Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1993-07-15
1995-05-23
Ballato, Josie A.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
303 20, B60T 826, B60T 896, B60T 836
Patent
active
054174856
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a brake system for an automotive vehicle with means for controlling the braking pressure.
BACKGROUND OF THE INVENTION
When a vehicle is braked, the brake forces introduced into the wheels cause a torque about the center of gravity of the vehicle. This results in an increase of the front-wheel load and a decrease of the rear-wheel load. Therefore, higher brake forces can occur at the front wheels than at the rear wheels. This has to be taken into consideration when dimensioning brake system. In the most simple case, the pressure which develops in the brake system is conducted to differently sized large surfaces, resulting in a linear relation between the brake forces at the front axle and at the rear axle. This relation is chosen such that, when a locking of the wheels cannot be avoided, first the front wheels and then the rear wheels will lock. This measure enhances considerably the directional stability of the vehicle during braking.
The desired brake force on the rear axle will not be achieved for a purely linear relation. Hence, proposals have been made to insert valves in the rear-wheel brake circuit which limit or reduce the pressure starting from a predetermined pressure point.
Further, anti-lock brake systems are known. In these brake systems, the rotational behavior of the wheels is monitored by means of sensors. The sensor signals are analyzed and processed to form control signals for a valve assembly composed of electromagnetically operable valves, by which the braking pressure is adjusted such that the wheels will not lock.
Further, German DE-OS 19 61 039 proposes using the solenoid valves not only for anti-lock control, but also for the control of the brake force distribution. To this end, the brake force at the front wheels and at the rear wheels must be measured directly or indirectly. From the comparison between the measured distribution and an optimal distribution, control signals for the solenoid valves of the rear-wheel brakes are derived.
Depending on how the linear brake force distribution inherent in the brake system is designed, it may happen that, on failure of the electronic control, the vehicle will reach an unstable condition during a braking operation because of locking of the rear wheels although the front wheels have not attained the locked condition.
SUMMARY OF THE INVENTION
To avoid this shortcoming, the present invention teaches that, in addition to the first current circuit, there is a second current circuit for the actuating magnet which is provided with a switch, and further that there is a relay which, in its inactive position, closes the second current circuit and interrupts the first current circuit and, in its excited position, closes the first current circuit and interrupts the second current circuit. The advantage of this arrangement is that, on failure of the electronic control for the anti-lock control or the brake force distribution, the second current circuit, which is now activated, will cause the solenoid valve in the connection between the master brake cylinder and the wheel brakes of the rear axle to respond to achievement of a predetermined pressure point in the master cylinder when the switch is a pressure switch, thereby limiting the pressure in the rear-wheel brakes. As a result, a simple brake force distribution, which operates independently of the electronic control, can be achieved with little additional effort.
Instead of a pressure switch, an operating switch, responsive to deceleration, can be used, so that the pressure in the rear-wheel brake is limited at a specific vehicle deceleration.
The present invention shall be explained in more detail with reference to the drawing.
BRIEF DESCRIPTION OF THE DRAWING
The single FIGURE illustrates a preferred embodiment of an automotive vehicle brake system constructed in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The system is composed of a master brake cylinder 1 to which wheel brakes 4, 5 are connected via brake
REFERENCES:
patent: 3862781 (1975-01-01), King et al.
patent: 4093313 (1978-06-01), Burckhardt
patent: 4482192 (1984-11-01), Leiber
patent: 4802710 (1989-02-01), Burgdorf et al.
patent: 5000520 (1991-03-01), Schmitt
Burgdorf Jochen
Kauschka Peter
Alfred Teves GmbH
Ballato Josie A.
LandOfFree
Brake controller with each valve connected to two separate elect does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Brake controller with each valve connected to two separate elect, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Brake controller with each valve connected to two separate elect will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2136095