JP2011226384A - Diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diesel engine which can suppress jetting of lubricating oil adhered on an outer peripheral face of a piston from scavenging holes.SOLUTION: The diesel engine includes: the piston 3 that slides in a cylinder bore 2; a scavenging chamber 10 provided around the cylinder bore 2 and supplied with compressed air; the scavenging holes 11 provided arranged in a plurality of numbers penetrating a wall face of the cylinder bore 2 in the circumferential direction, and communicating a combustion chamber with the scavenging chamber 10 when the piston 3 is in an explosion stroke in which the piston is moved toward a bottom dead center; scavenging ribs 21 each arranged between the plurality of scavenging holes 11; an oil injection port provided opened in the wall face of the cylinder bore 2 for supplying lubricating oil into the cylinder bore 2 for enhancing sliding performance of the piston 3; and a holding groove 22 for holding the lubricating oil at least at a part on the outer peripheral face of the piston 3 covered by the scavenging ribs 21 at an end of the explosion stroke.

Description

  The present invention relates to a diesel engine that improves the retention capability of lubricating oil used to smoothly slide a piston.

  A piston of a diesel engine is disclosed in Patent Document 1. The piston of this diesel engine is intended to reduce oil consumption by reliably removing oil adhering to the outer periphery of the piston. For this purpose, a recess for oil sump is provided on the outer periphery of the piston, and an oil passage hole is provided to connect the recess to the inner periphery of the piston. Patent Document 1 is described using a tractor as an example.

  Thus, the efficient use of oil (lubricating oil) has been researched and developed in various fields. However, even if a mechanism such as Patent Document 1 is diverted to, for example, a large marine diesel engine, oil (lubricating oil) cannot be efficiently used.

  In general, a large marine diesel engine is a uniflow type engine, in which compressed air flows from a plurality of scavenging holes provided in a lower part of a cylinder, which is combusted and exhausted from an exhaust port in the upper part of the cylinder. . When the piston sliding inside the cylinder is lowered and the outer peripheral surface of the piston overlaps with the scavenging hole, the pressure inside the cylinder is higher than the outside through the scavenging hole, so that air blows out from the inside to the outside (blowback phenomenon) Happens. At this time, there is a problem that the lubricating oil adhering to the outer peripheral surface of the piston also comes out together.

JP 2001-12296 A

  An object of the present invention is to provide a diesel engine that can prevent the lubricating oil adhering to the outer peripheral surface of the piston from being ejected from the scavenging holes in consideration of the above prior art.

  In order to achieve the above object, according to the first aspect of the present invention, a piston sliding inside the cylinder bore, a scavenging chamber provided around the cylinder bore and supplied with compressed air, and a wall surface of the cylinder bore are penetrated in the circumferential direction. And a plurality of scavenging holes that communicate between the combustion chamber and the scavenging chamber when the piston is in an explosion stroke in which the piston moves toward bottom dead center, and scavenging gas disposed between the plurality of scavenging holes. A rib, an opening provided in the wall surface of the cylinder bore, and an oil filler port for supplying lubricating oil for enhancing the slidability of the piston into the cylinder bore; and at least the scavenging rib at the end of the explosion stroke A diesel engine comprising a retaining groove for retaining the lubricating oil in a portion of the outer peripheral surface of the piston covered with a fuel is provided.

According to a second aspect of the present invention, in the first aspect of the present invention, the holding groove is formed only within a range covered by the scavenging rib.
According to a third aspect of the present invention, in the first aspect of the invention, the holding groove is bent downward only and is formed at a position covered by the scavenging rib, and the upper side of the downward bent portion and the It has the right and left both ends formed in the position corresponding to a scavenging hole, It is characterized by the above-mentioned.

  According to a fourth aspect of the present invention, in the first aspect of the present invention, the holding groove is bent downward only and formed at a position covered with the scavenging rib, and bent downward only and the downward bent portion. Further, an upward bending portion formed at a position corresponding to the scavenging hole is continuous with the circumferential direction of the outer peripheral surface of the piston.

  In the invention of claim 5, in the invention of claim 1, the piston is formed above a plurality of ring-shaped piston rings protruding continuously in the circumferential direction and the piston ring located at the uppermost side. It has the holding groove.

  According to the first aspect of the present invention, since the holding groove for holding the lubricating oil is provided on the piston surface, the lubricating oil can be collected in the holding groove during the sliding of the piston. This holding groove is formed at a position where the outer peripheral surface of the piston is covered with the scavenging ribs at least when the piston slides (when it slides near the bottom dead center). In this position, the phenomenon that the air is blown out from the inside to the outside of the cylinder bore through the scavenging holes (blowback phenomenon) does not occur, so that the lubricating oil held in the holding groove can be prevented from being blown out from the scavenging holes. .

  According to the second aspect of the present invention, since the holding groove is formed only within the range covered by the scavenging ribs, the lubricating oil flowing on the outer peripheral surface of the piston can be collected within this range as much as possible. Therefore, it can suppress that the lubricating oil hold | maintained at the holding groove is ejected from a scavenging hole.

  According to the invention of claim 3, the holding groove is formed in a position where the left and right ends correspond to the scavenging holes (a position where the surface is exposed from the scavenging holes when the piston is lowered) and is bent downward only. The bent portion is formed at a position covered with the scavenging rib. When the piston slides downward, the pressure in the upper combustion chamber is high in the cylinder, so that the lubricating oil that has flowed into the holding groove moves to the downward bent portion bent only downward. Therefore, the lubricating oil adhering to the position where the surface is exposed from the scavenging holes when the piston descends can be collected in the bent portion covered by the scavenging ribs. Thereby, it can suppress that the lubricating oil adhering to the piston surface is ejected from a scavenging hole.

  According to the invention of claim 4, the holding groove is bent downward only and is formed at a position covered with the scavenging rib, and is bent only upward and corresponds to the scavenging hole above the downward bent portion. An upward bent portion formed at a position where the piston is located is continuous in the circumferential direction of the piston surface. When the piston slides downward, the pressure in the upper combustion chamber is high in the cylinder, so that the lubricating oil that has flowed into the holding groove moves to the downward bent portion bent only downward. For this reason, when the piston descends, the lubricating oil adhering to the position where the surface is exposed from the scavenging holes can be collected in the bent portion covered with the scavenging ribs. Thereby, it can suppress that the lubricating oil adhering to the piston surface is ejected from a scavenging hole.

  According to the invention of claim 5, the piston is provided with a plurality of piston rings, and a holding groove is formed above the uppermost piston ring among these piston rings. Since a large amount of lubricating oil adheres to the upper part of the piston, it is possible to prevent a large amount of lubricating oil from being efficiently collected and ejected from the scavenging holes by providing the holding groove at the upper part of the piston.

1 is a schematic view of a diesel engine according to the present invention. It is the schematic of the piston periphery provided with the holding groove. It is the schematic of the piston periphery provided with another holding groove. It is the schematic of the piston periphery provided with another holding groove.

FIG. 1 is a schematic view of a diesel engine according to the present invention.
As shown in the figure, a diesel engine 1 according to the present invention is mainly used for ships, and includes a cylinder bore 2 and a piston 3. The cylinder bore 2 has a substantially cylindrical shape. Normally, the cylinder bore 2 is cast by casting a cylinder liner with improved slidability of the piston 3. The piston 3 slides up and down in the cylinder bore 2. The piston 3 is connected to the piston rod 5, and the piston rod 5 is connected to the cross head 6 and the connecting rod 7. The connecting rod 7 is connected to the crankshaft 8. A substantially sealed scavenging chamber 10 is provided around the lower side of the cylinder bore 2. A plurality of cylinder bores 2 are provided side by side through the wall surface of the cylinder bore 2, and at least when the piston 3 is at the bottom dead center, a combustion chamber (not shown) above the piston 3 and the scavenging chamber 10 are provided. A scavenging hole 11 that communicates is provided. An oil injection port 12 is provided on the upper side of the cylinder bore 2 to open the wall surface of the cylinder bore 2 and to be directed into the cylinder bore 2 so as to supply lubricating oil for improving the slidability of the piston 3.

  The sliding operation of the piston 3 is performed as follows. Air is compressed by the turbocharger 13, and this compressed air flows in the direction of arrow R, passes through a scavenging manifold (not shown), and is supplied to the scavenging chamber 10. A check valve such as a flap valve may be provided between the scavenging manifold and the scavenging chamber 10 as appropriate. The compressed air in the scavenging chamber 10 flows into the cylinder bore 2 (more specifically, the combustion chamber on the upper side of the piston) from the scavenging hole 11 when the piston 3 reaches bottom dead center, and from the injector 14 when the piston 3 moves up. Fuel is supplied and spontaneous ignition occurs. In this explosion process, the piston 3 is pushed down, the exhaust valve 15 above the cylinder bore 2 is opened, and the exhaust gas is exhausted therefrom.

  Then, when the piston 3 reaches the bottom dead center again, the compressed air flows into the cylinder from the scavenging hole 11. Such a sliding operation of the piston 3 moves the piston rod 5 up and down, and the crosshead 6 slides along the crosshead guide 9 accordingly. Further, the upper end of the connecting rod 7 also slides up and down, and the lower end of the connecting rod 7 rotates around the crankshaft 8. Then, the crankshaft 8 rotates. The drive oil for the exhaust valve 15 is supplied through the oil supply pipe 16. On the other hand, hydraulic oil for operating other valves and the like is supplied through an oil supply pipe 17. The fuel is supplied through the fuel pipe 19. The pressure of these hydraulic oil and fuel is controlled by the adjustment unit 18.

  The lubricating oil supplied from the oil inlet 12 is stretched by being sandwiched between a piston ring (described later) and the inner wall surface of the cylinder bore 2 by sliding of the piston 3. Then, the oil is discharged from a waste oil port (not shown) provided at the lower end of the cylinder bore 2.

FIG. 2 is a schematic view of the periphery of a piston having a holding groove.
As illustrated, the piston 3 includes a plurality of (four in the figure) piston rings 20 that continuously protrude in the circumferential direction. Actually, the outer peripheral surface of the piston ring 20 and the inner wall surface of the cylinder bore 2 are in contact with each other, and the piston 3 slides in the cylinder bore 2. In the figure, the scavenging holes 11 opened on the front side of the figure are drawn with dotted lines. Scavenging ribs 21 are arranged between the plurality of scavenging holes 11 described above. When the piston 3 slides (specifically, when the piston 3 moves near the bottom dead center at the end of the explosion process), a holding groove for holding the lubricating oil at a position where the outer peripheral surface of the piston is covered with the scavenging rib 21 22 is formed. Therefore, the lubricating oil adhering to the outer peripheral surface of the piston 3 is collected in the holding groove 22 as the piston 3 slides. For this reason, the phenomenon that air is blown out from the inside of the cylinder to the outside through the scavenging holes 11 at this position (blowback phenomenon) does not occur, so that the lubricating oil held in the holding groove 22 is blown from the scavenging holes 11. Can be suppressed.

  The holding groove 22 is formed within a range covered by the scavenging rib 21. In the figure, a plurality of holding grooves 22 are formed intermittently along the circumferential direction of the piston 3, and the left and right ends of the holding grooves 22 are formed to have the same length as the lateral width of the scavenging rib 21. Thus, by forming the holding groove 22 within the range covered by the scavenging ribs 21, it becomes possible to collect the lubricating oil flowing on the surface of the piston 3 as much as possible within this range. Therefore, it is possible to suppress the lubricating oil held in the holding groove 22 from being ejected from the scavenging holes 11. It is preferable to provide a plurality of holding grooves 22 (three in the figure) in the sliding direction of the piston 3. Thereby, more lubricating oil can be held in the holding groove 22.

  The holding groove 22 is formed above the uppermost piston ring 20. Since a large amount of the lubricating oil adheres to the upper part of the piston 3, by providing the holding groove 22 on the upper part of the piston, it is possible to further suppress a large amount of lubricating oil from being efficiently collected and ejected from the scavenging holes 11. The holding groove 22 may be provided below or in the middle of the piston. Further, the length of the scavenging rib 21 in the width direction may be increased. Thereby, the length of the holding groove 22 in the width direction can be increased, and more lubricating oil can be collected. In this case, the design is made so as to maintain an appropriate area and height of the scavenging holes 11.

FIG. 3 is a schematic view of the periphery of a piston provided with another holding groove.
As shown in the drawing, the holding groove 23 is formed at a position that is bent downward only and is covered with the scavenging ribs 21, and a position that is above the downward bending part 23 a and that corresponds to the scavenging holes 11. Left and right end portions 23b, 23c. That is, the holding groove 23 is formed in a substantially V shape when viewed from the front. When the piston 3 slides downward, the pressure in the upper combustion chamber is high in the cylinder bore 2, so that the lubricating oil flowing into the holding groove 23 bends downward from the left and right end portions 23 b and 23 c in the holding groove 23. It moves toward the part 23a (arrow D direction in the figure). That is, both the left and right end portions 23b and 23c are located at positions where their surfaces are exposed from the scavenging holes 11 when the piston 3 is lowered (moved near the bottom dead center). It can collect in the downward bending part 23a covered with a scavenging rib. Thereby, it can suppress that the lubricating oil adhering to the surface of the piston 3 is ejected from the scavenging hole 11. The number of the holding grooves 23 in the vertical direction may be one or more (two in the figure) as in the example shown in FIG. Other configurations, operations, and effects are the same as in the example of FIG.

FIG. 4 is a schematic view of the periphery of a piston provided with another holding groove.
As shown in the drawing, the holding groove 24 is bent downward only and is formed at a position where it is covered with the scavenging ribs 21, and the holding groove 24 is bent only upward and above the downward bending portion 24 a and into the scavenging holes 11. The upward bent portion 24b formed at the corresponding position is continuous in the circumferential direction of the surface of the piston 3. In other words, the holding groove 24 is formed in a wavy line having a substantially V-shape. Even with such a configuration, the lubricating oil adhering to the position that would be exposed to the scavenging holes 11 flows in the holding groove 24 in the direction of the arrow D and is collected in the downward bent portion 24a covered with the scavenging ribs 21. It is possible to suppress the lubricant oil adhering to the surface of the piston 3 from being ejected from the scavenging holes 11. Other configurations, operations, and effects are the same as in the example of FIG.

DESCRIPTION OF SYMBOLS 1 Diesel engine 2 Cylinder bore 3 Piston 5 Piston rod 6 Cross head 7 Connecting rod 8 Crankshaft 9 Cross head guide 10 Scavenging chamber 11 Scavenging hole 12 Oil inlet 13 Turbocharger 14 Injector 15 Exhaust valve 16 Oil supply pipe 17 Oil supply pipe 18 Adjustment unit 19 Fuel Pipe 20 Piston ring 21 Scavenging rib 22 Holding groove 23 Holding groove 23a Downward bent portions 23b, 23c Left and right ends 24 of holding groove Holding groove 24a Downward bent portion 24b Upward bent portion

Claims (5)

A piston sliding in the cylinder bore;
A scavenging chamber provided around the cylinder bore and supplied with compressed air;
Scavenging holes that are provided side by side in the circumferential direction through the wall surface of the cylinder bore, and that allow the combustion chamber and the scavenging chamber to communicate with each other when the piston is in an explosion stroke that moves toward bottom dead center;
Scavenging ribs respectively disposed between the plurality of scavenging holes;
An opening provided in the wall surface of the cylinder bore, and an oil filling port for supplying lubricating oil for enhancing the slidability of the piston into the cylinder bore;
A diesel engine comprising a retaining groove for retaining the lubricating oil at least at a portion of the outer peripheral surface of the piston covered by the scavenging rib at the end of the explosion stroke.   The diesel engine according to claim 1, wherein the holding groove is formed only within a range covered by the scavenging rib.   The holding groove is bent downward only and is formed at a position where it is covered by the scavenging rib, and left and right ends formed at positions above the downward bending part and corresponding to the scavenging holes. The diesel engine according to claim 1, comprising:   The holding groove is formed at a position that is bent only downward and is covered by the scavenging rib, and is formed at a position that is bent only upward and above the downward bent part and that corresponds to the scavenging hole. The diesel engine according to claim 1, wherein the upward bent portion is continuous in a circumferential direction of the outer peripheral surface of the piston.   The piston includes a plurality of ring-shaped piston rings continuously projecting in the circumferential direction, and the holding groove formed above the piston ring located on the uppermost side. Diesel engine as described in

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