Abstract:
A multistage jounce bumper, including a jounce bumper cushion integrated with a hydraulic jounce bumper, wherein provided are the damping characteristic of the hydraulic jounce bumper and the damping/spring characteristics of a jounce bumper cushion. The hydraulic jounce bumper hydraulic response is tunable via adjustment of hydraulic flow with respect to a communicating hydraulic fluid reservoir. When maximum jounce is approached, jounce force and energy are exchanged, at a first stage, with the jounce bumper cushion, then at a predetermined compression, jounce force and energy are exchanged, at a second stage, with the hydraulic jounce bumper. Thereafter, a mechanical abutment is provided as a third stage of jounce management.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to automotive suspension systems, particularly the bumper mount, the jounce bumper, and conventional dampers. More particularly, the present invention relates to a multistage jounce bumper which is a synthesis of a jounce bumper cushion and a hydraulic jounce bumper, the combination providing enhanced suspension system energy absorption and improved ride characteristics. 
       BACKGROUND OF THE INVENTION 
       [0002]    Motor vehicle suspension systems are configured so that the wheels are able to follow elevational changes in the road surface as the vehicle travels therealong. When a rise in the road surface is encountered, the suspension responds in “jounce” in which the wheel is able to move upwardly relative to the frame of the vehicle. On the other hand, when a dip in the road surface is encountered, the suspension responds in “rebound” in which the wheel is able to move downwardly relative to the frame of the vehicle. In either jounce or rebound, a spring (i.e., hydraulic fluid, leaf, torsion, etc.) is incorporated at the wheel in order to provide a resilient response to the respective vertical movements with regard to the vehicle frame. However, in order to prevent wheel bouncing and excessive vehicle body motion, a shock absorber is placed at the wheel to dampen wheel bounce. Additionally, when the limit of jounce is encountered, it is customary to provide a maximum jounce impact absorber in the form of a bumper cushion. 
         [0003]    Referring now to  FIGS. 1 through 1B , components of a conventional suspension system  10  are depicted which allow for jounce and rebound at a wheel of the subject motor vehicle  12 . 
         [0004]    Firstly with regard to  FIG. 1 , a control arm  14  is pivotally mounted with respect to the frame  16 , wherein, in the depicted example, a torsion spring  18  is utilized to provide resilient response for the jounce and rebound of the control arm relative to the frame. To provide control over the rate of jounce and rebound, a damper in the form of a shock absorber  20  is connected pivotally at one end to the frame  16  and connected pivotally at the other end to the control arm  14 . Alternatively, a damper in the form of a strut may be used in the suspension system, as for example disclosed in U.S. Pat. No. 5,467,971. To provide cushioning in the event a maximum jounce occurs, a jounce bumper cushion  22  is mounted to the frame  16  which is resiliently compressed by movement of the control arm as jounce approaches its maximum. 
         [0005]    Referring next to  FIG. 1A , the internal components and operational aspects of a conventional shock absorber  20 ′ (a remote reservoir high pressure gas type shock absorber being shown merely by way of example) can be understood. A valved piston  30  is reciprocably movable within a shock cylinder  32 . A shock rod  34  is attached to the valved piston  30  and is guided by a shock rod guide  36  at one end of the shock cylinder  32 . Below the valved piston  30  and above the shock rod guide  36  is a mutually interacting rebound limiter  38 . The instantaneous position of the valved piston  30  within the shock cylinder  32  defines a first interior portion  32 F and a second interior portion  32 S of the interior of the shock cylinder. In the example depicted at  FIG. 1A , the pressurization in the first and second interior portions  32 F,  32 S is provided by an hydraulic fluid O which is pressurized by pressurized gas, preferably nitrogen, G acting on a divider piston  40  of an hydraulic fluid reservoir cylinder  42 , wherein a tube  44 , including a base valve  44 V, connects the hydraulic fluid between the hydraulic fluid reservoir cylinder and the first interior portion. In operation, as the control arm undergoes jounce, the hydraulic fluid is displaced from the first interior portion into the hydraulic fluid reservoir cylinder, causing the pressure of the nitrogen gas to increase as its volume decreases and thereby causing an increased hydraulic pressure on the valved piston  30  in a direction toward the shock rod guide. Hydraulic fluid is able to directionally meter through valving  46  of the valved piston  30  in a manner which provides damping. 
         [0006]    Referring next to  FIG. 1B , the internal structure of a conventional jounce bumper cushion  22  can be understood. An optional skin  50  of a compliant material (i.e., having energy absorbing or damping properties) may, or may not, overlay an interior of resilient elastomeric material  52 , which may be for example a rubber, rubber-like material, or micro-cellular urethane. In operation as the control arm approaches maximum jounce, the jounce bumper cushion  22  compresses, delivering a reaction force on the control arm which increases with increasing compression so as to minimize the severity of impact of the control arm with respect to the frame at the limit of jounce. Immediately following the jounce, the rebound involves the energy absorbed by the compression of the conventional bumper cushion being delivered resiliently back to the suspension. 
         [0007]    In the art of motor vehicle suspension systems, it is known that a conventional jounce bumper cushion and related dampers can show wear. It is also known that when the energy absorbed from a particular bump or dip exceeds the capacity of a conventional jounce bumper cushion, a hard mechanical stop is engaged. This abrupt transfer of jounce force and energy to the frame manifests itself in the passenger compartment as a sharp jolt, which can create load management issues in addition to the discomfort of a rough ride. 
         [0008]    What remains needed in the art is a multistage jounce bumper, which can absorb an enhanced level of suspension system jounce force and energy as compared to a conventional jounce bumper cushion, while improving the feel and control of the ride. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention is a multistage jounce bumper, which absorbs additional jounce force and energy as compared with a conventional jounce bumper cushion of motor vehicles, while improving the feel and control of the ride. 
         [0010]    The multistage jounce bumper according to the present invention includes a jounce bumper cushion integrated with a hydraulic jounce bumper. The present invention allows for an enhancement of energy absorption as a vehicle wheel goes into a full jounce position. The present invention provides the damping characteristic of a hydraulic jounce bumper as well as the damping/spring characteristics of a jounce bumper cushion. The hydraulic jounce bumper hydraulic response to a jounce is tunable via adjustment of hydraulic fluid flow with respect to a communicating hydraulic fluid reservoir. 
         [0011]    In operation, as maximum jounce is approached, jounce force and energy are exchanged between the knuckle or control arm of the suspension system and the multistage jounce bumper. The jounce bumper cushion provides a first stage of response to the jounce force by providing a resilient reaction force against the jounce force and may absorb jounce energy until it is fully compressed (i.e., saturated). A second stage of response to the jounce force is provided by the hydraulic jounce bumper, which is engaged at a predetermined amount of compression of the jounce bumper cushion (which may be before saturation). Tuning of the initial response of the hydraulic jounce bumper provides a seamless transition of jounce force management to the hydraulic jounce bumper from the jounce bumper cushion. As the hydraulic jounce bumper increases reaction force against the jounce force and absorbs more jounce energy, the feel of the ride stiffens in an increasing manner to minimize the ride disruption and enhancement of load control. Once the hydraulic jounce bumper has absorbed a predetermined maximum amount of jounce energy and/or provides a predetermined maximum reaction force to the jounce force, a third stage of response to the jounce force is provided by a hard stop abutment engagement, either in the form of a mechanical abutment or a hydraulic lock (i.e., force transfer through the incompressible hydraulic fluid) of the hydraulic jounce bumper, whereby the remaining jounce force is transferred directly to the vehicle frame. 
         [0012]    Accordingly, it is an object of the present invention to provide a multi-stage jounce bumper, including a j ounce bumper cushion integrated with a hydraulic jounce bumper, which absorbs jounce energy beyond that possible of a conventional jounce bumper cushion alone, while improving the feel and control of the ride. 
         [0013]    This and additional objects, features and advantages of the present invention will become clearer from the following specification of a preferred embodiment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a perspective view of a conventional suspension system, including a control arm, a frame, a spring, a conventional shock absorber and a conventional bumper cushion. 
           [0015]      FIG. 1A  is a sectional view of a conventional shock absorber. 
           [0016]      FIG. 1B  is a sectional view of a conventional bumper cushion. 
           [0017]      FIG. 2  is a diagrammatic view of a multistage jounce bumper according to the present invention. 
           [0018]      FIGS. 2A through 2C  are diagrammatic views of the operation of the present invention, showing progressive stages of energy absorption from a maximum jounce. 
           [0019]      FIG. 3A  is a diagrammatic view of a first alternative embodiment of a multistage jounce bumper according to the present invention. 
           [0020]      FIG. 3B  is a diagrammatic view of a second alternative embodiment of a multistage jounce bumper according to the present invention. 
           [0021]      FIG. 4  is a graph showing the performance of the multistage jounce bumper according to the present invention as compared to a conventional jounce bumper cushion, each in terms of static load deflection. 
           [0022]      FIG. 5  is a graph showing the performance of the multistage jounce bumper according to the present invention as compared to a conventional jounce bumper cushion, each being subjected to low frequency ramp waves. 
           [0023]      FIG. 6  is a graph showing the performance of the multistage jounce bumper according to the present invention as compared to a conventional jounce bumper cushion, each being subjected to low frequency square waves. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0024]    Referring now to the Drawing,  FIG. 2  through  FIG. 6  depict various aspects of structure and function of a multistage jounce bumper according to the present invention. The multistage jounce bumper is a novel synthesis of a jounce bumper cushion, a tunable hydraulic jounce bumper, and related damper components. The resulting expanded jounce management provides improved feel of the ride and enhances the capacity for load control in high-energy, uneven terrain inputs. While any type of damper may be used with the present invention (see discussion of dampers hereinabove), the most preferred form of damper is a strut. 
         [0025]    Referring firstly to  FIG. 2 , the multistage jounce bumper  100  according to the present invention is depicted. A lower aspect AL of the multistage jounce bumper  100  consists of a damper  110  (i.e., a strut or shock absorber) which is connected to a knuckle or control arm of the suspension system as generally depicted with respect to the shock absorber  20  of  FIG. 1 , wherein the damper has connected to an end thereof a damper bump plate  112 , and wherein a damper rod  114  passes through the damper bump plate and is internally hydraulically operable in a shock absorber to provide jounce/rebound damping as generally described hereinabove with respect to  FIG. 1A  or operable in a strut type damper as for example disclosed in U.S. Pat. No. 5,467,971, the disclosure of which is hereby herein incorporated by reference. An upper aspect AU of the multi-stage jounce bumper  100  consists of a jounce bumper cushion  120  connected to a floating puck  124  of a hydraulic jounce bumper  126 , wherein the damper rod  114  passes therethrough to a connection at a top mount  140 , which is, itself, affixed with respect to the vehicle frame (such as is generally depicted at  FIG. 1 ). 
         [0026]    The jounce bumper cushion  120 , by way of preferred example, is composed of a resilient material, preferably a urethane material, as generally discussed with respect to  FIG. 1B . The jounce bumper cushion  120  has a predetermined maximum compression limit (i.e., saturation) when compressed or squeezed between the damper bump plate  112  and the floating puck  124  (see  FIG. 2B ), the details of which will be discussed further hereinbelow. 
         [0027]    The hydraulic jounce bumper  126  consists of a hydraulic cylinder  128  having a cylinder head  128   h . The floating puck  124  serves as a piston movably mounted with respect to the hydraulic cylinder  128 , which in combination with the hydraulic cylinder and the cylinder head, collectively define a hydraulic fluid filled cavity  130 , the hydraulic fluid O being preferably oil. A stop ring  134  is attached to the hydraulic cylinder exterior to the hydraulic fluid filled cavity which serves as a travel limiter of the floating puck. The cylinder head  128   h  is also affixed to the top mount  140 . 
         [0028]    The response of the hydraulic jounce bumper  126  of the multistage jounce bumper  100  is preferably hydraulically tunable. For example, hydraulic fluid flow may be adjusted through the use of a communicating reservoir  150  via a control valve (which may be in the form of multistage valving)  154  and line  152 , whereby the control valve is selectively set so that it meters, in a predetermined manner, hydraulic fluid flow between the hydraulic fluid filled cavity and the communicating reservoir. 
         [0029]    At the communicating reservoir  150 , a movable piston  156  separates the hydraulic fluid O from a pressurized gas chamber  160 . A gas valve  158  is located at the gas chamber  160  which provides for selective connection thereto to a source of pressurized gas G, and may serve as a pressure regulator. The hydraulic jounce bumper  126  may be further tuned by means of adjusting the pressure of the pressurized gas G in the gas chamber  160 . The piston  156  prevents the gas G mixing in the hydraulic fluid O and thus compromising the pressure response characteristics of the hydraulic jounce bumper  126 . 
         [0030]    Turning attention now to  FIGS. 2A through 2C , operation of the multistage jounce bumper  100  will be detailed. 
         [0031]    Referring first to  FIG. 2A , as a vehicle wheel approaches maximum jounce, the damper bump plate  112  makes contact with the jounce bumper cushion  120 . As the damper  110  moves further toward the top mount  140  (see arrow A in  FIG. 2 ), the jounce bumper cushion  120  is compressed or squeezed between the damper bump plate  112  and the floating puck  124  (which at present remains stationary); whereupon the jounce bumper cushion compresses providing a reaction force to the jounce force and absorption of energy from the jounce motion, which compression constitutes a first stage response of the multistage jounce bumper to the jounce force. 
         [0032]    Referring next to  FIG. 2B , once a predetermined amount of compression of the jounce bumper cushion  120  has been reached (ie., it is at a predetermined amount of saturation), the floating puck  124  force against the hydraulic fluid O in the hydraulic fluid filled cavity  130  is such that, based upon the hydraulic tuning at the control valve  154 , the hydraulic fluid begins a metered flow to the communicating reservoir  150 , whereupon the gas G becomes increasingly pressurized. The jounce bumper cushion may continue to compress further, if at the predetermined amount of compression, saturation of the jounce bumper cushion had not yet been reached. This now constitutes a second stage of response by the multistage jounce bumper to the jounce force. The transition between the first and second stages of response to the jounce force is characterized by the floating puck providing a reaction force to the jounce force which is seamlessly continuous with respect to that provided by the jounce bumper cushion at the point of its predetermined amount of compression. 
         [0033]    Referring finally to  FIG. 2C , the hydraulic fluid O in the hydraulic fluid filled cavity  130  will have absorbed a predetermined maximum of jounce energy, whereat a predetermined minimum volume and/or the hydraulic fluid a predetermined maximum pressure hydraulic fluid is attained. Now a third stage response of the multistage jounce bumper to the jounce force will occur, wherein the remainder of the jounce force and energy will be transferred to the frame of the vehicle through the top mount  140 . In a first scenario, the control valve  154  closes so as to stop hydraulic fluid flow at a preselected maximum pressure and/or the minimum volume, whereupon the hydraulic fluid O instantly provides a direct conduit of the jounce force to the top mount as it is incompressibly pressurized. In a second scenario, the damper  110  ceases to slide with respect to the damper rod by  114 , for example by being mutually abuttingly interconnected, whereupon the jounce force is transferred from the damper rod to the top plate. In a third scenario, a remotely located bump member connected with the moving wheel component abuttingly strikes a frame component. 
         [0034]    Turning attention now to  FIG. 3A , a first alternative embodiment of a multistage jounce bumper  100 ″ according to the present invention is depicted, which embodiment may be considered the most preferred embodiment. In this first alternative embodiment, the communicating reservoir  150 ′ is integrated with the hydraulic cylinder  128 ′. 
         [0035]    The communicating reservoir  150 ′ is integrated with the cylinder head  128   h ′ of a hydraulic cylinder  128 ′ of the hydraulic jounce bumper  126 ′, wherein a piston  156 ′ separates the hydraulic fluid O′ from the pressurized gas G′ of a gas chamber  160 ′. The pressurized gas G′ is introduced by a gas valve  158 ′. A floating puck  124 ′ serves as a movable piston with respect to the hydraulic cylinder  128 ′ and they collectively define a hydraulic fluid filled cavity  130 ′. A ring  134 ′ limits travel of the floating puck with respect to the hydraulic cylinder  128 ′. A control valve (which may be in the form of a multistage valve)  154 ′ tunably meters the flow of hydraulic fluid O′ between the hydraulic fluid filled cavity  130 ′ and the communicating reservoir  150 ′. A jounce bumper cushion  120 ′ is affixed to the floating puck  124 ′. A damper (not shown, but like  110  in  FIG. 2 ) has a damper plate (not shown, but like  112  in  FIG. 2 ), wherein a damper rod  114 ′ of the damper is connected with a top mount  140 ′. The top mount  140 ′ is connected to the head  160   h ′ of the gas chamber  160 ′. 
         [0036]    In operation, much like the operation described with respect to  FIGS. 2A  though  2 C, the damper moves toward the top mount  140 ′ during jounce, whereupon the damper plate abuts the jounce bumper cushion  120 ′ and compresses the jounce bumper cushion during the first stage response. Upon the jounce bumper cushion reaching a predetermined amount of compression, the hydraulic fluid O′ begins to meter through the control valve  154 ′ into the communicating reservoir  150 ′ in the manner described hereinabove with respect to the second stage response of  FIGS. 2A  though  2 C. Once the hydraulic fluid filled cavity  130 ′ has reached a minimum volume, whereat the hydraulic fluid O′ is pressurized to a predetermined maximum and/or the hydraulic fluid has reached a predetermined maximum pressure, the third stage response is implemented, wherein the jounce force and energy are transmitted to the frame, as for example by any of the second and third aforementioned scenarios. 
         [0037]    Turning attention now to  FIG. 3B , a second alternative embodiment of a multistage jounce bumper  100 ″ according to the present invention is depicted. In this second alternative embodiment, the order of the jounce bumper cushion  120 ″ and the hydraulic jounce bumper  126 ″ are reversed as compared to  FIGS. 2 and 3A , and, by way of example, the communicating reservoir  150 ″ is integrated with the hydraulic cylinder  128 ″. Although not specifically shown, it is clear that the hydraulic jounce bumper  126 ″ may alternatively be integrated within the damper  110 ″. 
         [0038]    The communicating reservoir  150 ″ is integrated with the cylinder head  128   h ″ of a hydraulic cylinder  128 ″ of the hydraulic jounce bumper  126 ″, wherein a piston  156 ″ separates the hydraulic fluid O″ from the pressurized gas G″ of a gas chamber  160 ″. The pressurized gas G″ is introduced by a gas valve  158 ″. A floating puck  124 ″ serves as a movable piston with respect to the hydraulic cylinder  128 ″ and they collectively define a hydraulic fluid filled cavity  130 ″. A ring  134 ″ limits travel of the floating puck with respect to the hydraulic cylinder  128 ″. A control valve (which may be in the form of a multistage valve)  154 ″ tunably meters the flow of hydraulic fluid O″ between the hydraulic fluid filled cavity  130 ″ and the communicating reservoir  150 ″. A jounce bumper cushion  120 ″ is affixed to a top mount  140 ″. A damper  110 ″ is connected, via a damper plate  112 ″, to the head  160   h ′ of the gas chamber  160 ″ and has a damper rod  114 ″ connected to the top mount  140 ″. 
         [0039]    In operation, much like the operation described with respect to  FIGS. 2A  though  2 C, the damper  110 ″ moves toward the top mount  140 ″ during jounce, whereupon the floating puck  124 ″ abuts the jounce bumper cushion  120 ″ and compresses the jounce bumper cushion during the first stage response. Upon the jounce bumper cushion reaching a predetermined compression, the hydraulic fluid O″ begins to meter through the control valve  154 ″ into the communicating reservoir  150 ″ in the manner described hereinabove with respect to the second stage of response of  FIGS. 2A  though  2 C. Once the hydraulic fluid filled cavity  130 ″ has reached a minimum volume and/or the hydraulic fluid has attained a predetermined maximum pressure, the third stage is implemented, wherein the jounce force and energy are transmitted to the frame, as for example by any of the second and third aforementioned scenarios. 
         [0040]      FIG. 4  shows a graph  200  of the performance of the multistage jounce bumper  100  as compared to a conventional jounce bumper cushion, each being subjected to two static loads. A first plot  202  shows the deflection in millimeters produced by a static force of 5,500 Newtons applied to the multistage jounce bumper. A second plot  204  shows the deflection of multistage jounce bumper when subjected to a static force of 3,500 Newtons. A third plot  206  shows the displacement produced by a static force of 5,500 Newtons applied to a conventional jounce bumper cushion. A fourth plot shows the deflection of a conventional jounce bumper cushion when subjected to a static force of 3,500 Newtons. These plots show that the multistage jounce bumper allows for an additional 18 millimeters of travel compared to the conventional jounce bumper cushion, thus allowing for an improved over-all management of the jounce force and energy. 
         [0041]      FIG. 5  shows a graph  220  of the performance of the multistage jounce bumper  100  as compared to a conventional jounce bumper cushion, each being subjected to low frequency ramp waves. A first plot  222  shows the deflection of a conventional jounce bumper cushion subjected to a 4 Hz frequency ramp wave with maximum amplitude of 25 millimeters. A second plot  224  shows the deflection of a conventional jounce bumper cushion subjected to a 2 Hz frequency ramp wave with maximum amplitude of 25 millimeters. A third plot  226  shows the deflection of a multistage jounce bumper subjected to a 2 Hz frequency ramp wave with maximum amplitude of 25 millimeters. A fourth plot  228  shows the deflection of a multistage jounce bumper subjected to a 4 Hz frequency ramp wave with maximum amplitude of 25 millimeters. These plots show that the multistage jounce bumper can absorb a load approximately 1,300 Newtons greater than the conventional jounce bumper cushion. 
         [0042]      FIG. 6  shows a graph  240  of the performance of the multistage jounce bumper  100  as compared to a conventional jounce bumper cushion, each being subjected to low frequency square waves. A first plot  242  shows the deflection of a conventional jounce bumper cushion subjected to a 2 Hz frequency square wave with maximum amplitude of 25 millimeters. A second plot  244  shows the deflection of a conventional jounce bumper cushion subjected to a 4 Hz frequency square wave with maximum amplitude of 25 millimeters. A third plot  246  shows the deflection of a multistage jounce bumper subjected to a 4 Hz frequency square wave with maximum amplitude of 25 millimeters. A fourth plot  248  shows the deflection of a multistage jounce bumper subjected to a 2 Hz frequency square wave with maximum amplitude of 25 millimeters. These plots show that the multistage jounce bumper can absorb a load approximately 1,500 Newtons greater than the conventional jounce bumper cushion. 
         [0043]    To those skilled in the art to which this invention appertains, the above described preferred embodiment may be subject to change or modification. Such change or modification can be carried out without departing from the scope of the invention, which is intended to be limited only by the scope of the appended claims.