FR3141978A1 - Hydraulic motor vehicle suspension shock absorber. - Google Patents

Abstract

The invention relates to a shock absorber (1) comprising a body (2) containing a main piston (3) connected to a rod (4) and intended to slide inside the body (2), containing a damping fluid, the piston main (3) dividing the body (2) into a first (5) and a second (6) chamber and comprising a first passage (7) allowing communication between the first (5) and the second (6) chamber and being in part provided in a first piston (8) in a first housing (9), the first leakage piston (8) comprising a first channel (10) designed to open or close the first passage (7) depending on the position of the first piston ( 8) which is formed of at least two stages (12a, 12b), each designed to move away from the first rest position under the effect of a pressure, exerted on the first piston (8), greater than one predetermined threshold pressure specific to each stage (12a, 12b). (Figure 1)

Description

Hydraulic shock absorber for automobile suspension.

The technical field concerns hydraulic shock absorbers for motor vehicle suspension, as well as motor vehicles equipped with such shock absorbers.

In a vehicle, the suspension system is necessary due to the irregularities of the road on which the vehicle is traveling. Indeed, the irregularities cause shocks and vibrations impacting the vehicle and its passengers. The suspension system is therefore designed to reduce mechanical fatigue and wear of the vehicle and to improve passenger comfort. In addition, the suspension system is essential to maintain contact between the vehicle's wheels and the ground and thus ensure adequate road holding.

Suspension systems typically include a shock absorber consisting of a piston, connected to a rod, moving in a cylinder delimiting two chambers with limited fluid passages allowing fluid to be transferred from one chamber to the other in order to slow the movements of this rod. The braking capacity of the rod movement must meet different constraints. In particular, the braking capacity must allow filtering several ranges of oscillation frequencies each characteristic of particular movements linked either to the state of the road or to natural oscillation frequencies typical of suspended mass systems.

Most known shock absorbers are effective, by design, in filtering oscillations in a given frequency range. The frequency range is more or less wide or narrow, depending on the design of the shock absorber, but designers must make compromises depending on the use for which the shock absorber is intended. Furthermore, the relatively high pressurization of the fluid in a conventional shock absorber, of the order of 15 to 30 bars for a passenger vehicle, limits the possibilities of optimizing both road holding and passenger comfort for a wide range of vehicles at a reasonable cost.

Also, given the tradeoffs, known shock absorbers do not provide optimized comfort for vehicle passengers in all situations.

Thus, there is a need for a solution that can improve the comfort of the shock absorbers and the ability to handle the irregularities of various roads.

The present invention aims to overcome the problems set out above. In this technical context, one aim of the present invention is to provide a shock absorber exhibiting improved behaviour over a wider frequency range and/or over several oscillation frequency ranges.

For this purpose, the present invention relates to a hydraulic shock absorber for a motor vehicle suspension comprising a body containing a main piston connected to a rod, the main piston being intended to slide inside the body, the body being intended to contain a damping fluid, the main piston dividing the body into a first chamber and a second chamber, the main piston comprising at least one first leakage passage allowing fluid communication between the first chamber and the second chamber, the first leakage passage being partly formed in a first leakage piston disposed inside a first housing of the main piston, the first leakage piston being able to slide from a first rest position in the first housing under the effect of an increase in fluid pressure in the first chamber generated by a movement of the main piston, the first leakage piston comprising at least one first channel, each being designed to progressively open or close the first leakage passage depending on the position of the first leakage piston in the first housing, the first leakage piston being formed of at least two stages, each stage being designed to move away from the first rest position under the effect of a pressure, exerted on the first leakage piston, greater than a predetermined threshold pressure specific to each stage.

The invention finally relates to a motor vehicle comprising at least one shock absorber according to the invention.

Thus, the shock absorber according to the invention makes it possible to control the passage of fluid from one chamber to the other according to the movement of the first leakage piston. The first leakage piston, thanks to the different stages designed to react to various threshold pressures, will exhibit different behavior depending on the stresses of the shock absorber, either in compression or in expansion, depending on whether an increase in pressure in the first chamber corresponds to a compression or expansion phase of the shock absorber. This differentiated behavior of the first leakage piston makes it possible to adapt the behavior by arranging the way in which the first fluid passage opens and/or closes according to the movement. It is thus possible, for example, to favor the behavior of the shock absorber during stresses at very low frequencies by maximizing the fluid leakage to optimize the behavior of the shock absorber on small deflections and gradually reduce the fluid leakage through the first fluid passage, by closing it gradually, to improve the body handling and the rolling behavior or the behavior of the vehicle when the road generates greater deflections. Thanks to the different stages, each with a differentiated threshold pressure, the behavior of the shock absorber can be optimized in several areas of interest, for example by choosing the threshold frequencies as well as the opening and closing modes of the first leakage passage.

According to one embodiment of the invention, the first leakage piston is provided with a first return device shaped to move the first leakage piston towards the first rest position when the first chamber is no longer subjected to fluid pressure generated by the movement of the main piston.

According to one possibility, the main piston comprises a second leakage piston arranged inside a second housing, distinct from the first housing, the second leakage piston being able to slide from a second rest position in the second housing of the main piston under the effect of an increase in fluid pressure in the second chamber generated by a movement of the main piston, the second leakage piston comprising at least one second channel, each designed to progressively open or close a second leakage passage, allowing fluid communication between the second and first chambers, depending on the position of the second leakage piston in the second housing.

Advantageously, the second leakage piston is also formed of at least two stages, each stage being designed to move away from the second rest position under the effect of a pressure, exerted on the second leakage piston, greater than a predetermined threshold pressure specific to each stage.

According to one possibility, the second leakage piston is provided with a second return device shaped to move the second leakage piston to the second rest position when the second chamber is no longer subjected to fluid pressure generated by the movement of the main piston.

According to one embodiment, the rod comprises a cavity in fluid communication with the second chamber, the cavity also being in fluid communication with a first volume of the first housing.

Advantageously, the cavity of the rod is in fluid communication with a second volume of the second housing.

Alternatively, each stage is spaced from another stage by a calibrated return spring designed to require a force greater than a predetermined threshold force, specific to each return spring, to compress.

According to one embodiment, the main piston further comprises at least one spring valve designed to allow the passage of fluid from one of the first and second chambers to the other of the first and second chambers under the effect of a movement of the main piston at a speed greater than a predetermined speed.

The invention will be better understood upon reading the detailed description which follows, given solely as a non-limiting example and made with reference to the appended drawings in which:

there , represents a sectional view of a hydraulic shock absorber according to the invention showing first and second leakage pistons respectively in the first and second rest positions;

there , represents a sectional view of spring valves provided in the main piston of the hydraulic shock absorber of the .

In these figures, the same references are used to designate the same elements.

A hydraulic shock absorber 1 for a motor vehicle suspension according to the invention, illustrated in the , comprises a body 2 containing a main piston 3 connected to a rod 4. The main piston 3 is intended to slide inside the body 2. The body 2 contains a damping fluid, such as oil for example. The main piston 3 divides the body 2 into a first chamber 5 and a second chamber 6.

The body 2 of the shock absorber 1 may be fixed to the body of the vehicle according to the invention while the rod 4 may be fixed to a suspension element. Alternatively, the configuration of the fixings may be reversed. Once installed on the vehicle according to the invention, the operation of the shock absorber 1 according to the invention is independent of its inclination on the vehicle.

The main piston 3 comprises at least a first leakage passage 7 which allows fluid communication between the first chamber 5 and the second chamber 6, in order to cause, when it is at least partially open, a movement of fluid from the first chamber 5 to the second chamber 6 when the movement of the main piston 3 causes an increase in the pressure in the first chamber 5. The first leakage passage 7 is partly formed in a first leakage piston 8 arranged inside a first housing 9 of the main piston 3. The first leakage piston 8 is able to slide from a first rest position, illustrated in FIG. , in the first housing 9 towards the rod 4 under the effect of an increase in fluid pressure in the first chamber 5 generated by a movement of the main piston 3, in a direction indicated by the arrow C of the . In order to allow the first passage 7 to be opened or closed gradually, the first leakage piston 8 comprises at least one first channel 10, illustrated in the . Each first channel 10 is designed to progressively open or close the first leak passage 7 depending on the position of the first leak piston 8 in the first housing 9. Thus, depending on the position of the first piston 8 in its first housing 9, the position of each first channel 10 makes it possible to completely or partially open or close the first leak passage 7.

It is for example conceivable that the first passage 7 is closed when the first piston 8 is in the first rest position, and that the first leakage passage 7 opens progressively as a function of the distance of the first piston 8 from its first rest position. It is conceivable, for example, that the first channel(s) 10 are configured so that the first passage 7 is closed when the first piston 8 reaches the end of its stroke. Alternatively, it is conceivable to design the first channel(s) 10 so that the first leakage passage 7 is open at least partially when the first piston 8 is in the first rest position, to open progressively throughout the distance of the first piston 8 from its first rest position.

To allow the first leakage passage 7, the main piston 3 obviously includes openings 11 arranged in the first piston 3 and placing the first housing 9 and the first chamber 5 or the second chamber 6 in fluid communication. Consequently, the opening or closing of the first passage 7 is determined by the relative position of each first channel 10 relative to the openings 11, positions which depend on the position of the first piston 8 in its first housing 9. It is obviously provided that there is at least one position of the first piston 8 in its first housing 9 at least partially opens the first passage 7. Advantageously, there is a position of the first piston 8 which closes the first passage 7.

The first leakage piston 8 is formed of at least two stages 12a, 12b. Each stage 12a, 12b is designed to move away from the first rest position under the effect of a pressure, exerted on the first leakage piston 8, greater than a predetermined threshold pressure specific to each stage 12a, 12b. In order to obtain a movement of the first piston 8 in its first housing 9, the hydraulic fluid thus exerts a pressure on a first force face 13 of the first piston 8 facing a side wall 14 of the body 2 and arranged in the first chamber 5.

In the example illustrated on the , the first piston 8 moves away from its first rest position when the main piston 3 moves in the direction indicated by the arrow C, corresponding to a compression phase of the shock absorber 1.

In order to allow the first piston 8 to return to its first rest position, the first leakage piston 8 is provided with a first return device 15 designed to move the first leakage piston 8 to the first rest position, when the first chamber 5 is no longer subjected to fluid pressure generated by the movement of the main piston 3.

As illustrated in the , the first return device 15 is composed, for example, of at least two return springs 16a, 16b. Each stage 12a is thus spaced from the other stage 12b by a return spring 16a. The stage 12b is for its part maintained in its rest position, when the first leakage piston 8 is in the first rest position by a return spring 16b bearing on a bottom wall 17 of the first housing 9.

The return springs 16a, 16b are calibrated springs and are designed to require a force greater than a predetermined threshold force, specific to each return spring 16a, 16b to compress. When a return spring 16a, 16b compresses, the stage 12a, respectively the stage 12b move closer to the stage 12b or to the bottom wall 17. Thus, when the first piston 8 moves away from its first rest position, the return spring 16a is first compressed, then, possibly, the return spring 16b is compressed. The stage 16a furthest from the bottom wall 17 thus moves first, followed, possibly depending on the intensity of the stress, by the other successive stages 16b.

The rod 4 of the main piston 3 comprises a cavity 18 in fluid communication with the second chamber 6 in order to obtain a balanced static pressure between the second chamber 6 and the cavity 18. As illustrated in the , the cavity 18 is also in fluid communication with a first volume 19 of the first housing 9 by means of a hole 20 formed in the bottom wall 17, the hole 20 allowing a calibrated movement of fluid. Advantageously, the calibrated hole 20 is provided with a valve, not illustrated, making it possible to control the movement of fluid entering or leaving the first volume 19. The first volume 19 comprises in particular the part of the first housing 9 arranged between the bottom wall 17 and the stage 12b as well as the space between the stages 12a, 12b. During the movement of the first piston 8, obtained by the successive compression of the return springs 16a, 16b, fluid is thus expelled from the first volume 19 towards the cavity 18 by leakage paths illustrated by the arrows F1 on the . Thus, the fluid contained in the first volume 19, in particular between the stages 12a, 12b, is expelled towards the cavity 18 by leakage paths which are provided around the stages 12a, 12b and/or formed by the movement of the stages 12a, 12b.

Similarly, the main piston 3 has a second leakage piston 21 arranged inside a second housing 22, distinct from the first housing 9, the second leakage piston 21 being able to slide from a second rest position towards the rod 4 in the second housing 22 of the main piston 3 under the effect of an increase in fluid pressure in the second chamber 6, generated by a movement of the main piston 3 in the direction indicated by the arrow D, corresponding to an expansion phase.

In order to obtain a movement of the second piston 21 in its second housing 22, the hydraulic fluid thus exerts pressure on a second force face 23 of the second piston 21 facing the side wall 14 of the body 2 and arranged in the second chamber 6.

While the first leakage piston 8 corresponds to a leakage piston in the compression phase, the second leakage piston 21 corresponds to a leakage piston in the expansion phase and the operation of the second leakage piston 21 operates in the same way as the first piston 8 when the shock absorber 1 is in the expansion phase. When the shock absorber 1 is in the compression phase, the second piston 21 remains in its second rest position. Conversely, when the shock absorber 1 is in the expansion phase, the first leakage piston 8 remains in its first rest position.

The second leakage piston 22 comprising at least one second channel 24 each being designed to progressively open or close a second leakage passage 25, allowing fluid communication between the second 6 and first 5 chambers, depending on the position of the second leakage piston 21 in the second housing 22.

Advantageously, the first 7 and second 25 leakage passages comprise non-return valves, not illustrated, designed to allow the passage of fluid only in the desired direction, while prohibiting the flow of fluid in the opposite direction. For example, a non-return valve is installed in the first leakage passage 7 so as to allow the passage of fluid from the first chamber 5 to the second chamber 6 during a compression phase, while prohibiting the flow of fluid through the first fluid passage 7 from the second chamber 6 to the first chamber 5 during an expansion phase. Conversely, a non-return valve is installed in the second leakage passage 25 so as to allow the passage of fluid from the second chamber 6 to the first chamber 5 during an expansion phase, while prohibiting the flow of fluid through the second fluid passage 25 from the first chamber 5 to the second chamber 6 during a compression phase.

In the embodiment illustrated in the , the second leakage piston 21 is also formed of at least two stages 12c, 12d, each stage being designed to move away from the second rest position under the effect of a pressure, exerted on the second leakage piston 21, greater than a predetermined threshold pressure specific to each stage 12c, 12d.

In the same way as for the first leakage piston 8, the second leakage piston 21 is also provided with a second return device 26 shaped to move the second leakage piston 21 to the second rest position when the second chamber 6 is no longer subjected to a fluid pressure generated by the movement of the main piston 3. The second return device 26 is made up of return springs 16c, 16d. In the example illustrated in the figures, the return spring 16d has a threshold force greater than the threshold force of the return spring 16c.

The cavity 18 is also in fluid communication with a second volume 28 of the second housing 22, the operating principle of which is the same as the first volume 19.

During the movement of the second piston 21, obtained by the successive compression of the return springs 16c, 16d, fluid is thus expelled from the second volume 28 towards the cavity 18 by leakage paths illustrated by the arrows F2 of the by means of a calibrated hole 29. Thus, the fluid contained in the second volume 28, in particular between the stages 12c, 12d is expelled towards the cavity 18 by leakage paths which are arranged around the stages 12c, 12d and/or formed by the movement of the stages 12c, 12d. Advantageously, the calibrated hole 29 is provided with a valve, not illustrated, making it possible to control the movement of fluid entering or leaving the second volume 28.

Seals are installed to ensure the various necessary seals, and in particular between the main piston 3 and the body 2 or in the first 8 and second 21 leakage pistons between the different stages 12a, 12b, 12c, 12d and the first 9 and second 22 housings respectively.

Advantageously, the main piston 3 further comprises at least one spring valve 30, as illustrated in the , designed to allow the passage of fluid from one 6 of the first 5 and second 6 chambers to the other 5 of the first 5 and second 6 chambers under the effect of a movement of the main piston 3 at a speed greater than a predetermined speed. Even more advantageously, the shock absorber 1 comprises a pair of spring valves 30 for the passage of fluid from the first chamber 5 to the second chamber 6 as well as another pair of spring valves 30 oriented so as to allow a passage of fluid in the opposite direction. Each spring valve 30 has, where appropriate, a different calibration by means of a corresponding calibrated spring 31. The spring valves 30 are, for example, arranged at 90° to the first 8 and second 21 leakage pistons.

Thus, the hydraulic shock absorber 1 according to the invention has an optimizable behavior both in compression, thanks to the first leakage piston 8, and in expansion, thanks to the second leakage piston 21. The choice of the threshold forces of the different return springs 16a, 16b, 16c, 16d makes it possible to define differentiated frequency ranges for the compression and expansion phases of the hydraulic shock absorber 1 in which the behavior of the shock absorber 1 can be adapted by modifying the way in which the leakage exchanges, through the first 7 and second 25 leakage passages, are carried out.

The invention is not limited to the embodiment of the shock absorber described above, only as an example, but other embodiments can be designed by those skilled in the art without departing from the scope and scope of the present invention.

Claims (10)

Hydraulic shock absorber (1) for suspension of a motor vehicle comprising a body (2) containing a main piston (3) connected to a rod (4), the main piston (3) being intended to slide inside the body (2), the body (2) being intended to contain a damping fluid, the main piston (3) dividing the body (2) into a first chamber (5) and a second chamber (6), the main piston (3) comprising at least a first leakage passage (7) allowing fluid communication between the first chamber (5) and the second chamber (6), the first leakage passage (7) being partly formed in a first leakage piston (8) arranged inside a first housing (9) of the main piston (3), the first leakage piston (8) being able to slide from a first rest position in the first housing (9) under the effect of an increase in fluid pressure in the first chamber (5) generated by a movement of the main piston (3), the first leakage piston (8) comprising at least a first channel (10), each being designed to progressively open or close the first leak passage (7) depending on the position of the first leak piston (8) in the first housing (9), the first leak piston (8) being formed of at least two stages (12a, 12b), each stage (12a, 12b) being designed to move away from the first rest position under the effect of a pressure, exerted on the first leak piston (8), greater than a predetermined threshold pressure specific to each stage (12a, 12b). Hydraulic shock absorber (1) according to claim 1, characterized in that the first leakage piston (8) is provided with a first return device (15) shaped to move the first leakage piston (8) towards the first rest position when the first chamber (5) is no longer subjected to a fluid pressure generated by the movement of the main piston (3). Hydraulic shock absorber (1) according to claim 1 or 2, characterized in that the main piston (3) comprises a second leakage piston (21) arranged inside a second housing (22), separate from the first housing (9), the second leakage piston (21) being able to slide from a second rest position in the second housing (22) of the main piston (3) under the effect of an increase in fluid pressure in the second chamber (6) generated by a movement of the main piston (3), the second leakage piston (21) comprising at least one second channel (24), each designed to progressively open or close a second leakage passage (25), allowing fluid communication between the second (6) and first (5) chambers, depending on the position of the second leakage piston (21) in the second housing (22). Hydraulic shock absorber (1) according to claim 3, characterized in that the second leakage piston (21) is also formed of at least two stages (12c, 12d), each stage (12c, 12d) being designed to move away from the second rest position under the effect of a pressure, exerted on the second leakage piston (21), greater than a predetermined threshold pressure specific to each stage (12c, 12d). Hydraulic shock absorber (1) according to one of claims 2 to 4, characterized in that the second leakage piston (21) is provided with a second return device (27) shaped to move the second leakage piston (21) towards the second rest position when the second chamber (6) is no longer subjected to a fluid pressure generated by the movement of the main piston (3). Hydraulic shock absorber (1) according to one of claims 1 to 5, characterized in that the rod (4) comprises a cavity (18) in fluid communication with the second chamber (6), the cavity (18) also being in fluid communication with a first volume (19) of the first housing (9). Hydraulic shock absorber (1) according to claim 6, in combination with claim 3, characterized in that the cavity (18) of the rod (4) is in fluid communication with a second volume (28) of the second housing (22). Hydraulic shock absorber (1) according to one of claims 1 to 7, characterized in that each stage (12a, 12b, 12c, 12d) is spaced from another stage (12a, 12b, 12c, 12d) by a calibrated return spring (16a, 16b, 16c, 16d) designed to require a force greater than a predetermined threshold force, specific to each return spring (16a, 16b, 16c, 16d), to compress. Shock absorber (1) according to one of claims 1 to 8, characterized in that the main piston (3) further comprises at least one spring valve (30) designed to allow the passage of fluid from one of the first (5) and second (6) chambers to the other of the first (5) and second (6) chambers under the effect of a movement of the main piston (3) at a speed greater than a predetermined speed. Motor vehicle comprising at least one shock absorber (1) according to one of claims 1 to 9.