Patent Publication Number: US-2011074123-A1

Title: Suspension Actuator for a Roll Control System

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. patent application Ser. No. 11/446,900, filed Jun. 5, 2006, the disclosure of which is incorporated herein by reference in entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates in general to a suspension system, and more specifically, to a roll control actuator. 
     Suspension systems for a motor vehicle are known which isolate the vehicle from irregularities in the road terrain over which the vehicle travels. 
     Suspension systems typically include a sway bar, also known as a roll bar or a stabilizer bar, which couples the suspension on each side of a vehicle to one another. The sway bar assists in maintaining even compression on each side of the vehicle suspension. For a vehicle in a cornering maneuver having no sway bar, one side of a vehicle suspension will be under compression and the other side will have no or very little compression applied. For a vehicle having a sway bar, compression is maintained on both sides of the vehicle during a cornering maneuver. Maintaining compression on both sides of the vehicle while going about a turn minimizes the chances of the vehicle wheels lifting off the ground and reducing the stability of the vehicle. 
     A semi-active suspension system normally includes a spring and damper connected between the sprung portions (e.g. body) and unsprung portions (vehicle frame) of the vehicle. Semi-active suspension systems are generally self-contained, and only react to the loads applied to them. In active suspension systems, by contrast, the reactions to the applied loads are positively supplied, typically by electronically controlled hydraulic or pneumatic actuators. 
     An actuator for a semi-active suspension system typically utilizes a spring biased piston assembly in cooperation with the self-contained hydraulic fluid chambers (damper) for dampening sudden deflections in the suspension system caused by irregularities in the road terrain and for maintaining a rigid suspension system when cornering. The actuator typically utilizes a high-pressure chamber and a storage chamber for transferring hydraulic fluid within the actuator for allowing the compression of the actuator. Typically, the high-pressure chamber is formed about the piston assembly and maintains a resistive force on the spring-biased piston for gradually controlling the axial movement of the actuator. In such an arrangement, when in a dampening mode, hydraulic fluid is allowed to flow from the high-pressure chamber to the storage chamber via the compression force exerted on the actuator. The resistive force of the spring biased piston and the withdrawal of hydraulic fluid from the high-pressure chamber provides for a gradual smooth movement of the actuator. When the force is no longer applied to the actuator, the spring-biased piston uncompresses and moves back to its extended position. As the piston moves back to the extended position, hydraulic fluid flows from the storage chamber to the high-pressure chamber via a vacuum or low pressure created by the piston assembly, which provides a gradual return to its extended position. 
     Typically, for straight road driving, a solenoid valve is in an open position for allowing hydraulic fluid to exit the high-pressure chamber of the actuator, which allows the actuator to compress and dampen deflections in the suspension system. When a vehicle is cornering, the solenoid valve is in a closed position for preventing hydraulic fluid from leaving the high-pressure chamber. This prevents the actuator from compressing so that a rigid suspension system is maintained. 
     As the vehicle travels over uneven terrain (with the solenoid valve in the open position), the actuator constantly compresses and uncompresses, thereby forcing hydraulic fluid in and out of both the high-pressure chamber and the storage chamber. The storage chamber is typically filled with a gas, such as nitrogen. Gas is produced within the hydraulic fluid in the storage chamber when the hydraulic fluid jets into the storage chamber and breaks the surface interface of the hydraulic fluid and air therein. If hydraulic fluid is allowed to jet into the storage chamber and break the surface of the hydraulic fluid in the storage chamber, gas bubbles will be produced within the hydraulic fluid. Hydraulic fluid is noncompressible; however, as gas bubbles are mixed into the hydraulic fluid, the hydraulic fluid within the high-pressure chamber becomes compressible due to the gas bubbles being compressible. The gas bubbles allow for compression in the high-pressure chamber even when the solenoid valve is in a closed position. This reduces the rigidity of the suspension system when a rigid suspension system is desired. 
     BRIEF SUMMARY OF THE INVENTION 
     In one aspect, the present invention has the advantage of utilizing a flow diverter in a roll control actuator for preventing gas bubbles from forming in a low-pressure accumulator as pressurized hydraulic fluid is transferred from a high-pressure chamber to the low-pressure accumulator. 
     In one embodiment of the invention, a hydraulically operated actuator is provided for controlling a roll of a vehicle. The actuator is connected between a first mass of the vehicle and a second mass of the vehicle. An upper mount assembly is coupled to the first mass of the vehicle. A lower mount assembly is coupled to the second mass of the vehicle. A variable high-pressure chamber is disposed between the lower mount assembly and the upper mount assembly, the variable high-pressure chamber having a variable volume of hydraulic fluid disposed therein for selectively dampening the movement between the upper mount assembly and the lower mount assembly. A low-pressure accumulator includes a portal for receiving hydraulic fluid from the high-pressure chamber. The hydraulic fluid is in fluid communication between the high-pressure chamber and the accumulator. An anti-aeration assembly for minimizing gas bubbles from transitioning between the high-pressure chamber and the accumulator, the antiaeration assembly being disposed within the accumulator. 
     In yet another embodiment of the invention, an actuator assembly is provided for controlling vehicle suspension rigidity. The actuator includes an upper mount assembly coupled to a suspension member. A lower mount assembly is coupled to a vehicle frame. A piston assembly includes a piston rod and a piston. The piston rod is coupled to the upper mount assembly for maintaining a variably spaced relationship between the upper mount assembly and the lower mount assembly. An accumulator is disposed between the upper mount assembly and the lower mount assembly for storing a variable amount of hydraulic fluid. The accumulator includes a first portal for receiving hydraulic fluid flow into the accumulator. A high-pressure chamber contains hydraulic fluid, the high-pressure chamber being selectively compressible. A solenoid valve is interposed between the high-pressure chamber and the accumulator for selectively controlling pressure within the high-pressure chamber by controlling the fluid flow from the high-pressure chamber to the accumulator. The solenoid valve when in an open position allows fluid flow from the high-pressure chamber to the accumulator as the high-pressure chamber is compressed. A flow diverter within the accumulator directs a flow of hydraulic fluid flow from the high-pressure chamber to the accumulator. The flow diverter minimizes the hydraulic fluid flow into the accumulator from forming gas bubbles in the hydraulic fluid. 
     In yet another embodiment of the invention, an anti-aeration system is provided for a gas and fluid filled reservoir in a hydraulic suspension actuator. The actuator is hydraulically operated for controlling a roll of a vehicle. The actuator is connected between a first mass of the vehicle and a second mass of the vehicle. The actuator includes an upper mount assembly coupled to the first mass of the vehicle and a lower mount assembly coupled to the second mass of the vehicle. A high-pressure chamber is disposed between the lower mount assembly and the upper mount assembly. The high-pressure chamber has a variable volume of hydraulic fluid disposed therein for selectively dampening the movement between the upper mount assembly and the lower mount assembly. A low-pressure accumulator includes a first portal for selectively receiving hydraulic fluid from the high-pressure chamber and a second portal disposed on a bottom surface of the accumulator for allowing hydraulic fluid to exit from the accumulator to the high-pressure chamber. A flow diverter for redirecting a flow of hydraulic fluid within the accumulator minimizes the formation gas bubbles in the hydraulic fluid within the accumulator. A fence portion is disposed around the second portal for minimizing gas bubbles suspended in the hydraulic fluid of the accumulator from entering the second portal. 
     In yet another embodiment of the invention, a hydraulic actuator for controlling the roll of a vehicle includes an anti-aeration assembly disposed within an accumulator for minimizing aeration of hydraulic fluid transitioning between the chamber and the accumulator. 
     In yet another embodiment of the invention, an actuator for controlling the roll of a vehicle has an anti-aeration assembly including an investment casting with an integral flow deflector. 
     In yet another embodiment, an actuator for controlling the roll of a vehicle includes a component affixed to upper and lower housing portions by metal fusing. 
     In yet another embodiment, a piston assembly for an actuator for controlling the roll of a vehicle includes a rod and a piston wherein an end of travel of the rod is dampened by a volume of fluid between a head of the rod and a respective end of a chamber of the piston. 
     In yet another embodiment, a piston assembly for an actuator for controlling the roll of a vehicle includes a rod and a piston. The piston assembly includes a cushion mounted on one end of the piston. The cushion dampens the travel of the piston as approaching the end of a piston housing 
     In yet another embodiment, an actuator for controlling the roll of a vehicle includes a piston housing and a piston assembly. The housing includes a collar that cooperates with an end of the piston to form a pocket of dampening hydraulic fluid. 
     In yet another embodiment, a piston assembly for an actuator for controlling the roll of a vehicle includes a piston having a snap fit check valve assembly in an end of the piston. 
     Other advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of an actuator for controlling the roll of a vehicle according to a first preferred embodiment of the invention. 
         FIG. 2  is partial cross section view of the actuator according to the first preferred embodiment of the present invention. 
         FIG. 3  is an enlarged view of the encircled portion of  FIG. 1  according to the first preferred embodiment of the present invention. 
         FIG. 4  is a perspective view of a flow diverter according to a second preferred embodiment of the present invention. 
         FIG. 5  is a perspective view of a flow diverter according to a third preferred embodiment of the present invention. 
         FIG. 6  is a perspective view of a flow diverter according to a fourth preferred embodiment of the present invention. 
         FIG. 7  is a perspective view of a flow diverter according to a fifth preferred embodiment of the present invention. 
         FIG. 8  is a perspective view of a flow diverter according to a sixth preferred embodiment of the present invention. 
         FIG. 9  is a perspective view of a portion of an accumulator according to a seventh preferred embodiment of the present invention. 
         FIG. 10  is a perspective view of a portion of an accumulator according to an eighth preferred embodiment of the present invention. 
         FIG. 11  is a perspective view of a portion of an accumulator according to a ninth preferred embodiment of the present invention. 
         FIG. 12  is a perspective view of a portion of an accumulator according to a tenth preferred embodiment of the present invention. 
         FIG. 12   a  is a cross-sectional view of the flow deflector of  FIG. 12 . 
         FIG. 13  is a partial cross-sectional perspective view of an actuator according to an eleventh preferred embodiment of the present invention. 
         FIG. 14  is a perspective view of a portion of an actuator according to a twelfth preferred embodiment of the present invention. 
         FIG. 15  is a perspective view of a portion of an actuator according to a thirteenth preferred embodiment of the present invention. 
         FIG. 16  is a partial cross-sectional perspective view of the actuator of  FIG. 15 . 
         FIG. 17  is a partially exposed view of an actuator according to a fourteenth preferred embodiment of the present invention. 
         FIG. 18  is a partially exposed view of the actuator of  FIG. 17  with the piston at the end of travel. 
         FIG. 19  is a cross-sectional perspective view of the actuator of  FIG. 17  nearing the end of travel. 
         FIG. 20  is a partial cross-sectional view of a portion of an actuator according to a fifteenth preferred embodiment of the present invention. 
         FIG. 21  is an exploded view of the check valve of  FIG. 20 . 
         FIG. 22  is a partial cross-sectional view of a portion of the check valve of  FIG. 20 . 
         FIG. 23  is a schematic view of a vehicle system utilizing an actuator for a roll control system according to a sixteenth preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, there is illustrated in  FIGS. 1 and 2  a self-contained hydraulic fluid actuator  10  for a semi-active roll control system. The actuator  10  includes an upper mount assembly  11  for attachment to a first mass  13  of a vehicle such as a vehicle frame member. The upper mount assembly  11  includes an upper ball joint assembly  12  having a pivot ball  14  interconnected to a socket  16  which allows for circumferential movement of the actuator  10  in relation to the attaching vehicle frame member. The pivot ball  16  is also coupled to a pivot shaft  18  for attachment to the vehicle frame member. 
     The upper mount assembly  11  also includes a dust cover  20 . The dust cover  20  functions as a protective guard against debris (e.g., stones) from the road that may cause damage to any underlying components of the actuator  10 . A piston assembly  22  is also coupled to the upper mount assembly  11 . The piston assembly  22  includes a piston rod  24 , a piston rod head  26 , a piston  28 , and a piston spring  29 . The piston rod  24  is coupled to the piston rod head  26  (e.g., threaded) or may be formed integral as one component. The piston  28  includes a check valve assembly  31  coupled to a bottom surface of the piston  28 . Preferably, the piston  28  is a free-floating piston that is slideable over the piston rod head  26  as described in co-pending application U.S. Ser. No. 10/892,484 filed Jul. 16, 2004, which is incorporated herein by reference. 
     The actuator  10  further includes a lower mount assembly  30 . The lower mount assembly  30  includes a fastening member  32  coupled to a second mass  33  of the vehicle such as a sway bar (sprung member). The lower mount assembly  30  further includes a lower housing portion  34 . An inner tubular member  36  spaced radially outward from the piston assembly  22  extends into the lower housing portion  34  and is coupled to the lower housing portion  34  therein. An outer tubular member  35  spaced radially outward from the inner tubular member  36  is sealing engaged to the lower housing portion  34 . A low-pressure accumulator  37  is formed between the outer tubular member  35  and the inner tubular member  36 . The accumulator  37  is partially filled with hydraulic fluid and partially filled with a gas, such as nitrogen. A high-pressure chamber  42  is formed between the inner tubular member  36  and the piston assembly  22 . 
     A cap assembly  40  is seated on top of the outer tubular member  35  and the inner tubular member  36 . The cap assembly  40  includes a centered aperture  43  for receiving the piston rod  24  axially therethrough for attachment to the upper mount assembly  11 . The piston spring  29  extends axially around the piston rod  24 . The ends of the piston spring  29  are bound by an abutment portion  44  of the upper cap assembly  40  and an abutment portion  46  of the piston  28 . 
     The cap assembly  40  is disposed above the high-pressure chamber  42  and is in fluid communication with the high-pressure chamber  42 . The cap assembly  40  includes a fluid conduit  46  that coupled to a transfer tube  48  disposed within the accumulator  37 . Pressurized hydraulic fluid exits from the top of the high-pressure chamber  42  via the first conduit  46  and is provided to the transfer tube  48 . The transfer tube  48  extends between the upper cap assembly  40  and the lower housing assembly  34  within the accumulator  37  for allowing fluid flow between the upper cap assembly  40  and a solenoid valve  56  disposed in the lower housing assembly  34 . The valve  56  is only schematically illustrated in  FIG. 2 . The valve  56  controls fluid flow between the interior of the lower housing assembly  34  and a first passageway  54  and the accumulator  37 . For example, the valve  56  maybe the valve shown in  FIG. 6  of PCT Patent Application Publication WO 2006/118576 A2. 
     Referring to  FIG. 3 , a flow deflector  50  is disposed within the accumulator  37  above a portal  57 . The flow deflector  50  includes a bore  51  for receiving the transfer tube  48  therethrough. The bore  51  of the flow deflector  50  is slideable over the exterior surface of the transfer tube  48 . The flow deflector  50  is secured to the transfer tube  48  by attaching a retaining ring  52  in a grooved section of the transfer tube  48  for locating the flow deflector  50  on the transfer tube  48  at a desired location within the accumulator  37 . The flow deflector  50  functions as a bushing for locating the transfer tube  48  when the transfer tube  48  is aligned and inserted into the lower housing assembly  34 . 
     The lower housing assembly  34  further includes the first passageway  54  that fluidically connects the transfer tube  48  to the solenoid valve  56  disposed within the lower housing assembly  34 . A second passageway  55  fluidically connects the accumulator  37  to the solenoid valve  56 . The solenoid valve  56  includes electrical leads  53  (shown in  FIG. 2 ) that receive power to energize the solenoid valve  56  to an open or closed position for allowing hydraulic fluid flow between the first passageway  54  and the second passageway  55 . When the solenoid valve  56  is actuated to allow hydraulic fluid flow from the high-pressure chamber  42  to the accumulator  37 , pressurized hydraulic fluid jets through the portal  57  leading into the accumulator  37 . Preferably, the flow passages from passageway  54  to passageway  55  includes a convergence/divergence section for increasing pressure and decreasing fluid flow rate to produce a venturi action for reducing the jet stream and turbulence and placing a backpressure on the solenoid valve  56 . A diverging portion  60  includes a gradual widened opening for decreasing fluid flow rate into the accumulator  37 . The gradual widened opening extending to the first portal  59  functions to decelerate the fluid flow rate and gradually allow the fluid flow to reach a substantially same pressure as that in the accumulator  37 . 
     A portion of the flow deflector  50  is positioned directly above the portal  57  for preventing hydraulic fluid from jetting above the surface of the hydraulic fluid stored in the accumulator  37 . Preventing the jetted hydraulic fluid from breaching the surface of the hydraulic fluid within the accumulator  37  substantially reduces the formation of gas bubbles within the hydraulic fluid. 
     A controller (not shown) provides control signals to energize the solenoid valve  56  between the open or closed position depending on the vehicle operating conditions. The controller senses a plurality of operating conditions, including but not limited to speed, lateral acceleration, and steering wheel angle. A semi-active roll control algorithm will process the information and, based on the sensed inputs, will produce a control command indicating whether to close or open the solenoid valve  56  for maintaining a rigid or non-rigid suspension system. 
     As the force exerted on the lower mount assembly  30  is removed, the piston spring  29  uncompresses and forces the piston  28  back to an extended position (or centered position). As the piston transitions from a compressed position to the extended position, the positioning of the piston in cooperation with a pressure differential causes hydraulic fluid to be drawn from the accumulator  37  back into the high-pressure chamber  42 . Hydraulic fluid is drawn from the accumulator  37  to the high-pressure high-pressure chamber  42  by a second portal  59  (shown in  FIG. 1 ). The second portal  59  is disposed on a bottom surface  86  of the accumulator  37 . The second portal  59  allows fluid to flow from the accumulator  37  to the high-pressure chamber  42  depending on the pressure differential and the placement of the piston. 
     The flow deflector  50  includes a substantially arc-shaped underbody surface  58 . The flow deflector  50  is positioned over the portal  57  of the second passageway  55 . Hydraulic fluid forced into the accumulator  37  under high pressure from the portal  57  jets into the accumulator  37  in a vertical upward direction. The jetted hydraulic fluid is gradually deflected in a substantially horizontal direction by the arc-shaped underbody surface  58  of the flow deflector  50 . Thus, the deflected hydraulic fluid flows in a horizontal circular direction and is prevented from flowing upward and breaching the surface of the existing hydraulic fluid within the accumulator  37 . Preventing the jetted hydraulic fluid from breaking the surface of the hydraulic fluid minimizes the gas bubbles within the hydraulic fluid in the accumulator  37 . 
       FIG. 4  illustrates an enlarged view of a flow diverter  61  attached to the lower housing portion  34  according to a second preferred embodiment. The flow diverter  61  includes an arc-shaped fluid conduit  62  extending from the portal  57  of the second passageway  55 . The fluid conduit  62  curves from a vertical direction to a substantially horizontal direction. Fluid jetting from the portal  57  of the second passageway  55  enters the flow diverter  61  and is redirected in a substantially horizontal direction. This prevents the hydraulic fluid exiting the flow diverter  61  from flowing in a direction that could break the surface of the hydraulic fluid stored within the accumulator  37 , thus minimizing the gas bubbles therein. 
       FIG. 5  is a third embodiment illustrating a flow diverter  66  for diverting the hydraulic fluid flow entering the accumulator  37  (such as one shown in  FIGS. 2 and 3 ). The flow diverter  66  includes a vertical tubular section  68  that is coupled to the portal  57  of the second passageway  55  (not shown in this figure). A flattened tubular section  70  extends substantially 90 degrees from the vertical tubular section  68 . An opening  72  of the flattened tubular section  70  includes a flattened widened mouth. The flow diverter  66  is preferably made of an elastomeric material such as rubber, but may be made of other types of materials if so desired. Fluid entering the accumulator  37  is directed in a substantially horizontal direction for preventing it from breaking the surface of the hydraulic fluid, thus minimizing gas bubbles in the hydraulic fluid. The flow diverter  66  functions as a venturi for hydraulic fluid flowing between the accumulator  37  and the high pressure chamber  42  (not shown in this figure). A narrowed neck section  73  between the vertical tubular section  68  and the widened mouth opening  72  functions as a convergent/divergent section for creating a venturi effect. 
     The flow diverter  66 , if made of an elastomeric material, also has the advantage of functioning like a check valve for preventing the return of hydraulic fluid from the accumulator  37  to the high-pressure chamber  42  via the flow diverter  66 . In the unlikelihood of a small amount of gas bubbles formed in the hydraulic fluid of the accumulator  37 , gas bubbles could return to the high-pressure chamber  42  via the perspective flow diverter. That is, gas bubbles formed in the liquid float upward; however, because of the viscosity of the hydraulic fluid (e.g., oil), the gas bubbles may not disperse above the surface of the hydraulic fluid in a timely manner that would be warranted. Rather, the gas bubbles may be slow to float to the surface and may remain suspended in the hydraulic fluid. Under such conditions, a respective flow diverter having an opening at a respective height above the bottom surface of the accumulator  37  may be susceptible to allowing gas bubbles suspended within the hydraulic fluid to flow therein to the high-pressure chamber  42 . Unlike portal  57  disposed on the bottom surface  86  of the accumulator  37 , as shown in  FIG. 3 , respective flow diverters extending into the accumulator  37  and having their respective portal openings at an elevated distance above the bottom surface  86  of the accumulator  37  are susceptible to allowing gas bubbles suspended in the accumulator  37  to flow to the high pressure chamber  42  back through the respective flow diverter. This is primarily due to a respective flow diverter having an elevated opening in a region of the accumulator  37  where gas bubbles may be suspended. The flow diverter  66 , as shown in  FIG. 5 , prevents hydraulic fluid flow from re-entering the opening  72  of the flow-diverter  66  as a result of the geometric shape of the tubular section  70  and its elastomeric properties. A vacuum flow created from the accumulator  37  to the high-pressure chamber  42  would cause the opening  72  to close and seal itself thereby restricting reverse flow through the flow diverter  66 . Fluid returning to high-pressure chamber  42  would exit the accumulator  37  via the second portal  59  (shown in  FIG. 1 ) disposed on the bottom surface of the accumulator  37 . 
       FIG. 6  is a flow diverter  74  according to a fourth preferred embodiment of the present invention. The flow diverter  74  is similar to the flow diverter  66  of  FIG. 4 . The flow diverter  74  includes a vertical tubular section  76 , which extends into the opening  57  of the second passageway  55  (not shown in this figure). A flattened tubular section  78  extends substantially 90 degrees from the vertical tubular section  76 . Fluid entering the accumulator  37  (now shown in this figure) is directed in a substantially horizontal direction, preventing the in-flowing hydraulic fluid from breaking the surface, thus minimizing gas bubbles in the hydraulic fluid. The flattened tubular section  78  includes a flattened uniform section that extends laterally to an opening  80 . The flow diverter  74  resembles that of Bunsen valve. A vacuum flow created from the accumulator  37  to the high-pressure chamber  42  (not shown in this figure) causes the opening  80  to close and seal itself thereby restricting reverse flow through the flow diverter  74 . 
       FIG. 7  shows a flow diverter  82  according to a fifth preferred embodiment of the present invention. The flow diverter  82  may be integral to the lower housing portion  34 . The flow diverter  82  includes a tubular segment  84  that extends laterally along the bottom surface  86  of the accumulator  37  (not shown in this figure). The flow diverter  82  includes a substantially horizontal passageway  88 , which extends from the opening  57  of the second passageway  55  (not shown in this figure) to the accumulator  37 . Hydraulic fluid exiting the flow diverter  82  is directed in a substantially horizontal direction into the accumulator  37 , thereby minimizing gas bubbles in the hydraulic fluid in the accumulator  37  that would otherwise be formed if the incoming hydraulic fluid broke the surface of the hydraulic fluid within the accumulator  37 . The flow diverter  82  can be seated low with respect to the bottom surface  86  when formed integral with the lower housing portion  34 . This minimizes the return of entrapped gas bubbles suspended in the hydraulic fluid from flowing through the flow diverter  82  since entrapped gas is typically not suspended close to the bottom surface  86 . 
       FIG. 8  shows a flow diverter  90  according to a sixth preferred embodiment of the present invention. The flow diverter  90  may be integral to the lower housing portion  34  or may be separately formed and coupled thereafter to the lower housing portion  34 . The flow diverter  90  includes a main body portion  91 . The main body portion  91  includes a wall section  92  that that has a first sloping surface  93  and a second sloping surface  94 . The first sloping surface  93  and the second sloping surface  94  intersect at an apex  95 . 
     A reed valve  96  is coupled to the main body  91  and extends laterally along the wall section  92 . The reed valve  96  is made of an elastomeric material, such as rubber, which allows the reed valve  96  to move the directions as shown by the direction indicator  97  when respective forces are exerted on the reed valve  96 . When no forces are acting on the reed valve  96 , a portion of the reed valve  96  abuts the apex  95 . Alternatively, the reed valve  96  may be positioned so that the reed valve  96  is in close proximity to the apex  95 . 
     A first chamber portion  98  is cooperatively formed by the first sloping surface  93  and reed valve  96 . The first chamber portion  98  is disposed above the portal  57  and is in fluid communication with the portal  57 . The first chamber  92  widens as it extends along the first sloped surface  93  from the apex  95  to an opposing end portion of the first chamber portion  98  that is in fluid communication with the portal  57 . 
     A second chamber portion  99  is cooperatively formed by the second sloping surface  94  and reed valve  96 . The second chamber portion  99  widens as it extends from its apex  95  to an opposing end of the second chamber portion  99  that is in fluid communication with the accumulator  37 . 
     A narrowed passageway  100  is formed between the apex  95  and the opposing section of the reed valve  96 , which allows fluid flow from the first chamber portion  98  to the second chamber portion  99 . When hydraulic fluid is forced from high-pressure chamber  42  (not shown) to the accumulator  37 , pressurized hydraulic fluid is forced into the first chamber portion  98  via portal  57 . As fluid flow increases into the first chamber portion  98 , pressure builds into the tapered portion of the first chamber portion  98  to force the reed valve  96  in the direction A as indicated by the direction indicator  97 . As fluid flows through the narrowed passageway  100 , fluid flow increases as pressure decreases. Hydraulic fluid flows into the second chamber portion  99 . The second chamber portion  99  widens as fluid flows from the apex  95 , and thereafter, into the accumulator  37 . As fluid flows into the widening second chamber portion  99 , fluid flow decreases and pressure increases thereby reducing abrupt pressure changes and minimizing the jetting fluid and turbulence. 
     The hydraulic fluid entering the accumulator  37  from the second chamber portion  99  is forced in a substantially horizontal direction that prevents hydraulic fluid from jetting above the surface of the hydraulic fluid thereby minimizing the formation of gas bubbles within the hydraulic fluid of the accumulator  37 . 
     When hydraulic fluid returns to the high-pressure chamber  42  from the accumulator  37 , fluid flow is prevented from re-entering the flow diverter  90 . As fluid attempts to re-enter the flow diverter  90  from the accumulator  37 , a vacuum is created from the high-pressure chamber  42 . The vacuum attempts to draw fluid from the accumulator  37  into the second chamber portion  99 . In response to the vacuum created by the reverse fluid flow, the reed valve  96  is forced in the direction B as indicated by the direction indicator  97 . The portion of the reed valve  96  collapses against the second sloped surface  93  and the apex  95  thereby stopping any additional hydraulic fluid from passing through flow diverter  90  and to the high-pressure chamber  42 . Any gas bubbles suspended within the hydraulic fluid, which may have formed, are prevented from flowing to the high-pressure chamber  42  through the flow diverter  90 . 
     It should be noted gas bubbles suspended in the high-pressure chamber  42  exit the high-pressure chamber  42  via first conduit  46  coupled to the top of the high-pressure chamber  42 . The gas bubbles travel through the transfer tube  48  and into the accumulator via the first portal  57  where the hydraulic fluid and gas bubbles disposed therein are redirected in the substantially horizontal direction by a respective flow diverter. These gas bubbles circulate within the accumulator  37  and gradually rise to the top surface as the hydraulic fluid flow rate decreases within the accumulator  37  thereby purging the gas bubbles within the high-pressure chamber  42 . 
       FIG. 9  shows a perspective view of a portion of the accumulator  37  according to a seventh preferred embodiment of the present invention. The accumulator  37  includes a portal  57  for allowing pressurized hydraulic fluid to enter the accumulator  37  from the high-pressure chamber  42  (shown in  FIG. 2 ). A portion of the flow deflector  50  is positioned directly above the portal  57  for preventing hydraulic fluid from jetting above the surface of the hydraulic fluid stored in the accumulator  37 . Preventing the jetted hydraulic fluid from breaching the surface of the hydraulic fluid within the accumulator  37  substantially reduces the formation of gas bubbles within the hydraulic fluid. 
     A fence portion  108  is disposed around the second portal  59  and extends vertically upward into the accumulator  37 . The fence portion  108  includes a mesh-type material having mesh-like openings  109  that allows for fluid flow therethrough. As fluid exits from the accumulator  37  through the second portal  59 , hydraulic fluid is drawn through fence portion  108 . The fence portion  108  screens gas bubbles suspended within the hydraulic fluid of the accumulator  37  as the hydraulic fluid passes through the fence portion  108  thereby minimizing gas bubbles from flowing through the second portal  59  and to the high-pressure chamber  42 . 
     The fence portion  108  may be extended to only a predetermined height for allowing flow over in the event the hydraulic fluid becomes highly viscous. Under certain conditions (e.g., cold weather), the hydraulic fluid within the accumulator  37  may have high viscosity. Depending upon the size of the mesh openings of the fence portion  108 , hydraulic fluid may be restricted from flowing through the mesh openings of the fence portion  108  or may flow at a very slow rate. By limiting the height of the fence portion  108 , the fence portion  108  may function as a weir for allowing hydraulic fluid to flow over a top unrestricted opening  110  of the fence portion  108  should the hydraulic fluid be too viscous to flow through the mesh-type openings  109  of the fence portion  108 . 
       FIG. 10  shows a perspective view of an anti-aeration assembly according to an eighth preferred embodiment of the present invention. The accumulator  37  includes the second portal  59  for allowing pressurized hydraulic fluid to enter the accumulator  37  from the high pressure chamber  42   
     Referring to  FIG. 9 , during cold temperatures, the viscosity of the hydraulic fluid within the accumulator rises. The thickness of the hydraulic fluid during the cold temperatures may not allow the hydraulic fluid to flow through the mesh-like openings  109 . In addition, having to too little of an existing volume of fluid within the fence portion  108  may deplete the hydraulic fluid from this region within the fence portion  108 , and as a result, gas may be drawn into the second portal  57  and to the high pressure accumulator  42 . 
     Referring again to  FIG. 10 , an anti-aeration system is shown for maintaining a sufficient volume of hydraulic fluid with the fence portion  108 ′. The fence portion  108 ′ is disposed radially outward and around the inner tubular member  36 . The second portal  59  is disposed on the bottom surface of the accumulator between the fence portion  108 ′ and the inner tubular member  36 . The fence portion  108 ′ extends to only a predetermined height above the second portal  59 . As stated earlier, under cold weather conditions, the hydraulic fluid within the accumulator  37  may be too thick to flow through the mesh-like opening  109  of the fence portion  108 ′. When hydraulic fluid enters the accumulator  37  from the first portal  57 , hydraulic fluid fills the region between the outer tubular member  35  and the fence portion  108 ′. As the hydraulic fluid reaches the top of the fence portion  108 ′, the fence portion  108 ′ functions as a weir by allowing hydraulic fluid to flow over a top unrestricted opening  110  of the fence portion  108 ′ and into the region between inner tubular member  36  and the fence portion  108 ′. The region between the fence portion  108 ′ and the inner tubular member  36  is sufficient so that when fluid is drawn out via the second portal  59 , the hydraulic fluid with this region is not depleted when exiting the second portal  59 . 
       FIG. 11  shows a perspective view of an anti-aeration assembly according to a ninth preferred embodiment of the present invention. In this embodiment, a second portal  59 ′ is disposed centrally about the inner tubular member  36  along the bottom surface of the accumulator  37  juxtaposed to the high-pressure accumulator  42 . As hydraulic fluid enters the accumulator  37  when the hydraulic fluid is cold and viscous, hydraulic fluid is allowed to flow over the top of the fence portion  108 ′ for maintaining a sufficient volume of fluid within this region so that gas is unable to exit through the second portal  59 . 
     In alternative embodiments, a respective fence portion may be designed utilizing difference diameters, heights, and geometrical configurations based on the size, location, and shape of a respective second portal. In addition, the fence portion can be utilized with the various embodiments of flow diverters as discussed above. Moreover, the centrally disposed second portal  59 ′ may be utilized without a respective fence since gas bubbles have a tendency to float upward and away from the lower central portion of the accumulator. 
     There is shown in  FIGS. 12 and 12   a  a portion of an accumulator  210  according to a tenth preferred embodiment of the present invention. The accumulator  210  includes an investment cast portion  212  with an integral flow deflector  214 . It must be understood, however, that the flow deflector  214  need not be integrally formed and that the portion  212  may be formed in any suitable manner such as other casting, stamping or forming. Preferably, the casting  212  and the deflector  214  are formed form plastic. Although it must be understood that the investment casting  212  and the deflector  214  may be made from any suitable material, such as metal, formed in any suitable manner, such as stamping molding, or pressing. 
     There is shown in  FIG. 13  a portion of an actuator  310  according to a eleventh embodiment. In this embodiment, the actuator  310  includes a high-pressure return tube  312 . The high-pressure return tube  312  is affixed to respective upper and lower housing portions  314  and  316  by metal fusing, such as brazing, soldering or welding, as indicated at  318  and  320 , respectively. Preferably, although not necessarily, the brazing is oven brazing performed in a neutral atmosphere furnace. In an alternative embodiment (not shown), the upper and lower housing portions  314  and  316  of the accumulator  310  may be joined in a threaded arrangement and include a plurality of o-rings for fluid sealing. 
     There is shown in  FIG. 14  a piston assembly  410  according to a twelfth embodiment. The assembly  410  includes a rod  412  and a piston  414 . The piston  414  includes a plurality of slots or apertures  416  that allow for fluid to flow into and out of an interior chamber of the piston  414 . In the illustrated embodiment, the apertures  416  are generally tapered or diamond-shaped apertures though the apertures may have other desired shapes. The apertures  416  are formed such that at the end travel of the piston rod  412  there is a portion or volume of fluid between a head (not shown) of the piston rod  412  and a respective end of the interior chamber of the piston  414  that is not in communication with the apertures  416 . In operation, the tapered geometry of the diamond shaped apertures  416  provides increased resistance to fluid flow around the head of the rod  412  at the end travel and thus dampens the travel of the rod  412 . 
     There is shown in  FIGS. 15 and 16  a piston assembly  510  according to a thirteenth embodiment. In this embodiment, the assembly  510  includes a rod  512 , a piston  514 , and a high-pressure seal and cushion  516 . The cushion  516  is mounted on one end  520  of the piston  514 . The cushion  516  includes a plurality, six shown, of protrusions  518  extending away from the end  520  of the piston  514  opposite the piston rod  512 . In operation, the cushion  516  dampens the travel of the piston  514  as the end  520  of the piston  514  approaches a piston housing (not shown). In operation, the protrusions  518  act as contact buffers between the piston  514  and the piston housing. Preferably, the protrusions  518  are made of a resilient elastomer or plastic, although such is not required. 
     There is shown in  FIGS. 17-19  an actuator  610  according to a fourteenth embodiment. In this embodiment, the actuator  610  includes a piston housing  612  and a piston  614 . An end face  616  of the piston  614  is formed with a protruding neck  618 . A collar  620 , in the form of an annular washer shaped metal plate, is disposed in an end  624  of the housing  612  facing the end face  616 . The collar  620  and the end face  616  cooperate to create a pocket of dampening hydraulic fluid  622  with in the housing  612 . In operation, hydraulic fluid is captured between the end face  616  of the piston  614  and the collar  620  to dampen the travel of the piston  614  as the piston  614  moves toward the end  624  of the housing  612 , the end of the piston travel being shown in  FIGS. 18 and 19 . 
     There is shown in  FIGS. 20-22  a portion of an actuator  710  according to a fifteenth embodiment. As shown in this embodiment, the actuator  710  includes a piston  712  having a check valve assembly  714 . In this embodiment, the check valve assembly  714  is disposed or secured in an end  716  of the piston  712  by a snap fit arrangement. The check valve assembly includes a cap  718 , a valve housing  720  and a spring  722  disposed therebetween. Preferably, the cap  718  and the valve housing are made from plastic. Most preferably, the cap  718  includes an over molded section  724  that acts as a seal between a main body  726  of the cap  718  and the end  716  of the piston  712 . As best shown in  FIG. 22 , in this embodiment the main body  726  of the cap  718  includes a plurality of fingers or tangs  728 . When the check valve assembly  714  is assembled the tangs  728  operatively engage a flange  730  within the housing  720  to secure the cap  718  and the housing  720  together. In an alternative embodiment, the check valve assembly  714  may be made from steel and press fit or otherwise secured to the end  716  of the piston  712  (not shown). In such an arrangement, the check valve assembly may also include a separate sealing member, such as o-ring. 
       FIG. 23  is a schematic view of a vehicle system utilizing an actuator for a roll control system according to a sixteenth preferred embodiment of the present invention. 
       FIG. 23  show a system  810  for controlling the roll of a motor vehicle. The system  810  comprises an anti-roll lock mechanism  812 . In the embodiment shown in  FIG. 23 , a second, rear anti-roll lock mechanism  821  is also provided. 
     Each of wheels  822 ,  824 ,  826  and  828  of the vehicle is rotationally mounted about a substantially horizontal axis to a member such as suspension arms  830 ,  832 ,  834  and  836 , respectively, which form part of an unsprung portion of the vehicle. The unsprung portion of the vehicle is in turn connected to a sprung portion of the vehicle through the anti-roll lock mechanisms  812  and  821  and anti-roll or anti-sway bars  838  and  840 . Each of the anti-roll lock mechanisms  812  and  821  includes a casing  842  and an input rod  844  reciprocally disposed in the casing. 
     The following description will describe the structure and operation of the lock mechanism  812  the associated roll bar  838  and the associated suspension arms  830  and  36 . Unless specifically stated otherwise the structure and operation of the lock mechanism  821 , the associated roll bar  840  and the associated suspension arms  832  and  834  will be similar. 
     One of the casing  842  and the input rod  844  of the anti-roll lock mechanism  812  is drivingly connected to the associated anti-roll bar  838 . The other of the casing  842  and the input rod  844  is drivingly connected to the suspension arm  830 . In the embodiment shown in  FIG. 23 , for example, the casing  842  of the front anti-roll lock mechanism  812  is connected to one free end of the front anti-roll bar  838 , while the portion of the input rod  844  extending generally downwardly from the casing  842  is connected to the front right suspension arm  830 . Similarly, the rear anti-roll bar  840  is coupled to the casing  842  of the right rear anti-roll lock mechanism  821  while the input rod  844  of the anti-roll lock mechanism  821  is connected to the suspension arm  832 . 
     An electronic control unit (ECU)  870  is provided to process inputs from one or more wheel speed sensors  872 , a lateral accelerometer sensor (accelerometer)  874 , and a steering angle sensor  876 . 
     In operation, the ECU  870  receives signals from the one or more wheel speed sensors  872 , the lateral accelerometer sensor (accelerometer)  874 , and the steering angle sensor  876  and controls each of the anti-roll lock mechanisms  812  and  821  as is described below. When the vehicle is traveling straight with little roll being introduced into the vehicle, the ECU  870  can unlock the anti-roll lock mechanism  812 . When the anti-roll lock mechanism  812  is unlocked, the input rod  844  can move relative to the casing  842 , thus permitting the associated free end of the anti-roll bar  838  to move freely relative to the suspension arm  830 . This gives the vehicle a more comfortable ride when traveling relatively straight, similar to a vehicle without any anti-roll bar. 
     However, as discussed above, when the vehicle is not traveling straight it is generally desirable to counter the roll of the vehicle for improved comfort and performance. The motor vehicle may begin a relatively high speed left hand turn, for example, which in absence of compensation by the system  810  would cause the unsprung portion of the vehicle to tend to roll generally clockwise about the longitudinal axis of the vehicle, helping urge the occupants of the vehicle to the outside of the turn (sliding downhill). 
     At the beginning of such a maneuver, the sensors  872 ,  874  and  876  of the present invention signal the instantaneous conditions to the ECU  870 . The ECU  870  in turn locks each of the anti-roll lock mechanisms  812  and  821 . This permits the anti-roll bars  838  and  840  to act to counteract the roll of the vehicle in a manner similar to conventional anti-roll bars. 
     To counteract anticipated vehicle roll in the opposite direction, for example as might be experienced during a right hand turn, the ECU  870  repeats this procedure and locks each of the anti-roll lock mechanisms  812  and  821 . In either case, as the sensors  872 ,  874  and  876  indicate an instantaneous or anticipated reduction or increase in the need for stability to deter vehicle roll, the ECU locks, unlock or maintains the state of each of the anti-roll lock mechanisms  812  and  821  as appropriate. 
     The principle and mode of operation of this invention have been explained and illustrated with regards to particular embodiments. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.