Brakes – Operators – Electric
Reexamination Certificate
1999-07-26
2001-07-31
Oberleitner, Robert J. (Department: 3613)
Brakes
Operators
Electric
C188S156000, C188S10600P
Reexamination Certificate
active
06267207
ABSTRACT:
BACKGROUND OF THE INVENTION
This application claims the priority of 198 33 304.8-21, filed Jul. 24, 1998, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to an apparatus for actuating a brake of vehicles, and more particularly, to a brake actuation apparatus having an electric motor and a coupling element which is coupled in terms of movement with the said electric motor, is linearly movable, can be connected to a brake tensioning mechanism and is transferred by the energized electric motor out of a braking position into a release position. An electrically actuated blocking device provides block on movement of the coupling element, at least in the release position. A spring energy store is movement coupled with the coupling element such that, in the release position of the coupling element, it assumes a storage position storing spring energy, and, when the block on movement is overridden, transfers the coupling element into the braking position by the released spring energy.
Apparatuses which, for actuating a brake, include an electric motor, a gear mechanism and a spring energy store are described in DE 25 46 470 A1; DE 27 10 585 C2; and DE 44 03 719 C1. In a release position of the known apparatus, not actuating the brake, the pre-loaded spring of the spring energy store assumes a position in which it stores spring energy. To maintain this release position, an electrically actuatable blocking device for the motor drive shaft or the gear mechanism is provided or the electric motor is supplied with a low holding voltage for its blocking. These known apparatuses have a disadvantage in that the spring energy store automatically relaxes if there is a power failure and the apparatus is consequently transferred into a braking position, thereby actuating the brake. This automatic braking operation may lead to considerable disturbances and safety risks in the operation of the vehicle.
A further apparatus for electronic brake actuation, disclosed in DE 30 48 766 A1, dispenses with a spring energy store for reaching the braking position. The braking position is achieved by a corresponding loading of the electric motor. In the event of a power failure, a shaft stub of the motor drive shaft must then be turned manually by a tool if braking is to be carried out. The driver finds this to be inconvenient. If this apparatus is used in a parking brake, a power failure makes it first necessary for the driver to leave a parked vehicle if he wishes to secure the vehicle by the parking brake. This necessity is either not possible at all, in particular on inclined carriageway surfaces, or entails considerable safety risks (risk of the vehicle rolling away) both to the driver and possibly other persons and to the vehicle.
SUMMARY OF THE INVENTION
An object of the present invention is to adapt the operating mode of an electric brake better to the functional requirements.
This object has been achieved by further providing that the blocking device is mechanically held in its blocking position, effecting the block on movement, and can be actuated electrically and optionally mechanically, for overriding the block on movement in the release position of the coupling element.
According to the present invention, the blocking device is mechanically held in its blocking position, effecting the block on movement, and can be actuated electrically, and optionally mechanically, for overriding the block on movement in the release position of the coupling element. In other words, the coupling element is mechanically blocked in the release position by corresponding blocking apparatus of the blocking device. The blocking device thus acts without electric current, i.e. independently of the electrical energy supply. Therefore, the blocking device remains effective even after a power failure or in the event of a defect of control electronics connected to the apparatus.
Consequently, undesired braking operations during driving caused by power failure or electrical defect are reliably avoided. By virtue of the additional (and when there is power, optional) mechanical actuating possibility of the blocking device, an automatic braking operation induced by power failure is also not required. In the event of a power failure, only wanted braking operations are possible in that the block on movement is overridden by mechanical actuation (for example manual) of the blocking device or its mechanical blocking apparatus. Thereafter, the braking operation takes place automatically by the released spring energy of the spring energy store. To summarize, a braking operation can be triggered electrically, and optionally mechanically, when the power supply is available, whereas a mechanical (emergency) triggering of the braking operation by the vehicle driver is possible after a power failure.
When the electrical energy supply for the blocking device is available again, the mechanical actuation of the blocking device can be replaced by an electrical actuation, in which an electrical signal or electrical energy is converted into a force acting on the blocking device, in order to remove its mechanical blocking means from the blocking position. An electrical switching device, which is coupled to the mechanical blocking apparatus via electrical lines (supply lines, control lines), switches (for example relays, overload switches etc.) and, if appropriate, further components, is preferably provided in the passenger compartment or the driver's cab of the vehicle for the electrical actuation.
Even if, when power is available, the blocking device can be mechanically actuated in the release position of the coupling element, the driver will normally choose the electrical actuation of the blocking device because of the greater operating convenience. The mechanical actuation or triggering of the braking operation is intended in particular for emergencies, e.g., power failure.
The block on movement when there is a power failure is preferably overridden manually from the driver's seat, which is particularly convenient for the driver. For a high level of safety, the driver also does not have to leave the vehicle if in the event of a power failure he wishes to override the mechanical blocking action of the blocking device. As a result, the securing of a vehicle, in particular on inclined carriageways, is particularly simple and safe by way of the apparatus according to the invention used in a parking brake.
In order in the event of a power failure to transfer the coupling element from the braking position into the release position, a suitable, manually actuatable release device or a tool must be available to act correspondingly on the coupling element. A braking operation triggered mechanically after a power failure is therefore a one-off event and the braking position is retained on account of the relaxed spring energy store if the abovementioned release device or the tool is not available. Consequently, in the event of a power failure, which often indicates an emergency, the vehicle can be reliably parked and secured.
The electric motor is, for example, a linear motor or motor with a motor drive shaft. Also within the scope of the present invention are electrically operated ultrasonic or travelling-wave motors. In any event, the electric motor is suitably coupled in terms of movement with the coupling element such that the coupling element can be driven in a linearly movable manner.
A reversible overriding of the block on movement can be provided, i.e. the block on movement can be restored. As a result, a renewed block on movement of the coupling element can be achieved when the braking operation is concluded. The blocking device preferably automatically resumes its blocking position; blocking the coupling element, when the electrical or mechanical actuation of the blocking device is ended. This advantageously takes place by a mechanical returning device, e.g., a spring element, acting on the blocking device.
The blocking device can have a movable blocking element as a mechanical blocking
Fleischer Horst
Titz Walter
Crowell & Moring LLP
Daimler-Chrysler AG
Kramer Devon
Oberleitner Robert J.
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