Land vehicles – Wheeled – Attachment
Reexamination Certificate
1997-10-31
2001-01-09
Dickson, Paul N. (Department: 3611)
Land vehicles
Wheeled
Attachment
C701S045000, C701S047000
Reexamination Certificate
active
06170864
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a passive vehicle occupant restraint, such as an air bag, for restraining a vehicle occupant in the event of an impact on a vehicle, and more specifically to a technique for controlling activation of such a passive vehicle occupant restraint.
2. Description of the Prior Art
An apparatus for controlling squib ignition in an air bag is one of known activation control apparatuses for controlling activation of passive vehicle occupant restraints. In the air bag, a squib ignites a gas-generating agent in an inflator on impact, and a gas accordingly evolves from the inflator to inflate a bag and protect a vehicle occupant from the impact of a collision.
The apparatus for controlling squib ignition in an air bag typically measures the impact on the vehicle as a deceleration by an acceleration sensor, calculates a function of the measured deceleration, compares the calculated value of the function with a preset threshold value, and controls the squib ignition based on the result of comparison. The acceleration sensor is disposed at a predetermined position in the vehicle, generally on a floor tunnel in the vehicle. In the description hereinafter, the acceleration sensor mounted on the floor tunnel is referred to as the floor sensor.
The threshold value is set to be greater than the maximum among the values of the function calculated from the decelerations measured by the floor sensor when impacts applied to the vehicle have such a degree that does not require activation of the air bag.
In the conventional activation control apparatus for a passive vehicle occupant restraint, the impact applied to the vehicle is detected only by means of the floor sensor, and activation of the passive vehicle occupant restraint is controlled based on the result of detection. The following problems arise in this conventional structure.
Collisions of the vehicle are classified into several types by the condition and the direction of the collision and the type of the object against which the vehicle collides; that is, a head-on collision, an oblique collision, a pole collision, an offset collision, and an under-ride collision as shown in FIG.
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. In the case of a head-on collision, the vehicle receives an impact of the collision by left and right side members thereof, so that an extremely large deceleration arises on the floor tunnel with the floor sensor mounted thereon within a predetermined time period after the collision. In the case of collisions other than the head-on collision, however, the vehicle does not receive the impact of the collision in such a manner, so that no such a large deceleration arises on the floor tunnel within the predetermined time period after the collision.
Namely the floor sensor has higher sensitivity of detection of the impact within a predetermined time period after the collision in the case of a head-on collision, than in the case of the other collisions.
The threshold value is thus set mainly based on the deceleration measured in the case of a head-on collision. More concretely the threshold value is set based on the function calculated from the deceleration measured by the floor sensor when a head-on collision applies an impact of such a degree that does not require activation of the air bag to the vehicle.
This method for setting the threshold value based on the deceleration measured in the case of a head-on collision gives a relatively large threshold value. In the case of collisions other than the head-on collision, the floor sensor has relatively low sensitivity of detection of the impact within a predetermined time period after the collision as mentioned above. A DSP (digital signal processor) is accordingly used for Fourier transform of the deceleration signal obtained in the event of the collision to characteristics of a specific frequency component. In the case of the other collisions (including an offset collision), the impact is detected based on the characteristics of the specific frequency component.
This technique requires the DSP and the other related devices as well as a high-performance computer, which undesirably increases the cost.
SUMMARY OF THE INVENTION
The object of the present invention is thus to provide an activation control apparatus of simple structure that enables a passive vehicle occupant restraint to be activated with high accuracy, irrespective of the type of a collision.
At least part of the above and the other related objects of the present invention is realized by a first activation control apparatus for controlling activation of a passive vehicle occupant restraint mounted on a vehicle. The first activation control apparatus includes: impact measurement sensor disposed at a predetermined position in the vehicle for measuring an impact applied to the vehicle; activation controller for comparing a value calculated from the measurement of the impact by the impact measurement sensor with a threshold value that varies according to a specified threshold variation pattern, and controlling activation of the passive vehicle occupant restraint based on the result of comparison; impact detector disposed at a position ahead of the impact measurement sensor in the vehicle for determining whether or not the impact applied to the vehicle is not less than a specified reference value; and threshold variation pattern changer for, when the impact detector determines that the impact applied to the vehicle is not less than the specified reference value, changing the specified threshold variation pattern to another threshold variation pattern.
The present invention is also directed to a first method of controlling activation of a passive vehicle occupant restraint mounted on a vehicle. The first method includes the steps of:
(a) measuring a value of impact at a first position in the vehicle when an impact is applied to the vehicle;
(b) comparing a value calculated from the measurement of the impact in the step (a) with a threshold value that varies according to a specified threshold variation pattern, and controlling activation of the passive vehicle occupant restraint based on the result of comparison;
(c) determining whether or not a value of impact detected at a second position, which is ahead of the first position in the vehicle, is not less than a specified reference value when the impact is applied to the vehicle; and
(d) when the value of impact detected at the second position is determined to be not less than the specified reference value in the step (c), changing the threshold variation pattern to another threshold variation pattern.
In the present invention, the passive vehicle occupant restraint includes air bags, seat belt pre-tensioners, inflatable curtains as well as devices for stopping a fuel supply to an engine in the event of a collision and devices for releasing door locks in the event of a collision. The measurement of the impact and the value calculated from the measurement include an acceleration or a deceleration, a velocity, a moving distance (obtained by integrating the deceleration twice with respect to time), a moving average (obtained by integrating the deceleration over a fixed time period), the intensity of the deceleration at a specific frequency, and a vector component representing the deceleration in the direction of the length or the width of the vehicle. These definitions are applicable to the other apparatuses and methods discussed below.
The first activation control apparatus and the first method of the present invention change the predetermined threshold variation pattern to another threshold variation pattern in case that the value of impact detected at the second position in the vehicle is not less than the predetermined reference value, even when the type of the collision causes the value of impact to be not readily detected at the first position. By way of example, it is assumed that the predetermined threshold variation pattern is changed to another threshold variation pattern that gives a lower threshold value. In this case
Akatsuka Takao
Fujishima Hiromichi
Fujita Koichi
Iyoda Motomi
Sakaguchi Tomokazu
Dickson Paul N.
Dunn David R.
Kenyon & Kenyon
Toyota Jidosha & Kabushiki Kaisha
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