JP4121531B2 - Fuel circulation common rail fuel injection system for large two-cycle diesel engines - Google Patents

Description

  The present invention relates to a fuel circulation common rail fuel injector for a large two-cycle diesel engine, and in particular, operates with heavy oil, and therefore the fuel in the fuel injector components even when the engine is not operating. The present invention relates to a common rail fuel injection device that needs to be kept warm in order to prevent solidification.

  A crosshead type large two-cycle diesel engine is used, for example, for propulsion of a large ship and as a main engine of a power plant. Not only from the overall size, this two-cycle diesel engine is different in structure from the other combustion engines. The use of heavy oil with a two-cycle nature and a viscosity at 50 ° C. of less than 700 cSt makes it a unique engine class.

  Due to the high viscosity of heavy oil, fuel does not flow at room temperature, so it is necessary to keep all the components of the fuel injection device warm during engine operation and engine shutdown. Fuel solidification inside the fuel system must be avoided in all situations. Known common rail fuel injectors for large two-cycle diesel engines include a heating service tank that combines a preheater with a supply line to the engine. The continuous flow of fuel during engine operation keeps the fuel injector components warm without the need for external heating. Another reason for keeping the fuel injector components warm while the engine is stopped is, for example, the sensitivity of the high precision components of the fuel valve to thermal shock. As described above, the fuel injection component that is kept warm while the engine is stopped can be manufactured with a minimum clearance, and thus operates more accurately.

While the engine is stopped, heavy oil circulates most of the fuel injector to keep the various parts of the fuel injector warm and degassed. However, particularly in the common rail type fuel injection device, it is difficult and often complicated to provide a circulation path for all components of the fuel injection device. Therefore, some components of the fuel injection device are kept warm by a fuel heater, a steam heater, or an electric heater element, such as an injection valve of a well-known common rail fuel injection device (EP99903) for a large two-cycle diesel engine. Yes. However, steam heaters and electric heaters add to the complexity of the equipment, and heaters or electric heaters need to be removed prior to overhaul and reinstalled after overhaul. Increase complexity. Furthermore, when external heating is used to keep the fuel valve warm while the engine is stopped, there is no degassing effect of the fuel circulation. Further, it has been proved difficult to maintain the high pressure of the fuel common rail while the engine is stopped in order to maintain the engine standby state while allowing the fuel to circulate through the injection valve. (A large two-cycle diesel engine has a prerequisite that it can maintain a standby state for at least 7 hours.)
European Patent Publication No. EP995903

  Against this background, an object of the present invention is to provide a large two-cycle diesel engine operating with heavy oil that overcomes or at least reduces the aforementioned problems. This object is achieved according to claim 1 by providing a crosshead type large two-cycle multi-cylinder diesel engine equipped with a fuel injection device operable with heavy oil. A low pressure pipe connected to the source, an intermediate pressure pipe connected to the intermediate pressure source, a high pressure fuel common rail connected to the high pressure fuel source, at least one fuel injection valve per cylinder, and from the common rail to the fuel injection valve A plurality of control valves for controlling the flow of fuel, and an injection pipe connecting the control valve to an intake port of the fuel injection valve, the control valve for applying pressure to the injection pipe at the start of fuel injection To the common rail, the injection pipe is connected to the low pressure pipe or the intermediate pressure pipe to lower the pressure of the injection pipe at the end of fuel injection, and the fuel valve is connected to the low pressure pipe. A connection has been outlet, for circulating the heavy fuel oil when the engine is not in operation, and a valve means for connecting said in pressure pipe to the injection pipe.

  By providing valve means for connecting the injection pipe to the intermediate pressure pipe when the engine is not operating, it is possible to provide heavy oil circulation to the injection valve while maintaining the common rail pressure. In this way, the engine can be put on standby while the injection valve can be kept warm without requiring a heater or electric heater means. Therefore, it is possible to maintain the ease of assembly and maintenance of the engine (it is not necessary to remove the heater for the purpose of overhauling), and it is easy to maintain the standby state.

  The control valve preferably connects the injection pipe to a branch pipe of the intermediate pressure pipe to lower the pressure of the injection pipe at the end of fuel injection, and further connects the intermediate pressure pipe to the injection pipe. It is preferable that the valve means includes two check valves arranged opposite to each other and arranged in each of the branch pipes of the intermediate pressure pipe connected to the control valve.

  The branch of the intermediate pressure pipe connected to the control valve may include a branch portion having two parallel pipes, and one of the two check valves arranged opposite to each other is one of the two parallel pipes. Placed in. One of the check valves must always apply a back pressure in some way so that the impact of the control valve and the injection valve does not become too strong due to the sudden pressure drop that would occur if there was no pressure control valve. It is necessary to apply. Another check valve serves to prevent high pressure fuel oil from flowing toward the intermediate pressure pipe during fuel injection. In this way, a simple and reliable connection is established between the intermediate pressure pipe and the injection pipe in order to circulate heavy oil while the engine is stopped.

  The control valve preferably connects the injection pipe to the low pressure pipe to lower the pressure of the injection pipe at the end of fuel injection, and further for circulation of heavy oil when the engine is not operating. The injection pipe is connected to the intermediate pressure pipe via a check valve that allows flow from the intermediate pressure pipe to the injection pipe but does not allow flow from the injection pipe to the intermediate pressure pipe. Is preferred. This variant of the invention also provides a simple and reliable connection between the intermediate pressure tube and the injection tube when the engine is stopped.

  The control valve may connect the injection pipe to the low pressure pipe to lower the pressure of the injection pipe at the end of fuel injection, and the medium for circulation of heavy oil when the engine is not operating. The injection pipe may be connected to the intermediate pressure pipe via an electronic control valve that establishes a connection between the pressure pipe and the injection pipe. This variant of the invention also provides a simple and reliable connection between the intermediate pressure tube and the injection tube when the engine is stopped.

  The control valve preferably connects the injection pipe to the low-pressure pipe to lower the pressure of the injection pipe at the end of fuel injection, and the branch of the low-pressure pipe connected to the control valve connects to the control valve Includes a spring check valve or other pressure control valve that keeps the pressure in the branch section of the low pressure pipe above the pressure in the low pressure pipe, and for the circulation of heavy oil when the engine is not operating Preferably, a control valve connects the intermediate pressure pipe to the branch pipe of the low pressure pipe connected to the control valve. This variant of the invention also provides an effective connection between the intermediate pressure tube and the injection tube.

  The fuel valve includes an injection nozzle and valve means for guiding high pressure fluid from the intake of the injection valve to the injection nozzle and for guiding intermediate pressure fluid from the intake of the injection valve to the outlet of the injection valve And may be included. Thus, medium pressure fuel oil is directed in the low pressure tube direction during heavy oil circulation while high pressure fuel oil is directed in the nozzle direction during fuel injection.

  The control valve may be of a type controlled by a solenoid valve.

  Further objects, functions, advantages and features of the large two-cycle diesel engine according to the present invention will become apparent from the detailed description.

Detailed Description of the Preferred Embodiment

  In the following detailed part of the description, the invention will be described in more detail with reference to the embodiments shown in the drawings.

  1 and 2 are a sectional view and a longitudinal sectional view (one cylinder), respectively, of an engine 1 according to a preferred embodiment of the present invention. The engine 1 is a crosshead type single-flow low-speed two-cycle crosshead diesel engine, which may be a propulsion system in a main engine of a ship or a power plant. These engines typically have 3 to 14 cylinders in a row. The engine 1 is assembled from the main bearing of the crankshaft 3 and the base plate 2.

  The crankshaft 3 is a semi-assembled type. Semi-assembled types are made from forged steel or cast steel connections connected at the spindle neck by shrink-fit connections.

  The base plate 2 can be created as a single body or can be divided into parts of an appropriate size according to the production facility. The base plate consists of a welded cross girder with side walls and bearing supports. The cross girder is also technically called “side down”. The oil receiver 58 is welded to the bottom of the base plate 2 to recover the oil returning from the forced lubrication cooling oil device.

  The connecting rod 8 connects the crankshaft 3 to the crosshead bearing 22. The crosshead bearing 22 is guided between the guide surfaces 23 in the vertical direction.

  The frame box 4 whose welding design is in the shape of A is attached to the base plate 2. The frame box 4 is a welded design. On the exhaust side of the frame box 4, there are safety valves for each cylinder, but on the camshaft side of the frame box 4, each cylinder has a large hinge mounting door. The crosshead guide surface 23 is incorporated in the frame box 4.

  The cylinder frame 5 is mounted on the frame box 4. The stay bolt 29 connects the base plate 2, the frame box 4, and the cylinder frame 5 to maintain the structure. The stay bolt 29 is tightened with a hydraulic jack.

  The cylinder frame 5 is ultimately a cast or welded design of one or more parts with the integrated camshaft frame 25. According to a modification (not shown) of this embodiment, the operation of the exhaust valve is controlled electronically, and there is no camshaft 28 or camshaft frame 25, but instead there is an electronically controlled hydraulic device.

  The cylinder frame 5 is provided with an access cover for cleaning the exhaust space and inspecting the scavenging port and the piston ring from the camshaft side. An exhaust space is formed together with the cylinder liner 6. The exhaust receiver 9 is fixed to the opening side of the cylinder frame 5. There is a piston rod stuffing box at the bottom of the cylinder frame, which is equipped with a sealing ring for exhaust and an oil-based scraper ring that prevents discharge from entering the space of the frame box 4 and the base plate 2. So in this way you will protect all the bearings in this space.

  The piston 13 includes a piston crown and a piston skirt. The piston crown is made of heat-resistant steel, and there are four ring grooves with hard chrome plating on both the upper and lower surfaces of the groove.

  The piston rod 14 is connected to the crosshead 22 with four screws. The piston rod 14 has two coaxial holes (not shown in the drawing), and together with the cooling oil pipe, forms an intake port and a discharge port for the cooling oil of the piston 13.

  The cylinder liner 6 is supported by the cylinder frame 5. The cylinder liner 6 is made of alloy cast iron and is suspended on the cylinder frame 5 by a flange located below. The uppermost part of the liner is surrounded by a cast iron cooling jacket. The cylinder liner 6 has a drill hole (not shown) for cylinder lubrication.

  The cylinder is a single-flow type, and has an exhaust port 7 in the air box. Exhaust gas pressurized by a turbocharger 10 (FIG. 1) is sent from an exhaust receiver 9 (FIG. 1).

  The engine includes one or more turbochargers 10 arranged on the rear side of a 4-9 cylinder engine and on the exhaust side of 10 or more cylinder engines.

  The air intake to the turbocharger 10 is made directly from the engine compartment through a turbocharger intake silencer (not shown). From the turbocharger 10, air is guided to the exhaust port 7 of the cylinder liner 6 through an intake pipe (not shown), an air cooler (not shown), and an exhaust receiver 9. The engine is provided with an electrically driven exhaust blower (not shown). The intake side of the blower is connected to the exhaust space after the air cooler. A check valve (not shown) is built in between the air cooler and the exhaust receiver, and automatically closes when the auxiliary blower enters air. The auxiliary blower helps the turbocharger compressor at low and medium load conditions.

  The fuel valve 50 is coaxially attached to the cylinder cover 12. At the end of the compression stroke, the injection valve 50 injects liquid from the injection nozzle into the combustion chamber 15 at a high pressure as a fine mist. The exhaust valve 11 is attached to the center of the cylinder cover 12 on the cylinder. At the end of the explosion stroke, the exhaust valve 11 opens before the engine piston 13 passes through the exhaust port 7 and passes through an exhaust path 16 where the combustion gas in the combustion chamber 15 above the piston 13 is open to the exhaust receiver 17. In order to flow out, the pressure in the combustion chamber 15 is released. The exhaust valve 11 is closed again while the piston 13 moves upward. The exhaust valve 11 is hydraulically operated.

  FIG. 3 displays a first embodiment of a fuel injection device according to the present invention. FIG. 3 shows only two engine cylinders to simplify the drawing for illustration / example purposes. However, it is understood that the engine 1 has more than two cylinders. The fuel injection device includes a heavy oil service tank 27 in which heavy oil is stored at a high temperature. Heavy oil is pumped at a low pressure (preferably between about 2 and 10 bar) by a low pressure feed pump 30 to a low pressure line 32 (for redundancy purposes, there will always be at least two feed pumps, but for simplicity) Only one of them is shown in the drawing). The low pressure pipe 32 includes a plurality of branch pipes 33 connected to the take-out port of the fuel valve 50. The low pressure supply pump 30 replenishes fuel according to the amount consumed by the engine 1.

  The low pressure pipe 32 includes 34 branches connected to the intake of the circulation pump 36 (for redundancy purposes, there are always at least two circulation pumps, but for simplicity only one of them is shown in the drawing. Is displayed). The circulation pump 36 pumps heavy oil into the intermediate pressure pipe 38 at a low pressure to maintain the pressure difference between the low pressure pipe and the intermediate pressure pipe at approximately 2 to 10 bar, but the pressure in the intermediate pressure pipe is in the range of 6 to 16 bar. It is preferable. The medium pressure pipe 38 branches into the intake of the high pressure fuel pump 40 (for redundancy purposes, there are always at least two high pressure fuel pumps, but for simplicity only one of them is shown in the drawing. In addition, there is usually an electrically driven high-pressure start pump that is not shown but is used to apply pressure to the common rail at the start of the engine).

  The high pressure fuel pump 40 feeds heavy oil into the fuel common rail 42 at a high pressure. The pressure in the fuel common rail may vary, but the pressure in the fuel common rail 42 is preferably maintained between 600 and 1200 bar. The feed pipe 44 branches from the common rail 42 to each of the cylinders. The control valve 46 connects each of the feed pipes 44 to the injection pipe 48. Each injection tube 48 connects to the intake of two fuel valves 50 associated with each cylinder (or only one or more than three fuel valves 50 can be associated with each cylinder. is there).

  Control valve 46 (which may be a proportional valve) is electronically controlled and receives a control signal from a non-displayed electronic control device via line 56. The control valve 46 has a first part that connects the feed pipe 44 to the injection pipe 48 and a second part that connects the injection pipe 48 to the intermediate pressure pipe 38 via a branch pipe 39 of the intermediate pressure pipe 38. The control unit commands the control valve 46 to take the first part when the fuel injection of the cylinder in question has to start, and the control unit is when the fuel injection of the cylinder in question has to end The control valve 46 is commanded to carry the second part. The controller receives signals from a tachometer (not shown) to determine the start and end times of various cylinder fuel injections.

  The spring check valve 58 prevents the pressure release of the injection pipe 48 at the end of fuel injection from being so rapid that the fuel valve 50 and the control valve 46 are not damaged by a strong inertial forward force. Typically, the spring check valve 58 maintains a back pressure of approximately 100 bar. It is also possible to use a pressure control valve (not shown) instead of the spring check valve.

  Since the branch pipe 39 of the intermediate pressure pipe 38 is branched, it is composed of two parallel pipe portions 61 and 62. The aforementioned check valve 58 is disposed in the contact portion 61 to allow the flow of the intermediate pressure tube 38 from the control valve 46, while another check valve 59 is disposed in the tube portion 62 to allow heavy oil when the engine is stopped. Allows the liquid to flow from the intermediate pressure tube 38 toward the check valve 46.

  While the engine is stopped, the pressure on the common rail 42 can be kept when the engine needs to be standby. If the engine standby is unnecessary, the common rail 42 controls the open valve 67 in the control of the open valve 66 that can open and close the connection formed between the common rail 42 and the low pressure pipe 32 according to a command from the control device. The pressure can be reduced. When the engine is stopped, the circulation pump 36 maintains the pressure in the medium pressure pipe approximately 4 bar higher than the pressure maintained by the supply pump 30 in the low pressure pipe 32. In this case, the control valve 46 is maintained in the second position to connect the intermediate pressure pipe 38 to the injection pipe 48.

  Fuel valve 50 includes a pressure-sensitive internal valve member (not shown) that connects the intake of fuel valve 50 to the outlet of the fuel valve when low pressure or medium pressure fluid is supplied to the intake of the fuel valve. The pressure-sensitive internal valve member connects the intake port of the fuel valve 50 to the injection nozzle of the fuel valve when high pressure fluid is supplied to the intake port of the fuel valve. The outlet of the fuel valve 50 is connected to the branch pipe 33 of the low pressure pipe 32. In this way, the medium-pressure heavy oil supplied by the intermediate pressure pipe 38 via the check valve 59, the control valve 46, and the injection pipe 48 can flow through the injection valve 50, and the injection valve 50 is connected to the injection valve outlet. Therefore, the fuel valve 50 can be kept warm and kept deaerated.

  In a preferred embodiment with a steam heater and insulation, there is a circulation loop formed by the medium pressure tube 38 and the low pressure tube 32.

  The bypass / back pressure valve 69 maintains a pressure difference between the intermediate pressure pipe 38 and the low pressure pipe 32.

  FIG. 4 shows a second embodiment of the present invention. (For practical reasons, only one cylinder is shown, but it is understood that this embodiment is applicable to engines with more than one cylinder.) In this embodiment, the control valve 46 is Controlled by a solenoid valve 70 commanded by the controller via command line 56. The position of the control valve 46 is determined by the hydraulic cylinder 72. The first pressure chamber 75 of the cylinder 72 with a slightly smaller effective piston portion allows the control valve 46 to be connected to the second pipe 44 of the common rail 42 via the connection of the piston and piston rod. Prompt to position. The second pressure chamber 77 of the cylinder 72 with a slightly larger effective piston portion urges the control valve 46 to the first position where the injection tube 48 is connected to the branch tube 39 of the intermediate pressure tube 38. The common rail branch pipe 44 is connected to the first pressure chamber 75 and the second pressure chamber 77 through a restriction 79. The branch pipe 44 is connected to the low-pressure pipe 32 via a limit 79, a limit 82, and a solenoid valve 70. The connection between the branch pipe 44 and the low pressure pipe 32 is only open when the solenoid valve 70 is in the open position. When the solenoid valve 70 is opened by a command from the controller, heavy oil begins to flow from the branch pipe 44 to the low pressure pipe 32 via the two restrictions 79 and 82 and the solenoid valve 70. Due to the flow through the restriction 79, the pressure is reduced, and the pressure in the pressure chamber 77 is slightly lower than the pressure in the pressure chamber 75. In this way, the cylinder 72 urges the control valve 46 to the first position where the branch pipe 44 is connected to the injection pipe 48, and fuel injection starts. As soon as the solenoid valve 70 is closed by a command from the control device, the pressure drop across the limit 79 disappears, so the slightly larger piston portion of the pressure chamber 77 causes the cylinder 72 to urge the control valve 46 to the second position, Thereby, the injection pipe 48 is connected to the branch pipe 39 of the intermediate pressure pipe 38.

  Since the control valve 46 is also in the second position while the engine is stopped, medium-pressure heavy oil can flow to the intake port of the fuel valve 50 via the check valve 59 and the control valve 46 and the injection pipe 48. it can. The heavy oil leaves the fuel valve 50 through the fuel valve outlet connected to the branch pipe 33 of the low-pressure pipe 32.

  FIG. 5 shows a third preferred embodiment of the present invention (only one cylinder is shown for practical reasons, but it is understood that this embodiment is applicable to engines with more than two cylinders. However, this example is similar to the embodiment shown in FIG. However, the injection pipe 48 is connected to the branch pipe 33 of the low pressure pipe 32 when the control valve 46 is in the second position. In this embodiment, a spring check valve 58 is arranged in the branch pipe 33 of the low-pressure pipe 32 in order to avoid damage due to pressure on the fuel valve 50 and the control valve 46. Between the control valve 46 and the check valve 58, the branch pipe 39 of the intermediate pressure pipe 38 is connected to the branch pipe of the low pressure pipe 33. An electronically controlled circulation valve 81 (single, the circulation valve can be used in all cylinders) is arranged in the branch 39. Circulation valve 81 is moved to its open position by a command from the control device when the engine is not operating, and is moved to its closed position by a command from the control device when the engine is operating.

  When the circulation valve 81 is in the open position, the medium pressure heavy oil can flow through the control valve 46 and the injection pipe 48 to the intake port of the fuel injection valve 50. Then, the injection pipe goes out to the branch pipe 33 of the low-pressure pipe 32.

  FIG. 6 shows a fourth preferred embodiment of the present invention (for practical reasons only one cylinder is shown, but this embodiment can be applied to an engine with more than two cylinders. Although understood, this example is similar to the embodiment shown in FIG. However, the branch pipe 39 of the intermediate pressure pipe 38 is not branched and includes only the spring check valve 58. Instead, the injection pipe 48 branches to the intermediate pressure pipe 38 via the pipe 41 without passing through the check valve 46. The check valve 59 is disposed in the pipe 41 in order to prevent the high-pressure fuel from flowing back into the pipe 41 and the intermediate pressure pipe 38. On the other hand, when the engine is stopped, medium-pressure heavy oil can flow from the intermediate-pressure pipe 38 to the intake pipe 48 and the intake valve 50 via the pipe 41 and the check valve 58. The heavy oil leaves the fuel valve 50 via the intake port of the fuel valve 50 connected to the branch pipe 33 of the low-pressure pipe 32.

  FIG. 7 shows a fifth preferred embodiment of the present invention (for practical reasons, only one cylinder is shown, but it is understood that this embodiment is applicable to engines with more than two cylinders. But this example is similar to the embodiment shown in FIG. However, the control valve 46 connects to the injection pipe 48 in the second position and to the pipe 33 'where the spring check valve 58 is located. The pipe 33 ′ branches to the intermediate pressure pipe 38 via the check valve 59. When the control valve 46 is in the second position during engine operation, the pressure in the injection tube 48 is released via the tube 33 'and the spring check valve 58 in the control method. When the engine 1 is not operating, medium pressure fuel oil is removed from the intermediate pressure pipe 38 through the check valve 59, the branch pipe 33 ', the control valve 46, the injection pipe 48, the fuel valve intake, the fuel valve 50, and the fuel valve Via the mouth, it can flow to the branch 33 of the low-pressure pipe 32 in order to circulate heavy oil through the fuel valve 50.

  The term “comprising” as used in the claims does not exclude other elements. As used in the claims, the term “a” does not exclude a plurality.

  Any reference signs used in the claims shall not be construed as limiting the scope.

  Although the present invention has been described in detail for purposes of illustration, it is understood that such details are for this purpose only and can be modified by one skilled in the art without departing from the scope of the invention.

1 is a cross-sectional view of an engine according to the present invention. FIG. 2 is a longitudinal sectional view of one cylinder portion of the engine displayed in FIG. 1. 1 is a symbolic representation of a first embodiment of an engine according to the invention. FIG. FIG. 3 is a symbolic representation of a second embodiment of an engine according to the invention. FIG. 6 is a diagram symbolically representing a third embodiment of the engine according to the invention. FIG. 6 is a symbolic representation of a fourth embodiment of an engine according to the present invention. FIG. 7 is a diagram symbolically showing a fifth embodiment of the engine according to the present invention.

Claims (8)

A crosshead type large two-cycle multi-cylinder diesel engine equipped with a fuel injection device operable by heavy oil, wherein the fuel injection device comprises:
A low pressure pipe connected to a low pressure source;
A medium pressure tube connected to a medium pressure source;
A high-pressure fuel common rail connected to a high-pressure fuel source;
At least one fuel injection valve per cylinder;
A plurality of control valves for controlling the flow from the common rail to the fuel injection valve;
An injection pipe connecting the control valve to the intake of the injection valve;
With
The control valve connects the injection pipe to the common rail to apply pressure to the injection pipe at the start of fuel injection, and controls the injection pipe to lower the pressure of the injection pipe at the end of fuel injection. Connected to the low pressure pipe or the medium pressure pipe,
The fuel valve comprises an outlet connected to the low pressure pipe, and valve means for connecting the intermediate pressure pipe to the injection pipe for circulation of heavy oil when the engine is not operating.   The control valve connects the injection pipe to a branch pipe of the intermediate pressure pipe to lower the pressure of the injection pipe at the end of fuel injection, and the valve means for connecting the intermediate pressure pipe to the injection pipe comprises: The engine according to claim 1, comprising two check valves arranged opposite to each other, which are arranged in each of the branch pipes of the intermediate pressure pipe connected to the control valve.   The branch pipe of the intermediate pressure pipe connected to the control valve includes a branch portion including two parallel pipes, and one of the two check valves arranged opposite to each other is one of the two parallel pipes. The engine according to claim 2, wherein The control valve connects the injection pipe to the low pressure pipe to reduce the pressure of the injection pipe at the end of fuel injection,
In order to circulate heavy oil when the engine is not in operation, the injection via a check valve that allows flow from the intermediate pressure tube to the injection tube but not from the injection tube to the intermediate pressure tube The engine of claim 1, wherein a tube is connected to the intermediate pressure tube. The control valve connects the injection pipe to the low pressure pipe to reduce the pressure of the injection pipe at the end of fuel injection,
The injection pipe is connected to the intermediate pressure pipe via an electronic control valve that establishes a connection between the intermediate pressure pipe and the injection pipe for circulating heavy oil when the engine is not operating. Item 4. The engine according to Item 1. The control valve connects the injection pipe to the low pressure pipe to reduce the pressure of the injection pipe at the end of fuel injection,
A branch pipe of the low pressure pipe connected to the control valve includes a spring check valve or other pressure control valve that keeps the pressure of the branch pipe portion of the low pressure pipe connected to the control valve to exceed the pressure of the low pressure pipe; 6. The engine of claim 5, wherein the electronic control valve connects the intermediate pressure pipe to the branch of the low pressure pipe connected to the control valve for heavy oil circulation when the engine is not operating.   The fuel valve includes an injection nozzle and a valve for guiding high-pressure fluid from the intake port of the injection valve to the injection nozzle, and for guiding intermediate pressure fluid from the intake port of the injection valve to the ejection port of the injection valve. The engine of claim 1 including means. The engine of claim 1, wherein the control valve is controlled by a solenoid valve.

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