Abstract:
A motor/pump aggregate ( 10 ), in particular for a servo-steering system of a motor vehicle, includes a motor/pump unit ( 14 ), and an outer housing ( 12 ) surrounding the motor/pump unit ( 14 ). The motor/pump unit ( 14 ) includes a motor unit ( 16 ) and a pump unit ( 18 ). At least one part of the motor/pump unit ( 14 ) is coupled to the outer housing ( 12 ) by means of a damping bearing.

Description:
TECHNICAL FIELD  
       [0001]     The invention relates to a motor/pump aggregate, in particular to a motor/pump aggregate for a servo-steering system of a motor vehicle.  
       BACKGROUND OF THE INVENTION  
       [0002]     In hydraulic systems, such as for example servo-steering devices used in motor vehicles, the energy providing components, in particular the motors and pumps, represent the main sources of noise, whereas the actuators of the systems only contribute a small amount to the overall noise. In a motor/pump aggregate of a servo-steering system including a motor unit and a pump unit with an outer housing surrounding the motor and pump units, in particular the outer surfaces of the outer housing emit noise to the exterior. Furthermore, in conventional motor/pump aggregates without particular sound-damping measures, the sound conducted through solids generated by the motor and pump units is passed on via the connected components into the passenger compartment and is emitted there as sound transmitted by air. The connected components can also be stimulated to natural oscillations, which in turn leads to the emission of sound transmitted by air.  
         [0003]     In conventional motor/pump aggregates, to avoid vibrations, damping elements are arranged between the motor unit and the pump unit. However, this means a high expenditure in terms of construction technology and may lead to inaccuracy in the relative positioning and alignment of components of the motor and of the pump and also of the two components as a whole.  
         [0004]     Thus, there is a desire for efficiently reducing the noise development in a hydraulic system with a motor/pump aggregate in a simple manner.  
       SUMMARY OF THE INVENTION  
       [0005]     A motor/pump aggregate according to the invention comprises a motor/pump unit and an outer housing surrounding the motor/pump unit, the motor/pump unit including a motor unit and a pump unit, at least one part of the motor/pump unit being coupled to the outer housing by means of a damping bearing. The invention is based on the finding that the undesired emission and passing on of the noises generated by the motor/pump aggregate is best prevented in that the path of the conducting of sound through solids is interrupted or at least restrained as close as possible to the sound source. Through the invention, an acoustic uncoupling of the outer housing with respect to the motor/pump unit is achieved, so that the outer surfaces of the outer housing do not represent, or at least only represent to a small extent, emission surfaces for sound conducted through solids.  
         [0006]     A passing of the sound conducted through solids on to vehicle components which are connected to the motor/pump aggregate can be prevented in that the damping bearing is coupled to a fastening part which is connected with the outer housing, the motor/pump aggregate being fastened in the vehicle by the fastening part.  
         [0007]     In a first embodiment of the invention, the damping bearing comprises several damping elements disposed between the motor/pump unit and the outer housing. The damping elements are preferably constructed as plastic ribs. In this embodiment, the damping elements are substantially of parallelpiped shape. It proves to be particularly advantageous to align at least one damping element vertically and/or to align at least one damping element horizontally with respect to a longitudinal axis of the motor/pump aggregate, which defines a vertical direction. By means of the number, placing, alignment and the actual dimensions of the damping elements, the rigidity and the damping characteristics for guiding functions of the damping bearing, like the supporting of the weight forces of the components of the motor/pump unit and the supporting of acceleration moments of the motor of the motor/pump unit, can be optimized in line with specific objectives.  
         [0008]     In a second embodiment of the invention, the damping bearing comprises an encircling damping element with respect to a longitudinal axis of the motor/pump aggregate. This damping element can seal a space between the outer housing and the motor unit from a space between the outer housing and the pump unit. In this case, the damping element undertakes the function of a dividing wall for the hydraulic fluid of the motor/pump aggregate, if for example only the pump unit is to have hydraulic fluid flowing around it. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  shows a perspective view of a motor/pump aggregate according to a first embodiment of the invention;  
         [0010]      FIG. 2  shows a top view of the motor/pump aggregate of  FIG. 1  without an upper housing part; and  
         [0011]      FIG. 3  shows a diagrammatic side view, in section, of a motor/pump aggregate according to a second embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0012]     The motor/pump aggregate  10  shown in  FIG. 1  comprises a metallic outer housing  12 , which is illustrated so as to be transparent, in order to make visible the components situated therein. In the outer housing  12 , a motor/pump unit  14  is housed, which is composed of a motor unit  16  and of a pump unit  18 . The outer housing  12  serves to delimit a hydraulic fluid reservoir and is divided into a first housing part  20  surrounding the motor unit  16  and a second housing part  22  surrounding the pump unit  18 . The housing parts  20 ,  22  are connected with each other by means of a fastening ring  24 , which also represents the mechanical connecting site to the vehicle body.  
         [0013]     The motor/pump unit  14  is held in the outer housing  12  by a damping bearing which is formed from several damping elements  26  and  28  arranged between the motor/pump unit  14  and the fastening ring  24  (see also  FIG. 2 ). The damping elements  26 ,  28  are flat plastic ribs, substantially of parallelepiped shape, which are distributed over the outer periphery of the motor/pump unit  14  and the inner periphery of the fastening ring  24 . The damping elements  26 ,  28  are vulcanized on the one hand to the inner periphery of the fastening ring  24  and on the other hand to a sheet metal ring  30 , which is shrunk onto a connecting plate  32 , on which both the motor unit  16  and also the pump unit  18  are fastened.  
         [0014]     In relation to the illustration of  FIG. 1 , in which the longitudinal axis A of the motor/pump unit  14  defines a vertical direction, hereinafter the damping elements  26  are designated as vertically aligned damping elements and the damping elements  28  arranged substantially perpendicularly thereto are designated as horizontally aligned damping elements. The vertically aligned damping elements  26  are rigid with respect to axial movements of the motor/pump unit  14  (down up and movements) and in particular support the inherent weight of the motor/pump unit  14 . The damping elements  26  are, however, flexible with respect to a rotation of the motor/pump unit  14  about the axis A relative to the outer housing  12 . The opposite occurs with the horizontally aligned damping elements  28 : these damping elements  28  are rigid with respect to a rotation, but flexible in axial direction. The damping elements  28  therefore provide for a support with respect to the acceleration and deceleration moments of the motor of the motor/pump unit  16 , the motor shaft of which is aligned parallel to the axis A. As can be seen in particular in  FIG. 2 , in the illustrated embodiment, vertically and horizontally aligned damping elements  26  and  28 , respectively, alternate in peripheral direction.  
         [0015]     The cooperation of all damping elements  26 ,  28  provides as a whole for a damped, vibration-equalizing bearing of the motor/pump unit  14  in the outer housing  12 . The damping elements  26 ,  28  separate the motor and the pump as noise sources from the emitting outer surfaces of the outer housing  12 .  
         [0016]     In the embodiment shown in  FIG. 3 , the motor/pump unit  14  is held by means of a diagrammatically illustrated, encircling damping element  34 . The encircling damping element  34  can be constructed so that it is impermeable to the hydraulic fluid surrounding the pump unit  18 . In this case, the space between the lower housing part  20  and the motor unit  16  is kept free of hydraulic fluid. The damping element  34  can, however, also be arranged or constructed so that it is permeable to the hydraulic fluid. This is suitable when the motor is a wet-running motor and a cooling of the motor unit  16  by the hydraulic fluid is desired.  
         [0017]     The damping bearings described above are also advantageous for motor/pump aggregates in which the motor unit and the pump unit are connected with each other by an intermediate housing. In this case, the damping bearing is coupled to the intermediate housing. Therefore, with only one damping bearing the entire motor/pump unit can likewise be uncoupled from the outer housing, so that the excitations of sound conducted through solids of the individual components, in particular of the motor unit and of the pump unit, do not need to be damped separately. In other embodiments of the motor/pump aggregate, however, also several damping bearings can be provided, for example a bearing for the motor unit and a separate bearing for the pump unit.