WO2000040850A1 - Reciprocating piston engine - Google Patents

Abstract

The invention relates to a reciprocating piston engine comprising at least one cylinder whose cylinder liner (2) is provided with at least one groove (9) which forms an oil pocket (8) and which is situated in the area of the running surface (4) of said liner, whereby the running surface (4) faces the piston (6) assigned to the cylinder. The aim of the invention is to create a particularly protective operating mode and thus attain a particularly long service life of the cylinder liner (2). To this end, the groove (9) has a depth which corresponds to the maximum depth of the wear of the cylinder liner (2). A filling (10) is allocated to said groove (9). The material used for the filling (10) in the groove (9) has a lower capacity of resistance to wear than the basic material of the cylinder liner (2).

Description

 Reciprocating machine

The invention relates to a reciprocating piston machine, in particular a large two-stroke diesel engine, with at least one cylinder, the cylinder liner of which is provided with at least one groove in the region of its running surface facing the associated piston to form an oil pocket.

A reciprocating internal combustion engine of this type is known from GB 1773058. In this known arrangement, the cross section of the oil pocket or oil pockets corresponds to the cross section of the respectively assigned groove cut into the cylinder liner. The depth of the grooves decreases with increasing wear on the cylinder liner. To the same extent, the depth of the oil pockets formed by the grooves themselves decreases in the known arrangement. Conditions therefore deteriorate with increasing service life. Another, very particular disadvantage of the known arrangement is, however, that material particles that have broken out of the cylinder liner due to possible heat corrosion etc. cannot be fixed in the grooves of the known arrangement. There is therefore a risk that these material particles between Cylinder liner and piston arrive and are ground or crushed there, which can lead to damage and to strong local heating and thus to acceleration of heat corrosion and / or seizure. The known arrangement therefore proves to be insufficiently reliable.

Proceeding from this, it is therefore the object of the present invention to improve the generic arrangement while avoiding the disadvantages described with simple and inexpensive means in such a way that a high level of operational reliability is achieved over a long period of time.

This object is achieved according to the invention in that a filling is associated with the groove, the depth of which corresponds at least to the maximum wear thickness of the cylinder liner, and in that the material forming the filling of the groove has a lower wear resistance than the base material of the cylinder liner.

When new, the groove can be completely closed due to the assigned filling. The result is a smooth, non-profiled surface that can be easily processed. Already during the running-in phase, as a result of the faster wear of the filling material compared to the base material, the desired oil pocket is formed, the depth of which, however, is smaller than the depth of the groove and progresses to an extent dependent on the wear of the cylinder liner. Despite the decreasing depth of the groove, there are therefore largely balanced conditions over a long period of time with respect to the cross section of the oil pocket, which is a long-term one Reliable lubrication is guaranteed in the assigned area of the cylinder liner and thus reliably prevents heat corrosion and seizing. The depth of the oil pocket or pockets that form correlates with the degree of wear. The greater the wear, the deeper the oil pockets and accordingly the more intensive the lubrication and vice versa. It practically results in a kind of self-regulation. It is therefore also possible to reduce the specific oil consumption. Another, very special advantage of the measures according to the invention can be seen in the fact that, as a result of unavoidable wear, material particles escaping from the cylinder liner can be pressed into the comparatively soft filling material and thus fixed. The free movement of these material particles is therefore stopped by the groove provided with a filling. The groove according to the invention provided with a filling accordingly also functions as a highly effective stop groove. The measures according to the invention thus also effectively prevent damage and malfunctions which can be caused by material particles broken out of the cylinder liner, for example material welding or caking, which would lead to an acceleration of heat corrosion and seizure. The measures according to the invention therefore advantageously ensure a long service life.

Advantageous refinements and appropriate further training of the higher-level measures are specified in the subclaims. Thus, the material forming the filling of the groove can expediently have greater thermal expansion than that Have the basic material of the cylinder liner. The result of this is that the filling expands faster than the base material in the event of overheating, as a result of which the piston is stabilized and so-called seizure can be prevented. This advantage is further increased if the filling material also advantageously has dry lubrication properties.

In an advantageous embodiment of the superordinate measures, the filling of the groove can at least partially consist of aluminum and / or aluminum bronze and / or graphite, wherein preferably an aluminum bronze with 9-11% Al, 0.5-2% Fe and the rest Cu can be used. A material of this type has the desired properties mentioned above to an excellent degree. But it would also be conceivable, e.g. to use a graphite alloy with preferably 15-25% graphite and 75-85% aluminum bronze. This material also has the desired properties to a high degree.

At least one helical groove can advantageously be provided. This results in a particularly good distribution and a particularly good transport of the oil over a larger area of the cylinder liner and thus particularly high reliability.

According to a further advantageous embodiment of the superordinate measures, the filling can be designed as a welding or spraying application, depending on the suitability of the materials used. This easily ensures a non-porous filling with reliable adhesion to the base material. Further advantageous refinements and expedient further developments of the superordinate measures are specified in the remaining subclaims and can be found in more detail in the following description of the examples with reference to the drawing.

In the drawing described below:

1 shows a cylinder of a large two-stroke diesel engine, partly in section,

FIG. 2 shows an enlarged representation of a region of the running surface of the cylinder liner provided with a groove according to the invention,

Figure 3 shows a variant with respect to the groove cross section and

Figure 4 shows another variant with respect to the groove cross section.

The present invention is used in reciprocating engines, in particular reciprocating internal combustion engines, preferably in the form of slow-running two-stroke large diesel engines. The structure and mode of operation of such arrangements are known per se and therefore require no further explanation in the present context.

The cylinder of a large two-stroke diesel engine shown in FIG. 1 contains a cylinder liner 2 provided with inlet slots 1, one of which is not shown here Exhaust arrangement containing cylinder head 3 is placed. The inside of the cylinder liner 2 is designed as a running surface 4 with which a piston 6 provided with circumferential piston rings 5 cooperates. The tread 4 is supplied with lubricating oil via lubricating oil supply lines 7.

In order to achieve a good distribution of the lubricating oil and in particular a good supply of lubricating oil from areas in which experience has shown that the supply of lubricating oil is inadequate, for example the upper area of the running surface 4, this is provided with suitable oil pockets 8, which are only indicated in FIG.

For this purpose, as can best be seen from FIG. 2, at least one incised groove 9 is provided in the area of the tread 4, in which an associated oil pocket 8 is formed. The groove 9 contains a filling 10, which consists of a material whose wear resistance is less than the wear resistance of the base material on which Z3dinderbucb.se is based. The cylinder liner is usually made of cast steel. An aluminum bronze can advantageously be used to form the filling 10. As experiments have shown, this should contain at least 2-20%, preferably 9-11% Al, 0.5-8%, preferably 0.5-2% Fe and a Cu residue. The special composition depends on the circumstances of the individual case. The higher the proportion of Fe, the greater the hardness of the material. In the case of a cylinder liner of a two-stroke large diesel engine, good results were achieved with an aluminum bronze with the following components: 2-20%, preferably 9-11% AI, 0.5 - 8%, preferably 0.5 - 2% Fe,

0.1-8% Mu, 0.1-2% Si, 0.1-1% Ni,

0.1-2% C, at least one of the components Sb, Co, Be, Cr, Sn,

Cd, Zn, Pb each with at most 5 - 20% and the rest Cu.

However, it would also be conceivable to use a graphite alloy such as nickel graphite or silicon graphite or aluminum graphite or aluminum bronze graphite, each with 5-60%, preferably 15-25% graphite and a proportion of 40-95%, preferably 75 - Use 85% of the other component. With an aluminum bronze graphite alloy, particularly good properties against corrosion and seizure can be achieved. The composition of the aluminum bronze can correspond to the composition mentioned above.

The filling 10 can advantageously be introduced into the previously produced groove 9 as a spray application applied by laser spraying or arc spraying, such as plasma spraying. Of course, the filling 10 of the groove 9 can also be produced as a welding job. An aluminum bronze with 9 - 11% Al, 1 - 3% Fe, 4 - 6% Ni, 1 - 2% Mu and the rest Cu is particularly suitable for this.

The filling of the groove 9 is advantageously carried out to the level of the tread 4. Then the tread 4 can be continuously machined, for example honed. Due to the lower wear resistance of the material forming the filling 10 compared to the base material of the cylinder liner 2, the wear of the filling 10 is already higher during the running-in phase than the wear of the cylinder liner 2. The removed material is washed away by the lubricating oil. This results in the desired oil pocket 8, which is retained throughout the life of the cylinder liner 2.

The depth of the groove 9 indicated at d in FIG. 2 therefore corresponds at least to the wear thickness of the cylinder liner 2 and is preferably somewhat larger. However, since this deep groove 9 is provided with the filling 10, which also wears as a function of the wear of the cylinder liner 2, with only a somewhat faster wear taking place, the cross section of the groove 9 is largely balanced over the entire service life of the cylinder liner 2 even different cross-sectional configurations of the oil pocket 8.

To form the filling 10, a material can advantageously be used which has the property that when heated it expands more than the base material on which the cylinder liner is based. The material proposed above has this property. In the event of local overheating, the filling 10 therefore expands more than the base material on which the cylinder liner 2 is based, as a result of which the piston 6 can be stabilized, as indicated in FIG. 2 by an elongation line 11 shown in broken lines. The material proposed above for the filling 10 also has good dry lubrication properties, which is particularly advantageous in the event of overheating. However, it would also be conceivable to integrate or embed an additional material with good dry lubrication properties in the filling material. One or more grooves 9 can be provided. These are expediently arranged where, according to previous experience, the risk of insufficient lubrication and, accordingly, the risk of heat corrosion etc. is great. This is especially the case in the upper area of the tread 4. In FIG. 1, a circumferential groove with a corresponding oil pocket 8 is provided in the region of the running surface 4 delimited by the first and second piston rings 5 in the top dead center position of the piston 6. Another groove with an associated oil pocket 8 is provided in the area below the lowest piston ring 5. In the example shown, further oil pockets 8, which are arranged even deeper, are indicated.

The grooves 9 on which the oil pockets 8 are based can be designed as circumferential radial grooves. Additionally or alternatively, one or more helically extending grooves 9 with an associated oil pocket 8 can also be provided. These can extend over an area or over the entire length of the tread 4.

The figure 2 is based on a helical groove 9. The pitch of this groove 9 indicated at P can be 1.5% to 20% of the diameter D of the tread 4. The pitch P can be constant over the entire length of the groove. However, a variable slope would also be conceivable in order to obtain a greater oil pocket density in particularly endangered areas than in less endangered areas. The above-mentioned depth d of the groove 9 is expediently in the range between 0.1% - 0.4% of the diameter D. The starting width w is expediently 1% - 2% of the diameter D. In the examples shown, the groove 9 has a cross section narrowing inwards from the starting width w. This takes into account the fact that the wear rate increases with increasing service life. In Figure 2, the groove 9 has an approximately U-shaped cross section with flanks inclined with respect to the groove bottom. The angle of inclination of the flanks indicated at α can be in the range between 30 ° - 60 °. The transitions between the groove bottom and the groove flanks are appropriately rounded, as indicated by a radius arrow.

The above design information also applies to the other variants on which FIGS. 3 and 4 are based. FIG. 3 shows a V-shaped groove 9 with an associated filling 10 containing the oil pocket 8. The groove 9 on which FIG. 4 is based has a cross-section in the form of a segment of a circle. This also results in an inwardly narrowing cross section and accordingly an inwardly decreasing width of the filling 10 and the oil pocket 8 formed therein.

Claims

claims 1. reciprocating piston machine, in particular a two-stroke large diesel engine, with at least one cylinder, the cylinder liner (2) of which in the area of its running surface (4) facing the associated piston (6) is provided with at least one groove (9) to form an oil pocket (8), characterized in that the groove (9), the depth of which corresponds at least to the maximum wear thickness of the cylinder liner (2), is assigned a filling (10) and in that the material forming the filling (10) of the groove (9) has a lower wear resistance than that Has basic material of the cylinder liner (2) 2. Reciprocating piston machine according to claim 1, characterized in that the material (10) of the groove (9) forming material has a greater thermal expansion than that of the cylinder liner (2) underlying material. 3. Reciprocating piston machine according to one of the preceding claims, characterized in that the material (10) of the groove (9) forming material has dry lubrication properties. 4. reciprocating piston machine according to one of the preceding claims, characterized in that the filling (10) the groove (9) forming material consists at least partially of aluminum and / or aluminum bronze and or graphite. 5. Reciprocating piston machine according to claim 4, characterized in that the aluminum bronze used to form the filling (10) of the groove (9) contains at least aluminum, iron and copper. 6. Reciprocating piston machine according to one of the preceding claims, characterized in that the aluminum bronze used to form the filling (10) of the groove (9) contains at least the following alloy components: 2 - 20%, preferably 9 - 11% Al 0.5 - 8%, preferably 0.5 - 2% Fe and a balance Cu. 7. Reciprocating piston machine according to claim 5 or 6, characterized in that the aluminum bronze used to form the filling (10) of the groove (9) has the following alloy components: 2 - 20%, preferably 9 - 11% AI, 0.5 - 8%, preferably 0.5 - 2% Fe, 0.1-8% Mu, 0.1-2% Si, 0.1-1% Ni 0.1-2% C, at least one of the components Sb, Co, Be, Cr, Sn, Cd, Zn, Pb each with a maximum of 5 - 20% and the rest Cu. 8. Reciprocating piston machine according to one of claims 4-7, characterized in that the filling (10) of the groove (9) forming material 5-60%, preferably 15-25% graphite and 40-95%, preferably 75-85% Contains aluminum and / or aluminum bronze and / or nickel and / or silicon. 9. Reciprocating piston machine according to one of the preceding claims, characterized in that at least one helical groove (9) is provided. 10. Reciprocating piston machine according to one of the preceding claims, characterized in that at least one groove (9) is provided at least in the upper region of the cylinder liner (4). 11. Reciprocating piston engine according to one of the preceding claims, characterized in that at least one groove (9) is provided at least in the region of the running surface (4) delimited by the first and second piston rings (5) in the top dead center position of the piston (6). 12. Lifting piston machine according to one of the preceding claims, characterized in that at least one groove (9) is provided at least in the region below the lowermost piston ring (5) in the top dead center position of the piston (6). 13. Reciprocating piston machine according to one of the preceding claims, characterized in that at least one groove (9) passes over the guide length of the tread (4). 14. Reciprocating piston machine according to one of the preceding claims, characterized in that the pitch of a helical groove (9) is 1.5% - 20% of the diameter of the tread (4). 15. Reciprocating piston machine according to one of the preceding claims, characterized in that the depth of the groove (9) is 0.1% - 0.4% of the diameter of the tread (4). 16. Reciprocating piston machine according to one of the preceding claims, characterized in that the Initial width of the groove (9) is 1% - 2% of the diameter of the tread (4). 17. Reciprocating piston machine according to one of the preceding claims, characterized in that the groove (9) has an inwardly tapering cross section. 18. Reciprocating piston machine according to one of the preceding claims, characterized in that the filling (10) of the groove (9) is designed as a welding or spray application.