Abstract:
An oil pump, in particular an electric or electromotive auxiliary pump for a motor vehicle, having a housing having an inlet on the admission side and an outlet on the pressure side, in addition to a pump rotor which is inserted in the housing such that it can rotate about an axis, and having at least one rotor part, a flexible housing component which is in the form of an elastic press plate and which extends over the cross-sectional surface of the pump rotor. The flexible pressure plate is maintained, in an advantageous manner, in the edge area of the second housing parts.

Description:
[0001]    This nonprovisional application is a continuation of International Application No. PCT/EP2015/079640, which was filed on Dec. 14, 2015, and which claims priority to German Patent Application No. 10 2014 018 587.7, which was filed in Germany on Dec. 17, 2014, and German Patent Application No. 10 2015 002 352.7, which was filed in Germany on Feb. 25, 2015, and which are all herein incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The present invention applies to the field of oil pumps, preferably the field of electric or electromotor-operated or driven oil pumps, and relates to an oil pump with a housing having an inlet on the suction side and an outlet on the pressure side, and with a pump rotor which is inserted in said housing such that it is rotatable about an axis and has at least one rotor part. An oil pump here is, in particular, an auxiliary or supplemental pump in a or for a motor vehicle. 
       Description of the Background Art 
       [0003]    An electric oil pump and, in particular, also a so-called auxiliary or supplementary pump, is used to convey oil as a lubricant for particularly moving parts or components, for example, of a vehicle (motor vehicle) which is powered by a combustion engine, hybridly or electrically. Owing to its conveying characteristics, such an oil pump usually produces an oil circuit, for example, with an oil sump for absorbing excess oil and/or leakage oil. An auxiliary or supplementary pump driven, for example, electrically or by an electromotor, frequently serves for at least temporary lubrication or additional lubrication of transmission parts of a vehicle transmission, in particular of an automatic transmission. In this case, the oil conveyed frequently also serves to cool components or additional components of the drive train of such a vehicle. 
         [0004]    Such oil pumps are designed or constructed for relatively large temperature ranges. The temperature range or range to be controlled or considered is typically between, for example, −40° C. and 130° C. To bear in mind here is also that the lubricant (oil) used has a certain or specific viscosity, which is temperature-dependent and decreases with increasing temperature, that is to say, which is greater at lower temperatures than at higher temperatures. 
         [0005]    Particularly at higher operating temperatures, or at rising temperatures due to operational reasons, the risk of leakage increases. The reason for this is that on the one hand, the avoidance of leakage is contingent on a correspondingly tight pump housing. On the other hand, because of the high temperature fluctuations, housing expansions, that is to say differing expansions of the pump housing and/or the relevant pump parts, tend to increasingly lead to leakages at increasing temperatures and thus decreasing viscosity of the oil or lubricant used, wherein said leakages exhibit a less significant tendency at low temperatures and, consequently, high viscosity of the oil or lubricant. 
         [0006]    The pump rotor in the form of ordinarily used rotor or gear sets for oil pumps, which also include rotary slide or vane cell pumps as positive displacement pumps, are therefore usually manufactured exactly. There are typically no compensating measures, or these are not considered. In addition, pressure compensating pistons (GPM) or material combinations are frequently used, which mutually compensate each other for their thermal linear expansion. 
         [0007]    Previous rotor or gear sets as pump parts for oil pumps are usually mounted in an aluminum pressure housing. In this case, the cast parts of the housing and the rotor sets are typically mechanically reworked or machined. Here, all individual parts must be manufactured as accurately (exact) as possible in their tolerances. In addition, it must be borne in mind that over virtually the entire, dimensioned temperature range, a clamping of moving, in particular rotating, parts of the oil pump is prevented, i.e., they are not allowed to clamp to other parts by striking or rubbing. On the other hand, the tolerances and/or the structural mechanical play of the, or of special, pump parts due to the undesired leakage losses should not be too great, that is to say, should be as small as possible. 
         [0008]    If aluminum is chosen in a material combination for the pump housing and steel is selected for the pump impeller or impellers, it should be borne in mind that these two different materials expand (extend) in a thermally non-uniform, in particular differing, manner. This often leads to the fact that with increasing temperature (oil or lubricant temperature), leakage losses increase. 
         [0009]    Pump types frequently used for such purposes are, for example, positive displacement pumps (external gear pumps), crescent pumps or vane cell pumps. A relatively inexpensive and in this case comparatively pulsation-free type of pump is an oil or auxiliary oil pump with a so-called gerotor (G-rotor pump). Such an oil pump has a rotor set (gear set) with an internally toothed outer ring (external gear ring) and an externally toothed inner rotor (internal gear ring). 
       SUMMARY OF THE INVENTION 
       [0010]    It is therefore an object of the present invention is to provide an oil pump which can be driven by an electromotor and which is particularly suitable in terms of leakage losses as low as possible, which can preferably be produced as cost-effectively as possible. 
         [0011]    The oil pump according to an exemplary embodiment of the invention has a housing with an inlet (suction port, suction nozzle, intake) and with an outlet (pressure port, pressure nozzle, discharge) and a pump rotor, which is preferably designed as a gerotor (G-rotor) with two gears or toothed rings, of which suitably one toothed wheel or toothed ring is driven. A flexible housing component in the form of a resilient side plate or diaphragm is arranged within the housing. This flexible housing component, preferably made of plastic, extends over the cross-sectional surface of the pump rotor. 
         [0012]    The pump drive, i.e., the drive of the pump rotor, is preferably actuated electrically, i.e., by an electromotor, by means of a preferably brushless direct current motor. For this purpose, the driven gear wheel, preferably the internal gear ring of the gerotor, is preferably seated on a shaft which is coupled to the motor shaft of an electric motor, or is a component (shaft section) thereof. 
         [0013]    In an embodiment, a side plate or a cover of a pump housing of an oil pump should not be rigid, but elastic or flexible. The housing component, which is hereinafter referred to as a flexible or elastic pressure plate, is preferably connected to the pressure side of the pump. Within the pump, only a comparatively small area is exposed to the pressure (pump pressure). Since the plate surface is considerably larger from or on the outside, this elastic pressure plate is pushed (pressed) against the pump rotor or gear set during pump operation by feeding a portion of the conveyed medium (oil) to the outside. 
         [0014]    The flexible (elastic) pressure plate can be a housing or pump component which operates in the manner of a diaphragm or is designed as such and is formed, for example, of steel or plastic. This diaphragm (elastic pressure plate) is preferably provided in addition to a cover-like housing part (housing cover) and, in the area of the opening edge of the pump housing, in particular of a housing base body (shell-shaped housing part) made as a steel pot or an aluminum basic body, is preferably attached at the edge and held fixedly and as far as possible, sealingly, by means of the housing cover in or on the pump housing. 
         [0015]    A space (clearance, pressure chamber) can be formed on the outer side of the flexible pressure plate or diaphragm located opposite the housing interior for accommodating the pump impeller (gear set), into which oil conveyed by means of the pump can be introduced or is introduced. The corresponding oil pressure of the oil introduced into said space presses the pressure plate (diaphragm) against the oil pressure acting from the inside (internal oil pressure). In doing so, for example, a desired equilibrium or at least a certain pressure equalization is established. 
         [0016]    This aspect of the invention is based on the realization that, when using a flexible (elastic) pressure plate, said plate expands as the oil temperature rises, just as the oil viscosity decreases or drops with increasing temperature. This results in a virtually automatic adjustment of the axial stroke of the pressure plate. This then balances the housing extension and the pressure plate so that leakage losses can be reduced, minimized or even completely prevented. 
         [0017]    In this way, on the one hand, the high requirements for the production tolerances can be reduced, and on the other hand, leakage losses can be reduced even with low oil viscosity. Moreover, the production of the oil pump is simple and inexpensive. Furthermore, comparatively high efficiencies, in particular, greater than 60%, can be achieved without the oil pump having to be oversized. 
         [0018]    In an embodiment, the pressure chamber provided on the outer side of the flexible pressure plate opposite the pump rotor is connected to the outlet side of the pumps, i.e., to the pressure side thereof. The pressure chamber formed in the axial direction between the flexible pressure plate and the housing cover expediently extends in the radial direction between an annular circumferential projection and an opening collar of the flexible pressure plate which is directed toward the pump rotor. A fluid channel opening into the pressure chamber can be inserted into the housing for a small partial flow of the conveyed medium. 
         [0019]    According to an embodiment, a suitably movably mounted and, in particular, rigid side plate is arranged between the flexible pressure plate and the pump rotor, with a passage opening which is suitably circular-arc-shaped and which is aligned with the outlet on the pressure side. In addition, the flexible pressure plate preferably has a bead-like formation which is open towards the pump rotor and at least partially overlaps the passage opening provided in the side plate. 
         [0020]    The pump housing can have a sleeve-like shaft feedthrough with a bearing sleeve disposed therein for the bearing and passage of a motor shaft of an electric motor to the pump rotor, and on the side of the pump rotor opposite the shaft feedthrough, a shaft receiver with a bearing sleeve for supporting the motor shaft. The outlet on the pressure side is expediently inserted into the housing on the cover side, and the inlet on the suction side is inserted on the bottom side of the housing base body. 
         [0021]    If the flexible pressure plate is made of steel, a supporting factor can be established by the sheet thickness of the pressure plate and/or by certain accommodation zones. If the pressure plate is produced from plastic, further design levels are particularly obtained in that the pressure plate, for example, has different heights at different points. In addition, as is known, the stiffness of the plastic decreases with increasing temperature. At the same time, the viscosity of the oil decreases with increasing temperature. As a result, a plastic plate as a pressure plate can ideally compensate for leakage at higher temperatures. 
         [0022]    Overall, the leakage losses of the oil pump can thus be significantly reduced by means of this principle. In addition, efficiency increases and the electrical components can be dimensioned smaller. Furthermore, tolerances from the production of the individual parts and assembly can be compensated for. The pump parts must therefore preferably be produced less precisely. Furthermore, different coefficients of expansion of the or of individual pump parts can be disregarded. 
         [0023]    A further advantage is that, with increasing pump pressure, the leakage gaps become smaller, that is to say, they particularly do not become larger due to operational reasons. A further advantage is that by selecting the material and design of the elastic pressure plate, the desired target variables can be set particularly reliably and/or simply. 
         [0024]    In the design of the pressure plate made of plastic, the low viscosity of the oil can also be compensated at higher temperatures. If the cover-like housing part (housing cover, side plate) is designed without initial basic pressing, the inserted electric motor can start in a simple manner without a sensor. The oil pump designed in such a way can also have one or two additional elastic side plates or individual parts which can be acted on by the output pressure of the pump. 
         [0025]    Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes, combinations, and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein: 
           [0027]      FIG. 1  is a perspective pressure-side view of an electrical or electromotor-driven oil pump having a housing shown in partial section and partially transparent, having therein a fixed side plate between an elastic pressure plate (diaphragm) and a gear set as a pump rotor (G-rotor); 
           [0028]      FIG. 2  is a representation according to  FIG. 1 , of the oil pump in a perspective suction-side view, with a view to the gear set (G-rotor); 
           [0029]      FIGS. 3 and 4  illustrate the oil pump in a perspective view, with a view to a suction opening (inlet) on the housing bottom side or to a shaft-side pressure opening (outlet); 
           [0030]      FIG. 5  is an axial sectional view of the oil pump; 
           [0031]      FIG. 6  is a section VI of  FIG. 5  in a larger scale with a view to a peripheral rim of the pressure plate in the housing and to a pressure chamber between a shaft feedthrough and a circumferential bead contour; and 
           [0032]      FIG. 7  is a sectional view along the line VII-VII in  FIG. 5 , with a view to the pressure side of the elastic pressure plate (diaphragm). 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    According to  FIGS. 1 to 4 , the oil pump  1  has a pump housing  2  formed, for example, of steel or aluminum, in the form of a shell-like (first) housing part, which is subsequently referred to as the housing base body  2   a , and a cover-like housing part, hereinafter referred to as housing cover  2   b . The housing base body  2   a  forms a cylindrical housing wall  3 , that is to say, in particular, a cylindrical interior space  4  and a housing base  5 , which is hereinafter also referred to as a first side plate, as well as a housing opening  6  axially opposite it. A bottom-side bearing opening  7 , which is extended in the manner of a collar, serves in conjunction with a bearing sleeve  8   a  seated therein for the sliding bearing of a motor shaft  9  of an electric motor. A corresponding sleeve-like shaft feedthrough  10  with a bearing sleeve  8   b , which in turn is seated therein, in the housing cover  2   b  serves for the passage of the motor shaft  9  from the outside into the housing  2  and there via a pump rotor  11  into the bearing opening  7 . 
         [0034]    In connection with  FIG. 5 , it can be seen that a gear set with an internally toothed external gear ring  11   a  and with an externally toothed internal gear ring  11   b  is inserted as a pump rotor  11  into the housing interior  4  of the housing base body  2   a . In each rotational position relative to the external toothed ring  11   a , the external toothing  12  of the internal gear ring  11   b  is partially intermeshed between or in the internal toothing  13  of the former. Some of the wavy teeth of the external toothing  12  are thereby inserted in the again wavy tooth gaps of the internal toothing  13  of the external gear ring  11   a  and vice versa, while other teeth of the external toothing  12  of the internal gear ring  11   b  can slide along a peripheral portion of the internal toothing  13  of the external gear ring  11   a  without tooth engagement. Such a gear set ( 11   a ,  11   b ) as a pump rotor  11  is also referred to as a gerotor (G-rotor). 
         [0035]    As indicated in  FIG. 5  by means of the dashed lines A i  and A a , the axis A i  is radially spaced apart (eccentric) from the central axis (center/symmetry axis) A a , which forms the axis of rotation of the external gear ring  11   a , as an axis of rotation of the internal gear ring  11   b —and thus the shaft feedthrough  10 —which internal gear ring is, for example, positively joined with the motor shaft  9 . To receive the shaft  10 , the internal gear ring  11   b  has a, for example, star-shaped contoured joining opening  14 . The latter is aligned with the shaft opening  10  of the housing base body  2   a.    
         [0036]    In contrast to the external gear pump, in the case of such an internal gear ring or gear ring pump as a special type of gear pump, the internal gear ring  11   b  thus runs as a driving gear eccentrically in the external gear ring (outer toothed ring)  11   a . In the case of this gear ring pump, the medium is conveyed between the tooth gaps of the gear rings  11   a  and  11   b  by the displacement space which is changing in the volume. In other words, in this gear pump, which is also referred to as a crescent pump, the medium to be conveyed is conveyed in the spaces between the tooth gaps of the two gear rings (gear wheels)  11   a  and  11   b , wherein the teeth are sealed by the crescent between the inwardly directed inner teeth of the external gear ring  11   a  and the outwardly directed outer teeth of the internal gear ring  11   b . In the case of the illustrated gear ring pump as oil pump  1 , the external gear ring  11   a  has exactly one tooth more than the internal gear ring  11   b  (trochoid toothing). 
         [0037]    The housing base body  2   a  is closed with the housing cover  2   b . The pressure-side pump outlet (pressure opening or pressure outlet)  16  is provided in the housing cover  2   b  ( FIGS. 3 and 4 ), while the suction-side pump inlet (suction openings)  15  is introduced into the housing bottom  5  of the housing base body  2   a.    
         [0038]    Within the housing  2 , a side plate  17 , which is penetrated by the motor shaft  9 , is fixed to the edge side of the housing opening  6  of the housing base body  2   a . This, preferably rigid, side plate  17  is located on the edge or outer circumference in an annular notch  18  of the housing base body  2   a . The rigid side plate  17  has a circular-arc-shaped passage opening  19  extending over a circumferential section. Between this side plate  17  and the housing cover  2   b , a flexible pressure plate  20 , hereinafter also referred to as a diaphragm, is inserted into the housing  2 . This preferably circular pressure plate  20  is clamped with its outer edge  20   a  between the housing base body  2   a  and the housing cover  2   b  on the opening or edge side and is therefore also fixed to the housing. By means of the flexible pressure plate  20 , in particular temperature-dependent partial expansions of housing or pump are reduced and/or compensated for. 
         [0039]    In the region of the passage opening  19  of the side plate  17 , a bead-like, indented outlet channel  21  is formed into the flexible pressure plate  20 , which outlet channel is aligned with the circular-arc-shaped passage opening  9  of the side plate  17  with respect to its shape and location (position), covering said side plate but leaving a passage  22  ( FIG. 7 ). This passage  22  is aligned with the cover-side pump outlet  16  which can be seen in  FIG. 4 . 
         [0040]    An opening collar  22 , which is pulled out in the direction of the housing cover  2   b , is formed or shaped in the region of the shaft feedthrough  10 , i.e., aligned with the latter, into the pressure plate  20  at its shaft feedthrough  20   b . In the region of the outer edge  20   a  or outer circumference of the flexible pressure plate  20 , a bead-like, annular circumferential formation  23  is likewise inserted in the direction of the housing cover  2   b . Between this formation  23  and the opening collar  22 , a pressure chamber (clearance/pressure equalization chamber)  24  is formed. A fluid channel (housing channel)  26  to this pressure chamber  24 , which is indicated by dashed lines, can be inserted into the housing wall  25  of the housing  2 . A partial flow of the conveyed medium (oil) M from the inlet-side suction side can pass through said fluid channel, between the flexible pressure plate  20  and the housing cover  2   b , into the pressure chamber  24 . 
         [0041]    In viewing the section shown in  FIG. 6  and the cross-section in  FIG. 7 , the flexible pressure plate (diaphragm)  23  which extends transversely to the axial direction A of the oil pump  1  in the radial direction R and thus practically across the entire housing cross-sectional area, and the pressure chamber (clearance/pressure chamber, pressure equalization space)  24  formed between the diaphragm and the housing cover  2   b  can be seen. In these, oil M can be introduced via the fluid channel  26 , i.e., a partial flow of the oil M conveyed through the pump  1 . When the pump is operated, this results in a force action F a  on the outer side of the flexible pressure plate  23  situated opposite the gear set  11   a ,  11   b . This pressure force F a  acts counter to the oil compressive force prevailing in the pump interior  4  and can thus produce at least some pressure equalization. 
         [0042]    The invention is not limited to the embodiments described above. Rather, other variants of the invention can also be derived from those skilled in the art without departing from the scope of the invention. In particular, all the individual features described in connection with the exemplary embodiments can also be combined with one another in another manner without departing from the subject matter of the invention. 
         [0043]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.