JP2009162104A - Marine 4-stoke diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a temperature rise of exhaust gas or a temperature rise in a combustion chamber while decreasing NOx. <P>SOLUTION: A suction valve 10 and an exhaust valve 12 in combustion chambers 5 of a plurality of cylinders 2 are controlled by an electronic control system 26. When the other cylinder is in an exhaust stroke and a piston descends in an intake stroke, the exhaust valve 12 of the cylinder 2 is controlled to open the electronic control system 26, and exhaust gas is led from an exhaust manifold 42 into the combustion chamber 5. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a marine four-stroke diesel engine, and mainly relates to an engine that reduces nitrogen oxide (NOx) emissions.

  From the viewpoint of protecting the global environment, regulations on NOx emissions have been implemented in order to prevent air pollution caused by NOx discharged from marine diesel engines. There is EGR as a technique for reducing NOx discharged from a diesel engine. In EGR, a part of the exhaust gas discharged from the combustion chamber of the diesel engine is branched from the exhaust pipe, and after the temperature is lowered by a cooler, it is led to the intake pipe and taken into the combustion chamber. There is a technique disclosed in Patent Document 1 as a technique to which this EGR is applied.

  In the technique of Patent Document 1, in a marine three-cylinder four-stroke diesel engine, the exhaust valve of the first cylinder is opened, and the exhaust from the first cylinder to the exhaust manifold is already performed. Exhaust gas is allowed to flow back from the exhaust manifold to the combustion chamber of the third cylinder so that the exhaust valve of the three cylinders does not close and then the intake valve of the third cylinder is opened. These intake valves and exhaust valves are opened and closed by cams.

  Generally, the intake pressure when the intake valve is opened is higher than the exhaust pressure on the already opened exhaust valve side. If the exhaust valve is opened when the intake valve of the third cylinder is opened, the intake pressure is higher than the exhaust pressure, so that the exhaust gas does not flow back through the exhaust valve into the combustion chamber. Therefore, in the technique of Patent Document 1, the timing of opening the intake valve of the third cylinder is delayed to cause the exhaust gas to flow back into the combustion chamber.

JP 2005-83326 A

  However, in the technique of Patent Document 1, since the opening timing of the intake valve is delayed, the overlap period between the period in which the exhaust gas is supplied and the period in which new air is supplied is short, and the amount of blown-through air is reduced. There is concern about an increase in exhaust gas temperature and an increase in the temperature of members in the combustion chamber. Therefore, there is a fear that the life of the supercharger that is driven by the exhaust gas and sends new air to the intake manifold is shortened, or the life of the combustion chamber is shortened. In addition, since the intake and exhaust valves are opened and closed by cams, the opening and closing timings of the intake and exhaust valves are always constant, and the opening and closing timing can be optimized in a wide range from low load to high load. Can not.

  The present invention can reduce NOx, prevent an exhaust gas temperature rise and a combustion chamber temperature rise, and open an exhaust valve at an optimum timing to widen a low load to a high load. An object is to provide a marine four-stroke diesel engine that can be optimized within a range.

  A marine four-stroke diesel engine according to an aspect of the present invention has a cylinder in which an intake valve and an exhaust valve are provided in a combustion chamber, and an electronic control system controls a drive unit that drives the intake valve and the exhaust valve. Is. A piston is provided in the cylinder. Fuel injection means is also provided. The electronic control system is configured to open the exhaust valve when the pressure in the combustion chamber is reduced during the intake stroke in which the intake valve is opened, for example, while the piston is being lowered. And exhaust gas is introduced into the combustion chamber.

  In the marine four-stroke diesel engine configured as described above, the pressure in the combustion chamber decreases while the piston is lowered, for example, while the intake valve is opened and new air is introduced into the combustion chamber. During the operation, the exhaust gas is introduced into the combustion chamber by opening the exhaust valve. This can reduce nitrogen oxides. Since the exhaust valve is thus opened when the pressure is reduced during the intake stroke, the intake valve can be opened while the exhaust valve is open during the exhaust stroke. That is, there is no need to delay the opening timing of the intake valve as in Patent Document 1 described above, the overlap time during which both the exhaust valve and the intake valve are open can be increased, and the amount of blown air is increased. The temperature of the exhaust gas and the temperature of the members in the combustion chamber can be prevented, the life of the combustion chamber can be extended, and even if a supercharger is provided, the life can be extended. it can.

  A plurality of the cylinders described above can be provided. In this case, the exhaust valve of each cylinder is connected via an exhaust manifold, and each intake valve is also connected via an intake manifold. The four strokes in each cylinder are set in different phases, and when each cylinder is in the intake stroke, any other cylinder is in the exhaust stroke.

  With this configuration, when a certain cylinder is in the intake stroke, the exhaust valve of the cylinder is opened to supply exhaust gas from other cylinders in the exhaust stroke to the combustion chamber of the cylinder via the exhaust manifold. be able to.

  The electronic control system can also control the exhaust valve driving means in accordance with the operating conditions of the diesel engine during the intake stroke. The operating status includes, for example, the rotational speed and output of a diesel engine.

  If comprised in this way, exhaust gas can be supplied to the cylinder in an intake stroke at the optimal timing and period according to the condition of load.

  As described above, according to the present invention, it is possible to reduce nitrogen oxides and to prevent a rise in exhaust gas temperature and a temperature rise in the combustion chamber. Optimization is possible over a wide range from low load to high load.

  A marine four-stroke diesel engine according to an embodiment of the present invention has a cylinder 2 as shown in FIG. The piston 4 is disposed in the cylinder 2 and can slide in the cylinder 2 along its length direction. The inside of the cylinder 2 on the upper side of the piston 4 is a combustion chamber 5. The piston 4 is connected to the crank via a connecting rod, but is not shown. An intake valve seat 6 and an exhaust valve seat 8 are formed in the combustion chamber 5. An intake valve 10 for opening and closing the intake valve seat 6 is provided, and an exhaust valve 12 for opening and closing the exhaust valve seat 8 is provided.

  The intake valve seat 6 is connected to a compressor 20 of a supercharger 18 via an intake pipe 14 and an air cooler 16. The exhaust valve seat 8 is connected to the turbine 24 of the supercharger 18 via the exhaust pipe 22. A turbine 24 drives the compressor 20.

  The intake valve 10 and the exhaust valve 12 are controlled by an electronic control system 26. As shown in FIG. 2, the electronic control system 26 includes a controller 28 including a control unit such as a CPU and a storage unit such as a memory. The controller 28 includes an intake valve driving device 30 and an exhaust valve driving device 32. By controlling, the intake valve 10 and the exhaust valve 12 are opened away from the valve seats 6 and 8 or are seated on the valve seats 6 and 8 and closed. Although not shown in FIG. 1, a fuel injection device 34 that injects fuel into the combustion chamber 5 is also provided and is controlled by the controller 28. The fuel injection device 34 is supplied with fuel from a fuel injection pump.

  In order to perform control, the controller 28 detects the angle of the crank, outputs the crank angle to the controller 28, detects the rotational speed of the diesel engine, and supplies the rotational speed to the controller 28. An output rotational speed detection unit 38 is provided. Further, the controller 28 determines the position of the piston 4 from the crank angle. Further, a scale sensor for detecting the scale of the rack of the fuel injection pump is provided, and the controller 28 calculates the output of the diesel engine from the output of this scale sensor and the output of the number detection unit 38.

  A plurality of, for example, three sets including the cylinder 2, the piston 4, the intake valve 10, the exhaust valve 12 and the like shown in FIG. 1 are provided. The intake valve seat 6 is connected to each other by an intake manifold 40, and an exhaust valve seat 8 is provided. Are connected to each other by an exhaust manifold 42. The electronic control system 26 can be provided for each cylinder 2 or only one unit can be provided for each cylinder 2 in common.

  This marine 4-stroke diesel engine operates, for example, as shown in FIG. In the following description, the three cylinders 2 included in the diesel engine are referred to as cylinders 2a, 2b, and 2c.

  For example, it is assumed that the piston 4 is at the bottom dead center in the cylinder 2 a and new air is supplied into the combustion chamber 5. From this state, the piston rises toward the top dead center and compresses the air in the combustion chamber 5 (compression stroke).

  From just before reaching the top dead center until after reaching the top dead center, the controller 28 causes the fuel injection device 34 to inject fuel into the combustion chamber 5 to cause an explosion of the fuel (explosion stroke). As a result, the piston 4 descends toward the bottom dead center.

  The controller 28 controls the exhaust valve drive device 32 so that the exhaust valve 12 is opened at a timing when the crank angle with respect to the bottom dead center is 60 degrees before reaching the bottom dead center. While the piston 4 moves from the bottom dead center toward the top dead center, exhaust is performed from the combustion chamber (exhaust stroke). The exhaust valve 12 is opened until the piston 4 reaches the top dead center and the crank makes an angle of 30 degrees with respect to the top dead center, and the controller 28 exhausts at the timing of making the angle of 30 degrees. The valve drive device 32 closes the exhaust valve 12.

  On the other hand, before the piston 4 reaches the top dead center, the controller 28 causes the intake valve driving device 30 to open the intake valve 10 at a timing when the crank makes an angle of 55 degrees with respect to the top dead center. The state in which the intake valve 10 is opened continues while the piston 4 reaches the top dead center and descends toward the bottom dead center, and further reaches the bottom dead center and then moves toward the top dead center. The intake valve 10 is opened until it moves and the crank makes an angle of 40 degrees with respect to the bottom dead center. During this time, new air is supplied into the combustion chamber 5 (intake stroke). The intake valve 10 is closed at a timing that forms an angle of 40 degrees. Hereinafter, similarly, the cylinder 2a repeats the operation.

  The cylinders 2b and 2c operate in the same manner, but the cylinder 2b operates with a crank angle delayed by 240 degrees with respect to the cylinder 2a, and the cylinder 2c operates with a crank angle advanced by 240 degrees with respect to the cylinder 2a. ing.

  In any of the cylinders 2a, 2b, and 2c, during the intake stroke, the controller 28 opens the exhaust valve 12 for a predetermined period, for example, 30 degrees at a crank angle while the piston 4 is descending. When any cylinder is in the intake stroke, the other cylinder is in the exhaust stroke. For example, when the cylinder 2a is in the intake stroke, the cylinder 2b is in the exhaust stroke, when the cylinder 2b is in the intake stroke, the cylinder 2c is in the exhaust stroke, and when the cylinder 2c is in the intake stroke, the cylinder 2a is in the exhaust stroke. is there. Accordingly, in any of the cylinders 2a, 2b, and 2c, when the exhaust valve is opened during the intake stroke, the exhaust gas is supplied through the exhaust manifold 42. When the exhaust valve 12 is opened, since the piston 4 is lowered, the pressure in the combustion chamber 5 is lower than the pressure of the exhaust gas and flows into the combustion chamber 5. Therefore, exhaust gas can be taken into the combustion chamber 5 during the intake stroke, and the amount of nitrogen oxides discharged can be reduced.

  Moreover, since the exhaust valve 12 is opened and the exhaust gas is introduced into the combustion chamber 5 at the timing when the piston 4 is descending in the intake stroke, the crank is raised before the piston 4 reaches the top dead center. The intake valve 10 can be opened from the timing at which the exhaust valve 12 is already opened, which forms an angle of 55 degrees with respect to the dead point. The overlapping state in which the exhaust valve 12 and the intake valve 10 are open continues until the crank is at an angle of 30 degrees with respect to the top dead center and the exhaust valve 12 is closed. As a result, the overlap time becomes longer, the amount of blown air increases, the temperature of the exhaust gas can be lowered, and the temperature rise of the members of the combustion chamber 5 can be prevented. Therefore, the lifetime of the supercharger 18 and the combustion chamber 5 can be extended.

  The angles at which the intake valve 10 and the exhaust valve 12 are opened and closed in the above embodiment are merely examples, and these angles may be changed depending on the engine type.

  In the above example, the opening and closing angles of the intake valve 10 and the exhaust valve 12 have been described as being constant without being changed during the operation of the diesel engine. However, these angles depend on changes in the rotational speed and output of the diesel engine. It can be changed to the optimal one. Therefore, the crank angle detection unit 36, the rotation speed detection unit 38, and the fuel pump rack scale sensor described above are connected to the controller 28, and the controller 28 also determines the output of the diesel engine.

  In the above embodiment, the three-cylinder diesel engine is shown. However, the present invention is not limited to this, and various engines can be used as long as they have a plurality of cylinders.

It is a lineblock diagram of the diesel engine of one embodiment of the present invention. It is a block diagram of the electronic control system of the diesel engine of FIG. FIG. 2 is an intake / exhaust stroke diagram of the diesel engine of FIG. 1.

Explanation of symbols

2 cylinder 4 piston 5 combustion chamber 10 intake valve 12 exhaust valve 26 electronic control system

Claims (3)

In a marine 4-stroke diesel engine comprising a cylinder provided with an intake valve and an exhaust valve in a combustion chamber, and controlling a drive means for driving the intake valve and the exhaust valve with an electronic control system,
The electronic control system controls the driving means to open the exhaust valve during a period when the pressure of the combustion chamber is decreasing during the intake stroke in which the intake valve is open, and exhausts the exhaust into the combustion chamber. Marine 4-stroke diesel engine that introduces gas.   The marine four-stroke diesel engine according to claim 1, wherein a plurality of the cylinders are provided, an intake valve of each cylinder is connected via an intake manifold, an exhaust valve of each cylinder is connected via an exhaust manifold, A marine four-stroke diesel engine in which the phases of the four strokes of the cylinders are different from each other so that any of the other cylinders is in the exhaust stroke when each cylinder is in the intake stroke.   The marine four-stroke diesel engine according to claim 1, wherein the electronic control system controls a driving means of the exhaust valve in accordance with an operation state of the diesel engine during the intake stroke.

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