Patent Publication Number: US-2019195307-A1

Title: Frequency-Dependent Damping Valve Assembly And Vibration Damper

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a U.S. national stage of application No. PCT/EP2017/069589, filed on Aug. 3, 2017. Priority is claimed on German Application No. DE102016217113.5, filed Sep. 8, 2016, the content of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is directed to a damping valve arrangement of a vibration damper for a motor vehicle with a frequency-dependent damping force characteristic. 
     2. Description of the Prior Art 
     The object of a vibration damper in a motor vehicle is to damp the vibrations excited by an uneven road surface. In doing so, it is always necessary to find a compromise between driving safety and driving comfort. A vibration damper having a damping valve arrangement adjusted to be hard and has a high damping force characteristic is optimal for highly safe driving. If there is a high demand for comfort to be met, the damping valve arrangement should be adjusted to be as soft as possible. It is very difficult to find this compromise in a vibration damper with a conventional damping valve arrangement which is not adjustable electronically by an actuator. 
     A generic damping valve arrangement with a frequency-dependent damping force characteristic is known from DE 10 2014 210 704. This damping valve arrangement comprises a check valve arranged inside a cylinder filled with a damping medium and which has at least one flow channel covered by a plurality of valve disks. The damping valve arrangement further comprises a control arrangement arranged coaxial to the check valve and which comprises a control pot with an axially displaceable control piston arranged in the control pot. The control piston axially limits a control space enclosed in the control pot and connected to the damping valve arrangement via an inlet connection. A spring arrangement is arranged between the control piston and the damping valve and axially introduces a spring force into the control piston on the one hand and into the damping valve on the other hand. When the control space is filled with damping medium, the control piston displaces in direction of the damping valve and, via the spring element, increases the pressing pressure of the valve disks of the damping valve, which increases the damping force. The spring arrangement comprises a plurality of plate spring-shaped spring elements arranged such that they are stacked with their central openings against one another, and the radial outer ends of the spring elements come in contact at least indirectly with the control piston or with the damping valve, respectively. 
     In damping arrangements of this type, it is very important that the individual component parts of the spring arrangement are centered very accurately relative to one another. If this is not ensured, a tilting of individual component parts and a clamping of the spring arrangement under load cannot be ruled out. Because of the manufacturing tolerances, however, the current requirement for accurate centering of the spring arrangement component parts can only be met with great difficulty and with the use of expensive additional machining processes. 
     SUMMARY OF THE INVENTION 
     It is the object of one aspect of the present invention to provide an alternative frequency-selective damping valve arrangement with a spring arrangement that avoids the risk of tilting of the component parts of the spring arrangement and prevents a clamping of the spring arrangement under load condition. 
     According to one aspect of the present invention the spring arrangement comprises at least a first disk-shaped spring element and a second disk-shaped spring element and at least one separating element arranged between the spring elements that is slidingly axially displaceable at the carrier surface, wherein the spring elements axially contact the separating element by their disk center and axially contact the damping piston and/or the control piston at least indirectly by their disk edge. 
     According to a further advantageous constructional variant, it is provided that the surface of the separating element facing the carrier has a sliding portion and at least a first clearance portion and a second clearance portion arranged, respectively, axially adjoining a side of the sliding portion, wherein the clearance portions in each instance radially limit a free space between the carrier and the separating element. The clearance portions help to prevent a clamping of the sliding element at the carrier in case of possible tilting of the separating element with respect to the longitudinal axis of the carrier. 
     In a very simple advantageous embodiment form, a clearance portion can be realized in a very simple manner, for example, by recessing the axial end portion of the separating element so that the latter is formed such that its free space forms an angle between the carrier and the separating element, wherein the angle tip is directed toward the sliding portion. 
     It is provided in an advantageous manner that the separating element can be constructed annularly as an open, i.e., slit, ring or as a closed ring. In this regard, the separating element can have any cross-sectional shape which meets the set requirements. In the simplest case, the separating element can have a circular cross section. 
     The separating element can be made from a metal or a plastic, with or without fiber reinforcement, which is suitable to transfer force from one spring element to the other spring element without deforming. 
     Advantageously, it can be provided that the separating element is constructed in such a way that the disk edge of the first spring element and the disk edge of the second spring element do not touch one another even under a maximum load of the spring arrangement so that the spring rate can be utilized to the maximum extent. In the simplest case, this effect can be achieved through the selection of the length of the axial extension of the separating element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described in more detail referring to the figures. 
       The drawings show: 
         FIG. 1  is a sectional view of an exemplary constructional variant of a frequency-dependent damping valve arrangement according to the invention in a cylinder of a vibration damper; and 
         FIG. 2  is a partial sectional view of an exemplary constructional variant of a spring arrangement according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
       FIG. 1  shows a portion of a vibration damper for a motor vehicle with a frequency-dependent damping valve arrangement  1  according to one aspect of the invention in a sectional view. 
     The latter comprises a cylinder  2  which is at least partially filled with a damping fluid. 
     Damping valve arrangement  1  is fastened to an axially displaceable piston rod  3  inside the cylinder  2 . Damping valve arrangement  1  comprises a damping piston  4  with at least one check valve  5 , this check valve  5  having at least a first flow channel  6  formed therein for the damping fluid, which flow channel  6  is covered by at least one valve disk  7 . 
     Damping piston  4  divides a first working chamber  8  from a second working chamber  9  inside cylinder  2  such that the ratio of the damping medium pressure in the two working chambers  8 ,  9  varies depending on the direction of axial movements of damping piston  4  in cylinder  2 . 
     Further, damping valve arrangement  1  has a control arrangement  10  that contains a control pot  11  with a cylindrical pot wall  12  and a disk-shaped pot base  13  and with a control piston  16  that is axially displaceably arranged in control pot  11  and axially limits a control space  14  enclosed in control pot  11 . 
     A spring arrangement  20  is arranged between damping piston  4  and control arrangement  1  and impinges with a defined spring force on valve disk  7  axially in direction of first flow channel  6  and on control piston  16  in direction of pot base  13 . 
     All of the structural component parts of damping valve arrangement  1  are arranged coaxial to one another at piston rod  3 . As shown in  FIG. 1 , damping valve arrangement  1  can comprise an additional guide sleeve  29  arranged so as to be threaded onto the piston rod and functions as a carrier  27  within the meaning of the invention. It is provided in the constructional variant shown in  FIG. 1  that the piston rod  3  extends centrally through damping piston  4  and a guide sleeve  29  functioning as a carrier  27 , which guide sleeve  29  in turn likewise extends centrally through spring arrangement  20  and control piston  16 . Guide sleeve  29  comprises a first guide portion  29   a  and a second guide portion  29   b  axially adjacent thereto. Control piston  16  can slide axially along first guide portion  29   a , and spring arrangement  20  can slide axially along second guide portion  29   b . The direction of the axial movements of control piston  16  depends on the damping medium pressure in control space  14 . 
     It is provided in the constructional variant shown in  FIG. 1  that the damping valve arrangement  1  comprises at least a second flow channel  15  formed at and/or in piston rod  3  and which connects the first working chamber  8  and/or second working chamber  9  with the control space  14 . 
     Control pot  11  of control arrangement  1  is connected to the piston rod in the area of pot base  13  with the aid of connection element  30 . Connection element  30  shown in  FIGS. 1 and 2  is a threaded nut. It will be appreciated that connection element  30  can also have a different suitable constructional form. In general, the connection between the piston rod and/or guide sleeve  29  and control pot  11  can be carried out by bonding engagement and/or positive engagement and/or frictional engagement. 
     Control piston  16  arranged inside control pot  11  is constructed so as to be axially displaceable so that when a damping fluid pressure persists over a longer period of time in control space  14  of control arrangement  1  the control piston  16  is displaced in direction of valve disk  7  of check valve  5  and tightens spring arrangement  20  so that the spring force acting on valve disk  7  through spring arrangement  20  and, therefore, the damping force of check valve  5  are increased. 
     As is shown in  FIG. 1 , control piston  16  has a seal arrangement  17  that seals control piston  16  relative to pot wall  12 . This seal arrangement  17  comprises a circumferential groove  19  formed at control piston  16  and has a seal ring  18  arranged therein. 
     Second flow channel  15  comprises an inlet restrictor  31 , which defines the flow of damping medium out of first working chamber  8  into control space  14 . 
     Further, an outlet restrictor  32  is formed at control piston  16  and influences the flow of damping medium out of control chamber  14 . This outlet restrictor  32  can also be formed at carrier  3 . 
     A first stop  33  and second stop  34  are formed at control arrangement  1  for defining the soft damping characteristic and hard damping characteristic. First stop  33  is formed as a stop ring in the constructional variants shown in  FIG. 1 , and second stop  34  is formed as an at least partial ridge of pot base  13 . It will be appreciated that second stop  34  can also be formed as a stop ring or as an additional stop element which can be arranged inside of control space  14 . 
     Spring arrangement  20  can be constructed in a variety of ways. In the constructional variant shown in  FIG. 1 , it is provided that spring arrangement  20  comprises a plurality of spring elements  21 ,  22  separated from one another by a separating element  26 . Spring elements  21 ,  22  and separating element  26  surround guide sleeve  29  and are arranged coaxial to the rest of the structural component parts of damping valve arrangement  1 . First spring element  21  is axially supported at control piston  16  on one side and at separating element  26  on the other side. Further spring elements are axially supported at least indirectly at separating element  26  on the one side and at valve disk  7  via a spacer ring  24  on the other side. 
     During a high-frequency excitation of the vibration damper, the damping fluid pressure persists only briefly in control space  14 , whereas the damping fluid pressure persists significantly longer in control space  14  during a low-frequency excitation of the vibration damper. 
     The control arrangement  10  of damping valve arrangement  1  is constructed such that when a damping fluid pressure persists over a longer period of time in control space  14  of control arrangement  10  the control piston  16  is displaced in direction of valve disk  7  of check valve  5  and tightens spring arrangement  20  so that the spring force acting on valve disk  7  through spring arrangement  20  and, therefore, the damping force of check valve  5  are increased. 
     As has already been mentioned, spring arrangement  20  comprises at least a first disk-shaped spring element  21  and a second disk-shaped spring element  22  and a separating element  26  arranged between spring elements  21 ,  22  and slidingly axially displaceable at the carrier surface  28 . Spring elements  21 ,  22  axially contact separating element  26  by their radially central portion  21   a ,  22   a  and at least indirectly axially contact damping piston  4  on one side and control piston  16  on the other side by their radial portion  21   b ,  22   b.    
       FIG. 2  shows particularly clearly that the surface of separating element  26  facing carrier  27  is divided into three portions. These three portions comprise a sliding portion  26   a , a first clearance portion  26   b , and a second clearance portion  26   c  which are arranged, respectively, axially adjoining a side of the sliding portion  26   a . The clearance portions  26   b ,  26   c  in each instance radially limit a free space  35 ,  36  between carrier  27  and separating element  26 . 
     According to the constructional variant shown in  FIG. 2 , clearance portions  26   b ,  26   c  are constructed such that free space  35 ,  36  in each instance forms an angle between carrier  27  and separating element  26 , and the angle tip is directed toward the sliding portion  26   a . It will be appreciated that the free spaces  35 ,  36  can also have other suitable cross-sectional shapes. 
     According to  FIGS. 1 and 2 , separating element  26  can be constructed annularly as a closed ring or as an open ring, i.e., slit ring, in the same way as at least one free space  35 ,  36  can be formed annularly. 
     Further, separating element  26  can be made from a metal or a suitable plastic, with or without fiber reinforcement. 
     In the constructional variants according to  FIGS. 1 and 2 , the length of the axial extension of separating element  26  has been selected such that the radial edge portion  21   b  of the first spring element  21  and the radial edge portion  22   b  of the second spring element  22  do not touch one another even under maximum loading of spring arrangement  20 . 
     Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.