Fluid-pressure and analogous brake systems – Speed-controlled – Odd condition or device detection
Reexamination Certificate
1999-06-11
2002-11-05
Butler, Douglas C. (Department: 3683)
Fluid-pressure and analogous brake systems
Speed-controlled
Odd condition or device detection
C188SDIG001, C303S020000, C303S003000, C303S125000, C303S135000, C303S113400, C180S271000
Reexamination Certificate
active
06474753
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of automatically applying vehicle brakes in response to a movement of a driver's foot.
DE-PS 40 28 290 discloses that a maximum brake pressure can be built up in dependence of the speed with which the brake pedal is depressed so as to cause an optimal braking of the vehicle. However, since the stopping time is made up of a reflex time, a reaction time, a brake response time, and the actual braking time, it may take a relatively long period of time before the vehicle stops or reaches the desired state of deceleration due to the reflex time, the remaining reaction time and the brake response time. In this connection, reflex time is understood to be the time that the driver needs to realize that he has to decelerate. The reaction time is the time that it takes the driver to remove his right foot from its current position (e.g. on the gas pedal) and to place it on the brake pedal. The brake response time describes the time until the driver initiates the braking procedure, i.e. until the vehicle actually begins to accelerate negatively, i.e. to decelerate. For this purpose, the brake pedal has to overcome a certain idle distance and suitable pressure has to be built up so that the brake pads are applied to the brake discs with sufficient force. The actual braking time is the time that is then still needed to stop the vehicle or until the vehicle reaches the desired lower speed.
Consequently, it becomes evident that the object of DE-PS 40 28 299 only causes the braking time to be reduced, since the brake is automatically applied with optimal force. The previously known brake system presupposes, however, an automatically controlled brake force, since the optimal brake pressure is considerably affected by weather and road conditions (dry roadway, icy roadway). It is known from DE-GM 8911963 that the brake system can be made to respond as soon as the driver's right foot leaves the gas pedal to depress the brake pedal. In this way, considerable reaction time and brake response time are saved. However, this system calls for a separate manipulation by the driver to bring the vehicle into a state, in which the desired behavior actually occurs. This manipulation can take the form of activating a switch with a foot (the left one) or hand. A disadvantage in this connection is that the driver has to intentionally move a switch in a dangerous situation in order to reduce the reaction time and brake response time.
From DE-OS 44 22 664 it is known that a signal can be transmitted to the brake system when the right foot moves very quickly from a first position to a second position, with such signal causing a braking procedure. In this respect, a change in the position of the foot is understood to be moving the foot from the gas pedal to the brake pedal. Although this does allow a considerable reduction in the reaction time in special cases, it must be taken into consideration that the position of the foot frequently is not changed prior to a necessary braking, for example when the vehicle is being braked on a downhill road without any prior activation of the gas pedal. The same also holds true for control devices that hold the vehicle speed constant without any activation of the gas pedal (Tempomat, Cruise Control). The above-mentioned known device also does not ensure that a massive braking procedure is not initiated when the driver quickly takes the foot from the gas pedal, for example for changing gears, and comes into the vicinity of the brake pedal.
U.S. Pat. No. 3726369 proposes that the brake system be activated automatically as soon as the driver's foot is taken from the gas pedal and placed on the brake pedal. For this purpose, two sensors are provided which control the movement of the foot. In principle the object of this document corresponds to the devices described in DE-OS 44 22 664, wherein the latter device saves additional reaction time in that the driver's foot does not have to come into contact with the brake pedal for initiating a braking reaction, but that a braking reaction occurs when a certain movement is detected in the vicinity of the brake pedal by an appropriate sensor.
The object of the invention is to adapt an automatically executed braking procedure as far as possible to the dangerous situation. In particular it should be prevented that an inappropriately strong braking procedure is initiated in a situation where this would result in far greater risks to the driver than the possible benefits of an automatic braking. Thus, it is the intention of the invention to render the initiation of the braking procedure independent of a previous activation of the gas pedal. Furthermore, it is the object of the invention to base the type and scope of actuation of the brake not only on one single procedure but to make it dependent on a combination of measured data and to adapt the automatic reaction of the brake to all of the measured data combined.
SUMMARY OF THE INVENTION
The object is achieved by making the type and scope of the automatic actuation of the brake system dependent on the size of an individual measured value or a combination of different types of measured values resulting from a movement of a foot relative to the brake pedal. In this connection there are numerous possibilities of actuation. For one the brake system may only be precharged, which means that although the brake pressure is increased to such an extent that the brake pads are applied to the brake disc, no braking procedure is initiated, i.e. the speed of the vehicle is not reduced by the brake. Another possibility would be initial braking, i.e. to apply the brake pads to the brake disc with a defined brake force for a specified period of time. The brake force needed for this purpose can be very low (e.g. 5 to 20 bar can be applied), i.e. a pressure range that is handled during a sudden change of pressure in a booster (jump-in function, jump-in value) (no ABS needed). Finally the optimal brake force can be applied to the brake discs, i.e. the optimal pressure can be made available automatically in the brake system. However, this means that there has to be a controlled brake system (ABS), since the optimal brake force depends significantly on the road conditions, the load carried by the vehicle and other factors, which can only be governed by an appropriate control system. If such a control system is not available, the preprogrammed automatic braking procedure must always only go so far that it doesn't result in any danger to the vehicle, also not under unfavorable conditions. Of course, it is possible to program or, if necessary, adapt the vehicle to seasons or the area where the vehicle is driven, since, for example, icy roadways are highly unlikely during certain times of the year or in certain regions. Hence, certain states defined by parameters can be provided for comparison with the measured values.
Based on the information provided above, it is evident that the type of actuation of the brake system not only should be uncritical but also should prevent any accidental actuation of the automatic braking procedure as far as possible. In this respect, measuring the movement of the foot with respect to the brake pedal is recommended. On the one hand this ensures that an initiation of braking procedures is improbable when it is not actually intended (does not depend on depression of the gas pedal); on the other hand a considerable amount of reaction time is saved by already actuating the brake system whenever it can be expected with a high degree of probability that the driver will want to brake. Finally, the chronological sequence of the change of position above the brake pedal (speed of change or foot acceleration) can indicate how strongly the driver wants to brake. When the driver's foot accelerates very quickly or the speed of movement towards the brake pedal is very fast, it can be assumed that the driver actually wants a strong braking procedure. This is also correct in view of the fact that he would p
Burgdorf Jochen
Eckert Alfred
Rieth Peter
Butler Douglas C.
Continental Teves AG & Co. OHG
Rader & Fishman & Grauer, PLLC
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