EP2005021A1

EP2005021A1 - Hydraulically actuable vehicle brake having a locking means

Info

Publication number: EP2005021A1
Application number: EP07723949A
Authority: EP
Inventors: Kurt Mohr; Manuel Schmitz
Original assignee: Lucas Automotive GmbH
Current assignee: ZF Active Safety GmbH
Priority date: 2006-04-07
Filing date: 2007-04-03
Publication date: 2008-12-24
Also published as: DE102006016543A1; US20090159381A1; WO2007115751A1; CN101421534A

Abstract

The present invention relates to a vehicle brake (10) having a housing (12), a brake piston (16) which is accommodated in the housing (12) and is coupled to a brake lining (20), a blocking device (26) for locking the brake piston (16) within the housing (12), and an electromechanical actuating device (42) for actuating the blocking device (26) in a parking brake situation, wherein the brake piston (16), together with the housing (12), delimits a fluid chamber (68) which can be loaded with hydraulic fluid, with the result that the brake piston (16) can be displaced hydraulically within the housing (12) along a piston longitudinal axis (A) for actuating the vehicle brake (10). There is provision in a vehicle brake of this type for the blocking device (26) to be assigned a locking arrangement (125) which acts mechanically on a component (36) of the blocking device (26) in a parking brake situation and blocks a restoring movement of said component (36).

Description

Hydraulically actuated vehicle brake with lock

Field of the invention

The present invention relates to a hydraulically actuated vehicle brake with a housing, a brake piston received in the housing, which is coupled to a brake pad, a locking device for locking the brake piston within the housing and an electromechanical actuator for driving the locking device in a parking brake situation, wherein the brake piston the housing bounded by a fluid chamber which can be charged with hydraulic fluid, so that the brake piston for actuating the vehicle brake is hydraulically displaceable within the housing along a piston longitudinal axis.

State of the art

Such a vehicle brake is already known. Thus, for example, the generic document DE 10 2004 040 261 A1 shows a vehicle brake of this type. In this vehicle brake, the brake piston is displaced in a service brake situation by charging the fluid chamber with hydraulic fluid within the housing and thereby the brake pad is pressed onto a rotating brake disc in order to decelerate it. To terminate the braking process hydraulic fluid is discharged from the fluid chamber, so that the brake piston with the brake lining attached thereto can move back to its starting position. In a parking brake situation in which, for example, a vehicle equipped with such a vehicle brake is to be parked and secured against unintentional rolling away, the blocking device is actuated by means of an electromechanical actuating arrangement. This pivoting of the lever causes a braking arrangement provided in the vehicle vehicle to spread within the housing and thus perform a lifting movement in the direction of the piston longitudinal axis. This lifting movement is transmitted to a blocking element of the blocking device, which then presses against the action of a return spring on the brake piston and axially displaced. To cancel the parking brake situation, in turn, the fluid chamber and the Actuator operated in opposite directions, whereupon the ramp assembly moves back from its spread position to its original position. Under the action of the return spring and the blocking element moves together with the brake piston in its initial position, so that the brake pad releases the brake disc. In this prior art, it has been shown that it would be helpful to mechanically lock the individual components in a parking brake situation better to exclude unwanted setting operations can.

In order to counteract the problem of high actuation forces, which are to be applied manually in particular, the prior art according to EP 0 551 397 D1, for example, shows a hydraulically actuated vehicle brake in which the brake piston is first hydraulically displaced to activate the parking brake function and subsequently an electric motor driven by a blocking rod until it contacts the brake piston. The blocking rod is provided with an external thread which engages with an internal thread provided in the housing. The mutually engaging threads are self-locking, so that mutual rotation between the locking bar and the housing is prevented in an axial force acting on the locking bar. As soon as the blocking rod contacts the brake piston, the hydraulic fluid is discharged from the chamber again. In this case, the brake piston tries to move back to its initial position, but what he is prevented by the voltage applied to her blocking rod. The brake is thus in its parking brake position. To release the parking brake action, in turn, the fluid chamber is charged with hydraulic fluid, so that the blocking rod is released from the brake piston. Then it can be moved back to its initial position via the electric motor and then the hydraulic fluid can be removed again from the fluid chamber. Although a parking brake effect can be activated by motor with this known arrangement. However, it is a relatively complex and space-demanding mechanics and correspondingly powerful electromotive components required. In particular, the provision of efficient components is again justified by the fact that the pressure rod has to be introduced into the pressurized fluid chamber and thereby has to be displaced against the hydraulic pressure prevailing in the fluid chamber. AIs further prior art is the document DE 103 20 884 Al call, wherein the vehicle brake described therein is a purely hydraulic actuated brake.

Task and solution according to the invention

It is an object of the present invention to provide a vehicle brake of the type described, which requires only low actuation forces to activate the parking brake function and which ensures a stable position of the components in a parking brake situation.

This object is achieved by a vehicle brake of the type described, in which the blocking device is associated with a locking arrangement which mechanically engages in a parking brake situation on a component of the blocking device and blocks it against a return movement.

By providing a locking arrangement which engages directly mechanically on a component of the blocking device in a parking brake situation and thus blocks the entire blocking device in the position assigned to the parking brake situation, unintentional release of the parking brake function can be even better prevented than the generic prior art described at the beginning. Also mechanical setting operations that can lead to an undesirable clamping force reduction can be further reduced by this measure.

A further development of the invention provides that the blocking device has a transmission element which can be displaced relative to the housing and depressurises the blocking device when actuated relative to a fluid pressure prevailing within the fluid chamber. By providing a displaceable in the housing transmission element, which is housed at least partially in the fluid chamber and is acted upon by the prevailing fluid pressure, it is possible in this embodiment of the invention to exploit the fluid pressure prevailing in the fluid chamber to the effect that pressure-related opposing forces, the act against a shift of the blocking device, at least partially compensated. In particular, can be provided according to the invention in this context that the transmission element at least one hydraulically active with hydraulic fluid from the Fluid chamber pressure-loaded pressure relief surface has. The hydraulically active pressure relief surface is preferably arranged so that it is pressurized upon pressurization of the fluid chamber in such a way that the transmission element is displaced together with corresponding components of the blocking device in the direction of a locking position of the blocking device or at least depressurized to facilitate such movement of remaining components. As a result, the actuating device only has to apply slight actuating forces in order to displace the blocking device for locking the brake piston within the housing. Preferably, the pressure relief surface is formed on a piston head. A substantially complete pressure relief can be achieved, for example, in that the transmission element is pressurized at least indirectly on both sides with respect to a displacement in the fluid chamber hydraulically active surfaces with hydraulic fluid from the fluid chamber. The transmission element and with this the blocking device thus behaves pressure neutral, so that only constructive frictional forces must be applied to enable the blocking device in a state in which the brake piston is blocked.

To control the blocking device can be provided that the actuating device is driven by a motor driven by a rotary drive or driven. A particularly simple and inexpensive variant according to the invention results, for example, when the drive is designed as a rotary electromagnet whose current position and / or current consumption can be tapped off as information about the functional state of the vehicle brake in a parking brake situation. Such conventional rotary electromagnets are available at low cost, but can only muster modest forces of small amount. Since - as already explained above - by the invention, however, a pressure-relieved operation of the blocking device is possible and thus also actuating forces small amount sufficient to operate the blocking device, the use of such a rotary electromagnet conventional design for the realization of the vehicle brake invention advantageously offers. As a result, the production of the vehicle brake can be significantly reduced and the brake can be made compact overall.

By tapping the current position order / and the current consumption can be reliably determined whether a parking braking position that meets the requirements was actually achieved. So can be for example by means of assigned electrical monitoring functions a minimum power consumption and / or a minimum path capture, so conditions that should be at least met to ensure a certain minimum parking brake force can. The minimum displacement away can be detected, for example, by determining a minimum angle of rotation, for which purpose a limit switch can be attached to the rotary magnet arrangement. In principle, however, it is also possible to detect only electronically the actual angular position of the rotary magnet. If you actually monitor both parameters, that is, the current position and the power consumption, so you have a double protection in terms of achieving a desired parking brake effect, which further increases the reliability of the system.

A development of the invention provides a blocking element which engages for locking the brake piston on this. The blocking element can then be displaced via further components of the blocking device, in particular by supporting the transmission element relative to the brake piston.

In order to keep the stroke to be traveled over the drive of the actuating device as low as possible, a development of the invention provides that the blocking element is in driving connection with the brake piston. This means that the blocking element is entrained in a hydraulic displacement of the brake piston with this, for example by means of a locking ring. Only for locking the brake piston, it is then necessary to actively control the blocking element via the actuating device - supported by the transmission element. Thereby, the reaction time of the vehicle brake, can be significantly reduced to a command to activate the parking brake effect. In addition, this offers advantages in the Verschlußnachstellung to keep constant the clearance of the vehicle brake.

A further development of the invention provides that the abovementioned piston head amounting to the pressure relief surface is guided in a fluid-tight manner in the blocking element. For this purpose, it can be provided that in the blocking element, a guide sleeve is used, in which the piston head by means of a sealing element, in particular a lip seal, is guided fluid-tight. For example, a lip seal can be used, as is also used in ABS pumps for sealing pressures of over 200 bar. According to one embodiment of the invention, it is provided that the blocking device has a ramp arrangement. The use of a ramp arrangement is well known in the art. It has the advantage that the blocking element can be locked by a simple low-friction rotational movement of the actuator, that beyond the resulting from the large clamping forces reaction forces can be reliably derived in the housing, and that the vehicle brake from a parking brake position with relatively little effort again can simply be transferred to a rest position. Another advantageous aspect of the use of a ramp arrangement is that the rotational forces to be applied can be kept relatively small due to the ramp-related translation. This again benefits the above-mentioned design of the drive as a rotary electromagnet, which - as already stated - can apply only small amounts of actuating forces, which lead to a torque of, for example, 2 Nm.

A development of this embodiment provides that the ramp arrangement has at least one first ramp surface, which is attached to the housing or is non-rotatably coupled therewith, and has at least one second ramp surface which is axially displaceable relative to the housing and coupled to the blocking element Ramp component is formed, wherein upon actuation of the actuating device, the two ramp surfaces slide for displacement of the blocking element to each other. To further reduce the actuating forces, in particular the frictional forces to be overcome, it can be provided according to the invention that rolling elements are provided between the at least one first ramp surface and the at least one second ramp surface via which the at least one first ramp surface is in contact with the at least one second ramp surface.

When the vehicle brake according to the invention with a ramp arrangement can be advantageously provided that the ramp component is coupled to the transmission element and displaced by this pressure relieved within the fluid chamber. Thus, the transmission element with its hydraulically active surface can be so effective that, due to the hydraulic pressure prevailing in the fluid chamber, it seeks to displace the ramp component in such a way that it urges the blocking element into a position in which it locks the brake piston. Eventually on the ramp component attacking hydraulic Conditional opposing forces can be reduced, compensated or even overcompensated. In the second and last-mentioned case, frictional forces must be overcome at best. Advantageously, the cross section of the hydraulically active surface of the transmission element is precisely matched to the cross section of the hydraulically oppositely active surface of the ramp component, so that in the ideal case, a complete compensation of the hydraulically induced opposing forces can be achieved. In other words, the hydraulic reaction forces acting on the transmission element and on the ramp component and caused by the fluid pressure of the fluid chamber cancel each other out in this solution according to the invention. The coupling between the ramp component and the transmission element may be a fixed mechanical coupling. Equally, this coupling can also provide only a common axial movement of these two components, wherein the two components are rotatable relative to each other.

A development of the invention provides that the locking arrangement is formed with a locking member which can be brought into interaction with the ramp component. In this case, for example, be provided that the locking member is biased by a biasing spring into the fluid chamber on the ramp component to in a locking position and is displaced by sufficient pressurization when feeding the fluid chamber with hydraulic fluid at a minimum pressure value is exceeded from the locking position into a release position. The locking member can therefore be actuated hydraulically and reacts to the prevailing in the fluid chamber fluid pressure. Thus, the locking assembly automatically switches when it reaches a certain minimum pressure in the release position and thus enables a release of the parking brake function. If the hydraulic fluid pressure prevailing in the fluid chamber drops below this minimum pressure, the locking member shifts back into its locking position under the action of the pretensioning spring, which leads to a stable holding of the blocking device in a parking brake situation and which is harmless in a service braking situation, since in the service braking situation the brake piston is displaced purely hydraulically anyway.

Alternatively to the formation of a purely hydraulically actuated locking arrangement may further be provided that the locking member by means of a magnet assembly in the fluid chamber into the ramp component in a Locking position is biased and is displaced by actuation of the magnet from the locking position into a release position. In this embodiment, for example, a pressure detection takes place in the fluid chamber, in accordance with the currently detected pressure taking into account the operator's request, that is, depending on whether the driver wants to activate the parking brake or not, a control of the magnet assembly and thus an actuation of the Locking organ takes place.

According to one embodiment, it is provided that the locking member is formed as a friction element, which is engageable with a friction surface in friction with a complementary friction of the ramp component. In this embodiment, the ramp component is held in its current position solely by sufficiently high frictional forces. Alternatively, however, a preferred embodiment of the invention provides that the locking member is designed as a locking element which can be brought with a locking profile in engagement with a complementary Verrieglungsprofil the ramp component. Instead of the above outlined frictional blocking of the ramp component, a positive locking of the ramp component is provided in this embodiment rather. As a result, unintentional, wear or contamination-related slipping can be even better prevented. For example, it may be provided that the locking profile has at least one locking tooth and that the complementary locking profile has a corresponding sawtooth formation, which is preferably arranged on a peripheral surface of the ramp component. For blocking, the at least one locking tooth can then be brought into engagement with the sawtooth formation. A saw tooth formation ensures particularly reliable engagement of the locking profile and complementary locking profile.

With regard to the operation of the vehicle brake according to the invention can be provided that in a service brake situation, the brake piston is displaced by loading and emptying the fluid chamber with hydraulic fluid within the housing and that in a Feststellbremssituation first the brake piston is displaced by charging the fluid chamber with hydraulic fluid within the housing, then the electromechanical actuating device is actuated for locking the brake piston, wherein the transmission element moves toward the brake piston, then the locking arrangement is activated and finally for a pressure reduction in the fluid chamber hydraulic fluid from the Fluid chamber is discharged. Thus, to activate the parking brake function applied via a hydraulic actuation and displacement of the brake piston clamping force for applying and applying the brake pad are used on the brake disc. The brake pad does not have to be additionally delivered by the drive of the vehicle brake according to the invention on the brake disc, which makes a low-power and thus cost-effective design of the drive - as already explained several times - possible. The activation of the latch assembly in the state of maximum fluid pressure within the fluid chamber ensures that the blocking device is blocked precisely when the maximum parking brake force is reached. The setting processes occurring in the sequence are minimal, which leads in particular to a positive locking arrangement to very high holding forces during the parking brake situation, that is, after reduction of the fluid pressure in the fluid chamber.

To solve the parking brake situation, it is possible in the above-described variant to re-charge the fluid chamber with hydraulic fluid in order to cancel a mechanical coupling between the brake piston and the blocking device. As a result, the locking arrangement is transferred to a state in which it releases the blocking device. The actuator can then be controlled accordingly and drive back the blocking element under low operating forces in its initial position, in which it in turn releases the brake piston. This is done again depressurized by action of the transmission element. Then, hydraulic fluid can be removed from the fluid chamber again, so that the brake piston can move back into a braking effect-free starting position.

The invention further relates to a method for actuating a vehicle brake of the type described above, wherein in a service brake situation, the brake piston is thereby displaced within the housing that hydraulic fluid is supplied to the fluid chamber or discharged therefrom, and that in a parking brake situation, first of all the brake piston by loading the Fluid chamber is displaced with hydraulic fluid within the housing, then the electromechanical actuator is actuated to lock the brake piston, wherein the transmission element moves to the brake piston, then the locking assembly is activated, and finally for a pressure reduction in the fluid chamber hydraulic fluid is discharged from the fluid chamber , Furthermore, it can be provided in the inventive method that for dissolving the parking brake situation, the fluid chamber is charged with hydraulic fluid, then the locking assembly and the blocking device are released and finally for a pressure reduction in the fluid chamber hydraulic fluid is discharged from the fluid chamber.

Furthermore, it can be provided in the inventive method that the blocking device is actuated with a rotary solenoid whose current position and / or current consumption is tapped as information about the functional state of the vehicle brake in a parking brake situation.

Brief description of the figures.

The invention is explained below by way of example with reference to the accompanying figures. They show:

Fig. 1 is a longitudinal sectional view of a first embodiment of the vehicle brake according to the invention;

FIG. 2 shows a sectional view along section line IHI from FIG. 1; FIG.

Fig. 3 is a sectional view corresponding to Figure 1 of a second embodiment of a vehicle brake according to the invention.

4 shows a sectional view along section line IV-IV of Figure 3;

5 shows a schematic overview of the second embodiment with the hydraulic circuit shown schematically, and

6 is a flowchart for explaining the operation of the vehicle brake according to the invention in a parking brake situation.

Description of preferred embodiments

In the following, the first exemplary embodiment will first be described with reference to FIGS. 1 and 2. In Figure 1, a vehicle brake according to the invention is generally designated 10. This is carried out with a housing 12 having a cylindrical opening 14. In the cylindrical opening 14, a brake piston 16 is slidably received fluid-tight. The brake piston 16 is mechanically coupled at its left in Figure 1 end with a brake pad carrier, not shown, to which a brake pad can be fastened. The brake pad is another brake pad opposite, which is attached to an opposite housing part 18. The brake pads are received in the housing 12 in a conventional manner according to the floating caliper principle.

The vehicle brake 10 further comprises a blocking device 26, by means of which the brake piston 16 can be locked in different axial positions along the piston longitudinal axis A. The blocking device 26 comprises in the first embodiment, a ramp assembly 28 with a ramp plate 30 which is fixed by means of a bolt 32 to the housing 12. On the housing-fixed ramp disc 30 three elongated in the circumferential direction, trough-like ramps are formed, each receiving a spherical spreader 34. The expansion body 34 cooperate with a respective ramp of a ramp component 36. This ramp component 36 has a shaft extension 38, which is mounted rotatably in the housing 12 in a rotatable manner. The shaft extension 38 is received in a bearing bush 39, which is sealingly received on its outer periphery in the housing 12 via an additional O-ring seal. Further, it has an O-ring seal on its inner periphery, which receives the shaft extension 38 sealing. The bushing 39 is preferably made of a copper-zinc wrought alloy, so that it has very good sliding properties. Connected to the shaft extension 38 is a gear 40 which is coupled in a rotationally fixed manner and which is rotatably drivable about the longitudinal axis A via a toothed belt 41 with a rotary magnet arrangement 42. Due to the rotationally fixed connection of the gearwheel 40 and the shaft extension 38, the ramp component 36 can thus be driven in rotation about the piston longitudinal axis A.

On the side facing the brake piston 16 side of the ramp member 36 is supported by a slide bearing 44 or alternatively a rolling bearing, in particular a needle bearing, a support member 46 from. The support member 46 is thus friction around the piston longitudinal axis A relative to the ramp member 36 rotatable. The support member 46 is biased by a compression spring 48 against the ramp member 36. The compression spring 48 is supported at its one end to the biased. The compression spring 48 is supported at one end on the large diameter flange of the support member 46 and at its other end to the bottom of a housing-fixed cup 50th

The support member 46 is formed with an axial through hole in which a weight saving and gaining additional pressure-compensating surface relatively thin trained shaft of a transmission element 52 is slidably received. The transmission element 52 is connected at its brake piston remote end at 54 with the ramp member 36, for example screwed into this (thread M4) or otherwise for common axial movement, but mutually rotatable connected. At its end near the brake piston, the transmission element 52 has a piston head 56. The piston head 56 is sealingly received in a guide sleeve 57 by means of a sealing lip element, which is pressed into a blocking element 58. The guide sleeve 57 is dimensioned such that it is flush with the left in Fig.l end of the blocking element 58 and contacted in Fig.l left end of the support member. The blocking element 58 is in turn displaceably guided in the brake piston 16. It has radial bores 59 and 59 'which allow a fluidic connection to its center for pressurizing the piston head 56. Further, it has at 60 a conical flange which is engageable with a corresponding inner cone on the brake piston 16 in engagement.

The blocking element 58 can be taken to the left via a securing ring 62 and a spring washer 64 during a movement of the brake piston 16 in FIG. It should further be noted that the blocking element 58 is threadedly coupled via a coarse thread pairing 66 to the support member 46, which has a well-defined thread clearance. Preferably, this coarse thread pairing 66 is designed to rotate the rotary magnet assembly 42 for aeration over a particular angle of rotation.

In addition, it should be noted that the surface Ai of the piston head 56 is at least as large as the non-lying in a fluid chamber 68 and therefore does not come into contact with hydraulic fluid in contact surface A ₂ of the tightly guided in the housing shaft extension 38. This is at Filling the designated in the figures 68 fluid chamber relieved from the ramp component 36 and transmission element 52 assembly relieved. In other words, all caused by the voltage applied to this module hydraulic pressure Reactive forces balanced, which is in particular to be supplied to the action of the hydraulically active surface H of the guide flange 56, which faces the fluid chamber 68.

If reference is also made to FIG. 2, a locking arrangement according to FIG. 1 in the orthogonal section can be seen there. In Figure 2 it can be seen that the ramp member 36 is provided at its outer periphery with a toothing 120. Furthermore, it can be seen that in the housing 12, a receiving bore 124 is incorporated with an internal thread into which a cartridge 126 is screwed. The cartridge 126 is formed as a hollow cylinder. In this, a locking member 128 is guided in the direction of a longitudinal axis A orthogonal transverse axis B displaced. The locking member comprises a flange 130 and a shaft 132. At the end of the shaft 132 remote from the flange, a toothing 134 corresponding to the toothing 120 is provided. The two teeth 120 and 134 are formed as a sawtooth profile.

In Fig.l and 2 is further shown that the flange 130 is biased by a helical compression spring 136 in the position shown in Fig.l and 2, in which the two gears 120 and 134 engage with each other. At the end of the helical compression spring 136 remote from the flange, a securing element 138 is screwed into the cartridge 126, on which the helical compression spring 136 is supported. The securing element 138 has a central opening 140, via which the interior of the cartridge 126 can be vented during a movement of the locking member 128.

As can be seen both in Fig.l and in Figure 2, the shaft 132 acts as a kind of piston, which is displaceable downward upon pressurization of the fluid chamber 68 in Figure 2 along the transverse axis B against the force of the compression coil spring 136. The spring 136 is designed to defy such displacement over a wide pressure range, but from a certain minimum pressure, a corresponding one

Displacement allows and is compressed. The minimum pressure can be around 160 bar.

As an alternative to the design shown with a compression spring, it is also possible to replace the compression coil spring 136 by a switching magnet arrangement which Pressure-dependent, for example, when exceeding the aforementioned minimum pressure, the locking member 128 moves.

The vehicle brake 10 according to FIGS. 1 and 2 functions as follows:

In a service brake situation, in which an existing between the brake pads, but not shown in the figures rotating brake disc is to be decelerated, the fluid chamber 68 is charged with hydraulic fluid and thereby the brake piston 16 is displaced within the housing 12. As long as this shift is not greater than that in the coarse thread pairing 66 between the support member 46 and the blocking element 58 existing thread play that corresponds to the intended brake clearance, the blocking member 58 moves completely with the brake piston 16 with.

However, if due to wear of the brake pads on the intended Bremslüftspiel beyond way of the brake piston 16 is required to apply the brake pads, not shown, to the brake disc, not shown, then the compression spring 48 prevents the support member 46 thereto, with hydraulic actuation, the entire displacement of the brake piston 16 to join the brake disc out. As a result, the conical flange 60 of the blocking member 58 against the resistance of the spring washer 64, which is weaker than the bias of the compression spring 48, slightly lifted from the inner cone. The blocking element 58 is therefore no longer prevented from rotating about the axis A.

The axial force transmitted by the coarse thread pairing 66, with which the support member 46 attempts to retain the blocking member 58 against the force of the spring 64, has a circumferential component. This results in a torque by which the blocking element 58 is now rotated such that it unscrews from the support member 46. As a result, the conical flange 60 comes again to the inner cone of the brake piston 16 for concern. Since the effective length of the assembly formed by the support member 46 and the blocking member 58 is now increased, the brake piston 16 is prevented after the brake operation, to return to its original starting position. The brake clearance has thus been reduced again to its nominal amount.

If, in the case of a powerful hydraulic brake actuation, a pressure of, for example, 20 bar or more arises within the fluid chamber 68, then, in particular in the Area of the brake pads and the housing 10 can be expected with elastic deformations. An adjustment that would compensate for such transient deformations is undesirable and is therefore avoided as follows: the pressure in the fluid chamber 68 also acts on the blocking element 58. Upon vigorous hydraulic actuation, those exerted by the spring washer 64 and the hydraulic pressure on the blocking element 58 total axial forces greater than the force exerted by the compression spring 48 on the brake piston remote flange of the support member 46. The compression spring 48 is thus no longer able to hold the support member 46. As a result, the conical flange 60 can not lift off the inner cone. The blocking element 58 is thus prevented from rotating so that the braking operation takes place without readjustment. Only when the hydraulic pressure has dropped below the said threshold of, for example, 20 bar, an adjustment can be made up if this has become necessary due to advanced pad wear of the brake pads.

Below is to be discussed on the activation of the parking brake function of the vehicle brake 10 according to the invention, in which the existing between the brake pads disc is to be blocked against unintentional rotation. In order to explain the parking brake function, reference should also be made to FIGS. 2 and 6.

For actuating the vehicle brake 10 in a parking brake situation upon actuation of a switch arranged in the vehicle interior (step S12 in FIG. 6), an ESP pump is activated and first hydraulic fluid is supplied to the fluid chamber 68 and the hydraulic pressure prevailing therein is set to a value of For example, 0 bar increased to a value of, for example, 200 bar. The hydraulic fluid may be supplied by the operation of the brake pedal by the driver or automatically independently or in addition to a brake pedal operation by means of a pump similar to an automatic braking operation, for example by means of a vehicle dynamics control, for example, controlled by an ECU 90. At this time, control valves are switched by the ECU (Fig. 6, step S14-S18). This results in a clamping force on the brake pads. By such pressurization, as already described above, the blocking element 58 is held in contact with the brake piston 16. The blocking element 58 draws on the steep thread pairing the support member 46, so that a small gap between the ramp member 36 and the thrust bearing 44 is formed. This small gap is for example two to three millimeters. The Thrust bearing 44 is held solely on the shaft of the transmission element 52.

As a result, the pressure in the fluid chamber 68 is substantially kept apart from setting operations (step S22). Due to the filling of the fluid chamber 68 with hydraulic fluid in a pressure range which is well above the above-mentioned minimum pressure for compression of the compression coil spring 136, the locking member 128 has been displaced out of the fluid chamber 68 by compression of the compression coil spring 136 in the interior of the cartridge 126 due to pressure. This means that the toothing 134 at the radially inner end of the locking member 128 is no longer in engagement with the toothing 120 at the peripheral region of the ramp component 36.

If this state is reached, the rotary magnet arrangement 42 is now controlled via the electronic control unit. This drives via the toothed belt 41 and the rotationally driven gear 40, the ramp member 36 so that it rotates about the axis of rotation A and caused due to a caused by the rolling elements 34 and the ramp surfaces spreading movement in the axial direction of FIG. 1 relative to the ramp plate 30 to the left ,

One aspect of the invention is that this movement of the ramp component 36 can be realized with very small actuating forces. This is due to the fact that the hydraulically active surface H of the piston head 56 of the transmission element 52 firmly coupled to the ramp component 36 compensates for those hydraulic opposing forces which would counteract a movement of the ramp component 36 into the fluid chamber 68. By suitable dimensioning of the piston head 56 and correspondingly small dimensioning of the diameter of the shank 52, even an overcompensation of the hydraulic opposing forces can be effected, so that a spreading movement of the ramp arrangement 20 can be promoted.

The effect of the counterforce compensation arises in particular when the hydraulically inactive (and therefore to be compensated) surface Ai of the shaft extension 38 is greater than or equal to the area A _{2 of} the guide flange 56. More precisely, the small dimensioned hydraulic inactive cross-sectional area of the shaft of the transmission element 52 would have to be removed from both surfaces. With such an area equality Ai> A ₂ , the relationship holds that the due The reaction forces Fi and F ₂ occurring in the fluid chamber 68 prevailing hydraulic pressure are also the same and thus cancel.

This principle is used according to the invention to design the rotary magnet assembly 42 as low-power as possible, in order to achieve cost savings in component procurement and a reduction in space. It is sufficient, with very small actuating forces, to displace the ramp component 36 over the above-mentioned gap by a spread relative to the ramp disk 30 in the direction of the axis A until it abuts the sliding bearing again.

Then, the fluid pressure in the fluid chamber 68 is released (step S30). At the beginning of this pressure reduction initially nothing happens. However, if the decisive for the compression of the compression coil spring 136 limit pressure falls below, it can relax again and push the locking member 128 into the fluid chamber 68 until it reaches its end position. In this it engages with its teeth 134 in the toothing 120 on the circumference of the ramp member 36 and defines this in its angular position. This is done automatically in the reduction of the fluid pressure in the fluid chamber 68. As a result of a continued pressure reduction, the brake piston 16 tries to shift back to the right in Figure 1, but relies on the blocking element 58, the support member 56 and the sliding bearing 44 on the in FIG 1 to the left displaced ramp component 36, which in turn is supported on the rolling elements 34 on the housing-fixed ramp disc 30 and is secured against rotation by the interlocking teeth (step S32). There is at most a minimal return movement due to setting operations, which is however negligibly small, so that the remaining clamping force is still large enough to continue to maintain a sufficient clamping effect even after complete reduction of the hydraulic pressure in the fluid chamber 68, which is sufficient. to secure the brake disc against unintentional rotation. Finally, the rotary magnet assembly 42 may be turned off (step S34). The locking process and the pressure relief should advantageously be carried out almost synchronously in order to exclude any losses in the clamping force.

To release the parking brake function after appropriate operation of the switch 96, the hydraulic pressure in the fluid chamber 68 is increased again until it reaches the above-mentioned value of, for example, 200 bar. This increases The clamping force also slightly again, until it finally reaches substantially the above-mentioned maximum clamping force value at which the support member 46 was again slightly shifted from the ramp member 36 in Figure 1 to the left. During the increase of the fluid pressure in the fluid chamber 68, the locking member 128 is displaced into the cartridge 126 again when the pressure limit for compression of the helical compression spring 136 is exceeded, and releases the ramp component 36 for rotational movement. Then there is a control of the rotary magnet assembly 42, so that the ramp member 36 can be displaced by the small restoring forces of the rotary magnet assembly 42 back to its original position. As a result, hydraulic fluid is discharged from the fluid chamber 58 so that it can empty and the brake piston 16 can return to its initial position shown in Figure 1.

With the first embodiment of the invention, it is thus possible to provide a secure parking brake function, which prevents inadvertent release due to the action of the latch assembly 125 and by using the hydraulic pressure in the fluid chamber and the above-mentioned counterforce compensation or overcompensation only very small actuating forces on the Rotary magnet assembly 42 required. The rotary magnet assembly 42 can be designed according to low performance.

Furthermore, it should be noted that a function check or monitoring can be carried out by monitoring certain operating parameters of the rotary magnet arrangement 42. As such operating parameters are, for example, the current consumption and the angular position of the rotary magnet assembly 42 in question, which can be easily monitored and give reliable with a safety-enhancing redundancy information about the current state of the brake. On the basis of this information can also be determined whether the latching on the two gears 120 and 134 has not occurred too early before reaching a parking brake ensuring position.

Figures 3 and 4 show a second embodiment of the invention. To avoid repetition and to simplify the description, only the differences of the second exemplary embodiment according to FIGS. 3 and 4 to the first exemplary embodiment according to FIGS. 1 and 2 will be discussed below. It will be the same for equivalent or similar components Reference numerals as used in the description of the first embodiment, but with the lowercase letter "a" readjusted.

The second embodiment according to Figures 3 and 4 differs from the first embodiment according to Figures 1 and 2 in the formation of the rotary magnet. This is designed as a push-pull electromagnet and has a ball-ramp plane, which converts an integrated linear movement of the electromagnet into a rotary motion. This rotational movement is transmitted to the shaft extension 38a, with the effects described above occur. The linear displacement along the longitudinal axis A is thus achieved directly by the lifting movement of the magnet arrangement 42a.

Otherwise, the arrangement according to FIGS. 3 and 4 functions exactly as described above with reference to FIGS. 1 and 2. In particular, the latch assembly 125a operates pressure dependent, as described above with respect to the latch assembly 125.

FIG. 5 shows a schematic representation of the hydraulic system coupled to the vehicle brake 10a and its components.

Specifically, these are a brake pedal 72a that cooperates with a brake booster master cylinder unit 74a. Via a pressure line 78a, hydraulic fluid is supplied from a reservoir 76a to a hydraulic system 80a, preferably an ABS / ESP system, in response to an actuating force F exerted on the brake pedal. This includes control valves 82a, 84a, 86a, 88a, which are controllable via an electronic control unit 90a. Furthermore, the hydraulic system comprises a motor-driven pressure pump 92a, which is also coupled to the electronic control unit 90a. In addition, a pressure sensor 94a may be provided to detect the hydraulic pressure introduced into the fluid chamber 68a when the control valve 86a is open. Unless a pressure sensor is provided, e.g. for cost reasons, the hydraulic pressure introduced into the fluid chamber 68a can be determined by a mathematical model. The electronic control unit 90a is controllable via a parking brake actuation switch 96a and connected via a connecting line 98a to the rotary magnet arrangement 42 according to FIG. 1 for driving the same and for picking up the above-mentioned parameters for function monitoring, namely the current rotational position of the electromagnet 42a and its current consumption.

Claims

claims

A vehicle brake (10; 10a) having a housing (12; 12a), a brake piston (16; 16a) accommodated in the housing (12; 12a) and being coupled to a brake lining (20; 20a), a blocking device (26 , 26a) for locking the brake piston (16; 16a) within the housing (12; 12a) and an electromechanical actuator (42; 42a) for driving the

The brake piston (16; 16a) with the housing (12; 12a) delimits a fluid chamber (68; 68a) which can be charged with hydraulic fluid so that the brake piston (16; 16a) is blocked. for actuating the vehicle brake (10; 10a) is hydraulically displaceable within the housing (12; 12a) along a piston longitudinal axis (A), characterized in that the blocking device (26; 26a) is associated with a locking arrangement (125; 125a) which in a parking brake situation mechanically on a component (36; 36a) of the blocking device (26; 26a) engages and blocks it against a return movement.

2. Vehicle brake (10; 10a) according to claim 1, characterized in that the blocking device (26; 26a) has a relative to the housing (12; 12a) displaceable transmission element (52; 52a), which the blocking device (26; 26a) depressurized when actuated relative to a fluid pressure prevailing within the fluid chamber (68; 68a).

3. Vehicle brake (10; 10a) according to claim 2, characterized in that the transmission element (52; 52a) has at least one hydraulically active pressure relief surface (H) pressurized with hydraulic fluid from the fluid chamber (68; 68a).

4. Vehicle brake (10; 10a) according to claim 3, characterized in that the pressure relief surface (H) on a piston head (56; 56a) is formed.

A vehicle brake (10; 10a) according to any one of the preceding claims, characterized in that the transfer element (52; 52a) at least indirectly on both sides of its hydraulically active surfaces with hydraulic fluid from the fluid chamber (68 ; 68a) is pressurized.

6. Vehicle brake (10; 10a) according to any one of the preceding claims, characterized in that the actuating device with a rotary drive (42; 42a) is driven by a motor or driven.

7. Vehicle brake (10; 10a) according to claim 6, characterized in that the drive as a rotary electromagnet (42; 42a) is formed, its current position and / or current consumption as information about the functional state of the vehicle brake (10; 10a) in a parking brake situation can be tapped.

8. A vehicle brake (10; 10a) according to one of the preceding claims, characterized by a blocking element (58; 58a) which acts on the brake piston (16; 16a) to lock it.

9. Vehicle brake (10; 10a) according to claim 8, characterized in that the blocking element (58; 58a) is in driving connection with the brake piston (16; 16a).

A vehicle brake (10; 10a) according to claims 4 and 9, characterized in that the piston head (56; 56a) is guided in a fluid-tight manner in the blocking element (58; 58a).

11. Vehicle brake (10; 10a) according to claim 10, characterized in that in the blocking element (58; 58a) a guide sleeve (57; 57a) is inserted, in which the piston head (56; 56a) is guided fluid-tight by means of a lip seal.

12. Vehicle brake (10) according to one of the preceding claims, characterized in that the blocking device (26) has a ramp arrangement (28).

13. Vehicle brake (10) according to claim 12, characterized in that the ramp arrangement (28) has at least one first ramp surface (at 30), which is attached to the housing (12) or is rotatably coupled thereto, and at least one second Ramp surface (at 36) formed on a relative to the housing (12) axially displaceable and with the blocking element (58) coupled ramp member (26), wherein upon actuation of the actuating device (42) the two ramp surfaces for displacement of the blocking element ( 58) slide off each other.

14. Vehicle brake (10) according to claim 13, characterized in that between the at least one first ramp surface and the at least one second ramp surface rolling elements (34) are provided, via which the at least one first ramp surface is in contact with the at least one second ramp surface.

15. Vehicle brake (10) according to claim 13 or 14, characterized in that the ramp component (36) coupled to the transmission element (52) and by this pressure relieved within the fluid chamber (68) is displaceable.

16. A vehicle brake (10; 10a) according to any one of claims 12 to 15, characterized in that the locking arrangement (125; 125a) is formed with a locking member (128; 128a) which interacts with the ramp component (36; 36a) is.

17. Vehicle brake (10) according to claim 16, characterized in that the locking member (128; 128a) by means of a biasing spring (136; 136a) into the fluid chamber (68; 68a) into the ramp component (36; 36a) to in a locking position is biased and by sufficient pressurization when loading the fluid chamber (68; 68a) is displaced with hydraulic fluid when a minimum pressure value is exceeded from the locking position into a release position.

18. Vehicle brake according to claim 16, characterized in that the locking member by means of a magnet arrangement in the fluid chamber into the ramp component in a Locking position is biased and is displaced by actuation of the magnet from the locking position into a release position.

19. Vehicle brake according to one of claims 16 to 18, characterized in that the locking member is designed as a friction element, which is engageable with a friction surface in friction with a complementary friction of the ramp component.

20. A vehicle brake (10; 10a) according to any one of claims 16 to 18, characterized in that the locking member (128; 128a) is designed as a locking element which is provided with a locking profile (134; 134a) in engagement with a complementary locking profile (120; 120a ) of the ramp component (36; 36a) can be brought.

21. A vehicle brake (10; 10a) according to claim 20, characterized in that the locking profile (134; 134a) has at least one locking tooth and in that the complementary locking profile (120; 120a) has a corresponding sawtooth formation which is preferably formed on a peripheral surface of the ramp component (36 ; 36a) is arranged.

22. A vehicle brake (10; 10a) according to any one of the preceding claims, characterized in that in a service brake situation, the brake piston (16; 16a) by supplying and emptying the fluid chamber (68; 68a) with hydraulic fluid within the housing (12; 12a) displaceable and that in a parking brake situation, first the brake piston (16; 16a) is displaced by supplying the fluid chamber (68; 68a) with hydraulic fluid within the housing (12; 12a), then the electromechanical actuator (42; 42a) for locking the brake piston (Fig. 16; 16a) is actuated, wherein the transmission element (52; 52a) moves towards the brake piston (16; 16a), then the locking arrangement (125; 125a) is activated and finally for a pressure reduction in the fluid chamber (68; 68a). Hydraulic fluid from the fluid chamber (68; 68a) is discharged.

23. A vehicle brake (10; 10a) according to claim 22, characterized in that hydraulic fluid is supplied to the fluid chamber (68; 68a) for releasing the parking brake situation, then the blocking device (58; 58a) and the locking arrangement (125; 125a) is released and finally for a pressure reduction in the fluid chamber (68; 68a) hydraulic fluid from the fluid chamber (68; 68a) is discharged.

24. A method for actuating a vehicle brake (10; 10a) according to one of the preceding claims, characterized in that in a service brake situation, the brake piston (16; 16a) is displaced within the housing (12; 12a) in that hydraulic fluid of the fluid chamber (68 68a), and that in a parking brake situation, first the brake piston (16; 16a) is displaced by supplying the fluid chamber (68; 68a) with hydraulic fluid within the housing (12; 12a), then the electromechanical actuator (16). 16a), wherein the transmission element (52; 52a) moves toward the brake piston (16; 16a), then the locking arrangement (125; 125a) is activated, and finally for a pressure reduction in the fluid chamber (68; 68a) hydraulic fluid from the fluid chamber (68; 68a) is discharged.

25. Method according to claim 24, characterized in that hydraulic fluid is supplied to the fluid chamber (68; 68a) for dissolving the parking brake situation, then the blocking device (58; 58a) and the locking arrangement (125; 125a) are released and finally for a pressure reduction hydraulic fluid is removed from the fluid chamber (68; 68a) in the fluid chamber (68; 68a).

26. The method according to claim 24 or 25, characterized in that the blocking device (58; 58a) with a rotary solenoid (42; 42a) is actuated, the current position and / or current consumption as information about the functional state of the vehicle brake (10; 10a) is tapped in a parking brake situation.

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