Safety braking device for a steering system, steering system

Abstract

The subject of the present invention is a safety braking device (1) for a steering system (100) of a vehicle, comprising a cylinder (2) that delimits a housing (3), a piston (4) housed in the housing (3) of the cylinder (2), wherein the piston (4), together with the housing (3), delimits a first chamber (5) and a second chamber (6), at least one connection element (7) configured to fluidically connect the first chamber (5) and the second chamber (6), wherein the first chamber (5), the second chamber (6), and the connection element (7) are configured to contain a working fluid (F), wherein the piston (4) is translatably movable in the housing (3) of the cylinder (2) by moving the working fluid (F) through the at least one connection element (7) from the first chamber (5) to the second chamber (6), and / or vice versa, wherein the piston (4) is indirectly connectable to a steering wheel (101) of the steering system (100) such that a rotation of the steering wheel (101) is transformed into a translation of the piston (4) in the housing (3) of the cylinder (2), and vice versa, and such that a translational speed of the piston (4) and a rotational speed of the steering wheel (101) are mutually correlated, wherein the safety braking device (1) comprises fluid resistance means (8, 9) arranged along the at least one connection element (7), wherein the fluid resistance means (8, 9) are configured to selectively control a fluid flow rate of the working fluid (F) from the first chamber (5) to the second chamber (6), and vice versa, such that when the fluid flow rate of the working fluid (F) is below a threshold flow rate and / or the translational speed of the piston is below a threshold translational speed and / or the rotational speed of the steering wheel is below a threshold rotational speed, the working fluid (F) passes through the at least one connection element (7) from the first chamber (5) to the second chamber (6), or vice versa, without hindering the translation of the piston (4) and the rotation of the steering system (100), and when the fluid flow rate of the working fluid (F) reaches the threshold flow rate and / or the translational speed of the piston reaches the threshold translational speed and / or the rotational speed of the steering wheel reaches the threshold rotational speed, the working fluid (F) is hindered or blocked from passing through the at least one connection element (7) from the first chamber (5) to the second chamber (6), or vice versa, thereby hindering or blocking the translation of the piston (4) and the rotation of the steering system (100).

Description

"Safety braking device for a steering system, steering system"***DESCRIPTION

[0001] . Field of the inventionThe subject of the present invention is a safety braking device for a steering system, as well as a steering system comprising said safety braking device.

[0002] . Prior art

[0003] . Steering systems are known which comprise a steering wheel, a steering shaft, a steering box, right-side steering arms and left-side steering arms connected respectively to the right wheel and to the left wheel. The driver of the vehicle acts on the steering wheel by rotating it to steer the vehicle, wherein the rotation of the steering wheel is transferred to the steering box through the steering shaft, and the steering box is configured to convert the rotation of the steering wheel into a translational-rectilinear motion that acts on the steering arms, moving the wheels to change the direction of the vehicle.

[0004] . In the event of a car accident, on the road or during a car race, the steering wheel may rotate at very high speed due to sudden and uncontrollable turns of the wheels during the impact, and if the driver does not manage to remove his / her hands from the steering wheel in time, the hands are also dragged at very high speed in torsion with the steering wheel, causing injuries and fractures to the hands and upper limbs.

[0005] . There is therefore a strongly felt need in the field to implement a safety braking device to block or limit the rotation of the steering wheel of a vehicle in case of an accident.

[0006] . Solution

[0007] . These and other aims are achieved by means of a safety braking device for a steering system of a vehicle, and a steering system according to the independent claims.

[0008] . Some advantageous embodiments are the subject of the dependent claims.

[0009] . According to one aspect, the solution makes it possible to hinder or block the rotation of the steering wheel when a speed threshold is reached by an element of the steering system, for example the speed threshold is a rotational speed threshold of the steering wheel, or of the wheels, or is a translational speed threshold of the steering box, regardless of the angular position of the steering wheel or the angular position of the wheels. In this way, the safety braking device is transparent for the driver, who does not notice its presence during normal use of the vehicle, and only once the speed threshold has been reached by the steering system, the safety braking device is perceptible by the driver by hindering or blocking the rotation of the steering wheel, thus giving the driver the possibility of avoiding the dragging of his / her hands by the steering wheel during sudden rotations at speedsexceeding a maximum safety speed.

[0010] . According to one aspect, a safety braking device or system is provided for a steering system of a vehicle which operates only if the front wheels of the vehicle steer abruptly, for example in case of collision, and which is instead completely transparent to the driver in all other vehicle manoeuvring situations, so as not to interfere with his / her driving.

[0011] . According to one aspect, the safety braking device comprises a cylinder or hydraulic cylinder, said cylinder providing a first chamber and a second chamber, mutually hydraulically connected by a connection element, for example through a hydraulic conduit, and containing a working fluid or hydraulic fluid free to flow between the two chambers, a piston or translating piston which can translate linearly as a function of the rotation of the steering wheel during manoeuvres performed by a driver, said piston physically separating said first chamber from said second chamber, being arranged for example in such a way that said first chamber is on the left of the translating piston and said second chamber is on the right of the translating piston, the connection element between the first and the second chambers being shaped so that the working fluid flows freely between said first and second chamber when the fluid flow rate has a value below a threshold value, and the connection element between the first and second chambers being suitably shaped so as to limit or prevent the fluid from flowing between said first and second chamber when the fluid flow rate has a value that exceeds the threshold value. For example, the connection element or the hydraulic conduit may provide a calibrated hole or a valve that allows or prevents the fluid from flowing between said first and second chamber depending on whether the flow rate value of the fluid is respectively lower than or equal to a threshold value.

[0012] . According to one aspect, the safety braking device can be directly connected to the steering box of the vehicle, for example it can be connected directly to the linear movement of the steering rack and pinion, or rack and pinion of a rack-and-pinion assembly, by fixing at least one side of the translating piston, or by fixing both sides of the translating piston.

[0013] . According to one aspect, the safety braking device can be connected to the steering shaft, for example indirectly, by means of a toothed wheel-rack and pinion assembly which allows the rotary movement of the shaft to be converted into translatory movement of the translating piston.

[0014] . thanks to the proposed solutions, it is possible to hinder or block the rotation of the steering wheel when the front wheels of the vehicle or the steering wheel turn abruptly at a speed equal to the threshold speed, with a safety braking device having a reduced number of components and implementable in a simple manner in a steering system of a vehicle.

[0015] . Figures

[0016] . Further features and advantages of the invention will appear from the description set out below of preferred embodiments thereof, given by way of non-limiting example, with reference tothe accompanying figures in which:

[0017] . - Figure 1 schematically and in section represents a safety braking device for a steering system of a vehicle, wherein the braking device comprises a cylinder inside which a piston is housed translatably, said piston being operatively connected to an element of the steering system in such a way that a rotation of the steering system, for example of the steering wheel, corresponds to a translation of the piston, wherein the piston internally separates the cylinder into two chambers containing a working fluid, the two chambers being fluidically interconnected by a connection element, so that the piston by translating displaces the working fluid from one chamber to the other varying their volume, wherein fluid resistance means are provided which selectively act on the flow rate of the working fluid from one chamber to the other when the flow rate of the working fluid reaches a predefined threshold, and consequently when the rotational speed of the steering system, for example of the steering wheel, as well as the translational speed of the piston, reach respective predefined thresholds, so that when the flow rate of the working fluid is lower than the predefined threshold, the fluid is free to flow from one chamber to the other, the piston is free to translate and the safety braking device does not influence the rotation of the steering system, and is therefore completely invisible to the driver, whereas when the flow rate of the working fluid reaches the predefined threshold, the passage of the fluid is hindered or possibly blocked, hindering or blocking the translation of the piston and the rotation of the steering wheel or preventing the translational speed of the piston and the rotational speed of the steering wheel from going beyond a maximum translational speed value and a maximum rotational speed value respectively;

[0018] . - Figure 2A schematically and in section illustrates a safety braking device for a steering system of a vehicle according to the present invention, wherein the fluid resistance means are arranged on the thrust head of the piston, for example in a conduit axially passing through the thrust head of the piston;

[0019] . - Figure 2B illustrates in a front view a piston implementable in the device of figure 2A, wherein four conduits are shown that pass through the thickness of the piston thrust head axially so as to fluidly connect the first chamber and the second chamber;

[0020] . axially so as to fluidly connect the first chamber and the second chamber;

[0021] . - Figure 3 schematically illustrates the safety braking device of figure 1 according to a first embodiment, wherein the fluid resistance means comprise a normally open valve, configured to close when the speed of the piston reaches the predefined threshold, wherein the normally open valve is in the open configuration;

[0022] . - Figure 4 illustrates the safety braking device of figure 3, wherein the normally open valve is in the closed configuration;

[0023] . - Figure 5 schematically illustrates the safety braking device of figure 1 or of figure 2according to a second embodiment, wherein the fluid resistance means comprise a calibrated hole which forms an obstruction to the passage of the fluid that affects the movement of the piston only when the speed of the piston reaches the predefined threshold, consequently hindering the translation of the piston and hindering the rotation of the steering system, for example of the steering wheel, and limiting the translational speed of the piston and the rotational speed of the steering wheel to a maximum translational speed value and to a maximum rotational speed value, wherein in the figure the piston is free to translate and the calibrated hole does not affect the translation of the piston;

[0024] . - Figure 6 illustrates the safety braking device of figure 5, wherein the calibrated hole has reached the flow rate limit of the passage of the working fluid from one chamber to the other, and a pressure difference is formed between the first chamber and the second chamber, when the predetermined speed threshold is reached, which hinders, slows down until preventing an increase in the translational speed of the piston and consequently an increase in the rotational speed of the steering system beyond a maximum translational speed value and a maximum rotational speed value;

[0025] . - Figure 7 illustrates a steering system according to the present invention comprising a safety braking device according to the present invention directly connected to the linear movement of the steering rack and pinion or to a translating element of the steering box;

[0026] . - Figure 8 illustrates a steering system according to the present invention comprising a safety braking device according to the present invention, connected to the steering shaft, preferably indirectly through a toothed wheel-rack and pinion assembly configured to transform the rotary movement of the steering shaft into a translatory movement of the rack and pinion and of the translating piston connected thereto.

[0027] . Description of some preferred embodiments

[0028] . In accordance with a general embodiment, a safety braking device 1 for a steering system 100 of a vehicle is denoted by the reference number 1 .

[0029] . The safety braking device 1 comprises a cylinder 2 delimiting a housing 3.

[0030] . The safety braking device 1 comprises a piston 4 at least partially housed in the housing 3 of the cylinder 2. The piston 4 delimits with the housing 3 a first chamber 5 and a second chamber 6.

[0031] . The safety braking device 1 comprises at least one connection element 7 configured to fluidly connect the first chamber 5 and the second chamber 6. The first chamber 5, the second chamber 6 and the connection element 7 are configured to contain a working fluid F. In accordance with an embodiment, the safety braking device 1 comprises the working fluid F which fills the first chamber 5, the second chamber 6 and the connection element 7. In one embodiment, the working fluid F is a brake fluid, or a fluid substantially incompressible at the normal operating temperatures of the vehicle.

[0032] . The piston 4 is translationally movable along an axial direction A-A in the housing 3 of the cylinder 2 by moving the working fluid F through the at least one connection element 7 from the first chamber 5 to the second chamber 6, and / or vice versa. In one embodiment, the first chamber 5 defines a first chamber volume and the second chamber 6 defines a second chamber volume, wherein the piston moves the working fluid from one chamber to the other increasing the first chamber volume and correspondingly reducing the second chamber volume, or vice versa.

[0033] . The piston 4 is indirectly connectable to a steering wheel 101 of the steering system 100 so that a rotation of the steering wheel 101 is transformed into a translation of the piston 4 in the housing 3 of the cylinder 2, and vice versa, and so that a piston translation speed or linear speed of the piston 4 and a steering wheel rotation speed or angular speed of the steering wheel 101 are mutually correlated.

[0034] . The safety braking device 1 comprises fluid resistance means 8, 9 arranged along the at least one connection element 7. In one embodiment the at least one connection element 7 comprises respective fluid resistance means 8, 9.

[0035] . The fluid resistance means 8, 9 are configured to control a fluid flow rate of the working fluid F from the first chamber 5 to the second chamber 6, and vice versa, so that when the fluid flow rate of the working fluid F is lower than a threshold fluid flow rate, the working fluid F passes through the at least one connection element 7 from the first chamber 5 to the second chamber 6, or vice versa, without hindering the translation of the piston 4 and the rotation of the steering system 100, and when the fluid flow rate of the working fluid F reaches the threshold fluid flow rate, the working fluid F is hindered or blocked from passing through the at least one connection element 7 from the first chamber 5 to the second chamber 6, or vice versa, hindering or blocking the translation of the piston 4 and the rotation of the steering system 100. In one embodiment, when the fluid flow rate of the working fluid F reaches the threshold fluid flow rate, the piston translation speed and the steering wheel rotation speed may increase up to a maximum translation speed value and a maximum rotation speed value with no possibility of going beyond said values.

[0036] . In one embodiment, since the fluid flow rate of the working fluid is directly correlatable to the piston translation speed and to the steering wheel rotation speed, the fluid resistance means 8, 9 are configured to selectively control the piston translation speed and / or the steering wheel rotation speed, so that when the piston translation speed is lower than a threshold translation speed and / or when the steering wheel rotation speed is lower than a threshold rotation speed, the working fluid F passes through the at least one connection element 7 from the first chamber 5 to the second chamber 6, or vice versa, without hindering the translation of the piston 4 and the rotation of the steering wheel 101 , and when the piston translation speed reaches the threshold translation speed and / or the steering wheel rotation speed reaches the threshold rotation speed, the working fluid F is hinderedfrom passing through the at least one connection element 7 from the first chamber 5 to the second chamber 6, or vice versa, hindering or blocking the translation of the piston 4 and the rotation of the steering system 100 or preventing the piston translation speed and the steering wheel rotation speed from increasing beyond a maximum translation speed value and a maximum rotation speed value. In one embodiment, the steering wheel rotation speed and the piston translation speed are correlated by a mathematical law. In one embodiment, the mathematical law depends on the kinematic chain of mechanical connections between the steering wheel and the safety device.

[0037] . Thanks to the proposed solution, the safety braking device, by virtue of the configuration of the at least one connection element 7 and / or of the fluid resistance means 8, 9, acts selectively on the rotation of the steering wheel and / or on the translation of the piston, so that for steering wheel rotation speeds below a threshold rotation speed, the rotation of the steering wheel is not affected, and when the rotation speed of the steering wheel reaches the threshold rotation speed, the rotation of the steering wheel is blocked or limited, to allow the driver to release the grip from the steering wheel. In this way it is possible to implement a safety braking device that is independent of the angular position of the steering wheel, and depends only on the angular speed or rotation speed of the steering wheel.

[0038] . In one embodiment, the fluid resistance means 8, 9 comprise a valve 9 interposed in the at least one connection element 7. In one embodiment, the valve 9 is controlled by a control unit 10. In one embodiment, the fluid resistance means 8, 9 comprise the valve 9 and the control unit 10. In one embodiment, the control unit 10 is configured to selectively close the valve 9 when the fluid flow rate of the working fluid F reaches the threshold fluid flow rate. In one embodiment, the control unit 10 is configured to selectively close the valve 9 when the piston translation speed reaches the threshold translation speed and / or the steering wheel rotation speed reaches the threshold rotation speed. In accordance with one embodiment, the control unit 10 is operatively connected to at least one sensor configured to detect a threshold value of the fluid flow rate or of the piston translation speed or of the steering wheel rotation speed. In one embodiment, the control unit 10 is operatively connected to at least one rotation speed sensor configured to measure the steering wheel rotation speed.

[0039] . In one embodiment, the valve 9 is a normally open valve, such as a solenoid valve, wherein the control unit 10, by closing the valve 9, prevents any passage of fluid from the first chamber 5 to the second chamber 6, or vice versa, blocking the translation of the piston 4 and preventing the rotation of the steering wheel 101 , and setting the piston translation speed and the steering wheel rotation speed to zero. In one embodiment, the fluid resistance means 8, 9 comprise said valve 9 for each connection element 7, avoiding the inclusion of additional valves.

[0040] . In one embodiment, the fluid resistance means 8, 9 comprise a calibrated hole 8. Inone embodiment, the calibrated hole 8 is interposed in the at least one connection element 7 between the first chamber 5 and the second chamber 6. In one embodiment, each connection element 7 comprises a respective calibrated hole 8. In one embodiment, the calibrated hole 8 is made as a separate piece with respect to the connection element or the hydraulic conduit, and inserted into the connection element or the hydraulic conduit.

[0041] . In one embodiment, when the fluid flow rate of the working fluid F reaches the threshold fluid flow rate, the calibrated hole 8 hinders the movement of the working fluid F between the first chamber 5 and the second chamber 6, or vice versa, limiting an increase in the piston translation speed to a maximum translation speed value greater than or equal to the threshold translation speed, and / or limiting the steering wheel rotation speed to a maximum rotation speed value greater than or equal to the threshold rotation speed, and generating a pressure difference of the working fluid F between the first chamber 5 and the second chamber 6.

[0042] . In one embodiment, the calibrated hole 8 is an orifice disk inserted in the at least one connection element 7.

[0043] . In one embodiment, the calibrated hole 8 is a machining made in the at least one connection element 7.

[0044] . In one embodiment, the calibrated hole 8 is a passive device. In one embodiment, the fluid resistance means 8, 9 comprise each calibrated hole 8, avoiding the inclusion of valves controllable by a control unit 10. In one embodiment, the fluid resistance means 8, 9 comprise each calibrated hole 8, making the safety braking device 1 a device always in operation and purely mechanical, without the need for any control unit to control the movement of the working fluid F between the first chamber 5 and the second chamber 6, or vice versa.

[0045] . In one embodiment, the calibrated hole 8 forms a calibrated geometric restriction in the at least one connection element 7 that is always open. In one embodiment, the calibrated hole 8 forms a calibrated geometric restriction in the at least one connection element 7 that is always open, without providing control or activation systems for the calibrated hole 8.

[0046] . In one embodiment, since the fluid flow rate of the working fluid F is directly correlatable to the piston translation speed and / or to the steering wheel rotation speed, when the piston translation speed reaches the threshold translation speed and / or when the steering wheel rotation speed reaches the threshold rotation speed, the calibrated hole 8 hinders the movement of the working fluid F between the first chamber 5 and the second chamber 6, or vice versa, limiting the piston translation speed to a maximum translation speed value greater than or equal to the threshold translation speed, and limiting the steering wheel rotation speed to a maximum rotation speed value greater than or equal to the threshold rotation speed, and generating a pressure difference of the working fluid F between the first chamber 5 and the second chamber 6. In one embodiment, thethreshold rotation speed is 1000 degrees / second. In one embodiment, the maximum rotation speed value is 3000 degrees / second.

[0047] . In one embodiment, the calibrated hole 8 has a calibrated hole diameter D comprised between a few tenths of a millimetre and several millimetres, depending on the size of the cylinder and the piston.

[0048] . In one embodiment, the at least one connection element 7 extends between a respective first chamber opening 11 facing and / or leading into the first chamber 5 of the housing 3 and a respective second chamber opening 12 facing and / or leading into the second chamber 6.

[0049] . In one embodiment, the at least one connection element 7 is a hydraulic conduit obtained in a wall of the cylinder 2, for example in the thickness of the side wall of the cylinder 2. In one embodiment, the at least one connection element 7 is a hydraulic conduit that is made in a separate piece with respect to the cylinder 2 and is configured to put the first chamber 5 and the second chamber 6 in fluid communication in a fluid-tight manner. In one embodiment, the piston 4 translates in a fluid-tight manner in the cylinder 2, thanks to seals with geometry and material of low coefficient of friction. In one embodiment, the first chamber opening 11 is obtained in a side wall 15 of the cylinder 2 facing the first chamber 5, so that the hydraulic conduit is in fluid communication with the first chamber, and the second chamber opening 12 is obtained in the side wall 15 of the cylinder 2, so that the hydraulic conduit is in fluid communication with the second chamber. In one embodiment, the first chamber opening 11 and the second chamber opening 12 are arranged on axially opposite parts with respect to the axial direction of translation of the piston 4 so that the hydraulic conduit is in fluid communication with the second chamber and with the first chamber for any operating position along the axial direction A-A of the piston 4.

[0050] . In one embodiment, the at least one connection element 7 is a conduit passing through a thrust head 16 of the piston 4. In one embodiment, the at least one connection element 7 comprises at least one, preferably at least two or at least four, conduits passing through a thrust head 16 of the piston 4. In one embodiment, the at least one connection element 7 comprises at least one, preferably four, conduits passing through the axial thickness of the thrust head 16 of the piston 4. In one embodiment, the at least one connection element 7 comprises at least a first connection element and a second connection element each forming a respective conduit passing through the thrust head 16 of the piston 4, wherein the safety braking device 1 comprises one fluid resistance means 8, 9 of said fluid resistance means 8, 9 for each connection element 7. In one embodiment, in each connection element 7 respective fluid resistance means are arranged. In one embodiment, in each connection element 7 a respective calibrated hole is arranged or made. In one embodiment, the first chamber opening 11 is obtained on a first thrust head surface 23 of the thrust head 16 which is facing the first chamber 5, so that the hydraulic conduit is in fluid communication with the first chamber 5,and the second chamber opening 12 is obtained on a second thrust head surface 24 of the thrust head 16 which is facing the second chamber 6, so that the hydraulic conduit is in fluid communication with the second chamber. In one embodiment, the first thrust head surface 23 and the second thrust head surface 24 are perpendicular to the axial direction A-A, axially opposite and separated by the thickness of the thrust head 16. In one embodiment, the first thrust head surface 23 and the second thrust head surface 24 have the same facing surface value respectively towards the first chamber and the second chamber, so that the piston 4 pushes the working fluid F symmetrically following one direction or the opposite direction along the axial direction.

[0051] . In one embodiment, the connection element 7 of the hydraulic conduit must not affect the fluid flow rate between the two chambers. In other words, the diameter of the connection element or of the hydraulic conduit is greater than the diameter of the calibrated hole. In one embodiment, the cylinder 2 comprises a first chamber bottom wall 13 and a second chamber bottom wall 14, opposite to each other along an axial direction A-A along which the piston 4 translates. In one embodiment, the cylinder 2 comprises at least one side wall 15 extending parallel to the axial direction A-A and connecting the first chamber bottom wall 13 and the second chamber bottom wall 14.

[0052] . In one embodiment, the piston 4 comprises a thrust head 16 housed in the housing 3 in a fluid-tight manner with the at least one side wall 15 and configured to push the working fluid from the first chamber 5 to the second chamber 6, and vice versa.

[0053] . In one embodiment, the piston 4 comprises at least one rod 17, 18 connected to the thrust head 16, and wherein the at least one rod 17, 18 has, on a side axially opposite to the thrust head 16, a respective connection interface 19, 20 to connect the piston 4 to the steering system 100. In one embodiment, the at least one rod 17, 18 is fluid-tight connected to a respective bottom opening 21 , 22 made in a respective one of the first chamber bottom wall 13 and the second chamber bottom wall 14, so that the respective connection interface 19, 20 is always outside the housing 3 of the cylinder 2 for any working position of the piston 4 in the cylinder 2.

[0054] . In one embodiment, the safety braking device 1 is independent of a power steering device, hydraulic or electrohydraulic or electromechanical, configured to assist the steering system 100. In one embodiment, the safety braking device 1 is not connected to a hydraulic circuit of a power steering device configured to assist the steering system 100 in changing the vehicle's direction.

[0055] . In one embodiment, the piston 4 comprises a first chamber rod 17 and a second chamber rod 18, connected to the thrust head 16 from axially opposite sides, for example at the first thrust head surface 23 and the second thrust head surface 24. In one embodiment, the first chamber rod 17 comprises a first connection interface 19 to connect the piston 4 on one side to the steering system 100, and the second chamber rod 18 comprises a second connection interface 20 to connect the piston 4 on an axially opposite side to the steering system 100. In one embodiment, the firstchamber rod 17 and the second chamber rod 18 pass in a fluid-tight manner respectively through a first chamber bottom opening 21 made in the first chamber bottom wall 13 and a second chamber bottom opening 22 made in the second chamber bottom wall 14, so that the first connection interface 19 and the second connection interface 20 are always outside the housing 3 for any axial working position of the piston 4.

[0056] . In one embodiment, the cylinder 2 delimits at least one vent port to discharge the working fluid F during a testing or maintenance step. In one embodiment, the cylinder 2 delimits at least one supply port to introduce the working fluid F into the housing and the connection element 7.

[0057] . In one embodiment, the thrust head 16 has a disc-shaped head body. In one embodiment, each rod 17, 18 has a cylindrical-shaped body.

[0058] .

[0059] . In one embodiment, the piston 4 has a T-shaped cross section in a section parallel to the axial direction A-A and passing through one of the at least one rod 17, 18 and the thrust head 16. In one embodiment, the piston 4 has a cross-shaped section in a section parallel to the axial direction A-A and passing through the first chamber rod 17 and the second chamber rod 18 and the thrust head 16.

[0060] . In one embodiment, the flow rate that a chamber can support is determined by the selected diameters of piston and rod and by the piston translation speed, which is mathematically correlated to the steering wheel rotation speed. The calibrated hole is sized to allow the flow to pass freely up to a threshold flow rate. Once the selected diameters of the piston and the rod are defined, the variable is the piston translation speed, so that below a threshold flow rate there is no slowing of the piston, and above it there is a slowing.

[0061] . The present invention also concerns a steering system 100 for a vehicle.

[0062] . The steering system 100 comprises a steering wheel 101 configured to be rotated by a driver of the vehicle, a steering device 107 configured to transform a rotation of the steering wheel 101 into a translation of at least one right-side steering arm 103 and of at least one left-side steering arm 104 to steer the vehicle, wherein the at least one right-side steering arm 103 and the at least one leftside steering arm 104 are connectable respectively to a right wheel 105 and to a left wheel 106.

[0063] . Advantageously, the steering system 100 comprises a safety braking device 1 according to any one of the embodiments previously described, wherein the piston 4 is indirectly connected to the steering wheel 101 of the steering system 100.

[0064] . In one embodiment, the steering wheel 101 is rotatable around a respective rotation axis by at least 180 degrees. In one embodiment, the steering wheel 101 is rotatable around a respective rotation axis by at least 360 degrees. In one embodiment, the steering wheel 101 is rotatable around a respective rotation axis by at least 720 degrees.

[0065] . In one embodiment, the steering system 100 comprises the at least one right-side steering arm 103 and the at least one left-side steering arm 104. In one embodiment, the steering system 100 comprises the right wheel 105 and the left wheel 106.

[0066] . In one embodiment, the steering device 107 is a steering box, and the piston 4 is directly connected to the steering box.

[0067] . In one embodiment, the steering device 107 comprises a steering rack and pinion 108, and the piston 4 is connected with one or both axial ends, namely the first connection interface 19 and the second connection interface 20, to the steering rack and pinion 108.

[0068] . In one embodiment, the steering system 100 comprises a steering shaft 102 connected to the steering wheel and rotatable with the steering wheel 101 , wherein the steering shaft 102 connects the steering wheel 101 to the steering device 107.

[0069] . In one embodiment, the piston 4 is connected to the steering shaft 102, through a toothed wheel-rack and pinion assembly 109 configured to transform the rotary movement of the steering shaft 102 into translatory movement of the piston 4. In one embodiment, the toothed wheelrack and pinion assembly 109 comprises a toothed wheel 110 connected to the steering shaft 102 and a rack and pinion 111 , and the piston 4 is connected with one or both axial ends, namely the first connection interface 19 and the second connection interface 20, to the rack and pinion 111.

[0070] . In one embodiment, the steering system 100 comprises a power steering device, hydraulic or electrohydraulic or electromechanical, configured to assist the steering system 100 in changing the direction of the vehicle. In one embodiment, the safety braking device 1 is independent of the power steering device.

[0071] . Below is described a mode of operation of the steering braking device.

[0072] . Under standard manoeuvring conditions of the vehicle, the steering braking device is completely transparent to the driver, wherein the rotation of the steering wheel generates translations of the piston which displace the fluid from the first chamber to the second chamber, or vice versa, at steering wheel rotation speeds and piston translation speeds respectively below a threshold rotation speed and a threshold translation speed, with a working fluid flow rate passing through the connection element, without generating pressure differences between the first chamber and the second chamber, wherein the fluid flow rate under standard manoeuvring conditions of the vehicle is below a threshold fluid flow rate. Within the present description, with steering braking device being completely transparent to the driver, it is meant that in the steering braking device as constructed, the mechanical friction generated during the piston movement is negligible as compared to the inertia of the steering system to which the steering braking device is connected.

[0073] . Under standard manoeuvring conditions of the vehicle, the piston translates towards the first chamber or towards the second chamber depending on the direction of rotation of thevehicle's steering wheel, wherein the translation of the piston modifies the volume associated with each of the two chambers and available to the hydraulic fluid contained therein, wherein the translation of the translating piston reduces the volume of one of said first or second chambers and simultaneously increases the volume of the other of said second or first chambers, and the working fluid contained in said second chamber is brought to flow towards said first chamber, without generating a pressure difference between said first and second chambers.

[0074] . In impact conditions of the vehicle with any obstacle, when the rotation speed of the steering wheel reaches the threshold rotation speed, then the translation speed of the piston reaches the threshold translation speed and the working fluid reaches the threshold fluid flow rate and the fluid resistance means block the flow from the first chamber to the second chamber, or vice versa, or limit the flow from the first chamber to the second chamber, or vice versa, blocking or limiting, generating a pressure difference between the first chamber and the second chamber, the translation of the piston and, consequently, the rotation of the vehicle's steering wheel.

[0075] . For example, as long as the steering wheel rotation speed is less than or equal to 1000 degrees / second, the steering braking device is completely transparent to the driver. When the steering wheel rotation speed is between 1000 degrees / second and 3000 degrees / second, the steering braking device is perceptible by the driver and hinders the rotation of the steering wheel.

[0076] . Thanks to the proposed solutions, the safety braking device for a steering system allows avoiding performance reductions of the steering system during normal operation, wherein the braking device is transparent to the driver.

[0077] . Thanks to the proposed solutions, the safety braking device for a steering system allows, in the event of an accident, to limit the steering speed or the steering wheel speed to a safety value whereby the driver has time to release his / her hands from the steering wheel and avoid their impact against the vehicle frame.REFERENCE LIST1 . safety braking device2. cylinder3. housing4. piston5. first chamber6. second chamber7. connection element8. fluid resistance means or calibrated hole9. fluid resistance means or normally open valve10. control unit11 . first chamber opening12. second chamber opening13. first chamber bottom wall14. second chamber bottom wall15. side wall16. thrust head17. first chamber rod18. second chamber rod19. first connection interface20. second connection interface21 . first chamber bottom opening22. second chamber bottom opening23. first thrust head surface24. second thrust head surface100 steering system101 steering wheel102 steering shaft103 right-side steering arm104 left-side steering arm105 right wheel106 left wheel107 steering device108 steering rack and pinion109 toothed wheel-rack and pinion assembly110 toothed wheel111 rack and pinionF working fluid

Claims

CLAIMS1. A safety braking device (1 ) for a steering system (100) of a vehicle, comprising a cylinder (2) delimiting a housing (3), a piston (4) housed in the housing (3) of the cylinder (2), wherein the piston (4) delimits with the housing (3) a first chamber (5) and a second chamber (6), at least one connection element (7) configured to fluidly connect the first chamber (5) and the second chamber (6), wherein the first chamber (5), the second chamber (6) and the connection element (7) are configured to contain a working fluid (F), wherein the piston (4) is translationally movable in the housing (3) of the cylinder (2) by moving the working fluid (F) through the at least one connection element (7) from the first chamber (5) to the second chamber (6), and / or vice versa, wherein the piston (4) is indirectly connectable to a steering wheel (101 ) of the steering system (100) so that a rotation of the steering wheel (101) is transformed into a translation of the piston (4) in the housing (3) of the cylinder (2), and vice versa, and so that a piston translation speed of the piston (4) and a steering wheel rotation speed of the steering wheel (101 ) are mutually correlated, wherein the safety braking device (1 ) comprises fluid resistance means (8, 9) arranged along the at least one connection element (7), wherein the fluid resistance means (8, 9) are configured to selectively control a fluid flow rate of the working fluid (F) from the first chamber (5) to the second chamber (6), and vice versa, so that when the fluid flow rate of the working fluid (F) is lower than a threshold fluid flow rate and / or the piston translation speed is lower than a threshold translation speed and / or when the steering wheel rotation speed is lower than a threshold rotation speed, the working fluid (F) passes through the at least one connection element (7) from the first chamber (5) to the second chamber (6), or vice versa, without hindering the translation of the piston (4) and the rotation of the steering system (100), and when the fluid flow rate of the working fluid (F) reaches the threshold fluid flow rate and / or the piston translation speed reaches the threshold translation speed and / or the steering wheel rotation speed reaches the threshold rotation speed, the working fluid (F) is hindered or blocked from passing through the at least one connection element (7) from the first chamber (5) to the second chamber (6), or vice versa, hindering or blocking the translation of the piston (4) and the rotation of the steering system (100).

2. A safety braking device (1 ) according to the preceding claim, wherein the fluid resistance means (8,9) comprise a valve (9) interposed in the at least one connectionelement (7) controlled by a control unit (10), wherein the control unit (10) is configured to selectively close the valve (9) when the fluid flow rate of the working fluid (F) reaches the threshold fluid flow rate and / or the piston translation speed reaches the threshold translation speed and / or the steering wheel rotation speed reaches the threshold rotation speed.

3. A safety braking device (1) according to the preceding claim, wherein the valve (9) is a normally open valve, wherein the control unit (10) by closing the valve (9) prevents any passage of fluid from the first chamber (5) to the second chamber (6), or vice versa, blocking the translation of the piston (4) and preventing the rotation of the steering wheel (101 ) and setting the piston translation speed and the steering wheel rotation speed to zero.

4. Safety braking device (1 ) according to the preceding claim, wherein the valve (9) is a normally an open solenoid valve.

5. Safety braking device (1 ) according to any one of claims 2 to 4, wherein the fluid resistance means (8, 9) comprise said valve (9) for each connection element (7), avoiding the inclusion of further valves.

6. Safety braking device (1 ) according to claim 1 , wherein the fluid resistance means (8, 9) comprise a calibrated orifice (8), wherein the calibrated orifice (8) is interposed in the at least one connection element (7) between the first chamber (5) and the second chamber (6), wherein when the fluid flow rate of the working fluid (F) reaches the threshold fluid flow rate and / or the translational speed of the piston reaches the threshold translational speed and / or the rotational speed of the steering wheel reaches the threshold rotational speed, the calibrated orifice (8) hinders the movement of the working fluid (F) between the first chamber (5) and the second chamber (6), or vice versa, limiting an increase of the translational speed of the piston to a maximum translational speed greater than or equal to the threshold translational speed, and / or limiting the rotational speed of the steering wheel to a maximum rotational speed greater than or equal to the threshold rotational speed, and generating a pressure difference of the working fluid (F) between the first chamber (5) and the second chamber (6).

7. Safety braking device (1) according to the preceding claim, wherein the calibrated orifice (8) is an orifice disc inserted in the at least one connection element (7), or wherein the calibrated orifice (8) is a machining made in the at least one connection element (7).

8. Safety braking device (1 ) according to any one of the preceding claims 6 to 7, wherein the calibrated orifice (8) is a passive device, and wherein the fluid resistance means (8, 9) comprise each calibrated orifice (8), avoiding the inclusion of valves controlled by a control unit (10).

9. Safety braking device (1 ) according to any one of the preceding claims 6 to 8, wherein the calibrated orifice (8) forms a calibrated geometrical restriction in the at least one connection element (7) which is always open, without providing control or activation systems for the calibrated orifice (8).

10. Safety braking device (1 ) according to any one of the preceding claims, wherein the at least one connection element (7) extends between a respective first chamber opening (11 ) that faces and / or flows into the first chamber (5) of the housing (3) and a respective second chamber opening (12) that faces and / or flows into the second chamber (6).

11. A safety braking device (1 ) according to the preceding claim, wherein the at least one connection element (7) is a hydraulic conduit obtained in a wall of the cylinder (2).

12. A safety braking device (1 ) according to claim 10, wherein the at least one connection element (7) is made in a separate piece with respect to the cylinder (2) and is configured to put the first chamber (5) and the second chamber (6) in fluid communication in a fluid-tight manner.

13. A safety braking device (1 ) according to claim 10, wherein the at least one connection element (7) is a conduit passing through a thrust head (16) of the piston (4).

14. A safety braking device (1 ) according to the preceding claim, wherein the at least one connection element (7) comprises at least a first connection element and a second connection element each forming a respective conduit passing through the thrust head (16) of the piston (4), wherein the safety braking device (1) comprises one fluid resistance means (8, 9) of said fluid resistance means (8, 9) for each connection element (7).

15. A safety braking device (1 ) according to any one of the preceding claims, wherein the cylinder (2) comprises a first chamber bottom wall (13) and a second chamber bottom wall (14), opposite to each other along an axial direction (A-A) along which the piston (4) translates, wherein the cylinder (2) comprises at least one side wall (15) extending parallel to the axial direction (A-A) and connecting the first chamber bottom wall (13) and the second chamber bottom wall (14), wherein the piston (4) comprises a thrust head (16) housed in the housing (3) in a fluid-tight manner with the at least one side wall (15) and configured to push the working fluid from the first chamber (5) to the second chamber (6), and vice versa, wherein the piston (4) comprises at least one rod (17, 18), preferably a first chamber rod (17) and a second chamber rod (18), connected to the thrust head (16), and wherein the at least one rod (17, 18) has, on a side axially opposite to the thrust head (16), a respective connection interface (19, 20) to connect the piston (4) to the steering system (100), wherein the at least one rod (17, 18) is fluid-tight connected to a respective bottom opening (21 , 22) made in a respective one of the first chamber bottom wall (13) and the second chamber bottom wall (14), so that the respective connection interface (19, 20) is always outside the housing (3) of the cylinder (2) for any working position of the piston (4) in the cylinder (2).

16. A safety braking device (1 ) according to any one of the preceding claims, wherein the safety braking device (1) is independent of a power steering device, hydraulic or electrohydraulic or electromechanical, configured to assist the steering system (100).

17. A steering system (100) for a vehicle comprising a steering wheel (101 ), a steering device (107) configured to transform a rotation of the steering wheel (101) into a translation of at least one right-side steering arm (103) and of at least one left-side steering arm (104) to steer the vehicle, characterized in that it comprises a safety braking device (1 ) according to any one of the preceding claims, wherein the piston (4) is indirectly connected to the steering wheel (101 ) of the steering system (100)18. A steering system (100) according to the preceding claim, wherein the steering device (107) is a steering box, and the piston (4) is directly connected to the steering box, and / or wherein the steering device (107) comprises a steering rack and pinion (108), wherein the piston (4) is connected at one or both axial ends to the steering rack and pinion (108).

19. A steering system (100) according to claim 17, wherein the piston (4) is connected to the steering shaft (102), by means of a toothed wheel-rack and pinion assembly (109) configured to transform the rotary motion of the steering shaft (102) into translatory motion of the piston (4), wherein the toothed wheel-rack and pinion assembly (109) comprises a toothed wheel (110) connected to the steering shaft (102) and a rack and pinion (111 ), wherein the piston (4) is connected at one or both axial ends to the rack and pinion (111).

20. A steering system (100) according to any one of the preceding claims from 17 to 19, comprising a power steering device configured to assist the steering system (100) in changing the direction of the vehicle, wherein the safety braking device (1) is independent of the power steering device.

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