WO2004001254A1

WO2004001254A1 - Electric automotive disc brake

Info

Publication number: WO2004001254A1
Application number: PCT/EP2003/006486
Authority: WO
Inventors: Andreas GRÜNDL; Bernhard Hoffmann; Friedrich MÖRTL
Original assignee: Compact Dynamics Gmbh
Priority date: 2002-06-21
Filing date: 2003-06-18
Publication date: 2003-12-31
Also published as: AU2003246561A1; DE10227828A1; DE10227828B4

Abstract

The invention relates to an electric automotive disc brake that comprises a caliper (10) and an actuation unit (12) disposed on said caliper. The brake further comprises two friction linings (14) that interact with one lateral face each of a brake disk. Said friction linings are restricted in their displaceability inside the caliper and can be frictionally engaged with the brake disk (16) by means of the actuation unit (12). Said actuation unit comprises an electric motor (20), having at least one stator (24) and at least one rotor (40) and a transmission unit (22), functionally interposed between the electric motor and a friction lining, for converting the rotational movement of the electric motor to a translational movement for the friction linings. The actuation unit comprises an energy accumulator (50) that takes up energy when the friction linings are applied and that causes the friction linings to open by discharging energy.

Description

Electric motor vehicle disc brake

description

Background of the Invention

The invention relates to an electric motor vehicle disc brake. In particular, the invention relates to a disc brake which enables the construction of a so-called dry brake system, i.e. without hydraulic or brake fluid, which is pressed into a cylinder / piston arrangement by a master brake cylinder when the driver actuates the brake pedal via a brake fluid line system. Rather, in the invention, a sensor pedal operated by the driver is used to generate control signals for an electric drive which brings the friction linings with the brake disc into and out of frictional engagement.

State of the art

From the generic DE 197 48 318 Cl a brake arrangement for a land vehicle with an electric motor is known, which is followed by a reduction gear, the output of which is connected to the input of a clamping / application device which acts on the friction linings of a brake arrangement. Here, the reduction gear is designed to be self-locking. With an actuating mechanism, the self-locking of the reduction gear can be canceled or produced, and an opening movement of the clamping / tightening device can be carried out in the sense of releasing the friction linings from a brake disc. A spiral spring is wound around a tie rod, which acts as a torsion spring. When the pull rod moves axially, the charged spring-loaded mechanism can set a pinion in rotation. This causes a spindle to rotate, which moves the friction linings away from the brake disc. This happens when the parking brake is released or during an emergency operation. The parking brake function can thus be released even without electrical actuation. To charge the spring accumulator, the (e.g. electromagnetically actuated) the

Drawbar moves axially and at the same time the electric motor is actuated. No torque is transmitted to the spindle of the reduction gear. Rather, the spring accumulator is tensioned in the sense of an energy charge.

From DE 197 11 382 AI a parking brake device on a brake caliper of a hydraulically actuated service brake is known, in which the parking brake device comprises an electric drive, which on at least one piston Service brake works. Arranged between the motor of the electric drive and the piston is a mechanical spring accumulator which can be loaded when the parking brake is actuated and has an integrated spring element. The spring element is designed as a torsion spring element, is arranged in the piston and prestresses the piston in the direction of the brake disc.

DE 100 50 352 Cl shows an example of such an electric motor vehicle disc brake, with a brake caliper and an actuating unit arranged on the brake caliper, which acts on two friction linings which interact with one side surface of a brake disc and are arranged displaceably in the brake caliper. The actuating unit has an electric motor and a gear unit, which is operatively arranged between the electric motor and the friction linings, for converting the rotational movement of the electric motor into a translational movement for the friction linings.

An essential aspect for the implementation and acceptance of this type of brake system is the fail safety or its fail-safe behavior. For this type of brake system, this means that even if the electrical power supply fails when the brake arrangement is actuated, the friction linings must be released from the brake disc so far that the corresponding wheel does not lock. This means that the torque-converting gearbox must not be self-locking. Usually a gear with a spindle / nut arrangement or the like is used here, which converts a rotary movement (of an electric motor) into a translatory movement (of the friction linings). Since these gears should not be self-locking, there are limits to the reduction ratio (which results from the thread pitch of the spindle). However, this also means that the drive motor must provide a relatively high torque with appropriate dynamics; this requires relatively large-scale arrangements of the electric motor.

No arrangements are known from the prior art which would be suitable for representing the required forces with a correspondingly small installation space with the required dynamics and reliability at the low costs required for a mass product.

Problem underlying the invention

The invention is therefore based on the problem of providing an electrically actuable motor vehicle disc brake which in particular the limited, in modern the space available for passenger motor vehicles for wheel brakes is used efficiently and a comparable fail-safe behavior and the high level of reliability of conventional hydraulic brakes are achieved

Solution according to the invention

To solve this problem, the electrically actuated motor vehicle disc brake described at the outset is further developed according to the invention by the features of patent claim 1.

Advantages and further refinements of the solution according to the invention

This arrangement makes it possible to use a self-locking gear arrangement which can have a considerably higher reduction ratio than non-self-locking gear arrangements. This also reduces the torque required on the input side. Either the electric motor can be made more compact, or the torque and consequently the braking force can be increased accordingly with the same installation space. To this end, the invention is based on the consideration that the energy store merely has the energy required for overcoming the friction in the transmission, the (de-energized) electric motor and in the other components (for example bearing of the brake pads, etc.) for a release movement of the Must provide friction linings away from the brake disc. In other words, the - if necessary preloaded - energy store, which is at least partially charged when the friction linings move towards the brake disc, in the event of a subsequent failure of the electric motor (i.e. when the friction linings are delivered) provides the energy for overcoming the holding moments and for the return movement by the amount of the brake clearance. But even with a functioning electric motor, the arrangement according to the invention has the advantage that a release process of the friction linings caused by the electric motor away from the brake disc is supported by the release of energy from the energy store. In any case, the required installation space is reduced on the one hand by the arrangement according to the invention and at the same time the failure safety of the brake is guaranteed.

The energy store is designed in such a way that a rotational movement of the rotor in a first direction - preferably in the sense of a feed movement of the friction linings - supplies energy to the energy store by a predetermined first angular amount, and that the energy store extends as far as the first predetermined angular amount is exceeded unloads that another rotational movement in the first direction is enabled. This ensures that the energy store only absorbs a defined maximum energy, even if the rest position of the link of the drive unit acting on the friction linings gradually shifts - for example because of the wear of the friction linings.

In a preferred embodiment of the invention, the gear unit is designed as a spindle / nut arrangement or as a spindle / ball bushing arrangement, in which the rotor of the electric motor is connected in a rotationally fixed manner to the nut or the ball bearing bushing as the input side of the gear unit, and the spindle is connected to one Friction lining works.

In order to ensure that after replacing worn friction linings, the gear unit or its spindle can easily be returned to the starting position for unused friction linings, the energy store is designed in such a way that when the rotor rotates in a second direction - preferably in In the sense of a restoring movement of the friction linings - the energy store is decoupled from the rotor and, when the rotor rotates in the first direction, the energy store is coupled to the rotor again. This configuration allows the spindle of the gear unit to be completely returned to the starting position without the energy store interfering with this return movement. Likewise, as soon as the spindle rotates again in the sense of a feed movement of the friction linings, the energy store is recharged as soon as the energy store is coupled to the rotor again.

In a preferred embodiment of the invention, the energy store is designed as a spiral spring arrangement, which is detachably coupled - directly or indirectly - to the rotor of the electric motor in the region of its first end and which is detachably coupled - directly or indirectly - to the stator in the region of its second end ,

For this purpose, the spiral spring has in the region of its second end a locking element which is oriented essentially radially outwards and which can be brought into or out of engagement with at least one locking device which is stationary relative to the stator. In its simplest configuration, this latching element can be the radially outwardly bent end of the spiral spring. As an alternative to this, however, an end piece designed to match the geometric shape of the fixed latching can also be fastened in the region of the second end of the spiral spring. The fixed latching can in particular have the shape of a recess. The design of the second (outer) end of the spiral which in cooperation with the latching / recess ensures that an energy supply to the coil spring by turning its inner (first) end beyond a predetermined amount of energy causes a substantially radial, inward tensile force on the second end of the coil spring, so that the holding force of the outer end at the latching is exceeded and the outer end of the coil spring is pulled radially inward from the latching. The result of this is that the coil spring relaxes again, expands radially and engages with its outer end in a further - or after a 360 ° movement of its outer end in the same - latching. Excessive charging of the energy store, that is, in the embodiment described above, an "overturning" of the spiral spring, is therefore effectively ruled out due to a correspondingly large number of rotations exerted on the inner end of the spiral spring.

The releasable coupling of the inner end of the spiral spring to the rotor or the nut or ball bushing of the gear unit driven directly or indirectly by the rotor is accomplished according to the invention in one embodiment in that the nut or ball bushing has at least one recess on the outer circumference , which can engage the inner end of the coil spring. The recess is arranged along an imaginary chord through the circular (ring-shaped) cross section of the nut. The chord encloses an essentially acute angle with an imaginary tangent at the point of intersection of the chord with the circumference. The chord and the tangent form an imaginary arrow pointing in the direction of the first direction of rotation (infeed movement).

Otherwise, the electric motor with the spring accumulator is an invention which can be used independently of the above-described application of the electric motor vehicle disc brake.

Further details, features and modifications of the invention are explained below with reference to the drawing.

Brief description of the drawing

Fig. 1 shows a schematic representation of an electric motor vehicle disc brake according to the invention in longitudinal section.

2a, 2b show schematic top views of a segment of a stator with two stator windings in different embodiments. FIG. 3 shows a schematic plan view of the rotor in the direction of arrows III in FIG. 1.

Detailed description of a preferred embodiment

1 shows an electrically actuable motor vehicle disc brake which has a brake caliper 10 which is essentially U-shaped in cross section and an electromechanical actuating unit 12 arranged on the brake caliper 10. Arranged in the brake caliper 10 on its two legs 10 ′, 10 ″ are two friction linings 14, 14 ′ (which are accommodated in guides which are not shown in any more detail). The two friction linings 14, 14 ′ are on both sides of a brake disk overlapped by the brake caliper 10 16 arranged and each interact with a side surface 16 ', 16 "of the brake disc 16 which is rotatably connected to an axle stub 18 only partially shown. The friction linings 14, 14 'are arranged in the brake caliper 10 towards the brake disc 16 or away from it. In the embodiment shown, this is a floating caliper arrangement in which one of the friction linings 14 can be brought into frictional engagement with the brake disk 16 by the actuating unit 12 directly and the other friction lining 14 'by the action of a reaction force applied by the brake caliper 10.

The actuating unit 12 is attached to the side of the brake caliper 10 and has an electric motor 20 and a gear in the form of a nut / spindle arrangement 22 arranged between the electric motor 20 and a friction lining 14. This gear 22 serves to convert the rotary movement of the electric motor 20 into a longitudinal movement for the friction linings 14, 14 '.

The electric motor 20 has a stator 24 with two annular stator windings 26, 26 '. On the two end faces of each stator winding 26, 26 'there is a ring of pole shoes 28a, 28b; 28a '28b' arranged (see also FIG. 2a), which partially overlap the outer lateral surface of the respective stator winding 26, 26 'with their free ends 30a, 30b, 30a', 30b '. The radially inner ends of the pole shoes 32a, 32b; 32a ', 32b' of a ring are connected to one another by a magnetically conductive, integrally molded ring (not designated further).

The radially outer (free) ends of the pole shoes 30a, 30b, 30a ', 30b' of two rings arranged on a stator winding 26, 26 'engage along the circumference of the respective stator winding 26, 26 'alternately into one another and each protrude laterally. To simplify manufacture, the two adjoining rings of pole shoes 28b, 28a ', which are arranged between the two stator windings 26, 26', are designed as uniform components which have an essentially T-shaped configuration (see FIG. 1 below). Each stator winding 26, 26 'is arranged on a ring 34, 34' made of sheet iron, which serves as a magnetic yoke.

In the embodiment shown, the pole pieces are made of sintered iron powder, the grains of which are electrically and magnetically insulated from one another by a plastic coating.

The electric motor 20 also has a rotor 40 in the form of an annular cylinder 40a, on the side facing away from the brake caliper 10, an end wall 40b is formed. The rotor 40 with its ring cylinder 40a engages around the stator windings 26, 26 'in the radial and in the axial direction. The end wall 40b of the rotor 40 is coupled to the input side of the gear unit 22 in such a way that the end wall 40b is connected to the nut 22a of the nut / spindle 22 in a rotationally fixed (welded or form-fitting) manner. On the inner wall of the ring cylinder 40a of the rotor 40, the free ends of the pole shoes 28a, 28b; 28a ¹ 28b 'opposite to form an air gap 42 rare earth magnets 44, 44' with their radially outer side each arranged on a ring 46, 46 'made of sheet iron. The magnets 44, 44 'are dimensioned and arranged such that they are connected to a pole piece 28a, 28b; 28a '28b' are aligned.

The magnets which are aligned with the pole shoes surrounding a stator winding and which are arranged on the rotor in the circumferential direction adjacent to one another have an alternating magnetic orientation.

The nut 22a of the nut / spindle arrangement 22 is rotatably mounted in a flange 48 formed on the leg 10 'of the brake caliper 10, but is not displaceable in the axial direction. The nut 22a is coupled to the spindle 22c via balls 22b, the spindle 22c moving in the longitudinal direction when the nut 22a rotates and thereby pushing the brake pad 14 toward the brake disk 16 or away from it via a pressure plate 52.

As shown in FIG. 1, on the side of the actuating unit 12 facing away from the friction linings 14, 14 ', an energy store in the form of a spiral spring 50 is provided on the end face. wall 40b of the rotor 40 arranged. In the area of its first, inner end 52, the spiral spring 50 is detachably coupled to the rotor 40 of the electric motor 20. Since the rotor 40 is non-rotatably seated on the nut 22a, the coil spring 50 is mounted surrounding the nut 22a. For this purpose, the nut 22a has a recess 60 into which the inner, angled end 52 of the spiral spring 50 can engage. The recess runs along an imaginary chord s through the circular cross section of the nut 22a or the recirculating ball bushing. The chord includes an essentially acute angle W with an imaginary tangent T at the intersection of the chord s with the circumference of the nut 22a. The chord s and the tangent T thus form an imaginary arrow which is oriented in the direction of the first direction of rotation R1. (see Fig. 3).

In the area of its second end 54, the spiral spring 50 is detachably coupled to the stator 24. For this purpose, the spiral spring 50 is angled in the region of its second end 54 to form an essentially radially outward-oriented latching element 56 in order to come into or out of engagement with a latching 58 which has a sawtooth-shaped shape, with a shape in the first direction R1 tooth flank growing radially outwards. It can be seen that a large number of such catches 58 are arranged one behind the other along the inner circumference of an annular web 62. In addition, a cover 64 for the spiral spring 50 (not shown in FIG. 1) is arranged on the ring web 62.

Claims

claims

1. Electric motor vehicle disc brake, with

- A brake caliper (10) and - An actuating unit (12) arranged on the brake caliper (10), and with

- Two, each with a side surface (16 ', 16 ") of a brake disc (16) cooperating and arranged in the brake caliper (10) to be limitedly displaceable friction linings (14, 14'), which are actuated by the actuating unit (12) with the brake disc (16) Frictional engagement can be brought about, wherein - the actuating unit (12) an electric motor (20) with at least one stator (24) and at least one rotor (40) as well as a gear unit (22) arranged between the electric motor (20) and a friction lining (14). for converting the rotational movement of the electric motor (20) into a translational movement for the friction linings (14, 14 '), wherein - the actuating unit (12) has an energy store (50) which generates energy during a feed movement of the friction linings (14, 14') receives and an opening movement of the friction blades (14, 14 ') by energy delivery, the energy storage device being designed such that a rotary movement of the rotor (40) in a first direction by a predetermined The first first angular amount supplies energy to the energy store (50), characterized in that when the first predetermined angular amount is exceeded, the energy store (50) discharges to such an extent that a further rotational movement in the first direction is made possible.

2. Electric motor vehicle disc brake according to claim 1, wherein - the gear unit (22) is designed as a spindle / nut arrangement or as a spindle / ball bearing bush arrangement, in which the rotor (40) of the electric motor (20) with the nut (22a ) or the recirculating ball bushing as the input side of the gear unit (22) is connected in a rotationally fixed manner, and the spindle (22c) acts on a friction lining (14).

3. Electric motor vehicle disc brake according to claim 1 or 2, wherein the energy store is designed such that when the rotor (40) rotates in a second direction, the energy store (50) decouples from the rotor (40) and when the rotor rotates (40) in the first direction again couples the energy store (50) to the rotor (40).

4. Electric motor vehicle disc brake according to one of the preceding claims, wherein the energy store (50) is at least partially precharged.

5. Electric motor vehicle disc brake according to one of the preceding claims, wherein the energy store (50) is arranged on the rotor or on the gear unit on the input side.

6. Electric motor vehicle disc brake according to one of the preceding claims, wherein the energy store is designed as a spiral spring (50) which is releasably coupled in the region of its first end (52) to the rotor (40) of the electric motor (20) and which is releasably coupled to the stator (24) in the region of its second end (54).

7. Electric motor vehicle disc brake according to one of the preceding claims, wherein the spiral spring (50) in the region of its second end (54) has an essentially radially outwardly oriented latching element (56), which has at least one relative to the stator (24) stationary locking (58) can be brought into or out of engagement.

8. Electric motor vehicle disc brake according to one of the preceding claims, wherein the second end of the coil spring (50) in cooperation with the latching (58) is designed such that an energy supply to the coil spring by screwing its first end (52) over a predetermined amount of energy also produces a substantially radial, inward tensile force on the second end (54) of the coil spring (50) so that the holding force of the outer end at the latch (58) is exceeded and the second end (54) of the coil spring (50) is pulled radially inwards out of the catch (58).

9. Electric motor vehicle disc brake according to one of the preceding claims, wherein the nut (22a) has at least one recess (60) into which the inner end (52) of the coil spring (50) can engage and which along an imaginary tendon ( s) is arranged through the circular (ring) cross section of the nut (22a) or the recirculating ball bushing, the chord (s) having an imaginary tangent (T) at the intersection of the chord (s) with the circumference of the nut ( 22a) encloses an essentially acute angle (W) and the chord (s) and the tangent (T) form an imaginary arrow which is oriented in the direction of the first direction of rotation.

10. Electric motor vehicle disc brake according to one of the preceding claims, wherein the fixed latching (56) is a sawtooth shape, preferably with a tooth flank growing radially outwards in the first direction.