Abstract:
Hydraulic, adjustable vibration damper, such as for motor vehicles, in which, parallel to the damping valves, there is a bypass whose control body can be closed by a simple hydraulically or pneumatically pressurized adjustment apparatus, and opened by the internal system pressure of the vibration damper. For this purpose, the control body is equipped with a pressure intensifier, whereby on its external circumferential surface, an annular surface is created by a smaller-diameter portion for the application of the system internal pressure.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a hydraulic, adjustable vibration damper, such as for motor vehicles, with a damping piston fastened to a piston rod, which damping piston divides the work cylinder into two chamber halves filled with damping fluid, whereby there is at least one pressure controlled valve located in a bypass which runs parallel to the valves of the damping piston, and an adjustment apparatus pressurizes a control body to control the bypass. 
     2. Background Information 
     Federal Republic of Germany Laid Open Patent Application No. 33 03 293 describes damping force regulation devices for telescoping shock absorbers on which there is an additional double-acting damping valve, which is incorporated into the damping piston itself. These damping valves are connected in series and can be separated from one another by means of a rotary disc valve. In a first valve position, only the valve of the damping piston is carrying a flow, so that a hard damping action can be achieved. In a second valve position, the valve in the damping piston and the additional valve both carry flows, so that a correspondingly mild damping characteristic can be achieved. 
     A disadvantage with such an embodiment is that the rotary disk valve must be pressurized by appropriate adjustment forces which are applied by an electrically operated positioning motor. 
     The prior art also includes adjustable vibration dampers, for example, German Patent No. 35 18 327, in which there is a coil in the upper portion of the piston rod. An armature can be moved axially in the coil, and a defined bypass opening can be formed between the upper and lower work chamber as a function of the current applied to the coil. However, vibration dampers with a magnetic coil are expensive to manufacture. 
     OBJECT OF THE INVENTION 
     The object of the invention is to create a hydraulic, adjustable vibration damper in which the control body of a bypass can be closed by a simple hydraulically or pneumatically activated adjustment device, and opened by the internal system pressure of the vibration damper. 
     SUMMARY OF THE INVENTION 
     This object is achieved by the invention, in that the control body is pressured by a pressure medium. Between the pressure medium and the control body there is an axially movable pressure intensifier which is sealed on its circumference. The outer circumferential surface of the control body has a first diameter and a second, smaller diameter. The second, or step, diameter may be formed by turning the control body on a lathe during the manufacturing process. 
     An important feature of an embodiment of the present invention is that the bypass operates parallel to the conventional throttle valves in the damping piston. By means of an axially-moving controllable valve body, the bypass valve can be positioned with the valves of the damping piston, so that there is a larger correspondingly reduced throttle action, that is, damping. In this manner, different damping characteristics with the required extensive variability can be produced. 
     One advantage of this solution is that the expense of a magnetic coil in the vibration damper can be eliminated, and that the use of a control body which is moved by a pneumatically or hydraulically activated membrane can be achieved particularly easily in motor vehicles which are already equipped with a pneumatic suspension. For utility vehicles, which are increasingly equipped with a pneumatic suspension, the use of a pneumatically activated adjustment apparatus is also possible. The technical complexity and expense of the pneumatic activation of the adjustment apparatus is thereby relatively low. Such an adjustment apparatus can be easily incorporated in passenger automobiles with pneumatic or hydropneumatic suspension systems, as well. 
     As a result of the use of a sealed pressure intensifier, the adjustment apparatus can perform reliably even with moist and dirty compressed air, while still avoiding corrosion. The parts which come into contact with the moist and dirty compressed air, such as the internal hole of the piston rod and the sealed pressure intensifier, could be manufactured from corrosion resistant material, forming a self-enclosed chamber. The adjustment of the control body is accomplished by adding pressure to the adjustment apparatus. The return movement of the control body is accomplished by the internal system pressure of the vibration damper when the adjustment apparatus is depressurized. 
     According to another essential feature of the invention, the pressure intensifier has a vent on the side facing away from the pressure medium to prevent a distortion of the control pressure. 
     In a technically simple and effective embodiment, the pressure intensifier, or pressure transmitter, is an elastic membrane tightly clamped on its circumference. In this embodiment, the pressure medium is advantageously separated from the adjustment apparatus itself, so that any corrosion problems which are experienced are generally, insignificant. 
     To achieve possible optimal switching, or adjusting, processes of the control, or steering, body, a particularly favorable embodiment of the invention specifies that the control body has a smaller-diameter cylindrical extension on the side facing the membrane. The cylindrical extension, or branch, is advantageously located and sealed in a hole or boring. One embodiment of the invention specifies that the larger-diameter region of the control body has at least one hole connecting the front side to the back side. 
     One aspect of the invention resides broadly in a hydraulic vibration damper with a hydraulic cylinder filled with damping fluid, the vibration damper comprising: piston device comprising a piston fastened to a piston rod, the piston device being disposed in the hydraulic cylinder, the piston having valves, the piston dividing the cylinder into two chambers, the piston rod having a longitudinal axis: bypass apparatus disposed to bypass damping fluid about the valves of the piston device, the bypass apparatus having valve mechanisms, the valve mechanisms being disposed parallel to the valves of the piston, the valve mechanisms comprising at least one valve which is pressure-controlled by a pressure medium originating externally of the damper: the at least one externally pressure-controlled valve comprising an orifice for bypassing damping fluid and a movable body, the movable body being disposed for opening and closing the orifice during adjusting operation of the vibration damper: the movable body being moved by the pressure medium originating externally of the damper, the pressure medium for being controlled by external pressure adjustment device; apparatus for transmitting pressure disposed between the pressure medium and the movable body, the apparatus for transmitting pressure being axially movable in the piston device: and the movable body having an outer circumferential surface, the outer circumferential surface having a first diameter and a second diameter, the second diameter being smaller than the first diameter, the second diameter being disposed to cover the orifice of the bypass means. 
     Another aspect of the invention resides broadly in a hydraulic vibration damper with adjustable damping with a hydraulic cylinder filled with damping fluid, the vibration damper comprising: piston device comprising a piston fastened to a piston rod, the piston device being disposed in the hydraulic cylinder, the piston having valves, the piston dividing the cylinder into two chambers, the piston rod having a longitudinal axis; bypass apparatus disposed to bypass damping fluid about the valves of the piston device, the bypass apparatus having valve mechanisms, the valve mechanisms being disposed parallel to the valves of the piston, the valve mechanisms comprising at least one valve which is pressure-controlled: the at least one pressure-controlled valve comprising an orifice and a movable body, the movable body being disposed for opening and closing the orifice during adjusting operation of the vibration damper; and the movable body being pressurized by a pressure medium, the pressure medium originating external to the hydraulic cylinder; device for conducting pressure of the pressure medium, originating external to the hydraulic cylinder, to the movable body. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the invention are illustrated in the accompanying drawings. 
     FIG. 1 shows a damping piston of a vibration damper with a detail of the adjustment apparatus in cross section. 
     FIG. 1A is similar to FIG. 1, showing additional structures. 
     FIG. 2 shows an embodiment which is the same in principle as the embodiment in FIG. 1, but with a different pressure intensifier. 
     FIG. 3 shows a damping piston which is the same in principle as the embodiment in FIG. 1, but with different disk area ratios of the control body. 
     FIG. 4 shows a damping piston which is the same in principle as the one illustrated in FIG. 3, but with a different pressure intensifier. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The vibration damper illustrated in FIG. 1 consists essentially of a piston rod 2 and a damping piston 3, which separates a work cylinder 1 into an upper and a lower chamber half. The damping piston 3 is equipped with valves 4a and 4b to generate a damping force. The upper chamber half is also connected via a bypass 5 to the lower chamber half. 
     In the bypass 5, a passage is pressurized by an axially-movable control body 8, whereby the control body 8 is pressurized by a pressure medium, an adjustment apparatus 7 and a pressure intensifier, or transmitter 9. The pressure-controlled valves 6a and 6b are also located in the bypass 5. The pressure-controlled valves 6a and 6b preferably comprise valve spring washers. 
     In this embodiment, the pressure intensifier, or transmitter 9 is comprised of a membrane 13 and a reinforcement plate 16. A vent 12 generally makes certain that substantially no pressure can accumulate between the membrane 13 and the controllable valve body 8. 
     The air pressure necessary for the control is fed, or pushed into the expansion chamber 18 via a connection part which is pressed onto a corrosion-resistant plug-in, or insertable part 17. The connection part 17 is inserted in a hollow portion of the piston rod 2. Consequently, the membrane 13 moves downward and the movable control body 8 substantially closes the bypass 5. The damping medium now preferably flows only through the valves 4a and 4b, and a relatively high damping force is achieved. 
     The return movement of the controllable valve body 8 of the bypass 5 is accomplished as follows: first the pressure medium to the membrane 13 is interrupted, and the control body 8 is pressurized via the smaller-diameter portion 11 on the external circumferential surface 10 in the decompression stage. As shown in FIG. 1A, chamber 11a is adjacent to the smaller-diameter portion 11 of the external circumferential surface 10, and chamber 11a is in communication with the upper chamber of work cylinder 1. 
     The pressure on the annular surface of the smaller-diameter portion 11 raises the movable control body 8. As a result of the pressure transmission to the entire surface of the control body 8b, the axially-movable control body 8 is fully raised. At this point, via the hole, or boring 15, both the forward end surface and the rear surface of the controllable valve body 8b are pressurized, whereby the cylindrical extension 8a of the control body 8 located in a hole, or boring 14 is not pressurized, on account of the seal. The result is a larger disk area ratio on the forward end surface, and the control body 8 can thus be raised. 
     When the axially-movable control body 8 is raised, the damping medium flows through the valves 4a and 4b, and also through the bypass 5, and thus through the pressure-controlled valves 6a and 6b. A soft damping force can be achieved by an appropriate configuration of these valves 6a and 6b. 
     In the embodiment of FIG. 1A, the external pressure source 7a is indicated. It is this external source of pressure which applies pressure to the pressure medium, thereby causing the diaphragm, or membrane 13 of the pressure transmitter 9 to effect a change in the position of the movable body 8, and consequently, to result in the damping of the vibration in the hydraulic cylinder. 
     In the embodiment of FIG. 2, there is preferably a stationary, rigid, or fixed component as the pressure intensifier, or transferrer 9, which is preferably sealed axially, and also on its outside circumference. 
     In the embodiments of FIG. 1 and FIG. 2, the surfaces of the pressure translator, or intensifier 9 are designed in relation to the cylindrical branch or extension 8a of the control body 8 so that the adjustment force can be provided with an increase in pressure of approximately 5 bar. This operating pressure is generally available in pneumatic suspension systems of a motor vehicle. 
     The embodiment of FIG. 3 shows a membrane 13 and a control body 8, in which the disk area ratios are more favorable for the opening of the control body 8. By means of a larger-diameter cylindrical extension 8a of the control body 8, it is easier to open the control body 8 by means of the system internal pressure. In this case, however, there must be a higher pressure of the adjustment apparatus available to close the control body 8. 
     The embodiment of FIG. 4 again shows the pressure intensifier, or transmitter 9 as a preferably, rigid component with a sealed outer circumference. The disk area ratios of the pressure intensifier 9 and of the movable control body 8 are similar to the embodiment illustrated in FIG. 3. 
     Possible examples of valve spring washers may be found in U.S. Pat. No. 4,723,640, issued on Feb. 9, 1988, entitled &#34;Adjustable Hydraulic Vibration Damper,&#34; which is hereby incorporated herein as if set forth in its entirety. 
     In summary, one feature of the invention resides broadly in a hydraulic, adjustable vibration damper for motor vehicles, with a damping piston fastened to a piston rod, which damping piston divides the work cylinder into two chamber halves filled with damping fluid, whereby there is at least one pressure-controlled valve located in a bypass which runs parallel to the valves of the damping piston, and that an adjustment apparatus pressurizes a control body to control the bypass, characterized by the fact that the control body 8 is pressurized by means of a pressure medium, whereby between the pressure medium and the control body 8 there is an axially movable pressure intensifier 9 sealed on the circumference, and that the outer circumferential surface 10 of the control body 8 has a diameter 11 possibly formed by turning on a lathe. 
     Another feature of the invention resides broadly in a vibration damper which is characterized by the fact that the pressure intensifier 9 has a vent 12 on the side facing away from the pressure medium. 
     Yet another feature of the invention resides broadly in a vibration damper which is characterized by the fact that the pressure intensifier 9 is an elastic membrane 13 which is tightly clamped on the circumference. 
     Still another feature of the invention resides broadly in a vibration damper which is characterized by the fact that the control body 8 has a smaller-diameter cylindrical extension 8a on the side facing the membrane 13. 
     Another feature of the invention resides broadly in a vibration damper which is characterized by the fact that the cylindrical extension 8a is sealed in a hole 14. 
     Yet another feature of the invention resides broadly in a vibration damper which is characterized by the fact that the larger-diameter region of the control body 8b has at least one hole 15 connecting the front side with the back side. 
     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 and publications recited herein 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 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.