Land vehicles – Wheeled – Attachment
Reexamination Certificate
2001-05-25
2003-06-03
Dickson, Paul N. (Department: 3611)
Land vehicles
Wheeled
Attachment
C250S221000, C340S556000
Reexamination Certificate
active
06572139
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an occupant sensor used in an airbag system for protecting a vehicle occupant and an airbag control apparatus provided therewith.
2. Related Background Art
Vehicles equipped with the airbag system for protecting the occupant in the event of a collision have quickly been increasing in recent years. This airbag system is constructed to store an airbag in a steering wheel on the driver side or in a dash board on the passenger side and protect the occupant by instantaneously inflating the airbag upon collision of an automobile. There has been the desire to measure the position of the occupant upon expansion of the airbag in order to implement more sophisticated airbag control.
Techniques using the triangulation have been developed heretofore for this desire. For example, there are a vehicle control system described in Japanese Patent Application Laid-Open No. H10-157563 and an occupant detecting system described in Japanese Patent Application Laid-Open No. 10-100858.
The vehicle control system described in the application Laid-Open No. H10-157563 is constructed to emit beams from nine LEDs into different directions and determine whether an object exists in the direction of emission of each beam, based on intensity of reflection of the beam. Then the system is configured to disable operation of an airbag driving circuit when it is determined that an object over a predetermined size exists in an airbag expansion area. This system is able to determine whether an object of predetermined size exists, for example, in the space between the front passenger seat and the dashboard. The vehicle control system described in the above application, however, has the problem that it takes a long time for the judgment on presence/absence of object, for example.
The occupant detecting system described in the above application No. H10-100858 is provided with an LED as a beam outputting means and a PSD (position sensitive detector) as a photo detector and is constructed to detect whether an object (occupant) exists in an area (alarm area) where inflation of the airbag is not optimal for the occupant, according to output of the PSD. This system is able to determine whether an object exists in the watching area.
As a technique using the triangulation there is an optical object detecting sensor described in Japanese Patent Application Laid-Open No. H07-218336. It is conceivable to apply this sensor to a vehicle and utilize it as an occupant sensor, but this sensor is designed to measure the distance from a light-emitting element to all objects existing in the traveling direction of light emitted from the light-emitting element. For that reason, the sensor will measure the distance to the object even if the light is reflected, for example, by an occupant's leg seated in an appropriate state on the passenger seat, i.e., even if the object exists in a region expected not to measure.
SUMMARY OF THE INVENTION
The present invention has been accomplished under such circumstances and an object of the invention is to provide an occupant sensor and an airbag control apparatus capable of quickly detecting presence/absence of only an object existing in a watching region.
An occupant sensor according to the present invention comprises a light projecting portion for forming a light curtain for detection of occupant in a space between a seat and an airbag housing, a photodetective (receiving) portion for a reflection of the light curtain reflected by an occupant, and a mask disposed in the photodetective portion and having an aperture for letting the reflection enter only a part of the photodetective portion.
More preferably, an occupant sensor according to the present invention is an occupant sensor for detecting existence of an object in a predetermined two-dimensional area of an airbag expanding region in a vehicle, which comprises a light projecting portion for projecting two-dimensional light (a light curtain) including the two-dimensional area, into directions of a spread of the two-dimensional area, a photodetective portion having a photosensitive surface capable of receiving a reflection of the two-dimensional light, and a mask covering at least a portion of the photosensitive surface and having an entrance port which light can enter, wherein the mask covers the photosensitive surface so that only when an object exists in the two-dimensional area, a reflection from the object enters the entrance port.
In this occupant sensor, when the two-dimensional light emitted from the light projecting portion reaches an object, a reflection of the two-dimensional light reflected by the object travels toward the photodetective portion, for example, consisting of a photodiode or the like.
The two-dimensional light is projected so as to embrace the two-dimensional area, into the directions of a spread of the predetermined two-dimensional area of the airbag expanding region, and only when an object exists in the two-dimensional area, a reflection there from enters the entrance port of the mask covering the photosensitive surface of the photodetective portion. Therefore, the photodetective portion detects the reflection only when the occupant or the like exists in the watching area. Thus the sensor does not have to make a judgment when the object exists in the region causing no influence on the expanding operation of the airbag.
The two-dimensional area herein means a flat area of a quadrate, a trapezoid, a circle, or the like located, for example, in the space between the driver's head and the center of an airbag cover provided in the steering wheel housing the airbag or in the space between the occupant's head and the center of an airbag cover on the front passenger side.
The light projected from the light projecting portion is two-dimensional light having a predetermined spread in the width direction or two-dimensional light consisting of an array of beams, and thus existence of the object can be quickly detected, when compared with a case wherein a plurality of light projecting means are provided to sequentially project their respective beams.
Since the existence of the object in the two-dimensional area can be detected simply by incidence of the reflection of the two-dimensional light into the entrance port of the mask, a judgment can be readily made on presence/absence of object.
In the occupant sensor, the light projecting portion is desirably constructed to comprise output means, for example, such as an LED or the like, for outputting light, and a cylindrical lens for widening the output light into a predetermined width to obtain the two-dimensional light.
The sensor is also desirably constructed so that there exist a plurality of two-dimensional areas in the vehicle, the light projecting portion projects a plurality of two-dimensional light beams corresponding to the respective two-dimensional areas, and the photodetective portion has a plurality of photosensitive surfaces capable of respectively receiving reflections of the two-dimensional light beams. When this structure is employed, it becomes feasible to make judgments on presence/absence of object in a plurality of areas in the airbag expanding region, whereby the detection of the object can be performed more accurately.
It is also desirable that the photodetective portion have a plurality of photosensitive surfaces arrayed in the width direction of the two-dimensional light. For example, supposing n photosensitive surfaces are provided in the width direction of the two-dimensional light, i.e., in the direction nearly perpendicular to the traveling direction of the two-dimensional light and n small areas are assumed by dividing the two-dimensional area in the width direction of the two-dimensional light, a reflection in each small area can enter a corresponding photosensitive surface.
Then the size of an object existing in the two-dimensional area is determined depending upon the number and positions of photosensitive surfaces receiving respective reflections.
Fu
Dickson Paul N.
Dunn David R.
Hamamatsu Photonics K.K.
Morgan & Lewis & Bockius, LLP
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