Fuel injection control system and dual-fuel engine

Abstract

The main fuel ignites reliably and stably, and misfires are suppressed even after ignition. [Solution] Used in a dual-fuel engine for ships that uses two types of fuel, each unit of a plurality of cylinder units has a main fuel injection pump, a pilot fuel injection pump, a first switching means for selectively switching the pilot injection to a range of a first injection amount on the fuel reduction side or a range of a second injection amount on the fuel increase side, and a second switching means for selectively stopping the main injection or switching it to a range of a predetermined injection amount. When the engine is started, the first switching means is switched so that the pilot injection is within the range of the second injection amount, and the second switching means is switched so that the main injection is stopped. After a clutch engagement command, the first switching means is switched so that the pilot injection is within the range of the first injection amount, and the second switching means is switched so that the main injection is within the range of a predetermined injection amount. When the main fuel injection pump starts fuel injection, the injection of the main fuel is restricted.

Description

Technical Field

[0001] The present invention relates to a fuel injection control system for a dual-fuel engine using two kinds of fuels and a dual-fuel engine equipped with the same.

Background Art

[0002] Conventionally, heavy oil has been commonly used as fuel for ships. When heavy oil is burned, a large amount of nitrogen oxides (NOx), soot (PM), sulfur oxides (SOx), etc. are emitted, causing air pollution. Therefore, under the recent improvement of environmental awareness, compared with heavy oil, a methanol fuel engine using methanol, which can reduce sulfur oxide (SOx) emissions during combustion by up to 99%, soot (PM) emissions by up to 95%, nitrogen oxides (NOx) by up to 80%, and carbon dioxide (CO2) by up to 15%, has attracted attention.

[0003] As a conventional dual-fuel engine, the applicant of the present application has previously filed a patent application for the following invention. This dual-fuel engine is characterized in that, at the start of the engine, the main fuel injection pump is stopped, and the pilot fuel injection pump is controlled within the range of the second injection amount on the fuel increase side. After the engine starts, the main fuel injection pump is unrestricted, and the pilot fuel injection pump is controlled within the range of the first injection amount on the fuel decrease side (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the invention of Patent Document 1 described above, there is a problem that when the main fuel injection amount suddenly becomes excessive at the start of the main fuel injection by the main fuel injection pump, misfire may occur, and there may be a case where the main fuel cannot be reliably ignited (misfire).

[0006] This invention was proposed in view of the above-mentioned problems, and its main objective is to provide a dual-fuel engine that reliably and stably ignites the main fuel and prevents misfires 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 for use in a dual-fuel engine for ships that uses two types of fuel, comprising 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 the fuel injection by the pilot fuel injection pump to a range of a first injection amount on the fuel reduction side or a second injection amount on the fuel increase side, a second switching means for selectively switching the fuel injection by the main fuel injection pump to stop or to a range of a predetermined injection amount, and when the engine starts, the fuel injection of the pilot fuel injection pump The system comprises: a first control means that switches the first switching means so that the injection is within the range of the second injection amount, and also switches the second switching means so that the fuel injection of the main fuel injection pump is stopped; and a second control means that, after a clutch engagement command, switches the first switching means so that the fuel injection of the pilot fuel injection pump is within the range of the first injection amount, and also switches the second switching means so that the fuel injection of the main fuel injection pump is within a predetermined injection amount range, and further comprises a main fuel limiting means that limits the injection of main fuel when the fuel injection of the main fuel injection pump starts.

[0008] In this configuration, when the engine is started, the main fuel injection pump is stopped, and the pilot fuel injection pump is controlled to the range of the second injection amount on the fuel increase side. As a result, only the pilot fuel, which has good ignition properties, is injected in conjunction with the operation of the governor. This ensures a smooth starting process.

[0009] Furthermore, after the clutch engagement command is issued, the main fuel is supplied from the main fuel injection pump, and the pilot fuel injection pump is controlled to the first injection amount range on the fuel reduction side. As a result, the main fuel is injected in conjunction with the governor, while the injection of pilot fuel is limited to the first injection amount or less. This means that after the clutch engagement command, the system operates using two types of fuel, main fuel and pilot fuel, and emissions of NOx, soot, and sulfur oxides can be reduced.

[0010] Furthermore, by providing a main fuel limiting mechanism, it is possible to prevent a sudden increase in fuel injection volume, thereby suppressing misfires and ensuring reliable ignition. The main fuel control mechanism could, for example, include a speed control valve that causes the cylinder that shuts off the main fuel to return slowly.

[0011] Furthermore, the above-mentioned various means can be implemented, for example, by controlling mechanisms such as a link system that connects the rack rod and governor that control the fuel injection of both fuel injection pumps via a unidirectional buffer mechanism capable of absorbing operation in the fuel increase direction. In this case, the first switching means can selectively switch the fuel injection by the pilot fuel injection pump to a range of either a first injection amount on the fuel decrease side or a second injection amount on the fuel increase side via the link system and rack rod, and the fuel injection by the main fuel injection pump can selectively switch to stop or to a range of a predetermined injection amount via the link system and rack rod. Various control means can also be implemented via these link system 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 set to an injection amount that allows the system to operate using only pilot fuel.

[0013] With this configuration, sufficient pilot fuel is injected when the engine starts, ensuring that the engine can reliably start and operate using only pilot fuel. Furthermore, even if a malfunction occurs in the main fuel injection system, operation can continue using only pilot fuel.

[0014] This fuel injection control system is characterized in that the second control means activates 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 range of the first injection amount, and at the same time switches the second switching means so that the fuel injection of the main fuel injection pump is within the range of a predetermined injection amount.

[0015] With this configuration, after the clutch engagement command is issued, a timer for a predetermined time is activated. After the engine speed stabilizes after the predetermined time has elapsed, the main fuel injection pump is activated, and the pilot fuel injection pump is controlled to stay within the range of the first injection amount on the fuel reduction side. This ensures reliable operation using both the main fuel and pilot fuel.

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

[0017] In 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 remains, resulting in operation using only pilot fuel.

[0018] This fuel injection control system is further characterized by comprising a fourth control means that, when the engine is normally stopped, switches the first switching means so that the fuel injection of the pilot fuel injection pump is within the range of the second injection amount, switches the second switching means so that the fuel injection of the main fuel injection pump is stopped, and then stops the pilot fuel injection pump.

[0019] According to this configuration, when the engine is stopped, instead of abruptly stopping the engine, first the main fuel is stopped, and after supplying only a predetermined amount of pilot fuel, the pilot fuel is also stopped, so that the engine can be smoothly stopped without applying an abrupt load to the engine.

[0020] This fuel injection control system further comprises fifth control means for switching the first switching means so that the fuel injection of the pilot fuel injection pump is in a stopped state and switching the second switching means so that the fuel injection of the main fuel injection pump is in a stopped state when the engine is in an emergency stop.

[0021] According to this configuration, in an emergency stop, by stopping both the main fuel and the pilot fuel, the engine can be quickly stopped. Also, by stopping both fuels, it is possible to prevent the spread of damage in case there is some malfunction in the injection system or the like.

[0022] This fuel injection control system is characterized in that a time difference is provided in the stopping of the fuels of both pumps such that the fuel injection of the pilot fuel is stopped after the fuel injection of the main fuel injection pump is stopped by the fifth control means.

[0023] According to this configuration, even in an emergency stop, by providing a time difference in the fuel stop of both pumps, that is, by stopping the fuel injection of the main fuel prior to the stop of the pilot fuel, it is possible to prevent unburned fuel of the main fuel from remaining in the cylinder.

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

[0025] According to this configuration, by setting the upper limit of the first injection amount of the pilot fuel to 15%, it is possible to perform hybrid operation mainly using the main fuel.

[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 where the upper limit exceeds 15% or the upper limit is 100%.

[0027] According to this configuration, by setting the range of the second injection amount of the pilot fuel such that the upper limit exceeds 15% or the upper limit is 100%, it becomes possible to operate only with the pilot fuel at the start or stop of the engine.

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

[0029] According to this configuration, by setting the upper limit of the injection amount range of the main fuel to 100%, it becomes possible to inject the main fuel to the maximum extent during normal operation, and operation mainly using the main fuel can be performed.

[0030] This fuel injection control system further includes pilot fuel limiting means for limiting the injection of pilot fuel to the pilot fuel injection pump, and the pilot fuel limiting means is characterized by having a limiting cylinder and a limiting valve for limiting the pilot fuel injection.

[0031] According to this configuration, the limiting cylinder and the limiting valve can prevent the injection amount of the pilot fuel from increasing rapidly at the start of the engine, etc., so that misfire can be suppressed and reliable ignition can be achieved.

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

[0033] With this configuration, the speed control valve prevents a sudden increase in the amount of main fuel injected when the clutch engages, thus suppressing misfires and ensuring reliable ignition.

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

[0035] This configuration allows for the shutdown of the main fuel supply to be handled by multiple systems, enabling the shutdown of the main fuel supply according to the situation.

[0036] This fuel injection control system is further characterized by comprising a bypass valve that is connected to the speed control valve and is used in emergency operation, and which bypasses the first stop valve.

[0037] With this configuration, even during emergency operation, such as when a malfunction occurs in the shut-off valve that shuts off the main fuel, the main fuel can be reliably shut off by providing a bypass valve.

[0038] This fuel injection control system is characterized by comprising 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] This fuel injection control system is further characterized by comprising a pressure sensor that monitors the pressure inside the cylinder of the cylinder unit.

[0040] This configuration allows for monitoring the combustion state by observing the internal pressure within the cylinder. Furthermore, it enables control of the pilot fuel injection amount when the combustion state becomes weak or misfired.

[0041] This fuel injection control system is characterized by using methanol as the primary fuel and heavy oil or hydrocarbon fuel as the pilot fuel.

[0042] This configuration allows for a dual-fuel engine where heavy oil or hydrocarbon fuels such as biofuels, methane-based fuels, or propane-based fuels are used as pilot fuel, and methanol is used as the main fuel.

[0043] A dual-fuel engine according to one embodiment of the present invention is characterized by comprising the fuel injection control system described above.

[0044] With this configuration, by incorporating the fuel injection control system described above, the engine ignites more reliably and stably than before, and misfires are prevented after ignition, resulting in a dual-fuel engine that can operate stably. [Effects of the Invention]

[0045] According to the configuration of the present invention, this fuel injection control system ensures more reliable and stable ignition of the main fuel than conventional systems, and prevents misfires after ignition. Furthermore, by incorporating this fuel injection control system into a dual-fuel engine, stable operation becomes possible. [Brief explanation of the drawing]

[0046] [Figure 1] This is a side view showing the schematic configuration of a dual-fuel engine according to one embodiment of the present invention. [Figure 2] This is a conceptual diagram showing the configuration of the fuel control system of a cylinder unit of a dual-fuel engine according to one embodiment of the present invention. [Figure 3] This graph shows the fuel injection of the cylinder unit of a dual-fuel engine according to one embodiment of the present invention. [Modes for carrying out the invention]

[0047] The following description of the dual-fuel engine according to the present invention will be based on the drawings, but the present invention is not limited to these embodiments. Furthermore, the components in the following embodiments include those that are easily substituted or substantially identical to those that are easily substituted by those skilled in the art. Moreover, the configurations described below can be combined as appropriate. In addition, various omissions, substitutions, or modifications of the configurations can be made without departing from the spirit of the present invention.

[0048] <1. Configuration of a dual-fuel engine> Figure 1 is a side view showing the configuration of a dual-fuel engine according to one embodiment of the present invention. As shown in Figure 1, the dual-fuel engine of this embodiment (hereinafter sometimes simply referred to as "engine") is a dual-fuel engine for ships 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 drive unit and a pilot fuel injection pump and drive unit on either the port side or the starboard side, and an intake and exhaust valve drive unit on the other side. In this embodiment, methanol is used as the main fuel, but ammonia may also be used, and although heavy oil A is used as the pilot fuel, petroleum-based heavy oil with good ignition properties or hydrocarbon-based fuels such as biofuels may also be used.

[0049] Figure 2 is a diagram showing the configuration of the fuel control system of the cylinder unit of a dual-fuel engine according to one embodiment of the present invention. As shown in Figure 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 is equipped with a movable rack rod 1a for adjusting the fuel injection amount, and the pilot fuel injection pump 2 is equipped with a movable rack rod 2a for adjusting the fuel injection amount. The fuel injection amount of the main fuel injection pump 1 is adjusted by the position of the moved rack rod 1a, and the fuel injection amount of the pilot fuel injection pump 2 is adjusted by the position of the moved rack rod 2a.

[0051] A main fuel injection volume adjustment shaft 4 is rotatably mounted, and one end of the rack rod 1a of the main fuel injection pump 1 is pivotally attached to the tip of a link member 4a, the base end of which is fixed to the injection volume adjustment shaft 4.

[0052] Furthermore, a pilot fuel injection volume adjustment shaft 5 is rotatably installed, and one end of the rack rod 2a of the injection pilot injection pump 2 is pivotally attached to the tip of a link member 5a, the base end of which is fixed to the injection volume adjustment shaft 5.

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

[0054] In other words, the base ends of the link members 4b and 5b are fixed to one end of the injection volume adjustment shafts 4 and 5, and the connecting rods 6b and 7b are pivotally attached to the tips of the link members 4b and 5b. When the arm 3a rotates in one direction, the injection volume adjustment shafts 4 and 5 on both sides are connected to rotate in either the fuel increase direction or the fuel decrease direction, respectively.

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

[0056] Furthermore, in each of the one-way damping mechanisms 8 and 9, when arm 3a of 3 rotates in the fuel increase direction, the coil springs 8b and 9b are compressed, and when arm 3a rotates in the fuel decrease direction, the rotational force is transmitted directly to the injection amount adjustment shafts 4 and 5, respectively, without compressing the coil springs 8b and 9b.

[0057] The other ends of the injection volume adjustment shafts 4 and 5 are connected to the tips of stop levers 11 and 12, respectively, so that the injection volume adjustment shafts 4 and 5 rotate simultaneously in the injection stop direction when the common fuel injection stop handle 10 is manually operated.

[0058] In other words, 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 closer to and further apart from each other by rotating the common fuel injection stop handle 10. The base ends of the stop levers 11 and 12 are pivotally attached to the tips of these link members 10b and 10c, respectively. Furthermore, the tips of each stop lever 11 and 12 are connected via link members 4c and 5c, whose base ends are fixed to injection amount adjustment shafts 4 and 5.

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

[0060] The piston rods 13a and 14a in the stop cylinders 13 and 14 are biased by springs 13b and 14b in the opposite direction to the stopping direction of the injection volume adjustment shafts 4 and 5. When control air is introduced into the stop cylinders 13 and 14, the piston rods 13a and 14a are actuated against the springs 13b and 14b, causing each injection volume adjustment shaft 4 and 5 to rotate 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 return to their original positions due to the springs 13b and 14b, allowing each injection volume adjustment shaft 4 and 5 to rotate to their maximum extent in the fuel increase direction.

[0061] A switching cylinder 15 is connected to the pilot fuel injection amount adjustment shaft 5 via a link member 5e. This switching cylinder 15 switches the amount of pilot fuel injected from the pilot fuel injection pump 1 between a first injection amount (fuel reduction) and a second injection amount (fuel increase) within a predetermined range in two stages.

[0062] In other words, the piston rod 15a inside the switching cylinder 15 is pivotally attached to the tip of the link member 5e, and the piston rod 15a is biased by the coil spring 15b in the direction that stops fuel injection on the injection amount adjustment shaft 5.

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

[0064] The main fuel injection volume adjustment shaft 4 is equipped with a limiting cylinder 16 that limits the injection volume to prevent a sudden increase in the amount of main fuel injected from the main fuel injection pump 1 when the main fuel injection starts.

[0065] The limiting cylinder 16 includes a piston rod 16a biased by a coil spring 16b in a direction that stops the injection of the main fuel. When control air is introduced into the limiting cylinder 16, the piston rod 16a moves in a direction opposite to that of the coil spring 16b. The tip of the piston rod 16a is connected to the injection volume adjustment shaft 4 via a link member 4e attached to the injection volume adjustment shaft 4.

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

[0067] As shown in Figure 2, the main fuel stop cylinder 13 is connected to a control air source A via a pipe 35 that connects to a pipe 36 and a pipe 37, which are equipped with a main fuel stop solenoid valve 22. By activating the main fuel stop solenoid valve 22, the injection of the main fuel can be stopped in the event of an emergency engine shutdown.

[0068] Piping 37 connects to control air source A via piping 39 with a starter valve 18 and piping 38 with a speed control valve 21. The speed control valve 21 delays the return speed of the main fuel stop cylinder 13, thereby gradually increasing the amount of main fuel injected and preventing sudden injection of main fuel during clutch engagement, thus suppressing misfires and facilitating adjustment of the amount of main fuel injected.

[0069] Piping 38 connects piping 40, which has a main fuel shut-off solenoid valve 20 interposed between it and the control air source A, and piping 41, which has a bypass valve 19 interposed between it and the control air source A. The bypass valve 19 is designed to shut off the main fuel in the event of a malfunction of the main fuel shut-off solenoid valve 20. In this embodiment, the bypass valve 19 is a manual valve.

[0070] The pilot fuel stop cylinder 14 is connected to the control air source A by a piping 33 that includes a pilot stop solenoid valve 24.

[0071] The switching cylinder 15 is connected to a control air source A via a pipe 31 with a starting valve 18 interposed between it and a pipe 30 to which a pipe 32 is connected via a three-way valve.

[0072] The limiting cylinder 16 is connected to the control air source A by a pipe 34 that includes a main fuel limiting solenoid valve 23. This configuration limits the amount of fuel injected to prevent a sudden increase when the main fuel injection starts, and also helps prevent black smoke when the clutch engages.

[0073] Furthermore, a rotational speed control valve 25 is interposed in the piping 42 connecting the control air source A and the governor 3, and a forward / reverse switching valve 26 is interposed in the 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 a reduction / reverse gear; a reverse gear with a built-in clutch, a reduction / reverse gear with a built-in clutch, a direct-drive variable-pitch propeller, etc., may also be used.

[0074] <2. Operation of a dual-fuel engine> Next, the operation of the dual-fuel engine of this embodiment, configured as described above, will be explained. First, when starting the dual-fuel engine, the starter valve 18 is pressed. When the starter valve 18 is opened, control air is supplied from the control air source A to the starter air guide valve P, and also 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, moving the rack rod 1a to the left side of the figure and stopping the injection of main fuel from the main fuel injection pump 1. The rack of the main fuel injection pump 1 then moves to the "0" position.

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

[0077] Furthermore, the starting air guide valve P is activated, and starting air is sequentially sent into each cylinder of the engine, forcibly driving the engine's pistons.

[0078] As the engine starts rotating and the rotational speed increases, the arm 3a of the governor 3 rotates to the fully open injection position (maximum position), but the main fuel is not injected. Instead, pilot fuel is injected from the pilot fuel injection pump 2. Once ignition occurs due to the injection of only pilot fuel, the engine starts and the rotational speed increases rapidly, so closing the starter valve 18 completes the starting process.

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

[0080] By releasing the starter valve 18, the starting air is shut off and the starting operation ends. When the starter valve 18 is closed, air is discharged from the main fuel stop cylinder 13 and the three-way valve 17, but the double check valve supplies air from the main fuel stop solenoid valve 22 side to the main fuel stop cylinder 13 and the three-way valve 17, shutting off the main fuel and keeping the pilot switching cylinder at the 40% position. The rotational speed stabilizes at a rotational speed equivalent to the pressure of the rotational speed control valve 25.

[0081] The governor 3's arm 3a rotates clockwise (fuel reduction direction) in response to a rapid increase in the engine's rotational speed, and the injection amount adjustment shaft 5 rotates counterclockwise, reducing the amount of pilot fuel injected and causing the engine's rotational speed to drop to idling. Note that the main fuel side injection amount adjustment shaft 4 is in the injection amount 0 position, so there is no injection of main fuel.

[0082] Next, the clutch engages when the forward / reverse switching valve 26 is operated while the engine is idling (pilot fuel operation).

[0083] When the clutch engages, the engine is loaded and the rotational speed decreases, but the amount of pilot fuel injected increases. When the clutch operating hydraulic pressure increases and the clutch engages, the main fuel shut-off solenoid valve 20 is released. Specifically, after the clutch engages, a timer is set so that the main fuel injection begins only after the engine rotational speed has stabilized. Then, the air from the three-way valve 17 is discharged, and the pilot fuel injection is fixed at 15%.

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

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

[0086] When the clutch engages, a load is placed on the engine, and the rotational speed decreases. As a result, the arm 3a of the governor 3 rotates counterclockwise (increasing fuel), and the injection amount adjustment shafts 4 and 5 rotate clockwise (increasing fuel). Consequently, injection of main fuel from the main fuel injection pump 1 begins, and at the same time, the injection amount of pilot fuel x from the pilot fuel injection pump 2 increases. However, the injection amount of pilot fuel is restricted to 15% or less of the heat output at full power by the switching cylinder 15 as described above, so it does not increase beyond that.

[0087] Furthermore, in the dual-fuel engine of this embodiment, in order to avoid sudden main fuel injection, such as at the start of main fuel injection, a main fuel limiting solenoid valve 23 is connected to a link member 4e connected to the injection amount adjustment shaft 4 via a limiting cylinder 16, and control air is introduced to achieve this.

[0088] Subsequently, as the engine's rotational speed setting is increased, the governor 3's arm 3a rotates further counterclockwise (in the direction of increased fuel), and only the injection amount adjustment shaft 4 rotates clockwise, increasing the injection amount of the main fuel. Meanwhile, the injection amount of pilot fuel is maintained at 15% of the maximum heat amount at full power by the switching cylinder 15.

[0089] When the clutch is disengaged, the clutch disengagement operation begins when the forward / reverse switching valve 26 is operated to the neutral position. The clutch hydraulic fluid pressure decreases. The main fuel shut-off 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, air is discharged from the pilot switching cylinder 15, and it moves from the upper limit 15% position to the 40% position.

[0090] In a normal shutdown from this pilot fuel-only operation state, fuel injection is stopped by operating the fuel injection stop handle 10. Note that in this state, only pilot fuel is being injected, so operating the fuel injection stop handle 10 will only stop the pilot fuel.

[0091] Furthermore, if a malfunction occurs in the main fuel injection system during engine operation, the main fuel shut-off solenoid valve 20 is opened, supplying control air to the main fuel stop cylinder 13 and the three-way valve 17. When the piston rod 13a of the main fuel stop cylinder 13 extends, the rack of the main fuel injection pump 1 moves to the "0" position, and the injection of the main fuel is stopped.

[0092] When the three-way valve 17 is activated, the air in the switching cylinder 15 is discharged and moves from the 15% position to the 40% position, allowing the pilot fuel injection amount to reach 40% of the heat amount at full power. Then, in response to the operation of the governor 3's arm 3a, only the pilot fuel is injected, enabling operation.

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

[0094] Next, after the set time has elapsed, the pilot stop solenoid valve 24 is activated, 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 stops. This configuration ensures that no unburned main fuel remains in the cylinder.

[0095] As described above, preferred embodiments of the present invention have been explained 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 starting valve is provided in this embodiment, a starting solenoid valve may also be used. Also, although heavy fuel oil A is used as the pilot fuel in this embodiment, hydrocarbon fuels such as biofuels, methane-based fuels, or propane-based fuels can also be used. [Explanation of Symbols]

[0096] 1. Main fuel injection pump 2 Pilot fuel injection pumps 3 Governors 4 Fuel injection amount adjustment shaft 5 Fuel injection amount adjustment shaft 6 Connection mechanism 7 Connection mechanism 8 One-way buffer mechanism 9 One-way buffer mechanism 10. Handle for stopping fuel injection 11 Stop lever 12 Stop lever 13 Main fuel shut-off cylinder 14 Pilot fuel shut-off cylinder 15 Switching Cylinder 16 Restriction Cylinder 17 Three-way valve 18 Starting valve 19 Bypass valve 20 Main fuel shutoff solenoid valve 21 Speed ​​control valve 22 Main fuel shutoff solenoid valve 23 Main fuel limiting solenoid valve 24 Pilot stop solenoid valve 25. Speed ​​control valve 26 Forward / Forward Switching Valve 100 Cylinder Unit A Controlled air source P Starting air guide valve

Claims

1. This is a fuel injection control system used in dual-fuel engines for ships that use two types of fuel. Equipped with multiple cylinder units, Each cylinder unit has a main fuel injection pump and a pilot fuel injection pump. A first switching means for selectively switching the fuel injection by the pilot fuel injection pump to a range of either a first injection amount on the fuel reduction side or a second injection amount on the fuel increase side, A second switching means for selectively switching the fuel injection by the main fuel injection pump to stop or to a predetermined injection amount range, A first control means, which, when the engine is started, switches the first switching means so that the fuel injection of the pilot fuel injection pump is within the range of the second injection amount, and also switches the second switching means so that the fuel injection of the main fuel injection pump is stopped, The system includes a second control means that, after a clutch engagement command, switches the first switching means so that the fuel injection of the pilot fuel injection pump is within the range of the first injection amount, and switches the second switching means so that the fuel injection of the main fuel injection pump is within a predetermined injection amount range, The invention further comprises a main fuel limiting means for limiting the injection of the main fuel when the main fuel injection pump starts fuel injection, Fuel injection control system.

2. The first control means is characterized in that the second injection amount of the pilot fuel injection pump is set to an injection amount that allows operation using only pilot fuel. The fuel injection control system according to claim 1.

3. The second control means is characterized by starting a timer for a predetermined time after the clutch engagement command, switching the first switching means after the predetermined time has elapsed so that the fuel injection of the pilot fuel injection pump is within the range of the first injection amount, and switching the second switching means so that the fuel injection of the main fuel injection pump is within the range of a predetermined injection amount. The fuel injection control system according to claim 1.

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

5. The system further comprises a fourth control means that, when the engine is normally stopped, switches the first switching means so that the fuel injection of the pilot fuel injection pump is within the range of the second injection amount, switches the second switching means so that the fuel injection of the main fuel injection pump is stopped, and then stops the pilot fuel injection pump. The fuel injection control system according to claim 1.

6. The system further comprises a fifth control means that, in the event of an emergency engine shutdown, switches the first switching means to stop the fuel injection of the pilot fuel injection pump, and also switches the second switching means to stop the fuel injection of the main fuel injection pump. The fuel injection control system according to claim 1.

7. The fifth control means is characterized in that a time difference is provided between the stopping of fuel from both pumps, such that the fuel injection of the pilot fuel is stopped after the fuel injection of the main fuel injection pump is stopped. The fuel injection control system according to claim 6.

8. The range of the first injection amount of the pilot fuel injection pump is characterized in that the upper limit is 15%. The fuel injection control system according to claim 1.

9. The range of the second injection amount of the pilot fuel injection pump is characterized in that the upper limit is greater than 15% or the upper limit is 100%. The fuel injection control system according to claim 1.

10. The main fuel injection pump is characterized in that the predetermined injection amount range is a range with an upper limit of 100%. The fuel injection control system according to claim 1.

11. The system further comprises pilot fuel limiting means for limiting the injection of pilot fuel to the pilot fuel injection pump, The pilot fuel limiting means is characterized by having a limiting cylinder and a limiting valve for limiting pilot fuel injection. The fuel injection control system according to claim 1.

12. A stop cylinder connected to the main fuel injection pump for stopping the supply of main fuel, The system includes a first stop valve connected to the main fuel injection pump via the stop cylinder, The device is further characterized by comprising a speed control valve interposed between the stop cylinder and the first stop valve. The fuel injection control system according to claim 1.

13. The present invention further comprises a second stop valve connected to the stop cylinder and used in emergency situations. The fuel injection control system according to claim 12.

14. The system is further characterized by comprising a bypass valve connected to the speed control valve and used during emergency operation, which bypasses the first stop valve. The fuel injection control system according to claim 12.

15. The system is characterized by comprising 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. The fuel injection control system according to claim 1.

16. The cylinder unit is further characterized by comprising a pressure sensor for monitoring the pressure inside the cylinder. The fuel injection control system according to claim 1.

17. The main fuel is methanol. A characteristic feature is that the pilot fuel is heavy oil or hydrocarbon fuel. The fuel injection control system according to claim 1.

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

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