Patent Publication Number: US-2016222968-A1

Title: Variable output centrifugal pump

Description:
BACKGROUND 
     The present disclosure relates to a pump, pump assembly, or pump system, and an associated method of magnetically coupling between an input drive member and an output driven member. It finds particular application in conjunction with a variable output pump, for example a centrifugal pump, that finds specific use in a fuel pump application, and will be described with reference thereto. However, it is to be appreciated that the present exemplary embodiment is also amenable to other like applications that encounter similar problems or require similar solutions. 
     High speed centrifugal (HSC) pumps typically encounter two problem areas when attempting to apply them to main engine fuel pump applications. First, at low starting speeds (for the engine) the centrifugal pump does not produce sufficient pressure to supply the fuel system for the start function. Second, once running, the centrifugal pump tends to over-generate pressure at operating conditions such as idle and cruise thereby wasting energy and increasing system operating temperatures. 
     This disclosure remedies both of these problems in a simple, reliable, effective, and inexpensive manner. 
     BRIEF DESCRIPTION 
     A variable output pump assembly includes an input drive member and a primary pump member operatively driven thereby. A second drive member supplements the pump assembly. A coupling is interposed between the input drive member and the second drive member to variably drive the pump assembly member. 
     The coupling is preferably a variable magnetic coupling interface between the input drive member and the second drive member. 
     The magnetic coupling interface includes a magnet and a magnet/ferro-magnetic member in spaced relation and the spacing therebetween is selectively altered to vary the magnetic coupling strength therebetween. 
     A primary advantage is the ability to reduce energy needs during certain operating conditions (e.g., cruise and idle). 
     Another benefit is associated with limiting the temperature increase to the system. 
     Another advantage is efficiently transmitting torque to the pump assembly. 
     Another benefit resides in adding normally lost torque to the output shaft and thereby improve torque transmission capability. 
     Still another advantage is associated with being able to generate additional pressure at desired operating conditions (e.g., engine start and take-off), and once running, to decrease the pressure. 
     Still other benefits and advantages will become apparent those skilled in the art after reading and understanding the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic representation of a first embodiment of a variable output centrifugal pump assembly. 
         FIG. 2  is a table providing exemplary characteristics of the variable output centrifugal pump assembly of  FIG. 1 . 
         FIG. 3  is a schematic representation of a second embodiment of a variable output centrifugal pump assembly. 
         FIG. 4  is a schematic view of the  FIG. 3  embodiment taken generally along the lines  4 - 4  of  FIG. 3 . 
         FIG. 5  is a schematic view of the embodiment of  FIG. 3  taken generally along the lines  5 - 5  of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1 , a variable output pump, pump assembly, or pump system (which terms may be used interchangeably herein), and more specifically a variable output centrifugal pump system,  100  is shown. A centrifugal pump  110  includes a fluid inlet  112  so that fluid (such as jet fuel for use in an aircraft engine, although this use is not intended to be limiting) is supplied to a primary impeller  114  rotatably received in housing  116 . The primary impeller  114  is driven by an input drive or drive shaft  118  rotating at a rotational speed ω ring  as is conventional in the art and thus rotates at the same rotary speed ω ring  as the input drive. The primary impeller  114  imparts energy to the fluid (e.g., increases the pressure of the fluid) which pressurized fluid exits generally radially from the primary impeller. 
     In addition, a secondary impeller  130  receives the pressurized fluid exiting the primary impeller  114  and imparts further energy to the fluid (again, further increases the pressure of the fluid). The secondary impeller  130  is schematically illustrated as part of the rotating housing  116  that receives the primary impeller  114 , although the secondary impeller and housing could be separate components as will be readily recognized by one skilled in the art. The housing  116  and thus the secondary impeller  130  rotate at a same rotary speed ω sun  whereby the additional energy is added to the fluid before the pressurized fluid enters into a radial diffuser/collector (not shown). 
     The rotational speed of the secondary impeller  130  may be varied relative to the input drive shaft  118  to vary the amount of additional energy (additional pressure) added to the fluid. In a first preferred arrangement, this variable output is achieved with a variable magnetic coupling interface, such as a magnetically coupled planetary gear transmission  140 , between the input drive shaft  118  and a secondary drive member  142  such that these drive components  118  and  142  (shown in a preferred concentric arrangement) can rotate at different rotational speeds. The magnetically coupled planetary gear transmission  140  is operatively connected to the input drive and configured for or capable of transmitting a variable speed drive to the secondary impeller  130 . That is, depending on the gearing and the amount of drive torque transmitted through the magnetically coupled planetary gear transmission  140 , the secondary impeller  130  will rotate at the same or a different rotational speed as the input drive  118 , and can be easily transitioned to a different rotational speed as will become apparent below. 
     More particularly, in one arrangement, the magnetic coupling  140  includes a planetary gear set carrier  148  that varies the output speed of a sun gear  146  which is attached to the secondary impeller  130  via the secondary drive member  142 . The torque balance of the secondary impeller load and magnetic coupling strength (as carried through the planetary gear ratio) sets the output rotational speed of the secondary impeller  130  and thus its level of output pressure. Control of the rotational speed of the secondary impeller  130  is achieved by varying an air gap  160  between a movable magnet  162  that is selectively moved by actuator  164  (e.g., slides along a linear axis that in the exemplary embodiment is parallel to the rotational axis of the input drive and the planetary gear set carrier  148 ). The actuator advances and retracts the magnet  162  relative to a magnetically coupled carrier  148  that includes a magnet or ferro-magnetic material  166  operatively associated with planets or planet gears  168  received in the gear set carrier  148 . The planets  168  are, in turn, operatively engaged with the sun gear  146  that is joined to the secondary drive member or hollow shaft  142  (received around the input drive shaft  118 ) to drive the housing  116  and secondary impeller  130 . The spacing or air gap  160  between the magnet  162  and the magnet/ferro-magnetic material  166  associated with the planets determines the amount of rotational torque that is transferred between the ring gear  144  (rotating at the same rotational speed ω ring  as the input drive) and the planets  168 . Thus, if the air gap  160  is small, the magnetic attraction is higher and an increased ratio of the rotational speed is transferred to the planets  168  when compared to a larger air gap which results in a reduced magnetic force between the magnet  162  and the magnet/ferro-magnetic material  166  attached to or part of carrier  148 , and likewise a reduced ratio of the rotational speed transferred to the planets. Thus, the rotational speed ω sun  of the planets  168 , sun gear  146  (operatively driven by the planets  168 ), and consequently the secondary drive shaft  142  (operatively driven by the sun gear) can be the same as the rotational speed ω ring  of the input drive  118 , or may be different, depending on the amount of torque transfer through the magnetic coupling achieved by varying the air gap  160  between the actuated magnet  162  and the magnet/ferro-magnetic material  166 . 
     Changing the magnetic coupling air gap  160  results in either a speed up or slow down of the rotational speed ω sun  of the secondary impeller  130  relative to the rotational speed ω ring  of the input drive  118 . The magnetic coupling mechanism  140  is preferred in this application because the speed control is readily achieved without adverse or ill failure mode effects that are potentially associated with a friction type clutch mechanism. 
     As can be seen from  FIG. 2 , changing the spacing of the magnetic coupling air gap  160  results in speeding up or slowing down of the rotational speed ω sun  of the secondary impeller  130  relative to the rotational speed ω ring  of the input drive  118 . Therefore, at engine start conditions, the air gap  160  is reduced or minimized and the secondary impeller  130  can turn sufficiently fast to achieve the desired fuel system pressure for engine start. Likewise, at engine idle and cruise speeds where high system pressure may not be required, the air gap  160  is increased or maximized so that the secondary impeller  130  can be significantly slowed to minimize pump output pressure which leads to minimization of power of the input drive  118  shaft and less fuel system heat build-up. At take-off, the air gap  160  is reduced/minimized and the speed of the secondary impeller  130  is increased by minimizing the air gap  160  to provide maximized pump pressure output to meet fuel system pressure needs. 
     A generally related concept of a magnetic coupling interface being used to vary the speed in a transmission assembly and, for example, a transmission assembly described in connection with one specific end use, namely a centrifugal pump assembly, is shown in a second exemplary embodiment of  FIGS. 3-5 . Again, there is a desire to efficiently and variably transmit torque to an output shaft, and preferably provide variable speed as a supplement or secondary drive input to a pump driven by a primary input. One manner of achieving this is to use a magnetic coupling, and more specifically another version of a variable speed planetary gear transmission is illustrated and described herein. This second exemplary arrangement not only varies the speed of the output shaft (relative to the input) but also incorporates features to add “normally” lost torque in such a device to the output shaft and thereby improve torque transmission capability. 
     A variable speed planetary gear set  200  is a part of the magnetic coupling illustrated in  FIGS. 3-5 . One potential use of the variable speed planetary gear set  200  is in connection with a variable output centrifugal pump  202  that includes a rotating impeller  204  that raises pressure of the fluid between an inlet  206  and outlet  208 . The variable centrifugal pump assembly  202  includes a connection between a drive member and the impeller to pressurize the fluid in the system. Here, however, details of the variable speed planetary gear set  200  are different than that shown and described in connection with the embodiment of  FIGS. 1 and 2 . 
     The input drive  210  has a rotational speed ω s  and drives or rotates a sun gear  212  at this same rotational speed ω s . The sun gear  212 , in turn, drives one or more planets  214  which drive a ring gear  216  that rotates at a rotational speed ω r  in a manner generally known by an ordinarily skilled artisan. In addition, the planets  214  are operatively associated with a first carrier  220  that is, in turn, operatively associated with an output drive  222 . Controlling a rotational speed ω r  of the ring gear  216  drives the output drive  222  at a desired rotational speed ω c . 
     The ring gear  216  includes a portion of a magnetic coupling  230 , namely, magnets  232  are disposed in circumferentially spaced arrangement along a face of the ring gear  216 . In addition, the magnetic coupling  230  includes one or more planets  234  that each have circumferentially spaced magnets or ferro-magnetic material  236 . An air gap  240  is provided between the planets  234  and the magnets  232  of the ring gear  216 . The air gap  240  is selectively varied, which varies the amount of torque transferred between these components, by axially moving the planets  234  toward and away from the magnets  232  of the ring gear  216 . Actuator  242  axially advances and retracts the planets  234  via a second carrier  244 . A spline or keyed connection  246  limits the movement of the second carrier  244  (and thus the planets  234 ) in an axial direction. As the air gap  240  is reduced or minimized, a greater amount of torque from the ring gear  216  is transferred to the planets  234 . The torque imposed on the planets  234  is then transferred to pinion gear  250  of the first carrier  220  and thus adds torque to the output at the rotational speed ω c  of the output drive  222  (which is the drive member for the impeller  204 ). 
     An intentional slipping of the ring gear  216  is used to vary a resultant rotational speed ω c  of the first carrier  220 . Specifically, controlling the rotational speed ω r  of the ring gear  216  drives the first carrier  220  and likewise the output drive  222  at a desired rotational speed ω c . More particularly, the pinion gear  250  of the first carrier  220  drives planets  234  of the second carrier  244  which mesh with the pinion gear  250 . This varies the resultant speed of the first carrier  220  and thus the output drive  222 . The magnetic coupling  230  flexibly transmits torque between the ring gear  216  and the planets  234  associated with the second carrier  244 . If the tangential velocity of the magnets  232  of the magnetic coupling  230  connected to the ring gear  216  is greater than the tangential velocity of the magnets/ferro-magnetic material  236  connected to the planets  234 , torque from the ring gear  216  will be added to the output drive  222  via the meshing of the planets  234  with the pinion gear  250 . 
     The speed of the output shaft  222  is set by the amount of torque used to hold or slow down the ring gear  216 . This torque is that which is transmitted to the output drive  222  via the flexible magnetic coupling  230 . The amount of torque transmission through the magnetic coupling  230  is a function of the air gap  240  between the halves of the magnetic pair. Thus, by varying the air gap  240  via the actuator  242 , the rotational speed of the output shaft  222  relative to the input shaft  210  can be varied. The air gap  240  is modulated by axial movement of the second carrier assembly  244  along the splined interface  246  with the transmission housing. The spline  246  allows the second carrier assembly  244  to slide axially while resisting the torque applied to hold the second carrier from rotating. The actuator  242  is used to slide the second carrier assembly  244  and thus set the air gap  240 . An assortment of open and closed loop controls can then be imparted to provide the desire speed outcome for the transmission. 
     The present disclosure also contemplates that the system may employ an electromagnetic arrangement to achieve a desired speed ratio or alter the speed ratio during operation. For example, rather than employing permanent magnets and/or ferro-magnetic materials that vary the strength of the magnetic field by varying the distance between the magnetic components (e.g., using the actuator in the above-described embodiments), the strength of the magnetic field in an electromagnetic arrangement can be easily varied by changing the amount of electric current through the wire or coil. Of course, further details of the structure and operation of electromagnets are known to those skilled in the art and will not be described herein for purposes of brevity. The use of an electromagnetic arrangement, however, is yet another type of magnetic coupling that achieves the desired control of the magnetic field and likewise the associated variation in the speed ratio and torque of the output shaft of above-described planetary gear transmission, which in one embodiment is used in a centrifugal pump assembly. 
     A first item of the present disclosure includes a variable output pump assembly that has an input drive member, a primary pump member operatively driven by the input drive member, a second drive member, and a variable torque coupling interposed between the input drive member and the second drive member to vary speed output of the second drive member. 
     A second item of the present disclosure includes the coupling as a variable magnetic coupling interface between the input drive member and the second drive member, and the second item may be used in combination with the first item. 
     A third item of the present disclosure includes the magnetic coupling interface having a magnet and a magnet/ferro-magnetic member in spaced relation and the spacing therebetween is selectively altered to vary the magnetic coupling strength therebetween, and the third item may be used in combination with either or both of the first and second items. 
     A fourth item of the present disclosure includes one of the magnet and magnet/ferro-magnetic member that is operatively connected to an actuator that selectively moves the one of the magnet and magnet/ferro-magnetic member toward and away from the other of the magnet and magnet/ferro-magnetic member, and the fourth item may be used in combination with any one or more of the first through third items. 
     A fifth item of the present disclosure includes the input drive member connected to the primary pump member which includes a primary impeller, and a secondary pump member operatively driven by the second drive member at a speed responsive to the coupling, and the fifth item may be used in combination with any one or more of the first through fourth items. 
     A sixth item of the present disclosure includes a ring gear of a planetary gear assembly also operatively connected to the input drive member for rotation therewith, and the sixth item may be used in combination with any one or more of the first through fifth items. 
     A seventh item of the present disclosure includes a planetary gear operatively driven by the ring gear such that the secondary pump member that includes a secondary impeller operatively associated with the planetary gear assembly rotates at a different rotational speed, and the seventh item may be used in combination with any one or more of the first through sixth items. 
     An eighth item of the present disclosure includes the carrier receiving one of the magnet and the magnet/ferro-magnetic member, and a fixed housing assembly receives the other of the magnet and magnet/ferro-magnetic member, and the eighth item may be used in combination with any one or more of the first through seventh items. 
     A ninth item of the present disclosure includes the planetary gear assembly having at least one planetary gear that receives a rotational drive input from the ring gear, and drives a sun gear in response thereto, and the ninth item may be used in combination with any one or more of the first through eighth items. 
     A tenth item of the present disclosure includes an inlet of the secondary impeller receiving output flow from an outlet of the primary impeller, and the tenth item may be used in combination with any one or more of the first through ninth items. 
     An eleventh item of the present disclosure includes the magnetic coupling interface having a magnet and a magnet/ferro-magnetic member, where one of the magnet and magnet/ferro-magnetic material is located on a first portion of a planetary gear arrangement, and the eleventh item may be used in combination with any one or more of the first through tenth items. 
     A twelfth item of the present disclosure includes the other of the magnet and magnet/ferromagnetic material located on a second portion of the planetary gear arrangement, and the twelfth item may be used in combination with any one or more of the first through eleventh items. 
     A thirteenth item of the present disclosure includes a magnet located on the transmission housing and the magnet/ferro-magnetic material located on the first portion of the planetary gear arrangement, and the thirteenth item may be used in combination with any one or more of the first through twelfth items. 
     A fourteenth item of the present disclosure includes a magnet located on a first carrier of the planetary gear arrangement and the magnet/ferro-magnetic material operatively associated with a planet of a second carrier, and the fourteenth item may be used in combination with any one or more of the first through thirteenth items. 
     A fifteenth item of the present disclosure includes the planet of the second carrier operatively associated with a pinion gear to supplement rotation of the input drive member, and the fifteenth item may be used in combination with any one or more of the first through fourteenth items. 
     A sixteenth item of the present disclosure includes an actuator that selectively advances and retracts the magnet/ferro-magnetic material of the planet toward the magnet of the first carrier, and the sixteenth item may be used in combination with any one or more of the first through fifteenth items. 
     A seventeenth item of the present disclosure is a method of varying speed output in a drive transmission assembly that includes providing a first drive member, providing a second drive member, and positioning a magnetic coupling between the first drive member and the second drive member to selectively vary the speed output of the second drive member relative to the first drive member. 
     An eighteenth item of the present disclosure includes placing one of a magnet and magnet/ferro-magnetic member in spaced relation in the magnetic coupling positioning step, and the eighteenth item may be used in combination with the seventeenth item. 
     A nineteenth item of the present disclosure includes selectively altering the spacing between the magnet and magnet/ferro-magnetic member to vary the magnetic coupling strength therebetween, and the nineteenth item may be used in combination with either or both of the seventeenth and eighteenth items. 
     A twentieth item of the present disclosure includes selectively moving one of the magnet and magnet/ferro-magnetic member toward and away from the other of the magnet and magnet/ferro-magnetic member, and the twentieth item may be used in combination with any one or more of the seventeenth through nineteenth items. 
     A twenty-first item of the present disclosure includes providing a primary pump member and driving an input shaft of the primary pump member via the first drive member, and the twenty-first item may be used in combination with any one or more of the seventeenth through twentieth items. 
     A twenty-second item of the present disclosure includes providing a secondary pump member and operatively driving the secondary pump member via the second drive member at a speed responsive to the magnetic coupling, and the twenty-second item may be used in combination with any one or more of the seventeenth through twenty-first items. 
     The disclosure has been described with reference to exemplary embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. For example, the description of a magnet on one component cooperating with a magnet or ferro-magnetic material on another component could be reversed. It is intended that the exemplary embodiments be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.