FR2628167A1 - ADJUSTABLE HYDRAULIC SHOCK ABSORBER - Google Patents

Abstract

A shock absorber comprises a cylinder 1 which contains a damping liquid, an axially movable piston rod 2 immersed in this cylinder and to which is attached a piston 3 which slides tightly in the cylinder 1 and shares the interior thereof. ci in two working chambers 4, 5, as well as a damping device, with provision of at least one hydraulic connection 25 generating a damping force, the useful section of which is variable by a valve 6. The valve cooperates with a membrane 7 mounted tight and on one side of which is formed a control chamber 8 to which is applied, through a bypass, the pressure prevailing on the hydraulic connection. The chamber 8 communicates with the flow orifice 10 of the hydraulic connection by a channel 12 which can be closed by a servo-control member 11, and in which the flow is adjustable by an axially movable shutter 13 of this member 11.

Description

6) RÉPUELIQUE FRAN AISE Publication no .: 2,628,167 (use only

  for NATIONAL INSTITUTE reproduction orders) OF INDUSTRIAL PROPERTY z INDUSTRIAL PROPERTY National registration number 89 02719 PARIS

    Int Ci4: F 16 F 9/46, 9/19; B 60 G 17/08.

Q A1 PATENT APPLICATION

  Filing date: March 2, 1989. Q Applicant (s): Company known as: BOGE AKTIENGESELL-

SCHAFT.- DE.

  ) Priority: DE, 5 March 1988, n P 38 07 322.6.

Q Inventor (s): Hubert Beck.

  Date of public availability of the

  application: BOPI "Patents" n 36 of September 8, 1989.

  References to other national documents appearing

rented: (r Holder (s):

  (Agent (s) Cabinet Beau de Loménie.

  (Adjustable hydraulic shock absorber.

  57 A shock absorber comprises a cylinder 1 which contains a

  damping liquid, an axially modulated piston rod 2

  bile immersed in this cylinder and to which is fixed a piston 3 which slides with a sealed seal in the cylinder 1 and divides the interior of the latter into two working chambers 4, 5, as well as a damping device, with forecast of at least 1

  a hydraulic link 25 generating a damping force

  ment whose useful section is variable by a valve 6. The BX p valve cooperates with a diaphragm 7 mounted leaktight and on one side of which is formed a control chamber 8 to which is applied, through a bypass, the pressure prevailing on the hydraulic connection. Room 8 communicates

  with the flow orifice 10 of the hydraulic connection by a.

  With channel 12 which can be closed by a servo control unit -

  11, and in which the flow is adjustable by a shutter

  13 axially movable of this member 11.

  LL D Sale of booklets at IMPRIMERIE NATIONALE, 27. rue de la Convention - 75732 PARIS CEDEX 15 The invention relates to an adjustable hydraulic shock absorber, comprising a cylinder which contains a damping liquid, an axially mobile piston rod plunging into this cylinder and to which is fixed a piston which slides with a tight seal in the cylinder and divides the latter into two working chambers, as well as a damping device, with provision for at least one hydraulic connection generating a damping force, the useful section of which is variable by a valve, which cooperates with a diaphragm mounted tightly and on one side of which is formed a control chamber, to which is applied, through a control bypass, the prevailing pressure on the

hydraulic connection.

  Hydraulic shock absorbers are known (for example by

  document DE-AS 12 42 945) whose damping characteristic

  ment is adjustable electromagnetically by varying the flow rate of the hydraulic damping fluid through the damping valves. For this device, two branch connections are provided, the first of which is generally used to adjust the damping force in the pulling or extension phase by

  compared to the damping force in the compression phase.

  The actuation of such a device is carried out electroma-

  genetically or by an electric motor, so there are limits

  imposed on the response speed.

  Shock absorbers are also known (for example from document DE-OS 36 09 862) on which a control bypass has been provided, having a servo-control member, to control the passage channel. For the control and regulation of the damping fluid, a pilot valve having a pilot stage with autonomous supply is used. In this case, the difference of

  pressure prevailing between the chambers and generating the damping force

  is used to adjust this force. In view of the varia-

  tion of different pressures to be established in the chamber, there is provided a valve or other adjustable distribution member as

  as a servo drive. For this purpose, regu-

  Known pressure readers, such as proportional control valves and two-way and two-position distributors, with or without rhythmic control or with pulse width modulation. The object of the invention is to create a damper with which the control of an adjustable pilot valve requires little space for incorporation and allows a high response speed. To this end, according to the invention, a hydraulic damper as defined at the start is characterized in that the control chamber communicates with the flow orifice of the hydraulic connection by a channel which can be closed by means of a servo control, the flow through this channel being controllable by an axially movable shutter of this servo control member. This solution has the advantage that the servo control unit, together with the pilot valve, can be integrated directly into the shock absorber. Another essential characteristic provides that the valve comprises, on one side of the membrane, at least one axially movable elastic washer connected to the membrane, which controls

  the hydraulic connection in cooperation with a valve seat.

  This arrangement has the advantage that the controlled membrane, axial-

  mobile, allows to simultaneously vary the preload of the

elastic washer.

  According to one embodiment of the invention, the shutter is a needle which acts on the orifice of the channel. The tip of this

  needle can be cylindrical, conical, spherical or stepped.

  In order to obtain a servo-control member of low height and thus avoid, in particular, a reduction in the stroke of the shock absorber in the event that the servo-control member is integrated in the shock absorber, the shutter is a circular plate held by its outer edge and of which at least the central part is axially movable.

  Yet another essential characteristic of the invention

  tion provides that the plate is metallic, bimetallic, ceramic

  piezoelectric or metal plate with piezoelectric ceramic

  reported cudgel. This gives the advantage that in case of use

  sation of a piezoelectric quartz, the low height of such a quartz allows advantageous integration into the damper. In this case, the shutter plate directly or indirectly controls the control bypass and the sending of an electric current to the piezoelectric quartz causes a change in the thickness or a bulging of the plate. The quartz power supply allows a displacement proportional to the intensity of the electric current. In one embodiment of the invention, the two faces of the plate communicate hydraulically with one another and are

hydraulically stressed.

  When the servo control unit is not supplied with electricity

  tricement, the shutter is held in a rest position by

a spring.

  According to another characteristic, the electrical connection for the piezoelectric material is a coaxial cable comprising a

  shield connected to ground and a central conductor connected directly-

  ment or indirectly to the piezoelectric material.

  In this case, it is advantageous for the central conductor

  ends up in a pot-shaped piece of non-conductive material

  electric tor and having a metallized internal surface, part in which the spring is disposed, itself continuously in

  contact, directly or indirectly, with the piezoelectric material

  stick. Other characteristics and advantages of the invention

  will emerge more clearly from the description which follows from

  several examples of preferred embodiments but in no way limited

  tatives, as well as accompanying drawings, in which: - Figure 1 is an axial section of a damper, shown in the compression phase, the bottom of which contains a pilot valve; - Figure 2 shows the damper of Figure 1 in the drawing phase; - Figure 3 shows on a larger scale the piloted valve while the shutter plate is electrically supplied; - Figure 4 shows the valve of Figure 3 then

  the shutter plate is not powered

  is lying; and - Figure 5 is a partial cross section of a shock absorber OS, showing a valve controlled in a bypass of the shock absorber. Figure I shows schematically a twin-tube damper having a cylinder 1, a piston rod 2 and a piston 3 fixed to this rod. The piston 3 shares the interior of the cylinder 1 in one

  upper working chamber 4 and a lower working chamber

  5. The piston 3 is provided with passage channels and a non-return valve 19. The bottom of the cylinder 1 contains another non-return valve 20, by which the damping fluid can reach from the equalization space 23 - formed by the envelope tube 22 and the additional tube 21 - in the lower working chamber 5. The interior of the additional tube 21 communicates through bores 24 with the upper working chamber 4 and

  by a hydraulic connection 25 with the valve 6.

  The valve 6 has a membrane 7 which is connected indi-

  directly to elastic washers 14 and which controls the hydraulic connection 25 in cooperation with the valve seat 15. When the valve 6 is open, the damping fluid passes through the flow orifice 10 in the equalization space 23. A spring 16 tends to hold the elastic washers 14 in a rest position. A small part of the damping fluid

  reaches from the hydraulic connection 25 and through the bypass

  control 9 into the control chamber 8.

  The control chamber 8 is connected to the drain opening.

  Lement 10 by a closable channel 12 which can be controlled by a

  servo control member 11 and an axial valve shutter 13

mobile.

  The damper shown in Figure 1 is in the compression phase. The non-return valve 19 on the piston 3 opens and the non-return valve 20 at the bottom closes. As the piston rod 2 penetrates further into the cylinder 1, an amount of damping fluid corresponding to the volume of the piston rod entering the cylinder is discharged through the channel.

  29 and the hydraulic connection 25 to the valve 6, where its flow

  ment is braked according to the pretensioning force of the elastic washers 14 and from where it reaches the equalization space

23.

  Figure 2 shows the shock absorber of Figure 1 in the pulling or extension phase. The non-return valve 19 on the piston 3 closes and the non-return valve 20 in the bottom of the

  cylinder 1 opens. Above piston 3, damping fluid

  This is driven by the annular surface of the piston 3 and through the channel 26 and the valve 6 into the equalization space 23, while the part of the damper located under the piston 3 sucks a corresponding amount of fluid. amortization since

  space 23 and through the non-return valve 20.

  It can be seen in FIGS. 1 and 2 that the delivery surfaces

  Both in the compression phase and in the pulling phase are

  different, so the damping behavior can also

  LEMENT be fixed according to the delivery surfaces or useful faces (cross section of the piston rod / annular surface of the

piston).

  FIG. 3 shows on a larger scale the valve 6 incorporated in the bottom of the cylinder 1. The hydraulic connection 25 is combined with the seat 15 and with the elastic washers 14. Damping fluid arrives from the hydraulic connection 25 and through the bypass 9 into the room

command 8.

  The shutter 13 is produced as a circular plate 13a which is tightened by its periphery and the middle part of which is axially movable. The plate is formed from a piezoelectric ceramic material which bulges when an electric current passes through it. The electrical connection 17 is a coaxial cable, the shielding braid 17b of which is connected to ground and the central conductor 17c of which is connected to a part 18 in the form of a pot, made of an electrically non-conductive material. As the internal surface of this part is metallized, the spring 27 transmits the current to the piezoelectric ceramic material of the plate 13 forming a shutter

  valve. The two faces of the plate 13a communicate hydraulically-

  between them and are hydraulically stressed through a

drilling 28.

  Sending an electric current to the piezoelectric plate

  plate 13a causes this plate to bulge, which uncovers the orifice in channel 12. The damping fluid flows through

  the recesses towards the equalization space 23. Like channel 12 -

  now open - has a larger section than the inlet of the control bypass 9, the control pressure in the chamber 8 drops so much that the damping pressure or the pressure of the spring 16 moves the membrane 7 jointly

  with the elastic washers 14 in the direction of the lower stop

  better. This corresponds to the maximum soft fit of the washers 14 since the preload with which these washers are

  applied against seat 15 is almost zero.

  Figure 4 shows the valve 6 while it is not electrically powered, which corresponds to the hard adjustment

  maximum of elastic washers 14. When the power supply

  plate is cut, the piezoelectric plate 13a returns to its posi-

  rest position where it closes the channel 12. This means that the control pressure in the chamber 8 rises and that, by the large face of the membrane 7, the washers 14 and the membrane 7 are displaced against the pressure reigning in the bond

  hydraulic 25, as well as against the pressure of the spring 16.

  This gives the maximum hard adjustment of the washers 14 since

  these are now pressed hard on seat 15.

  Figures 3 and 4 show the extreme positions of the hard adjustment and the soft or flexible adjustment of the elastic washers 14. However, the electrical supply of the obturator plate under different values of current and / or voltage

  allows to establish, in a similar way, any intermediate position.

  By means of a digital control, with switching on and off in different modes, for example by applying a pulse width modulation, it is also possible to obtain any intermediate position. FIG. 5 shows an exemplary embodiment where a valve 6 in the form of a separate component is installed in a bypass between the working chambers 4, 5 and the equalization space 23. This figure shows more precisely the cylinder 1 d a shock absorber, a bypass 29 formed by the tube

  21 and the equalization space 23. From the deri-

  vation 29, the damping fluid reaches through the hydraulic link 25 in an annular space where it exerts pressure on the membrane 7. With respect to the channel 10, the membrane 7 cuts off the flow of the damping fluid using the valve seat 15. At the same time, the damping liquid - under damping pressure - flows through the control branch 9 into the control chamber 8. From there, the control liquid reaches the channel 12. The obturator plate 13a makes it possible to vary the pressure in the control chamber 8. When the channel 12 is open, the damping liquid can flow into the equalization space 23 and, as soon as the force - defined by the pressure multiplied by the useful face of the membrane - in the control chamber 8 is less than that in the annular space, the membrane 7, by moving axially over a certain distance,

  allows, to the right of seat 15, the passage to the orifice

  Lement 10. The control bypass 9 then operates in the manner of a primary throttle and it suffices to pass the quantity of damping liquid necessary for actuation of the

membrane 7.

2628 1 67

Claims (2)

  1. Adjustable hydraulic shock absorber, comprising a cylinder which contains a damping liquid, an axially movable piston rod plunging into this cylinder and to which is attached a piston which slides with a sealed seal in the cylinder and divides the latter into two chambers working, as well as a damping device, with provision for at least one hydraulic connection generating a damping force, the useful section of which is variable by a valve, which cooperates with a membrane mounted tightly and on a side of which is formed a control chamber, to which is applied, through a control bypass, the pressure prevailing on the hydraulic connection, characterized in that the control chamber (8)   communicates with the drainage orifice (10) of the water connection   via a channel (12) which can be closed by means of a servo-control member (11), the flow through this channel (12) being able to be controlled by an axially movable shutter (13) of this servo control member (11).   2. Shock absorber according to claim 1, characterized in that the valve (16) comprises, on one side of the membrane (7), at least one elastic washer (14) axially movable and connected to the membrane (7), which controls the hydraulic link in cooperation with a valve seat (15).   3. Shock absorber according to claim 2, characterized in that the shutter (13) is a needle acting on the orifice of the channel (12).   4. Damper according to claim 3, characterized in that the end of the needle is cylindrical, conical, spherical or tier (s).   5. Shock absorber according to claim 2, characterized in that the shutter (13) is a circular plate (13a) held by its outer edge and of which at least the central part is axially movable. 6. Shock absorber according to claim 5, characterized in that the plate (13a) is metallic, bimetallic, piezoelectric ceramic or metal with added piezoelectric ceramic. 7. Shock absorber according to claim 5 or 6, characterized   in that the two faces of the plate (13a) communicate hydrau-   between them and are hydraulically stressed.   8. Shock absorber according to claim 2, characterized in that the shutter (13) is held in a rest position by a spring (16).   9. Damper according to claim 6, characterized in that the electrical connection (17) for the piezoelectric material is a coaxial cable (17a) comprising a shield (17b) connected to ground and of which a central conductor (17c) is directly connected or   indirectly to the piezoelectric material.   10. Shock absorber according to claims 8 and 9 taken   assembly, characterized in that the central conductor (17c) terminates in a part (18) in the form of a pot, made of an electrically non-conductive material and having a metallized internal surface,   part in which the spring (16) is arranged, itself conti-   only in contact with the piezoelectric material. 2628 1 67 1/5 26 9 OPEN   itzlUH ,,, 3 _ 4 _ t23 2/5 IIl CLOSED 1git2121 _20 OPEN 3/5 <616 12 8 13a 1 2. 8 '17. 17b __,,, FI.   4/5 ----------- 6l _ / 5 I '_6 23_5 FI6.5