FR2489458A1 - Hydraulic shock absorber e.g. for aeroplane - with absorption characteristic adapted in accordance with force to be absorbed - Google Patents

Abstract

The shock absorber has two parts (1,2) sliding one within the other and together with a piston (3) defining two variable volume chambers. The latter communicate via at least one conduit (11,22) with the section of the passage being dependant on the force to be absorbed. Pref. the section of the passage is controlled by a slider (17) contained in a bore (17) within the piston (3) between the two chambers and with openings (11,12..19,20) communicating with each of them. The displacement of the slider (16) within the bore (17) is controlled by the output signal from a sensor responsive to the applied force to be absorbed. The shock absorber can be used for a passenger aeroplane and provides a more comfortable ride.

Description

The present invention relates to shock absorbers, of the fluid type, such as

  those found on vehicles

such as aerodynes, etc. -

  In its most general configuration, a damper comprises a cylinder in which slides a rod, a part of which is formed in piston to delimit at least two chambers with variable volume as a function of the relative displacement of the cylinder and the rod, and setting means in communication of the two chambers generally through the piston. These two rooms generally enclose a

  incompressible fluid such as oil and a fluid

  pressible such as a gas such as nitrogen.

  To play its role of shock absorber, when the rod, for example sinks into the cylinder, part of the oil contained in one chamber passes into the other chamber by compressing the volume of gas whose pressure increases to provide the amortization which is the essential goal

  of such a device. The law that governs this kind of amor-

  weaver is well known and can be illustrated by a curve representing the force F as a function of the stroke C

  or, for example, pushing the rod into the cylinder.

  Figure 1 gives an example of such a function.

  Upon examination of such a curve we see that for a

  variation c of given stroke corresponds only to a varia-

force.

  The ratio 6 actually corresponds to the value of the tangent of the curve. To improve in particular the comfort of

  vehicles with shock absorbers of this type, it can

  It would be interesting to obtain at a point on the curve different values of this tangent, that is to say from the ratio Àc. This is impossible with a shock absorber as described above. To obtain such variations it would be necessary, ultimately, to change the damper, something that is impossible to do. However, there is already a way to obtain such an adaptation of the value of the tangent at a point. This means consists, when a significant variation of force occurs, in pumping part of the fluid contained in

  one of the chambers, preferably the supply chamber.

  This pumping is obtained by a servo pump controlled as a function for example of a signal emitted by a

force associated with the shock absorber.

  If in theory this means gives good results, it is however limited in its application essentially by the fact that its response time is too long, and it does not

  can satisfy only a few possible cases of depreciation

  is lying. The pump, moreover, must be able to absorb relatively high flow rates instantaneously which requires it to be oversized, which results in an excess of volume and weight which is always a drawback.

in the aeronautical field.

  The object of the present invention is to provide damping

  in which it is possible to adapt the value of the variation ratio of the force to the variation of the

  stroke for a given depression, in order to avoid

-enients of known shock absorbers.

  More particularly, the present invention relates to

  a force damper comprising two sliding parts

  health in one another, defining by means of a piston two chambers with variable volume, means for bringing the two chambers into communication, characterized in that said means consist of at least one conduit, the passage section is a

function of the force to be absorbed.

  Other features and advantages of this

  invention will appear during the following description

  value given in relation to the drawings annexed illus-

  trative but in no way limiting, in which: - Figure 1 represents a characteristic curve of a shock absorber giving the value of the stroke as a function of the force applied under static load and, - Figure 2 a part of an embodiment d 'a damper according to the invention and, - Figure 3 a block diagram explained in the form of an algorithm of a part of the associated damper

to that according to figure 2.

  Figure 1, already mentioned above, shows the characteristic curve of a given shock absorber. Referring to this curve, it can be considered that for a certain load f 1, the damper has a depression relative to a point of origin O of C-I. For this damper, if we admit that for a variation q 1 in the vicinity of this force i, there must correspond a variation of stroke AC 1, function of the tangent TI at the point of the curve having for coordinates f 1 and C 1. We

  conceive then that if the value of the slope of this tan-

  is important, the shock absorber will have a certain

  stiffness and this basically happens when it travels

  under heavy load, i.e. towards the end of

shock stroke.

  This is how for loaded planes traveling on a

  track in poor condition, it is interesting, with an amor-

  given weaver, which of course is impossible to replace

  place by another, to vary at a point in its

  stroke, example (tf: Cl), the value of its stiffness or tan-

  gente and give it lower values for example

  such as T2 or T3, when the plane goes on the road

  lant on a bump, to obtain just at this instant a more flexible or less stiff damper, but which resumes

  immediately its normal stiffness as of this asperity passed.

  The shock absorber designs shown on the

  gures 2 and 3 make it possible to obtain the result mentioned above. The shock absorber shown diagrammatically in FIG. 2 essentially comprises two parts 1 and 2 sliding one inside the other, which technicians are used to denote respectively the cylinder (1) and the rod (2). The rod 2 slides in the cylinder 1 by means of a piston 3 respectively defining two chambers 4 and 5, and optionally as in this embodiment an annular auxiliary chamber 6 between the

  two walls 7 and 8, the piston 3 and the end 9 of the cylinder

  dre shaped as a sealed passage 10 sliding on the outer surface of the wall 8. In a conventional damper, the piston comprises means for bringing

  communication between room 4 and the two rooms 5 and 6.

  These means are generally constituted by conduits passing through the piston with which are generally associated return brake valves which have defined orifices. In the present case, the piston comprises a plurality of conduits, 11,12,13,14,15,20, putting the chamber 4 into communication with the chambers 5 and -6, associated with a drawer 16 which can slide in a bore 17 made in the

rod 2.

  The drawer can move in this bore 17 and obtain

  different connections for different determination positions

mined from drawer 16.

  Thus, for the different possible positions of the drawer, it is possible to obtain a law of variation of the section for passage of communications between chambers 4,5 and 6. A curve of variation of this law is shown

  inset in Figure 2, which gives the value of the sec-

  passage is is a function of the linear displacement "x

of drawer 16.

  More specifically, in this illustrated embodiment, the rod is produced so that the chamber 5 is annular around a wall 18 delimiting the housing 17,

  this housing crossing right through, in its long axis

  tudinal, the rod to open in 19 in chamber 4.

  From this housing 17 leave respectively the conduits 11, 12 and 14 towards the annular chamber 6, and the conduits 13, 15

and 20 to room 5.

  The two chambers 5 and 6 are connected respectively by two sets of conduits (11,12,14) and (13,15,20) of which at least -an conduit of each set is terminated by a

  brake valve like valves 21 and 22.

  As has been said previously, the different orifices of each assembly are put into communication by means of a

  drawer 16 which slides in bore 17.

  This drawer generally consists of a cylindrical rod having at its periphery recesses which make it possible to put in communication different orifices of conduits as a function of the position of this drawer. Of course, this drawer can consist of a single rod, but it can

  also include a plurality of telescopic rods,

  trant one in the other to obtain a greater possibility

  bility of connection between the different orifices.

  The embodiment illustrated in Figure 2 comprises a drawer 16 formed of two rods 25 and 26, a portion of the rod

  full 26 sliding inside the rod 25.

  The inner rod 26 ends at one end 27 with a

  sliding part, of the same diameter as bore 17,

  towards (by a conduit 28 placing the chamber 4 in communication with the space 29 between the wall 18 of the bore 17 and the part of the rod 26 sliding inside the

  rod 25. This space 29 in fact constitutes an annular chamber

  area in which the hollow rod 25 moves.

  27 further comprises lateral openings 30 and 31 through

  sant this portion of the conduit 28 to its outer surface

  which slides against the wall of bore 17.

  Similarly, the rod 25 includes a recess 32 at its end 33, around the rod 26, co unicat by a small conduit

  34 with an annular groove 35 formed on its outer surface

  lower, that which is in contact with the wall of bore 17.

  Finally, these two rods end in their other ends.

  tees 36 and 37 respectively emerging from the rod 2 in the form of a piston 38 and 39 of a jack, cooperating respectively with two cylinders 40 and 41 formamt the body of the jacks. These

  two cylinder cylinders 40 and 41 being supplied respectively-

  ment by two pairs of supply conduits 42,43 and 414,45 allow, by an adequate supply from a source of fluid under pressure 46 controllable to position these

  two rods in desired positions.

  The two rods 25 and 26 each have fingers 47, 48 which respectively come out of the chambers 40 and 41 to visibly indicate the position of these rods, possibly

  coupled with for example schematic electronic means-

  represented in 50 and 51 to deliver signals represented

  sensing the position of the two rods 25 and 26.

  In addition, the finger 47 is mounted on the shoulder 53 subjected to the action of a spring 52 making it possible to keep this finger 47 constantly in contact with the piston head 38, so as to be able to easily decouple this head with the outside of the cylinder 40, since this finger cannot be integrated into this piston as is finger 48 on piston 39 of

the rod 26.

  As described above, the two rods can

  be moved in translation by an adequate supply

  required in pressurized fluid from the two control cylinders

  by the respective supply conduits 44.45 and 42.43.

  The positions of these two rods are controlled by asser-

  screwing to obtain the results recalled above. The

  FIG. 3 represents an embodiment in dry form.

  control system for the position of the two rods

and 26.

  The damper illustrated in Figure 2 is shown schematically on

  this figure 3, but the essential elements are there.

  In this case the cylinder 1, the rod 2, the chambers 4,5 and 6, the two rods 25 and 26, the position sensors 50

  and 51 respectively of the two rods 25 and 26.

  The servo means include a down sensor

  cement 60 of the rod 2 of the damper in the cylinder 1 which delivers at its output 61 a signal representative of the

  position of these two elements with respect to each other.

  This sensor can be produced in different ways such as, for example

  example, an optical sensor next to a ruler, position-

  born on the rod, with reflecting surfaces depending on the depression, or even a magnetic sensor fixed on one of the two elements cooperating with a magnetic means fixed on the other. Optionally, the sensor 60 may include a second output 62 which is capable of delivering a second signal giving the direction of relative movement of the two elements 2 and 1 which, applied to a differentiator 63 can be transformed into a signal, for example positive when the rod 2 sinks, and negative when the rod comes out, at the outlet

64 of this derivative.

  The output 61 of the depression sensor is connected to the input of a pre-programmed circuit 66 which can transform the signal obtained at the output of the sensor 60 representative of the depression or, as said previously, of the race, into a signal delivered at the output 67 representative of the force to which the shock is normally subjected according to a transformation function like that which is represented

in figure 1.

  The means also include a force sensor 68 allowing

  both to deliver at its output 69 an instantaneous signal

  sensitive to the effort to which the a-

mortiser (the aircraft).

  Normally, when the aircraft is static, the cap-

  sink sensor with the force sink transformer and the force sensor deliver at their outputs 67 and 69 respectively, the same signal. On the other hand, when the aircraft passes over a bump (negative or positive), it is subjected to an instantaneous effort and it is this effort that the shock absorber normally has to dampen, which modifies its sinking. Thus, the force sensor can be constituted for example

  by a strain gauge element, mounted in bridge, asso-

  linked to the part of the damper which is subject to these

instant efforts.

  The outputs 67 of the transformer 66 and 69 of the eff sensor

  fort 68 are connected respectively to the two entrances 70 and

  71 of a comparator 72 constituted for example by an amplifier

  differential ficator, the outlet 73 of which is connected to means 74 and 75 making it possible to control the source of fluid 46 supplying the two cylinders 40 and 41 for moving the two rods 25 and 26 of the slide 16. More precisely, the outlet 76 of the comparator 72 is connected

  respectively at the two 76,77 inputs of two logistic doors

  ques 78,79 of which the other two entries 80 and 81 are re-

  linked to the output 82 of the diverter 6. -

  The outputs 83 and 84 of these two logic gates 78 and 79 are respectively connected to the inputs 85 and 86 of two comparators 87 and 88 of which the other two inputs 89 and are respectively connected to the outputs 91.92 of the two position sensors 50.51 of the two rods 25 and 26,

in housing 17.

  The respective outputs 93, 94 of these two comparators 87 and 88 then control the power sources 95, 96, particular of the general power 46, of each

cylinder 40 and 41.

  This is how the outlet conduits 97 and 98 are connected to the inputs 44, 45 of the jack 41 and the outlet conduits

  99 and 100 are connected to inputs 42 and 43 of cylinder 40.

  The shock absorber works as follows: it will

  taking into account the two figures 2 and 3, more

  particularly Figure 2, when it comes to the particular structure of the fluidic damping system and the

  Figure 3 when it comes to servo control means

  sement. It is first assumed that the fluid system is in a position of equilibrium under the load for example of a

  aerodyne. Rod 2 in cylinder 1 has a certain

  darkly. When, for example, the aerodyne rolls on the runway and

  it does not have all the necessary rolling qualities

  the aircraft wheel can then meet aspersions

  rites like bumps, hollows, etc. This meeting is generally not smooth and therefore brutally

  the wheel, the leg and therefore the shock absorber, as a whole

  ble, is subject to an additional effort on a course

relatively short.

  In this case, as soon as the effort is felt, the effort sensor delivers at its output 69 a signal which is a function of this

  effort, which in this case is considered an increase

  tion. For its part, the transformation displays a signal

  representing a certain effort value for the

i5 - considered.

  If, at the instant before the shock, the two signals at the inputs 70 and 71 of the comparator were equal, due to the shock, an imbalance of these signals occurs and, consequently, the comparator delivers at its output

  73 a signal which is representative of this imbalance.

  The diverter 64, associated with the sink sensor indicates

  by the sign of its signal at output 82 the direction of the

  fundamentally which, applied to the two logic gates 78 and 79, lets the signal output from the comparator pass to one or the other supply of the two jacks 40 and 42

  with, for example, a control direction to move next

  vant the law chosen one and / or the other of the rods 25.and 26 of the drawer 16. This law will be determined according to different elements, in particular the mass of the vehicle on which this kind of shock absorber is mounted, diameters of the orifices between the various chambers 4,5,6 and their

  possible combinations, the structure of hydrau-

  he liques, etc. However, it is obvious that those skilled in the art

  can for example calculate and adjust these different circuits

  damping system, and build them from

  which will allow him to verify them.

  So depending on the different sign. # dam signals

  the case chosen to illustrate the functioning of the amor-

  weaver, that is to say an increase in effort, the rods can be ordered as follows "

  To reduce the stiffness of the shock absorber, it is necessary to increase

  lie about the passage of the hydraulic fluid from chamber 4

to the two bedrooms 5 and 6.

  We can then assume that the damping system is adjusted so that, for example, the rod 26 descends into the housing 17 and that it faces the orifices 12 and 30 as well as 31 and 14, and that the rod 25 rises for

  unblock the entry of the openings 15 and 20.

  In this case, the passage section of the rooms

  4 to 6 and 4 to 5 increased and the fluid can flow well

  more freely but not without being laminated to

get the desired depreciation.

  Generally, in the case of increasing force, the rod 25 is pressed into compression in the cylinder. So,

  when this extra effort stops, it is well needed

  make sure that the shock absorber returns to its equilibrium position

said to be relaxing.

  The end of the effort will therefore be detected by the eff-

  strong 68 which will deliver a corresponding signal which, combined

  in comparator 72 with that delivered by the transformer

  mateur, will be able to bring the rods into a position defining the orifice of passage corresponding to the chosen expansion law, and this until the damper returns to its equilibrium position like this

is shown in figure 2.

  Of course, the position of the two rods is defined by a signal at the output of the indicators 50 and 51 (for example potentiometric) and their control in determined position is obtained by a signal which is applied to the inputs of the

  comparators 87 and 88 which receive on their other en-

  signals from position indicators and which controls

  tooth, depending on the result of the comparison, negative or 1o positive, either the rise or fall of these two rods and until the result of the comparison obtained at outputs 93 and 94 respectively has reached the reference value by example a zero difference, and no longer controls one way or the other, the power supply

cylinders.

  The example that was given above in a particular case

  can, of course, take different forms and be used

  dried for other purposes and applications.

  In particular, drawers with two rods have been described.

  smoothing in translation to obtain different communications

  orifice cations, but we can achieve, depending on the needs

  care, rotating drawers and also combining the

two movements.

  But, more particularly, the device finds an application

  particularly advantageous cation in the case where, by

  example, it is necessary not to amortize considerably-

  ment when the shock absorber is subjected to the shock for example by not laminating considerably the fluid, whatever its direction of displacement, in compression or in relaxation but, on the other hand, by laminating in a more important way

  fluid when it returns to its equilibrium position.

  Such a shock absorber is particularly advantageous when for example it is on an aerodyne which is rolling on a runway

  formed of plates with joints of a thickness not born

  gligeable which actually form like steps.

  In this case, when the wheel of this aerodyne passes on a step, either the shock absorber relaxes, or it

  compresses easily because the rods are ordered to give

  ner important passage openings, and as soon as walking

  has passed, the rods are ordered in another posi-

  tion to restrict the cross-section of the fluid passages and then laminate it so that the damper returns slowly

to its equilibrium position.

Claims (8)

  1 / Force damper comprising two sliding parts (1,2), one inside the other, defining, by means of a piston (3), at least two chambers (4,6-4,5) variable volume, means of communication between the two chambers, characterized in that the said means consist of at least one conduit (11, 22 ...) the passage cross section of which is a function of the force to absorb.   2 / Shock absorber according to claim 1, character-   laughed at by the fact that it comprises means for capturing (68) the force to be absorbed, capable of delivering a first   signal representative of the force and the means of command   of the cross section of said conduit, depending on the value of said first signal.   3 / damper according to claim 2, character-   laughed at by the fact that said control means, in function   tion of the value of said first signal of the section of said conduit, comprise a housing (17) adjacent to said   two chambers (4,6-4,5), through openings (11,12 ...   19,20) of said housing (17) respectively in the two   said chambers (4,5,6), a drawer (16) movable in the-   said housing (17) means for controlling the movement   of said drawer, according to said first signal represented   force to control communication   said orifices between the two chambers and the housing.   4 / damper according to claim 3, charac-   terrified by the fact that said means for controlling the   displacement of said drawer as a function of said signal   take steps to deliver a second signal   sensitive to the position of said drawer in said housing (50,51), means for determining the displacement of the two said sliding parts (61,64) capable of delivering a third signal, means (66) for transforming   said third signal into a fourth signal represented   tif of a reference force, means (72,74,75) for comparing said first, second and fourth signals, said means being capable of delivering a fifth signal, and controllable means (46,40,41) for moving said   drawer according to the value of said fifth signal.   / Shock absorber according to claim 4, character-   laughed at by the fact that said controllable means for determining   place said drawer are constituted by a jack (40,41) coupled to said drawer, a source of fluid (46) controlled including two outputs (97,98) (99, 100) are connected to both   respective inputs (44,45) (42,43) of said cylinder (40,41).   6 / Shock absorber according to one of the pre- claims   cédentes, characterized in that said drawer is   consisting of a plurality of rods (25,26).   7 / shock absorber according to claim 6, character-   laughed at by the fact that said rods are sliding in translation.   8 / shock absorber according to claim 6, character-   laughed at by the fact that said rods are sliding in rotation.   9 / Shock absorber according to one of claims 4 to   8, characterized in that said means for determining   undermining the displacement of the two said sliding parts comprise means (60,64) for determining the amplitude and the direction of said movement.