DRUM BRAKE

Description

[0001] The present invention relates to a drum brake, in particular for a commercial vehicle, according to the preamble of claim 1.

[0002] Drum brakes of this type feature a cylindrical drum-shaped 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.

[0003] The simplest and currently most commonly used version of a drum brake is the so-called simplex drum brake. In this case, two brake shoes are pressed hydraulically or mechanically against the drum by a clamping device acting on one side of the brake shoes, for example, using a cam, a spreader lock, a spreader wedge, or a spreader lever.

[0004] The two brake shoes are rotatably mounted on opposite sides of the brake application device. Due to their geometric arrangement, the two oppositely arranged brake shoes exert different forces depending on the direction of rotation of the brake drum.

[0005] 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 pressure is increased by the leverage effect resulting from the position of the brake shoe bearing, the opposite effect occurs in the case of the leading brake shoe.

[0006] Accordingly, with this drum brake, the majority of the braking work is performed by the approaching brake shoe.

[0007] 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.

[0008] Another disadvantage of self-reinforcing braking is that the so-called braking coefficient (C* value) increases disproportionately with the friction coefficient of the friction lining. This can result in significantly different braking forces at the wheels and axles of the vehicle being braked.

[0009] On the other hand, such drum brakes have the advantage that the brake shoes are not directly exposed to the environment and thus the influence of dirt, splash water and road salt on the effect and condition of the brake shoes is considerably less than with disc brakes, for example.

[0010] Therefore, drum brakes are better suited for off-road use than disc brakes, for example.

[0011] A further advantage of drum brakes is that there is practically no residual drag torque with drum brakes, since with this type of brake the brake shoes are actively retracted into a non-braking position by means of brake shoe return springs, thus eliminating the possibility of the brake shoes dragging, as occurs with the brake shoes of disc brakes.

[0012] A further advantage of drum brakes is that they can collect the abrasion of the friction lining, thus relieving the surrounding area of ​​such brake dust and, moreover, preventing the irreversible loss of valuable material elements bound in the friction lining of the brake shoes.

[0013] To reduce self-reinforcing, it is known, for example, from DE 10 2010 003 250 A1 to press two oppositely arranged brake shoes against the inner surface of the brake drum using an actuating element along a brake carrier, radially to the rotational axis of the brake drum. A wedge drum brake for a vehicle is also known from DE 102 60 599 A1. The brake cylinder is equipped with two pistons that press the brake shoes against the inner circumference of the drum. These pistons are pushed outward by balls arranged between two inclined surfaces of a wedge and the pistons.

[0014] The object of the present invention is to develop a drum brake with a more compact design.

[0015] This object is achieved by a drum brake having the features of claim 1.

[0016] The drum brake according to the invention has a brake drum mounted so as to be rotatable about a rotation axis and a plurality of brake shoes mounted in a receiving space of the brake drum, each with a friction lining carrier and a friction lining arranged thereon.

[0017] The brake shoes can be pressed radially to a rotational axis of the brake drum against an inner surface of the brake drum designed as a friction surface.

[0018] In the receiving space of the drum brake, a brake cylinder arrangement is provided which is non-rotatably mounted on an armature housing for actuating the brake shoes.

[0019] On a side of the friction lining carrier facing away from the friction lining, a respective pressure wedge is arranged, which rests on a wedge mechanism that can be moved parallel to the axis of rotation of the brake drum.

[0020] The wedge mechanism can be moved from a non-braking position to a braking position by moving a service brake piston of the brake cylinder arrangement parallel to the axis of rotation of the brake drum.

[0021] A drum brake designed in this way is characterized by its compact design.

[0022] In particular, the space for the brake cylinder, which is usually located outside the brake drum, can be saved because it is now located inside the drum brake without having to significantly increase the volume of the drum brake.

[0023] By transferring the movement of the wedge mechanism parallel to the axis of rotation of the brake drum into the radial movement of the brake shoe, a number of further advantages arise.

[0024] Thus, the radial movement of the brake shoes and the short length of the brake shoes in the circumferential direction compared to those used in the prior art reduce the leverage effect that influences the brake shoes during the otherwise usual pivoting movement of the brake shoes.

[0025] Furthermore, the radial pressing of the brake shoes ensures stable friction behavior and even wear of the friction linings.

[0026] In contrast to conventional drum brakes and disc brakes, the lining wear on the individual brake shoes is identical, since all brake shoes are actuated or loaded in the same way.

[0027] Advantageous embodiments of the invention are the subject of the subclaims.

[0028] According to an advantageous embodiment, the brake cylinder arrangement has a housing fixedly fastened to the armature housing in the receiving space of the brake drum, a service brake piston displaceable relative to the housing parallel to the axis of rotation of the brake drum, a parking brake piston displaceable relative to the housing parallel to the axis of rotation of the brake drum and acted upon by the spring force of a spring element, and a tappet for transmitting a movement of the parking brake piston to the service brake piston.

[0029] Respective compressed air supplies are provided in a service brake pressure chamber between the housing and the service brake piston and a parking brake pressure chamber between the housing and the parking brake piston.

[0030] The spring element, in conjunction with the parking brake pressure chamber, enables a reliable parking brake function.

[0031] According to a further embodiment, the tappet is accommodated in a partition wall of the housing that separates the service brake pressure chamber from the parking brake pressure chamber.

[0032] In an alternative design variant, the tappet is accommodated in a partition wall of the housing that separates the service brake pressure chamber from the receiving chamber.

[0033] Both variants enable reliable brake application when the compressed air in the parking brake pressure chamber is released.

[0034] Depending on the installation situation, the two variants allow the spring element, which is preferably designed as a disc spring, to be fixed to a radially outer or a radially inner edge of the spring element.

[0035] According to a preferred development of the drum brake according to the invention, a respective pressure wedge is arranged on a side of the friction lining carrier facing away from the friction lining, which pressure wedge rests on a wedge ring displaceable parallel to the axis of rotation of the brake drum.

[0036] According to a further preferred embodiment, the wedge ring is adjustable via an adjusting device.

[0037] For this purpose, in a preferred development, a thread is arranged, in particular formed, on a surface of the wedge ring facing away from the pressure wedge, which thread meshes with a threaded sleeve of the adjusting device.

[0038] The threaded sleeve can be moved together with the wedge ring by moving the service brake piston of the brake cylinder arrangement parallel to the axis of rotation of the brake drum.

[0039] Firstly, this allows the threaded sleeve to be moved parallel to the axis of rotation of the brake drum during braking.

[0040] Secondly, rotation of the threaded sleeve enables adjustment of the wedge ring relative to the threaded sleeve, which adjusts the wedge ring depending on the wear condition of the friction lining of the brake shoes so that the air gap of the drum brake can always be kept constant.

[0041] According to a preferred embodiment, the threaded sleeve is coupled to an adjuster drive via a gear ring of the threaded sleeve.

[0042] According to a further preferred embodiment, a carriage with a plurality of rolling elements is arranged between the pressure wedge and the wedge ring, which enables the reduction of a frictional resistance between the pressure wedge and the pressure surface of the wedge ring.

[0043] According to an alternative embodiment, the wedge mechanism has a number of wedge plates that can be moved parallel to the axis of rotation of the brake drum, corresponding to the number of brake shoes.

[0044] According to a preferred development, each of the wedge plates has a pressure surface facing the pressure wedge of the respective brake piston and two sliding surfaces aligned at an angle to one another, against which wedge rings rest, which mesh on oppositely oriented threads of a threaded sleeve of the adjusting device, wherein the threaded sleeve, together with the wedge plates and the wedge rings, can be axially displaced by displacing the service brake piston of the brake cylinder arrangement parallel to the axis of rotation of the brake drum.

[0045] This enables a uniform radial lifting of the wedge plates for readjustment of the brake shoes due to lining wear.

[0046] Alternatively, it is also conceivable that the sliding surfaces of the sliding plate, which are aligned at an angle to one another, are aligned in such a way that a wedge ring rests on one of the sliding surfaces, which meshes with a thread of the threaded sleeve of the adjusting device, and the other of the sliding surfaces rests on a wall projecting radially from the threaded sleeve.

[0047] This variant also allows a uniform radial lifting of the wedge plates for adjusting the brake shoes.

[0048] For the adjustment movement of the brake shoes, the threaded sleeve has a gear ring coupled to an adjuster drive. By rotating the threaded sleeve in one adjustment direction, the wedge rings move closer to each other, or the first wedge ring moves closer to the wall, thus pressing the wedge plates radially toward the brake drum's rotational axis toward the inner surface of the brake drum.

[0049] In another alternative design variant, the brake shoes can be adjusted radially directly via the adjustment device.

[0050] According to a first variant, a rotationally fixed piston with an internal thread extends from the friction lining carrier of the brake shoe. The piston accommodates a threaded plunger with an external thread, which can be adjusted by rotating it around a radial axis of rotation with the adjustment device. The pressure wedge of the respective brake shoe is arranged on the plunger.

[0051] In a second variant, the adjustable piston with internal thread can be rotated with the adjustment device by turning it around a radial axis of rotation and a rotationally fixed threaded punch with external thread is accommodated in the piston.

[0052] To drive the piston or the threaded plunger, according to a preferred embodiment, the adjustment device comprises a gear ring and an adjuster drive coupled to an internal toothing of the gear ring. The gear ring further comprises a crown gear toothing that meshes with an external toothing of the rotatable threaded plunger or the rotatable piston of the respective brake shoe.

[0053] Preferred embodiments are explained in more detail below with reference to the accompanying drawings. They show: Fig. 1 an isometric representation of an embodiment variant of a drum brake according to the invention Fig. 2 an isometric representation of the drum brake according to Figure 1 with the brake drum hidden to show the arrangement of the brake shoes, Fig. 3 a schematic sectional view along the axis of rotation of the drum brake with a wheel rim overlapping the drum brake, Fig. 4 an isometric sectional view of the Fig. 1 shown drum brake, Fig. 5 a sectional view of an enlarged detail of the Fig. 4 shown drum brake, Fig. 6 an isometric sectional view of the drum brake according to Fig. 2 with hidden brake drum, Fig. 7 an isometric sectional view of the drum brake according to Fig. 1 in a further sectional plane, Fig. 8 an isometric view of the ring-shaped brake shoes, arranged on the wedge ring resting on the threaded sleeve, Fig. 9 a view opposite the Fig. 7 rotated isometric sectional view of the Fig. 7 shown arrangement, Fig. 10a - 10dSectional views of a section of the drum brake analogous to Fig. 5 in different functional positions, Fig. 11a - 11dden Fig. 10a - 10dcorresponding representations of the drum brake in an alternative embodiment, Fig. 12 a sectional view along the rotation axis of a further embodiment of the drum brake, Fig. 13a a sectional view of a section of the drum brake according to Fig. 12 in the service brake position, Fig. 13b sectional views of a section of the drum brake according to Fig. 12 in a non-braking position with partially worn friction lining and correspondingly adjusted brake shoe, Fig. 14 a further sectional view of a section of the drum brake according to Fig. 12 to show the drive of the adjustment device, Fig. 15a an isometric view of a section of the threaded sleeve of the adjustment device of the drum brake according to Fig. 12with adjusting rings placed thereon and wedge plate carried by them in a position for an unworn friction lining, Fig. 15b an isometric view of a section of the threaded sleeve of the adjusting device of the drum brake according to Fig. 12 with adjusting rings placed thereon and a wedge plate carried by them in a position for a worn friction lining, Fig. 16 and 17 schematic representations of further variants of adjusting rings and wedge plates, Fig. 18 a sectional representation along the axis of rotation of a further design variant of the drum brake, Fig. 19 an isometric representation of the threaded sleeves arranged in a ring on a wedge ring for adjusting the pistons of the brake shoes, Fig. 20 an isometric representation of the annular gear ring for driving the threaded sleeves, and Fig. 21 - 22 the Fig. 18 - 19 corresponding representations of another alternative design variant of a drum brake.

[0054] In the following description of the figures, terms such as top, bottom, left, right, front, rear, etc., refer exclusively to the exemplary representation and position of the drum brake, brake drum, brake shoe, brake cylinder, wedge ring, threaded sleeve, and the like chosen in the respective figures. These terms are not to be understood as limiting; i.e., these references may change due to different operating positions or the mirror-symmetrical design, etc.

[0055] In Figure 1 The reference numeral 1 denotes an embodiment of a drum brake according to the invention. The drum brake 1 has a brake drum 2 which is mounted rotatably about a rotation axis D and which, as shown in Figure 3 is shown, is connected in a rotationally fixed manner to a hub 13 and a rim 14 radially enclosing the brake drum 2.

[0056] In a space radially inside the brake drum 2, a plurality of brake shoes 3 mounted in a receiving space 22 of the brake drum 2 are arranged, each with a friction lining carrier 32 and a friction lining 31 arranged thereon.

[0057] In order to carry out a braking operation, the brake shoes 3 can be pressed radially to the axis of rotation D of the brake drum 2 against an inner surface 21 of the brake drum 2 designed as a friction surface.

[0058] To carry out this radial pressing movement of the brake shoes 3 against the inner surface 21 of the brake drum 2, a brake cylinder arrangement 4 is arranged in the receiving space 22 of the brake drum 2 on an armature housing 8 in a rotationally fixed manner.

[0059] As in the Figures 3 to 6 As shown in detail, the brake cylinder arrangement 4 preferably has a housing 41 fixedly fastened to the armature housing 8 in the receiving space 22 of the brake drum 2.

[0060] Relative to this housing 41, a service brake piston 42 is arranged displaceably parallel to the axis of rotation D of the brake drum 2.

[0061] Furthermore, the brake cylinder arrangement 4 has a parking brake piston 43 which can be displaced relative to the housing 41 parallel to the axis of rotation D of the brake drum 2 and can be acted upon by the spring force of a spring element 5.

[0062] The spring element 5 is preferably designed as a disc spring fixed in the housing 41, as is also shown for example in Figure 2 is shown.

[0063] The brake cylinder arrangement 4 further comprises a plurality of tappets 44 which serve to transmit a movement of the parking brake piston 43 to the service brake piston 42.

[0064] Furthermore, compressed air supplies are provided, which open firstly into a service brake pressure chamber 45 between the housing 41 and the service brake piston 42 and secondly into a parking brake pressure chamber 46 between the housing 41 and the parking brake piston 43.

[0065] In Figure 1 a first pressure fluid inlet 81 and a second pressure fluid inlet 82 for the supply / removal of compressed air into the service brake pressure chamber 45 and the parking brake pressure chamber 46 are shown.

[0066] Important for the actuation of the brake shoes 3 is always the movement of the service brake piston 42, which in the event of an intentional throttling of the speed of the commercial vehicle, a so-called service braking operation, is brought about by the supply of compressed air into the service brake pressure chamber 45.

[0067] In the event of an intentional brake application, which serves to prevent the commercial vehicle from accidentally rolling away in a parking situation, compressed air present in the parking brake pressure chamber 46 during driving operation is released from the parking brake pressure chamber 46, resulting in a displacement of the parking brake piston 43 toward the service brake piston 42. The displacement is caused by the force exerted by the spring element 5 on a rear side of the parking brake piston 43 facing away from the service brake piston 42.

[0068] In order to transmit the movement of the service brake piston 42 to the brake shoes 3, a respective pressure wedge 33 is arranged as part of a respective brake shoe 3 on a side of the friction lining carrier 32 facing away from the friction lining 31.

[0069] This pressure wedge 33 rests on a wedge ring 6 which can be moved parallel to the axis of rotation D of the brake drum 2.

[0070] The wedge ring 6 can be moved from a non-braking position into a braking position 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.

[0071] As in the Figures 4 to 6 As can be seen further, the wedge ring 6 is adjustable via an adjusting device 7.

[0072] In the preferred embodiment shown here, a thread 62 is arranged, in particular formed, on a surface of the wedge ring 6 facing away from the pressure wedge 33, which thread meshes with a threaded sleeve 71 of the adjusting device 7.

[0073] The threaded sleeve 71 can be moved together with the wedge ring 6 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.

[0074] To couple the service brake piston 42 with the threaded sleeve 42, an end face of the threaded sleeve 71 rests against the service brake piston 42. The wedge ring 6 is thereby held by a spring element 10, shown in the Figures 5 and 6 , always pressed in the direction of the service brake piston 42.

[0075] The movement of the brake shoes 3 back from the braking position to the non-braking position is, as mentioned above, ensured by the spring element 10, which, as shown for example in the Figures 5 and 6 can be seen, is supported on a contact section of the armature housing 8 and presses against a shoulder of the threaded sleeve 71.

[0076] To maintain the most constant possible clearance between the friction linings 31 of the brake shoes 3 and the inner surface 21 of the brake drum 2, an adjuster drive 75 is preferably used.

[0077] The adjuster drive 75 is preferably coupled to a gear ring 73 of the threaded sleeve 71. In the embodiment shown here, the gear ring 73 extends radially in a region between the end face 63 of the wedge ring 6 and the wedge-shaped base body 64 of the wedge ring 6, on one side of which the thread 62 is formed, which meshes with the thread 72 of the threaded sleeve 71 and whose other obliquely oriented pressure surface 61 faces the pressure wedge 33 of the brake shoes 3.

[0078] The toothing 74 of the gear ring 73, which is formed radially on the outside here, meshes with a Figure 7 shown gear wheel 77 of the adjuster drive 75, which is arranged on an adjuster shaft 76.

[0079] In order to reduce the friction between the brake shoes 3 and the wedge ring 6, in the embodiment shown here, a carriage with several rolling elements 92 is arranged between the pressure surface 61 of the wedge ring 6 and the pressure wedge 33 of the respective brake shoes 3.

[0080] The Figures 8 and 9 show as individual illustrations the arrangement of the brake shoes 3 on the wedge ring 6 and the arrangement of the wedge ring 6 on the threaded sleeve 71 of the adjusting device 7.

[0081] The spring element 5, which is preferably designed as a disc spring, can be fixed radially inside or radially outside on the housing 41 of the brake cylinder 4, depending on the design of the brake cylinder 4.

[0082] Thus, the spring element 5 is in the Figures 2 to 6 and 10a to 10d shown embodiment variant with a radially inner end region 51 radially inward (relative to the axis of rotation D of the brake drum 2), preferably fixed via screw bolts 53 and a clamping ring 52.

[0083] In the Figures 11a to 11d In the embodiment shown, the spring element 5 designed as a disc spring is fixed with a radially outer end region 51 radially outward on the housing 41 of the brake cylinder 4.

[0084] The Figures 10a to 10d show the operation of the drum brake 1 with spring element 5 mounted radially inside.

[0085] This shows Figure 10a a functional position of the drum brake 1 in which the brake shoes 3 are in a non-braking position and in which the friction linings 31 are unworn or almost unworn.

[0086] In this non-braking position, the parking brake pressure chamber 46 of the brake cylinder assembly 4 is filled with compressed air. The service brake pressure chamber 45, however, is empty, so that the service brake piston 42 rests against a first partition wall 48 between the service brake pressure chamber 45 and the parking brake pressure chamber 46. The compressed air present in the parking brake pressure chamber 46 preloads the spring element 5.

[0087] At the Figure 10b In the illustration shown, the components of the brake cylinder arrangement 4 are identical to those of the Figure 10a The friction lining 31 of the brake shoes 3 is partially worn here.

[0088] Accordingly, the wedge ring 6 is axially displaced a little way away from the spring element 5 relative to the illustration shown in Figure 9a relative to the threaded sleeve 71 of the adjusting device 7, which causes a slight displacement of the brake shoes 3 radially outwards and thus sets the clearance between the friction lining 31 and the inner surface 21 of the brake drum 2 to the specified nominal dimension, regardless of the lining wear.

[0089] The Figure 10c shows the service brake position of the drum brake 1. Relative to the Figure 10a In the position shown, compressed air was admitted into the service brake pressure chamber 45 to trigger the service brake. This moved the service brake piston 42 in the direction of the wedge ring 6. This displaces the wedge ring 6 and presses the brake shoes 3 radially outward against the inner casing surfaces 21 of the brake drum 2.

[0090] The Figure 10dFinally, it shows the state of a parking brake. During such a so-called parking brake application, instead of supplying compressed air to the service brake pressure chamber 45, the compressed air present in the parking brake pressure chamber 46 is released from the parking brake pressure chamber 46. This causes the spring element 5 to now press the parking brake piston 43 toward the service brake piston 42.

[0091] To stabilize the radial movement of the brake shoes 3, a support roller 35 is provided on a side surface of the radially extending pressure wedge 33, as is shown for example in Figure 8 is shown. The support roller 35 serves to absorb the force of the service brake piston 42 acting in the axial direction on the wedge mechanism.

[0092] The plunger 44 arranged on the inside of the parking brake piston 43 facing the service brake piston 42, which in this embodiment is accommodated in a first partition 48 of the housing 41 separating the service brake pressure chamber 45 from the parking brake pressure chamber 46, thereby presses the service brake piston 42 axially in the direction of the wedge ring 6 and thus the wedge ring 6 so far away from the first partition 48 of the housing 41 that the brake shoes 3 are pressed radially outwards into the parking brake position.

[0093] In the Figures 11a to 11d In the embodiment shown, the plunger 44 is accommodated in a second partition wall 49 of the housing 41, which separates the service brake pressure chamber 45 from the receiving chamber 22. Furthermore, in this embodiment, the spring element 5 is fixed radially outwardly on the housing 41 of the brake cylinder arrangement 4.

[0094] The initial position of the brake cylinder arrangement 4, as shown in Figure 11ashown corresponds to the one shown Figure 10a described position. The same applies to the partial wear position of Figure 11b , for the description of which see Figure 10b is referred to.

[0095] Service braking is also carried out analogously to that based on Figure 10c described manner.

[0096] The parking brake position of the Figure 11d This differs from the parking brake position of the Figure 10d that the plunger 44 is now arranged radially further inward in the embodiment shown.

[0097] The parking brake piston 43 here has a ring 431 projecting axially in the direction of the spring element 5 radially on the inside, which ring 431 enables the radially inner part of the spring element 5 to press the tappet 44 arranged in this area against the service brake piston 42 and thus to press the brake shoes 3 against the brake drum 2 by displacing the wedge ring 6 by releasing the compressed air from the parking brake pressure chamber 46.

[0098] Furthermore, in Figure 1 It can also be seen that a dust outlet 11 is arranged on a wall of an armature housing 8, through which it is possible to suck out brake dust generated during braking from an interior of the drum brake 1.

[0099] The closed design of the drum brake 1 shown here reliably prevents brake dust from being released into the environment during braking.

[0100] In the Figures 12 to 15ba further embodiment of a drum brake according to the invention is shown.

[0101] In this version, in contrast to the one based on the Figures 1 to 12 In the described embodiment of the drum brake 1 with a wedge mechanism designed as a wedge ring, a wedge plate 160 is provided for each of the brake shoes 130.

[0102] For the adjustment of the respective brake shoe 130, the wedge plate 160 is not itself provided with a thread on its underside, which meshes with a threaded sleeve and thus compensates for the gap between the friction lining and the inner surface 21 of the brake drum 2 due to friction lining wear by moving in the axial direction, but has a pressure surface 161 facing the pressure wedge 133 of the respective brake piston 130 and two sliding surfaces aligned at an angle to one another on the side facing away from the pressure wedge 133, against which adjusting rings 162, 163 designed as a wedge ring each rest.

[0103] These adjusting rings 162, 163 mesh on oppositely oriented threads 172a, 172b of a threaded sleeve 171 of the adjusting device 170. By approaching the adjusting rings 162, 163, as can be seen in the Figures 13a and 13b or the Figures 15a and 15b As can be seen, the wedge plates are pressed radially upwards and thus compensate for the gap between the friction lining and the inner surface 21 of the brake drum 2 due to friction lining wear.

[0104] In this embodiment, too, the threaded sleeve 171 together with the wedge plates 160 and the adjusting rings 162, 163 can be axially displaced by displacing the service brake piston 42 of the brake cylinder arrangement 4 parallel to the axis of rotation D of the brake drum 2 in order to carry out service braking.

[0105] The reset of the wedge plates 160 after service braking is carried out analogously to the Figures 1-12shown embodiment variant preferably with the aid of the return spring 10, which is supported on the one hand on the armature housing 8 and on the other hand on the service brake piston 42 of the brake cylinder arrangement 4.

[0106] To facilitate the sliding movement of the threaded sleeve 171, it is mounted relative to the armature housing 8 via a roller bearing 17, as is the case, for example, in the Figures 13a and 13b as well as in Figure 5 and Figure 6 is shown.

[0107] The wedge angle between the pressure wedge 133 and the pressure surface 161 of the respective wedge plate 160 or the carriage 9 mounted between the wedge plate 160 and the pressure wedge 133 is preferably between 9° and 15°, particularly preferably about 11°.

[0108] The wedge angle between the sliding surfaces of the wedge plate 160 facing away from the pressure surface 161 and the sliding surfaces of the adjusting rings 162, 163 resting against them is preferably between 30° and 40°, particularly preferably about 36°.

[0109] Depending on the height to be bridged, i.e. the radial height of the friction lining 31 of the respective brake shoe 3, these angles can vary.

[0110] While the angle adjustment of the sliding surfaces of the adjusting rings 162, 163 in the Figures 15a and 15b shown design variants are approximately equal in amount, it is, as shown in the Figures 16 and 17 As shown by way of example, it is also conceivable to design the angles of attack differently, as is the case in Figure 16 is shown.

[0111] It is also conceivable, as exemplified in Figure 17is shown, a variant with wedge plates 160 which are essentially triangular in cross-section and which are supported from radially below with a sliding surface on only one wedge-ring-shaped adjusting ring 162 which is moved for adjustment in the direction of a wall 164 which preferably projects radially on the threaded sleeve 171, so that the wedge plates 160 are fixed to the wall 164 in the axial direction and can be adjusted in the radial direction.

[0112] In the Figures 18 - 22 Two further design variants of a drum brake 1 are shown. In these design variants, the wear adjustment of the brake shoes 230 is not carried out by radially lifting the wedge ring 260 or in the Figures 12-17 shown wedge plates, but rather by radial adjustment of the brake shoes 230 themselves.

[0113] In contrast to the Figures 1 - 17In the embodiments shown, the pressure wedge 233 is not arranged in a fixed position via a pressure piece 133a on the friction lining carrier 132, but the connection between the friction lining carrier 232 and the pressure wedge 233 is made here via a piston / threaded stamp mechanism.

[0114] At the Figures 18 and 19 In the embodiment variant shown, a piston 234 which is rotationally fixed relative to the friction lining carrier 232 and has an internal thread 234a extends from the side of the friction lining carrier 232 of the brake shoe 230 facing away from the friction lining 231, in which a threaded stamp 235 which can be adjusted by rotating about a radial axis of rotation with the adjusting device 270 and has a flat foot and an external thread which can be screwed into the internal thread 234a of the piston 234 and on which the pressure wedge 233 of the respective brake shoe 230 is arranged is received.

[0115] A kinematically reversed arrangement is shown in the Figures 21 and 22shown. Here, extending from the friction lining carrier 232 of the brake shoe 230 is a piston 234, which is adjustable by means of the adjusting device 270 by rotation about a radial axis of rotation, also having an internal thread 234a, in which a rotationally fixed (rotationally fixed relative to the wedge ring 260) threaded plunger 235 with an external thread is received, on the base of which, not designed as a gear, the pressure wedge 233 of the respective brake shoe 230 is arranged.

[0116] In order to adjust the brake shoes 230, in this embodiment, an adjustment drive 75 is connected via a gear ring 271 to an external toothing 237 of the rotatable threaded stamp 235 in accordance with the Figures 18 and 19 shown embodiment or the rotatable piston 234 according to the Figures 21 and 22 shown design variant of the respective brake shoe 230.

[0117] For example, in the Figures 18 and 19In the embodiment shown, the base of the threaded stamp 235 is designed as a gear 236 with external teeth 237.

[0118] In the case of the Figures 21 and 22 In the design variant shown, an annular web with external teeth 237 is formed on the outer surface of the piston.

[0119] The one in a single presentation in Figure 20 The gear ring 271 shown has, on the one hand, an internal toothing 273 which, as shown in the Figures 18 and 21 shown, meshes with a gear of the adjuster drive 75.

[0120] The gear ring 271 further has a crown gear toothing 272 which meshes with the external toothing 237 of the threaded punch 235 or the rotatable piston 234. List of reference symbols

[0121] 1 drum brake 2Brake drum 21Inner casing surface 22Receiving space 3Brake shoe 31Friction lining 32Friction lining carrier 33Pressure wedge 34Sliding element 35Support roller 4Brake cylinder arrangement 41Housing 42Service brake piston 43Parking brake piston 44Tappet 45Service brake pressure chamber 46Parking brake pressure chamber 47Sealing ring 48First partition 49Second partition 5Spring element 51First end 52Clamping ring 6Tapered ring 61Pressure surface 62Thread 63End face 7Adjustment device 71Threaded sleeve 72Thread 73Sprocket 74Toothing 75Adjuster drive 76Adjuster shaft 77Gear wheel 8Armature housing 81First pressure fluid inlet 82Second pressure fluid inlet 9Slide 91Rolling element holder 92Rolling element 10Return spring 11Dust outlet 12Axle 13Hub 14Rim 15Screw bolt 16Lock ring 17Rolling bearing 130Brake shoe 131Friction lining 132Friction lining carrier 133Pressure wedge 133aPressure piece 133bWedge piece 134Sliding element 135Support roller 160Wedge plate 161Pressure surface 162First adjustment ring 163Second adjustment ring 164Wall 170Adjusting device 171Threaded sleeve 172aFirst thread 172bSecond thread 173Sprocket 174Toothing 230Brake shoe 231Friction lining 232Friction lining carrier 233Pressure wedge 234Piston 235Threaded punch 236Gear 237Toothing 260 wedge ring 270Adjustment device 271Sprocket 272Crown gear teeth 273Internal teeth DRotation axis xDirection yDirection zDirection

Claims

1. Drum brake (1), in particular for a utility vehicle, having - a brake drum (2) which is rotatably mounted about an axis of rotation (D), - a plurality of brake shoes (3, 130, 230) which are mounted in a receiving space (22) of the brake drum (2), each having a respective friction lining carrier (32, 132, 232) and a friction lining (31, 131, 231) arranged thereon, - wherein the brake shoes (3, 130, 230) are pressable radially with respect to an axis of rotation (AD) of the brake drum (2) onto a shell inner surface (21) of the brake drum (2) configured as a friction surface, - a brake cylinder arrangement (4), which is arranged fixedly for conjoint rotation on an armature housing (8) in the receiving space (22) of the brake drum (2), for actuating the brake shoes (3, 130, 230), characterized in that - a respective pressure wedge (33, 133, 233) is arranged on a side of the friction lining carriers (32, 132, 232) facing away from the friction lining (31, 131, 231), said pressure wedge lying on a wedge mechanism which is displaceable parallel to the axis of rotation (D) of the brake drum (2), - wherein the wedge mechanism is displaceable from a non-braking position into a braking position by way of displacement of a service brake piston (42) of the brake cylinder arrangement (4) parallel to the axis of rotation (D) of the brake drum (2).

2. Drum brake (1) according to claim 1, characterized in that the brake cylinder arrangement (4) has a housing (41) which is fastened in a stationary manner in the receiving space (22) of the brake drum (2) to the armature housing (8), the service brake piston (42) which is displaceable relative to the housing (41) parallel to the axis of rotation (D) of the brake drum (2), 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 acted upon by the spring force of a spring element (5), and a plurality of plungers (44) for transmitting a movement of the parking brake piston (43) to the service brake piston (42), wherein respective compressed air feeds into a service brake pressure space (45) between the housing (41) and the service brake piston (42) and into a parking brake pressure space (46) between the housing (41) and the parking brake piston (43) are provided.

3. Drum brake (1) according to claim 2, characterized in that the plungers (44) are received in a first dividing wall (48) of the housing (41), which first dividing wall separates the service brake pressure space (45) from the parking brake pressure space (46).

4. Drum brake (1) according to claim 2, characterized in that the plungers (44) are received in a second dividing wall (49) of the housing (41), which second dividing wall separates the service brake pressure space (45) from the receiving space (22).

5. Drum brake (1) according to any one of claims 2 to 4, characterized in that the spring element (5) is configured as a disk spring fixed to the housing (41).

6. Drum brake (1) according to any one of the preceding claims, characterized in that a slide (9) with a plurality of rolling bodies (92) is arranged between the pressure wedge (33, 133) and the wedge mechanism.

7. Drum brake (1) according to any one of the preceding claims, characterized in that the brake shoes (3, 130, 230) are adjustable radially via an adjusting device (7, 170, 270).

8. Drum brake (1) according to claim 7, characterized in that the wedge mechanism is adjustable via the adjusting device (7, 170, 270).

9. Drum brake (1) according to any one of the preceding claims, characterized in that the wedge mechanism has a tapered ring (6, 260) which is displaceable parallel to the axis of rotation (D) of the brake drum (2) and on which the pressure wedge (33, 133, 233) lies.

10. Drum brake (1) according to claim 9, characterized in that a thread (62) is arranged, in particular formed, on a surface of the tapered ring (6) facing away from the pressure wedge (33), which thread meshes with a threaded sleeve (71) of the adjusting device (7, 170, 270), wherein the threaded sleeve (71) is displaceable together with the tapered ring (6) by displacement of the service brake piston (42) of the brake cylinder arrangement (4) parallel to the axis of rotation (D) of the brake drum (2).

11. Drum brake (1) according to any one of claims 1 to 8, characterized in that the wedge mechanism has a number of wedge plates (160) corresponding to the number of brake shoes (3), which wedge plates are displaceable parallel to the axis of rotation (D) of the brake drum (2).

12. Drum brake (1) according to claim 11, characterized in that each of the wedge plates (160) has a pressure surface (161) facing the pressure wedge (133) of the respective brake piston (3) and two sliding surfaces oriented at an angle to one another, against which respective adjustment rings (162, 163) bear, which mesh with oppositely oriented threads (172a, 172b) of a threaded sleeve (171) of the adjusting device (170), wherein the threaded sleeve (171), together with the wedge plates (160) and the adjustment rings (162, 163), is axially displaceable by displacement of the service brake piston (42) of the brake cylinder arrangement (4) parallel to the axis of rotation (D) of the brake drum (2).

13. Drum brake (1) according to claim 11, characterized in that each of the wedge plates (160) has a pressure surface (161) facing the pressure wedge (133) of the respective brake piston (3) and two sliding surfaces oriented at an angle to one another, wherein an adjustment ring (162) bears against one of the sliding surfaces, which meshes with a thread (172a) of the threaded sleeve (171) of the adjusting device (170), and the other of the sliding surfaces bears against a wall (164) projecting radially from the threaded sleeve (171), wherein the threaded sleeve (171), together with the wedge plates (160) and the adjustment ring (162), is axially displaceable by displacement of the service brake piston (42) of the brake cylinder arrangement (4) parallel to the axis of rotation (D) of the brake drum (2).

14. Drum brake (1) according to claim 12 or 13, characterized in that the threaded sleeve (171) has a toothed rim (173) coupled to an adjuster drive (75), wherein by rotation of the threaded sleeve the wedge plates (160) are adjustable radially with respect to the axis of rotation (D) of the brake drum (2) in the direction of the shell inner surface (21) of the brake drum (2) by the adjustment rings (162, 163) approaching one another or the first adjustment ring (162) approaching the wall (164).

15. Drum brake (1) according to claim 7, characterized in that the brake shoes (230) are radially adjustable directly via the adjusting device (270).

16. Drum brake (1) according to claim 15, characterized in that a piston (234) fixed so as not to rotate and having an internal thread (234a) extends from the friction lining carriers (232) of the brake shoes (230), in which piston a threaded plunger (235) having an external thread is received, which piston is adjustable by the adjusting device (270) by rotation about a radial axis of rotation, on which threaded plunger the pressure wedge (233) of the respective brake shoe (230) is arranged.

17. Drum brake (1) according to claim 15, characterized in that a piston (234) having an internal thread (234a) and adjustable by the adjusting device (270) by rotation about a radial axis of rotation extends from the friction lining carriers (232) of the brake shoes (230), in which piston a threaded plunger (235) having an external thread and fixed so as not to rotate is received, on which threaded plunger the pressure wedge (233) of the respective brake shoe (230) is arranged.

18. Drum brake (1) according to claim 16 or 17, characterized in that the adjusting device (270) has a toothed rim (271) and an adjuster drive (75) coupled to an internal toothing system (273) of the toothed rim (271), wherein the toothed rim (271) further has a crown gear toothing system (272) which meshes with an external toothing system (237) of the rotatable threaded plunger (235) or of the rotatable piston (234) of the respective brake shoe (230).