Abstract:
A vibration damper for a vehicle suspension system includes a pumping cylinder concentrically aligned inside a housing defining a pumping chamber having a piston stroking therein for reducing the level of vehicle vibration. An intermediate cylinder defines an intermediate chamber with the pumping cylinder and an outer chamber with the housing. Suspension fluid flows throughout each of the chambers. A valve is operably connected to an air supply of a suspension system having an air pressure relative to a mass loaded on the vehicle. The controls the distribution of fluid between the chambers relative to the pressure of the air supply and controls the amount of vibration damping inside the pumping chamber relative to the mass loaded on the vehicle.

Description:
TECHNICAL FIELD 
     The subject invention relates generally to an improved damper assembly for a motor vehicle. More specifically, the subject invention relates to an adjustable damper for a motor vehicle. 
     BACKGROUND OF THE INVENTION 
     Suspension dampers are used in combination with vehicle suspension systems to reduce the amount of vibration transmitted through a motor vehicle from such variables as, for example, potholes, rough road surfaces, and unbalanced tires. These dampers are typically adjusted to meet the requirements of a particular mass of the vehicle. Often, the vehicle will be used to transport a load that will significantly increase the mass being supported by the suspension system. This adversely affects the damping properties of the suspension damper as is evident by increased amounts of vibration transmitted through a vehicle when a heavy load is being transported. 
     A typical suspension damper includes a housing with a pumping cylinder axially aligned inside the housing defining a pumping chamber. A piston and rod is located in the pumping cylinder so that the piston moves in relation to movements or vibrations in the suspension system. Damping fluid fills the pumping cylinder around the piston and partially fills the area between the housing and the pumping cylinder, which acts as a reservoir. A barrier (or base valve) is located at the end of the pumping cylinder away from the rod that separates the interior of the pumping cylinder from the area between the pumping cylinder and the housing. The piston and the barrier are equipped with a system of valves and orifices such that when the suspension damper is reacting to a suspension move, damping fluid is forced to flow through these valves and orifices. The resistance of the damping fluid to flow through the valves and orifices causes the suspension damper to generate a force resisting the movement of the suspension, thus damping the movement. The damping characteristics of this type of damper, as described, are generally non-adjustable after being manufactured. 
     The valves and orifices used to control a suspension damper of this type are setup so that both the piston and base valve have some damping control during a compression stroke and an extension (rebound) stroke of the damper. However, during a compression stroke, most of the damping restriction is in the base valve, and during a rebound stroke, most of the damping restriction is in the piston. During a compression stroke, as the rod is pressed into the area of the pumping cylinder, damping fluid is forced through the base valve into the reservoir area and through the piston in a direction away from the base valve. During a rebound stroke, damping fluid is forced through the piston in a direction toward the base valve and is drawn into the pumping cylinder, from the reservoir, through the base valve. It should be noted that in both cases, most damping control exerted by these valves is applied to damping fluid flowing in a direction toward the base valve and to the reservoir. 
     One method used to provide external control to this type of damper uses an additional axial cylinder to provide an additional damping fluid flow path from a location over the piston and base valve to the reservoir. An externally controllable electric valve and an additional valve and orifice set are positioned to control and damp the additional flow. Working in parallel with the other fixed valve and orifice sets, this allows external control of the suspension damper performance. Electrically controlled systems such as this require separate control systems that add significant cost to a vehicle. It would be desirable to utilize an adjustable damper having an actuation member that does not require a controller to adjust the characteristics of a suspension damper. 
     SUMMARY OF THE INVENTION 
     The present invention is a suspension damper assembly for a vehicle suspension system. A pumping cylinder is axially aligned inside a housing and defines a pumping chamber. An intermediate cylinder defines an intermediate chamber with the pumping cylinder and an outer chamber with the housing. Suspension fluid flows in the area between the pumping cylinder and the intermediate cylinder. The area between the intermediate cylinder and the housing functions as a reservoir. A piston strokes inside the pumping chamber damping the vibration derived from the suspension system. A valve controls the distribution of fluid between the chambers thereby controlling the amount of vibration damping inside the pumping chamber. 
     The valve includes a spring actuated member to restrict the flow of fluid between the outer chamber and the intermediate chamber. A locator system is provided as a means of applying external control to the spring actuated member. The locator system includes a bellows disposed inside an air chamber, such that as pressure inside the air chamber is increased, the bellows constricts or becomes shorter. A projection from the end of the bellows extends out of the air chamber and contacts the spring actuated member, acting against the spring. When pressure in the air chamber is relatively high, the bellows is constricted and the bellows projection is withdrawn allowing the spring actuated member spring to locate the valve member to restrict flow. When the pressure in the air chamber is reduced, the bellows expands correspondingly. The bellows projection, working against the spring, moves the valve member and allows increased flow. By increasing the amount of flow to the intermediate chamber, the overall level of damping provided by the suspension damper is reduced. Connecting this device, as shown, to an air leveling system could provide damping control corresponding to vehicle load. 
     The present invention adjusts the damping properties of the suspension damper without utilizing a controller or a sophisticated electrical valve. This type of system could be applied such that air pressure, used in some suspensions to maintain vehicle attitude under varying loads, could be used to automatically adjust suspension damping, again compensating for the vehicle load. The simple mechanical concept utilizing air pressure from the suspension system is lest costly and more durable than the prior art electric and pneumatic designs. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
     FIG. 1 is a cross-sectional view of the inventive damper; 
     FIG. 2 is a sectional view showing the inventive valve of the subject invention showing the spring actuated member in closed position; 
     FIG. 3 is a sectional view showing the inventive valve of the subject invention showing the spring actuated member in open position; 
     FIG. 4 is a sectional view of the inventive damper showing the fluid cap. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, a damper assembly is generally shown at  10 . The damper assembly includes a housing  12  and a pumping cylinder  14  concentrically aligned inside the housing  12 . The pumping cylinder  14  defines a pumping chamber  16  having a piston  18  slidably disposed therein. An intermediate cylinder  20  defines an intermediate chamber  22  with the pumping cylinder  14  and an outer chamber  24  with the housing  12 . A valve  26  is affixed to the housing  12  and controls the distribution of fluid between each of the chambers  16 ,  22 ,  24 . 
     The piston  18  is affixed to a piston shaft  28  having a distal end  30  projecting outwardly of the housing  12 . The distal end  30  includes a coupling  32  that attaches to the suspension system (not shown) of the vehicle. The piston  18  includes piston valving  34  that resists the flow of fluid when the piston shaft  28  is being stroked outwardly of the housing  12  by the suspension system. The piston valve  34  opens when the piston shaft  28  is being forced into the housing  12  providing little or no resistance to the flow of fluid through the piston  18 . 
     The piston shaft  28  is slidably inserted through a fluid cap  36 . The cap includes a notch  38  allowing a free flow of fluid between the intermediate chamber  22  and the pumping chamber  16 . A seal  40  prevents the flow of fluid from the outer chamber  24  into either the intermediate chamber  22  or the pumping chamber  16 . 
     A flow cap  42  is disposed at an opposite end of the housing from the fluid cap  36 . As best seen in FIGS. 2 and 3, the flow cap includes an inlet channel  44  and an outlet channel  46 . A valving stack  48  and spring  49  abuts the flow cap  42  inside the pumping chamber  16 . The valving stack  48  allows fluid flow in the outlet channel  46  and seals outward flow from the pumping chamber  16  through the inlet channel  44  while allowing flow into the pumping chamber  16  through the inlet channel  44 . Therefore, fluid can flow through the inlet channel  44  into the pumping chamber  16  with very little resistance. An outlet valving stack  50  is disposed at the opposite end of the outlet channel  46  from the inlet valving stack  48 . An inlet valving stack aperture  52  allows fluid from the pumping chamber  16  to enter the outlet channel  46 . Under enough pressure, the outlet valving stack  50  can be flexed allowing fluid to leave the pumping chamber  16  through the outlet channel  46 . A bracket cap  54  covers the flow cap  42  and seals to the housing  12 . The bracket cap  54  allows fluid from the outer chamber  24  to surround the flow cap  42 . Therefore, fluid from the outer chamber  24  can enter the pumping chamber  16  through the inlet channel  44 , and fluid from the pumping chamber  16  can enter the outer chamber  24  through the outlet channel  46 . Accordingly, when the piston shaft  28  is being driven into the housing  12 , the piston  18  forces fluid through the outlet channel  46  and into the outer chamber  24 . When the piston shaft  28  is telescoped outwardly of the housing  12  fluid will be drawn through the inlet channel  44  from the outer chamber  24 . 
     The valve includes a spring actuated member  56  and an air chamber  58 . A casing  60  surrounds the valve  26  securing the valve  26  to the housing  12 . The spring actuated members  56  includes a valve cap  62  having at least one valve cap aperture  64  disposed therein. A funnel  66  channels fluid from the intermediate chamber  22  into the spring actuated member  56 . The funnel  66  seals to the valve cap  62  thereby preventing fluid from leaking from the intermediate chamber  22  into the outer chamber  24  without having passed through the entirety of the spring actuated member  56 . 
     The spring actuated member  56  includes a sleeve  68  having a spool  70  slidably disposed therein. The sleeve  68  includes at least one sleeve aperture  72  allowing fluid to exit the spring actuated member  56  therethrough. The sleeve aperture  72  leads to a gap  74  formed between the casing  60  and the valve  26 . The gap  74  opens into the outer chamber  24 . Accordingly, a fluid path exists starting from the intermediate chamber  22  proceeding through the funnel  66 , through the valve cap aperture  64 , into the spring actuated member  56  through the sleeve aperture  72 , into the gap  74 , and into the outer chamber  24  (shown in FIG.  3 ). 
     A fastener  76  and nut  77  secure a deflector disk  78  over the valve cap aperture  64 . A channel disk  79  is disposed between the deflector disk  78  and the valve cap  62  for channeling fluid through the valve cap apertures  64 . The deflection disk  78  flexes allowing fluid to enter the spring actuated member  56  from the intermediate chamber  22  and returns to original position to prevent fluid from leaving the spring actuated member  56  in the reverse direction. A spring  80  is supported by the fastener  76  and is received by the underside of the spool  70 . The spring  80  biases the spool  70  for closing the sleeve apertures  72 . 
     A bellows  82  is disposed inside the air chamber  58 . The bellows  82  contracts when air pressure increases and expands when air pressure decreases. A nozzle  84  connects the air chamber  58  to an air supply, typically of a vehicle suspension system. When the vehicle is under a heavy load, the suspension system is compressed increasing the pressure in the air supply. The increased pressure is transferred to the air chamber  58  via the nozzle  84 . When the vehicle is subjected to a light load, the air supply for the suspension system has a lower pressure reducing the pressure in the air chamber  58 . A flow regulator  86  is inserted into the nozzle  84  for reducing pressure spikes in the air chamber  58  resulting from a rough road surface. A seal disk  88  separates the air chamber  58  from the spring actuated member  56 . The bellows  82  includes a pin  90  that is slidably inserted through the seal disk  88 . A pin seal  92  seals the pin  90  to the seal disk  88 . A valve seal  94  seals the seal disk  88  to the valve  26 . 
     The pin  90  engages the spool  70  providing a counter-biasing force to the spring  80 . When the air supply increases the air pressure in the air chamber  58 , the bellows  82  contracts drawing the pin  90  away from the spool  70  allowing the spool  70  to move inwardly under the force of the spring  80  thereby closing the sleeve aperture  72 . When the air supply reduces air pressure in the air chamber, the bellows  82  expands forcing the pin  90  outwardly against the spool  70  forcing the spool  70  away from the sleeve apertures  72 . As will now be explained, the amount of damping provided by the damper assembly  10  is automatically adjusted according to the load the vehicle is carrying due to the contraction and expansion of the bellows  82  from the air pressure in the suspension air supply. 
     When the vehicle is under a heavy load, it is desirable to have a more firm damping feel from the suspension system. Under the heavier load, the spring actuated member  56  is sealed preventing the flow of fluid through the valve  26 . Therefore, when the piston shaft  28  is forced into the housing  12 , fluid will be forced out of the pumping chamber  16  through the flow cap  42  and into the outer chamber  24 . As fluid leaves the pumping chamber  16  the pressure begins to drop drawing fluid from the intermediate chamber  22 . Because the spring actuated member  56  is closed, fluid will only be drawn from the intermediate chamber  22  into the pumping chamber  16  and not from the outer chamber  24 . Further, fluid is not drawn from the intermediate chamber  22  into the outer chamber  24 . Therefore, a high fluid pressure is maintained in the pumping chamber  16  providing a firm vibration damping feel to the vehicle. 
     When the vehicle is transporting a light load, the air supply from the suspension system transfers a low air pressure to the air chamber  58  allowing the bellows  82  to force the spool  70  downward opening the sleeve apertures  72  resulting in a change of the fluid flow throughout the assembly  10 . As shown in FIG. 3, Fluid is now drawn from the intermediate chamber  22  through the valve  26  and into the outer chamber  24 . This fluid flow pattern reduces the pressure in the intermediate chamber  22  thereby drawing fluid from the pumping chamber  16  through the notch  38 . This reduces the amount of fluid in the pumping chamber  16  giving the vibration damper a softer feel. The piston  18  still forces fluid into and out of the pumping chamber  16  through the flow cap  42  as is explained above. 
     The amount of vibration damping provided by the damper assembly  10  is adjusted according to the load on the vehicle. Various levels of vibration damping are provided by the damper assembly  10  with the pressure in the air supply of the suspension system, which is determined by the load on the vehicle assembly. Therefore, the damper assembly  10  is self-adjusting and operates without the assistance of any vehicle electronics. 
     The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, wherein reference numerals are merely for convenience and are not to be in any way limiting, the invention may be practiced otherwise than as specifically described.