Patent Publication Number: US-2020291947-A1

Title: Vehicle fluid pump

Description:
The invention is directed to a vehicle fluid pump, in particular to a fluid pump provided with an electronically commutated canned motor. 
     These vehicle fluid pumps are provided with an electronically commutated motor arranged within a pump housing for driving a pump wheel co-rotatably provided with a motor rotor. Vehicle fluid pumps can be, for example, used as coolant pumps or as lubricant pumps. The pump motor comprises a motor stator with a stator body, preferably a laminated stator body, and with a plurality of stator coils. The pump motor also comprises a permanently magnetized motor rotor and is provided with a motor electronics unit with an electric ground terminal. The motor electronics unit is electrically connected to the stator coils for energizing the stator coils and thereby driving the motor rotor and the co-rotatably provided pump wheel. 
     The motor stator and the motor rotor are fluidically separated by a cylindrical motor can. As a result, the permanently magnetized motor rotor can be arranged within the fluidic part of the pump and can be easily attached to the pump wheel. The electromagnetic stator with the energized stator coils and the motor electronics unit can be arranged on the dry side of the motor can. No dynamic sealings are needed. 
     Like all other electronic devices, electronically commutated motors emit electromagnetic interferences, in particular electromagnetic radiation, which can cause malfunction or failure of electronic devices in vicinity of the motor, for example vehicle traction motor electronics. As a consequence, electronic devices have to comply with electromagnetic compatibility (EMC) directives. 
     It is an object of the present invention to provide a vehicle fluid pump with an electronically commutated canned motor with good EMC-characteristics of the pump. 
     This object is achieved with a vehicle fluid pump with the features of claim  1 . 
     The vehicle fluid pump according to the invention is provided with a pump housing, an electronically commutated motor, and with a pump wheel which is co-rotatably provided with a motor rotor. Electronically commutated motors provide a high power to weight ratio, high rotational speeds and can be provided with an electronic closed-loop control. This allows providing a very compact vehicle pump which can be easily integrated into the vehicle electrical control system. Preferably, the vehicle pump is supplied with low DC supply voltages of less than 50 V. 
     The electronically commutated motor of the vehicle fluid pump according to the invention is provided with a motor stator comprising a stator body and a plurality of stator coils. The motor is also provided with a permanently magnetized motor rotor fluidically separated from the motor stator by a cylindrical metal motor can. The electromagnetic motor stator with the energized stator coils is arranged at the dry side of the motor can, and the permanently magnetized motor rotor is arranged at the wet side of the motor can. The generated stator magnetic field penetrates and travels through the metal motor can and drives the permanently magnetized motor rotor and, as a result, drives the pump wheel co-rotatably provided with the motor rotor. This allows a simple co-rotatable connection of the motor rotor and the pump wheel within the fluidic part of the pump, and also allows protecting the electrically energized stator coils and the electronics from being in contact with the pumping fluid. 
     The electronically commutated motor of the vehicle fluid pump according to the invention is also provided with a motor electronics unit with an electric ground terminal. The motor electronics unit is located at the dry side of the metal motor can to protect the sensitive motor electronics from being in contact with the pumping fluid. The motor electronics unit is electrically connected to the stator coils for energizing the stator coils for driving the motor rotor. The motor electronics unit comprises several power semiconductors for commutating the electric energy energizing the stator coils. 
     The electronically commutated motor of the vehicle fluid pump according to the invention is also provided with an electric connection means providing a direct electric connection of minimal electric resistance between the motor electronics unit ground terminal and the metal motor can. The direct electric connection provides an equipotential bonding between the metal motor can and the motor electronics. As a result, the metal motor can serves as an electromagnetic shielding significantly suppressing the emitted interferences of the electronically commutated pump motor so that the EMC of the vehicle pump can be dramatically improved. 
     Preferably, the pump housing is made of plastic. Plastics housings can be manufactured inexpensively, for example by injection molding, and are lightweight. As a result, the plastic housing allows reducing cost and weight of the vehicle pump. However, a plastic housing has no electric shielding effect. 
     In a preferred embodiment of the invention, the metal motor can is provided as a cylindrical metal tube. A cylindrical metal tube can be easily introduced in the cylindrical air gap between the motor stator and the motor rotor to fluidically separate both. The metal tube can be supported by the pump housing and can be fluid-tightly sealed by a bottom cap to fluidically separate the motor stator from the motor rotor. 
     Alternatively, the metal motor can can be provided as a cylindrical metal pot which can be easily introduced into the stator rotor air gap, the metal pot being supported by the pump housing and fluidically separating the motor rotor from the motor stator. 
     Preferably, the cylindrical metal pot providing the motor can is electrically contacted by the electric connection means at the center of the circular metal pot bottom. The electric connection means provides an electrical connection between the motor can and the ground terminal of the motor electronics unit so that the electric potentials are equalized. The motor electronics unit is preferably arranged close to the metal pot bottom. As a result, contacting the center of the circular metal pot bottom allows the electric connection means to be very short so that the EMC is excellent. 
     Alternatively, the electric connection means can be in electrical contact with the outside circumferential surface of the cylindrical metal motor can. This allows contacting metal motor cans with a non-conductive motor can bottom, for example a metal tube with a plastic cap. 
     In a preferred embodiment of the invention, the motor electronics unit is arranged at a thermally conductive axial end part of the motor can. The end part can be, for example, provided by a metal pot bottom. The electronics unit is electrically isolated from and thermally connected to the motor can by a thermal compound. The thermal compound allows a heat transfer between the motor electronics and the metal motor can to efficiently dissipate the heat which is generated by the motor electronics unit. 
     Preferably, the electric connection means is provided as a metal spring attached to the motor electronics unit ground terminal and being in electrical contact with the metal motor can. The metal spring provides a simple and reliable electrical contact. The metal spring allows to compensate oscillations of the motor can with respect to the motor electronics unit and allows a simple mounting process. 
     In a preferred embodiment of the invention, the electric connection means is directly electrically connected with the ferromagnetic motor stator body so that the electric potential of the motor electronics unit electric ground connection and of the stator body are equalized. This allows good EMC-characteristics of the vehicle pump. 
    
    
     
       An embodiment of the invention is described with reference to the accompanying drawings, wherein 
         FIG. 1  shows a schematic longitudinal section of a vehicle fluid pump according to the invention, 
         FIG. 2  shows an alternative motor can and an alternative connection means of the vehicle fluid pump of  FIG. 1 , and 
         FIG. 3  shows an alternative arrangement of a motor control unit and another alternative connection means of the vehicle fluid pump of  FIG. 1 . 
     
    
    
       FIG. 1  shows a schematic longitudinal section of a vehicle fluid pump  110  with a plastic pump housing  112 , a pump wheel  114  co-rotatably attached to a rotor shaft  116  of an electronically commutated motor  118 . The pump wheel  114  is an impeller. The electronically commutated motor  118  is provided with a motor stator  120 , a permanently magnetized motor rotor  122  co-rotatably provided with the rotor shaft  116  and rotatable around an axis of rotation A, a cylindrical metal motor can  124  and a motor electronics unit  126 . 
     The motor stator  120  comprises a ferromagnetic stator body  128 , preferably a laminated stator body  128 , and comprises several stator coils  130  electrically connected to the motor electronics unit  126 . 
     The cylindrical metal motor can  124  is provided as a cylindrical metal pot  132  axially supported by the pump housing  112 . The axial cylinder centerline C 1  of the motor can  124  corresponds to the axis of rotation A. The motor can  124  fluidically separates the motor stator  120  arranged at the dry radial outside of the motor can  124  from the motor rotor  122  arranged at the wet radial inside of the motor can  124 . 
     The motor electronics unit  126  is arranged axially outwardly of and close to the motor can bottom  134  at the dry side of the motor can  124 . The motor electronics unit  126  commutates the electric energy energizing the stator coils  130  for driving the motor rotor  122  and, as a result, for driving the co-rotatably provided pump wheel  114 . The motor electronics unit  126  comprises an electric ground terminal  136  which is directly electrically connected to the motor can  124  by an electric connection means  138 . The electric ground terminal  136  can be, for example, provided as a printed circuit path electrically connected to the chassis ground of the vehicle pump  110 . 
     The electric connection means  138  is provided as a metal coil spring  140  fixed, for example soldered, to the motor electronics unit electric ground terminal  136  and being in touching electric contact with the center of the motor can bottom  134 . The metal coil spring  140  is preloaded in axial direction to compensate axial oscillations of the motor electronics unit  126  with respect to the motor can  124  and, as a result, to assure a reliable electric connection. The electric connection means  138  equalizes the electric potentials of the motor electronics unit electric ground terminal  136  and of the motor can  124  so that the emitted interferences of the electronically commutated motor  118  are suppressed significantly. As a result, the EMC of the vehicle fluid pump  110  is improved. 
       FIG. 2  shows a motor stator  220  with a stator body  228  and with several stator coil  230 , a motor control unit  226  with an electric ground terminal  236 , an alternative motor can  224  and an alternative connection means  238  of the vehicle fluid pump  110 . 
     The motor can  224  comprises a cylindrical metal tube  232  axially supported by the pump housing  212 , and comprises a circular non-metallic motor can cap  233  fluid-tightly attached to the non-supported axial end of the metal tube  232 . 
     The motor electronics unit  226  is arranged axially outwardly of the motor can  224  and close to the non-metallic motor can cap  233  at the dry side of the motor can  224 . The motor electronics unit electric ground terminal  236  is directly electrically connected to the motor can  224  and to the stator body  228  by an electric connection means  238  provided as metal spring  240 . 
     The metal spring  240  is fixed to the motor electronics unit electric ground terminal  236 . The metal spring  240  is radially in contact with a circumferential surface  234  of the motor can  224  and axially in contact with the stator body  228 . The metal spring  240  is preloaded in axial direction to compensate axial oscillations of the motor electronics unit  226  with respect to the stator body  228 . The metal spring  240  is also preloaded in radial direction, in particular radially inwardly, to compensate radial oscillations of the motor electronics unit  226  with respect to the motor can  224 . 
     The electric connection means  238  assures a reliable electric connection between the motor electronics unit electric ground terminal  236 , the motor can  224  and the stator body  228  so that the electric potentials are equalized. As a result, emitted interferences of the electronically commutated motor  218  can be minimized and the EMC of the vehicle fluid pump  210  can be improved. 
       FIG. 3  shows a motor can  324  provided as a cylindrical metal pot  332 , a motor control unit  326  with an electric ground terminal  336  and another alternative connection means  338  of the vehicle fluid pump  110 . 
     The motor electronics unit  326  is arranged axially outwardly at the motor can bottom  334  at the dry side of the motor can  324 . The motor electronics unit  326  is electrically isolated from and thermally connected with the motor can  324  by a thermal compound  342 . The thermal compound  342  allows a heat transfer from the motor electronics unit  326  to the motor can  324  to efficiently dissipate heat generated in the motor electronics unit  326 . 
     The motor electronics unit electric ground terminal  336  is directly electrically connected to the motor can  324  by an electric connection means  338  provided as metal leaf spring  340 . The metal leaf spring  340  is fixed to the motor electronics unit electric ground terminal  336  and is in touching electric contact with the circumferential surface  335  of the motor can  324 . The metal leaf spring  340  is preloaded in radial direction, in particular radially inwardly, to compensate radial oscillations of the motor electronics unit  326  with respect to the motor can  324 . The electric connection means  338  assures a reliable electric connection between the motor electronics unit electric ground terminal  336  and the motor can  324  to equalize the electric potentials and, as a result, to improve the EMC of the vehicle fluid pump  310 . 
     REFERENCE LIST 
     
         
         
           
               110  vehicle fluid pump 
               112  plastic pump housing 
               114  pump wheel 
               116  rotor shaft 
               118  electronically commutated motor 
               120  motor stator 
               122  permanently magnetized motor rotor 
               124  cylindrical metal motor can 
               126  motor electronics unit 
               128  stator body 
               130  stator coils 
               132  cylindrical metal pot 
               134  motor can bottom 
               136  electric ground terminal 
               138  electric connection means 
               140  metal coil spring 
               220  motor stator 
               224  metal motor can 
               226  motor electronics unit 
               228  stator body 
               230  stator coils 
               232  metal tube 
               233  non-metallic motor can cap 
               236  electric ground terminal 
               238  electric connection means 
               240  metal spring 
               324  metal motor can 
               326  motor electronics unit 
               332  metal pot 
               334  motor can bottom 
               335  motor can circumferential surface 
               336  electric ground terminal 
               338  electric connection means 
               340  metal leaf spring 
               342  thermal compound 
             A axis of rotation 
             C 1  cylinder centerline 
             C 2  cylinder centerline