EP4196693A1

EP4196693A1 - Drum brake having compensation of brake-shoe transverse offset

Info

Publication number: EP4196693A1
Application number: EP21762605.0A
Authority: EP
Inventors: Martin GÄDKE; Adrian Messner; Uwe Bach; Ahmed Sefo; Matthias Schulitz; Jens Hoffmann; Christian Vey
Original assignee: Continental Automotive Technologies GmbH
Current assignee: Continental Automotive Technologies GmbH
Priority date: 2020-08-11
Filing date: 2021-08-05
Publication date: 2023-06-21
Also published as: DE102020210134A1; WO2022033642A1; KR20230022997A; CN116018470A; JP2023532585A; US20230296147A1; BR112022025419A2

Abstract

The invention relates to a drum brake (1) for a motor-vehicle electric braking system, wherein an actuation system, for example preferably a geared-motor drive module including a rotation-translation converter gear stage, a transmission means and a spreading device (2), optionally with support on an abutment (3), is in the force flow with movably mounted drum brake shoes (7, 8), which are suitable and intended for cooperating with a brake drum (5). The invention addresses the problem of further improving the efficiency, i.e. the force flow, in a preferably electromechanically actuatable drum brake (1) such that electric brake control which is as simple, fast and precise as possible is enabled, in conjunction with simple actuator control, and with reduced complexity, over the entire wear-prone service life of the brake shoes. According to the invention, in order to solve the problem, compensation of transverse offset is provided; for example, for this purpose a joint-disk-/joint-socket-type bearing geometry produced with special geometric profiling is to be provided, so that friction-lining support geometry further developed with profiling allowing mutual articulation is achieved such that the lining displacement perpendicular to the spreading direction, caused by offset, is prevented or at least reduced.

Description

Drum brake with brake shoe offset compensation

The invention relates to a drum brake that can be actuated, preferably electrically, in particular electrohydraulically or electromechanically, for a motor vehicle brake system, with actuators, such as a geared motor drive module including red-trans converter gear stage, transmission means and spreading device, or abutment support, which are in the power flow with movably mounted drum brake shoes. and are adapted and intended to cooperate with a brake drum.

The prior art knows hydraulically actuated drum brakes with actuators, mostly in the form of hydraulic wheel cylinders, which allow brake actuation forces to be applied via actuating elements (hydraulic pistons) to cooperating brake shoes and consequently to a brake drum (see, for example, page 129 of the brake manual ISBN 3-89059-008 -x; 9th edition 1986). Unfortunately, conventional hydraulic drum brakes are not readily suitable for guaranteeing all new control tasks with the required precision in a modern, electronically controlled drive train/brake system, maintenance-free over the life of the motor vehicle.

The applicant's DE 10 2018 215 979 A1 relates to a spreading device for spreading brake shoes of a drum brake for a motor vehicle, and a rotationally driven idle travel compensation device including a spring-loaded, rotatable adjustment screw is integrated into the spreading device.

There is a need for further improvement because the relevant prior art lacks further developed, practicable solutions which allow a reasonably complete handling of the effect of friction lining wear in modern motor vehicle drum brake systems.

The object is achieved for the first time very surprisingly in a patentable and still advantageous manner according to the invention on the basis of the combination of features according to patent claim 1, in that a compensation device for brake shoe transverse offset is provided adjacent to the expanding device and/or abutment in a brake drum interior, and this transverse offset compensation device is located laterally next to the spreading device and/or an abutment is inserted into the power flow of the drum brake. In the light of the present disclosure, the feature “transverse” is always elucidated on the basis of the transverse axis Q, arranged orthogonally, at right angles in relation to the spreading axis S of the spreading device 2 . If this written disclosure only speaks of an arrangement of the compensating means in the area of the spreading device in a simplified manner, then this does not imply any restriction, rather the compensating means can be switched on just laterally in the area of the abutment in the flow of forces, with the combination - as in the embodiment according to the drawing clarifies - offers.

The advantageous transverse offset compensation device is particularly preferably inserted directly into the interface between the spreading device and the brake shoe in a form-fitting manner. If the customer accepts it or needs it, it can easily be retrofitted as an adaptive modification, retrofitting an indirect insertion of the compensating device by positive locking via at least one exchangeable adapter component that is additionally inserted into the power flow, without departing from the basic idea of the invention.

In an advantageous embodiment, the compensating device contains a special articulated or movable mounting in your mutual contact area using a controlled forced guidance. For this purpose, a web guide can be realized in a 2-dimensionally curved arc shape based on the model of a flexible disk/joint socket. For the purpose of particularly rational production of the articulated (track) curve guide, it is advisable if the contact geometry also has at least one or more circular arc segments. In this case, it can advantageously be the case that the paired radii of the mutually paired circular arc segments for contact are each configured differently curved in the sense of mutual osculation. In the preferred embodiment, in a mutual comparison, the radius placed on the actuating element side is dimensioned gradually smaller than the radius placed on the brake shoe side. Seen in relation, the radius on the actuating element side can be dimensioned approximately in the order of magnitude of the brake drum diameter, whereas the counterpart with the radius on the brake shoe side can move approximately in the order of 1/5 - 1/10 of the brake drum diameter. It goes without saying that the mutual osculation as a side effect contributes very advantageously to the fact that in the power flow prevailing surface pressure can be better transmitted through the paired components.

In a further improved embodiment of the invention, it is also possible for increased effectiveness, i.e. it makes sense if necessary, to shift one or more middle centers of the relevant joint radii by a specific, predetermined offset offset, so to speak in the direction of the wheel axis of rotation, which makes a further expedient contribution to the purpose Reduction of lateral offset caused by wear.

In summary, the present invention is based on systematic, planned research into the interrelationships of the drum brake system in connection with the new finding that, in addition to idle travel compensation, further measures appear necessary and sensible in order to upgrade a drum brake for the modern age. Because the largely unavoidable, completely uneven drum brake shoe wear of a leading brake shoe and a trailing brake shoe in connection with the wear pattern of a brake drum that wears largely evenly concentrically causes a high degree of lateral offset for the power-transmitting bearing points over the service life of the system - in their relation to the adjacent, mostly immovable and /or components arranged fixed to the back plate (actuating element, spreading device, abutment). This in turn results in a change in the lever arm due to the degree of wear, which must be taken into account in terms of control technology, and the wear-related offset in relation to the expanding device can generate an oppositely directed pair of forces, which can introduce transverse forces into the drive train of the wheel brake. The solution according to the invention is based on the research findings explained above and therefore logically provides that the drum brake according to the invention is expediently equipped with the lateral offset compensation according to the invention.

In a preferred embodiment, which is to be understood as an example, the offset compensation carried out includes a particularly geometrically profiled, tailor-made, universal joint socket-like bearing geometry in indirect or direct contact between the actuating element and the brake shoe, with the very pleasing effect that the compensation by means of friction lining bearing geometry, which has been further developed according to the invention, compensates for the wear path-related Avoiding or at least reducing migration movements on the support by means of a geometrically profiled support design. According to the invention, the wear offset compensation is compensated automatically, without current, automatically, and in particular the controllability as well as in particular the efficiency and power flow of a preferably electromechanically actuated drum brake is improved.

The use of the invention is therefore basically suitable for all motor vehicle brake systems that have at least one drum brake. In this case, the wheel brakes, such as the drum brake(s) in particular, can be designed to be controlled preferably electrically, in particular electrohydraulically and/or electromechanically, by means of an electronic control unit (ECU). In particular, the present invention makes it possible for the currently preferred electrical brake-by-wire systems to reliably and reliably ensure simple, fast and sensitive electrical brake control in conjunction with simple electrical actuator control over the entire wear-prone brake shoe service life of a drum brake by mechanical design with the advantageous consequence that the invention is a perfect companion for the recuperative, flexible as needed, and networked dry brake system. The vehicle brake system does not necessarily have to have only drum brakes, but a mixed installation in connection with one or more types of brakes, such as in particular in connection with disc brakes, is possible and basically intended. It is advisable, but by no means mandatory, if the different types of brakes in the vehicle brake system are paired in the same way for each axle. Deviations from these principles are possible in special cases, which can affect brakes integrated in the drive train, for example.

The invention is particularly suitable in combination with brake systems that contain drum brake load sensors, and where the drum brake load sensors are arranged adjacent to the compensating device within a brake drum, fixed to an anchor plate.

Further features and details of the invention, which may be associated with advantageous exemplary embodiments of the invention designed in any combination according to the overall disclosure content, emerge from the subclaims in connection with the description based on the drawing as follows. In the drawing, this is mostly illustrated in a sketchy/principal/exemplary manner:

Fig. 1 illustrates wear-related transverse offset / bearing contact point, wandering” as an example on a drum brake shoe (about half scale) with a gradually rounded support. The trailing brake shoe 7 is subject (relative to a preferred direction of rotation II) at its supports/contact points to a very large transverse offset Y1a/Y1b (comparatively around 7.9/7.5 mm, for example) over the service life of the friction lining under consideration.

2 outlines how the transverse offset is improved, for example, on a drum brake with a compensating means/support profile according to the invention (“shell/disk design”). Over the life of the friction lining, the transverse offset at the bearing contact point decreases by a factor of approximately 4 on the trailing brake shoe 7, i.e. the migration movement is reduced to, for example, something 1.77/1.91 mm - based on an initial design as in FIG. The person skilled in the art also recognizes the particularly advantageous design according to the invention, in that the center of the relevant lining shoe radius is offset from its starting point by only the amount Y1c/Y1d.

In Fig. 3 + 4 a further development according to the invention is shown as an embodiment. Below is the variant with Y1 c/Y1 d offset to the Rk axis (shown in Fig. 3 in the new, unworn condition). Due to this offset offset, the contact point is about Y1 a/Y1 b above this “Rk” axis. With increasing pad wear, the contact point moves across the axis center from Rk to YTa/YTb, with the maximum degree of wear (cf. Fig. 4). Due to the offset, the maximum distance (Y1 a/Y1 b/Y1'a and YTb) around the axis of Rk is approx. times smaller than shown in Fig. 2., and

Fig. 5 shows the support with a geometrically designed transverse offset compensation as an example using detail V as an example in Fig. 2.

The invention relates very fundamentally to a drum brake 1 or an electronic brake system with one or more drum brakes 1 designed according to the invention for a motor vehicle. In principle, this can be an electrically open, assembled electrical service brake equipment as well as an electrically inhibited assembled one electric parking brake equipment and a combination using a combined parking and service brake equipment is also possible.

In this context, the schematic drawing illustrates in principle a drum brake 1 which, for the sake of simplification, is of the special simplex type as an example and is shown as a simple service brake, and in which a parking brake device that is fundamentally additionally possible and is to be provided in a de-energized manner is not shown for the sake of simplification. Finally, other types of brakes (e.g. duo-servo, duplex, duo-duplex) are also possible in principle.

For the purpose of actuation, the drum brake 1 preferably has on a front side F a hydraulically and/or electromechanically actuable spreading device 2 with at least one, but preferably with two, actuating elements 15, 16 that can be displaced translationally in relation to the anchor plate 4 and an abutment 3, each of which is on a Front side F of the anchor plate 4 are fixed, and the anchor plate 4 with its anchor plate-fixed components and add-on parts, which may include, in particular, an electromechanical wheel brake actuator that can be actuated individually for each wheel on the back of the anchor plate, which is arranged as a wheel brake actuating device that is fixed to the vehicle and cannot be rotated on the anchor plate 4. On the anchor plate 4, the brake shoes 7.8 are also movably mounted, which cooperate with a brake drum pot 6 of a wheel-fixed relative to the anchor plate 4, ie rotatably arranged, brake drum 5. Each brake shoe 7.8 has a largely rigid carrier for friction linings 9.10 which are gradually worn out and between the brake shoes 7.8 restoring springs 11, 12 can also be clamped elastically pretensioned in order to fundamentally impress a restoring force on the brake shoes 7.8 , respectively the brake shoes 7.8 - starting from an unworn and unactuated starting point "0" - to be held back in an unactuated end position.

The present invention is based on the finding that the technical reasons for the always uneven wear of the friction lining in cooperation with the brake drum in conventional drum brakes lead to a geometric transverse offset in the area of support contacts 13, 13', 14, 14', with the result that a support contact point to a certain extent orthogonal, transverse to the expansion axis S of the actuating elements 15,16 of the spreading device 2 emigrates. As a result, in the area of the spreader device 2 and the abutment 3 due to the mutually increasingly transversely offset support/system of the brake shoes 7.8 Couples of forces with the disadvantageous result that the spreading device 2 is not free from lateral forces, ie torque is fed in, with the result that in the power flow of the spreading device 2 a successively increasing lateral force stress occurs. At this point, the invention intervenes with a remedy and enables the compensation of transverse forces or the reduction of their harmful effects.

The electromechanical geared motor drive of an electric drum brake is designed in such a way that each drum brake can be equipped with an individually assigned, electromechanical wheel brake actuator for the purpose of wheel-specific control, just as it is possible for several drum brakes to be equipped with a common electromechanical actuator via a cable pull. There can be a central electronic control unit for the electrical supply/control/regulation of the actuator system, just as it is possible for each wheel brake module to have a local electronic control unit that can be networked with other electronic control units. The drum brake 1 can have force sensors

It is to have recognized the merit of the invention, as well as to have presented an advantageous simple solution to the problem in connection with electric drum brakes, that with drum brakes according to the known prior art, the contact point, which forms through the brake shoes to the spreader unit, migrates with wear (from new to fully worn pads) strongly along the contact line, which leads to a high lever arm around the axis center of the spreader unit (see also Figure 1). Furthermore, there is no optimized design, e.g.

The invention is intended to reduce the above-mentioned deficiency. The force transmission of the covering should be as centric as possible. Due to the more centric force guidance, possible piston jamming (which leads to increased residual torque) and increased friction are prevented or reduced in existing hydraulic brake drum cylinders. This leads to a higher efficiency of the spreading unit. This preferential introduction of force from the pads into the spreader unit helps in particular with electromechanical spreader units (e.g. KGT or ball ramp systems). In addition to the higher efficiency, the transverse forces can be absorbed by shorter guide lengths. Consequently, this leads to smaller dimensions of the electromechanical. spreading units. Another The advantage is the improved value acquisition of appropriately designed path/force measuring units at force transfer points, as they are preferably used in "dry" brake systems for braking torque monitoring. Lateral forces lead here, for example, to lateral deflection which falsifies the measured value.

With the development of the "contact design" we are aiming for from the force contact point of the drum brake lining to the spreader unit, the lining migration is greatly reduced by a "shell - disc design" (see also Figure 3). The design is to be selected in such a way that the lateral forces that cannot be avoided are kept as small as possible and supported favorably. In a version with an additional "offset", the lining wander from the center of the axle can be further reduced by moving the "starting point" of the contact surface over the center of the axle. As a result, the point of force contact moves across the center of the axle to the end point when there is wear (fully worn pads).

The expression of the design can also be introduced as a mirror image on the contact surfaces.

The invention makes it possible to reduce the transverse forces and allow the force contact point on drum brake linings to move. This reduction reduces the transverse forces in the components involved, which means that they no longer have to be designed to be as robust with regard to these forces.

In particular, it is very advantageous for new dry brake systems that use spindle or ball/ramp systems to apply the spreading force, for example, since the spindles are subjected to lower lateral forces and the individual balls are loaded more evenly in ball/ramp systems. The guide systems of these spreading units can be shortened. This can be used to design smaller components and thus smaller spreader units. In the case of dry systems, the pad support is also often used to determine the force and moment. Here, too, a central introduction of force is advantageous for the accuracy of the determination of the force and moment, as already described. In addition, this also benefits existing hydraulic systems with guided pistons. With these, the lateral forces are reduced and possible piston jamming is thereby avoided.

In principle, the invention can improve applications for all drum brake systems in which drum brakes are present (simplex, duplex, duo duplex, . . . ). As an advantageous design, a maximum small radius should be selected for Rk, and a maximum large one for Rg (up to the straight line). Due to the fact that Rg moves, care must be taken with Rg that the smallest possible angle 1a 1b 1'a° and 1'b° is created in the main area of use (see Figure 3a/b) if you want to reduce the transverse forces as much as possible. This is possible with an offset, for example, as shown. At Rk, the smallest radius is limited by the material properties.

In principle, it is possible to universally provide the supports (contact points) improved according to the invention on various components to be paired with one another, ie on drum brakes/drum brake shoes. According to the invention, it is also possible to provide the inventive development only on very specific drum brake linings, so that, for example, only one preferred direction of rotation experiences the improvement according to the invention, whereas other contact points, which may be subject to a different stress profile, can be designed differently. It is possible for the configuration of the contact points to be designed to be mirror images of one another, so to speak. Furthermore, the "shell-disc design" can also be replaced by differently curved curves or approximate geometries instead of circular shapes. Furthermore, the principle mentioned can also be implemented in a differential construction, in which the brake pad carrier and the counter bearing are implemented in several pieces.

Reference List

0 starting point - new condition (reference point)

1 drum brake

2 spreading device

3 abutments

4 anchor plate

5 brake drum

6 brake drum pot

7 Brake shoe (running off with primary brake drum rotation direction II)

8 Brake shoe (running up with primary brake drum rotation direction II)

9 friction lining

10 friction lining

11 return spring

12 return spring

13,13' bearing contact

14,14' bearing contact

15 actuator

16 actuator

ECU electric control unit eRB electric wheel brake

EMB electromechanical wheel brake ehRB electrohydraulic wheel brake

F front

Ax wheel rotation axis (axial direction) r radial direction

T tangential direction

U Primary direction of rotation of the brake drum (preferred direction of rotation/primary

direction of rotation)

U' secondary brake drum rotation direction x1a,b; X2a,b offset

Y1a,b, Y2a,b offset

R radius

S spread axis

Q transverse axis

D drum brake diameter

Ax friction lining thickness Z1 end offset point (friction lining worn)

Z2 end offset point (friction lining worn)

Y1c;y1d offset offset (in transverse direction -> projected towards middle center)

Claims

patent claims

1. Drum brake (1) for a motor vehicle brake system, with actuators, such as in particular electric geared motor drive module including red-trans converter gear stage, transmission means and/or spreading device (2) including actuating element (15,16), possibly with support on an abutment (3), via supports in the power flow with movably mounted brake shoes (7,8), which are suitable and intended to cooperate with a brake drum (5), characterized in that adjacent to the spreading device (2) and/or the abutment (3), a compensating device for brake shoe transverse offset is provided, and wherein the compensating device is inserted laterally next to the expanding device (2) and/or the abutment (3) between the force flow of the brake shoe (7, 8) of the drum brake (1). is.

2. Drum brake (1) for a motor vehicle brake system according to one or more of the preceding claims, characterized in that the compensating device is provided placed in a brake drum interior.

3. Drum brake (1) for a motor vehicle brake system according to one or more of the preceding claims, characterized in that the compensating device is positively fitted directly into an interface between the abutment (3) and the brake shoe (7,8) and/or between the actuating element (15,16) and brake shoe (7.8) is inserted.

4. Drum brake (1) for a motor vehicle brake system according to one or more of the preceding claims, characterized in that the compensating device is connected indirectly, in particular with the aid of at least one adapter component, to an interface between the spreading device (2) and the brake shoe (7,8) and/or or abutment (3) is inserted in a form-fitting manner.

5. Drum brake (1) for a motor vehicle brake system according to one or more of the preceding claims, characterized in that the compensating device has an articulated or movable bearing with forced guidance in your mutual contact area.

6. drum brake (1) for a motor vehicle brake system according to one or more of the preceding claims, characterized in that the Forced guidance of the compensating device between the spreading device (2)/actuating element (15,16) and brake shoe (7,8) and/or abutment (3) is implemented as a web guide in a 2-dimensionally curved arc shape in the manner of a joint disk/joint socket.

7. Drum brake (1) for a motor vehicle brake system according to one or more of the preceding claims, characterized in that the articulated curve guide has one or more arc segments.

8. Drum brake (1) for a motor vehicle brake system according to one or more of the preceding claims, characterized in that the various paired circular arc segments are each nestled in the same direction in their curvature but with a different radius R are pronounced.

9. Drum brake (1) for a motor vehicle brake system according to one or more of the preceding claims, characterized in that in mutual relation a (transmitter) radius R placed on the actuating element side is dimensioned gradually smaller than a (slave) radius R placed on the brake shoe side.

10. Drum brake (1) for a motor vehicle brake system according to one or more of the preceding claims, characterized in that a (transmitter) radius R placed on the actuating element side has at least about 0.6 - 1.5 x brake drum diameter in relation to the brake drum diameter, and the paired counterpart of the (slave) radius R on the brake shoe side has at least about 1/4 - 1/20 x the brake drum diameter.

11 . Drum brake (1) for a motor vehicle brake system according to one or more of the preceding claims, characterized in that one or more middle centers of radii R are provided offset by a specific, in particular predetermined, offset Y1 c; Y1 d in the transverse direction on a wheel axis of rotation Ax are.

12. drum brake (1) for a motor vehicle brake system according to one or more of the preceding claims, characterized in that all 14

Brake shoes (7, 8) are assigned at least one or more compensation devices for brake shoe transverse offset for all brake drum directions of rotation U, U'.

13. Drum brake (1) for a motor vehicle brake system according to one or more of the preceding claims, characterized in that each brake shoe (7,8) is assigned a compensation device for brake shoe transverse offset for a brake drum direction of rotation II, LT.

14. Drum brake (1) for a motor vehicle brake system according to one or more of the preceding claims, characterized in that the compensation device for brake shoe transverse offset is assigned exclusively for a brake drum direction of rotation U, U′ and exclusively to the drum brake shoe(s) (7, 8) placed downstream is.

15. Drum brake (1) for a motor vehicle brake system according to one or more of the preceding claims, characterized in that the compensating device is arranged fixed next to a load measuring device within a brake drum on an anchor plate.

16. Drum brake (1) for a motor vehicle brake system according to one or more of the preceding claims, characterized in that an electric motor vehicle brake system is designed with a control unit (ECU) for controlling and/or regulating the drum brake (1).

17. Drum brake (1) for a motor vehicle brake system according to one or more of the preceding claims, characterized in that the electric motor vehicle brake system has at least one or more wheel brakes that can be actuated electromechanically and/or electrohydraulically.

18. Drum brake (1) for a motor vehicle brake system according to claim 17, characterized in that the motor vehicle brake system formed has at least one disc brake.