FR2847871A1 - Motor vehicle parking disc brake, e.g. for bus, includes actuator for perpendicularly displacing locking pin that immobilizes the hydraulic disc brake piston after the brakes have been hydraulically applied - Google Patents

Abstract

The parking brake includes a mechanical blocking element having a pin (15) that can be transversely displaced by an actuator (25,29,31) between a first position in which the hydraulic brake piston can freely move, and a second position in which the pin blocks release of piston so that the vehicle brakes remain applied. The pin actuator includes a hydraulic chamber (29) and an electro-valve (25) that connects, on control (27), the hydraulic chamber to a source of high pressure brake fluid to actuate the pin. Independent claims are included for a braking system; and a process for immobilizing a motor vehicle by applying the mechanical blocking element after application of the hydraulic brake.

Description

PARKING BRAKE WITH HYDRAULIC ACTIVATION OF A MECHANICAL BLOCKING MEANS

  The present invention mainly relates to a parking brake with a fluid activation, typically hydraulic, the application of the parking brake and means for locking and / or mechanical locking of the brake in activated condition.

  EP 0526 273 discloses a disc brake with a parking brake actuated hydraulically by a pressure exerted by the driver on the vehicle brake pedal, ensuring the application of the pads on the opposite sides of the disc. While maintaining the foot on the brake pedal, the driver operates an electrical switch for powering an electric motor driving in rectilinear translation along the axis of the piston a sleeve coaxial with said piston, and until the locking of the piston in a position in which the pads are applied to the disc. The prior hydraulic application allows the implementation of a low power electric lock motor.

  The parking brake described in EP 0526 273 has many disadvantages. First of all, the driver is required to generate the hydraulic pressure necessary for the application of the pads on the disc. On the other hand, the electric motor recommended by EP 0526273 does not increase the application force of the pads on the disc. As a result, if the driver does not press the brake pedal at all or not hard enough, the vehicle will not be properly immobilized, resulting in an accident. EP 0995 659 and WO 99 48738 describe the architecture of a braking system comprising a parking brake actuated by a pressurized fluid with mechanical locking by locking a lever arm of application of friction elements on the disc. The mechanical parking brake locking devices of EP 0995 659 30 and WO 99 48738 do not appear to have sufficient reliability to allow their application to the automotive industry.

  It is therefore an object of the present invention to provide a reliable parking brake and safe operation.

  It is also an object of the present invention to provide a parking brake associated with a control system from the passenger compartment having a small footprint.

  It is also an object of the present invention to provide a parking brake having a small footprint at the wheel to be immobilized.

  It is also an object of the present invention to provide a parking brake having a low mass and in particular a low mass of the unsprung portion.

  It is also an object of the present invention to provide a parking brake cooperating with the trajectory control (ESP), antiskid (ASR), anti-lock (ABS), anti-roll and / or anticollision (ACC).

  It is also an object of the present invention to provide a simple construction parking brake. It is also an object of the present invention to provide a parking brake of a moderate cost price.

  It is also an object of the present invention to provide a parking brake easy to operate without significant effort of the driver.

  These objects are achieved by a parking disc brake comprising at least one piston that can be driven by a fluid under pressure, typically brake fluid, slidably mounted in a blind bore in a brake caliper, the bore forming a cylinder. A source of pressurized fluid advances the piston towards the disc and thus firmly applies the pads to the latter, ie with sufficient force to immobilize the vehicle. Preferably, consideration is given to a possible release of the parking brake d to the cooling of the brake. At this time, an actuator moves a piston immobilization key advantageously in a direction not parallel to the axis of the latter preventing its recoil with respect to the disc by a distance which might release the parking brakes 20 according to the invention. Advantageously, the actuator moves the key in rectilinear translation along an orthogonal axis or substantially orthogonal to the axis of the piston.

  However, displacement in oblique translation, in rotation or parallel to the axis of the piston is not beyond the scope of the present invention. In the preferred embodiment the key is blocking the recoil of a device, preferably nut screw type, catch-up pads wear bearing on the piston. Advantageously, the path of the blocking key is at the rear of the element to be locked (piston or skate wear compensator device). However, the implementation of keys or the like penetrating into a recess made in the element to be locked (piston or skate wear compensator device) is not outside the scope of the present invention. The actuator used is displaced by a fluid under pressure. In the preferred embodiment, the key forms a hydraulic piston driven by the brake fluid. The use of a high hydraulic pressure source, already available on a modern vehicle, makes it possible to limit the cost of the parking brake according to the invention.

  In addition, there are thus very important amplitude forces to manipulate the piston and the key.

  Advantageously, the parking brake, according to the present invention also provides the main service brake function.

  Avantaceusement. the parking brake according to the present invention is a floating brake for example of single piston type.

  Advantageously, the source of pressure fluid for actuating the hydraulic actuator is a pump and / or accumulator of a trajectory control system (ESP) of an electrohydraulic brake (EHBI) of an anti-skating system. (ASR) and / or anti-lock braking system (ABS).

  The main subject of the invention is a disk parking brake comprising a piston for applying skids to the disc, means for supplying a fluid under pressure sufficient to be able, on command, to firmly apply the pads on the disk, means for locking the piston in a first condition in which the pads are firmly applied to the disk characterized in that the locking means comprise a key and a displacement actuator on the control of said key, said actuator movement of the key comprises a hydraulic chamber and a valve capable of connecting, on command, said hydraulic chamber to a source of brake fluid under high pressure so as to drive the key between a first position in which the piston is free to retreat and a second position in which the key blocks the recoil of the piston. The invention also relates to a parking brake characterized in that it comprises at a first axial end of the key a first resilient biasing means and at a second axial end of the key a second elastic return means and in the elastic return means force is combined with the force exerted by the hydraulic pressure in the pressure chamber and the restoring force of the return means on the side of the pressure chamber is less than the force of elastic return exerted by the elastic return means disposed at the other end of the key.

  The invention also relates to a parking brake characterized in that the hydraulic chamber is defined axially, along the axis of the key on the one hand by an axial end of the key and on the other by a mounted auxiliary piston in translation in a cylinder arranged vis-à-vis said axial end of the key.

  The invention also relates to a parking brake characterized in that the auxiliary piston is pushed in the direction of said axial end of the key by the second elastic return means.

  The invention also relates to a parking brake characterized in that the key 35 moves along an axis not parallel to the axis of the piston between a first position of the key in which it does not oppose the recoil of the piston along its axis and a second position of the key in which it ensures a locking of the piston in the condition in which said piston firmly applies the pads on the disc.

  The invention also relates to a parking brake characterized in that the axis of displacement of said key is a rectilinear axis orthogonal or substantially orthogonal to the axis of the piston.

  The subject of the invention is also a parking brake characterized in that it further comprises a catch-up mechanism of brake pads bearing on a rear face of the piston opposite to the front face of the piston bearing on the brake shoe and in that the key is supported on the side of the wear compensating device of the brake pads opposite the side of the device bearing on the piston.

  The invention also relates to a parking brake characterized in that the key comprises along its axis, a first bearing zone before a first extension along the axis of the active piston in a first position where the key does not oppose not at the recoil of the piston along its axis and a second bearing zone having a second extension 5 along the axis of the cylinder, greater than said first extension along the axis of the piston of the first active bearing zone in a second position of the key in which the key is opposed to the recoil of the piston along its axis and in that the extension along the axis of the piston of the second zone varies with the position on the axis of the key so as to form a blocking slope.

  The invention also relates to a parking brake characterized in that said brake is a floating caliper brake in that said brake is also a service brake.

  The invention also relates to a parking brake characterized in that it comprises means for advancing the piston so as to create a rear space between the key and a part bearing on the key and preventing the recoil of the piston , the rear space facilitating the movement of the key between a first position in which the piston is free to move back and a second position in which the key directly or indirectly blocks the recoil of the piston. The subject of the invention is also a braking system comprising a computer, brakes and a source of pressurized brake fluid, characterized in that the valve is capable of connecting directly or via the cylinder, on command, the hydraulic chamber at said pressure source. The invention also relates to a method of immobilizing a motor vehicle characterized in that it comprises the steps of: - advancing a hydraulic piston towards a disc of a disc brake of to create a space at the back of the piston; - bring a piece for blocking the recoil of the piston in the space thus formed; and - releasing the force exerted on the piston so that it retracts so as to bear firmly on the recoil locking piece of the piston. The invention will be better understood by means of the following description and the appended figures given as non-limiting examples and in which: FIG. 1 is a fragmentary plan view of the preferred embodiment of FIG. a parking brake according to the invention at rest - Figure 2 is a top view partially broken away of the parking brake of Figure 1 in a first step of the parking brake clamping process; - Figure 3 is a top view partially broken away of the parking brake of Figure I during a second step of the parking brake clamping process; - Figure 4 is a top view partially broken away of the parking brake of Figure I in a third step of the parking brake clamping process - Figure 5 is a top view partially broken away of a first variant embodiment of a parking brake according to the present invention - Figure 6 is a sectional view of the rear portion of a second embodiment of a parking brake according to the invention.

  In Figures 1 to 6, the same references were used to designate the same elements. In Figures 1 to 4, there is shown the preferred embodiment of the brake according to the present invention. The preferred example is a floating caliper disc brake 1 also providing the main service brake function. In the example illustrated, there is shown a rear brake being understood that the implementation of a parking brake 15 according to the present invention on front wheels and / or a parking brake separate from the main service brake does not depart from the scope of the present invention.

  The stirrup 1 is provided with a blind bore 3 forming a hydraulic cylinder of a piston 5 provided with a brake shoe wear compensating device 7 comprising, in known manner, a nut 9 and a screw 11. unscrewing relative to the nut 9 as and when wear of brake pads. A rear portion 13 of the stirrup 1 comprises a. housing a mechanical locking key 15, direct or indirect. In the example shown, the blocking is effected by means of the device 7 to compensate for the wear of the pads, the piston 5 in a first condition in which the pads (not shown) are firmly applied to the disk ( also not shown).

  Firm application means an application for immobilizing vehicles, especially on a slope. It is commonly considered that such an application corresponds to a force of 10,000 N to 20,000 N. In a second condition, the key 15 does not oppose the recoil of the piston 5. In the preferred example illustrated, the key 15 is mounted in translation along an axis Y perpendicular to the axis X of the hydraulic piston 5. The key 15 comprises a first zone 17 of support of the rear face 19 of the nut 9 and a second bearing zone 21, shifted along the axis Y with respect to the zone 17 and having a forward extension, along the axis X, towards the hydraulic piston 5 greater than the extension along the axis X, in the same direction, of zone 17.

  In the illustrated preferred embodiment, the nut 9 is substantially cylindrical with an X axis, the rear face 19 has two zones spaced along the Y axis that are capable of coming into contact with the key 15. The latter comprises a first first zone 17 followed by a first second zone 21 followed by a second first zone 17 followed by a second second zone 21.

  Advantageously. the zone or zones 21 have a gentle slope forming a ramp 45 whose orientation facilitates the movement of the key 15 to the possible contact of the rear face 19. according to the arrow 23. In the example shown, the extension according to the X axis of the zones 21 increases from left to right.

  The brake according to the present invention comprises an actuator for moving, on command, for example when the driver presses a key, a lever, a pedal or the like, located in the passenger compartment, the key 15 along the axis Y, in the direction of the arrow 23. This movement for locking the parking brake can also be controlled by a computer, for example when the engine of the vehicle has been stopped and / or when the driver has left the vehicle. On the other hand, it is advantageous to use only hydraulic braking without mechanical locking of the piston when stopping at a red light or when starting on hill (Hill Holder in English terminology). In the preferred example illustrated, the actuation of the key 15 is hydraulic via a solenoid valve 25 of the closed type at rest connecting, on command 27, a pressure chamber 29 located at a first axial end of the key 15 to the pressure in the cylinder 3. The valve 25 is disposed at the hydraulic unit of the vehicle braking system or advantageously at the caliper 4. In the illustrated example, a chamber 29 is defined by an auxiliary piston 31 movable along the axis Y and axially displaced along the deflection 23 by a spring 33 and the face of the key 15, disposed opposite the auxiliary piston 31.

  The key 15 forms a hydraulic piston and is pushed axially along the Y axis in the direction opposite to the deflection 23 by a spring 35 exerting a force greater than that exerted by the spring 33.

  Alternatively, as illustrated in Figure 6, the spring 35 is replaced by a stepped key 15, the pressure application diameter on its two axial ends being different. The key 15 comprises seals 37 making it possible to isolate the chamber 29 with respect to the cylinder 3 and the housing of the spring 35. The piston 31 comprises a seal 39 enabling the chamber 29 to be isolated with respect to the pressure prevailing in the housing spring 33.

  The springs 33 and 35 are in isolated logrements of the brake fluid and for example filled with air. These housings can be connected to the atmosphere by unrepresented channels.

  The operation of the preferred embodiment of the parking brake according to the present invention will be explained hereinafter.

  The driver actuates the parking brake activation command, for example by pressing a key or a switch placed in the passenger compartment. Advantageously, an unrepresented computer, for example the computer of the braking system, verifies that the instructions of the driver correspond to satisfactory safety conditions. For example, if the speed of the vehicle is greater than 5km / h, the order of 40 to apply the parking brake is not directly executed but the driver is warned of the anomaly by a light signal and / or sound. The computer detects the change of state of the control key of the parking brake and controls the supply of the brake fluid under high pressure, for example between 10 Pa and 1.7 Pa in the cylinder 3 from a pressure source, not shown, such as a pneumatic brake booster (booster in English terminology) active controlled by an electric valve, a pump or an accumulator. Advantageously.

  a source of pressurized brake fluid already available in a modern vehicle is used, such as ABS pumps or accumulators, ESP pumps or accumulators, EHB pumps or accumulators or others. The pressure difference between the high pressure of the brake fluid prevailing in the cylinder 3 and the atmospheric pressure prevailing in particular at the front face of the piston 5 ensures the advancement thereof according to the arrow 41, towards the disk with clamping pads on the disk ensuring the immobilization of the wheel. Insofar as at least one vehicle train is equipped with the brakes according to the present invention, the immobilization of the vehicle is ensured. The play catch-up device 7 also advances in the direction of the arrow 41, as can be seen in FIG. 2, so as, on the one hand, to prevent an over-adjustment by rotational locking of the screw 11 by application of the conical bearing surfaces 43 of FIG. the screw 11 and the piston 5 and secondly, to provide a space 45 between the rear face 19 10 of the nut 9 and the first contact zone 17 of the key 15.

  In the example illustrated in FIG. 2, the space 45 has a thickness less than the difference between the extension along the X axis of the second zone 21 and the first zone 17 of the key 15. However, it is of course, the implementation of a space 45 greater than this extension difference along the X axis does not go beyond the scope of the present invention. Indeed, the thickness of the space 45 facilitates the movement of the key 15 according to the arrow 23.

  The computer generates the valve opening control signal 27 (FIG. 3), putting the cylinder 3 into communication with the chamber 29. The pressure in the chamber 29 is at this moment sufficient to overcome the force opposed by the spring 35 and moves the key 15 according to the arrow 23 as shown in Figure 3. The second bearing zones 21 of the key 15 are therefore facing the rear face of the nut 9. A Releasing pressure in the cylinder allows the piston to recoil. The computer controls the pressure drop in the cylinder 3 causing a firm application of the rear faces 19 of the nut 9 on the second bearing zone 21 of the key 15. Simultaneously, the brake fluid flows from the chamber 29 to the cylinder 3 through the valve 25, under the action of the auxiliary piston 31 driven by the spring 33 according to the arrow 23.

  The firm support ensures locking in translation of the key 15. As a result, the key 15 and the piston 5 (via the device 7) lock and / or lock each other preventing the translation of the key despite a significantly decreases the pressure in the chamber 29. The parking brake is therefore applied 35 in a perfectly stable condition even in the absence of hydraulic power, electrical or other.

  The computer then ensures the closing of the valve 25 isolating the chamber 29 of the cylinder 3 as illustrated in FIG.

  It should be noted that the application of the high pressure in the cylinder 3 ensures an elastic deformation of the stirrup 1, called the opening of the stirrup, which stores a considerable elastic energy ensuring parking braking. The amount of stored energy can be optimized by a particular design of the stirrup or the choice of materials used 45 promoting this deformation when it is subjected to significant constraints imposed by the high pressure of the hydraulic fluid. For example, it implements a stirrup cast iron, steel, composite material or a stirrup aluminum or cast iron with steel ansert. Similarly. this energy can be stored in elastic elements external to the stirrup, for example to improve the holding of the parking brake when cooling a brake applied at high temperature. In a variant, the braking system according to the present invention comprises means for measuring the clamping force of the parking brake and ensures an increase of this force by the cycles previously explained when this is necessary, for example as a result of the cooling of the parking brake. a brake applied hot after heavy service braking.

  It is understood that the present invention is not limited to the formation of a space 45 between the face 19 of the nut 9 and the key 15. It is perfectly possible without departing from the scope of the present invention to apply directly the parking brakes by moving the key 15 according to the arrow 23.

  The deactivation of the parking brake according to the present invention is carried out according to the following steps: The valve 25 is closed permanently. In the first instance, a pressure greater than that used to lock the parking brake, for example between 1.1 × 10 7 Pa and 2 × 10 7 Pa, is applied.

  The piston 5 and the device 7 for clearance play advance along the arrow 41 20 forming a space 45. In the absence of pressure in the chamber 29, the spring 35 returns the zones 17 facing the faces 19 of the nut 9 (translation of the key 15 in the opposite direction to the arrow 23). The pressure prevailing in the cylinder 3 is decreased and the parking brake is released.

  It is understood that the present invention is not limited to the implementation of a single valve 25 and a single pressure chamber 29. On the contrary, as for example illustrated in FIG. 5, it is possible to use a valve 25 'supplying, on command 27', a first chamber 29 'situated on the left of FIG. 5 for loosening the parking brake or a second chamber 29 "situated on the right of FIG. 30 making it possible to apply the parking brake to a source of high pressure, directly or indirectly, via the cylinder 3. In the example illustrated, the valve 25 'has three positions: a first position in which the cylinder 3 and the two chambers are isolated, a second position in which the chamber 29 'is fed while the chamber 29 "is isolated and a third position in which the chamber 29" is fed and the chamber 29 It is understood that the single three-way valve 25 'can be replaced by two two-way valves, each controlling the supply of one of the two chambers 29' or 29 ".

  It should be noted that in the event of failure of the pressure generating system, the parking brake according to the present invention can still be unlocked by exerting a very great force on the brake pedal. The parking brake according to the present invention may be associated with or combined with an emergency brake without departing from the scope of the present invention. Advantageously, each wheel of a front and / or rear axle of a vehicle is provided with a brake according to the present invention. The four wheel equipment with brakes according to the present invention is particularly advantageous in the case of four-wheel drive vehicles, especially sport utility vehicles (SL-V in term.inoloie ann] osaxone).

  The parking brake according to the present invention applies in particular to the automotive industry. The parking brake according to the present invention applies mainly to the braking industry for motor vehicles including passenger vehicles.

Claims (12)

CLAIMS S   1. Disk parking brake having a piston for applying skates to the disc, means for supplying a fluid under pressure sufficient to be able, on command, to firmly apply the pads to the disc, means for blocking the piston in a first condition in which the pads are firmly applied to the disk, characterized in that the locking means comprise a key (15) and an actuator (25, 29, 31) for moving said key ( 15), said actuator for moving the key (15) comprises a hydraulic chamber (29) and a valve (25) capable of connecting, on command (27), said hydraulic chamber (29) to a source of brake fluid under high pressure so as to drive the key (15) between a first position in which the piston is free to move back and a second position in which the key (15) blocks the recoil of the piston. (5).   2. parking brake according to claim 1 characterized in that it comprises at a first axial end of the key (15) a first elastic return means (35) and at a second axial end of the key (15) a second elastic return means (33) and that the elastic return means force (35, 33) is combined with the force exerted by the hydraulic pressure in the pressure chamber (29) and that the restoring force of the means of return located on the pressure chamber (29) side is less than the elastic restoring force exerted by the elastic return means (35) arranged at the other end of the key (15).   3. parking brake according to claim 7 or 8 characterized in that the hydraulic chamber (29) is defined axially, along the axis (Y) of the key (15) on the one hand by an axial end of the key ( 15) and secondly by an auxiliary piston (31) mounted in translation in a cylinder disposed vis-à-vis said axial end of the key (15).   4. parking brake according to claim 3 characterized in that the auxiliary piston (31) is pushed in the direction of said axial end of the key (15) by the second elastic return means (33).   5. parking brake according to any one of the preceding claims characterized in that the key 15 moves along an axis (Y) non-parallel to the axis (X) of the piston (5) between a first position of the key ( 15) in which it does not oppose the recoil of the piston (5) along its axis (X) and a second position of the key (15) in which it ensures a locking of the piston (5) in the condition in which said piston firmly applies the pads to the disc.   6. parking brake according to claim 5 characterized in that the axis (Y) of displacement of said key (15) is a rectilinear axis orthogonal or substantially orthogonal to the axis (X) of the piston (5). ] t   7. parking brake according to any one of the preceding claims characterized in that it further comprises a mechanism (7) for compensating for wear of brake pads bearing on a rear face of the piston (5) opposite to the front face of the piston (5) bearing on the brake pad and in that the key is supported on the side of the device (7) for compensating wear of the brake pads opposite the sides of the device (7) bearing on the piston (5).   8. parking brake according to claim 6 or 7 characterized in that the key (15) comprises along its axis (Y), a first bearing zone (17) having a first extension along the axis (X) of the piston (5) active in a first position where the key (15) does not oppose the recoil of the piston (5) along its axis (X) and a second bearing zone (21) having a second extension along the axis (X) of the cylinder, greater than said first extension along the axis (X) of the piston (5) of the first bearing zone (17) active in a second position of the key (15) in which the key s' opposed to the recoil of the piston (5) along its axis (X) and in that the extension along the axis of the piston (X) of the second zone (21) varies with the position on the axis (Y) of the key so as to form a blocking slope.   9. parking brake according to any one of the preceding claims characterized in that said brake is a stirrup brake (1) floating in that said brake is also a service brake.   10. parking brake according to any one of the preceding claims characterized in that it comprises means for advancing the piston (5) so as to create a rear space (45) between the key (15) and a part taking pressing on this key (15) and preventing the recoil of the piston (5), the rear space (45) facilitating the movement of this key (15) between a first position in which the piston is free to move back and a second position in which the key (15) blocks directly or indirectly the recoil of the piston (5).   11. Braking system comprising a computer, brakes according to claim 7 or 8, and a source of pressurized brake fluid characterized in that the valve (25) is capable of connecting directly or via the cylinder (3). ), on command (27), the hydraulic chamber (29) to said source of pressure. 12. A method of immobilizing a motor vehicle characterized in that it comprises the steps of: - advancing a hydraulic piston (5) towards a disk of a disk brake so as to create a space (45) at the rear of the piston; - bring a blocking piece (15) of the recoil of the piston in the space thus menace; and - releasing] a force exerted on the piston so that it retracts so as to bear firmly on the blocking piece (15) of the recoil piston (5).