Patent Publication Number: US-2021164467-A1

Title: Liquid pump, in particular for providing a supply to a transmission or to a clutch in the drive train of a motor vehicle

Description:
The invention relates to a liquid pump, in particular for providing a supply to a transmission or to a clutch in the drive train of a motor vehicle, having a drive motor, having a pump module which can be operated in two opposing directions of rotation, and having an inlet and multiple outlets, each of which is assigned at least one check valve. 
     A liquid pump of said type serves for supplying a lubricant, that is to say oil, to lubrication points in the transmission and/or clutch discs in a desired manner. 
     The possibility of operating the liquid pump in two opposing directions of rotation allows different outlets of the liquid pump to be provided with a supply in a different manner. For example, an outlet leading to a clutch may be provided, during operation in a first direction of rotation, with only a small lubricant stream (“minimum-quantity lubrication”), which leads for example to low drag losses with an open clutch, but, during operation in the opposite direction of rotation, with a larger lubricant stream. 
     The object of the invention is to provide a liquid pump which is characterized by a highly compact construction and which can nevertheless be produced with low costs. 
     For the purpose of achieving said object, it is provided, in the case of a liquid pump of the type mentioned in the introduction, that the pump module is assigned a valve plate in which, for each check valve, a valve seat and a receptacle for a valve element interacting with the valve seat are provided. The invention is based on the fundamental concept of assembling in one component, specifically the valve plate, the different check valves which make it possible, during operation in the opposing directions of rotation, for the desired oil stream to be delivered in each case. This makes it possible for all the check valves to be attached to the liquid pump so as to be directly integrated. 
     Preferably, each valve seat forms together with the assigned receptacle a throughflow channel which is arranged substantially in an axial direction. “An axial direction” means here a direction which is parallel to the drive shaft of the pump module. It is preferably also parallel to the outflow direction of the oil from the pump module. The particular advantage of axially oriented throughflow channels is that the valve plate may be manufactured in an undercut-free manner, for example by a casting process or by machining, without complicated transverse bores having to be present. 
     In the valve plate, there may be provided at least one flow transfer opening which extends from one throughflow channel to another throughflow channel and which is exposed at one of the flat sides of the valve plate. Such a flow transfer opening can be produced with little outlay and provide additional functionalities. 
     If the flow transfer opening is in the form of a throttle, it is possible for example to ensure a lubricant stream which is independent of the direction of rotation of the liquid pump. 
     It may be provided that the pump module has a pump plate, wherein the valve plate is arranged on the pump plate, and the pump plate has at least one flow transfer channel which connects two throughflow channels to one another. It is also possible with the flow transfer channel for additional functionalities or oil streams to be provided without complicated geometrical shapes of the valve plate being required for this purpose. 
     According to a preferred embodiment, a closure plate is arranged on that side of the valve plate facing away from the pump module and is provided with at least one inlet opening and at least two outlet openings. With the closure plate, the result is a particularly compact design in which the valve plate can be clamped between the closure plate and the pump module. 
     Proceeding from the closure plate, at least two cooling media channels may extend through the valve plate and the pump module to the drive motor. By means of the cooling media channels, a part of the lubricant stream can be branched off and guided through the drive motor in order to cool the latter. 
     Here, a throttle may be provided for at least one of the cooling media channels in the valve plate, so as to set the throughflow to a desired value. 
     According to one configuration of the invention, it is provided that the valve elements have a central body and multiple outer, axially extending guide wings. 
     With the guide wings, it is possible to ensure an adequate flow cross section between the walls of the receptacle and the central body, while at the same time the guide wings are able to limit the maximum adjustment distance of the valve elements in the opening direction. 
     According to one embodiment of the invention, it is provided that the valve elements are without a restoring spring. It has been found that restoring springs can be dispensed with, since the valve elements reliably close under the action of the pressure drop over the valve element and provide sufficient sealing by way of the prevailing pressure difference. 
    
    
     
       The invention will be described below on the basis of an embodiment which is illustrated in the appended drawings. In these drawings: 
         FIG. 1  shows a liquid pump according to the invention in a perspective view; 
         FIG. 2  shows a view from below of the liquid pump in  FIG. 1 ; 
         FIG. 3  shows a side view of the liquid pump in  FIG. 2 ; 
         FIG. 4  shows a perspective exploded view of the liquid pump; 
         FIG. 5  shows a hydraulic flow diagram for the liquid pump; 
         FIG. 6  shows a longitudinal cross section through the liquid pump; 
         FIG. 7  shows a further longitudinal cross section through the liquid pump; 
         FIG. 8  shows the detail VIII in  FIG. 7  on an enlarged scale; 
         FIG. 9  shows the valve plate used in the liquid pump in a perspective view; 
         FIG. 10  shows a further longitudinal section through the liquid pump; and 
         FIG. 11  shows the detail XI in  FIG. 1  on an enlarged scale. 
     
    
    
     The figures show a liquid pump  1 , which has, as main constituent parts, a drive motor  2 , a pump module  3 , a pump plate  4 , a valve plate  5  and a closure plate  6  (see in particular  FIGS. 1 to 4 ). 
     The drive motor  2  is an electric motor having a motor housing  10 , a stator  12  and a rotor  14  which drives a pump rotor  18  of the pump module  3  via a rotor shaft  16 . The pump rotor  18  is part of a toothed ring pump, which has an outer ring  20  in which the pump rotor  18  meshes. The outer ring  20  glides in a pump housing  22 . This pump type is also known as a “gerotor pump”. 
     The openings which lead to the pump space, which is delimited between the pump rotor  18  and the outer ring  20 , are provided in the pump plate  4 . Merely two cutouts  24  can be seen in  FIG. 4 . 
     A flow transfer channel  25  is provided in the pump plate  4  and serves for returning to the intake region leakage oil of the pump that can escape via the bearing arrangement of the drive shaft. At the same time, the bore can serve for weight reduction or for avoiding mass accumulations, which can be obstructive in some production processes. 
     The pump module  3  can be operated in opposing directions of rotation, so that the inlets and outlets have different functions according to direction of rotation; the opening, or the slot, which constitutes the suction side of the pump in one direction of rotation, is the pressure side in the opposite direction of rotation. 
     In the closure plate  6 , there are provided for the liquid pump  1  an inlet opening  26 , as an inlet, and three outlet openings  28 ,  30 ,  32 , which serve as pressure outlets of the liquid pump  1 , as outlets. 
     A total of six check valves, which are formed in the valve plate  5 , serve for the “switching” of the various fluid streams for different directions of rotation of the pump module  3 . 
     Each check valve is formed by a valve seat  34  with which in each case one valve element  36 ,  38 ,  39  interacts. Each valve element  36 ,  38 ,  39  is arranged in a receptacle  40 , which is likewise formed in the valve plate  5 . 
     Each of the valve elements  36 ,  38 ,  39  has a body  42  and multiple axially extending guide wings  44 . The guide wings are supported against the walls of the respective receptacle  40  and define between the wall of the receptacle  40  and the outer surface of the body  42  a throughflow channel. 
     Wherever one of the check valves is also to have the function of a pressure-limiting valve, it is assigned a restoring spring (see the restoring spring  46  for the valve element  39  in  FIG. 6 ). 
     The functioning of the liquid pump will be explained below on the basis of  FIG. 5 . For reasons of better clarity, the corresponding check valve is denoted below by the reference sign of “its” valve element. 
     If the liquid pump is operated in a first direction of rotation (assumed to be anticlockwise in this case), the opening B constitutes the suction side of the pump module  3 . The liquid pump  3  sucks in via the check valve  36  on the right in  FIG. 5  and the inlet opening  26  of the closure plate  6 . Here, the liquid pump  1  may be fitted on a transmission housing such that it sucks in directly from the transmission. Alternatively, it may suck in from a separate storage container. 
     The oil is delivered via the outlet opening A and is then guided through one of the check valves  38  to the outlet opening  32 , where an oil cooler  48  (illustrated schematically) is provided with a supply. If the throughflow resistance in the oil cooler is too high (for example in the case of a very low oil temperature), the check valve  39 , which constitutes a pressure-limiting valve on account of the spring preload, opens. 
     The oil stream through the pressure-limiting valve  39  then flows to the outlet opening  30  and via a throttle  50  and a further throttle  52  to the outlet opening  28 . The outlet opening  28  may lead to one or more clutches and ensure in particular minimum-quantity lubrication there. 
     The outlet opening  30 , which leads to lubrication points in the transmission, is furthermore provided with a supply. 
     If the liquid pump is operated in the opposite direction (clockwise then in this case), the opening A constitutes the suction side of the pump module  3 . The liquid pump  3  sucks in via the check valve  36  on the left in  FIG. 5  and the inlet opening  26  of the closure plate  6 . The oil flows from the suction side of the pump module  3  through the check valve  38  and the throttle  52  to the outlet opening  28 . Part of the oil furthermore flows through the throttle  50  to the outlet opening  28 . Parallel thereto, there may flow a further oil stream through the check valve  38  and a further throttle  54  to the outlet opening  30 . 
     A particular feature of the check valves is that, overall, they (at least substantially) extend in an axial direction, that is to say the receptacles and the flow cross sections formed by the valve seats define an oil stream in a direction which is parallel to the longitudinal axis of the pump and also to the direction of extent of the rotor shaft  16 . This also has advantages during the assembly, since all the parts are able to be assembled in an axial direction. 
     As can be seen in  FIG. 4 , use may be made of assembly screws  60 , by way of which the closure plate  6 , the valve plate  5 , the pump plate  4  and the pump housing  22  can be screwed to the motor housing  10  in an axial direction. In the process, the valve elements  36 ,  38 ,  39  of the check valves are also suitably fixed in the valve plate  5 , specifically between the corresponding valve seat and the pump plate (check valves  36 ) or the corresponding valve seat in the valve plate  5  and the closure plate  6  (check valves  38 ,  39 ). 
     On account of the axial arrangement of the check valves, the valve plate  5  may be designed in an undercut-free manner (see for example  FIGS. 6, 7 and 9 ). The valve plate  5  may be produced by a casting process, with no slides being necessary, or it may be produced by machining of a material block. No concealed transverse bores are required. 
     It can be seen in  FIG. 8  that the throttle  50  can be integrated into a check valve (the check valve  38  in this case), specifically in that a groove is provided in the valve seat. This ensures a particular minimum throughput without the check valve  38  having to be open. 
     As can be seen in  FIG. 9 , the connection between the outlet openings  28 ,  30  may be formed by a flow transfer opening  62  which is formed between two receptacles in the valve plate. The flow transfer volume can be set in the desired manner by way of the cross section. 
     Proceeding from the closure plate  6 , there are provided two cooling media channels  64  which extend through the valve plate  5  and the pump module  3  to the drive motor  2 . The cooling media channels  64  serve for branching off a part of the oil stream and for guiding said part through the drive motor  2 , so that the latter is cooled. 
     The flow through the cooling media channels can be set in the desired manner by way of a throttle point  66  in the valve plate (see  FIG. 11 ).