FR2761443A1 - JOINT BETWEEN TWO AXIALLY MOVABLE COMPONENTS ONE IN RELATION TO THE OTHER - Google Patents

Abstract

The invention relates to a joint between two axially movable components with respect to each other of an oscillation damper or of a spring force leg, the component carrying the joint being a damping piston 2 connected to a piston rod 1 or else a piston rod guide 5. The damping piston 2 is guided with sealing on the inner wall of a cylinder 3, while the piston rod 1 slides in the guide of piston rod 5, and the oscillation damper or the spring force leg is biased by transverse forces. The damping piston 2 or the piston rod guide 5 has a seal support 11, 12 non-detachably connected thereto, and the seal 13, 14, 23 has an end projecting inwards 16, 22 which is housed non-detachably in the seal support 11, 12.

Description

The invention relates to a joint between two components axially

  movable relative to each other and of circular cross section, in particular for oscillation dampers or hydropneumatic spring struts for motor vehicles, the component carrying the seal being a damping piston connected to a piston rod or a piston rod guide, and the damping piston sliding with seal on the inner wall of a cylinder and the piston rod sliding in the piston rod guide, while the seal connected to the damping piston or piston rod guide is preferably a sealing ring which is made of a material promoting sliding and which forms a respective bearing surface for the transverse forces acting on the unit. Document EP 0 345 561 A3 discloses a piston for an oscillation damper which has a sliding ring fitted around the cylindrical outer surface, which forms the support surface for the transverse forces which appear, and is intended to ensure on the periphery a constant seal and sliding relationships. To achieve this, it is necessary to ensure extremely precise manufacturing precision which thus leads to high costs, so that on the one hand no unwanted bypass section appears between the damping piston and the inner wall of the cylinder, and on the other hand that no wedging effect appears between the damping piston and the cylinder. This cannot be ensured in such a construction over the entire temperature range in which the oscillation damper must operate perfectly. In a piston comprising a piston ring for an oscillation damper, it is known from document DE 40 32 609 CI, to arrange the piston ring firmly and in a non-detachable manner on a support body, and to mount the body support is then on a piston heel. Such a construction of the piston also requires that the diameter of the heel of the piston be produced very precisely, and also an exact manufacture of the support body provided with the piston ring, so that the necessary seal between the inner wall of the cylinder d on the one hand and easy sliding on the sealing surface on the other hand are ensured. Preferably for pressurized fluid brakes, document DE-PS 843 780 discloses a piston seal which engages with a groove in a disc-shaped piston body, in which measures have been provided to prevent unwanted detachment of the piston seal from the piston body. In pressurized fluid brakes and similar constructions functioning as pumps, the piston seal or the piston body is not exposed to transverse forces, or at least not to significant transverse forces, which is why a such sealing cannot satisfy the

  requirements for the structure of the oscillation damper.

  In addition, it is known to install a plastics or sintered piston ring split in a piston groove of a damping piston, in which the dimensions of the groove and of the piston ring have to be adjusted extremely exactly, so that no clicking noise appears. Likewise, the document DE 195 01 792 AI1 describes a damping piston comprising a piston ring mounted under tension thereon, in which the piston ring has a width which is greater than the envelope surface of the damping piston , so that the protrusion is formed to form elastic ends which bear against surfaces on the front side of the damping piston. This is preferably done with slightly larger tolerances to prevent clicking noises and to obtain simpler and less costly manufacture of the piston body. However, the arrangement of the elastic ends after mounting the piston ring on the piston body is problematic, since the pressing force must be kept within predetermined limits vis-à-vis the relatively thick piston rings, to ensure the desired operation. On the other hand, when the finished piston ring is pulled on the damping piston or else inserted into the piston groove, the joint slot forms an unwanted bypass, so that an exact production linked to costs of high production is again necessary, so that different functional tolerances do not appear

  adversely affecting the power of the shock absorber.

  The underlying objective of the invention is to provide a joint between two components which are axially movable relative to each other, which ensures perfect sealing as independently as possible of the transverse forces which appear on the support surfaces of the components, which is simple to carry out and which ensures a realization

  economy of the damping piston.

  In accordance with the invention, this objective is achieved by the fact that the damping piston or the guide of the piston rod has a seal support connected in a non-detachable manner and preferably made of plastic, while that the seal has an end projecting inwardly which is embedded in a non-detachable manner in the seal support. The body of the damping piston, which is preferably made of a metallic material, can be made in the form of a stamped piece of steel or a sintered piece. The arrangement of the plastic seal support in the region of the outside diameter is advantageously carried out by injection around the piston body, whereby no high requirements are placed on the tolerance on the diameter of the piston body, and there is therefore a great deal of freedom with regard to the choice of materials and the production process, so that a

  economical manufacturing of the damping piston is ensured.

  A very simple and effective seal is obtained by the fact that it has at least one sealing lip which is arranged outside the bearing surface and radially movable relative to the sealing surface. The radial mobility of the seal ensures perfect sealing between the cylinder and the piston, both on the side of the support of the piston on the cylinder due to the transverse forces, and on the opposite side on which a slot is formed. We can therefore choose the piston diameter tolerance much wider and thus more economical, thanks to which we avoid jamming due to thermal expansion and we therefore ensure a sliding with low friction

  piston on the inner wall of the cylinder.

  According to an alternative embodiment, the seal lip of the seal is fixed in an inclination with respect to the sealing surface in the seal support, and the seal support is preferably formed by injection around the damping piston or of the piston rod guide. Correspondingly, this does not result in significant additional costs for fixing the seal in the seal holder, since this is done in one step with the arrangement of the seal holder on the piston body. As shown in the invention, the seal is preferably constituted by a film ring of flexibly elastic PTFE, which is connected in a non-detachable manner to the seal support simultaneously with the injection around the damping piston, the seal being preferably provided with recesses in the injected part, into which the material of the seal support penetrates. In this way, a very simple non-detachable connection of the seal is produced with the piston or with

guiding the piston rod.

  According to an advantageous development, the film ring forming the sealing lip surrounds the seal support on its bearing surface, and the sealing lip is formed by folding at the end of the film ring. In this way, a more solid sealing lip is produced which allows a simpler mounting of the oscillation damper thanks to a simpler positioning of the damping piston in the cylinder. In order to avoid excessive elongation of the sealing lip, it is very advantageous to provide a support shoulder for the sealing lip. According to another characteristic of the invention, the support for the piston rod guide seal has an axial annular heel which, together with an annular elastic sealing lip, forms a non-return valve acting as an air purge valve. Thanks to this, the seal support simultaneously creates the valve surface for the non-return valve which closes the compensation chamber towards the piston rod guide. Another embodiment is obtained by the fact that the film ring has in the region of the bearing surface an annular groove which is formed during the injection of the seal support, whereby a very good connection in cooperation of shapes of the film ring with the seal support. Thanks to this, it is possible without any problem that the film ring has at one of its axial ends a sealing lip and at the other end

  axial, the end projecting inwards in the seal support.

  An effective seal is obtained which acts perfectly in the two directions of displacement of the piston with respect to the interior wall of the cylinder when a seal acting on the outside of the surface of the cylinder is arranged on the damping piston. 'support and cooperating with the sealing surface. The seal is further pressed against the sealing surface by the differential pressure between the working chamber on the piston rod side and the lower working chamber, which results in extremely low friction operation of the seal during low differential pressure, which provides a good smooth response from the oscillation damper. This advantageous action of the seal also applies to the piston rod guide, when the seal support connected to the piston rod guide is non-detachably connected to a seal, the sealing lip preferably formed by bending the the end of the film ring being arranged so that it faces the

  working chamber on the piston rod side.

  According to another development of the invention, the damping piston is constituted by a perforated disc formed by punching, while the seal support substantially surrounds this disc and only the region used for fixing with the piston rod is produced. without seal support. Both the outside diameter and the passage openings associated with the damping of traction and pressure can be made jointly with the seal during injection around the perforated disc with the desired shape and precision in a single step.

of work.

  The invention will be explained in more detail in the following with reference to embodiments illustrated in the drawings. The figures show: Figure 1 a detail of an oscillation damper in the region of the piston rod guide and the damping piston; Figure 2 the damping piston shown in Figure 1 in an enlarged illustration; Figure 3 an embodiment of a damping piston, wherein the sealing lips are formed by folding a film ring; Figure 4 the cooperation of the seal shown in Figure 3 with the cylinder on the side discharged from the transverse force; FIG. 5 the damping piston according to FIG. 3, as it is pressed against the cylinder under the action of the transverse force; Figure 6 the arrangement of a piston ring cooperating with a film ring; FIG. 7 another embodiment of a damping piston provided with a film ring and a piston ring; and FIG. 8 a damping piston which has a disc perforated by

  punching substantially surrounded by the seal support.

  In the detail shown in Figure 1 of a two-tube hydropneumatic oscillation damper, the damping piston 2 firmly connected to the piston rod 1 slides on the inner wall of the cylinder 3 which is centered by means of the guide of piston rod 5 at the top in the container 4. The piston rod 1 is axially movably guided in the piston rod guide 5 and it is sealed towards the outside by means of a piston rod seal 6. The inner chamber of the cylinder 3 is filled with a damping liquid and it is subdivided by the damping piston 2 into a working chamber 7 on the piston rod side and into a working chamber 8, these working chambers 7 and 8 being in hydraulic connection in the direction of traction and pressure of the piston rod 1 via the damping valves provided in the damping piston 2. The lower working chamber 8 is connected via a bottom valve not shown to a chambercompensation 9 which has a gas or liquid filling and which is intended to compensate for the retracted or deployed volume da the piston rod. An air purge valve 10 which is designed as a non-return valve prevents gas from flowing out of the compensation chamber 9 via the piston rod guide 5 into the working chamber 7 on the rod side piston during the race

  under pressure from the piston rod 1.

  Since we can presuppose as known the structure and the mode of operation of a hydropneumatic oscillation damper, we will refer in the following only to the structure and the mode of operation of the seal for the piston

  for damping and for guiding the piston rod.

  To seal the damping piston 2 sliding axially on the interior wall of the cylinder 3, the piston body is provided according to FIGS. 1 and 2 with a seal support 11 preferably made of plastic, in which the seals 13 and 14 constituted for example by elastic PTFE film rings in flexion are embedded so as to extend obliquely with respect to the sealing surface. When the seal support 11 is projected around the piston body, the seals 13 and 14 are simultaneously placed at the ends 16 in the seal support 11, the plastic material of the seal support 1 1 penetrating into the recesses 17, and the non-detachable connection being thus produced. The sealing lips 15 of the seals 13 and 14 bear against the interior wall of the cylinder 3 even when the damping piston 2 is pressed against the opposite side not shown by the action of the transverse force, as shown in the Figures, and that a slot 18 is thus formed on the side illustrated. Since the sealing lips 15 are arranged outside of the bearing surface 25, only the low inherent stress of the sealing lips 15 acts on the interior wall of the cylinder 3 during a pressure equalization between the working chambers 7 and 8, so that when the oscillation damper responds, low friction prevails between the damping piston 2 and the inner wall of the cylinder 3. Only when the pressure difference between the working chambers 7 and 8, the sealing lip 15 is pressed additionally against the sealing surface in the pressure chamber, which promotes the sealing effect and which increases the friction in this phase, but which does not have a disadvantageous effect, because the oscillation damper responds in a flexible manner and without effect, "stick-slip" ("sticking-sliding", or in spurts) before the differential pressure whole, therefore

when depreciation takes effect.

  As shown in FIG. 1, the seal 23 on the piston rod guide 5 is non-detachably connected to the seal support 12 during injection. In this embodiment, the piston rod guide 5 consists of a piece formed from sheet metal and an angular ring made of sheet metal, which tighten, during compression, the end 22 of the film ring 21; the sealing lip 23 'being formed by folding the film ring. The sealing lip 23 ′ is arranged outside the bearing surface 24 and protrudes into the working chamber 7, while the front surface, directed radially inwards, of the angular ring forms a shoulder d 'support for the sealing lip 23' and prevents it from being excessively extended towards the outside. The film ring extends over the entire bearing surface 24, it is radially bent at the upper end and it is firmly connected to the seal support 12. The seal support 12 preferably made of plastic material present at its upper end an annular axial bead which forms a non-return valve 10 together with an elastic annular sealing lip which is produced so as to form part of the piston rod seal 6. This non-return valve 10 prevents gas flow out of the compensation chamber 9 into the sealing chamber of the piston rod seal 6 and via the piston rod guide 5 into the working chamber 7 on the piston rod side. The embodiment of the seal for the damping piston 2 according to Figures 3, 4 and 5 differs from that according to Figures 1 and 2 essentially by the fact that the film ring 26 is supported over the entire length of bearing 25 against the seal support 11, and that it forms the sliding surface with low friction on the internal wall of the cylinder 3. The sealing lips 27 and 28 are formed by bending the ends of the film ring 26, while the ends 16 of the film ring are provided with the recesses 17 and are housed in the seal support 11. To avoid excessive elongation of the sealing lips 27 and 28, a support shoulder 33 is provided which is preferably shaped by corresponding heels of the support

attached 11.

  In FIG. 4, the damping piston 2 in the cylinder 3 is arranged so that a slit 18 is formed between the film ring 26 and the interior surface of the cylinder 3, when the damping piston 2 is pressed against the opposite non-illustrated inner wall of the cylinder by the transverse force. On the other hand, FIG. 5 shows the damping piston 2 when it is pressed over the entire length of support against the interior wall of the cylinder 2 by the transverse force, the film ring 26 then resting on the surface d seal and the sealing lips 27 and 28 deviating radially so that they lie in a line with the surface

outside of the film ring.

  Figure 6 shows another embodiment which applies from

  preferably in a cylinder 3 having a longitudinal groove 29.

  The film ring 26 is housed at its ends 16 in a non-detachable manner in the seal support 11 and it has in the region of the bearing surface 25 an annular groove 30 in which is arranged a piston ring 31. This embodiment of the film ring 26 ensures good simple axial fixing on the seal support 11, and the piston ring 31 undoubtedly prevents the film ring 26 from being introduced into the longitudinal groove 29. The embodiment according to FIG. 7 differs from that according to FIG. 6 by the fact that an annular sealing groove 32 is formed at the lower end of the ring

  film in the seal support 11 to receive the piston ring 31.

  FIG. 8 illustrates an advantageous embodiment of the damping piston 2. This consists of a perforated disc by punching 19, the seal support 11 surrounding this perforated disc except for a region intended for fixing with the piston rod 1. On the left side of the piston, a seal has been arranged as described

  substantially in the foregoing with reference to Figures 3, 4 and 5.

  The right side of the piston, however, shows a seal, in which the film ring 26 has at its upper end the sealing lip 15 and has in the central region an annular groove 30, and in

  which the lower end 16 is injected into the seal support 11.

  The internal diameter, free of the seal support, of the perforated disc 19 allows a mechanical fastening with high solidity, such as a riveted connection, the rivet head 20 also resting on the metal surface of the perforated disc 19. This is also advantageous for other known firm connections of damping pistons 2 with a piston rod 1. With the exception of the internal diameter, the punched disc 19 can be produced relatively roughly, because the dimensions and the essential configurations of the piston , such that the outside diameter, the shape and the cross section of the passage openings are made with the desired shape and precision only when projecting the support

attached 11.

  The embodiments described above of the joint between two axially movable components relative to each other of an oscillation damper are all economical to produce, because the 1i joints are only placed or tightened in the mold d injection, and the seal support made of plastic material is projected around the piston body, so that the seals are non-detachably connected with the seal support together with the desired shape precision. Thanks to this, the seal support can be used without problems as a low friction sliding surface thanks to a

appropriate choice of materials.

Claims (12)

Claims   1. Joint between two axially movable components with respect to each other and having circular cross sections, in particular for hydropneumatic shock absorbers or legs, the component carrying the joint being a piston damping connected to a piston rod or a piston rod guide, and the sliding damping piston with seal on the inside wall of a cylinder and the piston rod sliding in the piston rod guide, while the gasket connected to the damping piston or to the piston rod guide is preferably a sealing ring which is made of a material promoting sliding and which forms a respective bearing surface for the transverse forces acting on the unit, characterized in that the damping piston (2) or the piston rod guide (5) has a seal support (11, 12) connected in a non-detachable manner and cons preferably made of plastic, while the seal (13, 14; 23) has one end projecting inwards (16, 22)   which is non-detachably embedded in the seal support (11, 12).   2. Joint according to claim 1, characterized in that it has at least one sealing lip (15, 23 ', 27) which is arranged outside the bearing surface (24, 25) and radially mobile   relative to the sealing surface.   3. Joint according to claims 1 and 2, characterized in that the lip   seal (15, 23 ', 27) of the seal (13, 14, 23) is fixed obliquely to the sealing surface in the seal support (11, 12), and in that the support seal (11, 12) is preferably formed by injection around the damping piston (2) or the rod guide piston (5).   4. Joint according to claims 1 to 3, characterized in that it is   preferably made of a bending ring of elastic PTFE film which is non-detachably connected to the seal support (1) simultaneously with the injection around the damping piston (2), the seal (13, 14) advantageously being provided with recesses (17) in the injected part, into which the material of the seal support penetrates (11).   5. Joint according to claims 1 to 4, characterized in that the ring   film (21, 26) forming the sealing lip (23 ', 27, 28) surrounds the seal support (11, 12) on its bearing surface (24, 25), and in that the lip seal (23 ', 27, 28) is formed by folding at the end of the film ring (21, 26).   6. Joint according to claims 1 to 5, characterized in that it is provided   a support shoulder (33) for the sealing lip (15, 23 ', 27, 28).   7. Joint according to claims 1 to 6, characterized in that the support   seal (12) of the piston rod guide (5) has an axial annular bead which, together with an elastic annular sealing lip, forms a non-return valve (10) acting as a check valve. air purge.   8. Joint according to claims 1 and 2, characterized in that the ring   film (26) has in the region of the bearing surface (25) an annular groove (30) which is formed during the injection of the support attached (l11).   9. Joint according to claims 1, 2 and 7, characterized in that the   film ring (26) has at one of its axial ends a sealing lip (15) and at the other axial end the penetrating end (16)   inward in the seal holder (11).   10. Seal according to any one of the preceding claims,   characterized in that there is provided on the damping piston (2) on each front side a seal (13, 14; 27, 28) acting outside the   bearing surface (25) and cooperating with the sealing surface.   11. Joint according to any one of the preceding claims,   characterized in that the seal support (12) connected to the piston rod guide (5) is non-detachably connected to a seal (23), the sealing lip (23 ') of the seal (23), formed preferably by folding the end of the film ring, is arranged so as to be directed   towards the working chamber (7) on the piston rod side.   12. Joint according to any one of the preceding claims,   characterized in that the damping piston (2) consists of a perforated disc (19) produced by punching, while the seal support (1 1) substantially surrounds this perforated disc (19), and in that preferably only the region of attachment with the piston rod (1) is made without seal support.