FR2813372A1 - METHOD FOR ADJUSTING THE THROTTLE EFFECT OF A VALVE - Google Patents

Abstract

The invention relates to a method for adjusting the throttling effect of a valve (13a; 13b; 21), comprising a valve body (23) having at least one passage channel (25; 27) for a flow fluid. work, the working fluid being subjected to a throttling effect due to the realization of the throttle channel (27), characterized in that it is modified by exploiting the heat development of a laser beam (55) the component or components of the valve (13a; 13b; 21) which determine the throttling effect of the valve (13a; 13b; 21) so as to minimize deviations from a predetermined throttle effect.

Description

The invention relates to a method for adjusting the throttling effect of a

  valve, comprising a valve body having at least one passage channel for a working fluid, the working fluid being subjected to a throttling effect due to the construction of the throttling channel. Document DE 43 15 458 C2 discloses a valve for a telescopic hydraulic oscillation damper whose structure allows individual adjustment of the valve discs. For this purpose, the valve body is connected separately to a piston rod and provided with valve discs. An adjustment sleeve or journal pressurizes the valve discs to a determined value, and the lifting force of the valve discs from a valve seat surface can be determined by a corresponding device. When the intended lifting force is reached, the trunnion or the adjustment sleeve is fixed. Therefore, a required damping force of the valve can be adjusted very precisely regardless of the

manufacturing tolerances.

  Document DE 44 24 437 A1 describes a valve in which the lifting force of the valve can also be adjusted. The valve has a valve housing against which a helical compression spring rests. By a targeted deformation of the valve housing, the prestressing stroke of the helical compression spring is modified, and thus the closing force. This type of valve adjustment can only be applied in a specific valve construction. In addition, it should be taken into account that a valve, in particular a damping valve, has different flow paths and means for establishing a required characteristic curve of the damping force. At low flow rates, a so-called pre-opening section is activated, the effect of which depends on the flow section. In a median range of the characteristic curve, the

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  Damping valve behavior is determined by valve discs which are preloaded on a valve seat surface. To influence this range of the characteristic curve, it must be possible to modify the prestressing force which acts on the valve disc. At very high flow velocities, depending on the design of the damping valve, the maximum available flow section is decisive for the damping force of the

damping valve.

  So far, large tolerances of the damping force have been admitted in the case of damping valves. However, the trend is towards more and more precisely adjusted damping forces. To this end, a very complex manufacturing complexity must be provided. The damping valves are mounted and checked against the characteristic curve of the damping force. In case of deviations from the prescribed tolerance, the valve is dismantled and reassembled with slightly modified components and checked again. The manufacturing work is all the more important. The objective underlying the present invention is to implement a method by means of which it is possible to precisely adjust valves of

  different types in relation to their choking behavior.

  According to the invention, this objective is achieved by modifying, by exploiting the development of heat of a laser beam, the component or components of the valve which determine the throttling effect of the valve. so as to minimize deviations from an effect

predetermined throttling.

  The essential advantage of this measure is to be able to reduce the production reject rate or to be able to increase the precision of the throttling effect of the valve, without having to increase the dimensional compliance in the individual components of the valve. . The working speed of the laser beam is very high. We are not confronted with any

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  disassembly of the valve. In addition, we can reduce the stock of valve parts, because we can adapt the basic elements of the valve.

  very simple way to the given requirements.

  According to a variant of the method, the cross section of the throttle channel is modified by means of the laser beam. A laser beam is used whose thermal effect is so strong that a "disappearance" of the volume parts of the valve body occurs. You can also break edges in the flow path or remove if necessary

  burrs that result from the manufacturing process.

  According to another advantageous development of the invention, it is possible to determine the cross section of the throttle channel by a valve disc, the valve disc having at the level of the throttle channel at least one recess produced by "burning "which increases the cross section of the throttle channel compared to an original mounting state. For the throttling effect, larger dimensions are deliberately chosen than necessary for the throttle channel, and the throttle channel is then limited by means of a valve disc. A valve disc has a material thickness significantly smaller than that of the valve body, so that a smaller burn by means of the laser beam is sufficient for the correct adjustment of the cross section of the throttle channel. Valve body constructions are known in which the throttle channels are separated over their entire length. When a valve disc is used in such a valve body which at least partially covers the throttle channels and then the valve disc is "burned" in a targeted manner to determine the cross-sections of the valve channels 'throttling, it must be ensured that the valve disc cannot move in the peripheral direction. Indeed, it may happen that the burnt area of the valve disc is no longer overlapped with the corresponding throttle channel. To take this possible source of error into account, the valve disc is fixed with the recess produced by burning through laser welding by

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  compared to the passage channel. It is not necessary to change heads at

  laser, but a modification of the laser beam is enough.

  The valve discs can also be used in a tight form on the valve body and so as to be elastically deformed and to rise from the valve body when the working fluid pressures it. The elastic preload of the valve disc is exploited to achieve a targeted throttling effect. To allow adjustment of the throttling effect in this case also, a modification is carried out by thermal action of the internal structure of a

  valve disc, intended to modify the elastic preload.

  It is also possible to make a modification by thermal action of the internal structure of a spring acting on a valve disc,

  1 5 intended to modify the elastic preload.

  In addition, at least two valve discs of different sizes can be provided stacked one on the other, the larger valve disc resting on the edge of the smaller valve disc during the flow of fluid through the throttle channel and the diameter of the edge being modified by means of the laser beam. Following a change in the diameter of the valve disc with the smaller diameter, the reversal point of the valve disc with the larger diameter changes, because the bearing surface has been reduced by the smaller valve disc. A modified reversal point has an essential influence on the characteristic of

  the elastic force of the batch of valve discs.

  According to another advantageous characteristic, there is the possibility of carrying out a control of the throttling effect of the valve. When several components of the valve have been optimized by means of the laser beam, it is also possible to carry out checks which are all the more frequent. In many cases, compressed air can be used

for controls.

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  In order to be able to apply the process in a particularly effective manner, it is provided that the components which determine the throttling effect of the valve are produced with a machining allowance for machining with the laser beam with respect to the tolerances of the determining parameters. the choke effect. We deliberately choose the mode of "extra work". There is thus the possibility of manufacturing the valve components with much less

  precision, because the final adjustment is made by means of the laser beam.

  The invention will be explained in more detail with reference to the

  description which follows of the figures. These show:

  Figure 1, a valve inside a vibration damper Figure 2, a characteristic curve of a throttle valve; Figure 3, a piston in the form of a structural group; Figure 4, an embodiment of the pre-opening section; and

  Figures 5, 6 and 7, steps of mounting the valve.

  FIG. 1 shows an oscillation damper 1 known per se of the double tube type, in which a piston rod 3 comprising a piston 5 is guided in axial displacement in a pressure tube 7. The piston 5 separates the pressure tube in an upper working chamber 9 and in a lower working chamber 11, the two working chambers

  being connected via throttle valves 13a; 13b in the piston.

  The pressure tube 7 is wrapped by a container tube 15, the inner wall of the container tube and the outer wall of the pressure tube forming a compensation chamber 17. At the lower end of the working chamber 11 is provided a background which includes

  a non-return valve 19 and a throttle valve 21.

  In the direction of deployment of the piston rod, the upper working chamber 9 is reduced and the working fluid therein is discharged through the throttle valve 13a. The check valve 19 is

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  open to avoid vacuum in the lower working chamber 11. When the piston rod retracts into the pressure tube, the throttle valve 13b and the throttle valve 21 act at the bottom of the working chamber 11. The the pumped volume of the piston rod is compensated by a change in volume in the working chamber 17. FIG. 2 shows a qualitative characteristic curve of a throttle valve 13a; 13b or 21 as a function of a throttling force with respect to the flow speed of the working fluid. The course of the characteristic curve is essentially determined by three throttling locations. At speeds

  of weak flow vô comes into action a section called pre-

  opening which is often made in the form of a diaphragm. The average range of flow velocity VF is often determined by the force of a spring which places a valve disc on a throttle section under preload. At higher flow velocities vQm of the working fluid in the throttle valve acts a larger constant section. In this case, the valve disc occupies

the maximum passage position.

  Figure 3 shows the piston 5 in the form of a structural group. A valve body 23 has throttle channels 25; 27 which connect the two working chambers 9; 11 to each other. The throttle channel 25 is covered by a valve disc 29 which is in turn prestressed by a star spring 31. Between the star spring and the valve disc 29 is arranged an inversion disc 33 whose outside diameter determines the lifting behavior of the valve disc 29. A stop disc 35 limits the lifting stroke of the valve disc

valve 29.

  In the right half of the section, a helical compression spring 37 is used in place of the star spring. Function

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  of the reversing disc 33 is satisfied by a heel 39 of the stop disc 35. As a variant with respect to the helical compression spring, it is possible to use a usual spring washer. We would go beyond the framework if we wanted to represent all the possible embodiments of known valve discs and springs. The throttle valve 13a has a valve disc 41 which overlaps with the throttle channel 27 and which determines the maximum flow section in the throttle channel 27. As required, a disc is used of valve with adapted external diameter, in order to be able to use a piston as standardized as possible. At the other end of the throttle channel are arranged valve discs 43; 45 which are clamped by a sleeve 47 on the valve body 23. The

  valve disc 43 can be produced in the form of a so-called pre-

  opening which includes a small notch 47 at the outside diameter which extends radially into the region of the throttle channel 27. The valve disc 45 serves as a disc for

  cover for the notch (see figure 4). The pre-

  opening is determined by the width b of the notch of the thickness of the

valve disc 43.

  The valve discs 43; 45 are prestressed on the valve body

  by a valve plate 49 in association with a valve spring 51.

  By means of an adjustment nut 53, the force of

valve spring preload.

  FIG. 5 shows a piston 5 in which the equipment for the throttle valve 13b has not yet been mounted and where the maximum effective section of the throttle channel 27 must be adjusted by means of the method in accordance with 'invention. To this end, the valve disc 41 is placed on the valve body 23. The outside diameter is clearly oversized, so that it is known beforehand that the maximum effective section of the throttle channel is dimensioned too small in this state. mounting. In a device, represented only by a wall, a pressure pl is established on one side of the valve and a pressure P2 on the other side by the fact that the valve piston is attacked

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  by a working fluid, for example by a gas or by a hydraulic fluid at a defined speed. The range of the characteristic curve VQm can be determined from the pressure difference pi - P2 in association with the known speed, and it can be compared with a predetermined plot of the characteristic curve. Depending on the deviation from the predetermined path of the characteristic curve, the outer contour of the valve disc is reduced by means of a laser beam 55 at the throttle channels 27. It may suffice to machine a kind chamfer at the outside diameter, but a complete conformation 57 achieved by "burning" may also be necessary in certain circumstances. Then, the pressure difference p1 - P2 is again measured and, if necessary, a resumption of machining. When measuring the pressure difference using a gaseous fluid, a continuous pressure difference measurement can be made during the application of the laser beam. So that the work result remains maintained and that the conformation 57 produced by burning is no longer overlapping with the throttling channel by rotation of the valve disc following other assembly steps, the valve disc 41 is fixed with the valve body 23 outside the throttle channels by at least one location

  welded 59 by means of the laser beam 55.

  In a second step of the process, the valve disc 29 is placed on the valve body 23 (FIG. 6) and the pressure difference pi - P2 is again measured at a low flow speed and compared with the plot predetermined characteristic curve. For the range vo of the characteristic curve (figure 2), two paths can be taken. On the one hand, it is possible to widen the notch in the valve disc 43 by means of the laser beam according to the principle illustrated in FIG. 5 or to create by burning a certain number of through openings 61 in the valve disc 29 which are overlapping with the throttle channel 25. The through openings 61 would then be active in the two directions of flow of the piston 5. On the other hand, one could also imagine carrying out a burn 57 on the body of

valve 23 itself.

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  Before mounting the valve plate 49 while the valve discs 43; 45 are already prestressed on the valve body 23, the structure can be modified by a targeted thermal action of the laser beam 55 and the inherent stress of the valve discs can be determined. The mean range VF of the characteristic curve is determined by the additive overlap of the preload of the valve disc and the force of the valve spring 51. Corresponding pressure measurements will be made before and after the heat treatment at speeds of defined flow of working fluid to

through the valve body.

  In FIG. 7, the reversing disc 33 is put in place. The corresponding function for the throttle valve 13 is ensured by the front surface of the sleeve 47. The force / speed measurements are again carried out for the medium speed range VF and a burnout 57 is carried out if necessary. of the external diameter of the front surface of the sleeve 47 and of the reversing disc 33. The lever arm is modified in support of the reversing disc which determines

  the lifting behavior of the valve disc 29 or 43; 45.

  Finally, the star spring or the helical compression spring and the valve spring are adjusted with respect to their prestressing force by means of a heat treatment by the laser beam 55 (FIG. 1), the applied heat providing a modification of the spring structure. We also carry out the measures described already several

  times by means of a fluid passing through the throttle channels 25; 27.

  A receiving device (not shown) can be provided for the piston which keeps the valve parts assembled and by means of which the structural unit can be brought to the intended mounting location. Alternatively, a solution can be chosen in which a trunnion is used as a support which is moved to a planned mounting position. By way of example, reference is made to document DE 196 49 247 A 1 which discloses a piston on a journal, the journal being able to be pressed together with the valve body in a

reception opening.

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  However, the invention is not limited only to shock absorbers

  oscillations, but it is applicable in various ways.

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Claims (9)

claims   1. Method for adjusting the throttling effect of a valve, comprising a valve body (23) having at least one passage channel (25; 27) for a working fluid, the working fluid being subjected to a throttling effect due to the construction of the throttling channel (25; 27), characterized in that the component (s) of the laser are modified by exploiting the heat development of a laser beam (55) valve (13a; 13b; 21) which determine the throttling effect of the valve (13a; 13b; 21) so as to minimize   deviations from a predetermined choke effect.   2. Method according to claim 1, characterized in that the cross section of the throttle channel (25; 27) is modified by means of the laser beam (55).   3. Method according to claim 2, characterized in that the cross section of the throttle channel (27) is determined by a valve disc (41), the valve disc having at least one recess in the throttle channel produced by burn (57) which increases the cross section of the throttle channel (27) by   comparison with an original mounting condition.   4. Method according to either of claims 1 and 3, characterized   in that the valve disc (29; 41; 43) having the burn-out recess (57) is fixed by laser welding (57) relative to the passage channel (25; 27).   5. Method according to claim 1, characterized in that one proceeds to a modification by thermal action of the internal structure of a valve disc (29; 43; 45), intended to modify the elastic prestress. 12 2813372   6. Method according to claim 1, characterized in that one proceeds to a modification by thermal action of the internal structure of a spring (31; 37; 51) acting on a valve disc (29; 43; 45) ,   intended to modify the elastic preload.   7. Method according to any one of claims 1 to 6, characterized   in that at least two valve discs (29; 33) of different sizes stacked one on top of the other are provided, the larger valve disc (29) resting on the edge of the valve disc ( 33) smaller during the flow of the fluid through the throttle channel (25) and the   edge diameter is changed by means of the laser beam (55).   8. Method according to any one of claims 1 to 7, characterized   by checking the throttling effect of the valve (13a; 13b; 21).   9. Method according to any one of claims 1 to 8, characterized   in that the components (29; 31; 33; 37; 41; 43; 45; 51) which determine the throttling effect of the valve (13a; 13b; 21) are produced with a machining allowance for the laser beam machining with respect to the tolerances of the parameters determining the throttling effect.