Abstract:
A jounce bumper for mounting in a vehicle suspension system having a bore extending therethrough, the bore configured to receive the piston rod, a nose having a predetermined inner diameter and a predetermined outer diameter, the nose being generally spherical or elliptical shaped and an undercut within the jounce bumper in the bore of the jounce bumper, the undercut creating an ununiformed thickness between the predetermined inner diameter and the predetermined outer diameter so as to provide improved handling characteristics of the jounce bumper.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This Application claims the benefit of U.S. Provisional Application 62/119,885 filed on Feb. 24, 2015, the contents of which are incorporated herein in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present application related generally to jounce bumpers. More specifically, the present application relates to a jounce bumper having an improved ride and handling during operation of a vehicle. 
       BACKGROUND 
       [0003]    Jounce bumpers are well known in the art and integrated into a vehicle suspension design. Jounce bumpers absorb impact and dampen noise, vibration, and harshness by preventing the articulated suspension components from fully compacting during shock impacts caused by heavy loads, potholes, curbs, or objects in the road. Jounce bumpers also act as a progressive compression spring under loads approaching full compression thereby offering a smooth ride and improved handling over a wide range of driving conditions. Previously known jounce bumpers have a generally spherical or elliptical shaped nose having an inner diameter generally matching the shape of the outer diameter of the nose. By way of example, a nose of the prior art includes an outer diameter (or surface) which is generally spherical shaped and an inner diameter mirroring the outer geometry. Accordingly, the overall thickness of the nose of the jounce bumper remains constant. 
         [0004]    A jounce bumper of the prior art typically includes a spherical outer surface and a corresponding mirrored inner surface. The inner surface, or inner diameter, is also generally spherical. The thickness also remains constant between the outer surface and the inner surface. A derivative curve is used to assess the stiffness.  FIGS. 1 and 2  illustrate the performance of the jounce bumper of the prior art. The curve of  FIGS. 1 and 2  depict a dramatic dip in the curve. It is desirable to make this curve as flat as possible to improve harshness and handling. 
         [0005]    Other versions of the prior art discloses a jounce bumper having and elliptical type outer surface and an inner surface without any undercut. The inner surface, or inner diameter, may also be generally spherical. A derivative curve is used to assess the stiffness. 
         [0006]    Load deflection curves are commonly created to assess the spring rate of the jounce bumper during compression of the jounce bumper. A derivative curve is used to assess the stiffness.  FIGS. 1 and 2  of the prior art illustrates the performance of the jounce bumper of the prior art. The curve of  FIGS. 1 and 2  illustrates a dramatic dip in the curve. It is desirable to make this curve as flat as possible to improve harshness and handling and to help retain optimum steering and handling over the wide range of road effects and velocity. However, existing jounce bumpers are not able to produce a flat curve. Accordingly, there exists a need in the art to provide an improved jounce bumper providing for a generally flat stiffness curve. 
       SUMMARY 
       [0007]    In one embodiment, a jounce bumper for mounting in a vehicle suspension system, where the vehicle suspension system having a shock absorber with a cylinder and a piston rod, the jounce bumper having a bore extending therethrough, the bore configured to receive the piston rod, a nose having a predetermined inner diameter and a predetermined outer diameter, the nose being generally spherical or elliptical shaped and an undercut within the jounce bumper in the bore of the jounce bumper, the undercut creating an ununiformed thickness between the predetermined inner diameter and the predetermined outer diameter so as to provide improved handling characteristics of the jounce bumper. 
         [0008]    In some embodiments, the nose is further defined by a predetermined height, the undercut is defined by a predetermined height and where the predetermined height of the nose is greater than the predetermined height of the undercut. The jounce bumper may be made of microcellular urethane. 
         [0009]    The undercut may include two sidewall surfaces extending into the jounce bumper to an innermost surface of the undercut. The innermost surface of the undercut may be configured to be spaced apart from the piston rod when the jounce bumper is installed around the piston rod in a use position. In some embodiments, the corner where the two sidewall surfaces meet the innermost surface of the undercut are radiused so as to create a smooth transition between the two sidewall surface and the innermost surface of the undercut. 
         [0010]    The undercut may symmetrical on the inner surface of the bore of the jounce bumper and may generally have a rectangular cross-section. 
         [0011]    In other embodiments, a jounce bumper for mounting in a vehicle suspension system, where the vehicle suspension system having a shock absorber with a cylinder and a piston rod, may include an elastically compressible jounce bumper having a bore extending therethrough, the bore configured to receive the piston rod where the bore has a generally cylindrical inner surface, the inner surface having an indentation extending around the inner surface so as to create a varying thickness of the jounce bumper so as to improve handling of the vehicle. 
         [0012]    In yet another embodiment, a suspension assembly for a vehicle may include a piston rod, a cylinder extending around the piston rod and a jounce bumper where the jounce bumper includes an elastically compressible jounce bumper having a bore extending therethrough, the bore configured to receive the piston rod, a nose having a predetermined inner diameter and a predetermined outer diameter, the nose being generally spherical or elliptical shaped and an undercut within the jounce bumper in the bore of the jounce bumper, the undercut creating an ununiformed thickness between the predetermined inner diameter and the predetermined outer diameter so as to provide improved handling characteristics of the jounce bumper. 
         [0013]    These and additional features provided by the embodiments described herein will be more fully understood in view of the following detailed description, in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The embodiments set forth in the drawings are illustrative and exemplary in nature and not intended to limit the subject matter defined by the claims. The following detailed description of the illustrative embodiments can be understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which: 
           [0015]      FIG. 1  depicts a stiffness curve created by a jounce bumper of the prior art; 
           [0016]      FIG. 2  depicts an additional stiffness curve created by a jounce bumper of the prior art; 
           [0017]      FIG. 3  depicts a jounce bumper of the present application installed on an exemplary strut assembly according to one or more embodiments shown and described herein; 
           [0018]      FIG. 4  depicts a cross sectional view of a jounce bumper according to one or more embodiments shown and described herein; 
           [0019]      FIG. 5  depicts a halved cross sectional view of the jounce bumper of  FIG. 4  according to one or more embodiments shown and described herein; 
           [0020]      FIG. 6  depicts a cross sectional view an alternative embodiment jounce bumper according to one or more embodiments shown and described herein; 
           [0021]      FIG. 7  depicts a halved cross sectional view a yet another alternative embodiment jounce bumper according to one or more embodiments shown and described herein; 
           [0022]      FIG. 8  depicts a halved cross sectional view a yet another alternative embodiment jounce bumper according to one or more embodiments shown and described herein; and 
           [0023]      FIG. 9  depicts an exemplary stiffness curve of an elliptical jounce bumper of the embodiments as illustrated in  FIGS. 3-8  having an undercut such as shown in  FIGS. 3-8  according to one or more embodiments shown and described herein. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    The present invention provides for an improved jounce bumper having new geometry which allows lower and more consistent entry stiffness. The specific geometry, ratios, and relationships of the improved jounce bumper as compared to the prior art dramatically improves the entry stiffness performance. Accordingly, the improved jounce bumper provides for a consistent and soft entry curve thereby improving ride and handling to the user. The improved jounce bumper includes an undercut in the inner diameter (hereinafter referred to as ID). 
         [0025]      FIG. 3  illustrates an exemplary assembly  10  having an upper mount  12  connected to a piston rod  14 . A jounce bumper  20  (described in more detail herein) is provided around the piston rod. A cylinder  16  is provided also extending around the piston rod  14 . A spring  15  may also be provided extending around the assembly including the piston rod  14  and the jounce bumper  20 . 
         [0026]    Now with reference to  FIGS. 4 and 5 , the present embodiment provides for a jounce bumper  20  having a generally spherical nose  21 . The nose  21  includes an outer surface  22  and a corresponding inner surface  24 . A bore  23  extends through the center portion of the nose  21  thereby forming the inner surface  24 . The bore  21  is configured to accept the piston rod of a suspension system. The inner surface  24  includes an undercut  26  incorporated into the inner surface  24 . The inner surface  24  is also referred to in the art as the inner diameter. The undercut  24  includes radiused portions  28  contributing to the overall geometry. The spherical nose  21  having the undercut  24  has a varying thickness T 1  which does not remain constant as illustrated by T 2  (also true for all embodiments here). The varying thickness is contrary to the prior are which provides for a jounce bumper of consistent thickness (if viewed at a cross section). Since the jounce bumpers of the present application have an inner surface which effectively mirrors the piston rod. In this embodiment, and all other embodiments described herein, T 2  is smaller than T 1 . In other embodiments, T 2  is smaller than T 1 . In all embodiments, T 2  T 1 . 
         [0027]    The undercut  26 , in the present embodiment, is generally rectangular in cross section but extending around the entire ID of the jounce bumper. The undercut  26  does not create a uniform thickness between the ID and the OD, such as in the present invention. The undercut includes a generally planar surface  24  extending along the entire ID of the bumper. Two side walls  25 ,  28  extend away from the surface  24  and a generally perpendicular angle. In other embodiments, the side walls  25 ,  28  may extend at different angles away from the surface  24 . 
         [0028]    The undercut  26  includes a height H 1 . The nose  21  further includes a height H 2 . In the preferred embodiment, the height H 2  is greater than the height H 1 . This configuration provides for the most desirable results in the stiffness curve. 
         [0029]    Similarily, in all embodiments, the jounce bumpers includes a first radius R 1  and a second radius R 2 . The first radius R 1  is measured from a center portion of the undercut whereas the second radius R 2  is measured from the center of the bore. On the spherical shaped noses, R 2  remains generally constant. On the elliptical shaped noses, R 2  may vary more. 
         [0030]    Further, all of the jounce bumpers having the undercuts include a depth D 1  which can vary in dimension from 1 mm-35 mm depending on the size of the nose of the jounce bumper. 
         [0031]    By way of example, in one embodiment, D 1  is 4.2 mm, H 1  is 29.8 mm, H 2  is 36 mm and T 1  is 11.5 mm. In this embodiment, R 1  mm and the radiused portion is 4.2. 
         [0032]    In other embodiments, a jounce bumper having a more elliptical configuration is provided, such as in  FIG. 6 . The jounce bumper of  FIG. 6  depicts a nose  41  having a generally elliptical shape. A bore  43  extends through the center portion of the nose  41  thereby &amp;timing the inner surface  44 . The bore  41  is configured to accept the piston rod of a suspension system. The elliptical nose  41  includes an outer surface  42  and a corresponding inner surface  44 . The inner surface  44  includes an undercut  46  having a height H 1 . The nose further includes a height H 2  where in the preferred embodiment the height H 2  is greater than the height H 1 . 
         [0033]    The undercut  46 , in the present embodiment, is generally rectangular in cross section but extending around the entire ID of the jounce bumper. The undercut creates an varying thickness between the ID and the OD. The undercut includes a generally planar surface  44  extending along the entire ID of the bumper. Two side walls  45 ,  48  extend away from the surface  44  and a generally perpendicular angle. In other embodiments, the side walls  45 ,  48  may extend at different angles away from the surface  44 . 
         [0034]      FIG. 7  illustrates a cross-sectional view of the jounce bumper  50  having the nose  51 . The undercut  56  is shown incorporated into the jounce bumper. The jounce bumper as illustrated in  FIG. 7  produces the flat entry stiffness curve. 
         [0035]    the present embodiment provides for a jounce bumper  50  having a generally spherical nose  51 . The nose  51  includes an outer surface  52  and a corresponding inner surface  54 . The inner surface  54  includes an undercut  56  incorporated into the inner surface  54 . The inner surface  54  is also referred to in the art as the inner diameter. The undercut  54  includes radiused portions  55  contributing to the overall geometry. A bore  53  extends through the center portion of the nose  51  thereby forming the inner surface  54 . The bore  51  is configured to accept the piston rod of a suspension system. The spherical nose  51  having the undercut  54  has a varying thickness T 1  which does not remain constant, in sharp contrast to the prior art. The thickness of all embodiments of the present application varies dramatically because of the undercuts. The varying thickness provides for a smooth curve and thus improved handling to the user. 
         [0036]    The undercut  56 , in the present embodiment, is generally rectangular in cross section but extending around the entire ID of the jounce bumper. The undercut  56  does not create a uniform thickness between the ID and the OD, such as in the present invention. The undercut includes a generally planar surface  54  extending along the entire ID of the bumper. Two side walls extend away from the surface  54  and a generally perpendicular angle. In other embodiments, the side walls may extend at different angles away from the surface  54 . 
         [0037]    The undercut  56  includes a height H 1 . The nose  51  further includes a height H 2 . In the preferred embodiment, the height H 2  is greater than the height H 1 . This configuration provides for the most desirable results in the stiffness curve. 
         [0038]    Now with reference to  FIG. 8 , a jounce bumper  60  having an alternative elliptical configuration is provided. The jounce bumper of  FIG. 8  depicts a nose  61  having a generally elliptical shape. The elliptical nose  61  includes an outer surface  62  and a corresponding inner surface  64 . The inner surface  64  includes an undercut  66  having a height H 1 . A bore  63  extends through the center portion of the nose  61  thereby forming the inner surface  64 . The bore  63  is configured to accept the piston rod of a suspension system. The nose further includes a height H 2  where in the preferred embodiment the height H 2  is greater than the height H 1 . 
         [0039]    The undercut  66 , in the present embodiment, is generally rectangular in cross section but extending around the entire ID of the jounce bumper. The undercut creates an varying thickness between the ID and the OD. The undercut includes a generally planar surface  64  extending along the entire ID of the bumper. Two side walls  65 ,  68  extend away from the surface  64  and a generally perpendicular angle. In other embodiments, the side walls  65 ,  68  may extend at different angles away from the surface  64 . 
         [0040]    The curve as illustrated in  FIG. 9  demonstrates the spring rate of the jounce bumper as the jounce bumper is compressed or deflected a corresponding amount of millimeters. During the initial compression of the jounce bumper as shown in the circle illustrated by reference numeral  80 , the spring rate remains generally constant during the initial deflection and compression of the jounce bumper. The jounce bumpers described herein maintain a generally even spring rate during the first ¼ to ½ of deflection of the jounce bumper. Accordingly, the jounce bumpers of the present invention improve handling and reduce harshness felt by the user. 
         [0041]    In the present embodiment, the jounce bumper is used in connection with a strut and corresponding coil in the suspension system. Other uses may be known such as using the jounce bumper in connection with a metal insert having an axle, specifically mounted to a frame or an axle. The jounce bumper may also be used with air spring suspension system or any other system using a jounce bumper. 
         [0042]    In the present invention, the jounce bumper is made from a microcellular urethane (hereinafter referred to as MCU). However, the jounce bumper may be made from any elastomer such as rubber, rubber-like, plastic, plastic-like, polymer, or polymer-like material performing to the same specifications. 
         [0043]    It is noted that the terms “substantially” and “about” may be utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. These terms are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue. 
         [0044]    While particular embodiments have been illustrated and described herein, it should be understood that various other changes and modifications may be made without departing from the spirit and scope of the claimed subject matter. Moreover, although various aspects of the claimed subject matter have been described herein, such aspects need not be utilized in combination. It is therefore intended that the appended claims cover all such changes and modifications that are within the scope of the claimed subject matter.