DE8811920U1 - Mechanical actuating device for a wheel brake of a motor vehicle - Google Patents

Description

Mechanical actuating device for a wheel brake of a motor vehicle

The invention relates to a mechanical actuating device for a wheel brake of a motor vehicle with

- a piston that is guided in a housing and can be operated either mechanically or hydraulically,

- an actuator to be operated by the driver of the motor vehicle for the parking brake,

- an actuator mounted on the housing,

- transmission elements between the actuating element and the final control element,

- an adjustment device by which the crater can be automatically adjusted when hydraulically actuated and is firmly connected to the actuator when not under hydraulic load,

- a stop against which the actuating element rests when the mechanical actuating device is released,

- a stop for the actuator and

- a return spring that loads the actuator towards its stop.

Such actuation devices have been installed in most passenger cars and trucks for many years. The actuation element for parking brakes is usually a handbrake lever, but can also be a pedal that is located away from a brake pedal intended for hydraulic service braking. The

■ · · &igr;

•■

· 1 ·

- 2 - lG-61

The actuator is usually a lever that can be pivoted around a pivot axis arranged transversely to the piston axis. The transmission elements are usually a cable and sheath of a

[ Bowden cables, in some cases also rod parts, are provided. In general, actuators of two rear wheel brakes are connected by separate transmission elements with a

■t connected to a common actuator.

For known generic actuating devices,

in the non-actuated state of the actuating element, the actuator of the or each associated brake is held against its stop by the return spring acting directly on the actuator in question. In

} Similarly, the actuator is provided with a

its own return spring is held against its stop. In many cases, the actuating element is assigned a switch which closes an electrical circuit of an indicator light which is interrupted in the stop position of the actuating element as soon as the actuating element is moved, even if only slightly, from its stop position.

% The transmission elements of known generic actuators

■* ing devices are adjusted during installation so that

that they are taut when the actuator is not actuated; however, strict attention is paid to ensuring that the actuator is held against its stop by its return spring with a pre-tension that is significantly greater than the tension of the transmission elements.

In the case of motor vehicles equipped with generic operating devices, it is generally not intended to subsequently replace the transmission elements in certain»

If maintenance intervals are correct, manually adjust them, as

'' Brake pad wear to a significant extent only with hydraulic ¹

The

- 3 « 1G-61

This occurs during service braking and is then automatically compensated for by the wax partial preload. The transmission links, which were initially set to be at least free of play, generally with a slight preload, become loose over time, as they become longer and/or have joints that are slightly worn out after a while. As a result, a shortened actuating path of the actuating element results in a smaller actuating path of the actuating element over time.

However, since a certain travel of the actuator must not be exceeded for a safe parking brake, the driver must ensure that the actuating element is moved further and further away from its stop over time for each parking brake in order to overcome a dead motion before the actual actuating path begins. This is particularly annoying with handbrake levers, which are moved further upwards with each parking brake due to the gradual elongation of a cable that serves as a transmission element. If the movement of the actuating element is finally exhausted and no adjustment of the transmission elements is then made, sufficient parking braking is no longer possible despite the perfectly functioning automatic adjustment device.

The invention is therefore based on the object of developing a generic actuating device in such a way that, in addition to the automatic compensation of brake pad wear, changes in the length of transmission elements between the actuating element and the adjusting element are also automatically compensated.

The task is to be solved by starting from a mechanical actuating device of the type described above.

With

· &iacgr;

- 4 - 16-61

Genus solved in that the transmission elements in the assembled and adjusted state are dimensioned _in such a way that the setting spring of the actuator acts on the actuating element via the transmission elements and holds this in contact with its stop when the mechanical actuating device is released, whereas the actuator is held at a distance from its stop by the transmission elements:..

This ensures that the force of the actuator's return spring or a force proportional to this force loads the transmission elements. Any elongation of the transmission elements over time only results in the distance between the actuator and its stop gradually becoming smaller. A sufficiently large distance during the original assembly, which generally only needs to be a few millimetres, is sufficient to prevent the transmission elements from becoming loose over the entire service life. As a result, the original, more or less

Relationship between the actuation path of the

actuator and the travel of the actuator are maintained at all times* For example, if the actuator is a handbrake lever, the user can be sure that a certain amount of pivoting of the actuator away from its stop will always achieve sufficient parking braking.

The stop for the actuator could thus in principle be omitted; however, it is expediently retained as a reference point from which a target position is determined that the actuator should assume when assembling and adjusting the transmission elements.

Appropriate further developments of the invention are described in the subclaims.

&bull; · · * Ii I < « Il &igr; &bull; · > I ■ II

-S- 1G-61 156

An exemplary embodiment of the invention is described in further detail below using schematic drawings. They show:

Fig. 1 is a view of a fastening device according to the invention including the associated brake, Fig. 2 is an enlarged detail from Fig. 1 and Fig. 3 is an axial section of the actuating device and the associated brake.

The actuating device according to the invention is explained using the example of a wheel brake 10, which is arranged as a floating caliper disc brake on a vehicle wheel 12 and interacts with a brake disc 14 attached to the latter.

The wheel brake 10 has a floating caliper 16 which is guided so as to be displaceable along an axis A parallel to the wheel axis and is formed in one piece with a housing 18. The floating caliper 16 engages over the brake disk 14 and two brake shoes 20 and 22. To actuate the wheel brake 10, a piston 24 is guided in a cylinder bore 26 in its housing 18. The brake shoe 20 can be applied directly to the brake disk 14 by means of the piston 24, and the brake shoe 22 can be applied by moving the floating caliper 16 along the axis A.

The piston 24 can be actuated either hydraulically by introducing brake fluid into the cylinder bore 26 or mechanically by rotating a shaft 28 mounted in the housing 18 transversely to the axis A. To rotate the shaft 28, an actuator 30 in the form of a lever is attached to it. A tappet 32 is eccentrically supported on the shaft 28 within the housing 18 and acts on the piston 24 via an automatic adjusting device 34.

fi 4« it 4 t

II. III« t . , ,

·

it

- 6 >* 1G-61

The adjusting device 34 is of conventional design; in the resting state it forms a rigid connection between the tappet 32 and the piston 24. The tappet 32 engages a

Rod 36, which is piston-like in the housing 18 along the

$ Axis A is movable and secured against rotation 38

secured against rotation. On the rod 36 is a

Disc 40 is attached to which a compression spring 42 is supported with its end remote from the piston 24. The other end of the compression spring 42 is supported on a spring cage 44, which is attached in the housing 18.

The rod 36 is provided with a non-self-locking thread at its end 46 remote from the shaft 28 and is screwed into a corresponding nut 48. A flange 50 is formed on the nut 48, which faces a locking ring 52 fastened behind it to the housing 18. Between the flange 50 and the locking ring 52 an axially resilient wave washer 54 is arranged, which exerts a forward-directed pressure on the flange 50 via axial roller bearings 56 and thereby holds a conical friction surface formed on the flange 50 against a complementary friction surface formed on an inner shoulder 58 of the housing 18. This normally prevents the nut from rotating.

The mode of operation of the automatic adjusting device 34 is known and therefore does not require detailed explanation; it is sufficient to point out that adjustment can only take place when the piston 24 is hydraulically actuated; the adjusting device 34 is rigid with respect to mechanical forces acting on it along the axis A in one direction or the ^other .

A return spring 60 is arranged on the actuator 30, which in the example shown is designed as a helical spring, with a tangentially projecting leg 62 in

- 7 - lG-61

a hole 64 of the actuator 30 and is supported by a second tangential leg 66 on a projection 68 of the housing 18. In the example shown, the projection 68 is a cylindrical pin that extends transversely to the axis A, forms a first stop 70 on one side, which is assigned to a first nose 72 of the actuator 30, while the opposite side of the projection 68 forms a second stop 74, which is assigned to a second nose 76 of the actuator 30. In this way, the pivoting range of the actuator is limited in both directions.

For assembly purposes, a spacer 78 is arranged between the first stop 70 and the associated nose 72, which prevents the return spring 60 from returning the actuator 30 to such an extent that the first nose 72 touches the associated stop 70. The effect of the spacer therefore corresponds to a slight mechanical actuation, in which the actuator 30, via the tappet 32 and the adjusting device 34, has pushed the piston 24, as shown in Fig. 3, slightly out of the housing 18 from its rear end position towards the brake disk 14.

An actuating member 80 in the form of a handbrake lever is provided for parking braking of the wheel brake 10. The actuating member 80 can be pivoted away from a stop 84 about a bearing pin 82 and can be locked into various actuating positions. A switch (not shown) is assigned to the stop 84, which closes an electrical control circuit as soon as the actuating member 80 has moved away from this stop.

The actuating element 80 is connected to the actuator 30 by f|

ifiehfeife one behind the other ¹ arranged transmission elements 86 S

.III It Il « Il Il '

■ &igr; Ii t &igr;&igr; > < ■ !

&igr;&igr;&igr;&igr;&igr; J "! &ldquor;' ! !

kill ( t i * Il

KIl III III ·· ··■· I·

- 8 - lG-61

connected, namely a pull rod 88/ which is hinged at one end to the actuating member 80 and at its other end is hinged to the middle of a balance beam-like two-armed lever 90. A cable 92 is attached to each of the two ends of the lever 90. The two cables 92, together with a dumbbell 94, form Bowden cables, only one of which is shown in full. The cable end of this Bowden cable which is remote from the balance beam-like lever 90 is attached to the actuating member 30; the associated casing 94 extends between a support 96 arranged on the vehicle near the lever 90 and a support 98 arranged on the housing 18.

After the wheel brake 10 has been installed in a vehicle, the piston 24 is hydraulically actuated several times so that any play between the brake disk 14 and the brake shoes 20 and 22 that exceeds the target clearance is eliminated. The actuating member 80 is brought into its rest position, in which it rests against its stop 84. Then the transmission members 86 are installed and tensioned in such a way that the spacer 78 can be removed without any effort or falls out of itself between the stop 70 and the nose 72. The "distance x originally determined by the spacer 78 between the stop 70 and the nose 72 is now maintained by the transmission members 86."

When the actuating member 80 is pivoted away from its stop 84 for a parking brake, the nose 72 of the actuating member 30 moves further away from its stop 70; the strongest possible mechanical brake actuation is achieved when the second nose 76 formed on the actuating member 30 hits its stop 74. To release the parking brake, the actuating member 80 is unlocked so that it pivots back against its stop 84;

iI

I I

- 9 - lG-61

the adjusting lever 30 then returns to the position in which its nose 72 has the original distance x from the stop 70.

As the transmission links 86 gradually lengthen over the course of the vehicle’s service life or as the joints arranged between them become distorted, the distance x decreases without ever reaching the value zero.

The transmission elements 86 are therefore constantly subjected to a tension generated by the return spring 60 and are thereby kept taut. At the same time, the actuating element 80 is held against its stop 84 in the non-actuated state without being assigned its own return spring.

Ii II

Claims (4)

PATENT ATTORNEYS; · » j j *.* J . .*', , " , iSR.-iNc.FKANZ vuesthoff WUESTHOFF-v.PECHMAN'M-B'EHRENi-GOE'fz"' ·>«·""«··"»*&trade;«&trade;off DIPL.-ING. GEKHARD PULS (l9JI-I97l) EUROPEAN PATENT ATTORNEYS d.pl-cheu.dr.e.pkeiherr vo« pechmann DR.-ING. DIETER BEHRENS DIPL.-ING. DIPL.-VI11TSCH.-ING. XUPERT GOETZ DIPL.-PHYS. DR. AXEL VON HELLFELD Lucas KOP-8681 D-8000 MUNICH 90 1G-61 156 SCHWEIGERSTRASSE 2 phone: (089)6620 ji 20 September 1988 telegram: protectpatent TEL: 524070 fax: (089) 663936 (in) Protection claims 1. Mechanical actuating device for a wheel brake (10) of a motor vehicle with - a piston (24) which is guided in a housing (18) and can be actuated either mechanically or hydraulically, - an actuating member (80) which is actuated by the driver of the motor vehicle vehicles for parking braking, - an actuator (30) mounted on the housing (18), - transmission elements (86) between the actuating element (PO) \ and the final control element (30)- - an adjusting device (34) by which the piston (24) is automatically adjustable during hydraulic actuation and is firmly connected to the actuator (30) in the hydraulically unloaded state, ■ - a stop (84) against which the actuating member (80) when the mechanical actuating device is released _e - a stop (70) for the actuator (30) and - a return spring (60) which loads the actuator (30) in the direction of its stop (7G), characterized in that the transmission members (86) in the assembled and adjusted state are dimensioned such that the return spring (60) of the actuator (30) acts on the actuating member (80) via the transmission members (86) and this, when the mechanical actuating device is released _(l!), rests against its stop (84) holds the actuator (jO) by the &bull; transmission elements (86) at a distance (&khgr;) from its ,; stop (70) is held. «Iflftltlflll it &igr; . - 2 - 1G-61 156 2* Actuating device according to claim l _t
characterized in that the distance (x) between the actuator (3Ö) and its stop (70) is greater than the elongation of the transmission member (86) to be expected during the service life of the actuating device. 3. Actuating device according to claim 1 or 2,
dsdüi^sh gsksriHEsichnet _; that the distance (x) between the actuator (30) and its stop (70) is maintained until the assembly and adjustment of the transmission element (86) is completed by a subsequently removable spacer (78)* 4. Actuating device according to one of the claims
1 to 3, characterized in that the actuator (30) is associated with a second stop (74) which limits the mechanical brake actuation, and that both stops (70, 74) associated with the actuator (30) are located on two sides of one and the same projection (68) of the ck...... /IQV /,«kil^ot- dAr\A