Drum brake for a motor vehicle, motor vehicle

Abstract

The invention relates to a drum brake (1) for a motor vehicle, comprising: a brake drum (2) and a support plate (3); a first and a second brake shoe (4, 5) which are arranged movably on the support plate (3) and are associated with the brake drum (2); a linear actuator (11) which can be controlled in order to move the brake shoes (4, 5); a force-transmission element (12) which is mounted slidably on the support plate (3); a lever (13) which is coupled at one end to the linear actuator (11) and at the other end to the force-transmission element (12); a first coupling rod (14) which is coupled at one end to the lever (13) and at the other end to the first brake shoe (4); and a second coupling rod (15) which is coupled at one end to the force-transmission element (12) and at the other end to the second brake shoe (5).

Description

[0001] R.415307

[0002] - 1 -

[0003] Description

[0004] title

[0005] Drum brake for a motor vehicle, motor vehicle

[0006] The invention relates to a drum brake for a motor vehicle and to a motor vehicle with at least one such drum brake.

[0007] State of the art

[0008] Drum brakes for motor vehicles with various types of actuation are known from the prior art. These drum brakes are typically of a simplex or duo-servo design. In passenger cars, the drum brakes are usually hydraulically actuated. Hydraulic pressure is built up in a double piston, which expands the piston, thereby exerting a force on each brake shoe of the drum brake. The design with pistons that can be moved on both sides and are coupled via a hydraulic fluid ensures that the forces on both brake shoes are always equal and that actuation with force compensation occurs.

[0009] For future passenger cars, hydraulic actuation could be replaced by electromechanical actuation. Mechanical actuation offers a wide variety of options. Mechanical actuators that allow force compensation, such as spreader locks, are typically mounted floating between the brake shoes. However, complete force compensation is not reliably guaranteed because the linkages used have many friction points and, due to their kinematics, result in unequal actuation forces. Furthermore, these friction points lead to limited reproducibility of the braking effect and reduced actuator efficiency. R.415307

[0010] - 2 -

[0011] Hybrid solutions are also known, with a hydraulic actuator for a service brake and an electromechanical actuator for a parking brake. For example, German patent application DE 102006009 089 A1 discloses a drum brake for a vehicle, comprising a first brake shoe with a first brake lining, a second brake shoe with a second brake lining, a brake drum, a hydraulically actuated wheel cylinder for a service brake of the vehicle, which is arranged between a first end of the first brake shoe and a first end of the second brake shoe, and a parking brake actuator for a separate parking brake, which can be actuated by an electric drive and presses the first and second brake shoes against the brake drum to secure the vehicle.

[0012] Disclosure of the invention

[0013] The drum brake according to the invention with the features of claim 1 is characterized in that it has a brake drum and a support plate, a first and a second brake shoe displaceably arranged on the support plate and associated with the brake drum, a linear actuator controllable for displacing the brake shoes, a force transmission element displaceably mounted on the support plate, a lever coupled at one end to the linear actuator and at the other end to the force transmission element, a first connecting rod coupled at one end to the lever and at the other end to the first brake shoe, and a second connecting rod coupled at one end to the force transmission element and at the other end to the second brake shoe.Such an actuator arrangement, which can be used for both service and parking braking, ensures advantageous low-friction force equalization between the two brake shoes, so that equal forces act on both brake shoes. The drum brake is thus designed as a purely electromechanical, hydraulic-free drum brake, which nevertheless ensures complete force equalization between the brake shoes. The brake drum is preferably rotatably mounted, and in particular, non-rotatably connected to a rotatably mounted wheel. The support plate can also be used as a back plate or backing plate R.415307.

[0014] - 3 -

[0015] The brake shoes are each displaceable towards the brake drum to generate a braking force, particularly in a radial direction. The force transmission element, the connecting rods, the lever, and the linear actuator are, in particular, components of an actuator assembly. Both the brake shoes and the force transmission element are displaceable or slidable on the support plate. In particular, the linear actuator itself is also pivotally mounted, for example, on the support plate. The lever is rotated by the linear actuator, thereby displacing the first brake shoe via the first connecting rod and simultaneously shifting the force transmission element and displacing the second brake shoe via the second connecting rod. The force transmission element is thus also displaced during a compensating movement of the actuator assembly.Active force is applied only to the first brake shoe, while indirect force transmission occurs to the second shoe via the compensating movement of the force transmission element. This avoids unequal actuation forces due to the lever kinematics. This force-compensating actuation allows the drum brake to advantageously utilize its self-reinforcing properties. Furthermore, the corresponding adjustability facilitates the compensation of tolerances within the drum brake. The force transmission element positions itself so that the forces on both brake shoes are equal, or rather, in a fixed ratio to each other, regardless of, for example, differences in the geometry of the brake shoes and / or an eccentricity of the brake drum. In addition, the positional forces that need to be supported are significantly reduced.The described design also allows for advantageous rolling bearing of the lever on or in the force transmission element. Overall, the invention avoids undesirable friction effects, and the total frictional influence can be considered significantly lower compared to other lever mechanisms, such as spreader locks and / or toggle levers. This low frictional influence ensures better reproducibility of the braking effect, as undesirable "stick-slip" effects are avoided. The design and operating principle ensure that no lateral forces can be transmitted to the brake shoes. This also advantageously increases the reproducibility of the braking effect because the brake shoes are loaded exclusively in the spreading direction (R.415307).

[0016] - 4 -

[0017] This will be a key difference and advantage, especially when compared to the other leverage mechanisms described above.

[0018] According to a preferred embodiment of the invention, the first connecting rod is coupled to the lever at a third coupling point with respect to the longitudinal extension of the lever, between a first coupling point of the lever to the linear actuator and a second coupling point of the lever to the force transmission element. Such an arrangement of the coupling points advantageously ensures that an actuating force generated by the linear actuator is distributed evenly to both brake shoes. The lever is thus designed as an eccentric lever due to the different distances between the coupling points. The distance between the first and the third coupling point is greater than the distance between the second and the third coupling point. In other words, the third coupling point is closer to the second coupling point than the first coupling point.

[0019] For example, the first coupling point is located at a first end of the lever and the second coupling point is located at or near a second end of the lever that is away from the first end.

[0020] Particularly preferably, the lever is arranged at least partially within the force transmission element and / or rotatably mounted in / on the force transmission element. Such an arrangement and / or mounting of the lever in relation to the force transmission element offers the advantage that the lever and the force transmission element form a single structural unit. The force transmission element is, in particular, designed as a housing that encloses the lever at least partially.

[0021] According to a preferred embodiment of the invention, the lever is pivotally connected to the linear actuator and / or pivotally connected to the force transmission element. Such a pivotal connection of the lever ensures particularly advantageous kinematics. The lever is connected to the linear actuator, in particular, by means of a cable.

[0022] The first connecting rod is preferably rigidly or flexibly connected to the first brake shoe and / or flexibly to the lever. (R.415307)

[0023] - 5 -

[0024] Such a rigid and / or articulated connection of the first connecting rod offers the advantage that the corresponding actuation of the linear actuator is kinematically transmitted precisely to the first brake shoe. Alternatively, the first connecting rod is operatively connected to the first brake shoe and / or to the lever via a pressure surface.

[0025] According to a preferred embodiment of the invention, the second connecting rod is rigidly or articulatedly connected to the second brake shoe and / or rigidly or articulatedly to the force transmission element. Such a rigid and / or articulated connection of the second connecting rod advantageously ensures that the corresponding actuation of the linear actuator is kinematically transmitted precisely to the second brake shoe. Alternatively, the second connecting rod is operatively connected to the second brake shoe and / or to the lever by means of a pressure surface.

[0026] Particularly preferably, the force transmission element is floatingly mounted on the support plate by means of a sliding bearing, in particular having at least one guide bushing. Such a floating sliding bearing offers the advantage that the force transmission element is moved with low friction when the linear actuator is actuated, so that frictional influences on the force compensation described above are at least largely avoided.

[0027] According to a preferred embodiment of the invention, a displacement direction of the linear actuator is aligned parallel to a displacement direction of the force transmission element. This parallel alignment of the displacement directions results in a particularly advantageous kinematics. The displacement direction of the linear actuator corresponds, in particular, to the displacement direction of a gear arrangement of the linear actuator.

[0028] The linear actuator particularly preferably comprises a motor-gearbox arrangement, in particular including an electric motor and / or a spindle gear arrangement. The use of such a motor-gearbox arrangement offers the advantage that the linear actuator is particularly R.415307

[0029] - 6 -

[0030] It can be precisely controlled. The lever is then connected, for example, to a movable spindle or spindle nut of the spindle gear assembly.

[0031] According to a preferred embodiment of the invention, the lever is rotatably mounted on the force transmission element by means of a bearing arrangement comprising a circular segment-shaped, in particular semicircular, bearing shell. The use of such a circular segment-shaped bearing shell advantageously ensures that the lever is geometrically unambiguously mounted on the force transmission element. In particular, the bearing shell limits the lever's range of rotation, preferably by a positive locking mechanism.

[0032] Particularly preferably, one end of the lever associated with the bearing shell has a circular segment shape corresponding to the bearing shell. Using this circular segment shape corresponding to the bearing shell offers the advantage that the lever has a defined bearing area.

[0033] According to a preferred embodiment of the invention, the bearing arrangement comprises a plurality of rolling elements arranged radially between the bearing shell and the end of the lever associated with the bearing shell. The use of appropriately arranged rolling elements advantageously ensures that the lever is mounted with low friction on the force transmission element, so that a corresponding displacement of the linear actuator is transmitted to the two brake shoes at least largely free from frictional influences.

[0034] The motor vehicle with the features of claim 13 is characterized by at least one drum brake according to the invention. This results in the advantages already mentioned. Preferably, the motor vehicle has at least one wheel to which the drum brake is assigned. For example, the brake drum of the drum brake is rotationally fixed to the wheel. Particularly preferably, the motor vehicle has at least one axle with two wheels, and more preferably at least two axles, each with two wheels, to which one of the drum brakes according to the invention is assigned. R.415307

[0035] - 7 -

[0036] Further preferred features and combinations of features will become apparent from the foregoing and from the claims. The invention will now be explained in more detail with reference to the drawings. These drawings show...

[0037] Figure 1 shows a drum brake, and

[0038] Figure 2 shows an advantageous actuator arrangement for the drum brake.

[0039] Figure 1 shows, in a schematic representation only, a known drum brake 1 as used in motor vehicles. A so-called simplex drum brake is shown as an example. The drum brake 1 has a brake drum 2, which can be connected to a wheel of the motor vehicle in a rotationally fixed manner and / or is rotatably mounted, and a stationary support plate 3.

[0040] The drum brake 1 further comprises a first brake shoe 4 and a second brake shoe 5. The brake shoes 4 and 5 are each assigned to the brake drum 2 and are displaceably arranged at a common bearing point 6 on the support plate 3, in particular radially in the direction of the brake drum 2. The drum brake 1 has a spring element 7, for example designed as a coil spring, as a return spring, wherein the spring element 7 is connected at one end to each of the brake shoes 4 and 5.

[0041] The brake shoes 4, 5 are geometrically adapted to the circular brake drum 2 and are accordingly segmented in a circular shape. Each brake shoe 4, 5 has a brake lining 9 on a surface corresponding to a circumferential annular inner surface 8 of the brake drum 2. The drum brake 1 has an actuator arrangement 10 to displace the brake shoes 4, 5 towards the inner surface 8 against the spring force of the spring element 7.

[0042] An advantageous embodiment of the actuator arrangement 10, which forms the core of the invention, is shown schematically in Figure 2. By means of the actuator arrangement 10, the two brake shoes 4, 5 are spread apart to fulfill a braking request in order to establish frictional contact between the R.415307

[0043] - 8 -

[0044] to create a braking force on the inner surface 8 of the brake drum 2 and the brake lining 9 of the respective brake shoe 4, 5.

[0045] The special type of spreading mechanism used in the actuator arrangement 10 ensures that a force balance is achieved between the brake shoes 4, 5 and that the force acts at least substantially along one direction of movement of the respective brake shoe 4, 5.

[0046] The actuator arrangement 10 includes a linear actuator 11, a force transmission element 12, a lever 13, a first connecting rod 14 and a second connecting rod 15, which can be controlled to move the brake shoes 4, 5.

[0047] The lever 13 is coupled at one end to the linear actuator 11 at a first coupling point 16, in this case by a pivot, and at the other end to the force transmission element 12 at a second coupling point 17, also by a pivot. The lever 13 is rotatably mounted in or on the force transmission element 11. In particular, it is also arranged at least partially within the force transmission element 11, such that the force transmission element 11 is designed as a housing that at least partially encloses the lever 13.

[0048] The first connecting rod 14 is connected at one end to a third coupling point 18, either pivotally or by means of a pressure surface, to the lever 13, and at the other end to a fourth coupling point 19, rigidly, pivotally, or by means of a pressure surface, to the first brake shoe 4. With respect to the longitudinal extent of the lever 13, the first connecting rod 14 is connected to the lever 13 at the third coupling point 18 between the first coupling point 16 and the second coupling point 17.

[0049] With respect to the longitudinal extension of the lever 13, the third coupling point 18 is thus arranged between the first coupling point 16 and the second coupling point 17. The distance between the first coupling point 16 and the third coupling point 18 is greater than the distance between the second coupling point 17 and the third coupling point 18. R.415307

[0050] - 9 -

[0051] The second connecting rod 15 is coupled at one end to a fifth coupling point 20, rigidly, articulated or by means of a pressure surface, with the force transmission element 12 and at the other end to a sixth coupling point 21, rigidly, articulated or by means of a pressure surface, with the second brake shoe 5.

[0052] The force transmission element 12 is slidably mounted on the support plate 3. In this case, the force transmission element 12 is floatingly mounted on the support plate 3 by means of a sliding bearing 22, which in particular has at least one guide bushing (not shown here). One direction of displacement of the linear actuator 11 is aligned parallel to a direction of displacement of the force transmission element 12.

[0053] The displacement directions of the linear actuator 11, in particular a gear arrangement of the linear actuator 11, as well as of the two brake shoes 4, 5, are indicated by corresponding arrows. Because the second brake shoe 5 is connected to the power transmission element 12, its displacement direction corresponds to the displacement direction of the second brake shoe 5.

[0054] The linear actuator 11 has a motor-gear arrangement 23, in this case comprising an electric machine 24 and a spindle gear arrangement 25, with a spindle or spindle nut connected to a rotor shaft of the machine 24 in a rotationally fixed manner and a spindle nut or spindle mounted accordingly so as to be displaceable thereon.

[0055] Instead of the spindle gear assembly 25, the electric machine 24 can also be designed as a linear motor; alternatively, for example, a rack and pinion mechanism is provided as the gear assembly. The machine 24 is mounted on a side facing away from the spindle gear assembly 25, for example rotatably, at a bearing point 26, in particular on the support plate 3.

[0056] The lever 13 is rotatably mounted on the force transmission element 12 by means of a bearing arrangement 27. The bearing arrangement 27 has a circular segment-shaped, in particular semicircular, bearing shell 28. EinR.415307

[0057] - 10 -

[0058] The end 29 of the lever 13 associated with the bearing shell 28 has a circular segment shape corresponding to the bearing shell 28. The second coupling point 17 forms the center point of the corresponding circular segment.

[0059] The bearing arrangement 27 comprises a plurality of rolling elements 30 for low-friction mounting of the lever 13 on the force transmission element 12. These rolling elements are arranged radially between the bearing shell 28 and the end 29 of the lever 13 associated with the bearing shell 28. For clarity, only one of the rolling elements 30 is provided with a reference numeral.

[0060] During braking, the linear actuator 11 pulls on the lever 13 at the first coupling point 16 in the direction of displacement shown, causing the lever to rotate. The described rolling bearing significantly reduces friction effects.

[0061] The third coupling point 18, as a connection between the lever 13 and the first connecting rod 14, due to its eccentricity, i.e. the distance of the third coupling point 18 from the pivot point of the lever 13 defined by the second coupling point 17, causes the first connecting rod 14 to be displaced in the same direction by the rotation of the lever 13.

[0062] The force of the linear actuator 11 is transmitted to the first brake shoe 4 via the lever 13. The resulting reaction force shifts the force transmission element 12 in a direction opposite to that of the first connecting rod 14 and the linear actuator 11. This causes an identical force to be exerted on the second brake shoe 5 via the second connecting rod 15, which is connected to the force transmission element 12, as is exerted on the first brake shoe 4.

[0063] This ensures advantageous actuation with automatic force compensation, which also utilizes the self-reinforcing properties of the drum brake 1 by transferring the forces from one brake shoe 4, 5 to the other.

Claims

R.415307 - 11 - Claims 1. Drum brake (1) for a motor vehicle, with a brake drum (2) and a support plate (3), with a first and a second brake shoe (4,5) arranged displaceably on the support plate (3) and assigned to the brake drum (2), with a linear actuator (11) that can be controlled to displace the brake shoes (4,5), with a force transmission element (12) slidably mounted on the support plate (3), with a lever (13) coupled at one end to the linear actuator (11) and at the other end to the force transmission element (12), with a first connecting rod (14) coupled at one end to the lever (13) and at the other end to the first brake shoe (4), and with a second connecting rod (15) coupled at one end to the power transmission element (12) and at the other end to the second brake shoe (5).

2. Drum brake according to claim 1, characterized in that the first connecting rod (14) is coupled with the lever (13) at a third coupling point (18) with respect to a longitudinal extension of the lever (13) between a first coupling point (16) of the lever (13) to the linear actuator (11) and a second coupling point (17) of the lever (13) to the force transmission element (12).

3. Drum brake according to one of the preceding claims, characterized in that the lever (13) is arranged at least partially within the force transmission element (11) and / or rotatably mounted in / on the force transmission element (11).

4. Drum brake according to one of the preceding claims, characterized in that the lever (13) is pivotally connected to the linear actuator (11) and / or pivotally connected to the force transmission element (12). R.415307 - 12 - 5. Drum brake according to one of the preceding claims, characterized in that the first connecting rod (14) is rigidly or pivotally connected to the first brake shoe (4) and / or pivotally connected to the lever (13).

6. Drum brake according to one of the preceding claims, characterized in that the second connecting rod (15) is rigidly or articulatedly connected to the second brake shoe (5) and / or rigidly or articulatedly connected to the power transmission element (12).

7. Drum brake according to one of the preceding claims, characterized in that the force transmission element (12) is floatingly mounted on the support plate (3) by means of a sliding bearing (22) which in particular has at least one guide bushing.

8. Drum brake according to one of the preceding claims, characterized in that a displacement direction of the linear actuator (11) is aligned parallel to a displacement direction of the force transmission element (12).

9. Drum brake according to one of the preceding claims, characterized in that the linear actuator (11) has a motor-gear arrangement (23), in particular comprising an electric machine (24) and / or a spindle gear arrangement (25).

10. Drum brake according to one of the preceding claims, characterized in that the lever (13) is rotatably mounted on the force transmission element (12) by means of a bearing arrangement (27) which has a circular segment-shaped, in particular semicircular, bearing shell (28).

11. Drum brake according to claim 10, characterized in that an end (29) of the lever (13) associated with the bearing shell (28) has a circular segment shape corresponding to the bearing shell (28). R.415307 - 13 - 12. Drum brake according to one of claims 10 and 11, characterized in that the bearing arrangement (27) has a plurality of rolling elements (30) arranged radially between the bearing shell (28) and the end (29) of the lever (13) associated with the bearing shell (28).

13. Motor vehicle characterized by at least one drum brake (1) according to one of the preceding claims.

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