Patent Publication Number: US-10760459-B2

Title: Oil supply system for an internal combustion engine

Description:
The invention relates to an oil supply system for an internal combustion engine with the features of the preamble of claim  1 . 
     In the case of oil supply systems for internal combustion engines known from the prior art, in a forced-feed lubrication, oil from an internal oil pan of the internal combustion engine is pumped to the consumers by an oil pump and is returned to the internal oil pan of the internal combustion engine under the influence of the gravity. It is also known that an oil level can be increased by increasing the oil volume involved in the circulation. For this purpose, for example, the internal oil pan of the internal combustion engine is connected to an additional oil reservoir, e.g. in the form of oil tanks. 
     However, in the operation of available oil supply systems with additional oil tanks, it has been found that oil taken via extracting lines from additional oil tanks often has only experienced a short dwell time in the additional oil tank prior to removal. 
     The object of this invention is therefore to provide an oil supply system with which the residence time of the oil in the additional oil reservoir is extended. 
     This object is achieved by an oil supply system with the features of claim  1 . Advantageous developments are indicated in the dependent claims. 
     By placing a removal opening of the return line near the base or in the base of the at least one oil tank, a better mixing of the oil in the additional oil tank and a prolonged dwell time in the additional oil tank prior to removal are provided. This ensures that unused (fresh) oil is removed via the return line. 
     It is preferably provided that the return line is connected to a removal line which extends to the base of the at least one oil tank, whereby the removal line has a removal opening near the base of the at least one oil tank. This describes the case where the removal of oil from the oil tank is performed by means of a separate removal line extending into the oil tank. Alternatively, it can be provided that the removal is performed through an opening in the base of the oil tank. However, due to the accumulation of deposits in the base of the oil tank, it is preferable to perform a removal via a removal line extending to the base of the at least one oil tank. 
     It is preferably provided that the supply line opens near the base of the at least one oil tank. This measure results in a favorable flow through and mixing of the oil tank, since the oil originating from the internal combustion engine enters at high temperature and charged with gas. Thus, it has the tendency to ascend in the oil tank. When the supply line opens near the base of the at least one oil tank, the ascending oil causes the circulation of the oil volume in the oil tank. 
     It may be provided that at least one flow guide device is provided in the at least one oil tank. This measure further improves the throughflow in the oil tank. The flow guide device can be designed e.g. in the form of guide plates. 
     It is preferably provided that a vent line is provided which connects the oil reservoir to a return line. This measure makes it possible to remove the gases dissolved in the oil originating from the internal combustion engine from the oil tank. This measure is important, because otherwise the pressure in the oil tank may increase and thus the oil tank may be partly emptied into the oil pan. The venting can now take place such that a vent line is connected to a return line near the cover of the oil tank. In this case, the gases, together with the recycled oil for the return line, are introduced into a crankcase of the internal combustion engine. 
     It can be provided that the removal line has at least one venting hole near the cover of the oil tank. This additional or alternative venting measure ensures that no gases are collected in the oil tank, and that they are removed from the oil tank via the removal line. 
     It is preferably provided that a preferably spring-loaded non-return valve is installed in the supply line between the internal combustion engine and the oil reservoir. 
     A non-return valve prevents the oil from the oil lines of the internal combustion engine or oil from the oil pan from being emptied into the oil reservoir when the internal combustion engine is at a standstill. In general, the internal combustion engine and the external oil reservoir arranged outside the internal combustion engine are set up on the same structural level. 
     It may be provided that at least two serially arranged oil tanks are present, whereby the feed line opens into a first oil tank and the at least two oil tanks are connected via connecting lines. This describes the case in which the external oil reservoir is implemented in the form of a plurality of series-arranged oil tanks. In the case of the connection line between individual oil tanks, the measure is also taken that the removal opening of the connecting line is located near the base of the upstream oil tank. The return line to the internal combustion engine is then connected to at least the second oil tank. 
     If only one oil tank is provided, the return line is connected to the at least one oil tank. 
     The invention is particularly suitable for stationary internal combustion engines, in particular with a generator to internal combustion engines coupled to a genset. 
     The invention is particularly suitable for applications of internal combustion engines with high oil wear, e.g. in the case of power-boosting engines with unchanged oil volume, in biogas or landfill gas applications, or engines with small internal oil pans due to their construction. 
     The invention has proven to be particularly favorable in connection with the use of steel pistons. 
    
    
     
       The invention is explained in more detail with reference to the figures. 
         FIG. 1  shows an exemplary embodiment of an oil supply system according to the invention. It shows an internal combustion engine  1  with an internal oil pan  2 . The oil supply system shown has a forced-feed lubrication  10 . 
     
    
    
     In this simplified illustration, the forced-feed lubrication  10  comprises the oil pan  2 , an oil pump  11 , a main oil line  14  and an oil filter  12 . The oil O is fed via the main oil line  14  to the consumers  13  in the internal combustion engine  1 . 
     In the exemplary embodiment shown, a supply line  4  branches off from the main oil line  14  upstream of the oil filter  12  and feeds a partial flow of oil O into an external oil reservoir  3 , in this case formed by two serially arranged oil tanks  7 . 
     The oil reservoir  3  can, of course, also be formed of only a single oil tank  7 . The oil level of the oil O in the two oil tanks  7  is indicated by the shaded area. Preferably, the oil level reaches as far as the lid of the oil tank  7 . 
     From the second oil tank  7  located downstream of the first oil tank  7 , the oil O is fed back to the internal combustion engine  1  via a return line  6 . 
     In the exemplary embodiment shown, the supply line  4  leads to the first of the two series-arranged oil tanks  7  and opens into a filling opening  5  near the base of the oil tank  7 . 
     A flow guide device  15 , here in the form of a guide plate, can be provided to further improve the throughflow of the oil tank  7 . 
     In the exemplary embodiment shown of two series-connected oil tanks  7 , a connecting line  19  is provided between the oil tanks  7 . In this case, a first removal line  9  leads via the connecting line  19  into the downstream oil tank  7 . The removal opening  8  of the removal line  9  opening into the connection line  19  is arranged near the base of the oil tank  7 . 
     If only one oil tank  7  is provided, the connecting line  19  is not included and the removal line  9  is connected directly to the return line  6 . 
     The removal opening  8  of the removal line  9  is arranged near the base of the oil tank  7 . 
     This results in favorable mixing of the oil O in the additional oil tank  7  (or the additional oil tank  7 ) and a prolonged dwell time of the oil O in the additional oil tank  7  before it is removed again and returned to the internal combustion engine  1 . Thus, fresh oil O is always taken out of the oil tank  7  or the oil tank  7  via the removal opening  8 . 
     Although not shown here, it is also conceivable for the removal opening  8  to be designed as an opening in the base of the oil tank  7 , where it opens into the return line  6 . 
     The oil O, charged with gas, enters the oil tank  7  from the internal combustion engine  1  at elevated temperature via the feed line  4  and the filling opening  5 . The hot oil O ascends in the oil tank  7  to the surface. By the arrangement of the removal opening  8  near the base of the oil tank  7 , on the one hand, good mixing of the oil O in the oil tank  7  is ensured, and on the other hand, it is ensured that non-hot oil just emerging from the internal combustion engine  1  is removed and fed back to the internal combustion engine  1 . 
     The gas G dissolved in the oil O is separated from the oil O in the oil tank  7  and ascends to the surface. So that the pressure in the oil tank  7  does not rise, a vent line  16  is provided, which feeds the gas G to the return line  6 . In this way, it passes again into a crankcase  20  of the internal combustion engine  1 . Alternatively or additionally, it can be provided that the removal line  9  has a venting hole  17 , via which the gas G can enter the return line  6  (or, in the case of several oil tanks, first into the connecting line  19 ). 
     The return line  6  opens into the crankcase  20  of the internal combustion engine  1 , preferably above the oil level of the oil O in the oil pan  2 . 
     In general, the internal combustion engine  1  and the external oil reservoir  3  arranged outside the internal combustion engine  1 are set up on the same structural level. It may be the case that when the internal combustion engine  1  and the oil reservoir  3  are installed, the oil pan  2  rises above a reference level in the oil tank  7 . This can lead to a leakage of oil O from the oil lines in the internal combustion engine  1  or a leakage of oil O from the oil pan  2  into the oil tank  7 . A leakage from the oil lines when the internal combustion engine  1  is at a standstill, e.g. lines between the main oil line  14  and the consumers  13 , is particularly unfavorable, because a pre-lubrication process is thus significantly prolonged before the internal combustion engine  1 is started. In a pre-lubrication process, oil O is supplied to the consumers  13  before starting the internal combustion engine  1 . The pre-lubrication is usually performed by a pre-lubrication pump  21 , which is designed to perform well under the oil pump  11  and bridges it during the pre-lubrication process. The pre-lubrication pump  21  provides e.g. 0.8 bar of oil pressure. 
     A preferably spring-loaded non-return valve  18  prevents the oil O from the oil lines and oil pan  2  from being emptied into the oil reservoir  3  when the internal combustion engine  1  is at a standstill. A further particular advantage of a spring-loaded non-return valve  18  is that it remains closed in the pre-lubrication process, and thus the oil O in the pre-lubrication process only needs to be pumped through the internal combustion engine  1  and not through the entire oil reservoir  3 . 
     The situation will be shown by means of a numerical example: 
     The external oil reservoir  3  is supplied with oil O by the supply line  4  via the main oil line  14 . Upstream of the oil filter  12  with a pressure of 3 to 10 bar, a cross-sectional taper of the supply line  4  versus the main oil line  14  to a cross-section of 2.5 mm produces an oil flow of 6 l/min at an oil pressure of 4.2 bar at the removal point in the supply line  4 . The circulation capacity of the oil pump  11  is 480 l/min. The temperature of the oil O emerging from the oil pan  2  is around 70° C. The pre-lubrication pump  21  provides e.g. 0.8 bar of oil pressure. The opening pressure of the non-return valve  18  is designed to be e.g. 1 bar. 
     The pressure of the pre-lubrication pump  21  is then below the opening pressure of the non-return valve  18 . 
     The oil reservoir  3  has approximately the same oil volume as the oil pan  2 . The oil volume involved in the oil circulation is thus doubled by the oil reservoir  3 . 
     LIST OF REFERENCE SIGNS 
       1  Internal combustion engine 
       2  Internal oil pan 
       3  External oil reservoir 
       4  Supply line 
       5  Filling opening 
       6  Return line 
       7  Oil tank 
       8  Removal opening 
       9  Removal line 
       10  Pressure circulation lubrication 
       11  Oil pump 
       12  Oil filter 
       13  Consumers 
       14  Main oil line 
       15  Flow guide device 
       16  Vent line 
       17  Vent hole 
       18  Non-return valve 
       19  Connecting line 
       20  Crankcase 
       21  Pre-lubrication pump 
     O Oil 
     G Gas