Weighing scales – Structural installation – Furniture or room fixture
Reexamination Certificate
2002-03-26
2004-08-10
Gibson, Randy W. (Department: 2841)
Weighing scales
Structural installation
Furniture or room fixture
C177S185000, C177S2100EM, C701S045000, C340S667000, C180S273000, C280S735000, C702S101000
Reexamination Certificate
active
06774319
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a seat-load measuring device for measuring a weight of a passenger and an object sitting on a car seat.
In a passenger car, control operations of winding a seatbelt and inflating an airbag are performed based on whether or not a car is occupied, whether an adult or a child is sitting on the seat, whether or not a child-seat is mounted, and the like. To achieve this purpose, a seat-load measuring device has been increasingly used for measuring the weight of the passenger and the object sitting on the car seat.
Such a seat-load measuring device has a configuration such that a load measuring section provided under the seat measures the overall weight of the seat, the passenger, and the object on the seat, and then a true load on the seat is obtained by subtracting the weight of the seat from the above overall weight. A strain gauge is typically used as a sensor of the load measuring section.
A measured value varies with noise caused by a motion of the passenger on board or acceleration of the car. Thus, the seat-load measuring device is required to remove such noise so as to maintain measurement accuracy within a predetermined range. In addition, a large load change takes place in a short period of time when the passenger is in a half-sitting posture on the seat upon opening and closing a door, or trying to pick something up. Even when such a large load change takes place, the seat-load measuring device is required to maintain the measurement variance within an acceptable range.
To achieve this, merely providing the measuring device with a low-pass filter is sufficient to remove small load changes. However, the low-pass filter with a large time constant, which can ignore a large temporary load change, has a risk of failing to detect a true load change during moving.
Also, it is necessary to measure the load as quick and accurate as possible to start the seatbelt control when the passenger sits on the seat. However, the above slow response load measuring device does not meet this requirement.
In view of these problems, the object of the present invention is to provide the seat-load measuring device that can perform a quick load measurement when the passenger sits on the seat, and become relatively insensitive to a load change after the passenger sits on the seat.
Further objects and advantages of the invention will be apparent form the following description of the invention.
SUMMARY OF THE INVENTION
The first aspect of the invention for solving the above problems provides a seat-load measuring device for measuring a weight of a passenger and an object sitting on a car seat. The measuring device has a function in which, when a load exerted on the seat exceeds a predetermined value, for example, when the passenger gets in or out of a car, an output from the load sensor through a slow response system is taken first as a measured load, and then the load sensor output through a fast response system is taken as the measured load.
According to the first aspect, the measuring device first determines whether or not a change in the load exerted on the seat goes beyond a predetermined value. When the seat is unoccupied or the passenger remains sitting on the seat in a normal manner, the load change is small even if the load varies. A large load change takes place when the passenger gets in or out of the car, or leaves the seat, for example, when trying to pick something up, or pushes the seat to get in the car. The first aspect is provided for determining if the latter case occurs.
In the latter case, the measuring device determines if the load change is temporary, and keeps the measured load unchanged if it is the case. At a point when the measuring device confirms that the load change is not temporary, the measuring device quickly starts to take an output from the load sensor through the fast response system.
To achieve this, even when the change in the load exerted on the seat exceeds the predetermined value, the measured load does not immediately reflect the change in the load, but takes an output from the load sensor through the slow response system as the measured value for the time being. Here, the slow response system means a filter with a slow response time or a system that holds a measured load, and also has a function of a low-pass filter.
Accordingly, for a certain period of time (which can be fixed or variable), the output from the load sensor is not taken as the measured load, or the output through the slow response is used as the measured load. Thus, if the passenger gets out of the seat when trying to pick something up or pushes the seat with a hand, for example, when getting in the car, the load associated with these instances is not used as the measured seat load.
If the measured value still continues to exceed the predetermined value after the above certain period of time, the output from the load sensor is taken through the fast response system and is set as an updated measured load, assuming that the passenger actually gets in or out of the car. Here, the fast response system means a filter with a fast response time, and also has a function of a low-pass filter.
According to this aspect, the output from the load sensor is processed through the slow response system when the load change is temporary, and through the fast response system after the load change continues for a fixed or variable predetermined time. Therefore, the measured load quickly comes close to the output from the load sensor when the passenger gets in or out of the car, while avoiding a situation in which the load change unrelated to getting in or out of the car is taken as the measured load.
The second aspect of the invention for solving the above problems provides a device in the first aspect further having a plurality of filters with different time constants. The device is capable of switching a state in which the output from the load sensor through the slow response system is taken as the measured load to another state in which the output from the load sensor through the fast response system is taken as the measured load. The switching timing is determined on the basis of a difference between outputs through at least two filters, one with a small time constant and the other with a large time constant.
The filter with the small time constant as mentioned above includes the one with a zero time constant, that is, the one that does not function as a filter. The difference between two outputs of the load sensor, one processed through the filter with the small time constant and the other processed through the filter with the large time constant, changes from “small” to “large” to “small” when the passenger gets in or out of the car. That is, a state of the large difference continues for a certain period of time. On the other hand, the state of the large difference continues only for a short period of time when the passenger is in a half-sitting posture to try to pick something up, or pushes the seat with a hand upon getting in the car.
By utilizing this feature, the measuring device determines whether the difference is caused by the passenger getting in or out of the car, or by a temporary load change. Only when the former is the case, the measuring device switches the state in which the output from the load sensor through the slow response system is taken as the measured load to the other state in which the output from the load sensor through the fast response system is taken as the measured load. Thus, the measuring device allows the measured load to quickly come close to the output from the load sensor when the passenger gets in or out of the car, while avoiding a situation in which the load change unrelated to getting in or out of the car is taken as the measured load.
In this means, two outputs of the load sensor, one through the filter with the small time constant and the other through the fast response system, may be the same, but are not necessarily the same. Likewise, two outputs of the load sensor, one throug
Aoki Hiroshi
Hida Hirokazu
Gibson Randy W.
Kanesaka & Takeuchi
Takata Corporation
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