Patent Publication Number: US-2021164558-A1

Title: Liquid pump, in particular for providing a supply to a transmission of an electric or hybrid drive module of a motor vehicle

Description:
The invention relates to a liquid pump, in particular for providing a supply to a transmission of an electric or hybrid drive module of a motor vehicle, having a pump housing in which a pump chamber and a pump rotor are arranged, wherein the pump housing has at least one intake opening. 
     Such a liquid pump may be used for supplying oil to a transmission or other components in a drive train. The liquid pump may, for example, be arranged on a housing of the transmission in such a way that the intake opening is arranged below the level of an oil reservoir in the transmission housing. 
     The object of the invention is to prevent, with little outlay, passing of impurities into the pump and possibly also to the lubrication points supplied with oil by the pump. 
     For the purpose of achieving said object, it is provided according to the invention, in the case of a liquid pump of the type mentioned in the introduction, that a filter plate which covers the at least one intake opening is attached to the pump housing. The invention is based on the fundamental concept of performing the filtering function with a single component which, on the one hand, can be produced with little outlay (by being provided with suitable filter openings) and which, on the other hand, can be mounted with very little outlay, specifically can be simply screwed to the housing. 
     Preferably, the filter plate has a multiplicity of filter openings which have an opening width of at most 0.4 mm, preferably at most 0.3 mm, and in particular at most 0.2 mm. In this way, the filtering action can be very easily set in the desired manner during the production of the filter plate. 
     In order to increase the overall available flow cross section, provision may additionally be made of filter slots through which oil can be sucked in. Said filter slots are provided between the filter plate and the pump housing and have dimensions which are comparable to those of the filter openings. 
     It is furthermore possible for the filter plate to be of planar form, if provision is made in the pump housing of recessed portions such that the filter slots are delimited between said recessed portions and the filter plate. 
     The filter plate may consist of a sheet metal, that is to say of a material which can be machined very well. Moreover, there is no risk of wear. 
     The filter plate may be etched, laser-cut or water jet-cut. By way of these machining processes, the filter openings can be produced with very high accuracy. 
     It is also possible for the filter plate to be a punched part, which leads to particularly low production costs. 
     In the case of a punched part, the filter openings may be formed between material portions of the filter plate that are bent relative to one another. This makes it possible to produce different filter plates, that is to say filter plates which differ with regard to the opening width of the filter openings, using an intrinsically identical production process. For this purpose, it is merely necessary for the material portions to be deformed relative to one another to a greater or lesser extent. 
     The filter plate may also be an injection-moulded part, with the result that it can be produced with little outlay, low costs and high precision. 
     Preferably, the filter openings are formed in an undercut-free manner, as viewed in a direction perpendicular to the plane of the filter plate. This makes it possible for the filter plate to be producible in an injection mould without slides. 
     According to one embodiment of the invention, it is provided that the filter plate is provided with at least one latching lug, by way of which it can be locked to the pump housing. This makes it possible for said filter plate to be pre-mounted on the pump housing such that the assembly composed of pump housing and filter plate can be checked in advance. It is thereby possible for any malfunctions to be detected before the liquid pump is completely assembled. 
     According to one configuration of the invention, provision is made of a pressure-limiting valve, which has a valve body and a spring, wherein the spring is supported against the filter plate. On account of its strength, the filter plate is suitable for acting as a counter bearing for the spring of the pressure-limiting valve. Consequently, no additional components are required for mounting the pressure-limiting valve. 
     According to one configuration of the invention, it is provided that the filter plate has a spring-centring means. This prevents inadvertent jamming of the spring during the opening and/or closing of the valve body. 
     The spring-centring means may be formed in particular by a plastically deformed portion of the filter plate. In this configuration too, no additional components are required. It is sufficient for the filter plate to be plastically deformed in such a way that, for the support of the spring, there is formed either a well, in which the spring is received, or a projection, which extends into the spring. 
     According to the preferred embodiment of the invention, provision is made of multiple mounting screws by way of which at least one bearing body and the pump housing are screwed to one another, wherein the mounting screws have screw heads which bear directly on the filter plate. On account of its mechanical strength, the filter plate acts in the manner of shims such that separate shims can be dispensed with, which simplifies the mounting and reduces the costs. 
    
    
     
       The invention will be described below on the basis of two embodiments which are illustrated in the appended drawings. In these drawings: 
         FIG. 1  shows a cross-sectional view of a liquid pump according to a first embodiment of the invention; 
         FIG. 2  shows the liquid pump in  FIG. 1  in a sectioned perspective view; 
         FIG. 3  shows a perspective view from below of the liquid pump in  FIGS. 1 and 2 ; 
         FIG. 4  shows the detail IV in  FIG. 1  in a perspective view; 
         FIG. 5  shows a detail of a liquid pump according to a second embodiment in a sectional view; 
         FIG. 6  shows a section along the plane VI-VI in  FIG. 5 ; 
         FIG. 7  shows a sub-assembly of a liquid pump according to a third embodiment in a perspective view; 
         FIG. 8  shows a side view of the sub-assembly in  FIG. 7 ; 
         FIG. 9  shows a sectional view through the sub-assembly in  FIG. 8 ; 
         FIG. 10  shows a further sectional view through the sub-assembly in  FIG. 8 ; 
         FIG. 11  shows the detail XI in  FIG. 10  on an enlarged scale; 
         FIG. 12  shows a liquid pump according to a fourth embodiment in a perspective view; 
         FIG. 13  shows a detail of the liquid pump in  FIG. 12  in a perspective sectional view; and 
         FIG. 14  schematically shows the detail XIV in  FIG. 13  on an enlarged scale. 
     
    
    
       FIGS. 1 and 2  show a liquid pump  10 , which is provided for being attached to a transmission of an electric or hybrid drive module of a motor vehicle. Of the transmission, a part of the transmission housing  12  is schematically shown here. 
     The liquid pump  10  has an electric motor, which has a stator  14  and a rotor  16 , wherein the rotation of the rotor  16  of the electric motor is transmitted to a pump rotor  18  by means of a shaft  17 . 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  slides in a pump housing  22 . This pump type is also known as a gerotor pump. 
     The liquid pump sucks in via an intake opening  24 , which is provided here in a bearing body  26  which serves for mounting the shaft  17 . The discharge is realized via an outlet opening  28 , which is likewise formed in the bearing body  26 . From there, the oil flows to a connection piece  30 . 
     The outlet opening  28  is assigned a pressure-limiting valve  32 , which has a valve body  34  and a spring  36 . 
     The pressure-limiting valve  32  opens if the pressure on the delivery side of the liquid pump becomes excessively high. In this case, delivered oil flows directly back to the suction side. 
     Here, the valve body  34  is accommodated displaceably in a suitable opening of the bearing body  26 . 
     The spring  36  is supported against a filter plate  40 , which covers the intake opening  24  at the outside and is attached to the pump housing  22 . Specifically, in the embodiment shown, the filter plate  40  is attached on that side of the bearing body  26  facing away from the electric motor. Any oil which is sucked in through the intake opening  24  by the liquid pump must therefore first pass through the filter openings  42 , which are provided in the filter plate  40 . 
     The filter plate consists of sheet metal. 
     The filter openings may be formed by different processes according to requirements and desired accuracy. For example, the filter openings  42  may be etched, laser-cut or water jet-cut. It is also possible for the filter openings  42  to be punched. 
     In order to connect the filter plate  40  to the liquid pump, multiple mounting screws  44  are provided (see in particular  FIGS. 1 and 3 ). These extend through the filter plate  40  and the bearing body  26  at least into the pump housing  22 . Since the filter plate  40  consists of metal, it has sufficient strength to serve as a “shim” for the mounting screws  44 . 
       FIGS. 5 and 6  show a second embodiment. The same reference signs are used for the components known from the first embodiment, and, in this respect, reference is made to the explanations above. 
     The difference between the first and second embodiments lies in the configuration of the filter plate  40 . 
     A first difference is that, in the second embodiment, a spring-centring means  46  is provided for the spring  36  of the pressure-limiting valve  32 . Said spring-centring means is formed here as a projection of the filter plate  40  that is directed towards the pressure-limiting valve  32 . At this position, the filter plate  40  may be deformed plastically in the manner of a deep-drawn formation. 
     As an alternative to the projection shown, it is also possible to use a well, that is to say a depression, in which the spring  36  is seated. 
     A second difference in comparison with the first embodiment is that, in the second embodiment, the filter openings  42  are formed not by cut-away regions of the material of the filter plate  40 , but by plastically deformed material portions of the filter plate that are bent relative to one another (see in particular  FIG. 6 ). This can be obtained by way of a combined punching and embossing step. 
     Irrespective of the manner in which the filter openings  42  are produced, the opening width of the filter openings can be set to a desired value. Said value depends on the size of dirt particles which are considered to be still permissible. Common values lie in the range from 0.2 mm to 0.4 mm. 
       FIGS. 7 to 11  show a sub-assembly of a liquid pump  10  according to a third embodiment. The same reference signs are used for the components known from the first two embodiments, and, in this respect, reference is made to the explanations above. 
     The sub-assembly shown in  FIGS. 7 to 11  consists of a part of the pump housing, specifically the bearing body  26 , and the filter plate  40 . 
     As in the second embodiment, the filter plate  40  is formed from metal, and the filter openings  42  are formed by plastically deformed material portions of the filter plate  40  that are bent relative to one another. 
     The difference between the second and third embodiments is on the one hand that, in the third embodiment, provision is made of additional filter openings, specifically in the form of filter slots  43 , which are provided between the filter plate  40  and the bearing body  26 . The filter slots  43  increase the available throughflow cross section. 
     In order to form the filter slots  43 , the bearing body is provided with multiple recessed portions  45  in the abutment surface at which the filter plate  40  bears against said bearing body (see in particular  FIG. 8 ), with the result that, there, a flow cross section is formed between the bottom side of the filter plate  40  and the base of the recessed portions  45 . 
     The dimensions of the filter slots correspond to the dimensions of the filter openings  42 , and so the same filtering action is obtained. The recessed portions  45  are thus set back by 0.2 to 0.4 mm in comparison with the level of the abutment surface for the filter plate  40 . 
     The difference between the second and third embodiments is on the other hand that, in the third embodiment, provision is made of multiple latching lugs  50  by way of which the filter plate  40  can be locked to the pump body. 
     In the exemplary embodiment shown, the latching lugs  50  are provided on the filter plate  40 , and they interact with latching noses  52  on the bearing body  42 . 
     By means of the latching lugs  50 , the filter plate  40  can be pre-mounted on the pump body (on the bearing body  26  in this case) such that the sub-assembly formed in this way can be tested for proper functioning thereof. For example, the functioning of the pressure-limiting valve  32  can be tested before the liquid pump  10  is completely assembled. 
     Also provided on the filter plate  40  are multiple centring lugs  54 , which engage into suitable cutouts in the bearing body  26 . This facilitates the mounting of the filter plate  40  on the bearing body  26  and ensures that the filter plate  40 , in its mounted state, is precisely in position. 
       FIGS. 12 to 14  show a liquid pump according to a fourth embodiment. The same reference signs are used for the components known from the preceding embodiments, and, in this respect, reference is made to the explanations above. 
     The most substantial difference between the fourth embodiment and the preceding embodiments is that, in the fourth embodiment, the filter plate  40  does not consist of sheet metal, but is a plastic component. 
     The filter plate  40  is injection-moulded, wherein all the geometrical features (for example the spring-centring means  46  and the centring lugs  54 ) can be moulded. Latching lugs may also be formed, in order to be able to pre-mount the filter plate on the pump body in the same manner as in the third embodiment. 
     As can be seen in particular in  FIG. 14 , the filter plate  40  may be designed in an undercut-free manner. The filter openings  42  are formed between two layers of webs  60 , which, in view of the demouldability, have a trapeziform cross section (which is illustrated in a slightly exaggerated manner here). 
     The mutually facing surfaces  62  of the webs  60  lie in planes which are at a distance H from one another. 
     The filter plate is therefore designed in an undercut-free manner (as viewed in a direction B which is perpendicular to the plane of the filter plate  40 ). It can therefore be injection moulded without the necessity of slides in the injection mould for this purpose. It is merely necessary that the parting surface between the two mould halves has a tooth-like engagement formation in the region of the filter openings  42 .