JP2011256794A - Fuel injection device and internal combustion engine for land and marine industrial use capable of accommodating various fuel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine, which accommodates various types of fuels, capable of restraining vibration and improving properties of exhaust emissions.SOLUTION: The internal combustion engine includes: a main fuel system that is mechanically controlled to supply main fuel; a sub fuel system that is electrically controlled to supply sub fuel; and a fuel injection valve 26 that is installed on the main fuel system and the sub fuel system in common and injects the main fuel and the sub fuel into cylinders. Injection of the main fuel and injection of the sub fuel are performed at a different timing from each other.

Description

  The present invention relates to a fuel injection device that injects fuel into a cylinder of an internal combustion engine and an internal combustion engine for land and marine industry, and more particularly to a fuel injection device that can handle various types of fuel and an internal combustion engine for land and marine industry using the same.

  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 type, and in order to be able to operate with various types of fuels, it is necessary to improve the combustibility by adjusting the fuel injection timing.

  For example, in a fuel injection device for a diesel engine, a configuration is disclosed in which low pressure pilot injection is performed before high pressure main injection at the time of fuel injection. In such a fuel injection device, a configuration including a high-pressure common rail for main injection and a low-pressure common rail for pilot injection is disclosed (see Patent Document 1 below). Moreover, the structure which provides separately the main injection nozzle for performing main injection in a combustion chamber, and the sub injection nozzle for performing pilot injection is disclosed (refer the following patent document 2). Moreover, the structure which provides the common fuel-injection nozzle for performing main injection and pilot injection in a combustion chamber is disclosed (refer the following patent document 3).

  In addition, in a fuel injection device for an internal combustion engine, a configuration is disclosed in which main injection for injecting high-pressure fuel and after-injection for injecting fuel after the main fuel at a lower pressure than the main injection are disclosed (see Patent Document 4 below). ). Here, the injection valve for performing main injection and the injection valve for performing after-injection are separately provided in the cylinders of the internal combustion engine.

  Further, when the main injection and the sub-injection such as pilot injection or after injection are combined, the engine combustion state is indirectly grasped based on the fuel injection amount and the engine speed, and the control mode is changed according to the combustion state. A technique is disclosed (see Patent Document 5 below). Further, when the main injection and the pilot injection are performed in combination, the pressure P in the cylinder of the internal combustion engine is detected, the combustion state and the ignition state are grasped based on the maximum pressure Pmax and dP / dθ, and the result is obtained as the pilot fuel. The structure which feeds back to a supply apparatus is disclosed (refer the following patent document 6).

JP 2008-111404 A Japanese Patent Laid-Open No. 10-184487 Japanese Patent Laid-Open No. 5-26127 JP 2007-71181 A JP 2003-120392 A JP-A-6-159182

  By the way, a conventional fuel injection system for a marine diesel engine has a configuration in which fuel is pressurized by a mechanical pump driven by the diesel engine, and fuel is injected into a cylinder of the diesel engine by a mechanical fuel injection valve. ing.

  For this reason, the pressure rise and injection timing of the pressurized fuel depend on the characteristics of the mechanical pump and the mechanical fuel injection valve, and it is difficult to control with high accuracy. There was also a problem from the improvement of exhaust gas characteristics.

  In recent years, in the field of automobiles, etc., an electrically controlled fuel that stores pressurized fuel in a common rail (pressure accumulator) and injects the fuel with an electrically controlled fuel injection valve to finely control combustion in a diesel engine. An injection system is used. Therefore, it is considered to increase the efficiency of the diesel engine and improve the exhaust gas characteristics by adding such an electrically controlled fuel injection system to the conventional marine diesel engine. In particular, there is a need for higher efficiency and improved exhaust gas characteristics of diesel engines that are compatible with multi-fuels such as biofuels and waste cooking oil, which are attracting attention as measures against environmental problems.

  A fuel injection device for injecting fuel into a cylinder of an internal combustion engine according to claim 1 is a mechanically controlled main fuel system that supplies main fuel, and an electrically controlled sub fuel that supplies sub fuel. A fuel injection valve that is provided in common to the main fuel system and the sub fuel system and injects the main fuel and the sub fuel into the cylinder, and the main fuel injection and the sub fuel The injection is performed at a different timing. That is, the main fuel and the auxiliary fuel are injected at different timings by controlling the valves provided in the main fuel system and the valves provided in the auxiliary fuel system at different timings. At this time, the auxiliary fuel system is electrically controlled with high accuracy.

  In the fuel injection device corresponding to claim 2, the injection pressure when the main fuel is injected differs from the injection pressure when the sub fuel is injected. The fuel combustion state is controlled by performing fuel injection at different timings at different injection pressures. For example, the injection pressure of the main fuel is determined based on conditions such as fuel properties, cylinder pressure, engine load conditions, geographical conditions, etc., and the sub fuel is controlled so as to suppress the vibration of the combustion chamber cylinders and the exhaust gas properties. Are determined at different injection pressures.

  In the fuel injection device corresponding to claim 3, the injection pressure at the time of injection of the sub fuel is higher than the injection pressure at the time of injection of the main fuel. Specifically, the auxiliary fuel is preliminarily pressurized using a pressure accumulating portion such as a common rail, and injected from the auxiliary fuel system at a pressure higher than that of the main fuel system. Thus, the auxiliary fuel is injected as finer particles than the main fuel.

  According to a fourth aspect of the present invention, the auxiliary fuel is pre-injected before the main fuel injection and before a time shorter than a half cycle of the main fuel injection. Pre-injection is also called pilot injection. The pre-injection is performed with higher accuracy by controlling the injection timing, the injection time (injection amount), the injection pressure, and the like than the main fuel system by using an electric control sub fuel system independent of the main fuel system. In particular, it is preferable to pre-inject the auxiliary fuel with a phase difference of about −15 ° to −22.5 ° at the crank angle when the piston top dead center timing is 0 °. Further, in order to improve the properties of the exhaust gas, the fuel injection amount at the time of pre-injection is reduced, and at least the injection amount of the auxiliary fuel in the pre-injection is made smaller than the injection amount of the main fuel. It is preferable.

  In the fuel injection device corresponding to claim 5, after the main fuel injection, the after injection of the sub fuel is performed after a time shorter than a half cycle of the main fuel injection. After-injection is also called post-injection. After-injection uses an auxiliary fuel system that is electrically controlled independently of the main fuel system, and controls the injection timing, injection time (injection amount), injection pressure, and the like with higher accuracy than the main fuel system. In particular, after the main injection is completed, it is preferable that the auxiliary fuel be after-injected with a phase difference of about 5 ° to 10 ° at the crank angle. Further, it is preferable to increase the fuel injection amount at the time of after injection, and at least to set a ratio of at least one injection amount of the auxiliary fuel to the injection amount of the main fuel at least in the after injection.

  In the fuel injection device corresponding to claim 6, the injection pressure in the pre-injection is different from the injection pressure in the after-injection. For example, pre-injection is performed under injection conditions such as injection timing, injection time (injection amount), injection pressure, etc. suitable for reducing / suppressing cylinder vibration in the combustion chamber, and after-injection is suitable for improving exhaust gas properties The injection is performed under injection conditions such as injection timing, injection time (injection amount), and injection pressure.

  In the fuel injection device corresponding to claim 7, the main fuel includes at least one of waste cooking oil, biofuel, and heavy oil.

  In the fuel injection device corresponding to claim 8, the internal combustion engine is a diesel engine, and the auxiliary fuel system has a pressure accumulating portion including a common rail for storing the pressurized auxiliary fuel. For example, sub-injection such as pre-injection and after-injection uses an auxiliary fuel system with a pressure accumulator that includes a common rail, and controls injection timing, injection time (injection amount), injection pressure, etc. with higher accuracy than the main fuel system. It is done while doing.

  The fuel injection device corresponding to claim 9 joins the main fuel system and the sub fuel system at a junction immediately before the fuel injection valve, and more than half of the piping of the main fuel system connected to the junction. A check valve is provided at at least one of a position near the merging portion and a position closer to the merging portion than half of the pipe of the auxiliary fuel system connected to the merging portion. When the check valve is provided in the main fuel system, it is closer to the junction than the half of the piping between the mechanical fuel injection pump included in the main fuel system and the junction between the main fuel system and the auxiliary fuel system. It is preferable to arrange in a position. When the check valve is provided in the auxiliary fuel system, it is closer to the junction than the half position of the pipe from the electric fuel injection valve included in the auxiliary fuel system to the junction of the main fuel system and the auxiliary fuel system. It is preferable to arrange in a position. And, the back flow of the fuel sent from the main fuel system or the sub fuel system to the pipe through the check valve is prevented, the volume of the portion pressurized by the fuel injection is reduced, the fuel pressure is increased and the response The fuel is injected into the combustion chamber with improved performance.

  The fuel injection device corresponding to claim 10 further comprises air column vibration detecting means for detecting air column vibration of a pipe line provided in the cylinder, and according to the air column vibration detected by the air column vibration detecting means. And controlling the injection condition of the auxiliary fuel.

  In the fuel injection device corresponding to claim 11, the air column vibration detecting means detects the air column vibration by a pressure sensor provided in a measuring cock constituting the pipe line. A pressure sensor that detects air column vibrations is provided, and sub-injection of auxiliary fuel is performed so that the detected pressure value of the pressure sensor becomes small.

  The fuel injection device corresponding to claim 12 injects the auxiliary fuel at a timing to reduce the air column vibration. For example, a detected pressure value of a pressure sensor that detects air column vibration is fed back to the system control unit, and feedback control is performed so that the amplitude of the detected pressure value is reduced. Further, feedback control may be performed so that the heat generation rate and the amplitude of dp / dθ are reduced.

  An internal combustion engine for land and marine industry corresponding to claim 13 includes the fuel injection device according to any one of claims 1 to 12. The internal combustion engine for the land and marine industry may be, for example, an internal combustion engine that is mounted not only on ships but also on other mobile engines such as railway vehicles and automobiles, power generation systems, and industrial equipment. The internal combustion engine may be an engine (such as a direct injection type Otto engine) that performs intermittent combustion other than the diesel engine.

  According to the fuel injection device of the present invention, a main fuel system that is mechanically controlled to supply main fuel, a sub fuel system that is electrically controlled to supply sub fuel, the main fuel system, and the sub fuel A fuel injection valve that is provided in common in the system and injects the main fuel and the sub fuel into the cylinder, and performs fuel injection by performing the main fuel injection and the sub fuel injection at different timings. Problems associated with the combustion of can be reduced and suppressed. Specifically, vibration of the cylinder in the combustion chamber can be reduced, or the properties of the exhaust gas can be improved. In particular, by electrically controlling the auxiliary fuel system, the injection timing of the auxiliary fuel with respect to the injection timing of the main fuel can be controlled with high accuracy, and a high effect is obtained in improving the vibration of the cylinder and the properties of the exhaust gas. It is done. In addition, since the fuel injection valve is provided in common for the main fuel system and the auxiliary fuel system, for example, when the auxiliary fuel system is retrofitted, there is no need to separately provide a mounting port in the cylinder, and only the fuel injection valve is replaced. Just do it.

  Further, according to the fuel injection device of the present invention, since the injection pressure at the time of the injection of the main fuel and the injection pressure at the time of the injection of the sub fuel are different, there is a problem associated with the combustion of the main fuel. It can be reduced / suppressed. For example, by making the injection pressure at the time of the injection of the auxiliary fuel higher than the injection pressure at the time of the injection of the main fuel, the particles of the auxiliary fuel are made finer before and after the injection of the main fuel, and the combustion of the auxiliary fuel is performed. By increasing the value, the effect of improving cylinder vibration and exhaust gas properties can be enhanced.

  Further, according to the fuel injection device of the present invention, the pre-injection of the auxiliary fuel is performed before the main fuel is injected and before the main fuel injection is shorter than a half cycle. It is possible to reduce the vibration of the cylinder and improve the properties of the exhaust gas. In particular, the effect of suppressing cylinder vibration can be achieved by pre-injecting auxiliary fuel with a phase difference of about −15 ° to −22.5 ° at the crank angle when the piston top dead center timing is 0 °. Becomes prominent. Moreover, the effect of improving the properties of the exhaust gas becomes significant by making the injection amount of the auxiliary fuel in the pre-injection smaller than the injection amount of the main fuel.

  Further, according to the fuel injection device of the present invention, after the injection of the main fuel, the after-injection of the auxiliary fuel is performed after a time shorter than a half cycle of the injection of the main fuel, so that the property of the exhaust gas Can be improved. In particular, after the main injection is finished, the effect of improving the properties of the exhaust gas becomes conspicuous by causing the auxiliary fuel to be after-injected with a phase difference of about 5 ° to 10 ° at the crank angle. In addition, by making the injection amount of fuel at the time of after-injection large, and at least setting the ratio of the injection amount of the auxiliary fuel to the injection amount of the main fuel at least in the after-injection, The effect of improving the gas properties becomes remarkable.

  Note that, by making the injection pressure in the pre-injection different from the injection pressure in the after-injection, different effects can be obtained in the pre-injection and the after-injection. For example, the pre-injection can reduce and suppress the vibration of the cylinder in the combustion chamber, and the after-injection can improve the properties of the exhaust gas.

  Further, according to the fuel injection device of the present invention, when the main fuel contains at least one of waste cooking oil, biofuel, and heavy oil, the effect of improving the exhaust gas property by the sub-injection of the sub-fuel is remarkable. It becomes.

  Further, according to the fuel injection device of the present invention, the internal combustion engine is a diesel engine, and the auxiliary fuel system has a pressure accumulating portion including a common rail that stores the pressurized auxiliary fuel. By storing auxiliary fuel in the pressure accumulating section in the performed state, the injection timing, injection pressure, and injection amount of pre-injection and after-injection can be controlled with high accuracy. In particular, in the case of a large-sized internal combustion engine, it becomes easy to apply a common rail fuel injection device used in an automobile.

  Further, according to the fuel injection device of the present invention, the main fuel system and the sub fuel system are merged at the junction just before the fuel injection valve, and half of the main fuel system pipe connected to the junction In addition, by providing a check valve in at least one of the position near the merging section and at a position closer to the merging section than half of the piping of the auxiliary fuel system connected to the merging section, fuel injection is performed downstream from the merging section. Thus, the volume of the pressurized portion can be reduced, the fuel pressure can be increased and the response can be improved, and the fuel can be injected while suppressing the decrease in the pressure of the main fuel or the sub fuel.

  The fuel injection device of the present invention further includes air column vibration detecting means for detecting air column vibration of a pipe line provided in the cylinder, and is adapted to detect air column vibration detected by the air column vibration detecting means. Accordingly, by controlling the injection condition of the auxiliary fuel, the vibration of the cylinder in the combustion chamber can be effectively reduced by the auxiliary injection that is the injection of the auxiliary fuel.

  In particular, the air column vibration detecting means is provided with a pressure sensor for detecting air column vibration by detecting the air column vibration by a pressure sensor provided in a measurement cock constituting the pipe, and the pressure sensor Sub fuel can be sub-injected so that the detected pressure value becomes small.

  Furthermore, it is preferable that the auxiliary fuel is injected at a timing at which the air column vibration is reduced. For example, the detected pressure value of a pressure sensor that detects air column vibration is fed back to the system control unit, and feedback control is performed so that the amplitude of the detected pressure value becomes small, so that the combustion chamber detected as air column vibration is detected. The vibration of the cylinder can be reduced more effectively.

  Further, according to the internal combustion engine for land and marine industry of the present invention, in the internal combustion engine mounted not only in the ship but also in other moving engines such as railway vehicles and automobiles, power generation systems and industrial equipment, the vibration of the cylinders in the combustion chamber is reduced. It can be reduced / suppressed and the properties of exhaust gas can be improved. For example, when a large-sized internal combustion engine for the land and marine industry is employed, a small automobile common rail having a high mass production effect can be employed for the auxiliary fuel system.

It is sectional drawing which shows schematic structure of the diesel engine of embodiment. It is a partial expanded sectional view which shows the structure of the cylinder head of embodiment. It is a figure which shows the block diagram of the fuel supply system of embodiment. It is a figure which shows the relationship of the timing of pre injection and main injection. It is a figure which shows the relationship of the timing of after injection and main injection. It is a control block diagram of a diesel engine in an embodiment. It is a figure which shows the relationship between the timing of pre-injection, and injection pressure. It is a figure which shows the relationship between the timing of pre-injection, and injection pressure. It is a figure which shows the relationship between the timing of pre-injection, a pressure fluctuation, and a heat release rate. It is a figure which shows the relationship between the timing of pre-injection, a pressure fluctuation, and a heat release rate. It is a figure which shows the injection pressure in the case of no pre-injection, a pressure fluctuation, a heat generation amount, and a heat generation rate. It is a figure which shows the injection pressure, pressure fluctuation, heat generation amount, and heat generation rate when there is pre-injection. It is a figure which shows the relationship between the timing of pre-injection, and the NOx density | concentration in exhaust gas. It is a figure which shows the relationship between the timing of pre-injection, and the CO density | concentration in exhaust gas. It is a figure which shows the relationship between the timing of pre-injection, and the smoke density | concentration in exhaust gas. It is a figure which shows the relationship between the injection time (injection amount) of pre-injection, and the NOx density | concentration in exhaust gas. It is a figure which shows the relationship between the injection time (injection amount) of pre-injection, and the CO density | concentration in exhaust gas. It is a figure which shows the relationship between the injection time (injection amount) of pre-injection, and the smoke density | concentration in exhaust gas. It is a figure which shows the relationship between the timing of after injection, and injection pressure. It is a figure which shows the relationship between the timing of after injection, a pressure fluctuation, and a heat release rate. It is a figure which shows the relationship between the timing of after injection, and the NOx density | concentration in exhaust gas. It is a figure which shows the relationship between the timing of after injection, and the THC density | concentration in exhaust gas. It is a figure which shows the relationship between the timing of after injection, and the CO density | concentration in exhaust gas. It is a figure which shows the relationship between the timing of after injection, and the smoke density | concentration in exhaust gas. It is a figure which shows the relationship between the injection time (injection amount) of after injection, and injection pressure. It is a figure which shows the relationship between the injection time (injection amount) of after injection, a pressure fluctuation, and a heat release rate. It is a figure which shows the relationship between the injection time (injection amount) of after injection, and the NOx density | concentration in exhaust gas. It is a figure which shows the relationship between the injection time (injection amount) of after injection, and the THC density | concentration in exhaust gas. It is a figure which shows the relationship between the injection time (injection amount) of after injection, and the CO density | concentration in exhaust gas. It is a figure which shows the relationship between the injection time (injection amount) of after injection, and the smoke density | concentration in exhaust gas. It is a figure which shows the reduction effect of CO density | concentration in smoke and smoke concentration by pre-injection.

  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 with a head bolt, and the cylinder head 22 is in contact with and closely contacts the opening of the upper portion 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 communicating with the combustion chamber, and an intake valve and an exhaust valve for opening and closing the opening of these ports with respect to the combustion chamber are arranged. The intake / exhaust valves 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.

  Further, as shown in the partially enlarged view of FIG. 2, the cylinder head 22 is provided with an indicator cock (measuring cock) 53. The indicator cock 53 is configured by forming a pipe line 53 a in the cylinder head 22 and measuring an end of the pipe line 53 a to the outside of the cylinder head 22 in order to measure the pressure and the like inside the cylinder liner 14. A valve 53c is provided at the end of the pipe 53a drawn to the outside of the cylinder head 22, and by opening this valve 53c, a part of fuel, air, etc. in the combustion chamber is extracted and its properties are measured. Can do.

  In the present embodiment, in order to measure air column vibration in the pipe line 53a, a pressure sensor 53b for measuring the pressure in the pipe line 53a is provided. The pressure sensor 53b detects the pressure in the pipe line 53a and outputs it to the system control unit 114 described later.

  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 and the exhaust valve. 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 and the exhaust valve, and the intake port and the exhaust port are opened and closed.

  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, and this pump pressurizes the fuel in the fuel tank 52 and supplies it to the fuel injection valve 26 through a fuel supply pipe 54 having a check valve 51. . 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.

  Another fuel supply system is referred to as a secondary fuel supply system. The auxiliary fuel supply system includes a 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. A common rail 60 is included. The pressurized fuel stored in the common rail 60 is sent to the main fuel supply pipe 54 via the fuel supply pipe 62 having the check valve 63 and the auxiliary fuel supply valve 64. 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 will be referred to as an auxiliary fuel system. The fuel tank 56 will be described as an auxiliary fuel tank 56, and a fuel supply pipe 62 will be described as an auxiliary fuel supply pipe 62. To do.

  Therefore, in the fuel supply system 48, the main and sub fuel systems share the components (for example, the fuel injection valve 26) downstream from the junction 65 of the main and sub fuel supply pipes 54 and 62.

  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. 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 main fuel sent downstream from the check valve 51 is prevented from flowing back to the mechanical fuel injection pump 50 side by the check valve 51. Moreover, the volume of the part pressurized by fuel injection can be made small, the fuel pressure can be increased and the response (pressurization speed) can be improved, and fuel can be injected.

  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 supply valve 64 is provided in the middle of the auxiliary fuel supply pipe 62 from the common rail 60 to the main fuel supply pipe 54. By opening the auxiliary fuel supply valve 64, the auxiliary fuel is supplied downstream from the junction 65. Is supplied. The auxiliary fuel supply valve 64 is an electrically controlled type that is electrically controlled.

  Thus, 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 previously stored and pressurized in advance at the fuel injection timing 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, the injection timing can be easily controlled, and the amount of fuel injected at the time of injection The injection pressure can also be easily controlled. Further, by injecting the auxiliary fuel at an injection pressure higher than that of the main fuel, the particles of the auxiliary fuel are injected in a finer state than the main fuel. Thereby, the ignitability and combustibility of the auxiliary fuel can be improved. Further, the pressure in the common rail can be easily changed. Specifically, for example, when an electric pump is adopted as the pressurizing pump 58, the common rail pressure can be adjusted by changing the rotational speed of the motor that drives the pump. 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. The internal pressure can be adjusted.

  The auxiliary fuel sent downstream from the junction 65 is prevented from flowing back to the common rail 60 by the check valve 63. Further, the check valve 51 prevents the outlet from flowing downstream. As the check valve 51 and / or the check valve 63, a delivery valve type having a suction stroke can be selected. Thereby, the residual pressure of the main fuel or the auxiliary fuel can be reduced, and the influence on the next injection can be reduced. Further, the fuel stored in the common rail 60 is sent to the fuel injection valve 26 through the main fuel supply pipe 54. 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 supply valve 64 is provided for each cylinder.

  Further, the check valve 63 prevents the back flow of the main fuel when the auxiliary fuel is not injected. The check valve 51 prevents this fuel from flowing downstream from the check valve 51 of the main fuel system when the auxiliary fuel is injected. Increasing the fuel pressure and improving the response (pressurization speed) can be expected by reducing the volume of the pipe pressurized by the auxiliary fuel. Although it is important to reduce the volume of the pipe line from the check valve 51 to the nozzle hole of the injection valve 26 as much as possible, the check valve 51 is half the pipe between the mechanical fuel injection pump 50 and the junction 65. If it is disposed at a position closer to the mechanical fuel injection pump 50 than the position, the pressure of the main fuel supplied from the main fuel system or the sub fuel supplied from the sub fuel system in the fuel supply pipes 54 and 62 is large. Thus, the injection pressure when fuel is injected from the fuel injection valve 26 into the cylinder is reduced. Therefore, the check valve 51 is preferably disposed at a position closer to the merging portion 65 than a half position of the pipe between the mechanical fuel injection pump 50 and the merging portion 65 of the main fuel supply pipe 54. When the check valve 63 is disposed at a position closer to the auxiliary fuel supply valve 64 than a half position of the pipe between the auxiliary fuel supply valve 64 and the junction 65, the main fuel is supplied to the fuel supply pipes 54 and 62. The pressure of the main fuel supplied from the system or the sub fuel supplied from the sub fuel system is greatly reduced, and the injection pressure when fuel is injected from the fuel injection valve 26 into the cylinder is reduced. Therefore, the check valve 63 is preferably disposed at a position closer to the junction 65 than a half position of the pipe between the auxiliary fuel supply valve 64 and the junction 65 of the auxiliary fuel supply pipe 62. Even if the positions of the check valve 51, the check valve 63, and the junction 65 cannot be changed due to the actual configuration of the pipeline, the pipeline from the junction 65 to the fuel injection valve 26 is, for example, a double pipe or a separate pipe. It is possible to bring the substantial merging portion to the vicinity of the fuel injection valve 26 as much as possible. In particular, the auxiliary fuel is introduced into the fuel supply pipes 54 and 62 while being preliminarily pressurized by the common rail 60 (pressure accumulating portion), and is injected into the cylinder from the fuel injection valve 26 at a pressure higher than that of the main fuel. Therefore, it is easily affected by the pressure drop due to the position of the check valves 51 and 63. Therefore, when the fuel supply system using the pressure accumulating section such as the common rail 60 is provided, the effect of arranging the check valves 51 and 63 as described above becomes remarkable. In addition, by adopting a cycle of pre-injection (sub fuel) → main injection (main fuel) → after injection (sub fuel), the pipeline is filled with sub fuel for pre injection that requires particularly precise control. It is possible to control the injection in the state where

  Further, by adding an auxiliary controllable fuel supply valve 64, it becomes easy to introduce a common rail system for automobiles. 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.

  Further, in the present embodiment, main injection for injecting main fuel supplied from the main fuel system and sub-injection for injecting sub-fuel supplied from the auxiliary fuel system at timings different from the main injection are performed. More specifically, as shown in the fuel injection timing chart of FIG. 4, the auxiliary fuel is injected before the main injection and before the half cycle (T / 2) of the main injection that is repeatedly performed. Perform pre-injection. Pre-injection is also called pilot injection. Further, as shown in the fuel injection timing chart of FIG. 5, after the main injection, after-injection is performed in which the auxiliary fuel is injected after a time shorter than the half cycle (T / 2) of the main injection that is repeatedly performed. . After-injection is also called post-injection. Pre-injection and after-injection may be performed in combination.

  In particular, by making the auxiliary fuel supply valve 64 electrically controlled, the injection conditions (fuel injection timing, fuel injection period ( This is advantageous when it is necessary to control the injection amount), the injection pressure, the injection pattern, and the like.

  The fuel injection valve 26 may be an electrically controlled fuel injection valve that performs electrical control for fuel injection. The electrically controlled injection valve functions as an injection valve that injects fuel into the cylinder, and also functions as a fuel control valve that controls the supply of main fuel and auxiliary fuel. The electrically controlled fuel injection valve receives a control signal and injects fuel of an injection amount indicated by the control signal from an injection nozzle having an electromagnetic valve. 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 every time the plunger stroke is caused by the cam 92. The fuel injection valve 26 may be a fuel injection valve in which a main fuel system and a sub fuel system exist independently in one valve body, and each function by a mechanical type, an electric control type, or a combination thereof. Further, since the fuel injection valve 26 is provided in common for the main fuel system and the auxiliary fuel system, for example, when the auxiliary fuel system is retrofitted to an internal combustion engine of an existing ship, it is necessary to separately provide an attachment port in the cylinder head 22. There is no need to replace the fuel injection valve 26. Further, even in the case of a newly built ship, drilling in the cylinder head 22 is only required in one place for each cylinder as before, and processing can be facilitated.

  The main and sub fuels may be the same type of fuel or a combination of different types of fuel. The main and auxiliary fuels preferably include at least one of waste cooking oil, biofuel, and heavy oil.

  Even in the case of using the same type of fuel, as will be described later, in the auxiliary fuel system, the fuel particles become fine by injecting at a high pressure from the initial stage of injection, and the ignitability and combustibility are improved. . In particular, the deterioration of ignitability at the time of low load due to the fuel injection valve described above 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 a fuel with poor ignitability is used as the main fuel, it is preferable to use light oil, biodiesel oil, GTL (Gas To Liquid), or DME (dimethyl ether) as the auxiliary fuel. When heavy oil is used as the main fuel, rapeseed oil or the like having relatively good ignitability may be used.

  FIG. 6 is a control block diagram regarding control of 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 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 100, a pressure sensor 102, and an exhaust gas sensor 104 are provided. Further, a main fuel flow sensor 106 and a sub fuel flow sensor 108 for detecting the amounts of main fuel and sub fuel actually supplied to the fuel injection valve 26 may be provided. The rotation sensor 100 is a sensor that detects the rotation speed of the crankshaft 18.

  As the pressure sensor 102, 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, the pressure sensor 102 may be a sensor based on the force that the combustion pressure in the combustion chamber acts on the cylinder head bolt.

  More specifically, the pressure sensor 102 may be provided on a cylinder head bolt that fastens the cylinder head 22 to the engine frame 20. A load washer, which is the pressure sensor 102, is arranged between the nut of the cylinder head 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. It is known that the force acting on this load washer has a good correlation with the cylinder internal pressure, and it is possible to measure the cylinder internal pressure with a load washer provided outside the cylinder instead of directly measuring the cylinder internal pressure. It is.

  Further, a strain gauge as the pressure sensor 102 may be used. The strain gauge used as the pressure sensor 102 is preferably attached to the shaft portion of the cylinder head bolt. The strain gauge 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 cylinder head bolt can be properly detected. For example, the cylinder head bolt may be mounted on a bolt shaft portion in the cylinder head 22.

  It has been found that the force acting on the elongation of the cylinder head bolt has a good correlation with the cylinder internal pressure, and instead of directly measuring the cylinder internal pressure, the cylinder internal pressure is determined by a strain gauge provided outside the cylinder. It is possible to measure. 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.

  The pressure sensor 102 can be provided for each cylinder, or can 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 102, the engine state estimation unit 110 estimates the operating state of the internal combustion engine.

  The exhaust gas sensor 104 is a sensor that detects nitrogen oxides (NOx), carbon monoxide (CO), particulate matter (PM), total hydrocarbons (THC), and the like in the exhaust gas of the internal combustion engine. These can be provided individually or in combination. The exhaust gas sensor 104 can be provided for each cylinder, or can be provided corresponding to one or more representative cylinders. The output signal from the exhaust gas sensor 104 is sent to the engine state estimation unit 110, and the engine state estimation unit 110 estimates the operating state of the internal combustion engine according to the properties of the exhaust gas.

  The engine state estimation unit 110 estimates the combustion state in the internal combustion engine based on at least one information of the exhaust gas property, ignition timing, indicated mean effective pressure, and maximum cylinder internal pressure. For example, by detecting the cylinder pressure by the pressure sensor 102 when the fuel injection timing of the main fuel is changed, the maximum cylinder pressure and the indicated mean effective pressure can be calculated, and the ignition rate is calculated from the heat generation rate obtained from the cylinder pressure. The time can be estimated. 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. Exhaust gas properties, ignition timing, illustrated mean effective pressure, maximum cylinder internal pressure, etc. change when the injection conditions such as the injection timing of main fuel and auxiliary fuel, injection pressure, injection amount (injected fuel ratio), etc. are changed. The injection conditions such as the injection timing, injection pressure, injection amount (injection fuel ratio) of the main fuel and sub fuel are controlled so that the parameters become predetermined values.

  Moreover, the engine state estimation part 110 estimates the combustion state of an internal combustion engine according to the property of exhaust gas. The concentration of nitrogen oxide (NOx), carbon monoxide (CO), smoke and total hydrocarbons (THC) in the exhaust gas changes with respect to the load of the internal combustion engine. Smoke corresponds to the amount of particulate matter (PM) in the exhaust gas. That is, the engine state estimation unit 110 receives from the exhaust gas sensor 104 at least one of measured values of nitrogen oxide (NOx), carbon monoxide (CO), smoke, and total hydrocarbons (THC) in the exhaust gas, The combustion state of the internal combustion engine is estimated from the received measurement values. Depending on the estimated combustion state of the internal combustion engine or the measured values of nitrogen oxide (NOx), carbon monoxide (CO), smoke and total hydrocarbons (THC) themselves, the injection timing of main fuel and sub fuel, the injection Control injection conditions such as pressure and injection amount (injection fuel ratio).

  The combustion state estimated by the engine state estimation unit 110 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. In addition, when a fuel with good ignitability is used, nitrogen oxide (NOx) in the exhaust gas increases, and with fuel with poor ignitability, carbon monoxide (CO), smoke and total carbonization. Hydrogen (THC) increases.

  The engine state estimator 110 determines the characteristics of the exhaust gas thus obtained, the ignition timing, the parameters such as the indicated mean effective pressure, the maximum cylinder internal pressure, the characteristics of the fuel, the detection value of the pressure sensor 102, and the detection of the exhaust gas sensor 104. A control signal for controlling the injection conditions such as the injection timing, injection pressure, injection amount (injected fuel ratio) of the main fuel and the auxiliary fuel based on the operating conditions such as values is output to the system control unit 114.

  Further, a pressure measurement value indicating air column vibration of the pipe line 53 a detected by the pressure sensor 53 b provided in the pipe line 53 a of the cylinder head 22 is also input to the system control unit 114. This pressure measurement value is also used to control injection conditions such as the injection timing, injection pressure, and injection amount (injected fuel ratio) of the main fuel and auxiliary fuel.

On the other hand, the operating conditions of the diesel engine 10 are determined based on the conditions input to the driving operation panel 120. Based on this, the detected values of the engine state estimating unit 110 and each sensor are fed back, and the system control unit 114 supplies the diesel engine 10 with a diesel engine. The engine 10 is controlled. The operation panel 120 is provided with an operation switch 122 for starting / stopping the diesel engine 10 and a throttle lever 124 for controlling the output level, and the regulation value and operation mode for the type and amount of fuel, exhaust gas, etc. An input condition setting unit 126 is provided. As the types of fuel, heavy oil, light oil, rapeseed oil, waste cooking oil, palm oil, biodiesel oil, GTL (Gas To Liquid), DME (dimethyl ether), and the like are assumed, and typical characteristics of each are stored in advance. ing. 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, CO regulation, smoke regulation, SOx regulation, CO ₂ emission amount regulation) 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 driving condition calculation unit 128 calculates driving conditions suitable for these conditions. Specifically, the ratio of main fuel and auxiliary fuel, fuel properties (cetane number, calorific value), exhaust temperature target value, efficiency target value, load condition, etc. are calculated.

  In addition, the GPS 130 may be mounted, the current position may be acquired based on GPS (Global Positioning System) information, radar information, and the like, and the driving conditions may be calculated together. 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 driving 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 may be used, and if the current position is the open ocean, the operation mode may prioritize fuel consumption. 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 location of countries, regions, cities, etc. in the world and the distance from the coast, it is possible to calculate operating conditions according to geographical conditions. In addition, GPS and radar can be commonly used for ships.

  Based on the operation condition calculated by the operation condition calculation unit 128, the operation condition setting unit 112 sets the operation condition of the diesel engine 10 in the system control unit 114. Based on the set conditions, the system control unit 114 controls injection conditions such as the injection timing, injection pressure, and injection amount (injected fuel ratio) of the main fuel and the auxiliary fuel.

  That is, the system control unit 114 determines the operating conditions of the internal combustion engine estimated by the engine state estimation unit 110, for example, ignition timing, combustion state of the internal combustion engine, fuel properties, detected values of the pressure sensors 102 and 53b, and the exhaust gas sensor 104. The mechanical fuel injection pump 50, the pressurization pump 58, the auxiliary fuel supply valve 64, and the fuel injection valve 26 are controlled in accordance with the detected value of the engine and the operating conditions of the internal combustion engine set in the operating condition setting unit 112. To adjust the injection timing, injection pressure, injection amount (injected fuel ratio), etc. of the main fuel and auxiliary fuel. Note that the control of the injection timing, the injection amount, and the injection fuel ratio with the main fuel is performed by controlling the auxiliary fuel supply valve 64 by the system control unit 114. Further, the pressure pump 58 may be controlled in order to control the fuel pressure of the auxiliary fuel. When the mechanical fuel injection pump 50 controls the injection amount of the main fuel and the injection fuel ratio with the auxiliary fuel, a mechanism for changing the phase of the cam 92 with respect to the crankshaft is provided. Further, the injection timing (timing) of the main fuel and the sub fuel to the internal combustion engine can be performed by opening / closing control of the fuel injection valve 26 when the fuel injection valve 26 is an electrically controlled fuel injection valve.

  In the fuel supply system 48 of the present embodiment, the main and sub fuel supply pipes 54 and 62 merge on the upstream side of the fuel injection valve 26. Therefore, the main fuel and the auxiliary fuel can be injected separately or simultaneously. In any case, the injection conditions such as the injection timing, injection time (injection amount), and injection pressure of the main fuel and the sub fuel according to the operating state of the internal combustion engine, for example, the load of the internal combustion engine and the properties of the exhaust gas, etc. Can be adjusted.

  In particular, in the present embodiment, control for performing sub-injection of sub fuel at a timing different from that of main injection of main fuel is performed. That is, the pre-injection and after-injection of the auxiliary fuel are performed at different timing from the main injection of the main fuel.

  First, the system control unit 114 uses the main fuel system according to the estimated operating conditions of the internal combustion engine, the detected values of the pressure sensors 102 and 53b, the detected value of the exhaust gas sensor 104, and the operating conditions of the internal combustion engine. Set the injection conditions. That is, injection conditions such as the timing of injection of the main fuel using the main fuel system, injection time (injection amount), and injection pressure so as to satisfy the combustion conditions that satisfy the operation conditions of the internal combustion engine set by the operation condition setting unit 112 Is set.

  When performing the main injection, the fuel is pressurized and injected only by the mechanical fuel injection pump 50. The fuel pressure Pi gradually increases according to the stroke of the plunger, and when 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 rack is controlled so that the effective stroke of the plunger becomes long. When the load is full, the maximum injection pressure Pmax is reached (crank angle α2). Thereafter, the fuel is slightly injected by the pressure remaining in the piping of the supply system and the like, 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 deteriorates at low loads, the exhaust gas properties deteriorate, the combustion of the diesel engine 10 suddenly burns, and vibration and noise are generated. It may get bigger.

  In order to reduce or suppress such combustion problems caused by main injection, pre-injection or after-injection of auxiliary fuel is performed.

  In the case of performing the pre-injection, the auxiliary fuel is injected before the main injection period and before the half period (T / 2) of the main injection. In the auxiliary fuel system, pre-injection is performed by storing auxiliary fuel that has been preliminarily pressurized in the common rail 60 serving as an accumulator, and controlling the auxiliary fuel supply valve 64 to open at a timing different from the main injection of the main fuel. I do.

  By performing the pre-injection, vibration generated in the internal combustion engine can be reduced or suppressed. 7 and 8 are diagrams illustrating temporal changes in the injection pressures of the main fuel and the auxiliary fuel when the pre-injection is performed at a timing different from that of the main injection. FIG. 7 shows temporal changes in injection pressure when pre-injection is performed at −10 °, −12.5 °, and −15 ° with respect to the crank top dead center crank angle in main injection. In the main injection, the temporal change of the injection pressure when the pre-injection is performed at -15 °, -17.5 °, -20 °, and -22.5 ° with respect to the crank angle at the top dead center of the piston is shown. Yes.

  Note that the angle indicating the timing indicates the phase at the crank angle in the case where the rotation of the piston is 360 ° from the top dead center. That is, it shows the phase difference of the pre-injection timing when the piston top dead center timing in the main injection is set at a crank angle of 0 °. In the figure, “cam” indicates an operation of only main injection without pre-injection.

  FIGS. 9 and 10 show the temporal variation of the pressure value detected by the pressure sensor 53b and the heat generation rate (dQ / dθ) in the cylinder when pre-injection is performed at each timing shown in FIGS. As shown in FIGS. 9 and 10, the earlier the pre-injection timing (the greater the timing difference from the main injection), the longer the detected pressure value of the pressure sensor 53b and the heat generation rate (dQ / dθ). It can be seen that the amplitude of the target change is reduced and the air column vibration in the pipe line 53a provided in the cylinder head 22 is reduced. However, if the pre-injection is performed more than -22.5 ° before the crank angle phase difference, combustion due to the pre-injection in the internal combustion engine may cause problems on the sliding surfaces of the piston ring and the cylinder liner. Therefore, it is preferable to pre-inject the auxiliary fuel with a phase difference of about −15 ° to −22.5 ° in the crank angle with respect to the cycle of the main injection. By performing the pre-injection at such timing, the effect of suppressing cylinder vibration becomes significant.

  Further, even if feedback control is performed in which the pressure of the pressure sensor 53b is detected and fed back to the system control unit 114, the timing of the pre-injection is changed according to the amplitude of the temporal variation of the detected pressure value of the pressure sensor 53b. Good. In this case, the system control unit 114 receives the detected pressure value from the pressure sensor 53b and grasps the pressure (P) and the heat generation rate (dQ / dθ) in the cylinder of the combustion chamber as shown in FIG. . Then, by shifting the pre-injection timing and repeating the process of setting the timing at which the fluctuation range of these values becomes smaller, it is finally set at the pre-injection timing at which the amplitude of the air column vibration is minimized. Can do. Alternatively, the pre-injection position may be fixed, the injection amount may be gradually increased, and the timing may be set so that the fluctuation range of the pressure (P) and the heat generation rate (dQ / dθ) becomes small. Thereby, as shown in FIG. 12, the vibration width of the pressure (P) and the heat generation rate (dQ / dθ) in the cylinder of the combustion chamber can be reduced. Note that the pressure fluctuation rate (dP / dθ) may be used as a parameter instead of the heat generation rate (dQ / dθ).

  Thus, by providing the pressure sensor 53b in the pipe line 53a of the indicator cock 53 and using the detected pressure value obtained by the pressure sensor 53b, vibration of the cylinder in the combustion chamber can be effectively reduced / suppressed. . Even if the pressure sensor 102 is not provided in the cylinder of the combustion chamber, the pressure sensor 53b can be easily attached by using the indicator cock 53.

  FIGS. 13-15 shows the relationship of the property of exhaust gas with respect to the injection timing of the auxiliary fuel in pre-injection. As shown in FIG. 13, the amount of nitrogen oxides (NOx) in the exhaust gas increased as the phase of the pre-injection timing progressed with respect to the main injection timing. This is presumably because the ignitability and combustibility of the main fuel were enhanced as the pre-injection timing progressed. Further, as shown in FIGS. 14 and 15, the concentrations of carbon monoxide (CO) and smoke in the exhaust gas are reduced by performing the pre-injection as compared with the case of not performing the pre-injection (cam). The phase of the injection timing decreased as it proceeded with respect to the main injection timing. Therefore, also in improving the properties of the exhaust gas, it is preferable to pre-inject the auxiliary fuel with a phase difference of about −15 ° to −22.5 ° in the crank angle with respect to the main injection cycle. By performing the pre-injection at such timing, the effect of improving the properties of the exhaust gas becomes remarkable.

  FIGS. 16 to 18 show the relationship of the exhaust gas properties with respect to the injection amount (injection time) of the auxiliary fuel in the pre-injection. As shown in FIG. 16, the concentration of nitrogen oxide (NOx) in the exhaust gas became substantially constant regardless of the injection amount (injection time) of the auxiliary fuel in the pre-injection. On the other hand, as shown in FIGS. 17 and 18, the concentrations of carbon monoxide (CO) and smoke in the exhaust gas decreased as the injection amount of the auxiliary fuel in the pre-injection decreased (injection time decreased). That is, the quality of the exhaust gas is improved by performing the pre-injection compared with the case where the pre-injection is not performed, but the effect of improving the properties of the exhaust gas as the injection amount (injection time) of the auxiliary fuel in the pre-injection is smaller (shorter) Becomes prominent. At this time, it is preferable that at least one injection amount of the auxiliary fuel in the pre-injection is smaller than one injection amount of the main fuel.

  Thus, by performing pre-injection, the ignitability and combustibility of the main fuel can be improved, and the properties of the exhaust gas can be improved. Along with this, the fuel consumption of the internal combustion engine can be improved.

  19 and 20 are diagrams showing temporal changes in the fuel injection pressure and the pressure in the cylinder of the combustion chamber when the after injection is performed at a timing different from that of the main injection. 19 and 20 show the fuel injection pressure and the cylinder of the combustion chamber when after injection is performed at 5 °, 10 °, 15 °, and 20 ° in the crank angle with respect to the crank angle of the piston top dead center in the main injection. It shows the time change of internal pressure.

  FIGS. 21 to 24 show the relationship of the exhaust gas properties with respect to the sub fuel injection timing in the after injection. As shown in FIG. 21, the amount of nitrogen oxides (NOx) in the exhaust gas is reduced by performing the after injection as compared with the case where the after injection is not performed, and the timing of the after injection is smaller than the timing of the main injection. It decreased as it was late. Also, as shown in FIGS. 22 to 24, the concentration of total hydrocarbons (THC), carbon monoxide (CO) and smoke in the exhaust gas can be obtained by performing after injection as compared with the case of not performing after injection. In particular, the after injection was remarkably reduced in the range of 5 ° to 10 ° with respect to the main injection. That is, in order to improve the properties of the exhaust gas, it is preferable to after-inject the auxiliary fuel with a phase difference of about 5 ° to 10 ° in the crank angle with respect to the cycle of the main injection. However, in reality, in the case of after injection, if the output (load) of the internal combustion engine is different, the crank angle at the end of the main injection changes, so it is more preferable to use the crank angle at the end of the main injection as a reference. . On the other hand, in the case of pre-injection, it is preferable to use the top dead center of the piston as a reference.

  25 and 26 show temporal changes in the fuel injection pressure and the pressure in the cylinder of the combustion chamber when the injection amount (injection time) of the auxiliary fuel is changed in the after injection. The figure shows temporal changes in the fuel injection pressure and the pressure in the cylinder in the combustion chamber when the injection time of the after injection is 1.5 ms, 2.0 ms, and 2.5 ms and when the after injection is not performed.

  27 to 30 show the relationship of the exhaust gas properties with respect to the injection amount (injection time) of the auxiliary fuel in the after injection. As shown in FIG. 27, the amount of nitrogen oxides (NOx) in the exhaust gas increases when the after-injection injection time is 1.5 ms, compared with the case where after-injection is not performed, and the injection time is 2 Reduced to 0.0 ms and 2.5 ms. Further, as shown in FIGS. 28 to 30, the concentration of total hydrocarbons (THC), carbon monoxide (CO) and smoke in the exhaust gas is increased by performing the after injection as compared with the case where the after injection is not performed. In particular, the decrease became larger as the injection time in the after injection became longer (the injection amount increased). It is preferable to set a ratio of at least one injection quantity of the auxiliary fuel to one injection quantity of the main fuel at least in the after injection.

  Thus, by performing after injection, the combustibility of the main fuel can be enhanced, and the properties of the exhaust gas can be improved. Along with this, the fuel consumption of the internal combustion engine can be improved.

  A combination of pre-injection and after-injection may be applied. The pre-injection and after-injection have different effects depending on the conditions. Therefore, the pre-injection and after-injection may be performed by changing the injection conditions (injection pressure, injection time, etc.). For example, pre-injection is performed under injection conditions such as injection timing, injection time (injection amount), injection pressure, etc. suitable for reducing / suppressing cylinder vibration in the combustion chamber, and after-injection is suitable for improving exhaust gas properties It is preferable to carry out under injection conditions such as injection timing, injection time (injection amount), injection pressure and the like.

  Further, it is preferable that the common rail 60 stores the fuel at a sufficient pressure so that the fuel can be injected at a pressure at which the fuel becomes fine particles. That is, in the auxiliary fuel system, by using the common rail 60, the injection pressure can be increased from the beginning of the fuel injection period. As described above, by using the common rail 60, it is possible to perform pre-injection and after-injection of auxiliary fuel in a short time at a high pressure from the initial stage of injection.

  At this time, by performing sub-injection of sub fuel at a pressure higher than that of main injection of main fuel, the sub-fuel can be made finer particles. Since the fuel becomes more ignitable as the particles become finer, by making the injection pressure of the auxiliary fuel higher than the injection pressure of the main fuel, the ignitability of the auxiliary fuel can be further increased, and the vibration of the cylinder in the combustion chamber It is possible to enhance the effect of suppressing the exhaust gas and improving the properties of the exhaust gas.

  In addition, by shortening the injection time of the auxiliary fuel (decreasing the injection amount), it is possible to suppress the consumption of the fuel stored in the common rail 60 and to prevent the pressure in the common rail from decreasing. . In order to secure the necessary fuel pressure, measures such as increasing the capacity of the common rail 60 and increasing the flow rate of the pressurizing pump 58 may be taken. In a multi-cylinder engine, the injection interval of the entire engine is shortened, so the need to recover the reduced pressure in the common rail more quickly or the need to increase its capacity so as not to lower the pressure in the common rail is more. Rise.

  Further, a large internal combustion engine for ships and the like has a large combustion chamber, 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 separately provided and an injection amount by the sub fuel system is small.

  FIG. 31 shows the properties of exhaust gas with and without pre-injection using biofuel (mixed oil of rapeseed oil 50% and A heavy oil 50%) and A heavy oil as the main fuel. In the drawing, “assist” is indicated for the case where pre-injection is performed.

  In the case of using biofuel (mixed oil of rapeseed oil 50% and A heavy oil 50%), the concentration of nitrogen oxide (NOx) did not decrease when pre-injection was performed (not shown). On the other hand, the concentration of carbon monoxide (CO) and smoke when using biofuel (mixed oil of rapeseed oil 50% and A heavy oil 50%) was significantly reduced by applying pre-injection. As described above, the effect of improving the properties of the exhaust gas by the pre-injection becomes prominent when biofuel (mixed oil of rapeseed oil 50% and A heavy oil 50%) is used as the main fuel.

  In addition, pre-injection and after-injection injection timing, injection time (injection amount), injection pressure, etc. are directly controlled according to the measured values of nitrogen oxide (NOx), carbon monoxide (CO), and smoke contained in the exhaust gas. May be. For example, a target value of nitrogen oxide (NOx) with respect to the load of the internal combustion engine is calculated by the operating condition calculation unit 128 and set in the system control unit 114 by the operating condition setting unit 112. The system control unit 114 determines the main injection of the main fuel according to the relationship between the measured value of nitrogen oxide (NOx) received from the engine state estimation unit 110 and the target value according to the set load of the internal combustion engine. While setting the conditions, the injection timing, injection time (injection amount), injection pressure, etc. of the auxiliary fuel may be adjusted.

  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. Furthermore, the present invention can be applied to a power generation system installed on land.

  10 Diesel Engine, 26 Fuel Injection Valve, 48 Fuel Supply System, 50 Mechanical Fuel Injection Pump, 51 Check Valve, 53 Indicator Cock, 53a Pipeline, 53b Pressure Sensor, 60 Common Rail, 63 Check Valve, 64 Secondary Fuel Supply Valve, 65 Junction unit, 104 Exhaust gas sensor, 110 Engine state estimation unit, 112 Operating condition setting unit, 114 System control unit.

Claims (13)

A fuel injection device for injecting fuel into a cylinder of an internal combustion engine,
A main fuel system that is mechanically controlled to supply main fuel;
A secondary fuel system that is electrically controlled to supply secondary fuel;
A fuel injection valve that is provided in common to the main fuel system and the sub fuel system, and injects the main fuel and the sub fuel into the cylinder;
With
The fuel injection device, wherein the main fuel injection and the sub fuel injection are performed at different timings. The fuel injection device according to claim 1,
The fuel injection device, wherein an injection pressure at the time of injection of the main fuel is different from an injection pressure at the time of injection of the sub fuel. The fuel injection device according to claim 2,
A fuel injection device, wherein an injection pressure at the time of injection of the sub fuel is higher than an injection pressure at the time of injection of the main fuel. The fuel injection device according to any one of claims 1 to 3,
The fuel injection device according to claim 1, wherein the auxiliary fuel is pre-injected before the main fuel injection and before a time shorter than a half cycle of the main fuel injection. The fuel injection device according to claim 4,
A fuel injection device that performs after-injection of the auxiliary fuel after the main fuel injection and after a time shorter than a half cycle of the main fuel injection. The fuel injection device according to claim 5,
The fuel injection device, wherein an injection pressure in the pre-injection is different from an injection pressure in the after-injection. The fuel injection device according to any one of claims 1 to 6,
The main fuel includes at least one of waste cooking oil, biofuel, and heavy oil. The fuel injection device according to any one of claims 1 to 7,
The internal combustion engine is a diesel engine;
The fuel injection device, wherein the auxiliary fuel system includes a pressure accumulating portion including a common rail for storing the pressurized auxiliary fuel. The fuel injection device according to any one of claims 1 to 8,
Merging the main fuel system and the sub fuel system at the junction just before the fuel injection valve,
Reverse to at least one of a position closer to the merge portion than half of the main fuel system pipe connected to the merge portion and a position closer to the merge portion than half of the sub fuel system pipe connected to the merge portion. A fuel injection device provided with a stop valve. The fuel injection device according to any one of claims 1 to 9,
Further comprising air column vibration detecting means for detecting air column vibration of a pipe line provided in the cylinder,
A fuel injection device that controls injection conditions of the auxiliary fuel in accordance with air column vibration detected by the air column vibration detecting means. The fuel injection device according to claim 10,
The air column vibration detecting means detects the air column vibration by a pressure sensor provided in a measurement cock constituting the pipe. The fuel injection device according to claim 10 or 11,
The fuel injection device, wherein the auxiliary fuel is injected at a timing to reduce the air column vibration.   An internal combustion engine for the land and marine industry equipped with the fuel injection device according to any one of claims 1 to 12.

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