Motor vehicles – With means for promoting safety of vehicle – its occupant or... – Responsive to engagement of portion of perimeter of vehicle...
Reexamination Certificate
1999-12-17
2001-07-31
Rice, Kenneth R. (Department: 2167)
Motor vehicles
With means for promoting safety of vehicle, its occupant or...
Responsive to engagement of portion of perimeter of vehicle...
Reexamination Certificate
active
06267194
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns a brake control system for a motor vehicle.
The document DE 40 28 290 C1 discloses a method of automatically shortening the braking distance in critical driving situations in order to compensate for certain reactions by the driver, in particular inadequate brake pedal pressure. A potentially hazardous situation is detected from the actuating speed of the brake pedal; if the brake-pedal actuating speed lies above a limit value, a hazardous situation is assumed and an automatic braking operation is triggered. In the automatic braking operation, an increased braking pressure, which is greater than the braking pressure resulting from the brake pedal position, is built up, so that a braking force exceeding that determined by the driver is produced. With this method or this device, which is also known by the term Braking Assistant, the braking distance can be shortened in emergency situations.
The Braking Assistant can indeed detect a potential emergency situation from the behavior of the driver and intensify the braking force, whereby accident situations can be prevented. However, owing to its design, the Braking Assistant is only capable of compensating for behavior of the driver which departs from optimum behavior, but not of overcoming the consequences of accident situations attributable to outside influences. In particular in the case of a rear-on collision of a vehicle, it may be expected from the momentum of the vehicle causing the collision that the vehicle hit will be propelled straight ahead or ahead at an angle. This gives rise to the risk of the forward thrust partly or completely compensating for a braking operation in the vehicle hit which began before the collision, so that the vehicle hit runs into an obstacle in front of it or in the region laterally in front of it, or comes off the carriageway. In addition to the forward thrust of the vehicle hit, it may also be expected that the already initiated braking operation will be interrupted by the braking foot slipping off or being thrown back, so that after the collision the vehicle hit is no longer subjected to any further braking action.
The invention is based on the problem of mitigating or preventing the consequences of accidents in the case of a rear-on collision.
SUMMARY OF THE INVENTION
In accordance with the novel brake system of the present invention, in the case of a rear-on collision a braking operation is triggered in the vehicle hit at the rear, with either braking being initiated or already initiated braking being continued and possibly intensified, depending on the situation. These measures allow the distance covered by the vehicle before it comes to a standstill to be shortened, which contributes to the avoidance of pile-ups and a potential reduction in the severity of the accident. The vehicle hit is in any case braked independently of the driver's reaction.
The braking signal initiating or continuing the braking operation is triggered if the comparison signal exceeds a given or calculated threshold value. Either the longitudinal acceleration of the vehicle or a variable correlated with the longitudinal acceleration of the vehicle or derived from the longitudinal acceleration of the vehicle, which can be obtained in particular by filtering, by integration or in some other way from the longitudinal acceleration of the vehicle, can be used in this case as the comparison signal.
The comparison signal can be obtained in a simple way from the acceleration sensors of an airbag system. Built into these systems are sensors for measuring the longitudinal and lateral acceleration of the vehicle; if the measuring signals exceed limit values for the acceleration, the airbag is triggered. The measuring signals of the sensors of the airbag system can be used as comparison signals for the automatic triggering of the braking operation. The level of the comparison signals advantageously serves here as a measure of the value of the braking signal to be generated, which determines the braking force. The higher the comparison signal, or the more the comparison signal exceeds the threshold value, the more intense the braking force to be generated, it being possible for the dependence of the braking signal on the comparison signal to be stored in characteristic maps or in functions of a control device and to be influenced if appropriate by further parameters and state variables.
Alternatively or in addition to the measured acceleration values supplied by the sensors of the airbag system, the comparison signals may also be supplied by additional acceleration sensors, which are expediently arranged at the rear of the vehicle.
According to a preferred configuration, in certain situations a switch-off signal is generated, by means of which the braking system can be deactivated. The switch-off signal allows additional functions, states or situations of the vehicle to be checked and used as a basis for the decision as to whether automatic braking is to be carried out. The system is deactivated, and the automatic braking operation consequently suppressed, in the event that the switch-off signal assumes or does not assume a given value or lies inside or outside a given bandwidth. The switch-off signal represents situations in which, for reasons of expediency, a triggering of the automatic braking is not desired. The switch-off signal assumes here the function of an on/off switch, which according to its position essentially allows or else generally suppresses or discontinues an automatic braking operation.
In addition to the longitudinal acceleration of the vehicle, checked by means of the comparison signal, the switch-off signal can be used to take into consideration the state of the transmission of the motor vehicle, the operating state and the actuation of the parking brake, the vehicle speed, the direction of movement and/or the actuation of the accelerator pedal as well as further functions, if appropriate. The deactivation may situationally take place here before the activation of the present braking system or else after activation of the system has taken place.
The triggering of the automatic braking operation is expediently suppressed when reverse gear is engaged and in particular during reverse travel at a vehicle speed below a limiting speed, in order to permit driving manoeuvres such as reversing into a parking space and driving over a kerbstone without automatic brake triggering in the event of minor collisions with obstacles.
In order to permit further driving of the vehicle after activation of the present braking system has taken place, the braking force automatically produced by the system must be decreased again. The switch-off signal is in this case generated in dependence on the operating state of the parking brake, the vehicle speed, the actuation of the accelerator pedal etc. For instance, in particular after automatic braking, it is checked whether the parking brake has been actuated and, if this is the case, the system has been deactivated by means of the switch-off signal. The system may also be deactivated if the vehicle has come to a standstill or the accelerator pedal has been actuated again after a predetermined dead time has elapsed.
It may on the other hand be expedient, however, to deactivate the system after triggering only if both the ignition has been switched off and the parking brake has been actuated, in order to ensure that after a collision accident a vehicle on a slope is not inadvertently set in motion by discontinuing the braking force.
The relative speed and the distance from the vehicle travelling in front and the vehicle travelling behind are preferably measured and taken into consideration in the determination of the braking force. The braking force expediently increases with an increasing differential speed of the vehicle travelling behind, in order to be able to compensate for the thrust in the event of a rear-on collision. With a decreasing distance both with respect to the vehicle travelling in front and with respect to the vehic
Bullinger Wilfried
Eberle Walter
Calcaterra Mark P.
Daimler-Chrysler AG
Rice Kenneth R.
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