Brakes – With condition indicator – Electrical
Patent
1998-08-17
2000-08-08
Graham, Matthew C.
Brakes
With condition indicator
Electrical
188 111R, 188181T, B60T 852
Patent
active
06098760&
DESCRIPTION:
BRIEF SUMMARY
The invention is based on a brake apparatus for vehicles claim 1 type defined in the preamble to claim 1.
In brake apparatuses for vehicles, the detection of the wheel brake moments in the individual vehicle wheels by means of so-called brake moment sensors is necessary in order to compensate for variances among the wheels during individual wheel braking by means of a brake moment control, as well as in order to be able to exactly adjust individual-wheel brake effects during drive slip control or to be able to detect a locking of the vehicle wheel during antilock brake control (ABS) in conjunction with the friction coefficient slip curve.
In a known brake apparatus of the kind mentioned at the beginning in a slip-controlled brake system (DE 36 00 647 A1), the brake moment sensor that has strain gauges at its disposal is inserted into the power flux of the transfer of force from the shaft to the vehicle wheel, wherein the sensor is embodied as a disk which is screwed to a wheel flange on one side and to a wheel rim on the other. The brake moment measured or an electrical signal that corresponds to the brake moment is output via an inductive transmitter. Alternatively, in the known brake apparatus, the proposal is made to install the brake moment sensor also on the brake anchor plate at a location that is deformed proportional to the brake moment.
ADVANTAGES OF THE INVENTION
The brake apparatus for vehicles according to the invention, has the advantage that the brake moment sensor, without modification, is suited for various embodiments of wheel brakes and can be used to sense brake moment, for example, in both disk brakes and drum brakes. It is small, requires only slight modifications to the chassis or to the brake parts for installation, and can be replaced with no trouble when defective. Since it has no direct access to hot brake parts, it functions reliably and has a long service life.
The force transducer which is used according to the invention as a brake moment sensor and whose function is based on the magneto-electric effect or the press ductor principle, according to which the magnetic properties of particular steel alloys and other metal alloys change with the influence of mechanical forces, is known as a so-called pillow block force transducer, which is used, for example, to control tensile stresses in mill trains. Since the two windings are disposed at right angles to each other, no magnetic coupling is produced between them as long as the metal block is not stressed. If the metal block is stressed, i.e. if a force is applied, then the magnetic field changes in such a way that its permeability decreases in the direction of the force. This leads to an altered symmetry of the power flux, which in turn leads to the fact that a part of the power flux in the secondary winding induces a voltage that is proportional to the load up to a particular load. The shear stress of the force transducer, which functions as a fastening element between the brake anchor plate and the chassis, is detected for the brake moment sensing according to the invention. Since the total volume of the metal block produces the measurement effect, when there is an oblique or uneven introduction of force in contrast to strain gauges, an averaging advantageously occurs.
Advantageous improvements and updates of the brake apparatus disclosed are possible by means of the measures taken hereinafter.
According to one advantageous embodiment of the invention, on each of the side faces that extend parallel to the primary winding and face away from each other, the metal block has a threaded pin protruding from it, which has an internal or external thread. This results in an extremely small force transducer, which must be calibrated, though, since strains are produced in the metal block as a result of its being tightened by way of the threaded pins, which cause an error in the sensor signal.
According to a preferred embodiment of the invention, the metal block is embodied as a double T-shaped in longitudinal section and has a center stru
REFERENCES:
patent: 4615419 (1986-10-01), Gaiser
patent: 4716994 (1988-01-01), Iwamoto
patent: 5279394 (1994-01-01), Wollenweber et al.
patent: 5582275 (1996-12-01), Arnold
Graham Matthew C.
Greigg Edwin E.
Greigg Ronald E.
Kramer Devon
Robert & Bosch GmbH
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