EP1952042A1

EP1952042A1 - Electromechanical brake comprising an energy accumulator and a downstream force multiplication unit

Info

Publication number: EP1952042A1
Application number: EP06793283A
Authority: EP
Inventors: Akos Semsey
Original assignee: Continental Automotive GmbH
Current assignee: Siemens AG
Priority date: 2005-10-12
Filing date: 2006-09-06
Publication date: 2008-08-06
Also published as: DE102005048884B3; CN101321966B; US8069962B1; WO2007042358A1; CN101321966A

Abstract

The invention relates to an electromechanical brake (10), especially for motor vehicles, which comprises an element (e.g., brake disk 12) to be braked, at least one friction lining (18) for frictionally engaging with the element to be braked, and an electric actuator (26) for displacing the friction lining (18) so that it frictionally engages with the element to be braked. The aim of the invention is to provide a constructively and energetically improved electromechanical brake (10). For this purpose, a reversible energy accumulator (e.g. spring 42) functionally coupled to the electric actuator (26) interacts with a force multiplication device (30, 32, 36) in such a manner that when the brake (10) is actuated by means of the actuator (26), the energy stored in the energy accumulator is successively supplied to the force multiplication device with increasing actuation travel of the actuator (26) and the device convert said energy in a set manner to an actuation torque that increases with increasing actuation travel of the actuator (26), said torque being transmitted indirectly or directly onto the friction lining (18). When the brake is released, a brake-inherent restoring force which reacts upon the force multiplication device via the friction lining (18) recharges the energy accumulator.

Description

description

Electromechanical brake with power storage and nachgeschal ^¬ ted power transmission unit

The present invention relates to an electromechanical brake according to the preamble of patent claim 1, which is provided in ^¬ special, but not exclusive, for use in vehicles. Electromechanical brakes only differ in the spread of the field of motor vehicles far ver ^¬ hydraulic or pneumatic brakes characterized in that the brake operating force is not hydraulic or pneuma ^¬ table, but is generated by electromechanical means.

Electromechanical motor vehicle brakes of the first generation tried to produce the necessary, significant brake actuation force by means of an electric motor to each wheel brake, which was usually followed by a reduction gear, so that the electric motor is not too large and thus too heavy. The elected, sometimes very large reduction ratios ranging from 1: 200 but the dynamic behavior of the brake deteriorated greatly, which such Lösun ^¬ gen total was considered to be unsatisfactory. Such solutions Lö ^¬ are so far never gone into production.

Significantly more promising are electromechanical brakes with self-boosting, since this type of electromechanical brakes requires only a relatively small electric actuator and fetches most of the required Bremsbetätigungs- force from the kinetic energy of the moving, braked member of the brake, for example, a turning in vehicle operation brake disc. The reason ^¬ additional operation of such electromechanical brakes with self-gain is attributed loading in German patent 198 19 654th Due to the principle of operation, however, high brake actuation forces can only be achieved if a vehicle in which such an electromechanical brake with self-boosting is installed moves. Therefore, there is still the desire for an electromechanical brake, the high power supply to obtain Bremsbetäti- both during a movement example of a Fahrzeu- ges and at a standstill, ie regardless of whether the starting ^¬ zubremsende member of the brake in Movement is or not, and moreover, regardless of the (rotational) direction of this member, a small electrical actuator needed only. General advantages of electromechanical motor vehicle brakes are the ease of installation in the vehicle ^¬ manufacture (previously required hydraulic lines omitted) and the ease of integration into the control and operation of the brake necessary electronic controls (driver assistance functions such as ABS, ESP, EBV, EDS, etc.) can be realized without expensive solenoid valves).

Starting from an electromechanical brake with a braked member, at least one friction pad to rub ^¬ locking engagement with the braked member, and an electric actuator for moving the friction lining in frictional engagement with the braked member, this object is achieved by an operatively connected to the electric actuator coupled reversible force accumulator which acts as together with a force transmission means that, for a taking place by means of the actuator betae ^¬ account the brake stored in the power storage power with increasing actuation of the actuator successively released in the power transmission device and converted by this into an actuation torque is that is indirectly or directly applicable transmitted to the friction lining, wherein the supply ^¬ Actuate the moment with increasing actuation of the actuator in a predetermined manner increases, and that a through d for a release of the brake en friction lining on the power transmission device retroactive, braking inherent restoring force recharges the power storage again.

The present invention is based on the idea that Need Beer ^¬ preferential brake force or the required Bremsbetäti- To cover moment of inertia substantially with the force stored in the force memory and to let the electric actuator only a small proportion steer compared with the required brake actuation force or the required brake actuation torque. In this context, "operatively coupled to the electric actuator reversible energy storage" is to be understood that automatically upon actuation of the electric actuator and the energy storage a force corresponding to the extent of actuation of the actuator to the power transmission device. The respective force applied to the force transmission device, which is composed of the proportion of the force originating from the energy accumulator and of the proportion of the force contributed by the electric actuator, is "amplified" by the force transmission device, by virtue of this force being transferred into an actuation ^element which is then gene on the friction lining übertra ^¬, sen to the latter against the braked member to pres ^¬ is reacted. The force transmission device is configured in such a way, for example by means of a variable lever arm, that the actuating torque increases with increasing actuation travel of the actuator in order to take account of the increased braking requirements which are associated with the increasing actuating travel of the actuator. The force transmission device thus ensures that, despite substantially the same input force, applied by the interaction of the Kraftspei ^¬ chers with the electric actuator, the transmitted from the power transmission device on the friction lining Ausgangsbe ^¬ actuating torque increases with increasing actuation of the actuator without the electric Actuator must increase its operating force significantly. The "rising in a predetermined manner actuating torque" means that you can specify by a corresponding design of the power transmission device a certain, desired course of the Ausgangssbetätigungsmomentes. Such a course can be linearly increasing, but it can also be progressive or degressive. By "bremseninhärenter restoring force" is meant that each brake power supply one of the Actuate the ^¬ when actuated, opposing force builds up, the Inventions according to is used to recharge the energy storage when releasing the brake, so that in the energy storage power is available for a new braking operation.

Preferably, the inventive electromechanical

Brake designed so that their energy storage is then completely or almost completely emptied when the electric actuator has reached its maximum actuation travel. Although it would also be possible to operate the energy store at levels between 100% and, for example, 50% of the force stored in it, full or almost complete emptying of the actuator at maximum braking is more favorable from an energy point of view. Such, energetically favorable operation, however, requires a relatively high power transmission by the power transmission device in the range of the maximum actuation travel of the actuator in order to achieve the then required high brake actuation torque can.

In preferred embodiments of the electromechanical brake according to the invention, the braking-inherent restoring force results from elastic deformation of the brake components involved in braking, e.g. Compression of the friction lining, expansion of a brake caliper in the case of an electromechanical brake in saddle design etc. The electromechanical brake itself behaves like a spring, which is tensioned when the brake is actuated and released when the brake is released. wherein the relaxation process is used to recharge the energy storage.

The increase in the actuating torque predetermined by means of the variable lever arm of the force transmission device via the actuating travel of the actuator preferably compensates at least approximately for the braking-inherent restoring force increasing with the actuating travel. This means for the elekt ^¬ innovative actuator that this whole over its actuation only to be able must provide an actuation force to deliver, which is small compared to the total required brake actuation force or the total required brake actuation torque. The electric actuator can therefore be designed easily and with a small size.

In some embodiments, the e lektromechanischen brake of the invention, the predetermined increase in the loading ^¬ tätigungsmoments is selected so that the rising of the actuation bremseninhärente restoring force is under-compensated, which means that the electric actuator voted a be ^¬ force component in the operating direction needs to be heading to the to achieve desired braking effect. Falls at a thus designed electromechanical brake actuator of the e lectric from the brake open state falls forcibly ih ^¬ ren unconfirmed back. Other exemplary embodiments are designed such that the braking-inherent restoring force increasing with the actuating travel is overcompensated, which means in normal braking operation that the electric actuator has a certain amount of force counter to that

Brake actuation direction must be controlled so that in total (only) the desired braking effect is achieved. If the electric actuator fails in such an exemplary embodiment, the electromechanical brake automatically assumes a closed, ie braking state. Such an interpretation is written for specific applications required by law ^¬, eg for truck brakes.

In all embodiments of the brake according to the invention, the force transmission device is preferably a transmission with a variable lever arm, ie with a lever arm which becomes larger with increasing actuating travel of the actuator. Any type of transmission which the aforementioned requirement ^¬ he filled, can be employed.

The braked member of the brake may be a rotatable member, such as a brake disc or a brake drum, it can but also be a linear member, between which and the brake takes place a relative movement.

As energy storage of the electromechanical brake according to the invention are particularly compressed springs that can be used individually or as a spring pack. There are also springs having a suitable power transmission device already installed, so to speak, for example, plate ^¬ or diaphragm springs as they are today in Kraftfahrzeugkupp- payments using. Such springs are already showing by itself (caused for example by its special geo ^¬ metry) the desired behavior of a rising with increasing betae ^¬ tigungsweg operating torque.

According to a particularly preferred embodiment, the electromechanical brake according to the invention is a floating-type disc brake for a motor vehicle.

An embodiment of an electromechanical brake according to the invention will be explained in more detail below with reference to the accompanying schematic figures. It shows:

Figure 1 is a diagram of an electromechanical brake according to the invention, designed as a floating-blade disc brake for a motor vehicle, and

2 shows a torque actuation angle diagram light illus- an exemplary curve of Figure 1 acting in the Ausführungsbei ^¬ game according forces.

In Figure 1, the structural design of an off ^¬ execution example of an electro-mechanical brake is schematically represents 10 Darge ^¬, which is designed here as a floating-caliper spot-type disc brake for a motor vehicle.

The brake 10 has a rotatable brake disk 12 which in the normal operating state of the brake fixed to the wheel of a not shown here vehicle is connected. An arrow D indicates the main direction of rotation of the brake disk 12 during operation, ie the direction of rotation when moving forward.

The brake disc 12 is covered by a floating caliper 14, the disc parallel to the not shown rotational axis of the brake ^¬ 12 is slidably attached to an only indicated here brake carrier 16, which is connected in the installed state of the brake 10 with a vehicle-fixed component, usually measured using a Part of a suspension. In the brake carrier 16 is a first friction lining 18 by means of a first lining carrier plate 20, with which the friction lining 18 is fixedly connected, guided so that it can be moved to the brake disc 12 and away from it. Compared with the first friction lining 18 of the brake disc 12 is arranged a second friction pad 22 on the other side, the carrier plate by means of an associated lining ^¬ 24 is attached to the floating caliper fourteenth

To actuate the brake 10 is an electrical actuator 26, for example, an electric motor, which is about a drive ^¬ pinion 28 rotatably mounted in the brake carrier 16, externally toothed disc 30 is able to rotate.

On the disc 30, a first pin 32 is fixed, on which a first sleeve 34 is rotatably mounted. Further, a second pin 36 is secured to the disc 30, on which a second sleeve 38 is rotatably mounted. A distance M between the center of the first pin 32 and the axis of rotation of the disc 30 is greater than a distance N between the center of the second pin 36 and the axis of rotation of the disc 30th

The first pin 32 is connected via its sleeve 34 in contact with the one side of a displaceably guided piston 40, on the other side of a compression spring 42 acts, which is at least in the initial state of the brake 10 shown in Figure 1 in a compressed state. The second pin 36 is in contact with an actuator via its sleeve 38. wedge 44, which is relative to the first friction lining 18, more precisely its lining carrier plate 20, parallel to the brake disc 12 slidably mounted. The actuating wedge 44 is supported in a likewise displaceably mounted manner at a wedge angle α on an abutment 46, which is attached to the floating caliper 14.

The function of the brake 10 will be explained in more detail below. To carry out a braking operation, the two friction linings 18, 22 must be moved into contact with the brake disk 12. For this purpose, the electric actuator 26 must rotate its drive pinion 28 in the counterclockwise direction and thereby apply a first actuation torque to the disc 30, which then begins to rotate in a clockwise direction. This first actuation torque acts on the actuating wedge 44 via the second journal 36 or the sleeve 38 mounted rotatably on it. Before the disk 30 rotates, the center point of the first journal 32 is on the line of action of the force of rotation of the disk 30 Force exerted by the spring 42 via the piston 40 on the first pin 32 (initial state). In this initial state, the spring 42 exerts no actuating torque on the actuating wedge 44, since the lever arm of the spring force with respect to the actuating wedge 44 in this initial state is zero. Due to the initiated by the first operating moment

Rotation of the disc 30 in a clockwise direction, however, the center of the first pin 32 moves away from the force ^{action ¬} line of the spring 42 (in Figure 1 down), so that now creates a second operating torque, the size of which acts on the piston 40 Spring force and the size of the lever arm generated by the rotation between the force line of action of the spring and the center of the first pin 32 results. Like the first actuating torque produced by the electric actuator 26 also acts as the second actuator moment about the second pin 36, more precisely via its sleeve 38, 44. on the actuating wedge on the Actuate the ^¬ supply wedge 44 thus acts a total operating torque, resulting from the addition of the first actuating torque and the second actuating torque results. The Gesamtbetätigungsmo- ment shifted triggered by the accompanying rotation of the disc 30, the actuating wedge 44 in Figure 1 to the left, whereby the actuating wedge 44, due to its taking place under the wedge angle α support on the abutment 46, at the same time the first friction lining 18 against the Brake disk 12 presses. Due to the resulting, those skilled in the known reaction forces of the floating ^¬ saddle 14 moves parallel to the axis of rotation of the brake disc 12 and thus ensures that even the second friction lining 22 is pressed against the brake disc 12th

With increasing total operating torque to be ^¬ behave agreed components of the brake 10, in particular the two friction linings 18 and 22 and the floating caliper 14, as a spring which is increasingly tensioned, because the material of the friction pads 18, 22 is compressed by the forces acting and the floating caliper 14 expands elastically. Thus, a braking-inherent restoring force arises, which counteracts the brake-actuating force or the brake-actuating torque and which must be overcome in order to produce a braking operation. As can be seen, this braking-inherent restoring force is always greater, the greater the total operating torque of the brake ^¬ se, which means nothing else than that to achieve an increasing braking force a likewise increasing total ^¬ actuation torque must be provided.

In the illustrated brake 10, the increasing Gesamtbetätigungsmo- ment required with increasing braking force in an elegant and energetically very advantageous manner by the force of the spring 42, the piston 40 and the power transmission device representing unit of disc 30, first pin 32 and second Pin 36 acts on the actuating wedge 44. With increasing angle of rotation of the disc 30 clockwise growing between the center of the first pin 32 and the force line of action of the spring 42 lever arm increases up to the maximum lever arm M, which is compared with a rotation of the disc 30 by 90 ° the initial state is achieved, while at the same time the lever arm formed between the center of the second pin 36 and the rotational ^¬ axis of the disc 30, starting from its maximum value N, which is present in the initial state of the brake 10 decreases continuously and reaches zero when the Disk 30 has rotated 90 degrees clockwise. In other words, the force transmission ratio of the power transmission device of the disc 30 increases with a clockwise rotation continuously and, after a rotation of the disc 30 by 90 degrees, at least theo retical ^¬ the value infinity. In this way, the force of the spring 42 provides the largest part of the respectively required actuating torque, while the electric actuator 26 only has to supply a small part of the required actuating torque. Preferably, serving as energy storage Fe ^¬ the 42 is designed so that it at maximum power transmission of the power transmission device, in the present case, when the disk 30 has rotated from its initial position by 90 degrees, is completely or at least almost fully relaxed ,

To clarify the described courses of the actuating torque, reference is made to FIG. 2, which shows a diagram in which the individual moments are plotted over the actuating angle of the actuator, more precisely the disk 30. A first curve A shows the course of the braking inherent restoring force which builds up during a braking operation with increasing actuating travel or the restoring torque resulting from this force. Since this return torque is directed counter to the actuating torque, it has a negative sign. A curve B shows the course of the actuation torque caused by the force of the spring 42 and the downstream force transmission device, which was referred to above as the second actuation torque. This second operating torque is the course over its readiness ge ^¬ entire course of magnitude smaller than the restoring torque according illustrates the curve A. A curve C of the electric actuator 26 via the operating angle Asked actuating torque, which has been referred to above as the first operating torque. For a given betae ^¬ actuating angle, the sum of the first and second ^¬ Actuate the resulting moment supply a magnitude value corresponding to the associated value of the restoring moment. It can be seen that the operating moment provided by the electric actuator 26 is in any case small compared to the actuating moment, which is generated by means of the force of the spring 42. The electric actuator 26 can therefore be made small and lightweight.

The force profile shown in Figure 2 is merely exempla ^¬ driven and can be modified by a different interpretation of the energy accumulator and / or downstream of the power transmission device such as it is for a given application at vorteilhaftesten. While an exemplary ^¬ example has been described, in which the electric Ak ^¬ tuator 26 is heading for a small portion of the total operating torque, can be provided in other embodiments, that resulting from the energy storage and the downstream power transmission device operating torque resulting from the braking inherent restoring force restoring moment overcompensated, so that the electric Ak ^¬ tuator must apply a moment for controlling the braking operation, which is opposite to the actuating torque, which is exerted by means of energy storage and downstream power transmission device. It is also understood that, instead of the illustrated and described force transmission device, any other force transmission device can be used which provides a desired force transmission variable over the actuation path. Also, the operation of the first friction pad 18 is not limited solution 44 used in the manner shown, an actuating wedge, son ^¬ countries it may instead be present other means for actuating the or of the friction linings. Also, the power transmission device can act directly on a friction lining. When releasing the brake 10, the described, bremsenhä ^¬ rent restoring force or resulting from this force restoring moment causes the above-described occurring during actuation of the brake operations reverse, ie the actuating wedge 44 shifts parallel to

Brake disk 12 in Figure 1 to the right, the disc 30 rotates counterclockwise back to its starting position shown in Figure 1, and the spring 42 is simultaneously compressed again or "charged" to provide for a renewed braking force available , The tensioning and relaxing the spring 42 is thus reversible, elekt ^¬ cal energy is thus consumed only for the relatively small part of the total actuation torque, which the electric ^¬ cal actuator 26 has to apply either in the direction of actuation or opposite the direction of actuation.

Claims

claims

1. Electromechanical brake (10), in particular for motor vehicles, with a member to be braked, at least one friction lining (18) for frictional engagement with the member to be braked, and an electric actuator (26) for moving the Reibbela- ges (18) in frictional engagement with the abzubremsenden member, characterized by a operatively coupled to the electric actuator (26) reversible force accumulator, which cooperates with a force translation device such that in an actuation of the brake (10) by means of the actuator (26) in the energy accumulator stored force with increasing Actu ^¬ supply path of the actuator (26) successively delivered to the Kraftüberset ^¬ tion device and is converted by this in an increasing actuating travel of the actuator (26) in a predetermined Wei ^¬ se increasing operating torque, the medium ^¬ bar or immediately is transferred to the friction lining (18), and that in a release of the Brake on the friction lining (18) on the power transmission device retroactive, braking inherent restoring force the energy storage again ^¬ loads.

2. Electromechanical brake according to claim 1, characterized in that the energy storage device when the electric actuator (26) has reached its maximum actuation ^path he ^¬ is completely or almost completely emptied.

3. Electromechanical brake according to claim 1 or 2, characterized in that the braking-inherent restoring force resulting from the elastic deformation of the brake components involved in the braking.

4. Electromechanical brake according to claim 3, characterized in that over the actuation path ^¬ given increase of the actuating torque at least approximately compensates for the increasing with the actuation travel Bremsesinhärente restoring force.

5. Electromechanical brake according to claim 4, characterized in that the lower with the actuating travel to ^¬ increasing braking inherent restoring force is undercompensated.

6. Electromechanical brake according to claim 4, characterized in that the with the actuating travel to ^¬ rising brake inherent restoring force is overcompensated.

7. Electromechanical brake according to one of the preceding claims, characterized in that the force transmission device is a transmission (30, 32, 36).

8. Electromechanical brake according to one of the preceding claims, characterized in that the member to be braked is a brake disc (12).

9. Electromechanical brake according to one of the preceding claims, characterized in that the energy accumulator is a compressed spring (42).

10. Electromechanical brake according to claim 9, characterized in that the spring is a plate spring whose output actuating torque increases with increasing actuation path.

11. Electromechanical brake according to one of the preceding claims, characterized in that the brake (10) is a Schwimmsat ^¬ tel-Teilbelagscheibenbremse.