Abstract:
An electronically-controlled damper arrangement includes a valve assembly. The valve assembly features a valve slide that carries at least two pistons. The first piston controls flow through two separate flow paths while the second piston controls damping provided by the valve slide. The first piston being both axially moveable and radially moveable within a valve housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit and priority to and is a U.S. National Phase of PCT International Application Number PCT/SE2006/000701, filed on Jun. 14, 2006, designating the United States of America and published in the English language, which claims priority under 35 U.S.C. §119 to Swedish Application Number 0501345-3, filed on Jun. 14, 2005. The disclosures of the above-referenced applications are hereby expressly incorporated by reference in their entireties. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to damping arrangements, such as dampers used in shock absorbers or steering assemblies, used in motor vehicle applications. More particularly, the present invention relates to a valve assembly used with such dampers that operates to remove undesired oscillations during use caused by an admixture of air and damper medium. 
     2. Description of the Related Art 
     The technology that has been used to date within the field is described in, for example, S9800775-0, S0400012-1, EP504624-A2 and EP400395-B1. The valves in question are described in these documents as pilot-controlled, with damping of the pilot cone not being described in certain cases, but with a solenoid&#39;s armature being damped in its cylinder. In other cases, as in EP400395, the damping is described as a throttling between two chambers. Among other things, it is common to the known technical solutions that the damping arrangement is located on the low pressure side, which is downstream of the valve function that is to be damped. 
     The problem with the valves in these references is that their damping is based on the sum of hydraulic damping in the solenoid or in its vicinity, and friction. The shock absorbers or steering dampers, etc, that are used within the car industry do not usually have so-called gas-separating pistons, for which reason the hydraulic fluid becomes saturated with gas. After hard driving with such dampers, gas collects in pockets and closed spaces and the volume of gas increases the lower the pressure. This means that the damping that relates to valve functions on the low pressure side can be lost under the circumstances. Remaining friction is insufficient to damp the valve function, which can cause oscillations with frequencies within the range 400-1500 Hz. This sound is particularly irritating to the human ear and is not acceptable to car users and car manufacturers. Increased friction has been tested and has been found not to solve the problem in a correct way. Certain features, aspects and advantages of some embodiments of the present invention are intended to solve this problem, among others. 
     There is also a desire for the valve in question, for example a proportional valve, to be able to be incorporated in a main valve in an integrated and space-saving way. 
     Certain features, aspects and advantages of some embodiments of the present invention also solve this problem. 
     SUMMARY OF THE INVENTION 
     Certain features, aspects and advantages of some embodiments of the present invention relate, among other things, to an arrangement with disturbance elimination for electronically-controlled dampers for vehicles. The dampers can be used in, for example, shock absorbers, steering dampers, etc. The electronic control can be carried out by computer or an actuator for so-called EC-function. The vehicles can be wheeled vehicles with two, three, four or more wheels. The invention also can be used for snow-scooters with runners, tracks, etc. 
     The arrangement can have, among other things, control equipment that comprises movement-detecting sensors that detect the movements of wheels, runners, tracks, etc, and that send control signals to one or more dampers in response to these movements. Each damper preferably comprises a cylinder containing a piston or piston device that operates in a medium utilized by the damper (for example, hydraulic oil with any desired additives). The piston or piston device divides the inner chamber of the cylinder into a first chamber compartment and a second chamber compartment. The damper also comprises or interacts with one or more valve assemblies in the form of pilot valves or partial step valves that control the pressure of the medium in the first and second chamber compartments. Thus, the damping carried out by the respective damper, for example in both directions, can be controlled by the control signals issued from the controller. Each valve assembly preferably comprises at least one electrical coil that is connected, or that can be connected, to the control signals, and a part that is controlled by the coil when the control signals are received. The part is able to move and preferably works with short strokes. Through its movements, this part in turn affects a first piston that moves in a first space in, for example, a valve housing, against the action of a spring, which first piston divides the first space into a first and a second partial space. In a first functional state, the first piston assumes a longitudinally displaced position that causes a first flow of medium to pass from the damper&#39;s first chamber compartment, via the partial space below the first piston and on through a first side opening (port) arranged in the inner wall of the housing, to a first duct connected to the second chamber compartment of the damper. In a second functional state, the first piston assumes a longitudinally displaced position where a second flow of medium, unaffected by the first piston, passes from the first partial space to a second side opening (port) that is preferably to be found in the same housing and on to the second chamber compartment of the damper via a second duct and a non-return element arranged in the flow path. When the second functional state is assumed, the first piston is arranged to be caused to move, because of the guide faces arranged on the valve piston and because of the guide faces in the housing that correspond to these, to a position in front of the first side opening where the first flow of medium has been reduced and the second flow of medium is initiated due to an increase in pressure in the partial space caused by the reduction in the first flow of medium and, hence opening the non-return element. 
     In addition, the first piston assumes the position in front of the first side opening under the influence of the spring and a reduction in pressure at the first side opening caused by the piston assuming the position alongside the first side opening. The first piston is arranged with passages between the partial spaces, which passages provide axial pressure relief in both of the functional states. 
     Certain features, aspects and advantages of some embodiments of the present invention also relate to a device for dampers for vehicles that comprises or interacts with disturbance-eliminating valves in the form of partial step valves or pilot valves. The damper comprises a piston arranged in such a way that it can move in a cylinder or a blade that can rotate in a cylinder, which piston or blade divides the inner space in the cylinder, the valve housing, etc, into a first and a second chamber, with the chambers being connected together by one or more ducts via the valve. The valve has a valve slide and a valve piston that can move in spaces arranged in the valve housing. The movements of the valve slide can be determined by a force that can be completely or partially initiated from an external actuator or a computer, for example a microcomputer. The movements can also be determined by a force that is determined by pressure acting upon the areas of the valve piston that can be affected by the flow of the working medium between the first and second chambers and by a spring or spring function. 
     Certain features, aspects and advantages of some embodiments of the present invention also relate to a device for disturbance-eliminating valves in the form of partial step valves or pilot valves that comprise a valve slide that can move in a space in the medium, which valve slide is arranged to have an effect on a passage for the medium through the valve because of guides that exert a pressure force on the slide and a pilot spring force, called a first force, in the opposite direction to an actuating force, called a second force, applied on the valve slide, whereby the body divides the space into a damping chamber and a pilot pressure chamber by a part. 
     Certain features, aspects and advantages of some embodiments of the present invention also relate to a method for eliminating disturbances caused by the admixture of gas in a damping medium in a partial step valve or pilot valve arranged in a vehicle. 
     The valve described above is able to operate silently and is believed to be completely unaffected by gas that is saturated in the oil in shock absorbers. In addition, the main stage of the valve can be provided with a double spring function that makes it possible to carry out very accurately set and low preloading with small variations in spite of the selection of a stiff spring constant. The whole valve can be assembled in sequence from one direction. 
     In accordance with certain features, aspects and advantages of some embodiments of the present invention, in the case with two functional states, the transitions between the different states can take place without any specific actions or resetting having to be carried out, for example without the vehicle having to be stopped in order to carry out the transition. The arrangement and the device according to certain features, aspects and advantages of some embodiments of the present invention can work with or can comprise dampers that are arranged with damping function in one or both directions. The dampers can consist of shock absorbers or steering dampers for vehicles between parts of the vehicle that can move in relation to each other. 
     The principal characteristic of an arrangement according to certain features, aspects and advantages of some embodiments of the present invention is, among other things, that the first piston is located on a valve slide that can move in a longitudinal direction and that extends into the first space and into a second space in the housing that is connected to the first space. In addition, a control edge for the valve slide is located at a transition to the second space, while at the same time the part of the slide that extends into the second space has an extension part upstream of the control edge with a second piston arranged on the extension part. The second piston divides the second space into third and fourth partial spaces. These partial spaces divide the area of action of the valve slide into a first part in association with the seat or control edge and a second part on the underside of the second piston. In addition, certain features, aspects and advantages of some embodiments of the present invention are characterized in that the second piston and an opposing inner guide face in the second space are arranged with a clearance between them that eliminates disturbance by ensuring that the pressure differences that arise in the second space (i.e., the cavity) at the second piston as a result of the speed of movement of the slide affect the second part of the area of action of the slide with a force that counteracts the movement. 
     It is typical of certain features, aspects and advantages of some embodiments of the present invention that disturbance elimination also works when the partial space is filled with gas, due to the fact that, as early as during the pressure-increasing phase or pressure-reducing phase, a force arises that prevents movement, as the gas inside the partial space first is compressed before movement of the slide can take place. 
     The valve thus works with damping on the high pressure side, that is upstream, which helps to solve the problem discussed above. 
     The principal characteristic of a device according to certain features, aspects and advantages of some embodiments of the present invention is, among other things that, at the high pressure side, that is upstream of the valve piston that was described above, there is a damping device that damps the movements of the valve piston irrespective of the state of the working medium, that is irrespective of the gas content in the medium. 
     The device according to the invention can also be said to be characterized in that, in a stationary control position of the body, the pressure in the damping chamber is arranged to assume a value that essentially corresponds to a pressure value in the pilot pressure chamber, in that, in the event of an urged movement from the stationary control position, the body is arranged to bring about a pressure difference at the part and in that, in the event of the movement, the pressure in the damping chamber undergoes a change in value that is essentially proportional to the speed of movement of the body and generates a damping force that coincides with the control force and that counteracts the movement of the body and thereby brings about the disturbance elimination, that can consist of preventing any admixture of gas in the medium affecting damping caused by the valve or preventing unwanted noises arising due to the admixture of gas. 
     Depending upon which part of the damping process is being described, it is also possible to characterize certain features, aspects and advantages of some embodiments of the present invention in that the damping force coinciding with the control force arises as soon as it is the case that the damping chamber is filled with gas in a pressure-increasing or pressure-reducing procedure for the reason that, on account of its compressibility, the gas in question cannot have a pressure-increasing or pressure-reducing effect on the area of action of the slide that is in the damping chamber. 
     By what is proposed in the above, a control function with control edge/seat/etc and piston-part/membrane/etc can be arranged on or in association with the slide or corresponding moving device. The function of the spring can alternatively be provided by other devices that have a spring function. By stiff spring constant is meant values between 40-500 N/mm. The abovementioned problems are solved by the creation of a damping force that constitutes part of the first force and, at the same time, is on the high pressure side, upstream of the control edge, seat, etc. 
     The method according to certain features, aspects and advantages of some embodiments of the present invention means that, in a first activated functional state, a second piston, arranged on the high pressure side or upstream of a valve piston that moves in the damping medium, is inserted into a space in a cylinder and divides this cylinder into an additional damping chamber, while at the same time it causes a change in pressure in the additional damping chamber. In a second functional state, called the inactivated or deactivated state, the damping medium flows more freely over the second piston and equalizes the pressure across the piston. The change in pressure thus generates an additional damping force that counteracts the movement of the valve slide irrespective of the admixture of gas in the damping medium in the first functional state but, however, not as much as in the second functional state. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A currently proposed arrangement, device and method for an embodiment of the invention will be described below with reference to the attached drawings, in which: 
         FIG. 1  schematically shows a vertical section of an arrangement with a damped proportional valve with two functional states arranged to interact with a shock absorber for a vehicle in the form of a car, with the valve assuming an activated first functional state; 
         FIG. 1   a  schematically shows in horizontal section a blade damper that can be connected to the arrangement according to  FIG. 1 ; 
         FIG. 2  schematically shows in vertical section the valve according to  FIG. 1  in a second inactivated functional state; 
         FIG. 3  shows in plan view the position function for the valve piston alongside a first side opening for a first flow of medium in the arrangement according to  FIGS. 1-2 ; 
         FIG. 4  shows in vertical section an embodiment of the valve with slots in the first functional state; 
         FIG. 5  shows in vertical section an embodiment of the valve with slots in the second functional state; 
         FIG. 6  shows in vertical section an embodiment of the valve with holes in the second functional state; 
         FIG. 6   a  horizontal section that defines the area A 3 ; 
         FIG. 6   b  vertical section that defines the area A 2 ; 
         FIG. 7  shows in horizontal section an embodiment of the valve with slots in the second functional state; 
         FIG. 8  shows in vertical section how the pilot valve is integrated with the main valve in a dual spring configuration with a spring holder; 
         FIG. 9  shows in vertical section how the pilot valve is integrated with the main valve in a dual spring configuration with shim spring; and 
         FIGS. 10-12  show in vertical section a number of simplified variants of pilot valves with only one functional state. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows the arrangement/valve with an activated valve actuator and  FIG. 2  shows the arrangement/faces towards the actuator provided with a disk-shaped first piston  2 , which is guided against valve in deactivated state. A valve piston  1  is on a part that an inner wall  3  of the pilot housing and which makes contact in an axial direction with an actuator pin  4  in a plane  5  perpendicular to the direction of movement. 
     The valve piston  1  of the pilot valve is acted upon in one direction by a first force F 1  from a spring  6  or a device exerting a biasing force and by forces that result from pressure exerted in the chambers e and f. The valve piston  1  also is acted upon in a second direction by a second force F 2  from an actuator  7  in the activated state. The pilot cone is normally located several hundredths from a control edge  8 . 
     In its extension, the valve piston  1  is provided with an extension part  1   a  and a second piston  1   b . A guide face  10  of the second piston  1   b  preferably has a clearance s 2  to an inner wall of a cylinder  1   d  that extends from the control edge  8 . A communicating gap s 2  is defined between the second piston  1   b  and the cylinder  1   d  and the second piston  1   b  divides the space into an additional two chambers: a damping chamber e and a pilot pressure chamber f. When the valve piston  1  is in the controlling position and is stationary, the pressure in the damping chamber e is the same as the pressure in the pilot pressure chamber f, whereby the first force F 1  is the sum of the effect of the pilot pressure f on the areas ( 1   f  and  1   g ). 
     When the valve piston  1  moves or there is an increase/decrease in pressure, the pressure in the damping chamber e changes essentially in proportion to the speed of the movement or the increase/reduction in pressure of the pilot cone. Thus, the change creates a damping force that always works against the direction of movement (i.e., that counteracts the movement). In other words, a damping or damping function is obtained. If there is gas in the damping chamber e, this makes no difference, as the damping force is a part of the first force F 1  and is located on the high pressure side, upstream of the control edge  8 . The clearance s 2  is arranged to have a narrow range and to have a size that is in proportion to the selected diameter of the second piston  1   b , for example from s=0.03 mm to s=0.05 mm for a piston diameter of 2.8 mm. That is, the ratio between the size of the clearance s 2  and the diameter of the piston  1   b  can be calculated as the quotient between s and dk and the ratio can thus vary between 0.010 and 0.018. 
     In the second functional state (i.e., the inactivated or deactivated state), which is shown in  FIG. 2 , the force of the spring  6  urges the pilot cone towards its opposite end position, which is determined by a surface a. A number of holes  9  pass through the first piston  2 . The holes provide communication between both sides of the first piston (i.e., space b and space c), which gives axial pressure relief on the pilot cone  1  in all positions and load conditions. 
     In order to create additional control and pressure relief towards the surface a, in an embodiment, a surrounding chamber can have a number of holes or slots g that provide communication between the chamber b and any chamber defined between the piston  2  and the surface a, which additionally contributes to pressure relief when the disk rests against the surface a. When the actuator of the valve piston  1  is deactivated, the first piston  2  moves towards the surface a that defines its end position in the illustrated embodiment and, before it has reached this position, a peripheral guide face  10  of its disk starts to close the radially-located port  11  to the flow q 11  that occurs when the actuator is activated. A smooth transition to the second functional state is carried out, which ultimately results in a connection of a permanently set non-return element  12 . The transition is smooth as a result of the gradual reduction of flow q 11  to q 12  in the side opening or throttle  13  with the final partial flow q 12  being in parallel with the second flow q 22 , a transition that is free of transients. The throttle is, for example, designed as a circular groove  14  from which the port  11  opens. 
     The return function from the second functional state to the first functional state takes place in a corresponding way, by a gradually reducing flow q 22  to a gradually increasing flow q 12 , meaning that no special resetting function is used. 
     An advantage can be obtained as far as production technology is concerned. The normally-required burring operation on the sensitive guide face is not required in some embodiments of the present invention because the outlet port  11  is never fully closed. Thus, no burrs interfere with the control of the slide disk. 
     The diameter D and the height H of the groove determine the size of the throttle and hence of the partial flow q 12 . This should preferably be precise and should be able to be repeated. The contact between the plane  5  and the plane a enables, however, the disk  2  to move radially, which it does when the second functional state is achieved because the disk is forced radially towards its closed position during its axial movement towards the outlet port  11  within the framework of the clearances s 1  and s 2 . The radial movement is extremely small or equal to the gap in question. 
       FIG. 1  also shows a second side opening  16  to a duct or space  17  provided with the non-return element  12 . The ducts  11  and  17  each lead to a chamber compartment in a shock absorber  18 . The chamber compartments above and below the piston  20  have the reference numerals  19   a  and  19   b . The shock absorber can be arranged for a vehicle wheel  21 , for example via a piston rod  20   a . The cylinder  19  can be connected to the chassis  22  of the vehicle. 
     One or more sensors  23  can be arranged on the wheel to detect and indicate the movements of the wheel relative to the chassis. A controller or computer device  24  or other computer function (i.e., a component functioning like a computer or controller) communicates with the sensor or sensors associated with one or more shock absorbers. The controller sends control signals  1   i  to one or more coils on one or more solenoids or corresponding electronic units. The control signals i 1  bring about the forces F 2  on the actuator pin or control device  4  of the solenoid part and hence the valve piston  1  in the valve. The detection signals from the sensor are given the reference numeral i 2 . 
     The duct between the valve  26   a  and the chamber compartment  19  is indicated by K 2  and the duct between the space  17  and the first chamber compartment is shown by a broken line  28 . When there is a complete or partial cessation or loss of the signals, the first piston  2  and the valve piston  1  assume the position shown in  FIGS. 2 and 3  under the influence of the spring  6  and a reduction in pressure that occurs across the opening  11 ,  13  when the second functional state is assumed. Thus, the arrangement defaults to the inactive state. 
     The reduction in pressure  27  creates flow conditions that attempt to pull the first piston in a radial direction towards the opening  11 ,  13 , as shown in  FIG. 2 . It has been found that the position can be repeated and that the piston assumes precisely or essentially the same position upon each assumption of the second functional state. 
     This is possible without inclining the disk-shaped first piston  2  if the clearances s 1  and s 2  are made as equal to each other as possible or essentially the same size. The present construction differs from Swedish Patent No. S0400012-1 in that the parts comprised in the pilot slide are guided at the points k 1  and k 2 , which are located a relatively large distance apart, for example approximately 8 mm, and in that the clearance between the first piston  2  and the inner wall  3  of the housing is made significantly smaller on account of the desired relationship between s 1  and s 2 . The damping that is achieved by the piston  1   b  can be eliminated, as it is not needed in the second functional state, by selecting a small value, for example approximately 0.1 mm, for the underlap/overlap ul in this position, as shown in  FIG. 2 .  FIG. 1  shows how the damping is activated by using a relatively large value, for example approximately 1 mm, for the overlap ol. Thus, where there is a relatively large overlap between the piston  1   b  and the opening  1   e , damping can occur with the piston  1   b  while, where there is a relatively small overlap or even an underlap, damping does not occur with the piston  1   b.    
       FIG. 3  shows that the area in the throttle  13  is A1=H*(Ds/2−Dd/2)*2 where Ds=the diameter of the circular groove  14 , H=the height of the circular groove and Dd=the diameter of the first piston  2 . Ds, Dd and H are preferably selected around 9.8, 10.1 and 0.6 mm. The valve piston  1  preferably is constructed so that the surfaces  5 ,  8  and a are flat and perpendicular (i.e., radially directed) to the direction of movement (i.e., axially directed). The first piston  2  can always assume an unambiguous, well-defined and particular position on account of the clearance s 2  that preferably is the same size as the clearance s 1  in order to allow a narrow range of the partial flow q 12 , which thereby constitutes an accurately determined leakage flow determined by, for example, the diameter Ds. 
     In the second functional state, which is shown in  FIGS. 5 and 6   b , the partial flow q 12  can also be accurately determined by the breadth B and height H 2  of the groove  42  by the area A 2 =H 2 *B*2 or, as in  FIGS. 6 and 6   b , by the hole  43  with the hole area A 3 =π/4*d^2. In both these cases, Ds is so large that no reduction in pressure arises in this zone. The measurements Ds, B and H are preferably selected around 12.8, 0.2 and 0.5 mm respectively. 
     The first functional state is shown in  FIG. 4 , showing the normal functional principle with its first flow q 11 . 
       FIGS. 5 ,  6  and  7  show the second functional state, showing the functional principle with a first partial flow q 12  and a second partial flow q 22 . 
       FIG. 8  shows an example of a production embodiment, with the valve in its entirety, which unit can be assembled from one direction, because the pilot housing  30  constitutes a separate component that can be assembled from the same direction as a main cone  31  and a main seat  32 . An innovation as far as functional technology is concerned is that the main cone of the valve has been provided with two springs connected in series, “dual springs”, one stiff spring  33  and one weak spring  34  adjusted so that the pre-stressing of the main cone is low and precisely determined by the weak spring, preferably selected around F0.5±0.4 N. The desired stiffness is in a range between K 1 =40-500 N/mm for the main function that is determined by the stiff spring. The weak spring, with a spring constant preferably around K 2 =1 N/mm, is preferably selected to work with an extremely short stroke, preferably around x=0.035 mm with small permitted variation ±0.03 mm, which in turn is achieved by a suitable choice of shims  35 . In the case shown, the springs are guided and held by a spring holder  36 . 
       FIG. 9  shows the described functions implemented by a flat thin spacer  37  with a thickness t of preferably approximately 0.4 mm and a thin shim spring  38  with a thickness t of preferably approximately 0.1 mm. This construction is only one example, and the components  37  and  38  can be designed as a single shim spring connected in series with the main spring. 
     Both  FIG. 8  and  FIG. 9  show that the pilot function  39  has an integrated position inside the main spring  33  in the center, which means that the total valve concept can be made compact. 
       FIGS. 10 ,  11  and  12  show three embodiments of the pilot valve  40  that is described above, utilizing a valve piston  1  without a deactivated state  41 . Simplified embodiments are possible, and accordingly the deactivated state can be removed in the described pilot valve design. 
     In  FIG. 1   a , the damper, for example the shock absorber, with a cylinder and a piston, has been replaced by a damper, for example a steering damper, in the form of a blade damper with housing  43  and blade  44 . The housing is designed with ducts  45  that make it possible to connect the connections  26 ′,  28 ′ and  28   a ′ to the first and second chamber compartments  46 ,  47  of the damper. 
     A method is provided for eliminating disturbances caused by the admixture of gas in a damping medium in a partial step valve or pilot valve arranged in a vehicle, where the valve comprises a valve slide that can move in a space (b, c, f) in the medium, arranged in ducts (K  1 , K 2 ) between a first ( 19   a ) and a second ( 19   b ) chamber filled with damping medium. The valve is constructed of a valve piston ( 1 ), an extension part ( 1   a ), a second piston ( 1   b ) and a first piston ( 2 ). The method according to the invention means that, in a first activated functional state, the second piston ( 1   b ) that is arranged on the high pressure side or upstream of the valve piston ( 1 ) is inserted into a space in a cylinder ( 1   d ) and divides this cylinder ( 1   d ) into an additional damping chamber (e), while at the same time it causes a change in pressure in the additional damping chamber (e). In a second functional state, called the inactivated state, the damping medium flows more freely over the second piston ( 1   b ) and equalizes the pressure across the piston ( 1   b ). 
     The method thus affects the flow of working medium over the second piston ( 1   b ) and brings about an additional damping force applied on the slide which coincides with a first force (F 1 ) determined by pressure acting on areas ( 1   f ,  1   g ) of the valve slide. The first force (F 1 ) is opposed to a second force (F 2 ) which can be completely or partially initiated by an external controllable actuator ( 7 ) or a computer function. The extension part ( 1   a ) and the second piston ( 1   b ) work in a fourth partial space (f) on the high pressure side, that is upstream, of the valve piston ( 1 ) so that the second piston ( 1   b ) divides the cylinder ( 1   d ) into the damping chamber (e) that is separated from the fourth partial space (f). 
     In its first functional state, the second piston ( 1   b ) is also arranged with a clearance (s 2 ) and an overlap (ol) in the cylinder ( 1   d ) so that, in a stationary control position for the valve slide, the damping medium is allowed to flow via the overlap (ol) through this clearance (s 2 ) in such a way that the pressure in the damping chamber (e) assumes a value that essentially corresponds to a pressure value in the fourth partial space (f). The size of the clearance (s 2 ) in relation to the diameter of the second piston ( 1   b ) is selected in such a way that, in the event of an urged movement of the valve slide from the stationary control position, the pressure in the damping chamber (e) undergoes a value change that is essentially proportional to the speed of movement of the valve slide and generates the damping force coinciding with the first force (F 1 ) that counteracts the movement of the valve slide and thereby brings about the disturbance elimination. 
     The invention is not limited to the embodiments described above, but can be modified within the framework of the following patent claims and concept of the invention.