Anti-lock device for a wheel and braking system provided with such a device

Abstract

The invention relates to an anti-lock device (1) for a wheel, arranged in a hydraulic pressure circuit between a master cylinder (2) and at least one brake caliper (3) of the wheel, in particular of an aircraft. According to the invention, the device comprises: - a centrifugal element (4) attached to a rim (5) of the wheel and movable from a retracted position when the wheel rotates below a threshold speed, to a position deployed by the centrifugal force generated when the wheel rotates beyond the threshold speed; - a pressure control system (6) comprising a hydraulic inlet (6a) connected to the master cylinder (2) and a hydraulic outlet (6b) connected to a hydraulic inlet of the brake caliper (3), the pressure control system (6) being movable between a closed position of the hydraulic circuit when the centrifugal element (4) is in the retracted position, and an open position of the hydraulic circuit driven by the centrifugal element (4) in the deployed position.

Description

Description Title of the invention: Anti-lock device for a wheel and braking system equipped with such a device Technical field

[0001] The present invention relates to the technical field of braking systems for vehicles, and more particularly to an anti-lock device for a wheel. The device is particularly suitable, but not exclusively, for braking systems of light aircraft, i.e. of the ULM type, or more generally aircraft weighing less than 5.7 tonnes. Prior art

[0002] In conventional braking systems, particularly for aircraft, hydraulic pressure is usually applied to the brake calipers to exert braking force on brake discs fitted to the wheels. However, in certain situations, particularly during sudden braking, the wheels can lock, resulting in loss of control of the vehicle.

[0003] To counter this problem, anti-lock braking systems, also known as "antiskid" systems, have been developed.

[0004] The antiskid is designed to improve braking capability and help maintain the aircraft's directional stability during critical takeoff and landing phases.

[0005] A well-known antiskid system uses sensors to measure the speed of the aircraft's wheels during braking. If the sensors detect that one of the wheels is beginning to lock, the antiskid system intervenes to automatically reduce the braking pressure on that specific wheel. By reducing the braking pressure, the antiskid system allows the wheels to continue turning, thus preventing the aircraft from locking up and losing control.

[0006] Wheel lock can lead to several undesirable consequences, including increased braking distance, excessive tire wear, uncontrolled skidding, or even loss of aircraft direction. Antiskid helps prevent these situations by enabling effective braking while maintaining the directional stability of the aircraft.

[0007] Prior art antiskid systems are generally expensive, complex and require a power supply, which can present a problem, for example, in the event of an electrical system failure.

[0008] Additionally, integrating antiskid systems into the hydraulic circuit of the braking system may require significant modifications to the existing braking system, which can be costly and complex.

[0009] Documents US4811994, US4809823 and US3632176 illustrate the prior art. Statement of the invention

[0010] One of the aims of the invention is to overcome the drawbacks of the prior art, by proposing an antiskid device which does not require any electrical power supply, which is of reliable design and which can be easily integrated into an existing braking system without requiring major modifications.

[0011] For this purpose, an anti-lock device for a wheel has been developed, placed in a hydraulic pressure circuit between a master cylinder and at least one wheel brake caliper.

[0012] According to the invention, the device comprises a centrifugal element fixed to a rim of the wheel, and movable from a retracted position when the wheel rotates below a threshold speed, to a deployed position by the centrifugal force generated when the wheel rotates beyond the threshold speed. This feature makes it possible to avoid the use of electronic sensors for detecting the rotation speed, thus improving the reliability of the system and avoiding the need for a power supply.

[0013] In addition, the device of the invention comprises a pressure regulation system comprising a hydraulic inlet connected on the one hand to the master cylinder and a hydraulic outlet connected to a hydraulic inlet of the brake caliper, the pressure regulation system being movable between a closed position of the hydraulic circuit when the centrifugal element is in the retracted position, and an open position of the hydraulic circuit driven by the element centrifugal in the deployed position, in particular in which it releases the hydraulic circuit and allows pressure distribution to the caliper. This feature guarantees a rapid and reliable response in the event of potential wheel lockup.

[0014] In practice, the pressure in the caliper opposes the centrifugal force. In other words, there is a pressure balance between the pressure generated by the deployment of the centrifugal element and the pressure inside the caliper. As the wheel speed decreases, the centrifugal force is less sufficient to maintain the pressure, and the pressure in the caliper therefore pushes the control system back into the closed circuit position.

[0015] Below the threshold speed, there is no longer any braking. To overcome this defect, it is possible to equip the braking system with two brake calipers, or with a bypass system as described below.

[0016] Another solution is to install a preloaded spring to push the regulation system into an intermediate opening position of the hydraulic circuit.

[0017] In this way, as soon as the centrifugal element is no longer able to provide pressure, the spring takes over and provides a lower pressure. For example, if the pressure is regulated at 40 bars with the centrifugal element, the pressure can fall back to 15 bars with the preloaded spring, instead of 0, when the wheel rotates below the threshold speed.

[0018] According to a particular embodiment, the device comprises a wheel spindle, the pressure regulation system of the hydraulic circuit is integrated into the wheel spindle, and the spindle comprises: - a lateral hydraulic inlet connected on the one hand to the master cylinder and on the other hand to the hydraulic inlet of the pressure regulation system; - an axial hydraulic output connected on the one hand to the hydraulic output of the pressure regulation system and on the other hand to the hydraulic inlet of the brake caliper.

[0019] This improves the integration of the pressure regulation system, reduces the complexity of the braking system, and allows for easier installation into existing braking systems.

[0020] According to a particular embodiment, the pressure regulation system comprises a rod mounted axially sliding in the spindle, intended to be pushed by the centrifugal element in the deployed position, and to push a valve to move from a closed position to an open position of the hydraulic circuit. This provides a smooth transition between the open and closed positions of the hydraulic circuit, thus increasing the efficiency of the braking system.

[0021] According to a particular embodiment, the centrifugal element comprises at least one pivoting arm, for example L-shaped, with a first weighted end and a second end intended to push the rod when the arm is pivoted into the deployed position. This particular design guarantees good sensitivity to centrifugal force, thus improving the precision of the system.

[0022] The valve is for example in the form of a tubular piston with two shoulders defining between them an annular chamber. The piston includes orifices between the two shoulders to form the hydraulic inlet of the pressure regulation system and to put the annular chamber in communication with the interior of the piston. The annular chamber is in communication with the hydraulic inlet of the rocket, and one end of the piston opposite the rod includes the hydraulic outlet of the pressure regulation system in communication with the hydraulic outlet of the rocket, closed by a ball, the ball being intended to be pushed by a protuberance secured to a fixed part of the rocket when the valve is pushed by the rod to open the hydraulic circuit.

[0023] Preferably, the ball is returned to the position of closing the hydraulic outlet of the pressure regulating system by a spring arranged in the tubular piston, so as to ensure precise control of the hydraulic pressure in the braking system.

[0024] The invention therefore presents a reliable, simple technical solution that can be easily integrated into an existing braking system, thus improving the safety and efficiency of the braking system, particularly for aircraft.

[0025] Preferably, the centrifugal element comprises a base to which two arms are articulated, intended to be positioned at the level of a hub of the rim, the arms are diametrically opposed relative to the base, and the base is fixed to the rim by a clamping system comprising at least two rods screwed into the base, diametrically opposed to the base, and terminated by shouldered ends so that the clamping of the rods grips the arms of the rim and securely fixes the centrifugal element to the rim.

[0026] The invention also provides a braking system for a wheel comprising at least one brake caliper hydraulically connected to a hydraulic output of a master cylinder via the aforementioned anti-lock device.

[0027] However, in this configuration with a single caliper, if the anti-lock device does not include a preloaded spring as described above, this means that below the threshold speed the braking system is no longer operational.

[0028] To overcome this drawback, it is possible to equip the braking system with a bypass line, known by the English term "by-pass", comprising pressure regulating means, such as a valve or a regulating valve, also hydraulically connecting the brake caliper to the hydraulic output of the master cylinder.

[0029] In this way, if a relatively high pressure, to be adjusted according to the pressure regulation means, is applied to the brake pedal, the pressure is injected into the caliper bypassing or bypassing the anti-lock device to enable braking.

[0030] According to another embodiment, the wheel comprises a second brake caliper hydraulically and directly connected to a second hydraulic output of the master cylinder. This allows easy integration of the device into existing braking systems, without requiring major modifications.

[0031] In this way, when the wheel rotation is blocked, or very significantly reduced, the system allows one of the calipers to be deactivated, and therefore to lose 50% of braking power on the wheel. Of course, the 50% can be modulated by acting on the diameter of the caliper pistons. Brief description of the drawings

[0032] [Fig.1] is a perspective view of a rim including a braking system with two calipers, an antiskid device, and illustrating the hydraulic circuit with the master cylinder.

[0033] [Fig.2] is a view illustrating the positioning of the master cylinders of an aircraft brake pedal assembly.

[0034] Fig. 3] is a longitudinal sectional view of a master cylinder implemented in the invention.

[0035] [Fig. 4] is an exploded perspective view of a rim of an aircraft and of a braking system incorporating the antiskid device according to the invention.

[0036] [Fig.5] is a longitudinal sectional view of the rim and braking system incorporating the antiskid device, assembled, of Figure 4.

[0037] [Fig.6] is a perspective and longitudinal sectional view of the tubular piston of the pressure regulation system implemented in the invention.

[0038] [Fig.7] is a perspective view of a rim comprising a braking system according to another embodiment, with a single caliper, an antiskid device, and illustrating the hydraulic circuit with the master cylinder and a bypass line.

[0039] [Fig.8] is a longitudinal sectional view of the rim, and the braking system incorporating the antiskid device, assembled, of Figure 4, incorporating a preloaded pressure-maintaining spring. Detailed description of the invention

[0040] With reference to Figures 1 to 8, the invention relates to an anti-lock device (1) for a wheel during braking, ideally designed for light aircraft, and commonly called "antiskid" in English. This device (1) is positioned in a hydraulic pressure circuit which connects a master cylinder (2) to at least one brake caliper (3) of the wheel.

[0041] Preferably, the braking system comprises two calipers (3), a first caliper of which is hydraulically connected to a first hydraulic output of the master cylinder (2), and a second brake caliper (3) is hydraulically connected to a second output of the master cylinder (2) via the anti-lock device (1).

[0042] In this way, when the device (1) according to the invention is activated, it prevents the distribution of pressure towards one of the calipers (3) so as to reduce, in the example above, the braking power by 50%.

[0043] Referring to Figure 2 which represents a brake pedal assembly of a light aircraft, that is to say with two brake pedals, one for each main wheel of the landing gear, each pedal actuates a master cylinder (2) by a push rod (2a).

[0044] Here, each master cylinder (2) has two push rods (2a), namely coaxial and opposed, two independent hydraulic outputs (2b), and two independent hydraulic inputs (2c). In this way, when the pilot presses a brake pedal, the push rods (2a) each exert a force on the master cylinder (2).

[0045] Referring to Figure 3, the master cylinder (2) comprises two separate chambers (2d), each connected to a different braking circuit for each of the calipers (3). Inside each chamber, there is a piston that moves when the brake pedal is pressed. The pressure exerted on the brake fluid by the movement of the pistons is transmitted to the hydraulic lines of the braking system.

[0046] When hydraulic pressure is generated, it is distributed to the brake calipers (3). This causes the brake pads to press against the brake disc, slowing or stopping the wheels from rotating.

[0047] With reference to Figures 4 to 6, the antiskid device (1) according to the invention mainly comprises a centrifugal element (4), securely attached to a rim (5) of the wheel. The centrifugal element (4) is capable of moving between a retracted position, illustrated in Figure 5, and observed when the wheel rotates at a speed below a certain threshold speed, for example 15 km / h, and a deployed position, which is induced by centrifugal force when the wheel exceeds the threshold speed, for example 20 km / h. The use of this centrifugal element (4) eliminates the need for electronic sensors, thus increasing the robustness of the device (1) and reducing maintenance efforts.

[0048] In addition to the centrifugal element (4), the device (1) incorporates a pressure regulating system (6). The latter comprises a hydraulic inlet (6a), connected to the master cylinder (2), and a hydraulic outlet (6b), connected to the hydraulic inlet of the brake caliper (3). The pressure regulating system (6) is designed to be moved between a closed position of the hydraulic circuit, illustrated in Figure 5, when the centrifugal element (4) is in the retracted position, in which the distribution of pressure towards the caliper (3) is prevented, and an open position of the hydraulic circuit, when the centrifugal element (4) is extended, in which the distribution of pressure towards the caliper (3) is permitted. This feature ensures precise modulation of the hydraulic pressure as a function of the wheel speed, thus preventing any risk of the wheel locking during braking.

[0049] The pressure regulating system (6) is preferably incorporated into a spindle (7) of the wheel, which simplifies the design of the braking system and facilitates its installation. The spindle (7) comprises a lateral hydraulic inlet (7a), connected to the master cylinder (2) and to the pressure regulating system (6), as well as an axial hydraulic outlet (7b), connected to the outlet (6b) of the pressure regulating system (6) and to the brake caliper (3).

[0050] The pressure regulating system (6) comprises a rod (8) mounted axially sliding and sealingly in the rocket (7). This is designed to be pushed by the centrifugal element (4) into the deployed position and to actuate a valve (9) also mounted sliding and sealingly in the rocket (7).

[0051] The centrifugal element (4) is for example provided with an L-shaped arm (4a), two arms (4a) in the illustrated embodiment and for balancing reasons, pivoting, with a first end (4a1) weighted and a second end (4a2) intended to push the rod (8) when it pivots into the deployed position.

[0052] The centrifugal element (4) comprises a base (4b) to which the arms (4a) are articulated. This base (4b) is intended to be positioned at the hub of the rim (5). The arms (4a) are substantially diametrically opposed relative to the base (4b). The base (4b) is fixed to the rim (5) by a clamping system comprising two rods (4c) screwed into the base (4b) and terminated by ends shoulders (4c1). The tightening of the rods (4c) grips the arms of the rim (5) like a vice and securely fixes the centrifugal element (4) to the rim (5).

[0053] With reference to Figure 6, the valve (9) intended to be pushed by the rod (8) is for example in the form of a tubular piston which has two shoulders (9a) defining an annular chamber (9b) between them. The piston has orifices (9c) between these two shoulders (9a) to put the annular chamber (9b) in communication with the interior of the piston and form the hydraulic inlet (6a) of the pressure regulation system (6). One end of the piston opposite the rod (8) integrates the hydraulic outlet (6b) which is in communication with the outlet (7b) of the rocket (7).

[0054] Preferably, a ball (10) is used to close the hydraulic outlet (6b) of the valve (9). It is pushed by a protuberance (11), integral with a fixed part (12) of the spindle (7), when the valve (9) is actuated by the rod (8) to open the hydraulic circuit. A spring (13) is arranged in the tubular piston to return the ball (10) to the position for closing the hydraulic outlet (6b) of the pressure regulation system (6). The fixed part (12) which has the protuberance is for example in the form of a plug which closes the end of the spindle (7), in which a conduit is provided which forms the hydraulic outlet (7b) of the spindle (7). The conduit opens into the spindle (7) eccentrically relative to the protuberance (11).

[0055] According to another embodiment, it is possible for the braking system to comprise only one caliper (3) per wheel. In this configuration, and in order to maintain operational braking when the wheel rotates below the threshold speed, the anti-lock device (1) may comprise a pre-loaded spring (15) mounted to push the pressure regulating system (6) into an intermediate opening position of the hydraulic circuit while ensuring a certain amount of pressure.

[0056] This example is illustrated in figure 8, the spring (15) being positioned around the push rod (8), in particular in the body of the rocket (7), pressing against a part of the rocket and counter-pressing against the valve (9).

[0057] According to another example illustrated in Figure 7, the braking system comprises a bypass line (14), also known by the English term "by-pass", equipped with pressure regulating means, such as a valve (14a) or a regulating valve (14b), which establish a hydraulic connection with the brake caliper (3) connected to the hydraulic outlet (2b) of the master cylinder (2).

[0058] When the brake pedal is pressed with a relatively high pressure, adjustable according to the characteristics of the pressure regulating means (14a or 14b), this pressure is injected into the caliper (3) in bypass or by-pass of the anti-lock device (1). This configuration has several advantages and technical effects:

[0059] In this way, it also ensures that the braking remains operational even in the event of an anti-lock device malfunction, thus improving the overall safety of the system.

[0060] It is clear from the above that the invention does indeed provide an antiskid device which requires no electrical power supply, which is of reliable design and which can be easily integrated into an existing braking system without requiring major modifications.

Claims

Claims 1. Anti-lock device (1) for a wheel arranged in a hydraulic pressure circuit between a master cylinder (2) and at least one brake caliper (3) of the wheel, in particular of an aircraft, characterized in that it comprises: - a centrifugal element (4) fixed to a rim (5) of the wheel and movable from a retracted position when the wheel rotates below a threshold speed, to a deployed position by the centrifugal force generated when the wheel rotates beyond the threshold speed; - a pressure regulation system (6) comprising a hydraulic inlet (6a) connected on the one hand to the master cylinder (2) and a hydraulic outlet (6b) connected to a hydraulic inlet of the brake caliper (3), the pressure regulation system (6) being movable between a closed position of the hydraulic circuit when the centrifugal element (4) is in the retracted position, and an open position of the hydraulic circuit driven by the centrifugal element (4) in the deployed position.

2. Device (1) anti-locking of a wheel according to claim 1, characterized in that it comprises a wheel spindle (7), the pressure regulation system (6) is integrated in the spindle (7), and the spindle (7) comprises: - a lateral hydraulic inlet (7a) connected on the one hand to the master cylinder (2) and on the other hand to the hydraulic inlet (6a) of the pressure regulation system (6); - an axial hydraulic output (7b) connected on the one hand to the hydraulic output (6b) of the pressure regulation system (6) and on the other hand to the hydraulic inlet of the brake caliper (3).

3. Anti-lock device (1) for a wheel according to claim 2, characterized in that the pressure regulation system (6) comprises a rod (8) mounted to slide axially in the spindle (7), intended to be pushed by the centrifugal element (4) into the deployed position, and to push a valve (9) to move from a closed position to an open position of the hydraulic circuit.

4. Anti-lock device (1) for a wheel according to claim 3, characterized in that the centrifugal element (4) comprises at least one pivoting arm (4a) with a first weighted end (4a1) and a second end (4a2) intended to push the rod (8) when the arm (4a) is pivoted into the deployed position.

5. Anti-lock device (1) for a wheel according to one of claims 3 to 4, characterized in that the valve (9) is in the form of a tubular piston having two shoulders (9a) defining between them an annular chamber (9b), the piston comprises orifices (9c) between the two shoulders (9a) to form the hydraulic inlet (6a) of the pressure regulation system (6) and to put the annular chamber (9b) in communication with the interior of the piston, the annular chamber (9b) being in communication with the hydraulic inlet (7a) of the spindle (7), and one end of the piston opposite the rod (8) comprises the hydraulic outlet (6b) of the pressure regulation system (6) in communication with the hydraulic outlet (7b) of the spindle (7), closed by a ball (10), the ball (10) being intended to be pushed by a protuberance (11) secured to a fixed part (12) of the spindle (7) when the valve (9) is pushed by the rod (8) to open the hydraulic circuit.

6. Anti-lock device (1) for a wheel according to claim 5, characterized in that the ball (10) is returned to the position for closing the hydraulic outlet of the pressure regulation system (6) by a spring (13) arranged in the tubular piston.

7. Anti-lock device (1) for a wheel according to one of the preceding claims, characterized in that it comprises a preloaded spring (15) pushing the pressure regulation system (6) into an intermediate open position of the hydraulic circuit.

8. Anti-lock device (1) for a wheel according to one of the preceding claims, characterized in that the centrifugal element (4) comprises a base (4b) to which two arms (4a) are articulated, intended to be positioned at the level of a hub of the rim (5), the arms (4a) are diametrically opposed with respect to the base (4b), and the base (4b) is fixed to the rim (5) by a clamping system comprising at least two rods (4c) screwed into the base (4b), diametrically opposed with respect to the base (4b), and terminated by shouldered ends (4c1) so that the clamping rods (4c) come to grip the arms of the rim (5) and securely fix the centrifugal element (4) to the rim (5).

9. A wheel braking system comprising at least one brake caliper (3) hydraulically connected to a hydraulic output (2b) of a master cylinder (2) via the wheel anti-lock device (1) of one of claims 1 to 8.

10. Braking system according to claim 9, characterized in that a bypass line (14) equipped with pressure regulating means, such as a valve (14a) or a regulating valve (14b), also hydraulically connecting the brake caliper (3) to the hydraulic outlet (2b) of the master cylinder (2).

11. Braking system according to claim 9, characterized in that the wheel comprises a second brake caliper (3) hydraulically and directly connected to a second hydraulic output (2b) of the master cylinder (2).

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