Crash sensor

Abstract: A crash detection sensor (21) having a supporting member (24-2) arranged in a space (16) in a door (10). The supporting member (24-2) has sufficient strength to maintain its state under normal conditions. First (36) and second (38) electrodes, usually spaced, are provided on the supporting member (24-2). A shock larger than a predetermined level applied to the door (10) causes the first (36) and the second (38) electrodes to be brought into contact with each other, thereby allowing a lateral impact to be detected in the door (10).

Description: The invention relates to a crash sensor according to the preamble of claim 1. US-A-4,966,388 discloses such a crash sensor comprising a strip switch consisting of first and second strips of electrical conducting material, which are mounted within the door panel in closely spaced parallel configuration, such that upon a penetrating impact of the outboard side of the door panel by another object, the closely spaced strips are crushed together to make electrical contact. The electrical contact concurrently activates an inflator to inflate an airbag. The strips have corrugated ridges and grooves formed therein, with the ridges in one strip nesting within the grooves of the other strip. GB-A-1 380 968 discloses an apparatus for use in a vehicle to detect a collision of said vehicle, comprising a mechanical pressure detector having a pressure member which, in the event of a collision with an object, directly collides with that object first of all, and an electrically conductive means which is connected to an electric circuit and which is deformable when said pressure member is subjected to a mechanical pressure greater than a predetermined value. WO 90/06 247 discloses a safety device for a door of a motor vehicle, wherein a sensor may comprise a switch which is formed from a printed circuit board carrying adjacent signal tracks with inter-digitated fingers which can be pressed against a contact pad. WO 91/17 907, which is a prior art document according to Art. 54(3) EPC discloses a means for detecting a side-on collision, which means consist of an elongated, fluid-filled sensor chamber inside the vehicle door, which is depressed in the event of a side-on collision, whereupon the fluid is compressed out of the sensor chamber, wherein the pressure rise may be used to make an electrical switching contact. The present invention aims to provide a sensor capable of a quick and precise detection of a lateral impact. This object is achieved by the features of claim 1. A lateral impact causes the shock to be transmitted to the supporting member via the door. The shock generates a deformation or displacement of the supporting member, which generates a signal that indicates an impact has occurred. BRIEF DESCRIPTION OF ATTACHED DRAWINGS Fig. 1 is a side view of a door of an automobile, partly broken to illustrate how a supporting member (cylindrical beam) is arranged in a space of a door. Fig.2 is a cross sectional view taken along line II-II in Fig. 1. Fig. 3 is a cross sectional view taken along line III-III in Fig. 1. Fig. 4-(A) is an enlarged view of Fig. 3 at a location indicated by a circle (a) under normal conditions. Fig. 4-(B) is similar to Fig. 4-(A), but shows when a lateral impact has occurred. Fig. 5 is a cross sectional view taken along line V-V in Fig. 4-(A). Fig. 6 is a diagrammatic view of an electric circuit for operating an air bag apparatus in which according to the present invention crash sensors in respective doors of the automobile are placed. Fig. 7 is similar to Fig. 3, but is directed to a second embodiment of the present invention. Fig. 8-(A) is an enlarged view of Fig. 7 at a location indicated by a circle (b) under normal conditions. Fig. 8-(B) is similar to Fig. 8-(A), but shows when a lateral impact has occurred. DESCRIPTION OF PREFERRED EMBODIMENTS Figs. 1 to 5 show a first embodiment of a crash sensor, according to the present invention, that is mounted in a side door of an automobile for detection of a lateral impact. In Fig. 1, a reference numeral 10 denotes, generally, a side door of an automobile, which is constructed, basically, as shown in Fig. 2, an outer panel 12 and 14 an inner panel 14 that are connected to each other at their top and bottom ends for creating a space 16 therebetween. The door assembly 10 is further provided with a window frame 18 in which a window pane 20 is arranged that is, when necessary, stored in the space 16. As shown in Fig. 3, arranged inside the door (a driver's seat door) is a first crash sensor 21 in the shape of a rod extending inside the door 10 and across the space horizontally along the width of the door 10. The crash sensor has opposite ends connected to the inner panel 14 at their end portions 14-1 and 14-2 by means of respective stays 24 and 26 that are connected to the portions 14-1 and 14-2, respectively by welding. As shown in Fig. 2, an inflator device 30 is arranged in the space 16 inside the door assembly 10. The inflator device 30 is provided with an air bag 32 that is, in Fig. 2, shown in its inflated state and occupying a space between the door 10 and the lateral side of a passenger (not shown) during an accident for protection thereat. As is also well known, the inflator device 30 has an ignition plug 30a for igniting material (not shown) in the inflator device 30 upon the occurrence of an impact. The inflator device 30 is further filled with gas generating material that generates a flow of a large amount of nitrogen gas upon ignition of the igniting material by the ignition plug 30a to thereby inflate the bag 32. In Fig. 4, which shows a detailed portion as circled by (a) in Fig. 3, the first crash sensor 21 includes a beam 33 that forms a cylindrical rod shape having an inner cylindrical wall on which a layer 34 made of electric insulating material is formed. On the insulating layer 34, a layer 36 as a first electrode member made of material having electric conductivity, is formed. A second electrode member 38 as a rod extends axially inside the cylindrical beam 33 along the axis thereof, so that the first and second electrodes 36 and 38 are usually spaced from each other so that electric contact does not take place therebetween. Suitable bearing members 40, only one of which is shown, are provided to support the second electrode (rod) 38 with respect to the outer beam, which prevents the electrode 38 from making electrical contact with the first electrode member (layer) 36. The second electrode 38 extends out of the cylindrical beam 33 so that it is electrically connected, via a lead wire 42, to a connector 44 for connection to an outside controller circuit. As shown in Fig. 5, the stay 24 is constructed by a plate portion 24-1 connected to the door panel portion 14-2 and a supporting portion 24-2 that is integral to the plate portion 24-1 and has a substantially closed cross sectional profile in which the end of the beam 33 is inserted to allow it to be supported by the stay 24. The construction of the opposite stay 26 is substantially the same as that of the first stay 24. It should be noted that a second crash sensor (not shown) is also arranged in the passenger's door. The second crash sensor has the same construction as the first crash sensor 21. Fig. 6 generally shows an electrical connection of the air bag system. The first and second electrodes 36 and 38 for the driver's door construct a normally closed first switch S1, which is, on one end (electrode 36), grounded, and is, on the other end (electrode 38), connected in series to a heater constructed by the first ignition plug 30a, and to a positive electrode of a battery (not shown). The same construction constructed by a series connection of a switch S2 and a heater H2 is also obtained for the passenger's door. Upon the occurrence of a lateral impact, an outside force is usually applied transverse to the door 10 as shown by an arrow F in Fig. 3, which causes the outer panel 12 to be deformed inwardly when an impact is larger than a predetermined value, so that the pipe shaped beam 33 of the sensor 21 collapses inwardly together with its insulating layer 34 and the inner layer 36 as the first electrode, which is brought into contact with the central rod 38 as the second electrode. As a result, a closed circuit is created in the heater H1 of the inflator 30a in the driver's door or the heater H2 of the inflator of the passenger's door, which causes a large amount of the nitrogen gas to be generated so as to inflate the air bag 32 as shown in Fig. 2, which occupies the space between the door and the passenger to protect and cushion the occupant from the impact during an accident. It should be noted that, in the first embodiment, the cross sectional shape of the beam 33 constructing the sensor 21 may not necessarily be circular, and another shape, such as a rectangular shape, can be employed. Figs. 7 and 8 shows a second embodiment of the present invention. A crash sensor 121 is, similar to the first embodiment, elongated horizontally in a space 116 of a door 110. The crash sensor 121 includes a cylindrical beam 133 having opposite ends supported by respective panels constructing the door 110 by means of stays 124 and 126. An electric insulating layer 134 is formed on the outer cylindrical wall of the beam 133, and a first electrode member 136 made of material having electrical conductivity is formed on the insulating layer 134. An outer cylindrical beam 150 is arranged outwardly and coaxially with the cylindrical beam 133, and the outer cylindrical beam 150 is connected to the first cylindrical beam 133 by a pair of spaced stays 152 (only one of which is shown) that are made of electrical insulating material. Formed on the inner cylindrical wall of the outer beam 150 is a layer 154 made of electric insulating material, and a layer 156 made of a material having electric conductivity as a second electrode member is formed on the inner surface of the electric insulating layer 154, so that an annular space 158 is formed between the inner and outer electrodes 136 and 156 as the layers made of the material having electric conductivity. The first electrode 136 is grounded, and the second electrode 156 is connected, via a lead wire 142, a connector 144 and a heater of the inflator, to a battery. It should be noted that, from the mechanical strength point of view, the outer cylindrical beam 150 is weaker than that of the inner cylindrical beam 133. During the operation of the crash sensor 121 in the second embodiment, upon a lateral impact owing to a force in a direction transverse to the door assembly 110, as shown by an arrow F in Fig. 8-(B), the outer beam of a mechanically weaker property collapses as shown, which causes the first electrode 136 on the outer cylindrical beam to be brought into contact with the inner second electrode 156 on the inner cylindrical beam. As a result, a closed circuit is obtained in a similar way as explained with reference to Fig. 6, causing the ignition plug 30a to be energized and ignite the ignition material thereby causing the gas generating material to be generated and the air bag 32 to be inflated so as to occupy the space between the side door and the passenger to protect the same.

Claims: A crash sensor to be attached to a door (10; 110) of an automobile, the door has a space (16; 116) extending along a width of the door; said crash sensor comprising: a supporting member (33; 150) extending along the width of the door in said space; said supporting member having axially spaced ends; means (24,26; 124,126) for mechanically connecting the supporting member to respective portions of the door; said supporting member having sufficient rigidity to cause the supporting member to maintain its original state under a normal conditions, and; means (36; 136) for detecting a shock occurring in the supporting member during an impact, and producing a signal indicating the occurrence of said impact, characterized in that said detecting means comprise a rigid member (38; 133) which extends to be coaxial with respect to the supporting member (33; 150), and means (152) for supporting the rigid member with respect to the supporting member so that they are usually spaced apart with each other, said rigid member and the supporting member having at least portions having electrical conductivity on their surfaces facing each other, which are usually spaced from each other, the occurrence of an impact allowing an electrical closed circuit to be created between the surfaces when they are brought into contact with each other upon displacement as a result of an impact occurring so as to obtain an electric signal indicating the occurrence of said impact. A crash sensor according to claim 1, wherein said supporting member (33) forms a cylindrical body having an axis of elongation, and wherein said rigid member forms a rod (38) which is arranged inside the cylindrical supporting member so as to be coaxial with each other to create an annular space therebetween, the supporting member (33) and the rigid member (38) having faced annular surfaces, said portions having electrical conductivity being formed on the faced surfaces. A crash sensor according to claim 1, wherein said supporting member (150) forms a cylindrical body having an axis of elongation, and wherein said rigid member (133) forms a cylindrical body which is arranged inside the supporting member so as to be coaxial with each other to create an annular space therebetween, the supporting member and the rigid member having faced annular surfaces, said portions having electrical conductivity being formed on the faced surfaces.

Inventors: FUJITA KOICHI TOYOTA JIDOSHA K, MATSUHASHI TOSHIAKI, TAGUCHI MASAHIRO, TOMINAGA MOTONORI, FUJITA, KOICHI, MATSUHASHI, TOSHIAKI, TAGUCHI, MASAHIRO, TOMINAGA, MOTONORI, FUJITA, KOICHI, TOYOTA JIDOSHA KABUSHIKI KAISHA
Applicants: NIPPON DENSO CO, NIPPON SOKEN, TOYOTA MOTOR CO LTD, NIPPON SOKEN, INC., NIPPONDENSO CO., LTD., TOYOTA JIDOSHA KABUSHIKI KAISHA
Application year: 1992
Main classification: B60R21
IPC codes: B60J5, H01H35, B60R21, G01P15