The invention relates to a disk brake, in particular a part-lining disk brake, having an electromechanical actuator and an application device of self-energizing type, which has a wedge arrangement designed to press a brake lining against a disk brake.
A self-energizing disk brake with a wedge arrangement is disclosed by German patent document DE 1 291 951, for example. This document describes a hydraulically actuated part-lining disk brake having a brake caliper or frame gripping around the brake disk, and an application device, actuated by a Bowden cable independently of the hydraulic actuation device, for application as a parking brake.
Wedge-shaped plates, which can be displaced against one another with their wedge faces bearing against one another, are arranged between the brake piston and the brake shoe or the brake lining, the plate facing the brake piston being braced against the brake cylinder or the brake caliper/frame. The plate acted upon by the brake piston in this example has pyramidal shape, preferably that of a truncated pyramid, counter-sliding wedges interacting with one pair of inclined faces for the mechanical brake actuation and counter-sliding wedges interacting with the other pair of inclined faces for adjustment of the brake clearance.
A disadvantage to this disk brake is the poor adjustability. It is therefore advisable to use an electric motor as actuator, which has the advantage of a good facility for adjustment and control. The adjustment can be computed in widely varying ways, where necessary incorporating a braking sensor or default variables.
Such an arrangement would still have the disadvantage, however, that it would have a relatively complicated construction. The embodiments of the invention eliminate this problem.
According to the invention, a disk brake is provided, in particular a part-lining disk brake, having an electromechanical actuator and an application device of self-energizing type, which as self-energizing device has a wedge arrangement designed to press a brake lining against a disk brake. At least two wedge elements moveable relative to one another are arranged on a brake caliper or frame or on an auxiliary frame for applying the application-side [brake lining], the elements being designed to act on the brake lining via a trapezoidal pressure plate, such as a wedge plate.
In an especially preferred embodiment of this arrangement, a unit which includes the wedge elements and the brake lining unit bearing against the brake disk can, during braking sequences, be moved together on the brake caliper or on the auxiliary frame parallel to the brake disk friction face against stops, against which it is braced during braking sequences.
Such bracing of the application forces against the brake caliper can advantageously be achieved, in this exemplary embodiment, without placing any stress on the actuator. The arrangement is suitable for braking both in a forward and in a reverse direction and in particular also for applications of a parking brake, even on ferries, where the inclination of the vehicle may change continuously. The brake moreover has a fundamentally simple design construction.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing.
The invention will be described in more detail with reference to the drawings and on the basis of exemplary embodiments, illustrating the working in detail and describing further advantages of the invention. In the drawings:
a shows a sectional sketch drawing of a first exemplary embodiment of a disk brake according to the invention, giving a simplified representation of the application device and omitting the drive in the form of an electric motor;
b shows a detail from
a-d show a braking action in a film-like sequence, including successive brake operating positions of the brake shown in
a-b show a part of a disk brake shown in
A brake lining unit 7, which is formed from a brake lining 8 and a pressure plate 9 arranged between the brake lining 8 and the wedge faces, is arranged between the two wedge elements 5, 6 and an application-side brake disk friction surface 2a. The brake lining 8 has a backing plate and a lining material (not shown here). The pressure plate 9 and the backing plate may also be integrally formed.
On the reaction side a reaction-side brake lining 10 is arranged between the brake frame and the brake disk 2. The brake caliper may be an immovable, fixed caliper, so that the brake disk is designed to move in an axial direction A. Floating and hinged caliper designs are also alternatively feasible. At least the application-side brake lining unit is arranged on the brake caliper so that it is moveable relative to the brake disk 1, both parallel to the brake disk axis of rotation X and parallel to the brake disk friction surface.
The exemplary auxiliary frame has a U-shape and is provided with a base member 11a, which extends parallel to the brake disk friction surface 2a. It is bounded at both ends by longitudinal members 11b, 11c, which extend from the base member 7 in the direction of the brake disk and which serve as stops for the wedge elements 5, 6 in their movements in a peripheral direction (according to the direction of rotation of the brake disk). In this way a stop for each of the wedge elements 5, 6 is achieved in both directions of rotation U1, U2.
In the top view in
In section and in the top view shown in
The movement of the wedge face elements 5, 6 relative to one another may be accomplished in any known manner. It is in a preferred embodiment achieved by a spindle 16, which is provided with a corresponding external thread and which engages in corresponding tapped holes 17, 18 having an internal thread in the wedge elements, the wedge elements 5, 6 being moved towards one another in the one direction of rotation of the electric motor-driven spindle 16 and away from one another in the other direction of rotation of the spindle 16.
a shows the unbraked position, in which the wedge elements are so far apart that the desired clearance exists between the brake lining 8 and the brake disk 2.
The wedge elements 5, 6 are then moved towards one another—in this exemplary embodiment by electromechanical turning of the spindle 15—which displaces the brake lining unit 7 and its brake lining 8 perpendicular (parallel to the arrow A) to the brake disk 2 turning in the direction of the arrow U (
This causes the entire unit having the brake lining unit 8 and the two wedge elements 5, 6 to be displaced in a peripheral direction on the auxiliary frame 4, until the unit comes to bear on the stop face situated to the fore in the peripheral direction—in this case the inner face of the member 11a of the U-shaped auxiliary frame 4 (
The actuator, which acts on the wedge elements 5, 6, is thereby significantly relieved of reaction forces, which are braced against the auxiliary frame 4.
If the direction of rotation of the brake disk 2 is reversed (for example, when parking on a ferry oscillating due to the motion of the sea), the unit which includes the brake lining and the two wedge elements moves against the opposing stop, now situated in the peripheral direction, in this case the inner face of the member 11c of the auxiliary frame 4.
The ratio of forces applied during braking are shown in
From the description of this exemplary embodiment, it will be apparent that according to the invention it is not the brake lining alone which is displaced against a wedge, but the wedge elements 5, 6 are also freely moveable against one another inside a cage or auxiliary frame 4 fixed to the brake caliper, which elements then press the brake lining unit 7 against the brake disk 2 (
Once the lining 8 has been brought to bear against the brake disk 2, the brake lining 8 and the two wedge elements 5, 6 are carried by the brake disk 2, until the wedge located in the direction of rotation of the disk bears against the wall of the cage, fixed to the brake caliper, situated in the direction of rotation. The braking force Fbrake and the component Fenerg of the application force resulting from self-energizing are now dissipated into the caliper, without placing any stress on the actuator.
The braking force Fbrake is then obtained (calculated without internal friction within the mechanism) as:
Fbrake=Fapplic·μ
μ=coefficient of friction between lining and disk
Fbrake=(Fapplic1+Fapplic2+Fenerg)·μ
where
Fapplic1=Fwedge/tan α1
Fapplic2=Fwedge/tan α2
Fenerg=Fbrake/tan α2
giving
Fbrake=(Fwedge/tan α1+Fwedge/tan α2+Fbrake/tan α2)·μ
Fbrake·(tan α2−μ)/tan α2=Fwedge·μ/tan α1+Fwedge·μ/tan α2
Fbrake=μ·(Fwedge/tan α1+Fwedge/tan α2)·tan α2/(tan α2−μ)
In the opposite direction of travel the indices must be reversed. By selecting different wedge angles for the forward and reverse travel (angles α1, α2) it is possible to set the self-energization differently for the directions of travel. Assuming the same wedge angles α1=α2=α for forward and reverse travel, this gives
From (1) and (2), given a wedge angle of α or α2=arctan μ a discontinuity will be observed, where Fbrake no longer varies as a function of Fwedge.
At smaller angles the sign is reversed between Fbrake and Fwedge, which implies that drag would be bound to occur, which would no longer be possible in the present arrangement. For this reason:
α,α1,α2 must be>arctan μ
The wedge elements 5, 6 can intrinsically be moved relative to one another by any transmission arrangements or force-transmitting components, which may be driven by an electric motor. Feasible exemplary transmission arrangements include:
The arrangement with more than one pair of wedges per direction of rotation is also represented by reference to the example of a pair of double wedges depicted in
The double wedge elements 5′, 6′ can be moved relative to one another by for example, using a spindle 15′ with an electric motor 35 (
In the event of a rapid change in the direction of rotation, for example at the instant when the brake lining is in contact with the brake disk 2, the entire inner construction is impelled against the wall now situated in the direction of travel—the stop on the member 11b, 11c. In order to prevent damage and excessive stresses, damping elements 37 may be fitted to the members 11b, 11c, for example between the wedge elements 5, 6 and the stops (
The following reference numerals are provided to simplify understanding of the specification and drawings.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
Number | Date | Country | Kind |
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10 2006 002 308 | Jan 2006 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2007/000411 | 1/18/2007 | WO | 00 | 12/29/2010 |
Publishing Document | Publishing Date | Country | Kind |
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WO2007/082744 | 7/26/2007 | WO | A |
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20110083927 A1 | Apr 2011 | US |