Adjustable vibration damper
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an adjustable vibration damper, in particular, for automotive vehicles. The adjustable vibration damper has a cylinder containing a damping fluid, an axially-movable piston rod projecting into the cylinder in a sealed manner, a damping piston fastened to the piston rod, which damping piston divides the cylinder into two work chambers, and a damping valve equipped with a valve seat. The damping valve, by means of an axially movable valve body, controls the effective cross section of a damping passage connecting the two work chambers of the cylinder. The valve body, starting from its pressurized end surface has at least one passage having a constant throttle cross section, which passage runs from the pressurized end surface toward the back side of the valve body, located on the other end. In addition, the valve body also has a throttle passage running in the outflow direction, which throttle passage is controlled by an axially movable, continuously positionable pilot control element. 
     2. Background Information 
     German Patent No. DE-PS 37 19 113, which corresponds to U.S. Pat. No. 4,880,086, and German Laid Open Patent Application No. DE-OS 38 35 705 disclose hydraulically adjustable vibration dampers, the damping force of which can be continuously adjusted in both the tension and compression direction. For this continuous adjustment, a damping valve having an axially movable valve body and a valve seat controls the effective cross section of a damping passage. The throttle cross section of the damping passage is thereby controlled by an axially movable, continuously positionable control needle which interacts with the valve body. However, one disadvantage of such an arrangement is that the need for additional flow connections and partitions between the valve body and the pilot control element increases the size of the overall system. 
     OBJECT OF THE INVENTION 
     The object of the invention is to create a vibration damper with a two-stage damping valve, in which the damping valve can be manufactured economically, has a low overall height and consists of essentially only a few parts, most of which parts are extremely simply to manufacture. 
     SUMMARY OF THE INVENTION 
     This object is achieved by the present invention, in that the pilot control element is located within a recess formed inside the valve body. 
     One advantage of this configuration is that, a pilot-controlled valve, having a self-supplied pilot stage can be used to control and regulate the damping medium in the vibration damper. To achieve this, the pressure difference which generates the damping force can be used to adjust the valve body. As a result of the installation of the pilot control element and the corresponding flow connections inside the valve body, an economical module can be manufactured, which module can consist of only a few, easily manufactured parts, but which module can still have a low overall height. 
     In accordance with an additional essential characteristic of the present invention, the pilot control element is preferably a ball. 
     In one configuration of the present invention, the pilot control element, which is axially movable in the valve body, can preferably be supported on the armature of an electromagnet by means of a connecting element. 
     In a additional favorable embodiment of the present invention, the valve body and the armature can be located so that they are axially movable in a common hole, or bore, within the valve. The valve body and the armature thereby can advantageously have the same outside diameter in the vicinity of their outside guide surfaces. 
     In accordance with an additional characteristic of the present invention, the valve body can consist of several pieces. 
     In an embodiment which is favorable from a manufacturing point of view, the valve body can consist of at least one molded piece that is preferably formed so that it requires no additional cutting. 
     In accordance with an additional essential characteristic, the valve seat of the valve body and/or the valve seat of the pilot control element can be formed by built-in discs having a high hardness. 
     In one further configuration of the present invention, a pressurized differential surface can be formed between the valve seat of the pilot control element and the outer guide surface of the connecting element. 
     In one favorable embodiment, the throttle cross section can have two segments which are connected by means of a chamber, whereby the segments preferably have different cross sections. 
     In summary, one aspect of the invention resides broadly in an adjustable vibration damper for motor vehicles, the adjustable vibration damper comprising: a cylinder, damping fluid disposed within the cylinder, a piston rod projecting into the cylinder and movable axially within the cylinder, a damping piston fastened to the piston rod to divide the cylinder into a first chamber and a second chamber, fluid communication device for providing communication of damping fluid between the first and the second chambers; and a damping valve for regulating flow of the damping fluid through the fluid communication device. The damping valve comprises: a fluid inlet, a fluid outlet, a valve seat, a first displaceable component for opening and closing against the valve seat to vary the cross-section of the fluid communication device between the fluid inlet and the fluid outlet, the first displaceable component having a first end portion for being disposed against the valve seat and a second end portion disposed opposite the first end portion, at least one first, constantly open, bypass orifice disposed from the first end portion to the second end portion for bypassing damping fluid from the first end portion at least to the second end portion, the first displaceable component defining a recess therein, a second bypass orifice being disposed in the first displaceable component, the second bypass orifice being disposed from the first end portion to the fluid outlet, a second displaceable component for varying flow of damping fluid through the second bypass orifice, the second displaceable component being disposed within the recess in the first displaceable component. 
     Another aspect of the invention resides broadly in an adjustable vibration damper for motor vehicles, the damper comprising a cylinder assembly having an arrangement for varying damping of a piston assembly disposed therein, the piston assembly having a piston rod and piston for dividing the cylinder into at least two chambers, each for containing damping fluid, the vibration damper comprising: a device for bypassing damping fluid between the at least two chambers; and a damping valve device for regulating flow of the damping fluid in the bypassing device. The damping valve device comprises: a fluid inlet, a fluid outlet, a principal valve seat, a first displaceable component having a first portion for being disposed against the principal valve seat and a second portion opposite the first portion, the first portion for moving towards and away from the principal valve seat to regulate flow of damping fluid from the fluid inlet to the fluid outlet by bypassing pressure buildup at the first surface to the fluid outlet; at least one first constantly open bypass orifice disposed at least in the first displaceable component for bypassing pressure build up at the first portion at least to the second portion of the first displaceable component, a second bypass orifice disposed within the first displaceable component for bypassing pressure buildup at the first portion to the fluid outlet, the second bypass orifice comprising a recess within the first displaceable component, and a second displaceable component disposed within the recess in the first displaceable component for varying flow of damping fluid through the second bypass orifice, the first displaceable component and the second displaceable component being independently displaceable relative to each other. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the present invention are schematically illustrated in the accompanying drawings, in which: 
     FIG. 1 shows a vibration damper, in cross section, with an external damping valve; 
     FIG. 2 shows a cross section through a vibration damper with a damping valve located laterally on the vibration damper; 
     FIG. 3 shows, on an enlarged scale, a valve body with a pilot control element; 
     FIG. 4 shows detailed view of a valve seat of the valve body; 
     FIG. 5 shows an end view of an additional embodiment of a valve body; 
     FIG. 6 shows a cross sectional view of the valve body of FIG. 5 taken along line VI--VI; 
     FIG. 7 show an opposite end view of the valve body of FIG. 6; and 
     FIG. 8 shows a detailed partial cross section of the valve body of FIG. 5 taken along the line VIII--VIII. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The embodiment illustrated in FIG. 1 shows a vibration damper 11 consisting of a piston 12, which piston 12 divides the work chamber 24 into two chambers 22 and 23. Check valves 13 essentially guarantee that the damping fluid will flow to damping valve 14 in only one direction. The damping fluid thereby flows out of damper 11 along connection 25 to the damping valve 14, through the damping valve 14 and back to the damper 11 along connection 26, and into equalization chamber 27. From equalization chamber 27, the damping fluid can return to the chamber 23 through orifices 28 and a check valve 13. 
     The damping valve 14 preferably consists of the valve body 3, in the recess 2 of which there is preferably a pilot control element 1, which pilot control element 1 can be in the shape of a ball. The pilot control element 1 can preferably be connected to an armature 5 of an electromagnet 6 by means of a connecting element 4. To simplify the manufacturing process, the armature 5 can preferably be located in the boring 7, to be guided by the guide surfaces 8 which are important for the valve body 3. 
     The valve body 3 forms a valve seat 9 through which the main current of the damping medium flows when the valve body 3 is open. The cross section of the passage at the valve seat 9 between the valve body 3 and the sleeve 20 can be defined by means of the pilot control element 1. For this purpose, the valve body 3, starting from its pressurized end surface 15, has a passage defined by passage segments 17a and 17b, which passage has a constant throttle cross section running toward the back end 16, located on the other end of the valve body. Starting from the recess 2, the valve body also preferably has an additional passage 18 in the outflow direction, through which passage 18, flow of damping medium is controlled by pilot control element 1. As a result of the corresponding pressure conditions on the front end surface 15 and on the back end 16, the pilot control element 1 can be continuously displaced axially, so that an appropriate cross section and thus an appropriate damping force are set between the valve body 3 and the sleeve 20. 
     FIG. 2 shows an additional embodiment of a damping valve 14. In this embodiment, the valve body 3a can preferably be made from two parts, and can have a hollow cylindrical element as the pilot control element 1a. Thus, in this embodiment, the valve body 3a can be designed in two parts, while the pilot control element 1a can be manufactured as a single piece in conjunction with the connecting element 4a. The armature 5a of the electromagnet 6 can in turn be directly connected by means of the connecting element 4a to the pilot control element 1a. The spring 19, in the base position, preferably exerts a corresponding force on the connecting element 4a. 
     FIG. 3 also shows an armature 5, which armature 5 acts by means of the connecting element 4 on the pilot control element 1, which is in the form of a ball. The valve body 3 can thereby be designed in several parts and can consist of appropriate moldings which can be manufactured using powder metallurgy technology. The valve seat 9 for the pilot control element 1 and the valve body 3 can be manufactured from discs having a high hardness, and can also be manufactured as punched parts, for example. 
     FIG. 4 shows a detail of the valve body 3, which is calked with the disc so that the latter acts as a valve seat 9, whereby the cylindrical ring 20 works together with the valve sea 9 by means of a control edge, or flange. 
     FIG. 5 shows one end view of the two-piece valve body 3 in a recess 2 of which the pilot control element 1 and the connecting element 4 are housed. A cross section of the two-piece valve body 3 taken along the line VI--VI is shown in FIG. 6. An end view of the opposite end is shown in FIG. 7, and a detailed partial cross section of the valve body 3 taken along the line VIII--VIII is shown in FIG. 8. This view in FIG. 8 essentially shows a site at which the two pieces of the valve body 3a and 3b are calked together by means of the flange 29 of valve body 3b, which flange extends over and thereby maintains the part 3a within the part 3b. The valve seat 9 can preferably be a disc, whereby the individual parts can preferably be inserted into one another and calked or pressed together. The entire valve body can thereby be formed simply by placing the control 1 into the recess 2 inside body piece 3a, placing the disc 9 thereon and calking the disc in place, and then inserting the entire assembled piece 3a into the body piece 3b and calking the entire assembly together. 
     One feature of the invention resides broadly in an adjustable vibration damper for automotive vehicles with a cylinder containing a damping fluid, an axially-movable piston rod projecting into it in a sealed manner, and a damping piston fastened to the piston rod dividing the cylinder into two work chambers, and a damping valve equipped with a valve seat which, by means of an axially movable valve body, controls the effective cross section of a damping passage, whereby the valve body, starting from its pressurized end surface has at least one constant throttle cross section running toward the back side located on the other end, and a throttle passage running from the back side in the outflow direction is controlled by an axially movable, continuously positionable pilot control element, characterized by the fact that the pilot control element 1 is located in a recess 2 inside the valve body 3. 
     Another feature of the invention resides broadly in a vibration damper characterized by the fact that the pilot control element 1 is a ball. 
     Yet another feature of the invention resides broadly in a vibration damper characterized by the fact that the pilot control element 1 which can move axially in the valve body 3 is supported by means of a connecting element 4 on the armature 5 of an electromagnet 6. 
     Still another feature of the invention resides broadly in a vibration damper characterized by the fact that the valve body 3 and the armature 5 are located so that they can move axially in a common hole or boring 7. 
     Another feature of the invention resides broadly in a vibration damper characterized by the fact that the valve body 3 and the armature 5 have the same outside diameter in the vicinity of their external guide surfaces 8. 
     Yet another feature of the invention resides broadly in a vibration damper characterized by the fact that the valve body is designed in several parts. 
     Another feature of the invention resides broadly in a vibration damper characterized by the fact that the valve body 3 consists of at least one molding formed without cutting. 
     Still another feature of the invention resides broadly in a vibration damper characterized by the fact that the valve seat 9 of the valve body 3 and/or of the pilot control element 1 is formed by built-in discs having a high hardness. 
     Another feature of the invention resides broadly in a vibration damper characterized by the fact that a pressurized differential surface is formed between the valve seat 9 of the pilot control element 1 and the external guide surface 10 of the connecting element. 
     Yet another feature of the invention resides broadly in a vibration damper characterized by the fact that the throttle cross section 17 has two segments 17a and 17b, which are connected by a chamber 21. 
     Another feature of the invention resides broadly in a vibration damper characterized by the fact that the segments 17a and 17b have different cross sections. 
     An example of an adjustable vibration damper can be found in U.S. Pat. No. 4,880,086 to Heinz Knecht and Norbert Ackerman. 
     All, or substantially all, of the components and methods of the various embodiments may be used with at least one embodiment or all of the embodiments, if any, described herein. 
     All of the patents, patent applications and publications recited herein, if any, are hereby incorporated by reference as if set forth in their entirety herein. 
     The details in the patents, patent applications and publications may be considered to be incorporable, at applicant&#39;s option, into the claims during prosecution as further limitations in the claims to patentably distinguish any amended claims from any applied prior art. 
     The appended drawings in their entirety, including all dimensions, proportions and/or shapes in at least one embodiment of the invention, are, if applicable, accurate and to scale and are hereby incorporated by reference into this specification. 
     The invention as described hereinabove in the context of the preferred embodiments is not to be taken as limited to all of the provided details thereof, since modifications and variations thereof may be made without departing from the spirit and scope of the invention.