Abstract:
The invention relates to a lubrication system of an internal combustion engine ( 2 ), wherein lubricant is conveyed by means of at least one lubricant pump ( 8 ) from a reservoir ( 12 ) to lubrication points within the internal combustion engine ( 2 ) via a hydraulic connection ( 10 ). A lubricant store ( 14 ) is arranged in the hydraulic connection ( 10 ) between the lubricant pump ( 8 ) and the internal combustion engine ( 2 ). The invention further relates to an internal combustion engine ( 2 ) having said lubrication system and to a method for operating the lubrication system, wherein the internal combustion engine ( 2 ) is lubricated by lubricant from the lubricant store ( 14 ) in the event of high load demand.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to a lubrication system of an internal combustion engine, a corresponding internal combustion engine and a method for operating a lubrication system according to the preamble of the independent claims. 
         [0002]    The German patent publication DE 10 2007 020 807 A1 discloses a lubrication circuit for an internal combustion engine. In the lubrication circuit, lubrication is conveyed by means of at least one lubricant pump from a reservoir to lubrication points in at least one cylinder head of the internal combustion engine. A lubricant collection tank is configured in the cylinder head, said tank being connected to the reservoir via at least one lubricant recirculation connection that acts as a concentrated lubricant recirculation. The German patent publication DE 10 2005 006 703 A1 discloses an oil pump which comprises a stator which can be pivoted about a bearing bolt for adjusting the delivery rate. The adjusting force required for the stator is produced by a piston which is hydraulically impinged with a control pressure. 
       SUMMARY OF THE INVENTION 
       [0003]    The inventive lubrication system of an internal combustion engine, the corresponding internal combustion engine and the method for operating a lubrication system having the distinguishing features of the independent claims have the advantage that by means of the arrangement of a lubricant store in the hydraulic connection between the lubricant pump and the internal combustion engine, the internal combustion engine can be lubricated by lubricant from the lubricant store as a function of the operating state of said internal combustion engine. 
         [0004]    Because the lubricant requirements of the internal combustion engine have to be met at every point in time, the lubricant requirements can also be met by a lubricant store being used in conjunction with the lubricant pump. 
         [0005]    Particularly when a high load demand is placed on the internal combustion engine, the delivery of lubricant by the lubricant pump can be interrupted so that the internal combustion engine is solely lubricated by lubricant from the lubricant store. By the use of the lubricant store, the power consumption of the lubricant pump can be reduced; thus enabling the operation of the internal combustion engine to improve with regard to the usable torque and the dynamics. Furthermore, the emissions performance with regard to NOx peaks can be improved. 
         [0006]    The use of an adjustable control pump as lubricant pump, the delivery rate of which is changed by means of an adjustable displacement volume, is advantageous because the adjustable control pump adapts to the lubricant requirements without the delivery rate being changed via an external control of the rotational speed. 
         [0007]    It is an advantage here if the adjustable displacement volume of the adjustable control pump can be controlled by a hydraulic feedback line because the displacement volume of the adjustable control pump is changed as a function of the pressure in the hydraulic feedback line. A hydraulic feedback line for controlling the adjustable displacement volume is positively characterized by the simple implementation thereof in the lubrication system because no further control devices are required besides an additional line. 
         [0008]    A means for decoupling the lubricant pump in the lubrication system, by means of which the delivery of lubricant by the lubricant pump can be interrupted in the direction of the internal combustion engine, is advantageous because in the event of the driver placing a high load demand on the internal combustion engine, e.g. during an acceleration phase, less additional load is produced by the lubricant pump. The power consumption of the lubricant pump is reduced by the use of the means for decoupling the lubricant pump so that the internal combustion engine is allowed to produce a smaller drive torque for the lubricant pump. 
         [0009]    The use of a check valve which is disposed between the lubricant pump and the lubricant store as a means for decoupling the lubricant pump is advantageous because the check valve is a cost effective component which can be easily integrated into the lubrication system. 
         [0010]    By using a proportional vale or a flow divider instead of the check valve, a gentle transition between the different operating modes can be implemented, which has a positive effect on the entire operating behavior. 
         [0011]    By means of a control unit which is connected to the internal combustion engine, the lubricant store and the means for decoupling the lubricant pump, an exact setting of the means for decoupling the lubricant pump is possible as a function of the operating state of the internal combustion engine and the pressure in the lubricant store. 
         [0012]    A method for operating a lubrication system of an internal combustion engine is advantageous, wherein the internal combustion engine is lubricated by lubricant from the lubricant store in the event of high load demand. This results from the fact that the lubrication during high load phases of the internal combustion engine is ensured and the power consumption of the lubricant pump is less due to the additional lubricant from the lubricant store. 
         [0013]    Checking the pressure in the lubricant store by the control unit in the event of a high load demand on the internal combustion engine is particularly advantageous because checking the pressure ensures that a sufficient amount of lubricant is available to the internal combustion engine. The means for decoupling the lubricant pump interrupts the delivery of lubricant from the lubricant pump to the internal combustion engine only if a sufficient amount of lubricant is available in the lubricant store. 
         [0014]    It is advantageous that the control unit actuates the means for decoupling the lubricant pump when the predetermined pressure value in the lubricant store is undershot; thus enabling the lubricant pump to deliver lubricant to the internal combustion engine, the internal combustion engine to be sufficiently supplied with lubricant and the lubricant store to again be filled with lubricant. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0015]    An exemplary embodiment of the invention is depicted in the drawing and is explained in detail in the following description. A lubrication system of an internal combustion engine is schematically depicted in the single FIGURE. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The FIGURE shows a lubrication system of an internal combustion engine  2 . The lubrication system has a lubricant pump  8  which conveys the lubricant from the reservoir  12  to the internal combustion engine  2  via a hydraulic line  10 . 
         [0017]    A filter  7  can be disposed in a section of line between the reservoir  12  and the lubricant pump  8  in order to filter contaminates out of the lubricant. The filter  7  can also be disposed in the hydraulic line  10  between the lubricant pump  8  and the internal combustion engine  2 . 
         [0018]    The drive of the lubricant pump  8  can be provided mechanically by the internal combustion engine  2  via clutch, gear or toothed belt. The lubricant pump  8  can alternatively have an electric drive which can be operated with variable power and therefore variable rotational speed or with constant power and rotational speed. 
         [0019]    Because there are may movable parts in the internal combustion engine  2 , such as, for example, the crankshaft with bearings, the connecting rod with bearings or the cam shaft with bearings, the internal combustion engine  2  requires a lubrication in order to prevent damage to the moving components during the operation of said internal combustion engine  2 . 
         [0020]    The lubricant pump  8  conveys lubricant via the hydraulic connection  10  to the internal combustion engine  2 . The liquid lubricant travels via internal channels of the internal combustion engine  2  to the lubrication points in said internal combustion engine  2 . A crankshaft of said internal combustion engine can contribute to an additional turbulence of the lubricant and thus to a cooling of the same by means of the rotational movement thereof. The lubricant which drips and escapes from the internal channels enters into the reservoir  12  via a lubricant discharge duct  30 . 
         [0021]    A lubricant store  14  is disposed in the hydraulic connection  10  between the lubricant pump  8  and the internal combustion engine  2 . As depicted in the figure, the lubricant store  14  is connected via a branch line  11  to the hydraulic connection  10  and is thus filled with lubricant during operation of the lubricant pump  8 . The lubricant store  14  can also be embodied as a pressure accumulator. 
         [0022]    The lubricant store  14  can also be disposed hydraulically in series with the lubricant pump  8  and the internal combustion engine  2  in the hydraulic line  10 . Lubricant which is conveyed from the lubricant pump  8  to the internal combustion engine  2  enters via a section of the hydraulic line  10  into the lubricant store  14  from the lubricant pump  8  and from there via a further section of the hydraulic line  10  into the internal combustion engine  2 . 
         [0023]    Lubricant under pressure for lubricating the internal combustion engine  2  is available in the lubricant store  14 . If the lubricant requirements of the internal combustion engine  2  cannot be met by the lubricant pump  8 , the internal combustion engine  2  is lubricated with lubricant from the lubricant store  14 . 
         [0024]    A means for decoupling  16  the lubricant pump  8  is disposed in the lubrication system. By means of said means for decoupling, the delivery of lubricant to the internal combustion engine  2  can be interrupted. 
         [0025]    The means for decoupling  16  the lubricant pump  8  is connected to an electrical control unit  20 . The means for decoupling  16  the lubricant pump  8  can be actuated by means of the control unit  20 . 
         [0026]    The control unit  20  is connected to the internal combustion engine  2 , the lubricant store  14  and the means for decoupling  16  the lubricant pump  8 . The control unit  20  monitors the operating state of the internal combustion engine  2  and the pressure in the lubricant store  14 . The control unit  20  actuates the means for decoupling  16  the lubricant pump  8  as a function of the operating state of the internal combustion engine  2  and as a function of the pressure in the lubricant store  14  and enables lubricant to be conveyed by means of the lubricant pump  8  to the internal combustion engine  2  or interrupts the conveyance of lubricant by the lubricant pump  8  to the internal combustion engine  2 . 
         [0027]    If there is high load demand on the internal combustion engine  2 , as, for example, in an acceleration phase, and the pressure in the lubricant store  14  exceeds a predetermined pressure value, the means for decoupling  16  the lubricant pump  8  is thus actuated in such a manner that the lubricant pump  8  does not convey any lubricant to the internal combustion engine  2 . 
         [0028]    At the end of the high load demand or if the pressure in the lubricant store has dropped below the predetermined pressure value, the means for decoupling  16  the lubricant pump  8  is actuated in such a manner that the lubricant pump  8  again conveys lubricant to the internal combustion engine  2 . 
         [0029]    In the figure depicted, the means for decoupling  18  the lubricant pump  8  is a check valve  16  which is disposed in the hydraulic line  10  between the lubricant pump  8  and the lubricant store  14  and can be opened and closed by the control unit  20 . Instead of the check valve  16 , a proportional valve or a pressure or flow divider can be used, by means of which a gentle transition between the individual operating modes is facilitated. 
         [0030]    An adjustable control pump  8  is used as the lubricant pump  8 , the delivery rate of which can be changed by means of an adjustable displacement volume. 
         [0031]    The adjustable displacement volume of the adjustable control pump  8  is controlled by a hydraulic feedback line  18 . The feedback line branches off from a section of line  17  between the lubricant pump  8  and the check valve  16  and acts on a control piston of the adjustable control pump  8 . The delivery volume of the adjustable control pump  8  can be changed by the control piston of said adjustable control pump  8 . 
         [0032]    If a high pressure acts on the control piston, a low delivery volume is then set so that the adjustable control pump  8  conveys little lubricant. If a low pressure acts on the control piston, a large delivery volume is then set; thus enabling the adjustable control pump  8  to convey much lubricant. The delivery rate of the adjustable control pump  8  can be continuously adjusted between a zero delivery rate and a maximum delivery rate. The maximum delivery rate is dependent on the design of the adjustable control pump  8  and is determined by the maximum cell volume. 
         [0033]    If there is a high load demand on the internal combustion engine  2  and if the pressure in the lubricant store  14  exceeds a predetermined pressure value, the check valve  16  is closed. By closing the check valve  16 , a high pressure builds up in the line section  17 . The high pressure acts on the control piston of the adjustable control pump  8  via the feedback line  18  and has the effect that the delivery volume of the adjustable control pump  8  is greatly reduced. With a further increase in the pressure in the line section  17 , the adjustable control pump  8  is governed to such an extent that it no longer conveys any lubricant. The power consumption of the adjustable control pump  8  is reduced to a very low value so that the internal combustion engine  2  has only to provide a low drive torque for the operation of the adjustable control pump  8 . 
         [0034]    Because no lubricant from the reservoir  12  is conveyed by the lubricant pump  8  to the internal combustion engine  2 , the lubricant requirements of the internal combustion engine  2  are met by the pressurized lubricant from the lubricant store  14 . 
         [0035]    After the high load demand on the internal combustion engine  2  or if the pressure in the lubricant store  14  drops below a predetermined pressure value, the control unit  20  actuates the check valve  16  in such a manner that said check valve  16  is opened and the lubricant pump  8  can again convey lubricant to the internal combustion engine  2 . 
         [0036]    By opening the check valve  16 , the pressure in the line section  17  and in the feedback line  18  drops so that the pressure on the control piston drops. A lower pressure on the control piston has the effect that the delivery volume of the adjustable control pump  8  increases and more lubricant is again conveyed to the internal combustion engine  2 . 
         [0037]    If the lubricant store  14  is not filled, the drop in pressure in the line section  17  and in the feedback line  18  is greater than when said lubricant store  14  is filled. Due to the lower pressure, a higher delivery volume is set in the adjustable control pump  8  via the control piston; thus enabling said adjustable control pump  8  to also transport additional lubricant for filling the lubricant store  14  besides providing lubricant for lubricating the internal combustion engine  2 .