Patent Application
20120326422
The following disclosure relates generally to motion sensors, and more specifically to sensors for detecting a rapid deceleration/acceleration event in a vehicle for initiation of airbags and/or other restraint systems.
Modern aircraft, automobiles, and other vehicles generally employ personal restraint systems to protect occupants from a rapid deceleration/acceleration event, such as a crash. These systems often include seat belts utilizing lap and/or shoulder portions, and may also include inflatable airbags to further protect occupants. Many of these personal restraint systems utilize sensors and electronic circuitry to facilitate or enhance their protective features. Seat belts in automobiles, for example, often utilize a latch sensor to detect whether the belt is fastened and initiate an audible signal to remind an occupant to fasten the belt. Additionally, some personal restraint systems utilize crash sensors to detect a collision and provide protective responses.
Various types of sensors are used to detect a crash or other rapid deceleration/acceleration event and initiate inflation of an airbag, lock or pretension a seat belt system, and/or initiate other responses. One type of sensor for use in airbag initiation utilizes a reed switch in cooperation with a spring-biased magnet. In general, a crash event causes the magnet to move into a position where it actuates (e.g., closes) the reed switch, thereby activating a circuit that deploys the airbag. Although these sensors can provide reliable initiation in a crash event, they may also be susceptible to external magnetic influence. For example, if a magnetic field is induced by a separate magnet or electromagnetic device of sufficient strength, the reed switch can be inadvertently actuated.
The following disclosure describes various embodiments of crash sensors for use with airbags and other restraint systems, and associated methods of manufacture and use. Certain details are set forth in the following description and
Many of the details and features shown in the Figures are merely illustrative of particular embodiments of the disclosure. Accordingly, other embodiments can have other details and features without departing from the spirit and scope of the present disclosure. In addition, those of ordinary skill in the art will understand that further embodiments can be practiced without several of the details described below. Furthermore, various embodiments of the disclosure can include structures other than those illustrated in the Figures and are expressly not limited to the structures shown in the Figures. Moreover, the various elements and features illustrated in the Figures may not be drawn to scale.
In the Figures, identical reference numbers identify identical, or at least generally similar, elements. To facilitate the discussion of any particular element, the most significant digit or digits of any reference number refer to the Figure in which that element is first introduced. Element 102, for example, is first introduced and discussed with reference to
In the illustrated embodiment, the EMA 102 includes a sensor 104, a power source 106 and a deployment circuit 108. As described in more detail below, a rapid deceleration or acceleration event activates the sensor 104, which initiates the deployment circuit 108. The deployment circuit 108 transmits a corresponding electrical signal to the inflators 112 which causes them to release pressurized gas (e.g., air) to rapidly inflate the respective airbags.
Although
In the illustrated embodiment, a magnetic shield 210 is movably or slidably disposed around the hollow tube portion 206. The shield 210 has a first end portion 212 spaced apart from a second end portion 214. The shield 210 screens magnetic fields and can be made from materials exhibiting a high magnetic permeability. In one embodiment, the shield 210 can be made from a mu-metal. Suitable nickel, iron and molybdenum mu-metal alloys, for example, are available from The MuShield Company, of 9 Ricker Avenue, Londonderry, N.H., USA 03053. A biasing member 216 is operably coupled between the first end portion 212 of the shield 210 and the opposing end wall of the cavity 204 to control movement of the shield 210 along the longitudinal axis 208. In the illustrated embodiment, the biasing member 216 is a coil spring that encircles the hollow tube portion 206. An end cap 230 can be inserted into an opening 232 in the housing portion 202 to enclose and seal the cavity 204 from ingress of liquids and/or debris.
The sensor 104 includes a magnetically operable device or switch 220 operably disposed within the tube portion 206. In some embodiments, the switch 220 can be a reed switch, such as a normally open reed switch (from, e.g., HSI Sensing of 3100 Norge Road, Chickasha, Okla., USA 73018), as shown in more detail in
The reed switch 220 is disposed within the hollow tube portion 206 and is operably coupled to a first wire 222a and a second wire 222b. The wires 222 extend from the reed switch 220 along the longitudinal axis 208 and out of the tube portion 206 on opposite ends of the housing 202. In the illustrated embodiment, the first wire 222a and the second wire 222b are operably coupled to a first terminal block 226a and a second terminal block 226b, respectively. The terminal blocks 226 can include connector pins 228, which can be used to mount the sensor 104 on a printed circuit board (PCB, not shown) or other electrical interfaces. The EMA 102 of
In the illustrated embodiment, the cavity 204, the hollow tube portion 206, the biasing member 216, the magnet 218 and the magnetic shield 210 are generally in the shape of annular cylinders. In other embodiments, however, these components can have other cross sectional shapes, such as rectangular shapes. Additionally, the magnetic shield 210 may be positioned between the magnet 218 and the reed switch 220 without encircling the reed switch 220. Furthermore, the biasing member 216 may be positioned on the other end of the housing 202 and operably connected to the end cap 230 rather than the opposing end wall of the cavity 204.
Returning to
Those skilled in the art will recognize that the components of the sensor 104 may be designed to provide for an initiation that is dependent upon the change in acceleration experienced by the sensor over a period of time. By way of example, an embodiment of the sensor 104 for use in commercial aviation applications can be designed to initiate upon a crash event resulting in a change in acceleration of 16 Gs over 90 milliseconds. In one embodiment, the sensor 104 can be further configured to initiate a response within 50 milliseconds. In other embodiments, however, other thresholds for the initiation and the time for response can be used.
In the illustrated embodiment, a rapid acceleration event with a force in the direction of A places a tension on the biasing member 216. However, the end cap 230 prevents the shield 210 from any significant movement in the direction of D that would expose the reed switch 220 to the magnetic field. Yet, in the embodiment discussed above with the biasing member 216 mounted on the opposite end of the housing 202, an acceleration event could result in activation of the reed switch 220. In such an embodiment, the internal cavity 204 would have space in the direction of D for the shield 210 to compress the biasing member 216 in the event of a rapid acceleration event. Additionally, yet other embodiments can include a biasing member 216 mounted in the same manner as shown in
As discussed above, the magnetic shield 210 prevents the magnetic field from the magnet 218 from activating the reed switch 220 while the magnetic shield 210 is in position A. One advantage of the embodiment described herein is that in addition to shielding the reed switch 220 from the magnetic field of the magnet 218, the magnetic shield 210 also shields the reed switch 220 from external magnetic fields, such as a stereo speaker placed near the device. External electronic or magnetic devices can generate substantial magnetic fields that could inadvertently actuate the deployment circuit. In alternative sensor designs that employ a movable magnet and no magnetic shield, these external magnetic fields can result in inadvertent initiation of the protective response. Hence, by providing for a moveable shield, rather than the moveable magnet of prior designs, the present disclosure significantly reduces the problem of inadvertent activation by an external magnetic field.
From the foregoing it will be appreciated that specific embodiments have been described herein for purposes of illustration, but that various modifications may be made without deviating from the spirit and scope of the various embodiments of the disclosure. Hence, although the illustrated embodiment includes a single sensor, it is within the scope of the present disclosure to include a plurality of sensors. In an embodiment employing multiple sensors, each sensor could be independently connected to the deployment circuit. Such a configuration may be used, for example, to provide for airbag initiation in the event of a vehicle impact from any angle, and/or a vehicle rollover. Further, while various advantages and features associated with certain embodiments of the disclosure have been described above in the context of those embodiments, other embodiments may also exhibit such advantages and/or features, and not all embodiments need necessarily exhibit such advantages and/or features to fall within the scope of the disclosure. Accordingly, the disclosure is not limited, except as by the appended claims.
