EP2133520A1 - Piston for a cylinder of a large motor, lubricating device and method with such a piston - Google Patents

Abstract

The piston (1) comprises a piston barrel, which has a storage chamber (5) for receiving lubricant. The piston barrel is narrowed by a piston skirt (16) in the peripheral side. The storage chamber is connected with the piston skirt by a lubricant line (10). A feed unit (7) is provided, which is formed for detachable connection with a lubricant source (2). The feed unit is guided into the storage chamber. The lubricant line flows into a lubricant collecting element (14). Independent claims are included for the following: (1) a lubrication device for a cylinder of a high-power engine; and (2) a lubrication method for a cylinder of a high-power engine.

Description

The invention relates to a piston for a cylinder of a large engine and a lubricating device and a lubricating method with such a piston according to the preamble of the independent claim of the respective category.

Large engines, especially in the design as large diesel engines, which may be configured as two-stroke or four-stroke internal combustion engines, are often used as drive units for ships or in stationary operation, e.g. used to drive large generators for generating electrical energy. The large engines usually run for long periods in continuous operation, which places high demands on the reliability and availability. Therefore, for the operator in particular long maintenance intervals, low wear and an economical handling of the operating materials are central criteria.

In the operating state, the piston slides on the serving as a running surface surface of the wall of the cylinder, which is usually designed in the form of a cylinder liner (liner) along. In this case, a cylinder or piston lubrication is provided. On the one hand, the piston must be as possible on the other hand, the piston must seal the combustion chamber in the cylinder as well as possible, in order to ensure efficient conversion of the energy released during the combustion process into mechanical work.

Therefore, during operation of the large diesel engine usually a lubricating oil is introduced into the cylinder to achieve good running characteristics of the piston and to minimize the wear of the tread, the piston and the piston rings. Furthermore, the lubricating oil is used to neutralize aggressive combustion products and to prevent corrosion. Because of these many requirements, very high quality and expensive substances are often used as lubricants.

There is therefore a need for a particularly efficient and economical operation of the engine to work with the lowest possible lubricating rates.

A proven method is the so-called internal lubrication, in which the lubricant, typically a lubricating oil, is conveyed through the interior of the piston and then via one or more lubrication points, which are provided on the surface of the piston from the piston interior to the piston or on the cylinder surface is applied. Such a method is used, for example, in EP-A-0 903 473 disclosed.

Based on this prior art, it is therefore an object of the invention to propose a piston for a cylinder of a large engine and a lubricating device and a corresponding method which allows the most efficient and easy lubrication of the piston or the cylinder in a large engine at low lubrication rates , Under large engine is to be understood in the episode a crosshead motor, In particular, the term is intended to include a large diesel engine or a gas engine.

Furthermore, a higher pressure is applied between the piston rings of the piston ring assembly of the piston than in the crankcase, in which the purge air pressure is applied. This pressure gradient causes an ejection of the located in the between piston and piston rings lubricant in the cylinder chamber on the piston bottom, that is, the side facing away from the combustion chamber of the piston. This creates a lubricant mist in the cylinder chamber, which is partially blown into the cylinder and thus partly contributes to the lubrication of the piston. However, some of the lubricant remains in the cylinder chamber, where it is burned, evaporated or withdrawn as smoke through the exhaust channel. This part of the lubricant is thus lost as emission. On the one hand, such an emission results in a loss of lubricant which is no longer available for the lubrication of the pistons and, on the other hand, poses a risk to the environment, since the combustion products can have a negative effect on the environment.

The objects of the invention solving this object are characterized by the features of the independent claims.

According to the invention, therefore, a piston for a cylinder of a large engine is proposed, which has a piston body which contains a reservoir for receiving a lubricant, wherein the piston body is peripherally bounded by a piston skirt, wherein the reservoir is connected via a lubricant line with the piston skirt, and an infeed is provided, which is designed for releasable connection with a lubricant source, wherein the feed opens into the reservoir and wherein the lubricant line opens into a lubricant collecting element.

Since a storage space for the lubricant and a closing member in the supply line to the lubrication point are provided in this piston, the lubrication can be adapted to the duty cycle of the engine without great expenditure on equipment. In the reservoir of the piston lubricant is always available and therefore can be applied to the cylinder surface or the piston surface if and only if it is particularly favorable and efficient in relation to the duty cycle. By means of the lubricant collecting element, the lubricant located on the running surface is collected and removed via an opening in the lubricant collecting element. This optimization can also significantly reduce the amount of lubricant required or the lubrication rate. The lubricant, which has been removed by means of the lubricant collecting element, passes through a lubricant line into the reservoir and is thus available for further lubrication. Alternatively, a lubricant removal device can be provided, which is connectable to the lubricant line.

In a preferred embodiment, a supply line is provided, which extends from the storage space to a lubrication point, which is provided on the surface of the piston, so that lubricant from the storage space to the lubrication point can be conducted, wherein in the supply line a closing member is provided.

In particular, a delivery device can be provided in the piston in order to convey the lubricant from the storage space through the supply line to the lubrication point. This conveyor serves to increase the pressure in the reservoir of the piston after its filling, so as to Apply lubricant through the supply line and lubrication point.

An apparatus of particularly simple design is obtained when the conveyor comprises a delivery piston for the lubricant, which is configured and arranged so that it can be acted upon in the operating state with the combustion chamber side pressure in the cylinder. Thus, in a simple manner, the pressure in the combustion chamber of the cylinder can be used to transport the lubricant to the lubrication point.

According to a further advantageous, simple apparatus embodiment, the conveyor comprises a spring-loaded delivery piston to promote the lubricant from the storage space to the lubrication point.

In a preferred embodiment, the piston has a plurality of piston rings, wherein the lubrication point is arranged between two piston rings with respect to the axial direction defined by the piston axis. Since the lubricant is introduced between the piston rings and not on the combustion chamber side, ie with respect to the normal position of use above the first piston ring, or above the Schmierstoffammelement, unnecessary burning of the lubricant and the associated adverse coking is at least significantly reduced.

Particularly advantageous is an embodiment in which three piston rings are provided, and two lubrication points, each of which is connected via a supply line provided with a closing member with the reservoir, wherein the two lubrication points with respect to the axis defined by the piston axis axial direction respectively disposed between adjacent piston rings are. In this embodiment, the lubricant is distributed by the uppermost, that is, the piston ring placed next to the piston ring, during the downward movement of the piston and through the lowermost Piston ring, the lubricant is distributed during the piston upward movement. Compared to today's conventional method in which the lubricant is partially introduced above, so the combustion chamber side, the uppermost piston ring, resulting in the advantage that a scraping of the lubricant is avoided in the combustion chamber inside. Lubricant, which is moved by the piston rings in the combustion chamber, namely for lubrication is no longer available and only leads to a strong, unwanted coking.

The piston skirt encloses at a first end a piston surface, that is the Kolbenmatel represents the edge of the piston surface. This piston surface adjacent to the combustion chamber, wherein the lubricant collecting element is preferably arranged outside the piston ring furthest away from the combustion chamber on the piston skirt. During the compression stroke of the piston, that is to say during a movement of the piston in the direction of the combustion chamber, any lubricant present on the running surface of the cylinder or on the piston skirt is thus introduced into the lubricant collecting element and optionally transported in the direction of the reservoir. The portion of the tread extending into the cylinder space is therefore substantially free of lubricant after the lubricant collecting element has moved along the tread in the direction of the combustion chamber. Thus, deposits of lubricant in the cylinder chamber can be prevented.

A preferred measure is that a piston ring is provided, which is designed as a lubricant distributor ring. The primary purpose of this lubricant distributor ring is to distribute the lubricant with respect to the circumferential direction of the cylinder surface. In particular, the lubricant distribution ring can be arranged between two piston rings, which distribute the lubricant mainly with respect to the axial direction.

In the lubricant line, a closing member may be provided. This arrangement is particularly advantageous when the lubricant line is used as a supply and discharge for lubricant. The closing member may in particular be set such that it has an opening pressure of 1 to 5 bar, preferably 2 to 5 bar, particularly preferably around 4 bar. In this case, the closing member remains closed to the pressure in the cylinder space, as long as it is not opened by means of a lifting device to drain lubricant or supply lubricant.

Furthermore, a closing member may be provided in each of the supply lines.

The closing member in each supply line and in the lubricant line is preferably designed as a check valve. By the opening pressure at which opens the check valve in the forward direction, then can be adjusted in a simple manner, the timing of lubrication based on the duty cycle.

In a further preferred embodiment, a locking device is provided, which is designed such that it closes the flow connection between the reservoir and each supply line in cooperation with the lubricant source. In this way it can be ensured that leakage of the lubricant through the supply lines and the lubrication points is avoided during the filling of the storage space.

Further, the invention proposes a lubricating device for the cylinder of a large engine, comprising a piston according to the invention, wherein the piston skirt is surrounded by a lubricating space for lubricating a running surface of a cylinder, and a lubricant source with a filling device, which is releasably connectable to the feed and cooperates with the piston so that only a lubricant from the lubricant source into the reservoir can be introduced when the filling device is connected to the feed, wherein the reservoir is connectable to a lubricant collecting element, so that lubricant from the lubricant chamber is traceable into the reservoir. By so doing, the reservoir of the piston can be filled with lubricant as needed, with the application of the lubricant to the tread and the collection of lubricant from the tread being decoupled from this process. The reservoir of the piston is thus filled, but the lubricant is only applied to the tread when it is cheap and efficient with respect to the duty cycle. In addition, lubricant, which is passed from the lubricant collecting element into the storage space, can be removed from the storage space via a lubricant removal device which can be docked to the feed. Thus, for example, contaminated lubricant can be removed from the storage space and the supply lines and replaced by correspondingly pure lubricant.

A variant is that the filling device or the lubricant removal device are arranged so that in the operating state, the feed and the filling device or lubricant removal device are connected at the bottom dead center of the movement of the piston and separate during the upward movement of the piston.

Another variant is that the filling device or lubricant removal device is arranged so that in the operating state, the feed and the filling device or lubricant removal device are connected at top dead center of the movement of the piston and separate during the downward movement of the piston.

The choice of suitable variant depends on the design of the piston.

Furthermore, the invention proposes a lubrication method for the cylinder of a large engine with a reciprocating piston arranged in the cylinder, in which method a supply of the piston during the movement of the piston is connected to a filling device of a lubricant source, a lubricant from the lubricant source the feed is introduced into a reservoir of the piston, the connection between the supply of the piston and the filling device is separated by the movement of the piston and then the lubricant is brought from the reservoir through a supply line to a lubrication point on the piston skirt.

By this method, it is possible in a simple manner to perform the lubrication of the cylinder surface or the piston exactly at the desired time and with the right amount of lubricant. This allows a particularly efficient and economically advantageous lubrication. In addition, any possible excess of lubricant can be returned to the storage space through the lubricant collecting element. This prevents lubricant from entering the cylinder chamber, so that oxidation reactions of the lubricant with the oxygen of the air in the cylinder chamber occur, which can lead to deposits in the cylinder chamber, so that coking can occur.

From the aspect of a particularly simple and uncomplicated process management, the lubricant is preferably introduced into the reservoir of the piston when the piston is in the top or bottom dead center of its movement.

Further, a large engine is proposed, which is designed with a piston according to the invention or with a lubricating device according to the invention, or which is operated with a method according to the invention.

Further advantageous measures and preferred embodiments of the invention will become apparent from the dependent claims.

Fig. 1:

ein erstes Ausführungsbeispiel eines erfindungsgemässen Kolbens und einer Schmiermittelquelle,

Fig. 2:

ein Ausführungsbeispiel einer Fülleinrichtung,

Fig. 3:

ein Diagramm zur Verdeutlichung des Drucks im Zylinder in Abhängigkeit vom Kurbelwinkel,

Fig. 4:

ein Diagramm zur Verdeutlichung der Schmiermittelzufuhr,

Fig. 5:

ein zweites Ausführungsbeispiel eines erfindungsgemässen Kolbens und der Schmiermittelquelle,

Fig. 6a:

eine Detaildarsatellung der Sperreinrichtung im geöffneten Zustand,

Fig. 6b

eine Detaildarsatellung der Sperreinrichtung im geschlossenen Zustand,

Fig. 7:

analog zu Fig. 3, jedoch für das zweite Ausführungsbeispiel,

Fig. 8:

ein Diagramm zur Verdeutlichung der Schmiermittelzufuhr,

Fig. 9:

eine Variante für die Ausgestaltung der Kolbenringe,

Fig. 10:

eine Seitenansicht auf einen Schmiermittelverteilerring,

Fig. 11:

eine Aufsicht auf den Schmiermittelverteilerring aus Fig. 10.

Fig. 12:

ein drittes Ausführungsbeispiel eines erfindungsgemässen Kolbens.

In the following, the invention will be explained in more detail both in terms of apparatus and process technology with reference to embodiments and with reference to the drawing. In the schematic, not to scale drawing show partly in section:

Fig. 1:

A first embodiment of a piston according to the invention and a lubricant source,

Fig. 2:

an embodiment of a filling device,

3:

a diagram to illustrate the pressure in the cylinder as a function of the crank angle,

4:

a diagram to illustrate the lubricant supply,

Fig. 5:

A second embodiment of a piston according to the invention and the lubricant source,

6a:

a detailed description of the locking device in the opened state,

Fig. 6b

a detailed description of the locking device in the closed state,

Fig. 7:

analogous to Fig. 3 but for the second embodiment,

Fig. 8:

a diagram to illustrate the lubricant supply,

Fig. 9:

a variant for the design of the piston rings,

Fig. 10:

a side view of a lubricant distributor ring,

Fig. 11:

a view of the lubricant distributor ring Fig. 10 ,

Fig. 12:

A third embodiment of an inventive piston.

Fig. 1 illustrates in a longitudinal sectional view a first embodiment of an inventive piston for a large engine, in particular for a large diesel engine, wherein the piston is generally designated by the reference numeral 1. Furthermore, an embodiment of a lubricant source 2 is shown, which forms an embodiment of a lubricating device 1,2 according to the invention together with the piston 1.

The large diesel engine can be designed as a two-stroke or four-stroke engine. In the following reference is made to the case that it is a longitudinally-flushed two-stroke large diesel engine.

The piston 1 has a piston axis A, which defines the axial direction, and is arranged in a known manner movable back and forth in a cylinder 3, which has a wall 31 which may be configured as a cylinder insert or liner or as a liner. The piston moves substantially in a bore of the cylinder The inwardly facing surface of the wall 31 forms a running surface 32, along which the piston 1 moves in the operating state. The piston 1 limited with his according to the upper end of a combustion chamber 4, in which the combustion process takes place, and usually has a plurality, here three piston rings 11, 12, 13, which are also referred to collectively as a piston ring package.

During operation of the large diesel engine, it is necessary to apply a lubricant, such as a lubricating oil on the tread 32, which lubricates the piston 1, the piston ring package and the tread 32 in order to achieve good running characteristics of the piston 1 and the wear of the cylinder wall, in particular the tread 32, the piston 1 and the piston rings 11, 12, 13 to keep as low as possible. Furthermore, the lubricant is used to neutralize aggressive combustion products and to prevent corrosion, such as sulfur corrosion. The lubricating oil forms on the running surface 32 a lubricating oil film, not shown, which is in constant contact with the piston rings 11, 12, 13.

The inventive piston 1 is designed for internal lubrication, that is, the lubricant is applied from the interior of the piston 1 out on the tread 32 and on the lateral surface of the piston 1.

Provided inside the piston 1 is a reservoir 5 for the lubricant, which can be designed as a cavity or as a tank. From this storage space 5, two supply lines 6 designed as bores each extend up to a lubrication point 61 on the piston skirt 16 of the piston 1.

The number of two leads 6 relates only to the axial direction. In the circumferential direction, a plurality of supply lines 6 may be provided at the same axial height. The number of supply lines depends on the need for a shoe.

In the supply lines 6, a closing member 62 is provided in each case, which is designed here in each case as a pressure holding or check valve 62. Each check valve 62 is designed to block in the direction of the storage space 5, that is, it prevents backflow of the lubricant or other fluids, e.g. of the combustion gas or the scavenging air from the lubrication point 61 into the storage space 5. In the passage direction from the storage space 5 to the lubrication point 61, the valve opens as soon as the pressure difference becomes greater than its opening pressure, which is referred to below as p1. This means that as soon as the pressure on the side facing the storage chamber 5 of the check valve 62 by the value p1 is higher than the pressure on the lubrication point 61 facing side, the flow connection opens from the storage space 5 in the direction of the lubrication point 61. Once the pressure difference Value of the opening pressure p1 below, the flow connection is closed.

The opening pressure p1 may be the same for the two check valves 61, but it is also possible that each of the check valves 61 has a different opening pressure p1.

The lubrication points 6 are arranged with respect to the axial direction defined by the piston axis A between two adjacent piston rings 11, 12, 13, that is, one of the two lubrication points 61 is provided between the first piston ring 11 and the second piston ring 12 and the second lubrication point 61 between the second piston ring 12 and the third piston ring 13 is provided. With the first piston ring 11 while the one piston ring is meant, which is located closest to the combustion chamber 4.

Furthermore, a feed 7 is provided, which is designed here as a feed channel or feed line, and which starts at the underside of the piston 1 according to the illustration and in the Reservoir 5 opens. The feed 7 is designed for detachable connection to the lubricant source 2, as will be explained later. In the feed 7, a further closing member 72 is provided, which is configured as a pressure-holding or check valve 72. The check valve 72 prevents with its blocking function a leakage of the lubricant from the reservoir 5 through the feed 7. In the reverse direction, the check valve 72 opens as soon as the applied pressure difference exceeds its opening pressure p2.

The lubricant source 2 is arranged stationary with respect to the motor housing and comprises a reservoir 21, in which the lubricant is provided, a filling device 22, which is provided for cooperation with the feed 7, and a pump 23, which supplies the lubricant from the reservoir 21 to the Filling device 22 promotes. The filling device has a closing member 24, which can be configured as a check valve. The closing member 24 prevents leakage of the lubricant from the filling device 22.

At the illustration of the upper end of the storage space 5, a conveyor 8 is provided to promote the lubricant from the storage space 5 through the leads 6 to the lubrication points 61. In this embodiment, the conveyor 8 is designed as a diaphragm piston with a membrane 81. As shown, above the membrane 81 is followed by a channel 82 which extends through the piston 1 and above, that is, the combustion chamber side of the first piston ring 11 opens into the surface of the piston 1. Through this channel 82, the side facing away from the reservoir 5 side of the diaphragm 81 is acted upon by the pressure in the combustion chamber 4 and the pressure in the cylinder above the first piston ring 11. The storage chamber 5 facing side of the diaphragm piston 8 is acted upon by the pressure of the lubricant in the reservoir 5.

The basic mode of operation of the piston 1 according to the invention is as follows: The lubricant source 2 with the filling device 22 functions as a "filling station" for filling the storage space 5 in the piston. The reservoir 5 in the piston 1 and the lubricant source 2 are cyclically coupled in the lower (or upper) dead center of the piston movement via the feed 7 and the filling device 22, so that during this interaction, the reservoir 5 is filled in the piston 1 with lubricant. Thus, there is enough lubricant for lubrication at least over a duty cycle in the piston 1 available.

The closing member 24, which prevents the lubricant from flowing out of the lubricant source 2, is opened during the coupling or while the infeed 7 and the filling device 22 are connected to one another, so that the lubricant can flow from the lubricant source 2 into the storage space 5. This opening of the closing member 24 can be purely mechanical, or by an electrical, hydraulic or pneumatic control.

The storage space 5 is connected via a lubricant line 10 with the piston skirt 16, wherein the lubricant line 10 opens into a lubricant collecting element 14. A lubricant collecting element 14 is arranged in an annular recess 19 of the piston skirt.

The lubricant collecting element 14 is thus according to Fig. 1 a piston ring having an annular body 20 which preferably has at least one groove 28 delimited by two lips 26, 27. The lips 26, 27 are in touching contact with the running surface 32. Between the lips, the outer peripheral groove 28 is formed. The lips 26, 27 thus form the sliding surface 32 of the lubricant collecting element 14 that slides along the running surface 32 and that is in frictional contact with the running surface 32. By formed in the circumferential direction groove 28, the Lubricant collecting element 14 in the operating state to collect lubricant in the recess 19 and store, so that locally excess lubricant can be collected. This collected lubricant is no longer available on the tread 32, but can be applied to the cylinder tread from the recess when needed at locations that have an increased lubricant requirement.

The lubricant collecting element 14 thus functions not only as a collecting element for the lubricant in the operating state of the large diesel engine, but also can remove lubricant from the running surface. In this function, it is similar to a lubricant scraper. In addition, the lubricant collecting element 14 also has a function as a lubricant distribution element. In particular, the body 29 may include an opening 30 through which lubricant from a source of lubricant may be introduced into the groove 28 of the lubricant collection element or, conversely, excess lubricant may be withdrawn from the tread 32.

The lubricant collecting element is in touching contact with the running surface 32 because it performs a sealing function with respect to gas from the cylinder space 20 containing the crankshaft. In large diesel engines, this cylinder chamber 20 is also referred to as a receiver space containing fresh air, which is usually provided by a turbocharger, not shown. In the cylinder chamber 20 is thus the pressure of the fresh air, which is supplied via scavenging ports to the combustion chamber 4 when the piston 1 is in the range of bottom dead center. The fresh air is under overpressure, which is usually in the range of 1 to 5 bar, preferably 2 to 5 bar, in particular, for example, the 4 bar.

In order to press the lubricant collecting element against the tread, a spring element 33 may be provided which extends between the Recess 19 and the body 29 of the lubricant collecting element is located.

The following will now be with reference to Fig. 2 an exemplary embodiment of the filling device 22 explained in more detail. Fig. 2 shows a sectional view of the filling device 22 and the closing member 24. The filling device 22 has a filling space 221, in which a coming of the pump 23 supply line 222 opens. In the supply line 222, a check valve 223 is provided. The filling space 221 further has a partially conically extending outlet 224, in which a cone 241 of the closing member 24 is located. The cone 241 is pressed by a spring 244 in the conical part of the output 224 so that it in the closed state, the in Fig. 2 is shown, the output 224 closes. The cone 241 has an inner channel 242, which is connected via bores 243 with the outer space of the cone 241.

By the pump 23, the lubricating oil or the lubricant is pumped through the supply line 222 into the filling space 221 of the filling device 22. The pump 23 introduces the lubricant into the filling space 221 with a filling pressure p3.

In the embodiment described here, a pin 73 is provided with an inner bore at the bottom of the piston 1 at the mouth of the feed 7, so that lubricant can flow through the pin 73 in the feed 7. The pin 73 is formed so that it can penetrate into an outlet of the filling device 22.

Now moves in the operating condition of the diesel engine, the piston 1 down (as shown in Fig. 1 and Fig. 2 ), so the pin 73 moves, as the arrow C in Fig. 2 indicates to the filling device 22. Approaches the piston 1 to the bottom dead center, the pin 73 penetrates into the output and pushes in the sequence the cone 241 against the force of the spring 244 in the filling space 221. Now the cone 241 is in the open state. The lubricant can penetrate through the holes 243 in the inner channel 242 and passes through the feed 7 into the reservoir 5 in the piston 1. In the subsequent upward movement of the piston 1, the cone 241 is pressed by the spring 244 back into its seat, so that the Exit 224 is closed. It can no longer flow more lubricant into the reservoir 5 and the check valve 72 prevents leakage of the lubricant through the feed 7. The check valves 62 ensure that during the filling of the reservoir 5 no lubricant passes through the leads 6 to the lubrication points 61. After filling, the lubricant in the reservoir 5 is substantially at the filling pressure p3, which is smaller than the opening pressure p1 of the check valves 62 and greater than the opening pressure of the check valve 72nd

After the piston has separated from the filling device 22, the air in the cylinder 3 is compressed on the combustion chamber side of the piston 1 during its upward movement. This pressure in the combustion chamber 4 or on the combustion chamber side of the first piston ring 11 is also applied to the membrane 81 of the conveyor 8 via the channel 82. This increases the diaphragm piston 8, the pressure in the reservoir 5. If the pressure has risen so far that the pressure difference across the check valves 62 is greater than the opening pressure p1 of the check valves 62, so they open and the lubricant passes through the leads 6 to the lubrication points 61 and from there to the tread 32. The lubrication begins. After the piston 1 has passed through top dead center, in the region of which the combustion process takes place, the pressure in the combustion chamber 4 decreases again during the downward movement of the piston 1, of course also by the opening of the exhaust valve (not shown). Once the pressure on the combustion chamber side of the piston 1, via the channel 82 also on the Diaphragm 81 loads, has fallen so far that the pressure difference across the check valves 62 is smaller than their opening pressure p1, so close this check valves 62, the leads 61, so that no lubricant can get to the lubrication points 61. The lubrication is finished.

The diaphragm piston 8 is adjusted so that it reacts as accurately as possible above a specified pressure. This makes it possible for the lubricant to be introduced into the cylinder 3 exactly where it is needed or where it is most efficient. The opening of the channel 82 is chosen sufficiently large that it does not come to a coking of this opening during operation. A coking is further prevented by the fact that the lubricant is injected not above, so the combustion chamber side of the first piston ring 11, but between the piston rings 11, 12, 13. This ensures safe operation.

The diaphragm piston 8 is designed so that it above the specified pressure on its piston displacement displaced as accurately as possible predetermined amount of lubricant from the reservoir 5 and presses on the leads 6 in the piston ring package. Advantageously, this ensures a load-dependent lubrication.

This is based on the 3 and 4 explained in more detail. Fig. 3 shows a diagram with the pressure curve p in the cylinder 3 in dependence on the crank angle KW, which is plotted on the horizontal axis. At the crank angle 0 and at the crank angle 360 °, the piston 1 is in the lower reversal point, that is, where the filling of the storage space 5 takes place. With ps that limiting pressure in the cylinder is designated, in which the pressure drop across the check valves 62 is just as large as the opening pressure p1 of the check valves 62. Thus, if the pressure in the cylinder 3, so the pressure on the combustion chamber side of the first piston ring 11 is meant higher is called the Limit pressure ps, so lubricant is conveyed from the storage space 5 through the leads 6 to the lubrication points 61, it is smaller than the limit pressure ps, so no lubricant can pass through the leads 6 to the lubrication points 61.

The solid curve in Fig. 3 shows the pressure curve for a medium load range of the large diesel engine, while the dashed curve shows the pressure curve at higher load. Like this Fig. 3 shows, only between the crank angles W1 and W2 lubricant can reach the lubrication points 61, because in this crank angle range, the pressure in the cylinder 3 is higher than the limit pressure ps. The area under the curve above the limit pressure ps describes the load dependency of the lubricant quantity. This load dependency can be coupled with the calculation of the mean effective pressure. At higher load (dashed curve), the closing process, in which the lubrication is terminated by closing the check valves 62, crank angle moderately shifts to later (higher) values.

For the supply of the lubricant by means of the diaphragm piston 8, it is possible to work with a constant stroke of the diaphragm piston 8. If then the limiting pressure ps is exceeded at the crank angle W1, the lubricant passes at a constant delivery rate to the lubrication points 61 until the pressure in the cylinder 3 falls below the value ps again. Another possibility is to design the diaphragm piston 8 as a proportional piston, so that the amount of lubricant that is conveyed between the crank angles W1 and W2 per time follows the pressure curve in the cylinder. For this purpose, the diaphragm piston 8 is designed such that its stroke or the distance traveled by it follows the pressure in the cylinder 3. These two possibilities are illustrated in the diagram Fig. 4 ,

In Fig. 4 In the upper diagram, the pressure curve in the cylinder 3 is again analogous to the crank angle KW in analogy Fig. 3 shown, in Fig. 4 the pressure curve is shown only for a load.

The two diagrams below show the flow rates F1 and F2 of lubricant as a function of the crank angle KW. The flow rate F1 corresponds to the variant with a constant stroke of the diaphragm piston 8, the flow rate F2 shows the case when the stroke of the diaphragm piston 8 follows the pressure curve in the cylinder 3.

In this way, the amount of lubricant introduced into the cylinder 3 can be adjusted very precisely, and the time or the time interval of the lubrication can be controlled very precisely. This results in a very efficient use of the lubricant, resulting in a very low consumption results. Lubricating rates of, for example, 0.6 g / kWh can be achieved.

Depending on the application, it may be that the storage space 5 does not have to be filled every working cycle, so not every time the piston 1 is at bottom dead center. For this purpose, for example, the pump 23 of the lubricant source 2 can be controlled so that it promotes lubricant only in every second, or third, or fourth, etc. work cycle in the reservoir. It is also possible to monitor the filling level of the storage space 5 with a sensor and only if necessary to control the pump 23 in such a way that lubricant is conveyed into the storage space.

Instead of the diaphragm piston, of course, other conveyors 8 may be provided, for example, hydraulic, pneumatic, electrical or combinations thereof, after filling the storage space 5 and after decoupling of the feed 7 from the filling device 22, the pressure in the storage space 5 to a predetermined Increase crank angle or time so that the opening pressure p1 of the check valves 62 is exceeded and the lubrication starts. Alternatively or additionally, it is of course also possible to replace the check valves 62 by other controllable closing members 62, for example by electrically controllable valves.

Furthermore, other placements and / or a different number of lubrication points 61 are possible. For example, it is possible in particular to provide at least one lubrication point in one of the piston rings, so that the lubrication also takes place through the piston ring. Such a piston ring may be configured, for example, as a lubricant distributor ring.

A lubricant collecting element 14 may be provided in place of each piston ring, with the exception of the piston ring nearest the combustion chamber 4.

Fig. 5 shows a second embodiment of a piston 1 according to the invention and a lubricant source 2. From the function of equal or equivalent parts are provided with the same reference numerals as in Fig. 1 , In the following, the differences to the first embodiment are mainly discussed. All explanations that were made in connection with the first embodiment of the inventive piston 1, apply in an analogous or analogous manner to the same for the second embodiment.

In the second embodiment, the reservoir 5 is designed as a tank which is arranged in a cavity 51 in the interior of the piston 1. The storage space 5 has in its wall two outlet openings 52 through which the lubricant can pass from the storage space 5 into the supply lines 6. In the storage space 5 is as a conveyor Delivery piston 8 is provided, which is supported by a spring 83 at the illustration according to the upper end of the storage space 5. During the filling process of the storage space 5, the delivery piston 8 is moved upward in accordance with the representation of the force of the spring 83. As a result of the spring tension thus produced, the delivery piston 8 moves downward after the filling process and thereby presses the lubricant through the supply lines 6 and the lubrication point 61 into the piston ring packet. In the second embodiment, the supply 7 is integrated in the storage space 5 and has the check valve 72 , Of course, it is also possible in the second embodiment to design the feed 7 as a feed channel or line or bore and / or a pin 73 as in Fig. 2 to be shown provided.

In the second exemplary embodiment, the storage space 5 is arranged movably in the cavity 51 with respect to the axial direction and is supported by a return spring 9 at the end of the cavity 51, which faces the combustion chamber 4. As a result, the storage space 5 designed as a tank functions together with the restoring spring 9 as a blocking device which, in cooperation with the lubricant source 2, closes the flow connection between the storage space 5 and each supply line 6, as will be explained in more detail below.

When filling the storage space 5, the delivery piston 8 must be tensioned against the force of the spring 83. This means that the filling pressure p3 must be at least as great as the maximum pressure that the delivery piston 8 can exert on the lubricant due to its spring loading. In order for this maximum pressure is sufficient to open the check valves 62 in the supply lines 6 for lubrication, it must be greater than the opening pressure p1 of the check valves 62. Without a locking device for closing the supply lines 6, this would mean that even when filling the Reservoir 5 at least a portion of the lubricant directly passes through the leads 6 to the lubrication points 61 and exits there. This prevents the locking device, as now based on the Fig. 6 is explained.

Fig. 6 shows the locking device in the left view in the open position and in the right view in the closed position, which is taken during the filling process. When the piston 1 comes to the bottom dead center in its downward movement, the storage space 5 by a lifting device 25 (see Fig. 5 ) of the lubricant source 2 in the axial direction against the force of the return spring 9 as shown shifted upward and takes the in the right representation of Fig. 6 shown position. In this position, the wall of the storage space 5 closes the entrance to the supply lines 6; the outlet openings 52 are no longer aligned with the supply lines 6, so that no lubricant can get into the supply lines 6.

The limited by the delivery piston 8 and the reservoir 5 compensation chamber 45 may in particular contain a compressible medium. The delivery piston 8 is provided at its periphery with a sealing element 46 which fluid-tightly separates the compensation chamber 45 ves the reservoir, which contains the lubricant.

The lifting device 25 is designed for example as a stop against which the storage space 5 starts before the closing member 24 of the filling device 22 is opened. Now, the filling of the storage space 5 is carried out in a similar manner as described in connection with the first embodiment. In this case, the delivery piston 8 is tensioned in the storage space 5, that is, it is moved against the force of the spring 83 as shown above. After filling the closing member is closed, the piston 1 moves upward and the storage space 5 loses contact with the lifting device 25, Thus, the reservoir 5 moves by the spring force of the return spring 9 relative to the piston 1 as shown below and takes the in Fig. 6 in the left illustration shown position. In this open position, the outlet openings 52 are aligned with the supply lines 6, so that lubricant can now pass from the storage space 5 through the outlet openings 52 into the supply lines 6 and to the lubrication points 61.

In contrast to the first embodiment results in the second embodiment, a different characteristic of the introduction of the lubricant in the piston ring package. The introduction of the lubricant takes place here, as long as the pressure in the cylinder remains below a limit pressure ps. Immediately after filling the storage space 5, when the piston 1 is still in the vicinity of the bottom dead center, prevails at the lubrication points 61 and in the supply lines 6 with respect to the duty cycle, the lowest pressure, namely substantially the scavenging air pressure. The pressure drop across the check valves 62 is then essentially determined by the difference between the pressure generated by the delivery piston 8 in the storage space 5 and the cylinder side on the check valves 62 pressure corresponding approximately to the scavenging pressure. As long as this pressure difference is greater than the opening pressure p1 of the check valves 62, lubricant exits from the storage space 5 through the supply lines 6 and the lubrication points 61 in the piston ring package. With progressive upward movement of the piston 1, the pressure in the cylinder 3 increases and thus also the pressure which loads the cylinder side on the check valves 62. As a result, the pressure drop across the check valves 62 reduces. When the limit pressure ps in the cylinder reaches the pressure difference across the check valves 62 is smaller than their opening pressure, so they close the supply lines 6. The lubrication is stopped. After the piston 1 has passed the top dead center, at which the combustion takes place, the pressure in the cylinder decreases with increasing downward movement of the piston more and more. If then the pressure difference over the Check valve when the pressure ps reaches the value p1 of the opening pressure of the check valves 62, the lubrication starts again.

This illustrates Fig. 7 in one too Fig. 3 analog representation in which the pressure p in the cylinder in dependence on the crank angle KW for a duty cycle and for a load condition of the engine is shown. The lubrication takes place in the hatched areas. In the area around the bottom dead center, ie at the crank angles 0 ° and 360 °, there is no lubrication, as the two small vertical lines in Fig. 7 indicate, because during the filling process of the storage space 5, the supply lines 6 are closed by the locking device relative to the storage space 5.

With this second embodiment, there is another way of supplying lubricant, because here the lubrication takes place mainly in the lower region of the running surface 32 of the cylinder 3. This also results in a changed characteristic of the flow rate F of the lubricant. This is in Fig. 8 for the second embodiment in a too Fig. 4 shown analog representation.

In order to achieve an introduction of the lubricant over the entire stroke or over the entire working cycle of the piston 1, it is possible to combine the first embodiment and the second embodiment with each other. For this purpose, for example, two storage spaces 5 can be provided and two lubricating sources 2, wherein one of the storage spaces 5 is filled and emptied, as described for the first embodiment and the other storage space 5 as described for the second embodiment.

A further variant for both embodiments is that the filling of the storage space 5 takes place in a similar manner in the same way when the piston is at top dead center.

In the following, a possibility for the design of the piston ring package for the distribution of the lubricant on the tread 32 will now be described. These variants, based on the FIGS. 9, 10 and 11 are explained in particular for both the first and for the second or the third embodiment described below Fig. 12 , Each of the variants is not limited to these embodiments, but is suitable for all pistons in cylinders of large diesel engines. It is therefore also suitable for pistons which are not designed according to the invention.

Fig. 9 shows a sectional view of the piston ring package with the piston rings 11, 12 and 13. On the representation of the leads 6 was in Fig. 9 omitted, they are preferably arranged so that the lubrication points 61 are arranged as described above in each case between two adjacent piston rings.

Like this in Fig. 9 is shown somewhat exaggerated, the first piston ring 11 and the third piston ring 13 are each designed crowned but asymmetrical. The first piston ring 11 is designed rounded on its side facing away from the combustion chamber 4 and the third piston ring 13 is rounded on its side facing the combustion chamber 4.

In contrast to today's conventional lubrication method, in which the lubricant is distributed with the top piston ring in the piston upward movement, the first piston ring 11 distributes the lubricant in the downward movement of the piston 1. This has the advantage that no lubricant is scraped into the combustion chamber 4 and so that it gets lost for lubrication. As a result, the lubricant consumption can be reduced. At the same time there is the advantage that a strong coking is counteracted, whereby, for example, the use of an "anti-polishing-rings" can be superfluous.

During the upward movement of the piston, the third piston ring 13 distributes the lubricant on the running surface 32.

Another advantageous measure is to design the second piston ring 12, which is arranged between the other two piston rings 11 and 13, as a lubricant distributor ring. Primarily, the lubricant distribution ring serves to distribute the lubricant over the circumference of the tread 32. One possible embodiment is in the 10 and 11 shown. Fig. 10 shows a side view of the designed as a lubricant distributor ring piston ring 12 and fig.11 a plan view of the piston ring 12. The piston ring has on its outer circumferential surface, which faces in the operating state of the wall 31 of the cylinder 3, a plurality of inclined grooves 122, of which in 10 and FIG. 11 only one is shown.

Due to the pressure difference in the annular space between the first piston ring 11 and the second piston ring 12 on the one hand and the annular space between the second piston ring 12 and the third piston ring 13 on the other hand, - ie the pressure drop across the second piston ring 12 - is forced through the grooves 122, a flow , which has a tangential component and thus the circumferential distribution of the lubricant is beneficial.

Of course, other profiles for the lubricant distributor ring are possible.

Fig. 12 shows a third embodiment of the inventive piston.

The piston 1, of which only a part is shown, carries the reference numeral 1 as in the preceding embodiments. Furthermore, a lubricant extraction device 40 is shown schematically. This lubricant removal device is optionally by a Lubricant source 2 replaceable, as described in connection with the first or second embodiment. An essential difference from the preceding embodiments is that the storage space 5 contains no conveyor 8 by means of which lubricant is passed between two piston rings 11,12,13 via a supply line into the lubricating space. The lubricating space extends between the piston skirt 16 and the running surface 32 on the wall 31 of the cylinder 3.

The lubricant is distributed via the lubricant collecting element 14 in the lubricating space and removed via the lubricant collecting element 14 from the lubricating space and fed via the lubricant line 10 to the storage space 5. The storage space 5 is a reservoir filled with lubricant, which is arranged in the piston body 34. From the storage space 5 leads on the one hand at least one lubricant line 10 to the lubricant collecting element 14 and at least one feed 7 to the cylinder chamber 20. In the feed a closing member 72 is arranged to prevent that contained in the reservoir 5 lubricant can run unintentionally into the cylinder chamber. The closing member 72 is designed in particular as a check valve.

To the feed 7, a lubricant source, not shown, can be connected, the operation of the in Fig. 1 and Fig. 2 corresponds to the lubricant source shown. By means of the lubricant source can be introduced periodically or if necessary lubricant into the storage space 5. In the reservoir, a measuring device can be arranged, which provides a measurement of the state of the lubricant in the reservoir, for example, measures the pressure of the lubricant. If the measured value falls below a threshold value, the lubricant source is connected to the feed 7. Alternatively, a measuring device can be arranged in the lubricating space, which provides a relevant for the amount and the condition of the lubricant characteristic.

The introduction of the lubricant into the lubricating space is similar to that described in connection with the second embodiment as long as the pressure in the lubricating space remains below a limiting pressure, which is also to be referred to here as ps. Near the bottom dead center, the lowest pressure is present at the lubricant collecting element, namely essentially the pressure in the cylinder chamber 20, that is to say the scavenging air pressure. The pressure of the lubricant is higher than the pressure in the cylinder space and the pressure drop across the lubricant collecting element 14 and the lubricant line 10. Accordingly, lubricant flows from the storage space 5 into the lubricating space. This lubricant flow continues until the pressure in the lubricant chamber reaches the limit pressure ps, ie equal to the pressure in the reservoir 5 plus the pressure drop across the lubricant collecting element 14 and the lubricant line 10.

The lubricant collecting element fulfills a function as a lubricant distribution element below the limit pressure. If the piston now moves further in the direction of top dead center, the increasing internal pressure in the lubricant space prevents the lubricant from escaping from the lubricant collecting element. The lubricant collecting element acts as a collecting element above the limit pressure ps, that is, the two lips 26, 27 detect lubricant in the lubricant space and guide it into the opening 30, into the lubricant line 10 and into the storage space 5. This measure prevents lubricant is entered into the combustion chamber 4 and on the other hand it is ensured that sufficient lubricant is present in the lubricant space.

Alternatively, a lubricant extraction device 40 can be connected to the feed 7. By means of the lubricant removal device contaminated or used lubricant can be removed from the lubricant circuit. The lubricant extraction device 40 includes an opening member to move the Closing member 72 to open mechanically. Since the lubricant is under a pressure which is higher than the pressure in the cylinder chamber 20, lubricant flows out of the storage space 5 and any lubricant present in the lubricant line 10 or in the lubricant collecting element 14 in an under atmospheric pressure lubricant removal device. To increase the outflow rate, the lubricant extraction device can also operate under a pressure that is less than the atmospheric pressure.

In addition, the lubricant can be drained off via the feed 7 or in addition to the same via another, not shown drain line. Of course, a plurality of such drain lines may be provided at different locations of the piston body, in particular when the storage space 5 is annular or opens into an annular channel extending in the piston body, from which a plurality of lubricant lines branches, leading to a plurality of lubricant collecting elements.

It is also possible to provide one or more lubricant collecting elements between each two piston rings. The placement of the lubricant collection elements depends on the need for lubricant on the piston skirt 16 or the associated running surface 32.

The lubricant collecting elements can be distributed along the circumference of the piston skirt, in particular be arranged at equal distances from each other.

Claims (15)

Piston (1) for a cylinder of a large engine, which has a piston body (34), which contains a reservoir (5) for receiving a lubricant, wherein the piston body (34) by a piston skirt (16) is peripherally limited, wherein the storage space ( 5) via a lubricant line (10) with the piston skirt (16) is connected, and a feed (7) is provided, which is designed for releasable connection to a lubricant source (2), wherein the feed (7) into the storage space (5 ), characterized in that the lubricant line (10) opens into a lubricant collecting element (14). Piston according to claim 1, wherein a supply line (6) is provided, which extends from the storage space (5) to a lubrication point (61) provided on the surface of the piston (1), so that lubricant from the storage space (5) to the lubrication point (61) can be conducted, wherein in the supply line (6) a closing member (62) is provided. Piston according to claim 1, wherein in the piston a conveying device (8) is provided to convey the lubricant from the storage space (5) through the supply line (6) to the lubrication point (61). Piston according to claim 2, wherein the conveyor (8) comprises a delivery piston for the lubricant, which is designed and arranged so that it can be acted upon in the operating state with the combustion chamber side pressure in the cylinder (3). Piston according to one of the preceding claims, wherein a plurality of piston rings (11,12,13) are provided on the piston skirt (16), wherein the lubrication point (61) is arranged with respect to the axial direction defined by the piston axis (A) between two piston rings. Piston according to one of the preceding claims, wherein the piston skirt (16) at a first end (17) enclosing a piston surface (18) which adjoins a combustion chamber (4), wherein the lubricant collecting element (14) outside the furthest from the combustion chamber (4 ) remote piston ring (13) on the piston skirt (16) is arranged. Piston according to one of the preceding claims, wherein a piston ring (12) is provided, which is designed as a lubricant distributor ring. Piston according to one of the preceding claims, wherein in the lubricant line (10) a closing member (35) is provided. Piston according to claim 8, wherein the closing member (35) in the lubricant line (10) is designed as a check valve. Piston according to one of the preceding claims comprising a locking device (5,9) which is designed such that it closes the flow connection between the reservoir (5) and each supply line (6) when interacting with the lubricant source (2). Lubricating device for the cylinder of a large engine comprising a piston (1) according to one of the preceding claims, wherein a A lubricant chamber (15) surrounding the piston skirt for lubricating a running surface of a cylinder, and a lubricant source (2) having a filling device (22) which is releasably connectable to the feed (7) and cooperates with the piston (1) only a lubricant from the lubricant source (2) in the storage space (5) can be introduced when the filling device (22) is connected to the feed (7), wherein the storage space (5) with a lubricant collecting element (14) is connectable, so Lubricant from the lubricating space (15) in the reservoir (5) is traceable. Lubricating method for the cylinder of a large engine with a reciprocating piston arranged in the cylinder, in which method a feed (7) of the piston (1) during the movement of the piston (1) connected to a filling device (22) of a lubricant source (2) is introduced, a lubricant from the lubricant source (2) through the feed (7) in a storage space (5) of the piston (1), the connection between the feed (7) of the piston (1) and the filling device (22) the movement of the piston (1) is separated, and then the lubricant from the storage space (5) through a supply line (6) to a lubrication point (61) on the piston skirt (16) is brought. A lubricating method according to claim 12, wherein the lubricant is introduced into the reservoir (5) of the piston (1) when the piston (1) is at the top or bottom dead center of its movement. A lubricating method according to claim 12, wherein the lubricant is discharged from the reservoir by means of a lubricant extraction device (40). Large engine with a piston according to one of claims 1-10 or with a lubricating device according to claim 11 or operated with a method according to any one of claims 12-14.

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