HYDRAULIC INERTIAL WHEEL SUSPENSION DEVICE, METHOD, SHOCK ABSORBER AND VEHICLE BASED ON SUCH A DEVICE

Description

[0001] The present invention claims priority from French application 2102628 filed on March 16, 2021, the content of which (text, drawings and claims) is incorporated herein by reference.

[0002] The invention relates to the field of hydraulic inertial suspension devices and systems. The invention finds a particularly advantageous, but not exclusive, application in the field of motor vehicles.

[0003] These are more specifically vertical vehicle suspension systems that allow for improved suspension comfort.

[0004] In this field, hydraulic inertial suspension devices use a fluid to create inertia instead of a conventional shock absorber. WO 2018 / 091795 A1 discloses a suspension device that equips a vehicle train comprising wheels capable of rolling. This device comprises: - a spring and a shock absorber mounted in parallel, - an inertial circuit comprising at least a first pipe having predefined lengths and sections, and capable of producing fluid inertia in a controlled manner, - a cylinder mounted in parallel with the spring and shock absorber and comprising a chamber coupled to the first pipe, and - control means capable of controlling the fluid inertia produced by the inertial circuit as a function of at least one item of information representative of a current value of at least one chosen parameter of the vehicle.Said first pipe comprises first and second ends coupled respectively to inlets / outlets of said chamber and of a fluid reservoir, and said control means comprise first acting means installed between said inlets / outlets of the chamber and of said fluid reservoir in order to control the connection / disconnection of said first pipe.

[0005] Unfortunately, on some steep-sided obstacles, cavitation can occur in the circuit. To limit this risk, it is possible to increase the static pressure of the circuit, but this generates more friction, particularly in the cylinder. However, this friction reduces the efficiency of the system, particularly in terms of providing vibration comfort to the vehicle. This disadvantage is observed in relaxation in certain architectures.

[0006] Thus, one objective of the invention is to propose a new architecture of hydraulic suspension device making it possible to limit both the risk of cavitation in the circuit, and also friction in the cylinder, in particular specifically during expansion.

[0007] To achieve this objective, the invention proposes a hydraulic inertial suspension device for a vehicle, the device comprising a cylinder comprising a body and a piston delimiting an expansion chamber and a compression chamber, a compensation chamber opposite the expansion chamber, a fluid circuit comprising an expansion branch putting the expansion chamber into fluid communication with the compensation chamber, and a compression branch putting the compression chamber into fluid communication with the compensation chamber via a bypass of the expansion branch upstream of the compensation chamber, the compression branch comprising a first inertial increaser upstream of the compensation chamber

[0008] According to a first aspect, the compression branch further comprises at least one second inertial increaser upstream of the first inertial increaser, the fluid circuit further comprising a hydraulic short circuit of the second inertial increaser, activated in attack.

[0009] Advantageously, the invention makes it possible to limit the increase in pressure by integrating a short circuit activated in attack, making it possible to reduce the inertia in the relaxation movement in this case.

[0010] According to other aspects taken in isolation, or combined in all technically feasible combinations: the hydraulic bypass is activated at frequencies greater than or equal to 20 Hz; and / or the hydraulic bypass is activated by means of a check valve oriented to bypass the second inertial augmentor in drive; and / or the compensation chamber is a compensation sphere; and / or the fluid of the fluid circuit comprises suspension oil; and / or the fluid of the fluid circuit comprises glycol.

[0011] The invention further relates to a method of implementing hydraulic inertial suspension for a hydraulic inertial suspension device comprising a cylinder comprising a body and a piston delimiting an expansion chamber and a compression chamber; a compensation chamber opposite the expansion chamber, a fluid circuit comprising an expansion branch putting the expansion chamber into fluid communication with the compensation chamber, and a compression branch putting the compression chamber into fluid communication with the compensation chamber via a bypass of the expansion branch upstream of the compensation chamber, the compression branch comprising a first inertial increaser upstream of the compensation chamber, the compression branch further comprising at least one second inertial increaser upstream of the first inertial increaser, the method comprising an expansion step in which the compression chamber fills and the expansion chamber empties, an attack step in which the compression chamber empties and the expansion chamber fills, and being characterized by if the vibration frequencies of the device are greater than or equal to a threshold in attack, preferably of approximately 20 Hz, a sub-step of flow deflection so as to short-circuit the second inertial increaser.

[0012] The invention further relates to a shock absorber for a vehicle, comprising an inertial suspension device according to the invention.

[0013] Another subject of the invention relates to a vehicle comprising an inertial suspension device according to the invention.

[0014] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which: [ Fig.1 ] schematically illustrates an inertial suspension device according to a preferred variant of the invention in attack with vibrations of frequency lower than 20Hz; [ Fig.2 ] illustrates the inertial suspension device of the previous figure in attack with vibrations of frequency greater than or equal to 20Hz; and [ Fig.3 ] illustrates the inertial suspension device of the previous figures in relaxation.

[0015] The invention relates to a hydraulic inertial suspension device. The invention finds a particularly advantageous, but not exclusive, application in the field of motor vehicles.

[0016] The inertial suspension device comprises a cylinder comprising a body and a piston P. The body and the piston P delimit an expansion chamber C1 and a compression chamber C2. In the illustrated variant, the expansion chamber C1 is arranged above the compression chamber C2. The piston rod extends into the expansion chamber C1.

[0017] The inertial suspension device further comprises a compensation chamber S1 opposite the expansion chamber C1. In particular, the compensation chamber S1 comprises a compensation sphere.

[0018] The inertial suspension device further comprises a fluid circuit Ci comprising a damping fluid moving between the chambers. The damping fluid may comprise suspension oil, such as that of the "LDS" (Steering and Suspension Fluid) type. The damping fluid may also comprise glycol, which is denser and therefore also more efficient, with the additional advantage of reducing pressure losses due to its reduced viscosity characteristic.

[0019] The fluid circuit Ci comprises an expansion branch Bd and a compression branch Bc. The expansion branch Bd connects the expansion chamber C1 to the compensation chamber S1 in fluid communication. In addition, the compression branch Bc connects the compression chamber C2 to the compensation chamber S1 in fluid communication. For this purpose, a first branch d1 is provided on the expansion branch Bd, preferably just before the connection of the expansion branch Bd to the compensation chamber S1. This can be referred to as a connection upstream of the compensation chamber S1.

[0020] Thus, the compression branch Bc is connected to the expansion branch Bd so that fluid leaving S1 can go into the expansion branch Bd or into the compression branch Bc, and vice versa.

[0021] Furthermore, the compression branch Bc includes a first inertial increaser IP1 upstream of the compensation chamber S1.

[0022] According to one aspect, the compression branch Bc further comprises at least one second inertial augmentor IP2 upstream of the first inertial augmentor IP1.

[0023] The inertial augmentors IP1, IP2 take the form of a column of fluid, for example. Preferably, the inertias of the inertial augmentors IP1, IP2 are identical.

[0024] In addition, the fluid circuit Ci further comprising a hydraulic short circuit Bp of the second inertial increaser IP2. In the context of the invention, the short circuit Bp is activated in attack.

[0025] Advantageously, the invention makes it possible to implement a different inertia in attack and in relaxation, whereas the known architectures of hydraulic inertial suspensions have symmetrical inertias.

[0026] Furthermore, the invention makes it possible to limit the increase in pressure by integrating a short circuit Bp activated in attack. This results in a reduction of inertia in the chosen direction, in the relaxation movement in this case.

[0027] The invention is particularly advantageous because cavitation could also have been limited by increasing the operating pressure, but this would increase the friction between the piston P and the cylinder. The invention makes it possible to limit the increase in pressure by integrating the aforementioned short circuit Bp.

[0028] Thus, a second derivation d2 is provided between the two inertial augmentors IP1, IP2, and a third derivation d3 is provided upstream of the second inertial augmentor IP2.

[0029] In particular, the hydraulic short circuit Bp is activated at frequencies greater than or equal to a threshold preferably of around 20 Hz. We can speak of high-frequency vibrations above the threshold, and low-frequency vibrations below the threshold.

[0030] To do this, the short-circuit Bp comprises a non-return valve Cl1 oriented to short-circuit the second inertial increaser IP2 in attack. In particular, the non-return valve Cl1 is configured to allow flow rates corresponding to frequencies greater than or equal to said threshold in attack. Below these frequencies, the fluid is blocked and passes in particular through the second inertial increaser IP2.

[0031] In expansion, the Cl1 check valve is configured to block the passage of fluid regardless of the frequency.

[0032] Preferably, the fluid circuit Ci further comprises a first parallel branch Br connecting the expansion branch Bd to the compression branch Bc. The first parallel branch Br is mounted in parallel with the inertial increasers IP1, IP2. The first parallel branch Br comprises a flow reducer R which can be adjustable.

[0033] The flow reducer R allows the compression chamber C2 and the expansion chamber C1 to be short-circuited in the event of high-frequency vibrations (calibrated for a threshold frequency). The flow reducer R is preferably calibrated according to the vehicle in which the device is used. For example, it is a throttle as shown in the figures.

[0034] Furthermore, preferably, the fluid circuit Ci comprises a second parallel branch Bt connecting the expansion branch Bd to the compression branch Bc. The second parallel branch Bt is mounted in parallel with the first parallel branch Br, in particular between the latter and the inertial increasers IP1, IP2. The second parallel branch Bt comprises a double bypass with on each side a non-return valve Cl2, Cl3 in opposite directions (head to tail).

[0035] The two non-return valves Cl2, Cl3 allow the compression chamber C2 and the expansion chamber C1 to be short-circuited in the event of high-frequency vibrations in order to prevent them from rising towards the vehicle body.

[0036] The invention further relates to a method of implementing hydraulic inertial suspension for a hydraulic inertial suspension device having a structure as described above.

[0037] The method comprises an expansion step in which the compression chamber C2 of the cylinder is decompressed and fills, and the expansion chamber C1 is compressed and empties.

[0038] The method further comprises an attack step in which the compression chamber C2 of the cylinder is in compression and empties, and the expansion chamber C1 is in decompression and fills.

[0039] During the attack step, if the vibration frequencies of the device are greater than or equal to a threshold, preferably approximately 20 Hz, then the method comprises a sub-step of diverting the fluid flow so as to short-circuit the second inertial increaser IP2. In particular, the flow diversion is carried out by means of a non-return valve Cl1 oriented to short-circuit the second inertial increaser IP2 in attack.

[0040] More specifically, at low frequencies (between 0 and 20Hz), the system releases all possible inertia. The fluid passes through the main inertial lines IP1 and IP2, allowing the inertial suspension to properly dampen the vehicle.

[0041] On the other hand, if the frequencies of the vibrations of the device are lower than a threshold or preferably said threshold in attack, then the method does not include said flow diversion sub-step. In particular, the fluid passes into the second inertial IP2, being blocked by the non-return valve Cl1 below the threshold.

[0042] More specifically, at high frequency (from 20Hz), the inertia provided by the suspension must be reduced in order to limit wheel bounce. The second main inertia IP2 is therefore short-circuited by the branch Bp equipped with the valve Cl1 forming a decompression valve.

[0043] In addition, for all frequency ranges, the accumulation sphere S1 makes it possible to avoid cavitation phenomena appearing mainly in the chamber C1 of the cylinder.

[0044] Furthermore, regardless of the frequency in relaxation, the method does not include said flow diversion sub-step, in particular due to a flow blockage by means of said non-return valve Cl1.

[0045] More specifically, during the expansion phase, the volume of the supplied chamber C2 is greater than the volume of the emptied chamber C1 due to the presence of the cylinder rod in the upper chamber C1, implying a high risk of cavitation. This risk of cavitation is compensated by the accumulation sphere S1 which provides the volume necessary to supply each of the chambers C1, C2 in all circumstances. The accumulation sphere S1 also ensures smoothing of the current throughout operation. Thus, the quantity of fluid circulating in the circuit Ci is constant throughout the movement.

[0046] The invention makes it possible to delay the occurrence of cavitation in the compensation chamber S1 during expansion movements, making it possible to limit the static pressure in the system and thus reduce friction in the system.

[0047] The invention also relates to a shock absorber for a vehicle, comprising an inertial suspension device as described above.

[0048] Another subject of the invention relates to a vehicle comprising an inertial suspension device as described above. This is in particular a motor vehicle.

Claims

1. Hydraulic inertial suspension device for a vehicle, the device comprising: cylinder comprising a body and a piston (P) delimiting an expansion chamber (Cl) and a compression chamber (C2), compensation chamber (S 1) facing the expansion chamber (Cl), fluid circuit (Ci) comprising an expansion branch (Bd) placing the expansion chamber (Cl) in fluid communication with the compensation chamber (S 1), and a compression branch (Bc) placing the compression chamber (C 2) in fluid communication with the compensation chamber (S 1) via a branch (dl) of the expansion branch (Bd) upstream the compensation chamber (S 1), the compression branch (Bc) comprising a first inertial augmentor (IP 1) upstream the compensation chamber (S 1), wherein the compression branch (Bc) further comprises at least one second inertial augmentor (IP 2) upstream to the first inertial augmentor (IP 1), the fluid circuit (Ci) further comprising a hydraulic short-circuit (Bp) of the second inertial augmentor (IP 2), activated in attack.

2. Inertial suspension device according to Claim 1, characterised in that the hydraulic short-circuit (Bp) is activated to frequencies greater than or equal to 20 Hz.

3. Inertial suspension device according to any one of Claims 1 to 2, characterised in that the hydraulic short-circuit (Bp) is activated by means of an anti-return valve (C11) orientated so as to short-circuit the second inertial augmentor (IP2) under attack.

4. Inertial suspension device according to any one of Claims 1 to 3, characterised in that the compensation chamber (S1) is a compensation sphere.

5. Inertial suspension device according to any one of Claims 1 to 4, characterised in that the fluid of the fluid circuit (Ci) comprises suspension oil.

6. Inertial suspension device according to any one of Claims 1 to 5, characterised in that the fluid of the fluid circuit (Ci) comprises glycol.

7. Method of using hydraulic inertial suspension for a hydraulic inertial suspension device comprising - a cylinder comprising a body and a piston (P) delimiting an expansion chamber (Cl) and a compression chamber (C2); compensation chamber (S 1) facing the expansion chamber (Cl), fluid circuit (Ci) comprising an expansion branch (Bd) fluidly connecting the expansion chamber (Cl) with the compensation chamber (Si), and a compression branch (Bc) fluidly connecting the compression chamber (C2) with the compensation chamber (Si) via a branch (dl) of the expansion branch (Bd) upstream the compensation chamber (Si), the compression branch (Bc) comprising a first inertial augmentor (IP 1) upstream the compensation chamber (Si), the compression branch (Bc) further comprising at least one second augmentor inertial (IP 2) upstream to the first inertial augmentation device (IP 1), the method comprising expansion step in which the compression chamber (C 2) is filled and the expansion chamber (C 1) is emptied, attack step in which the compression chamber (C 2) is vacuum and the expansion chamber (Cl) fills, and being characterised by if the vibration frequencies of the device are greater than or equal to a threshold under attack, preferably of about 20 Hz, a sub-step of flow deviation so as to bypass the second inertial augmentation device (IP 2).

8. A shock absorber for a vehicle, comprising an inertial suspension device according to any one of claims 1 to 6.

9. Vehicle comprising an inertial suspension device according to any one of Claims 1 to 6.