JP2015190328A - Fuel injection system of gas injection engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve heat efficiency without injecting a gas fuel at a pressure higher than a present pressure, and suppressing production of NOx, so that environmental conservation and cost reduction can be achieved.SOLUTION: A fuel injection system of a gas injection engine, includes: a main gas fuel injection valve 5 for injecting a gas fuel into a cylinder 1 at a high pressure; a pilot fuel injection valve 6 for pilot-injecting a diesel fuel into the cylinder; a main gas fuel supply device 8 for supplying the high pressure gas fuel to the main gas fuel injection valve; an auxiliary gas fuel injection valve 7 for further injecting the gas fuel into the cylinder; and an auxiliary gas fuel supply device 10 for supplying the gas fuel into the auxiliary gas fuel injection valve. The auxiliary gas fuel injection valve performs pre-injection into the cylinder while a part of the gas fuel necessary for combustion is supplied from the auxiliary gas fuel supply device, before the diesel fuel is pilot-injected from the pilot fuel injection valve, and the main gas fuel injection valve injects the remaining part of the gas fuel into the cylinder at a high pressure after the pilot injection.

Description

  The present invention relates to a fuel injection system for a gas injection engine using gas fuel such as natural gas as a main fuel.

  In recent years, a clean energy source has been demanded from the viewpoint of environmental conservation. From this point of view, a gas injection engine that uses gas fuel such as natural gas as its main fuel and injects high-pressure gas fuel into a cylinder after pilot fuel injection for ignition is expected. In the gas injection engine, it is necessary to inject the high-pressure gas fuel into the cylinder in a short period of time in order to improve the thermal efficiency from the characteristics of the fuel.

  The problem of knocking due to self-ignition occurs in an Otto cycle premixing type gas engine in which gas fuel is premixed and burned before pilot injection for ignition (for example, Patent Document 1). See), especially when the gas engine is under a high load or when the fuel injection amount is large. On the other hand, the knocking problem does not occur in the above-described gas injection engine serving as a diesel cycle. From this point of view, the spread of gas injection engines is expected.

  On the other hand, in a diesel engine having basically the same structure as a gas injection engine and using diesel fuel as a main fuel, multistage injection in which this diesel fuel is injected in multiple stages may be performed (for example, Patent Document 2). However, this is to perform the injection of diesel fuel after pilot injection in several times, such as pre-injection, main injection, post-injection, etc. after pilot injection. It is not an injection method suitable for a gas injection engine that needs to be injected into a cylinder.

JP-A-11-324805 JP-T 2002-0666813

  Thus, in recent years, a clean energy source is required from the viewpoint of environmental conservation. For this reason, the spread of gas injection engines that use gas fuel such as natural gas as the main fuel is expected. For this reason, gas injection engines also require further improvements in thermal efficiency to reduce costs by reducing the amount of gas fuel used and to contribute to environmental conservation by reducing the amount of exhaust gas. Yes.

  In addition, it is effective to inject gas fuel at a higher pressure as a method for improving thermal efficiency in a gas injection engine. However, in order to ensure safety against high-pressure gas, a higher level of safety measures is required. At the same time, there is a problem in that the power energy required to increase the pressure is increased.

  Furthermore, the conventional gas injection engine combusts basically in the same thermal cycle as that of a diesel engine, so that there is a problem that NOx is generated relatively frequently. For this reason, it is also necessary to further suppress the generation of NOx from the viewpoint of environmental conservation.

  The present invention has been made to solve such a problem, and can improve the thermal efficiency without injecting the gaseous fuel at a higher pressure than the current level, and can suppress the generation of NOx. It is an object of the present invention to provide a fuel injection system for a gas injection engine that can achieve environmental conservation and cost reduction.

  In order to solve the above problems, the present invention adopts a main gas fuel injection valve that is disposed in a cylinder head of a gas injection engine using gas fuel as a main fuel and injects the gas fuel into the cylinder at a high pressure. And a pilot fuel injection valve that pilot-injects diesel fuel into the cylinder before injection of gas fuel from the main gas fuel injection valve, and a main gas fuel supply device that supplies high-pressure gas fuel to the main gas fuel injection valve In the fuel injection method of the gas injection engine, the fuel injection system further includes a sub gas fuel injection valve that injects the gas fuel into the cylinder of the gas injection engine, and a sub gas fuel supply device that supplies the gas fuel to the sub gas fuel injection valve, The auxiliary gas fuel injection valve is required for combustion before diesel fuel is pilot injected from the pilot fuel injection valve. A part of the gas fuel supplied from the auxiliary gas fuel supply device is pre-injected into the cylinder, and the main gas fuel injection valve is required for the above-mentioned combustion after the diesel fuel is pilot injected from the pilot fuel injection valve. The remaining gas fuel is supplied from the main gas fuel supply device and injected into the cylinder at a high pressure.

  The fuel injection system of the gas injection engine according to the present invention includes a conventional main gas fuel injection valve that injects high-pressure gas and a pilot fuel injection valve that injects this diesel fuel, and also injects gas fuel into a cylinder of the gas injection engine. And a sub-gas fuel supply device for supplying gas fuel to the sub-gas fuel injection valve, wherein the sub-gas fuel injection valve is configured to inject diesel fuel from the pilot fuel injection valve. Before being injected, a part of the gas fuel required for combustion is supplied from the auxiliary gas fuel supply device and pre-injected into the cylinder, and the main gas fuel injection valve is required for the above-described combustion after the pilot injection. The remaining gas fuel is injected into the cylinder at high pressure.

  The gas fuel injected from the auxiliary gas fuel injection valve before the pilot fuel injection is ignited and burned by the combustion of the pilot injected diesel fuel. As a result, the gas temperature in the cylinder before the gas fuel is injected from the main gas fuel injection valve rises compared to the conventional gas injection engine. For this reason, the heat generation in the initial stage of combustion can be brought close to an ideal one, and the thermal efficiency by combustion of the gas fuel can be improved without further increasing the pressure of the gas fuel. Thereby, the thermal efficiency as the whole engine can be improved significantly.

  In addition, if a part of the gas fuel is injected before pilot injection and ignited by pilot injection in this way, the combustion becomes so-called lean burn combustion, which can reliably reduce the generation of NOx. .

  In the fuel injection system of the gas injection engine, it is desirable that the auxiliary gas fuel injection valve is disposed on the side of the cylinder and injects low-pressure gas fuel into the cylinder.

  In this way, the auxiliary gas fuel injection valve is disposed on the side of the cylinder, and low pressure gas fuel is injected into the cylinder from the auxiliary gas fuel injection valve, so that necessary and sufficient combustion can be obtained as pre-injection. At the same time, the amount of gas fuel that must be handled as high-pressure gas can be reliably reduced, and safety is improved. In addition, it is possible to suppress the power energy necessary for increasing the pressure of the gas fuel, thereby reducing the cost.

  In the fuel injection system of the gas injection engine, it is desirable that the auxiliary gas fuel injection valve pre-injects the gas fuel into the cylinder at a low pressure of (5 to 15) bar.

  Thus, by pre-injecting the gas fuel into the cylinder at a low pressure of (5 to 15) bar from the auxiliary gas fuel injection valve, the ignition by the pilot fuel injection and the subsequent gas temperature increase are idealized. be able to.

  In the fuel injection system of the gas injection engine, it is desirable that the auxiliary gas fuel injection valve pre-injects the gas fuel into the cylinder at a predetermined time within a range of (80 to 120) ° after the bottom dead center at the crank angle. .

  As described above, when the pre-injection is the low-pressure injection, the gas fuel is pre-injected into the cylinder at a predetermined timing within the range of (80 to 120) ° after the bottom dead center at the crank angle from the auxiliary gas fuel injection valve. Thereby, the ignition by pilot fuel injection and the subsequent gas temperature rise can be made ideal.

  In the fuel injection system of the gas injection engine, the auxiliary gas fuel injection valve is a main gas fuel injection valve that is disposed in the cylinder head and injects the main gas fuel into the cylinder at a high pressure. It is desirable to comprise a main gas fuel supply device for supplying high pressure gas fuel to the main gas fuel injection valve.

  The gas fuel injected from the auxiliary gas fuel injection valve before the pilot fuel injection does not necessarily have to be at a low pressure, and the heat generation at the initial stage of combustion is brought close to ideal by high pressure injection from the main gas fuel injection valve. Can do. Thus, by performing the high-pressure gas fuel injection from the main gas fuel injection valve before and after the pilot fuel injection, the thermal efficiency can be improved without further increasing the pressure of the gas fuel, and the overall thermal efficiency of the engine Can be greatly improved.

  In particular, the auxiliary gas fuel injection valve is a main gas fuel injection valve that is provided in the cylinder head and injects main gas fuel into the cylinder at a high pressure. It is not necessary to separately provide a gas fuel supply mechanism for supplying gas fuel to the injection valve, and an increase in cost can be avoided.

In the fuel injection system of the gas injection engine, it is desirable that the auxiliary gas fuel injection valve pre-injects the gas fuel into the cylinder at a high pressure of (200 to 300) bar.
Thus, by pre-injecting the gas fuel into the cylinder at a high pressure of (200 to 300) bar from the auxiliary gas fuel injection valve, the ignition by the pilot fuel injection and the subsequent gas temperature increase are idealized. be able to.

  In the fuel injection system of the gas injection engine, it is preferable that the auxiliary gas fuel injection valve pre-injects the gas fuel into the cylinder at a predetermined time within a range of (120 to 160) ° after bottom dead center at a crank angle. .

  Thus, when the pre-injection is high-pressure injection, the gas fuel is pre-injected into the cylinder from the auxiliary gas fuel injection valve at a predetermined time within the range of (120 to 160) ° after the bottom dead center at the crank angle. Thereby, the ignition by pilot fuel injection and the subsequent gas temperature rise can be made ideal.

  In the fuel injection system of the gas injection engine, the auxiliary gas fuel injection valve pre-injects the gas fuel in an amount of 50% or more in the mass ratio of the gas fuel necessary for combustion at the time of low load of the gas injection engine. Is desirable.

  A conventional premixed gas engine has a characteristic that occurrence of knocking due to gas injection is small in a low load region. Therefore, even when a relatively large amount of gas fuel is pre-injected at a low load, the possibility of knocking is low, and in particular, 50% or more of gas fuel in the mass ratio of gas fuel required for combustion is pre-injected into the cylinder. As a result, ignition by pilot fuel injection and subsequent increase in gas temperature can be made more ideal.

  In the fuel injection system of the gas injection engine, the auxiliary gas fuel injection valve pre-injects the gas fuel in an amount of 50% or less in the mass ratio of the gas fuel required for combustion at a high load of the gas injection engine into the cylinder. Is desirable.

  It is known that a conventional premixed gas engine has a high possibility of occurrence of knocking due to gas injection in a high load region. Therefore, it is necessary to keep the pre-injection amount of the gas fuel within a certain range at a high load, and in particular by pre-injecting the gas fuel in an amount of 50% or less in the mass ratio of the gas fuel necessary for combustion into the cylinder, While preventing the occurrence of knocking, ignition by pilot fuel injection and the subsequent increase in gas temperature can be made ideal.

  In the fuel injection system of the gas injection engine, it is desirable that the auxiliary gas fuel supply device includes an interlock mechanism that prevents the gas fuel from being injected from the auxiliary gas fuel injection valve beyond a predetermined time.

  As described above, the auxiliary gas fuel supply device includes the interlock mechanism that prevents the gas fuel from being injected from the auxiliary gas fuel injection valve beyond a predetermined time. Continuous injection of gas fuel is reliably prevented, and safety is improved.

  A fuel injection system for a gas injection engine according to the present invention includes a main gas fuel injection valve that is disposed in a cylinder head of a gas injection engine using gas fuel as a main fuel and injects the gas fuel into the cylinder at a high pressure, and the main gas fuel. A gas injection engine having a pilot fuel injection valve that pilot-injects diesel fuel into a cylinder before injection of gas fuel from the injection valve, and a main gas fuel supply device that supplies high-pressure gas fuel to the main gas fuel injection valve In the fuel injection system, the auxiliary gas fuel injection valve further includes an auxiliary gas fuel injection valve that injects the gas fuel into the cylinder of the gas injection engine, and an auxiliary gas fuel supply device that supplies the gas fuel to the auxiliary gas fuel injection valve. Is required for combustion before the diesel fuel is pilot injected from the pilot fuel injection valve Part of the gas fuel is supplied from the auxiliary gas fuel supply device and pre-injected into the cylinder, and the main gas fuel injection valve is required for combustion after the diesel fuel is pilot injected from the pilot fuel injection valve The remainder of the gas fuel is supplied from the main gas fuel supply device and injected into the cylinder at a high pressure.

  Therefore, in the gas injection engine, it is possible to improve the thermal efficiency without injecting the gaseous fuel at a higher pressure than the current level, and to suppress the generation of NOx, thereby achieving environmental conservation and cost reduction. There is an excellent effect of being able to.

1 is a simplified diagram showing an embodiment for carrying out a first invention of a fuel injection system for a gas injection engine of the present invention. FIG. 2 is a system diagram illustrating a sub gas fuel injection valve and a sub gas fuel supply device of the gas injection engine of FIG. 1. It is a figure which shows the relationship between the pre-injection of the gas injection engine of FIG. 1, pilot injection, and the gas fuel injection after pilot injection. It is a figure explaining the interlock mechanism of the subgas fuel supply apparatus of FIG. It is a simplified diagram showing a form for carrying out the 2nd invention of a fuel injection system of a gas injection engine of the present invention. FIG. 6 is a system diagram showing a sub gas fuel injection valve and a sub gas fuel supply device of the gas injection engine of FIG. 5. It is a figure which shows the relationship between the pre-injection of the gas injection engine of FIG. 5, pilot injection, and fuel injection after pilot injection. It is a figure explaining the interlock mechanism of the subgas fuel supply apparatus of FIG.

  A mode for carrying out the first invention of a fuel injection system of a gas injection engine of the present invention will be described in detail with reference to FIGS. The embodiment of the first invention is a case where the pre-injection is performed at a low pressure from the low-pressure gas fuel injection valve 7 shown in FIG.

  FIG. 1 shows a gas injection engine whose main fuel is gas fuel such as natural gas as an example. Reference numeral 1 is a cylinder of a gas injection engine, 2 is a cylinder head, 3 is a cylinder liner, 4 is a piston that slides up and down in the cylinder liner 1, and 9 is a combustion gas in the cylinder 1 provided in the cylinder head 2. The exhaust valve exhausts to the exhaust receiver that does not. The cylinder 1 is an inner cylindrical space formed by the cylinder head 2 and the cylinder liner 3.

  A high pressure gas fuel injection valve (main gas fuel injection valve) 5 for injecting gas fuel into the cylinder 1 at a high pressure into the cylinder head 2, and diesel fuel in the cylinder 1 before injecting gas fuel from the high pressure gas fuel injection valve 5 Pilot fuel injection valves 6 for pilot injection are respectively disposed.

  The high-pressure gas fuel injection valve 5 is supplied with high-pressure gas fuel of, for example, (200 to 300) bar from a high-pressure gas fuel supply device (main gas fuel supply device) 8. A low pressure gas fuel injection valve (sub gas fuel injection valve) 7 for injecting low pressure gas fuel into the cylinder 1 is disposed on the side of the cylinder liner 3. As will be described later, the low-pressure gas fuel injection valve 7 is supplied with low-pressure gas fuel from a low-pressure gas fuel supply device (sub-gas fuel supply device) 10.

  As shown in FIG. 2, the low-pressure gas fuel supply device 10 has the following configuration, for example, and when an abnormality occurs, the supply of gas fuel to the low-pressure gas fuel injection valve 7 is shut off by another system and forcedly An interlock mechanism capable of stopping the injection of gas fuel is provided. Low-pressure gas fuel is supplied from a gas fuel supply source (not shown) to the low-pressure gas fuel injection valve 7 via a hydraulically operated gas fuel on-off valve 12.

  The hydraulic pressure supplied from the hydraulic pump 13 is supplied to the gas fuel on-off valve 12 via an electromagnetically operated on-off valve 14 to open and close the on-off valve 12. At the same time, the hydraulic pressure passing through the on-off valve 14 is supplied to the low-pressure gas fuel injection valve 7 via the electromagnetically operated on-off valve 15, and the low-pressure gas fuel injection valve 7 can be opened by this hydraulic pressure.

  The two electromagnetically operated on / off valves 14 and 15 are electrically controlled by an engine controller 16 of a gas injection engine. The interlock mechanism includes an engine controller 16, an electromagnetically operated hydraulic on / off valve 14, and a hydraulically operated gas fuel on / off valve 12.

  During normal operation, the engine controller 16 opens the hydraulic on-off valve 14, thereby opening the gas fuel on-off valve 12 and supplying gas fuel to the low-pressure gas fuel injection valve 7. At the same time, when the engine controller 16 opens the hydraulic on-off valve 15, the hydraulic pressure is supplied to the low-pressure gas fuel injection valve 7 through the two on-off valves 14, 15, and the low-pressure gas fuel injection valve 7 is opened. Let

  Thereby, the low-pressure gas fuel injection valve 7 can inject low-pressure gas fuel supplied from a gas fuel supply source (not shown). Further, when the engine controller 16 closes the hydraulic on-off valve 15, the low-pressure gas fuel injection valve 7 is closed and the injection of the low-pressure gas fuel is stopped.

  Next, the operation of the fuel injection system of the gas injection engine will be described. As shown in FIG. 3, for example, diesel fuel is pilot-injected into the cylinder 1 from the pilot fuel injection valve 6 in the vicinity of the top dead center crank angle of 180 °. Also, for example, (200 to 300) bar high-pressure gas fuel is injected into the cylinder 1 from the high-pressure gas fuel injection valve 5 within a certain crank angle range immediately after the end of pilot fuel injection.

  On the other hand, the engine controller 16 sends the gas fuel from the low-pressure gas fuel injection valve 7 at a predetermined time within the range of (80 to 120) ° after the bottom dead center at the crank angle, for example, and before the pilot fuel injection. Then, pre-injection into the cylinder 1 is performed. The pre-injection from the low-pressure gas fuel injection valve 7 is performed at a low pressure of (5 to 15) bar, for example.

  Moreover, the engine controller 16 is 50% or more, for example, 50 to 95% or 50 to 100% in mass ratio of gas fuel necessary for combustion when the load of the gas injection engine is low, for example, when the load is 60% or less. The amount of gas fuel is pre-injected into the cylinder 1.

  This is because a relatively large amount of gas fuel can be pre-injected at low load because the possibility of knocking due to pre-injection is low in the low load region. Thereby, the ignition by pilot fuel injection and the subsequent gas temperature rise can be made ideal.

  On the other hand, when the gas injection engine has a high load, for example, when the load exceeds 60%, the engine controller 16 has a gas fuel amount of 50% or less, for example, 10 to 50% in terms of the mass ratio of the gas fuel required for combustion. Is pre-injected into the cylinder 1.

  This is because, when a large amount of gas fuel is pre-injected in a high load region, there is a possibility that knocking may occur due to this pre-injection. Because. Thereby, ignition by pilot fuel injection and subsequent gas temperature rise can be made ideal while preventing occurrence of knocking.

  Therefore, the high-pressure gas fuel injected from the high-pressure gas fuel injection valve 5 after the pilot injection becomes the remainder obtained by subtracting the amount of the pre-injected gas fuel from the amount of gas fuel necessary for combustion, and the remainder is the pilot. After fuel injection, it is injected into the cylinder 1 at a high pressure of (200 to 300) bar, for example.

  At this time, the engine controller 16 opens the electromagnetic hydraulic on-off valve 14 of FIG. 3 during normal operation. When the on-off valve 14 is opened, the gas fuel on-off valve 12 is opened by hydraulic pressure, and low-pressure gas fuel is supplied to the low-pressure gas fuel injection valve 7.

  The engine controller 16 opens the hydraulic on-off valve 15 shown in FIG. 2 and opens and closes the low-pressure gas fuel injection valve 7 at a predetermined time within the range of, for example, (80 to 120) ° after the bottom dead center at the crank angle. Apply hydraulic pressure. As a result, the low pressure gas fuel injection valve 7 is opened and the low pressure gas fuel is injected into the cylinder 1.

  As shown in FIG. 3, when the injection time has elapsed, the engine controller 16 closes the hydraulic opening / closing valve 15 and closes the opening / closing portion of the low-pressure gas fuel injection valve 7. Thereby, the pre-injection of the gas fuel from the low-pressure gas fuel injection valve 7 ends.

  The gas fuel injected from the low pressure gas fuel injection valve 7 before the pilot fuel injection is ignited and burned by the combustion of the diesel fuel injected by the pilot injection. Thereby, the gas temperature in the cylinder before the high pressure gas fuel injection is increased as compared with the conventional gas injection engine.

For this reason, the heat generation in the initial stage of combustion can be brought close to an ideal one, and the thermal efficiency by the combustion of the high-pressure gas fuel performed thereafter can be improved. Thereby, the thermal efficiency by combustion of the gas fuel of the whole engine improves significantly. In addition, since a part of the gas fuel is injected before the pilot injection and ignited by the pilot injection, the combustion is a so-called lean burn combustion, which can surely reduce the generation of NOx.
Moreover, it is not necessary to inject the gas fuel at a higher pressure in order to improve the thermal efficiency. Furthermore, the amount of the high-pressure gas fuel injected from the high-pressure gas fuel injection valve 5 after the pilot injection is reduced by the pre-injection of the low-pressure gas fuel as compared with the conventional gas injection engine. Therefore, the amount of gas fuel that must be handled as high-pressure gas can be reduced, safety can be improved, and motive energy required to increase the pressure of the gas fuel can be suppressed. As a result, environmental conservation and cost reduction can be achieved.

  In particular, the low-pressure gas fuel injection valve 7 supplies gas fuel into the cylinder 1 at a predetermined time within a range of (80 to 120) ° after the bottom dead center at the crank angle with a low pressure of (5 to 15) bar. Pre-inject. Therefore, the ignition by pilot fuel injection and the subsequent gas temperature increase can be made ideal.

  On the other hand, the engine controller 16 is shown in FIG. 4 as an interlock mechanism so that fuel is not continuously injected from the low-pressure gas fuel injection valve 7 for a certain period of time even when low-pressure gas fuel is present for safety reasons. When the window limiter 17 as shown in FIG. 1 is provided, and for some reason, the gas injection from the low pressure gas fuel injection valve 7 is continued or predicted to continue beyond the window limiter 17, The electromagnetic hydraulic on-off valve 14 is closed, and the gas fuel on-off valve 12 is closed.

  Thereby, the supply of the gas fuel to the low pressure gas fuel injection valve 7 is stopped. At the same time, the supply of hydraulic pressure to the low-pressure gas fuel injection valve 7 is also stopped by closing the on-off valve 14, and the open / close portion of the low-pressure gas fuel injection valve 7 is closed, so that gas injection cannot be performed. This ensures safety when an abnormality occurs.

  Next, the form for implementing 2nd invention of the fuel-injection system of the gas injection engine of this invention is demonstrated in detail with reference to FIG. 5 thru | or FIG. The embodiment of the second invention is a case where the pre-injection is performed at a high pressure from the high-pressure gas fuel injection valve 18 shown in FIG.

  FIG. 5 shows a gas injection engine whose main fuel is a gas fuel such as natural gas. The cylinder 1, the cylinder head 2, the cylinder liner 3, the piston 4, and the exhaust valve 9 are the same as those for carrying out the above-described first invention.

  Before injecting gas fuel into the cylinder head 2 from the high pressure gas fuel injection valve (main gas fuel injection valve, auxiliary gas fuel injection valve) 18 for injecting gas fuel into the cylinder at high pressure, diesel A pilot fuel injection valve 6 for pilot-injecting fuel into the cylinder 1 is provided.

  As shown in FIG. 6, a high-pressure gas fuel supply device (main gas fuel supply device, sub-gas fuel supply device) 20 that supplies high-pressure gas fuel to a high-pressure gas fuel injection valve has the following configuration, for example. It has an interlocking mechanism that can shut off the gas fuel injection by forcibly stopping the supply of the gas fuel to the high-pressure gas fuel injection valve 18 when another abnormality occurs.

  High-pressure gas fuel is supplied to a high-pressure gas fuel injection valve 18 from a gas fuel supply source (not shown) through an accumulator 21 and a hydraulically operated gas fuel on-off valve 22. The hydraulic pressure supplied from the hydraulic pump 23 is supplied to the gas fuel on-off valve 22 via an electromagnetically operated on-off valve 24 to open and close the on-off valve 22.

  At the same time, the hydraulic pressure that has passed through the on-off valve 24 is supplied to the high-pressure gas fuel injection valve 18 via the electromagnetically operated on-off valve 25, and the high-pressure gas fuel injection valve 18 can be opened by the supply of this hydraulic pressure. .

  The opening and closing of the two electromagnetically operated on / off valves 24 and 25 are electrically controlled by an engine controller 26 of a gas injection engine. The interlock mechanism includes an engine controller 26, an electromagnetically operated hydraulic on / off valve 24, and a hydraulically operated gas fuel on / off valve 22.

  Next, the operation of the fuel injection system of the gas injection engine will be described. As shown in FIG. 7, for example, the diesel fuel is pilot-injected into the cylinder 1 from the pilot fuel injection valve 6 in the vicinity of a crank angle of 180 ° at the top dead center. Also, for example, (200 to 300) bar of high-pressure gas fuel is injected into the cylinder 1 from the high-pressure gas fuel injection valve 18 within a certain crank angle range immediately after the end of pilot fuel injection.

  On the other hand, the engine controller 26 supplies gas fuel from the high-pressure gas fuel injection valve 18 at a predetermined time within the range of (120 to 160) ° after bottom dead center at the crank angle, and from the pilot fuel injection valve 6. Before the pilot fuel injection, pre-injection into the cylinder 1 is performed. The pre-injection from the high-pressure gas fuel injection valve 7 is performed at a high pressure of (200 to 300) bar, for example.

  Moreover, the engine controller 16 is 50% or more, for example, 50 to 95% or 50 to 100% in mass ratio of gas fuel necessary for combustion when the load of the gas injection engine is low, for example, when the load is 60% or less. An amount of gas fuel in the range of is pre-injected into the cylinder 1.

  This is because a relatively large amount of gas fuel can be pre-injected at low load because the possibility of knocking due to pre-injection is low in the low load region. Thereby, the ignition by pilot fuel injection and the subsequent gas temperature rise can be made ideal.

  On the other hand, when the gas injection engine has a high load, for example, when the load exceeds 60%, the engine controller 16 has a mass ratio of gas fuel required for combustion of 50% or less, for example, an amount in the range of 10-50%. Gas fuel is pre-injected into the cylinder 1.

  This is because, when a large amount of gas fuel is pre-injected in a high load region, there is a possibility that knocking may occur due to this pre-injection. Because. Thereby, ignition by pilot fuel injection and subsequent gas temperature rise can be made ideal while preventing occurrence of knocking.

  Therefore, the high-pressure gas fuel injected from the high-pressure gas fuel injection valve 5 after the pilot injection becomes the remainder obtained by subtracting the amount of the gas fuel pre-injected from the amount of gas fuel necessary for combustion, and the remainder is the pilot fuel. After the injection, the high pressure gas fuel injection valve 18 is injected into the cylinder 1 at a high pressure of (200 to 300) bar, for example.

  At this time, the engine controller 26 opens the electromagnetic hydraulic on-off valve 24 of FIG. 6 during normal operation. When the on-off valve 24 is opened, the gas fuel on-off valve 22 is opened by hydraulic pressure, and the gas fuel is supplied to the high-pressure gas fuel injection valve 18.

  When the crank angle reaches a predetermined time within the range of (120 to 160) ° after bottom dead center, the engine controller 26 opens the hydraulic on-off valve 25 of FIG. Apply hydraulic pressure. As a result, the high-pressure gas fuel injection valve 18 is opened to inject high-pressure gas fuel into the cylinder 1. As shown in FIG. 7, when the injection time has elapsed, the engine controller 26 closes the hydraulic on-off valve 25 and ends the pre-injection of gas fuel from the high-pressure gas fuel injection valve 18.

  The gas fuel injected from the high-pressure gas fuel injection valve 18 before the pilot fuel injection is ignited and burned by the combustion of the pilot-injected diesel fuel. As a result, the gas temperature in the cylinder before the high-pressure main gas fuel injection is increased as compared with the conventional gas injection engine.

  For this reason, the heat generation in the initial stage of combustion can be brought close to an ideal one, and the thermal efficiency by the combustion of the high-pressure main gas fuel performed thereafter can be improved. Moreover, it is not necessary to inject the gas fuel at a higher pressure in order to improve the thermal efficiency.

  In addition, since a part of the gas fuel is injected before the pilot injection and ignited by the pilot injection, the combustion is a so-called lean burn combustion, which can surely reduce the generation of NOx. As a result, environmental conservation and cost reduction can be achieved.

  In particular, in the fuel injection system of the present gas injection engine, the pre-injection from the high-pressure gas fuel injection valve 18 is performed at a high pressure of (200 to 300) bar and (120 to 160) after the bottom dead center at the crank angle. Performed at a predetermined time within the range of °. Therefore, the ignition by pilot fuel injection and the subsequent increase in gas temperature can be made ideal.

  On the other hand, the engine controller 26 uses a window limiter similar to that shown in FIG. 7 described above as an interlock mechanism so that fuel is not continuously injected from the high-pressure gas fuel injection valve 18 over a certain time when an abnormality occurs for safety reasons. If the gas injection from the high-pressure gas fuel injection valve 18 continues or is predicted to continue beyond the window limiter for some reason, the electromagnetic hydraulic on-off valve 24 is provided. The gas fuel on-off valve 22 is closed by closing the valve.

  Thereby, the supply of the gas fuel to the high-pressure gas fuel injection valve 18 is stopped. Moreover, the supply of hydraulic pressure to the high-pressure gas fuel injection valve 18 is stopped by closing the on-off valve 24, and the opening / closing portion of the high-pressure gas fuel injection valve 18 is closed, so that gas injection cannot be performed. This ensures safety when an abnormality occurs.

  Further, as shown in FIG. 8, the window limiter 27 has a constant continuous time between, for example, pre-injection before pilot fuel injection from the high-pressure gas fuel injection valve 18 and injection of high-pressure gas fuel after pilot fuel injection. It can also be set not to exceed the time.

  The above-described fuel injection system of the gas injection engine is merely an example, and various modifications can be made.

1 Cylinder 2 Cylinder Head 3 Cylinder Liner 4 Piston 5 High Pressure Gas Fuel Injection Valve (Main Gas Fuel Injection Valve)
6 Pilot fuel injection valve 7 Low pressure gas fuel injection valve (sub gas fuel injection valve)
8 High-pressure gas fuel supply device (main gas fuel supply device)
9 Exhaust valve 10 Low-pressure gas fuel supply device (sub-gas fuel supply device)
12 Open / Close Valve 13 Hydraulic Pump 14 Open / Close Valve 15 Open / Close Valve 16 Engine Controller 17 Window Limiter 18 High Pressure Gas Fuel Injection Valve (Main Gas Fuel Injection Valve, Sub Gas Fuel Injection Valve)
20 High-pressure gas fuel supply device (main gas fuel supply device, auxiliary gas fuel supply device)
21 accumulator 22 on-off valve 23 hydraulic pump 24 on-off valve 25 on-off valve 26 engine controller 27 window limiter

Claims (10)

A main gas fuel injection valve (5, 18) disposed in a cylinder head (2) of a gas injection engine using gas fuel as a main fuel and injecting the gas fuel into the cylinder (1) at a high pressure, and the main gas fuel injection A pilot fuel injection valve (6) for pilot-injecting diesel fuel into the cylinder before injection of the gas fuel from the valve, and a main gas fuel supply device (8) for supplying high-pressure gas fuel to the main gas fuel injection valve In the fuel injection system of a gas injection engine equipped with
A sub gas fuel injection valve (7, 18) for injecting the gas fuel into the cylinder of the gas injection engine, and a sub gas fuel supply device (10, 20) for supplying the gas fuel to the sub gas fuel injection valve The auxiliary gas fuel injection valve supplies a part of the gas fuel required for combustion from the auxiliary gas fuel supply device before the diesel fuel is pilot injected from the pilot fuel injection valve. The main gas fuel injection valve supplies the main gas fuel supply with the remainder of the gas fuel required for combustion after the diesel fuel is pilot injected from the pilot fuel injection valve. A fuel injection system for a gas injection engine, wherein the fuel injection system is supplied from an apparatus and is injected into the cylinder at a high pressure. The gas injection engine according to claim 1, wherein the auxiliary gas fuel injection valve (7) is disposed at a side portion of the cylinder (1) and injects the low-pressure gas fuel into the cylinder. Fuel injection system. The fuel of a gas injection engine according to claim 2, wherein the auxiliary gas fuel injection valve (7) pre-injects the gas fuel into the cylinder (1) at a low pressure of (5 to 15) bar. Injection method. The auxiliary gas fuel injection valve (7) pre-injects the gas fuel into the cylinder (1) at a predetermined time within a range of (80 to 120) ° after bottom dead center at a crank angle. A fuel injection system for a gas injection engine according to claim 2 or 3. The auxiliary gas fuel injection valve comprises the main gas fuel injection valve (18) that is disposed in the cylinder head (2) and injects the main gas fuel into the cylinder (1) at a high pressure. The fuel injection system for a gas injection engine according to claim 1, wherein the fuel supply device comprises the main gas fuel supply device (20) for supplying high-pressure gas fuel to the main gas fuel injection valve. 6. The fuel of a gas injection engine according to claim 5, wherein the auxiliary gas fuel injection valve (18) pre-injects the gas fuel into the cylinder (1) at a high pressure of (200 to 300) bar. Injection method. The auxiliary gas fuel injection valve (18) pre-injects the gas fuel into the cylinder (1) at a predetermined time within a range of (120 to 160) ° after bottom dead center at a crank angle. A fuel injection system for a gas injection engine according to claim 5 or 6. The auxiliary gas fuel injection valve (7, 18) pre-injects the gas fuel into the cylinder (1) in an amount of 50% or more by mass ratio of the gas fuel required for combustion when the gas injection engine is under a low load. A fuel injection system for a gas injection engine according to any one of claims 1 to 7. The auxiliary gas fuel injection valve (7, 18) pre-injects the gas fuel into the cylinder (1) in an amount of 50% or less in terms of the mass ratio of the gas fuel required for combustion when the gas injection engine is at a high load. 9. The fuel injection system for a gas injection engine according to claim 1, wherein the fuel injection system is a gas injection engine. The auxiliary gas fuel supply device (10, 20) is an interlock mechanism (12, 14, 16, 22) that prevents the gas fuel from being injected beyond a predetermined time from the auxiliary gas fuel injection valve (7, 18). , 24, 26). A fuel injection system for a gas injection engine according to any one of claims 1 to 9, characterized by comprising:

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