Hydraulic stop with inertial mass for motor vehicle suspension

Abstract

The invention discloses a hydraulic stop at the end of travel of a motor vehicle suspension, which decelerates axial movement in the forward direction (AV), comprising a rear compression chamber (22) which transmits its own fluid towards a container (16) via an inertial fluid column (36) during deceleration, maintaining the pressure in the fluid, the compression chamber (22) being connected to an axial sliding piston (20) which, during compression of the suspension, is subjected to a forward force from a thrust spring (40) connected to a suspension element (2) and a rearward force from a height compensation chamber (26) resting on the stop body (10), the height compensation chamber being supplied with pressurized fluid from the container (16) via a fluid channel restrictor (30).

Description

Technical Field

[0001] The present application claims priority from French application No. 1909466, filed on August 28, 2019, the content of which (text, drawings and claims) is incorporated herein by reference.

[0002] The invention relates to an end-of-travel hydraulic stop for a motor vehicle suspension, and to a motor vehicle comprising a suspension equipped with a hydraulic stop of this type. Background Art

[0003] Motor vehicles have a suspension for each wheel, comprising suspension springs and hydraulic telescopic dampers for decelerating the movement of the suspension. Each suspension typically includes an end-of-travel stop made of elastomer, forming a highly rigid damper that quickly stops at the end of travel in the event of a significant impact on the suspension, resulting in poor ride comfort.

[0004] In a variant, a known type of hydraulic end-of-stroke stop (notably shown in document FR-A1-3074244) comprises a bushing fixed to the front of the damping piston, said bushing nesting around the stop tube at the end of the stroke without clearance by gradually closing a perforation of said bushing. Depending on the vehicle's steady state (assiette), which corresponds to the vehicle's static state height (depending on the vehicle's load), a nesting plug (whose height is adjusted by a thrust spring) decelerating by hydraulic damping can block the perforation and modify the deceleration force of said hydraulic stop.

[0005] By using a more loaded vehicle with a lower steady state, the deceleration of the hydraulic stop can be increased in this way.

[0006] However, whatever the type of end-of-travel stop, a suspension travel is obtained between the steady-state position and the reached position at which the stop is reached, which is reduced for highly loaded vehicles with a lower steady-state position.

[0007] In particular, by using a suspension comprising: a relatively weak suspension spring rate and a reduced deceleration of the shock absorber over the main travel of the suspension in order to obtain a good level of filtering of excitations with higher frequencies, a severe degradation of the vehicle body performance is obtained, especially on degraded roads, which can cause low-frequency oscillations.

[0008] Thus, in the case where an end-of-stroke hydraulic stop is used, it is difficult to obtain a suitable adjustment of the stop for different loads and different steady states of the vehicle to provide a variable stroke before reaching the stop. Summary of the Invention

[0009] The object of the present invention is in particular to avoid these disadvantages of the prior art.

[0010] To this end, the present invention provides a hydraulic stop at the end of the stroke of the suspension of a motor vehicle, wherein the hydraulic stop decelerates the axial movement pointing in the forward direction, and the hydraulic stop includes a rear compression chamber, which transmits its own fluid toward the container via an inertial fluid column during deceleration to maintain the pressure in the fluid, and is characterized in that the compression chamber is connected to an axial sliding piston, which is subjected to a forward force from a thrust spring connected to the suspension element during compression of the suspension, and a rearward force from a height compensation chamber leaning on the stop body, and the height compensation chamber is supplied with pressurized fluid from the container via a fluid channel limiter.

[0011] The advantage of this hydraulic stop is that, for lightly loaded vehicles with a high steady-state position, the forward force exerted by the barely compressed thrust spring (connected to the suspension element) is minimal. The slightly compressed reservoir ends up completely filling the height compensation chamber via the limiter, pushing the piston backwards. The stop is in its rearmost position, providing a defined travel distance between the steady-state position and the arrival position of the stop.

[0012] For heavily loaded vehicles with a low steady-state position, the forward force exerted on the piston by the more compressed thrust spring is greater, resulting in a higher pressure in the compensation chamber, which ultimately empties at least partially with slow dynamics by returning the fluid towards the reservoir with the weaker pressure. A stop connected to the piston moves forward, which provides a substantially constant travel distance between the steady-state position and the arrival position of the stop.

[0013] When the vehicle has been unloaded and has assumed a re-raised steady state, the force of the propulsion spring decreases and the compensation chamber is refilled with slow dynamics to assume the starting position again.

[0014] The runout of the suspension before reaching the end-of-travel stop, which runout is slightly dependent on the load of the vehicle, is obtained in a simple, effective and economical manner and without the use of electrical controls.

[0015] The hydraulic stop according to the present invention may further include one or more of the following features which may be combined with each other.

[0016] Advantageously, the stopper body comprises a cylindrical bore receiving the piston, the piston separating the compression chamber from the height compensation chamber.

[0017] In this case, in particular, the piston can comprise a fluid input port coupled to the compression chamber, said fluid input port opening laterally to an orifice formed in a bore of the stopper body, said orifice being coupled to the inertia column.

[0018] Furthermore, advantageously, the aperture can receive a transverse fixed partition separating the height compensation chamber from the container and comprising the passage restrictor.

[0019] Advantageously, the container is closed at the front by a front elastic membrane.

[0020] Furthermore, the fixed partition may include a perforation including a fluid outlet opening to the container, the fluid outlet opening opening laterally to the inertia column.

[0021] Advantageously, the rear face of the compression chamber comprises a rear elastic membrane coupled to the thrust spring.

[0022] Advantageously, the urging spring is formed by a metal helical spring or by an elastomeric element.

[0023] Advantageously, the stop comprises a rear rest arranged parallel to the propulsion spring, the rear rest providing a direct rest of the suspension element onto the compression chamber following a compression stage of the propulsion spring.

[0024] The invention also aims to provide a motor vehicle comprising a suspension equipped with hydraulic stops at the ends of travel, characterised in that these stops comprise any one of the above-mentioned features. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The invention will be better understood and other advantages and features will become clearer on reading the following detailed description given by way of example and in conjunction with the accompanying drawings, in which:

[0026] - Figure 1 is an axial cross-sectional view of a hydraulic stop according to the present invention, wherein the vehicle has a high steady state;

[0027] - Figure 2 The stop is shown wherein the vehicle has a just lowered steady state when the vehicle is loaded;

[0028] - Figure 3 The stop is shown wherein the vehicle has a lowered steady state after a time delay; and

[0029] - Figure 4 The stop is shown in which the vehicle has a steady state which has just been raised again when the vehicle is unloaded. DETAILED DESCRIPTION

[0030] Figure 1 An end-of-travel stop is shown fixed to the body of the vehicle 12 and includes axial symmetry about an axis A (which is shown vertically in this example) and can be positioned anywhere in the vehicle. The axial direction of the stop, indicated by the arrow AV turned toward the top, is generally referred to as the front direction of the stop.

[0031] The suspension arm 2 is fixed to the body of the vehicle by a pivot 4 and oscillates with the bounce of the vehicle's wheels while resting in the forward direction under the end-of-travel stop at the end of the travel to strongly decelerate the end of the travel.

[0032] The stopper comprises a body 10 comprising an axial cylindrical hole in which a transverse fixed partition 14 is received, which forms the bottom of a container 16 which is closed at the top by an upper front elastic membrane 18 which can extend forward in the body, providing a slight pressure in the container.

[0033] An axially sliding piston 20 arranged below the fixed diaphragm 14 divides a compression chamber 22 enclosed by a lower rear elastic membrane 24 at the bottom, and a height compensation chamber 26 at the top, which is formed in the hole and between the piston and the fixed diaphragm.

[0034] The fluid channel 30 with a restrictor passing through the fixed partition 14 is capable of exchanging fluid from the compensation chamber 26 toward the container 16 with slow dynamics when the pressure in this chamber is greater than the pressure of the container, and conversely, exchanging fluid toward the compensation chamber under the retraction action of the upper membrane 18 when the pressure in the container is higher.

[0035] The fluid channel has an input port 32 formed in the compensation chamber 22 below the lower face of the piston 20 and passing laterally through the piston to reach an orifice 34 formed in the bore of the body 10 .

[0036] An inertia screw 36 is formed in the body 10 while surrounding the hole to provide a large length with a reduced cross-section. The inertia screw 36 opens at its lower portion to an orifice 34 (which opens to the input port 32) and at its upper portion to an output port 38 (which is formed in the fixed diaphragm 14). The output port includes a lateral portion and then an axial portion (which opens to the container 16). When the piston 20 slides axially along a specific stroke, the orifice 34 enables the lateral portion of the input port 32 formed in the piston to always face the orifice regardless of the axial position of the piston, thereby obtaining a constant passage for the fluid to pass from the input port 32 to the output port 38 via the inertia screw 36.

[0037] In a variant, the lower end of the inertia column 36 may open directly into the portion of the bore situated in the compression chamber 22 , this portion always remaining below the piston 20 and above the lower membrane 24 , making it possible not to use the orifice in this bore.

[0038] The bottom of the lower membrane 24 comprises an axial thrust spring 40 of low stiffness, which rests permanently on the suspension arm 2 to transmit a variable pressure to the fluid contained in the compensation chamber 22 , this variable pressure depending on the compression of this spring.

[0039] After a certain travel C of the suspension arm 2 , the thrust spring 40 is sufficiently compressed that the arm reaches below the rear rest 42 fixed below the lower membrane 24 to start decelerating the end of travel by the stop.

[0040] The operation of the end-of-stroke stop is as follows.

[0041] Figure 1 An almost unloaded vehicle is shown, which is at rest and has a high steady state, with the suspension arm 2 in a low position relative to the stop and the thrust spring 40 almost uncompressed.

[0042] The upper membrane 18 of the container 16 relaxes and at the same time the fluid is pressed with slow dynamics from the container towards the height compensation chamber 26 via the limiter 30. When the height compensation chamber 26 is full, the piston 20 is in its lower position.

[0043] The movement of the suspension about its high steady state actuates the thrust spring 40 in both directions about its rest position, which provides slight pressure variations about the midpoint in the compensation chamber 26. The fluid hardly passes through the restrictor 30, which provides a slow filling dynamic, the piston 20 being kept at a constant height.

[0044] When large accidental forces occur on the suspension after stroke C, the suspension arm 2 comes to rest on the lower part 42, the hydraulic stop at the end of the stroke thereby effectively decelerating the end of the stroke via the inertia column 36, which adds a strong inertia due to the fluid speed achieved in the column.

[0045] Figure 2 The vehicle is shown in a stationary state, just loaded, with the vehicle's steady state lowered and the suspension arm 2 pivoted, providing a reduced travel C1 between the suspension arm 2 and the lower rest portion 42 .

[0046] The thrust spring 40 is permanently compressed and adds pressure to the compression chamber 22 with its own force F, which is transmitted to the compensation chamber 26 by means of the piston 20, which ends with a specific delay causing the passage of fluid through the restrictor 30 and simultaneously emptying the compensation chamber to fill the container 16.

[0047] A slow advancement of the piston 20 and a relaxation of the advancement spring 40 are obtained until the reduction of the force F exerted by this spring ends in equilibrium with the pressure rise in the container 16 which tightens its upper membrane 18 .

[0048] Figure 3 The advanced end of the piston 20 is shown with a new stroke C2 close to the starting stroke C, which is available for suspension movement before deceleration at the end-of-stroke stop.

[0049] Regardless of the load and steady state of the vehicle, a substantially constant bounce of the suspension is obtained before reaching the end-of-travel stop. Furthermore, the operation of the end-of-travel stop remains consistent with an unchanged deceleration force, since the inertia column 36 always provides the same deceleration mass.

[0050] Figure 4 The vehicle is shown in a stationary state after being unloaded, and has a stable state in which it is rising again. The suspension arm 2 descends while pulling the propulsion spring 40 with a force F', and providing a stroke C3 greater than the initial stroke.

[0051] Conversely, this results in a decrease in the pressure in the compression chamber 22 (transmitted by the piston 20 to the compensation chamber 26 ), which ends with a slow dynamic transfer of fluid from the container 16 towards the compensation chamber through the restrictor 30 .

[0052] The piston 20 descends to end at the recovery position after a determined delay. Figure 1 The initial state is shown.

[0053] The lower thrust spring 40 can be made in any way forming a flexible element that rests on the suspension arm 2 without generating noise, in particular a metal helical spring or an elastomeric element with weak stiffness.

Claims

1. A hydraulic stop at the end of travel of a suspension of a motor vehicle, said hydraulic stop decelerating an axial movement directed in the forward direction (AV), said hydraulic stop comprising a rear compression chamber (22) which, during deceleration, transmits its own fluid towards a container (16) via an inertial fluid column (36), maintaining the pressure in said fluid, characterized in that The rear compression chamber (22) is connected to an axial sliding piston (20), which during compression of the suspension is subjected to a forward force from a thrust spring (40) connected to the suspension element (2), and a rearward force from a height compensation chamber (26) resting on the stop body (10), the height compensation chamber being supplied with pressurized fluid from the container (16) via a fluid channel restrictor (30).

2. The hydraulic stopper according to claim 1, characterized in that: The stopper body (10) includes a cylindrical bore for receiving the axially sliding piston (20) which separates the rear compression chamber (22) from the height compensation chamber (26).

3. The hydraulic stopper according to claim 2, characterized in that: The axially sliding piston (20) includes a fluid input port (32) coupled to the rear compression chamber (22), the fluid input port laterally leading to an orifice (34) formed in a hole in the stopper body (10), the orifice being coupled to the inertial fluid column (36).

4. The hydraulic stopper according to claim 2 or 3, characterized in that: The cylindrical bore receives a transverse fixed partition (14) which separates the height compensation chamber (26) from the container (16) and includes the fluid path restrictor (30).

5. The hydraulic stopper according to claim 4, characterized in that: The container (16) is closed at the front by a front elastic membrane (18).

6. The hydraulic stopper according to claim 4, characterized in that: The fixed partition (14) includes a perforation including an outlet (38) leading to the container (16), the outlet leading laterally to the inertial fluid column (36).

7. The hydraulic stopper according to claim 5, characterized in that: The fixed partition (14) includes a perforation including an outlet (38) leading to the container (16), the outlet leading laterally to the inertial fluid column (36).

8. The hydraulic stopper according to any one of claims 1 to 3 and 5 to 7, characterized in that: The rear surface of the rear compression chamber (22) includes a rear elastic membrane (24) coupled to the propulsion spring (40).

9. The hydraulic stopper according to any one of claims 1 to 3 and 5 to 7, characterized in that: The propulsion spring (40) is formed by a metal coil spring or an elastomer element.

10. The hydraulic stopper according to any one of claims 1 to 3 and 5 to 7, characterized in that: The hydraulic stop comprises a rear rest (42) arranged parallel to the propulsion spring (40), which provides a direct rest of the suspension element (2) against the rear compression chamber (22) following the compression stage of the propulsion spring (40).

11. A motor vehicle comprising a suspension equipped with hydraulic stops at the ends of travel, characterized in that The hydraulic stops are hydraulic stops according to any of the preceding claims.

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