KR100475584B1 - An internal combustion engine for driving a propeller shaft - Google Patents

Abstract

The rearmost main bearing 5 of the internal combustion engine is aligned between the throw of the crankshaft and the thrust cam of the thrust bearing. Thrust segments 20 are aligned between the forward-facing sliding surface 22 on the thrust cam and the rearward-facing support surface 18 on the fixed main bearing housing. In the peripheral region, the thrust cam 14 has an arc-shaped recess 28 which is rotationally symmetrical, which extends radially inward to the middle level of the thrust segment 20 at most.

Description

AN INTERNAL COMBUSTION ENGINE FOR DRIVING A PROPELLER SHAFT}

The present invention has a thrust bearing in the rearmost main bearing disposed between the throw of the crankshaft in the axial direction of the crankshaft and the thrust cam of the thrust bearing. An internal combustion engine for driving, wherein the thrust cam is rotatable with a crankshaft and is disposed between an axially oriented support surface on the fixed housing of the main bearing of the pedestal of the internal combustion engine and an axially forward sliding surface on the thrust cam. Thrust segments are aligned.

If the internal combustion engine has such a thrust bearing incorporated in the pedestal at the rearmost main bearing of the engine, it is advantageously a short engine. Such engines are generally the main engines of large ships, such as container ships, where very large torque must be transmitted from the engine to the propellers through the propeller shaft. When the propeller propels the ship forward, it exerts a forward-facing force on the propeller shaft that is transmitted through the pedestal to the thrust bearing against the engine foundation.

The transfer of force from the rotating shaft to the pedestal is through thrust segments, which are substantially fixed relative to the support surface on the main bearing housing. The sliding surface on the thrust cam slides on the bearing surface of the thrust segment, and a lubricant film is maintained between the bearing surface and the sliding surface by the lubrication system of the thrust bearing.

Each thrust segment is individually adjusted with respect to the thrust cam, and the total load capacity of the thrust bearings corresponds to the sum of the load capacities of each thrust segment. Therefore, it is desirable for the load capacity of the thrust segments to be fairly uniform in operation, which becomes difficult in a thrust bearing incorporated in the main bearing, because the thrust segment in the upward sector opposite the removable upper part of the main bearing. Because they do not exist. Therefore, the upper part of the thrust cam is generally not axially supported by the thrust segment.

It is an object of the present invention to improve the load capacity of a thrust bearing of an internal combustion engine.

According to this object, the internal combustion engine of the present invention is characterized in that in the peripheral region, the thrust cam has a rotationally symmetric arc-shaped recess that extends radially inwards to the level of the center of the thrust segments at most.

In full load operation, where the load capacity of the thrust bearing is maximally utilized, the arc-shaped recess in the peripheral region is such that the thrust cam is pressed slightly less firmly against the radially outermost region of the thrust segment in the peripheral region. it means.

First, it means that the thrust center is moved slightly inward radially. The fixing part of the main bearing is formed integrally with the transverse wall of the pedestal, which transverse wall is made of heavy material and has rib-shaped reinforcement. Thus, the support surface is more rigid in its radially outermost region than in the radially innermost region adjacent to the shaft hole of the main bearing. Under operating loads, the region with greater stiffness of the support surface is less deformed in the axial direction, which causes the greatest load in the radially outermost region of the thrust segments. The arc-shaped recess of the thrust cam reduces the axial pressure from the thrust cam of the radially outermost region, thus compensating for greater rigidity of the support surface of the region.

Secondly, the arc-shaped recess provides a more uniform pressure distribution in the region of the thrust bearing, in which the thrust cam changes from an unsupported state to a supported state. In the unsupported area of the thrust cam, its peripheral area tends to be deflected, and upon successive downward rotation of the peripheral area into the supported area, the deflection will be reduced, which is the first placed thrust segment Expose them to extra load. Partial compensation for such excess load is provided by the arc-shaped recess, which reduces the thrust load on the segment, especially in the radially outermost region where the thrust cam deflection is greatest.

If the recess extends further radially inward than in the middle of the thrust segments, an undesirable reduction of the largest thrust that can be delivered by the segment may occur.

Preferably, the arc-shaped recess extends inwardly to the level of the radially outermost 30 percent of the thrust segments at the maximum, because the radially innermost region that may have the greatest impact on the thrust is thrust. This is because it can include advantageously large areas of the segment.

In a suitable embodiment, the arc-shaped recess is disposed on the outer surface of the thrust cam. The recess provides greater deflection flexibility in the radially outermost region of the thrust cam. When the load on the thrust bearing is low, the pressure on the thrust cam is too low to deform the thrust cam, and the sliding surface can extend substantially parallel to the support surface. If the pressure on the thrust cam is high, the radially outermost region opposite the recess will deflect laterally towards the recess due to the greater flexibility provided by the recess. Such a deflection means that most of the thrust load is absorbed by the radially inner region of the thrust segments. Thus, this embodiment provides the advantage that the sliding surface alone, depending on the load, is adjusted to a shape such that an effective and appropriate thickness of lubricant film can be maintained between the thrust segment and the sliding surface.

In one embodiment, the arc-shaped recess is associated with at least one tube for supplying coolant. By supplying coolant which is a normal lubricant to the arc-shaped recess, cooling to both the front and the rear of the radially outermost region of the thrust cam is achieved, so that the temperature can be kept lower, which is, more Cooled lubricant can be pressurized to deliver greater thrust without loss, contributing to improved load capacity. Since such coolant does not need to lubricate the arc-shaped recess, the feed rate can be adapted only to the cooling needs.

In one embodiment, the thrust cam of the internal combustion engine has a radially projecting collar, to which the sprocket wheel is fixed at a position disposed radially outward of the arc-shaped recess. In some cases, a thrust bearing may be provided, for example, to the chain drive for the camshaft at the rear end of the engine, in which case the sprocket wheel may be of the thrust cam provided by the arc-shaped recess. It is possible to limit the flexibility of the radially outermost region. By fixing the sprocket wheel to the collar, the sprocket wheel is rh-set to the thrust cam only at one side of the arc-shaped recess, so that the other side of the recess sufficiently retains the desired flexibility.

In a variant design, the thrust cam has two cylindrical surfaces axially on respective sides of the arc-shaped recess, with two annular members of the sprocket wheel being connected to each one of the cylindrical surfaces. It is fixed. Dividing the sprocket wheel into two members having appropriate mutual flexibility in the axial direction also prevents the sprocket wheel from losing flexibility in the radially outermost region of the thrust cam.

Alternatively, arc-shaped recesses may be provided on the sliding surface facing forward in the axial direction of the thrust cam. However, this creates a larger gap in the radially outermost region than in the radially innermost region between the bearing surface and the sliding surface of the unloaded thrust bearing, which leads to an oil film in the radially outermost region at low load. Can be thicker. However, this does not cause operational problems. If the thrust bearing is sufficiently loaded and the radially outermost region is deflected more than the radially innermost region, a more uniform gap will be formed between the sliding surface and the support surface, which will result in a uniform load on the thrust segments Promote an increase in load capacity.

Due to a more uniform load throughout the radial range of thrust segments, the present invention is particularly advantageous for diesel type large two-stroke crosshead engines having a maximum continuous power of at least 40,000 kW. For example, due to the very large power typically delivered at low rpms, such as the rpm range of 70 to 200, the axially oriented thrust force becomes very large, and the thrust bearings With thrust segments. Thus, the film thickness between the segments and the sliding surface is smaller than the size of the thrust segments, and an irregular distribution of thrusts across the segments can have a significant effect on the load capacity.

Embodiments of the present invention will now be described in more detail with reference to the schematic accompanying drawings.

1 shows an internal combustion engine 1 connected to a propeller shaft 3 with a propeller 4 through an intermediate shaft 2. The engine may be a two-stroke engine or a four-stroke engine, such as Applicants' ME or MC type two-stroke crosshead engines well known to those skilled in the art. The engine may have, for example, a bore in the range of 30 to 120 cm, a number of cylinders in the range of 5 to 20, and an rpm in the range of 60 to 300 rpm for a crosshead engine. . The output of the engine can be in the range of 3,000 to 130,000 kW, for example. The engine preferably has a relatively large power, such as at least 3,000 kW, at least eight cylinders and a bore of at least 70 cm.

In the rearmost main bearing 5 for the crankshaft 6 of the engine, the internal combustion engine 1 has a thrust bearing 7 shown in the rear view in FIG. 2 and in the longitudinal section in FIG. The main bearing 5 has a fixed housing molded integrally with the transverse wall in the pedestal 8 of the engine. The wall is reinforced by a relatively large rib 9 so as to have great rigidity. The main bearing housing also includes a removable top 10. The main bearing housing faces the bearing metal 11 on the inner surface forming the shaft bore, the journal 12 is aligned and connected to the crank arm 13 at the rearmost throw of the crankshaft, It is formed integrally with the thrust cam 14. On the rear side of the thrust cam, the same shaft portion continues to the journal 15 journaled to the rearmost shaft bearing 16. The journal 15 terminates in a flange 17 for fastening with the propeller shaft 3 directly or with the intermediate shaft 2, depending on the spacing between the engine rear end and the stern tube of the hull.

On the rear side of the fixed main bearing housing there is a support surface 18 extending annularly around the lower part of the main bearing in a plane substantially perpendicular to the longitudinal centerline 19 of the main bearing. In the embodiment shown, the support surface extends beyond 22/36 of the shaft circumference. On the support surface, several, for example eight Mitchell type thrust segments 20 are aligned. The segments are held in place by yokes 21 extending axially past the sides of the two top thrust segments so that they do not rotate with the thrust cams. The yoke 21 is removable, which enables the removal of thrust segments without the removal of the shaft with the thrust cam from the thrust bearing. Instead of the yoke, two protruding collars may be used on the removable portion on the main bearing housing, or two separate end stops may be used which are removably fixed to the bearing housing.

On the side facing the support surface, the thrust segments 20 have radially extending edges, with which the segments can be deflected with respect to the edges and are thus adjusted with respect to the load from the thrust cams. The thrust segments are planes on their opposing bearing surfaces facing towards the thrust cam.

The thrust cam has a sliding surface 22 facing forward, which is rotationally symmetrical and extends substantially parallel to the support surface 18. By the forward axial force corresponding to the thrust of the propeller, the sliding surface is pressed towards the thrust segment, but a lubricating oil film is formed continuously between the sliding surface and the bearing surface of the thrust segment. The lubricant is provided from the delivery tube 23 which supplies lubricant to the U-shaped distributor tube 24. The distributor tube passes downward past the radially innermost section of the thrust segment, as indicated by the segment on the right side of FIG. Several spray tubes 25 branch off from the distributor tube, for example to lubricate the thrust segment in such a way that a separate spray tube is arranged in each thrust segment.

The thrust segments mentioned above are only valid when the ship is propelled forward by the engine 1. If the engine is fixed to a propeller shaft with a fixed-pitch propeller, it is necessary to reverse the operation of the engine to reverse the ship.

In order to absorb the axially oriented shaft forces that occur upon reversal, the thrust bearing has a second thrust segment 27 with the thrust cam aligned on an axial forward facing support surface in front of the shaft bearing 16. It can be designed as a double acting thrust bearing with a second annular sliding surface 26 associated with it.

Around the radially outward direction of the thrust cam, the thrust cam shown in FIG. 3 has an arc-shaped recess 28 extending rotationally symmetrically around the entire circumference of the thrust cam. The arc shape may in each case be selected in accordance with the stress of the thrust cam prevailing for the engine. The arc shape can be, for example, parabolic, oval or any other shape that is properly curved.

The spacing shown in FIG. 3 extends radially from the circumference of the thrust cam to the starting level of the recess 28 to a point about the middle level of the range of thrust segments in the radial direction. In the embodiment of Figure 3, the recess extends radially over a radial distance corresponding to about 25 percent of the range of thrust segments. For the transfer of large thrust forces, it is advantageous for the widest possible part of the thrust segment to be supported by the rigid insulator material of the thrust cam. The recess can reduce the axial rigidity of the thrust cam so that the radially outermost region of the thrust cam can be flexibly axially bent.

The sprocket wheel 29 can be aligned around the thrust cam 14. The sprocket wheel is shaped as a toothed rim, in which the number of rows of teeth 30 corresponds to the number of chains in the chain drive. 4 shows an embodiment in which the sprocket wheel 29 is fixed to a collar 31 which projects radially from the outer surface of the thrust cam. The sprocket wheel associated with the collar 31 can be freely adjusted in the axial direction. In the embodiment of Fig. 4, the rearmost row 30 of teeth is arranged in the axial displacement position with respect to the fixing collar 31. Alternatively, it is also possible to mount a sprocket wheel having a row of teeth 30 arranged axially symmetrically on both sides of the collar 31. In such a case, the sprocket wheel can be shrunk onto the collar or secured with bolts extending radially and / or axially.

Figure 5 shows a variant embodiment in which the sprocket wheel is divided into two annular members 32, with each annular member being shrink fit to the cylindrical surface 32 on the outer surface of the thrust cam. The two annular members 32 are elastic to one another in the axial direction.

6 shows another embodiment in which the arc-shaped recess 28'is disposed on a sliding surface 22 opposite the thrust segment. The recess 28 'may have a parabolic course or any other course that provides a suitable stress distribution for the material. When the bearing is no load, the radially outermost edge is arranged at a distance b further spaced from the bearing surface on the thrust segment 20. When the bearing is to be fully loaded, the radially outermost region of the thrust cam is arranged to be axially deformed towards the thrust segment. The deformation is such that the sliding surface and the support surface are substantially parallel at full load.

Details from the various embodiments described above can be combined in a new embodiment.

According to the present invention there is an advantage that the load capacity of the thrust bearing of the internal combustion engine for propeller shaft driving is improved.

1 is a side view of an internal combustion engine according to the present invention.

FIG. 2 shows a rear view of the thrust bearing of the internal combustion engine of FIG. 1.

3 shows a cross-sectional view of the thrust bearing of FIG. 2.

4 and 5 show segments of the portion corresponding to FIG. 2 of another embodiment of the present invention.

Figure 6 shows a cross section of a thrust cam and a thrust segment of a further embodiment.

Claims (9)

It has a thrust bearing in the rearmost main bearing disposed between the throw of the crankshaft 6 and the thrust cam of the thrust bearing in the axial direction of the crankshaft, the thrust cam being rotatable together with the crankshaft, In an internal combustion engine for driving a propeller shaft in which the thrust segments 20 are aligned between an axially oriented support surface 18 on the stationary housing of the main bearing of the pedestal 8 and an axially forward sliding surface on the thrust cam, The thrust cam has a rotationally symmetric arc-shaped recess 28, 28 ′ extending radially inwardly up to the level of the center of the thrust segments 20 in a section facing the thrust segment. An internal combustion engine for driving a propeller shaft. 2. The internal combustion engine according to claim 1, wherein the arc-shaped recess (28 ′) extends inwardly to a level of radially outermost 30 percent of the thrust segments (20) at a maximum. An internal combustion engine according to claim 1, characterized in that the arc-shaped recess (28) is arranged on an outer surface of the thrust cam. 4. Internal combustion engine according to claim 3, characterized in that the arc-shaped recess (28) is associated with at least one tube for supplying coolant. 5. The sprocket wheel according to claim 3 or 4, wherein the thrust cam has a radially projecting collar, the collar having a sprocket wheel in a position disposed radially outward of the arc-shaped recesses 28, 28 '. An internal combustion engine, characterized in that 29 is fixed. 5. The thrust cam according to claim 3 or 4, wherein the thrust cam has two cylindrical surfaces axially on each side of the arc-shaped recess 28, and two of the sprocket wheels on each of the cylindrical surfaces. Internal combustion engine, characterized in that two annular members (32) are fixed. 7. An internal combustion engine according to claim 6, wherein the two annular members of the sprocket wheel are mutually flexible in the axial direction. 3. An internal combustion engine according to claim 1 or 2, characterized in that the arc-shaped recess (28 ') is arranged on the sliding surface (22) of the thrust cam facing forward in the axial direction. An internal combustion engine according to claim 1, wherein said internal combustion engine is a diesel two-stroke crosshead engine having a maximum continuous power of at least 40,000 kW.