Fluid-pressure and analogous brake systems – Speed-controlled – Odd condition or device detection
Reexamination Certificate
1999-06-10
2001-05-29
Oberleitner, Robert J. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Odd condition or device detection
C303S149000, C180S169000
Reexamination Certificate
active
06238021
ABSTRACT:
BACKGROUND OF THE INVENTION
1 Field of the Invention
The present invention relates to a brake control system for a vehicle which, based on a relative position between the vehicle and an object sensed by an object sensing device such as a laser radar, automatically operates the braking device in order to prevent contact of the vehicle with the object.
2 Description of the Prior Art
Such a brake control system for a vehicle is already known as for example, in Japanese Patent Application Laid-open No. 6-298022. This system has an arrangement in which, when contact of the vehicle with an object can be avoided by operation of the steering alone, the avoidance of the contact is carried out by operating the steering alone without carrying out automatic braking, and in an emergency when contact of the vehicle with an object cannot be avoided by operating the steering alone, automatic braking is carried out to prevent contact.
When carrying out automatic braking in order to avoid contact with a vehicle travelling in front if, for example, the coefficients of friction of the road surface are different for the right and left wheels, a yaw movement is caused, and the behavior of the vehicle becomes unstable and thus there is a possibility that prevention of contact of the vehicle by automatic braking, cannot be carried out effectively.
The present invention has been made with consideration of the above-mentioned circumstances and an objective thereof is to prevent the vehicle from becoming unstable due to abnormal road surface conditions in which the coefficients of friction of the road surface are different for the right and left wheels when carrying out automatic braking, to prevent contact with an object.
SUMMARY OF THE INVENTION
In order to achieve the above-mentioned objective, the present invention is a brake control system for a vehicle comprising an object sensing device for sensing an object positioned in the direction in which the vehicle is advancing, braking devices for braking the vehicle, a determination means coupled to the object sensing device for determining the possibility of contact between the vehicle and the object based upon the relative positions of the vehicle and the object, based on the output of the object sensing device, an automatic braking means coupled to the determination means for carrying out an automatic braking by operating of the braking devices based on the output of the determination means. An abnormal road surface condition sensing means, coupled to the automatic braking means, for sensing an abnormal road surface condition wherein the coefficients of friction of the road surface are different for right and left wheels of the vehicle, and wherein when the abnormal road surface condition sensing means senses an abnormal road surface condition, the automatic braking means sets a rising gradient for the braking force for automatic braking which is lower than the rising gradient when an abnormal road surface condition is not sensed.
With the above-mentioned arrangement, when the object sensing device senses an object which is present in the direction in which the vehicle is advancing, based on the sensing results, the determination means determines the possibility of making contact with the object from the relative positions of the vehicle and the object, and when it is determined that there is a possibility of contact, the automatic braking means operates the braking device to carry out automatic braking in order to avoid contact with the object. When the abnormal road surface condition sensing means senses an abnormal road surface condition in which the coefficients of friction of the road surface for the right and left wheels are different, the automatic braking means sets the rising gradient of the braking force of the automatic braking low, and prevents the vehicle from becoming unstable due to the occurrence of an undesirable yaw movement and thus the avoidance of contact can be achieved with certainty.
The present invention is characterized in that the abnormal road surface condition sensing means senses an abnormal road surface condition based on a difference in the slip rate between the right and left wheels at the time of starting automatic braking.
With the above-mentioned arrangement, in an abnormal road surface condition in which the coefficients of friction of the road surface for the right and left wheels are different, since the slip rate of the wheel on the road surface having a smaller coefficient of friction becomes higher than that of the wheel on the road surface having a larger coefficient of friction, the abnormal road surface condition can be sensed with certainty based on the difference in the slip rate between the right and left wheels.
The present invention is further characterized in that the abnormal road surface condition sensing means senses an abnormal road surface condition based on the operational status of the antilock brake system of the vehicle, at the time of starting automatic braking.
With the above-mentioned arrangement, in an abnormal road surface condition in which the coefficients of friction of the road surface for the right and left wheels are different, since the wheel on the road surface having a smaller coefficient of friction slips to an excess extent due to the automatic braking thus causing the operation of the antilock brake system, the abnormal road surface condition can be sensed with certainty based on the operational status of the antilock brake system. In particular, since an existing antilock brake system is used, not only can the calculation load on the abnormal road surface condition sensing means can be lessened, but it can also contribute to a reduction in cost.
The present invention is still further characterized in that the abnormal road surface condition sensing means senses an abnormal road surface condition based on a yaw rate or lateral acceleration of the vehicle at the time of starting automatic braking.
With the above-mentioned arrangement, in an abnormal road surface condition in which the coefficients of friction of the road surface for the right and left wheels are different, since the wheel on the road surface having a smaller coefficient of friction slips due to the automatic braking sooner than the wheel on the road surface having a larger coefficient of friction thus causing the yaw rate or lateral acceleration, the abnormal road surface condition can be sensed based on the yaw rate or lateral acceleration.
The present invention is also characterized in that test braking in order to sense an abnormal road surface condition is carried out at the time of starting automatic braking and during this test braking the abnormal road surface condition sensing means carries out the sensing of an abnormal road surface condition.
With the above mentioned arrangement, since the abnormal road surface condition is sensed by carrying out test braking at the time of starting automatic braking, the control to lower the rising gradient of the braking force can be performed without delay during an actual automatic braking following the test braking, and thus the behavior of the vehicle can be prevented from becoming unstable with certainty. Furthermore, by subjecting the driver's body to a sensation of deceleration as an alarm accompanying the test braking, active braking can be induced.
The present invention is characterized in that only the front wheels are braked during the test braking.
With the above mentioned arrangement, by putting a sufficient braking force on the front wheels, an abnormal road surface condition can be sensed with certainty, at the same time the deceleration due to the test braking which is sensed by the driver's body, can be suppressed to a low level and thus disagreeable sensations can be eliminated.
REFERENCES:
patent: 5540298 (1996-07-01), Yoshioka et al.
patent: 6035251 (2000-03-01), Hac et al.
patent: 6092882 (2000-07-01), Matsuno
patent: 6-298022 (1994-10-01), None
Arent Fox Kintner & Plotkin & Kahn, PLLC
Honda Giken Kogyo Kabushiki Kaisha
Oberleitner Robert J.
Siconolfi Robert A.
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