Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
1999-11-22
2001-06-19
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
C701S078000, C701S083000, C303S155000, C303S167000
Reexamination Certificate
active
06249737
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a parking brake system for vehicles, in particular passenger cars, having a power-assistance-generating actuator unit for pulling on or releasing at least one control cable for a braking device of the vehicle, having an electronic control device whose output variable is used to activate the actuator unit, the control device being supplied with input variables, in particular from an operator device, from sensors and/or switches or the like, and it being possible to change the output variable as a function of the input variable.
DESCRIPTION OF THE RELATED ART
DE 42 05 590 A1 has already disclosed such a parking brake system for motor vehicles with a foot-activated brake pedal. Here, an additional electromotive actuator unit which acts directly on the brake pedal via a coupling device is provided. By pressing a momentary contact switch which is located, for example, in the operating reach of the vehicle gear mechanism, the direction of rotation of the electric motor of the actuator unit is reversed in each case so that the brake pedal is pivoted downward electromotively and released upward again. The mechanical arresting of the brake pedal is carried out here by means of the actuator unit gear mechanism which is of self-locking design. Furthermore, the design of the coupling device permits the brake pedal to be pressed down by the operator at any time. The parking brake system has an electronic control device with which additional functions can be implemented. Thus, for example the power-assisted parking brake system can be protected against unintentional release by virtue of the fact that after the ignition is switched off the actuator unit is no longer actuated electrically. Also, the detection of the operating current of the electric motor, and the detection of the angle of rotation of the spur gear of the gear mechanism can provide an indication of the braking force and the instantaneous position on the travel path of the brake cable, from which indications of the state of the friction linings of the parking brake system and the state of the braking force-transmitting connecting elements can be obtained. Furthermore, the braking force can also be applied under the control of a characteristic diagram by means of the operating current of the electric motor, in which case an activation speed which is dependent on the travel of the brake cable can also be implemented.
However, the known parking brake system proves disadvantageous insofar as it is extremely inflexible in its handling and takes little account, or no account at all, of the individual load states of the control cable and/or of the braking device. Furthermore, it proves disadvantageous that the activation force which acts on the control cable and/or on the brake takes place indirectly via a measurement of the current flowing into the electric motor of the actuator unit. On the one hand, this measurement method is extremely imprecise since the current flowing into the electric motor of the actuator unit is also dependent on environmental influences such as temperature or the like. On the other hand, it is, at any rate, then impossible to measure a force if the electric motor is out of operation.
Furthermore, JP-A-5-286424 has disclosed a parking brake for motor vehicles in which, after an activation lever is pulled on by the driver, a pressure sensor detects the reaction force of the parking brake which is exerted on a sliding element. In the event of the reaction force which is measured being smaller than a predefined value, an actuator motor is driven in the forward direction with the aid of a controller, the activation lever being raised, together with the sliding element, by means of a cable line. As a result, the intention is that the brake cable will continue to be pulled and the effective force on the parking brake will be increased. As soon as the pressure sensor detects that the activation force has reached a predefined value, the motor is stopped, the activation lever being held in the raised position. A disadvantage with the known system is that the force exerted on the control cable is not directly detected so that the measurement may be subject to considerable errors.
SUMMARY OF THE INVENTION
In contrast to the above, the invention is based on the object of developing a parking brake system for vehicles with the features mentioned at the beginning to the effect that flexible handling is ensured and the individual load states of the parking brake system can be detected reliably and precisely.
This object is essentially achieved according to the invention with the parking brake system having the features mentioned at the beginning in that a force sensor for directly detecting the force which is exerted on the control cable is arranged on or in the control cable, the signals of the force sensor being supplied to the control device as an input variable.
The actuation movement of the power-assistance-generating actuator unit is converted into a translatory movement for activating or pulling on or releasing the control cable for a braking device. A force sensor which directly measures the force acting on the brake line or the brake and passes on this force as an actual value to the control device is arranged on or in the control cable. In particular, with the parking brake system according to the invention it is also possible to measure a force directly when the vehicle is stationary so that continuous monitoring of the braking force at a given moment is made possible without the power-assistance-generating actuator unit having to be in operation. This is not possible with the parking brake system according to the prior art. In this way, the parking brake system according to the invention can be automatically re-adjusted if there is any kind of failure of the braking force, even if the vehicle has been parked in the deactivated state for a relatively long time.
According to a first advantageous refinement of the invention there is provision for the dynamometer to have an elastic element which is arranged on or in the control cable and whose deformation, for example its expansion or torsion, is used to determine the force exerted on the control cable. This makes it possible, in a structurally simple way, to sense the force on the control cable directly. A spring, for example, is possible as the elastic element, said spring being integrated into the control cable or being coupled, at one end of the line, in articulated fashion with respect to the signal transmitter or pickup unit. By sensing the spring travel it is then possible to draw conclusions about the corresponding force.
According to a further advantageous refinement of the invention there is provision for the control cable to be assigned a displacement sensor for sensing the travel of the control cable, the signals of which sensor are supplied to the control device as an input variable. In this way, the travel or adjustment displacement can be sensed by means of the displacement sensor both when pulling on and releasing the brake or the control cable, and can be used, if appropriate, for evaluating the braking characteristics and for possible fault diagnostics. A further advantage is that an additional position detection, by means of limit switches or the like is not necessary as a result of the use of the displacement sensor.
In this context, according to a further development of the invention, it is possible for the control device to have a memory device and a comparator, at least value pairs, “travel of the control cable/force acting on the control cable” being stored as reference values in the memory device and the reference values being compared with the instantaneous values and/or actual values in the comparator. For example, the position of the control cable which has been determined by the displacement sensor can be assigned the corresponding output value of the force sensor, all the data of a braking procedure being stored in the memory device. When there is further parking brake procedure, th
Arthur Gertrude
Cuchlinski Jr. William A.
Kuster & Co. GmbH
Liniak, Berenato, Longrace & White
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