JP2010133391A - Fuel injection device for coping with multiple kinds of fuel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device for an internal combustion engine for coping with multiple kinds of fuel. <P>SOLUTION: A diesel engine includes a main and an auxiliary fuel system. The main fuel system supplies and injects fuel by a mechanical fuel injection pump 50. The auxiliary fuel system injects high pressure fuel accumulated in a common rail 60. The fuel supplied by the auxiliary fuel system is injected at a high pressure from the beginning of injection and fuel particles are atomized. When the main and auxiliary fuel are the same kind of fuel, atomization of particles is as well advantageous for ignitability. When fuel of bad ignitability is used as the main fuel, fuel of good ignitability is used as the auxiliary fuel, and the main fuel is burned with the auxiliary fuel used as a source of fire. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel injection device that injects fuel into a cylinder of an internal combustion engine, and more particularly to a fuel injection device that can handle various types of fuel.

  There is a need for an internal combustion engine that can be operated with various types of fuel and a fuel injection device used for such an internal combustion engine against the background of depletion of petroleum resources and global warming. For example, it has been proposed to use lower quality petroleum-based fuels and biofuels. Fuels have different ignitability depending on the species, and in order to be able to operate with various types of fuel, it is necessary to cope with fuels with poor ignitability. In the case of using a fuel with poor ignitability, a technology is known in which a fuel with better ignitability than this fuel is injected first, ignited, and this fuel is used as a fire type to burn fuel with poor ignitability (see below, patents) Reference 1).

JP-A-6-159182

  As described above, in order to be able to cope with various types of fuel, it is necessary to make it possible to burn even a fuel with poor ignitability. Moreover, in the above-mentioned Patent Document 1, it is necessary to prepare a fuel with good ignitability for use as a fire type separately from the main fuel. In addition, when the fuel type is changed, it is desired that the injection control corresponding to this is executed.

  An object of the present invention is to solve at least one of the above problems or problems.

  The fuel injection device corresponding to claim 1 has a main fuel system that injects fuel, and a sub fuel system that injects fuel at a pressure higher than the injection pressure of the main fuel system in the initial stage of the fuel injection period. The fuel injected at a high pressure from the auxiliary fuel system is injected as finer particles.

  A fuel injection device corresponding to claim 2 includes a main fuel system that injects fuel, and a sub fuel system that injects fuel at a pressure higher than the injection pressure of the main fuel system when injecting simultaneously with the main fuel system, Have The fuel injected at a high pressure from the auxiliary fuel system is injected as finer particles.

  Further, it is possible to have a control means for changing the fuel injection condition of the auxiliary fuel system depending on the property of the fuel.

  Further, it is possible to provide pressure detecting means for detecting the pressure in the cylinder and control means for changing the injection condition of the auxiliary fuel based on the detected pressure. The property of the fuel affects the pressure in the cylinder. Conversely, the property of the fuel can be estimated by monitoring this pressure.

  Further, the pressure detecting means can be means for indirectly detecting the pressure in the cylinder outside the cylinder. The pressure detection means can be installed without major modifications to the engine body. As such a pressure detection means, one using a strain gauge for measuring the elongation of the cylinder head bolt can be used. Further, it is possible to use a load cell that measures the elongation of the cylinder head bolt and the force applied to the bolt. Also, the equipment attached to the cylinder head and partially exposed to the combustion chamber, such as the extension of the bolt that fixes the indicator cock and fuel injection valve to the cylinder head, and the pressure in the cylinder based on the force applied to the washer of this bolt You may make it detect.

  Further, it is possible to provide a control means for changing the injection condition of the auxiliary fuel system in accordance with the load condition of the internal combustion engine. In particular, when the load condition is a low load, the injection of only the auxiliary fuel system or the injection of the auxiliary fuel system together with the main fuel system can be performed. The main fuel system is controlled according to the load, and the sub fuel system is controlled in accordance with this control.

  Further, the internal combustion engine can be mounted on the moving body, and can have control means for changing the injection condition of the auxiliary fuel system in accordance with the geographical condition of the current position of the moving body. For example, when the moving body is a ship, the control of the auxiliary fuel system is changed depending on the distance from the land and whether or not the vehicle is in a harbor.

  Further, the internal combustion engine can be a multi-cylinder engine, and can be provided with a combustion state detecting means for detecting the combustion state of each cylinder for each cylinder, and the injection condition of the sub fuel system is changed based on the detected combustion state. It is possible to have a control means. The combustion state detection means can detect the combustion state based on at least one of the maximum cylinder internal pressure, the ignition timing, the exhaust temperature, and the indicated mean effective pressure, for example.

  In addition, it is possible to have control means for changing the injection conditions of the auxiliary fuel system based on at least one of the flow rates of the main fuel and auxiliary fuel and the exhaust temperature of the internal combustion engine.

  Further, the auxiliary fuel system can have a pressure accumulating section for storing pressurized fuel. By accumulating fuel in the accumulator, high-pressure fuel is instantaneously injected. The pressure accumulating section can be a common rail, for example.

  The internal combustion engine can be a diesel engine.

  Furthermore, the auxiliary fuel system may have an electrically controlled valve that controls the supply of pressurized fuel. The injection timing and the injection amount are easily changed by the electrically controlled valve.

  The main fuel injected by the main fuel system and the auxiliary fuel injected by the sub fuel system can be different types of fuel. For example, the auxiliary fuel can be a fuel having a higher cetane number than the main fuel. Further, for example, the auxiliary fuel can be light oil. For example, the main fuel can be heavy oil.

  Further, the main fuel system and the auxiliary fuel system can share one fuel injection valve, and the main fuel system and the auxiliary fuel system can be joined upstream of the fuel injection valve.

  Further, the main fuel system and the auxiliary fuel system can share one fuel injection valve, and the main fuel system and the auxiliary fuel system can be merged in the fuel injection valve.

  In addition, the main fuel system and the sub fuel system can have one injection valve having two types of nozzles that are controlled independently, and the main fuel from one type of nozzle and the sub type from the other type of nozzle. Fuel can be injected.

  Further, the main fuel system and the sub fuel system can have independent fuel injection valves respectively arranged for one cylinder.

  Also, a plurality of sub fuel systems can be provided, and different fuels can be injected for each sub fuel system. Also, by having a plurality of sub fuel systems, more fuel can be injected when the injection amount is insufficient with one sub fuel system.

  25. A fuel injection device for injecting fuel into a cylinder of a diesel engine of a ship corresponding to claim 24, wherein a main fuel system for injecting fuel, and a pressure higher than an injection pressure of the main fuel system at an early stage of the fuel injection period And a control means for changing the injection conditions of the auxiliary fuel system based on at least one of the characteristics of the main fuel and the auxiliary fuel, the cylinder internal pressure, the engine load condition, and the geographical condition. Have.

  26. A fuel injection device for injecting fuel into a cylinder of a marine diesel engine corresponding to claim 25, wherein a main fuel system for injecting fuel and an injection of the main fuel system for simultaneous injection with the main fuel system A sub fuel system that injects fuel at a pressure higher than the pressure, and the injection conditions of the sub fuel system are changed based on at least one of the characteristics of the main fuel and the sub fuel, cylinder internal pressure, engine load conditions, and geographical conditions Control means.

  According to the fuel injection device of the present invention, by providing the auxiliary fuel system that injects the fuel at a pressure higher than that of the main fuel system, the injected fuel particles become finer and the ignitability is improved. By injecting the auxiliary fuel at the initial stage of the fuel injection period, the fuel particles can be made fine even when the pressure of the main fuel system is insufficient at the initial stage. In addition, when the main and sub fuel systems are simultaneously injected, the sub fuel system injects fuel at a pressure higher than that of the main fuel system, so that more fine fuel particles can be supplied.

  Further, by changing the injection conditions of the auxiliary fuel system depending on the properties of the fuel, at least one of ignitability, fuel consumption, and exhaust gas treatment is improved.

  Further, by detecting the pressure in the cylinder and changing the injection conditions of the auxiliary fuel system based on the detected pressure, an appropriate combustion state can be obtained. Further, by detecting the pressure outside the cylinder, it is not necessary to change the design or make a major modification, and it becomes easy to retrofit the pressure detecting means.

  Further, by changing the injection condition of the auxiliary fuel system according to the load condition, it is possible to obtain a combustion state suitable for the load condition. In addition, the auxiliary fuel system capable of high pressure injection can flexibly cope with load fluctuations.

  In addition, by injecting the auxiliary fuel system during low-load operation, even when the fuel pressure of the main fuel system is low during low-load operation, fuel is injected at a high pressure, fuel particles are refined, and ignitability is improved. Improved. Both main and auxiliary fuels can be injected, or only auxiliary fuel can be injected.

  When the internal combustion engine is mounted on a moving body, the internal combustion engine can be operated in accordance with the geographical condition by changing to an injection condition corresponding to the geographical condition of the current position of the moving body. The driving conditions required for the moving body vary depending on the geographical position, and the internal combustion engine can be operated under the driving conditions corresponding to the current position.

  In addition, by detecting the combustion state for each cylinder and changing the injection condition of the auxiliary fuel system for each cylinder based on this, it is appropriate for each cylinder and the overall balance is small with little variation among the cylinders. It becomes possible to be in a combustion state. The combustion state for each cylinder can be appropriately grasped by detecting based on at least one of the maximum cylinder internal pressure, the ignition timing, the exhaust temperature, and the indicated mean effective pressure. Since the maximum cylinder internal pressure, ignition timing, exhaust temperature, and indicated mean effective pressure are all physical quantities that are points related to the combustion state, the combustion state can be properly grasped.

  In addition, by changing the injection conditions of the auxiliary fuel system based on at least one of the flow rates of the main fuel and auxiliary fuel and the exhaust temperature of the internal combustion engine, the fuel consumption, engine efficiency, and exhaust gas state are estimated and Can be controlled to various conditions.

  By providing the auxiliary fuel system with a pressure accumulating section for storing pressurized fuel, fuel injection at a high fuel pressure can be realized with a simple configuration. In particular, a high pressure can be obtained from the beginning of injection. In addition, since the auxiliary fuel system controls the fuel supply by an electrically controlled valve, the injection condition can be easily changed.

  In addition, a diesel engine based on in-cylinder fuel injection by pressure is adopted as the internal combustion engine, and the accumulator of the auxiliary fuel system is a common rail, so that at the initial stage of the fuel injection period or simultaneously with the main fuel system The sub fuel system pressure can be easily controlled.

  In addition, by using different types of fuel as the main fuel and the sub fuel, it is possible to use various types of fuel, for example, fuel with poor ignitability. Further, by using the auxiliary fuel as a fuel having a higher cetane number than the main fuel, the main fuel having poor ignitability can be burned using the auxiliary fuel as a fire type. Moreover, the auxiliary fuel system for motor vehicles which uses light oil can be diverted by using light oil as auxiliary fuel. In addition, by using heavy oil as the main fuel, it can be applied to engines using heavy oil such as ships.

  In addition, by adopting a configuration in which the main fuel system and the sub fuel system share one fuel injection valve, and the main fuel system and the sub fuel system merge on the upstream side of the fuel injection valve, for example, an existing engine In addition, the auxiliary fuel system can be easily retrofitted, and the present invention can be easily realized. Further, by adopting a configuration in which the main fuel system and the sub fuel system are merged in the fuel injection valve, for example, the present invention can be realized without modifying the engine body such as a cylinder head.

  Further, by providing a dedicated injection nozzle for each of the main fuel system and the sub fuel system, fuel injection by the main and sub fuel systems can be controlled independently. In order to provide a dedicated injection nozzle, two independent nozzles may be provided in one fuel injection valve, or two independent fuel injection valves may be provided.

  By having a plurality of auxiliary fuel systems, it is possible to selectively inject a plurality of types of auxiliary fuels, or to combine several types of auxiliary fuels. Further, by injecting the same kind of fuel from a plurality of sub fuel systems, it is possible to cope with a case where the injection amount is insufficient in one system.

  An injection period in which the injection pressure of the main fuel system is insufficient by installing an auxiliary fuel system in the diesel engine of the ship and performing fuel injection by the auxiliary fuel system at a pressure higher than the injection pressure of the main fuel system. Even in the initial stage, the fuel particles can be made finer. Further, when both the main fuel system and the secondary fuel system inject simultaneously, the sub fuel system injects fuel at a pressure higher than that of the main fuel system, so that more fine fuel particles can be supplied. Also, by controlling the injection conditions of the auxiliary fuel system in consideration of the properties of the main fuel and auxiliary fuel, cylinder internal pressure, engine load conditions, geographical conditions, etc., the optimum operating state of the internal combustion engine at that time is realized it can.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of an internal combustion engine, particularly a marine diesel engine 10. The diesel engine 10 is a multi-cylinder engine, and a plurality of cylinders are arranged in series in a direction penetrating the page of FIG. The piston 12 reciprocates while sliding along the cylinder inner peripheral surface of the cylinder liner 14, and this reciprocating motion is converted into rotational motion of the crankshaft 18 via the connecting rod 16. The cylinder liner 14 is supported by the engine frame 20, and a water jacket through which cooling water flows is formed between the cylinder liner 14 and the engine frame 20. A portion of the engine frame 20 that surrounds and supports the cylinder liner and the cylinder liner 14 constitute a cylinder. The engine frame 20 is provided with a bearing for supporting the crankshaft 18, but is omitted in FIG.

  A cylinder head 22 is fastened to the upper portion of the engine frame 20 by a head bolt 24 (see FIGS. 11 and 13), whereby the cylinder head 22 abuts against and closely contacts the opening of the cylinder liner 14. A combustion chamber is formed by the top surface of the piston 12, the lower surface of the cylinder head 22 facing the piston 12, and the inner peripheral surface of the cylinder liner 14. A fuel injection valve 26 is provided at a portion corresponding to the center of the combustion chamber of the cylinder head 22. The arrangement of the fuel injection valve may be appropriately determined depending on the combustion state, such as how to spread the spray of the injected fuel, and may be provided in a portion other than the center. The cylinder head 22 is formed with an intake port and an exhaust port that communicate with the combustion chamber. Further, an intake valve 28 and an exhaust valve 30 for opening and closing the opening of these ports with respect to the combustion chamber (see FIGS. 11 and 13). Is placed. The intake / exhaust valves 28 and 30 are arranged on the rear side and the front side of the fuel injection valve 26, and are not shown in FIG. The intake port communicates with the intake pipe 32 and the exhaust port communicates with the exhaust pipe 34.

  A camshaft 36 that is driven by the crankshaft 18 via a transmission device such as a gear or a chain is disposed on the side of the cylinder. The cam shaft 36 is disposed in parallel with the cylinder arrangement direction, and includes cams 38 corresponding to the intake valves and exhaust valves of the respective cylinders. A cam follower 40 is provided in contact with the cam surface of the cam 38, and is further connected to the cam follower 40, and a push rod 42 extends toward the cylinder head 22. A rocker arm 44 is disposed on the cylinder head 22, a push rod 42 is connected to one end of the rocker arm 44, and the other end is connected to a stem end 46 of the intake valve 28 and the exhaust valve 30. As the cam shaft 36 rotates, the cam 38 swings the cam follower 40, and this movement is transmitted to the rocker arm 44 via the push rod 42. Then, the rocker arm 44 is also swung to drive the intake valve 28 and the exhaust valve 30 to open and close the intake port and the exhaust port.

  Fuel is supplied to the fuel injection valve 26 by a fuel supply system 48. The diesel engine 10 is provided with two fuel supply systems. One fuel supply system includes a mechanical fuel injection pump 50, which pressurizes the fuel in the fuel tank 52 and supplies the pressurized fuel to the fuel injection valve 26 through the fuel supply pipe 54. This fuel supply system will be described as a main fuel supply system, the fuel tank 52 will be described below as the main fuel tank 52, the fuel supply pipe 54 as the main fuel supply pipe 54, and the fuel supplied through the main fuel supply system as the main fuel. Further, the main fuel supply system and the fuel injection valve for supplying the main fuel are referred to as a main fuel system.

  Another fuel supply system is referred to as a secondary fuel supply system. The auxiliary fuel supply system includes an auxiliary fuel tank 56 that stores auxiliary fuel supplied to the fuel injection valve 26, a pressurizing pump 58 that pressurizes and sends the auxiliary fuel, and a pressure accumulating unit that stores pressurized fuel sent by the pressurizing pump. Common rail 60. Further, it includes an auxiliary fuel control valve 64 that opens and closes and controls the pressurized fuel stored in the common rail 60 to be sent to the main fuel supply pipe 54 via the auxiliary fuel supply pipe 62. The fuel delivered to the main fuel supply pipe 54 is further directed to the fuel injection valve 26, from where it is injected into the combustion chamber. A system for injecting auxiliary fuel from the auxiliary fuel tank 56 to the fuel injection valve 26 is referred to as an auxiliary fuel system. Therefore, in the fuel supply system 48, the main and sub fuel systems share components (for example, fuel injection valves) downstream from the junction of the main and sub fuel supply pipes 54 and 62. When the mechanical fuel injection pump 50 does not have a configuration for preventing backflow, a check valve is provided on the upstream side of the main fuel supply pipe 54 from the junction of the main fuel system. Prevents backflow due to pressure from the fuel system.

  The auxiliary fuel system including the common rail can be used for an automobile system. The demand for automobiles is greater than that for ships, and the cost of introducing a secondary fuel system can be suppressed by mass production effects. In addition, if light oil is used for the auxiliary fuel system, the number of modifications for introducing the system for automobiles is reduced, and further reduction of the introduction cost can be expected. Further, when the capacity of an automobile system is insufficient for a ship, a plurality of systems are provided, and fuel can be injected from a plurality of common rail systems into one cylinder. In order to increase the fuel injection amount, the volume of the common rail may be increased.

  When the secondary fuel system is retrofitted to an existing internal combustion engine, even if the secondary fuel system has reached the end of its life while navigating the open ocean, it can be easily replaced. Furthermore, by using a common rail system for automobiles as the auxiliary fuel system, even if it has a shorter life than an internal combustion engine for ships, it can be easily replaced with less economic burden.

  FIG. 2 is a partial cross-sectional view showing a schematic configuration of the mechanical fuel injection pump 50. A barrel 72 having an inflow hole 68 and an escape hole 70 on the side surface is housed in the pump housing 66. The inner peripheral surface of the barrel 72 is a cylinder, and the plunger 74 is slidably positioned in the inner peripheral surface of the cylinder. The plunger 74 extends below the barrel 72, and its lower end contacts a cam 92 (see FIG. 3), and reciprocates by this cam. The plunger 74 is urged by a plunger spring 76 so that the lower end is always in contact with the cam. The cam 92 is driven by the crankshaft 18 in synchronization therewith. The plunger 74 is further provided with a pinion 78, and a rack 80 is slidably provided on the pump housing 66 correspondingly. A collar 82 having a through hole is provided at the tip of the barrel 72, and the through hole is blocked by a discharge valve biased by a spring. A pump chamber 86 is formed by the front end surface of the plunger 74, the inner peripheral surface of the barrel 72, and the surface of the collar 82 facing the front end surface of the plunger.

  A longitudinal groove 88 and a deformed groove 90 are formed on the side surface of the plunger 74 located in the barrel 72. The longitudinal groove 88 extends from the distal end surface of the plunger 74 along the axial direction and reaches the deformed groove 90. The deformed groove 90 has a shape similar to a substantially triangular shape or a sector of a quarter of a circle when expanded. The width of the deformed groove 90 in the circumferential direction of the plunger surface increases as the distance from the tip of the plunger increases.

  When the plunger 74 is pushed by the cam and advances, the volume of the pump chamber 86 decreases, and after the inflow hole 68 and the relief valve 70 are blocked by the side surface of the plunger 74, the fuel in the pump chamber 86 loses the escape field and is added. Pressed. When the pressure in the pump chamber 86 increases and overcomes the force of the spring that urges the discharge valve 84, the discharge valve 84 opens and the fuel is discharged. When the plunger 74 further advances and the escape hole 70 is in the deformed groove 90, the fuel in the pump chamber 86 flows out of the escape hole 70 through the deformed groove 90 from the vertical groove 88. As a result, the pressure in the pump chamber 86 is reduced, the discharge valve 84 is closed, and the fuel discharge is stopped. That is, of the stroke of the plunger 74, the effective stroke in the fuel discharge is from the end of the plunger closing the inflow hole 68 and the escape hole 70 until the escape hole 70 is opened by the irregular groove 90.

  As described above, the circumferential width of the deformed groove 90 varies depending on the distance from the distal end of the plunger 74. Therefore, the effective stroke can be changed by rotating the plunger 74 around the axis and shifting the position of the deformed groove 90 with respect to the position of the escape hole 72 in the circumferential direction. The rack 80 and the pinion 78 are provided to rotate the plunger 74 about the axis. The plunger 74 can be rotated to a position where the deformed groove 90 does not engage with the escape hole 70. At this time, fuel is discharged to a position where the plunger 74 is most advanced. The rack 80 is controlled in the forward / backward direction according to the required output of the diesel engine 10, thereby controlling the fuel discharge amount.

  FIG. 3 is a diagram showing the fuel supply system 48 and the fuel injection valve 26. In the main fuel system, the main fuel stored in the main fuel tank 52 is pressurized and sent by the mechanical fuel injection pump 50, and sent to the fuel injection valve 26 through the main fuel supply pipe 54. The fuel injection valve 26 has a valve that opens the flow path by the pressure of the fuel, and the fuel is injected when the fuel pressure by the fuel injection pump 50 exceeds a predetermined value (injection start pressure). The injected fuel spreads in the cylinder as fine particles (droplets), and self-ignitions and burns when the temperature in the cylinder rises due to compression by the piston. In the main fuel system, fuel is pressurized each time the plunger 74 is stroked by the cam 92. That is, the fuel required at that time is pressurized by the fuel injection pump 50 for each fuel injection. Since the fuel must be pressurized, delivered, and injected in accordance with the fuel injection timing (timing) of each cylinder, the mechanical fuel injection pump 50 is provided independently for each cylinder.

  In the auxiliary fuel system, the auxiliary fuel stored in the auxiliary fuel tank 56 is pressurized and delivered by the pressurizing pump 58 and stored in the common rail 60 in a high pressure state. An auxiliary fuel control valve 64 is provided in the middle of the auxiliary fuel supply pipe 62 from the common rail 60 toward the main fuel supply pipe 54. When the auxiliary fuel control valve 64 is opened, the fuel stored in the common rail 60 is sent to the fuel injection valve 26 through the main fuel supply pipe 54 and is injected into the cylinder from here. The pressurizing pump 58 and the common rail 60 are provided in common for all cylinders or a plurality of cylinders, and the auxiliary fuel control valve 64 is provided for each cylinder.

  When the auxiliary fuel control valve 64 is electrically controlled, it becomes easier to introduce a common rail system for an automobile having this configuration. Further, by adopting the electric control type, the fuel injection timing, the fuel injection period (injection amount), the fuel injection pattern, and the like can be controlled by electric signals, and the degree of freedom of control is expanded. Further, in a ship, load fluctuations related to the wave period may occur due to the influence of waves, but this can be suitably dealt with by adopting an electric control system with a high degree of freedom of control.

  As described above, in the main fuel system, fuel pressurization is performed independently for each fuel injection, whereas in the sub fuel system, the fuel is pre-pressurized and pressurized. The fuel that has been stored in the state and pressurized in advance at the timing of fuel injection is supplied. In the main fuel system, at the initial stage of fuel injection, the pressure is low and the injected fuel particles are relatively large. On the other hand, in the auxiliary fuel system, since the fuel is pressurized in advance, it can be injected at a high pressure from the beginning of the injection period, and the fuel particles become finer. The pressure in the common rail can be changed. Specifically, for example, when an electric pump is used as the pressurizing pump 58, the rotation speed of the motor that drives the pump is changed to adjust the pressure in the common rail. When a mechanical pump is used as the pressurizing pump 58, a pressure regulating valve is provided in the return path for returning the auxiliary fuel from the common rail 60 to the auxiliary fuel tank 56, and the pressure at which the pressure adjusting valve is opened is changed to change the common rail. Adjust the internal pressure.

  4 and 5 are image diagrams showing changes in fuel injection pressure. FIG. 4 shows a case where only the main fuel system is used, and FIG. 5 shows a case where fuel is injected by the main and sub fuel systems. Also, the broken line indicates the change in fuel pressure at low load, and the solid line indicates the change in fuel pressure at high load.

  When fuel is pressurized and injected only by the main fuel system, that is, only by the mechanical fuel injection pump 50, the fuel pressure Pi gradually increases according to the stroke of the plunger 74, and the fuel pressure Pi reaches the injection start pressure Po ( Crank angle α1) Fuel is injected from the fuel injection valve 26. When the load is high, the advance / retreat of the rack 80 is controlled so that the effective stroke of the plunger 74 becomes long. When the load is full, the maximum injection pressure Pmax is reached (crank angle α2). Thereafter, a slight amount of fuel is injected due to the pressure remaining in the piping of the supply system, but basically the crank angle α1 to α2 is the fuel injection period. On the other hand, when the load is low, the effective stroke of the plunger is shortened, and the fuel injection period is up to the crank angle α3 closer to the top dead center than the crank angle α2. At the crank angle α3, the fuel pressure only reaches P1, which is lower than the maximum pressure Pmax. For this reason, the fuel injection pressure is low when the load is low, and the injected fuel particles are large. When the particle size of the fuel is large, the ignitability deteriorates. For this reason, when fuel is supplied only by a mechanical fuel injection pump, the ignitability tends to deteriorate at low loads.

  When fuel injection is performed using both the main fuel system and the auxiliary fuel system, the injection by the auxiliary fuel system is performed at the beginning of the fuel injection period. During the injection period (α4 to α5) of the auxiliary fuel system, fuel injection of the auxiliary fuel system is performed at a pressure equal to or higher than the fuel pressure of the main fuel system alone. The common rail 60 stores fuel at a pressure sufficient to enable injection at a pressure at which the fuel becomes fine particles. The fuel pressure of the auxiliary fuel system is high from the beginning of the injection period and is substantially constant during the injection period. As described above, in the case of a mechanical fuel injection pump, the fuel pressure gradually increases, and during the injection period of the auxiliary fuel system, the crank angle α5 is the highest (pressure P3). The fuel pressure P2 of the auxiliary fuel system is higher than the pressure P3, and the fuel can be made finer than when the fuel is injected by the main fuel system. In FIG. 5, the fuel pressure P2 due to the auxiliary fuel system is shown as a value lower than the maximum pressure Pmax due to the main fuel system, but is not limited to this and may be set to a pressure equal to or higher than the maximum pressure Pmax. At high load, fuel injection by the auxiliary fuel system starts at the crank angle α4 and stops at the crank angle α5. Thereafter, since the pressure by the main fuel system has increased, injection is performed only by the main fuel system. The reason why the injection by the auxiliary fuel system is performed only at the initial stage of the injection period is that when a large amount of fuel stored in the common rail 60 is injected, the pressure in the common rail decreases. In order to ensure the required fuel pressure at the time of the next injection, measures such as increasing the capacity of the common rail 60 and increasing the flow rate of the pressurizing pump 58 can be considered. However, in either case, the size of the apparatus is increased. In a multi-cylinder engine, since the injection interval of the entire engine is shortened, it is necessary to recover the reduced pressure in the common rail more quickly, or it is necessary to increase the capacity so as not to reduce the pressure in the common rail. Increase more. In the fuel supply system 48 of the present embodiment, the injection by the auxiliary fuel system is limited to the initial stage of the injection period in which the fuel pressure by the main fuel system is low, and the injection amount of the auxiliary fuel system is suppressed, whereby a small common rail, It is possible to use a pressure pump.

  Moreover, in a large-sized internal combustion engine such as a ship, the combustion chamber is large, and the amount of fuel injected per time is larger than that of a small engine such as an automobile. For this reason, in order to cover the total injection amount with the fuel stored in the pressure accumulating portion such as the common rail, it is necessary to increase the volume of the pressure accumulating portion or increase the pump flow rate. For this reason as well, it is desirable to employ a configuration in which a main fuel system and a sub fuel system are provided and the injection amount by the sub fuel system is small.

  The start time (α4) and end time (α5) of the injection of the auxiliary fuel system can be adjusted. For example, when using fuel with poor ignitability, in order to improve the ignitability by increasing the fuel to be vaporized, the injection period is increased in order to increase the proportion of fine particles and lengthen the vaporization time. Try to make it longer. The start of injection may be advanced. In addition, when a fuel with relatively good ignitability is used, the injection period of the auxiliary fuel system may be shortened. As long as sufficient ignitability is ensured, only the main fuel system may be injected at high loads. Thereby, consumption of auxiliary fuel can be suppressed.

  At the time of low load, as shown in FIG. 5, injection is performed by the auxiliary fuel system during the injection period (α4 to α5). In the control of FIG. 5, the injection period (α4 to α5) of the auxiliary fuel is the same at high load and low load, but the injection period (timing, length) is changed depending on the load. May be.

  In the fuel supply system 48 of the present embodiment, the main and sub fuel supply pipes 54 and 62 are merged on the upstream side of the fuel injection valve 26, and fuel is supplied by the high pressure sub fuel system. The main fuel system does not supply fuel. However, as will be described later, when the main and sub fuel systems are configured to be independent, fuel supply by the main fuel system is possible even at low loads. In this case, the injection periods of the main and sub fuel systems can be set independently. For example, in the low load injection period (α4 to α5) shown in FIG. 5, the main fuel system performs injection over this entire period, and the auxiliary fuel system performs injection only for a period shorter than this period. be able to. In addition, the injection of the auxiliary fuel system is preferably performed at the beginning of the injection period of the main fuel system, and can be started before the injection of the main fuel system.

  The main and sub fuels may be the same type of fuel or a combination of different types of fuel. Even when the same kind of fuel is used, as described above, in the auxiliary fuel system, the fuel can be injected at a high pressure from the beginning of injection, the fuel particles become fine, and the ignitability is improved. In particular, the deterioration of ignitability at the time of low load by the above-described mechanical fuel injection valve can be improved.

  If sufficient ignitability cannot be obtained even if the same type of fuel is injected by the auxiliary fuel system, different types of fuel can be used as the main and auxiliary fuels. In this case, a fuel with good ignitability can be used as the auxiliary fuel, and the fuel with poor ignitability can be burned by using the auxiliary fuel as a fire type. The ignitability in a diesel engine is evaluated by a cetane number. In this case, a fuel having a high cetane number is used as a secondary fuel, and a fuel having a low cetane number is used as a main fuel. When using a fuel with poor ignitability as the main fuel, it is preferable to use light oil as the auxiliary fuel. Heavy oil may be used as the main fuel.

  In the fuel supply system 48, a part of the fuel supply pipe 54 and the fuel injection valve 26 are shared by the main and sub fuel systems, and when the sub fuel is to be supplied, the common fuel is supplied to this common part at the time of the previous injection. It is desirable that the main fuel is not left or its amount is small. For this reason, it is desirable that the junction of the main and sub fuel supply pipes 54 and 62 is close to the fuel injection valve 26. Further, at the end of the fuel injection period, auxiliary fuel is supplied, and the auxiliary fuel is filled in the piping and the fuel injection valve 26 downstream from the junction of the supply pipes 54 and 62. Fuel may be injected.

  FIG. 6 is a diagram showing another configuration example of the fuel supply system and the fuel injection valve. The description of the same components as those already described is omitted. In this example, two fuel injection valves that inject fuel directly into the cylinder are provided. The illustrated fuel supply system 94 supplies main fuel and sub fuel independently to each of the two fuel injection valves 96 and 98. The main fuel injection valve 96 is supplied with fuel from the mechanical fuel injection pump 50 through the main fuel supply pipe 100. The configuration of the main fuel injection valve 96 is the same as that of the fuel injection valve 26 described above. In this example, the main fuel injection valve 96 is used as a dedicated injection valve for main fuel. Sub fuel is supplied to the sub fuel injection valve 98 from the common rail 60 through the sub fuel supply pipe 102. The auxiliary fuel injection valve 98 functions as an injection valve that injects fuel into the cylinder, and also functions as an auxiliary fuel control valve that controls the supply of auxiliary fuel. In this example, the opening and closing of the auxiliary fuel control valve 98 is controlled by an electromagnetic solenoid, but it may be a mechanical control using a piezoelectric element or a cam. In the fuel supply system 94, the main and sub fuel systems can be controlled independently, so that the main and sub fuels can be injected simultaneously. Further, in the case of the injection control shown in FIG. 5, only the auxiliary fuel is injected at low load, but when the main and auxiliary fuel systems are independent as shown in FIG. The fuel can be injected, and the auxiliary fuel can be injected at the beginning of the injection period.

  FIG. 7 is a diagram showing still another configuration example of the fuel supply system and the fuel injection valve. The description of the same components as those already described is omitted. In this example, one fuel injection valve is provided, but a flow path for supplying main and sub fuels independently to the nozzle is formed inside the injection valve. A fuel supply system 106 that supplies fuel to the fuel injection valve 104 supplies main and sub fuels independently. The main fuel supply pipe 108 supplies main fuel to the fuel injection valve 104, and the main fuel is injected from the nozzle 112 through the main fuel flow path 110 provided in the injection valve 104. The main fuel supply pipe 108 is provided with a check valve 111 to prevent the auxiliary fuel from flowing back into the main fuel flow path 110 and the main fuel supply pipe 108. The nozzle is opened and closed by the fuel pressure as in the fuel injection valve 26 described above. That is, when the fuel pressure is increased to a predetermined value by the mechanical fuel injection pump 50, the valve body moves and opens the nozzle.

  The auxiliary fuel system includes an auxiliary fuel supply pipe 114 that supplies auxiliary fuel from the common rail 60 to the fuel injection valve 104 and an auxiliary fuel control valve 116 that controls supply of the auxiliary fuel. The auxiliary fuel control valve 116 performs the same function as the auxiliary fuel control valve 64 of the fuel supply system 48. The fuel sent to the fuel injection valve 104 is injected from the nozzle 112 through the auxiliary fuel flow path 118 provided separately from the main fuel flow path 110 in the fuel injection valve 104. The nozzles 112 to which main and sub fuels are supplied are common. The pressure in the common rail 60 is set sufficiently higher than the injection start pressure of the fuel injection valve 104, and the auxiliary fuel is injected at a high pressure from the beginning of injection.

  FIG. 8 is a diagram showing still another configuration example of the fuel supply system and the fuel injection valve. The description of the same components as those already described is omitted. In this example, the fuel injection valve is a single fuel injection valve 120 in which two independent fuel injection valves 96 and 98 shown in FIG. 6 are integrated. The fuel injection valve 120 includes a main fuel injection unit 120A and a sub fuel injection unit 120B. The fuel supply system 122 includes a main fuel supply pipe 124 that supplies main fuel from the mechanical fuel injection pump 50 to the main fuel injection unit 120A as a main fuel system, and sub fuel from the como rail 60 as sub fuel. A sub fuel supply pipe 126 for supplying the injection unit 120B is included. The main fuel injection unit 120A has its injection controlled by the pressure of the supplied fuel. On the other hand, in the auxiliary fuel injection unit 120B, the injection control is performed separately from the pressure of the supplied fuel using an electromagnetic solenoid or the like.

  The fuel supply systems 48, 94, 106, and 122 described above have a supply system such as a main system and a sub system, but a plurality of sub fuel supply systems may be used. The plurality of sub fuel supply systems may have different fuel pressures, or may supply different fuels.

  FIG. 9 is a control block diagram relating to control of the injection conditions of the main fuel system and the sub fuel system. This control block diagram is a control block diagram for a configuration example shown in FIGS. 1 and 6 in which the fuel injection valve, particularly the nozzle, is shared in the main and sub fuel systems. The components already described are denoted by the same reference numerals and description thereof is omitted. In order to detect the operating state of the diesel engine 10, a rotation sensor 128, a pressure sensor 130, and an exhaust temperature sensor 132 are provided, and detect the amounts of main fuel and auxiliary fuel that are actually supplied to the fuel injection valve 26, respectively. A main fuel flow sensor 134 and a sub fuel flow sensor 136 are provided. The rotation sensor 128 is a sensor that detects the rotation speed of the crankshaft 18. As the pressure sensor 130, a sensor that directly detects the pressure in the combustion chamber can be used. However, as a simpler method, the pressure can be detected by a retrofit or external sensor. For example, a sensor based on the force that the combustion pressure in the combustion chamber acts on the cylinder head bolt can be used. The pressure sensor will be described in detail later. The pressure sensor 130 can be provided for each cylinder, and can also be provided corresponding to one or more representative cylinders. If the cylinder arrangement is a V-type engine, one pressure sensor can be provided in each of the left and right banks. When a pressure sensor is provided for each cylinder, the injection conditions can also be controlled for each cylinder. Further, when a pressure sensor is provided for each of several cylinders, such as for each V-type bank, injection control can be performed for each bank and each cylinder group.

  Based on the cylinder internal pressure detected by the pressure sensor 130, the engine state estimation unit 138 estimates the combustion state based on at least one of the ignition timing, the indicated mean effective pressure, the maximum cylinder internal pressure, and the exhaust temperature. FIG. 10 is a graph showing the cylinder internal pressure, the heat generation amount, and the heat generation rate when the fuel injection timing is changed. By detecting the cylinder pressure, the maximum cylinder pressure and the indicated mean effective pressure can be calculated, and the ignition timing can be estimated from the heat generation rate obtained from the cylinder pressure. In estimating the ignition timing from the heat generation rate, the estimation can be performed using a threshold value determined from the maximum value and the minimum value of a certain cycle. For example, a value obtained by adding 10% of the difference between the maximum value and the minimum value of the heat generation rate to the minimum value is set as a threshold value, and when this value is exceeded in a certain cycle, the ignition timing of the cycle can be set. As can be understood from the figure, the cylinder internal pressure, the ignition timing, and the like change when the fuel injection timing is changed, and the parameters obtained based on the detected value of the pressure sensor become predetermined values by using this. As described above, the injection timing of at least one of the main and sub fuels can be controlled. The injection timing / injection amount is controlled by controlling the auxiliary fuel control valve 64 by the pump / valve control unit 140. Further, the pressure pump 58 may be controlled in order to control the fuel pressure of the auxiliary fuel. When the fuel injection timing is controlled by the mechanical fuel injection pump 50, a mechanism for changing the phase of the cam 92 with respect to the crankshaft is provided. If the fuel flow rate measured by the main and sub fuel flow sensors 134 and 136 is larger than the reference fuel corresponding to the load at that time, it is determined that more fuel is consumed, that is, the efficiency is poor. Change the fuel injection timing. Further, if the fuel flow rate increases before and after the fuel injection timing is changed, it is determined that the efficiency has deteriorated, and the injection timing is returned to the original or changed to the original return. Further, when the exhaust gas temperature is lower than the reference exhaust gas temperature corresponding to the load at that time, it is determined that the operating condition is good, and the injection timing is maintained. Further, even when the exhaust gas temperature decreases before and after the injection timing is changed, it is determined that the efficiency is high, and the injection timing is maintained.

  The combustion state estimated by the engine state estimation unit 138 reflects the properties of the fuel. For example, when a fuel with good ignitability is used, ignition tends to occur early with respect to the injection timing, and conversely, with fuel with poor ignitability, ignition tends to be delayed. Therefore, the engine state estimation unit 138 has a function as means for detecting the fuel property. Further, the exhaust temperature and the flow rates of the main and auxiliary fuels can also be used as parameters for determining the fuel properties. In the detection or estimation of the fuel property, data indicating the relationship between the fuel whose property is known and the cylinder internal pressure when the fuel is operated under a predetermined operating condition or a parameter calculated based on the fuel is stored in advance. By referring to this, the property of the fuel is detected or estimated. In other words, the fuel used is obtained by operating the fuel under unknown operating conditions under predetermined operating conditions, obtaining the cylinder internal pressure at this time or a parameter based thereon, and referring to the previously stored data. Estimate the properties of The operating condition for estimating the property of the fuel may be an operating condition in which only one of the auxiliary fuel and the main fuel is injected.

The operation conditions of the diesel engine 10 are determined based on the conditions input to the operation control panel 142, and based on this, the detected values of the engine state estimation unit 138 and each sensor are fed back, and the pump / valve control unit 140 controls the diesel engine. The engine 10 is controlled. The operation panel 142 is provided with an operation switch 144 for starting / stopping the diesel engine 10 and a throttle lever 146 for controlling the output level. In addition, a regulation value and an operation mode for the type and amount of fuel, exhaust gas, and the like are set. An input condition setting unit 148 is provided. As the types of fuel, heavy oil, light oil, rapeseed oil, waste cooking oil, palm oil, and the like are assumed, and typical characteristics of each are stored in advance. In addition, it is possible to set which kind of fuel is used for each of the main fuel and the sub fuel. Further, exhaust gas regulation values (NOx regulation, SOx regulation, CO ₂ emission amount) and the like can be set. Further, it is possible to select an operation mode for setting the environment as important or setting the fuel efficiency as important. The operator performs these operations and inputs, and the operation condition calculation unit 150 calculates operation conditions suitable for these conditions. Specifically, the ratios of main and sub fuel, fuel properties (cetane number, calorific value), exhaust temperature target value, efficiency target value, and load condition are calculated.

  Further, the current position may be acquired based on GPS (Global Positioning System) information, radar information, and the like, and the operation conditions may be calculated together with the current position. The distance from the land, the azimuth and distance from the destination, and the positional relationship with the target at the time of navigation can be acquired by GPS or radar, and the operation conditions according to these can be calculated. For example, if the current position is in a harbor or near the land, the operation mode prioritizes exhaust gas purification can be used, and if the current position is the open sea, the operation mode can prioritize the fuel consumption rate. The target at the time of navigation is, for example, a lighthouse or another ship to be followed if the ship is following. When exhaust gas regulations and environmental regulations differ depending on the geographical position of countries, regions, cities, etc. in the world and the distance from the coast, it is possible to calculate operational conditions according to geographical conditions. In addition, GPS and radar can be commonly used for ships.

  Based on the operation conditions calculated by the operation condition calculation unit 150, the operation condition setting unit 152 sets the fuel injection pattern (injection timing and injection amount) for each main and sub fuel system, and is calculated. The target values of ignition timing, maximum cylinder internal pressure, indicated mean effective pressure, and exhaust temperature, which are assumed corresponding to the operating conditions, are set. Based on the set condition, control by the pump / valve control unit 140 is executed. Further, the operating condition setting unit 152 combines several parameters such as the above parameters indicating the combustion state (ignition timing, indicated mean effective pressure, maximum cylinder internal pressure), exhaust temperature, fuel flow rate, and the like. Depending on the characteristics, the once set operating conditions can be changed according to the current situation. For example, the operating condition can be changed by controlling the ratio of the injection amount of the main fuel and the auxiliary fuel. The ratio of the injection amount is controlled by changing the injection amount of at least one of the main fuel and the sub fuel. In addition, when sub fuel having better combustibility or ignitability than main fuel is used, the sub fuel injection timing can be controlled to be effective for improving combustion. When the ignitability of the main fuel is poor, different fuels with good ignitability can be mixed in the main fuel system. Further, the mixing ratio can be changed. In order to mix different types of fuel, a plurality of main fuel tanks may be provided, and different types of fuel may be stored in separate tanks, mixed as needed, and supplied to the fuel injection pump. Furthermore, a tank for storing the mixed fuel may be provided, and different types of fuel may be supplied to the tank at a predetermined ratio, and the fuel may be supplied from there to the fuel injection pump.

  As described above, heavy oil, light oil, rapeseed oil, waste cooking oil, and palm oil are assumed as the fuel. However, it is also possible to use a mixed fuel obtained by mixing different types of fuel. In addition, since the engine state estimation unit 138 estimates and monitors the combustion state, even if the type of main fuel is unknown, the engine can be operated by controlling the main and sub fuel systems corresponding to the combustion state. It is. For example, when it is determined that the ignition timing is delayed, the ignition timing is controlled to an appropriate value by increasing the injection amount of the auxiliary fuel or by increasing the injection timing of at least one of the main and auxiliary fuels. To.

  FIG. 11 is a schematic diagram showing a configuration around the combustion chamber of the diesel engine 10, and in particular, a diagram showing an arrangement of the load washer 154 as the pressure sensor 130. The cylinder head 22 is fastened to the engine frame 20 by a cylinder head bolt 24. A load washer 154 is disposed between the nut of the bolt and the cylinder head. The load washer is subjected to an axial force applied when the cylinder head is tightened and an axial force generated by receiving the cylinder internal pressure. FIG. 12 shows changes in (a) cylinder internal pressure and (b) force acting on the load washer (bolt axial force) with respect to the crank angle. By comparing the two figures, it can be understood that the force acting on the load washer has a good correlation with the cylinder internal pressure. Therefore, it is possible not to directly measure the cylinder internal pressure but to measure the cylinder internal pressure with a load washer provided outside the cylinder.

  FIG. 13 is a schematic diagram showing a configuration around the combustion chamber of the diesel engine 10, and in particular, a diagram showing an arrangement of the strain gauge 156 as the pressure sensor 130. The strain gauge 156 is attached to the shaft portion of the cylinder head bolt 24. In the illustrated example, the strain gauge 156 is attached in correspondence with the gap between the engine frame 20 and the cylinder head 22. However, it may be mounted anywhere as long as the extension of the bolt 24 can be detected appropriately. For example, the bolt 24 may be mounted on a bolt shaft portion in the cylinder head 22. FIG. 14 shows (a) a change in cylinder internal pressure with respect to a crank angle, and (b) a change in bolt elongation (bolt axial force) detected by a strain gauge. Comparing the two figures, it can be understood that the force acting on the bolt elongation has a good correlation with the cylinder pressure. Therefore, it is possible not to directly measure the cylinder internal pressure but to measure the cylinder internal pressure from a strain gauge provided outside the cylinder. Since both the load washer type and the strain gauge type can be installed outside the cylinder, it is easy to install a common rail system as an auxiliary fuel system later, or to replace it at the time of failure or at the end of its life by simply removing and attaching bolts. Further, when the bolt is loose or the tightening torque is insufficient, an abnormality can be detected.

  As described above, the present invention can be applied to a marine internal combustion engine. By using the fuel injection device according to the present invention, an internal combustion engine capable of using various types of fuels having different properties such as ignitability and calorific value, such as low-quality petroleum-based fuels and carbon-neutral fuels other than petroleum-based fuels. Institution can be provided. In one internal combustion engine, even if the type of fuel is changed, an operation suitable for the property of the fuel can be performed. As the type of fuel, heavy oil can be used as the main fuel, rapeseed oil, waste cooking oil, palm oil, or the like can be used as the auxiliary fuel. Also, rapeseed oil, waste cooking oil, palm oil, etc. can be used as the main fuel, and light oil can be used as the auxiliary fuel. Ships need to sail to many countries and regions around the world and refuel at the port of call. For this reason, it is necessary to deal with fuels having a wide range of properties, but according to the present invention, this can be realized.

  A common rail system for automobiles can be diverted to the auxiliary fuel system. When the capacity of the common rail is insufficient, it is possible to provide a plurality of common rail systems for one internal combustion engine and a plurality of systems for one cylinder.

  In the above embodiment, although it demonstrated in relation to the diesel engine for ships, this invention is applicable also to another moving body, for example, a rail vehicle, a motor vehicle, etc. The present invention can also be applied to an engine (such as a direct injection type Otto engine) that performs intermittent combustion other than a diesel engine.

It is sectional drawing which shows schematic structure of the diesel engine of this embodiment. It is a fragmentary sectional view which shows the structure of a mechanical fuel injection pump. It is a figure which shows an example of a fuel supply system and a fuel injection valve. It is a figure which shows the fuel pressure by the main fuel system. It is a figure which shows the fuel pressure by the main fuel system and a sub fuel system. It is a figure which shows the other example of a fuel supply system and a fuel injection valve. It is a figure which shows the further another example of a fuel supply system and a fuel injection valve. It is a figure which shows the further another example of a fuel supply system and a fuel injection valve. It is a control block diagram of the diesel engine of this embodiment. It is a figure which shows the relationship between a fuel-injection time and a combustion state. It is a figure which shows arrangement | positioning of the load washer as a pressure sensor. It is a figure which shows the relationship between cylinder internal pressure and bolt axial force. It is a figure which shows arrangement | positioning of the strain gauge as a pressure sensor. It is a figure which shows the relationship between cylinder internal pressure and the elongation of a volt | bolt.

Explanation of symbols

  10 diesel engine, 12 piston, 14 cylinder liner, 20 engine frame, 22 cylinder head, 24 cylinder head bolt, 26 fuel injection valve, 48, 94, 106, 122 fuel supply system, 50 mechanical fuel injection pump, 60 common rail, 64 Sub fuel control valve, 96 Main fuel injection valve, 98 Sub fuel injection valve, 104 Fuel injection valve, 120 Fuel injection valve, 120A Main fuel injection unit, 120B Sub fuel injection unit, 130 Pressure sensor, 132 Exhaust temperature sensor, 134 Main fuel flow rate sensor, 136 Sub fuel flow rate sensor, 138 Engine state estimation unit, 140 Pump / valve control unit (control unit), 152 Operating condition setting unit (control unit).

Claims (25)

A fuel injection device for injecting fuel into a cylinder of an internal combustion engine,
A main fuel system for injecting fuel;
An auxiliary fuel system that injects fuel at a pressure higher than the injection pressure of the main fuel system at the beginning of the fuel injection period;
A fuel injection device. A fuel injection device for injecting fuel into a cylinder of an internal combustion engine,
A main fuel system for injecting fuel;
When injecting simultaneously with the main fuel system, a sub fuel system that injects fuel at a pressure higher than the injection pressure of the main fuel system,
A fuel injection device.   3. The fuel injection device according to claim 1, further comprising a control unit that changes injection conditions of the auxiliary fuel system depending on the properties of the fuel.   4. The fuel injection device according to claim 1, wherein a pressure detecting unit that detects a pressure in a cylinder of the internal combustion engine, and a pressure of the auxiliary fuel based on the pressure detected by the pressure detecting unit. 5. A fuel injection device having control means for changing injection conditions.   5. The fuel injection device according to claim 4, wherein the pressure detection means is means for indirectly detecting the pressure in the cylinder outside the cylinder.   6. The fuel injection device according to claim 1, further comprising a control unit configured to change an injection condition of a sub fuel system in accordance with a load condition of the internal combustion engine.   The fuel injection device according to claim 6, wherein the fuel injection device performs injection of a sub fuel system during low load operation of the internal combustion engine.   8. The fuel injection device according to claim 1, wherein the internal combustion engine is mounted on a moving body, and an injection condition of a sub fuel system is set according to a geographical condition of a current position of the moving body. A fuel injection device having control means for changing. The fuel injection device according to any one of claims 1 to 8,
The internal combustion engine is a multi-cylinder engine;
Combustion state detection means for detecting the combustion state of the cylinder for each cylinder;
Control means for changing the injection condition of the auxiliary fuel system for each cylinder based on the detected combustion state;
A fuel injection device.   10. The fuel injection device according to claim 9, wherein the combustion state detecting means detects the combustion state based on at least one of a maximum cylinder pressure, an ignition timing, an exhaust temperature, and an indicated mean effective pressure. apparatus.   11. The fuel injection device according to claim 1, wherein the injection condition of the auxiliary fuel system is changed based on at least one of a flow rate of the main fuel and the auxiliary fuel and an exhaust temperature of the internal combustion engine. A fuel injection device comprising control means for   The fuel injection device according to any one of claims 1 to 11, wherein the auxiliary fuel system includes a pressure accumulating unit that stores pressurized fuel.   13. The fuel injection device according to claim 12, wherein the auxiliary fuel system has an electrically controlled valve that controls supply of pressurized fuel.   14. The fuel injection device according to claim 12, wherein the internal combustion engine is a diesel engine, and the pressure accumulating unit includes a common rail.   15. The fuel injection device according to claim 1, wherein the main fuel injected by the main fuel system and the auxiliary fuel injected by the sub fuel system are different types of fuel. Injection device.   15. The fuel injection device according to claim 14, wherein the auxiliary fuel injected by the auxiliary fuel system is a fuel having a higher cetane number than the main fuel injected by the main fuel system.   The fuel injection device according to claim 16, wherein the auxiliary fuel is light oil.   The fuel injection device according to claim 16 or 17, wherein the main fuel is heavy oil.   The fuel injection device according to any one of claims 1 to 18, wherein the main fuel system and the sub fuel system share one fuel injection valve, and the main fuel system and the sub fuel system are upstream of the fuel injection valve. A fuel injection device where fuel systems merge.   The fuel injection device according to any one of claims 1 to 18, wherein the main fuel system and the auxiliary fuel system share one fuel injection valve, and the main fuel system and the auxiliary fuel system are included in the fuel injection valve. A fuel injection device that joins.   The fuel injection device according to any one of claims 1 to 18, wherein the main fuel system and the sub fuel system have one injection valve having two kinds of nozzles controlled independently, A fuel injection device in which main fuel is injected from one type of nozzle and secondary fuel is injected from the other type of nozzle.   The fuel injection device according to any one of claims 1 to 18, wherein the main fuel system and the sub fuel system have independent fuel injection valves respectively arranged for one cylinder.   The fuel injection device according to any one of claims 1 to 22, wherein the fuel injection device has a plurality of sub fuel systems and injects different fuels for each sub fuel system. A fuel injection device for injecting fuel into a cylinder of a marine diesel engine,
A main fuel system for injecting fuel;
An auxiliary fuel system that injects fuel at a pressure higher than the injection pressure of the main fuel system at the beginning of the fuel injection period;
A fuel injection apparatus, comprising: a control unit that changes injection conditions of the auxiliary fuel system based on at least one of properties of main fuel and auxiliary fuel, cylinder pressure, engine load condition, and geographical condition. A fuel injection device for injecting fuel into a cylinder of a marine diesel engine,
A main fuel system for injecting fuel;
When injecting simultaneously with the main fuel system, a sub fuel system that injects fuel at a pressure higher than the injection pressure of the main fuel system,
A fuel injection apparatus, comprising: a control unit that changes injection conditions of the auxiliary fuel system based on at least one of properties of main fuel and auxiliary fuel, cylinder pressure, engine load condition, and geographical condition.

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