Abstract:
A vibration damper with adjustable damping force, having a cylinder in which a piston is guided with a piston rod so as to be axially movable. The piston divides the cylinder into a first and a second work space. At least one damping valve is arranged in a flow connection of one of the two work spaces and is adjustable via an external adjusting device. The damping valve has a sleeve-shaped housing in which a valve body is arranged so as to be movable. The housing of the damping valve is closed at the end by a cover which has, on the outer side, an engagement for the adjusting device which can be mounted separate from the damping valve.

Description:
SUMMARY OF THE INVENTION 
     1. Field of the Invention 
     The invention is directed to a vibration damper with adjustable damping force. 
     2. Discussion of the Prior Art 
     German reference DE 195 42 293 A1 describes a vibration damper with adjustable damping force, wherein the vibration damper comprises a cylinder with an axially movable piston which is fastened to a piston rod and which divides the cylinder in two work spaces. An externally adjustable damping valve is connected to one of the work spaces and throttles the damping medium which is displaced from the adjoining work space so that a damping action takes place. The externally adjustable damping valve has no fixing means for a determined damping force adjustment which should be reproducible. 
     German reference DE 197 24 328 C1 shows a further development of DE 195 42 293 A1. A locking device has been assigned to the damping valve to enable a desired adjustment of damping force in an exactly reproducible manner. The damping valve according to DE 197 24 328 A1 does not present any difficulties with respect to function. The problem lies in the difficult assembly because a large number of structural component parts, some of which are very small, must be assembled under pretensioning by spring. The expenditure on manual assembly is considerable. 
     European reference EP 0 601 982 B1 discloses a damping valve which is formed of two valve cartridges for different pressure ranges. The exact construction of the valve is not described. However, there is a locking device by which a valve adjustment can be reproduced once it has already been adjusted. For assembly, a pressure spring of more robust dimensioning is first inserted into a valve receiving opening. The bottom part of a valve housing is then inserted into the valve receiving opening until it contacts the pressure spring. The bottom part of the housing receives a valve body which is pretensioned by a closing spring. The closing spring is supported at a spring clamp whose rear side contacts a top part of the valve housing which is screwed into the valve receiving opening. An adjusting cap which is connected by a clamping screw with the spring clamp is fitted to the top part of the valve housing. This assembly also involves considerable expenditure because, in addition to the pressure spring and the closing spring, several additional springs of the locking device act on the adjusting cap, which makes handling of the entire damping valve more difficult. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an adjustable damping valve which is improved with respect to ease of assembly. 
     According to the invention, this object is met in that the housing of the damping valve is closed on the end by a cover which has, on the outer side, a contact or engagement for the adjusting means which can be mounted separate from the damping valve. 
     The essential advantage compared to the prior art cited above is that the adjusting means and the actual damping valve form two constructional units which can be mounted separately and each of which can be closed in itself. Assembly is appreciably facilitated by the strict function and spatial separation of the two damping valve constructional units. 
     In a further embodiment, the adjusting means have a fastening ring for the damping valve in which an adjusting bolt or adjusting pin is arranged, wherein locking means engage between the adjusting pin and the fastening ring. The fastening ring takes over the function of spatially holding the adjusting means and the adjusting pin takes over the adjusting movement function. 
     Accordingly, it is provided that the fastening ring, depending on the provided damping force steps of the damping valve, has locking recesses in which a locking body engages, which locking body is pretensioned by spring force. The locking device connects the fastening ring and the adjusting pin to a sufficient extent to form a constructional unit. 
     According to another embodiment, the locking recesses are constructed in the circumferential direction in the fastening ring, so that the adjusting pin carries out a rotational operating movement. 
     For the purpose of a simple transmission of the adjusting movement, a wrench connection is provided between the adjusting pin and the cover of the damping valve housing which transmits a rotational movement of the adjusting pin to the cover and changes the distance between the base and the cover of the damping valve housing by means of a transmission arrangement. 
     In order that the mounting process for the two constructional units, namely, the adjusting means and damping valve, proceeds as quickly as possible, the damping valve housing has torque transmission surfaces in the direction of the fastening ring which are contacted by corresponding contact surfaces of the fastening ring, so that the screwing in movement of the fastening ring is transmitted to the damping valve housing. A further advantage is that the tool for screwing in the damping valve housing is greatly simplified. A commercially available crescent wrench, ring wrench or open jaw wrench can be used on the fastening ring. 
     In this further embodiment, the adjusting pin travels over an axial engagement path in the wrench connection to the cover of the damping valve housing relative to the fastening ring independent from the common mounting movement of the constructional unit comprising the adjusting means and damping valve. 
     In this regard, the fastening direction has two rows of locking recesses in an axial arrangement, wherein one row defines the position of the adjusting pin in which the wrench connection between the cover of the damping valve housing and the adjusting pin is not engaged. 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows an overall view of a vibration damper pursuant to the present invention; 
     FIG. 2 shows a longitudinal section through the vibration damper; 
     FIG. 3 shows a valve block with a pressure pipe as an individual part; 
     FIG. 4 shows a section IV—IV through the valve block in FIG. 3; 
     FIG. 5 shows a section V—V through the valve block in FIG. 3; and 
     FIGS. 6 to  9  show construction variants of the constructional units of the adjusting means and damping valve. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a three-dimensional view of a vibration damper  1  in which a piston rod  3  is arranged so as to be axially movable. The vibration damper  1  has an upper reservoir pipe portion  5  and a lower reservoir pipe portion  7  which are fastened to a valve block  9 . Damping valves  11 ;  13 ;  15 ;  17  are arranged in the valve block  9  for both movement directions of the piston rod  3 , wherein the damping valves work separately according to flow direction and flow rate. With respect to the flow rate, additional damping valves can also be used, so that the damping force of the vibration damper can be adjusted more sensitively. 
     FIG. 2 shows the vibration damper of FIG. 1 in longitudinal section. A piston  19  is fastened to the piston rod  3  and divides a pressure pipe  21  into an upper and a lower work space  23 ;  25 . Additional damping valves whose damping forces combine with the damping valves  11  to  17  (FIG. 1) can be arranged in the piston  19  if necessary. 
     The two reservoir pipe portions  5 ,  7  and the pressure pipe  21  form fluid connections  27 ;  29  to the valve block  9 . A circumferentially extending web  31  with a seal  33  separates the two fluid connections. The upper work space  23  has a fluid opening  35  at the fluid connection  27 , so that the work medium which is displaced during the upward movement of the piston  19  is displaced at least partly in the fluid connection up to the damping valves  11 ;  13 . A portion of the medium can be displaced by the above-mentioned piston valves into the lower work space  25 . 
     The lower work space  25  is likewise connected via a fluid opening  37  in the pressure pipe  21  with the fluid connection  29  and is accordingly connected to the damping valve  15 ;  17 . A gas-filled compensation space  41 , which is separated by a dividing piston  39 , adjoins the lower work space  25 . 
     FIG. 3 shows the valve block  9  together with the pressure pipe  21  as a constructional unit. This view shows how the damping medium flows out of the upper fluid connection  27  (FIG. 2) via a flow-in opening  43  into the valve block  9 , continues out of the first damping valve  11  which determines the damping in the lower flow velocity range, via a connection duct  45  past the damping valve  13  for the upper flow velocity range, and then exits the valve block via a flow-out opening  47 . A corresponding flow path is provided for the damping valves  15 ;  17 . The damping valves  11 ;  13  and  15 ;  17  are hydraulically connected in parallel. 
     FIGS. 4 and 5 show sectional views through the valve block  9  in section planes of the damping valves  11 ;  15 . The damping valves are screwed into receiving openings  49  which extend parallel to one another and at right angles to the longitudinal axis of the damper. In this way, a very compact valve block  9  is achieved. Due to its central arrangement, the flow paths have a uniform length in the pulling and pushing directions. 
     FIG. 6 shows one of the damping valves  11 ;  15  independent from the valve block  9 . The damping valve  11 ;  15  comprises two self-enclosed and independent constructional units. First, the actual damping valve is arranged in a damping valve housing  51  and comprises an axially adjustable valve body  53  which determines a throttle cross section  55  depending on its axial position. The valve body  53  is constructed in one piece with a cover  57  of the housing  51 , wherein the cover  57  closes the housing  51 . The damping valve housing  51  includes a base  59  which has a flow-in opening  61  that is covered by a spring-loaded check valve body  63 . The check valve body  63  ensures in both damping valves that a single through-flow direction is maintained in the damping valve pairs  11 ;  13  and  15 ;  17 . 
     For mounting purposes, the valve body  53  is provided with a return spring  65  which has only a very slight pretensioning and which is guided radially in the valve body  53 . Subsequently, the check valve body  63  is fitted on the valve body  53  and the latter is screwed into the damping valve housing  51 . This completes the damping valve constructional unit. Adjusting means  67  which adjoin the damping valve housing  51  axially are assigned to the damping valve  11 ;  15 . The adjusting means  67  comprise a fastening ring  69  and an adjusting pin  71 . The adjusting pin  71  has a stop shoulder  73  which is supported at a step of the fastening ring  69 . A definitive axial position of the two structural component parts is realized in this way. The adjusting means have locking means which include spherical bodies  75  in combination with a pretensioning spring  77  inside a transverse bore hole of the adjusting pin  71 , which spherical bodies  75  engage in locking recesses  79  of the fastening ring  69 . 
     For mounting purposes, the pretensioning spring  77  is inserted with the spherical bodies  75  into the transverse bore hole of the adjusting pin  71 . The adjusting pin  71 , which is provided with a circumferential seal  81 , is then pushed into the fastening ring  69  until the stop shoulder  73  contacts the step of the fastening ring  69 . The adjusting pin  71  is then turned until the locking means take effect. The locking means fix the adjusting pin  71  relative to the fastening ring  69  and ensure the presence of an adjusting means constructional unit. 
     Finally, the damping valve constructional unit is screwed into one of the receiving openings  49 , for which purpose the damping valve housing  51  has an external thread  83 . The fastening ring  69  is fastened to the damping valve housing  51  in the same receiving opening, likewise by an external thread  85 . A seal  87  hermetically closes the receiving opening  49 . 
     For adjusting the damping valve, the adjusting pin  71  has a wrench connection  89  to the cover  57  similar to a screwdriver. In this respect, the cover  57  with valve body  53  is considered as a screw which is moved higher or lower axially in the damping valve housing by means of a screwing movement and accordingly determines the throttle cross section  55 . As the case may be, the wrench connection  89  must be produced by a small rotating movement of the adjusting pin  71  relative to the cover  57  of the damping valve. 
     FIG. 7 shows one of the damping valves  13 ;  17  which are used for damping in the upper flow velocity range. It is very important that the same adjusting means  67  can be used for all damping valves. There are slight differences only in the actual damping valve, namely, the valve body  53  and an associated pressure spring  91 ; in particular, these differences consist in that the pretensioning of the pressure spring  91  is very much higher than the pretensioning of the return spring  65 . The pressure spring  91 , in connection with the surface A at the valve body  53  to which pressure is applied, determines the damping behavior of the damping valves  13 ;  17 . 
     FIG. 8 shows a modification of FIG. 7 which has been improved with respect to ease of assembly. The cover  57  of the housing  51  has a guide sleeve  93  which, in its central opening, at least partly receives and radially guides the pressure spring  91  and the valve body  53 . The manner of operation of the damping valve is identical to that of the construction according to FIG.  7 . 
     FIG. 9 shows a modification of FIG.  7 . Of course, the idea realized in FIG. 9 can also be used in the damping valves  11 ;  15 . The essential difference in the construction according to FIG. 9 consists first in that the adjusting means  67  in the fastening ring  69  have two rows of locking recesses  79   a;    79   b  and the adjusting pin  71  can accordingly occupy two operating positions. After the adjusting means are mounted in accordance with the description in FIG. 7, the stop shoulder  73  contacts the step of the fastening ring  69 . 
     The other difference in this construction consists in that the fastening ring  69  has a plurality of contact surfaces  95  in the shape of tooth segments at the circular end of the fastening ring  69  oriented in the direction of the damping valve housing  51 . The damping valve housing  51  has torque transmission surfaces  97  whose arrangement is adapted to the contact surfaces  95  of the fastening ring  69 , so that the contact surfaces  95  and the torque transmission surfaces  97  engage in one another like a claw coupling. 
     During the process of screwing in the entire damping valve, the adjusting pin  71  is adjusted in such a way that the locking means act in the upper switching position. In so doing, the wrench connection  89  between the adjusting pin  71  and the cover  57  is not produced. The fastening ring  69  and the housing  51  are assembled, so that the contact surfaces  95  and the torque transmission surfaces  97  form the above-mentioned claw coupling. The housing  51  can then be screwed into the receiving opening  49  (FIGS. 4 and 5) via the fastening ring  69 . As soon as a secure fit of the two constructional units is ensured, the wrench connection  89  can be produced after movement along an axial engagement path  99  and a damping force adjustment can be carried out, where appropriate, in that the cover  57  executes a rotating movement which is converted by an adjusting thread  101  between the cover  57  and the damping valve housing  51  into an axial movement of the cover  57 , so that the installation length and, therefore, the pretensioning of the pressure spring  91  changes. This adjusting process is identical in all of the damping valves  13 ;  17  regardless of the specific construction. 
     When the adjustment of damping force is concluded, the adjusting pin  71 , whose locking means engage in the locking recesses  79   b,  can be moved back again into the upper position. Two advantages can be achieved with this construction. Firstly, no negligent adjustment of damping force can take place. Secondly, the adjusting means  67  can also be removed again independent from the damping valve housing and, if necessary, replaced by a simple cover. This possibility represents a genuine economizing on weight, which is to be considered as a great advantage particularly in racing applications. 
     The invention is not limited by the embodiments described above which are presented as examples only but can be modified in various ways within the scope of protection defined by the appended patent claims.