Abstract:
A damper assembly with a bypass for a vehicle comprises a pressure cylinder with a piston and piston rod for limiting the flow rate of damping fluid as it passes from a first to a second side of said piston. A bypass provides fluid pathway between the first and second sides of the piston separately from the flow rate limitation. In one aspect, the bypass is remotely controllable from a passenger compartment of the vehicle. In another aspect, the bypass is remotely controllable based upon one or more variable parameters associated with the vehicle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of U.S. provisional patent application Ser. No. 61/143,152, filed Jan. 7, 2009, which is herein incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    Embodiments of the present invention generally relate to a damper assembly for a vehicle. More specifically, the invention relates to a remotely operated bypass device used in conjunction with a vehicle damper. 
         [0003]    Vehicle suspension systems typically include a spring component or components and a dampening component or components. Typically, mechanical springs, like helical springs are used with some type of viscous fluid-based dampening mechanism and the two are mounted functionally in parallel. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention generally comprises a damper assembly having a bypass. In one aspect, the assembly comprises a cylinder with a piston and piston rod for limiting the flow rate of damping fluid as it passes from a first to a second portion of said cylinder. A bypass provides fluid pathway between the first and second portions of the cylinder and may be independent of, or in conjunction with, the aforementioned flow rate limitation. In one aspect, the bypass is remotely controllable from a passenger compartment of the vehicle, In another aspect, the bypass is remotely controllable based upon one or more variable parameters associated with the vehicle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    So that the manner in which the above recited features can be understood in detail, a more particular description may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0006]      FIG. 1  is a section view showing a suspension damping unit with a remotely operable bypass, the bypass in a closed position. 
           [0007]      FIG. 2  is a section view showing the suspension damping unit of  FIG. 1  with the bypass in an open position. 
           [0008]      FIG. 3  is a schematic diagram showing a control arrangement for a remotely operated bypass. 
           [0009]      FIG. 4  is a schematic diagram showing another control arrangement for a remotely operated bypass. 
           [0010]      FIG. 5  is a graph showing possible operational characteristics of the arrangement of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    As used herein, the terms “down” “up” “downward” upward” “lower” “upper” and other directional references are relative and are used for reference only.  FIGS. 1 and 2  are section views of a suspension damping unit  100 . The damper includes a cylinder portion  102  with a rod  107  and a piston  105 . Typically, the fluid meters, from one side to the other side of piston  105 , by passing through flow paths  110 ,  112  formed in the piston  105 . In the embodiment shown, shims  115 ,  116  are used to partially obstruct the flow paths  110 ,  112  in each direction. By selecting shims  115 ,  116  having certain desired stiffness characteristics, the dampening effects can be increased or decreased and dampening rates can be different between the compression and rebound strokes of the piston  105 . For example, shims  115  are configured to meter rebound flow from the rebound portion  103  of the cylinder  102  to the compression portion  104  of the cylinder  102 . Shims  116 , on the other hand, are configured to meter compression flow from the compression portion of the cylinder to the rebound portion. In one embodiment, shims  116  are not included on the rebound portion side leaving the piston essentially “locked out” in the compression stroke without some means of flow bypass. Note that piston apertures (not shown) may be included in planes other than those shown (e.g. other than apertures used by paths  110  and  112 ) and further that such apertures may, or may not, be subject to the shims  115 ,  116  as shown (because for example, the shims  115 ,  116  may be clover-shaped or have some other non-circular shape). 
         [0012]    A reservoir  125  is in fluid communication with the damper cylinder  102  for receiving and supplying damping fluid as the piston rod  107  moves in and out of the cylinder. The reservoir includes a cylinder portion  128  in fluid communication with the damper cylinder  102 . The reservoir also includes a floating piston  130  with a volume of gas on a backside (“blind end” side) of it, the gas being compressible as the reservoir cylinder  128  fills with fluid due to movement of the damper rod  107  and piston  105  into the damper cylinder  102 . Certain features of reservoir type dampers are shown and described in U.S. Pat. No. 7,374,028, which is incorporated herein, in its entirety, by reference. The upper portion of the rod  107  is supplied with a bushing set  109  for connecting to a portion of a vehicle wheel suspension linkage. In another embodiment, not shown, the upper portion of the rod  107  (opposite the piston) may be supplied with an eyelet to be mounted to one part of the vehicle, while the lower part of the housing shown with an eyelet  108  is attached to another portion of the vehicle, such as the frame, that moves independently of the first part. A spring member (not shown) is usually mounted to act between the same portions of the vehicle as the damper. As the rod  107  and piston  105  move into cylinder  102  (during compression), the damping fluid slows the movement of the two portions of the vehicle relative to each other due to the incompressible fluid moving through the shimmed paths  110 ,  112  (past shims  116 ) provided in the piston  105  and or through the metered bypass  150 , as will be described herein. As the rod  107  and piston  105  move out of the cylinder  102  (during extension or “rebound”) fluid meters again through shimmed paths  110  and  112  and the flow rate and corresponding rebound rate is controlled by the shims  115 . 
         [0013]    In one embodiment as shown in the Figures, a bypass assembly  150  is designed to permit damping fluid to travel from a first side of the piston to the other side without traversing shimmed flow paths  110 ,  112  that may otherwise be traversed in a compression stroke of the damper. In  FIG. 1 , the bypass  150  is shown in a closed position (e.g. a valve  170  obstructs fluid passage through entry way  160 ) and in  FIG. 2  the bypass is shown in an open position (e.g. valve  170  is open and fluid may flow through passage  160 ). In  FIG. 2 , the piston is shown moving downward in a compression stroke, the movement shown by arrow  157 . The bypass includes a cylindrical body  155  that communicates with the damper cylinder  102  through entry  160  and exit  165  pathways. In  FIG. 2 , with the bypass open, the flow of fluid through the bypass is shown by arrow  156 . In one embodiment an entry valve  170  is located at the entry pathway  160  with a valve member  175  sealingly disposed and axially movable within the valve body. A needle-type check valve  180 , allowing flow in direction  156  and checking flow in the opposite direction, is located proximate exit pathway  165 . The needle valve sets flow resistance through the bypass  150  during compression and restricts fluid from entering the bypass cylinder  150  during a rebound stroke of the damper piston  105 . In one embodiment the needle valve  180  is spring loaded and biased closed. The initial compression force of the biasing spring  182  is adjusted via adjuster  183  thereby allowing a user to preset the needle valve opening pressure and hence the compression damping fluid flow rate (hence damping rate) through the bypass. The biasing force of the needle valve spring  182  is overcome by fluid pressure in the cylinder  155  causing the needle valve  180  to open during a compression stroke. 
         [0014]    The entry pathway  160  and entry valve  170  in the embodiments shown in  FIGS. 1 and 2 , are located towards a lower end of the damper cylinder  102 . In one embodiment, as selected by design, the bypass will not operate after the piston  105  passes the entry pathway  160  near the end of a compression stroke. This “position sensitive” feature ensures increased dampening will be in effect near the end of the compression stoke to help prevent the piston from approaching a “bottomed out” position (e.g. impact) in the cylinder  102 . In some instances, multiple bypasses are used with a single damper and the entry pathways for each may be staggered axially along the length of the damper cylinder in order to provide an ever-increasing amount of dampening (and less bypass) as the piston moves through its compression stroke and towards the bottom of the damping cylinder. Certain bypass damper features are described and shown in U.S. Pat. Nos. 6,296,092 and 6,415,895, each of which are incorporated herein, in its entirety, by reference. 
         [0015]    In one embodiment the bypass  150 , as shown in  FIGS. 1 and 2 , includes a fluid (e.g. hydraulic or pneumatic) fitting  201  disposed at an end of the entry valve body  170 . The fluid fitting  201  is intended to carry a control signal in the form of fluid pressure to the valve member  175  in order to move the valve  170  from an open to a closed position. In one embodiment, valve member  175  is biased open by an annular spring  171  located between an upper end of the valve member  175  and the lower axial end face of tube  155 . 
         [0016]    In one example, the valve  170  is moved to a closed position and the bypass feature disabled by remote control from a simple operator-actuated switch located in the passenger compartment of the vehicle. In one embodiment, fluid pressure for controlling (e.g. closing) the valve  170  is provided by the vehicle&#39;s own source of pressurized hydraulic fluid created by, for example, the vehicle power steering system. In one embodiment, pneumatic pressure is used to control (e.g. close) the valve  170  where the pneumatic pressure is generated by an on-board compressor and accumulator system and conducted to the valve  170  via a fluid conduit. In one embodiment, a linear electric motor (e.g. solenoid), or other suitable electric actuator, is used to move valve member  175  axially within valve body. A shaft of the electric actuator (not shown) may be fixed to the valve member  175  such that axial movement of the shaft causes axial movement of the valve member  175 . In one embodiment, the electric actuator is configured to “push” the valve member  175  to a closed position and to “pull” the valve member  175  to an open position depending on the direction of the current switched through the actuator. In one embodiment, the valve  170  is spring biased, for example, to an open position as previously described herein, and the actuator, being switched by a potentiometer or other suitable current or voltage modulator, moves the valve member  175  against the biasing spring to a closed position or to some position of desired partial closure (depending on the operation of the switch). Such partial closure increases the compression stiffness of the damper but does not provide the more rigid dampening of complete bypass closure. In such electrical embodiments, the solenoid is wired (e.g. via electrical conduit) into the vehicle electrical system and switched to move the valve  170  as described herein. 
         [0017]      FIG. 3  is a schematic diagram illustrating a sample circuit  400  used to provide remote control of a bypass valve using a vehicle&#39;s power steering fluid (although any suitable fluid pressure source may be substituted for reservoir  410  as could an electrical current source in the case of an electrically actuated valve member  175 ). As illustrated, a fluid pathway  405  having a switch-operated valve  402  therein runs from a fluid (or current) reservoir  410  that is kept pressurized by, in one embodiment, a power steering pump (not shown) to a bypass valve  170  that is operable, for example, by a user selectable dash board switch  415 . The valve  402  permits fluid to travel to the bypass valve  170 , thereby urging it to a closed position. When the switch  415  is in the “off” position, working pressure within the damper, and/or a biasing member such as a spring  171  (as described herein in relation to  FIGS. 1 &amp; 2 ) or annular atmospheric chamber (not shown), returns the bypass to its normally-open position. Hydraulically actuated valving for use with additional components is shown and described in U.S. Pat. No. 6,073,536 and that patent is incorporated by reference herein in its entirety. While  FIG. 3  is simplified and involves control of a single bypass valve, it will be understood that the valve  402  could be plumbed to simultaneously provide a signal to two or more bypass valves operable with two or more vehicle dampers and or with a single damper having multiple bypass channels and multiple corresponding valves (e.g.  175 ). Additional switches could permit individual operation of separate damper bypass valves in individual bypass channels, whether on separate dampers or on the same multiple bypass damper, depending upon an operator&#39;s needs. While the example of  FIG. 3  uses fluid power for operating the bypass valve, a variety of means are available for remotely controlling a valve. For instance, a source of electrical power from a 12 volt battery could be used to operate a solenoid member, thereby shifting valve member  175  in bypass valve  170  between open and closed positions. The signal can be either via a physical conductor or an RF signal (or other wireless such as Bluetooth, WiFi, ANT) from a transmitter operated by the switch  415  to a receiver operable on the bypass valve  175 . 
         [0018]    A remotely operable bypass like the one described above is particularly useful with an on/off road vehicle. These vehicles can have as much as 20′ of shock absorber travel to permit them to negotiate rough, uneven terrain at speed with usable shock absorbing function. In off-road applications, compliant dampening is necessary as the vehicle relies on its long travel suspension when encountering off-road obstacles, Operating a vehicle with very compliant, long travel suspension on a smooth road at higher speeds can be problematic due to the springiness/sponginess of the suspension. Such compliance can cause reduced handling characteristics and even loss of control. Such control issues can be pronounced when cornering at high speed as a compliant, long travel vehicle may tend to roll excessively. Similarly, such a vehicle may pitch and yaw excessively during braking and acceleration. With the remotely operated bypass “lock out” described herein, dampening characteristics of a shock absorber can be completely changed from a compliantly dampened “springy” arrangement to a highly dampened and “stiffer” system ideal for higher speeds on a smooth road. In one embodiment where compression flow through the piston is completely blocked, closure of the bypass  150  results in substantial “lock out” of the suspension (the suspension is rendered essentially rigid). In one embodiment where some compression flow is allowed through the piston (e.g. ports  110 ,  112  and shims  116 ), closure of the bypass  150  results in a stiffer but still functional compression damper. In one embodiment, the needle valve  180  is tuned (using adjuster  183 ), and the shims  116  sized, to optimize damping when the bypass  150  is open and when bypass  150  is closed based on total anticipated driving conditions. In one embodiment the needle valve adjuster  183  is connected to a rotary electrical actuator so that adjustment of the needle valve4  180  may be performed remotely as disclosed herein referencing the bypass valve  170 . 
         [0019]    In addition to, or in lieu of, the simple, switch operated remote arrangement of  FIG. 3 , the remote bypass can be operated automatically based upon one or more driving conditions.  FIG. 4  shows a schematic diagram of a remote control system  500  based upon any or all of vehicle speed, damper rod speed, and damper rod position. One embodiment of  FIG. 4  is designed to automatically increase dampening in a shock absorber in the event a damper rod reaches a certain velocity in its travel towards the bottom end of a damper at a predetermined speed of the vehicle. In one embodiment the system adds dampening (and control) in the event of rapid operation (e.g. high rod velocity) of the damper to avoid a bottoming out of the damper rod as well as a loss of control that can accompany rapid compression of a shock absorber with a relative long amount of travel. In one embodiment the system adds dampening (e.g. closes or throttles down the bypass) in the event that the rod velocity in compression is relatively low, but the rod progresses past a certain point in the travel. Such configuration aids in stabilizing the vehicle against excessive low rate suspension movement events such as cornering roll, braking and acceleration yaw and pitch and “g-out.” 
         [0020]      FIG. 4  illustrates, for example, a system including three variables: rod speed, rod position and vehicle speed. Any or all of the variables shown may be considered by processor  502  in controlling the valve  175 . Any other suitable vehicle operation variable may be used in addition to or in lieu of the variables  515 ,  505 ,  510  such as for example piton rod compression strain, eyelet strain, vehicle mounted accelerometer data or any other suitable vehicle or component performance data. In one embodiment, a suitable proximity sensor or linear coil transducer or other electro-magnetic transducer is incorporated in the dampening cylinder to provide a sensor to monitor the position and/or speed of the piston (and suitable magnetic tag) with respect to the cylinder. In one embodiment, the magnetic transducer includes a waveguide and a magnet, such as a doughnut (toroidal) magnet that is joined to the cylinder and oriented such that the magnetic field generated by the magnet passes through the piston rod and the waveguide. Electric pulses are applied to the waveguide from a pulse generator that provides a stream of electric pulses, each of which is also provided to a signal processing circuit for timing purposes. When the electric pulse is applied to the waveguide a magnetic field is formed surrounding the waveguide. Interaction of this field with the magnetic field from the magnet causes a torsional strain wave pulse to be launched in the waveguide in both directions away from the magnet. A coil assembly and sensing tape is joined to the waveguide. The strain wave causes a dynamic effect in the permeability of the sensing tape which is biased with a permanent magnetic field by the magnet, The dynamic effect in the magnetic field of the coil assembly due to the strain wave pulse, results in an output signal from the coil assembly that is provided to the signal processing circuit along signal lines. By comparing the time of application of a particular electric pulse and a time of return of a sonic torsional strain wave pulse back along the waveguide, the signal processing circuit can calculate a distance of the magnet from the coil assembly or the relative velocity between the waveguide and the magnet. The signal processing circuit provides an output signal, either digital or analog, proportional to the calculated distance and/or velocity. Such a transducer-operated arrangement for measuring rod speed and velocity is described in U.S. Pat. No. 5,952,823 and that patent is incorporated by reference herein in its entirety. 
         [0021]    While a transducer assembly located at the damper measures rod speed and location, a separate wheel speed transducer for sensing the rotational speed of a wheel about an axle includes housing fixed to the axle and containing therein, for example, two permanent magnets. In one embodiment the magnets are arranged such that an elongated pole piece commonly abuts first surfaces of each of the magnets, such surfaces being of like polarity. Two inductive coils having flux-conductive cores axially passing therethrough abut each of the magnets on second surfaces thereof, the second surfaces of the magnets again being of like polarity with respect to each other and of opposite polarity with respect to the first surfaces. Wheel speed transducers are described in U.S. Pat. No. 3,986,118 which is incorporated herein by reference in its entirety. 
         [0022]    In one embodiment, as illustrated in  FIG. 4 , a logic unit  502  with user-definable settings receives inputs from the rod speed  510  and location  505  transducers as well as the wheel speed transducer  515 . The logic unit is user-programmable and depending on the needs of the operator, the unit records the variables and then if certain criteria are met, the logic circuit sends its own signal to the bypass to either close or open (or optionally throttle) the bypass valve  175 . Thereafter, the condition of the bypass valve is relayed back to the logic unit  502 . 
         [0023]      FIG. 5  is a graph that illustrates a possible operation of one embodiment of the bypass assembly  500  of  FIG. 4 . The graph assumes a constant vehicle speed. For a given vehicle speed, rod position is shown on a y axis and rod velocity is shown on an x axis. The graph illustrates the possible on/off conditions of the bypass at combinations of relative rod position and relative rod velocity. For example, it may be desired that the bypass is operable (bypass “on”) unless the rod is near its compressed position and/or the rod velocity is relatively high (such as is exemplified in  FIG. 5 ). The on/off configurations of  FIG. 5  are by way of example only and any other suitable on/off logic based on the variable shown or other suitable variables may be used. In one embodiment it is desirable that the damper become relatively stiff at relatively low rod velocities and low rod compressive strain (corresponding for example to vehicle roll, pitch or yaw) but remains compliant in other positions. In one embodiment the piston rod  107  includes a “blow off” (overpressure relief valve typically allowing overpressure flow from the compression side to the rebound side) valve positioned in a channel coaxially disposed though the rod  107  and communicating one side of the piston (and cylinder) with the other side of the piston (and cylinder) independently of the apertures  110 , 112  and the bypass  150 . 
         [0024]    In one embodiment, the logic shown in  FIG. 4  assumes a single damper but the logic circuit is usable with any number of dampers or groups of dampers. For instance, the dampers on one side of the vehicle can be acted upon while the vehicles other dampers remain unaffected. 
         [0025]    While the examples illustrated relate to manual operation and automated operation based upon specific parameters, the remotely operated bypass can be used in a variety of ways with many different driving and road variables. In one example, the bypass is controlled based upon vehicle speed in conjunction with the angular location of the vehicle&#39;s steering wheel. In this manner, by sensing the steering wheel turn severity (angle of rotation), additional dampening can be applied to one damper or one set of dampers on one side of the vehicle (suitable for example to mitigate cornering roll) in the event of a sharp turn at a relatively high speed. In another example, a transducer, such as an accelerometer measures other aspects of the vehicle&#39;s suspension system, like axle force and/or moments applied to various parts of the vehicle, like steering tie rods, and directs change to the bypass valve positioning in response thereto. In another example, the bypass can be controlled at least in part by a pressure transducer measuring pressure in a vehicle tire and adding dampening characteristics to some or all of the wheels in the event of, for example, an increased or decreased pressure reading. In still another example, a parameter might include a gyroscopic mechanism that monitors vehicle trajectory and identifies a “spin-out” or other loss of control condition and adds and/or reduces dampening to some or all of the vehicle&#39;s dampers in the event of a loss of control to help the operator of the vehicle to regain control. 
         [0026]    While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.