Strain sensor having improved accuracy
a technology of strain sensor and accuracy, applied in the field of strain sensor, can solve the problems of reducing the output range available, rendering the sensor useless, and insufficient ceramic materials in some applications, and achieve the effect of improving manufacturability and increasing accuracy
Inactive Publication Date: 2006-08-17
CTS CORP ELKHART
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Benefits of technology
[0014] The present invention provides a strain sensor with increased accuracy and improved manufacturability.
Problems solved by technology
Thus, the amount of flexing or compression may be limited, resulting in a corresponding reduction in the output range available in the sensor
If the paint were applied to a conductive material, the substrate would effectively provide a short circuit across the resistive material, rendering the sensor useless.
However, ceramic materials are not adequate in some applications such as seat weight sensors where excessive stress or bending can occur.
One problem that is common to all types of substrate materials used in strain sensors is warping and lack of flatness.
Since most substrates are pressed or stamped, imperfections in the substrate material or stamping die can introduce unwanted variations in the thickness and planarity of the substrate during manufacturing.
Unfortunately, a substrate that has as little as 0.001 inch of warp across a 1-inch diameter substrate can cause a strain resistor to be inaccurate and have a non-linear output.
Unfortunately, machining each substrate is costly, time consuming and introduces excessive cycle time for a high volume manufacturing operation.
Method used
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Strain Sensor
[0026] Referring to FIGS. 1-5, a strain sensor 10 is shown. Strain sensor 10 has a planar circular substrate 12. Substrate 12 has a top surface 14, a bottom surface 16 and an outer peripheral edge 18. Several notches 20 and flat sections 22 are located along the outer peripheral edge 18 for placement and alignment of sensor 10 during assembly.
[0027] Substrate 12 is preferably formed using fine blanking of 430 stainless steel. Other materials and other common methods of forming such as stamping and machining can also be used. Substrate 12 can have typical dimensions of 24.8 mm in diameter and 3.17 mm in thickness. Other substrate dimensions can be used. However, there are practical limits on the dimensions of substrate 12. For example, substrate thickness less than 2 mm can be too weak and subject to permanent deformation under load. Substrate thickness greater than 5 mm do not allow enough strain to be imparted to the sensor and leads to poor signal output. Substrate...
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A strain sensor that is suited for use as an occupant weight sensor in a vehicle seat is disclosed. The strain sensor includes a substrate having a top surface and a bottom surface. Several bumps are located on the top surface. The bumps extend above the top surface. The bumps are arranged in a pattern. A dielectric material is located on the top surface. At least one strain sensitive resistor is located on the dielectric material. Several conductive traces are formed on the dielectric material and are electrically connected with the strain sensitive resistor.
Description
BACKGROUND [0001] 1. Field of the Invention [0002] This invention relates to strain sensors. The invention relates more particularly to a strain sensor design that has increased accuracy and that has improved manufacturability. [0003] 2. Description of Related Art [0004] The United States government has identified air bag inflation control as an important area for development. It has mandated that thirty-five percent of automobiles sold in the United States starting in model year 2004 incorporate a system capable of detecting the weight of the occupant and deploying the air bag with varying force depending on that weight. [0005] One approach to measuring occupant weight relies on a load bearing member in the seat structure having a strain-dependent electric resistance or strain sensor. The change in electrical resistance of the load bearing member serves as an indication of occupant weight. [0006] Strain-dependent resistance may be provided by thick film resistive systems in conjunc...
Claims
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IPC IPC(8): G01D7/00
CPCG01L1/2231
InventorD. COOK, KIMBLOOM, TERRY R.
OwnerCTS CORP ELKHART