Fuel injection control system and dual fuel engine

Abstract

To reliably and stably ignite main fuel and suppress misfires even after ignition. [Solution] The system is used in a dual fuel engine for a ship that uses two types of fuel, and each unit of a plurality of cylinder units has a main fuel injection pump and a pilot fuel injection pump, first switching means for selectively switching the pilot injection to a first injection amount range on the fuel reduction side or a second injection amount range on the fuel increase side, and second switching means for selectively stopping the main injection or switching it to a predetermined injection amount range, and at engine start, the first switching means is switched so that the pilot injection is within the second injection amount range and the second switching means is switched so that the main injection is stopped, and after a clutch engagement command is received, the first switching means is switched so that the pilot injection is within the first injection amount range and the second switching means is switched so that the main injection is within the predetermined injection amount range, and when fuel injection from the main fuel injection pump begins, injection of the main fuel is limited.

Description

[Technical field]

[0001] The present invention relates to a fuel injection control system for use in a dual-fuel engine that uses two types of fuel, and a dual-fuel engine equipped with the same. [Background technology]

[0002] Traditionally, heavy oil has been the norm for ship fuel. When heavy oil is burned, it emits large amounts of nitrogen oxides (NOx), soot (PM), sulfur oxides (SOx), etc., causing air pollution. In light of the recent increase in environmental awareness, compared to heavy oil, it has been developed to reduce sulfur oxide (SOx) emissions by up to 99%, soot (PM) emissions by up to 95%, nitrogen oxides (NOx) by up to 80%, and carbon dioxide (CO 2 Methanol-fueled engines, which use methanol as fuel and can reduce CO2 emissions by up to 15%, are attracting attention.

[0003] The applicant of this application has previously filed a patent application for the following invention regarding a conventional dual-fuel engine. This dual-fuel engine is characterized in that, when the engine is started, the main fuel injection pump is stopped and the pilot fuel injection pump is controlled within a second injection amount range on the fuel increase side, and after the engine is started, the main fuel injection pump is controlled without limit and the pilot fuel injection pump is controlled within a first injection amount range on the fuel decrease side (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 5-195900 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the invention of Patent Document 1 described above had a problem in that when the main fuel injection pump starts to inject the main fuel, the amount of main fuel injected may suddenly become excessive, causing a misfire, and the main fuel may not be able to be ignited reliably (misfire).

[0006] The present invention has been proposed in view of the above-mentioned problems, and has as its main object to provide a dual-fuel engine in which the main fuel ignites reliably and stably and in which misfire is prevented even after ignition. [Means for solving the problem]

[0007] A fuel injection control system according to one aspect of the present invention is a fuel injection control system used for a dual-fuel engine for a ship that uses two types of fuel, and includes a plurality of cylinder units, each cylinder unit having a main fuel injection pump and a pilot fuel injection pump, a first switching means for selectively switching fuel injection by the pilot fuel injection pump to a first injection amount range on the fuel reducing side or a second injection amount range on the fuel increasing side, a second switching means for selectively switching fuel injection by the main fuel injection pump to a stop or to a predetermined injection amount range, and a second switching means for selectively switching fuel injection by the pilot fuel injection pump to a first injection amount range on the fuel reducing side or a second injection amount range on the fuel increasing side. a first control means for switching the first switching means so that fuel injection from the pilot fuel injection pump is within the second injection amount range and for switching the second switching means so that fuel injection from the main fuel injection pump is stopped, and a second control means for switching the first switching means so that fuel injection from the pilot fuel injection pump is within the first injection amount range and for switching the second switching means so that fuel injection from the main fuel injection pump is within a predetermined injection amount range after a clutch engagement command is issued, Rate of increase in volume The fuel injection system further comprises a primary fuel restriction means for restricting the amount of fuel injected into the engine.

[0008] With this configuration, when starting the engine, the main fuel injection pump is stopped and the pilot fuel injection pump is controlled to the second injection amount range on the fuel increase side, so that only pilot fuel with good ignition properties is injected as the governor operates, thereby ensuring smooth starting.

[0009] In addition, after a clutch engagement command is issued, main fuel is supplied from the main fuel injection pump and the pilot fuel injection pump is controlled to within the range of the first injection amount on the fuel reduction side, so that main fuel is injected in conjunction with the governor and pilot fuel injection is suppressed to the first injection amount or less. As a result, after a clutch engagement command is issued, the engine runs on two types of fuel, main fuel and pilot fuel, and emissions of NOx, soot, and sulfur oxides can be reduced.

[0010] In addition, by providing the main fuel limiting means, it is possible to prevent the fuel injection amount from increasing suddenly, thereby preventing misfires and enabling reliable ignition. Note that the main fuel control means may be, for example, a speed adjustment valve that allows the cylinder that cuts off the main fuel to return slowly.

[0011] The various means described above may be implemented, for example, by controlling mechanisms such as a rack rod that controls fuel injection from both fuel injection pumps, and a link system that connects the governor via a one-way buffer mechanism capable of absorbing operation in the fuel increase direction. In this case, the first switching means selectively switches fuel injection by the pilot fuel injection pump to a first injection amount range on the fuel decrease side or a second injection amount range on the fuel increase side via the link system and rack rod, and fuel injection by the main fuel injection pump is selectively switched to stop or to a predetermined injection amount range via the link system and rack rod, and the various control means may also be implemented via these link systems and rack rod.

[0012] This fuel injection control system is characterized in that the second injection amount of the pilot fuel injection pump of the first control means is an injection amount that allows operation with pilot fuel only.

[0013] According to this configuration, a sufficient amount of pilot fuel is injected when the engine is started, so that the engine can be reliably started and operated using only pilot fuel, and also, even if a malfunction occurs in the main fuel injection system, the engine can continue to operate using only pilot fuel.

[0014] This fuel injection control system is characterized in that a second control means starts a timer for a predetermined time after the clutch engagement command, and after the predetermined time has elapsed, switches the first switching means so that the fuel injection of the pilot fuel injection pump is within the first injection amount range, and at the same time switches the second switching means so that the fuel injection of the main fuel injection pump is within a predetermined injection amount range.

[0015] With this configuration, after a clutch engagement command is issued, a timer is started for a predetermined time, and once the engine speed has stabilized after the predetermined time has elapsed, the main fuel injection pump is caused to inject fuel, and the pilot fuel injection pump is controlled to be within the first injection amount range on the fuel reduction side, thereby making it possible to reliably operate the engine using main fuel and pilot fuel.

[0016] This fuel injection control system is characterized by further comprising third control means that, after the clutch is disengaged, switches the first switching means so that fuel injection from the pilot fuel injection pump is within the second injection amount range, and switches the second switching means so that fuel injection from the main fuel injection pump is stopped.

[0017] According to this configuration, when the clutch is disengaged, fuel injection from the main fuel injection pump is stopped and only fuel injection from the pilot fuel injection pump occurs, resulting in operation using only pilot fuel.

[0018] This fuel injection control system is characterized in that it further includes a fourth control means that, during a normal stop of the engine, switches the first switching means so that fuel injection from the pilot fuel injection pump is within the second injection amount range, and switches the second switching means so that fuel injection from the main fuel injection pump is stopped, and thereafter brings the pilot fuel injection pump to a stopped state.

[0019] According to this configuration, when the engine is stopped, the engine is not stopped suddenly, but first the main fuel is stopped, and after the supply of only a predetermined amount of pilot fuel is stopped, the pilot fuel is also stopped, so that the engine can be stopped smoothly without applying a sudden load to it.

[0020] This fuel injection control system is characterized by further comprising a fifth control means for switching the first switching means so that fuel injection from the pilot fuel injection pump is stopped, and for switching the second switching means so that fuel injection from the main fuel injection pump is stopped, when an engine emergency stop occurs.

[0021] According to this configuration, in the event of an emergency stop, the engine can be stopped quickly by stopping both the main fuel and the pilot fuel. Also, by stopping both fuels, it is possible to prevent damage from spreading if any malfunction occurs in the injection system, etc.

[0022] In this fuel injection control system, the fifth control means provides a time difference in stopping the fuel injection from both pumps so that the fuel injection of the pilot fuel is stopped after the fuel injection from the main fuel injection pump is stopped.

[0023] According to this configuration, even in the event of an emergency stop, by providing a time lag in stopping the fuel supply to both pumps, i.e., by stopping the main fuel injection before stopping the pilot fuel injection, it is possible to prevent unburned main fuel from remaining in the cylinder.

[0024] This fuel injection control system is characterized in that the first injection amount range of the pilot fuel injection pump has an upper limit of 15%.

[0025] According to this configuration, by setting the upper limit of the first injection amount of pilot fuel at 15%, hybrid operation mainly using the main fuel can be achieved.

[0026] This fuel injection control system is characterized in that the range of the second injection amount of the pilot fuel injection pump is a range whose upper limit exceeds 15% or a range whose upper limit is 100%.

[0027] According to this configuration, by setting the range of the second injection amount of pilot fuel to a range exceeding 15% with an upper limit or to 100%, it becomes possible to operate the engine using only pilot fuel when starting or stopping.

[0028] This fuel injection control system is characterized in that the range of the predetermined injection amount of the pilot fuel injection pump is a range whose upper limit is 100%.

[0029] According to this configuration, by setting the upper limit of the range of the main fuel injection amount to 100%, the main fuel can be injected to the maximum during normal operation, enabling operation mainly using the main fuel.

[0030] The fuel injection control system further includes pilot fuel limiting means for limiting injection of pilot fuel into the pilot fuel injection pump, the pilot fuel limiting means having a limiting cylinder and a limiting valve for limiting pilot fuel injection.

[0031] According to this configuration, the limiting cylinder and limiting valve can prevent the amount of pilot fuel injected from increasing suddenly when starting the engine, etc., thereby preventing misfires and ensuring reliable ignition.

[0032] This fuel injection control system comprises a stop cylinder connected to the main fuel injection pump for stopping the supply of main fuel, and a first stop valve connected to the main fuel injection pump via the stop cylinder, and further comprises a speed regulating valve interposed between the stop cylinder and the first stop valve.

[0033] According to this configuration, the speed regulating valve can prevent the amount of main fuel injected from increasing suddenly when the clutch is engaged, etc., thereby preventing misfires and ensuring reliable ignition.

[0034] This fuel injection control system is characterized by further comprising a second stop valve connected to the stop cylinder and used during an emergency stop.

[0035] According to this configuration, it is possible to handle the shutdown of the main fuel using multiple systems, making it possible to shut down the main fuel according to the situation.

[0036] This fuel injection control system is characterized by further comprising a bypass valve connected to the speed regulating valve and used during emergency operation to bypass the first stop valve.

[0037] According to this configuration, even during emergency operation, such as when a malfunction occurs in the stop valve that cuts off the main fuel, the main fuel can be reliably cut off by providing the bypass valve.

[0038] This fuel injection control system is characterized by including a stop cylinder connected to the pilot fuel injection pump for stopping the supply of pilot fuel, and a switching cylinder for switching the amount of pilot fuel supplied.

[0039] The fuel injection control system is characterized by further comprising a pressure sensor for monitoring the pressure within the cylinder of the cylinder unit.

[0040] According to this configuration, the combustion state can be monitored by monitoring the internal pressure in the cylinder, and the amount of pilot fuel injected can be controlled when the combustion state becomes weak or a misfire state.

[0041] This fuel injection control system is characterized in that the main fuel is methanol and the pilot fuel is heavy oil or a hydrocarbon fuel.

[0042] According to this configuration, a dual-fuel engine can be configured in which the pilot fuel is heavy oil or a hydrocarbon fuel such as biofuel, methane fuel, or propane fuel, and the main fuel is methanol.

[0043] A dual-fuel engine according to one aspect of the present invention is characterized by including the above-mentioned fuel injection control system.

[0044] According to this configuration, by being equipped with the above-mentioned fuel injection control system, the engine ignites more reliably and stably than conventionally, and misfires are prevented even after ignition, resulting in a dual-fuel engine that can be operated stably. Effect of the Invention

[0045] According to the configuration of the present invention, the fuel injection control system ignites the main fuel more reliably and stably than conventionally, and prevents misfires after ignition. Furthermore, by providing a dual-fuel engine with this fuel injection control system, stable operation is possible. [Brief description of the drawings]

[0046] [Figure 1] 1 is a side view showing a schematic configuration of a dual-fuel engine according to an embodiment of the present invention. [Diagram 2] 1 is a conceptual diagram showing a configuration of a fuel control system for a cylinder unit of a dual-fuel engine according to an embodiment of the present invention. [Diagram 3] 4 is a graph showing fuel injection of a cylinder unit of a dual fuel engine according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] A dual fuel engine according to the present invention will be described below with reference to the drawings, but the present invention is not limited to this embodiment. In addition, the components in the following embodiment include those that are replaceable and easy for a person skilled in the art, or those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. In addition, various omissions, substitutions, or modifications of the configuration can be made without departing from the gist of the present invention.

[0048] <1. Dual fuel engine configuration> FIG. 1 is a side view showing the configuration of a dual-fuel engine according to an embodiment of the present invention. As shown in FIG. 1, the dual-fuel engine (hereinafter, sometimes simply referred to as "engine") of this embodiment is a dual-fuel engine for a ship that uses methanol as the main fuel and heavy oil A as the pilot fuel, and is equipped with six cylinder units 100. The six cylinder units 100 are arranged in a line in the longitudinal direction. Each cylinder unit 100 has a main fuel injection pump and a drive unit and a pilot fuel injection pump and a drive unit arranged on either the port or starboard side, and an intake and exhaust valve drive unit arranged on the other side. In this embodiment, methanol is used as the main fuel, but ammonia may be used, and heavy oil A is used as the pilot fuel, but a hydrocarbon fuel such as petroleum-based heavy oil with good ignition properties or biofuel may be used.

[0049] Fig. 2 is a diagram showing the configuration of a fuel control system of a cylinder unit of a dual-fuel engine according to one embodiment of the present invention. As shown in Fig. 2, the dual-fuel engine of this embodiment mainly comprises a main fuel injection pump 1 that uses methanol as the main fuel, and a pilot fuel injection pump 2 that uses heavy oil A as the pilot fuel.

[0050] The main fuel injection pump 1 has a freely movable rack rod 1a for adjusting the fuel injection amount, and the pilot fuel injection pump 2 has a freely movable rack rod 2a for adjusting the fuel injection amount. The fuel injection amount of the main fuel injection pump 1 is adjusted depending on the position to which the rack rod 1a is moved, and the fuel injection amount of the pilot fuel injection pump 2 is adjusted depending on the position to which the rack rod 2a is moved.

[0051] A main fuel injection amount adjustment shaft 4 is installed so as to be able to rotate freely, and one end of a rack rod 1a of the main fuel injection pump 1 is pivotally attached to the tip end of a link member 4a, the base end of which is fixed to this injection amount adjustment shaft 4.

[0052] In addition, a pilot fuel injection amount adjustment shaft 5 is installed so as to be able to rotate freely, and one end of a rack rod 2a of the injection pilot injection pump 2 is pivotally attached to the tip end of a link member 5a whose base end is fixed to this injection amount adjustment shaft 5.

[0053] One end of the injection amount adjustment shaft 4 is connected to an end of the arm 3 a of the governor 3 by a connection mechanism 6 equipped with a one-way buffer mechanism 8, and one end of the injection amount adjustment shaft 5 is connected to an end of the arm 3 a of the governor 3 by a connection mechanism 7 equipped with a one-way buffer mechanism 9.

[0054] That is, the base ends of the link members 4b and 5b are fixed to one ends of the injection amount adjustment shafts 4 and 5, and the connecting rods 6b and 7b are pivotally connected to the tip ends of the link members 4b and 5b. When the arm 3a rotates in one direction, the injection amount adjustment shafts 4 and 5 on both sides rotate in the direction to increase or decrease fuel, respectively.

[0055] The one-way buffer mechanism 8 has a coil spring 8b built inside a cylindrical body 8a, and the one-way buffer mechanism 9 has a coil spring 9b built inside a cylindrical body 9a. One ends of the connection rods 6a and 6b of the connection mechanism 6 are fixed to both ends of the cylindrical body 8a, one ends of the connection rods 7a and 7b of the connection mechanism 7 are fixed to both ends of the cylindrical body 9a, and the other end of the connection rod 7a is fixed to a link member 7c.

[0056] In each of the one-way buffer mechanisms 8 and 9, when the arm 3a of 3 rotates in the direction to increase fuel, the coil springs 8b and 9b are compressed, and when the arm 3a rotates in the direction to decrease fuel, the rotational force is transmitted directly to the injection amount adjusting shafts 4 and 5, respectively, without the coil springs 8b and 9b acting as a compression governor.

[0057] The other ends of the injection amount adjustment shafts 4 and 5 are connected to the tips of stop levers 11 and 12, respectively, so that the injection amount adjustment shafts 4 and 5 are simultaneously rotated in the injection stop direction by manually operating a common fuel injection stop handle 10.

[0058] That is, the base ends of two link members 10b and 10c are connected to a rotating shaft 10a that rotates integrally with the fuel injection stop handle 10 so that the base ends of the left and right stop levers 11 and 12 move toward or away from each other by rotating the common fuel injection stop handle 10, and the base ends of the stop levers 11 and 12 are pivotally attached to the tips of these link members 10b and 10c. In addition, the tips of the stop levers 11 and 12 are connected via link members 4c and 5c whose base ends are fixed to the injection amount adjustment shafts 4 and 5.

[0059] Separate from the manual operation of the fuel injection stop handle 10, the tip of piston rod 13a of main fuel stop cylinder 13, which rotates injection amount adjustment shaft 4 in the stopping direction, is connected to injection amount adjustment shaft 4 via link member 4d, and the tip of piston rod 14a of pilot fuel stop cylinder 14, which rotates injection amount adjustment shaft 5 in the stopping direction, is connected to injection amount adjustment shaft 5 via link member 5d.

[0060] The piston rods 13a and 14a in the stop cylinders 13 and 14 are urged by springs 13b and 14b in the direction opposite to the stopping direction of the injection amount adjustment shafts 4 and 5, and the introduction of control air into the stop cylinders 13 and 14 operates the piston rods 13a and 14a against the springs 13b and 14b, rotating each of the injection amount adjustment shafts 4 and 5 in the stopping direction. On the other hand, when the introduction of control air into the stop cylinders 13 and 14 is stopped, the piston rods 13a and 14a are returned to their original positions by the springs 13b and 14b, allowing each of the injection amount adjustment shafts 4 and 5 to rotate to their maximum extent in the fuel increase direction.

[0061] A switching cylinder 15 is connected to pilot fuel injection amount adjustment shaft 5 via link member 5e for switching the amount of pilot fuel injected from pilot fuel injection pump 1 in two stages within a predetermined range to a first injection amount on the fuel reducing side and a second injection amount on the fuel increasing side.

[0062] That is, a piston rod 15a in the switching cylinder 15 is pivotally attached to the tip end of a link member 5e, and the piston rod 15a urges the injection amount adjustment shaft 5 by a coil spring 15b in a direction in which fuel injection is stopped.

[0063] In this embodiment, by introducing control air into the switching cylinder 15, the piston rod 15a moves to a position where the amount of pilot fuel injected is, for example, 40% or less of the second injection amount, while by ceasing the introduction of the control air, the piston rod 15a returns to a position where, for example, the amount is 15% or less of the first injection amount due to the biasing force of the coil spring 15b.

[0064] A limiting cylinder 16 is provided on the main fuel injection amount adjustment shaft 4 to limit the injection amount so that the amount of main fuel injected from the main fuel injection pump 1 does not increase suddenly when the main fuel injection starts.

[0065] This limiting cylinder 16 is equipped with a piston rod 16a biased by a coil spring 16b in a direction to stop the injection of the main fuel, and when control air is introduced into the limiting cylinder 16, the piston rod 16a moves in a direction against the coil spring 16b. The tip of the piston rod 16a is connected to the injection amount adjustment shaft 4 via a link member 4e attached to the injection amount adjustment shaft 4.

[0066] Next, the control circuits for the main fuel cutoff cylinder 13, the pilot fuel cutoff cylinder 14, the switching cylinder 15 and the limiting cylinder 16 will be described.

[0067] 2, the main fuel stop cylinder 13 is connected to a pipe 35 which is connected to a pipe 36 and a pipe 37, each of which has a main fuel stop solenoid valve 22 interposed therebetween, and to a control air source A. By operating the main fuel stop solenoid valve 22, it is possible to stop the injection of the main fuel in the event of an emergency stop of the engine.

[0068] The piping 37 is connected to a piping 39 with a start valve 18 and a piping 38 with a speed control valve 21 connected to the control air source A. The speed control valve 21 makes it easy to adjust the amount of main fuel injected by slowing down the return speed of the main fuel stop cylinder 13, thereby preventing the main fuel from being suddenly injected when the clutch is engaged, thereby suppressing misfires, and so on.

[0069] The piping 38 is connected to a piping 40 having a main fuel cutoff solenoid valve 20 interposed therein and to a controlled air source A, and a piping 41 having a bypass valve 19 interposed therein and to a controlled air source A. The bypass valve 19 is adapted to cut off the main fuel in the event that the main fuel cutoff solenoid valve 20 fails, for example. The bypass valve 19 in this embodiment is a manual valve.

[0070] The pilot fuel stop cylinder 14 is connected to a control air source A via a pipe 33 having a pilot stop solenoid valve 24 interposed therebetween.

[0071] The switching cylinder 15 is connected to a pipe 31 having a start valve 18 interposed therebetween to a control air source A, and to a pipe 30 to which a pipe 32 is connected via a three-way valve.

[0072] The limiting cylinder 16 is connected to a pipe 34 with a main fuel limiting solenoid valve 23 interposed therebetween to a control air source A. This configuration limits the fuel injection amount so that it does not increase suddenly when the main fuel injection starts, and contributes to preventing black smoke when the clutch is engaged.

[0073] Furthermore, a speed control valve 25 is provided in piping 42 connecting the control air source A and the governor 3, and a forward / reverse changeover valve 26 is provided in piping 43 connecting the control air source A and the reduction / reverse gear. However, although piping 43 is connected to the reduction / reverse gear in this embodiment, it is not limited to the reduction / reverse gear, and may be a reverse gear with a built-in clutch, a reduction / reverse gear with a built-in clutch, a direct-coupled variable pitch propeller, or the like.

[0074] <2. Operation of dual fuel engine> Next, the operation of the dual fuel engine of this embodiment configured as described above will be described. First, when starting the dual fuel engine, the start valve 18 is pressed. Then, when the start valve 18 is opened, control air is supplied from the control air source A to the start air guide valve P, and is also supplied to the main fuel stop cylinder 13 and the three-way valve 17 on the main fuel injection amount adjustment shaft 4 side.

[0075] The piston rod 13a in the main fuel stop cylinder 13 is pushed against the spring 13b, causing the injection amount adjustment shaft 4 to rotate counterclockwise via the link member 4d, and the rack rod 1a moves to the left side of the figure, stopping the injection of main fuel from the main fuel injection pump 1. The rack of the main fuel injection pump 1 reaches the "0" position.

[0076] When the three-way valve 17 operates, the piston rod 15a in the switching cylinder 15 moves against the coil spring 15b, allowing the pilot fuel from the pilot fuel injection pump 2 to be injected at up to 40% of the full power heat amount.

[0077] Furthermore, the starting air guide valve P operates to send starting air into each cylinder of the engine in sequence, forcibly driving the pistons of the engine.

[0078] When the engine starts to rotate and the rotation speed increases, arm 3a of governor 3 rotates to the full injection position (maximum position), but main fuel is not injected and pilot fuel begins to be injected from pilot fuel injection pump 2. When ignition is achieved by injection of pilot fuel alone, the engine starts and the rotation speed increases rapidly, so the starting operation is completed by closing start valve 18.

[0079] When the engine operating level is exceeded, the main fuel stop solenoid valve 22 operates, and air is sent to the main fuel stop cylinder 13 and the double check valve located before the three-way valve 17.

[0080] Releasing the starting valve 18 shuts off the starting air, and the starting operation is completed. Closing the starting valve 18 exhausts the air from the main fuel stop cylinder 13 and the three-way valve 17, but the air on the main fuel stop solenoid valve 22 side is supplied to the main fuel stop cylinder 13 and the three-way valve 17 by the double check valve, shutting off the main fuel, and the pilot switching cylinder is held at the 40% position. The rotation speed is stabilized at the pressure equivalent to the rotation speed control valve 25.

[0081] In response to a sudden increase in engine speed, the arm 3a of the governor 3 rotates clockwise (in the direction of decreasing fuel), and the injection amount adjustment shaft 5 rotates counterclockwise, decreasing the amount of pilot fuel injected and causing the engine speed to drop to an idling state. Note that, since the injection amount adjustment shaft 4 on the main fuel side is in the injection amount 0 position, no main fuel is injected.

[0082] Next, when the engine is in an idling state (pilot fuel operation), the forward / reverse switching valve 26 is operated to start engaging the clutch.

[0083] When the clutch begins to engage, a load is placed on the engine, causing the engine speed to drop, but the amount of pilot fuel injected increases. When the clutch actuation hydraulic pressure increases and the clutch engages, the main fuel cutoff solenoid valve 20 is released. Specifically, after the clutch engages, a timer is set and main fuel injection begins once the engine speed has stabilized. Then, air is discharged from the three-way valve 17, and the pilot fuel injection is fixed at 15%.

[0084] Specifically, after a clutch engagement command is issued, piston rod 15a of switching cylinder 15 is returned to its original position (15%) by coil spring 15b, injection amount adjustment shaft 5 rotates in the fuel reducing direction, and pilot fuel from pilot fuel injection pump 2 can only inject up to 15% of the full power heat amount.

[0085] Furthermore, piston rod 13a in main fuel stop cylinder 13 is returned to its original position by spring 13b, injection amount adjustment shaft 4 rotates clockwise (increasing fuel), and the main fuel injection pump 1 is able to inject main fuel up to its maximum (100%). Figure 3 is a graph showing the injection amounts of main fuel injection pump 1 and pilot fuel injection pump 2 after the clutch is engaged.

[0086] When the clutch is engaged, a load is placed on the engine and the rotation speed drops, so that arm 3a of governor 3 rotates counterclockwise (to increase fuel) and injection amount adjustment shafts 4 and 5 rotate clockwise (to increase fuel). As a result, main fuel injection from main fuel injection pump 1 begins, and at the same time the amount of pilot fuel x injected from pilot fuel injection pump 2 increases. However, the amount of pilot fuel injected is restricted to 15% or less of the heat amount at full power by switching cylinder 15 as described above, so it cannot increase any more than that.

[0087] In the dual fuel engine of this embodiment, in order to avoid abrupt main fuel injection at the start of main fuel injection, etc., the main fuel limiting solenoid valve 23 is connected via the link member 4e connected to the injection amount adjustment shaft 4 and the limiting cylinder 16, and this is realized by introducing control air.

[0088] Thereafter, when the set value of the engine speed is increased, the arm 3a of the governor 3 rotates further counterclockwise (increasing fuel), and only the injection amount adjustment shaft 4 rotates clockwise, increasing only the injection amount of the main fuel. Meanwhile, the injection amount of the pilot fuel is maintained at the upper limit of 15% of the full power heat amount by the switching cylinder 15.

[0089] When disengaging the clutch, the forward / reverse switch valve 26 is operated to neutral, and the clutch disengagement operation begins. The clutch hydraulic oil pressure drops. The main fuel cutoff solenoid valve 20 operates, and air is supplied to the main fuel stop cylinder 13 and the three-way valve 17. The piston rod 13a of the main fuel stop cylinder 13 extends, causing the rack of the main fuel injection pump 1 to move to the "0" position. When the three-way valve 17 operates, the air in the pilot switch cylinder 15 is exhausted, and it moves from the upper limit 15% position to the 40% position.

[0090] In the case of a normal stop where the engine is stopped from such an operating state with only pilot fuel, fuel injection is stopped by operating the fuel injection stop handle 10. Note that in this state, since only pilot fuel is being injected, operating the fuel injection stop handle 10 only stops the pilot fuel.

[0091] Furthermore, if a malfunction or the like occurs in the main fuel injection system while the engine is running, the main fuel cutoff solenoid valve 20 is opened, and control air is supplied to the main fuel stop cylinder 13 and the three-way valve 17. The piston rod 13a of the main fuel stop cylinder 13 extends, causing the rack of the main fuel injection pump 1 to move to the "0" position, and the injection of main fuel is stopped.

[0092] When the three-way valve 17 operates, the air in the switching cylinder 15 is discharged and the engine moves from the 15% position to the 40% position, making it possible to inject up to 40% of the full-power heat amount through pilot fuel injection. Only pilot fuel is injected in accordance with the operation of the arm 3a of the governor 3, enabling the engine to operate.

[0093] On the other hand, when the engine needs to be stopped in an emergency, the dual fuel engine of this embodiment is configured to stop the fuel injection of the main fuel first, and then stop the fuel injection of the pilot fuel. Specifically, the main fuel stop solenoid valve 22 is actuated first, pressurized air is supplied to the main fuel stop cylinder 13, the piston rod 13a is operated, and the rack of the main fuel injection pump 1 is set to the "0" position. As a result, the supply of the main fuel is stopped first.

[0094] Next, after a set time has elapsed, the pilot stop solenoid valve 24 operates, pressurized air is supplied to the pilot fuel stop cylinder 14, the piston rod 14a moves, the rack of the pilot fuel injection pump 2 moves to the "0" position, the supply of pilot fuel is stopped, and the engine is stopped. This configuration prevents unburned main fuel from remaining in the cylinder.

[0095] As described above, the preferred embodiment of the present invention has been described with reference to the drawings, but various additions, modifications, or deletions are possible without departing from the spirit of the present invention. For example, although a start valve is provided in this embodiment, a start solenoid valve may be used. In addition, although heavy oil A is used as the pilot fuel in this embodiment, it is also possible to use a hydrocarbon fuel such as biofuel, methane fuel, or propane fuel. [Explanation of symbols]

[0096] 1 Main fuel injection pump 2 Pilot fuel injection pump 3. Governor 4 Fuel injection amount adjustment shaft 5 Fuel injection amount adjustment shaft 6 Attachment mechanism 7 Attachment 8 One-way buffer mechanism 9 One-way buffer mechanism 10 Fuel injection stop handle 11 Stop lever 12 Stop lever 13 Main fuel shutoff cylinder 14 Pilot fuel stop cylinder 15 Switching cylinder 16 Restricting Cylinder 17 Three-way valve 18 Starting valve 19 Bypass valve 20 Main fuel shutoff solenoid valve 21 Speed ​​control valve 22 Main fuel stop solenoid valve 23 Main fuel limiting solenoid valve 24 Pilot stop solenoid valve 25 Speed ​​control valve 26 Forward / reverse switching valve 100 Cylinder Unit A Controlled Air Source P Start air guide valve

Claims

1. A fuel injection control system for a dual fuel engine for a ship that uses two types of fuel, A plurality of cylinder units are provided, Each cylinder unit has a main fuel injection pump and a pilot fuel injection pump, a first switching means for selectively switching fuel injection by the pilot fuel injection pump to a first injection amount range on a fuel decreasing side or a second injection amount range on a fuel increasing side; a second switching means for selectively switching fuel injection by the main fuel injection pump to a state where the fuel injection is stopped or within a range of a predetermined injection amount; a first control means for switching the first switching means so that fuel injection from the pilot fuel injection pump falls within the second injection amount range at the time of starting the engine, and switching the second switching means so that fuel injection from the main fuel injection pump is stopped; a second control means for switching the first switching means after a clutch engagement command so that the fuel injection of the pilot fuel injection pump falls within the first injection amount range, and for switching the second switching means so that the fuel injection of the main fuel injection pump falls within a predetermined injection amount range, The present invention is characterized in that the main fuel injection pump further comprises a main fuel limiting means for limiting an increase rate of an injection amount of the main fuel when the main fuel injection pump starts to inject fuel. Fuel injection control system.

2. The first control means controls the second injection amount of the pilot fuel injection pump to an injection amount that allows the pilot fuel injection pump to operate only with pilot fuel.

2. The fuel injection control system of claim 1.

3. the second control means starts a timer for a predetermined time after the clutch engagement command, and after the predetermined time has elapsed, switches the first switching means so that the fuel injection of the pilot fuel injection pump is within the first injection amount range, and switches the second switching means so that the fuel injection of the main fuel injection pump is within a predetermined injection amount range.

2. The fuel injection control system of claim 1.

4. a third control means for switching the first switching means so that the fuel injection of the pilot fuel injection pump is within the second injection amount range after the clutch is disengaged, and for switching the second switching means so that the fuel injection of the main fuel injection pump is stopped, 2. The fuel injection control system of claim 1.

5. and a fourth control means for switching the first switching means so that the fuel injection of the pilot fuel injection pump is within the second injection amount range during a normal stop of the engine, and for switching the second switching means so that the fuel injection of the main fuel injection pump is stopped, and thereafter, for stopping the pilot fuel injection pump.

2. The fuel injection control system of claim 1.

6. a fifth control means for switching the first switching means so that fuel injection from the pilot fuel injection pump is stopped, and for switching the second switching means so that fuel injection from the main fuel injection pump is stopped, when an engine emergency stop occurs.

2. The fuel injection control system of claim 1.

7. The fifth control means provides a time difference between the stopping of fuel from both pumps so that the fuel injection from the main fuel injection pump is stopped after the fuel injection from the pilot fuel injection pump is stopped. Characterized in that 7. The fuel injection control system of claim 6.

8. The range of the first injection amount of the pilot fuel injection pump is a range having an upper limit of 15%.

2. The fuel injection control system of claim 1.

9. The range of the second injection amount of the pilot fuel injection pump is a range whose upper limit exceeds 15% or a range whose upper limit is 100%.

2. The fuel injection control system of claim 1.

10. The range of the predetermined injection amount of the main fuel injection pump is a range having an upper limit of 100%.

2. The fuel injection control system of claim 1.

11. a pilot fuel limiting means for limiting injection of pilot fuel into the pilot fuel injection pump; The pilot fuel limiting means has a limiting cylinder and a limiting valve for limiting pilot fuel injection.

2. The fuel injection control system of claim 1.

12. a stop cylinder connected to the main fuel injection pump for stopping the supply of main fuel; a first stop valve connected to the main fuel injection pump via the stop cylinder; The invention further comprises a speed regulating valve interposed between the stop cylinder and the first stop valve.

2. The fuel injection control system of claim 1.

13. The invention further comprises a second stop valve connected to the stop cylinder and used in an emergency stop.

13. The fuel injection control system of claim 12.

14. The present invention further comprises a bypass valve connected to the speed regulating valve and used during emergency operation to bypass the first stop valve.

13. The fuel injection control system of claim 12.

15. a stop cylinder connected to the pilot fuel injection pump for stopping the supply of pilot fuel, and a switching cylinder for switching the supply amount of pilot fuel.

2. The fuel injection control system of claim 1.

16. The cylinder unit further includes a pressure sensor for monitoring a pressure in the cylinder.

2. The fuel injection control system of claim 1.

17. The main fuel is methanol, The pilot fuel is heavy oil or a hydrocarbon fuel.

2. The fuel injection control system of claim 1.

18. A dual fuel engine comprising a fuel injection control system according to any one of claims 1 to 17.

Images