HK1121794B - Two-stroke large diesel engine - Google Patents

Description

Two-stroke large diesel engine

Technical Field

The invention relates to a two-stroke large diesel engine.

Background

One such arrangement is known from DE 10161438 a 1. The supply of oil to the annular gap between the guide surface of the guide sleeve and the valve stem ensures that combustion residues from the exhaust channel are reliably prevented from entering the annular gap, which in the past would lead to corrosion of the valve stem and damage to the sealing ring of the sealing arrangement. In the device known from DE 10161438 a1, the annular gap is supplied with oil diverted from a hydraulic actuating device associated with the exhaust valve by means of an associated metering device. The dosing devices provided on the known devices result in an expensive construction with high production and maintenance costs.

Disclosure of Invention

Starting from this, the object of the invention is therefore to improve a device of the type mentioned above by means of simple and cost-effective measures in such a way that the hitherto required dosing device can be dispensed with, but a reliable oil supply of the annular gap between the valve stem and the guide sleeve is ensured, and a reliable function of the restoring device designed as an air spring is ensured.

The two-stroke large diesel engine according to the invention comprises at least one cylinder, the combustion chamber of which has an exhaust port which can be controlled by means of an exhaust valve which can be actuated by means of an actuating device, said actuating device comprising a drive device and a restoring device, a valve sleeve being fitted on the cylinder head of said cylinder, said valve sleeve comprising an exhaust channel which is connected to the exhaust port of the combustion chamber and a guide sleeve which passes through its upper wall and is intended for a valve stem of the exhaust valve which passes through the exhaust channel, wherein the restoring device has a piston which is mounted on the valve stem and a working chamber which is delimited by the piston and is supplied with compressed air and which passes through a gap which is arranged above the annular gap and which communicates with the exhaust channel in the region of the guide sleeve and the mutually facing guide surface of the valve stem, said gap being arranged in a region which is remote from the end of the exhaust channel, The sealing device with at least one sealing ring seals, the annular gap can be supplied with oil, characterized in that an oil sump is provided above the sealing ring of the sealing device facing the venting channel, the oil sump can be filled with oil on the upper side of the sealing device facing the venting channel and facing away from the venting channel, and the filling oil submerges the sealing ring in order to continuously supply the annular gap with oil from above. This object is achieved according to the invention in that an oil sump is provided above the sealing ring of the sealing device facing the exhaust duct, said oil sump being filled with oil on the upper side of the sealing ring facing away from the annular gap.

These measures ensure that the sealing means, which are arranged at the upper "cold" end of the annular gap, the sealing ring facing the exhaust channel, is always flooded from above by the oil present in the oil sump. In this case, the oil which is forced into the sealing gap of the sealing device by the pressure in the working chamber of the pneumatic resetting device and by the movement of the valve stem and flows through this sealing gap advantageously leads not only to a gas-tight sealing of the working chamber of the resetting device and to a good lubrication of the sealing ring bearing surfaces, but at the same time also to a controlled supply of oil into the annular gap located below the sealing ring. The oil sump arranged above the sealing ring accordingly also serves as an oil source for the above-mentioned annular gap oil, which reliably prevents combustion residues from entering the annular gap. Since this oil is transported by the pressure in the working chamber and the movement of the valve rod, a simplest and maintenance-free construction is also created. The oil consumption can be maintained within defined limits by means of the geometry of the sealing ring, so that a reliable dosing and a low oil consumption are ensured despite a simple design. The measures according to the invention therefore generally result in a very good economy.

Advantageous configurations and expedient further developments of the more important measures are explained below.

The oil sump is preferably at least partially supplied with leakage oil flowing out of the hydraulic propulsion device assigned to the exhaust valve. This results in a particularly simple and inexpensive construction.

The exhaust valve is usually associated with a hydraulic propulsion device and a return device arranged below it, which is designed as an air spring and has a piston arranged on the valve stem and having a working chamber supplied with air which is limited thereby. In this case, leakage oil which flows out of the hydraulic actuating device can drip onto the piston of the air spring and then enter the working chamber via the circumferential guide surface of the piston. In this case, the oil is expediently collected in the region of the bottom of the working chamber, as a result of which the required oil sump is created, wherein a return line branching off from the oil sump is provided in a targeted manner, wherein a safety valve for the pressure relief of the working chamber is provided. By adjusting the opening pressure of the safety valve, the desired oil level in the oil sump can be maintained here.

According to a particularly advantageous embodiment, an overflow pipe which projects into the oil sump can be provided in front of the safety valve, the overflow edge of the overflow pipe being positioned higher than the oil-flooded sealing ring. This simplifies the adjustment of the safety valve, since the oil level is determined by the overflow pipe, the upper edge of which acts as an overflow edge.

The resetting device is arranged below the hydraulic actuating device and is a pneumatic resetting device, the bottom region of the working chamber of which, which is opposite the piston, comprises an oil sump and can be relieved by a safety valve which is arranged in an oil return line branching off from the oil sump.

The annular groove extends to the upper edge of the cover cap, which forms an overflow edge.

The supply pipe is connected to a source of oil located outside the working chamber. In the event of insufficient leakage oil, the working chamber of the air spring can be supplied with oil and/or oil mist simply by means of an external oil source. In order to produce oil mist, an oil mixing device can be simply provided for the compressed air pipe for supplying compressed air in which the working chamber is provided.

A further advantageous measure can be seen in that a cover overlapping the sealing device has, above the sealing ring facing the exhaust duct, at least one radial gap which communicates with the oil sump and leads to the bore of the valve stem. In this way, a particularly reliable flooding of the exhaust-facing channel of the sealing device can be achieved.

In a further particularly advantageous embodiment of the more important measure, the cover has, above the sealing ring facing the exhaust channel, an internal annular groove containing an oil sump, into which oil can be introduced via a supply line. In this case, a particularly space-saving design is achieved with a very compact oil sump which can be filled with a relatively small amount of oil.

The annular groove can expediently extend to the upper edge of the cover. In this case, the upper edge acts as an overflow edge, as a result of which the desired oil level in the oil sump is achieved in a simple manner.

In the case of the use of leakage oil for supplying the annular groove oil, the supply line assigned to it can be connected in a simple manner to a collecting groove formed in the working chamber and overlapping below the dripping edge. Wherein the working chamber itself does not comprise any oil sump at the bottom side, which provides design freedom in the arrangement of the safety valve.

A further advantageous embodiment of the more important measure can consist in that the sealing device has two sealing rings arranged one above the other, the annular gap region arranged between these sealing rings being connected to a supply line and a drain line in order to form an oil sump. This results in a particularly compact construction. Since the oil sump always flows through here, a reliable oil supply is also produced.

At least the sealing ring of the sealing device facing the exhaust gas duct has a cross section symmetrical to the horizontal plane, said cross section having a two-sided wedge-shaped inlet and a wide contact surface.

The annular gap defined by the guide surfaces of the guide sleeve and the valve rod facing each other is supplied with air and/or oil mist via a supply line below the sealing ring facing the exhaust channel.

Further advantageous configurations and expedient further developments of the more important measures are described below and can be further derived from the following example description with the aid of the drawings.

Drawings

In the drawings described below:

fig. 1 shows a first exemplary embodiment of the invention in a vertical section through the upper region of a cylinder of a two-stroke large diesel engine with an associated exhaust valve device;

FIG. 2 shows a second embodiment of the invention by means of a partial view taken from a vertical section corresponding to FIG. 1, which partial view comprises an upper end region of a guide sleeve assigned to the valve stem;

fig. 3 shows a third exemplary embodiment of the invention, which is illustrated in fig. 2;

fig. 4 shows a radial section through a sealing ring of the sealing device arranged in the upper end region of the guide sleeve.

Detailed Description

The main field of application of the invention is large two-stroke diesel engines such as their use in marine drives. The structure and the principle of action of such devices are known per se.

Such a motor generally has a plurality of cylinders 1 arranged in parallel. In fig. 1, the upper region of a cylinder 1 of this type is shown. It comprises a cylinder liner, not shown in fig. 1, and a cylinder head 2 fitted over it. In the cylinder there is a combustion chamber 3 which is provided with an upper, coaxial exhaust port 4 which can be controlled by means of an associated exhaust valve 5.

The exhaust valve 5 has a valve disk 6 which interacts with a valve seat arranged in the region of the exhaust port 4 and is mounted on the lower end of a spindle-shaped valve stem 7. An exhaust channel 8 is associated with the exhaust port 4 and opens towards the combustion chamber 3 when lifted from the seat with which the exhaust valve is associated, or vice versa. The exhaust valve 5 is provided with an exhaust valve housing 9 which is fitted to the cylinder head 2 and which comprises an exhaust channel 8. A seat ring 9a embedded in the cylinder head 2 and including a valve seat for restricting the exhaust port 4 is mounted on the valve sleeve 9. The valve housing 9 furthermore comprises a guide sleeve 10 associated with the stem 7 of the venting valve 5. The guide sleeve is arranged coaxially with the exhaust port 4 and extends from the punched hole of the valve stem through the upper wall region of the exhaust channel 8 to the upper region of the valve sleeve 9. The guide sleeve 10 passes through the upper wall region of the exhaust duct 8, so that an annular gap 11 between the guide sleeve 10 and the mutually facing guide surfaces of the stem 7 of the exhaust valve 5 can be accessed from the direction of the exhaust duct 8.

The valve stem 7 passes through the guide sleeve 10 and projects with its part beyond the guide sleeve 10 into a structure 12 accommodated on the valve sleeve 9, which comprises an actuating device assigned to the exhaust valve 5 for carrying out the opening and closing movement. The operating device comprises a propulsion device designed as a hydraulic unit and a restoring device designed as an air spring. The structure 12 has a two-part housing, the upper part 12a of which comprises the hydraulic unit constituting the propulsion means and the lower part 12b of which comprises the air spring constituting the return means.

The hydraulic unit forming the propulsion system comprises a piston 13 which is arranged at the upper end of the valve rod 7 and a pressure chamber 14 which is delimited by the piston and is arranged in the upper part 12a and which, by means of a pressure source, not shown in any more detail, is expediently designed as a pump which can be driven by a motor and which can introduce hydraulic oil at a high pressure in a stroke-dependent manner. The air spring, which is arranged below the hydraulic unit and acts as a return device, comprises a piston 15, which is fastened thereto and is penetrated by the valve stem 7, which delimits a working chamber 17, which is surrounded by a rim formed on the lower part 12b and into which compressed air can be introduced via a compressed air line 18 connected to a compressed air source. In order to reduce the excess pressure in the working chamber 17, it is provided with an outlet which is provided with an adjustable safety valve 19 which opens at a set pressure.

The rim 16, which delimits the working chamber 17 and acts as a cylinder assigned to the piston 15, projects with an axial and radial play into an associated end-face recess of the upper part 12a, wherein an open gap 20 results between the upper part 12a and the lower part 12 b. Oil leaking from the hydraulic unit above the gap 20 enters the gap 20, from which a pressureless return line 21 can be led. This return line is expediently connected to the region of the gap 20 surrounding the bottom of the rim 16.

The working chamber 17 into which compressed air can be introduced is sealed by a sealing device comprising at least one sealing ring 22 against the annular gap 11 between the mutually facing guide surfaces of the valve stem 7 and the guide sleeve 10. The sealing device can be designed as a packing sleeve comprising at least one sealing ring 22. According to the embodiment of fig. 1 and 2, a sealing ring 22 is provided. In the embodiment according to fig. 3, sealing rings 22, 23 are provided in an overlapping arrangement.

Since the annular gap 11 between the mutually facing guide surfaces of the valve stem 7 and the guide sleeve 10 is open to the exhaust gas duct, there is the risk that combustion residues enter the annular gap 11, which can lead to damage to the guide surfaces, in particular to the lower sealing ring 22, i.e. the sealing ring 22 of the sealing arrangement facing the exhaust gas duct 8. In order to prevent this, oil is supplied to the annular gap 11 from above. Oil can flow into the exhaust passage 8, which can be burned, at the lower end portion of the seal ring 11.

In order to supply the annular gap 11 with oil, an oil sump 24 capable of supplying oil is provided above the sealing ring 22 of the sealing device, which oil sump is located above the sealing ring 22 on the upper side facing away from the annular gap 11 and which oil sump submerges the sealing ring and serves as an oil source for supplying oil to the annular gap from above and for lubricating the sealing ring 22.

In the embodiment according to fig. 1, the oil that first leaks out of the pressure chamber 14 of the hydraulic aggregate is used to feed the oil sump 24. The same applies to fig. 2. As mentioned above, the above-mentioned leakage oil drips into the gap 20 and at least partially reaches the upper side of the piston 15 of the air spring device. From there, the leakage oil enters the working chamber 17 in the region of the piston surface on the circumferential side, where it can collect on the bottom side and form an oil sump 24, as shown in fig. 1.

In general, enough leakage oil from the hydraulic unit enters the pressure chamber 17 to ensure an adequate supply of the oil sump 24. If this is not the case, it is of course possible to introduce additional oil into the pressure chamber 17. This is illustrated in fig. 1 by a supply line 25 which opens into the lower region of the pressure chamber 17. The supply pipe 25 can be provided with an external oil source. However, it is also possible to simply divert the oil which is guided via the supply line 25 from the oil which is guided into the pressure chamber 14 of the hydraulic assembly. Alternatively or additionally, the working chamber 17 can also be supplied with oil mist. For this purpose, the compressed air line 18 is provided with an oil mixing device 26. Oil separated from the compressed air is injected into the working chamber 17 in the form of an oil mist. The oil mist falls on the walls and drips into the oil sump.

If the piston 15 moves downwards, the already compressed air present in the working chamber 17 is further compressed. The higher the oil level in the oil sump 24, the stronger the air is compressed. Starting from a certain pressure, the safety valve 19 opens. The oil level in the oil sump 24 can therefore be maintained at a desired height by corresponding regulation of the safety valve 19. As mentioned above, the relief valve 19 controls a flow path leading from the sump to a return line 21.

In the exemplary embodiment shown in fig. 1, the safety valve 19 is assigned an overflow 27 which projects into the oil sump 24, the upper end of which forms an overflow edge and accordingly defines the height of the oil level in the oil sump 24. The safety valve 19 can be adjusted to a fixed pressure in this embodiment regardless of the oil level of the oil sump 24, which simplifies the setting. However, a constant oil level is obtained in the oil sump 24. The overflow edge formed by the upper end of the overflow 27 is naturally higher than the sealing ring 22, so that the sealing ring is reliably flooded with oil.

The guide sleeve 10, which accommodates the sealing ring 22, is supported on the valve sleeve 9 with an upper rim 10 a. The sealing ring 22 is inserted into an annular groove which is open at the top and has a flange 10a which is overlapped by a cap 28. The cover is provided with radial passage gaps 29 in a region below the oil level of the oil sump 24 and above the sealing ring 22, which are correspondingly guided from the oil sump 24 to the part of the annular gap 11 above the sealing ring 22, thereby facilitating the flooding of the sealing ring 22 with oil. The radial gap 29 can be designed as a bore or a milled section or the like.

In the exemplary embodiment according to fig. 2, the bore of the cover 28, which is penetrated by the valve stem 7, has a radially larger dimension than the diameter of the valve stem 7, so that an annular groove 31 is obtained which surrounds the valve stem 7 and can receive an oil reservoir 32, which can be supplied with oil via a supply line 33 connected to the annular groove 31. The supply pipe 33 can be connected to an external oil source or the like as the supply pipe 25 of the embodiment of fig. 1. In the embodiment shown, the spilled oil is again used to feed the oil sump 32 as described above.

The leakage oil entering the working chamber 17 in the area of the guide surface of the piston 15 drops to the lower edge of the cylindrical rolling surface assigned to the piston 15. This drip edge 34 is surrounded by a collecting groove 35 from below, from which the supply line 33 leads out. The annular groove 31, which includes the oil sump 32, extends to the upper side of the cover 28, which accordingly forms an overflow edge, by means of which a constant oil level in the oil sump is ensured. The overflow oil enters the bottom region of the working chamber 17, from which a flow path controlled by a safety valve 19 is led out, through which excess oil can be conducted away. The relief valve 19 can be adjusted here irrespective of the oil level in the oil sump 32, which simplifies the setting. In this embodiment, an overflow pipe arranged upstream of the safety valve 19 is not required, which is preferred in many respects for reasons of space.

In the embodiment according to fig. 3, two sealing rings 22, 23 are provided, which are arranged one above the other at a distance from one another. The part of the annular gap 11 defined by the two sealing rings 22, 23 is supplied with oil so as to form an oil sump 36. In the illustrated embodiment, the oil supply is carried out in intermittent load continuous operation. The annular gap portion is connected to a supply line 37 and an emptying line 38. The supply line 37 may be connected to an external oil source. The drain pipe 38 may be connected to a non-pressurized return pipe. In this embodiment, the sealing ring facing the venting channel 8, in this case the lower sealing ring 22, i.e. the lower sealing ring of the sealing device, must also be flooded with oil, as a result of which the annular gap 11 is reliably supplied with oil. The forced supply of the oil sump 36 results in a particularly high reliability.

Normally, the introduction of oil entering through the sealing ring 22 into the annular gap 11 reliably prevents the entry of combustion residues into the annular gap 11. To support this effect, compressed air can additionally be fed into the annular gap 11, which is expediently fed below the sealing ring 22, as is illustrated in fig. 1 by a pipe 39 which is positioned below the sealing ring 22 and leads into the annular gap 11. It is also conceivable to introduce oil mist and/or additional oil through a tube of this type.

The amount of oil passing through the annular gap 11 can be relatively small and amounts to about one liter per day on a two-stroke large diesel engine. The oil leakage from the hydraulic unit is about 10 liters per day on one such engine, and therefore the oil consumption for supplying the annular gap 11 can easily be met.

The introduction of oil into the annular gap 11 takes place next to the sealing ring and can be influenced by its geometry. The starting point here is that a hydrodynamic lubricating oil film is produced between the sealing ring 22 and the valve rod 7, the thickness of which film is essentially dependent on the geometry of the sealing ring 22 and other fixed, defined parameters such as the relative speed. A wedge-shaped entrance to the gap between the oppositely moving faces facilitates the formation of a lubricating oil film. The width of the bearing surface associated with the inlet also affects the thickness of the lubricating oil film.

In the embodiment according to fig. 4, the sealing ring 22 has a cross section which is symmetrical to a horizontal plane of symmetry and has two wedge-shaped inlet openings 41 and a wide bearing surface 40. The wedge shape of the inlet has a relatively large wedge angle. The bearing surface 40 is wide and extends almost the entire height of the sealing ring 22. With such a geometry of the sealing ring 22, an oil penetration of the above-mentioned order of magnitude can be achieved on a two-stroke large diesel engine.

Claims (16)

1. Two-stroke large diesel engine, comprising at least one cylinder (1) whose combustion chamber (3) has an exhaust opening (4) which can be controlled by means of an exhaust valve (5) which can be actuated by means of an actuating device which comprises a drive device and a restoring device, a valve sleeve (9) which is fitted on the cylinder head (2) of the cylinder and comprises an exhaust duct (8) which is connected to the exhaust opening (4) of the combustion chamber (3) and a guide sleeve (10) which passes through its upper wall and is intended for a valve stem (7) of the exhaust valve (5) which passes through the exhaust duct (8), wherein the restoring device has a piston (15) which is mounted on the valve stem (7) and a working chamber (17) which is delimited by the piston and is supplied with compressed air and which is situated opposite a valve stem (7) with respect to a guide surface which is situated between the guide sleeve (10) and a mutually facing guide surface of the valve stem (7), The annular gap (11) which communicates with the exhaust channel (8) is sealed by a sealing device which is arranged above the annular gap (11) in the region of the end remote from the exhaust channel and has at least one sealing ring (22), wherein oil can be supplied to the annular gap, characterized in that an oil sump (24, 32, 36) which can be supplied with oil is arranged above the sealing ring (22) of the sealing device which faces the exhaust channel (8), and that the oil filling of the oil sump is located on the upper side of the sealing device which is arranged at the upper end of the annular gap and faces the sealing ring (22) of the exhaust channel and faces away from the exhaust channel (8), and the oil filling floods the sealing ring (22) in order to continuously supply oil to the annular gap from above.

2. A large two-stroke diesel engine according to claim 1, characterized in that the exhaust valve (5) can be placed in the open position against the force of the return means by means of a hydraulic propulsion device acting on the valve stem (7) of the exhaust valve, and that the oil sump (24, 32) can be at least partially supplied with leakage oil flowing out of the hydraulic operating device.

3. A large two-stroke diesel engine according to claim 1 or 2, characterized in that the oil level in the oil sump (24, 32) is defined by a spill edge.

4. A large two-stroke diesel engine according to claim 1 or 2, characterized in that the resetting device is arranged below the hydraulic operating device and is a pneumatic resetting device, the bottom region of the working chamber (17) of which, opposite the piston (15), comprises an oil sump (24) and can be relieved by means of a safety valve (19) which is arranged in a return line (21) which branches off from the oil sump (24).

5. A large two-stroke diesel engine according to claim 4, characterized in that an overflow pipe (27) extending into the oil sump (24) is provided before the safety valve (19), the upper end of the overflow pipe forming the overflow edge being positioned higher than the oil-flooded sealing ring (22).

6. A large two-stroke diesel engine according to claim 1 or 2, characterized in that the working chamber (17) can be supplied with oil from the outside at least partly through an associated supply pipe (25).

7. A large two-stroke diesel engine according to claim 1 or 2, characterized in that the working chamber (17) is at least partly supplied with oil mist via an associated supply duct (25).

8. A large two-stroke diesel engine according to claim 7, characterized in that the working chamber (17) is supplied with compressed air via a compressed air line (18), and that the compressed air line (18) is provided with an oil mixing device (26).

9. A large two-stroke diesel engine according to claim 1 or 2, characterized in that the guide (10) is provided with a cover (28) overlapping the sealing means, which cover has above the oil-flooded sealing ring (22) at least one radial gap (29) communicating with the oil sump (24) and directed towards the hole of the cover through which the valve stem (7) passes.

10. A large two-stroke diesel engine according to claim 1 or 2, characterized in that the guide (10) is provided with a cover (28) overlapping the sealing means, which cover has an internal annular groove (31) above the oil-submerged sealing ring (22) and comprising an oil sump (32), which annular groove can be supplied with oil via a supply pipe (33).

11. A large two-stroke diesel engine according to claim 10, characterized in that the resetting device is designed as an air spring arranged below the hydraulic actuating device, which air spring has the piston (15) mounted on the valve rod (7) and the working chamber (17) delimited by the piston and supplied with compressed air, in which working chamber a drop edge (34) is formed, which drop edge is surrounded from below by a collecting gutter (35), from which the supply line (33) branches off.

12. A large two-stroke diesel engine according to claim 10, characterized in that the annular groove (31) extends to the upper edge of the cover (28) forming an overflow edge.

13. A large two-stroke diesel engine according to claim 10, characterized in that the sealing means have sealing rings (22, 23) arranged one above the other, and that the annular gap region arranged between these sealing rings (22, 23) for forming an oil sump (36) is connected to a supply line (37) and a drain line (38).

14. A large two-stroke diesel engine according to claim 13, characterized in that the supply pipe (37) is connected to a source of oil outside the working chamber (17).

15. A large two-stroke diesel engine according to claim 1 or 2, characterized in that at least the sealing ring (22) of the sealing means facing the exhaust channel (8) has a cross-section symmetrical to the horizontal plane, said cross-section having a wedge-shaped inlet (41) on both sides and a wide contact plane (40).

16. A large two-stroke diesel engine according to claim 1 or 2, characterized in that the annular gap (11) defined by the guide surfaces of the guide sleeve (10) and the valve rod (7) facing each other is supplied with air and/or oil mist through a supply duct (39) below the sealing ring (22) facing the exhaust channel (8).