Machine element or mechanism – Control lever and linkage systems – Foot operated
Reexamination Certificate
1998-09-21
2001-07-03
Oberleitner, Robert J. (Department: 3613)
Machine element or mechanism
Control lever and linkage systems
Foot operated
C074S526000, C267S044000, C267S158000
Reexamination Certificate
active
06253635
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention lies in the automotive field. More specifically, the invention relates to a brake pedal configuration, in particular to such a configuration for an automobile equipped with electrically actuated wheel brakes. The system detects actuations of a brake pedal by means of sensors and it is provided with a spring configuration that opposes the brake actuation forces exerted on the brake pedal with a resistance force and that has a nonlinear spring characteristic.
In conventional automobile brake systems, the braking force is generated by the driver via the brake pedal. The force is usually boosted and transmitted via hydraulic delivery lines to the wheel brake cylinders. In power brake systems, there is no mechanical, pneumatic or hydraulic connection between the actuating unit, that is to say the brake pedal, and the wheel brakes. Although the driver, by actuating the brake pedal, can influence the braking force by means of suitable control devices, his physical strength is not utilized either fully or partially for generating the braking force when the brake pedal is actuated. If the power brake system is controlled electronically and the wheel brakes are actuated by means of electric energy, then it is necessary, in order to detect the driver's deceleration request, to have a special brake pedal configuration which detects actuations of the brake pedal by means of sensors and generates electric signals which are transmitted in electronic form to a brake control unit (see German patent DE 196 15 186 C1; and ATZ 98, 1996, No. 6, pages 328-32).
In conventional hydraulic brake systems, the pedal characteristic can be modified only within very narrow limits. This is so because, due to the hydraulic coupling between the actuating unit and the wheel brakes, this characteristic depends on the design of the brake system, that is to say the size of the wheel brake cylinders and the design of the brake booster and hydraulic fluid volume.
The force/travel characteristic of a known brake pedal for activating an electric brake system is generated by means of a cup spring assembly which is connected to the brake pedal via a rod that is articulated at the pedal (German published patent application DE 195 40 705 A1). There, the cup spring assembly is composed of cup springs having different characteristics.
In another published brake pedal configuration for electric brake systems (European EP 0 708 006 A1), the reactive force to the actuation of the brake pedal is generated by two helical springs which have different spring characteristics and which surround a piston rod that is articulated at the brake pedal.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a brake pedal configuration, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which provides, at little outlay, a brake pedal configuration which makes it possible to actuate the brakes in an ergonomically favorable way. Moreover, its pedal characteristic is to be capable of being adapted to the respective automobile type and intended use. Thus, for example in the case of a sports vehicle, it is to be possible to set a somewhat harder pedal characteristic, requiring a higher actuating force for the same pedal travel, than, for example, in the case of a limousine brake system where the emphasis is on comfort.
With the foregoing and other objects in view there is provided, in accordance with the invention, a brake pedal configuration, particularly a brake pedal configuration that is suitable for automobiles with electrically actuated wheel brakes, comprising:
a brake pedal;
a spring configuration disposed so as to provide a resistance force opposing a brake actuation force exerted on the brake pedal;
the spring configuration having a nonlinear spring characteristic and including an arcuately curved spring with a first end fastened at a support, a second end articulated at the brake pedal, and a middle region; and
a stop disposed opposite the middle region of the spring such that the spring comes to bear against the stop after a partial deflection thereof.
The brake pedal configuration is provided with a spring that opposes the brake actuation forces exerted on the brake pedal and that has a nonlinear spring characteristic, in particular a progressive spring characteristic. An advantage of this is that, during braking with low decelerations, that is to say during normal braking, the brake pedal, which is initially relatively soft over a sufficiently long pedal travel, makes it possible to meter the braking effect with high sensitivity. By contrast, during emergency braking, the brake pedal is depressed quickly and operated with great foot force. In order to keep the reaction time short, it is useful for the pedal travel to be as short as possible. The soft zone with low pedal force is traversed rapidly and, thereafter, the pedal force rises sharply over a very short pedal travel.
Advantageously, the brake pedal configuration is designed in such a way that the maximum pedal force which is to be applied by a normal driver occurs when the pedal travel is the most ergonomically favorable. Since there is no mechanical connection between the brake pedal and the electrically actuated brakes, the pedal sensation can be determined freely, irrespective of the design of the brake system and the vehicle type.
In accordance with an added feature of the invention, the spring is a leaf spring.
In accordance with an additional feature of the invention, the stop and the spring define a wedge-shaped annular gap therebetween. The gap widens in a direction from the first end toward the second end.
Alternatively, the stop is a bolt with a round cross section.
In accordance with another feature of the invention, the spring is a torsion spring disposed coaxially about a pivot axis of the brake pedal, and including a supporting rod articulated at the brake pedal and a helical spring articulated at a stationary point relative to the brake pedal and mounted relative to the supporting rod such that, when the brake pedal is actuated, the helical spring is compressed after an initial idle travel of the brake pedal has been overcome. In accordance with a further feature of the invention, the helical spring bears upon an elastic stop.
In accordance with again a further feature of the invention, a pushrod is attached to the brake pedal, the pushrod having a spherical head, and an elastic molding disposed such that, when the brake pedal is actuated, the elastic molding is compressed by the spherical head after an idle travel has been overcome.
In accordance with another feature of the invention, several sensors are disposed and connected so as to sense actuations of the brake pedal.
In accordance with a concomitant feature of the invention, a progressive force/travel spring characteristic is designed such that, during braking with low decelerations, highly sensitive metering of a braking effect becomes possible and, for braking with high decelerations, an additional short pedal travel is required.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a brake pedal configuration, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
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patent: 4695819 (1987-09-01), Bowsher
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patent: 5934152 (1999-08-01), Aschoff et al.
patent: 42 01 444 A1 (1992-08-01), None
patent: 19540705A1 (1997-05-01), None
patent
Greenberg Laurence A.
King Bradley
Lerner Herbert L.
Oberleitner Robert J.
Siemens Aktiengesellschaft
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