FR2636012A1 - VEHICLE SUSPENSION COMPRISING A CYLINDER AND PISTON SUSPENSION LEG BETWEEN THE BODY AND AN AXLE - Google Patents

Abstract

The upper 18 and lower 19 chambers of a suspension strut are connected to each other and to an accumulator spring 24 through non-return valves 22, 23 mounted in opposition and damping chokes 25, 26 provided in parallel with them for the formation of a passive suspension part. This is combined with an active suspension part comprising a quick-opening valve 27 to connect the chambers 18, 19 of the working cylinder 11, forming the suspension strut, or at a supply pressure p1 which is higher than the average pressure ps m required to compensate for the static axle load, ie at a pressure relief side in.

Description

The invention starts from a suspension for vehicles, including

  nant a suspension strut disposed between the body and an axle and having a working cylinder in which slides a piston provided with a piston rod and which contains upper and lower working pressure chambers, relative to the cylinder, which are connected to each other and to a pressure accumulator (accumulator spring) through non-return valves

mounted in opposition.

  For the suspension and damping of wheel suspensions, for example of motor vehicles and similar vehicles,

  we know a large number of concepts, ranging from simple amortization

  spring loaded to complex combined suspension units

and depreciation.

  The known suspension concepts can be divided basically into three main categories, a first category of which includes so-called passive suspensions in which, in order to influence a suspension action which takes place rapidly, no energy considered in this sense as external is provided or in which external interventions are carried out only slowly. This is the case for example for a conventional steel spring with a hydraulic shock absorber, but is valid

  also for an oleopneumatic spring with level correction.

  For some time now, so-called semi-active suspension concepts have been known, the principle of which consists in appropriately influencing, by rapid adjustment interventions, the progress over time of the transformation of clean energy during the suspension process. . The semi-active suspension attempts to

  somehow simulate a fraction of active suspension in modi-

  confident - at the time when due to the instantaneous course of the suspension, The contribution of external energy, therefore The variation

  active suspension action would be required - possibilities

  existing depreciation rates are adjusted, in sign and value, so that the mismatch is reduced to a minimum

(DE-OS 35 24 862).

  Finally, the so-called active suspensions of the third category

  gorie include a transmission of support forces, by which any desired amount of energy can be supplied to the suspension zone from an independent energy source,

  a hydraulic pump for example, from the outside in a way.

  Consequently, such an active suspension offers, on the one hand, the widest possibilities of influencing a suspension system, but requires on the other hand very high hydraulic powers, which also means that provision must be made for

expensive order.

  The invention therefore aims to create a suspension for vehicles

  cules, including a suspension leg, which links a concept of

  active suspension to a passive base fraction of the suspension.

  To this end, according to the invention, damping throttles

  weaving are arranged in parallel with the non-return valves and are also connected to the accumulator spring (passive part of the suspension) and, in combination with these elements and as an active part of the suspension, the chambers of the working cylinder are connected through a quick-opening valve, either at a supply pressure which is higher than the average pressure required to compensate for the static axle load, or at the side

dump.

  One of the advantages obtained is that the invention thus provides, as a variant both with respect to an active suspension and with respect to a semi-active suspension, a combination of a suspension which is effectively active and of a passive suspension carried out in a particular way. A specific advantage lies in the use of a common structural component, namely a suspension strut or a hydraulic cylinder, for the active and passive fractions of the suspension, component at

  means by which, according to an advantageous embodiment of the invention,

  tion, iL is possible in addition to performing level correction.

  It is also very advantageous that the passive basic fraction is designed with a soft suspension characteristic and allows the damping values to be adjusted in both directions. The active suspension fraction can also be freely designed; for example, it can be designed for the transmission of 20 X dynamic forces or for the transmission of 70% of dynamic forces, but taking into account that

  The requirements to be met by Hydraulics, Control and Electricity

  also increase as the percentage represented

  felt by the active suspension believes.

  Another advantage is that the invention makes it possible to considerably lower the costs of the entire system since, alongside the suspension strut, serving at the same time as a passive base spring and a positioning cylinder for the active fraction of the forces to be provided, it suffices to provide a quick-opening valve and mechanical and electronic control means which are coordinated with it, as well as a pressure supply designed

Consequently.

  It is advantageous that the suspension according to the invention comprises a sensor which detects at least the elastic stroke of the suspension strut in both directions and the signals of which are applied to a central control circuit which controls the valve at

quick opening.

  According to another advantageous improvement, the two connecting channels leading to the working chambers of the leg

  suspension, can be connected simultaneously and continuously

  increasing or decreasing, by the quick-opening valve, at the higher supply pressure, higher than the pressure

  static axle load, or on the discharge side.

  According to one embodiment of the quick-opening valve, this valve has a pressure-controlled drawer which connects at least the channel connections of the working chambers, as well as at the supply pressure or at the discharge side, connections which open at the same height in the said valve, the continuous displacement of the slide being produced using a solenoid valve controlled at a high frequency by an electronic control circuit and changing continuously, according to its average opening section , the pressure acting on one of the faces of the drawer. For pressure compensation in such an embodiment, the supply pressure can act on

  a smaller useful face on the other side of the drawer.

263 601 2

  Another advantageous characteristic of the invention provides that the suspension comprises a servo-valve which acts by a positioning member, charged by the supply pressure, on the side of the drawer remote from the continuously variable working pressure and a device for rappeL is intended for the function of

  valve controlled by the electronic control circuit. This provision

  recall device may include an electromagnetic part acting

  on the positioning member of the servo-valve.

  According to yet another very advantageous embodiment, the accumulator spring, the connections directed towards each other of the non-return valves and the damping throttles mounted in parallel with them, can, by their channel mouth in the valve quick opening and by means of this valve, also be connected to the two other channel connections of the suspension leg working chambers, as well as, depending on the position of the drawer, either at the supply pressure or at the

discharge side.

  Among the improvements and embodiments described above, the realization of the quick-opening valve

  like a slide valve, which can be controlled by an electro-

  valve actuated at high frequency, using pressure from the pressure supply, is a solution

particularly advantageous.

  With the help of the active force fraction, it is therefore possible not only to carry out interventions which amount to a variation, i.e. a change in the damping or the hardness of the suspension, it also allows, to extend the

  operating possibilities, generating accelerated forces

  trices - which are then external forces in the direction considered

  here - between the body and the axle.

  Other characteristics and advantages of the invention

  will emerge more clearly from the following description of a

  nonlimiting example of embodiment, as well as of the single figure of the appended drawing, showing by a partially schematic representation the fundamental concept of an active suspension with a

passive base fraction.

  The present invention is based on the simul-

  tane, under increased working pressure, of the two working chambers of a suspension strut which simultaneously represents the passive base spring and the positioning cylinder for the

  active suspension, feeding which operates according to the

  Slowly instantaneous of the suspension action and under the control of a central logic circuit of adequate conformation, receiving for example values of displacement and speed. As one of the chambers has a smaller surface area under pressure

  applied for the displacement of the piston in the posi-

  operation, of course, due to the extension outside

  of the sealed piston rod, the design of the suspension strut

  sion, in combination with The passive base fraction of the suspen-

  sion, offers a multitude of possibilities of intervention for adjustments, which allows to obtain an optimal adaptation to

  instant suspension action.

  In the drawing, the essential components of the suspension

  active with passive base fraction according to the invention are shown

  felt in a state schematically separated from each other by dashed lines; the passive part of the suspension, enclosing at the same time the positioning cylinder for the active part, is designated by a, the part comprising the opening valve

  fast by b and pressure supply by c.

  The suspension strut 10, used for the passive base suspension, comprises a working cylinder 11 in which a piston 12 provided with a piston rod 13, can slide with a tight seal

  being guided. Assuming - in order to facilitate understanding -

  that the working cylinder 11 is mounted stationary (by an articulation

  culation) at 14, compression is obtained at a point fixed on the piston rod 13, for example at its fixing eye 15, depending on the suspension action taking place at a given moment. say a displacement in the direction of a race + s, or a detente, that is to say a displacement in the direction of a race -s. At least one sensor 16 can be provided which detects the instantaneous strokes or deflections of the suspension, converts them

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  and sends, for example, corresponding control values for displacement, speed and other quantities to a circuit

  logic 17, as will be described in more detail below.

  Due to the sealed mounting of the piston rod 13 in the working cylinder, the latter is divided by the piston into an upper pressure or working chamber 18 and a

  working pressure or lower 19, the piston section, DEL

  mitering by a wall the upper chamber 18, being designated by

  F3, while the section of the piston rod is designated by F4.

  The upper 18 and lower 19 working chambers are connected

  between them and to a pressure chamber, forming an accumulated spring

  mulator 24, by connecting channels 20 and 21 and non-return valves 22 and 23 mounted in opposition. In addition to the valves 22 and 23, damping throttles 25 and 26 are mounted, having throttling sections f2 and f3, which are also connected, by their other end fittings, to the accumulator spring 24. These elements represent the passive part of the suspension, therefore including the suspension strut, the accumulator spring, the damping throttles and the corresponding non-return valves, part which initially is not

  not influenced by the active part, which also provides

  The advantage is that in the event of failure of elements of the suspension

  active suspension and pressure supply, the passive suspension can continue to operate. This presupposes, however, that part b), comprising the quick-opening (and switching) valve, is in the starting or rest position, where the three connections for channel extensions in part b), namely the connection of channel I as central connection of the accumulator spring and the combined connections of non-return valves 22, 23 and damping throttles 25, 26, as well as the connections of channels II and III, communicating respectively with the upper working chamber 18 and the lower working chamber 19 of the suspension strut, are not interconnected. The connections I, II and III are thus separated from each other at this central or rest position of the quick-opening valve, which is designated in the figure by 27. This valve can be of any desired type, but it must be able to control relatively large sections. In its preferred embodiment shown by the

  drawing; it represents a kind of 5-way valve and 3 posi-

  tions, comprising a drawer 27a slidably mounted in a valve body and mutually insulating or connecting together the different mouths, as will be described in more detail in what follows. In any event, the basic operation of the quick-opening valve 27 is such that, apart from the central position of the valve shutter, and therefore of the slide 27a in this example, at least the channel connections II and III are connected to a pressure P1 which is higher than the average pressure Psm on both sides of the suspension strut, or that the channels II and III and preferably also, in all cases, the channel I, are connected to the discharge side (pressure po). These connections are preferably established with a continuous transition, that is to say gradually from the fully closed position to a final fully open position, depending on the

steering.

  One possibility of making such a quick-opening valve consists in opening the three connections of channels I, II and III under uniform angular spacings around the axis of the body of the valve and being isolated from each other.

  others, in the bore 27b of the valve, as shown

  felt by a schematic plan view next to the passive part

suspension.

  Above this region the mouths of channels I, II

  and III, there is then the mouth of channel 28 coming from the

  pressure mentation; connection 29 for the discharge side, having the pressure po0, is provided below. The plan view on the left and next to the passive part, represents by

  therefore a cut along the line XX '.

  The structure of the quick-opening valve 27 is completed by a 2-way and 2-position solenoid valve 30, piloted through a connection line 17a by the central control circuit, preferably by a timing of this high-frequency solenoid valve, by a servo valve 31 for pressure equalization, as well as by a return device 32 which acts stabilizing on the main drawer, that is to say the drawer

  27a, via the servo positioning member

  valve. The higher supply pressure, P1, comes from a central pressure supply device, comprising a pump

  34, an accumulator 33 and a pressure regulator 35. Vacuum side

  ration, The pump 34 is connected to the discharge side, for example to a suitable pressure fluid reservoir having the pressure pO; the supply pressure in P1 must be higher than the average pressure Psm required in the suspension strut for

  compensate for static axle load. According to an example of reali-

  preferred position, the pressure regulator 35 is adjusted so that it sets the pressure P1 to a value equal to or approximately equal to 3 p. Thus, half of the mean pressure Psm of the leg of 2 Sm S suspension is available for the acceleration on this leg,

  as will be described in more detail below.

  The basic operation of the quick-opening valve is such that during the control of the solenoid valve 30 by the central control circuit 17, the positioning pressure PR

  acting on the end face 27c of the drawer 27a can be changed

  continuously controlled, depending on the momentary suspension action, since, under the effect of the solenoid valve 30, the pressure (variable) PR derived from the supply pressure Pl can be lowered considerably when the solenoid valve 30 is largely open, by the opening towards the discharge side presenting the pressure po - which is made possible by an additional damping throttle 36 having the throttling section f1 - or can be increased, when the solenoid valve 30 is closed or almost closed, to the point that the slide 27a is moved regularly, that is to say continuously downward from the middle position or rest position shown; in the first case, a displacement of the drawer 27a is obtained upward in the plane of the drawing. Therefore, the channels II and III are first, in all cases, interconnected when the slide 27a is moved from its central position; then they are connected in addition, according to the direction of movement of the drawer, either with the supply pressure

  P1 higher, ie with the discharge side in. During this function

  turing, the positioning pressure PR acts on the section F1 of the slide 27a, while the supply pressure P1 acts permanently, through the connecting pipe 37, on the area of

  lower section F2 = F1 / 2 of the positioning member or piston

31a of the servo valve 31.

  It is therefore possible to bring the two useful faces F3 and F3-F4 of the suspension strut 10, as well as the accumulator spring 24, directly and actively to a new pressure level ps prefixed by the circuit regulator

central control unit 17.

  It goes without saying that the conformations of the controlled sections of the connections of channels I, II and III on the valve 27 can

  differ from each other, for example in such a way that a strange effect

  slip is produced on the channel mouth I, which is connected directly to the accumulator spring 24 and to the corresponding connection sides of the non-return valves 22, 23 and of the damping throttles 25, 26. Ultimately, the channel connection I can also be eliminated completely, which means that the pressure equalization in the accumulator spring 24 takes place in this case through the throttles 25, 26 and the non-return valves 22, 23. It is also possible to provide, at

  willingness, as necessary, to overlap or overlap

  between the movements of opening or closing the mouthpieces

chures of channels I, II and III.

  Since the change in vehicle load

  also causes the change in mean pressure Psm corres-

  depending on the static axle load, it is advantageous, if the system is designed to also provide level correction, that a level corrector - additionally provided in such cases and not shown in the drawing - also provides the enslavement, at least roughly, of the pressure Pl, in order to create, in all

  cases, a comparable excess of pressure for the dynamic intervention

  "active" mique. The level correction device can also

  ment part of the central control circuit 17, in which case it acts accordingly on the pressure regulator 35 through a control line 35a. The energy to be supplied by the pressure supply device depends, in particular, on the excess

  desired pressure, controlled sections on the valve to open

  fast and efficient sections of the working chambers in

the suspension leg.

  It can also occur, as already mentioned, situations where the suspension works exclusively in a passive manner, namely as long as the signals of displacement, speed and other quantities of the sensor 16, signals which describe the state of oscillation , show in the electronic control circuit 17 that the basic design of the suspension is

  optimally adapted to the instant suspension action.

  This basic design (passive basic fraction) is intended to give a very soft suspension characteristic, so that there is a wide spectrum of possibilities for intervention by

active pressure setting.

  When, as a function of the momentary suspension action, the valve 27 is moved from its central position, the partial adjustment circuit formed by this valve and the suspension strut

  , has an integral behavior. The suspension strut is

  méée or extended to one of its two limit stops, unless a movement signal on the suspension strut imposes another characteristic in the closed circuit

setting.

  In principle, the regulation strategy, stored in the central electronic control circuit 17, can be of any type; it goes without saying that this circuit can be produced according to an analog, digital or hybrid technique and that iL can comprise or be constituted partially or entirely by digital systems controlled by program, therefore microprocessors,

  microcomputers and the like. In particular, the fundamental principle

  of the active suspension according to the invention, comprising a passive base fraction, can also be contained in the circuit

  central control unit 17 in the form of a stored program.

  All the characteristics appearing in the description,

  The following claims and the drawing are applicable

  both individually and in any combination

  for the implementation of the invention.

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Claims (11)

  1. Suspension for vehicles, comprising a suspension strut arranged between the body and an axle and having a working cylinder in which slides a piston provided with a piston rod and which contains upper and lower working pressure chambers, by relative to the cylinder, which are connected to each other and to a pressure accumulator (accumulator spring) through non-return valves mounted in opposition, characterized in that damping throttles (25, 26) are arranged in parallel with the non-return valves (22, 23) and are also   connected to the accumulator spring (24) (passive part of the suspension   ) and that, in combination with these elements and as an active part of the suspension, the working chambers (18, 19) of the working cylinder (11) are connected through a quick-opening valve (27), either at a supply pressure (pl) which is higher than the average pressure (PSm) necessary to compensate for the static axle load, i.e. at the discharge side (pressure p0o).   2. Suspension according to claim 1, characterized in that it comprises a sensor (16) which detects at least the elastic stroke of the suspension strut (+ s; -s) in both directions and whose output signals are applied to a control circuit   central (17) which controls the quick opening valve (27).   3. Suspension according to claim I or 2, characterized in that the two connecting channels (20, 21) leading to the working chambers (18, 19) of the suspension strut, can be connected simultaneously and continuously or decreasing,   via the quick-opening valve (27), at the supply pressure   tion (p1) higher, higher than axle load pressure   static, or on the discharge side (po0).   4. Suspension according to any one of claims 1   to 3, characterized in that the quick-opening valve (27) has a pressure-controlled slide (27a) which connects at least the channel connections II together with the supply pressure or the discharge side , III of the working chambers (18, 19), connections which open at the same height in said valve (27), and that, for the continuous movement of the slide (27a), a solenoid valve (2-way solenoid valve 30 is provided and 2 positions) controlled at a high frequency by a   electronic control circuit (17) and continuously changing   naked, depending on its average opening section, the pressure (pR) acts   sant on one of the end faces (27c) of the drawer (27a).   5. Suspension according to claim 4, characterized in that, for pressure compensation, the supply pressure (p2) acts on a smaller working face on the other side of the slide (27a).   6. Suspension according to any one of claims 1   to 5, characterized in that it comprises a servo-valve (31) which acts by a positioning member (31a), charged by the supply pressure (p1), on the side of the slide (27a) remote from the continuously variable working pressure (pR), and a return device (32) is also provided for the valve function   controlled by the electronic control circuit (17).   - 7. Suspension according to claim 6, characterized in that the return device comprises an electromagnetic part   (32) acting on the positioning member (31a) of the servo valve (31).   8. Suspension according to any one of claims 1   7, characterized in that the accumulator spring (24), the connections directed towards each other of the non-return valves (22, 23) and the damping throttles (25, 26) mounted in parallel with them, can , by their channel mouth (I) in the quick-opening valve (27) and by means of this valve, also be connected to the two other channel connections (II, III) of the working chambers (18, 19) of the suspension strut, likewise   depending on the position of the drawer, either at the supply pressure   tation (pl), ie on the discharge side.   9. Suspension according to any one of claims 1   to 8, characterized in that the controlled sections of the connections   channel elements (I, II, III) opening into the quick-opening valve (27) differ from one another and possibly have a choke effect.   10. Suspension according to any one of claims 1   9, characterized in that the pressure supply device supplying the supply pressure (p1) comprises, in addition to an accumulator (33) and a pump (34), a pressure regulator (35) which regulates the pressure supply or working pressure (p1) to a value higher than the average pressure (psm)   compensating for static axle load.   11. Suspension according to claim 10, characterized in   what the supply pressure (p1) 3 * Pm.