Measuring and testing – Tire – tread or roadway
Reexamination Certificate
2003-10-01
2004-12-28
Oen, William (Department: 2855)
Measuring and testing
Tire, tread or roadway
C340S444000
Reexamination Certificate
active
06834543
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an underinflation detector and a method of correcting an output of a sensor using the same.
In order to achieve stable driving of a vehicle, a variety of systems have been developed, such as antilock brake systems and systems for detecting loss or insufficiency of inflation pressure of tires. Typically, these systems include sensors for detecting a speed, a yaw rate, and the like of the vehicle, and perform prescribed arithmetical operations to exercise auxiliary or active control over behavior of the vehicle.
The systems for detecting insufficiency of inflation pressure (underinflation) of tires fall roughly into two approaches: one that detects inflation pressure directly by a pressure sensor attached to each tire; and the other that determines change in inflation pressure from a difference in rotational speeds of tires by making use of outside diameters of the tires which changes in accordance with change in the inflation pressure. The approach that determines change in inflation pressure from differences in rotational speeds of the tires has an advantage that a rotational speed sensor attached to the tire for the antilock brake system or the like in ordinary vehicles can be used to construct the system.
Among techniques for detecting insufficiency of inflation pressure through the latter approach in which difference in rotational speeds of the tires is utilized is, for example, a method adopted by an apparatus disclosed in JP 49-85701 A in which the sum of the numbers of revolutions per unit time of the left front wheel and the right rear wheel is calculated, the sum of the numbers of revolutions per unit time of the right front wheel and the left rear wheel is calculated, and the sums of the numbers of revolutions per unit time as thus calculated are compared. This apparatus can accordingly achieve improved accuracy of detection by offsetting the difference in the numbers of revolutions per unit time between the right wheel and the left wheel which arises while a vehicle makes a turn in a curved road, and the difference in the numbers of revolutions per unit time between the front wheel and the rear wheel which is derived from the difference between the driving wheel and the wheel driven by the driving wheel.
Another technique for detecting insufficiency of inflation pressure through the approach in which difference in rotational speeds of the tires is utilized is disclosed in JP 6-92114 A, in which a control unit is programmed so as not to detect the difference in the rotational speeds of the tires in transient states of behavior of the vehicle, for example, where the vehicle drives at a very low speed, or the speed of the vehicle increases or decreases suddenly, or the vehicle undergoes a great lateral acceleration. Thus-configured apparatus can accordingly prevent a possible error in detection, thereby increasing reliability.
However, according to the underinflation detector as described above in which comparison is made between the sum of the numbers of revolutions per unit time of the left front wheel and the right rear wheel and the sum of the numbers of revolutions per unit time of the right front wheel and the left rear wheel, when tires of the two wheels at the same sides (i.e., the front and rear right wheels, or the front and rear left wheels) undergo decrease of inflation pressure at the same time, the sums for use in the above comparison would both be affected by insufficiency of inflation pressure, and thus could possibly make no significant difference as a result of the arithmetical operation. Therefore, accurate detection cannot be achieved by the above underinflation detector for some particular cases. Further, there is an increasing demand of detection with higher precision, even when only a tire of one wheel is underinflated.
On the other hand, sensors for determining stability of behavior of a driving vehicle could be affected by torque applied on attachment, change with passage of time, temperature change, and the like, so that a measurement would involve an offset. Since the sensors used in the aforementioned systems should constantly output an accurate value in order to ensure that stable driving of the vehicle will be achieved, the output of the sensors may preferably be corrected as necessary, so that no offset is involved.
In view of the circumstances as described above, the present invention has been made to address the above disadvantages. It is thus an exemplary general object of the present invention to provide means for detecting insufficiency of inflation pressure of tires of a vehicle with high reliability. Another exemplary object of the present invention is to provide means for correcting the output of a prescribed sensor by making use of the inventive means for detecting insufficiency of inflation pressure of tires of a vehicle.
SUMMARY OF THE INVENTION
An underinflation detector for a four-wheeled vehicle provided according to one aspect of the present invention includes: a driving direction sensor that detects a direction of movement of the vehicle and outputs a detected value as a first value of a parameter related to the direction of movement of a vehicle; a rotational speed sensor that detects rotational speeds of wheels of the vehicle; and a controller that determines from outputs of the driving direction sensor and the rotational speed sensor whether inflation pressure of a tire of any of the wheels has decreased. The controller obtains the first value of the parameter from the driving direction sensor, calculates a second value of the parameter from a difference between rotational speeds of the front wheels, calculates a third value of the parameter from a difference between rotational speeds of the rear wheels, calculates a rate of change of deviation of the second value from the first value with respect to change of vehicle speed by the least-squares method, calculates a rate of change of deviation of the third value from the first value with respect to change of the vehicle speed by the least-squares method, and if at least one of the rates of change of deviation exceeds a prescribed threshold, determines that inflation pressure of a tire of at least one of the wheels has decreased.
The above underinflation detector utilizes three values of a parameter related to the direction of movement of a vehicle, among which the first value is an actually measured value detected by the driving direction sensor, the second and third values are calculated from the difference between rotational speeds of the front wheels and from the difference between rotational speeds of the rear wheels, respectively. In operation, comparison is made between the first value and the second value to detect insufficiency of inflation pressure of tires of the front wheels, and comparison is made between the first value and the third value to detect insufficiency of inflation pressure of tires of the rear wheels. To be specific, for the tires of the front wheels, the deviation of the second value from the first value and the vehicle speed determined at a time when the deviation is observed are paired as a data unit, and a plurality of such data units are obtained to apply the least-squares method, by which a rate of change of deviation with respect to change of the vehicle speed is calculated. Similarly, for the tires of the rear wheels, a rate of change of deviation of the third value from the first value with respect to change of the vehicle speed is calculated by the least-squares method. Thus-obtained rates of change of the deviation each indicate a tendency of the difference of the rotational speeds between the right and left (front or rear) wheels, and thus if any of the rates of change of the deviation exceeds a prescribed threshold, it is determined that the inflation pressure of a tire of at least one of the wheels has decreased. Since detection of insufficiency of inflation pressure of tires of the front wheels and detection of insufficiency of inflation pressure of tires of the rear wheels can
Kin Keiyu
Yano Osamu
Honda Motor Co. Ltd.
Oen William
LandOfFree
Underinflation detector and method of correcting output of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Underinflation detector and method of correcting output of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Underinflation detector and method of correcting output of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3337539