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DE-102021115785-C5 - drum brake

DE102021115785C5DE 102021115785 C5DE102021115785 C5DE 102021115785C5DE-102021115785-C5

Abstract

drum brake (1), in particular for a commercial vehicle, having - a brake drum (2) rotatably mounted about an axis of rotation (D), - several brake shoes (3) mounted in a receiving space (22) of the brake drum (2) with a respective friction lining carrier (32) and a friction lining (31) arranged on it, - wherein the brake shoes (3) can be pressed radially towards an axis of rotation ( AD ) of the brake drum (2) against an inner surface (21) of the brake drum (2) designed as a friction surface, - a brake cylinder assembly (4) arranged in the receiving space (22) of the brake drum (2) on an anchor housing (8) in a rotationally fixed manner for actuating the brake shoes (3), - wherein the brake cylinder arrangement (4) comprises a housing (41) fixedly attached to the anchor housing (8) in the receiving space (22) of the brake drum (2) and a service brake piston (42) displaceable relative to the housing (41) parallel to the axis of rotation (D) of the brake drum (2), characterized in that - the brake cylinder assembly (4) comprises a parking brake piston (43) which is displaceable relative to the housing (41) parallel to the axis of rotation (D) of the brake drum (2) and is subjected to the spring force of a spring element (5), and several plungers (44) for transmitting a movement of the parking brake piston (43) to the service brake piston (42), - wherein respective compressed air supplies are provided into a service brake pressure chamber (45) between the housing (41) and the service brake piston (42) and a parking brake pressure chamber (46) between the housing (41) and the parking brake piston (43), and - on a side of the friction lining carrier (32) facing away from the friction lining (31) a respective pressure wedge (33) is arranged, which rests on a wedge ring (6) which is movable parallel to the axis of rotation (D) of the brake drum (2), - wherein the wedge ring (6) can be moved from a non-braking position to a braking position by moving the service brake piston (42) of the brake cylinder assembly (4) parallel to the axis of rotation (D) of the brake drum (2).

Inventors

  • Johann Iraschko

Assignees

  • Knorr-Bremse Systeme für Nutzfahrzeuge GmbH

Dates

Publication Date
20260513
Application Date
20210618

Claims (8)

  1. Drum brake (1), in particular for a commercial vehicle, comprising: - a brake drum (2) rotatably mounted about an axis of rotation (D), - several brake shoes (3) mounted in a receiving space (22) of the brake drum (2), each with a friction lining carrier (32) and a friction lining (31) arranged thereon, - wherein the brake shoes (3) can be pressed radially against an axis of rotation ( AD ) of the brake drum (2) against an inner surface (21) of the brake drum (2) designed as a friction surface, - a brake cylinder assembly (4) arranged in the receiving space (22) of the brake drum (2) on an anchor housing (8) so as to be non-rotatably mounted thereon for actuating the brake shoes (3), - wherein the brake cylinder assembly (4) comprises a housing (41) fixedly mounted in the receiving space (22) of the brake drum (2) on the anchor housing (8) and a service brake piston displaceable relative to the housing (41) parallel to the axis of rotation (D) of the brake drum (2). (42) has, characterized in that - the brake cylinder arrangement (4) has a parking brake piston (43) which is displaceable relative to the housing (41) parallel to the axis of rotation (D) of the brake drum (2) and is subjected to the spring force of a spring element (5), and several plungers (44) for transmitting a movement of the parking brake piston (43) to the service brake piston (42), - wherein respective compressed air supply points are provided to a service brake pressure chamber (45) between the housing (41) and the service brake piston (42) and a parking brake pressure chamber (46) between the housing (41) and the parking brake piston (43), and - a respective pressure wedge (33) is arranged on a side of the friction lining (31) of the friction lining carrier (32), which rests on a wedge ring (6) which is displaceable parallel to the axis of rotation (D) of the brake drum (2), - wherein the wedge ring (6) is moved by shifting the The service brake piston (42) of the brake cylinder assembly (4) can be moved parallel to the axis of rotation (D) of the brake drum (2) from a non-braking position to a braking position.
  2. drum brake (1) according Claim 1 , characterized in that the plungers (44) are received in a first partition (48) of the housing (41) separating the service brake pressure chamber (45) from the parking brake pressure chamber (46).
  3. drum brake (1) according Claim 1 , characterized in that the plunger (44) is received in a second partition (49) of the housing (41) separating the service brake pressure chamber (45) from the receiving chamber (22).
  4. Drum brake (1) according to one of the preceding claims, characterized in that the spring element (5) is designed as a disc spring fixed to the housing (41).
  5. Drum brake (1) according to one of the preceding claims, characterized in that the wedge ring (6) is adjustable via an adjusting device (7).
  6. drum brake (1) according Claim 5 , characterized in that a thread (62) is arranged, in particular formed, on a surface of the wedge ring (6) facing away from the pressure wedge (33), which meshes with a threaded sleeve (71) of the adjusting device (7), wherein the threaded sleeve (71) together with the wedge ring (6) is displaceable by moving the service brake piston (42) of the brake cylinder arrangement (4) parallel to the axis of rotation (D) of the brake drum (2).
  7. drum brake (1) according Claim 6 , characterized in that the threaded sleeve (71) has a toothed ring (73) coupled to an adjusting drive (75).
  8. Drum brake (1) according to one of the preceding claims, characterized in that a slide (9) with several rolling elements (92) is arranged between the pressure wedge (33) and the wedge ring (6).

Description

The present invention relates to a drum brake, in particular for a commercial vehicle, according to the preamble of claim 1. Drum brakes of this type feature a cylindrical rotor with friction surfaces arranged on the inside of the rotor, also known as the brake drum. Braking force is generated by brake shoes that are pressed against the inner friction surface of the brake drum. The simplest and currently most commonly used type of drum brake is the so-called simplex drum brake. In this type, two brake shoes are pressed against the drum by a clamping device acting on one side of the brake shoes, either hydraulically or mechanically, for example using a cam, a spreader lock, a spreading wedge, or a spreading lever. The two brake shoes are rotatably mounted on opposite sides of the clamping device. Due to the geometric arrangement, different forces are exerted on the two opposing brake shoes, depending on the direction of rotation of the brake drum. While in the case of the so-called leading brake shoe, whose bearing is located behind a friction lining of the brake shoe in the direction of rotation of the brake drum, the contact force is increased by the leverage effect resulting from the position of the brake shoe bearing, the opposite effect occurs in the case of the so-called trailing brake shoe. Accordingly, with this drum brake, the majority of the braking work is performed by the leading brake shoe. This results in an uneven distribution of the contact force and the thermal load on the two brake shoes, which means that the wear of the friction lining of the two brake shoes is different. One disadvantage of self-reinforcing brakes is that the so-called braking coefficient (C* value) increases disproportionately with the coefficient of friction of the brake pad. This can result in significantly different braking forces at the wheels and axles of the vehicle being braked. On the other hand, such drum brakes have the advantage that the brake shoes are not directly exposed to the environment and are therefore considerably less affected by dirt, splash water and road salt on the function and condition of the brake shoes than, for example, disc brakes. Therefore, drum brakes are better suited for off-road use than disc brakes, for example. Another advantage of drum brakes is that there is practically no residual grinding torque with drum brakes, since in this type of brake the brake shoes are actively pulled back into a non-braking position by brake shoe return springs, thus preventing the grinding of the brake shoes, as occurs with brake shoes of disc brakes. Another advantage of drum brakes is that they can collect the abrasion from the friction lining, thus relieving the surroundings and environment of such brake dust and, moreover, preventing the irreversible loss of valuable material elements bound in the friction lining of the brake shoes. To reduce self-reinforcement, for example, it is possible to... DE 10 2010 003 250 A1 It is known to press two oppositely arranged brake shoes against the inner surface of the brake drum by means of an actuating element along a brake carrier radially to the axis of rotation of the brake drum. From the DE 666237 A and the US 2527126 A Drum brakes are known in which brake cylinders for actuating the brake shoes are installed inside the drum brake. At the US 2527126 A Two brake cylinders are provided for actuating opposing brake shoes attached to armature housings. Each opposing end of the armature housing can be advanced by means of a plunger protruding from the pressure chamber of the respective brake cylinder, which is wedge-shaped at its end. This plunger presses the brake shoes against an inner wall of the brake drum between rollers arranged at the opposite ends of the armature housings, with the rollers pressing against plungers attached to the ends of the armature housings. Simultaneous actuation of both brake cylinders is crucial, as otherwise uneven wear of the brake shoes will occur. The object of the present invention is to develop a drum brake with a more compact design and stable friction behavior. This problem is solved by a drum brake having the features of claim 1. The drum brake according to the invention has a brake drum rotatably mounted about an axis of rotation and several brake shoes mounted in a receiving space of the brake drum, each with a friction lining carrier and a friction lining arranged on it. The brake shoes can be pressed radially towards a rotational axis of the brake drum against an inner surface of the brake drum designed as a friction surface. Inside the drum brake, a brake cylinder assembly is provided, which is fixed to an armature housing and is designed to actuate the brake shoes. On one side of the friction lining carrier facing away from the friction lining, a respective pressure wedge is arranged, which rests on a wedge ring that can be moved parallel to the axis of rotation of the brake drum. The wedge ring can be moved from a