Shock absorber with variable preload.

Abstract

The invention relates to a hydraulic shock absorber (1) comprising a body (2), a rod (4) connected to a main piston (3), dividing the body (2) into a first (5) and a second (6) chamber and comprising a first housing receiving a first piston (8) sliding from a first rest position under the effect of an increase in fluid pressure in the first chamber (5), the main piston (3) comprising a first preload passage allowing unidirectional fluid communication, in a first direction of flow, between the first (5) and second (6) chambers, each first piston (8) comprising a first channel for progressively opening or closing a first preload passage depending on the position of the first piston (8), each first passage comprising blocking means for blocking the fluid in the first direction of flow when the pressure upstream of the first passage is less than a threshold pressure. (Figure 1)

Description

Title of the invention: Shock absorber with variable preload.

[0001] The technical field relates to hydraulic shock absorbers for motor vehicle suspension and vehicles equipped with such shock absorbers.

[0002] 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. Furthermore, the suspension system is essential to maintain contact between the vehicle's wheels and the ground, and thus ensure adequate road holding.

[0003] Suspension systems generally comprise a shock absorber consisting of a piston, linked to a rod, moving in a cylinder delimiting two chambers with limited fluid passages, making it possible to transfer fluid from one chamber to the other, in order to brake the movements of this rod. The braking capacity of the movement of the rod must respond to different constraints. In particular, the braking capacity must make it possible to filter 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.

[0004] Most known shock absorbers are effective, by construction, in filtering oscillations of 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.

[0005] Also, given the compromises, the known shock absorbers do not provide optimized comfort for the vehicle's passengers in all situations, and in particular for significant shock absorber travel.

[0006] Thus, there is a need for a solution to improve the comfort of the shock absorbers beyond certain travels, to reduce the amplitudes of movement.

[0007] The object of the present invention is 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 behavior over wider speed and travel ranges.

[0008] To this end, the present invention relates to a hydraulic shock absorber of 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 housing, at least one first adjustment piston being arranged inside each first housing of the main piston, each first adjustment piston being able to slide in its first housing from a first rest position under the effect of an increase in fluid pressure in the first chamber generated by a movement of the main piston, the main piston comprising at least one first preload passage, each allowing unidirectional fluid communication, in a first direction of circulation, between the first and second chambers and through a first housing,each first piston comprising at least a first channel, each being designed to progressively open or close a first preload passage depending on the position of the first piston in the first housing, each preload passage comprising blocking means designed to block the passage of the fluid in the first direction of circulation, when the pressure upstream of the first preload passage is lower than a predetermined threshold pressure specific to each preload passage.

[0009] The invention finally relates to a motor vehicle comprising at least one shock absorber according to the invention.

[0010] Thus, the shock absorber according to the invention makes it possible to control the passage of fluid from one chamber to the other as a function of the movement of the first preload piston and in particular the pressure in the first chamber. Indeed, the opening or closing of each preload passage is controllable by the pressure upstream of the passage, that is to say in the first chamber, using the locking means. In addition, the behavior of each preload passage is adjustable by the movement of each first adjustment piston which depends in particular on the speed of movement of the shock absorber and the amplitude of travel. Thus, the behavior of the shock absorber is adjustable, to improve the response and comfort over a wider range of speeds and travels, by judiciously choosing the position of each first channel.

[0011] According to one embodiment of the invention, each first adjustment piston is provided with first return means shaped to move the first adjustment 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.

[0012] According to one possibility, each first adjustment piston is shaped to slide in its first housing along a sliding axis, each first channel having an elongated contour along the sliding axis so as to varying the cross-section of the corresponding preload passage as a function of the displacement of the first adjustment piston and when the first channel allows circulation in the corresponding first preload passage.

[0013] According to one embodiment, the blocking means of each preload passage comprise a calibrated spring valve.

[0014] Advantageously, the shock absorber comprises at least one second housing in which at least one second adjustment piston slides from a second rest position and comprising at least one second conduit, cooperating with a second preload passage designed to allow unidirectional fluid circulation in a second direction opposite to the first direction.

[0015] Advantageously, the first and / or second adjustment pistons also comprise at least one leak conduit each cooperating with a leak passage which allows the transfer of fluid between the first and second chambers with a maximum flow rate depending on the position of the first and / or second adjustment piston respectively.

[0016] According to one possibility, the rod comprises a cavity in fluid communication on the one hand with the second chamber, and on the other hand, with each first housing and / or each second housing.

[0017] In one embodiment of the shock absorber, each first and / or second adjustment piston is formed of at least two stages, each stage being designed to move away from the first or second rest position under the effect of a pressure, exerted on the first or second adjustment piston, greater than a predetermined threshold pressure specific to each stage.

[0018] According to one possibility, 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.

[0019] The invention will be better understood on reading the detailed description which follows, given solely by way of non-limiting example and made with reference to the appended drawings in which:

[0020] [Fig-1] [Fig.l] represents a partial exploded view of a shock absorber according to the invention;

[0021] [Fig.2] [Fig.2] represents a partial view of a main piston showing a first adjustment piston, top view in the first rest position;

[0022] [Fig.3] [Fig.3] represents a view of the first adjustment piston of [Fig.2], seen from above, in an intermediate position different from the first rest position;

[0023] [Fig.4] [Fig.4] represents a partial sectional view of a main piston showing a portion of a preload passage and its locking means;

[0024] [Fig.5] [Fig.5] represents several responses of the shock absorber according to the invention in function of the piston displacement speed, each curve being representative of a preload passage with a particular calibration.

[0025] In these figures, the same references are used to designate the same elements.

[0026] A hydraulic shock absorber 1 for suspension of a motor vehicle according to the invention, illustrated in [Fig.l], 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.

[0027] 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.

[0028] The main piston 3 comprises at least one first preload passage 7a, 7b, 7c which allows unidirectional 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 in a first direction, in this case 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. Each first preload passage 7a, 7b, 7c is partly formed in a first adjustment piston 8 disposed inside a first housing 9 of the main piston 3 and therefore passes through the first housing 9. The first adjustment piston 8 is able to slide from a first rest position, illustrated in [Fig.2], 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 [Fig.2]. Each first adjustment piston 8 comprises a wall 10 in contact with the fluid present in the first chamber 5.

[0029] In order to allow each first passage 7a, 7b, 7c to be opened or closed progressively through the first housing 9, the first adjustment piston 8 comprises at least one first channel 11a, 11b, 11e, illustrated in [Fig. 2]. Each first channel 11a, 11b, 11e is designed to open or close progressively the corresponding first preload passage 7a, 7b, 7c depending on the position of the first adjustment 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 11a, 11b, 11e allows the first preload passage 7a, 7b, 7c to be opened or closed entirely or partially. corresponding. Each first channel 11a, 11b, 11c forms a part of the corresponding first passage 7a, 7b, 7c when the first adjustment piston 8 is positioned to open the corresponding first passage 7a, 7b, 7c.

[0030] By way of example, it is conceivable that a first passage 7a is closed when the first piston 8 is in the first rest position, and that this first preload passage 7a 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 adjustment piston 8 completely releases another first passage 7b when the first adjustment piston 8 is in its first rest position and that the distance of the first adjustment piston 8 from its first rest position causes a partial closing of the same first passage 7b.

[0031] Finally, as illustrated in Figures 2 and 3, a first channel 1 e is configured so that the first passage 7c is partially open when the first adjustment piston 8 is in its first rest position and so that the first channel 1 e closes progressively when it reaches the end of its travel.

[0032] As illustrated in Figures 2 and 3, each first adjustment piston 8 is shaped to slide in its first housing 9 along a sliding axis A, each first channel 11a, 11b, 11c having an elongated contour 12a, 12b, 12c along the sliding axis A so as to vary the cross-section of the corresponding preload passage 7a, 7b, 7c as a function of the movement of the first adjustment piston 8 and when the first channel 11a, 11b, 11c allows circulation in the corresponding first preload passage 7a, 7b, 7c.

[0033] In the example illustrated in Figures 2 and 3, a contour 12a has a semi-circular shape while the contours 12b, 12c have a circular shape extended by a slot 13 of variable dimensions.

[0034] As illustrated in [Fig. 4], each preload passage 7a, 7b, 7c comprises blocking means 14 designed to block the passage of the fluid in the first direction F of circulation, illustrated in [Fig. 4], when the pressure upstream of the first preload passage 7a, 7b, 7c is lower than a predetermined threshold pressure specific to each preload passage 7a, 7b, 7c. When the pressure upstream of the first passage 7a, 7b, 7c is higher than the predetermined threshold pressure, then the blocking means 14 allow the circulation of fluid in the first preload passage 7a, 7b, 7c. In the example described, the first direction F of circulation allows the fluid to circulate from the first chamber 5 to the second chamber 6.The circulation of the fluid in each preload passage 7a, 7b, 7c being unidirectional, the blocking means 14 are designed to block the circulation of the fluid in the direction opposite to the first direction F, in this case from the second chamber 6 to the first chamber 5, whatever the pressures in the first 5 and second 6 chambers. In . the example illustrated in [Fig.4], the locking means 14 of each preload passage 7a, 7b, 7c comprise a calibrated spring valve 15.

[0035] The rod 4 of the main piston 3 comprises a cavity 16, shown diagrammatically in [Fig.l], in fluid communication with the second chamber 6 in order to obtain a balanced static pressure between the second chamber 6 and the cavity 16. As illustrated in [Fig.l], the cavity 16 is also in fluid communication with the first housing 9 by means of a calibrated hole, not shown, allowing a calibrated movement of fluid. Advantageously, the calibrated hole is provided with a valve, not shown, making it possible to control the movement of fluid entering or leaving the first housing 9.

[0036] Advantageously, the first adjustment piston 8 is formed of at least two stages 17a, 17b. Each stage 17a, 17b 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 17a, 17b. In order to obtain a movement of the first piston 8 in its first housing 9, the hydraulic fluid thus exerts a pressure on the wall 10 in contact with the fluid arranged in the first chamber 5.

[0037] As illustrated in Figures 2 and 3, in order to allow each first adjustment piston 8 to return to its first rest position, each first piston 8 is provided with first return means 18 shaped to move the first adjustment 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. In the example described in the figures, the first return means 18 are composed, for example, of at least two return springs 19a, 19b. Each stage 17a is thus spaced from the other stage 17b by a return spring 19a. The stage 17b is held in its rest position, when the first adjustment piston 8 is in the first rest position by a return spring 19b bearing on a bottom wall, not shown, of the first housing 9.

[0038] The return springs 19a, 19b are calibrated springs and are designed to require a force greater than a predetermined threshold force, specific to each return spring 19a, 19b, to compress. When a return spring 19a, 19b compresses, the stage 17a, respectively the stage 17b move closer to the stage 17b or to the bottom wall. Thus, when the first piston 8 moves away from its first rest position, there is first a compression of one return spring 19a, 19b and then, possibly, a compression of the other return spring 19a, 19b depending on the intensity of the stress.

[0039] Similarly but not illustrated, the shock absorber 1 comprises at least one second housing in which at least one second adjustment piston slides. from a second rest position and comprising at least one second conduit, cooperating with a second preload passage designed to allow unidirectional fluid circulation in a second direction opposite to the first direction. Each second adjustment piston also comprises second return means for returning the second adjustment piston to its second rest position. The operations of the second preload passages, second adjustment pistons, second conduits are identical to the respective elements described previously, only the direction of fluid circulation being reversed between the first 5 and second 6 chambers.

[0040] Advantageously again, the first 8 and / or second adjustment pistons also comprise at least one leakage conduit, not shown, each cooperating with a leakage passage, not shown, which allows the transfer of fluid between the first 5 and second 6 chambers with a maximum flow rate depending on the position of the first 8 and / or second adjustment piston respectively. A leakage passage differs from a preload passage 7a, 7b, 7c by the absence of blocking means 14.

[0041] Finally, the shock absorber 1 optionally comprises an additional passage 20 open whatever the position of the first adjustment piston 8. Such an additional passage 20 is, as required, provided with locking means 14.

[0042] Thus, the hydraulic shock absorber 1 according to the invention has an optimal behavior both in compression, thanks to the first adjustment piston 8, and in expansion, thanks to the second adjustment piston. The choice of the threshold forces of the different return springs 19a, 19b as well as the respective calibrations of each spring valve 15 makes it possible to define differentiated speed 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 preload exchanges, through the first 7a, 7b, 7c and second preload passages, are carried out. As illustrated in [Fig. 5], the preload passages 7a, 7b, 7c make it possible to adapt in particular the inflection points 21 in order to provide additional hydraulic braking beyond a certain travel.

[0043] The invention is not limited to the embodiment of the shock absorber described above, only by way of 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

Claims

1. 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 one first housing (9), at least one first adjustment piston (8) being arranged inside each first housing (9) of the main piston (3), each first adjustment piston (8) being able to slide in its first housing (9) from a first rest position under the effect of an increase in fluid pressure in the first chamber (5) generated by a movement of the main piston (3), the main piston (3) comprising at least one first preload passage (7a, 7b, 7c),each allowing unidirectional fluid communication, in a first direction (F) of circulation, between the first (5) and second (6) chambers and through a first housing (9), each first piston (8) comprising at least one first channel (11a, 11b, 11c), each being designed to progressively open or close a first preload passage (7a, 7b, 7c) depending on the position of the first piston (8) in the first housing (9), each preload passage (7a, 7b, 7c) comprising blocking means (14) designed to block the passage of the fluid in the first direction (F) of circulation, when the pressure upstream of the first preload passage (7a, 7b, 7c) is lower than a predetermined threshold pressure specific to each preload passage (7a, 7b, 7c).

2. Shock absorber (1) according to claim 1, characterized in that each first adjustment piston (8) is provided with first return means (18) shaped to move the first adjustment piston (8) towards 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).

3. Shock absorber (1) according to claim 1 or 2, characterized in that each first adjustment piston (8) is shaped to slide in its first housing (9) along a sliding axis (A), each first channel (11a, 11b, 11c) having an elongated contour (12a, 12b, 12c) along the sliding axis (A) so as to vary the cross-section of the corresponding preload passage (7a, 7b, 7c) as a function of the movement of the first adjustment piston (8) and when the first channel (11a, 11b, 11e) allows circulation in the corresponding first preload passage (7a, 7b, 7c).

4. Shock absorber (1) according to one of claims 1 to 3, characterized in that the locking means (14) of each preload passage (7a, 7b, 7c) comprise a calibrated spring valve (15).

5. Shock absorber (1) according to one of claims 1 to 4, characterized in that it comprises at least one second housing in which at least one second adjustment piston slides from a second rest position and comprising at least one second conduit, cooperating with a second preload passage designed to allow unidirectional circulation of fluid in a second direction opposite to the first direction (F).

6. Shock absorber (1) according to claim 5, characterized in that the first (8) and / or second adjustment pistons also comprise at least one leakage conduit each cooperating with a leakage passage which allows the transfer of fluid between the first (5) and second (6) chambers with a maximum flow rate depending on the position of the first (8) and / or second adjustment piston respectively.

7. Shock absorber (1) according to claim 5 or 6, characterized in that the rod (4) comprises a cavity (16) in fluid communication on the one hand with the second chamber (6) and, on the other hand, with each first housing (9) and / or each second housing.

8. Shock absorber (1) according to one of claims 5 to 7, characterized in that each first (8) and / or second adjustment piston is formed of at least two stages (17a, 17b), each stage (17a, 17b) being designed to move away from the first respectively second rest position under the effect of a pressure, exerted on the first (8) respectively second adjustment piston, greater than a predetermined threshold pressure specific to each stage (17a, 17b).

9. Shock absorber (1) according to claim 8, characterized in that each stage (17a, 17b) is spaced from another stage (17a, 17b) by a calibrated return spring (19a, 19b) designed to require a force greater than a predetermined threshold force, specific to each return spring (19a, 19b), to compress.

10. Motor vehicle comprising at least one shock absorber (1) according to one of claims 1 to 9.