FR3094435A1 - INERTIAL DOUBLE CHAMBER SHOCK ABSORBER FOR AUTOMOTIVE VEHICLE SUSPENSION - Google Patents

Abstract

The invention relates to a shock absorber (2) for a motor vehicle suspension, which comprises first and second elements (4, 6) forming a damping hydraulic circuit and an inertial hydraulic circuit, with, between the first element (4) and the second element (6), with a cylindrical intermediate wall (20) positioned, said intermediate wall (20) comprising an intermediate chamber (22) which comprises a hydraulic fluid and at least one intermediate piston (12) integral with said first element (4) and able to slide along the intermediate chamber (22), said intermediate chamber (22) comprising return means (27) positioned between the intermediate piston (12) and the intermediate wall (20), said intermediate chamber (22) comprising , for at least one positioning of the intermediate piston (12) along said intermediate chamber (22), leakage means (24) which allow hydraulic fluid to pass on either side of the intermediate piston ( 12). Figure for the abstract: Fig. 1

Description

DOUBLE INERTIAL CHAMBER SHOCK ABSORBER FOR MOTOR VEHICLE SUSPENSION

The invention relates to the field of shock absorption, more particularly at the level of motor vehicle suspensions.

The published patent document US 2013/0037362 A1 discloses different shock absorber configurations, in particular for motor vehicle suspension. More particularly, the damper illustrated in Figures 14 and 15 of this document essentially comprises a first element forming a cylindrical envelope and a second element comprising a rod supporting a first and a second piston, said pistons sliding axially in the cylindrical envelope. . The latter is separated axially into two hydraulic chambers, the first of said chambers forming with the first piston a first so-called inertial hydraulic circuit. The latter further comprises a pipe forming a winding around the generally cylindrical first element, so that the movement of the first piston relative to the first chamber moves a hydraulic fluid in the chamber through the pipe, this movement forming inertial damping. The second of the chambers forms, with the second piston, a second hydraulic circuit called damping in that the piston comprises a leak passage of reduced section for a hydraulic fluid. This damper is interesting in that it combines two types of damping, namely conventional damping, the force of which is a function of the speed of the relative sliding movement between the rod and the cylinder, and inertial damping, the force of which is a function of the acceleration of said movement. However, it has a significant axial bulk. In addition, the production, shaping and installation of the spiral conduit presents difficulties, particularly in terms of sealing with the body of the cylindrical casing. Corrosion resistance of spiral conduit can also present challenges. Also, with this shock absorber, the inertial damping function cannot be easily calibrated differently without profoundly modifying the shape of the ducts, which poses a problem in the case of several applications on different vehicles of different masses.

• un premier élément destiné à être soit fixé à une partie mobile de la suspension et soit à une partie fixe du véhicule ; et
• un deuxième élément positionnée concentriquement autour du premier élément, apte à coulisser axialement par rapport audit premier élément et destiné à être fixé à l’autre desdites parties mobile ou fixe ;

The object of the invention is to have a shock absorber for a motor vehicle suspension, which comprises:

• a first element intended to be either fixed to a movable part of the suspension and either to a fixed part of the vehicle; and
• a second element positioned concentrically around the first element, able to slide axially with respect to said first element and intended to be fixed to the other of said movable or fixed parts;

the first and second elements forming a damping hydraulic circuit and an inertial hydraulic circuit, such that, between the first element and the second element, is positioned a cylindrical intermediate wall capable of sliding along the outer wall of the first element. The intermediate wall comprises an intermediate chamber, only emerging in a sealed manner along the outer wall of said first element. The intermediate chamber comprises a hydraulic fluid and at least one intermediate piston integral with the first element and able to slide along the intermediate chamber. The intermediate chamber comprises return means positioned between the intermediate piston and the intermediate wall. The intermediate chamber comprises, for at least one positioning of the intermediate piston along said intermediate chamber, leakage means which allow passage of the hydraulic fluid on either side of the intermediate piston.

According to a first characteristic of the invention, the leakage means comprise a helical groove formed in the intermediate wall, said helical groove opening out into the intermediate chamber and has a variable pitch to vary the flow rate of hydraulic fluid from the leakage passage in depending on the position of the piston along to the intermediate wall.

According to a second characteristic of the invention, the intermediate piston extends axially over at least two turns of the helical groove.

According to a third characteristic of the invention, the intermediate piston delimits two portions of the intermediate chamber and comprises at least one closing valve capable of leaving open an axial discharge passage for small variations in pressure of the hydraulic fluid on both sides. other of the intermediate piston and capable of closing said axial discharge passage for large variations in pressure of the hydraulic fluid on either side of the intermediate piston between the two portions of the intermediate chamber.

According to a fourth characteristic of the invention, the return means comprise at least two springs, a first spring being positioned bearing between a first axial face of the intermediate piston and a first edge facing the intermediate chamber and a second spring being positioned resting between a second axial face of the intermediate piston and a second edge facing the intermediate chamber.

According to a fifth characteristic of the invention, the first element comprises an inner cylinder forming an inner cylindrical chamber and along its outer wall, the intermediate piston. The second element comprises an outer cylinder adapted to guide in translation the inner cylinder of the first element and an inner piston mounted to slide in the inner chamber and a rod securing the inner piston to the outer cylinder. The outer cylinder of the second element comprises an outer chamber, only emerging in a sealed manner along the outer wall of the inner cylinder of the first element, said outer chamber comprising a hydraulic fluid and a ring which delimits said outer chamber into two portions. The ring comprises at least one relief valve which allows an exchange of hydraulic fluid between the two portions of the outer chamber beyond a certain fluid pressure in one of said two portions and a leak valve allowing a permanent calibrated leak of the hydraulic fluid between the two portions of the outer chamber.

The present invention also relates to a vehicle which comprises a suspension equipped with a shock absorber which comprises at least one of the preceding characteristics.

The accompanying drawings illustrate the invention:

shows a schematic sectional view of a shock absorber according to the invention.

shows a view along section VV in Figure 1.

Figures 1 and 2 are schematic views, in longitudinal section, of a shock absorber 2.

Throughout the description is understood by the term axial wall a wall oriented along a vertical axis of the damper 2 in the orientation of Figure 1 and by the term radial wall a wall oriented along a horizontal axis of the shock absorber 2 always following the orientation of figure 1.

The longitudinal section passes through the axis of symmetry of shock absorber 2.

The damper 2 comprises a first element 4 and a second element 6, capable of sliding relative to each other.

Each of the first and second elements 4 and 6 is intended to be fixed, as desired, to a moving part of the suspension of a vehicle or to a fixed part of the bodywork of said vehicle, respectively.

More particularly, the first element 4 comprises an inner cylinder 8 delimiting a generally cylindrical inner chamber 10.

The second element 6 comprises an inner piston 14 supported by a rod 16 and mounted to slide in the inner chamber 10.

To this end, the inner cylinder 8 is closed at each of its two axial ends, the upper closure being crossed by the rod 16 (in the orientation of FIG. 1) and comprises sealing means (not shown) with the rod 16, these sealing means being in themselves well known to those skilled in the art.

The inner chamber 10 comprises a hydraulic fluid, advantageously viscous with a viscosity greater than or equal to that of Citroën® suspension fluid (LDS), namely greater than or equal to 18 mm ² /s at 40° C. and/or 5.9 mm ² /s at 100°C.

The inner piston 14 comprises one or more potentially variable restriction passages depending on the pressure difference (not shown), connecting the two portions of the inner chamber 10, so that a relative sliding between, on the one hand, the inner piston 14 and the rod 16, and on the other hand the inner cylinder 8 causes a forced circulation of the hydraulic fluid through the restriction passage(s) on the inner piston 14.

The resistance to flow through this or these passages generates at the level of the rod 16 and at the level of the inner cylinder 8, forces which are essentially proportional to the fluid flow speed and therefore to the relative sliding speed. between the inner piston 14 and the inner cylinder 8, this damping principle being well known per se to those skilled in the art.

The second element 6 of the shock absorber 2 comprises, in addition to the inner piston 14 and the rod 16, an outer cylinder 18 surrounding the inner cylinder 8 of the first element 4, and, therefore, the rod 16 and the inner piston 14.

Outer cylinder 18 is rigidly bonded to stem 16. More specifically, outer cylinder 18 is slidably mounted on the outer cylindrical surface of inner cylinder 8.

Outer cylinder 18 has a cavity formed along its inner cylindrical surface.

The outer cylinder 18 is positioned in a sliding and sealed manner, at both ends of said cavity, around the inner cylinder 8.

In said cavity of the outer cylinder 18 is positioned an intermediate element 20 of cylindrical shape.

Between the inner cylindrical surface of the cavity of the outer cylinder 18 and the outer cylindrical surface of the intermediate element 20 and the outer cylindrical surface of the inner cylinder 8, is delimited an outer chamber 25.

The intermediate element 20 has a cavity which is formed along its inner cylindrical surface.

The intermediate element 20 is positioned in a sliding and sealed manner, at these two ends, around the inner cylinder 8.

Between the inner cylindrical surface of the cavity of the intermediate element 20 and the outer cylindrical surface of the outer cylinder 18 is delimited an intermediate chamber 22.

The inner cylinder 8 has a flange, projecting from its outer cylindrical surface, which forms an intermediate piston 12, of annular shape, able to slide along the intermediate chamber 22 according to the relative movement between the inner cylinder 8 and the intermediate element 20.

The intermediate piston 12 separates the intermediate chamber 22 into two portions 22.1 and 22.2. Following the orientation of the damper 2 as shown in Figure 1, is formed an upper portion 22.1 of the intermediate chamber 22 and a lower portion 22.2 of the intermediate chamber 22.

On either side of the intermediate piston 12 is positioned a spring 27 bearing between each of the two axial edges of the intermediate chamber 22 and the corresponding face of the annular piston 12, so that, always following the orientation of the damper as as shown in Figure 1, a first top spring 27.1 is positioned in the upper portion 22.1 of the intermediate chamber 22 and a second bottom spring 27.2 is positioned in the lower portion of the intermediate chamber 22.2.

The intermediate element 20 has along its radial inner surface a groove 24 formed in a helical manner, in particular by machining in the thickness of the intermediate wall 20 from its radial inner surface.

The annular piston 12 extends axially over at least one turn of the helical groove 24, preferably over at least two turns of said helical groove 24, more preferably still over at least three turns or more.

It should also be noted that the winding pitch of the helical groove can be variable along the radial inner surface of the intermediate element 20, so as to vary the inertial mass as a function of the degree of depression of the shock absorber. 2.

The intermediate piston 12 comprises at least one axial leakage passage 26 and at least one closing valve 28 held in the axially neutral position by springs 30 positioned on either side of said closing valve 28.

Stops 32 positioned at both ends of the axial leakage passage 26 form bearing surfaces for the springs 30 of the intermediate piston 12.

In the neutral position as shown, the closure valve 28, although closing off at least the major part of the passage 26, can move axially between the stops 32.

The intermediate chamber 22 is filled with a hydraulic fluid, preferably different from that of the inner chamber 10.

This fluid is advantageously a heavy fluid of low viscosity, in this case of viscosity less than or equal to that of the glycol.

A ring 23 delimits the outer chamber 25 in two portions 25.1 and 25.2.

The outer chamber 25 is separated from the intermediate chamber 22 and from the inner chamber 10, making it possible to provide therein a hydraulic fluid potentially different from that in particular of the intermediate chamber 22.

Various valves are provided along the ring 23, in particular a first relief valve 33 which allows an exchange of fluid from the first portion 25.1 of the outer chamber 25 to the second portion 25.2 of the outer chamber 25.

A second relief valve 34 which allows an exchange of fluid from the second portion 25.2 of the outer chamber 25 to the first portion 25.1 of the outer chamber 25.

A leak valve 35 allowing a permanent calibrated leak of the hydraulic fluid between the two portions 25.1 and 25.2 of the outer chamber 25.

During a relative sliding movement between the first and second elements 4 and 6 of the damper 2, in addition to the phenomena of passage of the fluid from the inner chamber 10 through the piston 14, mentioned above, the volumes of portions 22.1 and 22.2 of the chamber 22 will vary in opposite directions and, therefore, cause a passage of fluid through and along the portion of the groove 24 which is located vis-à-vis the annular piston 12.

The volume of this portion of the groove 24 being filled with hydraulic fluid, the corresponding mass of said fluid thus forms a mass which is set in motion by the relative sliding between the first and second 4 and 6, thus generating a damping force which is proportional to the acceleration of the relative sliding movement between the first and second elements 4 and 6.

More specifically, the intermediate wall 20 is held axially in the central position by the springs 27.

The intermediate piston 12 advantageously does not include relief valves, these being provided on the ring 23 which delimits in two portions 25.1 and 25.2 the outer chamber 25.

The operation of the shock absorber is therefore as follows.

In the event of stresses with small deflections, the closure valve 28 fails to abut against the seats 32, which has the effect that the inertial hydraulic circuit does not generate any significant force and is consequently inactive.

In the event of larger deflections, in this case deflections which have the effect of bringing the closing valve 28 against at least one of the stops 32, the hydraulic fluid of the chamber 22 is moved along the groove portion 24 opposite the piston 12, thus generating a resistant force of the inertial type.

This resistant force which tends to move the wall 20 is taken up by an increase in pressure in the portion of the outer chamber 25 whose volume tends to decrease by the movement of the wall 20. This pressure is transmitted to the relief valves 33 and 34 and the leak valve 35 on ring 23.

When the clearance generates a pressure greater than or equal to the opening limit pressure of the relief valve(s), the latter/these open and allow passage of the fluid from the portion of the outer chamber 25 which is under pressure. towards the other portion of said outer chamber 25, which has the effect of limiting the resistive force generated by the inertial hydraulic circuit.

A fluid other than the inertial fluid can be used to cooperate with the relief valves 33 and 34.

This provides more fine tuning of the behavior of the inertial circuit, in particular at the level of its deactivation threshold.

Since the activation circuit is not connected to the inertial circuit, the operating modes are independent and better controllable.

It should be noted that it is preferable that the deactivation of the inertial circuit can be done in both directions, that is to say when the shock absorber is in compression or attack, and when it is in extension or relaxation.

Alternatively, to the two relief valves, a single relief valve able to work in both directions can be provided.

The calibrated leakage valve intervenes only slightly during the operation of the shock absorber and during the operation of the inertial circuit, but allows the assembly to reposition itself in the neutral position after having been requested for a next use knowing that the two relief valves are then in the closed position.

Claims (10)

Shock absorber (2) for motor vehicle suspension, comprising a first element (4) intended to be fixed either to a mobile part of the suspension and either to a fixed part of the vehicle and a second element (6) positioned concentrically around the first element (4), able to slide axially with respect to said first element (4) and intended to be fixed to the other of said movable or fixed parts, the first and second elements (4, 6) forming a damping hydraulic circuit and a hydraulic circuit inertial, characterized in that, between the first element (4) and the second element (6), is positioned a cylindrical intermediate wall (20) capable of sliding along the outer wall of the first element (4), said intermediate wall ( 20) comprising an intermediate chamber (22), only emerging in a sealed manner along the outer wall of said first element (4), said intermediate chamber (22) comprising a hydraulic fluid and at least one piston in intermediate chamber (12) integral with said first element (4) and able to slide along the intermediate chamber (22), said intermediate chamber (22) comprising return means (27) positioned between the intermediate piston (12) and the wall intermediate chamber (20), said intermediate chamber (22) comprising, for at least one positioning of the intermediate piston (12) along said intermediate chamber (22), leakage means (24) which allow passage of the hydraulic fluid from and on the other side of the intermediate piston (12). Shock absorber (2) according to Claim 1, characterized in that the leakage means (24) comprise a helical groove (24) formed in the intermediate wall (20), the said helical groove opening out into the intermediate chamber (22) and having a variable pitch to vary the flow rate of hydraulic fluid from the leakage passage (24) according to the position of the piston (12) along the intermediate wall (20). Shock absorber (2) according to Claim 2, characterized in that the intermediate piston (12) extends axially over at least two turns of the helical groove (24). Shock absorber (2) according to any one of the preceding claims, characterized in that the intermediate piston (12) delimits two portions (22.1, 22.2) of the intermediate chamber (22) and comprises at least one closure valve (28) capable to leave open an axial relief passage (26) for small variations in pressure of the hydraulic fluid on either side of the intermediate piston (12) and capable of closing said axial relief passage (26) for large variations in pressure hydraulic fluid on either side of the intermediate piston (12) between the two portions (22.1, 22.2) of the intermediate chamber (22). Shock absorber (2) according to any one of the preceding claims, characterized in that the return means (27) comprise at least two springs (27.1, 27.2), a first spring (27.1) being positioned in contact between a first axial face of the intermediate piston (12) and a first edge facing the intermediate chamber (22) and a second spring (27.1) being positioned in abutment between a second axial face of the intermediate piston (12) and a second edge facing the chamber intermediate (22). Shock absorber (2) according to any one of the preceding claims, characterized in that the first element (4) comprises an inner cylinder (8) forming an inner cylindrical chamber (10) and along its outer wall, the intermediate piston ( 12). Shock absorber (2) according to Claim 6, characterized in that the second element (6) comprises an outer cylinder (18) adapted to guide the inner cylinder (8) of the first element (4) in translation and an inner piston (14) slidably mounted in the inner chamber (10) and a rod (16) securing the inner piston (14) to the outer cylinder (18). Shock absorber (2) according to Claim 7, characterized in that the outer cylinder (18) of the second element (6) comprises an outer chamber (25), only opening out in a sealed manner along the outer wall of the inner cylinder (8) of the first element (4), said outer chamber (25) comprising a hydraulic fluid and a ring (23) which delimits in two portions (25.1, 25.2) said outer chamber (25). Shock absorber (2) according to Claim 8, characterized in that the ring (23) comprises at least one relief valve (33, 34) allowing an exchange of hydraulic fluid between the two portions (25.1, 25.2) of the outer chamber ( 25) beyond a certain fluid pressure in one of said two portions (25.1, 25.2) and a leak valve (35) allowing a permanent calibrated leak of hydraulic fluid between the two portions (25.1, 25.2) of the chamber outside (25). Vehicle comprising a suspension equipped with a shock absorber (2) according to any one of the preceding claims.