Occupant weight sensor for vehicular seats, method for making and system therefor

A strain gauge sense element comprising:

• a first generally cylindrical body having a first longitudinal axis and a portion formed with a circular generally planar sense surface lying in a plane generally perpendicular to the first longitudinal axis, the body having an outer periphery circumscribing the sense surface, a first post extending outwardly from the body along the first longitudinal axis,
• a plurality of strain gauges disposed on the sense surface,
• a second body having a sidewall forming a recess and being attached to the outer periphery of the first body, the second body having a second longitudinal axis generally coincident with the first longitudinal axis when the first and second bodies are attached to one another, a second post extending outwardly from the second body along the second longitudinal axis, and
• a circumferential groove formed in the outer surface of the first body forming a web extending between the outer periphery of the first body and the portion of the first body formed with the planar sense surface so as to define the strain fields on the sense surface sensed by the strain gapes.

An occupant weight sensor comprising:

• a sense element having a first generally cylindrical metallic body having a first longitudinal axis and having a generally planar sense surface lying in a plane generally perpendicular to the first longitudinal axis, the first body having an outer periphery and a first post extending outwardly from the first body along the first longitudinal axis,
• a full Wheatstone bridge comprising four piezoresistors affixed to selected locations on the sense surface,
• a printed circuit board disposed on the sense surface and being configured to leave an opening over each piezoresistor,
• conditioning electronics mounted on the printed circuit board and formed with selected electrical paths, the piezoresistors electrically connected to form a bridge and electrically coupled to the conditioning electronics and selected circuit paths,
• a ring circumscribing the printed circuit board and being attached to the first body, the ring formed with contact holder retention features,
• a contact holder having ring retention features cooperating with the contact holder retention features, the contact holder received on the ring and attached thereto through the retention features,
• a plurality of contact members mounted on the contact holder,
• a second generally cylindrical body having a second longitudinal axis and having a sidewall formed with a recess, the sidewall fixed to the outer periphery of the first body with the second longitudinal axis generally coincident with, the first longitudinal axis, a second post extending outwardly from the second body along the second longitudinal axis, an opening formed in the sidewall, and
• a connector received through the opening, the connector having a plurality of electrical terminals and the contact members of the contact holder extending from the respective terminals of the connector to respective selected circuit paths on the printed circuit board.

An occupant weight sensor particularly adapted for vehicular seats wherein the vehicular seats are supported on the chassis by a seat mechanism and the sensor is interposed between the chassis and the seat mechanism comprising:

• a sense element having a first body with a generally planar sense surface and having an outer periphery and a longitudinal axis, a post extending outwardly from the first body along the longitudinal axis for attachment to one of the chassis and the seat mechanism,
• a second body formed with a force transfer portion permanently attached to the sense element along the outer periphery thereof and having a mounting portion for attachment to the other of the chassis and the seat mechanism so that the sensor is disposed intermediate to the chassis and the seat mechanism, the second body comprising an elongated plate like element having first and second ends, the force transfer portion is centrally located between the first and second ends and is formed by an opening in the second body and is welded to the outer periphery of the first body, the elongated plate formed with a mounting hole adjacent to each end for attachment to the seat mechanism,
• a full Wheatstone bridge having piezoresistors attached to the generally planar sense surface and having a bridge output,
• conditioning electronics supported on one of the first and second bodies electrically connected to the bridge for conditioning the bridge output signal, and
• a connector for providing electrical power for the bridge and for providing an electrical output.

An occupant weight sensor particularly adapted for vehicular seats wherein the vehicular seats are supported on the chassis by a seat mechanism and the sensor is interposed between the chassis and the seat mechanism comprising:

• a sense element having a first body with a generally planar sense surface and having an outer periphery and a longitudinal axis, a post extending outwardly from the first body along the longitudinal axis for attachment to one of the chassis and the seat mechanism,
• a second body formed with a force transfer portion permanently attached to the sense element along the outer periphery thereof and having a mounting portion for attachment to the other of the chassis and the seat mechanism so that the sensor is disposed intermediate to the chassis and the seat mechanism, the second body having a second longitudinal axis, an end wall and a tubular sidewall defining a recess, the sidewall serving as the force transfer portion and a second post extends outwardly from the end wall along the second longitudinal axis, when the first body and the second body are attached to one another the second longitudinal axis is generally coincident with the first longitudinal axis and the recess extends over the sense surface,
• a full Wheatstone bridge having piezoresistors attached to the generally planar sense surface and having a bridge output,
• conditioning electronics supported on one of the first and second bodies electrically connected to the bridge for conditioning the bridge output signal, and
• a connector for providing electrical power for the bridge and for providing an electrical output.

An occupant weight sensor particularly adapted for vehicular seats wherein the vehicular seats are supported on the chassis by a seat mechanism and the sensor is interposed between the chassis and the seat mechanism comprising:

• a sense element having a first body with a circular planar sense surface and having an outer periphery and a longitudinal axis, a post extending outwardly from the first body along the longitudinal axis for attachment to one of the chassis and the seat mechanism,
• a second body formed with a force transfer portion permanently attached to the sense element along the outer periphery thereof and having a mounting portion for attachment to the other of the chassis and the seat mechanism so that the sensor is disposed intermediate to the chassis and the seat mechanism,
• a full Wheatstone bridge having piezoresistors attached to the generally planar sense surface and having a bridge output, said full Wheatstone bridge comprising first and second half bridges with the four piezoresistors disposed along a common diameter of the circular sense surface, the first half bridge has a first piezoresistor disposed adjacent to the outer periphery of the sense surface at one end of the common diameter and a second piezoresistor disposed adjacent to the center of the circular sense surface and the second half bridge has a third piezoresistor disposed adjacent to the center of the circular sense surface and a fourth piezoresistor disposed adjacent to the outer periphery of the sense surface at the opposite end of the common diameter,
• conditioning electronics supported on one of the first and second bodies electrically connected to the bridge for conditioning the bridge output signal, and
• a connector for providing electrical power for the bridge and for providing an electrical output.