JP2009144725A - Cam-drive exhaust valve operation system for large-sized two-cycle diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To save energy by flexibly controlling the opening/closing timing of an exhaust valve. <P>SOLUTION: The following cross-head large-sized two-cycle diesel engine is provided as an example. The engine comprises a plurality of cylinders each having at least one exhaust valve 11; at least one camshaft 28 having an exhaust cam 29 for operating the at least one exhaust valve for each cylinder; hydraulic actuators 34 installed in the exhaust valves, respectively, for moving the exhaust valves in the opening direction; hydraulic piston pumps 32 installed in the hydraulic actuators, respectively, and driven by corresponding cams on the camshaft; operating oil pipes 36 connected to the exhaust valves, respectively, for connecting the hydraulic piston pumps to the corresponding hydraulic actuators, respectively; additional gas exchange valves 46 installed in the cylinders, respectively; and an operation system for controlling the opening and closing of the additional gas exchange valves independently of the camshaft. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a cam-driven exhaust valve operating system for an internal combustion engine, and more particularly to a cam-driven hydraulic exhaust valve operating system for a large two-cycle diesel engine.

  A crosshead type large two-cycle diesel engine is used as, for example, a propulsion engine of a large ocean-going ship or a main prime mover of a power plant. These two-cycle diesel engines are not only in size, but different in configuration from other internal combustion engines. It is a unique class in the engine field due to the two-cycle principle and the use of heavy oil with a viscosity of 700 cSt or less at 50 ° C (oil does not flow at room temperature).

  The demand for improved performance and reduced exhaust gas has led to the development of common rail electrohydraulic control exhaust valve actuation systems for these two-cycle diesel engines. The advantage of these systems is that the timing for opening and closing the exhaust valve can be freely selected according to the operating conditions of the engine. However, these common rail electrohydraulic systems are relatively expensive, consume more energy than necessary during the opening process, and are not compensated for during the closing process, which is more than conventional cam drive systems. A lot of energy is consumed. These two drawbacks negate the many advantages of electronically controlled engines.

  Under such circumstances, an object of the present invention is to provide an energy-saving cam-driven exhaust valve system that flexibly controls the opening / closing timing of the exhaust valve.

  The object is a crosshead type large two-cycle diesel engine, each of which operates a plurality of cylinders each having at least one exhaust valve and at least one exhaust valve associated with each of the plurality of cylinders. At least one camshaft comprising a plurality of cams and a hydraulic pushrod corresponding to each of the plurality of cylinders, wherein the hydraulic pushrod is driven by a corresponding cam on the camshaft Each actuator is equipped with a pump for each actuator, a hydraulic actuator for moving the corresponding exhaust valve in the opening direction, and a hydraulic oil pipe for connecting the hydraulic piston pump to the corresponding hydraulic actuator for each exhaust valve, and a corresponding push rod A device for controllably adding or removing hydraulic oil to the Characterized in that it is connected to the respective pressure pushrod is achieved by providing a crosshead type large two-stroke diesel engines.

  By controllably adding hydraulic oil to the hydraulic push rod, the hydraulic valve actuator can be actuated at a desired time. Therefore, the exhaust valve can be opened before the opening time determined by the shape of the cam on the cam shaft by adding the hydraulic oil to the hydraulic oil pipe before the time when the cam operates.

  Further, by adding hydraulic oil during the cam operation period and withdrawing it after the cam operation period, the closing of the exhaust valve can be delayed so that the exhaust valve is closed after the time determined by the shape of the cam.

  The apparatus can include a controllable pressurized hydraulic fluid source connected to each of the hydraulic push rods and a controllable hydraulic fluid outlet connected to each of the hydraulic push rods.

  The apparatus can be configured to add a predetermined amount of hydraulic oil to the hydraulic push rod before or during the operation phase of the cam associated with the corresponding cylinder.

  The apparatus can be configured to draw a predetermined amount of hydraulic oil from the hydraulic push rod during or after operation of the cam associated with the corresponding cylinder.

  The amount added or removed can be varied.

  The apparatus can comprise an electronically controlled hydraulic valve configured to alternately connect hydraulic push rods to a pressurized hydraulic oil source or hydraulic oil outlet.

  The apparatus can further include a capacity limiter between the electronically controlled hydraulic valve and the hydraulic push rod.

  The engine further includes a position sensor operably coupled to the exhaust valve, and the electronically controlled hydraulic valve is controlled in response to a signal from the position sensor.

  The engine can include an elastic member for moving the exhaust valve in the closing direction for each exhaust valve.

  This object is also a cross-head type large two-cycle diesel engine, each of which operates a plurality of cylinders each having at least one exhaust valve and at least one exhaust valve associated with each of the plurality of cylinders. And at least one camshaft comprising a plurality of cams, and a hydraulic piston pump driven by the corresponding cam on the camshaft for each actuator, and a hydraulic actuator for moving the exhaust valve in the opening direction And a hydraulic pipe for connecting the hydraulic piston pump to the corresponding actuator for each exhaust valve, an additional gas exchange valve associated with each cylinder, and an additional gas exchange valve independent of the camshaft Crosshead type large two-cycle diesel engine with an operating system for controlling the opening and closing of the vehicle It is achieved by providing a gin.

  By providing an additional gas exchange valve that can be controlled independently of the camshaft, the additional gas exchange valve is opened before the exhaust valve closes and / or after the exhaust valve is closed. It is possible to control the compression pressure and the blowback from the cylinder while keeping the gas exchange valve open.

  The operating system can electronically control the opening and closing of additional gas exchange valves.

  The additional gas exchange valve can be made relatively small compared to the exhaust valve.

  The additional gas exchange valve can be connected to a cylinder corresponding to the exhaust gas receiver.

  The additional gas exchange valve can be connected to a cylinder corresponding to the scavenging receiver.

  The actuation system can further comprise a hydraulic actuator operably connected to the additional gas exchange valve.

  The actuation system can be configured to control the blowback of the corresponding cylinder and its compression pressure.

  The operating system can be configured as a dedicated system for controlling the compression pressure.

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

In the following detailed part of the description, the invention will be described in more detail with reference to exemplary embodiments shown in the drawings.
1 is a cross-sectional view of an engine according to the present invention. FIG. 2 is a longitudinal sectional view of one cylinder section of the engine shown in FIG. 1. 1 is a symbolic view of a first embodiment of an exhaust valve actuation system according to the present invention. FIG. It is the figure which showed the 2nd embodiment of the exhaust-valve operating system by this invention symbolically. It is the figure which showed the 3rd embodiment of the exhaust-valve operating system by this invention symbolically. It is the figure which showed the 4th embodiment of the exhaust-valve operating system by this invention symbolically.

  1 and 2 show a sectional view and a longitudinal sectional view of an engine 1 according to a preferred embodiment of the present invention (one cylinder), respectively. The engine 1 is a crosshead type single-flow low-speed two-cycle crosshead diesel engine, and can be a marine vessel propulsion system or a main prime mover of a power plant. These engines typically have 4 to 14 cylinders in series. The engine 1 is assembled from a base plate 2 having a main bearing for the crankshaft 3.

  The crankshaft 3 is a semi-assembled type. The semi-assembled mold is formed of forged steel or cast steel throw that is connected to the main journal by shrink fitting.

  The base plate 2 can be formed of a single part or divided into parts of suitable size according to the production facility. The base plate is composed of a side wall and a welded cross beam including a bearing support. The cross beam is also referred to as “crossing beam” in the prior art. The oil receiver 58 is welded to the bottom of the base plate 2 and collects return oil from the forced lubrication and cooling oil system.

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

  A welded design A-shaped frame box 4 is mounted on a base plate 2. The frame box 4 is a welding design. The exhaust side of the frame box 4 is provided with a relief valve for each cylinder, and the camshaft side of the frame box 4 is provided with a large hinged door for each cylinder. The crosshead guide surface 23 is integrated into the frame box 4.

  The cylinder frame 5 is placed on top of the frame box 4. The retaining bolt 27 connects the base plate 2, the frame box 4, and the cylinder frame 5, and uniformly maintains the structure. The reserve bolt 27 is tightened with a hydraulic jack.

  The cylinder frame 5 is cast into one or more parts and is ultimately cast with an integral camshaft housing 25 or is a welded design. According to another embodiment (not shown), the camshaft 28 is housed in a separate camshaft housing attached to the cylinder frame.

  The cylinder frame 5 includes an access cover for purifying the scavenging space and inspecting the scavenging port and the piston ring from the cam shaft side. The cylinder frame 5 forms a scavenging space together with the cylinder liner 6. The scavenging receiver 9 is fixed to the cylinder frame 5 with bolts together with the opening side thereof. There is a piston rod stuffing box at the bottom of the cylinder frame, which is equipped with a seal ring for scavenging and an oil scraper ring to prevent exhaust from entering the space of the frame box 4 and the base plate 2. Protect all bearings present in this space.

  The piston 13 includes a piston crown and a piston skirt. The piston crown is made of heat resistant steel and has four annular grooves with hard chrome plated 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 figure) that form a cooling oil inlet / outlet for the piston 13 in conjunction with the cooling oil pipe.

  The cylinder liner 6 is carried by the cylinder frame 5. The cylinder liner 6 is made of alloy cast iron and is suspended in the cylinder frame 5 by a lower flange. The top of the liner is surrounded by a cooling jacket made of cast iron. The cylinder liner 6 has a drill hole (not shown) for cylinder lubrication.

  The cylinder is a single flow type and has a scavenging port 7 located in the air box. The air box is supplied with scavenging air pressurized by the turbocharger 10 (FIG. 1) from the scavenging receiver 9 (FIG. 1). The

  The engine is fitted with one or more turbochargers 10 arranged on the rear end of the engine for 4 to 9 cylinders and on the exhaust side for engines of 10 or more cylinders.

  Intake into the turbocharger 10 is performed directly from the engine room via an intake silencer (not shown) of the turbocharger. Air is guided from the turbocharger 10 to a scavenging port 7 of the cylinder liner 6 through an air supply pipe (not shown), an air cooler (not shown), and a scavenging receiver 9.

  The engine includes an electric scavenging blower (not shown). The suction side of the blower is connected to the scavenging space behind the air cooler. A check valve (not shown) is installed between the air cooler and the scavenge receiver that automatically closes when the auxiliary blower supplies air. The auxiliary blower assists the turbocharger compressor at low and medium load conditions.

  The fuel valve 40 is placed concentrically within the cylinder cover 12. At the end of the compression stroke, the injection valve 40 injects fine mist fuel at high pressure into the combustion chamber 15 via these injection nozzles. The exhaust valve 11 is placed at the upper center of the cylinder in the cylinder cover 12. At the end of the expansion stroke, the exhaust valve 11 opens before the piston 13 of the engine descends past the scavenging port 7, so that the combustion gas in the combustion chamber 15 above the piston 13 opens to the exhaust receiver 17. It flows out through the flow path 16, and the pressure in the combustion chamber 15 is reduced. The exhaust valve 11 is closed again while the piston 13 moves upward. The exhaust valve 11 is hydraulically operated.

  FIG. 3 shows a first embodiment of an exhaust valve actuation system according to the present invention. The exhaust valve actuation system is for all of the embodiments shown for a single cylinder. In a multi-cylinder engine, the same conditions are applied to each cylinder. The exhaust valve actuation system includes a camshaft 28 with a cam 29 (only one is shown). The roller 30 is connected to the piston of the positive displacement pump 32 and operates according to the cam surface. The positive displacement pump 32 is connected to an exhaust valve actuator 34 via a conduit (hydraulic oil pipe) 36. The exhaust valve actuator 34 acts on the shaft of the exhaust valve 11. The gas spring 38 is also connected to the shaft of the exhaust valve, and the gas pressure in the pressure chamber of the gas spring 38 moves the exhaust valve 11 in the closing direction. When the valve actuator 34 is pressurized, the gas pressure moves the exhaust valve in the opening direction. The position of the exhaust valve is measured by a sensor 39 connected to the engine's electronic control system. During operation, the camshaft 28 rotates with the engine crankshaft in the direction of the arrow above the “TDC” display indicating the top dead center of the corresponding piston. The shape of the cam 29 determines the operation of the positive displacement pump 32. When the positive displacement pump 32 moves upward, hydraulic oil is pressed into the valve actuator 34 via the conduit 36. The actuator 34 opens the exhaust valve 11 against the pressure in the combustion chamber and the gas spring 38. When the positive displacement pump 32 operates in the downward direction, the gas spring 38 moves the exhaust valve and the exhaust valve actuator 34 upward so that the hydraulic oil in the exhaust valve actuator 34 flows back into the positive displacement pump 32. Most of the energy transmitted to the exhaust valve actuator 34 during the opening operation of the exhaust valve 11 is returned to the camshaft 28 by the pressure generated in the positive displacement pump 32 during the return stroke of the exhaust valve actuator 34. Therefore, only a small part of the hydraulic energy required to open the exhaust valve 11 is dissipated. The opening profile defined by the cam 29 is represented by the lower thin curve in the graph 42.

  The exhaust valve system according to this embodiment further includes a 3/2 valve 33 having one port connected to the conduit 36 via a capacity limiter 41. The inlet of the 3/2 valve 33 is connected to a pressurized hydraulic oil source 49, and the outlet of the 3/2 valve 33 is connected to a drain or a tank.

  The 3/2 valve 33 is electronically controlled by an electronic control system. During operation, the 3/2 valve 33 can add and remove hydraulic fluid from the conduit 36 at a desired point in the operating cycle. Graph 42 illustrates the potential for the addition and removal of hydraulic fluid from conduit 36. The upper curve of the graph 42 represents the position of the exhaust valve 11 when a volume of hydraulic fluid is added to the conduit 36. The exhaust valve 11 can be opened earlier than defined by the shape of the cam 29 by adding hydraulic oil to the conduit 36 with the 3/2 valve 33 before the cam 29 begins to operate. The added hydraulic oil can be removed before or after the exhaust valve defined by the cam 29 is closed by changing the position of the 3/2 valve 33. Capacitance limiter 41 prevents the amount added to or removed from conduit 36 from becoming too great. When the added hydraulic oil is removed before the closing time of the exhaust valve 11 defined by the shape of the cam 29, the exhaust valve closes as defined by the cam 29. If the added hydraulic oil is removed after the closing time of the exhaust valve 11 defined by the shape of the cam 29, the exhaust valve will remain open for a longer time. The exhaust valve actuation system according to this embodiment provides the possibility of profiling, that is, changing the timing of opening the exhaust valve 11 and changing the timing of closing the exhaust valve 11. By controlling the 3/2 stage-valve 33, the exhaust valve actuation system according to this embodiment can change between the upper and lower curves of the graph 42 at a desired point in the engine cycle. . The blowback and compression pressure from the cylinder can be adjusted by changing the timing for opening and closing the exhaust valve 11. Algorithms and data for optimal timing / profiling for opening and closing the exhaust valve 11 are stored in an electronic control system and applied based on operating conditions and engine characteristics.

  FIG. 4 shows a second embodiment of the exhaust valve actuation system according to the present invention, which is essentially the same as the embodiment described with reference to FIG. 3 except for the following differences. The 3/2 valve is replaced with a hydraulic control servo valve 35. The servo valve is connected to a pressurized hydraulic oil source 49 and a tank. The servo valve 35 is hydraulically controlled by a control valve 37 that is electrically controlled by an electronic control system of the engine. The engine's electronic control system uses the signal from the position sensor 39 to determine the proper position of the servo valve 35. The graph 42 shows the possibility of changing the profile for opening and closing the exhaust valve 11, which can be obtained by this embodiment. The amount of hydraulic oil added to or removed from the conduit 36 can be freely selected, but the amount is determined by the capacity limiter in the embodiment of FIG. Any position in between can be obtained. Therefore, this embodiment further increases the flexibility in determining the opening / closing profile of the exhaust valve 11.

  FIG. 5 shows a third embodiment of the present invention. In this embodiment, the hydraulic valve actuation system also uses a hydraulic push rod system that includes a positive displacement pump 32 connected to a hydraulic valve actuator 34 by a conduit 36. However, in this embodiment, the cylinder 6 is provided with an additional gas exchange valve 46. The additional gas exchange valve 46 is relatively small compared to the exhaust valve 11 and provides a small opening in the exhaust gas conduit. The additional gas exchange valve 46 is opened and closed by a small hydraulic actuator 44 that is controlled by the engine's electronic control system. The operation of the actuator 44 is completely independent of the operation of the camshaft driven exhaust valve actuation system. Therefore, the timing for opening and closing the additional gas exchange valve 46 can be optimally selected according to the situation. Blow-back can be reduced by opening an additional gas exchange valve 46 prior to the point in time at which the cam 29 determines to open the exhaust valve 11. The compression pressure can be reduced by leaving the additional gas exchange valve 46 open after the point in time when the exhaust valve 11 is determined to be closed by the cam 29. Graph 42 shows the profiling possibilities according to this embodiment. The solid curve represents the movement of the exhaust valve 11, and the dashed curve represents the movement of the additional gas exchange valve 46.

  FIG. 6 shows a fourth embodiment of the invention, but the embodiment described with reference to FIG. 5 except that an additional gas exchange valve 46 is connected via a duct 47 to the scavenge receiver. Is essentially the same. Therefore, in this embodiment, only the compression pressure can be adjusted by an additional gas exchange valve. Graph 42 shows the profiling possibilities according to this embodiment. The solid curve represents the movement of the exhaust valve 11, and the dashed curve represents the movement of the additional gas exchange valve 46.

  The term “comprising”, used in the claims, does not exclude other elements. Of the terms used in the claims, those not described as “plurality” do not exclude a plurality.

  Although the present invention has been described in detail for purposes of illustration, it is to be understood that this detail is merely for that purpose and that one skilled in the art can make changes without departing from the scope of the invention.

Claims (8)

A crosshead large two-cycle diesel engine,
A plurality of cylinders each having at least one exhaust valve;
At least one camshaft having an exhaust cam for actuating the at least one exhaust valve of the cylinder for each of the plurality of cylinders;
A hydraulic actuator provided in each of the exhaust valves for moving the exhaust valve in the opening direction;
A hydraulic piston pump provided by each of the hydraulic actuators and driven by a corresponding cam on the camshaft;
A hydraulic oil pipe for connecting the hydraulic piston pump to the corresponding hydraulic actuator provided in each of the exhaust valves;
An additional gas exchange valve provided in each of the cylinders;
An actuation system that controls the opening and closing of the additional gas exchange valve independently of the camshaft;
A crosshead type large two-cycle diesel engine equipped with   The engine of claim 1, wherein the operating system electronically controls opening and closing of the additional gas exchange valve.   The engine according to claim 1 or 2, wherein the additional gas exchange valve is relatively smaller than the exhaust valve.   The engine according to any one of claims 1 to 3, wherein the additional gas exchange valve connects the corresponding cylinder to an exhaust gas receiver.   The engine according to any one of claims 3 to 3, wherein the additional gas exchange valve connects the corresponding cylinder to a scavenging receiver.   The engine according to any of claims 1 to 5, wherein the operating system further comprises a hydraulic actuator connected to the additional gas exchange valve to operate the additional gas exchange valve.   The engine according to any of the preceding claims, wherein the operating system is configured to control the blowback of the corresponding cylinder.   8. An engine according to any preceding claim, wherein the operating system is configured to control its compression pressure.

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