An air damped crash sensor including a thin planar hinged inertial sensing mass which rotates within a sealed housing with a small clearance between the edges of the mass and the walls of the housing so as to create a restriction to the flow of a gas from one side of the sensing mass to the other side as the sensing mass rotates in response to accelerations during a crash of an automobile. The flow of gas within the sealed housing is designed to be in the inertial regime such that the damping force on the mass is proportional to the velocity of the mass squared and thus affected by the gas density but not temperature. The sensor may include (i) a thin hinge which is insert molded into the sensing mass and sensor body through a unique two step molding process whereby the hinge, typically made of plastic, is supported so that it does not deform, (ii) gas storage reservoirs placed to the side of the main cavity, (iii) a biasing contact designed so that it remains in contact with the sensing mass during the crash, and (iv) optionally an integral connector. With these elements, the sensor is ideally suited for sensing side impacts for the purpose of deploying a side impact passenger protection device.
A deign method to eliminate any micro-openings in a very high pressure sensor assembly is provided. The method involves sealing an elongated silicon pressure sensor into a fitting using an alloy and glass based materials. The materials are selected so that their thermal coefficients of expansion are progressively increasing relative to the silicon sensing element. This allows strong bonding among the materials, thereby minimizing any pressure leakage.
A micromechanical acceleration switch of silicon or similar materials, comprising a resilient electrode element, a proof mass, a housing and a spring element connecting the electrode element and the proof mass to the housing. The electrode element is mechanically connected adjacent to the proof mass. The proof mass has its centre of gravity located at a given distance from the axis through the spring element, so that when the proof mass is pivoting about the axis of the spring element in response to an externally applied acceleration, with a component in a direction parallel with the first axis. The electrode element also pivots about this axis. The pivot angle being essentially proportional to the magnitude of this component of the acceleration. The resilient electrode element has a mass considerably smaller than the proof mass, and is provided with at least one electrical contact point giving electrical contact and co-operation with corresponding contact areas in said switch housing at a given pivot angle of the electrode element.
A method of making a micro-miniature switch device (10), which has at least one member (68) movable relative to a substrate (12) upon which the device is provided, includes providing a layer of sacrificial non-photolithography material upon a stratum connected to the substrate. A template is provided via photolithographing step that uses a photoresist material upon a stratum connected to the substrate. A layer is provided to include at least a portion of the movable member. The photoresist material and the sacrificial non-photolithography material are removed using photoresist developer. Preferably, at least two photolithography process steps utilize a single photolithographic mask. Also preferably, substrate material is removed to create a recess and at least one channel into the substrate, wherein the channel intersects the recess. At least a portion of the movable member is provided at a location within the recess and at least a portion of the movable member is provided at a location within the channel.
A micro-miniature switch apparatus (10) includes a substrate (12) having a surface (14) with first and second channels (16, 18) extending from the surface (14) into the substrate (12). The first and second channels (16, 18) are spaced apart from each other, with a channel axis (20) extending longitudinally through the first and second channels (16, 18). A body (68) that is movable relative to the substrate (12) includes two arms (70, 72). Each of the arms (70, 72) extends into one of the first and second channels (16, 18) to support the body (68) for movement relative to the substrate (12) between first and second electrical conditions of the switch apparatus (10).
