Brakes – Operators – Multiple
Reexamination Certificate
1999-06-29
2001-08-28
Oberleitner, Robert J. (Department: 3613)
Brakes
Operators
Multiple
C188S162000, C074S3880PS
Reexamination Certificate
active
06279692
ABSTRACT:
The invention relates to a parking brake system according to the preamble of Claim
1
.
From German Patent Document DE 41 29 934 C2, a parking brake system is known, in the case of which, as a rule, the parking brake is operated by a motor-driven actuating unit. By way of a threaded spindle, the actuating unit drives a spindle nut which carries a two-armed coupling lever. By way of the first lever arm of the coupling lever, the parking brakes of the vehicle are operated. A muscle-force-operated emergency operating device is applied to the second lever arm by way of a cable pull.
It is an object of the invention to provide a triggering device for a parking brake whose power operating device and emergency operating device interact such that, independently of the preceding type of operation (power or muscle force) an operation of the parking brake is possible without limitation from any position of the triggering device by means of power as well as by means of muscle force.
This object is achieved by means of the characteristics of Claim
1
. In this case, it is the core idea to cause both devices to act by way of mechanical transmissions directly onto the threaded spindle. As the result of the used mechanical transmission, a simple and compact construction is obtained while simultaneously the weight is low. Both mechanical transmissions may be arranged in a common housing. The mechanical transmissions may be designed and mutually coordinated such that an unlimited operation is possible by means of power as well as by means of muscle force.
According to Claim
2
and
3
, the mechanical transmissions of the emergency operating device and of the power operating device are preferably designed as worm gear systems. Worms gear systems are distinguished by their low space requirements. As the result of the mutually crossing shafts of the worm and of the worm gear, advantages are obtained with respect to the various possibilities of the arrangement of the individual components of the triggering device, particularly of the emergency operating device, because shaft angles S can be implemented which deviate from 90°.
Claim
4
describes an alternative with a straight-toothed gear of the emergency operating device, whereby a rotation of the threaded spindle is prevented in a simple manner (see Claims
5
to
7
).
Naturally, other mechanical transmissions (such as bevel gear pairs, spur gears, etc.) can also be used according to the load, ratio, position of shafts, etc.
According to Claim
5
, for the normal power operation, the threaded spindle, which is secured against a rotation, is pushed in the axial direction through the worm gear operated by the actuating unit. This pure linear movement is converted into an adjusting movement on the parking brake.
According to the advantageous further development of the invention according to Claim
6
, for the normal power operation, the mechanical transmission of the emergency operating device is designed in a self-locking manner. As the result, the threaded spindle on the part of the mechanical transmission of the emergency operating device is prevented from rotating in a simple manner.
Claim
7
suggests a longitudinal groove in the threaded spindle by means of which the threaded spindle is connected, for example, by means of an adjusting spring, with the gear wheel of the emergency operating device in a non-rotatable manner and in the process displaceably in the axial direction. As an alternative, the form closure can take place, for example, by way of a flattening on the threaded spindle. The longitudinal groove or the flattening may be arranged either inside or outside the thread area of the spindle. In the former case, a short constructional length is obtained of the unit consisting of the power operating device and the emergency operating device which, however, results in increased manufacturing expenditures (deburring of the thread in the area of the groove or flattening). If the longitudinal groove is arranged outside the thread area, the spindle must be lengthened by the amount of the adjusting range.
Another possibility consists of fixedly connecting the gear wheel of the emergency operating device with an intermediate shaft which, in turn, is axially displaceably and non-rotatably (for example, by way of an adjusting spring) guided in a hollow threaded spindle, whereby the constructional length of the threaded spindle can be reduced.
Claim
4
describes another alternative of a protection against rotation with a degree of freedom in the axial direction, in the case of which the linear guiding of the threaded spindle is taken over by the straight toothing, which extends in the longitudinal direction of the threaded spindle, of the gear of the emergency operating device fixedly connected with the threaded spindle. It should be taken into account in this case, that the width of the toothing must be constructed corresponding to the adjusting path of the threaded spindle plus the required covering.
If the target conflict between a small ratio and a self-locking locking in the mechanical transmission of the emergency operating device allows no self-locking toothing geometry, the protection against a rotation must be represented by a separate locking element. The locking element may, for example, be constructed while utilizing the transmission ratio as a spring-loaded ball or frictional element. The self-locking can also be represented by means of an increased coefficient of friction of the bearing of the mechanical transmission of the emergency operating device.
Analogously, according to Claim
8
, during a muscle force operation of the parking brake system, the threaded-spindle-side gear of the power operating device is fixed with respect to a rotation. As a result, during an emergency operation, the threaded spindle screws through the stationary gear and in this manner causes an axial displacement of the threaded spindle with a resulting operation of the parking brake. The fixing of the worm gear in the mechanical transmission of the power operating device can take place, for example, by a self-locking design of this mechanical transmission or by increased friction (Claim
9
).
Naturally, by a reversal of the effect, analogously, the gear wheel of the power operating device can be non-rotatably and axially displaceably connected with the threaded spindle. In this case, during the power operation, the threaded spindle screws through the gear wheel of the emergency operating device while, during the emergency operation, a purely linear movement of the threaded spindle takes place.
By the alternating locking of those gear wheels of the power operating device and the emergency operating device which are in a direct contact with the threaded spindle, it is achieved, in combination with the non-rotatable arrangement of one of the two gear wheels, that an alternating between the operation by power and by muscle force is arbitrarily possible, independently of the respective preceding operating mode. In the case of the described triggering device, a resetting into an initial or reference position is not required. The full remaining adjusting path is available for both operating modes in any arbitrary spindle position.
Between the threaded spindle and the wheel brakes of the vehicle, for operating the parking brake, a power transmission device is provided, for example, in the form of a linkage or of a Bowden cable arrangement. Since, during an emergency operation (or in the case of the described corresponding reversal of the effect in the case of the power operation), the threaded spindle is displaced not only in the axial direction, but also rotates, a bearing device must be provided corresponding to Claim
10
which prevents that, for example, the cable pull of a Bowden cable arrangement will twist. By means of the bearing device, the screwing movement of the threaded spindle is converted into a pure linear movement. The bearing device is advantageously arranged on the end section of the threaded spindle. For reasons of space, the bearing device m
Boedrich Harald
Gutt Axel
Niklas Johann
Reis Wolfgang
Siepker Achim
Bayerische Motoren Werke Aktiengesellschaft
Crowell & Moring LLP
Oberleitner Robert J.
Rodriguez Pamela J.
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