Patent Publication Number: US-8535030-B2

Title: Gerotor hydraulic pump with fluid actuated vanes

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Provisional Application No. 61/305,211, filed on Jan. 26, 2010. The disclosure of the above application is incorporated herein by reference. 
    
    
     FIELD 
     The present invention relates to gerotor type hydraulic pump; and more particularly to an inner rotor assembly with improved volumetric efficiency. 
     BACKGROUND 
     The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
     Gerotor pumps have wide range of application. These devices are used as compressor for air conditioner, hydraulic motor to drive mechanical systems, pump to deliver oil to lubricate the internal components in motion of the engine, pump in the automatic transmission to provide hydraulic power to actuate the clutch or dual clutch systems, just to name a few. However, pursuit to increase volumetric efficiency of gerotor pumps as well as to prevent or mitigate galling and gauging of pump components during operation has never come to an end. 
     Gerotor pump includes a housing member, an outer rotor and an inner rotor operatively engaged to form a rotor set disposed within the housing member. A thrust plate and a pressure plate within the housing member define an axial space where the rotor set is enclosed and driven by an input shaft. During operation, teeth of the inner rotor travel over a conjugate inner surface of the outer rotor to form expanding volume chambers for fluid intake, and contracting volume chamber for providing pressurized fluid output. A clearance between the inner rotor and the outer rotor is necessary to allow the inner rotor to rotate within the outer rotor; however, fluid leakage may also result due to the clearance and result in a lower volumetric efficiency. Pressure capability may also be reduced as the clearance between inner and outer rotor grows arising out of normal wear and tear but without means of compensation. 
     The rotor set rotates inside the space defined by the thrust plate and the pressure plate. It is desirable that axial ends of the outer rotor and inner rotor make tight sealing engagement with adjacent axial end surfaces of the thrust plate and pressure plate to avoid fluid leakage. A tight sealing engagement, however, may result in undesirable galling and gauging of the rotors and the plates, resulting in device damage. Fluid may be pumped to the mechanical clearances between the rotor set and the thrust and pressure plates to provide lubrication to prevent the galling and gauging of component. 
     SUMMARY 
     In one feature, the disclosure describes a gerotor pump. The gerotor pump has an outer rotor, a thrust plate, a pressure plate, an inlet chamber for fluid intake through the thrust plate to be pressurized, and an outlet chamber for outputting pressurized fluid from the pressure plate. The outer rotor defines an inner surface of the outer rotor. The gerotor pump includes an inner rotor assembly in rotating engagement with the outer rotor. The inner rotor assembly rotates about an axis. The inner rotor assembly includes a rotor body and a plurality of vanes. The rotor body includes N (an integer greater than one) vane slots and N of inner openings around the axis. Each inner opening adjoins with a vane slot. The vane slot defines a first sealing surface. The vane defines a second sealing surface. The vane is disposed in the vane slot. The vane is sealing engagement with the rotor body via the first and second sealing surfaces. The inner rotor assembly is in sealing engagement with the outer rotor by the vane engaging on the inner surface of the outer rotor. 
     In another feature, the disclosure describes another gerotor pump. The gerotor pump has an outer rotor, a thrust plate, a pressure plate, an inlet chamber for fluid intake through the thrust plate to be pressurized, and an outlet chamber for outputting pressurized fluid from the pressure plate. The gerotor pump includes an inner rotor assembly. The inner rotor assembly is in rotating engagement with the outer rotor. The inner rotor assembly rotates about an axis. The inner rotor assembly includes a rotor body and a plurality of vane assemblies. The rotor body has a plurality of vane slots and a plurality of inner openings. The vane assembly is disposed in the vane slot. The vane assembly includes a vane head and a vane seat. The vane seat has a trough to receive the vane head. The vane head and the vane seat are in sealing engagement in the trough. The inner rotor assembly is in sealing engagement with the outer rotor by the vane head engaging on the inner surface of the outer rotor. 
     In other features, the disclosure describes a gerotor pump. The gerotor pump has a thrust plate, a pressure plate, an inlet chamber for fluid intake through the thrust plate to be pressurized, and an outlet chamber for outputting pressurized fluid from the pressure plate. The gerotor pump includes an outer rotor rotating about a first axis. The gerotor pump includes an inner rotor rotating about a second axis. The second axis is parallel with the first axis. The inner rotor defines a plurality of rotor openings around the second axis, and the inner rotor is in rotating engagement with the outer rotor. The inner and outer rotors are disposed between, and in sealing engagement with a first axial end surface of the thrust plate and a second axial end surface of the pressure plate. The thrust plate defines a first annular groove on the first axial end surface, and the pressure plate defines a second annular groove on the second axial end surface. The second annular groove has a plurality of fluid communication holes. The fluid communication holes are in fluid communication with the first annular groove, the second annular groove and the rotor openings. The radius of any of the first and second annular grooves is comparable to a distance between the rotor openings and the second axis. 
     Advantageously, the present invention uses vanes to replace external teeth of the inner rotor of a gerotor pump, utilizing centrifugal force and outlet port fluid pressure and/or mechanical spring to force the vanes slightly in outward direction radially for a tight sealing engagement against the conjugate surface of the outer rotor internal teeth (lobes) thus providing high volumetric efficiency and high output pressure capability. 
     Advantageously, the present invention provides continuous lubrication to clearances between the rotor set and the plates adjacent thereto via annular groove and fluid communication holes in the pressure plate, annular groove in the thrust plate and inner opening in the inner rotor. 
     Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  shows an axial cross sectional view of a hydraulic pump or compressor according to the principles of the present invention; 
         FIG. 2  shows another cross sectional view of a hydraulic pump or compressor according to the principles of the present invention; 
         FIG. 3  shows cross sectional views of two inner rotor assemblies according to the principles of the present invention; 
         FIG. 4  shows cross sectional views of an inner rotor body according to the principles of the present invention; 
         FIG. 5  shows an isometric view of a vane member according to the principles of the present invention; 
         FIG. 6  shows an isometric view of a pressure plate according to the principles of the present invention; 
         FIG. 7  shows an isometric view of a thrust plate according to the principles of the present invention; 
         FIG. 8  shows an exploded view of a fluid displacement mechanism according to the principles of the present invention; 
         FIG. 9  shows an isometric view of a vane assembly according to the principles of the present invention; 
         FIG. 10  shows cross sectional views of a vane head according to the principles of the present invention; 
         FIG. 11  shows an isometric view of a vane seat according to the principles of the present invention; 
         FIG. 12  shows an isometric view of another vane member according to the principles of the present invention; 
         FIG. 13  shows cross sectional views of another inner rotor body according to the principles of the present invention; and 
         FIG. 14  shows a cross sectional view of another inner rotor assembly according to the principles of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. For purposes of clarity, the same reference numbers with or without a single or multiple prime symbols appended thereto will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical or. It should be understood that steps within a method may be executed in different order without altering the principles of the present disclosure unless otherwise specified. 
     A gerotor pump in accordance with the disclosure provides hydraulic power to mechanical actuation systems. The gerotor pump includes a drive shaft that engages an inner rotor. The inner rotor is disposed in the outer rotor, and the inner and outer rotor jointly form a rotor set. The inner rotor may be an inner rotor assembly that includes vane members performing as teeth of the inner rotor. The outer rotor defines lobes (teeth), whereby rotation of the inner and outer rotors defines an expanding volume chamber in fluid communication with a fluid inlet port of the gerotor pump, and a contracting volume chamber in fluid communication with the fluid outlet port. 
     Referring now  FIG. 1 , an axial cross sectional view of a hydraulic gerotor pump or compressor  10  is shown. The gerotor pump or compressor  10  may include a housing member  12  and an end cap  14 . The housing member  12  and the end cap  14  are held together in tight sealing engagement by means of a plurality of bolts  16 . The housing member  12  defines a fluid inlet port  18  and a fluid outlet port  20 . The inlet port  18  opens into an inlet chamber  22 , while the outlet port  20  is open to, and in fluid communication with an outlet chamber  24 . The gerotor pump  10  may include a input (drive) shaft  26  that extends through an opening in a journal bearing  28  for receiving and rotatably supporting the input shaft  26 . The input shaft  26  extends axially almost to the bottom of the center pocket  29  of a pressure plate  30 . The journal bearing  28  may be replaced by a typical ball bearing or a needle bearing. 
     Referring now also to  FIG. 2 , in conjunction with  FIG. 1 , a cross sectional view of the gerotor pump  10  looking from line L 1 -L 1 ′ is shown. The input shaft  26  extends through a thrust plate  56 , and is in driving engagement with a pumping element or fluid displacement mechanism, generally designated  32 . In the subject embodiment, the fluid displacement mechanism  32  may include a gerotor of the internally generated rotor (IGR) type. The IGR type gerotor may include an inner rotor assembly  34 . The inner rotor assembly  34  may include a rotor body  36  and a plurality of vanes  42  disposed in the rotor body  36  to define teeth of the inner rotor assembly  34 . The rotor body  36  defines about it&#39;s inside diameter a plurality of serrations  38 . The rotor body  36 , and therefore the inner rotor  34 , is in driven engagement with the input shaft  26  by means of the serrations  38 . 
     The gerotor pump  10  also includes an outer rotor  48 . The outer rotor  48  defines an axis of rotation A 1  (illustrated in  FIG. 8 ) about which it rotates. The the inner rotor assembly  34  defines an axis of rotation A 2  (also illustrated in  FIG. 8 ), about which it rotates. The pumping element or fluid displacement mechanism  32  in the subject embodiment may be of the “fixed axis” type, wherein both of the axes of rotation A 1  and A 2  remain fixed or stationary, and neither axis orbits about the other axis, as occurs in orbiting gerotor type devices. 
     Referring also to  FIG. 3 , a cross sectional view of the inner rotor assembly  34  is shown in  FIG. 3(A)  and a cross sectional view of another inner rotor assembly  34 ′ is shown in  FIG. 3(B) . As illustrated in  FIG. 3(A) , the inner rotor assembly  34  includes the rotor body  36  and a plurality of the vanes  42  disposed in the rotor body  36  so that the vanes  42  operate as teeth of the inner rotor assembly  34  of the gerotor pump  10 . The vane  42  is disposed in the vane slot  40  in radial direction, and each vane  42  is in sealing engagement with the rotor body  36  when disposed in the rotor body  36  (explained in  FIGS. 4 and 5 ). A bottom side of the vane  42  may be exposed to an inner opening (cavity)  64  that is adjoining and below the vane slot  40  when the vane  42  is disposed in the vane slot  40 . Hydraulic fluid pressure may be present in the inner opening  64  to force the vane  42  slightly in outward direction radially for a tight sealing engagement for improved pump volumetric efficiency. Mechanical spring may also be placed inside the inner opening  64  to exert radially outward force upon the vane  42 . 
     Referring also to  FIG. 4 , cross sectional views of the rotor body  36  is shown. The cross sectional view  36 A is a view looking from line L 2 -L 2 ′ at the rotor body  36 . The rotor body  36  may define five (or N, where N is an integer) vane slots  40 . The vane slots  40  may be generally stepped rectangular slots. The vanes  42  are disposed within each of the vane slots  40 . The vane slot  40  has a pair of sealing surfaces  44  and  44 ′. The vane  42  may be in contact with the vane slot  40  at the sealing surfaces  44  and  44 ′ when disposed therein, and may make sealing engagement with the rotor body  36  at the vane slot  40  via the sealing surfaces  44  and  44 ′. 
     The rotor body  36  may also define a plurality of inner openings  64  between the vane slots  40  and the rotating axis A 2  that the rotor body  36  rotates about. The vane slot  40  and the inner opening  64  are open to, and adjoining each other; and the inner opening  64  is further inside into the rotor body  36  from the vane slot  40 . In one embodiment as depicted in  FIG. 4  the inner openings  64  is stepped rectangular slots. The width W 2  of the inner opening  64  is sufficiently smaller than the width W 1  of the vane slot  40  to prevent the vane  42  from sliding into the inner opening  64 . In other embodiments the inner opening  64  may be wider than the vane slot  40  or of the same width. Mechanical spring (not shown) may also be placed in the inner opening  64  to exert force upon the vane  42  radially outward. 
     Referring also to  FIG. 5 , an isometric view of the vane  42  is shown. The vane  42  defines a pair of sealing surfaces  46  and  46 ′ and a bottom surface  66 . The sealing surface  46  of the vane  42  may be in contact with the sealing surface  44  of the vane slot  40  when the vane  42  is disposed in the vane slot  40 . Those skilled in the art of gerotor pump can appreciate that thin film of fluid may fill a slight clearance between the sealing surfaces  42  and  44  to make sealing engagement between the vane  42  and the rotor body  36  at the vane slot  40 . The bottom surface  66  of the vane  42  is exposed to the inner opening  64  when the vane  42  is disposed in the vane slot  40 . The vane  42  may have a convex top surface  47  so the convex top surface  47  operates like the lobe (tooth) for the inner rotor assembly  34 . The top surface  47  may be characterized by a radius R T . The bottom surface  66  may have a flat surface with straight edges. 
     Referring now to  FIG. 3 , in one embodiment, the vane  42  of the inner rotor assembly  34  in  FIG. 3(A)  may be replaced by a vane assembly  42 ′ shown in  FIG. 3(B) . Referring now also to  FIG. 9 , an isometric view of the vane assembly  42 ′ is shown. The vane assembly  42 ′ may be used in lieu of the vane  42  in a gerotor pump according to the principles of this disclosure. The vane assembly comprises a vane head  42 ′- 1  and a vane seat  42 ′- 2 . The vane head  42 ′- 1  provides a convex surface  47 ′ similar to the convex top surface  47  of the vane  42 . The vane head  42 ′- 1  may be a cylindrical roller with radius R T  as illustrated in  FIG. 10 .  FIG. 10  shows cross sectional views of the vane head  42 ′- 1 . A cross sectional view  42 ′- 1 A viewed from the top of the vane head  42 ′- 1  and a cross sectional view  42 ′- 1 B viewed from the side of the vane head  42 ′- 1  are shown. When the inner rotor and the outer rotor are in rotating engagement, the vane head  42 ′- 1  is in sealing engagement with the inner surface  50  of the outer rotor  48 . The cylindrical roller serves as a bearing between the outer rotor  48  and the vane seat  42 ′- 2 .  FIG. 11  shows an isometric view of the vane seat  42 ′- 2 . The vane seat  42 ′- 2  includes a trough  42 ′- 3  to receive the vane head  42 ′- 1 . 
     The vane seat  42 ′- 2  defines a pair of sealing surfaces  46  and  46 ′ and a bottom surface  66 . The sealing surface  46  of the vane seat  42 ′- 2  may be in contact with the sealing surface  44  of the vane slot  40  when the vane seat  42 ′- 2  is disposed in the vane slot  40 . Those skilled in the art of gerotor pump can appreciate that thin film of fluid may fill a slight clearance between the sealing surfaces  42  and  44  to make sealing engagement between the vane seat  42 ′- 2  and the rotor body  36  at the vane slot  40 . The bottom surface  66  of the vane seat  42 ′- 2  is exposed to the inner opening  64  when the vane seat  42 ′- 2  is disposed in the vane slot  40 . 
     Referring now to  FIG. 12 , an isometric view of another vane  42 ″ is shown. The vane  42 ″ may be used in lieu of the vane  42  in a gerotor pump  10  according to the principles of this disclosure. By comparing the vane  42  and vane  42 ″ the difference therebetween can be appreciated. The vane  42 ″ has a convex bottom surface  66 ″ while the vane  42  has a flat bottom surface  66 . The convex bottom surface  66 ″ may be characterized by a radius R B  which may be the same as, or different from a radius R T  that characterizes the convex top surface  47  of the vane  42 ″. 
     In one embodiment, the vane  42 ″ may be used in the rotor body  36  depicted in  FIG. 4 . In another embodiment, the vane  42 ″ may be used in another rotor body  36 ″ depicted in  FIG. 13 . The rotor body  36 ″ defines an inner opening  64 ″ and the vane slot  40  where the width W 3  of the inner opening  64 ″ is larger than the width W 1  of the vane slot  40 . The inner opening  64 ″ may have an oval shape in general. The inner opening  64 ″ may also have a shape other than oval, for example, rectangular (not shown).  FIG. 14  illustrates an inner rotor assembly  34 ″ comprising the rotor body  36 ″ and the vane  42 ″. 
     Referring now also to  FIG. 3(A) , a slight clearance  39  between the vane  42  and the inner rotor vane slot  40  (substantially occupied by the vane  42  in the drawing) allows the vane  42  to move slightly in radial direction either inward or outward. Pressurized fluid in the inner opening  64  in fluid communication with the outlet port  20  pressurizes the bottom surface  66  of the vane  42  and forces the vane  42  in radial (outward) direction. The centrifugal force exerted on the vane  42  combines with the fluid pressure on the bottom surface  66  causes the vane  42  to seal tightly against the conjugate inner surface  50  of the outer rotor  48 , thus providing for improved volumetric efficiency and higher output pressure. 
     Referring now to  FIGS. 1 and 2 , the housing member  12  defines a cylindrical opening  54 . An eccentric ring  70  is disposed within the cylindrical opening  54 . The outer rotor  48  is journalled within a cylindrical opening of the eccentric ring  70 , which is in contact with, and also defines a cylindrical outside surface  52  of the outer rotor. The inner rotor assembly  34  is eccentrically disposed within an outer rotor  48 , and is in contact with the outer rotor  48  at the inner surface  50  of the outer rotor  48 . 
     The eccentric ring  70  stacks between the thrust plate  56  and the pressure plate  30 , defines a cylindrical chamber or opening to receive the outer rotor  48  and the inner rotor assembly  34 , and defines an axial end wear surface  72  with the thrust plate  56  and an axial end wear surface  74  with the pressure plate  30 . The outer rotor  48  and the inner rotor assembly  34  are in rotating engagement, and may be in sealing engagement with the thrust plate  56  at the wear surface  72  where the outer rotor  48  and the inner rotor assembly  34  may otherwise contact with the thrust plate  56 . The outer rotor  48  and the inner rotor assembly  34  may be in sealing engagement with the pressure plate  30  at the wear surface  74  where the outer rotor  48  and the inner rotor assembly  34  may otherwise contact with the pressure plate  30 . 
     Rotation of the inner rotor assembly  34  and the outer rotor  48  defines an expanding volume chamber  80  in fluid communication with the fluid inlet port  18 , and a contracting volume chamber  82  in fluid communication with the fluid outlet port  20 . 
     Referring also to  FIG. 6 , an isometric view of the pressure plate  30  is shown. The pressure plate  30  may have an annular groove  58  on the wear surface  74  of the pressure plate  30 . The annular groove  58  defines fluid communication with the plurality of inner openings  64  of the inner rotor body  36 . The radius of the annular groove  58  may be comparable to a distance between the inner opening  64  and the rotating axis A 2  of the inner rotor body  36  (illustrated in  FIG. 4 ) so that the annular groove  58  is aligned with the inner openings  64 . The annular groove  58  may be equipped with a plurality of fluid communication holes (ports)  60  formed or drilled through the opposite side  76  of the pressure plate  30 . These fluid communication holes  60  define fluid communication between the outlet chamber  24  and the inner opening  64  to provide fluid pressure to the bottom surface  66  of the vane  42 . Pressurized fluid supplied from the inner opening  64  to the annular groove  58  may further be pressurized into a clearance  92  ( FIG. 1 ) between the pressure plate  30  and the rotor set formed by the inner rotor  34  and the outer rotor  48  to provide lubrication between the pressure plate  30  and rotor set, thus prevent galling and gauging and avoid pump damage. 
     The pressure plate  30  may include an outlet fluid chamber  78  and an inlet port  84 . The inlet port  84  of the pressure plate  30  is aligned with the expanding volume chamber  80  in fluid communication with the inlet chamber  22 . The outlet fluid chamber  78  is aligned with the contracting volume chamber  82  in fluid communication with the fluid outlet port  20 . 
     Referring now to  FIG. 7 , an isometric view of the thrust plate  56  is shown. The thrust plate  56  may include an annular groove  62  on the wear surface  72  of the thrust plate  56 . The annular groove  62  defines fluid communication with the plurality of inner openings  64  of the inner rotor body  36 . The radius of the annular groove  62  may be comparable to a distance between the inner opening  64  and the rotating axis A 2  of the inner rotor body  36  (illustrated in  FIG. 4 ) so that the annular groove  62  is aligned with the inner openings  64 . Pressurized fluid supplied from the inner opening  64  to the annular groove  62  may further be pressurized into a clearance  90  ( FIG. 1 ) between the thrust plate  56  and the rotor set formed by the inner rotor  34  and the outer rotor  48  to provide lubrication between the thrust plate  56  and rotor set, thus prevent galling and gauging and avoid pump damage. 
     The thrust plate  56  may include an inlet fluid chamber  86  and a discharge port  88 . The inlet fluid chamber  86  of the thrust plate  56  may be aligned with the expanding volume chamber  80  in fluid communication with the inlet port  18 . The discharge port  88  may be aligned with the contracting volume chamber  82  in fluid communication with the outlet port  20 . 
     Referring now to  FIG. 8 , a fragmentary, somewhat schematic, exploded view of the fluid displacement mechanism  32  is shown. This figure illustrates the component assembly configuration of the fluid displacement mechanism  32 . The schematic illustrates the input shaft  26 , two dowel pins  68 , the thrust plate  56 , the inner rotor assembly  34  with including a plurality of the vanes  42  and its rotating axis A 2 , the outer rotor  48  and its rotating axis A 1 , the eccentric ring  70 , and pressure plate  30 . 
     Referring now to  FIG. 1 , the slight clearances  90 ,  92  between the rotors  34 ,  48  and the thrust plate  56  and pressure plate  30 , respectively allow the outlet fluid in the inner openings  64  to pressurize and lubricate the end surfaces of the inner and outer rotors. This layer of fluid with continuous flow eliminates the galling or gouging (seizure) between the pressure and thrust plates  30 ,  56  and the inner and outer rotors  34 ,  48  end surfaces. In effect, the pump or compressor  10  maintains its high volumetric efficiency and high output pressure capability. 
     The description above is only exemplary for illustration of preferred embodiments. Many alternatives may be made on a gerotor pump without departure from the principles of the disclosure. For example, a fluid flow regulator (flow control valve), a fluid pressure regulator (pressure control valve), an integrated electric motor, or an integrated fluid reservoir may further be combined with a gerotor pump based on the principles of this disclosure for better packaging or precision control applications. 
     The eccentric ring  70  may also be eliminated by incorporating an eccentric cylindrical opening in the housing member  12  to receive the rotary fluid displacement mechanism and achieve the same result. 
     This invention can be coupled with and driven by a prime mover such as an electric motor or an engine to perform hydro-mechanical actuation tasks or to provide hydraulic power (pressure) to actuate mechanical systems, or to provide high pressure fluid (oil) to lubricate the components in motion of the machine. 
     This invention can also be used as a compressor for air conditioner, a hydraulic motor to drive mechanical systems, a pump to deliver oil to lubricate the internal components in motion of the engine, a pump in the automatic transmission to provide hydraulic power to actuate a clutch or dual clutch transmission systems. 
     The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification, and the following claims.