This invention relates to an arrangement for lubricating a piston engine. The invention also relates to a method of lubricating a piston engine.
Forced circulation lubricating systems are commonly used for lubricating of various rotational and moving parts of combustion engines. Typically lubricating medium is fed by means of a delivery ductwork system from a container to lubrication targets, after which the lubricating medium is accumulated and led back to the container. In modern diesel engines the pressure for circulating the lubricating medium is provided by oil pumping means. Typically an oil pump sucks oil from the oil sump of the engine and pumps the oil through a cooler and filter to the ductwork or channels leading to the various lubrication targets. From the lubricated targets the oil drains back to the bottom of the crankcase to the oil sump. The system is designed so that the pressure of the oil is suitable for lubricating the lubrication targets. However, with this known kind of system, there are the disadvantages that the pressure of the oil is dependent on the rotating speed of the engine and the oil pressure is approximately constant at various parts of the lubricating system. Thus the system does not take into account specific requirements for different lubrication targets or operational circumstances.
Specifically the feeding of lubricating oil for piston units includes drawbacks in the case of large two-stroke engines. In EP-A-0903473 there is shown a lubricating system for a large two-stroke engine, in which the lubricating medium is delivered to the piston by means of separate linked levers provided with flow channels. A separate oil feeding device is provided for each cross head, which device operates by the effect of reciprocating movement of the cross head. In this known system the feed of lubricating medium is also set to a certain level, which is not adjustable during the operation of the engine and thus does not necessarily correspond to the optimum lubrication for all operating circumstances.
Another known lubricating system is shown in GB-A-2058952. This known lubricating system utilises fully electronically controlled valves. However this known solution is unnecessarily complicated.
The main bearings of engine crankshafts are usually hydrodynamic bearings. The efficiency of lubricating such bearings is based on creating a film of oil between the bearing surfaces. The settling of the shaft is dependent on, among other matters, the peripheral velocity of the shaft pin. Thus the lubrication is not ideal, for example, during engine start-up.
It is an aim of the present invention to provide a lubricating arrangement for a piston engine which minimises the shortcomings of the prior art. Specifically an aim of the invention is to provide a lubricating arrangement by means of which the feeding of lubricating medium for lubricating engine parts, e.g. pistons, takes place reliably and efficiently. It is also an aim of the invention to provide a method of lubricating a piston engine, in which shortcomings of the prior art are minimised.
According to one aspect of the present invention there is provided an arrangement for lubricating a piston engine comprising a source of lubricating medium, pressure elevation means for the lubricating medium, and a first ducting means for leading the lubricating medium to lubrication targets of the engine. Additionally the arrangement comprises a second ducting means, which is separate from the first ducting means, and which has been provided with a valve arrangement controllable by external control for controlling flow of lubricating medium in the second ducting means. The second ducting means is connectable in flow communication with a source of lubricating medium through the valve arrangement.
The second ducting means preferably comprises second pressure elevating means separate from the first pressure elevating means, which facilitates better independent control over the process.
The separate second ducting means may be arranged as a section of the first ducting means of the piston engine, whereas the engine comprises both a traditional forced circulating lubricating system and a separate delivery ductwork section which is provided with a valve arrangement controllable by an external control unit. Hence it is advantageous that the separate second ducting means is connected to the first ducting means, i.e. to the traditional forced circulating lubrication system, as a first branching duct in a flow direction of the lubricating medium after the pressure elevating means, whereas the obtainable pressure level is at its highest.
Preferably the arrangement comprises a pressure accumulator in flow communication with the source of lubricating medium, to which accumulator the second ducting means is connectable by means of said valve arrangement. Lubricating medium is fed by a pressure elevating means first to a pressure accumulator, in which a predetermined pressure level is maintained and from which the lubricating medium is fed by means of the valve arrangement to ductwork leading to respective lubrication targets. By means of the pressure accumulator it is possible to separate the production of pressure and distribution of lubricating oil, whereby the lubrication becomes more effective and better corresponds with actual requirements. Thus the feed of lubricating medium may be controlled, for example so that the starting moment of the feed and/or its duration, is controlled by an external control unit.
In a preferred embodiment the second ducting means is connected to a lubricating channel leading to a piston unit of the engine, whereby the benefits of the invention are especially efficiently utilised. In this case a pressure driven non-return valve or the like is preferably arranged n the piston unit.
In the arrangement according to the invention the valve arrangement is arranged to co-operate with a control unit adapted to control the operation of the valve arrangement. The control unit receives measurement signals sent by sensors measuring parameters of lubrication targets of the engine. The valve arrangement for separate ductwork sections connected to different lubrication targets, and measurement sensors measuring parameters, such as bearing temperatures, of the different lubrication targets are connected to the control unit. Thus, the lubrication of each lubrication target is independently adjustable in dependence on the measurement signals from the sensors. The control unit controls the valve arrangement in dependence on the measurement signals sent by sensors measuring the parameters of the engine and/by stored control information. It is possible to supply measuring value defining parameters of respective lubrication targets to the control unit. Thus the control unit may control each lubrication target independently of other lubrication targets based on the measurement signals and/or stored information. Advantageously the feeding lubricating medium may be controlled so that the starting time and/or duration is controlled by the external control unit.
If the arrangement comprises a separate section with pressure elevating means separate from the pressure elevating means for the lubricating medium delivery ductwork of other parts of the engine, the control unit preferably also controls the operation of the separate pressure elevating means.
According to another aspect of the present invention there is provided a method of lubricating a piston engine comprising feeding lubricating medium from a source of lubricating medium by means of a pump or the like pressure elevating means to a lubricating medium delivery ductwork. From the delivery ductwork the lubricating medium is further fed to at least one lubrication target of the engine. Part of the lubricating medium fed to the at least one lubrication target is preferably fed through a separate pressure elevating means independent from operation of other pressure elevating means for the lubricating medium, to a certain lubrication target by means of a valve arrangement provided in connection with the separate ductwork. The valve arrangement is controlled by an external, independent control.
The invention results in several benefits. The lubrication may be carried out precisely according to requirements of the lubrication target. Additionally lubrication may be controlled based on actual, for example measured, engine values, whereby the lubrication corresponds to the needs set by operating conditions. Moreover, by means of the invention it is possible to take the quality of lubricating medium into account, for example so that lubrication is altered according to service life of the lubricating medium.
Embodiments of the invention will be described, by way of example only, with particular reference to the accompanying drawings, in which:
The arrangement of the invention may be utilised, for example, in hydrodynamic bearings. The main bearings 6.2, amongst other bearings, are commonly hydrodynamic bearings. By utilising the invention it is possible, for example, to separate the bearing surfaces from each other by opening the valve 9.2 for a period of time during the starting stage of the engine 1, while the operation of the bearing has not yet stabilised with respect of its rotation speed. In this way it is possible to avoid overheating of the bearing, whereby its service life and replacement interval are considerably increased. According to the timing controlled lubrication of the invention it is possible to positively affect on other lubrication targets as well.
Sensors 13.1, 13.2 are provided for monitoring and measuring the parameters of the engine 1. Based on the measurement signals provided by the sensors it is possible to control the lubrication. The valve arrangement 9.1,9.2, independently controllable by external control, is arranged in co-operation with a control unit 8. The control unit 8 is adapted to control the operation of the valve arrangement 9.1,9.2 by receiving measurement signals from the sensors 13.1, 13.2 measuring the parameters of the lubrication targets 6.1,6.2, respectively, of the engine. This may be realised advantageously so that a valve arrangement 9.1,9.2 of a ductwork section connected to a certain lubrication target 6.1,6.2, and a measurement sensor 13.1, 13.2 measuring parameters of the same lubrication target, such as bearing temperature, are connected in cooperation with the control unit 8, whereby the lubrication of the lubrication target is independently adjustable based on measurement information. The control unit 8 may have other information or set values stored therein or fed thereto influencing or affecting the lubrication, its requirements and efficiency.
The arrangement of
The duration of the feed of the lubricating medium may at its shortest be even parts of a millisecond. In lubricating rotating bearings (6.2) the pressure pulse may be triggered to be, for example, in synchronism with passing of lubrication openings of a rotating part of the bearing.
A preferred application of the invention is piston lubrication for low speed, large two-stroke engines. This application is schematically illustrated in
The invention has been described above in connection with a large two-stroke engine, but it is clear that the invention may be adapted to other types of piston engines. Additionally the invention is applicable to lubrication of several targets, such as sliding show in cross head engines. Thus it is clear that the solutions described above are only exemplary. The invention is not limited to the embodiments shown but several modifications of the invention are reasonable within the scope of the attached claims.
Number | Date | Country | Kind |
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20001450 | Jun 2000 | FI | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/FI01/00555 | 6/13/2001 | WO | 00 | 12/9/2002 |
Publishing Document | Publishing Date | Country | Kind |
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WO01/98638 | 12/27/2001 | WO | A |
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Number | Date | Country | |
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20030131819 A1 | Jul 2003 | US |