CN111749806A

CN111749806A - Marine diesel engine, cylinder liner and parts constituting the engine, and maintenance method for the engine

Info

Publication number: CN111749806A
Application number: CN202010223667.3A
Authority: CN
Inventors: 穴井恒平; 龙井隆佳; 赤荻祐亮; 森勇人
Original assignee: Hitachi Zosen Corp
Current assignee: Hitachi Zosen Corp
Priority date: 2019-03-27
Filing date: 2020-03-26
Publication date: 2020-10-09
Also published as: TW202100859A; JP2020159328A; KR20200115153A

Abstract

In a marine diesel engine, a piston ring replacement operation can be performed without accompanying a piston extraction operation. The disclosed device is provided with: a cylinder liner upper part (31) which is provided with a top part (31a) positioned at the outer side of the cylinder frame when the cylinder liner upper part is arranged on the cylinder frame, and a base part (31c) extending from the through hole of the cylinder frame to the scavenging chamber; and a cylinder liner lower part (32) which is detachably connected to the lower end of the base part (31 c).

Description

Marine diesel engine, cylinder liner and parts constituting the engine, and maintenance method for the engine

Technical Field

The present invention relates to a marine diesel engine, and relates to the engine itself, a cylinder liner and parts thereof constituting the engine, and a maintenance method of the engine.

Background

In a marine diesel engine, a piston pulling-out operation is required as one of maintenance operations. As an example of the piston extracting operation, non-patent document 1 below discloses a downstream process.

1. After the cooling water, the lubricating oil, and the like of the main engine (diesel engine for a ship) are extracted, the respective pipe systems connected to the upper stage of the main engine are removed, and the cylinder head as the upper structure is removed.

2. And detaching the lower connecting part of the piston and pulling the piston out of the cylinder.

3. Cleaning, measurement, and recording (imaging) of the piston ring and the cylinder liner of the sliding portion are performed.

4. After the piston, the cylinder liner, the penetrating portion of the piston rod, and the like are maintained, the piston ring is assembled to the extracted piston, and the cylinder oil is applied to the piston and stored in the cylinder.

5. After the lower part of the piston rod is connected, the cylinder cover is restored.

6. After the connection pipe system at the upper part of the main machine is restored, leakage and the like are checked by cooling water, lubricating oil and the like.

7. A test run is performed, the status is confirmed, and the operation is ended.

Documents of the prior art

Patent document

Non-patent document 1: the general society of law, japan society of marine engineers, "introduces a piston extraction operation as an in-ship operation. "[ Online ] [ search for 2 months and 22 days in 31 years ] Internet < http:// www.marine-Engineer. or. jp/images/piston _ Shokui. pdf >

Disclosure of Invention

Technical problem to be solved

According to non-patent document 1, the piston extracting work requires a large number of people and sufficient preparation, and is one of important works, and the engine portion requires about 6 people in total, and usually about 8 to 10 hours. In addition, since the piston pulling-out operation of the DF engine (two-fuel engine) requires the disassembling operation of the piping for the fuel gas and the like, the operation time and the operation load are larger than those of the conventional marine diesel engine. Further, the description of non-patent document 1 is based on the assumption that a mechanically controlled engine is used, and the work of removing the pistons of an electronically controlled engine requires the work of removing electronic devices such as sensor cables in addition to the work of removing the pipe systems, and therefore the work time and work load are larger than those of the mechanically controlled engine.

In a conventional marine diesel engine, maintenance on the inside of a cylinder liner may not be performed without a piston pull-out operation, or may be performed without a piston pull-out operation, but the workability may be poor.

The former includes maintenance requiring attachment and detachment of piston rings, such as replacement of piston rings.

The latter includes measurement of the amount of wear of the cylinder liner, and local inspection/cleaning of the piston head/piston rod. These operations can be performed by inserting a tool or the like into the cylinder liner from a scavenging hole formed in the cylinder liner. However, since the scavenging holes are generally small, the workability of maintenance through the scavenging holes is poor.

Accordingly, an object of the present invention is to provide a marine diesel engine, a component thereof, and a maintenance method for a marine diesel engine, which can expand the range of maintenance that can be performed without the piston pulling-out operation, or can improve the workability of maintenance that can be performed without the piston pulling-out operation.

(II) technical scheme

In order to solve the above-described problems, a cylinder liner for a marine diesel engine according to one aspect of the present invention includes: a cylinder liner upper part having a top part located outside a cylinder frame for mounting a cylinder head when the cylinder liner upper part is provided to the cylinder frame in which a scavenging chamber is formed, and a base part extending from a through hole formed in the cylinder frame toward the scavenging chamber; and a cylinder liner lower portion detachably connected to a lower end of the base portion.

In the structure in which the cylinder liner is not vertically divided and integrated, particularly, maintenance work for the inside of the cylinder liner cannot be performed without performing a piston extraction work, or workability is poor.

In contrast, in the above-described configuration, even if the piston is not removed, the lower liner portion can be removed from the upper liner portion, so that maintenance work for the inside of the liner, particularly, the vicinity of the connection position between the upper liner portion and the lower liner portion can be partially performed, or the workability can be improved.

A marine diesel engine according to an aspect of the present invention includes: the cylinder liner, the cylinder frame, a piston head reciprocating in the cylinder liner, and a piston rod connected to the piston head.

A liner member of a marine diesel engine according to an aspect of the present invention is configured by the liner lower portion configuring the liner.

A maintenance method for a marine diesel engine according to an aspect of the present invention includes: a step of detaching a lower portion of a cylinder liner from a base portion of the cylinder liner provided on a cylinder frame having a scavenging chamber formed therein, the base portion being provided to extend from a through hole formed in the cylinder frame toward the scavenging chamber; the lower part of the cylinder sleeve is detachably connected with the lower end of the base part; a step of performing maintenance work on a portion where work can be performed or work becomes easy by detaching a lower portion of the cylinder liner; and a step of attaching the lower portion of the cylinder liner to the base portion.

(III) advantageous effects

According to one embodiment of the present invention, the range of maintenance that can be performed without the piston extracting operation can be expanded, or the workability of maintenance that can be performed without the piston extracting operation can be improved.

Drawings

Fig. 1 is a partial sectional view of a marine diesel engine according to an embodiment of the present invention.

Fig. 2 is a front view showing a state in which a cylinder liner is provided in a cylinder frame in the marine diesel engine of fig. 1.

Fig. 3 is a front view showing the whole of the cylinder liner of fig. 2.

Fig. 4 is a perspective view of an upper portion of a cylinder liner constituting the cylinder liner of fig. 2.

Fig. 5 is a perspective view of a lower portion of a cylinder liner constituting the cylinder liner of fig. 2.

Fig. 6 is a front view showing a state of a cylinder liner in a piston ring replacing operation.

Description of the reference numerals

1-marine diesel engines; 10-a crankcase; 11-a crankshaft; 12-crosshead; 13-a connecting rod; 14-a piston head; 14 a-a piston ring; 15-a piston rod; 20-a cylinder frame; 21-a stuffing box; 22-a scavenging chamber; 23-a scavenging port; 24-a lifting mechanism; 30-cylinder liner; 31-the upper part of the cylinder sleeve; 31 a-top; 31 b-a protrusion; 31 c-a base; 32-the lower part of the cylinder sleeve; 32 a-the component that constitutes the lower part of the cylinder liner; 32 b-the components that make up the lower portion of the liner; 32 c-a stop; 32 e-scavenging holes; 40-cylinder cover; 50-an exhaust manifold; 60-a supercharger; 70-a scavenging air box; 80-exhaust valve driving means.

Detailed Description

Fig. 1 is a partial cross-sectional view showing a marine diesel engine 1 according to an embodiment of the present invention. In the claims and the description of the present application, "upper"/"lower",

the concept of "top"/"bottom" is defined with reference to the reciprocating direction of the pistons of the marine diesel engine 1, and the top dead center side and the bottom dead center side of the pistons are respectively defined as "top"/"bottom"),

Top/bottom.

[ integral Structure of Marine Diesel Engine ]

The marine diesel engine 1 includes: a crank case 10, a cylinder frame 20, a cylinder liner 30, a cylinder head 40, an exhaust manifold 50, a supercharger 60, a scavenging air case 70, and a fuel injection/exhaust valve driving device 80.

A crankshaft 11, a crosshead 12, and a connecting rod 13 connecting them are disposed inside the crankcase 10. A part of the piston rod 15 is inserted into the crankcase 10 from above. The piston rod 15 has a piston head 14 at the upper front end and reciprocates up and down. This motion is transmitted to the connecting rod 13 via the crosshead 12, and is converted into rotational motion by the connecting rod 13 and the crankshaft 11.

The cylinder frame 20 is disposed at the top of the crankcase 10. A through hole is formed in the bottom of the cylinder frame 20, and a stuffing box 21 is provided in the through hole. The stuffing box 21 maintains airtightness between the inside of the crank case 10 and the inside of the cylinder frame 20, and has the piston rod 15 inserted therethrough.

The cylinder liner 30 is partially inserted into the cylinder frame 20 through a through hole formed in the top of the cylinder frame 20, and the other part protrudes above the cylinder frame 20. The cylinder liner 30 houses the piston head 14 and a part of the piston rod 15.

The cylinder head 40 is disposed at the top of the liner 30, and maintains airtightness between the space above the piston head 14 inside the liner 30 and the outside of the liner 30. An exhaust port 41 is formed in the cylinder head, and an exhaust valve 42 is provided in the exhaust port 41.

The cylinder liners 30 and the cylinder heads 40 are arranged, for example, six in the direction perpendicular to the drawing sheet of fig. 1, and constitute a six-cylinder engine. The crosshead 12, the connecting rod 13, the piston head 14, the piston rod 15, the stuffing box 21, and the like are also provided in the same number as the cylinder liner 30 and the cylinder head 40.

The exhaust manifold 50 is a pipe that communicates with the exhaust port 41 of each cylinder head 40 and the supercharger 60. The exhaust manifold 50 is used to convey the gas discharged from each exhaust port 41 to the supercharger 60.

The supercharger 60 compresses external air by the flow of exhaust gas sent through the exhaust manifold 50 and supplies the compressed external air to the purge tank 70.

The scavenging air tank 70 is used to supply the compressed air supplied from the supercharger 60 to the scavenging chamber 22 formed inside the cylinder frame 20. The cylinder frame 20 has scavenging ports 23 (see fig. 2) formed in the side walls thereof at positions facing the respective cylinder jackets 30. A plurality of scavenging holes 32e are formed in the circumferential wall of the liner 30 along the circumferential direction thereof (see fig. 3). The compressed air is introduced into the cylinder liner 30 through the scavenging port 23 and the scavenging hole 32 e.

The purge box 70 is provided with an inspection door 71. By opening the inspection door 71, the operator can enter the scavenging box 70 and reach the scavenging chamber 22 through the scavenging port 23.

The fuel injection/exhaust valve drive device 80 is disposed on the side of the cylinder liner 30 at the top of the cylinder frame 20. The fuel injection/exhaust valve driving device 80 supplies fuel to the cylinder head 40, and performs hydraulic control for hydraulically driving the exhaust valve 42.

[ operation of Marine Diesel Engine ]

The marine diesel engine 1 operates as follows.

In the state where the piston head 14 is at the bottom dead center, the top of the piston head 14 is located below the scavenging hole 32e of the cylinder liner 30, and the exhaust valve 42 is opened. Thereby, scavenging is performed. That is, the compressed air supplied from the scavenging tank 70 to the scavenging chamber 22 and introduced into the cylinder liner 30 through the scavenging hole 32e ejects the combustion gas of the previous cycle from the exhaust port 41 to fill the cylinder liner 30.

When the piston head 14 rises from the bottom dead center, the piston head 14 moves upward from the scavenging hole 32e, so that the inside of the cylinder liner 30 and the scavenging chamber 22 are sealed, and the exhaust valve 42 is closed.

When piston head 14 further rises and reaches near top dead center, the compressed air is compressed and heated above the ignition point of the fuel. In this state, fuel is injected into the cylinder liner 30 by the fuel injection/exhaust valve drive device 80, and the fuel is self-ignited.

The piston head 14 is turned downward through the top dead center, and is driven downward by the expansion of the combustion gas generated by the ignition. Thereafter, exhaust valve 42 opens and piston head 14 again returns to bottom dead center.

The vertical reciprocating motion of the piston head 14 generated by repeating the above operations is converted into a rotary motion as described above, and becomes an output of the marine diesel engine 1.

[ setting and Structure of Cylinder liner ]

Fig. 2 is a front view showing a state in which the cylinder liner 30 is provided to the cylinder frame 20, and fig. 3 is a front view showing the entire cylinder liner 30. Fig. 2 and 3 are views of the cylinder liner 30 and the like as viewed from the scavenging-chamber side in fig. 1. In fig. 1, the structure of the cylinder liner 30 and the like is partially simplified and shown.

The liner 30 includes: a liner upper portion 31, a liner lower portion (liner member) 32, a connecting ring 33 connecting them and preventing them from rotating with each other, and a rotation stopper 34.

The liner upper portion 31 includes: the top portion 31a of the cylinder head 40, the protruding portion 31b protruding from the cylinder frame 20, and the base portion 31c provided to extend from a through hole formed in the cylinder frame 20 toward the scavenging chamber 22.

The liner lower portion 32 is detachably connected to a lower end of the base portion 31c of the liner upper portion 31. One cylinder liner 30 is constructed by fitting a liner lower portion 32 to a liner upper portion 31. The connecting position of the liner upper portion 31 and the liner lower portion 32 is a position on the top dead center side than the top of the piston head 14 when the piston head 14 is at the bottom dead center.

The liner lower portion 32 has a plurality of the above-described scavenging holes 32e formed in its circumferential surface along its circumferential direction. The liner lower portion 32 includes two

members

32a and 32b divided into two by a plane including the central axis of the liner 30, and eight stoppers 32c detachably combined with each other. In fig. 2 and 3, four stoppers 32c are shown, but the remaining four stoppers are arranged on the opposite side of the two stoppers so as to be symmetrical with respect to the two stoppers.

As shown in the perspective views of fig. 4 and 5, the connection between the liner upper portion 31 and the liner lower portion 32 is a bayonet type using a connecting ring 33.

As shown in fig. 4, the connection ring 33 is embedded in the lowermost outer periphery of the base portion 31c of the liner upper portion 31 and fastened by a screw. The substantially lower half of the connection ring 33 overlaps the outer periphery of the base portion 31c, and protrudes downward beyond the lower end of the base portion 31 c. Four inner claws 33a protruding inward are provided at equal intervals on the inner periphery of the protruding portion. Two notches 33b are formed in the protruding portion.

As shown in fig. 5, four outer claws 32d protruding outward are formed on the uppermost outer periphery of the liner lower portion 32.

When the liner lower portion 32 is connected to the liner upper portion 31, first, the liner lower portion 32 is fitted into the connecting ring 33 so that the outer claws 32d of the liner lower portion 32 enter the gaps of the inner claws 33a of the connecting ring 33. Then, by rotating the liner lower portion 32 with respect to the attachment ring 33, the outer claws 32d of the liner lower portion 32 and the inner claws 33a of the attachment ring 33 are respectively engaged in the up-down direction. In this state, two rotation stoppers 34 are fitted into the two notches 33b of the coupling ring 33, respectively, and these rotation stoppers 34 are screwed to the liner lower portion 32. Thereby, the liner lower portion 32 is positioned in the vertical direction and the rotational direction with respect to the liner upper portion 31, and they are integrated.

[ Cylinder liner associated tools ]

Three fixing tools 35 are mounted around the periphery of the liner lower portion 32. As will be described later, the fixing tool 35 is used for disassembling and assembling the liner lower portion 32, and can be detached in advance when the marine diesel engine 1 is operated.

Two lifting mechanisms (placement tables) 24 are provided below the liner lower portion 32. The lifting mechanism 24 is also a tool for lifting the cylinder liner lower portion 32 when the cylinder liner lower portion 32 is attached and detached, and can be detached in advance when the marine diesel engine 1 is operated.

The lifting mechanism 24 includes: a base 24a attached to the bottom surface (not shown in fig. 3) of the cylinder frame 20, a jack bolt 24b screwed to the base 24a, and a top plate 24c attached to the top of the jack bolt 24 b. The two elevating mechanisms 24 correspond to the two

members

32a and 32b constituting the liner lower portion 32, respectively.

[ Replacing work of piston ring ]

Next, a replacement operation of the piston ring 14a (see fig. 6) attached to the piston head 14 will be described as an example of a maintenance operation of the marine diesel engine 1 on the premise of the cylinder liner 30 having the above-described structure.

Fig. 6 is a front view showing a state of the liner 30 during the replacement operation of the piston ring 14 a. The replacement work of the piston ring 14a is based on the following steps. The following operation 2 and later is performed by an operator who enters the scavenging chamber 22.

1. By driving the inspection motor and rotating the crankshaft 11, the piston head 14 to be replaced is moved to the vicinity of the bottom dead center.

2. Three fixing tools 35 are attached around the liner lower portion 32, and the two

members

32a and 32b constituting the liner lower portion 32 are fastened with a predetermined force (see fig. 3). This is to prevent the two parts 32a/32b from being accidentally knocked by the repulsive force of the piston ring 14a when they are disassembled.

3. The lifting mechanism 24 is installed below each of the two members 32a/32b, and the jack bolt 24b is rotated to support the members 32a/32b from below. This is to prevent the parts 32a/32b from falling down suddenly at a burst.

4. The rotation stoppers 34 are removed and the liner lower portion 32 is rotated by 45 so that the outer claws 32d of the liner lower portion 32 are offset from the inner claws 33a of the coupling ring 33 and located in their gaps.

5. By rotating the jack bolts 24b of the respective elevating mechanisms 24, the liner lower portion 32 is lowered, and the liner lower portion 32 is separated from the liner upper portion 31.

6. Eight stoppers 32c are removed, and three fixing tools 35 are removed, so that the parts 32a/32b are moved apart from each other in the horizontal direction, and the piston heads 14 are exposed from their clearances.

7. The piston ring 14a is removed from the piston head 14 by inserting the expander into the gap (see fig. 6).

8. The piston ring 14a is replaced with a new component, and the cylinder liner 30 is assembled in a sequence substantially reverse to the above-described steps.

[ frequency of piston ring replacement/piston extraction work ]

In a marine diesel engine, the life of the cylinder liner and the piston head is 60000 hours (which means the operating time of the marine diesel engine 1, and the same applies hereinafter), and the life of the piston ring is 16000 hours, compared to 30000 hours, which is the time when the overhaul interval is half the life.

In the case of a conventional marine diesel engine provided with an integral inseparable cylinder liner, a piston extraction (piston opening) operation is required even if a piston ring is replaced. Therefore, the piston pulling-out operation needs to be performed every 16000 hours. In this case, the number of times of piston drawing operation until the life of the cylinder liner and the piston head is reached (60000 hours) is: 60000 h/16000 h 3.75 times.

In contrast, in the marine diesel engine 1 of the present embodiment, the replacement operation of the piston ring 14a can be performed without involving the piston extraction operation. Therefore, the number of times the marine diesel engine 1 performs the piston extraction work is: 60000 h/30000 h 2 times. Therefore, in the calculation, if the number of times of comparison is compared with the above 3.75 times, the piston extracting operation can be omitted 1.75 times.

However, if the actual situation of maintenance is taken into consideration, the piston extracting work including the replacement of the piston ring is actually performed together with the inspection of the dock once before or after 30000 hours. In consideration of this, in the case of a conventional marine diesel engine provided with an integral cylinder liner, the piston extracting operation was performed at 16000 hours, 32000 hours, 48000 hours, and 60000 hours, respectively. On the other hand, in the marine diesel engine 1 of the present embodiment, the piston extracting operation is performed at 32000 hours and 60000 hours, but the piston ring 14a can be replaced without the piston extracting operation at 16000 hours and 48000 hours. As described above, in the marine diesel engine 1 of the present embodiment, the piston pulling-out operation can be omitted 2 times as compared with the conventional marine diesel engine having an integral cylinder liner until the life of the cylinder liner and the piston head is reached (60000 hours).

[ modified examples ]

The marine diesel engine 1 described above can be modified in structure as follows.

The marine diesel engine 1 has an inline structure in which the cylinder liners 30 and the like are arranged in an inline manner, and may be a V-shaped configuration in which the cylinder liners are arranged in a V-shape.

The cylinder liner 30 may be divided into two parts along the vertical direction, or may be divided into three or more parts, and at least 1 of the connecting positions may be located in the cylinder frame 20. When the cylinder head is divided into three or more parts, a portion located above an arbitrary connecting position in the cylinder frame 20 may be regarded as the liner upper portion 31 and a portion located below the connecting position may be regarded as the liner lower portion 32 with reference to the arbitrary connecting position.

In order to release the connection at the connection position and enable replacement of the piston ring 14a, the connection position needs to be located closer to the top dead center side than the top of the piston head 14 when the piston head 14 is located at the bottom dead center. However, even when the aforementioned connecting position is located below this position, it is possible to measure the amount of wear of the liner 30, and to inspect and clean a part of the piston head 14 and a part of the piston rod 15, and the like, with good workability, inside the liner 30, particularly in the vicinity of the aforementioned connecting position.

In the liner 30, the boundary between the liner upper portion 31 and the liner lower portion 32 is along a plane perpendicular to the longitudinal direction of the liner 30, but may be along a plane inclined with respect to the longitudinal direction. Also, the boundary between the liner upper portion 31 and the liner lower portion 32 may not be in a plane, and may be, for example, a wave shape. By inclining or forming the boundary into a waveform, it is possible to suppress the mechanical influence of the piston ring 14a from the minute gap of the boundary when the piston ring 14a passes through the boundary portion.

The connection method of the liner upper portion 31 and the liner lower portion 32 is not limited to the bayonet type, and may be any detachable connection method.

The liner lower portion 32 is configured as two members 32a/32b that can be divided into two, and the liner lower portion 32 may be configured as three or more members. If the number of divisions becomes large, the number of stoppers 32c required increases, and the work of attaching and detaching the stoppers increases, but the work of operating the divided members of the liner lower portion 32 becomes good because the weight of each member becomes light.

The liner lower portion 32 is not necessarily divided into two parts by a plane including the central axis of the liner 30, and may be detachable from each other in a direction different from the longitudinal direction of the liner 30 (preferably, in a direction perpendicular to the longitudinal direction).

In addition, when a sufficient space for lowering the liner lower portion 32 to expose the piston rings 14a can be secured below the liner lower portion 32, the liner lower portion 32 does not need to be configured to be separable.

The two

members

32a and 32b of the liner lower portion 32 may be fixed to the front and rear surfaces by stoppers 32c, and one of the members may be replaced with a hinge.

[ conclusion ]

As described above, the cylinder liner according to one embodiment of the present invention includes: a cylinder liner upper part 31 having a top part 31a located outside the cylinder frame 20 for mounting the cylinder head 40 when installed in the cylinder frame 20 having the scavenging chamber 22 formed therein, and a base part 31c extended from a through hole formed in the cylinder frame 20 toward the scavenging chamber 22; and a liner lower portion 32 detachably connected to a lower end of the base portion 31 c.

In contrast, in the above configuration, the liner lower portion 32 can be detached from the liner upper portion 31 without performing the piston extracting operation. This enables maintenance work to be partially performed on the inside of the liner, particularly, in the vicinity of the connection position between the liner upper portion 31 and the liner lower portion 32, or the workability to be improved.

The liner lower portion 32 is formed by detachably combining a plurality of

members

32a and 32b that can be detached and separated from each other in a direction different from the longitudinal direction of the liner 30.

In the above-described structure, the liner lower portion 32 is detached from the liner upper portion 31, and the plurality of members 32a/32b constituting the liner lower portion 32 are detached and separated from each other in a direction different from the longitudinal direction of the liner 30, typically in a direction perpendicular to the longitudinal direction, so that a working space below the base portion 31c is easily secured.

Further, a marine diesel engine 1 according to an embodiment of the present invention includes: cylinder liner 30, cylinder frame 20, piston head 14 reciprocating within cylinder liner 30, and piston rod 15 connected to piston head 14 as described above.

The connecting position of the liner upper portion 31 and the liner lower portion 32 is a position closer to the top dead center side than the top of the piston head 14 when the piston head 14 is at the bottom dead center.

In the above configuration, the piston head 14 can be exposed by positioning the piston head 14 near the bottom dead center and detaching the liner lower portion 32 from the liner upper portion 31. This enables maintenance work for the piston head 14, such as replacement of the piston ring 14a, and maintenance work for a portion on the top dead center side inside the cylinder liner 30.

In addition, a maintenance method for a marine diesel engine according to an embodiment of the present invention includes: a step of detaching a liner lower portion 32 from a base portion 31c of the liner 30, the liner lower portion 32 being detachably connected to a lower end of the base portion 31 c; a step of performing maintenance work on a portion where work can be performed or work becomes easy by detaching the liner lower portion 32; and a step of attaching the liner lower portion 32 to the base portion 31 c.

In the above method, a part of the maintenance work can be performed without accompanying the piston extracting work, or the workability can be improved.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims, and embodiments obtained by appropriately combining the technical means disclosed in the embodiments are also included in the technical scope of the present invention.

Claims

1. A cylinder liner of a marine diesel engine, characterized by comprising:

a cylinder liner upper portion having: a top part located outside the cylinder frame for assembling a cylinder cover when the cylinder frame is provided with a scavenging chamber formed inside, and a base part extending from a through hole formed in the cylinder frame to the scavenging chamber; and

and a cylinder liner lower portion detachably connected to a lower end of the base portion.

2. The cylinder liner as defined in claim 1,

the lower portion of the cylinder liner is formed by combining a plurality of detachable components that can be detached and separated from each other in a direction different from the longitudinal direction of the cylinder liner.

3. The cylinder liner as defined in claim 1,

the upper part of the cylinder sleeve is connected with the lower part of the cylinder sleeve in a bayonet type.

4. The cylinder liner as defined in claim 1,

the lower portion of the cylinder liner is formed with scavenging holes in its circumferential surface.

5. A marine diesel engine is characterized by comprising:

the cylinder liner of any one of claims 1 to 4;

the cylinder frame;

a piston head reciprocating within the cylinder liner; and

a piston rod connected to the piston head.

6. The marine diesel engine according to claim 5,

the connecting position of the upper cylinder liner portion and the lower cylinder liner portion is a position closer to the top dead center side than the top of the piston head when the piston head is at the bottom dead center.

7. A cylinder liner component of a marine diesel engine is characterized in that,

constituted by the lower portion of the liner intended to constitute a liner as claimed in any one of claims 1 to 4.

8. A maintenance method for a marine diesel engine, comprising:

a step of detaching a lower portion of a cylinder liner from a base portion of the cylinder liner provided on a cylinder frame having a scavenging chamber formed therein, the base portion being provided to extend from a through hole formed in the cylinder frame toward the scavenging chamber; the lower part of the cylinder sleeve is detachably connected with the lower end of the base part;

a step of performing maintenance work on a portion where work can be performed or work becomes easy by detaching a lower portion of the cylinder liner; and

and a step of mounting the lower portion of the cylinder liner to the base.

9. The maintenance method of a marine diesel engine according to claim 8,

when the lower portion of the cylinder liner is attached and detached, a lifting mechanism for lifting the lower portion of the cylinder liner is used.

10. The maintenance method of a marine diesel engine according to claim 8 or 9,

further comprising: and a step of moving a piston head reciprocating in the cylinder liner so that a top portion of the piston head is closer to a bottom dead center side than a connecting position of the base portion and the cylinder liner lower portion.