduit 23 for the first cylinder group is connected to one distributor 24. A fuel conduit 23 for the second cylinder group is connected to one distributor 24. In each cylinder group, the distributor 24 and the fuel conduit 23 for two cylinders correspond to a distributor, and each distributor branches the gas fuel injected from the gas fuel injection valve 21 to each first branch corresponding to the same cylinder group. It is distributed and discharged to the tube portion 13a.

FIG. 2 is a time chart showing the relationship between the stroke order in each cylinder of the engine 10 and the injection timing of the gas fuel.

2, TX1 is the fuel injection timing of the gas fuel injection valve 21 for the first cylinder group, and TX2 is the fuel injection timing of the gas fuel injection valve 21 for the second cylinder group. In this case, for the first cylinder group, gas fuel is injected from the gas fuel injection valve 21 in the # 2 expansion stroke and exhaust stroke corresponding to the pre-combustion cylinder in which the combustion order comes first, and then # 2 The gas fuel is sucked into each of the cylinders (# 2, # 1) in the intake stroke of # 1 and the intake stroke of # 1 corresponding to the post-combustion cylinder. The delay time corresponding to the intake delay from the fuel injection by the gas fuel injection valve 21 to the fuel intake in each cylinder is TXd2 in # 2, and TXd1 in # 1.

The fuel injection timing is determined based on the injection end timing. Specifically, a predetermined timing or a predetermined crank angle position in the exhaust stroke of # 2 which is the previous combustion cylinder in the first cylinder group is determined as the injection end timing, and the injection is performed based on the required injection amount at each time. The injection start timing ahead of the end timing is determined.

For the second cylinder group, gas fuel is injected from the gas fuel injection valve 21 in the expansion stroke and exhaust stroke of # 3 corresponding to the pre-combustion cylinder in which the combustion order comes first, and then the # 3 In the intake stroke of # 4 corresponding to the intake stroke and the post-combustion cylinder, gas fuel is sucked into each of the cylinders (# 3, # 4). The delay time corresponding to the intake delay from the fuel injection by the gas fuel injection valve 21 to the fuel intake in each cylinder is TXd3 in # 3 and TXd4 in # 4.

In FIG. 2, the fuel injection of the gas fuel injection valve 21 is performed so that the fuel injection is completed in the exhaust stroke of the pre-combustion cylinders (# 2, # 3) in each cylinder group. In each cylinder group, the fuel injection of the gas fuel injection valve 21 may be performed so that the fuel injection ends in the first half of the intake stroke of the pre-combustion cylinders (# 2, # 3). In other words, when fuel injection is performed for each cylinder group, the gas fuel may flow into the cylinder reliably in the intake stroke of the pre-combustion cylinder.

For comparison with FIG. 2, FIG. 3 shows a case in which the combustion order is divided into two cylinder groups each having two cylinders, and gas fuel is injected from the same gas fuel injection valve 21 to each cylinder group. Show. Specifically, the four cylinders are divided into a two-cylinder group including a third cylinder group “# 1 and # 4” and a fourth cylinder group “# 2 and # 3”. In FIG. 3, TY1 is the fuel injection timing for the third cylinder group, and TY2 is the fuel injection timing for the fourth cylinder group. In this case, for the third cylinder group, gas fuel is injected from the gas fuel injection valve 21 in the # 1 expansion stroke and exhaust stroke, and in the subsequent # 1 intake stroke and # 4 intake stroke, respectively. Gas fuel is sucked into the cylinders (# 1, # 4). Since the fuel injection timing TY1 also reaches the intake stroke of # 4, it is assumed that a part of the injected fuel is sucked into # 4 before the intake stroke of # 1. The delay time corresponding to the intake delay from the fuel injection by the gas fuel injection valve 21 to the fuel intake in each cylinder is TYd1 for # 1, and TYd4 for # 4.

For the fourth cylinder group, gas fuel is injected from the gas fuel injection valve 21 in the expansion stroke and exhaust stroke of # 2, and each of the cylinders in the subsequent intake stroke of # 2 and intake stroke of # 3. Gas fuel is sucked into (# 2, # 3). The delay time corresponding to the intake delay from the fuel injection by the gas fuel injection valve 21 to the fuel intake in each cylinder is TYd2 for # 2, and TYd3 for # 3.

Here, in FIG. 2, the longest intake delay is TXd1 and TXd4, and in FIG. 3, the longest intake delay is TYd3 and TYd4. Comparing the case of FIG. 2 and the case of FIG. 3, the case of FIG. 2 has a shorter intake air delay and is superior in transient response. That is, in the case of FIG. 2, each cylinder belonging to the same cylinder group has a continuous intake stroke, and therefore it is possible to shorten the intake delay.

In the case of FIG. 2 described above, since the intake air delay is short, the time during which the gas fuel injected from the gas fuel injection valve 21 stays in the fuel conduit 23 is short, and the gas fuel injection valve 21 The gas fuel injected from the fuel flows into each cylinder at an early stage. That is, it is difficult for gas fuel to flow out from the fuel conduit 23 to other parts or spaces, resulting in a problem that the air-fuel ratio is disturbed.

On the other hand, at the time of acceleration acceleration of the vehicle, there is a risk that fuel shortage may occur in the cylinders in the same cylinder group whose combustion order is later, as the engine load increases. Therefore, during acceleration transition, the fuel shortage of the subsequent cylinder is predicted from the change in the intake air amount, and additional fuel injection is performed as necessary, so that the fuel shortage during the transition is resolved.

FIG. 4 is a flowchart showing the procedure of the gas fuel injection control process, and this process is repeatedly performed by the control unit 60 at predetermined time intervals or at predetermined crank angles.

4, in S11, the control unit 60 calculates the intake air amount and the engine rotation speed (NE) from the detection values of the air flow meter and the crank angle sensor. In subsequent S12, the control unit 60 calculates the required injection amount based on the intake air amount and the engine speed. At this time, the control unit 60 calculates the fuel amount for the two cylinders as the required injection amount by combining the first cylinder group and “the second cylinder group. After that, in S13, the control unit 60 now calculates the required injection amount. In this embodiment, the fuel injection corresponds to the first injection, and in this embodiment, from the expansion stroke of the pre-combustion cylinder among the two cylinders of the same cylinder group. The set timing of the first injection is determined so that the fuel injection corresponding to the required injection amount can be performed during the exhaust stroke, and the set timing of the first injection corresponds to the first timing.

If the determination in S13 is YES, the control unit 60 proceeds to S14 and sets the injection pulse of the gas fuel injection valve 21 for injecting the required injection amount. In this case, the injection pulse of the gas fuel injection valve 21 corresponds to the injection pulse of the first injection. Further, the injection pulse is set so that the first injection is completed in the first half of the exhaust stroke or the intake stroke of the pre-combustion cylinder. S14 corresponds to the first control unit.

When the determination in S13 is NO, the control unit 60 proceeds to S15, and determines whether or not the present time is the fuel injection based on acceleration transient (set timing of the fuel injection in this case. The fuel injection in this case is the second injection. In this embodiment, of the two cylinders in the same cylinder group, the period from the exhaust stroke of the rear combustion cylinder to the first half of the intake stroke or the second half of the intake stroke of the pre-combustion cylinder to the first half of the intake stroke of the rear combustion cylinder, The set timing of the second injection is determined so that the additional fuel injection can be performed, and the set timing of the second injection corresponds to the second timing.

If the determination in S15 is YES, the control unit 60 proceeds to S16 and determines whether or not the current state is an acceleration transient state. The determination of acceleration transient is made based on the change amount of the intake air amount from the set timing of the first injection to the set timing of the second injection. If the change amount is equal to or greater than a predetermined amount, the acceleration transient state is indicated. Determine.

If the determination in S16 is YES, the control unit 60 proceeds to S17 and calculates an additional fuel amount corresponding to the increase in the intake air amount. At this time, it is also possible to take into account the amount of change in the engine speed. In subsequent S18, the injection pulse of the gas fuel injection valve 21 for injecting the additional fuel amount is set. In this case, the injection pulse of the gas fuel injection valve 21 corresponds to the injection pulse of the second injection. Further, the injection pulse is set so that the second injection is completed in the first half of the exhaust stroke or the intake stroke of the post-combustion cylinder. S17 and S18 correspond to a second control unit.

Further, if the determination in S15 or S16 is NO, the control unit 60 ends this process as it is without performing S17 and S18. In other words, based on the engine operating state, a state in which only the first injection among the first injection and the second injection is performed and a state in which both the injections are performed are switched. In this case, S15 and S16 correspond to a switching unit.

When the second injection is performed based on the acceleration transient, the additional amount of gas fuel injected from the gas fuel injection valve 21 is distributed to the two fuel conduits 23 communicated by the distributor 24, respectively. In this case, since the second injection is performed in the exhaust stroke or the first half of the intake stroke of the post-combustion cylinder of the cylinder group, the post-combustion cylinder immediately enters the cylinder in the intake stroke before, after, or overlaps with the execution of the second injection. However, for the pre-combustion cylinder, additional fuel remains in the fuel conduit 23 and the inflow into the cylinder is carried over next time. Therefore, in S14, when the control unit 60 calculates the fuel amount of the first injection in consideration of the fuel amount of the previous second injection (residual amount in the fuel conduit 23) at the next first injection set timing. Good. For example, the control unit 60 calculates the fuel amount of the first injection by subtracting ½ of the fuel amount of the previous second injection from the required injection amount.

FIG. 5 is a time chart for explaining the injection control of gas fuel more specifically. In FIG. 5, the engine 10 is in a steady operation before the timing ta, and the intake air amount is increased by the acceleration operation that is the accelerator depression operation at the timing ta. As the intake air amount increases, the fuel amount necessary for combustion in each cylinder is increased.

Now, at the timing t1 before the timing ta, the intake amount is Q1, and the first injection which is the injection of the gas fuel for the first cylinder group is performed with the required injection amount based on the intake amount Q1. Thereafter, when an acceleration operation occurs at timing ta, at time t2, which is the set timing of the second injection, an increase in fuel with respect to the previous required injection amount, which is generated due to acceleration transient, is calculated. The second injection is performed. In this case, the timing t2 corresponds to the determination timing of the additional injection. Further, additional injection based on the difference (Q2−Q1) between the intake air amount Q1 at the previous timing t1 and the intake air amount Q2 at the timing t2 is performed.

The first injection based on the required injection amount and the second injection based on the acceleration transient are performed so as to end in the first half of the exhaust stroke or the first half of the intake stroke of the first cylinder group. Specifically, in FIG. 5, the first injection based on the required injection amount is performed so as to end in the exhaust stroke of # 2 which is the pre-combustion cylinder, and the second injection based on the acceleration transient is performed in the post-combustion cylinder. It is carried out so as to end in the first half of a certain # 1 intake stroke.

Thereafter, at timing t3, the first injection, which is the injection of the gas fuel for the first cylinder group, is performed again with the required injection amount based on the intake amount Q3 at that time. Thereafter, at timing t4, second injection, which is additional injection based on the difference (Q4-Q3) between the intake air amount Q3 at the previous timing t3 and the intake air amount Q4 at the timing t4, is performed.

The same processing is performed in the second cylinder group. Specifically, as the injection of gas fuel for the second cylinder group, at timing t11, the first injection, which is the injection of gas fuel, is performed at the required injection amount based on the intake air amount Q11 at that time. Thereafter, at timing t12, the second injection that is the additional injection based on the difference (Q12−Q11) between the intake air amount Q11 at the previous timing t11 and the intake air amount Q12 at the timing t12 is performed.

In the second cylinder group, fuel injection is performed at the same time as the first cylinder group. Specifically, in FIG. 5, the first injection based on the required injection amount is performed so as to end in the exhaust stroke of # 3 which is the pre-combustion cylinder, and the second injection based on the acceleration transient is performed in the post-combustion cylinder. It is executed so as to end in the first half of a certain # 4 intake stroke.

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

A gas fuel injection valve 21 is provided for each cylinder group of two cylinders in which the combustion order is continuous, and the gas fuel injected from the gas fuel injection valve 21 is distributed via a distributor 24 and a distributor corresponding to the fuel conduit 23. It was made to supply to each cylinder of the same cylinder group. Then, the control unit 60 calculates the required amount of gas fuel for two cylinders in the same cylinder group, and controls the fuel injection by the gas fuel injection valve 21 for each cylinder group based on the required amount. In such a configuration, since the fuel injection is performed collectively for the two cylinders by the same gas fuel injection valve 21, the configuration can be simplified.

Also, the two cylinders belonging to the same cylinder group have a continuous combustion order, and the intake strokes are continuous in these two cylinders. Therefore, in the configuration in which the gas fuel for two cylinders is collectively injected by the gas fuel injection valve 21, it is possible to reduce the intake air delay that occurs before the cylinder flows after the fuel injection. For example, in a situation where an increase in fuel is required due to acceleration transients, even if the increase in required amount is insufficient in the post-combustion cylinder after the combustion order, the influence of the insufficient amount can be reduced.

In addition, since the intake strokes of two cylinders belonging to the same cylinder group are continuously gathered, the duration of the non-intake stroke period in which neither of the cylinders is in the intake stroke is lengthened, and the gas fuel injection period is secured. Is easy. In particular, in the case of gas fuel, since the volume of the injected fuel is larger than that of the liquid fuel and the injection period is longer, it is easy to ensure the injection period. Further, it is possible to suppress a difference in mixing performance between the gas fuel and the air for the two cylinders belonging to the same cylinder group, thereby suppressing variation in combustion. As described above, it is possible to achieve proper combustion in the engine 10 while simplifying the configuration.

The first injection which is the fuel injection by the gas fuel injection valve 21 is controlled so that the fuel injection is completed in the first half of the exhaust stroke or the intake stroke of the pre-combustion cylinder among the two cylinders in the same cylinder group. Thereby, the injected fuel for two cylinders sequentially flows into the cylinders in the intake stroke of each cylinder in the same cylinder group that continues after the injection. In this case, in-cylinder inflow can be accelerated with respect to fuel injection, and transient response can be improved.

As the first injection, the fuel injection of the gas fuel injection valve 21 is performed so that the fuel injection is completed in the first half of the exhaust stroke or the intake stroke of the pre-combustion cylinder among the two cylinders in the same cylinder group. The fuel injection of the gas fuel injection valve 21 is performed so that the fuel injection ends in the first half of the exhaust stroke or the intake stroke of the post-combustion cylinder. Thereby, when the request | requirement of fuel increase arises after 1st injection, the fuel injection of a post-combustion cylinder can be implemented suitably, responding to the increase request.

The case where only the first injection is required and the case where both the first and second injections are required can vary depending on the operating state of the engine 10. Since the first injection and the second injection are appropriately performed based on the engine operating state, it is possible to realize appropriate fuel injection control according to the engine operating state.

The fuel injection by the gas fuel injection valve 21 is controlled so that both the first injection and the second injection are performed when it is determined that the state is an acceleration transient state. When acceleration transient occurs, the intake air amount increases with time, and the required amount of fuel in the engine 10 increases accordingly. In such a case, the required amount of fuel increase can be supplemented by the second injection. Thereby, the request | requirement with respect to the acceleration transient of the engine 10 can be respond | corresponded suitably.

(Other examples)
For example, the above embodiment may be modified as follows.

(A) In the above embodiment, when it is determined that the acceleration is transient, the second injection, which is an additional injection that is performed so that the fuel injection is completed in the first half of the exhaust stroke or the intake stroke of the post-combustion cylinder, is performed. However, this may be changed. For example, when the engine operating state is a high load state and the required injection amount of gas fuel is increased, the fuel injection is completed in the exhaust stroke or the first half of the intake stroke of the pre-combustion cylinder. In this case, it may be difficult to perform the first injection which is the first injection. In such a case, as the first injection, an amount of fuel that can be completed in the exhaust stroke or the first half of the intake stroke of the pre-combustion cylinder among the required injection amounts is injected, and then as the second injection. The remaining amount of the requested injection amount is injected.

Further, when a request for enrichment occurs after the first injection, the second injection may be performed. As a request for enrichment, for example, there is a risk of enrichment for removal of adsorbed oxygen in an exhaust purification catalyst.

(B) In the above embodiment, the present disclosure is applied to a bi-fuel engine that uses gas fuel and liquid fuel as combustion fuel. However, the present disclosure is changed to a gas engine that uses only gas fuel. It is also possible to apply.

(C) In the above embodiment, the CNG fuel is used as the gas fuel. However, other gas fuels that are gases in the standard state can be used. For example, methane, ethane, propane, butane, hydrogen, DME, etc. are the main components. The fuel may be used. Further, the liquid fuel is not limited to gasoline fuel, and for example, light oil or the like may be used.

(D) In the above embodiment, an in-line four-cylinder engine is exemplified as a multi-cylinder engine. However, other embodiments can be realized, and the invention is widely applied to engines having an even number of cylinders such as a six-cylinder engine and an eight-cylinder engine. Applicable. In addition to the in-line engine, the present invention can be applied to a V-type engine and a horizontally opposed engine.

Although the present disclosure has been described based on the embodiments, it is understood that the present disclosure is not limited to the embodiments and structures. The present disclosure includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, as well as other combinations and forms including only one element, more or less, are within the scope and spirit of the present disclosure.

Claims

A fuel injection device applied to an internal combustion engine (10) having an even number of cylinders, in which gas fuel is used for combustion,
A gas fuel injection valve (21) that is provided for each cylinder group of two cylinders in which the combustion order continues in the internal combustion engine, and injects the gas fuel into the cylinder group;
Gas injected from the gas fuel injection valve, having a first end connected to the gas fuel injection valve and a second end connected to an intake portion (13a) of each cylinder in the same cylinder group A distribution section (23, 24) for distributing and releasing fuel to each intake section of the same cylinder group;
An injection control unit (60) for calculating a required amount of gas fuel for two cylinders in the same cylinder group and controlling fuel injection by the gas fuel injection valve for each cylinder group based on the required amount;
A fuel injection device for an internal combustion engine.
The injection control unit is configured to perform fuel injection by the gas fuel injection valve so that fuel injection is completed in an exhaust stroke or a first half of an intake stroke of a pre-combustion cylinder that has the first combustion order among the two cylinders in the same cylinder group. The fuel injection device for an internal combustion engine according to claim 1, which controls the engine.
The injection control unit is configured to perform fuel injection by the gas fuel injection valve so that fuel injection ends in an exhaust stroke or a first half of an intake stroke of a pre-combustion cylinder that has a first combustion order among the two cylinders in the same cylinder group. And the second injection for performing the fuel injection by the gas fuel injection valve so that the fuel injection ends in the exhaust stroke or the first half of the intake stroke of the post-combustion cylinder after the combustion order. The fuel injection device for an internal combustion engine according to claim 1 or 2.
The injection control unit is a switching unit that switches between a state in which only the first injection of the first injection and the second injection is performed and a state in which both the injections are performed based on the operating state of the internal combustion engine. The fuel injection device for an internal combustion engine according to claim 3, having 60, S15, S16).
A transient determination unit (60, S16) for determining whether the internal combustion engine is in an acceleration transient state;
The injection control unit performs fuel injection by the gas fuel injection valve so that both the first injection and the second injection are performed when the transient determination unit determines that the state is an acceleration transient state. The fuel injection device for an internal combustion engine according to claim 4 to be controlled.
The injection control unit
A first control unit that calculates a required injection amount based on an operating state of the internal combustion engine at a first timing before the start of the first injection, and implements the first injection based on the required injection amount;
Second control for calculating the additional injection amount based on the difference in the operating state from the first timing at the second timing before the start of the second injection, and performing the second injection based on the additional injection amount. And
The fuel injection device for an internal combustion engine according to claim 5, comprising: