Abstract:
A motor/pump unit, particularly for a power-steering arrangement in a motor vehicle, includes a housing, a hydraulic pump unit having a pump module and a motor unit with a drive motor. At least one damping element is provided between the pump unit and a portion of the housing to decouple the noise of the pump unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to German Patent Application No. 10 2006 030 188.9 filed Jun. 30, 2006, the disclosures of which are incorporated herein by reference. 
       BACKGROUND 
       [0002]    Various embodiments of a motor/pump unit are described herein. In particular, the embodiments described herein relate to an improved motor/pump unit for a power-steering arrangement in a motor vehicle. 
         [0003]    A motor/pump unit comprising a housing, a hydraulic pump unit with a pump module, and a motor unit with a drive motor is shown in DE 203 02 534 U1, and corresponding US 2006/039804 which published on Feb. 23, 2006. In a motor/pump unit of this type, the outer surfaces, in particular of the outer housing surrounding the motor and pump units, emit sound outwards. Furthermore, in conventional motor/pump units without special sound-absorbing and sound-damping measures, the structure-borne sound generated by the motor and pump units is passed on through the connected components into the passenger compartment and is emitted there as sound transmitted by air. The connected components may also be stimulated to natural vibrations which again leads to the emission of air-borne sound. 
         [0004]    In DE 203 15 224 U1, and corresponding US 2005/0053487 which published on Mar. 10, 2005, to reduce the noise development in a hydraulic system with a motor/pump unit, it is proposed to couple at least a portion of the motor/pump unit to the outer housing via a damping bearing which can be realized only at a relatively high cost. 
       SUMMARY 
       [0005]    The present application describes various embodiments of a motor/pump unit with a simplified possibility for efficiently reducing the noise development. 
         [0006]    One embodiment of the motor/pump unit includes a housing, a hydraulic pump unit with a pump module, and a motor unit with a drive motor. The motor/pump unit further comprises at least one damping element which is provided between the pump unit and a portion of the housing to decouple the noise of the pump unit. The damping element provides for a damping of the vibrations of the pump unit, which occurs as the sound source. In this way, an interruption to the propagation of sound is provided close to the source. 
         [0007]    Other advantages of the motor/pump unit will become apparent to those skilled in the art from the following detailed description, when read in light of the accompanying drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  shows a perspective exploded view, partially in section, of a motor/pump unit; and 
           [0009]      FIG. 2  shows a perspective sectional view of a portion of the assembled motor/pump unit of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    In the Figures, a motor/pump unit  10  is shown for a power-steering arrangement in a motor vehicle, the structure of which is very similar to that of the motor/pump unit shown in DE 203 02 534 U1, which is incorporated herein by reference. The motor/pump unit  10  comprises a pump unit  12  with a pump module  14  and a motor unit  16  with a drive motor (not shown). The pump unit  12  and the motor unit  16  are accommodated in a shared outer housing  18 , the pump unit  12  and the motor unit  16  being separated from each other by a flange  20 . In the illustrated example embodiment, the outer housing  18  is formed as one piece, but it may also be divided, e.g. into a housing for the pump unit  12 , a housing for the motor unit  16  and possibly an intermediate housing arranged between the pump unit  12  and the motor unit  16 . The upper end side of the housing  18  is closed by a cover  22 . 
         [0011]    The end sides of the pump module  14  are closed by two covers  24 ,  26  which are screwed to each other. The pump module  14  is arranged in a resonator chamber which is bounded radially by a section  28  of the outer housing  18  and which surrounds the pump module  14  in a ring shape. The cover  22  of the housing  18  is therefore designated below as the resonator cover  22 . The resonator cover  22  can be ascribed both to the outer housing  18  and to the pump unit  12 . 
         [0012]    The axial fixing of the pump module  14  in the housing  18  takes place by means of an elastically deformable spring element  30 , which is inserted between the cover  24  of the pump module  14  and the resonator cover  22 . The spring element  30  is corrugated (not illustrated) and is held in a matching recess of the cover  24 , in order to prevent a lateral slippage. The spring element  30  presses the pump module  14  against the flange  20  and thus provides for an axial bracing of the pump module  14  in the housing  18 . Positioning pins  32 , which engage into corresponding recesses of the respectively opposite component, are provided on the pump module  14  (or alternatively on the flange  20 ) for correct positioning and fastening, particularly with respect to a rotation of the pump module  14  relative to the flange  20 . 
         [0013]    The coupling of the drive motor to the pump, which is formed in the pump module  14 , takes place by means of a coupling  34  which connects a motor shaft  36  of the drive motor with a drive shaft  38  of the pump. 
         [0014]    Various measures are described below which serve to decouple the noise of the pump from the outer housing  18  of the motor/pump unit  10 . According to the actual requirements (which depend particularly on the frequency of the vibrations caused by the pump), the measures can be provided individually or in any desired combination. 
         [0015]    A damping element  40  is provided between the lower cover  26  of the pump module  14  and the flange  20 . The damping element  40  is constructed as a sheet metal part which is coated on both sides with an elastomer, but a coating only on one side or a component with an elastomer layer arranged between two sheet metal layers is also possible. Through this, a noise decoupling of the pump module  14  from the flange  20  is achieved, and hence also from the outer housing  18 , particularly from the part of the housing  18  which surrounds the drive motor. The damping element  40  also serves as a sealing element for sealing the pump module  14  with respect to the flange  20 . Furthermore, the damping element  40  may also undertake the separation of the high pressure zone from the low pressure zone of the pump unit  12 . The construction of the lower cover  26  and/or of the opposite flange  20  is simplified if the damping element  40  is constructed as a flat seal. In this case, in fact no grooves have to be worked in for additional sealing elements. The flat seal may possibly be provided with corrugations in order to optimize the sealing capability. 
         [0016]    As a further measure to prevent the transfer of vibrations from the pump module  14  to the flange  20 , the positioning pins  32  are coated with elastomer or are covered with a shrink tube. 
         [0017]    A noise uncoupling of the pump module  14  from the resonator cover  22  is achieved in that an elastomer spring is used as spring element  30 , which secures the pump module  14  axially. 
         [0018]    A damping element  42  is arranged between the resonator cover  22  and the housing section  28 , adjacent to the resonator cover  22 , which delimits the resonance chamber. The damping element  42  provides for a distinct reduction in the vibrations transmitted from the resonator cover  22  to the housing section  28 . The damping element  42  is preferably constructed like the previously described damping element  40 . An even better decoupling is achieved through the use of washers  44  between the heads of the screws  46 , which connect the resonator cover  22  with the housing section  28 , and the resonator cover  22 . 
         [0019]    The drive shaft  38  of the pump and the motor shaft  36  of the drive motor are preferably connected with each other by means of an Oldham coupling  34  made of steel, which is held together in the centre by a vibration-damping elastomer element  48 . Alternatively, a plastic coupling, e.g. made of PEEK, may be provided. In addition to steel or plastic couplings, steel/plastic or steel/elastomer couplings are also possible. 
         [0020]    In accordance with the provisions of the patent statutes, the principle and mode of operation of the motor/pump unit have been explained and illustrated in its preferred embodiment. However, it must be understood that the motor/pump unit described herein may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.