Abstract:
The invention relates to an electric fluid pump with a semi-axial construction, in which a motor housing part ( 9 ), situated at the pressure end, has a conduction device ( 42 ). The conduction device ( 42 ) allows an almost completely irrotational flow to be achieved so that the kinetic energy of the tangential component of the flow velocity is converted into pressure energy with negligible friction losses. This feature of the invention increases the efficiency of the fluid pump. The dimensions of the electric motor can therefore be reduced while maintaining the same delivery quantity.

Description:
[0001]    This is a National Phase Application in the United States of International Patent Application No. PCT/EP2006/009763 filed Oct. 10, 2006, which claims priority on German Patent Application No. 10 2005 054.027.9, filed Nov. 11, 2005. The entire disclosures of the above patent applications are hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention is directed to a fluid pump for internal combustion engines, comprising an electric motor with a rotor arranged in a motor housing and a stator, the rotor being arranged on a drive shaft at least in a manner secured against rotation, an impeller fastened on the drive shaft, at least one set of guide vanes arranged behind the impeller in the flow direction of the fluid to be conveyed, and a pump housing enclosing the motor housing, the impeller and the guide vanes and at which a pressure port and an intake port are arranged opposite the axial ends. 
       BACKGROUND OF THE INVENTION 
       [0003]    Fluid pumps for internal combustion engines are used especially as coolant pumps in the cooling circuit. Whereas, in the past, a direct coupling with the engine speed existed and the pumps were driven by belt or chain drives, more recent engines increasingly use electric variable speed coolant pumps with a can, so as to realize a modern thermal management. Thus, an excessive delivery rate can be prevented, so that, for example, the internal combustion engine can be heated up faster after a cold start. The delivery rate can be controlled according to the actually required cooling capacity. 
         [0004]    Such a pump is known, for example, from MTZ No. 11, vol. 2005 (p. 872-877). This electric coolant pump comprises an EC motor as the drive unit and has a pump head with an axial inlet and a tangential outlet. The components and especially the housing parts used therein are rather large for the power input of the pump, since a relatively large drive motor has to be used. 
         [0005]    Thus, US 2002/0106290 A1 discloses an electric fluid pump of semi-axial construction, whereby, with the same power input to the electric motor, the electric motor can be made smaller to obtain higher speeds, so that the same delivery rate can be obtained with a more compact structure. It comprises a completely enclosed electromotor with a guide vanes provided at the outer side thereof. However, behind the guide vanes, seen in the flow direction, obstacles are formed that hinder the establishing of the electric contacting to the electronic unit. On the impeller side, the entire motor is sealed with gaskets from the environment. It is at least debatable whether such a sealing at the rotating parts is sufficient. 
         [0006]    The pump housing is bipartite and has various steps and through holes for electric contacting. Depending on the desired maximum delivery rate, different electric motors and housings must be designed. 
         [0007]    Likely, a completely irrotational flow is not achieved due to the rather short guide vanes. Further, the pressure loss due to the passages of the electric contacts is rather high so that the gain in the power input of the electric motor is partly thwarted by the pressure losses occurring. 
         [0008]    DE 202 01 183 U1 discloses an axial pump with an electric motor enclosed by a housing part having straight supporting ribs intended to serve as a guide vanes. Due to their straight design, the pressure loss is very high. In addition, it is most probable that an irrotational flow is not achieved with this structure. 
         [0009]    It is therefore an object of the invention to achieve an irrotational outflow with pressure losses as small as possible and to thereby increase the efficiency while reducing the package size. Further, various maximum delivery rates are to be achieved, while using the same housing parts. 
       SUMMARY OF THE INVENTION 
       [0010]    This object is achieved by providing a pressure-side motor housing part with a conduction device. This conduction device allows to obtain an almost completely irrotational flow so that the kinetic energy of the tangential component of the flow velocity is converted into pressure energy with low friction losses. This increases the efficiency of the fluid pump. Thus, in order to obtain an unaltered delivery rate, it is also possible to reduce the overall size of the electric motor. 
         [0011]    In a further developed embodiment, the conduction device is formed by recirculation vanes manufactured integrally with the pressure-side motor housing part and formed on the surface thereof, so that no additional components are required and an irrotational flow with little loss of energy is guaranteed. The recirculation vanes serve to convert the tangential flow component into an axial flow component without any significant pressure losses. The efficiency is increased and the number of components is reduced. 
         [0012]    Preferably, the pressure-side motor housing part is tapered in the flow direction and surrounded by a correspondingly shaped pressure-side pump housing part. Thus, the radial ends of the recirculation vanes are delimited by the pump housing, so that it is reliably prevented that the vanes are flown over. 
         [0013]    It is advantageous to form grooves in the pressure-side pump housing part, the radial ends of the recirculation vanes extending into these grooves. This again reduces the flow resistance by preventing an overflowing of the vanes and defines the position of the motor housing part with respect to the pump housing part, so that, in turn, assembly errors are avoided, since the grooves serve as guiding grooves upon assembly. 
         [0014]    In a further developed embodiment, the pressure-side motor housing part is adapted to be slid into a receiving opening of an axially adjoining motor housing part by slipping the pressure-side pump housing part onto the pressure-side motor housing part, with interposition of a gasket, wherein the pressure-side motor housing part is fixed by fastening the pressure-side pump housing part at a pump housing part situated radially outward with respect to the axially adjoining motor housing part. Accordingly, no fastening elements have to be used to fasten the pressure-side motor housing part. The fastening of the pump housing part alone guarantees for a tight fastening of the motor housing, so that the assembly effort is reduced. 
         [0015]    Preferably, the pressure-side pump housing part has a flange via which the fluid pump can be fastened to an internal combustion engine. Due to the simplicity of the pump housing parts, the pressure port can be made integrally with the flange, so that the fluid pump can be flange-mounted directly on a motor housing, for example, without additional intermediate lines. 
         [0016]    It is particularly advantageous if a plurality of fluid pumps are connected in series via a flange connection, the flanges being formed at the pressure-side pump housing part of the first pump and a suction-side pump housing part of a downstream pump. It is possible to provide a series connection without additional components, allowing to realize a higher required maximum volume flow. This becomes possible especially because of the irrotational flow in the outlet port caused by the conduction device. Thus, it is possible, in a restricted package space, to achieve a different delivery flow with different motor sizes, without any redesigning and without changing the components. Thereby, costs can be reduced. 
         [0017]    Thus, a fluid pump is provided that supplies an irrotational flow at the outlet and operates with negligible pressure losses by friction and the like. This increases the efficiency, since a large part of the kinetic energy is actually converted into pressure energy. A series connection allows to obtain various delivery rates with the same components in a compact space. 
         [0018]    An embodiment of the invention is illustrated in the drawing and will be detailed hereinafter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0019]    The FIGURE is a side elevational sectional view of a fluid pump according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    The fluid pump illustrated in the FIGURE, which is particularly suited as a coolant pump in internal combustion engines, is driven by an electronically commuted electric motor  1 , formed by a stator  2  and a rotor  4  arranged on a drive shaft  3 . The axial end of the drive shaft  3  is provided with an impeller  5  that is realized in a semi-axial construction and by whose rotation the fluid to be conveyed, especially a coolant, is conveyed substantially axially from an intake port  6  through the fluid pump to a pressure port  7 . 
         [0021]    The electric motor  1  is arranged in a motor housing formed by a first, suction-side motor housing part  8  and a second, pressure-side motor housing part  9 . The drive shaft  3 , on which the impeller  5  is arranged, is passed through the suction-side motor housing part  8 . For this purpose, the suction-side motor housing part  8  has a bore  10  with a first bearing  11  being arranged therein for supporting the drive shaft  3 . Behind the first bearing  11 , seen from the suction side, an ceramic axial sliding bearing  12  as well as a rubber sleeve  13  and a spacer  14  are situated. This assembly allows to achieve a sufficiently vibration-damped support of the impeller side of the drive shaft  3  of the electric motor  1 . The spacer serves to widen the distance between the first bearing  11  and a second bearing  15 , whereby an angular error caused when making the bore  10  for receiving the bearings can be compensated better. 
         [0022]    Further, behind the spacer  14 , a rotor pack  16  is arranged on the shaft, comprising axially extending slits for receiving magnets  17  corresponding with a stator coil  18  in a manner known per se. The rotor  4  is delimited axially and radially by an enclosure  19 . The stator coil  18  is wound on an insulating body  20  and axially delimits a stator pack  21  in a manner known per se. To close the magnetic circuit, this stator pack  21  is positively connected with a magnetic yoke  22 . This magnetic yoke  22  rests against an abutment  23  formed on an inner surface of the first suction-side motor housing part  8 . 
         [0023]    The rotor  4  is separated from the stator  2  by a can  24  resting on the suction side of the pump in a corresponding receiving opening  25  of the suction-side motor housing part  8 , and whose opposite axial end is arranged, in turn, in a corresponding receiving opening  26  of the pressure-side motor housing part  9 . The stator  2  with its sensitive coil  18  is thus situated in a dry space separated by the two motor housing parts  8  and  9  and the can  24 . 
         [0024]    Provided at the pressure-side end of the can  24  is a closure member  27  in which the second bearing  15  is arranged to support the drive shaft  3 . This closure member  27  is secured axially by the pressure-side motor housing part  9 , which, with the interposition of a gasket  28 , is arranged in a receiving opening  29  of the suction-side motor housing part  8 . 
         [0025]    The stator coil  18  is contacted, via a bore  30 , in the radial direction through the pressure-side motor housing part  9 . To prevent flow losses caused by such additional built-in means, this bore is made through supporting ribs  31 , as known in prior art, which ribs are required to provide a pump housing with sufficient strength and for mounting the same. For this purpose, the supporting ribs  31  are sufficiently wide and are shaped similar to an airfoil, so that no constriction of the cross section is formed. Thus, an electric contact element, not illustrated, can be passed through the bore  30  to an electronic unit (also not illustrated) for controlling the motor  1 . 
         [0026]    In the embodiment illustrated, the supporting ribs  31  are formed such that they simultaneously serve as the guide vanes, so that no additional guide vanes is needed immediately behind the impeller  5 . This allows for a simple manufacturing of the suction-side motor housing  8  as one piece, with the supporting ribs and a cylindrical radially outer pump housing part  32 . This pump housing part  32  encloses the radially inner motor housing part  8 , as well as the entire electric motor  1 . 
         [0027]    On the downstream and the upstream side of the housing part  8 ,  31 ,  32 , two respective identical pump housing parts  33 ,  34  are fastened by a screw connection, with a gasket  50  interposed therebetween. The suction-side pump-housing part  33 , flaring in the direction of flow, comprises the intake port  6  configured as a cylindrical section  35 , as well as an adjoining flaring section  46 . The semi-axial impeller  5  of the fluid pump is arranged in the transition  37  between the first section  35  and the second section  36 . In the present embodiment, the flaring section  36  is adjoined by another short cylindrical section  38  of larger diameter to achieve a smooth transition to the cylindrical pump housing part  32 . 
         [0028]    Corresponding sections tapering in the direction of flow and cylindrical sections are also provided at the pressure-side pump housing part  34 , the same reference numerals being used because of the identity of the parts. 
         [0029]    Moreover, the identical pump housing parts  33 ,  34  are formed with grooves  39  into which radial ends  40  of recirculation vanes  41  engage. These recirculation vanes  41  serve as the conducting device  42  by means of which a completely irrotational flow is obtained behind the pressure port  7 . This conducting device  42  is formed on a surface  43  of the pressure-side motor housing part  9  and becomes necessary, because the supporting ribs  31  serving as guide vanes are made rather short and a completely irrotational flow is usually not achieved in this part of the fluid pump. Moreover, the pressure-side motor housing part  9  can be made of plastic material, whereas the suction-side motor housing part should possible be made of aluminum and is thus more expensive. Such a configuration of the guide vanes in this portion would require a rather expensive production method, whereas the conduction device at the plastic housing part  9  is simple and economic to manufacture. 
         [0030]    The grooves  39  also define the position of the pressure-side pump housing part  34  with respect to the pressure-side motor housing part  9 . When the pump is assembled and the screws are tightened to fasten the pressure-side pump housing part  34  to the cylindrical pump housing part  32 , the pressure-side pump housing part  34 , by the recirculation vanes  40 , presses the motor housing part  9  against the motor housing part  8  or into the receiving openings  29  of the motor housing part  8 . Further, the motor housing part  9  is thereby pressed against the closure member  27  and the can  24 , respectively, so that no additional fastening of the two motor housing parts  8 ,  9  is required. 
         [0031]    When the pump is running, the rotation of the impeller  5  formed by a plurality of impeller vanes  44  conveys the fluid to be conveyed, in particular the coolant, through the space between the pump housing  32 ,  33 ,  34  and the motor housing  8  and  9 , the fluid flows past the supporting ribs  31 , where a part of the flow rotation is already removed due to their function as guide vanes, and it flows on through the conduction device  42  where the still existing rotation of the flow is removed completely so that the energy spent is converted as completely as possible into pressure energy and thus into an axial flow without incurring high friction losses. 
         [0032]    Behind the impeller  5 , a part of the fluid flows through bores  45  formed in the suction-side motor housing part  8 . Another part of the fluid also flows behind the impeller  5  to the drive shaft  3 , where it flows through between the first bearing  11  and the drive shaft  3 , so that the sliding bearing present is sufficiently lubricated. Thus, cooling liquid is in the rotor space, which is conveyed further between the drive shaft  3  and the second bearing  16 , as well as through non-illustrated bores in the closure member  27  and into a space  46  behind the same. This space  46  is connected with the space behind the same via another bore  47  extending axially through the pressure-side motor housing part  9 . Thus, both a lubrication of the bearings  11 ,  15  and a possibility for cooling and discharging possibly existing volumes of air in the rotor space are obtained. 
         [0033]    This semi-axial pump is especially characterized in that it can be of a particularly compact structure, since with the same power input the same delivery rate can be obtained though with a smaller motor size and an increased speed when compared with known pumps. This is achieved especially by the extremely reduced pressure losses in such a design, but also by the semi-axial construction. 
         [0034]    Moreover, such a pump can be produced very economically, since fewer differently designed components exist. At the same time, this reduces the occurrence of possible errors during assembly. By omitting the additional set of guide vanes and by integrating the electric contacting in the supporting ribs, additional components are avoided and pressure losses are reduced. Thus, on the whole, a higher efficiency is achieved. 
         [0035]    Because of the simplicity of the pump housing parts  33 ,  34 , it is of course also possible to provide the same with a flange situated at the pressure port or the intake port, respectively. This allows both a direct connection to a motor housing and to connect a plurality of pumps in series to increase the fluid volume flow conveyed. This becomes possible especially by the fact that the conduction device  42  creates an irrotational flow so that the impeller  5  of a downstream pump could be flown to directly without incurring energy losses. Therefore, when twice the delivery rate of a pump is required, it is not necessary to build a larger pump with a corresponding larger motor, but, due to the identity of the components, one may simply connect the corresponding required number of pumps in series. 
         [0036]    It is also conceivable, due to the simplicity of the suction-side pump housing part  33 , in particular, to form the same integrally with valve housing parts so that the pump housing parts  33  could comprise a receptacle for a bypass or an integrated heat valve. Parts of the housing of an annular slide valve could also be made integrally with the suction-side pump housing part  33 . 
         [0037]    It should be noted that the embodiment illustrated merely is a possible embodiment of the invention, whose structure may be altered in several respects without leaving the scope of protection of the claims.