Patent Publication Number: US-11384663-B2

Title: Cooling lubrication system comprising a dry sump

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit and priority of German Patent Application No. 10 2019 201 863.7 filed on Feb. 13, 2019. The entire disclosure of the above application is incorporated herein by reference. 
     FIELD 
     The invention relates to a cooling lubrication system comprising a dry sump and an oil tank, wherein a pump system operates the oil circuit in which an oil pump delivers oil from the dry sump into the oil tank. 
     BACKGROUND 
     A dry-sump lubrication for four-wheeled vehicles had only been provided for sports and racing cars and for extreme terrain cars—this is currently changing. 
     In dry-sump lubrication, the lubricating oil is carried in an oil tank and delivered to the lubrication points by means of pressure pumps. In contrast to wet-sump lubrication, the lubricating oil dripping off the lubricating points, which is partially foamed, is sucked off from the oil sump and various collection points by means of further suction pumps. The air is then separated and the oil is returned to the oil tank. 
     A general advantage of dry-sump lubrication pumps is the reduction of the installation height. For example, the engine can be mounted deeper in vehicles owing to the lower design of the oil sump. The center of gravity of the vehicle decreases by this and driving stability is increased. Moreover, the engine is better cooled since larger quantities of oil are in circulation. 
     Dry-sump lubrication requires at least a second oil pump and a reservoir for wet-sump lubrication. 
     The realization of a cooling lubrication system with a dry sump thus requires an optimum use of pumps. 
     Known from DE 102 47 518 A1 is a vane cell pump comprising a rotor driven by a drive shaft, which is rotatably disposed inside a stroke ring between two end plates and in the circumferential surface of which are provided essentially radially extending slots, in which vanes are arranged in a radially displaceable manner in order to deliver fluid from a suction area to a pressure area, the suction area being connected to at least one suction kidney and the pressure area being connected to at least one pressure kidney which are formed in one of the end plates in which under-vane grooves are formed radially inside the area between the suction kidney and the pressure kidney, which are connected to under-vane chambers provided in the slots, the under-vane groove disposed in the area of the pressure kidney being connected to the pressure kidney. 
     In conventional vane cell pumps, all of the under-vane grooves are subjected to high-pressure so as to ensure the retraction movement of the vanes and to keep the vane heads resting on the inner face of the stroke ring. According to DE 102 47 518 A1, only the under-vane grooves located in the pressure area are connected to the pressure kidney and are thus subjected to high pressure. The under-vane grooves located in the suction area are not connected to the pressure kidney, but to the pressure chamber of an additional delivery device. The additional delivery device is designed to maintain sufficient pressure in the connected under-vane grooves, which, however, is significantly lower than the pressure in the pressure area of the vane cell machine. Such an integrated delivery device is a gerotor pump which delivers oil from a tank to a pressure connection channel and finally to the under-vane grooves. 
     Double-flow vane cell pumps are also known, for example, from DE 11 2011 104423 A5, in which the flows are used independently of each other. 
     SUMMARY 
     It is the object of the invention to provide a cooling lubrication system comprising a dry sump with optimized pumps. 
     The object is solved by means of a cooling lubrication system comprising a dry sump and an oil tank, wherein a pump system operates the oil circuit in which an oil pump delivers oil from the dry sump into the oil tank, with the pump system comprising a vane cell pump and a gerotor pump on a shaft. 
     Owing to the common drive by an electric machine on a common shaft, the pump system can be structurally configured such that it is very small. 
     It is an advantage that the vane cell pump is of double-flow design and comprises two independent suction points in the dry sump. 
     Thus, one pump solves the problem that the dry sump must be pumped out at several points, and the use of multiple oil pumps is avoided. 
     Advantageously, the double-flow vane cell pump comprises a first pressure outlet and a second pressure outlet, with which the oil is delivered as volume flow into an oil tank and to a consumer. 
     It is an advantage that the gerotor pump is connected on the pressure outlet side to under-vane grooves in the vane cell pump, thus eliminating initial problems of the vane cell pump. 
     Advantageously, the gerotor pump supplies on the pressure side a cooling for an electric machine. 
    
    
     
       FIGURES 
         FIG. 1  shows an inventive embodiment of the cooling lubrication system with a dry sump. 
         FIG. 2  shows an embodiment for two pumps. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a cooling lubrication system  1  equipped with a dry sump  3  and an oil tank  6 , with a pump system  2  ensuring the circulation of the lubricant. 
     The pump system  2  consists of three pumps  4  driven on a common shaft  5  by a common electric machine EM. 
     The pump P 1  comprises two suction ports  10  P 1  and  11  P 1 . The pump P 1  sucks the oil from the dry sump  3  at two points and delivers the oil into the oil tank  6  via the pressure outlet  12  P 1  and the oil tank inlet  6   a.    
     The two suction points S in the dry sump  3  independently suck oil from the dry sump such that one of the two suction points S still delivers oil, even if the other suction point already sucks air or an air-oil mixture. 
     The pump P 1  is a vane cell pump of a double-flow design, with the two flows being configured separately from each other. In this way, two separate delivery circuits are created which are each connected to a suction point S in the dry sump  3 . The two delivery circuits are connected to each other on the pressure side. 
     Disposed adjacent to the vane cell pump P 1 , on the same shaft  5 , is a gerotor pump P 3 . The gerotor pump P 3  delivers oil from the oil tank  6  via the port  6   b  and the pump inlet  16 P 3 , for example for cooling an electric machine  8 . 
     The supply of the consumers, the gear and the electric machine is merely an example since further consumers are also conceivable. 
     In the pump system  2 , the gerotor pump P 3  is also used, in addition to its delivery function, for cooling an electric machine in order to preload the vane cell pump P 1  in terms of pressure. In vane cell pumps, the problem arises that during start-up the vanes of the vane cell pump do not initially rest on the stroke ring, thus impairing the efficiency of the pump. To prevent this, a vane cell pump comprising at least one under-vane groove is used, into which oil is fed at a specific pressure such that the vanes are brought towards the stroke ring. 
     The gerotor pump P 3  therefore comprises at its pump outlet a branch  15  P 3  with which oil is applied under pressure to the inlet  13  P 1  of the under-vane grooves  30  of the vane cell pump P 1 . 
     The under-vane grooves  30  are further connected to a pressure outlet  14 P 1  which provides the oil supply for a gear. 
     A complicated integrated gerotor pump in the vane cell pump, as suggested in prior art, is thus avoided. The vane cell pump P 1  thus comprises two separate suction points S and two separate pressure areas which, on the one hand, fill an oil tank  6  and, on the other hand, provide the oil supply for a gear  7 . The pump system  2  allows a small construction and thus a reduction of costs. 
       FIG. 2  schematically demonstrates how the two pumps P 1  and P 3  are connected to each other. Via the branch  15  P 3 , the gerotor pump P 3  is on the outlet side connected to the inlet  13 P 1  to the under-vane area of the vane cell pump P 1 . Starting from the branch  15  P 3 , the gerotor pump P 3  feeds in oil for cooling the electric machine  8 . 
     The under-vane grooves  30  are thus connected to the gerotor pump P 3  and also on the outlet side to the oil supply for a gear  7 . The usual pressure outlet  31  of the pump is connected to the oil tank  6 .