KR20200124603A - Diesel engine for ship - Google Patents

Abstract

The present invention relates to a diesel engine for a ship, which is able to reduce combustion residues which may be generated from using fossil fuel or alternative fuel. According to the present invention, the diesel engine (1) for the ship comprises: a fuel spray valve (30) which has a spray port (31) for spraying fossil fuel and alternative fuel; a fuel pump (41) which transfers a first fuel which is made of one of the fossil fuel and the alternative fuel toward the fuel spray valve (30); a fuel path (L) which reaches from the fuel pump (41) to the spray port (31); injection systems (50, 60) which inject a second fuel, which is made of the other of the fossil fuel and the alternative fuel, to certain positions (P1, P2) in the fuel path (L); and a control unit (92) which controls the injection systems (50, 60). The fuel spray valve (30) sprays the first fuel and the second fuel in a layered shape. The control unit (92) controls the injection systems (50, 60) to allow fuel layers (F1, F2, F3) made of the first fuel and fuel layers (A1, A2) made of the second fuel to be of two or more layers.

Description

Marine diesel engine {DIESEL ENGINE FOR SHIP}

The technology disclosed here relates to a marine diesel engine.

As a method for reducing nitrogen oxides (NOx) contained in exhaust gas of a marine diesel engine, it is widely known to inject a plurality of types of fuel from one fuel injection valve.

For example, the dual fuel injection system disclosed in Patent Document 1 discloses a layered injection of a pilot fuel for ignition consisting of fossil fuels such as heavy oil or diesel A and a main fuel consisting of methanol as an alternative fuel. have.

In the injection system disclosed in Patent Document 1, by injecting the ignition pilot fuel into the main fuel in the fuel injection valve, the ignition pilot fuel and the fuel in a stratified manner of the main fuel can be injected into the combustion chamber. According to the document, the injection amount of the pilot fuel for ignition is increased when the ignition is unstable, and is decreased when the ignition is stable.

Japanese Laid-Open Patent Publication No. Hei 6-159182

By the way, in the configuration described in Patent Document 1, among the fuel layers injected into the combustion chamber, the fuel layer composed of the main fuel and the fuel layer composed of the pilot fuel for ignition both form one layer.

In this case, the main fuel injected subsequent to the ignition pilot fuel is accelerated by combustion by the ignition pilot combustion, but the inventors of the present application have realized that combustion residues may be generated in the main fuel.

That is, the injection amount of the main fuel increases or decreases according to the load of the engine or the like. Even if the injection amount of the pilot fuel for ignition is increased, if the main fuel injected subsequent thereto is not reduced, there is a possibility that combustion residues are generated in the main fuel.

Here, the case where fossil fuel is used as the pilot fuel for ignition and an alternative fuel is used as the main fuel is described as an example. It is also common when used. Depending on the composition of the alternative fuel, since it can also be used as a pilot fuel for ignition, a problem of combustion residues of the main fuel made of fossil fuel may arise.

The technique disclosed herein has been made in view of these points, and its object is to reduce combustion residues that may occur in fossil fuels or alternative fuels.

The technology disclosed here relates to a marine diesel engine. This marine diesel engine includes a cylinder for partitioning a combustion chamber, a fuel injection valve formed to face the combustion chamber and having an injection port for injecting fossil fuel and alternative fuel, and toward the fuel injection valve, the fossil fuel and the substitute A fuel pump for pumping a first fuel consisting of one of the fuels, a fuel path from the fuel pump to the injection port, and a second consisting of the other of the fossil fuel and the alternative fuel at a predetermined position in the fuel path And an injection system for injecting fuel, and a control unit for controlling the injection system, and the fuel injection valve comprises the first fuel pumped by the fuel pump and the second fuel injected by the injection system. Spray in layers in an alternately arranged state.

And, the control unit controls the injection system so that both of the fuel layers made of the first fuel and the fuel layers made of the second fuel among the fuel layers injected from the fuel injection valve are at least two layers. .

Here, "fossil fuel" refers to a general fuel that can be refined from crude oil, such as diesel fuel, effluent oil, and residual oil. On the other hand, "alternative fuel" refers to a fuel that replaces natural petroleum, and refers to a general fuel that can replace petroleum, such as ammonia, biofuel, methanol, and ethanol.

According to this configuration, the injection system injects the second fuel into the fuel path through which the first fuel flows. By injecting the second fuel into the fuel path, for example, the first fuel, the second fuel and the first fuel are sequentially injected from the fuel injection valve in a layered manner.

In this case, one of the first and second fuels is burned as the main fuel that generates power for driving the marine diesel engine, while the other of the first and second fuels is a pilot for igniting the main fuel. It functions as fuel. Here, the control unit controls the injection system so that the fuel layer composed of the first fuel and the fuel layer composed of the second fuel are both two or more layers.

By controlling in this way, for example, the first fuel, the second fuel, the first fuel, the second fuel, and the first fuel are sequentially injected from the fuel injection valve in a layered manner. Here, assuming that the first fuel functions as the main fuel and the second fuel functions as the assist fuel, the first fuel injected following the first second fuel is the first second fuel. It is divided into two: one promoted by combustion and then promoted by the second fuel injected after that. The first fuel to be accelerated combustion can be divided into two, and combustion of each of the two divided first fuels can be promoted by the second fuel divided into two in the same manner as the first fuel. As a result, combustion of the first fuel as the main fuel is promoted more reliably, and it becomes possible to suppress the generation of combustion residues.

This behavior is the same when the first fuel functions as an assist fuel and the second fuel functions as the main fuel. In that case, the second fuel injected subsequent to the first fuel is said to be promoted by combustion by the first fuel and by the second fuel injected thereafter. It will be 2 minutes. Thereby, combustion of the second fuel as the main fuel is promoted more reliably, and it becomes possible to suppress the generation of combustion residues.

Further, the injection system includes a first injection system for injecting the second fuel to a predetermined first injection position in the fuel path, and a second injection system upstream of the first injection position in the fuel path. In the position, it has a second injection system for injecting the second fuel, the fuel injection valve, the first fuel pumped by the fuel pump, the second fuel injected by the first injection system, the A layered liquid comprising a fuel layer in sequence of the first fuel pumped by a fuel pump, the second fuel injected by the second injection system, and the first fuel pumped by the fuel pump, the combustion chamber It may be sprayed inside.

According to this configuration, combustion of the first fuel is promoted more reliably, and it is advantageous in suppressing the generation of combustion residues.

In addition, the control unit, according to the load of the marine diesel engine, the first injection system so that at least a part of the injection period by the first injection system and the injection period by the second injection system overlap. The timing of starting the injection of the second fuel and the timing of starting the injection of the second fuel by the second injection system may be controlled.

According to this configuration, the amount of the first fuel interposed between the second fuel injected by the first injection system and the second fuel injected by the second injection system can be adjusted according to the engine load. . Thereby, it becomes possible to ensure the performance of a marine diesel engine.

In addition, the control unit is located between a fuel layer composed of the second fuel injected by the first injection system and a fuel layer composed of the second fuel injected by the second injection system, and the first The timing at which the first injection system starts injection of the second fuel so that the amount of the fuel layer made of fuel becomes a constant ratio with respect to the injection amount per injection of the first fuel, and the second injection system includes the The timing at which injection of the second fuel is started may be controlled.

According to this configuration, it is advantageous in securing the performance of a marine diesel engine.

In addition, the control unit calculates a predetermined waiting time based on the load of the marine diesel engine, and determines a timing at which the first injection system starts injection of the second fuel by the calculated waiting time. Alternatively, the second injection system may be delayed from the timing at which the injection of the second fuel starts.

According to this configuration, it is advantageous in securing the performance of a marine diesel engine.

In addition, the control unit calculates a predetermined waiting time based on the load of the marine diesel engine, and determines a timing at which the second injection system starts injection of the second fuel by the calculated waiting time. Alternatively, the timing at which the first injection system starts injection of the second fuel may be delayed.

According to this configuration, it is advantageous in securing the performance of a marine diesel engine.

In addition, the control unit, regardless of the load of the marine diesel engine, so that the ratio of the injection amount of the second fuel by the first injection system and the injection amount of the second fuel by the second injection system is constant, The first injection system and the second injection system may be controlled.

According to this configuration, it is advantageous in securing the performance of a marine diesel engine.

As described above, according to the marine diesel engine, it is possible to reduce combustion residues that may occur in fossil fuels or alternative fuels.

1 is a schematic diagram illustrating a configuration of a marine diesel engine.
2 is a schematic diagram illustrating a configuration of a fuel injection device.
3 is a longitudinal cross-sectional view illustrating a combustion chamber of a marine diesel engine.
4 is a diagram illustrating a layered liquid in a fuel path.
5 is a diagram illustrating a timing of injecting a second fuel.
6 is a diagram for describing an amount of the first fuel.
7 is a diagram for describing an injection amount according to an engine load.
Fig. 8 is a view corresponding to Fig. 5 in the first modified example of a marine diesel engine.
9 is a view corresponding to FIG. 6 in the first modification of the marine diesel engine.
Fig. 10 is a view corresponding to Fig. 2 showing a second modified example of the marine diesel engine.
Fig. 11 is a diagram corresponding to Fig. 3 in a second modified example of a marine diesel engine.

Hereinafter, embodiments of the present disclosure will be described based on the drawings. In addition, the following description is an example. 1 is a schematic diagram illustrating a configuration of a marine diesel engine (hereinafter, also simply referred to as "engine 1"). In addition, FIG. 2 is a schematic diagram illustrating the configuration of the fuel injection device 100 in the engine 1, and FIG. 3 is a longitudinal cross-sectional view illustrating the combustion chamber 17 of the engine 1.

The engine 1 is an in-line multi-cylinder diesel engine provided with a plurality of cylinders 16. This engine 1 is configured as a two-stroke one-cycle engine employing a uniflow scavenging system, and is mounted on large-sized ships such as tankers, container ships, and automobile carriers.

The engine 1 mounted on a ship is used as a main engine for propulsion of the ship. That is, the output shaft of the engine 1 is connected to the propeller (not shown) of a ship via a propeller shaft (not shown). When the engine 1 is operated, its output is transmitted to the propeller, and the ship is configured to propel.

In particular, the engine 1 according to the present disclosure is configured as a so-called cross-head type internal combustion engine in order to realize the long stroke. That is, in this engine 1, the piston rod 22 supporting the piston 21 from below and the connecting rod 24 connected to the crankshaft 23 are connected by the crosshead 25.

(1) Main composition

Hereinafter, main parts of the engine 1 will be described.

As shown in Fig. 1, the engine 1 includes a base plate 11 positioned below, a furniture 12 formed on the base 11, and a cylinder formed on the furniture. It has a jacket (13). The base 11, the furniture 12, and the cylinder jacket 13 are fastened by a plurality of tie bolts and nuts extending in the vertical direction. The engine 1 also has a cylinder 16 formed in the cylinder jacket 13, a piston 21 formed in the cylinder 16, and an output shaft that rotates in connection with the reciprocating motion of the piston 21 (e.g. For example, it is provided with a crankshaft 23).

The base plate 11 constitutes the crankcase of the engine 1 and houses the crankshaft 23 and a bearing 26 that supports the crankshaft 23 so that it can rotate freely. The crankshaft 23 is connected to the lower end of the connecting rod 24 via the crank 27.

The furniture 12 houses a pair of guide plates 28, a connecting rod 24, and a cross head 25. Among these, a pair of guide plates 28 is made of a pair of plate-like members formed along the piston shaft direction, and are arranged at intervals in the width direction of the engine 1 (in the left and right directions in FIG. 1). . The connecting rod 24 is disposed between a pair of guide plates 28 with its lower end connected to the crankshaft 23. The upper end of the connecting rod 24 is connected to the lower end of the piston rod 22 via a cross head 25.

Specifically, the cross head 25 is disposed between a pair of guide plates 28 and slides in the vertical direction along each guide plate 28. In other words, the pair of guide plates 28 is configured to guide the sliding of the cross head 25. The cross head 25 is connected to the piston rod 22 and the connecting rod 24 via a cross head pin 29. The cross head pin 29 is connected to the piston rod 22 so as to move up and down integrally, while with respect to the connecting rod 24, the upper end of the connecting rod 24 is set as a point, and the connecting rod 24 is rotated ( It is connected to make it possible.

The cylinder jacket 13 is formed by arranging a cylinder liner 14 as an inner cylinder. Inside the cylinder liner 14, the above-described piston 21 is arranged. The piston 21 reciprocates in the vertical direction along the inner wall of the cylinder liner 14. Moreover, the cylinder cover 15 is fixed to the upper part of the cylinder liner 14. The cylinder cover 15 constitutes the cylinder 16 together with the cylinder liner 14.

Further, the cylinder cover 15 is provided with an exhaust valve 18 operated by a valve device (not shown). The exhaust valve 18 partitions the combustion chamber 17 together with the cylinder 16 constituted by the cylinder liner 14 and the cylinder cover 15 and the front face of the piston 21. The exhaust valve 18 opens and closes between the combustion chamber 17 and the exhaust pipe 19. The exhaust pipe 19 has an exhaust port through the combustion chamber 17, and the exhaust valve 18 is configured to open and close the exhaust port.

Moreover, a fuel injection valve 30 for supplying fuel to the combustion chamber 17 is formed in the cylinder cover 15. As shown in FIGS. 2 and 3, the fuel injection valve 30 is formed in an attitude facing the interior of the combustion chamber 17 and has an injection port 31 for injecting fossil fuels and alternative fuels.

Specifically, the fuel injection valve 30 is disposed in the combustion chamber 17 in an attitude toward the injection port 31, and is composed of a first fuel composed of one of a fossil fuel and an alternative fuel, and the other of a fossil fuel and an alternative fuel. It is possible to inject the formed second fuel in a layered state while alternately arranged.

Here, one of the first and second fuels functions as a main fuel that generates power for the engine 1, and the other of the first and second fuels functions as a pilot fuel for igniting the main fuel. Is done. Therefore, of the first and second fuels, at least one of the pressure and temperature leading to compression ignition is lower in the other functioning as a pilot fuel than in the other functioning as the main fuel.

In the present embodiment, a pattern in which the first fuel functions as a pilot fuel and the second fuel functions as a main fuel is described as an example, but is not limited to this example. As shown in the second modification to be described later, the first fuel may function as the main fuel and the second fuel may function as the pilot fuel.

In addition, in the present embodiment, a pattern using fossil fuel as the first fuel and alternative fuel as the second fuel is described as an example, but is not limited to this example. As shown in the second modification to be described later, an alternative fuel may be used as the first fuel and a fossil fuel may be used as the second fuel.

Specifically, as the first fuel according to the present embodiment, diesel fuel (so-called "diesel oil") as fossil fuel can be used, and as the second fuel according to the embodiment, ammonia as an alternative fuel is used. Can be used. That is, the fossil fuel according to the present embodiment has at least one of the pressure and temperature leading to compression ignition lower than that of the alternative fuel according to the embodiment.

Although it will be described later in detail, the engine 1 according to the present embodiment includes a fuel pump 41 that pressurizes the first fuel to the fuel injection valve 30, and injects the second fuel into the path through which the first fuel is pumped A first injection pump 51 and a second injection pump 61 are provided.

1, the fuel pump 41, the 1st injection pump 51, and the 2nd injection pump 61 are laid out in the vicinity of the cylinder 16, and the internal path 32, the fuel It is fluidly connected to the fuel injection valve 30 via the injection pipe 42, the downstream injection pipe 52, the upstream injection pipe 62, and the like.

Among these, the fuel pump 41 is connected to the fuel injection valve 30 through a fuel path L from the fuel pump 41 to the injection port 31, and is first directed toward the fuel injection valve 30. Pump fuel. This fuel path L consists of a first internal path 32 and a fuel injection pipe 42 (also includes a branch pipe 42a to be described later), and connects the fuel pump 41 and the injection port 31 It is configured as a path. Moreover, the 1st injection pump 51 and the 2nd injection pump 61 are connected with the fuel path L via the downstream injection pipe 52 and the upstream injection pipe 62, respectively, and this The second fuel is injected into the fuel path L.

By configuring in this way, the fuel injection valve 30 uses the first fuel pumped from the fuel pump 41 and the second fuel injected by the first injection pump 51 and the second injection pump 61 as fuel. By the pressure-feeding action of the pump 41, the combustion chamber 17 can be sprayed alternately (that is, layered).

Thus, the fuel injection valve 30 supplies the first fuel and the second fuel to the combustion chamber 17 and causes combustion in the combustion chamber 17. This combustion causes the piston 21 to reciprocate in the vertical direction. At this time, when the exhaust valve 18 is operated to open the combustion chamber 17, the exhaust gas generated by combustion is pushed out to the exhaust pipe 19, and gas is introduced into the combustion chamber 17 from the scavenging port (not shown). do.

Moreover, when the piston 21 reciprocates by combustion, the piston rod 22 reciprocates together with the piston 21 in the vertical direction. Thereby, the crosshead 25 connected to the piston rod 22 reciprocates in the vertical direction. This crosshead 25 allows rotation of the connecting rod 24, and makes the connecting rod 24 rotate with the connection portion with the crosshead 25 as a point. Then, the crank 27 connected to the lower end of the connecting rod 24 cranks, and the crank shaft 23 rotates in accordance with the crank motion. In this way, the crankshaft 23 converts the reciprocating motion of the piston 21 into rotational motion, and rotates the propeller of the ship together with the propeller shaft. Thereby, the ship propels it.

(2) Configuration related to the fuel injection device

Hereinafter, the fuel injection valve 30 and various devices for supplying the first fuel and the second fuel to the fuel injection valve 30 are collectively referred to as a fuel injection device, and the reference numeral ``100'' is given to this, and description Do it. In Fig. 2, an arrow indicated by a solid line indicates the circulation of the first fuel and the second fuel, and the arrow indicated by a broken line indicates the transmission and reception of electric signals.

As shown in FIG. 2, the fuel injection device 100 according to the present embodiment, as a main component, includes a plurality of (three in this embodiment) fuel injection valves 30 and for pumping the first fuel. A pressure feed system 40, an injection system 50, 60 for injecting the second fuel, and a control unit 92 for controlling the pressure feed system 40 and the injection systems 50, 60 are provided.

Among them, the fuel injection valve 30 has an injection port 31 for injecting fossil fuel as a first fuel and an alternative fuel as a second fuel, as described above, and the fuel through the fuel path L It is connected to the pump 41.

On the other hand, the injection systems 50 and 60 are configured to inject the second fuel into predetermined positions P1 and P2 in the fuel path L. In particular, the injection systems 50 and 60 according to the present embodiment include a downstream injection system 50 for injecting a second fuel into a predetermined first injection position P1 in the fuel path L, and a fuel It has an upstream injection system 60 for injecting a second fuel into a second injection position P2 on the upstream side of the first injection position P1 in the path L.

The fuel injection device 100 is another component, as an alternative fuel supply pump 71 for supplying the second fuel to the injection systems 50 and 60, the pressure delivery system 40, and the injection system 50, 60. ), and a detection unit 91 for inputting a detection signal to the control unit 92.

Hereinafter, a fuel injection valve 30, a pressure delivery system 40, a downstream injection system 50, an upstream injection system 60, an alternative fuel supply pump 71, an accumulating part 81, a detection part 91 and The configuration of the control unit 92 will be described in order.

(Fuel injection valve 30)

The plurality of fuel injection valves 30 are injection valves for injecting the first fuel and the second fuel into the combustion chamber 17 in the cylinder 16 in a layered manner, as described above. Each of the fuel injection valves 30 is formed in each cylinder 16 of the engine 1 (in the example shown in FIG. 3, only one is shown for convenience of explanation). Each of these plurality of fuel injection valves 30 is configured in the same manner. Therefore, hereinafter, a configuration related to the fuel injection valve 30 will be described by taking one of the plurality of fuel injection valves 30 as an example.

As shown in FIG. 2, the fuel injection valve 30 is connected to the fuel pump 41 in the pressure delivery system 40 through a fuel injection pipe 42 or the like. In addition, the fuel injection valve 30 is an upstream injection pipe 62 and a downstream injection, respectively, from the first injection pump 51 and the second injection pump 61 in the injection systems 50 and 60 It is connected through a pipe 52 or the like. As shown in FIG. 3, the fuel injection valve 30 includes the first fuel (diesel fuel as fossil fuel) pumped by the fuel pump 41 and the second fuel injected by the downstream injection system 50 ( Ammonia as an alternative fuel), a first fuel pumped by the fuel pump 41 (diesel fuel as a fossil fuel), a second fuel injected by the upstream injection system 60 (ammonia as an alternative fuel), and a fuel Layered liquid 200 including fuel layers F1, A1, F2, A2, F3 sequentially arranged in the order of the first fuel (diesel fuel as fossil fuel) fed by the pump 41 is transferred from the injection port 31 to the combustion chamber ( 17) Spray it inside.

Specifically, as shown in FIG. 2, the fuel injection valve 30 includes the injection port 31 configured as described above, two internal paths 32 and 33 connected to the injection port 31, and two It has check valves 34a and 34b.

One of the two internal paths 32 and 33 is a path mainly for circulating the first fuel, and a branch pipe 42a in the fuel injection pipe 42 and an injection port 31 You are connecting. Hereinafter, one internal path 32 is referred to as "the first internal path 32". In this first internal path 32, an upstream injection pipe 62 in the upstream injection system 60 (specifically, a branch pipe 62a in the upstream injection pipe 62) is checked. It is connected through the valve 34a. The upstream injection pipe 62 extends from the second injection pump 61 and is a pipe through which the second fuel pumped from the second injection pump 61 flows. Accordingly, not only the first fuel but also the second fuel injected from the upstream side injection pipe 62 flows through the first internal path 32.

Further, the first internal path 32 according to the present embodiment, together with the fuel injection pipe 42, constitutes a fuel path L from the fuel pump 41 to the injection port 31. The portion at which the branch pipe 62a is connected to the first internal path 32 indicates a position in which the second fuel is injected by the upstream injection system 60 in the fuel path L. This position is the same as the "second injection position P2" described above.

In addition, the other of the two internal paths 32 and 33 is a path for circulating the second fuel, and the downstream injection pipe 52 in the downstream injection system 50 (specifically By way of example, the branch pipe 52a in the downstream injection pipe 52 and the portion near the injection port 31 in the first internal path 32 are connected. Hereinafter, the downstream injection pipe 52, which is called the other internal path 33 as "the 2nd internal path 33", extends from the 1st injection pump 51, and this 1st injection pump 51 It is a pipe that distributes the second fuel pumped from ). Accordingly, the second fuel that has passed through the downstream injection pipe 52 flows through the second internal path 33.

In addition, the part to which the 2nd internal path 33 is connected with respect to the 1st internal path 32 represents the position in which the 2nd fuel is injected by the downstream injection system 50 in the fuel path L. have. This position is the same as the "first injection position P1" described above. As shown in FIG. 2, the second injection position P2 is formed on the upstream side of the first injection position P1 in the fuel path L. In addition, the "upstream side" referred to here refers to the upstream side in the flow direction of the first fuel. In addition, "the flow direction of the first fuel" refers to a direction from the fuel pump 41 to the injection port 31 through the fuel injection pipe 42 or the like.

One of the two check valves 34a and 34b allows the flow of the second fuel from the upstream side injection system 60 to the first internal path 32, and the second Prevents backflow of fuel. The other check valve 34b is formed at an intermediate portion in the second internal path 33. This other non-return valve 34b allows the flow of the second fuel from the downstream injection system 50 to the first internal path 32 via the second internal path 33, and 2 Prevent backflow of fuel.

(Pressure system (40))

The pressure feeding system 40 is a facility for pressure feeding the first fuel to the fuel injection valve 30. As shown in FIG. 2, the pressure feed system 40 includes a fuel pump 41, a fuel injection pipe 42, and a control valve 45.

The fuel pump 41 is a hydraulic driven pump that pressurizes fuel using the pressure of hydraulic oil. Specifically, the fuel pump 41 is connected to a fuel tank (not shown) in which fossil fuel as a first fuel is stored through a pipe or the like, and receives fuel from this fuel tank. The fuel pump 41 pressurizes the fuel received from the fuel tank to the fuel injection valve 30 via the fuel injection pipe 42. In addition, the pressure feeding action of the fuel pump 41 can also cause the fuel injection valve 30 to perform layered injection of the first fuel and the second fuel.

The fuel injection pipe 42 is a pipe for circulating fuel between the fuel pump 41 and the fuel injection valve 30. For example, as shown in FIG. 2, one end of the fuel injection pipe 42 is connected to the discharge port of the fuel pump 41. Moreover, the branch part 43 is formed in the middle part of the fuel injection pipe 42. The fuel injection pipe 42 is branched into a plurality of branch pipes from the branch portion 43 toward the other end. Specifically, the fuel injection pipe 42 according to the present embodiment is branched from the branch portion 43 into three branch pipes 42a, 42b, and 42c. Among these branch pipes 42a, 42b, 42c, the first branch pipe 42a is connected to the first internal path 32 of one fuel injection valve 30 as shown in FIG. 2. The fuel injection pipe 42 communicates the first internal path 32 in the fuel injection valve 30 with the fuel pump 41 via the branch pipe 42a. Similarly to this, the remaining branch pipes 42b and 42c are connected to different fuel injection valves 30, respectively.

In addition, the configuration in which the branch portion 43 is formed in the middle portion of the fuel injection pipe 42 is not essential. Instead of forming the branching portion 43, a plurality of fuel injection pipes 42 (for example, three) may be used.

The control valve 45 is a valve for controlling the supply of hydraulic oil from the accumulating portion 81 to the fuel pump 41. Specifically, the control valve 45 is constituted by an electric on-off valve such as a solenoid valve, and although not shown, by opening and closing a logic valve driven by the control valve 34, as shown in FIG. 2, It is formed so that the fuel pump 41 and the accumulating part 81 can communicate. The control valve 45 is in an open state during a period in which the first fuel is injected (hereinafter, simply referred to as “injection period”), and supplies the hydraulic oil in the accumulating portion 81 to the fuel pump 41. The fuel pump 41 pressurizes the first fuel to the fuel injection valve 30 using the pressure of the supplied hydraulic oil. On the other hand, the control valve 45 enters a closed state in a period other than the injection period of the first fuel, and stops supply of hydraulic oil from the accumulating portion 81 to the fuel pump 41. Opening and closing of the control valve 45 is controlled by the control unit 92.

(Downstream injection system (50))

As shown in FIG. 2, the downstream injection system 50 is the 1st injection pump 51 mentioned above, the downstream injection pipe 52, the check valve 54, and the 1st control valve 55 Have. The downstream injection system 50 is an example of the "first injection system" in the present embodiment.

The first injection pump 51 is a hydraulic-driven pump that injects a second fuel using the pressure of hydraulic oil. Specifically, the first injection pump 51 receives the alternative fuel from the alternative fuel supply pump 71 via the supply pipe 72 or the like. The first injection pump 51 pressurizes the received alternative fuel as the second fuel. The second fuel pumped from the first injection pump 51 is the same fuel injection valve 30 through the downstream injection pipe 52 and the second internal path 33 in the fuel injection valve 30. It reaches the 1st internal path 32 in. In this way, the 1st injection pump 51 injects the substitute fuel as a 2nd fuel into the 1st injection position P1 of the fuel path L.

The downstream injection pipe 52 is a pipe for circulating the second fuel injected into the fuel path L by the first injection pump 51. For example, as shown in FIG. 2, one end of the downstream injection pipe 52 is connected to the discharge port of the first injection pump 51. Further, a branch portion 53 is formed in the middle portion of the downstream injection pipe 52. The downstream injection pipe 52 is branched from this branch 53 toward the other end into a plurality of branch pipes. Specifically, the downstream injection pipe 52 according to the present embodiment is branched from the branch portion 53 into three branch pipes 52a, 52b, 52c. Among these branch pipes 52a, 52b, 52c, the first branch pipe 52a is connected to the second internal path 33 of one fuel injection valve 30 as shown in FIG. 2. The downstream injection pipe 52 makes the 2nd internal path 33 in this fuel injection valve 30 and the 1st injection pump 51 communicate with the branch pipe 52a. Similarly to this, the remaining branch pipes 52b and 52c are respectively connected to different fuel injection valves 30.

In addition, the configuration in which the branch portion 53 is formed in the middle portion of the downstream injection pipe 52 is not essential. Instead of forming the branch portions 53, a plurality of downstream injection pipes 52 (for example, three) may be used.

The check valve 54 is a valve for regulating the flow direction of the second fuel in the downstream injection pipe 52 in one direction and preventing reverse flow of the second fuel. As shown in FIG. 2, the check valve 54 is formed at an intermediate portion in the downstream injection pipe 52, for example, at a portion between the first injection pump 51 and the branch portion 53. . The check valve 54 allows the flow of the second fuel from the first injection pump 51 to the second internal path 33 via the branch 53 and prevents the reverse flow of the second fuel. prevent.

The first control valve 55 is a valve for controlling the supply of hydraulic oil from the accumulating portion 81 to the first injection pump 51. Specifically, the first control valve 55 is constituted by an electric on-off valve such as a solenoid valve, and as shown in FIG. 2, the first injection pump 51 and the pressure accumulating portion 81 can be communicated with each other. Is formed. The first control valve 55 is a period in which the second fuel pumped from the first injection pump 51 is injected into the fuel path L (hereinafter, referred to as “injection period of the downstream injection system 50”, “ It is opened during the injection period by the downstream injection system 50" or simply referred to as "first injection period"), and the hydraulic oil in the accumulating portion 81 is supplied to the first injection pump 51. The first injection pump 51 pressurizes and injects the second fuel to the first injection position P1 in the fuel path L using the supplied hydraulic oil pressure. On the other hand, the first control valve 55 is in a closed state during periods other than the injection period by the downstream injection system 50, and stops supply of hydraulic oil from the accumulating portion 81 to the first injection pump 51 do. The opening and closing of the first control valve 55 is controlled by the control unit 92.

(Upstream injection system (60))

As shown in FIG. 2, the upstream injection system 60 includes the second injection pump 61 described above, the upstream injection pipe 62, the check valve 64, and the second control valve 65. Have. The upstream injection system 60 is an example of the "second injection system" in the present embodiment.

The second injection pump 61 is a hydraulically driven pump that injects a second fuel using the pressure of the hydraulic oil. Specifically, the second injection pump 61 receives the substitute fuel from the substitute fuel supply pump 71 via the supply pipe 72 or the like. The second injection pump 61 pressurizes the received alternative fuel as the second fuel. The second fuel pumped from the second injection pump 61 reaches the first internal path 32 in the fuel injection valve 30 through the upstream injection pipe 62. In this way, the second injection pump 61 injects the alternative fuel as the second fuel into the second injection position P2 of the fuel path L.

The upstream injection pipe 62 is a pipe for circulating the second fuel injected into the fuel path L by the second injection pump 61. For example, as shown in FIG. 2, one end of the upstream injection pipe 62 is connected to the discharge port of the second injection pump 61. Moreover, the branch part 63 is formed in the middle part of the upstream side injection pipe 62. The upstream injection pipe 62 is branched from the branch portion 63 toward the other end into a plurality of branch pipes. Specifically, the upstream injection pipe 62 according to the present embodiment is branched from the branch portion 63 into three branch pipes 62a, 62b, 62c. Among these branch pipes 62a, 62b, 62c, the first branch pipe 62a is a first internal path of one fuel injection valve 30 via a check valve 34a, as shown in FIG. 32). The upstream injection pipe 62 communicates the first internal path 32 in the fuel injection valve 30 with the second injection pump 61 via the branch pipe 62a. Similarly to this, the remaining branch pipes 62b and 62c are respectively connected to different fuel injection valves 30.

In addition, the configuration in which the branch portion 63 is formed in the middle portion of the upstream injection pipe 62 is not essential. Instead of forming the branch portions 63, a plurality of upstream injection pipes 62 (for example, three) may be used.

The check valve 64 is a valve for regulating the flow direction of the second fuel in the upstream side injection pipe 62 in one direction and preventing reverse flow of the second fuel. As shown in FIG. 2, the check valve 64 is formed at an intermediate portion in the upstream side infusion pipe 62, for example, at a portion between the second infusion pump 61 and the branch portion 63. . The check valve 64 allows the flow of the second fuel from the second injection pump 61 to the first internal path 32 via the branch part 63, and prevents the reverse flow of the second fuel. prevent.

The second control valve 65 is a valve for controlling the supply of hydraulic oil from the accumulating portion 81 to the second injection pump 61. Specifically, the second control valve 65 is constituted by an electric on-off valve such as a solenoid valve, and as shown in FIG. 2, the second injection pump 61 and the pressure accumulating portion 81 can be communicated with each other. Is formed. The second control valve 65 is a period in which the second fuel pumped from the second injection pump 61 is injected into the fuel path L (hereinafter, referred to as ``injection period of the upstream injection system 60'', `` It is opened during the injection period by the upstream injection system 60", or simply referred to as the "second injection period"), and the hydraulic oil in the pressure accumulating part 81 is supplied to the second injection pump 61. The second injection pump 61 pressurizes and injects the second fuel into the second injection position P2 in the fuel path L by using the supplied hydraulic oil pressure. On the other hand, the second control valve 65 is in a closed state during a period other than the injection period by the upstream injection system 60, and stops supply of hydraulic oil from the accumulating portion 81 to the second injection pump 61 do. The opening and closing of the second control valve 65 is controlled by the control unit 92.

(Alternate fuel supply pump 71)

The alternative fuel supply pump 71 is a pump for supplying the substitute fuel injected into the fuel path L as the second fuel to the first injection pump 51 and the second injection pump 61. As shown in FIG. 2, the alternative fuel supply pump 71 is connected so as to be able to communicate with the first injection pump 51 and the second injection pump 61 via a supply pipe 72 or the like.

Specifically, one end of the supply pipe 72 is connected to the alternative fuel supply pump 71, and the other end of the supply pipe 72 is divided into two, and the first injection pump 51 and the second injection pump 61 ). Specifically, the supply pipe 72 is branched into the branch pipes 72a and 72b at the intermediate portion thereof. One of the branch pipes 72a branched from the supply pipe 72 is connected to the first injection pump 51 via a check valve 73a. Among the branches, the other branch pipe 72b is connected to the second infusion pump 61 via a check valve 73b.

The alternative fuel supply pump 71 according to the present embodiment is connected to a tank (not shown) storing an alternative fuel as a second fuel, and the alternative fuel stored in this tank is supplied with branch pipes 72a, 72b. ) And the like to the first injection pump 51 and the second injection pump 61.

The check valve 73a allows flow of the second fuel from the alternative fuel supply pump 71 to the first injection pump 51 and prevents the reverse flow of the second fuel. The check valve 73b allows flow of the second fuel from the alternative fuel supply pump 71 to the second injection pump 61 and prevents the reverse flow of the second fuel.

(Compression unit (81))

The pressure accumulator 81 accumulates hydraulic oil for operating the pressure feeding system 40 and the injection systems 50 and 60, respectively. The pressure storage unit 81 is a hollow structure having a pressure storage chamber capable of storing hydraulic oil, and is connected to the high pressure pump 82 as shown in FIG. 2. The pressure accumulating part 81 stores the hydraulic oil pressure-fed from the high-pressure pump 82 and condenses this. The pressure of the hydraulic oil in the pressure storage unit 81 is adjusted by the amount of hydraulic oil discharged from the high pressure pump 82 to the pressure storage unit 81. The pressure of the hydraulic oil in the accumulating part 81 is the fuel pump 41 in the pressure delivery system 40, the first injection pump 51 in the downstream injection system 50, and the upstream injection. It is shared by the second infusion pump 61 in the system 60.

(Detector (91))

The detection unit 91 detects the crank angle of the engine 1. The detection unit 91 according to the present embodiment detects the rotation angle (so-called "crank angle") of the crank 27 that rotates with the reciprocating motion of the piston 21 in one cycle. At that time, the detection unit 91 detects the rotation angle of the crank 27 from the reference state as a crank angle. In addition, as a reference state of the crank 27, the state of the crank 27 when the piston 21 is located at the bottom dead center or top dead center, etc. are mentioned, for example. The detection unit 91 detects a crank angle that changes with the passage of time, and transmits an electric signal indicating the detected crank angle to the control unit 92 each time.

(Control unit 92)

The control unit 92 includes a control valve 45 of the pressure feed system 40, a first control valve 55 in the downstream injection system 50, and a second control valve of the upstream injection system 60 ( 65) open and close control. Accordingly, the control unit 92 controls the layered injection timing by the fuel injection valve 30, the timing at which the downstream injection system 50 injects the second fuel, and the upstream injection system 60 supplies the second fuel. You can control the timing of injection.

In addition, in this embodiment, the laminar injection timing by the fuel injection valve 30 means the timing of injecting the 1st fuel and the 2nd fuel from the fuel injection valve 30 into the combustion chamber 17 in a layered manner.

In addition, at the timing at which the downstream injection system 50 injects the second fuel, the timing at which the downstream injection system 50 starts injection of the second fuel (hereinafter referred to as ``first layer injection start timing'') and , A timing at which the downstream injection system 50 finishes injection of the second fuel (hereinafter referred to as "first-layer injection completion timing") is included. Similarly, at the timing at which the upstream injection system 60 injects the second fuel, the timing at which the upstream injection system 60 starts injection of the second fuel (hereinafter referred to as ``second injection start timing''). And a timing at which the upstream injection system 60 ends the injection of the second fuel (hereinafter referred to as "second injection end timing").

Specifically, the control unit 92 is constituted by a CPU, a memory, a sequencer, and the like for executing various programs. The control valve (45) of the pressure feed system (40) receives an electric signal from the detection unit (91) and opens at a timing when the crank angle indicated in the received electric signal becomes a predetermined rotation angle. Control the opening and closing of The control unit 92 controls the timing at which the fuel pump 41 operates through the control of the control valve 45. Thereby, the control unit 92 controls the laminar injection timing by the fuel injection valve 30.

In particular, the control unit 92 according to the present embodiment includes two or more fuel layers composed of the first fuel and the fuel layer composed of the second fuel among the fuel injected into the combustion chamber 17 at the layered injection timing. The injection systems 50 and 60 are controlled so as to be.

At this laminar injection timing, the first fuel of a required amount according to the engine load among the first fuels pressurized to the fuel path L by the fuel pump 41 and the fuel path L by the first injection pump 51 The second fuel injected into the first injection position P1 of the fuel pump 41 and the second fuel injected into the second injection position P2 of the fuel path L by the second injection pump 61 It is injected into the combustion chamber 17 from the fuel injection valve 30 in a layered manner by the pressure feeding action of.

As a result, the fuel injection valve 30 according to the present embodiment, as shown in FIG. 3, is the first fuel pumped by the fuel pump 41 and the second fuel injected by the downstream injection system 50 , The first fuel pressurized by the fuel pump 41, the second fuel injected by the upstream injection system 60, and the first fuel pressurized by the fuel pump 41, respectively, in the order of the layered liquids in the combustion chamber. (17) will be sprayed inside. After that, the fuel path L illustrated in FIGS. 2 and 3 is filled with the remaining first fuel without being injected.

In addition, the control unit 92, in a period other than the above-described laminar injection timing of the first fuel and the second fuel, in the fuel path L in a state filled with the first fuel, in particular, in the fuel path L In order to inject the second fuel into each of the first injection position P1 and the second injection position P2, the timing at which the downstream injection system 50 injects the second fuel, and the upstream injection system 60 Controls the timing of injecting the second fuel.

At this time, the control unit 92, according to the load of the engine 1 (hereinafter, simply referred to as "engine load") so that at least a part of the first injection period and the second injection period overlap, the downstream injection system ( 50) The timing at which the injection of the second fuel is started and the timing at which the upstream injection system 60 starts injection of the second fuel are controlled.

(3) Control according to engine load

Hereinafter, among the processing executed by the control unit 92, control according to the engine load will be described in detail. 4 is a diagram illustrating a layered liquid in the fuel path L, and FIG. 5 is a diagram illustrating a timing for injecting a second fuel. Moreover, FIG. 6 is a figure for demonstrating the amount of a 1st fuel, and FIG. 7 is a figure for demonstrating the injection amount according to an engine load.

In this embodiment, by injecting the second fuel into the fuel path L in a state filled with the first fuel, the layered liquid containing at least the first fuel of the third layer and the second fuel of the second layer is the fuel path L ) Is formed within. The "injection port side" in FIG. 4 refers to the injection port 31 side of the fuel injection valve 30, that is, the downstream side in the flow direction of the first fuel in the fuel path L. In addition, the "fuel pump side" in the drawing refers to the fuel pump 41 side of the pressure feeding system 40, that is, the upstream side in the flow direction of the second fuel in the fuel path L. The layered liquid 200 illustrated in FIG. 4 is a plurality of liquid layers arranged from the injection port side toward the fuel pump side, for example, the first liquid layer L1, the second liquid layer L2, and the third liquid layer. It is constituted by (L3), a fourth liquid layer (L4) and a fifth liquid layer (L5).

The first liquid layer L1 is a liquid layer in the lowermost stream of the layered liquid 200. The first liquid layer L1 is a fuel layer made of the first fuel in the present embodiment. Hereinafter, this fuel layer is referred to as "downstream fuel layer" and a reference numeral "F1" is given. The downstream fuel layer F1 is the first fuel layer counted from the injection port side among fuel layers composed of a plurality of (three in the drawing example) first fuels contained in the layered liquid 200, and is the first fuel layer. It consists of a predetermined amount of fuel present in the lowermost stream in the circulation direction. The downstream fuel layer F1 is formed of the first fuel flowing through the fuel path L.

The second liquid layer L2 is a liquid layer immediately upstream of the first liquid layer L1 in the layered liquid 200. The second liquid layer L2 is a fuel layer made of a second fuel in this embodiment. Hereinafter, this fuel layer is referred to as "downstream injection layer" and a reference numeral "A1" is given. The downstream injection layer A1 is the first fuel layer counted from the injection port side among fuel layers made of a plurality of (two in the drawing example) second fuel contained in the layered liquid 200. This downstream injection layer A1 is formed by injecting a required amount of second fuel into the first injection position P1 by the first injection pump 51.

The third liquid layer L3 is a liquid layer immediately upstream of the second liquid layer L2 in the layered liquid 200. The third liquid layer L3 is a fuel layer made of the first fuel in this embodiment. Hereinafter, this fuel layer is referred to as "intermediate fuel layer" and a symbol "F2" is given. The intermediate fuel layer F2 is a second fuel layer counted from the injection port side among fuel layers made of a plurality of first fuels contained in the layered liquid 200. The intermediate fuel layer F2 includes a second fuel injected into the first injection position P1 among the first fuels flowing through the fuel path L and a second fuel injected into the second injection position P2. It consists of the first fuel sandwiched between.

The fourth liquid layer L4 is a liquid layer immediately upstream of the third liquid layer L3 in the layered liquid 200. The fourth liquid layer L4 is a fuel layer made of the second fuel in this embodiment. Hereinafter, this fuel layer is referred to as "upstream injection layer" and a symbol "A2" is given. The upstream injection layer A2 is a second fuel layer counted from the injection port side among fuel layers made of a plurality of second fuels contained in the layered liquid 200. This upstream injection layer A2 is formed by injecting a required amount of second fuel into the second injection position P2 by the second injection pump 61.

The 5th liquid layer L5 is the uppermost liquid layer among the layered liquid 200. The fifth liquid layer L5 is a fuel layer made of the first fuel in this embodiment. Hereinafter, this fuel layer is referred to as "upstream fuel layer" and a symbol "F3" is given. The upstream fuel layer F3 is the third fuel layer counted from the injection port side among the fuel layers made of a plurality of first fuels contained in the layered liquid 200. This upstream fuel layer F3 is made of a first fuel present immediately upstream of the fourth liquid layer L4 among the first fuels flowing through the fuel path L.

The layered liquid 200 composed of the first fuel and the second fuel is injected from the injection port 31 into the combustion chamber 17 for each reciprocating motion of the piston 21 in one cycle. At this time, the injection amount per injection of the first fuel to the combustion chamber 17, that is, the total amount of the first fuel contained in the layered liquid 200 (hereinafter, also referred to simply as the ``first fuel injection amount'') (Qfa) is , The sum of the amount (Qf1) of the downstream fuel layer (F1), the amount (Qf2) of the intermediate fuel layer (F2), and the amount (Qf3) of the upstream fuel layer (F3) (= Qf1 + Qf2 + Qf3) Represented by This first fuel injection amount Qfa increases with the increase of the engine load, and decreases with the decrease.

In addition, in the layered liquid 200, the amount of the first fuel positioned between the downstream and upstream injection layers A1 and A2 made of the second fuel, that is, the first fuel in the intermediate fuel layer F2 The quantity (Qf2) of is the timing at which the downstream injection system 50 starts injection of the second fuel (first layer injection start timing) and the timing at which the upstream injection system 60 starts injection of the second fuel It is controlled through (2nd layer injection start timing). At that time, the amount of the first fuel Qf2 in the intermediate fuel layer F2 can be controlled to be a constant ratio with respect to the first fuel injection amount Qfa determined in accordance with the engine load.

On the other hand, the injection amount per second of the second fuel to the combustion chamber 17, that is, the total amount of the second fuel contained in the layered liquid 200 (hereinafter, also simply referred to as the ``second fuel injection amount'') (Qaa) is, It is represented by the sum (= Qa1 + Qa2) of the injection amount Qa1 of the second fuel in the downstream injection layer A1 and the injection amount Qa2 of the second fuel in the upstream injection layer A2. This second fuel injection amount Qaa increases when it is determined that the ignition of the first fuel is unstable based on the driving state of the engine 1, and decreases when it is determined that the ignition of the first fuel is stable. . At this time, the injection amount Qa1 of the second fuel in the downstream injection layer A1 formed by the downstream injection system 50 and the upstream injection layer formed by the upstream injection system 60 ( It is preferable that the ratio of the injection amount Qa2 of the second fuel in A2) is constant.

Next, the control for adjusting the amount Qf2 of the first fuel in the intermediate fuel layer F2 will be described in detail with reference to FIGS. 5 and 6. In FIG. 5, the first control signal S1 is a control signal for opening and closing the first control valve 55 related to the first injection pump 51. The second control signal S2 is a control signal for opening and closing the second control valve 65 related to the second injection pump 61. Reference numeral "201" in FIG. 6 denotes a columnar first fuel remaining in the fuel path L.

As described above, the control unit 92 controls the first layer injection start timing and the second layer injection start timing according to the engine load so that at least a part of the first injection period and the second injection period overlap.

At this time, the control unit 92 is positioned between the downstream injection layer A1 formed by the downstream injection system 50 and the upstream injection layer A2 formed by the upstream injection system 60 The first layer injection so that the amount of the first fuel (the amount of the first fuel in the intermediate fuel layer F2) (Qf2) becomes a constant ratio to the first fuel injection amount Qfa determined according to the engine load. The start timing and the second layer injection start timing can be controlled.

Specifically, the control unit 92 calculates a predetermined waiting time (ΔT) based on the engine load. The waiting time (ΔT) represents a period between the injection start timing of the first layer and the injection start timing of the second layer. This waiting time ΔT is, for example, the engine rotation speed (engine rotation speed per unit time) corresponding to the engine load, the first fuel injection amount (the injection amount per first fuel), and the second fuel injection amount ( The amount of the second fuel injected into the first fuel for one injection) is represented by the following equation (1) by the function f(x, y, z) when the independent variables x, y, and z are respectively used.

ΔT = f(x, y, z) … (One)

For example, the control unit 92 calculates the waiting time ΔT so that the waiting time ΔT increases with the increase of the engine load, and the waiting time ΔT decreases with the decrease of the engine load. . In addition, the function f(x, y, z) can be derived based on, for example, simulation and experimental results of the engine 1. In the control unit 92, equation (1) is previously stored.

The control unit 92 calculates the waiting time ΔT1 of the downstream injection system 50 as the waiting time ΔT based on the equation (1). The control unit 92 delays the injection start timing of the first layer from the injection start timing of the second layer by the amount of this waiting time (ΔT1).

Specifically, the control unit 92 acquires the crank angle appearing in the electric signal received from the detection unit 91 as the crank angle at the time of detection (hereinafter, referred to as “current crank angle”). The control unit 92 outputs an electric signal to the second control valve 65 of the upstream injection system 60 at the timing T1 at which the current crank angle becomes the predetermined first crank angle R1, Make it open. When this second control valve 65 is in an open state, the second injection pump 61 in the upstream injection system 60 starts operation. That is, this timing T1 is the same as the "second layer injection start timing" at which the upstream injection system 60 starts injection of the second fuel. At this second layer injection start timing T1, injection of the second fuel 202 is started to the second injection position P2 in the fuel column 201 as shown in FIG. 6.

In addition, in the period T0 from the end of the previous layer injection to the second layer injection start timing T1, as shown in FIG. 6, the second fuel is not injected into the fuel column 201. not. The amount of fuel in the fuel column 201 at this time corresponds to the above-described first fuel injection amount Qfa.

Next, the control unit 92 performs the injection of the second fuel by the downstream injection system 50 at a timing delayed from the second layer injection start timing T1 by a minute of the waiting time ΔT1 calculated as described above. Start. Specifically, the control unit 92 converts the waiting time ΔT1 of the downstream injection system 50 into a change amount ΔR of the crank angle based on the engine rotation speed and the elapsed time of the engine rotation. The control unit 92 calculates the second crank angle R2 by adding the obtained change amount ΔR of the crank angle and the first crank angle R1 at the time of the second layer injection start timing T1. As shown in FIG. 5, the control unit 92 transmits an electric signal to the first control valve 55 of the downstream injection system 50 at the timing T2 at which the current crank angle becomes the second crank angle R2. Output, and make it open. When the first control valve 55 is in an open state, the operation of the second injection pump 61 continues, and the first injection pump 51 in the downstream injection system 50 starts to operate. That is, this timing T2 is the same as the "first layer injection start timing" at which the downstream injection system 50 starts injection of the second fuel. At this first layer injection start timing T2, as shown in FIG. 6, the second fuel 202 is continuously injected into the second injection position P2 in the fuel column 201, The injection of the second fuel 203 into the first injection position P1 is started.

After that, the second injection pump 61 continues to inject the second fuel into the second injection position P2 for a period until the second control valve 65 is in a closed state. In parallel with this, the first injection pump 51 continues to inject the second fuel into the first injection position P1 during the period until the first control valve 55 is closed.

As illustrated in FIGS. 5 and 6, the period ΔT2 from the second crank angle R2 to the predetermined third crank angle R3 (> R2) is at the second injection position P2. While the injection of the second fuel 202 proceeds, the injection of the second fuel 203 at the first injection position P1 proceeds. With the injection of the second fuel 203 at the first injection position P1, the first fuel located between the first injection position P1 and the second injection position P2 is the second injection position It passes over the second fuel 202 in (P2) and is pushed back to the upstream side in the circulation direction. Thereby, the amount of the first fuel located between the first injection position P1 and the second injection position P2 is adjusted to decrease.

Subsequently, at the timing T3 at which the current crank angle becomes the third crank angle R3, the second fuel 202 at the second injection position P2 is distributed throughout the width direction of the fuel column 201. It is injected until spread. The "width direction" referred to herein is a direction orthogonal to the flow direction of the first fuel, and indicates the width direction of the fuel path L. At this time, the second fuel 202 at the second injection position P2 is a downstream fuel column 201 located on the downstream side from the second injection position P2 as illustrated in FIG. 6. It is divided into a side fuel 201a and an uppermost fuel 201b positioned upstream from the second injection position P2. In this step, the fuel located between the first injection position (P1) and the second injection position (P2) is, even if the injection of the second fuel 203 in the first injection position (P1) proceeds. The second fuel 202 in the second injection position P2 is not pushed back to the upstream side in the circulation direction. Thereby, the adjustment of the amount of the first fuel positioned between the first injection position P1 and the second injection position P2 is ended, and the total amount of the downstream fuel 201a is determined.

Thereafter, as illustrated in FIG. 5, the control unit 92 at the timing T4 at which the current crank angle became a predetermined fourth crank angle R4 (> R3) of the upstream injection system 60 An electric signal is output to the second control valve 65, and this is brought into a closed state. When the second control valve 65 is in a closed state, the second injection pump 61 stops operating while the first injection pump 51 continues to operate. Thereby, the 2nd injection pump 61 finishes the injection of the 2nd fuel to the 2nd injection position P2. That is, the timing T4 at which the current crank angle becomes the fourth crank angle R4 is the same as the "second layer injection end timing" at which the upstream side injection system 60 ends the injection of the second fuel. On the other hand, the first injection pump 51 continues to inject the second fuel into the first injection position P1.

As illustrated in FIGS. 5 and 6, the period ΔT3 from the third crank angle R3 to the fourth crank angle R4 is the second fuel 202 at the second injection position P2. A is further injected while spreading all over the width direction of the fuel column 201, and the injection of the second fuel 203 at the first injection position P1 continues to proceed. In this step, the injection of the second fuel 203 at the first injection position P1 includes the second fuel 202 at the second injection position P2 together with the downstream fuel 201a. It is carried out while pressing it upstream in the circulation direction.

In addition, when the current crank angle becomes the crank angle corresponding to the second injection end timing T4, the required amount of the second fuel 202 at the second injection position P2 is injected. On the other hand, the second fuel 203 at the first injection position P1 is in a state injected until it spreads over the entire width direction of the fuel column 201. The second fuel 203 in this state includes the downstream fuel 201a of the fuel column 201, the most downstream fuel 201c positioned on the downstream side of the first injection position P1, and the first and second fuels. It is divided into the injection-layer fuel 201d fitted to the second fuels 202 and 203 at the two injection positions P1 and P2. Thereby, the total amount of fuel 201d between injection layers, that is, the amount of fuel between injection layers (=Qf2) and the amount of the downstream fuel 201c are determined. In addition, the timing to be injected until the second fuel 203 at the first injection position P1 spreads throughout the width direction of the fuel column 201 is the second fuel at the second injection position P2 202 may be the same as the timing T4 in which the required amount was injected, may be a timing before timing T4, or may be a timing after timing T4.

Thereafter, as illustrated in FIG. 5, the control unit 92 at the timing T5 at which the current crank angle became a predetermined fifth crank angle R5 (> R4), the downstream injection system 50 An electric signal is output to the 1st control valve 55 in this, and this is made into a closed state. When the first control valve 55 is in a closed state, the first injection pump 51 stops operating. Thereby, the 1st injection pump 51 finishes the injection of the 2nd fuel to the 1st injection position P1. That is, the timing T5 at which the current crank angle becomes the fifth crank angle R5 is the same as the "first layer injection end timing" at which the downstream injection system 50 ends the injection of the second fuel.

As illustrated in FIGS. 5 and 6, in the period from the fourth crank angle R4 to the fifth crank angle R5, the second fuel 203 at the first injection position P1 is It is further injected while spreading all over the width direction of the pillar 201. In this step, the injection of the second fuel 203 at the first injection position P1 is carried out in the same manner as the period from the timing T3 to the timing T4 described above, and the second fuel ( 203) is continued until the required amount is reached. And at the timing T5 corresponding to the 5th crank angle R5, the injection of the 2nd fuel at the 1st injection position P1 and the 2nd injection position P2 both ends. As a result, the downstream fuel layer F1 made of the first fuel (especially the downstream fuel 201c), the downstream injection layer A1 made of the second fuel 203, and the first fuel (especially, Intermediate fuel layer F2 made of interlayer fuel 201d, upstream injection layer A2 made of second fuel 202, and upstream made of first fuel (especially, uppermost fuel 201b) A layered liquid 200 in which the fuel layer F3 is arranged from the upstream side in the flow direction is formed in the fuel path L.

Here, in this embodiment, the injection period (second injection period) of the upstream injection system 60 corresponds to the fourth crank angle R4 at the timing T1 corresponding to the first crank angle R1. It is a period until the timing T4 to do. That is, the second injection period is a period obtained by adding the waiting time (ΔT1), the period (ΔT2), and the period (ΔT3) illustrated in FIG. 5. This second injection period is determined by the time required when injecting the required amount of the second fuel 202 into the second injection position P2 shown in FIG. 6. That is, the fourth crank angle R4 corresponding to the second layer injection end timing T4 related to the upstream side injection system 60 is the first crank angle R1 corresponding to the second layer injection start timing T1 and , Is calculated based on the time required for injection of the required amount of the second fuel 202.

In addition, the injection period (first injection period) of the downstream injection system 50 is the timing T5 corresponding to the fifth crank angle R5 at the timing T2 corresponding to the second crank angle R2 It is the period until. This first injection period is determined by the time required when injecting the required amount of the second fuel 203 into the first injection position P1. That is, the fifth crank angle R5 corresponding to the first layer injection end timing T5 related to the downstream injection system 50 is the second crank angle R2 corresponding to the first layer injection start timing T2 and , Calculated based on the time required for injection of the required amount of the second fuel 203.

In this embodiment, the period in which the first injection period and the second injection period overlap is equivalent to the period (ΔT4) from the second crank angle R2 to the fourth crank angle R4, as shown in FIG. 5. do. This period (ΔT4) is a period (ΔT2) in which the amount of the first fuel between injection layers is adjusted to decrease by the downstream injection system 50, and the adjustment of the first fuel between injection layers is finished. Then, it is the time which added the period (ΔT3) until the injection of the upstream injection system 60 is finished. The first level injection start timing by the downstream injection system 50 is the upstream injection system so that the period ΔT2 decreases with an increase in the engine load and the period ΔT2 increases with the decrease in the engine load. It is adjusted to a timing slow by the waiting time ΔT1 from the second layer injection start timing T1 by (60). That is, this waiting time DELTA T1 increases with the increase of the engine load, and decreases with the decrease of the engine load. In addition, when this waiting time (ΔT1) is a zero value (ΔT1 = 0), the first layer injection start timing by the downstream injection system 50 is at the same time as the second layer injection start timing by the upstream injection system 60 Is controlled by the timing of.

Here, the horizontal axis in FIG. 7 represents the engine load, and the vertical axis in the same figure represents the total injection amount per one shot of the layered liquid 200 injected from one fuel injection valve 30 into the combustion chamber 17. . This total injection amount is represented by the sum (= Qfa + Qaa) of the first fuel injection amount Qfa and the second fuel injection amount Qaa according to the engine load.

In the present embodiment, the total injection amount is controlled through the first layer injection start timing by the downstream injection system 50 and the second layer injection start timing by the upstream injection system 60. As illustrated in FIG. 7, the total injection amount of the layered liquid 200 increases with an increase in the engine load and decreases with a decrease in the engine load. At that time, in the layered liquid 200, the amount of the first fuel in the intermediate fuel layer F2 sandwiched between the downstream injection layer A1 and the upstream injection layer A2 (that is, the amount of fuel between injection layers ) Is adjusted to an appropriate amount according to the engine load. Preferably, as illustrated in FIG. 7, the first liquid layer L1 to the fifth liquid layer L5 (that is, the downstream fuel layer F1, the downstream injection layer A1), and the intermediate fuel layer ( In the case where the layered liquid 200 consisting of F2), the upstream injection layer A2 and the upstream fuel layer F3) is formed, the amount of the first fuel between the injection layers (intermediate fuel layer F2 ) Is adjusted (optimized) so that it becomes a constant ratio with respect to the first fuel injection amount Qfa which increases or decreases according to the engine load. Furthermore, in the layered liquid 200, the injection amount Qa1 of the second fuel in the downstream injection layer A1 and the injection amount Qa2 of the second fuel in the upstream injection layer A2 The ratio is constant regardless of the engine load.

(4) Effects exerted by injection of the second fuel

As described above, according to the present embodiment, the injection systems 50 and 60 can inject the second fuel into the fuel path L through which the first fuel flows. By injecting the second fuel into the fuel path L, for example, the first fuel, the second fuel, the first fuel, and the second fuel are sequentially injected in a layered manner.

In this case, the second fuel burns as the main fuel that generates power for driving the engine 1, while the first fuel functions as a pilot fuel for igniting the main fuel. Here, the control unit 92 includes, among the fuel layers injected from the fuel injection valve 30, the fuel layers F1, F2, and F3 made of the first fuel and the fuel layers A1, A3 made of the second fuel. The injection systems 50 and 60 are controlled so that both have two or more layers.

By controlling in this way, as illustrated in FIG. 3, the first fuel, the second fuel, the first fuel, the second fuel, and the first fuel are sequentially injected into the combustion chamber 17 in a layered manner. In this case, the second fuel injected following the first first fuel (the first fuel constituting the downstream fuel layer F1) is burned by the first first fuel, as illustrated in FIG. 6. The combustion is accelerated by the second fuel (the second fuel forming the downstream injection layer A1) and the second fuel injected thereafter (the first fuel forming the intermediate fuel layer F2). It is divided into 2 parts of the used second fuel (the second fuel forming the upstream injection layer A2). The second fuel to be accelerated combustion can be divided into two, and combustion of each second fuel divided into two can be accelerated by the divided first fuel in the same manner as the second fuel. As a result, combustion of the second fuel is promoted more reliably, and it becomes possible to suppress the generation of combustion residues.

In addition, as illustrated in FIG. 7, the downstream injection layer A1 is injected by the downstream injection system 50, and the upstream injection layer A2 is injected by the upstream injection system 60. Thus, the amount of the first fuel Qf2 in the intermediate fuel layer F2 sandwiched between can be adjusted according to the engine load. Thereby, it becomes possible to ensure the performance of the engine 1.

That is, as illustrated in FIG. 5, at least a part of the injection period (first injection period) by the downstream injection system 50 and the injection period (second injection period) by the upstream injection system 60 The timing at which the downstream injection system 50 and the upstream injection system 60 start injection of the second fuel, respectively, is controlled in accordance with the engine load so as to overlap. Thereby, it becomes possible to control so that the ratio of the 1st fuel injection quantity Qfa determined in accordance with the engine load and the fuel quantity Qf2 in the intermediate fuel layer F2 does not become excessive or excessive. Thereby, the operation of the engine 1 can be stabilized, and it becomes possible to ensure its performance.

Further, by using fossil fuel as the first fuel, the pressure feed system 40 can be configured by utilizing a facility for pressure feeding diesel fuel or the like. Thereby, the manufacturing cost of a ship can be suppressed.

(5) Modified example of control according to engine load (first modified example)

In the above embodiment, the control unit 92 calculates the waiting time ΔT1 based on the equation (1), and by the amount of the waiting time ΔT1, the downstream injection system 50 is used as the second fuel. The timing to start injection of the (first layer injection start timing) was configured to be delayed from the timing at which the upstream injection system 60 starts injection of the second fuel (the second layer injection start timing), but this configuration is limited. It doesn't work.

For example, in the modified example shown below (hereinafter referred to as the ``first modified example''), the control unit 92 calculates a predetermined waiting time (ΔT11) based on the engine load and calculates It is comprised so that the second layer injection start timing may be delayed from the first layer injection start timing by the amount of the waiting time ?T11.

FIG. 8 is a view corresponding to FIG. 4 in the first modification example of the engine 1, and FIG. 9 is a view corresponding to FIG. 5 in the first modification example of the engine 1. In the following description, the same names and reference numerals as those in the above embodiment are used for constituent elements configured in the same manner as in the above embodiment. Description of their components is appropriately omitted.

In the control unit 92 in the first modification, the equation (1) set in the same manner as in the above embodiment is stored in advance. The control unit 92 is not, for example, the waiting time ΔT1 of the downstream injection system 50 as in the above embodiment as the waiting time ΔT based on the formula (1), but the upstream injection system 60 ) To calculate the waiting time (ΔT11). This waiting time (ΔT11) is the time from when the downstream injection system 50 starts injection of the second fuel until the upstream injection system 60 starts injection, that is, the first injection pump 51 It is the time from when) starts operation until the second infusion pump 61 starts operation. The control unit 92 controls the timing at which the upstream injection system 60 starts injection of the second fuel by the amount of the waiting time ΔT11 thus calculated, and the downstream injection system 50 controls the second fuel injection. It is later than the timing to start the injection.

Specifically, the control unit 92, based on the detection result by the detection unit 91, at the timing T11 at which the current crank angle became the first crank angle R11, in the downstream injection system 50 An electric signal is input to the first control valve 55 of, and it is set to an open state. Thereby, the 1st injection pump 51 starts injection of the 2nd fuel to the 1st injection position P1 in the fuel path L. That is, the timing T11 corresponding to the first crank angle R11 is the first layer injection start timing in the downstream injection system 50. At this timing T11, injection of the second fuel 203 into the first injection position P1 of the fuel pillars 201 in the fuel path L is started as illustrated in FIG. 9. With the start of injection of the second fuel 203 into this first injection position P1, the first fuel located between the first injection position P1 and the second injection position P2 is the second injection position It goes over (P2) and begins to be pushed back to the upstream side in the circulation direction. Thereby, the amount of fuel located between the first injection position P1 and the second injection position P2 starts to be adjusted to decrease.

In addition, in the period T0 from the end of the previous layer injection to the first layer injection start timing T1, the second fuel is injected into the fuel column 201 as illustrated in FIG. 9. Not. The amount of fuel in the fuel column 201 at this time corresponds to the above-described first fuel injection amount Qfa.

Next, the control unit 92 performs the injection of the second fuel by the upstream injection system 60 at a timing delayed from the first layer injection start timing T11 by a minute of the waiting time ΔT11 calculated as described above. Start. Specifically, the control unit 92 converts the waiting time ΔT11 of the upstream injection system 60 into a change amount ΔR of the crank angle based on the engine speed and the elapsed time of the engine rotation. The control unit 92 calculates the second crank angle R12 by adding the obtained crank angle change amount ΔR and the first crank angle R11 at the time of the first layer injection start timing T11. As shown in FIG. 8, the control unit 92 transmits an electric signal to the second control valve 65 of the upstream injection system 60 at the timing T12 at which the current crank angle becomes the second crank angle R12. Output, and make it open. When the second control valve 65 is in an open state, the operation of the first injection pump 51 continues, and the second injection pump 61 in the upstream injection system 60 starts to operate. . That is, this timing T12 is the same as the "second layer injection start timing" at which the upstream injection system 60 starts injection of the second fuel. At this second layer injection start timing T12, as shown in FIG. 9, the second fuel 203 is continuously injected into the first injection position P1 in the fuel column 201, The injection of the second fuel 202 into the second injection position P2 is started.

Thereafter, the first injection pump 51 continues to inject the second fuel into the first injection position P1 during the period until the first control valve 55 is in the closed state. In parallel with this, the second injection pump 61 continues to inject the second fuel into the second injection position P2 during the period until the second control valve 65 is in the closed state.

As illustrated in FIGS. 8 and 9, the period (ΔT13) from the first crank angle R11 to the predetermined crank angle Ra (> R12) is the second in the first injection position P1. The fuel 203 is injected. In addition, during this period (ΔT13), during the peak of the period (ΔTa) from the second crank angle R2 to the crank angle Ra, the injection of the second fuel 203 at the first injection position P1 While this progresses, the injection of the second fuel 202 at the second injection position P2 proceeds. With the injection of the second fuel 203 at this first injection position P1, the first fuel located between the first injection position P1 and the second injection position P2 is the second injection It passes over the second fuel 202 in the position P2 and is pushed back to the upstream side in the circulation direction. Thereby, the amount of the first fuel located between the first injection position P1 and the second injection position P2 is adjusted to decrease at the height of the period ΔT13.

In addition, during this period (ΔT13), at the timing T13 corresponding to the predetermined third crank angle R13, the second fuel 203 at the first injection position P1 is the fuel column 201 It is injected until it spreads all over the width direction of. At this time, the second fuel 203 at the first injection position P1 is the fuel column 201 in the fuel path L as illustrated in FIG. 9, and the first injection position P1 ), and an upstream fuel 201e located on the upstream side of the first injection position P1. In this step, the total amount of the first fuel constituting the downstream fuel 201c is determined. In addition, in the period from the third crank angle R13 to the predetermined fourth crank angle R14 (> R13), the second fuel 203 at the first injection position P1 is the fuel column ( The second fuel 202 at the second injection position P2 is continuously injected while being further injected while spreading all over the width direction of 201). In this step, the injection of the second fuel 203 at the first injection position P1 includes the first fuel located between the first injection position P1 and the second injection position P2. 2 It is carried out while pushing it back from the injection position P2 to the upstream side in the circulation direction.

On the other hand, at the timing corresponding to the crank angle Ra, the second fuel 202 at the second injection position P2 is injected until it spreads all over the width direction of the fuel pillar 201. At this time, the second fuel 202 at the second injection position P2 is the upstream fuel 201e among the fuel pillars 201 and the uppermost fuel located upstream from the second injection position P2. It is divided into 201b, the second fuel 202 at the second injection position P2, and the injection interlayer fuel 201d fitted to the second fuel 203 at the first injection position P1. do. In this step, the fuel between the first injection position P1 and the second injection position P2 is the second injection position even when the injection of the second fuel 203 to the first injection position P1 proceeds. It will not be pushed back to the upstream side in the circulation direction beyond the 2nd fuel 202 in (P2). Thereby, the adjustment of the amount of the first fuel located between the first injection position P1 and the second injection position P2 is ended, and the amount of fuel 201d between injection layers, that is, the first fuel between injection layers The amount of (= Qf2) is determined.

Further, the timing corresponding to the crank angle Ra may be the same as the timing T14 at which the required amount of the second fuel 202 is injected at the second injection position P2, and a timing prior to this timing T14 This may be the same or a timing after the timing T14. Of these timings, which timing becomes the timing corresponding to the crank angle Ra is determined by the waiting time ΔT11 according to the engine load. In the example shown in Fig. 9, when the timing corresponding to the crank angle Ra is the same as the timing T14 at the fourth crank angle R14.

In addition, as illustrated in FIG. 9, the control unit 92 in the first modification is applied to the downstream injection system 50 at the timing T14 at which the current crank angle becomes the fourth crank angle R14. A control signal is output to the 1st control valve 55 in this case, and this is made into a closed state. Thereby, the control unit 92 stops the operation of the first injection pump 51 in the downstream injection system 50 while continuing the operation of the second injection pump 61. In this way, the first injection pump 51 finishes the injection to the first injection position P1 in the fuel path L. That is, the timing T14 corresponding to the fourth crank angle R14 is the same as the "first layer injection end timing" at which the downstream injection system 50 ends the injection of the second fuel. On the other hand, the second injection pump 61 continues to inject into the second injection position P2 in the fuel path L. As shown in FIG. 9, at the timing T14 corresponding to the fourth crank angle R14, the required amount of the second fuel 203 is injected into the first injection position P1.

Thereafter, as shown in FIG. 8, the control unit 92, at the timing T15 at which the current crank angle became a predetermined fifth crank angle R15 (> R14), the upstream injection system 60 2 A control signal is output to the control valve 65, and this is brought into a closed state. Thereby, the 2nd injection pump 61 of the upstream side injection system 60 stops operation. And the 2nd injection pump 61 finishes the injection to the 2nd injection position P2 in the fuel path L. That is, the timing T15 corresponding to the fifth crank angle R15 is the same as the "second layer injection end timing" at which the upstream injection system 60 ends the injection of the second fuel.

As illustrated in FIG. 9, in the period from the timing T14 corresponding to the fourth crank angle R14 to the timing T15 corresponding to the fifth crank angle R15, the second injection position P2 is The second fuel 202 is further injected while spreading all over the width direction of the fuel column 201. On the other hand, the injection of the second fuel 203 to the first injection position P1 has already ended at the timing T14 described above. In this step, the injection of the second fuel 202 at the second injection position P2 is performed in the same manner as the period from the timing T13 to the timing T14 described above, and the second fuel 202 ) Is continued until the required amount is reached. And at the timing T15 corresponding to the 5th crank angle R15, the injection to the 2nd injection position P2 and the 1st injection position P1 is finished. As a result, a downstream fuel layer (F1), a downstream injection layer (A1), an intermediate fuel layer (F2), an upstream injection layer (A2), and an upstream fuel layer (F3) are sequentially arranged. The layered liquid 200 is formed in the fuel path L.

Here, in the first modification, the injection period (first injection period) of the second fuel by the downstream injection system 50 is the fourth crank at the timing T11 corresponding to the first crank angle R11. It is a period up to the timing T14 corresponding to the angle R14. That is, the first injection period is a period obtained by adding the waiting time (ΔT11) illustrated in FIG. 8 and the period (ΔT12). This first injection period is determined by the time required when injecting the required amount of the second fuel 203 into the first injection position P1 illustrated in FIG. 9. That is, the fourth crank angle R14 corresponding to the first layer injection end timing (timing T14) in the downstream injection system 50 is the first crank angle R11 corresponding to the first layer injection start timing And, it is calculated based on the time required for injection of the required amount of the second fuel 203.

In addition, the injection period (second injection period) of the second fuel by the upstream injection system 60 corresponds to the fifth crank angle R15 at the timing T12 corresponding to the second crank angle R12. It is a period until the timing T15 to perform. This second injection period is determined by the time required when injecting the required amount of the second fuel 202 into the second injection position P2 illustrated in FIG. 9. That is, the fifth crank angle R15 corresponding to the second layer injection end timing (timing T15) in the upstream side injection system 60 is the second crank angle R12 corresponding to the second layer injection start timing. And, it is calculated based on the time required for injection of the required amount of the second fuel 202.

In the first modification, the period in which the injection period (first injection period) of the downstream injection system 50 and the injection period (second injection period) of the upstream injection system 60 overlap is illustrated in FIG. As described above, it corresponds to the period ΔT12 from the second crank angle R12 to the fourth crank angle R14. During this period (ΔT12), the period (ΔTa) from the second crank angle (R12) to the crank angle (Ra) is an intermediate fuel layer located between injection layers by injection from the downstream injection system 50 It is a part of the period in which the 1st fuel is reduced in (F2). Further, the waiting time ΔT11 from the first crank angle R11 to the second crank angle R12 is the remainder of the period in which the first fuel is reduced in the intermediate fuel layer F2. That is, these waiting times (ΔT11) and the reduction period (ΔT13) obtained by adding the period (ΔTa) becomes the total period in which the first fuel is reduced in the intermediate fuel layer F2. The second layer injection start timing by the upstream injection system 60 is so that the reduction period ΔT13 decreases with the increase of the engine load, and the reduction period ΔT13 increases with the decrease of the engine load. It is controlled at a timing that is as slow as the waiting time (ΔT11) from the start timing of the second layer injection. That is, this waiting time DELTA T11 decreases with an increase in the engine load, and increases with a decrease in the engine load. In addition, when this waiting time (ΔT11) is a zero value (ΔT11 = 0), the second layer injection start timing by the upstream injection system 60 is the first layer injection start timing by the downstream injection system 50 It is controlled at the same timing as and.

By controlling in this way, the first fuel, the second fuel, the first fuel, the second fuel, and the first fuel are sequentially injected from the fuel injection valve 30 in a layered manner as in the above embodiment. As a result, combustion of the second fuel (substitute fuel) as the main fuel is promoted more reliably, and generation of combustion residues can be suppressed.

In addition, as illustrated in FIGS. 8 and 9, the downstream side so that at least a part of the first injection period by the downstream injection system 50 and the second injection period by the upstream injection system 60 overlap. The timing at which the injection system 50 and the upstream injection system 60 start injection of the second fuel, respectively, is controlled according to the engine load. Thereby, it becomes possible to control so that the ratio of the 1st fuel injection quantity Qfa determined in accordance with the engine load and the fuel quantity Qf2 in the intermediate fuel layer F2 does not become excessive or excessive. Thereby, the operation of the engine 1 can be stabilized, and it becomes possible to ensure its performance.

(6) Modification example of the first fuel and the second fuel (second modification)

In the above embodiment and its first modification, the first fuel is configured to function as a pilot fuel and the second fuel is configured to function as the main fuel, but the technique disclosed herein is not limited to this configuration.

In addition, in the above-described embodiment and its first modification, it was configured to use an alternative fuel as the first fuel and to use a fossil fuel as the second fuel, but the technique disclosed herein is not limited to this configuration as well. Does not.

For example, in a modified example shown below (hereinafter referred to as a ``second modified example''), the first fuel functions as the main fuel that generates the power of the engine 1, and the second fuel is , It functions as a pilot fuel for igniting the main fuel. As the first fuel according to the second modification, ammonia as an alternative fuel can be used, and as the second fuel according to the modification, diesel fuel as the fossil fuel can be used. That is, similarly to the above-described embodiment and the first modification, the fossil fuel according to the second modification has at least one of the pressure and temperature leading to compression ignition lower than that of the alternative fuel related to the modification.

FIG. 10 is a diagram corresponding to FIG. 2 showing a second modification example of the engine 1 (especially the fuel injection device 100), and FIG. 11 is a diagram corresponding to FIG. 3 in the second modification example of the engine 1 to be. In the following description, the same names and reference numerals as those in the above embodiment are used for constituent elements configured in the same manner as in the above embodiment. About these constituent elements, description is omitted appropriately.

As illustrated in FIGS. 10 and 11, the fuel injection device 100 ′ according to the second modification can inject an alternative fuel as a first fuel and a fossil fuel as a second fuel in a layered manner. In this case, a carbon-free fuel (specifically, ammonia) can be used as an alternative fuel, while diesel fuel can be used as a fossil fuel.

The fuel pump 41' according to the second modification is connected to a fuel tank (not shown) in which an alternative fuel as the first fuel is stored through a pipe or the like, and receives fuel from the fuel tank.

Further, the fuel injection device 100' according to the second modification is provided with a fossil fuel pump 71' instead of the alternative fuel supply pump 71. The fossil fuel pump 71' transfers the fossil fuel stored in a tank (not shown) storing fossils as a second fuel to the first injection pump 51 through branch pipes 72a, 72b, etc. It is supplied to the 2nd infusion pump 61.

In addition, the control unit 92 according to the second modified example includes, among the fuel layers injected from the fuel injection valve 30, a fuel layer made of an alternative fuel as the first fuel and a fuel layer made of a fossil fuel as the second fuel. The injection systems 50 and 60 configured in the same manner as in the above embodiment are controlled so that both have two or more layers.

By configuring in this way, the fuel injection valve 30 is provided by the first fuel (ammonia as an alternative fuel) pumped by the fuel pump 41' and the downstream injection system 50, as illustrated in FIG. 11. The injected second fuel (diesel fuel as fossil fuel), the first fuel pumped by the fuel pump 41' (ammonia as an alternative fuel), and the second fuel injected by the upstream injection system 60 (fossil fuel) The layered liquid arranged in order of diesel fuel as fuel) and the first fuel (ammonia as an alternative fuel) pumped by the fuel pump 41' is injected from the injection port 31 into the combustion chamber 17. Thereby, combustion of the first fuel (substitute fuel) as the main fuel is promoted more reliably, and it becomes possible to suppress the generation of combustion residues.

That is, by injecting fuel as described above, the first fuel, the second fuel, the first fuel, the second fuel, and the first fuel are sequentially injected in a layered manner as illustrated in FIG. 11. In this case, the first fuel (substitute fuel) injected subsequent to the first second fuel (fossil fuel) is accelerated by the first second fuel (fossil fuel) as illustrated in FIG. It is divided into two parts: a first fuel (alternative fuel) to be used, and a first fuel (alternative fuel) whose combustion is accelerated by a second second fuel (fossil fuel) injected thereafter. The first fuel (substitute fuel) to be accelerated combustion is divided into two, and the combustion of each divided first fuel (substitute fuel) is divided into two parts as the first fuel (substitute fuel). Fuel). As a result, combustion of the first fuel (substitute fuel) is promoted more reliably, and it becomes possible to suppress the generation of combustion residues.

Further, by using an alternative fuel such as ammonia as the main fuel, consumption of fossil fuels including diesel fuel can be suppressed. In particular, by suppressing the combustion residue of the fuel as in the second modification, more alternative fuels can be burned.

(7) Other embodiments

In the above embodiment, and in the first and second modifications, the fossil fuel used as one of the first and second fuels is compared with the alternative fuel used as the other of the first and second fuels, the pressure leading to compression ignition and At least one of the temperatures was configured to be low, but it is not limited to this configuration. Alternative fuels that have at least one of the pressures and temperatures leading to compression ignition that are lower than fossil fuels may be used. For example, as another configuration example, while using diesel fuel as a fossil fuel, methanol may be used as an alternative fuel. In this case, the fossil fuel becomes the main fuel and the alternative fuel becomes the pilot fuel, but the fossil fuel may be the first fuel and the alternative fuel may be the second fuel (pattern C described later), and the alternative fuel is the first fuel. Then, fossil fuel may be used as the second fuel (pattern D described later). In any case, the other can be divided into two by one of the first and second fuels, and the fuel layer made of the first fuel and the fuel layer made of the second fuel can be made into two or more layers. Thereby, it is possible to suppress the combustion residue of the fuel.

Table 1 shows combinations of the first and second fuels in the above embodiment, the first modification, the second modification, and other configuration examples. In Table 1, pattern A refers to the combination of fuels in the above embodiment and the first modification, pattern B refers to the combination of fuels in the second modification, and patterns C and D are, Both refer to combinations of fuels in other configuration examples.

"Combustibility" in Table 1 indicates the ease of ignition of the first and second fuels. This combustibility can be determined, for example, based on at least one of the pressure and temperature leading to compression ignition. The combustibility is not an absolute index, but is only a relative index when the first fuel and the second fuel are compared.

Specifically, in Pattern A, a fossil fuel (eg, diesel fuel) is used as the first fuel, and an alternative fuel (eg, ammonia) is used as the second fuel. In the above embodiment corresponding to the pattern A, the combustibility of the first fuel is improved compared to the second fuel.

In addition, in the pattern B, unlike the pattern A, an alternative fuel (eg, ammonia) is used as the first fuel, and a fossil fuel (eg, diesel fuel) is used as the second fuel. In the second modification corresponding to the pattern B, unlike the pattern A, the combustibility of the second fuel is improved compared to the first fuel.

Further, in the pattern C, similarly to the pattern A, a fossil fuel (eg, diesel fuel) is used as the first fuel, and an alternative fuel (eg, methanol) is used as the second fuel. In the above other configuration examples corresponding to the pattern C, unlike the pattern A, the combustibility of the second fuel becomes better than that of the first fuel.

Further, in the pattern D, similarly to the pattern B, an alternative fuel (eg, methanol) is used as the first fuel, and a fossil fuel (eg, diesel fuel) is used as the second fuel. In the above other configuration examples corresponding to the pattern D, unlike the pattern B, the combustibility of the first fuel becomes better than that of the second fuel.

The technique disclosed here is applicable to all of these patterns A to D.

In addition, in the above embodiment and its first modification, when the downstream injection system 50 and the upstream injection system 60 each control the timing to start injection of the second fuel, it is calculated according to the engine load. The crank angle was calculated from one waiting time (ΔT1, ΔT11), and the timing at which the calculated crank angle coincided with the current crank angle by the detection unit 91 was set as the injection start timing following the previous injection start timing. This disclosure is not limited to this. For example, the downstream injection system 50 and the upstream injection system 60 may be controlled based on the driving time of the engine 1, and in this case, the elapsed time from the previous injection start timing is determined by the engine load. The timing at which the corresponding waiting time has been reached may be referred to as the timing of the subsequent injection start.

In addition, in the above-described embodiment and the first and second modifications, the fuel injection device 100 provided with three fuel injection valves 30 for each cylinder 16 was illustrated, but the present disclosure is limited to this. It does not become. For example, the number of fuel injection valves 30 may be one, or two or more may be arbitrary.

1 engine (ship diesel engine)
16 cylinder
17 combustion chamber
30 fuel injection valve
31 nozzle
32 1st internal path (fuel path)
41 fuel pump
42 fuel injection pipe (fuel path)
42a branch pipe (fuel path)
50 downstream injection system (first injection system)
60 Upstream injection system (2nd injection system)
92 Control
100 fuel injector
200 lamellar liquid
A1 downstream injection layer (fuel layer consisting of the second fuel injected by the first injection system)
A2 upstream injection layer (fuel layer consisting of the second fuel injected by the second injection system)
F2 intermediate fuel layer (fuel layer consisting of the primary fuel)
L fuel path
P1 first injection position
P2 second injection position
Qfa 1st fuel injection quantity (injection quantity per 1st fuel injection)
Qf2 amount of intermediate fuel bed
ΔT1 waiting time
ΔT11 waiting time

Claims (7)

A cylinder that partitions the combustion chamber,
A fuel injection valve formed to face the combustion chamber and having an injection port for injecting fossil fuel and alternative fuel,
A fuel pump that pressurizes a first fuel comprising one of the fossil fuel and an alternative fuel toward the fuel injection valve;
A fuel path from the fuel pump to the injection port,
An injection system for injecting a second fuel comprising the other of the fossil fuel and the alternative fuel at a predetermined position in the fuel path;
And a control unit for controlling the injection system,
The fuel injection valve injects layered in a state in which the first fuel pumped by the fuel pump and the second fuel injected by the injection system are alternately arranged,
The control unit controls the injection system so that both of the fuel layers made of the first fuel and the fuel layers made of the second fuel among the fuel layers injected from the fuel injection valve are at least two layers. Marine diesel engine. The method of claim 1,
The injection system,
A first injection system for injecting the second fuel to a predetermined first injection position in the fuel path;
In the fuel path, a second injection system for injecting the second fuel at a second injection position upstream of the first injection position,
The fuel injection valve is provided to the first fuel pumped by the fuel pump, the second fuel injected by the first injection system, the first fuel pumped by the fuel pump, and the second injection system. A marine diesel engine, characterized in that a layered liquid including a fuel layer in sequence of the second fuel injected by the fuel pump and the first fuel pumped by the fuel pump is injected into the combustion chamber. The method of claim 2,
The control unit, according to the load of the marine diesel engine, the first injection system is the second fuel so that at least a part of the injection period by the first injection system and the injection period by the second injection system overlap. A marine diesel engine, characterized in that the timing of starting injection of the fuel and the timing of starting injection of the second fuel by the second injection system are controlled. The method of claim 3,
The control unit is located between a fuel layer composed of the second fuel injected by the first injection system and a fuel layer composed of the second fuel injected by the second injection system, and is used as the first fuel. The timing at which the first injection system starts injection of the second fuel, and the second injection system starts the injection of the second fuel so that the amount of the formed fuel layer becomes a constant ratio with respect to the injection amount per injection of the first fuel. A marine diesel engine, characterized in that the timing of starting fuel injection is controlled. The method according to claim 3 or 4,
The control unit calculates a predetermined waiting time based on the load of the marine diesel engine, and determines a timing at which the first injection system starts injection of the second fuel by the calculated waiting time. A marine diesel engine, characterized in that the second injection system is delayed from a timing at which the injection of the second fuel starts. The method according to claim 3 or 4,
The control unit calculates a predetermined waiting time based on the load of the marine diesel engine, and determines a timing at which the second injection system starts injection of the second fuel by the calculated waiting time. A marine diesel engine, characterized in that the first injection system is delayed from a timing at which the injection of the second fuel starts. The method according to any one of claims 2 to 6,
The control unit is configured such that the ratio of the injection amount of the second fuel by the first injection system and the injection amount of the second fuel by the second injection system becomes constant regardless of the load of the marine diesel engine. Marine diesel engine, characterized in that controlling the first injection system and the second injection system.

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