Patent Publication Number: US-11028847-B2

Title: Gear pump for venting trapped volume

Description:
TECHNICAL FIELD 
     The present disclosure relates to pumps, specifically to positive-displacement pumps for use in automotive vehicles. 
     BACKGROUND 
     A pump is a device that raises, transfers, delivers, or compresses fluids by suction or pressure of both. Vehicles may employ one or more pumps that provide fluid e.g., coolant or oil to a desired component within the vehicle. Mechanically driven pumps are generally coupled to and powered by internal combustion engine. Powering a pump by an electric motor decreases the load or work required from the engine, thus increasing the efficiency of the engine. 
     A positive displacement pump is a pump that displaces a known volume of fluid per unit cycle. One category of a positive displacement pump is a gear pump that includes two or more gears that are disposed within a pump housing. The gears may be rotatably coupled to an end plate that extends between an outer wall of the housing. The gears are arranged so that the teeth of each of the gears trap and displace fluid to create a low-pressure area, near an inlet of the pump, and a high-pressure area, near the discharge of the pump. 
     SUMMARY 
     According to one embodiment, an external gear pump is provided. The external gear pump may include a housing, a first gear, a second gear, and an end plate. The housing may include a peripheral wall forming an enclosure and defining an inlet and a discharge port. The first gear may include a first tooth and a second tooth. The second gear may be disposed within the housing and include a third tooth that engages the first tooth and the second tooth to form a pressure pocket. The end plate may be disposed within the housing. The first gear and the second gear may each be rotatably coupled to the end plate. The end plate may define a discharge channel and a bridge portion. The discharge channel may extend between the discharge port and the bridge portion. The bridge portion may define a relief portion and the relief portion may be configured such that fluid is communicated from the pressure pocket to the discharge port. 
     The relief portion may be at least partially defined by an axial surface by one of the teeth. 
     The relief portion may be comprised of a plurality of recessed finger cuts. 
     In one or more embodiments, when the first gear and the second gear are arranged in a first relative position, a first recessed finger cut of the plurality of recessed finger cuts may be partially eclipsed by the pressure pocket in an axial direction of the first and second gears. 
     The second gear may be provided with a fourth tooth, and when the first gear and the second gear are arranged in the first relative position, the third tooth, the fourth tooth, and the first tooth may define a second pressure pocket. A second recessed finger cut of the plurality of recessed finger cuts may at least partially eclipse the second pressure pocket in the axial direction of the first and second gears. 
     In one or more embodiments, when the first gear and the second gear are arranged in a second relative position, the first tooth, the second tooth, and the third tooth may define a third pressure pocket. A third recessed finger cut of the plurality of recessed finger cuts may at least partially eclipse the third pressure pocket in the axial direction of the first and second gears. 
     The second gear may be provided with a fifth tooth. When the first gear and the second gear are arranged in a second relative position, the second tooth, the third tooth, and the fifth tooth may define a fourth pressure pocket. A fourth finger cut of the plurality of recessed finger cuts may least partially eclipse the fourth pressure pocket in the axial direction of the first and second gears. 
     According to another embodiment, an external gear pump is provided. The external gear pump may include a peripheral wall that may form an enclosure and define an inlet and a discharge port. The gear pump may also include an end plate that may be disposed within the housing and the end plate may define a first recessed area. a second recessed area, and a bridge portion. The bridge portion may be disposed between a discharge channel and an inlet channel, that may each be defined by the second recessed area. The pump may include a first gear, that may include a first tooth and a second tooth, disposed within the first recessed area and configured to rotate about a first rotational axis. The pump may also include a second gear, disposed within the second recessed area and configured to rotate about a second rotational axis. The second gear may include a third tooth. When the first gear and the second gear are arranged in a first relative position, the third tooth may engage the first tooth and the second tooth to form a pressure pocket. The bridge may define a relief portion that may be configured to communicate fluid from the pressure pocket to the discharge port. 
     According to yet another embodiment, a gear pump is provided. The gear pump may include a housing that may include a peripheral wall forming an enclosure and defining an inlet and a discharge port. An end plate may be disposed within the housing and define a first recessed area, a second recessed area, and a bridge portion. The bridge portion may be disposed between a discharge channel and an inlet channel, each defined by the second recessed area. And the bridge portion may define a first recessed notch. The pump may also include a first gear, including a plurality of first gear teeth, disposed within the first recessed area and configured to rotate about a first rotational axis, and a second gear including a plurality of second gear teeth, disposed within the second recessed area and configured to rotate about a second rotational axis. When the first gear and the second gear are arranged in a first relative position, a first pair of teeth of the plurality of first gear teeth engages a first tooth of the plurality of second gear teeth to form a first pressure pocket. when the first gear and the second gear are arranged in a second relative position, a second pair of teeth of the plurality of first gear teeth engages a second tooth of the plurality of second gear teeth to form a second pressure pocket, and wherein the first recessed notch is positioned such that when the first gear and the second gear are arranged in either the first relative position or the second relative position, the first recessed notch is at least partially eclipsed by either the first pressure pocket or the second pressure pocket, respectively. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an exemplary pump. 
         FIG. 2  is a plan view of an interior portion a prior-art pump. 
         FIG. 3  is a plan view of an interior portion the exemplary pump. 
         FIG. 4  is a schematic diagram of a set of gears of the exemplary pump in a first relative position. 
         FIG. 5  is a schematic diagram of the set of gears of the exemplary pump and includes dimensions of the gear geometry. 
         FIG. 6  is a schematic diagram of the set of gears of the exemplary pump in a second relative position. 
         FIG. 7  is a schematic diagram of the set of gears of the exemplary pump in a third relative position. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the embodiments. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations. 
     The terms “first,” “second,” “third” etc. are merely exemplary and do not indicate a specific order. Rather, the terms “first,” “second,” “third” etc. are used to identify and distinguish one element from another. 
     The term “substantially” or “about” may be used herein to describe disclosed or claimed embodiments. The term “substantially” or “about” may modify a value or relative characteristic disclosed or claimed in the present disclosure. In such instances, “substantially” or “about” may signify that the value or relative characteristic it modifies is within ±0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% or 10% of the value or relative characteristic. 
       FIG. 1  illustrates an exemplary pump assembly  10  that is provided with a housing  12 . The cover of the pump  10  is hidden in this view so the internal portion of the pump is shown. The housing  12  includes an inlet  14  that may be disposed within a sump or reservoir (not illustrated) that holds oil or other fluid that may be carried to the discharge or outlet  16 . Two or more gears may be disposed within the housing  12 . One of the gears, such as a drive gear  18  may be rotated by a drive shaft  20 . The drive gear  18  may engage one or more slave gears, such as  22   a  and  22   b . The drive gear  18  and the slave gears  22   a  and  22   b  may be arranged so that the teeth of each of the gears trap and displace fluid e.g., oil, creating a low-pressure area, near the inlet of the pump, and a high-pressure area, near the discharge of the pump. 
     As fluid enters from the inlet  14  of the housing  12  the fluid is trapped between the teeth positioned nearest to the inlet and an inner surface e.g.,  127   a  of the outer wall of the housing  12 . Because the fluid is trapped between the teeth and the inner surface of the outer wall, the fluid is carried around the outside of the gears towards the discharge of the pump. The high-pressure area within the housing is formed by the fluid disposed between the discharge  16  of the pump and the gear teeth. The teeth of each of the gears  22   a ,  18 , and  22   b  are sized and arranged to create a seal between the faces of each of the teeth that are engaged with one another. While some fluid may seep between the end plate and the gears, or the cover and the gears, or both, the seal prevents fluid from seeping from the high-pressure side to the lower pressure side. 
       FIG. 2  illustrates the exemplary pump assembly  10  that includes a prior-art end plate  24 . The prior-art end plate  24  defines a first recessed area  26   a , that receives a first gear  22   a , a second recessed area  28 , that receives a second gear  18 , and a third recessed area  26   b , that receives a third gear  22   b . The second gear  18  may be rotated by a drive shaft  20 . The second gear  18  may be referred to as a drive gear and the first gear  22   a  and the third gear  22   b  may each be referred to as slave gears. The end plate  24  of the prior art defines a first outlet channel  32   a  and a second outlet channel  32   b  that are each disposed near the outlet of the pump assembly  10 . The prior-art end plate  24  also defines a first inlet channel  30   a  and a second inlet channel  30   b  that are disposed near the inlet of the pump assembly  10 . Fluid that is not discharged through the discharge outlet may collect within the first outlet channel  32   a  and the second outlet channel  32   b . As fluid enters the pump assembly  10 , a portion of the fluid may collect within the first inlet channel  30   a  and the second inlet channel  30   b.    
     A transverse axis T A  may extend between rotational axes of each of the gears. A portion of the pump  10  located above the transverse axis T A  may be referred to as the outlet side or high-pressure side of the pump  10  and a portion of the pump  10  located below the transverse axis T A  may be referred to as the inlet side or low-pressure side of the pump  10 . 
     As will be described in greater detail below, the seal created by the arrangement of the teeth may prevent fluid seeping from the high-pressure side to the lower pressure side, the gear teeth may form pockets that may contain or trap fluid as the gears rotate. The rotation of the gears may compress the fluid and increase fluid pressure within the pocket, creating a “pressure pocket.” The increase in pressure within the pressure pocket, may increase the torque required to rotate the gears. And this increase in torque may decrease the efficiency of the pump. 
       FIG. 3  illustrates a pump assembly  10  according to one or more embodiments and  FIG. 4  through  FIG. 5  illustrate a portion of the pump assembly  10  within the dashed lines A-A in  FIG. 3 . The pump housing  12  includes an outer peripheral wall that may form an enclosure of the internal portion of the pump housing  12 . The peripheral wall defines the inlet  14  and the discharge port  16  ( FIG. 1 ). 
     Referring to  FIGS. 3-5 , the pump assembly  10  includes an end plate  124  that extends between the outer peripheral wall of the housing  12 . The end plate  124  may define a first recessed area  128 , that may receive a first gear  18 , a second recessed area  126   b , that may receive the second gear  22   b , and a third recessed area  126   a , that may receive the third gear  22   a . The first gear  18  may be configured to rotate about a first rotational axis R A1  and the second gear  22   b  may be configured to rotate about a first rotational axis R A2 . In one or more embodiments, the first gear  18  may be driven by the drive shaft  20 . The drive shaft  20  may be coupled to an electric motor (not illustrated) that transfers rotational motion to the first gear  18 . The drive gear may rotate in a clock-wise direction from the reader&#39;s perspective. 
     The arrangement and geometry of the first gear  18 , the second gear  22   b , and the portion of the end plate  124  adjacent to the first are symmetrically opposite e.g., mirrored, to the arrangement and geometry of the first gear  18 , the third gear  22   a , and the adjacent portion of the end plate  124 . As such, the description of the first gear  18 , the third gear  22   a , and the adjacent portion of the end plate  124 , illustrated in  FIG. 4  through  FIG. 6 , need not be repeated to describe the arrangement and geometry of the first gear  18 , the second gear  22   b , and the adjacent portion of the end plate  124 . Also, in one or more embodiments, the pump assembly  10  may not include the third gear  22   a.    
     A first discharge channel  132   b , may be defined by the end plate  124  and extend between the discharge port  16  and a first bridge portion  131   b . A first inlet channel  130   b  may be defined by the end plate  124  and extend between an inlet port  14  and the first bridge portion  131   b . The bridge portion  131   b  may define one or more relief portions e.g.,  152   a ,  152   b ,  150   a ,  150   b ,  156   a ,  156   b ,  158   a , and  158   b , that may be configured to route fluid from a pressure pocket, formed by the gear teeth, to the discharge port  16 . 
     In one or more embodiments, the bridge portions  131   a ,  131   b  may be referred to as a “bridge.” Also, the relief portions may be referred to as a plurality of recessed finger cuts or as a plurality of recessed notches. 
     Referring specifically to  FIG. 4  and  FIG. 5 , a schematic diagram illustrates the arrangement of the first gear  18  and the second gear  22   b , in a first relative position. The bridge portion  131   b  and first gear diameters D 1  and second gear diameter D 2  are shown to illustrate their relative size and position with respect to the first gear  18  and the second gear  22   b . The first gear  18  may include a first tooth  182  having a first face  184  and a second face  186 . The first gear  18  may also include a second tooth  188  having a first face  190  and a second face  192 . The second gear  22   b  may include third tooth  170  that may include a first face  172  and a second face  174 . The second gear  22   b  may also include a fourth tooth  176  that may include a first face  178  and a second face  180 . 
     When the first gear  18  and the second gear  22   b  are arranged in the first relative position, the first tooth  182  and the second tooth  188  of the first gear  18  may engage the third tooth  170  of the second gear  22   b  to form a first pressure pocket  193 . The first recessed finger cut  152   b  defined by the bridge portion  131   b  is positioned so that the first pressure pocket  193  eclipses the first recessed finger cut  152   b . The first recessed finger cut  152   b  may allow fluid to move from the first pressure pocket  193  to the outlet channel  132   b  ( FIG. 3 ). Because the fluid moves from the first pressure pocket  193  to the outlet channel  132   b  ( FIG. 3 ) the pressure within the first pressure pocket may be limited, thus reducing the torque required to rotate the first gear  18  and the second gear  22   b.    
     The first pressure pocket may be bound by a first face  190  of the second tooth  188 , the second face  186  of the first tooth, a root portion of the first gear  18  extending therebetween, and a second face  174  of the third tooth  170 . 
     The second gear  22   b  may be provided with a fourth tooth  176  that engages the first tooth  182  of the first gear  18 , when the first gear  18  and the second gear  22   b  are in the first relative position. The third tooth  170  and the fourth tooth  176  of the second gear  22   b  engages the first tooth  182  to form a second pressure pocket  194 . The bridge portion  131   b  may define a second recessed finger cut  158   b . The second recessed finger cut  158   b  may be positioned so that the second pressure pocket  194  is eclipses the second recessed finger cut  158   b . The second recessed finger cut  158   b  may allow fluid to flow from the second pressure pocket  194  to the inlet cooling channel  130   b  ( FIG. 3 ). The fluid received by the inlet cooling channel  130   b  from the second recessed finger cut may be carried by one of the teeth of the second gear  22   b  along an inner wall  127   b  of the second recessed area  126   b  to the outlet cooling channel  132   b  and the discharge outlet  16 . 
     The fourth gear may include a first face  178  and a second face  180 . The second pressure pocket may bound by a root portion of the second gear  22   b  that extends between the first face  178  of the fourth tooth  176  and the second face  174  of the third tooth  170 . 
     The bridge portion  131   b  may include a third recessed finger cut  150   b  that may be connected to the first recessed finger cut  152   b  by an intermediate portion  164 . The bridge portion may also include a fourth recessed finger cut  156   b  that is connected to the third recessed finger cut  158   b  by a second intermediate portion  166 . 
     Referring to  FIG. 6 , a schematic diagram illustrates the arrangement of the first gear  18  and the second gear  22   b , in a second relative position. Here, the first gear  18  has rotated in a clockwise direction by a predetermined rotational angle from the position illustrated in  FIG. 4  and  FIG. 5 . The rotation of the first gear  18  causes the second gear  22   b  to rotate in a counter-clockwise direction by a predetermined rotational angle, as shown in  FIG. 6 . 
     The second gear  22   b  may include a fifth tooth  198 . The fifth tooth  198  and the third tooth  170  may each engage the second tooth  188  to form a third pressure pocket  200 . When the gears  18 ,  22   b  are in the second relative position, the third pressure pocket  200  may substantially eclipse the third recessed finger cut  150   b . The third recessed finger cut may provide the same function described above with respect to the first recessed finger cut  152   b.    
     In the second relative position, the first tooth  182  and the second tooth  188  may engage the third tooth  170  to form a fourth pressure pocket  202 . When the gears  18 ,  22   b  are in the second relative position, the fourth pressure pocket  202  may substantially eclipse the fourth recessed finger cut  156   b . The fourth recessed finger cut  156   b  may provide the same function described above with respect to the second recessed finger cut  158   b.    
     Referring to  FIG. 7 , a schematic diagram illustrates the arrangement of the first gear  18  and the second gear  22   b , in a third relative position. Here, the first gear  18  has rotated in a clockwise direction by a predetermined rotational angle from the position illustrated in  FIG. 6 . The rotation of the first gear  18  causes the second gear  22   b  to rotate in a counter-clockwise direction by a predetermined rotational angle, as shown in  FIG. 7 . 
     The first gear  18  may include a sixth tooth  196 . The sixth tooth  196  and the second tooth  188  may engage the fifth tooth  198  of the second gear  22   b  to form a fifth pressure pocket  204 . When the gears  18 ,  22   b  are in the third relative position, the fifth pressure pocket  204  may substantially eclipse the first recessed finger cut  152   b . In the third relative position, the fifth tooth  198  and the third tooth  170  may engage the second tooth  188  to form a sixth pressure pocket  206 . The sixth pressure pocket  206  may substantially eclipse the second recessed finger cut  158   b.    
     Referring to  FIG. 5 , a schematic view of the first gear  18  and second gear  22   b  and a number of dimensions of the bridge portion  131   b  and relief portions are illustrated. The first gear  18  may define a first root diameter D 1  and the second gear  22   b  may define a second root diameter D 2  that may be less than the first root diameter D 1 . The first rotational axis R A1  of the first gear  18  and the second rotational axis R A2  of the second gear  22   b  may be spaced apart by a first distance L 1 . 
     The bridge portion  131   b  may be divided into an upper portion and a lower portion. The upper portion may be the portion that is disposed above the transverse axis T A  and the lower portion of the bridge portion  131   b  may be disposed below the transverse axis T A . The upper portion of the bridge portion  131   b  may define the first recessed finger cut  152   b  and the third recessed finger cut  150   b . The lower portion of the bridge portion may define the second recessed finger cut  158   b  and the fourth recessed finger cut  156   b . The first intermediary portion  164  may be spaced apart from the transverse axis T A  by a first height H 1  and the second intermediary portion  166  may be spaced apart from the transverse axis T A  by a first height H 2 . In one or more embodiments, the second height H 2  may be greater than the first height H 1 . The first intermediary portion  164  may define a second length L 2 , measured from end points of the first recessed finger cut  152   b  and the third finger cut  150   b . The second intermediary portion  166  may define a third length L 3 , measured from end points of the fourth recessed finger cut  156   b  and the second finger cut  158   b . In one or more embodiments, the second length L 2  may be greater than the third length L 3 . 
     An end portion of the third recessed finger cut  150   b  may be spaced apart from the second rotational axis R A2  by a fourth length L 4  and an end portion of the second recessed finger cut  158   b  may also be spaced apart from the second rotational axis R A2  by a fifth length L 5 . In one or more embodiments, the fourth length L 4  may be greater than the fifth length L 5 . An end portion of the fourth recessed finger cut  156   b  may be spaced apart from the first rotational axis R A1  by a sixth length L 6  and an end portion of the first recessed finger cut  152   b  may be spaced apart from the first rotational axis R A1  by a seventh length L 7 . In one or more embodiments, the sixth length L 6  may be less than the seventh length L 7 . 
     The first recessed finger cut  152   b  may define a first radius R 1  and the third recessed finger cut  150   b  may define a third radius R 3 . In one or more embodiments, the first radius R 1  may be larger than the third radius R 3 . The radii of the first recessed finger cut  152   b  and the third recessed finger cut  150   b  may be sized to receive a sufficient volume of fluid to decrease the pressure of the respective pressure pockets. However, increasing the radii may beyond a predetermined threshold may decrease the amount of fluid moved by the gear teeth, thereby decreasing the efficiency of the pump assembly  10 . The second recessed finger cut  158   b  may define a second radius R 2  and the fourth recessed finger cut  156   b  may define a fourth radius R 4 . In one or more embodiments, the second radius R 2  may be greater than the fourth radius R 4 . 
     In one or more embodiments, the end plate  124  may be integrally formed e.g., one piece, to the pump housing  12 . 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes can include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, to the extent any embodiments are described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics, these embodiments are not outside the scope of the disclosure and can be desirable for particular applications. 
     PARTS LIST 
     The following is a list of reference numbers shown in the Figures. However, it should be understood that the use of these terms is for illustrative purposes only with respect to one embodiment. And, use of reference numbers correlating a certain term that is both illustrated in the Figures and present in the claims is not intended to limit the claims to only cover the illustrated embodiment.
         pump assembly  10     pump housing  12     discharge outlet  16     first gear  18     drive shaft  20     prior—art end plate  24     recessed area  28     end plate  124     recessed area  128     first intermediary portion  164     second intermediary portion  166     third tooth  170     first face  172     second face  174     fourth tooth  176     first face  178     second face  180     first tooth  182     first face  184     second face  186     second tooth  188     first face  190     second face  192     first pressure pocket  193     second pressure pocket  194     sixth tooth  196     fifth tooth  198     third pressure pocket  200     fourth pressure pocket  202     fifth pressure pocket  204     sixth pressure pocket  206     second gear  22   b      recessed area  26   a      recessed area  26   b      first inlet channel  30   a      second inlet channel  30   b      first outlet channel  32   a      second outlet channel  32   b      first recessed area  126   a      second recessed area  126   b      inner wall  127   b      inlet channel  130   b      first bridge portion  131   a      second bridge portion  131   b      outlet channel  132   b      first recessed finger cut  152   b      second finger cut  158   b      third recessed finger cut  150   b      fourth recessed finger cut  156   b