EP2395208A1 - Large motor with a cylinder lubrication device and method for lubricating a cylinder of a large motor - Google Patents

Abstract

The giant motor has two cylinders (20), where each cylinder has a hole (B) and a longitudinal axis (A). A lubrication device (10) is arranged for a pump (1) of each cylinder. A distributer (3) is provided with two lubricant lines (8,18), where each lubricant line has a shutoff element (5,15). An independent claim is also included for a method for lubricating a bearing surface of a cylindrical wall of a cylinder of a giant motor.

Description

The invention relates to a large engine with a cylinder lubricating device, and a method for lubricating a running surface of a cylinder wall of a cylinder of a large engine. A large engine is a reciprocating internal combustion engine, which is used in particular as a slow-running large diesel engine, for example in shipbuilding. Large engines are often used as drive units for ships or even in stationary operation, e.g. used to drive large generators for generating electrical energy. The 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 fuels and supplies are central criteria for the operation of the machines. Among other things, the piston running behavior of such large-bore slow-running large engines is a determining factor for the length of the maintenance intervals, the availability and the lubricant consumption also directly for the operating costs and thus for the economy. Thus, the complex problem of lubrication of large engines is becoming increasingly important.

In large engines, but not only these, the piston lubrication takes place by lubricating devices in the reciprocating piston or in the cylinder wall, by the lubricating oil on the running surface of the cylinder wall is applied to minimize the friction between the piston and the tread and thus the wear of the tread and the piston rings. For example, today's engines, such as Wärtsilä's RTA engines, wear less than 0.05 mm of tread over an operating period of 1000 hours. The lubricant delivery rate is about 1.3 g / kWh and less in such engines and should not least be further reduced for cost reasons as possible, while the wear is to be minimized.

As lubrication systems for lubricating the treads quite different solutions are known, both in terms of the actual execution of the lubrication devices themselves, as well as the procedures for lubrication. Thus, lubrication devices are known in which the lubricating oil is applied to the piston passing through the lubricant opening by a plurality of lubricant openings accommodated in the circumferential direction in the cylinder wall, wherein the lubricant is distributed by the piston rings both in the circumferential direction and in the axial direction. The lubricant is not applied over a large area on the running surface of the cylinder wall, but more or less selectively between the piston rings on the side surfaces of the piston according to this method.

In this case, other methods are known. For example, in the WO 00/28194 proposed a lubricating system in which the lubricating oil is sprayed under high pressure by means of atomizing nozzles, which are housed in the cylinder walls, substantially tangential to the cylinder wall in the scavenging air located in the combustion chamber, wherein the lubricating oil is atomized into small particles. As a result, the atomized lubricating oil is finely distributed in the scavenging air and thrown against the running surface of the cylinder wall by the centrifugal force as a result of the twist, which carry the scavenging air and thus also finely dispersed therein lubricating oil particles.

In another method, in the moving piston are preferably a plurality of lubricant nozzles, wherein the term may comprise a simple outlet opening and / or a unit with a check valve, accommodated, so that the lubricant can be applied over substantially the entire height of the tread anywhere.

The manner in which the lubricant is applied to the tread of the cylinder wall, its metering and the time at which the lubricant is introduced into the cylinder of the large engine, have a significant influence on the quality of the lubrication.

The quantity of lubricant to be applied to the running surface per unit of time and area can depend on many different parameters during operation of the large engine. For example, the chemical composition of the fuel used, in particular its sulfur content plays an important role. In addition to the lubrication of the cylinder, so the reduction of the friction between the piston and cylinder surface, more precisely between the piston rings and the tread of the cylinder wall, the lubricant is used, inter alia, for the neutralization of aggressive acids, especially sulfur-containing acids that arise during the combustion process in the combustion chamber of the engine , Therefore, depending on the fuel used different grades of lubricant can be used, which differ, inter alia, in their neutralization ability, for which the so-called BN value of the lubricant is a measure. Thus, it may be advantageous to use a lubricant having a higher BN value at a high sulfur content in the fuel than a fuel having a lower sulfur content, because a lubricant having a higher BN value has a stronger acid neutralization effect.

Often, however, it is also possible that the same type of lubricant must be used for fuels of different quality. In such cases, for example, by a corresponding increase or decrease in the amount of lubricant used, a higher or lower acid content in the combustion products can be compensated.

Another problem with the metering of the amount of lubricant to be applied are temporal and / or local variations of the State of the lubricant film, in particular the thickness of the lubricant film in the operating state of the reciprocating internal combustion engine.

Of course, the necessary amount of lubricant, for example, from a variety of operating parameters, such as the speed, the combustion temperature, the engine temperature, the cooling power for cooling the engine, the load and many other operating parameters more dependent. So it may be possible that at a given speed and higher load a different amount of lubricant must be applied to the tread of the cylinder, as with the same speed and lower load.

Furthermore, the state of the internal combustion engine itself can have an influence on the amount of lubricant. For example, it is known that, depending on the state of wear of the cylinder surface, piston rings, pistons and so on, the amount of lubricant to be used can vary greatly. Thus, in a cylinder with a new, not yet retracted cylinder tread and / or with new piston rings in the break-in phase, increased friction is to some extent quite desirable in order for the mating partners, e.g. The piston rings, piston ring groove and running surface can be ground in and optimally adjusted to each other. Among other things, this can be achieved by using a different amount of lubricant in the running-in phase of a cylinder than in the case of a cylinder which is already in operation for a considerable number of operating hours. Therefore, in a multi-cylinder engine, the amount of lubricant is often separately adjustable, particularly for each cylinder.

Also, in general, the cylinder tread will wear differently both circumferentially and longitudinally depending on the number of hours of operation performed. This applies analogously, for example, for the piston rings and the piston itself.

Thus, the amount of lubricant in a reciprocating internal combustion engine not only depending on the number of hours worked, but the amount of lubricant should also within a and the same cylinder at different points of the tread of the cylinder wall depending on the requirements of time and locally different dosable.

Therefore, it has long been known to provide in a running surface of a cylinder or in the moving piston in different areas lubricant nozzles, which are preferably all individually controllable, so that the amount of lubricant can be varied both temporally and locally depending on the requirements.

In order to determine the amount of lubricant to be introduced by a particular lubricant nozzle at a particular time, various methods are known. In simple cases, the amount of lubricant, possibly taking into account the quality of the fuel used and the lubricant itself, simply controlled depending on the operating state of the reciprocating internal combustion engine, for example as a function of load or speed, due to already performed operating hours and the state of wear of the mating partner Can be considered.

Thus, the expert distinguishes the field of so-called hydrodynamic lubrication, the state of lack lubrication and the mixed lubrication. Hydrodynamic lubrication is used when a lubricant film of such thickness is formed between the mating partners, that is to say, for example, between the running surface of a cylinder wall and the piston ring of a piston so that the surfaces of the mating partners are separated from one another by the lubricant film, so that they are separated do not touch. Another limiting case is the so-called mixed friction or mixed lubrication condition. In the case of mixed friction, the lubricant film between the mating partners is, at least in part, so thin that the mating partners touch each other directly. In this case, there is a risk of scuffing and ultimately the training of a piston eater. Between these two borderline cases the so-called lack lubrication is settled. In the state of deficient lubrication, the lubricant film is just so thick that the counterpart partners no longer touch; the amount of lubricant between the mating partners However, it is not enough that hydrodynamic lubrication could build up. Previously, both the condition of the mixed lubrication, and the lack of lubrication prevented as possible. That is, the thickness of the lubricant film was preferably selected to set a state of hydrodynamic lubrication between the mating partners.

The operation in the field of hydrodynamic lubrication naturally results in a correspondingly high lubricant consumption. On the one hand, this is not only extremely uneconomical, but it has also surprisingly been found that not only a lack of lubricant, but also an excess of lubricant can lead to damage of the mating partner in the cylinder.

This problem was successfully solved for the first time by determining a parameter characteristic of the lubricant film by means of a sensor and, after evaluation of the sensor signal by means of a control unit, a state parameter of the lubricant film on the cylinder surface, in particular the thickness of the lubricant film, preferably locally by appropriate metering the lubricant supply has been optimized. The corresponding device and the associated method have already been described by the Applicant in the EP 1 505 270 A1 detailed.

Although the problem of determining the necessary amount of lubricant which must be supplied to a specific location of the cylinder surface has been optimally solved by this innovative method, it has always been difficult to determine the optimal time for the injection of the lubricant into the cylinder.

In this case, the optimum point in time may depend on many parameters, in particular on the different operating states under which the internal combustion engine is operated. Many of the parameters that can play a role are the same ones that are relevant to the correct lubricant film thickness and have already been mentioned in the beginning. Above all, the right time naturally depends primarily on the various lubrication methods described above. Thus, the timing for the injection of the lubricant is of course sensitive to whether For example, the lubricant is to be fed into the purge air or, for example, to be injected directly onto the passing piston, for example into the piston ring package of the piston.

It is immediately clear that, therefore, the timing of the lubricating oil injection depends inter alia on static and dynamic geometric parameters of the large engine, in particular the position of the piston between the lower dead zone and the upper dead zone relative to the location of the lubricant nozzle. That is, to ensure optimum lubricant injection into the cylinder, the position, ie the position X of the piston with respect to the longitudinal axis of the cylinder at the time of lubricant injection must be known as accurately as possible.

Heretofore, the position X of each piston between the lower dead zone and the upper dead zone in the cylinder has been determined by determining the instant crank angle of the large engine for all pistons of the engine from a single central crank angle measurement, for example via a chain drive directly with a Wave is coupled to the lubricant pump.

In general, the current crank angle of the large engine is measured in the operating state until today, and calculated from this central crank angle measurement, the position of all pistons in the cylinder. From this calculated from the measured crank angle position X of a piston in the cylinder, the time of the lubricant injection is then calculated in the cylinder in question.

However, this method used so far has the distinct disadvantage that the positions of the pistons in the cylinder thus calculated are subject to great errors, which are in fact not tolerable under special operating conditions, such as under full load, high or full speed or other extreme operating conditions are.

But even under normal operating conditions, these errors, which have the consequence that the lubricant just not at the optimum time in the cylinder is introduced, lead to premature wear, shortened maintenance intervals and thus to higher costs, in the worst case to serious damage to the cylinder components.

The reason for this erroneous position determination is, inter alia, the elasticity of the engine and its movable and immovable parts and the massive vibrations and torsional movements of the crankshaft.

This has the consequence in particular that the measured at a certain point or assembly of the large engine crank angle can not be accurately correlated in one-to-one with the actual position of a particular piston in the cylinder, but at most with an accuracy that contains a non-calculable error and the depending on circumstances, eg depending on the load of the large engine, or the speed, or another operating parameter of the large engine may well be several degrees crank angle. The lubricant may then be injected at a completely wrong time. In the worst case, this is then not used for lubrication at all, because it is e.g. in a compression stroke is not sprayed on the piston wall, but under the piston and thus does not contribute to the lubrication at least in this stroke of the piston.

What aggravates the problem is the fact that the error for each cylinder of the large engine, which often but not necessarily many cylinders, e.g. is more than 6, 8, 10, 12, 14 cylinders arranged preferably in series, another error is that, depending on which section or at which location of the crankshaft the cylinder is, the above-mentioned vibrations, torsions, etc. other amplitudes, possibly other frequency spectrums and thus have different effects.

In addition, for fine adjustment of the engine or for fine adjustment of the compression in each cylinder individually, the upper deadband of the piston is adjusted, for example by means of special washers or spacers, ie it will be at a suitable location on the attachment of the piston, piston rod, the crosshead or other fasteners of the piston so-called "compression shims" individual for each cylinder provided, whereby the compression in each cylinder is optimized. This has the consequence that, even if the position of the piston in the cylinder would be exactly correlated with the measured at a certain point crank angle, the position of the piston in the cylinder could not be calculated exactly because due to the different adjustment of the individual pistons by means of compression shims, the calculation of the position of each piston with a different, usually not known per se correction factor should be performed.

However, since these correction factors are not known, the error is usually amplified in the previously performed calculation of the position of the piston in the cylinder.

In addition, even an electronically controlled lubrication system can not necessarily prevent an excessive amount of lubricant from getting onto the tread. The reason for this is that when adding a predetermined amount of lubricant can not be considered whether the large engine is operated under full load conditions.

The dose of lubricant is usually in a lubrication system, such as in the EP 2 177 720 A1 shown, given. The lubrication system includes a pump-nozzle unit for supplying each of the lubrication points on the tread of the cylinder with a specified amount of lubricant. The pump is designed as a reciprocating pump. The lubricant in the pump chamber is conveyed to one or at most two lubrication points during a stroke of a working piston. The working piston is operated by means of a hydraulic medium. The stroke is triggered when a means leading to the working piston hydraulic line is opened by means of a switching valve, so that the working piston is acted upon by hydraulic medium.

The switching valve switches depending on an operating state of the large engine, such as the speed, the load, the position and / or the position of the crankshaft. The operating state is detected at the large engine by means of a sensor unit, converted into an electrical signal, which is fed into a control unit. The controller unit checks, whether the electrical signal corresponds to an operating state which requires the supply of lubricant and optionally sends a corresponding output signal to the switching valve.

A disadvantage of this arrangement is the fact that the lubrication point or the pair of lubrication points only a single, predetermined by the size of the pump chamber amount of lubricant can be supplied. This predetermined amount must be so large that sufficient lubrication is ensured even at full load operation of the large engine.

On the other hand, if the large engine is operated at partial load, the amount of lubricant supplied to the lubrication point can be too great, so that one gets into the area of hydrodynamic lubrication described above.

It was in the EP 1 426 571 B1 also proposed to provide a valve for each lubrication point, the opening time can be controlled individually. For this purpose, a central accumulator for lubricants is used, from which all lubrication points of all cylinders of the large engine can be supplied with lubricant. Although it is possible with this lubrication system to accurately set the amount of lubricant by controlling the opening time, a variety of operating parameters must be monitored. Apart from increased costs, this regulatory effort also means considerable additional expenditure if the operational safety has to be ensured for a large period of time.

Furthermore, a pump is provided which conveys into the pressure accumulator. Should the amount of lubricant in the pressure accumulator not be completely required because the large engine operates, for example, in partial load operation, a connected to the pressure accumulator valve is opened, so that lubricant can be circulated.

The lubrication points supplied lubricant quantity is thus determined only by the opening time of the located in the lubricant lines between pressure accumulator and lubrication point switching valves.

In the EP1582706 It has therefore been proposed to forward lubricant delivered by a single pump into a common lubricant supply to all cylinders via lubricant lines to injectors associated with each cylinder. Each lubrication point is thus assigned a separate injector. Each of these injectors is equipped with an electrically controllable solenoid valve to provide each of the lubrication points with lubricant independently. This means that according to this method, the lubricant quantity and the time of lubricant delivery can be set arbitrarily.

It is also out EP0368430 known to provide small lubricant reservoirs or accumulators, which are arranged in the lubricant supply to each cylinder. The supply of lubricant to the lubrication points on the cylinder is controlled by a single common electrically controllable solenoid valve. The solenoid valve is disposed between the accumulator and the lubricant distribution valve. The lubricant distribution valve can simultaneously open all supply lines to all lubrication points of a cylinder. That is, after this solution, although the time of lubrication and the amount of lubricant that is supplied to this cylinder, can be regulated. However, the amount of lubricant which is supplied to each individual lubrication point can no longer be influenced, since downstream of the lubricant distribution valve no obturator is provided any longer. Therefore, the control of the amount of lubricant and the timing of lubrication is not independent of each other.

However, it has proved to be disadvantageous that the amount of lubricant to be supplied to each cylinder can not be changed when the opening time of the switching valve, z. B. the solenoid valve of EP1 582 706 A2 stays the same. That is, the amount of lubricant can only be changed over the opening time of the switching valve. The volume flow which passes through the switching valve per unit time, however, is fixed.

Furthermore, it has proven to be disadvantageous that a monitoring of the viscosity of the lubricant was required, since the lubricant partly due to the central pressure accumulator must travel long distances to the lubrication point. On the way to the lubrication point, the Temperatures to which the lubricant lines are exposed, vary widely, which has a significant influence on the viscosity of the lubricant. In particular, it should be avoided that lubricant solidifies in individual lubricant lines and thus misplaced the lines. To remedy this problem, the viscosity and / or temperature must be provided at least in the lubricant lines, which are particularly long or need to pass the zones low temperature.

Therefore, in the EP 1 767 751 A1 developed another lubrication system in which each cylinder is assigned its own lubrication module. The lubrication module contains an intermittently pumping lubricant pump, by means of which the lubricant is metered and pulse-like supplied to the lubricant nozzles. The pump is designed as a reciprocating pump, which has a plurality of delivery pistons. The delivery piston is arranged to be movable in a pumping space. The pump room determines the volume of lubricant that can be delivered to each lubrication point with each stroke.

Each lubrication point is assigned a delivery piston. When the pump executes a stroke, the volume of lubricant in the pump chamber is delivered to the appropriate lubrication point. This means that with each stroke, a certain, unchanging lubricant volume reaches the lubrication point. The stroke frequency, that is, the number of delivery strokes within a certain time unit, can be changed. The pump is operated by servo oil. To carry out a stroke, the delivery pistons are moved by a working piston. The working piston is charged with the servo oil. A switching valve controls the movement of the working piston. The switching valve is controlled in dependence on an operating parameter of the internal combustion engine. That is, the number of strokes per unit time can be changed via the control unit, which controls the changeover valve.

The object of the invention is therefore to propose an improved lubricating device and an improved method for lubricating a running surface of a cylinder of a large engine, by which the problems described above are avoided and by their use optimal time for the introduction of the lubricating oil in the cylinder can be determined.

The objects of the invention which solve these objects in terms of apparatus and method are characterized by the features of the independent claim of the respective category.

The respective dependent claims relate to particularly advantageous embodiments of the invention.

A large engine comprises at least first and second cylinders, each of the cylinders having a bore (B) and a longitudinal axis (A), and in which a piston is reciprocally movable along a tread. A lubricating device is provided for the cylinder lubrication, which comprises at least two lubrication points, via which a lubricant can be applied to the running surface, and a lubricant line for conveying the lubricant from a lubricant reservoir to the lubrication points. The lubricating device comprises a respective pump for each of the cylinders, a distributor, at least two lubricant lines and at least one respective shut-off element, which is arranged in the lubricant line. By means of the pump, the lubricant can be conveyed into the distributor and conveyed from the distributor through the lubricant line to the lubrication point as long as the shut-off element is held in an open position. The position of the shutoff depending on an operating condition of the large engine is controlled by a central unit that the shutoff can be opened at any predetermined time depending on the operating state of the large engine, so that a supply of the corresponding lubrication point can be done with lubricant and the lubricant the tread of the corresponding cylinder can be applied. The period of time in which the shut-off element is kept open in dependence on the operating state of the large engine is independent of the time regulated, so that the amount of lubricant supplied to the lubricating point is arbitrarily adjustable according to the operating state of the large engine.

As operating parameters, for example, speed and / or load and / or the cylinder temperature and / or the temperature in the combustion chamber and / or other current operating parameters are determined.

In particular, inter alia, the resources used and their properties, for example the fuel used, especially its sulfur content and / or the type of lubricant used and / or the BN value of the lubricant, for the optimal injection time or for the optimal duration the lubricant injection can play a central role, they can also be used to determine the desired value advantageous and constantly monitored if necessary or advantageous during operation by suitable measuring device.

It is understood that the above list of parameters and / or data of the operating state of the reciprocating internal combustion engine, which can be used to determine the setpoint for the optimum time or interval for the lubricant injection advantageous is not exhaustive, but also more for the determination of the setpoint can contain relevant parameters and data.

The shut-off element can be kept open at least once during each third revolution of the large motor, so that the lubricant can be supplied to the lubrication point at least once. In particular, the lubrication can always be done at the same time or always at the same piston position, so that the lubrication process can be determined very precisely.

The shut-off can be kept open at least once per tenth of a second up to at least once a minute, so that the lubrication point can be supplied with lubricant. This allows a particularly simple control of the lubrication process can be achieved. In particular, in the case of emergency lubrication, it may be necessary to ensure a periodic supply of lubrication point with lubricant. A delivery cycle of half a second each is particularly advantageous. In particular, the operating state can be determined by measuring the crank angle and / or the rotational speed and / or the torque and / or the position of the piston in the cylinder of the large engine.

The manifold may be formed as a common rail reservoir for the lubricant, which is connected to all lubricant lines for each cylinder. This ensures that the same pressure is present in each of the lubricant lines.

The lubrication points may be located at different positions of the cylinder wall with respect to the axial direction defined by the longitudinal axis (A) of the cylinder. If the lubricant is fed not only at several points distributed around the cylinder circumference, but also in different axial positions, the lubricant can be distributed evenly over a larger surface of the tread. The application of the lubricant can be done simultaneously, ie all shut-off are opened at the same time. But it is also possible to make the supply of lubricant at different times, that is, for example, that the lubrication leads the movement of the piston.

The pump may in particular be designed as a piston pump, which has a plurality of delivery pistons. The delivery pistons are preferably driven by a camshaft. In particular, the camshaft can be driven by an electric motor. The speed of the camshaft, that is, the number of delivery strokes per unit time is therefore arbitrarily variable within the speed range predetermined by the electric motor. The delivery piston may be connected according to a further variant with a working piston, wherein the working piston is movable by a fluid pressure medium, so that a delivery stroke is executable.

The delivery pistons convey the lubricant into the distributor. If the delivery pistons of a rotary piston pump perform their delivery strokes in succession, the pressure fluctuations in the distributor can be reduced, in particular if the cams of the camshaft are arranged angularly offset from one another.

The fluid pressure means may be lubricant provided from an additional supply of lubricant. In particular, this lubricant reservoir may be under higher pressure than the lubricant reservoir used for lubrication. This lubricant supply can be under a pressure of up to 50 bar. The lubricant for the lubricating device is provided in particular from a supply of lubricant which is under a pressure of up to 30 bar. The use of two lubricant reservoirs, ie mostly lubricant reservoirs or lubricant reservoirs under different pressure, allows the pump to be lubricated. This obviates the need to provide a seal between the drive fluid and the operating fluid, i. lubricant for lubrication. As a result, can be dispensed with the provision of sealing elements in the pump, which has a cost-effective production of the pump and a simplification in operation and maintenance result.

The pressure of the lubricant supply for the lubricating device is preferably less than the pressure of the lubricant supply for the actuation of the working piston of the pump.

The invention further relates to a method for lubricating a running surface of a cylinder wall of a cylinder of a large engine, wherein the cylinder has a bore (B) and a longitudinal axis (A), and in which a piston along a running surface is moved back and forth, wherein a Lubrication device is provided for the cylinder lubrication, which comprises at least two lubrication points, which are provided in the cylinder wall, via which a lubricant is applied to the tread, wherein the lubricant passes from a lubricant reservoir to the lubrication points. A pump conveys the lubricant from the lubricant reservoir into a manifold, the manifold conveying at least two lubricant lines and at least one shut-off element located in each lubricant line to deliver the lubricant to the lubrication points on the cylinder surface tread when there is a fluid-conducting connection between the manifold and the corresponding lubrication point so that the lubricant from the lubricant line is conveyed to the lubrication point, as long as the shut-off in an open position is located, wherein the position of the shutoff is regulated in response to an operating condition of the large engine, so that the shutoff is kept open from any time to any period of time depending on the operating state of the large engine, so that a supply of the corresponding lubrication point is carried out with lubricant being the large engine at least a first and a second cylinder and the lubricating device comprises a pump for each of the cylinders.

The adjustment of the shut-off element preferably takes place as a function of the load of the large engine. As a result, the lubricant supply can be adapted exactly to the needs.

The setting of the shut-off element takes place in particular as a function of the crank angle and / or the rotational speed and / or the torque and / or the position of the piston in the cylinder of the large engine.

According to a particularly simple variant, the delivery of the lubricant to the running surface of the cylinder wall is prevented when the pressure in the cylinder space is higher than the delivery pressure of the lubricant. This can ensure that no lubricant enters the combustion chamber of the cylinder when the piston is near top dead center. This can be avoided that lubricant is in the combustion chamber during the combustion process and there is a combustion of lubricant, which can lead to undesirable deposits and exhaust gases.

The pressure of the lubricant can be measured in the distributor, for example by means of a pressure sensor and transmitted to the central unit. The central unit checks whether the pressure is within a predetermined pressure range, which is limited by an upper limit value and a lower limit value, and if the upper limit value of the pressure range is exceeded, the injection is prolonged and / or the shut-off element is forcibly kept open and / or a safety valve is actuated and / or the pump is switched off and an alarm is triggered when the pressure falls below the pressure. Falling below the pressure, especially over a longer period of time may be due to a leak in the Lubricator indicate which must be checked immediately to avoid damage due to lack of lubrication.

• Fig. 1 ein Zylinder eines Zweitakt-Grossdieselmotors mit einer konventionellen Schmiervorrichtung;
• Fig. 2 ein Zylinder eines Zweitakt-Grossdieselmotors mit einer erfindungsgemässen Schmiervorrichtung;
• Fig. 3 eine Graphik des Druckverlaufs im Brennraum in Abhängigkeit vom Kurbelwinkel sowie des Schmiermitteldrucks nach einer ersten Variante;
• Fig. 4 eine Graphik des Druckverlaufs im Brennraum in Abhängigkeit vom Kurbelwinkel sowie des Schmiermitteldrucks nach einer zweiten Variante;
• Fig. 5 eine Einspritzcharakteristik mit einem System gem. Fig. 1;
• Fig. 6a eine Einspritzcharakteristik gemäss der Erfindung;
• Fig. 6b den Druckverlauf für Fig. 6a.

The invention will be explained in more detail below with reference to the schematic drawings. Show it:

• Fig. 1 a cylinder of a two-stroke large diesel engine with a conventional lubricating device;
• Fig. 2 a cylinder of a two-stroke large diesel engine with a lubricating device according to the invention;
• Fig. 3 a graph of the pressure curve in the combustion chamber as a function of the crank angle and the lubricant pressure according to a first variant;
• Fig. 4 a graph of the pressure curve in the combustion chamber as a function of the crank angle and the lubricant pressure according to a second variant;
• Fig. 5 an injection characteristic with a system acc. Fig. 1 ;
• Fig. 6a an injection characteristic according to the invention;
• Fig. 6b the pressure curve for Fig. 6a ,

In Fig. 1 schematically is a cylinder of a two-stroke large diesel engine with a conventional lubricating device shown in section. Each cylinder of the two-stroke large diesel engine is assigned its own lubrication module 100. The lubricating module contains an intermittently conveying lubricant pump 101, by means of which the lubricant is metered and pulse-like the lubricant nozzles 107, 117 is supplied. The pump 101 is designed as a reciprocating piston pump which has a plurality of delivery pistons 138. The delivery piston 138 is movably arranged in a pumping space 136. The pumping space 136 determines the volume of lubricant that can be delivered to each lubrication point with each stroke. Each lubrication point is assigned a delivery piston 138. When the pump 101 performs a stroke, which is located in the corresponding pump chamber 136 Lubricant volume promoted to the appropriate lubrication point. That is, with each stroke reaches a certain, unchanging lubricant volume to the lubrication point, ie to each of the lubricant nozzles 107, 117th

The pump chambers 136 of the pump 101 are all the same size, so that each lubrication point is supplied with the same amount of lubricant.

The stroke frequency, that is, the number of delivery strokes within a certain time unit, can be changed. The pump is operated by servo oil. To carry out a stroke, the delivery pistons 138 are moved by a working piston 133. The working piston 133 is charged with the servo oil. A changeover valve 132 controls the movement of the working piston. The switching valve 132 is controlled in response to an operating parameter of the internal combustion engine. That is, the number of strokes per unit time can be changed via the control unit 150, which controls the switching valve 132.

Since the pump 101 is operated with servo oil, a sealing of the drive-side working piston space 135 against the delivery piston-side working piston space 134 is required. In the delivery piston-side working piston space 134 lubricant is fed, which is provided for example by a common rail memory 111. From the common rail memory 111, a lubricant line 112 leads to the working piston 134. This arrangement is repeated for each cylinder, here is still a lubricant line 162 indicated that leads to a lubrication module 200, not shown for another cylinder of the two-stroke large diesel engine.

The lubricant, which is fed into the working piston chamber 134, passes through an opening 139 in the pump chamber 136. The opening 139 is connected to the working piston space 134 as long as the working piston is in the working piston chamber 135, that is, the stroke of the pump yet did not start. As soon as the working piston in the working piston space 135 is charged with servo oil, it starts to move against the resistance of the return means 137. Each of the openings 139 is closed by the delivery piston 138 and the lubricant in the pump chamber 136 is compressed. When the pressure of the lubricant in the pumping chamber reaches the required pressure, the exhaust valves 163 open and lubricant passes into the lubricant lines 108, 118, which lead to the corresponding lubricant nozzles 107, 117. If the pump rooms all have the same volume, the same amount of lubricant will be delivered to each lubrication point per delivery stroke.

This amount of lubricant can not be changed. If the two-stroke large diesel engine is operated, for example, in the partial load range, only a fraction of the amount of lubricant provided would actually be required. An adaptation to the actual need for lubricant is therefore not possible with the conventional lubrication module.

For the operation of the lubricating module according to the prior art also two circuits are required, on the one hand, the lubricant circuit, represented by the common rail memory 111 and on the other hand, the servo oil circuit, represented by the servo oil reservoir 130, 131st

In Fig. 2 is schematically a cylinder of a two-stroke large diesel engine with a lubricating device 10 according to the invention shown in section. The two-stroke large diesel engine of Fig. 2 comprises a plurality of cylinders 20, wherein for reasons of clarity, only one cylinder 20 is shown by way of example. The cylinder 20 comprises a cylinder wall 22 which delimits an inner space 23 of the cylinder 20 in a manner known per se in the circumferential direction. Within the cylinder 20, a piston 25 is provided, which is arranged with respect to an axial direction A of the cylinder 20 along a running surface 21 of the cylinder wall 22 back and forth. The tread 21 is in the specific example of Fig. 1 provided on a surface layer 24, which is applied to a surface of the cylinder wall 22, for example by thermal spraying. In the cylinder wall 22 at least one lubrication point 7, 17, in particular a lubricant nozzle 26 46 is arranged, which is fed by the pump 1 in a conventional manner with lubricant, so that in the operating state Lubricant film on the tread 21 of the cylinder wall 22 can be applied.

According to the invention, the lubrication point 7, 17 is connected to the pump 1 via a lubricant line 8, 18. Each of the lubricant lines has a shut-off element 5, 15. The lubricant lines are part of a distributor 3, which may also be designed as a common rail memory. The pump 1 delivers lubricant from a lubricant reservoir 30 through the distributor 3 to the lubrication points 7, 17.

The pump 1 may have the same type, which in Fig. 1 already shown. However, unlike the prior art, the pump can be operated with lubricant and not with servo oil. This means that the lubricant reservoir 30 provides lubricant with a pressure of around 20 bar. The working piston 33 of the pump 1 is operated with lubricant, which is supplied from a lubricant reservoir 31 which is under higher pressure than the lubricant reservoir 30. In general, the pressure in the lubricant reservoir 31 is between 40 and 50 bar, in particular around 50 bar.

The lubricant, which is fed into the working piston chamber 34, passes through an opening 39 in the delivery chamber 36. The opening 39 is connected to the working piston space 34 as long as the working piston is in the working piston space 35, that is, the stroke of the pump. 1 has not started yet. As soon as the working piston in the working piston space 35 is acted upon by lubricant, it sets itself against the resistance of the restoring means 37 in motion. Each of the openings 39 is closed by the delivery piston 38 and the lubricant located in the delivery chamber 36 is compressed. Since the delivery chamber 36 is in fluid-conducting connection with the distributor 3, the lubricant in the distributor 3 or the lubricant lines 8, 18 is also compressed.

When the delivery stroke has ended, the lubricant in the lubricant lines 8, 18 has reached the required pressure. By means of a pressure sensor in the manifold 3 can be monitored whether the pressure is is within a given bandwidth required to provide lubrication. This bandwidth is generally in a range of 20 to 50 bar.

The lubricant is thus provided in the lubricant lines 8, 18 so as to be applied to the tread 21 of the cylinder 20 at the desired time. The desired time is determined by the central unit 50, which transmits a signal for opening the corresponding shut-off means 5, 15 via the signal transmission lines 42, 43. Thus, the time of lubrication is completely determined by the central unit.

Of course, the time of closing the shut-off means 5, 15 can also be arbitrarily specified by the central unit 50. As a result, the amount of lubricant required for this particular lubrication cycle can be precisely adjusted.

In Fig. 2 an example of a measuring device 40 is shown with which a characteristic value for the operating state of the two-stroke large diesel engine is detected. The measuring device 40 generates an electrical signal which is characteristic of the characteristic value and transmits this signal in a signal transmission line 41 to a central unit 50, which serves to control the lubrication system. The signal is evaluated in the central unit 50. If the evaluation results in a lubricant requirement, a signal is transmitted from the central unit to the shut-off elements 5, 15 via the signal transmission lines 42, 43, so that they are actuated, that is, opened or closed for the flow of lubricant. The signal can also be used to control the pump 1. This can be used for pumps in which the flow rate can be varied, such as for rotary pumps, such as centrifugal pumps, impeller pumps. For example, the speed of a motor driving the pump can be changed, so that the volume flow delivered per unit time by the pump is changed. This possibility also exists for a rotary piston pump. Such a rotary piston pump usually includes a plurality of pistons, which via a driven by an electric motor camshaft to be moved. As the rotational speed of the camshaft is increased, the number of piston strokes per unit of time is increased and thus the volume flow delivered by the pump is changed. Of course, a pump with a single delivery piston can be used, wherein the delivery piston can be movable hydraulically or via a camshaft.

In the present case, the switching frequency of the switching valve 32 can be changed. In this case, a signal will be sent from the CPU 50 to the switching valve 32 via the signal transmission line 44. The switching valve 32 is designed in particular as a solenoid valve. The switching valve 32 can assume two positions. In the first position, a connection between the working piston 33 and the lubricant reservoir 30 is opened so that lubricant from the working piston space 34, in which the working piston 33 is located, can be returned to the lubricant reservoir 30. A connecting line between the lubricant reservoir 30 and the delivery chamber 36 is opened so that lubricant can flow into the delivery chamber 36.

The working piston 33 is brought by a return means 37, here a spring, in its upper end position and is now ready to carry out a delivery stroke. When the switching valve 32 receives a signal to execute a delivery stroke by a signal from the CPU 50, it switches so that a connection to the lubricant reservoir 31 is opened. Lubricant under high pressure is introduced from the lubricant reservoir 31 in the working piston chamber 35 and the working piston 33 performs a delivery stroke, that is, lubricant is pumped by means of the delivery piston 38 from the delivery chamber into the manifold 3. Furthermore, the working piston does not need to be sealed from the pumping chamber. A seal of the drive-side working piston space 35 against the delivery piston-side working piston space 34 is thus not required.

Based on the measured value of the measuring device 40, the shut-off elements 5, 15 are opened for a certain period of time, so that lubricant is applied to the running surface 21. The period of time in which each of the shut-off elements 5, 15 is kept open is individual adaptable and dependent on the measured value, which has been detected with the measuring device 40.

Of course, a plurality of measuring devices may be provided which determine different parameters of the large engine.

The regulation of the flow rate of the pump need not be coupled in any way with the regulation of the opening times of the shut-off elements.

The method for operating the lubricating device according to the invention comprises the following steps: a desired value for the time and / or duration of injection of the lubricant on the running surface 21 of the cylinder 20 is determined as a function of various operating parameters of the large engine, in particular as a function of the rotational speed and / or the load and / or the cylinder temperature and / or the crank angle and / or another operating parameter and / or depending on the composition of the fuel used and / or the lubricant and / or other operating materials. With its help can from various relevant current and / or for the large engine specific global operating parameters B and / or depending on the composition of the operating materials used, in particular the fuel or the lubricant used, and / or taking into account other relevant factors, a current date and / or the duration of the injection of the lubricant into the cylinder can be determined.

The time or duration of the lubricant injection is optimized in the operating state of the large engine to the target value.

For example, by means of a position sensor, a measured variable corresponding to the current position X of the piston or a curve corresponding to the time profile of the position X is measured and the measured value of the central unit 50, which in particular comprises a data processing system and control means, is supplied. In this case, a plurality of position sensors offset in the axial direction A are preferred for determining the Position X of the piston provided. Such a position sensor can also be used to measure the crank angle.

For example, if the position sensors are passive structure-borne sound sensors, inter alia, by determining propagation time differences of the signals detected by the position sensors, and / or using the known technique of correlating signals, i. the investigation of the corresponding correlation function of the signals, the position X of the piston are determined in particular also time-dependent.

It is understood that in practice, other types of position sensors can be used instead of structure-borne sound sensors, in particular pressure sensors, with which the gas pressure or the time dependence of the gas pressure in the interior of the cylinder 20 can be measured, pressure characteristics that characteristically with the position X of the piston in the cylinder.

However, other types of sensors may also be used to advantage, such as an electrical position sensor, such as an inductive position sensor. Depending on the type of sensor used, the piston may also contain a marking agent, e.g. contain a magnetic marking agent, so that the contour of the piston is better recognizable by the position sensor.

In addition, further, not shown here measuring means may be provided which determine various operating parameters B, such as, inter alia, the speed, the load or the cylinder temperature of the large engine and optionally additionally supply the central unit 50.

A particularly simple variant is obtained if spring-loaded shut-off valves are provided at the lubrication point, which release access to the cylinder interior for the lubricant only when the pressure in the cylinder interior is within a certain range.

It is also possible to adjust the pressure of the lubricant so that it lies between the maximum pressure prevailing in the combustion chamber and the minimum pressure. The pressure is in the combustion chamber during at least during the last phase of the compression stroke and at the time of ignition of the fuel-air mixture and at the beginning of the expansion phase above the lubricant pressure, so that no lubricant can enter the combustion chamber. Only when the pressure in the combustion chamber during the expansion phase, the fresh air supply or the first phase of the compression stroke is below the pressure of the lubricant, an entry of lubricant on the tread of the cylinder is possible. Alternatively, an entry of lubricant is possible if the piston has passed the lubrication point in the compression stroke, that is, the lubrication point opens into the cylinder space filled with purging air, which is below the corresponding purge air pressure. The purge air pressure is usually slightly above the ambient air pressure, usually around 3 bar. Thus, there is a relationship between the position of the lubrication point and the piston. If the piston, ie the piston ring package above the lubrication point, is located at the shut-off elements essentially the purge air pressure, while the pressure in the combustion chamber, that is, the cylinder space between the piston ring package and exhaust valve, is significantly higher FIG. 3 and FIG. 4 show graphs showing the pressure in the combustion chamber as a function of the crank angle. The crank angle is plotted on the x-axis, and the pressure in the combustion chamber is plotted on the y-axis. The pressure curve 60 of the lubricant is in Fig. 3 represented by a horizontal line. In this case, the pressure of the lubricant is constant.

Thus, if the lubrication point is within a range swept by the piston ring pack during the compression stroke, lubricant may leak into the cylinder space as the piston approaches near top dead center as the lubricant in the cylinder space is delivered is because the pressure scavenging air side is much lower than the combustion chamber side pressure around the cylinder chamber.

In Fig. 4 the case is shown that the pressure curve 60 of the lubricant varies depending on the crank angle. This variation can For example, by regulating the flow rate of the pump come about.

The lubricating device according to the invention and the method of the present invention not only significantly increase the service life of the piston, piston rings and cylinder running surface, but also simultaneously minimize the lubricant consumption and extend the maintenance intervals appreciably. In addition, the inventive lubricating device comes with very simple and therefore less error-prone control circuits, which the probability of failure compared to systems, as for example in the EP 1 426 571 B1 are shown, significantly reduced.

Fig. 5 shows the course of the injection by means of lubricant nozzle with a lubrication module 101 according Fig. 1 , In the Fig. 5 The graph shown shows the pressure curve, which is plotted on the y-axis, as a function of time, which is plotted on the x-axis. The present measurement was carried out at engine standstill, for a type RT-flex96C-B engine with an injection volume of 310 mm3 per lubrication port.

The graph shows large fluctuations, wherein the pressure curve was recorded at the pump outlet, ie immediately downstream of an outlet valve 163.

Fig. 6a shows the course of the injection at a lubrication point 7, 17 with a lubricating device 10 according to Fig. 2 , In the Fig. 6 The graph shown shows the volume flow, which is plotted on the y-axis as a function of the time, which is plotted on the x-axis. This course of the volumetric flow found by means of simulation suggests low pressure fluctuations, as shown in the corresponding diagram Fig. 6b for the pressure curve in the distributor 3, 8, 18 according to Fig. 2 is shown. Fig. 6b thus shows the pressure curve at a lubrication point as a function of time.

Of course, the inventive effect is not limited to the particular embodiments shown in the figures, but arises for each lubrication system according to the invention.

Claims (15)

A large engine comprising at least a first cylinder (20) and a second cylinder, wherein each of the cylinders has a bore (B) and a longitudinal axis (A), and in which a piston (25) along a running surface (21) arranged to move back and forth wherein a lubricating device (10) is provided for the cylinder lubrication, which comprises at least two lubrication points (7, 17), via which a lubricant can be applied to the running surface (21), and a lubricant line for conveying the lubricant from a lubricant reservoir (30 ) to the lubrication points (7, 17), characterized in that the lubricating device (10) comprises a pump (1) for each of the cylinders, a distributor (3), at least two lubricant lines (8, 18) and at least one shut-off element each (5, 15) which is arranged in the lubricant line (8, 18), wherein the lubricant by means of the pump (1) in the distributor (3) and from the distributor (3) by the lubricant line to the lubrication point (7, 17) is conveyed, as long as the shut-off element (5, 15) is held in an open position, wherein the position of the shut-off element (5, 15) in response to an operating state of the large engine in such a central unit (50 ) is controllable that the shut-off element (5, 15) can be opened at any predetermined time depending on the operating state of the large engine, so that a supply of the corresponding lubrication point (7, 17) can be done with lubricant and the lubricant on the tread (21 ) of the corresponding cylinder (20) can be applied, as well as the time duration in which the shut-off element (5, 15) is kept open in dependence on the operating state of the large engine, independent of the point in time that the lubrication point (7, 17) supplied amount of lubricant according to the operating state of the large engine is arbitrarily adjustable. Large engine according to claim 1, wherein the shut-off element (5, 15) during each revolution of the large engine at least at each third turn is kept open once, so that the lubricant can be supplied to the lubrication point. Large engine according to one of the preceding claims, wherein the shut-off element (5, 15) is kept open at least once per tenth of a second to at least once a minute, so that the lubricating point (7, 17) can be supplied with lubricant. Large engine according to one of the preceding claims, wherein the operating state by a measurement of the crank angle and / or the rotational speed and / or the torque and / or the position of the piston (25) in the cylinder (20) of the large engine is determined. Large engine according to one of the preceding claims, in which the distributor (3) is designed as a common-rail reservoir for the lubricant, which is connected to all lubricant lines (8, 18) for each cylinder (20). Large engine according to one of the preceding claims, wherein the lubrication points (7, 17) are arranged at different positions of the cylinder wall (22) with respect to the axial direction defined by the longitudinal axis (A) of the cylinder (2). Large engine according to one of the preceding claims, wherein the pump (1) is a piston pump, which has a plurality of delivery pistons (38). Large engine according to claim 7, wherein the delivery piston can be driven by a camshaft. Large engine according to claim 7 or 8, wherein the delivery pistons convey the lubricant into the distributor (3). Large engine according to one of the preceding claims, wherein a pressure sensor in the distributor (3) is arranged. A method for lubricating a running surface (21) of a cylinder wall (22) of a cylinder (20) of a large engine, the cylinder (20) having a bore (B) and a longitudinal axis (A), and in which a piston (25) along a Running surface (21) is reciprocated, wherein a lubricating device (10) is provided for the cylinder lubrication, which comprises at least two lubrication points (7, 17) provided in the cylinder wall (22), via which a lubricant on the tread (21) is applied, wherein the lubricant from a lubricant supply (30) to the lubrication points (7, 17) passes, wherein a pump (1) conveys the lubricant from the lubricant reservoir (30) in a distributor (3), wherein the distributor ( 3) at least two lubricant lines (8, 18) and at least one in each lubricant line (8, 18) arranged shut-off element (5, 15) the lubricant to the lubrication points (7, 17) on the running surface (20) of the cylinder wall (22 ), if a fluid-conducting connection between the distributor (3) and the corresponding lubrication point (7, 17), so that the lubricant from the lubricant line (8, 18) is conveyed to the lubrication point, as long as the shut-off (5, 15) in an open Position, wherein the position of the shut-off element (5, 15) is controlled in response to an operating condition of the large engine, so that the shut-off (5, 15) is kept open from any time to any period of time depending on the operating state of the large engine, so a supply of the corresponding lubrication point (7, 17) is carried out with lubricant, characterized in that the large engine has at least a first and a second cylinder and the lubricating device (10) each comprise a pump (1) for each of the cylinders. Method according to claim 11, wherein the setting of the shut-off element (5, 15) takes place in dependence on the load of the large-diameter motor. The method of claim 11 or 12, wherein the setting of the shut-off element (5, 15) in dependence on the crank angle and / or the speed and / or the torque and / or the position of the piston (25) in the cylinder (20) of the large engine takes place. Method according to one of claims 11 to 13, wherein the promotion of the lubricant on the running surface (21) of the cylinder wall (22) is prevented when the pressure in the cylinder chamber is higher than the delivery pressure of the lubricant. A method according to claim 14, wherein the pressure of the lubricant in the manifold (3) is measured and transmitted to the central processing unit (50), the central unit checking to see if the pressure is within a predetermined pressure range which is defined by an upper limit and an upper limit is limited when the upper limit of the pressure range, the injection is prolonged and / or the shut-off is forcibly kept open and / or a safety valve is actuated and / or the pump (1) is switched off and tripped when the pressure falls below an alarm becomes.

Images