Abstract:
A pump assembly includes a pump housing including an inner surface, a pump inlet and an excess flow passage, a filter assembly including a spout extending into the housing, and an insert located within and secured to the housing, and including a first surface spaced from the inner surface and producing therebetween an annular nozzle communicating with said excess flow passage, the nozzle directing a first fluid stream exiting the excess flow passage toward a second fluid stream exiting the spout, the fluid streams flowing toward the pump inlet.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation and claims the benefit of U.S. non-provisional patent application Ser. No. 12/466,443, filed May 15, 2009, which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates generally to the field of hydraulic pumps. In particular, the invention pertains to a nozzle for boosting pump inlet pressure using excess recirculation oil flow in an automatic transmission. 
         [0004]    2. Description of the Prior Art 
         [0005]    Positive displacement hydraulic pumps often operate at variable speeds, especially when the pump is in a vehicle power steering system or a vehicle automatic transmission. The pump is driven by the vehicle engine and therefore must operate through the entire engine speed range. The speed at which the pump is driven can exceed 6000 rpm. 
         [0006]    A fixed displacement pump produces more flow than needed at high speed, the excess flow being routed to the pump inlet and bypassing a pump filter. 
         [0007]    Fixed displacement pumps used in automatic transmissions typically reach a speed at which the supply pressure is insufficient to force fluid into the pumping volume during the intake period. This lack of fluid cavitates the pumping chamber causing reduction in flow volume, durability wear due to cavitation implosions, and the production of cavitation noise, which is objectionable to the vehicle occupants. 
         [0008]    A need exists for a jet pump nozzle that is retained in position with a controlled gap that provides fluid velocities required of an effective jet pump nozzle. 
       SUMMARY OF THE INVENTION 
       [0009]    A pump assembly includes a pump housing including an inner surface, a pump inlet and an excess flow passage, a filter assembly including a spout extending into the housing, and an insert located within and secured to the housing, and including a first surface spaced from the inner surface and producing therebetween an annular nozzle communicating with said excess flow passage, the nozzle directing a first fluid stream exiting the excess flow passage toward a second fluid stream exiting the spout, the fluid streams flowing toward the pump inlet. 
         [0010]    Flow exits the nozzle at a high velocity relative to that of make-up oil drawn from the sump. The mixed flow from the sump and excess flow through the nozzle produces an elevated pump inlet pressure, which elevates the pump speed at which cavitation occurs. 
         [0011]    The nozzle reduces pump noise across a range of speeds and temperatures. It improves the controllability of the hydraulic control elements using pump oil by reducing air in the oil. 
         [0012]    Erosion wear of the pump inlet surfaces is reduced producing longer pump life and less fluid borne contamination. 
         [0013]    The annular nozzle is quite effective in boosting pressure at the pump inlet to delay the onset of cavitation. These nozzle inserts can be contained in a housing used in any fixed displacement pump application, such as an automobile automatic transmission, where the rate of flow required to fill the pump at higher speeds exceeds the rate of flow provided by the available atmospheric pressure head. 
         [0014]    The scope of applicability of the preferred embodiment will become apparent from the following detailed description, claims and drawings. It should be understood, that the description and specific examples, although indicating preferred embodiments of the invention, are given by way of illustration only. Various changes and modifications to the described embodiments and examples will become apparent to those skilled in the art. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0015]    The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which: 
           [0016]      FIG. 1  is a schematic diagram showing a hydraulic system; 
           [0017]      FIG. 2  is a cross section taken at a diametric plane through a first embodiment of the nozzle assembly; 
           [0018]      FIG. 3  is a cross section taken at a diametric plane through the insert of  FIG. 2 ; 
           [0019]      FIG. 4  is a cross section taken at a diametric plane through a second embodiment of the nozzle assembly; 
           [0020]      FIG. 5  is an end view of the nozzle insert of  FIG. 4 ; and 
           [0021]      FIG. 6  is a cross section taken at a diametric plane through a third embodiment of the nozzle assembly. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0022]    Referring now to the drawings,  FIG. 1  shows a schematic diagram of a hydraulic system  10 , which includes a sump  12  containing hydraulic fluid at relatively low pressure; a pump  14 ; a fluid filter assembly  16 ; a line  18  for hydraulically connecting the filter&#39;s outlet  20  and the pump&#39;s inlet  22 ; a transmission  24 , a supply line  26  for hydraulically connecting the pump&#39;s outlet  28  and the transmission&#39;s inlet  30 ; a passage  32  for returning lubricant and leakage flow from the transmission  24  to the source  12 ; an engine  34 ; and a pressure regulator valve  36  connecting line  26  and line  18 . 
         [0023]    The transmission  24  includes a torque converter  38  and a lubrication and cooling circuit  39 . Engine  34  drives torque converter  38  and pump  14  at a variable rotational speed. 
         [0024]    Pump  14 , which draws fluid from the sump  12  through filter  16 , delivers pressurized hydraulic fluid to the transmission  24 . 
         [0025]    Regulator valve  36  regulates pressure at the pump outlet to a desired pressure, in response to a balance of opposed forces on the valve produced by a spring  42 , a variable force produced by a controlled pressure acting in the same direction as spring  42 , and a force produced by pressure in supply line  26 . 
         [0026]    Regulator valve  36  returns excess flow from the pump outlet  28  preferably to the nozzle assembly  40 , provided that the flow rate in line  26  first satisfies the requirements of (i) the transmission  24 , (ii) torque converter  38 , and (iii) lube and cooling circuit  39 . 
         [0027]    The excess flow is delivered through a bypass flow passage  44  from the pressure regulator valve  36  to the nozzle assembly  40 . The bypassed fluid is carried in passage  44  at relatively a high velocity and an elevated pressure greater than pressure in the sump  12 , which is substantially at atmospheric pressure. 
         [0028]      FIGS. 2 and 3  show the components in the vicinity of the nozzle assembly  40 . The outlet  20  of filter assembly  16  is formed with a spout  50 , which is fitted into a pump inlet housing  52  and sealed against the inner surface  54  of housing  52  in this illustration by an O-ring  56 , retained in a recess  58  in the spout  50 . The inner surface  60  of spout  50  is essentially sized to match the inner surface  84  of nozzle insert  74  to reduce flow losses from rapid expansions or contractions. 
         [0029]    The pump inlet housing  52  is formed with a shoulder  64 , a circular cylindrical inner surface  66 , and a conical inner surface  68  aligned with axis  70 . Housing  52  also contains a fluid mixing chamber  72  located downstream from the filter assembly  16 . 
         [0030]      FIGS. 2 and 3  show a nozzle insert  74  having a flange  76 , which abuts shoulder  64  to establish its axial position in housing  52 , and which is fitted with a press-fit against a cylindrical inner surface  54  coaxial with axis  70 , thereby securing the insert in position within housing  52 . Insert  74  includes hollow circular cylinder  80  extending axially downstream from flange  76  and bounded by an outer circular cylindrical surface  82  and an inner circular cylindrical surface  84 . An end surface  86  of insert nozzle  74  is preferably flat and formed with a circular outer corner  88 . The shape and size of the nozzle exit  94  is formed from the relative locations of the circular outer corner  88  and the conical inner surface  68 . 
         [0031]    In operation, fluid drawn from the fluid sump  12  enters the nozzle assembly  40  through the central opening  60  of the filter assembly  16  and flows along axis  70  toward fluid mixing chamber  72 . Excess fluid, carried in passage  44 , enters pump inlet housing  52  radially and spirals around the outer surface of the nozzle insert  74 , flows axially in an annular passage  90  between cylindrical surfaces  66 ,  82 , flows into the nozzle passage  92  created by conical surface  68  and cylindrical surface  82 , and through the annular nozzle exit  94 , located between surface  68  and the circular outer corner  88  of nozzle insert  74 . The cross sectional area of the nozzle passage  92  decreases and velocity of the flow in passage  92  increases as distance from fluid mixing chamber  72  decreases. The flow exiting through nozzle exit  94 , creates a mixing vortex in the fluid mixing chamber  72  with the flow drawn from the fluid sump  12 , whereupon the combined fluid volume travels through the fluid mixing chamber  72  and enters the pump  14  at inlet  22 . 
         [0032]      FIGS. 4 and 5  illustrate an alternate embodiment, in which the axial position of a nozzle insert  100  is established by contact of three angularly spaced nubs  102 , located at an axial end of the insert, and the conical inner surface  68  of the pump inlet housing  52 . The nozzle insert  100  includes a cylindrical portion  104 , whose outer cylindrical surface  106  is adjacent to and guided toward its correct position along the cylindrical inner surface  54  of pump inlet housing  52 . The outer surface  106  of nozzle insert  100  is bonded to the cylindrical inner surface  54  of pump inlet housing  52  using an adhesive. 
         [0033]    After the nozzle insert  100  is installed in housing  52 , the filter assembly  16  is installed in housing  52  and sealed against the inner surface  154  of the nozzle inlet  100  by an O-ring  56 , retained in a recess  58  in the spout  50 . 
         [0034]    Fluid drawn from the fluid sump  12  enters the nozzle assembly  40  through the outlet  20  of the filter assembly  16  and flows along axis  70  toward fluid mixing chamber  72 . The inner surface  60  of the spout is essentially sized to match the inner surface  84  of the nozzle insert  100 . Excess fluid, carried in passage  44 , enters pump inlet housing  52  radially and spirals around the outer surface  108  of the nozzle insert  100  along the circular cylindrical surface  66  of the housing  52 , flows axially in an annular nozzle passage  92  between the inner conical surface  68  of the housing  52  and an outer conical surface  110  of nozzle insert  100  and through a nozzle exit  112  between surfaces  68  and  110  at the axial end  86  of the nozzle insert  100 , past the outer corner  88  defined by the intersection of the end  86  and the conical surface  110 . Upon exiting through nozzle exit  112 , the excess flow creates a mixing vortex in the fluid mixing chamber  72  with the flow drawn from the fluid sump  12 , whereupon the combined fluid volume travels through the mixing chamber  72  and enters the pump  14  at inlet  22  (shown in  FIG. 1 ). 
         [0035]      FIG. 6  shows an alternate embodiment of the nozzle assembly  40 , in which the axial position of the nozzle insert  120  is established by contact between the nubs  102  and the conical inner surface  68  of the pump inlet housing  52 . The nozzle insert  120  includes a cylindrical portion  124 , whose outer cylindrical surface is formed with threads  126 , which engage threads formed on the inner surface of a cylindrical portion  128  of housing  52 . In this way, nozzle insert  120  is retained in its correct position in the pump inlet housing  52 . 
         [0036]    The axial position of the nozzle insert  120  can be established by applying an axially-directed elastic force to the insert urging the nubs  102  into contact with the conical inner surface  68  of the pump inlet housing  52 . Additional methods of retaining the nubs against the conical inner surface  68  of the pump inlet housing  52  can be a force applied by a lock washer, a wavy snap ring, or compression spring  130  (shown schematically) located between the filter assembly  16  and one of the surfaces  132 ,  134  of the nozzle insert  120 . Additionally a press fit, as illustrated in  FIG. 2  could be employed. In these ways, nozzle inserts  74 ,  100 ,  120  are retained in the correct position in the pump inlet housing  52  to provide precise control of nozzle exit  94 ,  112 . 
         [0037]    Preferably the spout  50  of filter assembly  16  is of molded plastic, the pump housing  52  is of cast aluminum alloy, and the nozzle inserts  74 ,  100 ,  120  are of anodized machined aluminum alloy or hardened powder metal. 
         [0038]    Fluid drawn from the fluid sump  12  enters the nozzle assembly  40  through the outlet  20  of the filter assembly  16  and flows along axis  70  toward fluid mixing chamber  72 . The inner surface  60  of the spout is essentially sized to match the inner surface  84  of the nozzle insert  120 . Excess fluid, carried in passage  144 , enters pump inlet housing  52  radially and spirals around the outer surface  108  of the nozzle insert  120  along the circular cylindrical surface  66  of the housing  52 , flows axially in an annular nozzle passage  92  between the inner conical surface  68  of the housing  52  and an outer conical surface  110  of nozzle insert  120  and through a nozzle exit  112  between surfaces  68  and  110  at the axial end  86  of the nozzle insert  120 , past the outer corner  88  defined by the intersection of the end  86  and the conical surface  110 . Upon exiting through nozzle exit  112 , the excess flow creates a mixing vortex in the fluid mixing chamber  72  with the flow drawn from the fluid sump  12 , whereupon the combined fluid volume travels through the mixing chamber  72  and enters the pump  14  at inlet  22  (shown in  FIG. 1 ). 
         [0039]    In accordance with the provisions of the patent statutes, the preferred embodiment has been described. However, it should be noted that the alternate embodiments can be practiced otherwise than as specifically illustrated and described.