Collision Detecting Inertia Switch

1. Field of the Invention

The present invention relates to a collision detecting apparatus which detects a collision of a vehicle or the like to actuate a driver or passenger protecting apparatus such as an air-bag or the like.

2. Description of the Prior Art

There have hitherto been proposed various collision detecting apparatuses which are interposed between a power supply and a driver or passenger protecting apparatus installed on a vehicle in order to actuate the driver or passenger protecting apparatus by generating a signal in an emergency such as a collision of the vehicle and supplying an electric current to the driver or passenger protecting apparatus from the power supply. It is known that such collision detecting apparatuses comprise a weight whose movement is caused mainly by the effect of acceleration to open or close an electrical contact. It is required that such collision detecting apparatuses surely supply an electric signal caused by the opening or closing of the electrical contact to the outside thereof and at the same time have a simple construction so that they may be manufactured with an easy assembly operation.

However, there has been a problem that conventional apparatuses, which in order to provide a stable signal and to be relatively free from malfunction, have a complicated construction which causes reliability and at the same time requires a difficult assembly operation.

A first object of the present invention is to provide a collision detecting apparatus comprising a rotational member having a weight positioned eccentrically from the center axis of a shaft, which supports the rotational member, two cam members which rotate synchronously with the rotational member, and electrical contact elements actuated by the two cam members, respectively, thereby enabling sure operation of the electrical contact mechanism as a signal source, maintaining a constant gap between the paired electrical contacts and preventing malfunction from being caused by mechanical vibration, etc., thus assuring highly reliable contacting performance of the electrical contacts.

A second object of the present invention is to provide a collision detecting apparatus for a vehicle or the like, in view of the aforesaid problem, in which a case and an end plate form an enclosed space, a cylindrical housing is installed within the enclosed space, a rotational member, which rotates in response to acceleration or deceleration caused by a collision of the vehicle or the like, is supported in the housing, both end openings of the housing are closed with a lid member and a base member, respectively, and an elastic member intervening between the case and the lid member presses and holds the respective component parts by its elastic force, thereby providing a construction which includes a smaller number of component parts and easily enables the unidirectional assembly of the collision detecting apparatus with an automatic assembly machine.

The present invention can provide a highly reliable collision detecting apparatus which comprises a rotational member having a weight positioned eccentrically from the center axis of a shaft, which supports the rotational member, and a spring member connected to the rotational member to counteract its rotational movement, two cam members which rotate synchronously with the rotational member, and an electrical contact mechanism with its spring arms, which carry electrical contacts, respectively, touching the respective cam members, thereby preventing malfunction from being caused by mechanical vibration, etc. and assuring reliable opening or closing operation of the electrical contacts. Further, the present invention brings a remarkable advantage such that the selection of the cam profiles of the cam members makes it possible to determine exactly a length of the gap between the paired electrical contacts and to render the closing time of the paired electrical contacts sufficiently long as desired.

Furthermore, since the collision detecting apparatus of this invention has a construction such that the apparatus can be assembled by supplying necessary component parts from one side in the axial direction, it is possible to assemble the apparatus in a short time by using an automatic machine. The apparatus may also be constructed using a simple assembly operation which does not require skilled labour. Thus, the present invention has a great advantage to provide a collision detecting apparatus of the type to detect a collision of a vehicle or the like by the rotational movement of a rotational member which is of low price but has excellent collision detecting capability.

FIG. 1(a) is a perspective general-assembly drawing showing an embodiment of the collision detecting apparatus according to the present invention;

FIG. 1(b) is an alternate perspective view of the lid shown in FIG. 1(a);

FIG. 1(c) is an alternate perspective view of the housing shown in FIG. 1(a);

FIG. 2 shows a longitudinal section of the collision detecting apparatus according to the present invention shown in FIG. 1 but in the assembled state; and

FIG. 3 is a cross-sectional view of the collision detecting apparatus according to the present invention shown in FIG. 2 as viewed in the direction of arrows along the cutting-plane line III--III.

The present invention will be described hereunder with reference to the accompanying drawings which illustrate a preferred embodiment of the present invention.

Referring to FIGS. 1(a), 1(b), 1(c), 2 and 3, reference numeral 1 designates a cup-like case made of iron having a nickel-plated surface, a flanged end portion 1a which is to be joined to an end plate 2 by a ring-projection welding method, and an embossed portion 1b which engages with a slot 6d of a housing 6 to prevent the rotational shift of the latter. The end plate designated by the reference numeral 2 is made of iron and its peripheral portion is joined later to the flanged end portion 1a of the case 1 by a ring-projection welding method thereby to provide a completely sealed space within the case 1. Reference numeral 3 designates a base made of a resin material which has a bearing portion 3a for rotatably supporting a shaft 7e, which supports a rotational member 70 of the collision detecting apparatus, and a notch 3b in which projections 6a of the housing 6 are fitted. Reference numerals 4 and 5 designate electrical contact members to be fixed to the base 3 by a method of caulking with preheating, etc. The electrical contact members 4 and 5 have leaf spring portions 4a and 5a, respectively, which touch cam members 7c and 7d of the rotational member 70, respectively. The cam members 7c and 7d are made of an insulating material. The end portions of the leaf spring portions 4a and 5a carry electrical contacts 4b and 5b which have been spot-welded thereto, respectively. The housing designated by the reference numeral 6 is made of a resin material, and comprises the abovementioned projections 6a which are fitted into the notch 3b of the base 3, slit portions 6b to which an outer end portion 8b of a spiral spring 8 is fixed, a notch 6c in which a projection 10b of a lid 10 made of a resin material is fitted, the abovementioned slot 6d which engages with the embossed portion 1b of the case 1 to prevent the rotational shift of the housing 6 itself, and stopper portions 6e and 6f which define the range of the angle of rotation of the rotational member 70.

Further, the stopper portion 6e determines the home position of a weight 7a, which is eccentrically attached to a wheel 7 of the rotational member 70, and hence the maximum angle of rotation of the weight 7a which may be reached when a collision takes place. The rotational member 70 comprises the wheel 7, the weight 7a eccentrically attached thereto, a fixing portion 7b for fixing an inner end portion 8a of the spiral spring 8 thereto by means of a cap 9, and the cam members 7c and 7d which make the electrical contacts 4b and 5b of the electrical contact members 4 and 5, respectively, contact each other when the rotational member 70 rotates to exceed a predetermined angle of rotation. Here, the cam members 7c and 7d may be incorporated with the wheel 7 forming a single body. Both ends of the shaft 7e are supported rotatably by the bearing portion 3a of the base 3 and a bearing portion 10a of the lid 10, respectively, and further the shaft 7e and the rotational member 70 are held in freely rotatable engagement with each other.

The spiral spring designated by the reference numeral 8 urges the weight 7a of the rotational member 70 against the stopper portion 6e of the housing 6 to maintain the weight 7a normally in its home position. The cap designated by the reference numeral 9 fixes the inner end portion 8a of the spiral spring 8 to the fixing portion 7b of the rotational member 70, as above mentioned, and has a slit 9a for holding the inner end portion 8a of the spiral spring 8 therein. The lid designated by the reference numeral 10 has the bearing portion 10a for rotatably supporting the shaft 7e and the projection 10b which is fitted into the notch 6c of the housing 6 to thereby prevent the occurrence of misadjustment when combining the lid 10 with the housing 6. Reference numeral 11 designates a retaining spring member shown as a wave washer which is an elastic member used to press the base 3, the housing 6 and the lid 10 toward the end plate 2. Reference numeral 12 designates a resistor fixed to the electrical contact members 4 and 5 by soldering. The resistor 12 is used to provide an electric path which allows a small electric current to flow therethrough even when contact is not established between the electrical contacts 4b and 5b, which serves for the purpose of checking the operation of an external electric circuit associated with the collision detecting system. Reference numeral 13 designates electric terminal pins for external connection which are fixed to the end plate 2 with an insulating material 13a intervening therebetween and which are also connected to the respective electrical contact members 4 and 5 by soldering.

The operation of the collision detecting apparatus having the abovedescribed construction will be explained hereinafter.

When there occurs a collision of a vehicle or the like having the collision detecting apparatus of the present invention mounted thereon in the direction of an arrow A shown in FIG. 3 and a deceleration force is applied to the collision detecting apparatus, the rotational member 70 having a center of mass shifted by the weight 7a eccentrically from the center axis of the shaft 7e will tend to start its rotation in the direction of an arrow B shown in FIG. 3. If the acceleration or deceleration of the collision detecting apparatus caused by an impact exceeds a predetermined value, the rotational member 70 will be given a forward torque to overcome an initial countertorque load set by the spiral spring 8. When the rotational member 70 starts to rotate, the two cam members 7c and 7d also rotate in the direction of the arrow B, which causes the cam member 7c to push the leaf spring portion 4a of the electrical contact member 4 away from the shaft 7e and causes the cam member 7d to allow the leaf spring portion 5a of the electrical contact member 5 to lean toward the shaft 7e. When the rotational member 70 has rotated to exceed a predetermined angle of rotation, the electrical contacts 4b and 5b are brought into contact with each other to establish electrical conduction therebetween and thereby generate a collision signal. On the other hand, if the acceleration or deceleration of the collision detecting apparatus, which occurs when the vehicle or the like travels on a rough road or when sudden braking is applied, does not exceed a predetermined value, the rotational movement of the rotational member 70 remains restrained by the spiral spring 8 and is not allowed to reach the predetermined angle of rotation, and hence electrical conduction can not be produced between the electrical contact members 4 and 5.

Next, the process of assembling the abovedescribed collision detecting apparatus embodying the present invention will be explained.

Firstly, the base 3 is attached to the end plate 2 which has the electric terminal pins 13 fixed thereto, and the electrical contact members 4 and 5 are fixed to the base 3, and then the resistor 12 is fixed to the electrical contact members 4 and 5. Thus the base assembly is completed. Next, the housing 6 is combined with the base assembly with the projections 6a thereof fitted into the notch 3b of the base 3. The spiral spring 8 is beforehand fixed to the fixing portion 7b of the rotational member 70 at the inner end portion 8a of the spiral spring 8. Then, the rotational member 70 is joined to the combination of the housing 6 and the base assembly by inserting one end of the shaft 7e in the bearing portion 3a of the base 3, adjusting the weight 7a of the rotational member 70 to abut against the stopper portion 6e of the housing 6 and fixing the outer end portion 8b of the spiral spring 8 to the housing 6 at its slit portions 6b. Next, the lid 10 is set onto the lastmentioned combination by making the bearing portion 10a of the lid 10 engage with the shaft 7e, with the other end of the shaft 7e being inserted in the bearing portion 10a, and by fitting the projection 10b of the lid 10 into the locating notch 6c of the housing 6. Thus, the assembly of the main body of the apparatus is completed which comprises a housing assembly and the rotational member 70 supported by the shaft 7e within the housing assembly. Lastly, the case 1 is put on the housing assembly, which contains the rotational member 70 therein, to cover the housing assembly with the wave washer 11 intervening between the inner bottom surface of the case 1 and the outer surface of the lid 10 of the housing assembly and acting as an elastic member for pressing the lid 10, the housing 6 and the base 3 toward the end plate 2. Thereafter, as mentioned before, the flanged end portion 1a of the case 1 and the peripheral portion of the end plate 2 are joined together by a ring-projection welding method.

As explained hereinabove, the collision detecting apparatus of this invention has a construction which enables the assembly thereof to be carried out smoothly and surely in one direction, namely, in the direction of the center axis of the shaft 7e and therefore facilitates the assembly thereof with an automatic machine.

In addition, it should be noted that the present invention is not restricted to the abovedescribed single embodiment. Namely, the rotational member 70, the shaft 7e and the bearing portions 3a and 10a have been described to be in freely rotatable engagement with one another in the abovedescribed embodiment. However, it must be understood that the present invention covers other cases: where the rotational member 70 and the shaft 7e are fixed to each other, while the shaft 7e remains in freely rotatable engagement with the bearing portions 3a and 10a; and where the shaft 7e and the bearing portions 3a and 10a are fixed to one another, while the rotational member 70 remains in freely rotatable engagement with the shaft 7e. Further, the wheel 7 has been described to be a disk in the abovedescribed embodiment, however, it does not necessarily follow that the wheel 7 is a disk. Namely, the shape of the rotational member 70 does not matter if only the rotational member 70 is constructed to have a predetermined magnitude of moment of inertia and to comprise an eccentrically positioned weight of a predetermined weight value.

In addition, the electrical contacts 4b and 5b have been described to close when the rotational member 70 rotates to reach a predetermined angle of rotation in the abovedescribed embodiment, however, the contacts 4b and 5b may stay initially in a closed state and then be opened upon the rotation of the rotational member 70 to reach such an angle of rotation.