Abstract:
A number of embodiments of four-wheeled vehicle suspension systems have interrelated front and rear shock absorbers so as to provide good control under normal suspension travel as well as resistance toward leaning, pitching, diving and squatting. In each embodiment, the normal fluid dampers having only a single shock absorber valve therein are interrelated with pressure controls that comprise four hydraulic cylinder portions which communicate with each other through various paired arrangements so as to provide this control and simplification of damping.

Description:
BACKGROUND OF INVENTION  
         [0001]    This invention relates to a suspension system for a four-wheeled vehicle and more particularly to an improved, simplified and more effective suspension system for controlling all running conditions, which the vehicle encounters.  
           [0002]    An arrangement has been proposed for suspending four-wheeled vehicles that employs individual shock absorbers at each wheel which have a relatively simple damping arrangement in them. However, the shock absorbers of paired wheels are coupled together with a pressure control mechanism that provides additional damping under certain characteristics. This type of system is show in Japanese Published Application. Hei 06-72127 and in its United States equivalent, U.S. Pat. No. 5,486,018, entitled “SUSPENSION SYSTEM FOR FOUR-WHEELED VEHICLES” issued Jan. 23, 1996 and the assigned to the assignee hereof. That patent shows a number of arrangements of such interrelated suspension systems. One that shows considerable sophistication appears in FIG. 13 of that U.S. patent and is reproduced here a FIG. 1. The details of the interrelationship between the various shock absorbers and the control arrangement is shown in more detail in FIG. 2.  
           [0003]    As shown therein, there are four shock absorbers indicated at  11 LF,  11 RF,  11 LR and  11 RR comprising the cushioning units associated with the four wheels of the vehicle at its corners. Each of the shock absorbers  11  is mounted between the wheel suspension system and the vehicle body in a manner, which will be generally described, as will the individual construction of each shock absorber  11 , which are identical.  
           [0004]    Each shock absorber  11  includes a body portion  12  that defines a cylinder bore in which a piston  13  is supported. The piston  13  divides the cylinder bore into an upper chamber  14  and a lower chamber  115 . A piston rod  16  extends through the upper chamber  14  and has a trunion  17  for attachment to the wheel suspension system or the vehicle body. A trunion  18  on the cylinder  12  accommodates the other connection.  
           [0005]    A passageway  19  extends between the chambers  14  and  15  and has an orifice  21  for providing individual wheel damping control.  
           [0006]    The individual shock absorbers  11  are interconnected with each other by means of an interconnecting control arrangement, indicated generally by the reference numeral  22 . This control arrangement  22  includes individual passageways  23 ,  24 ,  25  and  26 , which interconnect the chambers  15  of the shock absorber  11 LF,  11 RF,  11 LR and  11 RR with a pressure control, indicated generally by the reference numeral  27 .  
           [0007]    This pressure control  27  is shown in more detail in FIG. 2 and includes a body  28  in which four cylinder bores  29 ,  31 ,  32  and  33  are formed. Pistons  34 ,  35 ,  36  and  37  reciprocate in the cylinder bores  29 ,  31 ,  32  and  33 , respectively. These pistons  34 ,  35 ,  36  and  37  are all connected for simultaneous movement by means of a bridging member  38 , which extends into a pressurized gas chamber  39 . This chamber  39  is pressurized to a suitable pressure with an inert gas such as nitrogen.  
           [0008]    Thus, each shock absorber chamber  15  is in communication with a respective one of pressure control volumes  41 ,  42 ,  43  and  44  formed in the control body  28  between the pistons  34 ,  35 ,  36  and  37  and the cylinder bores  29 ,  31 ,  32  and  33 , respectively.  
           [0009]    Certain of the shock absorber chambers  15  are paired with each other via communicating passageways  45 ,  46  and  47  which connect the control pressure chambers  41  and  42 ,  42  and  43 , and  43  and  44  together. Flow controlling orifices  48 ,  49  and  51  are positioned in the passages  45 ,  46  and  47 , respectively.  
           [0010]    When each wheel encounters the same obstacle at substantially the same time, each piston  13  will move in its respective shock absorber  11  to decrease the volume in the chamber  15 . This motion is dampened by the flow through the orifice  21  into the chamber  14 . However, since the piston rod  16  extends into the chamber  14  and displaces some of its volume, more fluid is expelled through the conduits  23 ,  24 ,  25  and  26  than the chambers  14  can accommodate. This excess displaced fluid flows to the chambers  41 ,  42 ,  43  and  44 , respectively. Since equal volume of fluid is displaced from each shock absorber  11 , the pistons  34 ,  35 ,  36  and  37  will move uniformly and the control device  27  will provide no additional damping.  
           [0011]    If, however, there is a pitching motion, which tends to cause the vehicle weight to shift to the front, there will be more compression in the chambers  15  and  16  of the shock absorbers  11 LF and  11 RF than in the shock absorbers  11 LR and  11 RR. In fact, these shock absorbers will tend to move in the opposite direction. When this occurs, flow will pass through the orifices  48  and  51  from the chambers  41  and  44  into the chambers  42  and  43 , respectively. Hence, this will provide damping from the pitching action, which might otherwise occur in addition to the damping provided by the individual shock absorbers  11 .  
           [0012]    In a similar manner, if the vehicle is rounding a curve which tends to cause the body to roll to the right i.e. when making a left-had turn, fluid will flow from the shock absorber  11 LR to the shock absorber  11 RR through the orifice  49  so to resist roll. However, there is no such roll resistance provided at the front and thus, it is very difficult to set the arrangement for overall damping to suit all conditions.  
           [0013]    It is, therefore, a principal object to this invention to provide an improved shock absorber and suspension arrangement for a four-wheeled vehicle that will provide good damping for individual wheel suspension travels and also so as to preclude roll and pitch in all directions.  
           [0014]    It a further object to this invention to provide an improved and simplified suspension system of this type and that will achieve these results.  
         SUMMARY OF INVENTION  
         [0015]    A first feature of this invention is adapted to be embodied in a suspension system for a vehicle having at least four wheels, each of which is supported for suspension movement by a vehicle body. Each of four damping elements, each having a pair of relatively moveable members defining a respective first chamber, are interposed between a respective one of the wheels and the vehicle body for varying the volume of the first fluid chamber upon suspension movement of the respective one wheel. Each of the damping elements has a respective damping arrangement for damping the flow of fluid from the respective one of the first fluid chambers. A first conduit interconnects a first pair of the first fluid chambers of two of the damping elements and a first control arrangement is provided for precluding fluid flow through the first conduit in response to a first suspension condition and for providing a damped flow through the first conduit in response to a second suspension condition. A second conduit interconnects the second pair of the first fluid chambers of the remaining two of the damping units. A second control arrangement is provided in the second conduit for precluding fluid flow through the second conduit in response to a first suspension condition and for providing a damp flow through the second conduit in response to a second condition. A third conduit interconnects a third pair of the first fluid chambers other than those paired by the first and second conduits. A third control arrangement is provided in the third conduit for precluding fluid flow through the third conduit in response to a first suspension condition and for providing a damped flow through the third conduit in response to a second suspension condition. A fourth pair of the first fluid chambers other than those paired by the first, second and third conduits are interconnected by a fourth conduit. A fourth control arrangement is provided in the fourth conduit for precluding fluid flow through the fourth conduit in response to a first suspension condition and for providing a damped flow through the fourth conduit in response to a second suspension condition.  
           [0016]    Another feature of the invention is embodied in an accumulator and control device for interconnection between four hydraulic damping units for controlling their respective damping action. The device comprises a housing defining first, second, third and fourth fluid chambers each adapted to exchange fluid with a respective one of said damping units. First, second, third and fourth accumulator pistons are each received in a respective one of the fluid chambers. The pistons and fluid chambers each define a fluid side for exchanging hydraulic fluid with the respective hydraulic damping unit and an accumulator side for maintaining a pressure in the hydraulic fluid. Four conduits each having a flow control therein interconnect different pairs of the fluid chambers and control the flow therebetween. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0017]    [0017]FIG. 1 is a partially schematic view of a prior art type of vehicle suspension system.  
         [0018]    [0018]FIG. 2 is an enlarged cross sectional view showing the control damping arrangement for this prior art type of construction.  
         [0019]    [0019]FIG. 3 is a schematic view, in part similar to FIG. 1, but showing a first embodiment of the invention.  
         [0020]    [0020]FIG. 4 is an enlarged cross sectional view, in part similar to FIG. 2, but shows the damping control arrangement for this embodiment.  
         [0021]    [0021]FIG. 5 is an enlarged cross sectional view, in part similar to FIG. 4, and shows a second embodiment of the invention.  
         [0022]    [0022]FIG. 6 is a cross sectional view, in part similar to FIGS. 4 and 5, and shows a third embodiment of the invention.  
         [0023]    [0023]FIG. 7 is a cross sectional view, in part similar to FIGS. 4, 5 and  6 , and shows a fourth embodiment of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0024]    Referring first to the embodiment of FIGS. 3 and 4, this embodiment employs components, which are generally similar to those of the prior art type of construction as illustrated in FIGS. 1 and 2, respectively. Therefore, when these similar components are described in conjunction with this embodiment, the same references numerals will be utilized to identify the components and those components will only be described further only insofar as is necessary to understand the construction and operation of this embodiment.  
         [0025]    As has been noted in the section entitled “BACKGROUND OF INVENTION”, the disadvantage with the prior art constructions is that there is no interconnection and damping arrangement between the chambers  15  of the two front shock absorbers  11 LF and  11 RF.  
         [0026]    That problem is rectified in this embodiment by the provision of an interconnecting conduit  61 , which is formed in the control member, indicated here by the reference numeral  62 . The conduit  61  interconnects the chambers  41  and  44  associated with the front two shock absorbers  11 LF and  11 RF. In addition, there is a flow controlling orifice  63  in this conduit  61 .  
         [0027]    Hence, when the vehicle is rounding a curve and there is a tendency for body roll to occur, the flow between the chambers  41  and  44  is possible and this flow is restricted by the orifice  63 . Thus, in combination with the rear damping orifice  49 , there will be similar damping at both the front and rear wheels. This facilitates not only the handling of the leaning when negotiating curve but also makes the internal damping arrangement for each wheel simpler, thus avoiding the problems in the prior art type of construction.  
         [0028]    [0028]FIG. 5 shows another embodiment of the invention which is generally similar to the embodiment of FIGS. 3 and 4 but which provides a more compact construction. In the embodiments of FIGS. 3 and 4, the chambers  41 ,  42 ,  43  and  44  have all been positioned in side-by-side relationship and this provides a rather long assembly. In this embodiment, the control member, indicated generally by the reference numeral  71  has an outer housing  72  that defines four stepped bores comprised of a first bore  73 , a second bore of slightly smaller diameter  74 , a third bore of still further smaller diameter  75  and a final bore  76  of a yet further smaller diameter.  
         [0029]    An integral piston assembly is contained in the housing  72 . This piston assembly is comprised of a piston rod  77  that integrally connects stepped pistons  78 ,  79 ,  81  and  82 , that are received in the bores  73 ,  74 ,  75  and  76 , respectively.  
         [0030]    The upper piston  78  divides the construction into a first cylindrical chamber  83 , which constitutes an accumulator chamber that is charged with an inert gas such as nitrogen under pressure. Below this is formed a first fluid chamber  84  which has an effective cross sectional area  84   a  equal to the area of the piston  78  less the area of the piston  79  and the piston rod  77 . This effective area is equal to the effective cross sectional area  85   a  of a second fluid chamber  85  formed between the pistons  79  and  81 . This effective area  85   a  is equal to the area of the piston  79  less the effective area of the piston  81 . The underside of the piston  81  defines a third fluid chamber  86 , which has an effective area  86   a  equal to the area of the piston  81  less the effective area of the piston  82 . Finally, the underside of the piston  82  defines a final volume  87  which has an effective area  87   a  equivalent to its cross sectional area less that of the piston rod  77 . That is:  
         [0031]    [0031] 84   a = 85   a  = 86   a  = 87   a    
         [0032]    The conduits  24  and  26  from the right front and rear shock absorbers  11  RF and  11  RR extend to the chambers  87  and  86 , respectively. Damping between these chambers is provided by a flow passage  88  in which an orifice  89  is positioned.  
         [0033]    The left shock absorbers and specifically the front and rear ones thereof  11 LF and  11 LR communicate via the conduits  23  and  25  with the chambers  84  and  85 , respectively.  
         [0034]    Damping between these two chambers  84  and  85  is provided by a flow passage  91  that extends through the piston portion  79  and in which a flow controlling orifice  92  is positioned. The chamber  84  is connected with the chamber  87  by means of a conduit  93  in which a flow controlling orifice  94  is provided. This provides left to right damping against leaning at the front. Leaning at the rear is dampened by flow through an passage  95  in the piston  81  in which an orifice  96  is positioned.  
         [0035]    [0035]FIG. 6 shows another embodiment of the invention and is in part similar to FIG. 5 in that it does not show the individual shock absorbers but merely their interconnecting conduits  23 ,  24 ,  25  and  26 . In this embodiment, a pressure control  101  is provided to achieve the same results as with the previously described embodiment.  
         [0036]    The pressure control  101  includes an outer housing  102  which defines a pair of upper and lower cylinder bores comprised of an upper left hand bore portion  103  and an upper right hand bore portion  104 . Below these upper bore portions  103  and  104  are provided smaller diameter, lower bore portions  105  and  106 . The area above an internal, stepped dividing wall having an upper portion  107  and a lower portion  108  forms an accumulator chamber above the bores  103  and  104 . This accumulator chamber is indicated by the reference numeral  109 . A stepped piston assembly  111  having a pair of piston portions is interconnected by a bridging member  112  that extends into the accumulator chamber  109 .  
         [0037]    The piston assembly  111  is formed with respective left side pistons  113  and  114  that extend into the left hand bore portions  103  and  105 . Also the piston assembly  111  has right hand pistons  115  and  116  that extend into the right hand bore portions  104  and  106 .  
         [0038]    Thus, there are defined four fluid chambers comprised of an upper left hand fluid chamber  117 , an upper right hand chamber  118 , a lower left hand chamber  119  and a lower right hand chamber  121 . As with the previously described embodiments, the effective areas of the piston portions  113 ,  114 ,  118  and  121  in the bores  117 , 119 , 118  and  112 , respectively, are all equal.  
         [0039]    The left front shock absorber  11 LF communicates with the chamber  117  through the conduit  23  while the right front shock absorber  11 RF communicates with the right hand upper chamber  118  through the conduit  24 . The left and right rear shock absorbers communicate with the chambers  119  and  121 , respectively via the conduits  25  and  26 .  
         [0040]    A passageway  122  through the piston portion  114  is provided with an orifice  123 , which dampens front to rear pitching and squat motions at the left side of the vehicle. Similar motions at the right side of the vehicle are damped by a flow passage  124  in which a flow controlling orifice  125  in the piston  116 .  
         [0041]    Left to right roll at the front is controlled by a passageway  126  that extends through the dividing wall portions  107  and  108  at their juncture and in which a flow controlling orifice  127  is provided. Similar dampening at the rear is provided by a flow passage  128  that extends between the chambers  119  and  121  and which a flow controlling orifice  129  is provided. Hence, with this embodiment, the damping front to rear and side-to-side is provided equally at the front and rear and left and right sides of the vehicle.  
         [0042]    [0042]FIG. 7 shows a yet further embodiment, which in some ways is quite similar to that of FIG. 6 and, therefore, where components of this embodiment are the same as that embodiment or substantially the same, they have been identified by the same reference numerals and will described again only insofar as is necessary to understand the invention. in this embodiment, the two pairs of pistons  113  and  114  and  115  and  116  rather than being integrally connected to each other by the bridging portion  112  are hydraulically connected to each other. Hence, it is possible to mount the components in spaced apart locations. Because the piston portions  113  and  114  and  115  and  116  are separate from each other and not mechanically interconnected, it is not necessary that they be disposed in the same housing.  
         [0043]    However, in whatever housing they are supported, there is provided a pair of further fluid chambers  201  and  202  formed above the chambers  117  and  118 , respectively. These chambers are in fluid communication with an accumulator device, indicated generally by the reference numeral  203  and which also can be separately located because of the lack of mechanical interconnection.  
         [0044]    Fluid interconnection is provided by means of a pair of conduits  204  and  205  that extend from a pair of equal effective area fluid chambers  206  and  207 , respectively, formed in the housing  203 . A piston having first and second portions  208  and  209  is received in bore portions  211  and  212  respectively thereof. An incompressible fluid such as an oil is contained in the chambers  206  and  207 , conduits  204  and  105  and chambers  201  and  202  so as to insure uniform movement there between.  
         [0045]    The area above the piston  209  is filled with an inert gas under pressure in a chamber indicated by the reference numeral  213  so as to accommodate for the difference in piston rod displacements and to insure good control. Thus, since this embodiment operates the same as that previously described, further description of it is not believed to be necessary to permit those skilled in the art to practice the invention.  
         [0046]    Thus from the foregoing described and preferred embodiments, it should be apparent that a highly effective and yet quite simple four wheel vehicle suspension system is possible that effectively dampens all types of expected loadings. Of course these embodiments are only preferred embodiments and various changes and modifications are possible without departing from the spirit and scope of the invention as set out in the appended claims.