Underinflation detector

• US 20040111198A1
• Filed: 10/17/2003
• Published: 06/10/2004
• Est. Priority Date: 10/29/2002
• Status: Active Grant

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: Yano, Osamu, Kin, Keiyu
• Granted Patent: US 6,865,456 B2
• Time in Patent Office: Days
• US Class Current: 701/29
• CPC Class Codes: B60C 23/061 by monitoring wheel speed measuring distance traversed on the ground by vehicles G01C22/00

Abstract

A rotational speed V1 of a left front wheel T1, a rotational speed V2 of a right front wheel T2, a rotational speed V3 of a left rear wheel T3, and a rotational speed V4 of a right rear wheel T4 are detected by rotational speed sensors S1-S4, respectively. A front-wheel yaw rate γF arising due to a rotational speed difference between the front wheels T1, T2 and a rear-wheel yaw rate γR arising due to a rotational speed difference between the rear wheels T3, T4 are monitored. When a significant disparity between the both rotational speed differences is observed, it is determined that tire inflation pressure of any of the wheels T1-T4 has decreased. Upon detection, correction is made to an apparent yaw rate that would be observed in the properly inflated wheel as a result of steering for correction by a driver, thereby improving detection accuracy of underinflation of the tires.

Claims

1. An underinflation detector for a four-wheeled vehicle comprising:

a rotational speed sensor that detects rotational speeds of two front wheels and two rear wheels of the vehicle; and

a controller that determines that inflation pressure of a tire of any of the wheels has decreased, if a parameter calculated from outputs of the rotational speed sensor exceeds a threshold, wherein a first value of the parameter is calculated using a disparity between a front-wheel rotational speed difference and a rear-wheel rotational speed difference; and

wherein correction is made to the first value of the parameter to obtain a second value of the parameter to be compared with the threshold by canceling a deviation of one of the front-wheel rotational speed difference and the rear-wheel rotational speed difference caused by a steering operation which a driver performs so as to cancel the other of the front-wheel rotational speed difference and the rear-wheel rotational speed difference arising due to underinflation of the tire.

2. An underinflation detector according to claim 1, wherein the correction to the first value of the parameter is made by retrieving a correction value from a map with a yaw rate calculated from the rotational speed difference arising due to the underinflation of the tire, and multiplying the yaw rate by the correction value.

3. An underinflation detector according to claim 1, wherein the correction to the first value of the parameter is made by retrieving a correction value from a map with a first yaw rate calculated from the rotational speed difference arising due to the underinflation of the tire, and dividing a second yaw rate calculated from the rotational speed difference caused by the steering operation by the correction value.

4. An underinflation detector according to claim 1, wherein the correction to the first value of the parameter is made by calculating a yaw moment acting on one of a front axle shaft and a rear axle shaft with an increase of a rolling resistance arising due to the underinflation of the tire, obtaining from the yaw moment a yaw rate deviation corresponding to the increase of the rolling resistance, and subtracting the yaw rate deviation from a yaw rate calculated from the rotational speed difference arising due to the underinflation of the tire.

5. An underinflation detector according to claim 1, wherein the correction to the first value of the parameter is made by calculating a yaw moment acting on one of a front axle shaft and a rear axle shaft with an increase of a rolling resistance arising due to the underinflation of the tire, obtaining from the yaw moment a yaw rate deviation corresponding to the increase of the rolling resistance, and adding the yaw rate deviation to a yaw rate calculated from the rotational speed difference caused by the steering operation.

6. An underinflation detector according to claim 1, wherein a wheel diameter ratio is calculated from the first value of the parameter to which the correction has been made;

and

wherein the second value of the parameter to be compared with the threshold is obtained by multiplying the wheel diameter ratio by normalized values of indicators of straight-ahead driving of the vehicle, and taking moving averages thereof.