Abstract:
A variable capacity vane pump ( 20 ) is provided having a pump control ring ( 44 ) that is moveable to alter the capacity of the pump ( 20 ). A control chamber ( 60 ) is formed between the pump casing ( 22 ) and the control ring ( 44 ). The control chamber ( 60 ) is operable to receive pressurized fluid to create a force to move the control ring ( 44 ) to reduce the volumetric capacity of the pump ( 20 ). A primary return spring ( 56 ) acts between the control ring ( 44 ) and the casing ( 22 ) to bias the control ring ( 44 ) towards a position of maximum volumetric capacity. A shaft is coupled at one end to the control ring and a second end of the shaft is positioned a predetermined distance from the casing ( 22 ). A secondary return spring ( 62 ) is mounted about the shaft and is configured to engage the control ring ( 44 ) after the control ring ( 44 ) has moved a predetermined amount. The secondary return spring ( 62 ) biases the control ring ( 44 ) towards a position of maximum volumetric capacity. The secondary return spring ( 62 ) acts against the force of the control chamber ( 60 ) to establish a second equilibrium pressure.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to U.S. Provisional Patent Application No. 61/544,841, filed Oct. 7, 2011, in the name of Matthew Williamson, and entitled PRE-COMPRESSION DUAL SPRING PUMP CONTROL, the entire contents of which are incorporated herein for all purposes. 
     
    
     FIELD 
       [0002]    The present disclosure relates generally to an improved pump device. More particularly, the present disclosure relates to an improved pump and control device for providing better control of the output of the variable capacity pump having particular application as an oil pump for use in an engine for use in a vehicle. 
       BACKGROUND 
       [0003]    Generally it is known to use a pump for incompressible fluids, such as oil. Often such pumps are of the variable capacity vane type. Such pumps include a moveable pump ring, which allows the rotor eccentricity of the pump to be altered to vary the capacity of the pump. 
         [0004]    Having the ability to alter the volumetric capacity of the pump to maintain a pressure is desirable in environments such as automotive lubrication or oil pumps, wherein the pump will be operated over a range of operating speeds. In such environments, to maintain an equilibrium pressure it is known to employ a feedback supply of the working fluid (e.g. lubricating oil) from the output of the pump to a control chamber adjacent the pump control ring or slide, the pressure in the control chamber acting to move the control ring, against a biasing force applied to the control ring from a return spring, to alter the capacity of the pump. 
         [0005]    Typically, for such oils pumps that are operated by the engine of the vehicle, the pressure at the output of the pump increases as the operating speed of the pump increases, the increased pressure is applied to the control ring (or slide) to overcome the bias force of the return spring and to move the control ring to reduce the capacity of the pump, thus reducing the output volume and hence the pressure at the output of the pump. 
         [0006]    As the pressure at the output of the pump drops when the operating speed of the pump decreases, the pressure applied to the control chamber adjacent the control ring (or slide) decreases. When the pressure applied to the control chamber adjacent the control ring decreases the bias force of the return spring moves the control ring to increase the capacity of the pump, raising the output volume and hence pressure of the pump. In this manner, an equilibrium pressure is obtained and/or maintained at the output of the pump. 
         [0007]    Conventionally, the equilibrium pressure is selected to be a pressure that is acceptable for the expected operating (e.g., speed) range of the engine. Necessarily, the selected equilibrium pressure is a compromise because the engine operates over a generally very wide range of speeds. The equilibrium pressure is selected so the oil pump will operate acceptably (to supply sufficient oil to the engine) at lower operating speeds with a lower working fluid pressure than is required at higher engine operating speeds (to supply a greater amount of oil to the engine). To limit undue wear or other damage to the engine, the engine designers will generally select an equilibrium pressure for the pump which meets the worst case (high operating speed) conditions. When this is the case, generally, at lower speeds, the pump will be operating at a capacity greater than necessary for those speeds thereby wasting energy pumping the surplus, unnecessary, working fluid. 
         [0008]    Accordingly, there remains a significant need to improve the performance characteristics of a variable capacity vane pump having at least two equilibrium pressures and providing for greater packaging flexibility while providing a more compact pump. 
       SUMMARY 
       [0009]    In at least one exemplary embodiment according to the present invention, there is disclosed a system and method of controlling the capacity of a variable capacity pump that mitigates and even obviates at least one disadvantage of the prior art. In the least one exemplary embodiment according to the present invention, there is disclosed a variable capacity pump that mitigates and may even obviate at least one disadvantage of the prior art. In the least one exemplary embodiment according to the present invention, the variable capacity provides for greater packaging flexibility while providing a more compact pump. 
         [0010]    In at least one exemplary embodiment according to the present invention, there is disclosed a variable capacity pump, in particular a variable capacity vane-type pump, having a moveable pump control ring (or slide). The moveable pump control ring alters the capacity of the pump based upon the operating speed of the pump. In one exemplary embodiment, the pump is operable at two selected equilibrium pressures. The pump has a casing having a pump chamber therein and a vane pump rotor is rotatably mounted in the pump chamber. A control ring encloses the vane pump rotor within the pump chamber and is moveable within the pump chamber to alter the capacity of the pump. The control ring enclosing the vane pump rotor defines a control chamber along with the pump casing. The control chamber receives pressurized fluid which pressure acts on the control ring to move the control ring within the control chamber to reduce the volumetric capacity of the pump. 
         [0011]    In at least one exemplary embodiment according to the present invention the variable capacity pump includes a primary return spring acting between the control ring (or slide) and the casing (or other base) to apply a biasing force to move the control ring toward a position of maximum volumetric capacity and away from the position of minimum volumetric capacity. The primary return spring acts against the force of the control chamber applied to the control ring to move the control ring toward the biasing spring which net out to establish a first equilibrium pressure. In one exemplary embodiment, a secondary return spring is mounted, in one embodiment it is mounted in the casing, and is configured to engage the control ring after the control ring has moved a predetermined amount. The secondary return spring also biases the control ring towards a position of maximum volumetric capacity. The force of secondary return spring is designed to act against the force of the control chamber, in addition to the force of the first return spring, to establish a second equilibrium pressure. In an alternate exemplary embodiment, the secondary spring is pretensioned and includes a gap for delaying the action of the biasing force of the second pretensioned spring. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  shows a partial, graphic plan view of a variable capacity pump in accordance with the present invention; 
           [0013]      FIG. 2  shows a partial, graphic plan view of a control ring or slide utilized in the variable capacity pump of  FIG. 1 ; 
           [0014]      FIG. 3  shows a partial, schematic elevational view of the secondary spring system of the variable capacity pump of  FIG. 1 ; 
           [0015]      FIG. 4  shows a graph illustrating performance of a variable capacity pump of  FIG. 1 ; 
           [0016]      FIG. 5  shows a partial, graphic plan view of a variable capacity pump in accordance with an alternate exemplary embodiment of the present invention; 
           [0017]      FIG. 6  shows a partial, schematic elevational view of a secondary dual spring system according to an alternate embodiment for use in a variable capacity pump; 
           [0018]      FIG. 7  shows a partial, schematic elevational view of a modular, secondary spring system according to an alternate embodiment for use in a variable capacity pump; 
           [0019]      FIG. 8  shows a partial, schematic elevational view of a combination dual spring system according to an alternate embodiment for use in a variable capacity pump; 
           [0020]      FIG. 9  shows a partial, schematic elevational view of a modular, secondary spring system according to a further alternate embodiment for use in a variable capacity pump; 
           [0021]      FIG. 10  shows a partial, schematic elevational view of a combination dual spring system according to a further alternate embodiment for use in a variable capacity pump; and 
           [0022]      FIG. 11  shows a partial, schematic elevational view of a combination dual spring system according to a further alternate embodiment for use in a variable capacity pump. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Referring generally to  FIGS. 1 through 11 , and in particular to  FIGS. 1 through 3 , there is disclosed a variable capacity vane pump  20  in accordance with an embodiment of the present disclosure as best shown  FIG. 1 . The pump  20  includes a casing  22  with a front face  24  which is sealed with a pump cover (not shown) using any known or appropriate sealing device such as a suitable gasket seal. The pump  20  is coupled and sealed with an engine (not shown) or the like for which the pump  20  will supply a pressurized working fluid such as oil. 
         [0024]    The pump  20  includes a drive shaft  28  which is driven by any suitable driving device, such as a power take off from the engine or other mechanism to operate pump  20 . As drive shaft  28  is rotated, a pump rotor  32  located within a pump chamber  36  is driven by the drive shaft  28 . A series of movable or slidable pump vanes  40  rotate as the rotor  32  rotates. An outer end of each vane  40  engages an inner circumferential surface of a pump control ring  44  which forms the outer wall of pump chamber  36 . The pump vanes  40  and the outer wall of pump chamber  36  divide the pump chamber into a series of expanding and contracting pumping chambers  48  that is further defined by the inner surface of the pump control ring  44  and the pump rotor  32 . 
         [0025]    Pump control ring  44  is mounted within the casing  22  at a pivot pin  52  that allows the center of pump control ring  44  to be moved relative to the center of rotor  32 . As the center of pump control ring  44  is located eccentrically with respect to the center of pump rotor  32  and each of the interior of pump control ring  44  and pump rotor  32  are circular in shape, the volume of working fluid chambers  48  changes as the chambers  48  rotate around pump chamber  36 , with their volume becoming larger at the low pressure side (the left hand side of pump chamber  36  in  FIG. 1 ) of pump  20  and smaller at the high pressure side (the right hand side of pump chamber  36  in  FIG. 1 ) of pump  20 . This change in volume of working fluid chambers  48  generates the pumping action of pump  20 , drawing working fluid from an inlet port  50  and pressurizing and delivering it to an outlet port  54 . 
         [0026]    By moving pump control ring  44  about pivot pin  52  the amount of eccentricity, relative to pump rotor  32 , can be changed to vary the amount by which the volume of working fluid chambers  48  change from the low pressure side of the pump  20  to the high pressure side of the pump  20 , thus changing the volumetric capacity of the pump  20 . Still referring to  FIGS. 1 and 2 , a primary return spring  56  engages tab  55  of control ring  44  and casing  22  to bias pump control ring  44  to the position, shown in  FIG. 1 , wherein the pump  20  has a maximum eccentricity. 
         [0027]    Control chamber  60  is formed between pump casing  22 , pump control ring  44 , pivot pin  52  and a resilient seal  68 , mounted on pump control ring  44  and abutting casing  22 . In the illustrated embodiment as best shown in  FIG. 1 , the control chamber  60  is in direct fluid communication with pump outlet  54  such that pressurized working fluid from the pump  20  which is supplied to pump outlet  54  also fills control chamber  60 . However, control chamber  60  need not be in direct fluid communication with pump outlet  54  and can instead be supplied from any suitable source of working fluid, such as from an oil gallery in an automotive engine being supplied by pump  20 . 
         [0028]    Referring now in particular to  FIG. 2 , the secondary control of the pump  20  is provided by the control ring  44  having a secondary tab  58  circumferentially spaced from the first or primary tab  55 . Casing  22  is configured to house a secondary spring  62  in a pre-loaded state. Secondary spring  62  is a high rate spring relative to spring  56 , preferably, which is a low rate spring. Referring now in particular to  FIGS. 1 and 3 , the casing  22  is configured to house spring  62  in a pre-loaded or compressed state or position. The secondary tab  58  of the control ring  44  is spaced a predetermined distance from the spring  62  by a gap  64 , while the control ring  44  is in a maximum flow capacity state. 
         [0029]    In operation, pressurized working fluid in control chamber  60  acts against the pump control ring  44 . When the force resulting from the pressure of the pressurized working fluid on pump the control ring  44  is sufficient to overcome the biasing force of the return spring  56 , the pump control ring  44  pivots about pivot pin  52 , in a counter-clockwise direction as shown in  FIGS. 1 and 2 , to reduce the eccentricity of the pump  20 . When the pressure of the pressurized working on the control ring  44  is not sufficient to overcome the biasing force of return spring  56 , the pump control ring  44  remains pivoted clockwise about pivot pin  52  due to the force of the return spring  56 , to increase the eccentricity of pump  20 . The characteristics of the fluid (pressure and flow) at the output of the pump  20  can be graphed as a function of the operating speed of the pump. Referring to  FIG. 4 , segment “a” of the graph represents the performance of the pump  20  when the eccentricity of the pump  20  is at a maximum when the control ring  44  is at the greatest clockwise position due to the force of the return spring  56  on the control ring  44 . The flow of the fluid output by the pump  20  follows a fixed or maximum capacity line and the pressure of the fluid follows a load resistance curve that relates to this fixed capacity. 
         [0030]    Segment “b” on the graph represents the point at which the pre-load of the low rate return spring  56  is overcome by the pressure acting on the control ring  44  and the control ring  44  pivots. The pressure and flow of the fluid at the output remain substantially constant according to the equilibrium between the pressure and the spring force of the primary return spring  56 . At this point, the secondary tab  58  is not in contact with the high rate spring  62 . 
         [0031]    Segment “c” of the graph represents when the gap  64 , as best shown in  FIG. 3 , closes to zero and the secondary tab  58  contacts the high rate or secondary spring  62 , but the pressure in chamber  60  is not sufficiently high enough to overcome the pre-load of the secondary spring  62 . The eccentricity of the pump  20  therefore remains constant at this intermediate value and the output flow follows another (smaller) fixed capacity line. The pressure of the flow follows a new load resistance curve that relates to this lower value of pump displacement. 
         [0032]    Segment “d” of the graph of  FIG. 4  represents when the fluid pressure acting in chamber  60  on the control ring  44  overcomes the pre-load of the high rate spring  62  and the control ring  44  again moves counter-clockwise on the pivot  52 . The pump outlet pressure and flow remain substantially constant according to the equilibrium between the pressure in chamber  60  and the combined forces of springs  56  and  62 . When the pressure of the pressurized working fluid in chamber  60  is not sufficient to overcome the combined biasing forces of return springs  56  and  62 , pump control ring  44  pivots about pivot pin  52 , in the clockwise direction to increase the eccentricity of pump  20 . 
         [0033]    The arrangement of the first and second springs  56  and  62 , respectively, is illustrated in  FIGS. 1-3  as being in separate housings within the casing  22 . While it is apparent to those skilled in the art that the two springs  56  and  62  could be arranged in other configurations, including concentric springs within the same housing, without departing from the scope of the present disclosure, other arrangements have been found that provide particular packaging and performance improvements that are considered not apparent. In one particular example disclosed in  FIG. 5  there is shown an alternate arrangement of the second spring  62  as compared to  FIGS. 1 through 3 . In this alternate exemplary embodiment in  FIG. 5 , the variable capacity pump  20  of an alternate embodiment includes a first control spring  62  associated with a first tab or extension member  55  of the control ring  44  similar to the embodiment of  FIG. 1 . The pump  20  of  FIG. 5  further includes the second spring  62  acting on the tab or second extension member  58  of the control ring  44 . The pump  20  of  FIG. 5  further includes a shaft having a first end passing through a hole or passage in the tab  58  and the shaft extends distal there from to a second end defining a gap (g) with the housing  22 . The first end of the shaft is coupled to the tab  50  of the control ring  44  using a pair of nuts for securing the shaft to the control ring  44  but may be coupled using any known or appropriate fastener or similar device. The second end of the shaft includes a pretension element formed or coupled at the second end to define a shoulder for trapping the spring  62  between the tab  58  and the pretension element of the second end of the shaft. The operation of the pump  20  of  FIG. 5  can be similar to that of the embodiment of  FIGS. 1-4 . 
         [0034]    Referring now to the alternate embodiment of the pump  20  shown in  FIG. 6 , pump  20  is generally very similar to the pump  20  of the other alternate exemplary embodiment of  FIG. 5  except the shaft in  FIG. 6  is coupled or secured in the passage in the tab  58  of the control ring  44  using a press-fitted collar. The press-fitted collar is designed to be secured to the first end of the shaft such that the shaft pretensions the second spring, trapped between the shoulder of the pretension element of the second end of the shaft and the tab  58  of the control ring while also defining the Gap (g) desired for having the variable capacity vane pump  20  according to  FIG. 6  operate according to preferred operating curve shown in  FIG. 4 . 
         [0035]    Referring now to the alternate embodiments of the pumps  20  shown in  FIGS. 7 and 9 , the pumps  20  are generally very similar to the pumps  20  of  FIG. 1  or  5 , except that the pumps  20  include a modular or second housing  80  for operating or holding the second control spring  62  and defining the Gap (g). The second housing  80  is a generally rectangular (in cross-section as shown in the figures) member having a first end aligned with the tab  58  of the control ring  44  and a second end distal from the first end. In  FIG. 7  the second end is advantageously closed using a press-fitted plug for holding the second control spring  62  within the second housing  80  and transferring the force of the second spring  62  to the slide or control ring  44 . In the alternate exemplary embodiments of  FIGS. 7 and 9 , the tab or extension member  58  of the control ring  44  includes a first portion and a second portion aligned at an angle from the first portion. Preferably the second portion is aligned toward the first end of the housing  80  to pass through a passage in the first end of the housing  80  and contact a first member for transferring the forces between the control ring  44  and the second spring  62 . The opening in the first end of the housing  80  is designed to define the Gap (g) using the length of the first end of the housing  80 . As the pressure in the pump  20  of  FIGS. 7 and 9  increases with the speed of the pumps  20 , the second portion of the tab  58  travels through the Gap (g) distance until it contacts the first member transferring the force to the second spring  62  as the first member moves in the housing  80  toward the second end. The second portion of the tab  58  extending at an angle with respect to the second portion of the tab  58  can be advantageously used to define a limit of travel for the tab  58  and thus the control ring  44 . 
         [0036]    Referring now to the alternate exemplary embodiment of the pump  20  including a spring housing  80  and first and second springs  56  and  62 , respectively as shown in  FIG. 8 , the housing  80  is shown holding the first and second control springs  56  and  62 , respectively. The housing  80  of  FIG. 8  provides significantly improved packaging flexibility in the pumps  20  since the first and second control springs  56  and  62 , respectively, may be more closely co-located. In particular, the first and second control springs  56  and  62 , respectively, are aligned parallel or side-by-side within the housing  80  and the first end of each of the first and second control springs  56  and  62 , respectively, act against a common first portion or wall  82  extending within the housing  80 . Similar to the alternate exemplary embodiments of  FIGS. 7 and 9 , the spring housing  80  can be made more modular such that it can be manufactured either unitarily with the housing  22  of the pump  20  or separately and then made integral with the housing  22  or other part of the pump  20 . Such a design for the housing  80  provides significantly greater design flexibility and utilization of the pump  20 . While the housing  80  is shown having a generally rectangular cross section, it should be understood that other shapes are possible. 
         [0037]    Referring now to the alternate exemplary embodiments as shown in  FIGS. 10 and 11 , the pump  20  includes the housing  80  and arrangements of the first and second springs  58  and  62 , respectively. The common housing  80  is shown holding the first and second control springs  56  and  62 , respectively, in an in-line or series arrangement as compared to the side-by-side or parallel arrangement shown in  FIG. 8 . The housing  80  of  FIGS. 10 and 11  also provides significantly improved packaging flexibility in the pump  20  since the first and second control springs  56  and  62 , respectively, may be more closely aligned and co-located. In particular, the first and second control springs  56  and  62 , respectively, are aligned in-line within the housing  80 . Referring in particular to  FIG. 10 , the first spring  56  is located closest to the tab  58  of the control ring or slide  44  and the second control spring  62  is located distal. A pin having a substantially t-shape is located between the first and second springs  56  and  62 , respectively. The tab  58  will first act on the spring  56  (Spring  1 ) over a given distance until the tab  58  contacts the pin and begins compressing the second spring  62  (Spring  2 ). The alternate embodiment shown in  FIG. 11  is similar to that of  FIG. 10  except the t-shaped pin is located between the first control spring  56  and the tab  58  of the control ring or slide  44  and a retainer is provided between the second control spring  62  and the second and of the pin such that once the first control spring  56  (Spring  1 ) compresses a given distance, the force from the tab  58  will begin to be applied against the force of the second control spring  62  (Spring  2 ). 
         [0038]    Any numerical values recited herein or in the figures are intended to include all values from the lower value to the upper value in increments of one unit provided that there is a separation of at least 2 units between any lower value and any higher value. As an example, if it is stated that the amount of a component or a value of a process variable such as, for example, temperature, pressure, time and the like is, for example, from 1 to 90, preferably from 20 to 80, more preferably from 30 to 70, it is intended that values such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 etc. are expressly enumerated in this specification. For values which are less than one, one unit is considered to be 0.0001, 0.001, 0.01 or 0.1 as appropriate. These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this application in a similar manner. As can be seen, the teaching of amounts expressed as “parts by weight” herein also contemplates the same ranges expressed in terms of percent by weight. Thus, an expression in the Detailed Description of the Invention of a range in terms of at “‘x’ parts by weight of the resulting polymeric blend composition” also contemplates a teaching of ranges of same recited amount of “x” in percent by weight of the resulting polymeric blend composition.” 
         [0039]    Unless otherwise stated, all ranges include both endpoints and all numbers between the endpoints. The use of “about” or “approximately” in connection with a range applies to both ends of the range. Thus, “about 20 to 30” is intended to cover “about 20 to about 30”, inclusive of at least the specified endpoints. 
         [0040]    The disclosures of all articles and references, including patent applications and publications, are incorporated by reference for all purposes. The term “consisting essentially of” to describe a combination shall include the elements, ingredients, components or steps identified, and such other elements ingredients, components or steps that do not materially affect the basic and novel characteristics of the combination. The use of the terms “comprising” or “including” to describe combinations of elements, ingredients, components or steps herein also contemplates embodiments that consist essentially of the elements, ingredients, components or steps. By use of the term “may” herein, it is intended that any described attributes that “may” be included are optional. 
         [0041]    Plural elements, ingredients, components or steps can be provided by a single integrated element, ingredient, component or step. Alternatively, a single integrated element, ingredient, component or step might be divided into separate plural elements, ingredients, components or steps. The disclosure of “a” or “one” to describe an element, ingredient, component or step is not intended to foreclose additional elements, ingredients, components or steps. 
         [0042]    It is understood that the above description is intended to be illustrative and not restrictive. Many embodiments as well as many applications besides the examples provided will be apparent to those of skill in the art upon reading the above description. The scope of the invention should, therefore, be determined not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and publications, are incorporated by reference for all purposes. The omission in the following claims of any aspect of subject matter that is disclosed herein is not a disclaimer of such subject matter, nor should it be regarded that the inventors did not consider such subject matter to be part of the disclosed inventive subject matter.