Method and Device for the Operation of a Hydraulic Vehicle

Abstract

A method for the operation of a hydraulic vehicle brake is provided. The brake includes a brake housing in which a hydraulic working pressure chamber is delimited by a displaceable brake piston, which is movable into operative connection with a brake disc in order to achieve a braking effect. A parking brake device acts on the brake piston and, in a condition where the brake piston is in operative connection with the brake disc, is lockable by a locking device. The locking device is activated by a force-transmitting element, which is operable by an electromagnetic actuator with at least one coil, one yoke and one armature, wherein the position of the force-transmitting element connected to the armature is determined because the change in inductance of the coil is determined depending on the armature movement in such a way that the result of the determination is independent of the ambient temperature.

1 .- 8 . (canceled) 
   
   
       9 . A method for the operation of a hydraulic vehicle brake, including a brake housing ( 1 ) in which a hydraulic working pressure chamber ( 7 ) is delimited by a displaceable brake piston ( 6 ), which is movable into operative connection with a brake disc in order to achieve a braking effect, and wherein a parking brake device acts on the brake piston ( 6 ) and, in a condition where the brake piston ( 6 ) is in operative connection with the brake disc, is lockable by means of a locking device, the said locking device being activated by a force-transmitting element ( 2 ), which is operable by means of an electromagnetic actuator ( 3 ) comprising at least one coil ( 25 ), one yoke ( 26 ) and one armature ( 23 ), the method comprising the step of measuring a change in inductance of the coil ( 25 ) due to an armature movement, calibrating the measured change of inductance with respect to temperature, determining the position of the force-transmitting element ( 2 ) connected to the armature ( 23 ) based on the calibrated change of inductance. 
   
   
       10 . The method as claimed in  claim 9 ,
 wherein the calibration is performed in such a way that the result of the position determination is independent of the temperature of at least one member of the group consisting of the coil ( 25 ), the yoke ( 26 ) and the armature ( 23 ).   
   
   
       11 . The method as claimed in  claim 9 ,
 wherein the position determination is performed with the following steps:   (i) determining the electric resistance of the coil ( 25 );   (ii) comparing the determined electric resistance with previously defined values and determining the temperature of the coil ( 25 ), the yoke ( 26 ), and the armature ( 23 );   (iii) determining the magnetic resistance of the yoke ( 26 ) and the armature ( 23 );   (iv) determining the eddy current in the yoke ( 26 ) and in the armature ( 23 ), and   (v) introducing a square-wave voltage signal into the coil ( 25 ) and measuring the current that flows through the coil ( 25 ).   
   
   
       12 . The method as claimed in  claim 11 ,
 wherein the temperature-responsive component of the eddy current in the yoke ( 26 ) and in the armature ( 23 ) is taken into consideration when measuring the current that flows through the coil ( 25 ), and the result of measurement is corrected accordingly.   
   
   
       13 . The method as claimed in  claim 11 ,
 wherein the previously defined values of the electric resistance of the coil ( 25 ) are found by calibration.   
   
   
       14 . The method as claimed in  claim 13 ,
 wherein the calibration takes place before the initiation of the hydraulic vehicle brake and/or in regular intervals during the operation.   
   
   
       15 . A hydraulic vehicle brake system, including a brake housing ( 1 ) in which a hydraulic working pressure chamber ( 7 ) is delimited by a displaceable brake piston ( 6 ), which is movable into operative connection with a brake disc in order to achieve a braking effect, and wherein a parking brake device acts on the brake piston ( 6 ) and, in a condition where the brake piston ( 6 ) is in operative connection with the brake disc, is lockable by means of a locking device, the said locking device being activated by a force-transmitting element ( 2 ), which is operable by means of an electromagnetic actuator ( 3 ) comprising at least one coil ( 25 ), one yoke ( 26 ) and one armature ( 23 ), and wherein the position of the force-transmitting element ( 2 ) connected to the armature ( 23 ) is determined because the change in inductance of the coil ( 25 ) is determined depending on the armature movement, wherein a calibration system is provided, which calibrates the position determination of the force-transmitting element ( 2 ) in such a way that the result is independent of the temperature ambient temperature, the temperature of at least one member contained in the group consisting of the coil ( 25 ), the yoke ( 26 ) and the armature ( 23 ). 
   
   
       16 . The hydraulic vehicle brake system as claimed in  claim 15 , wherein the calibration system performs the following steps:
 (i) determining the electric resistance of the coil ( 25 );   (ii) comparing the determined electric resistance with previously defined values and determining the temperature of the coil ( 25 ), the yoke ( 26 ), and the armature ( 23 );   (iii) determining the magnetic resistance of the yoke ( 26 ) and the armature ( 23 );   (iv) determining the eddy current in the yoke ( 26 ) and in the armature ( 23 ), and   (v) introducing a square-wave voltage signal into the coil ( 25 ) and measuring the current that flows through the coil ( 25 ).