阅读说明：本技术 用于鼓式制动器的具有微调装置的张开装置 (Opening device with fine adjustment device for drum brake ) 是由 U·巴赫 M·格德克 H·冯海因 A·塞弗 J·霍夫曼 A·梅斯纳 W·里特尔 F·佩 于 2019-09-25 设计创作，主要内容包括：本发明涉及一种用于鼓式制动器(4)的改进的张开装置(1),其包括具有其中可借助于弹簧加载的卡锁装置(12)锁止的微调螺钉(9)的集成的微调装置(8),为了在减小的力水平时可靠的微调功能,张开装置设置成,卡锁装置(12)实现微调螺钉(9)的规定的空转行程(L),通过在第一环绕方向上作用的第一止挡部(13)和在相反的环绕方向上作用的第二止挡部(14)在结构上确定空转行程。(The invention relates to an improved release device (1) for a drum brake (4), comprising an integrated fine adjustment device (8) having a fine adjustment screw (9) which can be locked by means of a spring-loaded detent device (12), wherein, for a reliable fine adjustment function at reduced force levels, the release device is designed in such a way that the detent device (12) implements a defined idle travel (L) of the fine adjustment screw (9), which is determined structurally by a first stop (13) acting in a first circumferential direction and a second stop (14) acting in the opposite circumferential direction.)

1. An opening device (1) for opening brake shoes (2, 3) of a drum brake (4) for vehicles along an opening axis (A), comprising a housing (5) having a fine adjustment device (8) arranged therein for compensating for an increased opening travel due to brake lining wear, wherein the fine adjustment device (8) comprises a fine adjustment screw (9) arranged coaxially with respect to the opening axis (A) and having a thread (16) which, by rotation in a first circumferential direction, causes an axial movement of at least one opening piston (10, 11) in an opening direction (S, S'), and which, by means of a spring-loaded latching device (12), can lock the rotation of the adjustment screw in the opposite circumferential direction, characterized in that the latching device (12) can realize a defined idle travel (L) of the fine adjustment screw (9), the free-wheeling path is structurally defined by a first stop (13) acting in a first direction of rotation and a second stop (14) acting in the opposite direction of rotation.

2. The opening device (1) according to claim 1, characterized in that the opening device (1) is rotatably driven and has at least one ball ramp assembly (6, 7) for converting a rotary driving motion into a translational opening motion along an opening axis (a).

3. The spreading device (1) according to at least one of the preceding claims, wherein the fine adjustment device (8) has a locking element (15) which is arranged to be axially elastically pretensioned against the fine adjustment screw (9), the latching device (12) being arranged between the locking element (15) and the fine adjustment screw (9).

4. The spreading device (1) according to claim 3, wherein the latching device (12) comprises a first latching tooth (17) which is formed on the end face of the fine adjustment screw (9) and a second latching tooth (18) which is formed on the end face of the locking element (15) and interacts with the first latching tooth (17) in such a way that a rotation relative to one another in one circumferential direction and a rotation relative to one another in the opposite direction can be locked in the event of an axially acting force.

5. The spreading device (1) according to at least one of claims 3 or 4, characterized in that the locking element (15) is supported in a manner rotatable in the circumferential direction relative to the spreading piston (11) between the stops (13, 14).

6. The spreading device (1) according to claim 5, wherein the stops (13, 14) are configured as sides of a sector of a recess (19) in a component, which recess cooperates with a radial projection (20) configured on the other component.

7. The spreading device (1) according to claim 6, characterised in that the recess (19) is configured in the spreading piston (11) and the locking element (15) has at least one shank (33) with at least one radial projection (20) arranged thereon, which projection projects into the recess (19).

8. The spreading device (1) according to at least one of the preceding claims, characterized in that the spreading device (1) is operated by a drive sleeve (21), which for this purpose is provided at least in sections with an external toothing (22) and is rotatably supported in a housing (5).

9. The opening device (1) according to claim 8, characterized in that a fine adjustment piston (23) with a fine adjustment screw (9) screwed therein and a support piston (24) are arranged in the drive sleeve (21), wherein the fine adjustment piston (23) and the support piston (24) are mounted in a rotationally fixed manner and axially displaceable relative to the drive sleeve (21), wherein the support piston (24) is axially supportable on the fine adjustment screw (9) in a direction towards the fine adjustment piston (23).

10. The opening device (1) according to claim 9 and at least one of claims 2 to 8, characterized in that a first ball ramp assembly (6) is configured between the trimming piston (23) and the first opening piston (24) and a second ball ramp assembly (7) is configured between the opening piston (24) and the second opening piston (11).

11. Drum brake (4) comprising at least one spreading device (1) according to at least one of the preceding claims.

Technical Field

The present invention relates to a spreading device for a drum brake according to the preamble of claim 1 and to a corresponding drum brake.

Background

It is known to use drum brakes designed as service brakes in vehicles, in particular in electric vehicles. Drum brakes usually have a rotationally driven spreading unit. In many cases, an electric motor with a subsequent reduction gear serves as a drive for the expansion unit.

Furthermore, in opening units of this type it is known to use simple and stable ball ramp assemblies in order to convert the rotational movement of the drive part into a translational opening movement of the drive part. In the ball ramp assembly, usually three or more balls are clamped between two disks between ramps machined into them, which are oriented opposite in the circumferential direction, so that when one of the disks rotates, the balls roll in the ramps and thereby press the disks apart from one another.

A characteristic feature in ball ramp assemblies is the relatively small travel, which is limited by the diameter of the ball and disk and the depth of the ramp, which are severely limited by construction space. The individual strokes of the ball ramp assemblies often do not adequately balance the wear of the brake linings of the drum brake due to operation. It is therefore known to provide the expansion unit with a ball ramp assembly with an integrated fine adjustment device to compensate for the wear distance.

For background, reference is made here, for example, to patent document DE 102014226270 a 1. Therein, an opening device with two ball ramp assemblies is described, in which a fine adjustment of the wear distance in a fine adjustment direction is effected by rotating a separate threaded fine adjustment screw arranged coaxially with respect to the opening axis, wherein the rotation of the fine adjustment screw in the opposite direction is prevented by means of a latching device.

In the case of known opening devices with integrated fine adjustment means in general and with steep ball ramp assemblies in particular, it is disadvantageous that the fine adjustment takes place at high opening forces, which leads to relatively high internal force levels during the fine adjustment process. This may cause higher friction between the rotatable components, for example during the release process, and negatively affect other aspects, such as efficiency during the back rotation, stability of the adjustment process, wear of the friction pairs and other components, etc.

Disclosure of Invention

It is therefore an object of the present invention to provide an improved opening device for a drum brake with an integrated fine adjustment device, which allows a reliable fine adjustment function, in particular at lower force levels.

According to the invention, this object is achieved by an expanding device having the combination of features according to claim 1. The dependent claims present further embodiments and further developments according to the invention.

The invention provides that the locking device provides a defined free-running path of the fine adjustment screw, which is defined structurally by two stops acting in the circumferential direction and spaced apart from one another.

In this way, the tightening of the fine adjustment screw required for fine adjustment is delayed in a targeted manner to the operating point during the release process when the majority of the opening force has been reduced. Thus, fine adjustment can be achieved with low applied forces, friction and wear are reduced, the service life is increased, and the adjustment process is made uniform by avoiding abrupt changes in force, especially due to traction. By significantly reducing the load on the components for the trimming device, an additional trimmer outside the opening device can be dispensed with.

In a preferred embodiment, the opening device is driven in a rotatable manner and has at least one ball ramp assembly for converting a rotational drive movement into a translational opening movement.

The opening device is thereby designed to be particularly rigid and stable in the opening direction and can be used in any motor vehicle type, in particular in an electric vehicle.

Furthermore, the invention provides that the fine adjustment device has a locking element which is arranged to be axially elastically pretensioned relative to the fine adjustment screw, and that the detent device is arranged between the locking element and the fine adjustment screw.

In this way, a coaxial drive for automatic fine adjustment can be realized in a particularly efficient, space-saving and stable manner, but even in the case of new brakes, initial adjustment can be realized and the drive is decoupled from the opening force.

In order to further improve, in particular to control the fine adjustment in a stable and uncomplicated manner, the detent device can comprise a first detent toothing on the end face of the fine adjustment screw and a second detent toothing on the end face of the locking element, which second detent toothing, in cooperation with the first detent toothing, allows a rotation relative to one another in one circumferential direction under the formation of an axially acting force and blocks a rotation relative to one another in the opposite direction.

The free-wheeling travel according to the invention can be realized particularly simply and reliably if the locking element is mounted rotatably in the circumferential direction relative to the spreading piston between the stops.

In this case, the stop can be configured simply and stably as a side of the sector of the recess, against which the radial projection of the other component rests. In this case, the free-wheeling travel can be determined in a clear and reliable manner in terms of design by designing the angle of the segment together with the width of the projection.

A particularly efficient manufacturability of the assembly is achieved if the recess is formed in the spreading piston and the locking element has at least one shank with at least one radial projection arranged there, which projects into the recess. The expansion piston is thus produced from sheet metal, for example, by simple stamping.

In order to be compact and at the same time to be able to interact simply with an electromechanical actuating drive, the spreading device can be actuated by means of a drive sleeve, which is provided at least in regions with external teeth and is mounted in a rotatable manner in a housing of the spreading device.

A preferred embodiment of the invention provides that a fine adjustment piston with a fine adjustment screw screwed therein and a support piston are arranged in the drive sleeve, wherein the fine adjustment piston and the support piston are mounted in a rotationally fixed and axially displaceable manner relative to the drive sleeve, and wherein the support piston is axially supportable on the fine adjustment screw in the direction of the fine adjustment piston.

It is particularly preferred that the invention be extended by a first ball ramp assembly being configured between the trim piston and the first flaring piston and a second ball ramp assembly being configured between the flaring piston and the second flaring piston.

This results in a particularly compact and rigid construction of the spreading device with symmetrical force profiles for a continuous adjustment curve and high efficiency and a smaller number of components that move translationally and frictionally.

Furthermore, the invention claims a drum brake comprising at least one expansion unit according to the invention. In this case, the spreading unit according to the invention can also be used successfully in drum brakes of different types, for example in double-servo or simple drum brakes.

Drawings

Further features, advantages and applications of the invention result from the following description. Wherein:

figure 1 shows a top view of a drum brake with a spreading unit according to the invention when the brake drum is removed,

figure 2 shows a first embodiment of the splaying unit according to the invention in axial section,

figure 3 shows a second embodiment of the splaying unit according to the invention spatially in a partial sectional view with a schematic force flow course,

figure 4 shows the embodiment according to figure 3 in an initial position which is not manipulated,

figure 5 shows the embodiment according to figure 3 in the actuated position directly after the idle stroke,

figure 6 shows the embodiment according to figure 3 in a position of continued manipulation relative to figure 5 before starting the fine-tuning process,

figure 7 shows the embodiment according to figure 3 in a position of continued manipulation with respect to figure 6 in the switching point when starting the fine-tuning process,

figure 8 shows the embodiment according to figure 3 in the release position after the return of the idle stroke before the start of the fine adjustment,

figure 9 shows the embodiment according to figure 3 in a release position which is continued further in relation to figure 8 during trimming,

fig. 10 shows the force-displacement diagram of the spreading device during brake actuation and fine adjustment.

Detailed Description

Since the basic operating principle of the drum brake and ball ramp assembly is already sufficiently known, only the functional characteristics that are important for the invention are explained below.

FIG. 1 shows a schematic view of a

Fig. 1 shows the drum brake 4 by way of example when the brake drum is removed. The spreading device 1 spreads the two brake shoes 2, 3 with the brake linings 25 fixed thereto apart from one another toward a brake drum, not shown. As a result of the wear of the brake linings 25, the opening travel required for braking increases continuously up to a defined wear limit. The increased wear distance is compensated for in stages by a fine adjustment device 8, described below, arranged in the housing 5.

In order to prevent the linings 25 from bearing asymmetrically and unevenly on the brake drum, the housing 5 of the opening device 1 is mounted so as to be floating along the opening axis a.

FIG. 2

Fig. 2 shows an embodiment of the expanding device 1 in an initial state without fine adjustment in an axial section through the expansion axis a. In this embodiment, the opening device 1 is actuated by a not shown electromechanical drive unit by a rotary drive movement. In this case, a torque is introduced via the radial external toothing 22 into a drive sleeve 21, which is mounted in the housing 5 so as to be rotatable about the expansion axis a by means of radial bearings 31, 32, for example by means of a gear or a drive belt, not shown.

Within the drive sleeve 21, a fine adjustment piston 23 and a support piston 24 are mounted rotationally and axially displaceably. For this purpose, radial ribs 29, 29' are provided on the trimming piston 23 or the support piston 24, which are guided in a sliding manner in longitudinal grooves 30 in the drive sleeve 21.

The fine adjustment screw 9 is positively connected to the fine adjustment piston 23 by means of a thread 16, so that the fine adjustment piston 23 is axially displaced when the fine adjustment screw 9 is screwed around the opening axis a. The support piston 24 is supported axially on the fine adjustment screw 9 in the direction of the fine adjustment piston 23.

Furthermore, the spreading device 1 has two spreading pistons 10 and 11 in its housing 5, which in this embodiment act on the brake shoe receptacles 26, 26' via an interposed disk spring. The support pistons 10, 11 are axially movable relative to the housing 5 and are mounted in a rotationally fixed manner in the circumferential direction.

In the present invention, embodiments in which the rotation prevention portion is specifically implemented differently may be applied. In the embodiment shown, the rotation prevention is realized, for example, by the brake shoe holders 26, 26 'which are supported in the circumferential direction with their receiving grooves 36, 36' on the flat brake shoes 2, 3.

The ball ramp assembly 7 is constructed between the trimming piston 23 and the opening piston 10 or between the support piston 24 and the opening piston 11, respectively. When the drive sleeve 21 is actuated by the drive unit, the opening piston 24 and the trimming piston 23 are rotated together and a translational opening of the two opening pistons 10, 11 is brought about by the ball ramp assemblies 6, 7.

The trimming means 8 comprise a locking element 15 arranged substantially coaxially to the opening axis a inside the support piston 24. The spring element 31, which is supported on the support piston 24, always axially pretensions the locking element 15 elastically against the trimming screw 9.

Between the locking element 15 and the fine adjustment screw 9, a latching device 12 in the form of two axial latching teeth 17, 18 which engage in one another in a complementary manner is arranged. The first latching tooth 17 is formed on the end face on the fine adjustment screw 9, and the second latching tooth 18 is formed on the end face on the locking element 15. The two latching tooth sections 17, 18 are each designed in the form of a ratchet tooth section with a plurality of teeth 37, 37' distributed over the circumference, wherein in each case one flank is embodied as a more gradual slope and the other flank is embodied as a steeper slope end face. A rotation relative to one another in only one circumferential direction between the locking element 15 and the fine adjustment screw 9 is achieved by the detent toothing 17.

FIG. 3

Fig. 3 shows a further preferred embodiment of the expansion device 1 in partial section. In contrast to the embodiment according to fig. 2, the two spreading pistons 10, 11 are fixed in rotation by radially projecting guide lugs 27, which project into axial guide grooves 28 in the housing 5. Furthermore, the spring element 31 is arranged as a helical spring instead of a disk spring stack as in fig. 2.

In addition, the force flow through the spreading device 1, which is caused by the spreading force Fs acting on the spreading device 1 from the brake shoes 2, 3, is shown here in a simplified manner. Since the support piston 24 is mounted in the drive sleeve 21 together with the fine adjustment screw 9 and the fine adjustment piston 23 in a floating manner, the support piston is axially in force equilibrium when the brake shoes 2, 3 are spread apart.

FIG. 4

Fig. 4 shows the spreading device 1 according to fig. 3.

The locking element 15 is mounted rotatably in the circumferential direction relative to the spreading piston 11 between the two stops 13, 14. The angle of rotation between the two stops 13, 14 structurally defines the idle stroke L.

For this purpose, a shank 33 is formed on the locking element 15, and two ribbed radial projections 20, 20' are formed on the shank, for example in the form of a wedge shaft with two wedges.

A recess 19 is arranged in the spreading piston 11, which recess is embodied as an axial recess. However, a countersunk recess is also permissible in the present invention. The recess has the form of a central bore in cross section with two substantially sector-shaped parts 35, 35' radially protruding from the bore. The side edges of the sector-shaped part 35, 35' form the stop 13, 14 or 13', 14 '. The locking element 15 projects with the shank 33 into the recess 19 so that the projection 20 is located in the portion 35. The locking element 15 can thus be rotated within the idle stroke L to a limited extent relative to the opening piston 11, wherein the limitation is achieved by the projection 20 abutting with its side end face either against the stop 13 or against the stop 14.

The free-wheeling distance L together with the number of teeth in the detent toothing 17 and the pitch of the thread 16 are decisive parameters for the properties of the fine adjustment device 8.

According to a further embodiment according to the invention, not shown here, the association of the shank 33 and the recess 19 can be interchanged for certain applications in such a way that the shank 33 is arranged on the spreading piston 11 and the recess 19 is arranged in the locking element 15 with one or more projections 20, …. As a result, although the expansion piston 11 is more expensive to produce, its tilting safety in the assembly can be increased, for example.

In the embodiment shown, the shank 33 is designed for having two opposite identical projections 20, 20' in cross section, axially symmetrically. However, in the present invention, other variants with only one or more than two projections or asymmetrical embodiments with correspondingly adapted recesses 19 are possible at all times.

In the non-actuated initial state shown here, the projection 20 rests against the stop 14.

FIG. 5

During braking, the drive sleeve 21 is actuated in the actuating direction B and rotates together with the fine adjustment piston 23, the fine adjustment screw 3, the support piston 24 and the locking element 15 until the idle stroke L has elapsed and the projection 20 abuts against the stop 13.

FIG. 6

On further actuation, the locking element 15 remains upright, limited by the stop 13, whereas the fine adjustment piston 23 rotates further together with the fine adjustment screw 3 and the support piston 24. The locking teeth 17, 18 are moved toward one another by the fine adjustment screw 9 or the locking element 15, and the locking element 15 is displaced axially against the spring force of the spring element 31 in the direction of opening the piston 11.

If the wear of the brake linings 25 is below a defined threshold value, the opening travel is limited in this position and the opening device 1 returns from this state completely reversibly after the braking process has ended.

FIG. 7

If the wear of the brake linings 25 is above a threshold value, the opening travel increases, so that the drive sleeve 21 continues to rotate relative to the position according to fig. 6. As a result, the teeth 37, 37' pass over one another and the latching teeth 17, 18 latch in a position displaced in the changing circumferential direction due to the spring force of the spring element 31. Thereby, the fine adjustment process is started.

FIG. 8

After the brake release, starting from the position according to fig. 7, the drive sleeve 21 is rotated back together with the fine adjustment piston 23, the fine adjustment screw 3, the support piston 24 and the locking element 15 until the free-wheeling travel L is passed again in the opposite direction and the projection 20 abuts against the stop 14. During this rotation, the expansion pistons 10, 11 are likewise retracted axially opposite the expansion direction S, thereby correspondingly reducing the force level in the ball ramp assemblies 6, 7.

FIG. 9

On further movement in the release direction, the fine adjustment of the fine adjustment piston 23 is started after the position according to fig. 8.

Further rotation of the fine adjustment screw 9 is prevented by the detent 17 being held at the locking element 15 by the stop 14. However, as the drive sleeve 21 continues to rotate with the fine adjustment piston 23 to the initial position, the fine adjustment piston is caused to rotate on the thread 16 relative to the fine adjustment screw 9 and is moved axially by the fine adjustment distance N. In the non-actuated initial position, the axial distance between the spreading pistons 10 and 11 is thereby increased. Thereby, wear of the brake linings 25 is balanced.

Here, essentially only relatively small frictional forces also act in the thread 16 and on the contact surface between the support piston 23 and the fine adjustment screw 9, eliminating high clamping forces in the ball ramp assembly 6, 7 due to the idle stroke L.

FIG. 10 shows a schematic view of a

In fig. 10, a simplified force-displacement diagram of the spreading device 1 according to the invention is shown during a braking maneuver and during fine adjustment.

The solid lines represent the manoeuvres at the new state b0 and at the worn states b1, b2 below the threshold Wv determined for fine tuning. The dashed line bn represents a manipulation with successful fine-tuning.

The vertical axis shows the level of the opening force Fs acting on the system through the opening pistons 10, 11. The horizontal axis shows the opening travel Ws or the angle of rotation α s associated therewith.

In phase I at the beginning of the actuation, the idle travel L (position according to fig. 4, 5) is first passed. In this case, the brake shoes 2, 3 are brought into contact with the brake drum and tensioned against the latter, and the braking force Fs is increased to its operating value Fsb.

In phase II, the detent teeth 17, 18 start to rotate relative to each other, however, without having to pass over the teeth 37, 37' (position according to fig. 6). The extended stroke Ws is continuously increased according to the wear states b1, b 2. In this phase, the spreading device 1 can be completely and reversibly returned into the initial state without fine adjustment when the brake is released and the spreading force Fs is removed.

In the switching point U, beyond the teeth 37, 37', the catch 12 is latched in the new position and the fine adjustment process (position according to fig. 7) is started.

In phase III, after the brake is released, the free-wheeling travel L is first returned to the stop 14, where the opening force Fs is significantly reduced to its residual value Fsn (position according to fig. 8) during the fine adjustment.

In phase IV, when the clamping force Fs is reduced, a rotation of the trimming piston 23 relative to the trimming screw 9 is carried out, resulting in a trimming distance N (position according to fig. 9).

List of reference numerals

1 opening device

2 brake shoe

3 brake shoe

4 drum brake

5 casing

6 ball slope subassembly

7 ball ramp assembly

8 Fine adjustment device

9 Fine adjustment screw

10 expanding piston

11 expanding piston

12 locking device

13 stop part

14 stop part

15 locking element

16 screw thread

17 latch tooth

18 latch tooth

19 recess

20 projection

21 driving sleeve

22 external tooth part

23 Fine adjustment piston

24 support piston

25 brake linings

26 brake shoe receiving part

27 guide nose

29 guide groove

29 rib

30 longitudinal grooves

31 spring element

32 radial bearing

33 handle

34 holes

35 part of

36 accommodating groove

37 teeth

A opening axis

B steering direction

L idle stroke

N fine tuning distance

S direction of opening