JP6280763B2 - Liquid fuel supply system - Google Patents

Description

  The present invention relates to a liquid fuel supply system for a dual fuel engine.

  For example, a dual fuel engine (dual fuel engine) that generates power using both liquid fuel and gaseous fuel as disclosed in Patent Document 1 is known as a power source for ships.

Japanese Patent No. 3432998

  The dual fuel engine has a diesel mode (only for fuel oil) that uses only liquid fuel (fuel oil) and a gas mode that uses both liquid fuel and gaseous fuel (combustible gas) (two-fuel mode). It is operable. The diesel mode is a system in which liquid fuel is supplied to the combustion chamber and the supplied liquid fuel is burned. The gas mode is a system in which the gaseous fuel supplied to the combustion chamber at an arbitrary timing is ignited and burned starting from a pilot flame with a small amount of liquid fuel supplied to the combustion chamber.

  In the gas mode, if the supply amount of the liquid fuel for generating the pilot flame is not accurately controlled, the performance of the dual fuel engine may be deteriorated. For example, if the supply amount of the liquid fuel is excessive, the consumption amount of the liquid fuel increases and the possibility that NOx is generated increases. On the other hand, if the amount of liquid fuel supplied is too small, it will be difficult to stably supply a certain amount of liquid fuel, or foreign matter will adhere to the liquid fuel injection port, making it impossible to supply liquid fuel smoothly. There is a possibility.

  An object of this invention is to provide the liquid fuel supply system of the dual fuel engine which can supply a small amount of liquid fuel stably.

  A liquid fuel supply system according to the present invention is a liquid fuel supply system that supplies liquid fuel to a combustion chamber of a dual fuel engine, an injection valve that injects the liquid fuel into the combustion chamber, and the combustion from the injection valve. A control device capable of adjusting an injection pressure of the liquid fuel injected into the chamber, the injection pressure being an injection at the start of the liquid fuel when the injection of the liquid fuel from the injection valve is started The control device includes the start injection pressure in a gas mode in which both the liquid fuel and the gaseous fuel are supplied to the combustion chamber, and the liquid fuel is supplied to the combustion chamber and the gaseous fuel is supplied to the combustion chamber. It adjusts so that it may become higher than the said starting injection pressure in the diesel mode which is not performed.

  According to the present invention, when liquid fuel is injected into the combustion chamber, the starting injection pressure of liquid fuel when injection of liquid fuel from the injection valve is started is higher in the gas mode than in the diesel mode. By adjusting in this way, it is possible to stably supply a small amount of liquid fuel while suppressing foreign matter from adhering to the injection port of the injection valve.

  In the liquid fuel supply system according to the present invention, a pump having a piston and capable of supplying the liquid fuel to the injection valve, a high-pressure passage filled with a working liquid capable of operating the piston, and an inner position of the high-pressure passage A main valve that is disposed at the inner position and closes the high-pressure passage and is disposed at the outer position and opens the high-pressure passage; and is connectable to the high-pressure passage; A supply passage through which the working liquid supplied from the high pressure passage to the main valve flows, a spill passage connectable to the supply passage, and the supply passage and the high pressure passage are connected to the high pressure passage. Then, the main valve may be switched from one to the other in a state where the main valve is disposed at the inner position and a state where the supply passage and the spill passage are connected and the main valve is disposed at the outer position. Movement of the main valve when the main valve moves from the inner position toward the outer position by adjusting the flow rate of the working liquid that is disposed in the solenoid valve and the spill passage and flows out of the supply passage A sub solenoid valve capable of adjusting a speed, and the control device controls the main solenoid valve and the sub solenoid valve to adjust the injection pressure, and in the diesel mode, the main valve has a first speed. By moving the main solenoid valve and the sub solenoid valve so that the main valve moves from the inner position at a second speed higher than the first speed in the gas mode. The starting injection pressure in each of the diesel mode and the gas mode may be adjusted. In a liquid fuel supply system having a main solenoid valve and a sub solenoid valve, the main valve moves by opening the main solenoid valve to open and close the high-pressure passage. When the supply passage and the high pressure passage are connected and the working liquid is supplied to the main valve, the main valve moves to the inside of the high pressure passage and closes the high pressure passage. On the other hand, when the supply passage and the spill passage are connected and the working liquid in the supply passage flows into the spill passage, the main valve moves outside the high-pressure passage to open the high-pressure passage. As a result, the piston of the pump is operated to supply the liquid fuel to the injection valve, and the liquid fuel is injected from the injection valve. A sub solenoid valve is disposed in the spill passage. When the main valve moves so that the high-pressure passage is opened, the sub solenoid valve adjusts the flow rate of the working liquid flowing out from the supply passage. The moving speed of the main valve is adjusted by adjusting the flow rate of the working fluid. In the gas mode, the main valve moves from the high-pressure passage at a high second speed. As a result, the pressure of the working liquid in the high-pressure passage acting on the piston changes rapidly, and as a result, liquid fuel is injected from the injection valve at a high speed. Therefore, even when a small amount of liquid fuel is injected from the injection valve, it is possible to stably supply a small amount of liquid fuel by suppressing foreign matter from adhering to the injection port of the injection valve.

  In the liquid fuel supply system according to the present invention, the spill passage includes a quick spill passage and a slow spill passage narrower than the quick spill passage, and the sub solenoid valve is configured such that the working liquid from the supply passage is You may switch from the state which flows through a quick spill channel | path, and the state where the said working liquid from the said supply channel does not flow through the said quick spill channel | path to the other. When the working liquid from the supply passage flows into both the quick spill passage and the slow spill passage, the working liquid in the supply passage suddenly flows out of the supply passage. Thereby, the main valve can move at high speed. On the other hand, when the working liquid from the supply passage flows only into the slow spill passage, the working liquid in the supply passage gently flows out of the supply passage. Thereby, the main valve can move at a low speed.

  In the liquid fuel supply system according to the present invention, the sub solenoid valve may include a solenoid. Since the operating speed of the sub solenoid valve is adjusted by the solenoid, the moving speed of the main valve can be finely adjusted.

  In the liquid fuel supply system according to the present invention, in the diesel mode, the main valve moves at the first speed in the first half of the movement period from the inner position to the outer position, and the second valve in the second half of the movement period. You may move at a speed higher than one speed. By moving the main valve at a low first speed in the first half of the main valve movement period, the injection amount (injection rate) of the liquid fuel injected from the injection valve in the first half of the injection period in which the liquid fuel is injected is reduced. Is done. Thereby, combustion temperature is reduced, for example, the production | generation of NOx is suppressed. By moving the main valve at a high speed in the latter part of the main valve movement period, the injection amount increases in the latter part of the injection period, and liquid fuel necessary for combustion in the diesel mode is supplied to the combustion chamber.

  According to the liquid fuel supply system for a dual fuel engine according to the present invention, a small amount of liquid fuel can be stably supplied.

FIG. 1 is a schematic diagram illustrating an example of a dual fuel engine according to the present embodiment. FIG. 2 is a schematic diagram illustrating an example of the operation of the dual fuel engine according to the present embodiment. FIG. 3 is a plan view schematically showing an example of a state in which fuel is injected into the combustion chamber in the gas mode. FIG. 4 is a diagram schematically illustrating an example of a state in which fuel is burning in the gas mode. FIG. 5 is a plan view schematically showing an example of a state in which fuel is combusted in the gas mode. FIG. 6 is a cross-sectional view showing an example of the liquid fuel supply system according to the present embodiment. FIG. 7 is a diagram illustrating an example of the operation of the liquid fuel supply system according to the present embodiment. FIG. 8 is a diagram illustrating an example of the operation of the liquid fuel supply system according to the present embodiment. FIG. 9 is a diagram illustrating an example of the operation of the liquid fuel supply system according to the present embodiment. FIG. 10 is a diagram illustrating an example of a sub solenoid valve according to the present embodiment. FIG. 11 is a diagram for explaining an example of operations of the main solenoid valve and the sub solenoid valve in the diesel mode according to the present embodiment. FIG. 12 is a diagram for explaining an example of operations of the main solenoid valve and the sub solenoid valve in the gas mode according to the present embodiment. FIG. 13 is a diagram for explaining an example of the operation of the liquid fuel supply system in the diesel mode according to the present embodiment. FIG. 14 is a diagram for explaining an example of the operation of the liquid fuel supply system in the diesel mode according to the present embodiment.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings, but the present invention is not limited thereto. The requirements of the embodiments described below can be combined as appropriate. Some components may not be used.

  FIG. 1 is a schematic diagram illustrating an example of a dual fuel engine 1 according to the present embodiment. The dual fuel engine 1 according to the present embodiment includes a crosshead type diesel engine, and is used as a propulsion engine for a ship or the like, for example.

  The dual fuel engine 1 includes a base plate 18, a frame (main body) 12 provided on the base plate 18, and a jacket 13 provided on the frame 12.

  The dual fuel engine 1 includes a cylinder 2 provided in the jacket 13, a piston 3 that reciprocates inside the cylinder 2, a piston rod 14 connected to the piston 3, a connecting rod 19, a piston rod 14, A cross head 16 for connecting the connecting rod 19 and a crankshaft 4 connected to the connecting rod 19 via a crank pin 17 are provided.

  The cylinder 2 includes a cylinder liner 2A provided on the jacket 13 and a cylinder cover 2B provided on the cylinder liner 2A. The crosshead 16 moves along a guide portion 12G provided on the frame 12 and transmits mechanical power from the piston rod 14 to the connecting rod 19. The crankshaft 4 is disposed on the base plate 18 and outputs mechanical power transmitted from the piston 3.

  The top surface of the piston 3 and the ceiling surface of the cylinder 2 face each other. An exhaust valve 11 is provided at the center of the ceiling surface of the cylinder 2. A combustion chamber 7 is formed between the piston 3, the cylinder 2 and the exhaust valve 11.

  The dual fuel engine 1 includes a detection device 6 that detects a rotation angle (crank angle) of the crankshaft 4, a gaseous fuel supply system 15 that includes a gaseous fuel injection valve 8 that supplies gaseous fuel PG to the combustion chamber 7, and A liquid fuel supply system 20 including a liquid fuel injection valve 9 for supplying liquid fuel FO to the combustion chamber 7 and a control device 10 for controlling the dual fuel engine 1 are provided.

The gaseous fuel injection valve 8 can inject gaseous fuel PG into the combustion chamber 7. The gaseous fuel PG refers to, for example, one kind or a mixed gas of all combustible gases such as natural gas and H ₂ (hydrogen gas). In the present embodiment, two gaseous fuel injection valves 8 are arranged in the combustion chamber 7. The number of gaseous fuel injection valves 8 is arbitrary.

  The liquid fuel injection valve 9 can inject liquid fuel FO into the combustion chamber 7. The liquid fuel FO includes, for example, at least one of light oil, heavy oil, and heavy oil. In the present embodiment, two liquid fuel injection valves 9 are arranged in the combustion chamber 7. The number of liquid fuel injection valves 9 is arbitrary.

  The detection device 6 includes a crank angle sensor and detects the crank angle of the crankshaft 4. The detection device 6 may detect the crank angle with reference to the top dead center of the piston 3. For example, the crank angle sensor detects a crank angle from a rotational position of a measurement member (a disk, a detection gear, etc.) attached to the crankshaft 4 and outputs a crank angle signal. The crank angle sensor may be optical or electromagnetic. The detection device 6 may detect the crank angle from the rotational position of the crankshaft 4 or the position of the piston 3. Further, the position information (reference position information) of the crankshaft 4 when the piston 3 is located at the top dead center is detected using the top dead center sensor, and based on the position information and the rotational speed information of the crankshaft 4. The crank angle may be obtained.

  The detection result of the detection device 6 is output to the control device 10. The crank angle and the position of the piston 3 are associated with each other. The control device 10 can determine the position of the piston 3 including the top dead center and the bottom dead center based on the detection result of the detection device 6. Moreover, the control apparatus 10 is based on the output of the built-in timer and the detection result of the detection apparatus 6, for example, when the piston 3 is disposed at the top dead center and when it is disposed at the bottom dead center. Can be requested. The control device 10 controls the opening / closing of the exhaust valve 11, the injection of the gaseous fuel PG from the gaseous fuel injection valve 8, and the injection of the liquid fuel FO from the liquid fuel injection valve 9 based on the crank angle. Is output.

  FIG. 2 is a schematic diagram illustrating an example of the operation of the dual fuel engine 1. In the present embodiment, the dual fuel engine 1 is a two-stroke one-cycle uniflow scavenging diesel engine, and new air is introduced into the combustion chamber 7 from the scavenging port when the piston 3 is disposed near the bottom dead center. During the transition from the top dead center to the bottom dead center, the gas in the combustion chamber 7 is discharged from the exhaust port. The operation of the dual fuel engine 1 includes an intake process (A) for taking in new air and sending it to the combustion chamber 7, a compression process (B) for compressing the air in the combustion chamber 7 with the piston 3, and injecting fuel into the combustion chamber 7. The combustion process (C) for burning the fuel and the exhaust process (D) for discharging the gas in the combustion chamber 7 after the combustion process from the exhaust valve 11 are included.

  The dual fuel engine 1 can be operated in a diesel mode using only the liquid fuel FO and a gas mode using both the liquid fuel FO and the gaseous fuel PG.

  The diesel mode is a mode in which the liquid fuel FO is supplied to the combustion chamber 7 and the gaseous fuel PG is not supplied. The diesel mode may be referred to as a fuel oil dedicated mode. The diesel mode is a system in which liquid fuel FO is injected from the liquid fuel injection valve 9 into the combustion chamber 7 and the injected liquid fuel FO is burned. In the diesel mode, the gaseous fuel PG is not injected from the gaseous fuel injection valve 8 into the combustion chamber 7. In the diesel mode, after the air in the combustion chamber 7 is compressed in the compression process, the liquid fuel FO is injected from the liquid fuel injection valve 9 into the combustion chamber 7 in the combustion process. When the liquid fuel FO is injected into the high-temperature and high-pressure air, the liquid fuel FO spontaneously ignites and burns.

  The gas mode is a mode in which both the liquid fuel FO and the gaseous fuel PG are supplied to the combustion chamber 7. The gas mode may be referred to as a two-fuel mode. The gas mode is a system in which the gaseous fuel PG supplied to the combustion chamber 7 at an arbitrary timing is ignited and burned starting from a pilot flame by a small amount of liquid fuel FO supplied from the liquid fuel injection valve 9 to the combustion chamber 7. It is.

  Next, details of the gas mode will be described with reference to FIGS. 3, 4, and 5. FIG. 3 is a plan view schematically showing an example of a state in which the gaseous fuel PG is injected from the gaseous fuel valve 8 to the combustion chamber 7 and the liquid fuel FO is injected from the liquid fuel valve 9 to the combustion chamber 7 in the gas mode. FIG. FIG. 4 is a diagram schematically illustrating an example of a state in which the liquid fuel FO is burning in the gas mode. FIG. 5 is a plan view schematically showing an example of a state in which the gaseous fuel PG is burning in the gas mode.

  In the compression process, the air in the combustion chamber 7 is compressed. As shown in FIG. 3, in the combustion process, gaseous fuel PG is injected from the gaseous fuel injection valve 8 into the combustion chamber 7. A small amount of liquid fuel FO is injected from the liquid fuel injection valve 9 into the combustion chamber 7. When the piston 3 is disposed in the vicinity of the top dead center, the liquid fuel FO and the gaseous fuel PG are injected into the combustion chamber 7 almost simultaneously. In the gas mode, the main fuel is gaseous fuel PG.

  As shown in FIG. 3, the gaseous fuel injection valve 8 has a plurality of injection ports 8S for injecting the gaseous fuel PG. The liquid fuel injection valve 9 has a plurality of injection ports 9S that inject the liquid fuel FO. The gaseous fuel injection valve 8 injects the gaseous fuel PG outward with respect to the radial direction with respect to the axis of the gaseous fuel injection valve 8. The liquid fuel injection valve 9 injects the liquid fuel FO outward in the radial direction with respect to the axis of the liquid fuel injection valve 9. Each of the gaseous fuel injection valve 8 and the liquid fuel injection valve 9 injects the gaseous fuel PG and the liquid fuel FO so that the gaseous fuel PG and the liquid fuel FO intersect each other.

  A small amount of the liquid fuel FO injected from the liquid fuel injection valve 9 spontaneously ignites and generates a pilot flame. The gaseous fuel injection valve 8 injects high-pressure gaseous fuel PG. The high-pressure gaseous fuel PG has a pressure of 100 bar or more and 400 bar or less (for example, about 300 bar). In the gas mode, the gaseous fuel PG is ignited and burned starting from a pilot flame by a small amount of liquid fuel FO injected into the combustion chamber 7 filled with high-temperature and high-pressure air. 4 and 5 show an example of the state. In the gas mode, the gaseous fuel PG is burned as the main fuel.

  Next, an example of the liquid fuel supply system 20 according to the present embodiment will be described. FIG. 6 is a cross-sectional view showing an example of the liquid fuel supply system 20 according to the present embodiment. 7, 8, and 9 are diagrams illustrating an example of the operation of the liquid fuel supply system 20 according to the present embodiment.

  The liquid fuel supply system 20 supplies the liquid fuel FO to the combustion chamber 7 of the dual fuel engine 1. The liquid fuel supply system 20 is controlled by the control device 10. The liquid fuel supply system 20 includes a liquid fuel injection valve 9 that injects liquid fuel FO into the combustion chamber 7, a piston 25, a liquid fuel pump 21 that can supply the liquid fuel FO to the liquid fuel injection valve 9, and a liquid And a pressure accumulator 22 for controlling the fuel pump 21. The liquid fuel pump 21 is disposed on the upper surface of the housing of the pressure accumulator 22. The liquid fuel pumps 21 are provided in the same number as the number of the combustion chambers 7 of the double fuel engine 1. In the present embodiment, the liquid fuel FO is supplied from one liquid fuel pump 21 to the two liquid fuel injection valves 9. FIG. 6 shows one liquid fuel injection valve 9 for convenience.

  The liquid fuel injection valve 9 is a needle valve type that opens the injection port 9S when a predetermined pressure is applied. The liquid fuel injection valve 9 is connected to the liquid fuel pump 21 via the supply pipe 23 and injects the liquid fuel FO supplied from the liquid fuel pump 21 via the supply pipe 23 into the combustion chamber 7.

  The liquid fuel pump 21 includes a cylinder 24 and a piston 25 at least a part of which is disposed inside the cylinder 24. The piston 25 has an upper surface 251 and a lower surface 252. The upper surface 251 of the piston 25 forms a fuel chamber (accommodating space) 26 in which the liquid fuel FO is accommodated with the inner surface of the cylinder 24. The liquid fuel pump 21 is in contact with at least a part of the piston 25, an inlet 27 that supplies the liquid fuel FO to the fuel chamber 26, an outlet 28 that discharges excess liquid fuel FO from the fuel chamber 26. And a spring 29 to be arranged.

  The piston 25 can reciprocate inside the cylinder 24. The piston 25 is movable between the upper end position Pu and the lower end position Pd. The upper end position Pu is the uppermost position in the movable range of the piston 25. The lower end position Pd is the lowest position in the movable range of the piston 25.

  The piston 25 has a small diameter portion 25A and a large diameter portion 25B. The small diameter portion 25A is disposed on the upper portion of the large diameter portion 25B. The fuel chamber 26 is provided between the inner surface of the cylinder 24 and the upper surface 251 of the small diameter portion 25A. When the piston 25 moves upward, the volume of the fuel chamber 26 decreases. When the piston 25 moves downward, the volume of the fuel chamber 26 increases.

  The inlet 27 is connected to the fuel chamber 26 and supplies liquid fuel FO to the fuel chamber 26. The outlet 28 is connected to the fuel chamber 26 and discharges excess liquid fuel FO in the fuel chamber 26.

  The spring 29 is disposed around the small diameter portion 25A. The spring 29 is disposed between the large diameter portion 25 </ b> B and at least a part of the inner surface of the cylinder 24. The spring 29 applies a force (biasing force) to the piston 25 so that the piston 25 moves downward.

  The fuel chamber 26 is connected to the supply pipe 23 via the check valve 30. When the liquid fuel FO is supplied from the inlet 27 to the fuel chamber 26 and the piston 25 moves upward to reduce the volume of the fuel chamber 26, the liquid fuel FO in the fuel chamber 26 is injected into the liquid fuel via the supply pipe 23. Supplied to the valve 9. Excess liquid fuel FO in the fuel chamber 26 is discharged from the outlet 28.

  The pressure accumulator 22 is connected to the high-pressure passage 31 filled with hydraulic oil (working liquid) capable of operating the piston 25, the low-pressure passage 32 filled with hydraulic oil, and the high-pressure tank connected to the high-pressure passage 31 and containing hydraulic oil. 38 and a low-pressure tank 39 connected to the low-pressure passage 32 and containing hydraulic oil.

  The accumulator 22 includes a main valve 33 capable of opening and closing the high pressure passage 31, a spill valve 34 capable of opening and closing the high pressure passage 31, and a spring 43 disposed so as to contact at least a part of the main valve 33. A spring 44 disposed so as to be in contact with at least a part of the spill valve 34, a first passage (supply channel) 41 for supplying hydraulic oil to the main valve 33, and hydraulic oil to supply the spill valve 34 A second passage 42 for connecting, a third passage 40 connected to the high-pressure passage 31, a spill passage 50 connectable to the first passage 41, a pilot solenoid valve 35 for moving the main valve 33 and the spill valve 34, It has. The pilot solenoid valve 35 includes a main solenoid valve 36 and a sub solenoid valve 37 that operates separately from the main solenoid valve 36. The main solenoid valve 36 and the sub solenoid valve 37 are controlled by the control device 10.

  The high pressure passage 31 is connected to the high pressure tank 38. High pressure hydraulic oil is supplied from the high pressure tank 38 to the high pressure passage 31. The high pressure passage 31 is filled with high pressure hydraulic oil. The lower surface 252 of the piston 25 faces the high pressure passage 31. The hydraulic oil of the high pressure passage 31 is supplied to the lower surface 252 of the piston 25. The hydraulic oil in the high-pressure passage 31 applies a force to the lower surface 252 of the piston 25.

  The low pressure passage 32 is connected to each of the high pressure passage 31 and the low pressure tank 39. Low pressure hydraulic oil is supplied from the low pressure tank 39 to the low pressure passage 32. The low pressure passage 32 is filled with hydraulic oil having a pressure lower than that of the high pressure passage 31. A check valve 45 is disposed in the low pressure passage 32. The check valve 45 suppresses the hydraulic oil in the high pressure passage 31 from flowing into the low pressure passage 32.

  The main valve 33 can open and close the high-pressure passage 31. When the high pressure passage 31 is opened by the main valve 33, the high pressure tank 38 and the high pressure passage 31 below the piston 25 are connected. When the high pressure passage 31 is closed by the main valve 33, the high pressure tank 38 and the high pressure passage 31 below the piston 25 are shut off. The main valve 33 is movable between an inner position and an outer position of the high pressure passage 31. When the main valve 33 is disposed inside the high pressure passage 31, the high pressure passage 31 is closed. When the main valve 33 is disposed outside the high pressure passage 31, the high pressure passage 31 is opened. The spring 43 applies a force to the main valve 33 so that the main valve 33 moves from the inner position to the outer position of the high-pressure passage 31. That is, the spring 43 applies a force to the main valve 33 so that the main valve 33 retracts from the high pressure passage 31 and opens the high pressure passage 31.

  The spill valve 34 can open and close the high-pressure passage 31. When the high pressure passage 31 is opened by the spill valve 34, the low pressure tank 39 and the high pressure passage 31 below the piston 25 are connected. When the high pressure passage 31 is closed by the spill valve 34, the low pressure tank 39 and the high pressure passage 31 below the piston 25 are shut off. The spill valve 34 is movable between an inner position and an outer position of the high pressure passage 31. When the spill valve 34 is disposed inside the high-pressure passage 31, the high-pressure passage 31 is closed. When the spill valve 34 is disposed outside the high-pressure passage 31, the high-pressure passage 31 opens. The spring 44 applies a force to the spill valve 34 so that the spill valve 34 moves from the inner position to the outer position of the high-pressure passage 31. That is, the spring 44 applies a force to the spill valve 34 so that the spill valve 34 retracts from the high pressure passage 31 and opens the high pressure passage 31.

  In the following description, the inner position of the high-pressure passage 31 is appropriately referred to as a closed position. By disposing the main valve 33 at the closed position, the high-pressure passage 31 is closed by the main valve 33 (closed state). Further, the outer position of the high-pressure passage 31 is appropriately referred to as a retracted position. By disposing the main valve 33 at the retracted position, the high-pressure passage 31 is in an open state (open state). In the present embodiment, the open state includes states other than the closed state. That is, in this embodiment, the open state is a concept that includes not only a state in which the high-pressure passage 31 is fully opened but also a state in which the high-pressure passage 31 is slightly opened. In other words, the main valve 33 can adjust not only the opening / closing of the high-pressure channel 31 but also the opening degree of the high-pressure channel 31. The pilot solenoid valve 35 (the main solenoid valve 36 and the sub solenoid valve 37) controls the timing at which the high pressure flow path 31 is opened by the main valve 33 and the speed at which the high pressure flow path 31 is opened. The same applies to the spill valve 34.

  The first passage 41 can supply hydraulic oil to the main valve 33. The first passage 41 can be connected to the high-pressure passage 31. When the first passage 41 and the high pressure passage 31 are connected, hydraulic oil is supplied from the high pressure passage 31 to the first passage 41. The hydraulic fluid supplied from the high pressure passage 31 to the main valve 33 flows through the first passage 41 in a state where the first passage 41 and the high pressure passage 31 are connected. The main valve 33 is moved by the pressure of the hydraulic oil in the first passage 41. When high-pressure hydraulic oil from the high-pressure passage 31 is supplied to the first passage 41, the hydraulic oil in the first passage 41 exerts a force on the main valve 33 so that the main valve 33 moves from the retracted position to the closed position. Add As a result, the high pressure passage 31 is closed by the main valve 33.

  The second passage 42 can supply hydraulic oil to the spill valve 34. The second passage 42 can be connected to the high-pressure passage 31. When the second passage 42 and the high-pressure passage 31 are connected, hydraulic oil is supplied from the high-pressure passage 31 to the second passage 42. With the second passage 42 and the high-pressure passage 31 connected, the hydraulic oil supplied from the high-pressure passage 31 to the spill valve 34 flows through the second passage 42. The spill valve 34 is moved by the hydraulic oil pressure in the second passage 42. When the high pressure hydraulic oil from the high pressure passage 31 is supplied to the second passage 42, the hydraulic oil in the second passage 42 exerts a force on the spill valve 34 so that the spill valve 34 moves from the retracted position to the closed position. Add As a result, the high pressure passage 31 is closed by the spill valve 34.

  The third passage 40 is connected to the high-pressure passage 31 between the first passage 41 and the second passage 42. The third passage 40 includes a main channel connected to the high-pressure passage 31, and a branch channel 40A and a branch channel 40B branched from the main channel.

  The main solenoid valve 36 controls the operations of the main valve 33 and the spill valve 34. The main solenoid valve 36 connects the first passage 41 and the high-pressure passage 31 so that the main valve 33 is disposed inside the high-pressure passage 31, and connects the first passage 41 and the spill passage 50 to the main solenoid valve 36. The state in which the valve 33 is disposed outside the high-pressure passage 31 is switched from one to the other. The main solenoid valve 36 connects the second passage 42 and the high-pressure passage 31 and connects the second passage 42 and the low-pressure passage 32 with the spill valve 34 disposed at an inner position of the high-pressure passage 31. The spill valve 34 is switched from one of the states where the spill valve 34 is disposed outside the high-pressure passage 31 to the other.

  In the present embodiment, the main solenoid valve 36 is a so-called spool type. The main solenoid valve 36 includes a cylindrical spool valve 46 and a solenoid 47 and a solenoid 48 that move the spool valve 46 in the axial direction. The solenoid 47 is disposed above the solenoid 48. When the upper solenoid 47 is turned on, the spool valve 46 is raised by the action (magnetic force) of the solenoid 47 and is disposed at the first position P1 as shown in FIG. When the lower solenoid 48 is turned on, the spool valve 46 is lowered by the action (magnetic force) of the solenoid 48 and is disposed at the second position P2 as shown in FIG.

  That is, the spool valve 46 is movable between the first position P1 and the second position P2 by the action of the solenoid 47 and the solenoid 48. The first position P <b> 1 is the uppermost position in the movable range of the spool valve 46. The second position P <b> 2 is the lowest position in the movable range of the spool valve 46.

  The spool valve 46 has a groove 46A and a groove 46B. The groove 46 </ b> A and the groove 46 </ b> B are formed in the circumferential direction on the outer surface of the spool valve 46.

  The pressure accumulator 22 has a spill passage 50 into which at least a part of the hydraulic oil in the first passage 41 can flow. The spill passage 50 is connected to the low pressure passage 32. When at least a part of the hydraulic oil in the first passage 41 flows into the spill passage 50, the pressure of the hydraulic oil in the first passage 41 decreases. The spill passage 50 includes a quick spill passage 50A for rapidly reducing the pressure of the hydraulic oil in the first passage 41 and a slow spill passage 50B for gently reducing the pressure of the hydraulic oil in the first passage 41. The slow spill passage 50B is narrower than the quick spill passage 50A. That is, the passage area of the slow spill passage 50B is smaller than the passage area of the quick spill passage 50A. In the present embodiment, the orifice 53 is disposed in the slow spill passage 50B. The orifice 53 reduces the size (passage area) of the slow spill passage 50B.

  The sub solenoid valve 37 is disposed in the quick spill passage 50A. The sub solenoid valve 37 adjusts the flow rate of the hydraulic oil flowing out from the first passage 41 to adjust the moving speed of the main valve 33 when the main valve 33 moves from the inner position to the outer position of the high pressure passage 31. To do. The sub solenoid valve 37 is switched from one of the state in which the hydraulic oil from the first passage 41 flows through the quick spill passage 50A and the state in which the hydraulic oil from the first passage 41 does not flow through the quick spill passage 50A to the other. The moving speed of the main valve 33 is adjusted.

  As shown in FIG. 7, when the solenoid 47 is turned on and the spool valve 46 is raised and disposed at the first position P1, the first passage 41 is connected to the spill passage 50 via the groove 46A. . In the state shown in FIG. 7, the first passage 41 is connected to the low pressure passage 32 via the groove 46 </ b> A and the spill passage 50. By connecting the first passage 41 and the low pressure passage 32, at least a part of the hydraulic oil in the first passage 41 flows to the low pressure passage 32 via the spill passage 50. As a result, the pressure of the hydraulic oil in the first passage 41 decreases, and the pressure of the hydraulic oil that acts on the main valve 31 decreases. When the hydraulic oil pressure in the first passage 41 decreases, the main valve 33 moves from the closed position to the retracted position by the force of the spring 43. Thereby, the high-pressure passage 31 is opened.

  In the state shown in FIG. 7, the branch passage 40 </ b> A of the third passage 40 is closed by the outer surface of the spool valve 46. On the other hand, the branch passage 40B of the third passage 40 is connected to the second passage 42 through the groove 46B. That is, the high-pressure passage 31 and the second passage 42 are connected via the branch passage 40B and the groove 46B. Thereby, the pressure of the hydraulic oil in the second passage 42 increases, and the pressure of the hydraulic oil acting on the spill valve 34 increases. When the hydraulic oil pressure in the second passage 42 increases, the spill valve 34 moves to the closed position by the hydraulic oil pressure. As a result, the high pressure passage 31 is closed by the spill valve 34.

  When the main valve 33 is disposed at the retracted position and the spill valve 34 is disposed at the closed position, the high pressure hydraulic oil in the high pressure passage 31 applies a force to the lower surface 252 of the piston 25. The piston 25 moves (rises) toward the upper end position Pu by the force of the high pressure hydraulic oil in the high pressure passage 31. When the piston 25 is moved by the force of the hydraulic oil to reduce the volume of the fuel chamber 26 and the liquid fuel FO in the fuel chamber 26 is compressed, the liquid fuel FO in the fuel chamber 26 is compressed and the supply pipe 23 The pressure of the hydraulic oil and the pressure of the hydraulic oil of the liquid fuel injection valve 9 are increased. When the pressure becomes larger than the valve opening pressure of the liquid fuel injection valve 9, the injection port 9S of the liquid fuel injection valve 9 is opened, and the liquid fuel FO is injected from the injection port 9S into the combustion chamber 7 of the dual fuel engine 1. .

  As shown in FIG. 8, when the solenoid 48 is turned on and the spool valve 46 is lowered and arranged at the second position P2, the first passage 41 is branched from the third passage 40 via the groove 46A. It is connected to the path 40A, and is connected to the high-pressure path 31 through the groove 46A and the third path 40. On the other hand, the branch passage 40 </ b> B of the third passage 40 is closed by the outer surface of the spool valve 46. By connecting the first passage 41 and the high-pressure passage 31, at least part of the high-pressure hydraulic oil in the high-pressure passage 31 flows to the first passage 41 via the third passage 40. Thereby, the pressure of the hydraulic oil in the first passage 41 increases, and the pressure of the hydraulic oil acting on the main valve 33 increases. When the hydraulic oil pressure in the first passage 41 increases, the main valve 33 moves from the retracted position to the closed position by the hydraulic oil pressure. Thereby, the high pressure passage 31 is closed by the main valve 33.

  In the state shown in FIG. 8, the second passage 42 is connected to the low-pressure passage 32 via the groove 46B. By connecting the second passage 42 and the low pressure passage 32, at least a part of the hydraulic oil in the second passage 42 flows into the low pressure passage 32. As a result, the pressure of the hydraulic oil in the second passage 42 decreases, and the pressure of the hydraulic oil that acts on the spill valve 34 decreases. When the hydraulic oil pressure in the second passage 42 decreases, the spill valve 34 moves to the retracted position by the force of the spring 44. Thereby, the high-pressure passage 31 is opened.

  The hydraulic oil in the high pressure passage 31 does not flow to the low pressure passage 32 by the check valve 45, so that the pressure in the low pressure passage 32 and the second passage 42 is maintained.

  When the main valve 33 is disposed at the closed position and the spill valve 34 is disposed at the retracted position, the pressure of the hydraulic oil acting on the lower surface 252 of the piston 25 decreases. When the pressure of the hydraulic oil acting on the piston 25 decreases, the piston 25 moves (lowers) toward the lower end position Pd by the action of the spring 29.

  Thus, in the present embodiment, the main valve 33 moves between the retracted position and the closed position based on the hydraulic oil pressure in the first passage 41. The main valve 33 opens and closes the high-pressure passage 31 by moving between the retracted position and the closed position.

  The main solenoid valve 36 is hydraulic oil supplied to the main valve 33 via the first passage 41 so that the main valve 33 changes from one of a closed state in which the high-pressure passage 31 is closed by the main valve 33 and an open state to the other. Switch the pressure.

  The main solenoid valve 36 connects the first passage 41 and the spill passage 50 (low pressure passage 32) by disposing the spool valve 46 at the first position P1. Thereby, the pressure of the hydraulic oil in the first passage 41 becomes the same value as the pressure Pr1 of the hydraulic oil in the low-pressure passage 32. By connecting the first passage 41 and the spill passage 50, the main valve 33 is disposed at the retracted position, and the high-pressure passage 31 is opened.

  The main solenoid valve 36 connects the first passage 41 and the high-pressure passage 31 by disposing the spool valve 46 at the second position P2. As a result, the pressure of the hydraulic oil in the first passage 41 becomes the same value as the pressure Pr2 of the hydraulic oil in the high-pressure passage 31. By connecting the first passage 41 and the high-pressure passage 31, the main valve 33 is disposed at the closed position, and the high-pressure passage 31 is in a closed state.

  Thus, the main solenoid valve 36 can switch the pressure of the hydraulic oil in the first passage 41 from one of the pressure Pr1 and the pressure Pr2. Similarly, the main solenoid valve 36 can switch the pressure of the hydraulic oil in the second passage 42 from one of the pressure Pr2 and the pressure Pr1 to the other. As a result, the high-pressure passage 31 changes from one of an open state in which the hydraulic oil at the pressure Pr2 is applied to the piston 25 and a closed state in which the hydraulic oil at the pressure Pr1 is applied.

  In the following description, the state where the main valve 33 is disposed at the retracted position by the main electromagnetic valve 36 is appropriately referred to as an open state of the main electromagnetic valve 36. Further, a state in which the main valve 33 is disposed at the closed position by the main electromagnetic valve 36 is appropriately referred to as a closed state of the main electromagnetic valve 36. The operation of moving the main valve 33 to the retracted position by the main electromagnetic valve 36 is appropriately referred to as the opening operation of the main electromagnetic valve 36. The operation of moving the main valve 33 to the closed position by the main electromagnetic valve 36 is appropriately referred to as a closing operation of the main electromagnetic valve 36.

  The opening operation of the main solenoid valve 36 is an operation for opening the high-pressure passage 31 and moving the spool valve 46 to the first position P1. Further, the opening operation of the main electromagnetic valve 36 includes an operation of moving the spill valve 34 to the closed position.

  The closing operation of the main solenoid valve 36 is an operation for closing the high-pressure passage 31 and moving the spool valve 46 to the second position P2. Further, the closing operation of the main electromagnetic valve 36 includes an operation of moving the spill valve 34 to the retracted position.

  In the present embodiment, when the main electromagnetic valve 36 repeats the opening operation and the closing operation, the pressure of the hydraulic oil acting on the lower surface 252 of the piston 25 changes from one of the pressure Pr2 and the pressure Pr1 to the other. The pressure Pr2 is larger than the force of the spring 29. The pressure Pr1 is smaller than the force of the spring 29. When the pressure of the hydraulic oil changes from one of the pressure Pr2 and the pressure Pr1 to the other, the piston 25 moves between the upper end position Pu and the lower end position Pd, and the volume of the fuel chamber 26 is changed. Thereby, injection of the liquid fuel FO from the liquid fuel injection valve 9 is performed.

  In the present embodiment, when the main electromagnetic valve 36 is in an open state, injection of the liquid fuel FO from the liquid fuel injection valve 9 is started. When the main solenoid valve 36 is in the closed state, the injection of the liquid fuel FO from the liquid fuel injection valve 9 is stopped.

  Next, the sub electromagnetic valve 37 will be described. The sub solenoid valve 37 adjusts the flow rate per unit time of the hydraulic oil flowing out from the first passage 41 through the spill passage 50 to the low pressure passage 32, and the main valve 33 moves from the closed position toward the retracted position. The moving speed of the main valve 33 is adjusted. By adjusting the flow rate per unit time of the hydraulic oil flowing out from the first passage 41, the change amount (pressure change rate) of the hydraulic oil per unit time in the first passage 41 is adjusted. By adjusting the pressure change speed of the hydraulic oil in the first passage 41, the moving speed of the main valve 33 when the high pressure passage 31 changes from the closed state to the open state is adjusted. That is, by adjusting the pressure change speed of the hydraulic oil in the first passage 41, the moving speed of the main valve 33 when the main valve 33 moves from the closed position to the retracted position is adjusted.

  The sub solenoid valve 37 is disposed in the quick spill passage 50A. In the present embodiment, the sub solenoid valve 37 is a so-called spool type. The sub electromagnetic valve 37 includes a cylindrical spool valve 51 and a solenoid 52 that moves the spool valve 51 in the axial direction.

  The spool valve 51 has a groove 51A. The groove 51 </ b> A is formed in the circumferential direction on the outer surface of the spool valve 51.

  When the solenoid 52 is turned on, the spool valve 51 is raised by the action (magnetic force) of the solenoid 52 and is disposed at the third position P3 as shown in FIGS. When the solenoid 52 is turned OFF, the spool valve 51 is lowered by the action of gravity and is disposed at the fourth position P4 as shown in FIG.

  As shown in FIGS. 7 and 8, when the solenoid 52 is turned on and the spool valve 51 is raised and arranged at the third position P3, the quick spill passage 50A is connected to the low pressure passage 32 via the groove 51A. Connected.

  As shown in FIG. 9, when the solenoid 52 is turned off and the spool valve 51 is lowered and disposed at the fourth position P <b> 4, the quick spill passage 50 </ b> A is closed by the outer surface of the spool valve 51.

  When the spool valve 51 of the sub solenoid valve 37 is disposed at the third position P3 and the quick spill passage 50A and the low pressure passage 32 are connected, the spool valve 46 of the main solenoid valve 36 is moved from the second position P2 to the first position. When moved to the position P1, at least a part of the hydraulic oil in the first passage 41 having the pressure Pr2 flows at high speed toward the low-pressure passage 32 through the groove 46A, the quick spill passage 50A, and the groove 51A. Further, at least a part of the hydraulic oil in the first passage 41 flows toward the low-pressure passage 32 through the slow spill passage 50B. As a result, the pressure of the hydraulic oil in the first passage 41 rapidly decreases from the pressure Pr2 to the pressure Pr1. As a result, the main valve 33 arranged at the closed position moves from the closed position to the retracted position at a high speed (second speed) V2.

  When the main valve 33 moves from the closed position to the retracted position at a high speed, the high-pressure passage 31 rapidly changes from the closed state to the open state. Therefore, the pressure of the hydraulic oil in the high pressure passage 31 acting on the lower surface 252 of the piston 25 increases rapidly. Thereby, piston 25 raises rapidly. Accordingly, the volume of the fuel chamber 26 is rapidly reduced, and the pressure of the liquid fuel FO in the fuel chamber 26 and the pressure of the liquid fuel FO in the liquid fuel injection valve 9 are rapidly increased and injected from the liquid fuel injection valve 9. The speed of the liquid fuel FO increases.

  The spool valve 46 of the main solenoid valve 36 has moved from the second position P2 to the first position P1 while the spool valve 51 of the sub solenoid valve 37 is disposed at the fourth position P4 and the quick spill passage 50A is closed. In this case, the hydraulic oil in the first passage 41 having the pressure Pr2 flows at a low speed toward the low-pressure passage 32 through the groove 46A and the slow spill passage 50B. Since the slow spill passage 50 </ b> B is provided with the orifice 53 for reducing the passage area, the hydraulic oil in the first passage 41 flows slowly toward the low pressure passage 32 due to the flow resistance of the orifice 53. In a state where the spool valve 51 of the sub electromagnetic valve 37 is disposed at the fourth position P4, the hydraulic oil from the first passage 41 does not flow through the quick spill passage 50A. Thereby, the pressure of the hydraulic oil in the first passage 41 gradually decreases from the pressure Pr2 to the pressure Pr1. As a result, the main valve 33 arranged at the closed position moves from the closed position to the retracted position at a low speed (first speed) V1. The second speed V2 is higher (high speed) than the first speed V1.

  When the main valve 33 moves from the closed position to the retracted position at a low speed, the high pressure passage 31 gradually changes from the closed state to the open state. Therefore, the pressure of the hydraulic oil in the high pressure passage 31 that acts on the lower surface 252 of the piston 25 gradually increases. Thereby, piston 25 raises gently. Accordingly, the volume of the fuel chamber 26 gradually decreases, and the pressure of the liquid fuel FO in the fuel chamber 26 and the pressure of the liquid fuel FO in the liquid fuel injection valve 9 gradually increase and are injected from the liquid fuel injection valve 9. The speed of the liquid fuel FO is low.

  As described above, in the present embodiment, the sub solenoid valve 37 adjusts the flow rate per unit time of the hydraulic oil flowing out from the first passage 41 to adjust the pressure of the hydraulic oil per unit time acting on the main valve 33. Adjust the amount of change (pressure change rate). Thereby, the moving speed of the main valve 33 when the main valve 33 moves from the closed position to the retracted position can be adjusted to at least one of the first speed V1 and the second speed V2. The rising speed of the piston 25 is adjusted by adjusting the moving speed of the main valve 33. Thereby, the injection speed of the liquid fuel FO injected from the liquid fuel injection valve 9 is adjusted.

  In the following description, the state where the quick spill passage 50A is opened and the hydraulic oil in the first passage 41 flows into the low pressure passage 32 through both the quick spill passage 50A and the slow spill passage 50B is appropriately opened. It is called a state. In addition, the state where the quick spill passage 50A is closed and the hydraulic oil in the first passage 41 does not flow through the quick spill passage 50A but flows through the slow spill passage 50B to the low pressure passage 32 is appropriately closed. Called. In addition, the operation of opening the quick spill passage 50A is appropriately referred to as the opening operation of the sub solenoid valve 37. Further, the operation of closing the quick spill passage 50A is appropriately referred to as a closing operation of the sub electromagnetic valve 37.

  The open state of the sub solenoid valve 37 includes a state in which the main valve 33 in the closed position moves toward the retracted position at the second speed V2. The closed state of the sub solenoid valve 37 includes a state in which the main valve 33 in the closed position moves toward the retracted position at the first speed V1 that is lower than the second speed V2.

  FIG. 10 is a diagram illustrating an example of the sub electromagnetic valve 37 according to the present embodiment. As shown in FIG. 10, the solenoid 52 of the sub solenoid valve 37 includes an inner solenoid 52A and an outer solenoid 52B arranged around the inner solenoid 52A. In the state where the same voltage is applied to each of the inner solenoid 52A and the outer solenoid 52B, the outer solenoid 52B generates a larger force (magnetic force) than the inner solenoid 52A. In the present embodiment, the force generated by the outer solenoid 52B is about twice the force generated by the inner solenoid 52A. For example, the forces generated by the inner solenoid 52A and the outer solenoid 52B can be made different by making the number of turns of the coil different.

  The sub solenoid valve 37 includes a power supply 54 for applying a voltage to the inner solenoid 52A, a switch 55 for switching whether or not to apply a voltage from the power supply 54 to the inner solenoid 52A, a power supply 56 for applying a voltage to the outer solenoid 52B, and a power supply 56. And a switch 57 for switching whether or not to apply a voltage to the outer solenoid 52B. Thereby, electric power is individually given to each of the inner solenoid 52A and the outer solenoid 52B.

  In the present embodiment, the control device 10 operates the switch 55 and the switch 57 to selectively apply a voltage to each of the inner solenoid 52A and the outer solenoid 52B. Thereby, the control apparatus 10 can change the force (magnetic force) which the solenoid 52 generate | occur | produces in several steps.

  For example, when a voltage is applied only to the inner solenoid 52A, the solenoid 52 generates a force F1. When a voltage is applied only to the outer solenoid 52B, the solenoid 52 generates a force F2 that is greater than the force F1. When voltage is applied to both the inner solenoid 52A and the outer solenoid 52B, the solenoid 52 generates a force F3 that is greater than the forces F1 and F2.

  In the present embodiment, by changing the force of the solenoid 52 of the sub electromagnetic valve 37, the moving speed of the main valve 33 can be finely adjusted, and the rising speed of the piston 25 can be finely adjusted. Therefore, the injection speed of the liquid fuel FO from the liquid fuel injection valve 9 can be finely adjusted.

  That is, when the force of the solenoid 52 of the sub solenoid valve 37 is weakened, the moving speed of the spool valve 51 is lowered, and the time until the sub solenoid valve 37 is opened is lengthened. Therefore, the moving speed of the main valve 33 becomes low. Therefore, the injection speed of the liquid fuel FO injected from the liquid fuel injection valve 9 is reduced. On the other hand, when the force of the solenoid 52 is increased, the moving speed of the spool valve 51 is increased, and the injection speed of the liquid fuel FO injected from the liquid fuel injection valve 9 is increased.

  Next, an example of the operation of the liquid fuel supply system 20 according to the present embodiment will be described. In the present embodiment, the control device 10 controls the main electromagnetic valve 36 and the sub electromagnetic valve 37 to adjust the pressure (injection pressure) of the liquid fuel FO injected from the liquid fuel injection valve 9 into the combustion chamber 7. Can do. The injection pressure of the liquid fuel FO is the pressure (start of the liquid fuel FO when the injection of the liquid fuel FO from the liquid fuel injection valve 9 is started from the state where the liquid fuel FO is not injected from the liquid fuel injection valve 9. Injection pressure). The starting injection pressure is the amount of change in the pressure of the liquid fuel FO injected from the liquid fuel injection valve 9 when the injection of the liquid fuel FO from the liquid fuel injection valve 9 to the combustion chamber 7 is started (per unit time). Pressure increase). The control device 10 can adjust the injection pressure (increase in pressure per unit time) of the liquid fuel FO including the start-time injection pressure by adjusting the moving speed of the main valve 33.

  FIG. 11 is a diagram for explaining an example of operations of the main solenoid valve 36 and the sub solenoid valve 37 in the diesel mode. In the graph shown in FIG. 11, the horizontal axis represents time. The vertical axis indicates the pressure of the liquid fuel FO in the liquid fuel injection valve 9 (or the fuel chamber 26). FIG. 11 also shows the states (open state or closed state) of the main electromagnetic valve 36 and the sub electromagnetic valve 37 corresponding to time.

At time T _0, each of the main solenoid valve 36 and the sub-solenoid valve 37 is closed. Thus, at time T _0, the liquid fuel FO from the liquid fuel injection valve 9 is not injected.

  The control device 10 opens the main electromagnetic valve 36 at the time Ta. At time Ta, the sub solenoid valve 37 is in a closed state. When the main electromagnetic valve 36 is in the open state, the main valve 33 in the closed position starts moving toward the retracted position at time Ta. Further, at the time point Ta, the injection of the liquid fuel FO from the liquid fuel injection valve 9 is started.

  The control device 10 sets the sub solenoid valve 37 to the open state while maintaining the open state of the main solenoid valve 36 at the time Tb after the time Ta. That is, at the time Tb, both the main solenoid valve 36 and the sub solenoid valve 37 are opened. At time Tb, the main valve 33 has not reached the retracted position. At time Tb, the main valve 33 is disposed at an intermediate position between the closed position and the retracted position.

  The control device 10 closes both the main solenoid valve 36 and the sub solenoid valve 37 at the time Tc after the time Tb. Accordingly, at the time Tc, the injection of the liquid fuel FO from the liquid fuel injection valve 9 is stopped. At time Tc, the main valve 33 is placed in the retracted position. When the main electromagnetic valve 36 is closed at the time Tc, the main valve 33 is returned to the closed position.

  In the period from the time point Ta to the time point Tb, the main electromagnetic valve 36 is in the open state and the sub electromagnetic valve 37 is in the closed state, so the main valve 33 moves from the closed position to the intermediate position at the first speed V1. . In the period from the time point Ta to the time point Tb, the main valve 33 moves at a low speed (first speed) V1, and the pressure of the hydraulic oil acting on the lower surface 252 of the piston 25 gradually increases, so the pressure of the liquid fuel FO Rises moderately.

  In the period from the time point Tb to the time point Tc, the main solenoid valve 36 is in the open state and the sub solenoid valve 37 is also in the open state, so the main valve 33 moves from the intermediate position to the retracted position at the second speed V2. . In the period from the time point Tb to the time point Tc, the main valve 33 moves at a high speed (second speed) V2, and the pressure of the hydraulic oil acting on the lower surface 252 of the piston 25 rapidly increases, so the pressure of the liquid fuel FO Rises rapidly.

  In the present embodiment, in the diesel mode, the main valve 33 moves at the first speed V1 in the first half of the moving period from the closed position to the retracted position (the period from the time point Ta to the time point Tb) and the second half of the moving period ( During a period from time Tb to time Tc), the vehicle moves at a second speed V2 higher than the first speed V1. Thereby, the injection of the liquid fuel FO injected from the liquid fuel injection valve 9 in the first half of the injection period (the period from the time point Ta to the time point Tc) in which the liquid fuel FO is injected (the period from the time point Ta to the time point Tb). The amount (injection rate) can be reduced and the combustion temperature can be reduced. Therefore, for example, generation of NOx can be suppressed. In the later stage of the injection period (the period from time Tb to time Tc), the liquid fuel FO necessary for combustion in the diesel mode can be supplied to the combustion chamber 7 by increasing the injection rate.

  Next, an example of the operation of the liquid fuel supply system 20 in the gas mode will be described. FIG. 12 is a diagram for explaining an example of operations of the main solenoid valve 36 and the sub solenoid valve 37 in the gas mode. In the graph shown in FIG. 12, the horizontal axis indicates time. The vertical axis indicates the pressure of the liquid fuel FO in the liquid fuel injection valve 9 (or the fuel chamber 26). FIG. 12 also shows the states (open state or closed state) of the main electromagnetic valve 36 and the sub electromagnetic valve 37 corresponding to time. In the graph of FIG. 12, a line L1 shows an example of the operation of the main electromagnetic valve 36 and the sub electromagnetic valve 37 in this example, and a line L2 shows the main electromagnetic valve 36 and the sub electromagnetic valve described with reference to FIG. An example of the valve 37 is shown.

At time T _0, each of the main solenoid valve 36 and the sub-solenoid valve 37 is closed. Thus, at time T _0, the liquid fuel FO from the liquid fuel injection valve 9 is not injected.

  The control device 10 simultaneously opens the main solenoid valve 36 and the sub solenoid valve 37 at time Ta. When the main electromagnetic valve 36 is in the open state, the main valve 33 in the closed position starts moving toward the retracted position at time Ta. Further, at the time point Ta, the injection of the liquid fuel FO from the liquid fuel injection valve 9 is started.

  The control device 10 closes both the main electromagnetic valve 36 and the sub electromagnetic valve 37 at time T1 after time Ta. Therefore, at the time point T1, the injection of the liquid fuel FO from the liquid fuel injection valve 9 is stopped. The period from time Ta to time T1 is shorter than the period from time Ta to time Tb described with reference to FIG. At time T1, the main valve 33 has not reached the retracted position. At time T1, the main valve 33 is disposed at an intermediate position between the closed position and the retracted position. When the main electromagnetic valve 36 is closed at the time Tc, the main valve 33 is returned from the intermediate position to the closed position.

  At time Ta, both the main solenoid valve 36 and the sub solenoid valve 37 are in the open state, so the main valve 33 moves from the closed position toward the retracted position at the second speed V2 higher than the first speed V1. In the present embodiment, the main valve 33 moves at a high speed (second speed) V2 from the closed position to the intermediate position in the period from the time point Ta to the time point T1. Therefore, in the period from the time point Ta to the time point T1 in the gas mode, the pressure of the hydraulic oil acting on the lower surface 252 of the piston 25 increases rapidly, and the pressure of the liquid fuel FO increases rapidly.

  In FIG. 12, each of the area AR1 and the area AR2 corresponds to the supply amount of the liquid fuel FO. The area of the area AR1 is equal to the area of the area AR2. As shown in FIG. 12, in this example, it can be seen that the pressure of the liquid fuel FO is high and a predetermined amount of the liquid fuel FO can be supplied in a short time.

  According to the present embodiment, when a small amount of liquid fuel FO is supplied to the combustion chamber 7 in the gas mode, the control device 10 rapidly changes the pressure of the liquid fuel FO of the liquid fuel injection valve 9 to change the liquid fuel. The liquid fuel FO is injected from the injection port 9S of the injection valve 9 at a high speed in a short time. Therefore, it is possible to stably supply a small amount of liquid fuel FO while suppressing foreign matter from adhering to the injection port 9S.

  That is, in the present embodiment, the main electromagnetic valve 36 is changed from the closed state to the open state, and the liquid fuel FO is injected from the liquid fuel injection valve 9 from the state where the liquid fuel FO is not injected from the liquid fuel injection valve 9. Change to the state to be. The pressure of the liquid fuel FO (starting injection pressure) when the injection of the liquid fuel FO from the liquid fuel injection valve 9 is started from the state where the liquid fuel FO is not injected is higher in the gas mode than in the diesel mode. . In other words, the liquid injected from the liquid fuel injection valve 9 when the main electromagnetic valve 36 is changed from the closed state to the open state and injection of the liquid fuel FO from the liquid fuel injection valve 9 to the combustion chamber 7 is started. The amount of change in the pressure of the fuel FO (the amount of increase in pressure per unit time) is larger in the gas mode than in the diesel mode.

  FIGS. 13A and 13B are diagrams illustrating an example of a control method of the sub solenoid valve 37 in the diesel mode. FIG. 13A shows the relationship between the fuel index FI that is an index of the amount of fuel injected into the combustion chamber 7 and the load of the dual fuel engine 1. FIG. 13B shows the difference between the time when the main solenoid valve 36 is opened and the time when the sub solenoid valve 37 is opened (the delay time until the sub solenoid valve 37 is opened). The relationship with the fuel index FIO that is an index of the injection amount of the liquid fuel FO injected into the combustion chamber 7 is shown. The fuel index FI is a fuel index for all fuels including both the gaseous fuel PG and the liquid fuel FO. The fuel index FIO is a fuel index related to the liquid fuel FO.

  As shown in FIG. 13A, in the diesel mode, the fuel index FI coincides with the fuel index FIO that is an index of the injection amount of the liquid fuel FO.

  As shown in FIG. 13B, the control device 10 reduces the delay time when reducing the injection amount of the liquid fuel FO, and increases the delay time when increasing the injection amount of the liquid fuel FO. Good. That is, in the diesel mode, when reducing the injection amount of the liquid fuel FO, the control device 10 reduces the difference between the time point Ta and the time point Tb described with reference to FIG. 11 and increases the injection amount of the liquid fuel FO. When doing so, the difference between the time point Ta and the time point Tb may be increased.

  FIGS. 14A and 14B are diagrams illustrating an example of a control method of the sub electromagnetic valve 37 in the gas mode. FIG. 14A shows the relationship between the fuel index FI and the load. FIG. 14B shows the relationship between the delay time until the sub solenoid valve 37 is opened and the fuel index FIO, which is an index of the injection amount of the liquid fuel FO injected into the combustion chamber 7.

  As shown in FIG. 14A, in the gas mode, the fuel index FI includes a fuel index FIO that is an index of the injection amount of the liquid fuel FO and a fuel index FIG that is an index of the injection amount of the gaseous fuel PG. The sum matches. The fuel index FIG is a fuel index related to the gaseous fuel PG.

  As shown in FIG. 14B, the control device 10 reduces the delay time when reducing the injection amount of the liquid fuel FO, and increases the delay time when increasing the injection amount of the liquid fuel FO. Good. In the present embodiment, in the gas mode, the liquid fuel FO is injected into the combustion chamber 7 so that the value of the fuel index FIO is 10. As shown in FIG. 14B, when the value of FIO is 10, the delay time (the difference between the time point Ta and the time point T1 described with reference to FIG. 12) is zero.

  In the embodiment described with reference to FIG. 12, the main solenoid valve 36 and the sub solenoid valve 37 are simultaneously opened in the gas mode. As shown in FIG. 14B, in the gas mode, when the FIO value is large (when the injection amount of the liquid fuel FO to the combustion chamber 7 is increased), the main electromagnetic valve 36 is opened, and then the sub electromagnetic The valve 37 may be opened. That is, in the gas mode, whether or not to open the main solenoid valve 36 and the sub solenoid valve 37 at the same time may be determined based on the injection amount of the liquid fuel FO to the combustion chamber 7. The time when 36 is opened and the time when the sub solenoid valve 37 is opened may be different, and the time when the main solenoid valve 36 is opened and the time when the sub solenoid valve 37 is opened. The difference (delay time) may be adjusted.

  As described above, according to the present embodiment, when the injection of the liquid fuel FO from the liquid fuel injection valve 9 to the combustion chamber 7 is started, the pressure of the liquid fuel FO in the gas mode is higher than that in the diesel mode. By adjusting the pressure so as to be higher than the pressure, it is possible to stably supply a small amount of liquid fuel FO while suppressing foreign matter from adhering to the injection port 9S. That is, in the gas mode, when a small amount of liquid fuel FO is injected into the combustion chamber 7, the pressure of the liquid fuel FO of the liquid fuel injection valve 9 is rapidly increased to increase the liquid fuel FO from the injection port 9S at a high speed. Since the injection is performed, it is possible to stably supply a small amount of liquid fuel FO while suppressing foreign matter from adhering to the injection port 9S.

  Further, according to the present embodiment, in the diesel mode, the injection amount (injection rate) of the liquid fuel FO injected from the liquid fuel injection valve 9 is reduced in the first half of the injection period in which the liquid fuel FO is injected. As a result, the combustion temperature can be reduced. Therefore, for example, generation of NOx can be suppressed. Further, since the injection rate is increased in the later stage of the injection period, the liquid fuel FO necessary for combustion in the diesel mode can be supplied to the combustion chamber 7.

DESCRIPTION OF SYMBOLS 1 Dual fuel engine 7 Combustion chamber 9 Liquid fuel injection valve 20 Liquid fuel supply system 24 Cylinder 25 Piston 26 Fuel chamber (accommodating space)
31 High pressure passage 33 Main valve 36 Main solenoid valve 37 Sub solenoid valve 251 Upper surface 252 Lower surface FO Liquid fuel PG Gas fuel

Claims (5)

A liquid fuel supply system for supplying liquid fuel to a combustion chamber of a dual fuel engine,
A liquid fuel injection valve for injecting the liquid fuel into the combustion chamber;
A control device capable of adjusting an injection pressure of the liquid fuel injected from the liquid fuel injection valve into the combustion chamber,
The injection pressure includes a starting injection pressure of the liquid fuel when the injection of the liquid fuel from the liquid fuel injection valve is started,
The control device is configured such that the starting injection pressure in the gas mode in which the liquid fuel is supplied from the liquid fuel injection valve to the combustion chamber and the gaseous fuel is supplied from the gaseous fuel injection valve, and the liquid fuel is supplied to the combustion chamber. liquid fuel supply system to be adjusted to be higher than the start time injection pressure in a diesel mode in which the supplied the gas fuel is not supplied. A pump having a piston and capable of supplying the liquid fuel to the liquid fuel injection valve;
A high pressure passage filled with a working liquid capable of actuating the piston;
A main valve that is movable between an inner position and an outer position of the high-pressure passage, is disposed at the inner position to close the high-pressure passage, and is disposed at the outer position to open the high-pressure passage;
A supply passage that is connectable to the high-pressure passage and through which the working liquid supplied from the high-pressure passage to the main valve is connected to the high-pressure passage;
A spill passage connectable with the supply passage;
A state where the main valve is disposed at the inner position by connecting the supply passage and the high pressure passage, and a state where the main valve is disposed at the outer position by connecting the supply passage and the spill passage. A main solenoid valve for switching from one to the other,
The moving speed of the main valve when the main valve moves from the inner position toward the outer position can be adjusted by adjusting the flow rate of the working liquid that is arranged in the spill passage and flows out from the supply passage. A sub solenoid valve,
The control device controls the main solenoid valve and the sub solenoid valve to adjust the injection pressure, and in the diesel mode, the main valve moves from the inner position at a first speed, and in the gas mode, the The start time in each of the diesel mode and the gas mode by controlling the main solenoid valve and the sub solenoid valve so that the main valve moves from the inner position at a second speed higher than the first speed. The liquid fuel supply system according to claim 1, wherein the injection pressure is adjusted. The spill passage includes a quick spill passage and a slow spill passage narrower than the quick spill passage,
The sub electromagnetic valve switches from one of a state in which the working liquid from the supply passage flows through the quick spill passage and a state in which the working liquid from the supply passage does not flow through the quick spill passage from one to the other. A liquid fuel supply system according to claim 1.   The liquid fuel supply system according to claim 2 or 3, wherein the sub solenoid valve includes a solenoid.   In the diesel mode, the main valve moves at the first speed in the first half of the movement period from the inner position to the outer position, and moves at a speed higher than the first speed in the second half of the movement period. Item 5. The liquid fuel supply system according to any one of Items 2 to 4.

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