Active suspension for vehicles

Abstract

The suspension 10 includes a hydraulic actuator 12 and a supply hydraulic circuit 14 connected to the hydraulic actuator 12 for supplying hydraulic fluid to a compression chamber 20 and a rebound chamber 22 of the hydraulic actuator 12. The supply hydraulic circuit 14 includes a hydraulic pump 26, a high pressure line 28 connected to an outlet port 30 of the hydraulic pump 26, a low pressure line 32 connected to an inlet port 34 of the hydraulic pump 26, and a flow control valve 36 connected on one side to the compression chamber 20 and the rebound chamber 22 of the hydraulic actuator 12 and connected on the other side to the high pressure line 28 and the low pressure line 32. The flow control valve 36 is a rotary spool valve with a spool 40 that is continuously rotatable between a plurality of operating positions provided in a first direction between a rest position and a first end operating position and provided in a second direction opposite to the first direction between the rest position and a second end operating position. The flow control valve 36 is configured to connect at least one of the compression chamber 20 and the expansion chamber 22 of the hydraulic actuator 12 to the high pressure line 28 at each operating position of the spool 40 between a first end operating position and a second end operating position.

Description

[Technical field]

[0001] The present invention relates generally to the field of vehicle suspensions, and more particularly to the field of automotive suspensions. More specifically, the present invention relates to an active suspension for a vehicle and to a vehicle equipped with such a suspension. [Background technology]

[0002] The use of suspensions in vehicles is known to improve the driving comfort and handling of the vehicle, to filter road surface irregularities, and to control the relative movement of the sprung mass of the vehicle (including the vehicle body) to the unsprung mass of the vehicle (including the wheels).

[0003] The use of so-called active suspensions in vehicles is also known, which comprise, for each wheel, an electronically controlled actuator arranged to control the relative movement of the wheel with respect to the vehicle body under the supervision of an electronic control unit. The actuators are typically hydraulic actuators, which receive a supply of working fluid under pressure provided by a pump that generates a hydraulic force with a given magnitude and in a given direction (extension or compression) to counteract forces generated between the wheel and the vehicle body, for example as a result of road irregularities or during acceleration or braking phases of the vehicle.

[0004] An active suspension is known from EP 3216632 (A1) and US 10076943 (B2), which comprises a hydraulic pump, a pressure control valve for regulating the pressure in a high pressure line downstream of the pump, and a flow control valve switchable between two operating positions for sending a hydraulic fluid under pressure to a first or a second chamber of a damper of the suspension in order to generate a hydraulic force in the direction of the extension movement of the damper or in the direction of the compression movement of the damper. In particular, the flow control valve can also assume a safety position (fail-safe position), in which the first chamber, the second chamber, the high pressure line and the low pressure line communicate with each other, allowing the suspension to operate conventionally in the event of failure of either the controller of the flow control valve or the controller of the pressure control valve.

[0005] A further example of an active suspension for a vehicle is known from US patent application No. 2018 / 022179.

[0006] According to this known solution, the suspension comprises a hydraulic actuator connected at its upper end to the vehicle body and at its lower end to the wheel, arranged concentrically and parallel to a cylindrical helical spring, the hydraulic actuator being connected to a supply hydraulic circuit comprising a hydraulic pump, a high pressure line connected to the delivery port of the pump, a low pressure line connected to the suction port of the pump, a pressure accumulator connected to the high pressure line and a spool valve connected on one side to the compression and extension chambers of the hydraulic actuator and on the other side to the high pressure and low pressure lines. The spool valve can be configured to start from a central position in which the spool closes both flow paths connected to the hydraulic actuator, i.e. the flow path connected to the compression chamber of the hydraulic actuator and the flow path connected to the extension chamber of the hydraulic actuator, in a first direction, between a first intermediate position in which the spool also opens the flow path connected to the extension chamber of the hydraulic actuator, thereby putting that chamber in hydraulic communication with the low pressure line, while the flow path connected to the compression chamber of the hydraulic actuator remains closed, and a second intermediate position in which the spool also opens the flow path connected to the compression chamber of the hydraulic actuator, thereby putting the compression chamber in hydraulic communication with the high pressure line, thus putting the pressure in the chamber of the hydraulic actuator in hydraulic communication with the high pressure line. The suspension is switchable between a first end position, which results in an extension of the rod of the hydraulic actuator as a result of a pressure difference, a second intermediate position, in which in a second direction opposite to the first direction the spool opens the passage connected to the compression chamber of the hydraulic actuator, thereby putting said chamber in hydraulic communication with the low pressure line, while the passage connected to the extension chamber of the hydraulic actuator remains closed, and a second end position, in which the spool also opens the passage connected to the extension chamber of the hydraulic actuator, putting the extension chamber in hydraulic communication with the high pressure line, thus causing a retraction of the rod of the hydraulic actuator as a result of a pressure difference in the chambers of the hydraulic actuator. The suspension operates in active mode when the spool valve is in the first or second end position, i.e. when one of the two chambers of the hydraulic actuator is in hydraulic communication with the high pressure line.Only when the spool valve is in the first or second intermediate position does the suspension operate in semi-active mode, since there is no energy supply to the hydraulic actuator, but the stiffness of the hydraulic actuator is changed as a result of the fluid flowing out of one of the two chambers of the hydraulic actuator towards the low pressure line. In the central position of the spool valve, the fluid is prevented from flowing out of the compression or extension chamber. Therefore, in case of a valve control failure, the suspension cannot operate as a conventional suspension.

[0007] WO 2021 / 260586, an international patent application in the name of the applicant on which the preamble of the attached independent claim 1 is based, discloses an active suspension for a vehicle comprising, for each wheel of the vehicle, a respective hydraulic actuator having a compression chamber and a tension chamber, and a spool valve connected on one side to the compression chamber and tension chamber of the hydraulic actuator and on the other side to a high pressure line and a low pressure line, for fluid communication of the chamber of the hydraulic actuator with the high pressure and low pressure lines. The spool valve comprises a spool arranged to translate continuously between a plurality of operating positions arranged in a first direction between a rest position and a first end position and arranged in a second direction opposite to the first direction between the rest position and the second end position, the spool valve being arranged to connect at least one of the compression chamber and tension chamber of the hydraulic actuator to the high pressure line in each operating position of the spool.

[0008] Additionally, EP 0 446 543 discloses a control system for a hydraulic actuator, for example for use in a vehicle suspension, the control system comprising a rotary spool valve, an electric motor for driving and rotating the valve spool, and a transmission mechanism for transmitting motion from a drive shaft of the electric motor to a driven disk drivingly connected to the valve spool for rotation. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] European Patent No. 3216632(A1) [Patent Document 2] US Patent No. 10076943(B2) [Patent Document 3] U.S. Patent Application No. 2018 / 022179 [Patent Document 4] International Publication No. 2021 / 260586 [Patent Document 5] European Patent No. 0446543 Summary of the Invention [Problem to be solved by the invention]

[0010] It is an object of the present invention to provide an active suspension for a vehicle of the type that is improved over the prior art discussed above. [Means for solving the problem]

[0011] This and other objects are fully achieved by an active suspension for a vehicle as defined in the attached independent claim 1.

[0012] Preferred embodiments of the active suspension for a vehicle according to the invention are defined in the dependent claims.

[0013] In summary, the invention is based on the idea of ​​providing an active suspension for a vehicle of the type specified above, in which the valve controlling the flow of working fluid between high and low pressure lines and the extension and compression chambers of a hydraulic actuator is a rotary spool valve configured to connect at least one of the two chambers of the hydraulic actuator to the high pressure line in each operating position.Furthermore, according to the invention, an electric motor driving the spool to rotate it is mounted coaxially with the spool, the spool being rigidly connected to the shaft of the electric motor, in particular being formed integrally with it.

[0014] With such a configuration, the active vehicle suspension of the present invention allows the force generated by the hydraulic actuator to be adjusted quickly and accurately by appropriately controlling the operating position of the flow control valve. In addition, the use of a rotary spool valve instead of a translating spool valve as the flow control valve allows the overall size in the axial direction to be reduced, and allows the operation (in this case the operating torque) to be ensured regardless of the position of the rotor of the electric motor driving the valve and the position of the spool, and allows the linearity of the system to be ensured from a mathematical point of view due to the fact that the torque transmitted from the electric motor to the spool is linearly proportional to the current exciting the electric motor. In addition, due to the fact that the valve spool is rigidly connected to the shaft of the electric motor, in particular formed integrally, a motion transmission system with high stiffness is achieved that ensures the operating delay between the electric motor and the spool is minimized. As both the spool and the electric motor are immersed in oil, no hydraulic seals are required, which allows the friction to be reduced and the mechanical efficiency of the system to be increased, as well as the size of the electric motor to be reduced (since a smaller electric motor can be used when a lower operating torque is required). In addition, such a configuration allows position sensors for controlling the electric motor to be mounted at either end of the rotor.

[0015] According to one embodiment, the flow control valve is configured to provide a safe position of the spool, in the event of a failure or disturbance of the valve, and in particular of the valve actuation system, the spool is pushed by suitable elastic means (e.g. a torsion bar) to reach this safe position, in which both the compression and extension chambers of the hydraulic actuator are connected only to the low pressure line.

[0016] Further characteristics and advantages of the invention will become apparent from the following detailed description, given purely as a non-limiting example.

[0017] In the following detailed description of the invention, reference is made to the accompanying drawings. [Brief description of the drawings]

[0018] [Figure 1] 1 is a schematic diagram of an active vehicle suspension in accordance with the present invention; [Diagram 2] FIG. 2 is a perspective view of a hydraulic actuator and flow control valve assembly of the suspension of FIG. 1. [Diagram 3] FIG. 3 is a cross-sectional view of the hydraulic actuator and flow control valve assembly of FIG. 2. [Figure 4] 4 is a cross-sectional view of the hydraulic actuator and flow control valve assembly of FIG. 2 taken through a cross-sectional plane perpendicular to the cross-sectional plane of FIG. 3. [Diagram 5] FIG. 5 is a perspective view of an inner sleeve of the flow control valve of the assembly of FIGS. 2 to 4. [Figure 6] FIG. 5 is a perspective view of a spool of the flow control valve of the assembly of FIGS. 2 to 4. [Figure 7] FIG. 7 is a cross-sectional view of the spool of FIG. [Figure 8a] FIG. 5 is a schematic diagram showing the relative arrangement of ports and longitudinal channels throughout the inner sleeve of the spool of the flow control valve of the assembly of FIGS. 2 to 4 with the spool in the zero position. [Figure 8b]8a is a graph showing the values ​​of the flow cross-sectional area of ​​the ports of the inner sleeve associated respectively with the high pressure and low pressure lines of the suspension supply hydraulic circuit for each of the two chambers of the hydraulic actuator of the assembly of FIGS. 2 to 4 with the spool in the position of FIG. 8a; [Figure 9a] 8b is a view similar to FIG. 8a with the spool moving between the zero position and the first end operating position; [Figure 9b] 8b, with the spool moving between the zero position and the first end operating position; FIG. [Figure 10a] 8b is a view similar to FIG. 8a with the spool moving between the zero position and the first end operating position; [Figure 10b] 8b, with the spool moving between the zero position and the first end operating position; FIG. [Figure 11a] 8b is a view similar to FIG. 8a with the spool moving between the zero position and the first end operating position; [Figure 11b] 8b, with the spool moving between the zero position and the first end operating position; FIG. [Figure 12a] 8b is a view similar to FIG. 8a with the spool moving between the zero position and the second, end operating position; [Figure 12b] 8b, with the spool moving between the zero position and the second, end operating position; FIG. [Figure 13a] 8b is a view similar to FIG. 8a with the spool moving between the zero position and the second, end operating position; [Figure 13b] 8b, with the spool moving between the zero position and the second, end operating position; FIG. [Figure 14a] 8b is a view similar to FIG. 8a with the spool moving between the zero position and the second, end operating position; [Figure 14b] 8b, with the spool moving between the zero position and the second, end operating position; FIG. [Figure 15]FIG. 5 is a schematic diagram showing the relative arrangement of ports and longitudinal channels of the sleeve of the spool of the flow control valve of the assembly of FIGS. 2 to 4 with the spool in a safe position ("fail-safe" position) in the event of a malfunction or failure. [Figure 16] FIG. 1 is a schematic diagram of an active vehicle suspension architecture according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Referring initially to FIG. 1, an active suspension for a vehicle (hereinafter simply referred to as the suspension) according to one embodiment of the present invention is shown generally at 10.

[0020] The suspension 10 basically comprises a hydraulic linear actuator 12 (hereinafter simply referred to as the actuator) interposed between the wheel W of the vehicle and the body B of the vehicle, and a supply hydraulic circuit 14 connected to the actuator 12.

[0021] The actuator 12 comprises a cylinder 16 connected to the wheel W and oriented with its longitudinal axis (indicated z) e.g. vertically or slightly inclined from the vertical, and a piston 18 slidably mounted inside the cylinder 16 for sliding movement along the longitudinal axis z so as to divide the internal volume of the cylinder 16 into a pair of variable volume chambers containing a working fluid, in particular oil, namely a compression chamber 20 and an extension chamber 22. The actuator 12 also comprises a rod 24, which at its lower end is connected to the piston 18 so as to be drivingly connected for movement therewith, which protrudes from the cylinder 16 on the side of the extension chamber 22 and which is connected at its upper end to the body B of the vehicle. In a manner not shown but known per se, the piston 18 is advantageously equipped with pressure limiting valves V1 and V2 (known per se and therefore only diagrammatically shown in FIG. 1 ), namely a compression valve and a rebound valve, respectively, whose function is to limit the force exerted on the piston by the fluid pressure in the chambers 20 and 22 of the cylinder, preventing cavitation phenomena at high speeds. More specifically, the compression valve V1 acts during the compression stroke to allow the flow of working fluid from the compression chamber 20 to the rebound chamber 22 when a given pressure limit in the compression chamber 20 is exceeded, and the rebound valve V2 acts during the rebound stroke to allow the flow of working fluid from the rebound chamber 22 to the compression chamber 22 when a given pressure limit in the rebound chamber 22 is exceeded.

[0022] The supply hydraulic circuit 14 includes a hydraulic pump 26 (hereinafter simply referred to as the pump) and a high pressure line 28 (hereinafter referred to as the pressure p H ) and a low pressure line 32 (hereinafter, the pressure of which is denoted as p Land a flow control valve 36 connected on one side to the compression chamber 20 and the expansion chamber 22 of the actuator 12 and on the other side to the high pressure line 28 and the low pressure line 32 for placing the two chambers 20 and 22 of the actuator 12 in fluid communication with the two lines 28 and 32 of the supply hydraulic circuit 14 according to a predetermined mode of operation (described below).

[0023] The supply hydraulic circuit 14 preferably includes a first pressure accumulator (not shown, but of a type known per se) connected to the high pressure line 28 and a second pressure accumulator (also not shown, but of a type known per se) connected to the low pressure line 32.

[0024] Pump 26 is preferably a fixed displacement pump. Depending on the particular application, there may be only one pump on the vehicle configured to supply all the actuators on board the vehicle (one for each wheel), or there may be several pumps, in particular one pump for the actuators on the front axle of the vehicle and one pump for the actuators on the rear axle of the vehicle, or one pump for each actuator.

[0025] Pressure p in high pressure line 28 H can be constant or, alternatively, can be continuously adjusted. For example, the pressure p H is between 30 and 40 bar. Meanwhile, the pressure p L is, for example, between 5 and 10 bar.

[0026] 2 to 4, the flow control valve 36 is configured as a rotary spool valve and includes a valve body 38, a spool 40 rotatably mounted in the valve body 38 about a rotation axis x, and an actuation unit 42 arranged to drive the spool 40 to rotate in one direction or the other about the rotation axis x. More specifically, the valve body 38 includes an outer body 44 serving as an outer housing for the entire valve including the actuation unit 42, and an inner sleeve 46 inserted in a cylindrical inner cavity 44a of the outer body 44. The inner sleeve 46 has a cylindrical inner cavity 46a whose axis defines the rotation axis x, and into which the spool 40 is inserted.

[0027] The actuation unit 42 is formed by a rotary electric motor (hereinafter simply called "motor 42") comprising a rotor 48 and a stator 50. The motor 42 is mounted coaxially with the spool 40, more particularly the rotor 48 is mounted around and drivingly connected for rotation therewith by a shaft 52 which is rigidly connected to, and in particular formed integrally with, the spool 40. The motor 42 is suitably driven by an electronic control unit (not shown) so as to position the spool 40 in the desired position each time.

[0028] Preferably, the spool 40 is connected to the valve body 38 by a torsion bar 54, or more generally, a resilient connecting member, configured to exert a resilient reaction torque on the spool 40 tending to move the spool to a predetermined angular position, hereinafter referred to as a safety or "fail-safe" position. For example, the torsion bar 54 is inserted coaxially into a cylindrical cavity 56 provided in the shaft 52.

[0029] As shown in Figures 1, 3 and 4, the outer body 44 of the flow control valve 36 has one or more first inlet ports (in this case, one first inlet port 58) connected to the high pressure line 28, one or more second inlet ports (in this case, two second inlet ports 60' and 60") connected to the low pressure line 32, a first outlet port 62' connected to the compression chamber 20 of the actuator 12, and a second outlet port 62" connected to the expansion chamber 22 of the actuator 12.

[0030] 5, the inner sleeve 46 has a plurality of cylindrical regions, designated 64, 66, 68, 70 and 72, respectively, from bottom to top in the perspective of a person viewing Figures 1 to 5, which are provided with fluid passage ports extending through the entire thickness of the inner sleeve 46, and a plurality of annular sectors 74, which have a larger diameter than the cylindrical regions 64, 66, 68, 70 and 72 and space the cylindrical regions 64, 66, 68, 70 and 72 from one another in a liquid-tight manner. Each of the annular sectors 74 has a respective peripheral groove 76 into which is inserted a respective seal 78, which cooperates with a cylindrical surface of the inner cavity 44a of the outer body 44.

[0031] Still referring specifically to Figures 5 and 1, the cylindrical regions 64 and 72, i.e. the axially outermost cylindrical regions, face the second inlet port 60' and the second inlet port 60" (i.e. the inlet ports connected to the low pressure line 32), respectively, and have a plurality of first low pressure ports 80' and a plurality of second low pressure ports 80", respectively, each of which in particular comprises four ports arranged at a 90 degree angle relative to each other. Preferably, further, the first low pressure port 80' of the cylindrical region 64 is offset at an angle of 45 degrees from the second low pressure port 80" of the cylindrical region 72. The cylindrical region 68, i.e. the central cylindrical region, faces the first inlet port 58 (i.e. the inlet port connected to the high pressure line 28) and has a plurality of first and second high pressure ports 82′, 82″ disposed on two adjacent circumferential edges, the first high pressure ports 82′ being disposed on the first circumferential edge, for example 90 degrees apart, and the second high pressure ports 82″ being disposed on the second circumferential edge, for example also 90 degrees apart, offset at a particular angle, in particular an angle of less than 45 degrees, to the first high pressure port 82′. The cylindrical region 66, i.e. the intermediate cylindrical region disposed between the axially outermost cylindrical region 64 and the central cylindrical region 68, faces the first outlet port 62′ of the outer body 44 (i.e. the outlet port connected to the compression chamber 20 of the actuator 12) and has a plurality of first ports 84, e.g. four ports disposed at an angle of 90 degrees to each other, made in the form of circumferentially elongated slots. Similarly, the cylindrical region 70, i.e., the intermediate cylindrical region disposed axially between the outermost cylindrical region 72 and the central cylindrical region 68, faces the second outlet port 62″ of the outer body 44 (i.e., the outlet port connected to the extension chamber 22 of the actuator 12) and has a plurality of second ports 86 in the form of circumferentially elongated slots, e.g., four ports disposed at 90° angles relative to each other.

[0032] 6 and 7, the spool 40 has, on its outer cylindrical surface (designated 40a), a series of first longitudinal channels 88, specifically four longitudinal channels arranged at 90 degree angles relative to one another, that extend parallel to the longitudinal axis or axis of rotation x of the spool 40. The first longitudinal channels 88 extend from the outermost cylindrical region 64 to a portion of the central cylindrical region 68, and thus have a length and configuration that allows them to selectively overlap with the first low pressure port 80' of the cylindrical region 64, the first port 84 of the cylindrical region 66, and the first high pressure port 82' of the cylindrical region 68 as a result of rotation of the spool 40 about the axis of rotation x. The spool 40 also has, on its outer cylindrical surface 40a, a series of second longitudinal channels 90, specifically four longitudinal channels arranged at 90 degree angles relative to one another, that are each aligned with a respective first longitudinal channel 88. The second longitudinal channels 90 extend from the outermost cylindrical region 72 to a portion of the central cylindrical region 68 and thus have a length and configuration that allows them to selectively overlap with the second low pressure port 80″ of the cylindrical region 72, the second port 86 of the cylindrical region 70 and the second high pressure port 82″ of the cylindrical region 68 as a result of rotation of the spool 40 about the rotation axis x. The first longitudinal channels 88 are in fluid communication with each other via first radial channels 92 (shown in detail in FIG. 7 ), specifically four channels extending perpendicular to each other. Similarly, the second longitudinal channels 90 are in fluid communication with each other via second radial channels 94 (shown only partially in FIG. 6 ), specifically four channels extending perpendicular to each other.

[0033] The fact that the first low pressure port 80', the second low pressure port 80", the first high pressure port 82' and the second high pressure port 82" of the sleeve 46 are equally angularly spaced apart in the circumferential direction, in particular, as described above, at an angle of 90 degrees to each other, and similarly, the fact that the first longitudinal channel 88 and the second longitudinal channel 90 of the sleeve 40 are also equally angularly spaced apart in the circumferential direction, in particular, as described above, at an angle of 90 degrees to each other, results in a balance of the pressures acting in the channels of the sleeve, and thus the resulting forces acting on the sleeve are cancelled or at least minimised, thereby resulting in improved operation of the valve.

[0034] The various positions that the spool 40 can assume as a result of its rotation about the axis of rotation x, and hence the operation of the suspension, will now be illustrated with reference to Figures 8 to 15.

[0035] Starting from the zero position (FIGS. 8a and 8b), the spool 40 can be rotated in a first direction until it reaches a first end operating position (FIGS. 11a and 11b) and in a second direction opposite to the first direction until it reaches a second end operating position (FIGS. 14a and 14b). In the illustrated example, the angular movement between the zero position and the first end operating position and between the zero position and the second end operating position is equal to 15 degrees, but of course this can be more or less than 15 degrees depending on the particular application.

[0036] The spool 40 is continuously movable between these positions and can therefore assume any intermediate position between the zero position and the first end operating position and between the zero position and the second end operating position, thus making it possible to continuously adjust the fluid pressure in the chambers 20 and 22 of the actuator 12.

[0037] As can be seen from these figures, in any position of the spool 40 between the first and second end operating positions, the first longitudinal channel 88 of the spool 40 is superimposed on the first port 84 of the inner sleeve 46 and thus in fluid communication with the compression chamber 20 of the actuator 12 via the first outlet port 62', and similarly, the second longitudinal channel 90 of the spool 40 is superimposed on the second port 86 of the inner sleeve 46 and thus in fluid communication with the extension chamber 22 of the actuator 12 via the second outlet port 62'.

[0038] With the spool 40 in the zero position (FIGS. 8a and 8b), the first longitudinal channel 88 of the spool 40 has a maximum cross-sectional flow area A max 1. The second longitudinal channel 90 of the spool 40 overlaps with the first high pressure port 82' but does not overlap with the first low pressure port 80' to an extent that the cross-sectional flow area is approximately equal to half of the cross-sectional flow area defined by the first high pressure port 82'. Additionally, the second longitudinal channel 90 of the spool 40 overlaps with the second high pressure port 82' but does not overlap with the second low pressure port 80', specifically so as to define a cross-sectional flow area equal to the cross-sectional flow area defined by the first high pressure port 82'. As a result, both the compressor chamber 20 and the expansion chamber 22 of the actuator 12 are supplied with only high pressure fluid, and thus both are supplied with the same pressure p H (high pressure). Thus, an upward force is exerted on the piston 18 of the actuator 12 by the difference between the areas over which the fluid pressure acts in chambers 20 and 22. Additionally, in this position, the compression chamber 20 and the expansion chamber 22 of the actuator 12 communicate with each other via the outlet ports 62' and 62", the longitudinal channels 88 and 90, and the high pressure ports 82' and 82".

[0039] If, starting from the zero position shown above, the spool 40 is moved towards the first end operating position (thus in Figures 9a, 10a and 11a the first longitudinal channel 88 and the second longitudinal channel 90 of the spool 40 are moved upwards relative to the ports provided in the inner sleeve 46), the degree of overlap between the first longitudinal channel 88 and the first high pressure port 82' increases gradually, in particular increases linearly, for example reaching its maximum value (maximum flow cross-sectional area A) at the midpoint of the angular movement between the zero position and the first end operating position. max (corresponding to pressure p ) (FIG. 10a) and then maintains this maximum value until the first end operating position (FIG. 11a). The compression chamber 20 of the actuator 12 thus continues to be supplied with high pressure fluid, and hence the pressure p H With respect to the second longitudinal channel 90 of the spool 40, as it moves from the zero position to the first end operating position, the degree of overlap with the second high pressure port 82″ decreases, for example, until it reaches zero at the midpoint of the angular movement between the zero position and the first end operating position ( FIG. 10 a), and in particular decreases linearly, and then remains at zero until the first end operating position ( FIG. 11 a), while the degree of overlap with the second low pressure port 80″ reaches its maximum value (maximum flow cross-sectional area A max ), in particular increasing linearly (FIG. 11a). As a result, in the tension chamber 22 of the actuator 12, the pressure increases to a value p H (FIG. 8b) the value p at the midpoint of the angular movement between the zero position and the first end operating position L (low pressure) (FIG. 10b) and then to the first end operating position with a value p L is kept constant at (Figure 11b).

[0040] Thus, the upward force exerted on the piston 18 of the actuator 12 increases between the zero position and the first end operating position until it reaches its maximum value at the intermediate position of Figures 10a and 10b and then remains at its maximum value up to the first end operating position.

[0041] As can be seen in Figures 12a-b to 14a-b, when the spool 40 is moved from the zero position to the second end operating position (whereby, in the schematic diagrams of Figures 12a, 13a and 14a, the first longitudinal channel 88 and the second longitudinal channel 90 of the spool 40 move downwards relative to the ports provided in the inner sleeve 46), the change in the flow cross-sectional area of ​​the ports of the inner sleeve 46 associated with the high pressure line 28 and the low pressure line 32 is symmetrical to that described above with reference to the movement of the spool from the zero position to the first end operating position. The course of the flow cross-sectional area during this movement will therefore not be described in detail, but reference is made to the observation of these figures.

[0042] The pressure in the compression chamber 20 of the actuator 12 varies between the zero position and the second final operating position with a value p H From the value p L while the pressure in the tension chamber 22 remains at a constant value p L As a result, an initial state in which the resultant force on the piston 18 of the actuator 12 is directed upwards is followed by an end state in which the resultant force is directed downwards. Specifically, the resultant force is directed downwards and is maintained at its maximum value in the angular range between the intermediate position of Figures 13a and 13b and the second final operating position of Figures 14a and 14b.

[0043] Finally, FIG. 15 shows the spool 40 in a safe position (or “fail-safe” position) in the event of a failure or disturbance of the valve, and in particular of the valve actuation system. This position is reached thanks to the elastic connecting member (in this case the torsion bar 54) connecting the spool 40 to the valve body 38. In other words, the safe position of the spool 40 corresponds to the rest position of the elastic connecting member, i.e. the position in which the elastic reaction torque exerted by the elastic connecting member on the spool 40 (in this case the elastic reaction torque exerted by the torsion bar 54) is zero. In the illustrated example, the angular movement between the zero position and the safe position is 45 degrees, but of course this may be more or less than 45 degrees (as long as it is greater than the movement between the zero position and the first or second end operating position, in this case 15 degrees), depending on the particular application. Furthermore, in the present case the safety position is rotated relative to the zero position in the same direction as the second end operating position, but alternatively it may be rotated in the same direction as the first end operating position.

[0044] In the safety position, the first longitudinal channels 88 of the spool 40 do not overlap with the first ports 84 of the inner sleeve 46, but are nevertheless in fluid communication with these ports via a first safety groove 96 that extends along the periphery of the spool 40 and connects the first longitudinal channels 88 to each other, and thus in fluid communication with the first outlet port 62' (FIG. 6). Similarly, the second longitudinal channels 90 of the spool 40 do not overlap with the second ports 86 of the inner sleeve 46, but are nevertheless in fluid communication with these ports via a second safety groove 98 that extends along the periphery of the spool 40 and connects the second longitudinal channels 90 to each other, and thus in fluid communication with the second outlet port 62' (FIG. 6).

[0045] Thus, in the safety position, both the compression chamber 20 and the extension chamber 22 of the actuator 12 are in fluid communication with the low pressure line 32 through the aforementioned first safety groove 96 and the aforementioned second safety groove 98, respectively. The first safety groove 96 and the second safety groove 98 have a reduced cross-sectional flow area relative to both the first and second longitudinal channels 88, 90 of the spool 40 and the first and second ports 84, 86 of the inner sleeve 46, which allows movement of the rod 24 of the hydraulic actuator 12 to be "restrained" during both the extension and compression strokes.

[0046] A pair of check valves 100 and 102, hereinafter referred to as the first and second check valves, respectively, mounted on a valve block 104 attached to the valve body 38 (FIGS. 2 and 4) of the flow control valve 36, are also arranged to intervene in this condition. The first check valve 100 is arranged in the flow path indicated by arrow F1 in FIG. 4 between the second inlet port 60' (connected to the low pressure line 32) and the first outlet port 62' (connected to the compression chamber 20 of the hydraulic actuator 12), and is configured to allow hydraulic fluid to flow only in the direction from the second inlet port 60' to the first outlet port 62'. The second check valve 102 is arranged in the flow path indicated by arrow F2 in FIG. 4 between the second inlet port 60'' (also connected to the low pressure line 32) and the second outlet port 62'' (connected to the expansion chamber 22 of the hydraulic actuator 12), and is configured to allow hydraulic fluid to flow only in the direction from the second outlet port 62'' to the second inlet port 60''. If the rod 24 of the hydraulic actuator 12 is pushed downwards (compression movement), the working fluid cannot flow freely from the compression chamber 20 to the low pressure line 32, because this flow is prevented by the first check valve 100. However, at this stage, the working fluid can flow through both the first safety groove 96 and the second safety groove 98. The maximum pressure in the compression chamber 20 is then limited in turn by the pressure limiting valve V1 of the piston 18 of the hydraulic actuator 12, which regulates the pressure in the compression chamber 20 relative to the extension chamber 22, and by the second check valve 102, which regulates the pressure in the extension chamber 22 relative to the low pressure line 32. On the other hand, if the rod 24 of the hydraulic actuator 12 is pushed upwards (extension movement), the working fluid can flow from the extension chamber 22 to the low pressure line 32 through both the second safety groove 98 and the second check valve 102. The opening pressure of the latter valve can be varied using springs 106 with different stiffnesses and preloads to vary the damping characteristics of the hydraulic actuator 12 in the safe state.At this stage, hydraulic fluid is allowed to flow freely from the low pressure line 32 through the first check valve 100 to the compression chamber 20 of the hydraulic actuator 12, avoiding cavitation phenomena in this chamber.

[0047] When applied to a four-wheel vehicle as shown in the diagram of Fig. 16, the active suspension according to the invention includes, for each wheel, a respective actuator 12a, 12b, 12c, 12d and a respective flow control valve 36a, 36b, 36c, 36d configured as a rotary spool valve for controlling the force exerted by the actuator between the wheel of the vehicle associated with the actuator and the vehicle body. Each actuator 12a, 12b, 12c, 12d is connected to a respective high pressure line 28a, 28b, 28c, 28d and a respective low pressure line 32a, 32b, 32c, 32d via a respective flow control valve 36a, 36b, 36c, 36d. Each first pressure accumulator 100a, 100b, 100c, 100d is connected to each high pressure line 28a, 28b, 28c, 28d. On the other hand, as far as the low pressure lines 32a, 32b, 32c, 32d are concerned, in this example they are all connected to the same second pressure accumulator 102. In addition, in this example, a single pump 26 is provided that is capable of supplying pressurized fluid to all the high pressure lines 28a, 28b, 28c, 28d and therefore to all the actuators 12a, 12b, 12c, 12d. Alternatively, there may be two pumps, each arranged to supply pressurized fluid to two actuators associated with the wheels of one respective axle (front and rear axle) of the vehicle, or there may be four pumps, each arranged to supply pressurized fluid to actuators associated with one respective wheel of the vehicle.

[0048] The present invention has been described herein with reference to preferred embodiments thereof, it being understood that other embodiments may be envisioned that share the same inventive core as the embodiments described herein, as defined by the following claims.

Claims

1. An active suspension (10) for a vehicle, a hydraulic actuator (12) designed to be disposed between each wheel (W) of the vehicle and a body (B) of the vehicle, the hydraulic actuator (12) comprising a cylinder (16) and a piston (18) slidably mounted inside the cylinder (16) so as to divide the internal volume of the cylinder (16) into a pair of variable volume chambers (20, 22), a compression chamber (20) and a tension chamber (22), both of which contain a working fluid; a supply hydraulic circuit (14) connected to the hydraulic actuator (12) for supplying the hydraulic fluid to the compression chamber (20) and the expansion chamber (22); Including, the supply hydraulic circuit (14) comprises a hydraulic pump (26), a high pressure line (28) connected to a delivery port (30) of the hydraulic pump (26), a low pressure line (32) connected to a suction port (34) of the hydraulic pump (26), and a flow control valve (36) connected on one side to the compression chamber (20) and the extension chamber (22) of the hydraulic actuator (12) and connected on the other side to the high pressure line (28) and the low pressure line (32) so as to fluidly connect the compression and extension chambers (20, 22) of the hydraulic actuator (12) with the high pressure and low pressure lines (28, 32) of the supply hydraulic circuit (14); The flow control valve (36) is a spool valve including a spool (40) that is continuously movable between a plurality of operating positions in a first direction between a zero position and a first end operating position, and in a second direction opposite to the first direction between the zero position and a second end operating position; 1. An active suspension (10), comprising: a flow control valve (36) configured to connect at least one of the compression chamber (20) and the expansion chamber (22) of the hydraulic actuator (12) to the high pressure line (28) at each operating position of the spool (40) between the first and second end operating positions, 1. An active suspension (10), characterized in that the spool (40) of the flow control valve (36) is a rotating spool configured to move between the first and second end operating positions by rotation about an axis of rotation (x), the flow control valve (36) further comprising an actuation unit (42) for driving the spool (40) to rotate in one direction or the other about the axis of rotation (x), the actuation unit (42) being formed by an electric motor comprising a rotor (48) mounted coaxially with the spool (40), a stator (50) and a shaft (52) on which the rotor (48) is mounted in driving connection for rotation therewith, the shaft (52) being rigidly connected to the spool (40).

2. The suspension of claim 1 , wherein the shaft (52) of the electric motor is integrally formed with the spool (40).

3. 3. The suspension of claim 1 or 2, wherein the flow control valve (36) further comprises an outer body (44) serving as an outer housing for the valve including the actuation unit (42), and an inner sleeve (46) inserted into a cylindrical inner cavity (44a) of the outer body (44) and having a cylindrical inner cavity (46a), the axis of which defines the rotation axis (x), and within which the spool (40) is inserted.

4. the outer body (44) of the flow control valve (36) has at least one first inlet port (58) connected to the high pressure line (28), at least one second inlet port (60', 60") connected to the low pressure line (32), at least one first outlet port (62') connected to the compression chamber (20) of the actuator (12), and at least one second outlet port (62") connected to the expansion chamber (22) of the actuator (12); the inner sleeve (46) of the flow control valve (36) has a plurality of cylindrical regions (64, 66, 68, 70, 72) with fluid passage ports (80', 80", 82", 82") therein extending through the entire thickness of the inner sleeve (46), and a plurality of annular sectors (74) having a diameter greater than the diameters of the cylindrical regions (64, 66, 68, 70, 72) and spaced apart from one another in a fluid-tight manner; The plurality of cylindrical regions (64, 66, 68, 70, 72) are a pair of axially outermost cylindrical regions (64, 72) facing said at least one second inlet port (60') and said at least one second outlet port (60"), respectively, and having a plurality of first low pressure ports (80') and a plurality of second low pressure ports (80"), respectively; a central cylindrical region (68) having a plurality of first and second high pressure ports (82') and (82") disposed adjacent to two circumferential edges of the central cylindrical region (68) opposite the at least one first inlet port (58); a pair of axially intermediate cylindrical regions (66, 70) each disposed between a respective axially outermost cylindrical region (64, 72) and said central cylindrical region (68), one (68) of said axially intermediate cylindrical regions (66, 70) facing said at least one first outlet port (62') and having a plurality of first ports (84), and the other (70) of said axially intermediate cylindrical regions (66, 70) facing said at least one second outlet port (62") and having a plurality of second ports (86); Including, The spool (40) has on its outer cylindrical surface (40a) a plurality of first longitudinal channels (88) extending parallel to the axis of rotation (x) and having a length and configuration selectively overlapping with the first low pressure port (80'), the first port (84) and the first high pressure port (82'), and a plurality of second longitudinal channels (90) extending parallel to the axis of rotation (x) and each being specifically aligned with a respective first longitudinal channel (88) and having a length and configuration selectively overlapping with the second low pressure port (80'), the second port (86) and the second high pressure port (82'); the first longitudinal channel (88) and the second longitudinal channel (90) are circumferentially equally angularly spaced apart; 4. The suspension of claim 3, wherein the first longitudinal channels (88) are in fluid communication with each other via a first radial channel (92) and the second longitudinal channels (90) are in fluid communication with each other via a second radial channel (94).

5. 5. The suspension of claim 4, wherein the first low pressure port (80') and the second low pressure port (80") are disposed equally angularly spaced in the circumferential direction, and each of the first low pressure ports (80') and the second low pressure ports (80") preferably comprises four ports disposed at an angle of 90 degrees relative to each other, and the first low pressure port (80') is in particular offset at an angle of 45 degrees relative to the second low pressure port (80").

6. 6. The suspension of claim 4 or 5, wherein the first high pressure ports (82') are arranged on a first periphery at equal angular intervals, in particular at an angle of 90 degrees relative to each other, and the second high pressure ports (82') are arranged on a second periphery at equal angular intervals, in particular at an angle of 90 degrees relative to each other, and are offset at a particular angle, in particular an angle of less than 45 degrees, relative to the first high pressure ports (82').

7. 7. The suspension according to claim 4, wherein the first ports (84) and the second ports (86) are made in the form of slots elongated in the circumferential direction and are arranged angularly equally spaced in the circumferential direction, in particular there are four first ports (84) and four second ports (86) arranged at an angle of 90 degrees to one another.

8. 8. The suspension of claim 4, wherein the spool (40) of the flow control valve (36) further comprises a first safety groove (96) extending along the periphery of the spool (40) and connecting the first longitudinal channels (88) to one another, and a second safety groove (98) extending along the periphery of the spool (40) and connecting the second longitudinal channels (90) to one another, the first and second safety grooves (96, 98) having a reduced flow cross-sectional area compared to both the first and second longitudinal channels (88, 90) of the spool (40) and the first and second ports (84, 86) of the inner sleeve (46).

9. 9. The suspension of claim 4, further comprising: a first check valve (100) disposed in a flow path (F1) between the at least one second inlet port (60') and the at least one first outlet port (62') and configured to allow the working fluid to flow only in a direction from the at least one second inlet port (60') to the at least one first outlet port (62'); and a second check valve (102) disposed in a flow path (F2) between the at least one second inlet port (60') and the at least one second outlet port (62') and configured to allow the working fluid to flow only in a direction from the at least one second outlet port (62') to the at least one second inlet port (60').

10. The flow control valve (36) In the null position of the spool (40), both the compression chamber (20) and the expansion chamber (22) of the hydraulic actuator (12) are connected only to the high pressure line (28) and to each other via the flow control valve (36); In the first end operating position of the spool (40), the compression chamber (20) is connected only to the high pressure line (28) while the expansion chamber (22) is connected only to the low pressure line (32); at each intermediate operating position of the spool (40) between the zero position and the first end operating position, the compression chamber (20) is connected only to the high pressure line (28), while the expansion chamber (22) is connected to the high pressure line (28) and / or the low pressure line (32); In the second end operating position of the spool (40), the expansion chamber (22) is connected only to the high pressure line (28) while the compression chamber (20) is connected only to the low pressure line (32); 10. The suspension according to claim 1, wherein in each intermediate operating position of the spool (40) between the zero position and the second end operating position, the expansion chamber (22) is connected only to the high pressure line (28), while the compression chamber (20) is connected to the high pressure line (28) and / or the low pressure line (32).

11. 11. The suspension of claim 1, wherein the flow control valve (36) is also configured such that the spool (40) is movable to a safe position in which both the compression chamber (20) and the expansion chamber (22) of the hydraulic actuator (12) are connected only to the low pressure line (32).

12. 12. The suspension of claim 8 and 11, wherein the flow control valve (36) is configured such that, in the safety position, the compression chamber (20) and the expansion chamber (22) of the hydraulic actuator (12) are connected to the low pressure line (32) via the first safety groove (96) and the second safety groove (98), respectively.

13. 13. The suspension according to claim 11 or 12, wherein the flow control valve (36) further comprises elastic means (54), in particular a torsion bar, arranged to exert an elastic reaction torque on the spool (40) tending to move the spool (40) towards the safe position.

14. A vehicle comprising a body (B), a plurality of wheels (W) and, for each wheel (W), a respective suspension (10) according to any one of claims 1 to 13.

15. 15. The vehicle of claim 14, wherein the supply hydraulic circuit (14) comprises a single hydraulic pump (26) adapted to supply all the hydraulic actuators (12a, 12b, 12c, 12d) via respective high pressure lines (28a, 28b, 28c, 28d) or a first hydraulic pump adapted to supply all the hydraulic actuators associated with the wheels of a first axle of the vehicle via respective high pressure lines and a second hydraulic pump adapted to supply all the hydraulic actuators associated with the wheels of a second axle of the vehicle via respective high pressure lines, and / or for each hydraulic actuator a respective hydraulic pump adapted to supply it via a respective high pressure line.

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