Brake unit for automotive vehicles with electric drive

Fluid-pressure and analogous brake systems – Multiple systems – Fluid pressure and electric

Patent

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Details

303 15, 303 20, 303 221, 188181C, 188182, B60T 1110, B60T 818

Patent

active

054722640

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention is related to a brake unit for automotive vehicles with electric drive and with a driven and a non-driven axle. The brake unit is configured in the shape of a multiple-circuit compound system consisting of hydraulic friction brakes and of an electroregenerative brake system. The electroregenerative brake system utilizes the electric driving motor or at least one of the electric driving motors of the automotive vehicle for braking and for energy recovery. Three brake circuits are provided. The first brake circuit is comprised of a pedal-actuated brake pressure master unit and of friction brakes acting upon the non-driven wheels. The second brake circuit is constituted by the electroregenerative brake system which is directly or indirectly coupled to the brake pedal and which acts upon the driven wheels. The third brake circuit is comprised of friction brakes which also act upon the driven wheels and are coupled to the brake pedal.


BACKGROUND OF THE INVENTION

A brake unit of this kind is known, for example, from German patent application No. 2,545,542 published without examination. In the prior-art brake unit, the brakes associated with the driven wheels are preceded by a combination of two valves arranged in parallel and consisting of an electromagnetically actuatable valve and of a pressure-actuated valve. Only two switching conditions can be realized by this valve combination. In one switching condition, the brakes acting upon the driven wheels are connected to the brake pressure master unit in an unobstacled way. In the other, the hydraulic pressure existing in these brakes is limited in the event of a regenerative braking action, respectively of an emergency stop.
The fact that there is no possibility of recognizing the behavior of the electric driving motor and adapting the hydraulic portion of the brake power in an optimum manner to its characteristic is a disadvantage in the state-of-the-art brake unit.


SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to configure the brake unit of the present invention in such a way that during a braking action the hydraulic portion of the brake power is continuously adapted in accordance with the behavior of the driving motor in order to achieve an optimum energy recovery.
According to the invention, this object is attained in that the actuation of the friction brakes which are connected to the second or to the third brake circuit and the distribution of the brake power to the front axle and to the rear axle are controllable with the aid of an electronic controller. The electronic controller is fed with information on the position of the brake pedal and/or on the brake pressure caused by the actuation of the pedal or on the brake torque, on the position of the accelerator pedal, on the vehicle speed, and on the charging condition of the vehicle batteries or at least with some of these types of information. The electronic controller evaluates this information for the control of the brakes acting on the driven wheels. The aim achieved by these provisions is that the friction brakes which are associated with the driven wheels are not involved in the most frequent braking actions, since on account of its torque characteristic the driving motor alone furnishes the required brake power. In addition, it will be possible to realize different characteristic curves of brake power distribution in accordance with the demands for an ideal distribution of the brake power and for a maximum energy recovery.
Furthermore, it will be advantageous in some applications when in addition to the electroregenerative brake system and to the friction brakes acting upon the driven wheels, the brake unit is equipped with an electrohydraulic or with an electromechanical drive, and with an actuating mechanism. On the other hand, also a hydraulic system may be envisaged in which through electrically actuatable hydraulic valves an auxiliary pressure source, and a pressure balancing tank, is connectible. In this context, the a

REFERENCES:
patent: 3621929 (1971-11-01), Oberthur et al.
patent: 4181366 (1980-01-01), Dobner
patent: 4270806 (1981-06-01), Venkataperumal et al.
patent: 4425005 (1984-01-01), Warwick
patent: 4671577 (1987-06-01), Woods
patent: 4861115 (1989-08-01), Petersen
patent: 5002343 (1991-03-01), Brearley et al.

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