KR20010012501A - A cylinder liner for an internal combustion engine of the diesel type - Google Patents

Abstract

The cylinder liner 1 for a diesel internal combustion engine has at least one inwardly open oil groove with an outward supply of lubricating oil and at least first and second groups of inwardly open recesses, each group being a liner It has at least two recesses 14 having a discontinuous range in the circumferential direction of. The groups of recesses 14 are arranged in the upper 15 percent of the length of the slide surface 6, so that the other groups of recesses 14 have mutually separated in the longitudinal direction of the liner 1, and also the liner 1. Are arranged so as to be mutually arranged in the circumferential direction.

Description

CYLINDER LINER FOR AN INTERNAL COMBUSTION ENGINE OF THE DIESEL TYPE}

With regard to the cylinder liner, it is a known problem that in some situations a seizure can occur between the sliding surface of the cylinder liner and the piston rings. Such sticking appears to occur without constant conditions, in that it occurs both during commissioning and during normal operation of the new liner. Initiation of this type of sticking is believed to occur at the top of the cylinder liner, where the piston ring and slide surface are exposed to the greatest load.

During the compression stroke of the piston, an increase in pressure occurs above the piston, where the scavenged air supplied from the turbocharger is, for example, 100 to 150 bar at the highest position of the piston from an initial pressure of 3 to 4 bar, for example. Compressed to a fairly high pressure. In the first part of the compression stroke, the increase in pressure is slow and most of the increase in pressure does not necessarily occur until the piston reaches its highest position. Near the highest position of the piston, the fuel valves open, fuel is injected into the cylinder and ignited, while the cylinder pressure during combustion is increased to, for example, a maximum combustion pressure of 160 to 200 bar, while the temperature at the top of the cylinder Increased to 500 ° C. During combustion, a large pressure rise in the combustion chamber above the piston crown causes combustion gas to penetrate into the annular space between the groove of the piston ring and the piston rings, where the pressure affects the rear of the rings so that the sliding surface of the liner Press the rings against. The high temperature during combustion also causes lower viscosity of the lubricating oil film on the sliding surface, so that the oil film is more easily broken. The risk of oil film destruction is further increased by the relatively slow movement of the piston near its highest position. The slide speeds of the slide surface and the piston ring, which are necessary to maintain the oil film on the slide surface, are very low. During the expansion stroke, the piston is pushed downward and most of the pressure increase occurs in the first half of the expansion stroke, after which the pressure decreases relatively slowly, and the pressure is generally approximately just before the piston passes through the submachine. The pressure of the scavenging air can be reduced. Therefore, the pressure load in the region near the highest position of the cylinder is very large compared to the pressure load in the rest of the cylinder. Thus, the area near the highest portion of the liner becomes the sliding surface portion exposed to the highest load at all points. Various attempts have been made to prevent the delamination occurring in the lower region of the liner from spreading to other portions and spreading to a wider region. Danish patent No. 170430 discloses a cylinder liner having two annular recesses in the form of grooves, which are open only towards the inside of the cylinder and are disposed directly above and just below the prop. The recess collects a portion of the lubricating oil pushed downward by the piston rings during the expansion stroke, and the lagging phenomenon initiated and developed in the area under the balloon by the skirt of the piston in contact with the cylinder liner is directed to the area above the recess. Prevent deployment.

Japanese Patent Laid-Open No. 62-32207 has an inlet for lubricating oil at the top of the liner and a recessed circumferential zigzag oil reservoir disposed at the bottom three quarters of the liner slightly above the prop. Present one cylinder liner. The recess opens only towards the inside of the liner, which serves to improve the distribution of lubricant, during which the piston moves downwards through the recess and the lubricant collects in the recess and is then discharged back into the piston ring. Since the recess is zigzag, oil is dispensed along the ring as the piston moves upwards past the oil reservoir after passing through a lower position below its substructure. Thus, the recess holds lubricant which can be lost in the prop.

These embodiments of the recess of the sliding surface are arranged at the bottom of the liner, which means that the piston ring passes through the recess sufficiently without heavy load, since the pressure in the combustion chamber is low at such a position of the piston.

The sticking occurs through local breakdown of the oil film, whereby the piston ring is in direct contact with the sliding surface, causing the sticking to occur, and the sticking causes local overheating and, if examined later, the thermal liner and piston ring It is known that damage to the material of the can be observed. Formation of the sticking has been assumed to be caused by scuffing of the surface until now due to lack of lubrication, which generates harmful heat during the ongoing operation, causing discoloration of the sticking phenomenon in the material.

It is an object of the present invention to design a cylinder liner in such a way that during operation, sticking between the piston rings and the area of the slide surface where the contact pressure between the piston rings and the slide surface is particularly high is avoided.

The present invention is a diesel type having a sliding surface in the form of a generally cylindrical inner surface and having at least one inwardly opened oil track having only at least one recess opening only inwardly of the cylinder and an outer supply of lubricating oil. A cylinder liner for an internal combustion engine.

1 is a partial side view and a partial longitudinal cross-sectional view of a cylinder liner when the piston is at top dead center.

Figure 2 is an exploded partial view of the top section of a cylinder liner with recesses on the inner surface.

3 is an exploded partial view corresponding to FIG. 2 of a second embodiment of a top section of a cylinder liner with recesses on its inner surface;

4 is an enlarged enlarged fragmentary view of a third embodiment of the top section of a cylinder liner with recesses on its inner surface.

FIG. 5 is an exploded partial view corresponding to FIG. 2 of a fourth embodiment of a top section of a cylinder liner with recesses on the inner surface; FIG.

Fig. 6 is an enlarged cross sectional view of a recess in the sliding surface of a cylinder liner having an associated piston ring and a piston.

For this purpose, the cylinder liner according to the invention comprises a first and a second group each having at least two recesses in which the recesses have a discontinuous range in the circumferential direction of the liner, the recesses of the group Disposed in the upper 15 percent of the length of the slide surface, the other group of recesses are arranged to have mutual separation in the longitudinal direction of the liner, with any line on the slide surface parallel to the axis of the cylinder liner by at least one recess And interalign in the circumferential direction of the liner so as to intersect.

The top of the slide surface is disposed in the longitudinal position of the liner, where the upper piston ring has its top dead center, and the slide surface extends downward to the bottom dead center of the bottom piston ring. Thus, the length of the slide surface is longer than the stroke by approximately the height of the ring pack.

Placing the recess adjacent to the top of the sliding surface of the area with the largest load can, in effect, eliminate the support area for the rings and introduce discontinuous ring support, which results in greater load and increase on the ring. Although this causes a risk of sticking, in spite of such a phenomenon, wear of the ring and liner is reduced because the recesses interfere with the initial formation of the sticking phenomenon.

To date, the general perception of the underlying mechanism of formation is seen to be inaccurate, because it presupposes a constantly gradual process, which leads to the phenomenon of accumulation over time. The sticking phenomenon is initiated by sudden, very local overheating caused by excessive friction between the piston ring and the sliding surface, resulting in short-term total welding between the piston ring and the sliding surface. Such welding phenomenon occurs during expansion stroke by high combustion pressure which pushes the piston ring through the oil film on the slide surface. In addition, since the combustion pressure exerts a very large downward impact on both the piston and the piston ring, the piston ring is immediately destroyed and loosened, and at the same time, the material of the slide surface is destroyed and the slide surface becomes rough. Such breakdown generates more heat, thereby allowing another welding phenomenon. At the same time as the passage of the piston rings continues, the local sticking phenomenon can spread or develop over the wider sliding surface.

Even the placement of very narrow recesses on the slide surface intersecting the direction of movement of the piston rings interferes with the initial initial formation of the phenomenon of sticking in the area around the recess. Increased temperature levels are a prerequisite for the welding phenomenon to occur. If the piston ring breaks the oil film, heat will be generated due to increased friction between the ring and the sliding surface. At the moment the ring passes through the recess of the sliding surface, the heating will temporarily turn into cooling, and since both the piston ring and liner material have a moderately low average temperature, heat is constantly conducted from the heated point of the piston ring. I'm going. Thus, the momentary interruption of heat generation is sufficient to prevent the initial formation of sticking phenomenon.

Apart from leaving the onset of the sticking phenomenon, the recess according to the invention has the additionally known additional advantage of acting as a passive oil reservoir and preventing the developed sticking phenomenon from developing.

It is not straightforward to place a recess in the slide surface at the position where the piston rings are pushed against the slide surface and also where the temperature and the lubricant state become critical as described above. Since the recesses remove some support area for the ring, it risks deformation in the groove of the piston as it passes through the recess, because the relatively thin and elastic ring is exposed to high loads. If the ring is deformed, the ring can be damaged by impinging on the edge of the recess.

Such deformation of the piston rings and consequent wear of the piston ring can be avoided according to the invention, which forms a recess with circumferentially discontinuous areas of the liner and also aligns them with the longitudinal mutual separation of the liner. have. When the piston ring passes through part of the recess, it is supported by the remaining sliding surface between the recesses.

Arranging the discontinuous recesses such that any line on the sliding surface parallel to the axis of the cylinder liner is crossed by at least one recess, any position around the piston rings can cause one or more cooling recesses in each piston stroke. Will pass.

The group of recesses can be formed as grooves extending in the circumferential direction of the liner, which allows simple manufacture of the liner. The grooves may for example be cut or ground into the slide surface.

The group of recesses is preferably arranged at the same longitudinal position of the liner, which requires less positioning steps during machining, thus simplifying manufacturing.

Further, each group of recesses preferably has a full range in the circumferential direction of the liner of up to 80 percent, preferably up to 60 percent, of the circumference of the slide surface. If a group of recesses have a full range in the circumferential direction of the liner of at least 80 percent of the circumference of the slide surface, the piston rings need to have an inadequately high stiffness to avoid excessive deformation of the grooves of the piston ring. . If one group of recesses has the full range in the circumferential direction of the liner up to 60 percent of the circumference of the slide surface, this provides satisfactory support of the piston rings, while only two groups of recesses slide Can cover the entire circumference of

A particularly advantageous balance of the need to avoid the sticking phenomenon against the need to minimize deformation of the piston rings when passing through the recess is achieved by each group comprising at least five, preferably at least eight recesses. Can be. If five, preferably eight recesses are included in each group, the distance between the support regions for the piston ring in the circumferential direction is not large.

Moreover, each group of recesses can be distributed evenly along the circumference of the slide surface, thereby simplifying the manufacture of the liner and minimizing the length of the piston ring section through the recess.

In a suitable embodiment, the sliding surface is intended for use of the piston rings of the piston, the piston rings having a predetermined minimum height, the groups of recesses being smaller than the minimum height of the piston rings, preferably Up to 75 percent of the minimum height, suitably with a height between 1 and 3 mm. If the height of the recess is greater than the minimum height of the piston rings, they will shortcircuit the seal to the sliding surface of the at least one piston ring as it passes through the recess. Since the recesses are placed in the region with the maximum pressure during compression and combustion, this short circuit will negatively affect the engine's efficiency. If the height of the recess is up to 75 percent of the minimum height of the piston ring, it will effectively prevent leakage and improve the support of the piston ring. A recess height of 1 to 3 mm will effectively prevent the formation of a sticking phenomenon, while maintaining good support of piston rings having a ring height of generally 10 mm or more.

Recesses belonging to another group may have a mutual spacing of at least 35 mm in the longitudinal direction of the liner. In this way, interference between stress concentrations in areas around the ends of different groups of recesses is avoided.

The present invention also has at least one inwardly open oil track and cylinder having a substantially cylindrical inner surface constituting a sliding surface for piston rings having a predetermined minimum height of the piston and having an outer supply of lubricating oil. A cylinder liner for a diesel-type internal combustion engine having at least one groove that opens only inwardly of the cylinder liner, wherein the cylinder liner extends around the entire inner surface of the liner and has a minimum height of piston rings. Having a height of less than 30 percent of the grooves, the grooves having a greater depth in the radial direction of the liner than half of their height in the longitudinal direction of the liner and located at the top 15 percent of the length of the sliding surface do.

As a result deformation of the piston rings in the piston ring grooves, accompanied by wear of the piston ring, is prevented in this embodiment by at least one groove having a height of 30 percent or less of the minimum height of the piston rings. Thus, the piston ring is always supported by the sliding surface over an area corresponding to at least 70 percent of the height of the piston ring, and thus can pass through the groove without excessive deformation of the ring groove. As mentioned above, the grooves prevent the onset of lagging.

Proper life of the liner may be achieved by grooves having a depth greater in the radial direction of the liner than half of the height of the groove in the longitudinal direction of the liner. For example, if the minimum height of the piston rings is 6 mm and the sliding surface wears down about 0.02 mm per 1000 hours of operation during normal smooth operation, the groove will be 0.6 mm and last about 3.4 years. It will not wear out completely after operation. In general, marine engines are designed to have approximately two years of continuous operation between every change inspection, and in that respect, the determined depth of the grooves is considered to be a reasonably lower limit.

Each groove may extend along the circumference of the slide surface at a constant longitudinal position of the liner. Thus, as mentioned above, the groove prevents shorting of the piston rings.

Moreover, at least three grooves can be made. Since the grooves according to the present embodiment are relatively narrow, it is advantageous to align three or more grooves adjacent to each other to improve the prevention of the sticking phenomenon.

For the top 10 percent of the length of the sliding surface, the distance between the grooves can be less than eight times the groove height. Due to this relatively adjacent arrangement in the uppermost region of the sliding surface, the formation of a sticking phenomenon in the region of the sliding surface with the largest load can be largely prevented.

In a second embodiment, each groove may extend upwards and downwards between the ends of the cylindrical section of the sliding surface, the height of the section being less than the minimum height of the piston ring. In this way, the grooves prevent shorting of the piston rings, while the support area of the rings is increased with respect to the same area of the grooves.

In the two embodiments of the invention described above, the recesses or grooves are suitably at least 2 mm deep in the newly manufactured liner, without the need for remachining of recesses or grooves on the inner surface. Long lifespan can be guaranteed.

The oil tracks are disposed below the recesses or grooves to prevent the supply of oil from being affected by the high pressure generated at the top of the liner.

The invention will now be described in more detail by way of example with reference to the accompanying drawings.

1 shows a cylinder liner 1 for a large two-stroke crosshead engine. Depending on the size of the engine, cylinder liners can be manufactured in different sizes with bores generally 250 mm to 1000 mm apart and corresponding lengths generally 100 cm to 420 cm apart. The liner 1 is generally made of cast iron and the liner can be made in one piece or divided into several sections and assembled to the extensions of each other. In the case of split liners, the upper section may be made of steel coated with a suitable sliding layer. The crosshead engine of the type described above can have a high effective compression ratio, for example of 1:16-1:20, which results in a high load on the piston rings.

The liner 1 can be mounted to the engine (not shown) in a known manner by placing an annular downward surface 2 on the engine's frame box or the top plate of the cylinder block, and then the piston 3 ) Is mounted to the cylinder liner, and the cylinder cover 4 is placed on top of the liner on the annular upward surface 5 and fastened to the top plate by a cover stud (not shown).

The liner 1 has a substantially cylindrical inner surface, which forms a sliding surface 6 for the piston rings 7 on the piston 3. In the lower section of the cylinder liner, annular rows of small openings 8 are arranged. The piston 3 is movable in the longitudinal direction of the liner between the top dead center and the bottom dead center, in which the upward surface 9 of the piston is arranged in the bore of the cylinder cover 4, at the bottom dead center the upward of the piston The surface is disposed just below the lower end of the apparatus 8. The sliding surface 6 extends from an upper edge 10 disposed just above the top dead center of the top piston ring to a lower edge 11 arranged just below the bottom dead center of the bottom piston ring. A corrugated lubricant track 12 may be disposed on the inner surface of the liner below the upper third branch of the sliding surface, and the inlet 13 for lubrication of the sliding surface 6 on the inner surface of the liner. Lubricating oil is introduced into the lubricating oil track 12 through this.

In the area indicated by (a), which corresponds to the upper 15 percent of the length of the slide surface, a plurality of recesses are arranged in the slide surface 6, which are only open toward the inside of the cylinder liner.

6 is an enlarged longitudinal sectional view of the slide surface 6 and the piston 3 portion. The piston 3 has a piston ring groove 16 in which the piston ring 7 is arranged in a known manner. The piston ring groove 16 is above the piston ring 7 and an annular space in which combustion gases during combustion exist between the lower part of the ring groove 16 and the cylindrical inner surface of the piston ring through the gap 17 from above. (18) It spreads within. Due to the high-pressure combustion gas, the elastic piston ring 7 is pushed in the direction indicated by the arrow with respect to the sliding surface 6 covered with the lubricating oil film 19, so that the piston ring 7 with respect to the sliding surface 6 Seal the piston (3). The sliding surface 6 has a recess 14, which in this embodiment is formed as a groove with sharp edges, but it also has a curved edge 20 at the transition to the sliding surface 6. It may have. When the piston moves up and down, lubricant enters the recess 14.

The height of the recess 14 is significantly smaller than the height of the piston ring 7, so that the piston ring is sufficiently supported by the sliding surface 6 when passing through the recess 14. In a second embodiment (not shown), the height of the recess 14 is greater than the height of the piston ring 7, allowing for constant leakage of gas over one or more of the piston rings 7. do.

If a point 22 on the outer surface of the piston ring 7 is overheated, this point cools down as it passes through the recess 14. Contrary to anticipation, when welding occurs between the point 22 on the piston ring 7 and the sliding surface 6, such welding can be prevented from developing by the point passing through the recess 14, Any unevenness can be made flexible by one of the edges 20 of the recess.

FIG. 2 shows a developed partial view of the top section of the cylinder liner, in which the region a (see FIG. 1) has two groups of recesses 14 on the sliding surface 6. Each group forms a row of recesses arranged to have a gap 21 in the form of a groove 14 disposed along a line perpendicular to the longitudinal axis of the liner. The gap 21 forms a support surface for supporting the piston rings 7 when passing upwards or downwards across the rows of grooves so that the rings 7 do not deform in the ring grooves. The rows of grooves 14 are spaced apart from each other in the longitudinal direction of the liner, with the grooves in the top row slightly overlapping the grooves in the lower row in the circumferential direction, so that any one or more grooves on the sliding surface parallel to the longitudinal direction of the liner ( 14). The grooves are uniformly distributed in the circumferential direction and have the same length. For example, for a cylinder liner 1 of 700 cm diameter, each group suitably comprises grooves having a length of 125 mm, a height of 2-3 mm, and a depth of 2-3 mm, respectively. If only two groups are applied, the top row of grooves may be disposed about 100 to 200 mm from the top edge 10 of the sliding surface, and the bottom row of grooves may be disposed about 50 mm below the top row. . The more groups, the more the anti-sticking effect is improved, but the manufacturing cost of the liner is increased accordingly.

Figure 3 shows another embodiment of a cylinder liner, according to this embodiment, three groups of recesses in the form of grooves 14, 15 are arranged on the slide surface 6, separated from one another in the longitudinal direction of the liner. . Both the upper and lower groups consist of rows of spaced grooves 14 aligned along a line perpendicular to the longitudinal axis of the liner. The middle group consists of rows of grooves inclined alternately upwards and downwards. The grooves overlap slightly in the circumferential direction such that they intersect any one or more grooves 14, 15 on the sliding surface parallel to the longitudinal direction of the liner.

4 shows another embodiment of a cylinder liner, wherein the recesses comprise three groups, each having a row of circular recesses in the form of bores 23. The bores 23 are uniformly distributed and mutually arranged in the circumferential direction, and they have a diameter suitable to slightly overlap in the circumferential direction.

According to the invention, the expression group of recesses should be understood in a broad sense. Regarding the embodiment of Fig. 4, each group can be understood as three bores arranged obliquely to each other since the groups are arranged in a circumferential direction. One group of recesses may include recesses aligned at different longitudinal positions of the liner.

Figure 5 shows another embodiment of the present invention wherein the recess comprises five narrow circular grooves 24, which extend continuously around the entire circumference of the slide surface and are arranged adjacent to each other. The height of the grooves is up to 30 percent of the minimum height of the piston ring, which is roughly equivalent to the contour of FIG. These narrow grooves allow the piston ring to pass through the grooves without causing deformation to cause the edges of the ring to collide against the edges of the grooves.

Within the scope of the present invention, it is possible to form recesses having various other forms, for example, corrugated courses, straight or angular courses, and also combine other embodiments. For example, when the recesses have a small height, discontinuous recesses may be arranged closer to each other in the circumferential direction.

Placing recesses or grooves in the top region of the slide surface exposed to the greatest load can have a destructive effect on the mechanism causing the delamination. If there is no sticking in the top region, the piston rings cannot actually cause the sticking because the load on the slide is much less.

Claims (15)

At least one having a sliding surface in the form of a generally cylindrical inner surface 6 and having at least one recess 14, 15, 23 opening only toward the inner side of the cylinder and an outer supply 13 of lubricating oil In a cylinder liner (1) for a diesel internal combustion engine having an inwardly open oil track (12), the recesses (14, 15, 23) have at least two recesses having a discontinuous range in the circumferential direction of the liner ( At least a first and a second group having 14, 15, 23, respectively, the recesses 14, 15, 23 of the group being disposed in the upper 15 percent of the length of the sliding surface 6, and the other group. Recesses 14, 15, 23 of the liner are arranged to have mutual separation in the longitudinal direction of the liner 1 and at least one recess 14 on any line on the sliding surface 6 parallel to the axis of the cylinder liner. Circumferentially aligned with the liner so that they intersect by Diesel-type internal combustion engine according to Gong a cylinder liner (1). The cylinder liner (1) according to claim 1, characterized in that the recesses of the group are formed as grooves (14) extending in the circumferential direction of the liner. The cylinder liner (1) according to claim 1 or 2, characterized in that the group of recesses (14, 15, 23) are arranged in the same longitudinal position of the liner (1). 4. The circumferential entirety of the liner according to claim 1, wherein the recesses 14, 15, 23 of each group are up to 80 percent, preferably 60 percent, of the circumference of the sliding surface 6. Cylinder liner (1) for a diesel internal combustion engine, characterized in that it has a range. 5. The cylinder liner for a diesel internal combustion engine according to claim 1, wherein each group comprises at least five, preferably at least eight recesses 14, 15, 23. One). 6. A cylinder liner for a diesel engine according to any one of claims 1 to 5, characterized in that the recesses (14, 15, 23) of each group are evenly distributed along the circumference of the sliding surface (6). (One). The sliding surface 6 is intended for use of the piston rings 7 of the piston 3, wherein the piston rings 7 have a predetermined minimum height. The recesses 14, 15, 23 of the group have a height smaller than the minimum height of the piston rings 7, preferably at most 75 percent of the minimum height, suitably between 1 and 3 mm apart. A cylinder liner (1) for a diesel internal combustion engine, characterized in that. 8. A diesel internal combustion engine according to any one of the preceding claims, wherein the recesses (14, 15, 23) belonging to different groups have at least 35 mm of mutual spacing in the longitudinal direction of the liner (1). Cylinder liner (1). At least one of the pistons 3 having a substantially cylindrical inner surface constituting the sliding surface 6 for the piston rings 7 having a predetermined minimum height and having an outer supply 13 of lubricating oil. In a cylinder liner (1) for a diesel internal combustion engine having an inwardly open oil track (12) and at least one groove (24) opening only toward the inside of the cylinder, the at least one groove (24) is a liner ( Extending around the entire inner surface 6 of 1) and having a height of no more than 30 percent of the minimum height of the piston rings 7, the grooves 24 having their height in the longitudinal direction of the liner 1. A cylinder liner (1) for a diesel internal combustion engine, characterized in that it is located at the top 15 percent of the length of the slide surface (6), having a greater depth in the radial direction of the liner than half. 10. The cylinder liner (1) according to claim 9, wherein each groove (24) extends along the circumference of the sliding surface (6) at a constant longitudinal position of the liner (1). A cylinder liner (1) for a diesel engine according to claim 9 or 10, characterized in that the grooves (24) comprise at least three grooves (24). 12. Diesel according to one of the claims 9 to 11, characterized in that at the top 10 percent of the length of the sliding surface 6, the spacing between the grooves 24 is less than eight times the height of the grooves. Cylinder liner for internal combustion engines (1). 13. The groove according to any one of claims 9, 11 or 12, wherein each groove 24 extends upwardly and downwardly between the ends of the cylindrical section of the slide surface 6, the height of which is a piston ring (14). Cylinder liner (1) for a diesel internal combustion engine, characterized in that it is smaller than the minimum height of 7). 14. A diesel internal combustion engine according to any of the preceding claims, wherein the recesses (14, 15, 23, 24) or grooves have a depth of at least 2 mm in the newly manufactured liner (1). Cylinder liner (1). The cylinder liner (1) according to any one of the preceding claims, characterized in that the oil track (12) is arranged under the recesses (14, 15, 23, 24) or grooves. ).