Patent Publication Number: US-2021164534-A1

Title: Hydraulic damper and a piston for the hydraulic damper assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the benefits of U.S. Provisional Application Ser. No. 62/942,055, filed on Nov. 29, 2019, and Chinese Patent Application No. 202011116638.3, filed on Oct. 19, 2020, the entire content of which are incorporated herein by reference in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a hydraulic damper assembly and a piston for the hydraulic damper assembly. 
     2. Description of the Prior Art 
     Hydraulic suspension dampers typically comprise a tube filled with working liquid, inside of which a slidable piston assembly is placed. The piston assembly is attached to a piston rod led outside the damper through the piston rod guide, and comprises a piston with rebound and compression valve assemblies, which control the flow of working liquid passing through the piston assembly during the rebound and the compression stroke of the damper. Some dampers comprise also a base (bottom) valve assembly with separate rebound and compression valve assemblies controlling the flow of working liquid passing in and out of the compensation chamber, usually formed between the inner and the outer tube of the damper. 
     Each valve assembly usually comprises a stack of resilient disks, often with an additional compression spring, covering the flow passages of the piston and acting as one way valve, deflecting or moving under the pressure of the working liquid to allow the medium flow. Number, shape, diameter, and thickness of each disk provide, among others, an adjustable compression and rebound damping forces. 
     Typical damper characteristic of damping force vs. piston velocity is a trade-off between improvement of the car handling properties and reduction of the unwanted car vibrations (a so called NVH—Noise, Vibration, Harshness requirements). Although dampers featuring low compression forces with degressive characteristics are required to improve the passengers comfort, during severe road and/or drive conditions they also often lead to maximally admissible wheel-knuckle displacements in damper compression direction leading to a suspension closure or jounce bumper engagement, which in turn affects the car safety, comfort, durability, and noise issues. 
     One such a damper is disclosed in U.S. Pat. No. 9,067,471. The damper includes a housing extending along a center axis between an opened end and a closed end. The housing defines a fluid chamber extending therebetween for containing a working fluid. A piston is slidably disposed in the fluid chamber dividing the fluid chamber into a compression chamber and a rebound chamber. A piston rod extends along the center axis and couples to the piston for moving the piston between a compression stroke and a rebound stroke. The piston has a compression surface and a rebound surface. The piston defines at least one compression channel, and at least one rebound channel for allowing the working fluid to flow through the piston during the compression stroke and the rebound stroke. The at least one compression channel radially spaced from an exterior surface of the piston and extending from the compression surface to the rebound surface. The at least one rebound channel, radially and circumferentially spaced from the at least one compression channel, extends from the exterior surface toward the compression surface. 
     There exists a need of independent tuning of damper force characteristic for primary and secondary rides. It is difficult to fulfill such a requirement for existing passive valve systems because standard valve components have influence as on low as high velocity damper characteristic 
     SUMMARY OF THE INVENTION 
     The present invention in its broadest aspect provides for a hydraulic damper assembly having an improved damper characteristics for low and medium velocity ranges. The present invention also reduces damper harshness, e,g, transition between low speed and medium speeded damping, improves the ride comfort and balance of a vehicle. In addition, the present invention provides a hydraulic damper assembly having improved tunability. 
     It is one aspect of the present invention to provide a hydraulic damper assembly. The hydraulic damper assembly comprises a housing extending along a center axis between an opened end and a closed end. The housing defines a fluid chamber extending therebetween for containing a working fluid. A piston is slidably disposed in the fluid chamber dividing the fluid chamber into a compression chamber and a rebound chamber. A piston rod extends along the center axis and couples to the piston for moving the piston between a compression stroke and a rebound stroke. The piston has a compression surface and a rebound surface. The piston defines at least one compression channel, at least one rebound channel, and at least one additional channel, for allowing the working fluid to flow through the piston during the compression stroke and the rebound stroke. The at least one compression channel radially spaced from an exterior surface of the piston and extending from the compression surface to the rebound surface. The at least one rebound channel, radially and circumferentially spaced from the at least one compression channel, extends from the exterior surface toward the compression surface at an oblique angle relative to the center axis. The at least one additional channel, located between the center axis and the at least one compression channel, extends along the piston toward the compression surface. A compression valve is located on the rebound surface of the piston covering the at least one compression channel for limiting working fluid flow through the piston during the compression stroke. A rebound valve is located in the compression chamber and covering the at least one rebound channel for limiting working fluid flow through the piston during the rebound stroke to provide a damping force during the rebound stroke. A proportional bleeding system is located between the compression valve and the piston to establish a bleeding flow passage between the at least one rebound chamber and the additional channel for reducing operation harshness of the hydraulic damper assembly. 
     It is another aspect of the present invention to provide a piston for a hydraulic damper assembly. The piston comprises a body extending along a center axis between a compression surface and a rebound surface. The body defines at least one compression channel, at least one rebound channel, and at least one additional channel, for allowing working fluid to flow through the body. The at least one compression channel is radially spaced from an exterior surface of the body and extends from the compression surface to the rebound surface. The at least one rebound channel is radially and circumferentially spaced from the at least one compression channel and extends from the exterior surface toward the compression surface at an oblique angle relative to the center axis. The at least one additional channel is located between the center axis and the at least one compression channel and extends along the body in a parallel relationship with the center axis toward the compression surface. A compression valve is located on the rebound surface of the body covering the at least one compression channel for limiting working fluid flow through the body during the compression stroke. A rebound valve is located in the compression chamber and covering the at least one rebound channel for limiting working fluid flow through the body during the rebound stroke to provide a damping force during the rebound stroke. A proportional bleeding system is located between the compression valve and the body to establish a bleeding flow passage between the at least one rebound chamber and the additional channel for reducing operation harshness of the hydraulic damper assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
         FIG. 1  is a fragmentary view of a vehicle suspension including a hydraulic damper assembly constructed in accordance with one embodiment of the present invention, 
         FIG. 2  is a cross-sectional perspective view of the hydraulic damper assembly, 
         FIG. 3  is a cross-sectional perspective view of a piston for the hydraulic damper assembly according to one embodiment of the present invention; 
         FIG. 4  is a sectional perspective view of the piston of the hydraulic damper assembly; 
         FIG. 5  is a cross-sectional exploded view of the piston of the hydraulic damper assembly; and 
         FIG. 6  is a graphical illustration of rebound force vs. rebound velocity for the hydraulic damper assembly including the piston according to an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE ENABLING EMBODIMENT 
     Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a hydraulic damper assembly  20  constructed in accordance with one embodiment of the present invention is generally shown in  FIGS. 1-5 . 
       FIG. 1  schematically illustrates a fragment of an exemplary vehicle suspension including the hydraulic damper assembly  20  being attached to a vehicle chassis  22  via a top mount  24  and a number of fasteners  26  disposed on a periphery of an upper surface of the top mount  24 . The top mount  24  connects to a coil spring  28 . The hydraulic damper assembly  20  connects to the steering knuckle  30  supporting a vehicle wheel  32 . 
     As best shown in  FIGS. 2 , the hydraulic damper assembly  20  comprises a housing  34 , having a generally cylindrical shape, disposed on a center axis A. The housing  34  extends between an opened end  36  and a closed end  38 . The housing  34  defines a fluid chamber  40 ,  42  extending along the center axis A between the opened end  36  and the closed end  38  for containing a working fluid. A mounting ring  44 , having a generally circular shape, attaches to the closed end  38  for securing the housing  34  to the vehicle. 
     A piston  46  including a body  48 , having a generally cylindrical shape, is slidably disposed in the fluid chamber  40 ,  42  dividing the fluid chamber  40 ,  42  into a compression chamber  40  and a rebound chamber  42 . The compression chamber  40  extends between the closed end  38  and the piston  46 . The rebound chamber  42  extends between the opened end  36  and the piston  46 . A piston rod guide  50  is located in the rebound chamber  42 , adjacent to the opened end  36  of the housing  34  and in sealing engagement with the opened end  36  of the housing  34  to close the fluid chamber  40 ,  42 . The piston rod guide  50  defines a bore  52 , having a generally cylindrical shape, extending along the center axis A and in communication with the rebound chamber  42 . A piston rod  54 , having a generally cylindrical shape, extends along the center axis A, through the bore  52 , and into the rebound chamber  42  to a distal end  56 . The piston rod  54  couples to the piston  46  for moving the piston  46  in said fluid chamber  40 ,  42  between a compression stroke and a rebound stroke. During the compression stroke, the piston rod  54  and the piston  46  move towards the closed end  38  of the housing  34 . During the rebound stroke, the piston rod  54  and the piston  46  moving toward the opened end  36  of the housing  34 . 
     The piston rod  54  includes a projection  58  extending outwardly from the distal end  56  of the piston rod  54  and through the piston  46  to a terminal end  60 , spaced apart from the piston  46 , to couple the piston  46  to the piston rod  54 . The body  48  of the piston  46  defines a hole  62 , having a generally cylindrical shape, extending along the center axis A and receiving the projection  58  to allow the projection  58  to extend through the piston  46 . A retaining member  64 , located at the terminal end  60 , couples to the projection  58  to secure the body  48  of the piston  46  to the piston rod  54 . 
     According to an embodiment of the present invention and as best shown in  FIGS. 3-4 , the body  48  of the piston  46  has a compression surface  66  and a rebound surface  68 . The compression surface  66 , located in the compression chamber  40 , faces the closed end  38 . The rebound surface  68 , located in the rebound chamber  42 , faces the opened end  36 . The body  48  of the piston  46  defines a cavity  70  located on the compression surface  66  extending from the compression surface  66  toward the rebound surface  68 . 
     The body  48  of the piston  46  defines a plurality of channels  72 ,  74 ,  76  for allowing the working fluid to flow through the piston  46  during the compression stroke and the rebound stroke. According to an embodiment of the present invention, the body  48  of the piston  46  defines at least one compression channel  72 , at least one rebound channels  74 , and at least one additional channel  76 . The channels  72 ,  74 ,  76  extend through the piston  46  for allowing the working fluid to flow through the piston  46  during the compression stroke and the rebound stroke. The at least one compression channel  72 , radially spaced from an exterior surface  78  of the body  48  of the piston  46 , extends from the compression surface  66  to the rebound surface  68 . The at least one rebound channel  74 , radially and circumferentially spaced from the at least one compression channel  72 , extends from the exterior surface  78  toward the compression surface  66  at an oblique angle relative to the center axis A. The at least one additional channel  76 , located between the center axis A and the at least one compression channel  72 , extends along the piston  46  toward the compression surface  66 . The body  48  of the piston  46  defines a groove  77  in fluid communication with the cavity  70  and the at least one additional channel  76 . The groove  77  extends about the center axis A and toward the rebound surface of the body  48  of the piston  46 . 
     According to an embodiment of the present invention, the at least one compression channels  72  includes a plurality of compression channels  72 . The plurality of compression channels  72  are located about the center axis A and circumferentially spaced from one another. The compression channels  72  extend from the compression surface  66  to the rebound surface  68  in a parallel relationship with the center axis A. The at least one rebound channels  74  includes a plurality of rebound channels  74 . The plurality of rebound channels  74  are located about the center axis A, radially spaced from the compression channels  72  and circumferentially spaced from one another. Each rebound channel  74  of the set of rebound channels  74  is located on the exterior surface  78  and between adjacent compression channels  72  of the set of compression channels  72 . The rebound channels  74  extend from the exterior surface  78  toward the compression surface  66  at an oblique angle a relative to the center axis A. According to an embodiment of the present invention, the oblique angle a is less than 90° relative to the center axis A. The at least one additional channel  76  includes a plurality of additional channels  76 . The plurality of additional channels  76  are located between the center axis A and the compression channels  72  and about the center axis A. The additional channels  76  are circumferentially spaced from one another. In other words, the additional channels  76  are located closer to the center axis A than the compression channels  72  and the rebound channels  74 . The additional channels  76  are in fluid communication with the cavity  70  and extend along the body  48  of the piston  46  in a parallel relationship with the center axis A toward the compression surface  66 . 
     The rebound surface  68  of the piston  46  defines at least one orifice  80  in fluid communication with the at least one additional channel  76 . According to an embodiment of the present invention, the at least one orifice  80  includes a plurality of orifices  80 , located adjacent to the bore  52  and about the center axis A. The orifices  80  are circumferentially spaced from one another wherein each orifice  80  of the plurality of orifices  80  is in and in fluid communication with an additional channel  76  of the plurality of additional channels  76  for allowing the working fluid to flow through the body  48  of the piston  46 . According to one embodiment of the present invention, each orifice  80  of the plurality of orifices  80  has a diameter less than a diameter of each additional channel  76  of the plurality of additional channels  76 . It should be appreciate that the size of the diameter of the orifices  80  can be fined tune or calibrated depending on a user&#39;s preference. 
     As best illustrated in  FIG. 5 , a compression valve  82  including a plurality of discs with each disc having a generally circular shape, is located on the rebound surface  68  of the body  48  of the piston  46  covering the at least one compression channel  72  for limiting working fluid flow through the piston  46  during on compression stroke to provide a damping force during the compression stroke. According to an embodiment of the present invention, the compression valve  82  can include a plurality of five discs stacked on top of one another and sandwiched between the rebound surface and the distal end  56  of the piston rod  54 . A rebound valve  84 , including a plurality of discs with each disc having a generally circular shape, is located in the cavity  70  and sandwiched between the body  48  of the piston  46  and the retaining member  64  covering the at least one rebound channel  74  for limiting working fluid flow through the piston  46  during the rebound stroke to provide a damping force during the rebound stroke. According to an embodiment of the present invention, the rebound valve  84  can include a plurality of five discs stacked on top of one another and sandwiched between the piston  46  and the retaining member  64 . It should be appreciated that each of the compression valve  82  and the rebound valve  84  can include up to ten discs. 
     A compression valve seat  86 , located on the rebound surface  68  between the at least one compression channel  72  and the at least one additional channels  76 , extends outwardly from the rebound surface  68  and annularly about the center axis A. The compression valve seat  86  is in an abutment relationship with the compression valve  82 . As best illustrated in  FIG. 4 , the compression valve seat  86  defines at least one slot  88  in alignment with the at least one compression channel  72  and the at least one additional channel  76 . According to an embodiment of the present invention, the at least one slot  88  can includes a plurality of slots  88 . The plurality of slots  88  are located about the center axis A and circumferentially spaced from one another. 
     Each slot  88  of the plurality of slots  88  is in an alignment with a compression channel  72  of the plurality of compression channels  72  to establish fluid communication between the at least one slot  88  and the at least one compression channel  72 . According to an embodiment of the present invention, the slots  88  are located radially inwardly from the set of compression channels  72  wherein each slot  88  is in a radial alignment with each compression channel  72  of the plurality of compression channels  72 . 
     A proportional bleeding system  90  is located between the compression valve  82  and the body  48  of the piston  46  to establish a bleeding flow passage between the at least one rebound channel  74  and the at least one additional channel  76  for reducing operation harshness of the hydraulic damper assembly  20 . According to an embodiment of the present invention, the proportional bleeding system  90  includes an additional valve  92 ,  94 , located between the compression valve  82  and the body  48  of the piston  46 , covering the at least one additional channel  76  to provide a damping force to the working fluid flowing through the at least one additional channels  76 . 
     According to an embodiment of the present invention, the additional valve  92 ,  94  of the proportional bleeding system  90  includes a deflective disc  92  and a spacer  94 . The deflective disc  92 , having a generally circular shape, is located adjacent to the piston  46  covering the set of additional channels  74 . The spacer  94 , having a generally circular shape, is located between the deflective disc  92  and the compression valve  82  to axially space the deflective disc  92  from the compression valve  82 . According to an embodiment of the present invention, the spacer  94  has a diameter D 1  less than a diameter D 2  of the deflective disc  82  to allow the deflective disc  82  to flex in response to working fluid flowing through the additional channels  76 . A protrusion  96 , located between the compression valve seat  86  and the at least one additional channels  76 , extending outwardly from the rebound surface  68  and annularly about the center axis A and in an abutment relationship with the deflective disc  92 . 
     Referring back to  FIG. 5 , the retaining member  64  includes a top portion  98 , a bottom portion  100 , and a spring  102 . The spring  102  is compressed between the top portion  98  and the bottom portion  100 . The bottom portion  100  includes a bushing  104 , having a generally cylindrical shape, extending about the center axis A and coupled to the projection  58  of the piston rod  54 , thereby securing the retaining member  64  to the piston rod  54 . A bottom flange  106  extends radially outwardly from the bottom portion  100  for receiving one end of the spring  102 . The top portion  98  includes a sleeve  108 , having a generally cylindrical shape, extending about the bushing  104 . A top flange  110  extends radially outwardly from the top portion  98  for receiving another end of the spring  102 . It should be appreciated that the present invention is applicable to various passive or controlled hydraulic dampers such as but not limited to mono-tube or twin-tube type hydraulic damper assemblies. 
     In operation, during a compression stroke, the piston rod  54  and the piston  46  move toward the closed end  38  of the housing  34 . In response to the movement of the piston rod  54  and the piston  46 , the working fluid contained in the compression chamber  40  becomes compressed and moves towards the rebound chamber  42  through the at least one compression channel  72  and the compression valve  82 . Accordingly, the pressure of the compression valve  82  restricts the amount of working fluid flowing through the body  48  of the piston  46 , thereby generating a damper force during the compression stroke. 
     As best illustrated in  FIG. 3  wherein the arrows indicate the flow of the working fluid, during the rebound stroke, the piston rod  54  and the piston  46  move toward the opened end  36  of the housing  34 . In response to the movement of the piston rod  54  and the piston  46 , the working fluid contained in the rebound chamber  42  becomes compressed and moves toward the compression chamber  40  through the at least one rebound channel  74  and the rebound valve  84 , as indicated by the hollow arrows. At the same time, the working fluid also flows toward the compression chamber  40  via the compression channels  72 . In particular, as indicated by solid arrows, the working fluid flows through the at least one rebound channel  74  into the groove  77 . Since the groove  77  is in fluid communication with the at least one additional channel  76 , the working fluid flows through the at least one additional channel  76  and the at least one orifice  80  and into the at least one compression channel  72  via the proportional bleeding system  90 . This arrangement causes the damping characteristic of the hydraulic damper assembly  20  to be more progressively for low speed thereby improving the handling of the vehicle. In other words, this arrangement provides smooth transition between states of closed and opened valves by reducing the effective gradient of the characteristic in transition area. It reduces the accelerations and jerks acting on the car body thereby improving the ride comfort of the vehicle. 
       FIG. 6  is a graphical illustration comparing the performance of a hydraulic damper assembly  20  constructed in accordance with the present invention and a standard hydraulic damper assembly. As illustrated in  FIG. 6 , the hydraulic damper assembly  20  constructed in accordance with the present invention shapes the rebound characteristic below the valve opening velocity. In addition, the hydraulic damper assembly  20  enables extra bleed opening point. It should be appreciated that the force for additional channels and the apertures can be adjust independently in wide velocity range. Accordingly, the damping characteristic of the hydraulic damper assembly can be more progressively set for low speed thereby improving the handling of the vehicle handling. Above the extra bleed opening point, e.g. indication of the opening of the deflective disc, the slope of the damping characteristic is much lower thereby providing a smoother transition between a closed state and an opened state of the deflective disc. In addition, this arrangement reduces the accelerations and jerks acting on the vehicle body which simultaneously improves the comfort. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings and may be practiced otherwise than as specifically described while within the scope of the appended claims. The use of the word “said” in the apparatus claims refers to an antecedent that is a positive recitation meant to be included in the coverage of the claims whereas the word “the” precedes a word not meant to be included in the coverage of the claims.