A device for fixing mechanical parts to the body of a motor vehicle

Abstract: A device is described for fixing to the floor of a motor-vehicle body (2), by screwing from above, a mechanical part (7) which has previously been brought up to the floor from below. The mechanical part (7) to be fixed carries at least one locating element (1) which engages a corresponding hole formed in the body (2). The locating element has a threaded hole which is engaged by a screw (3) on which the smaller-diameter portion (11) of a sleeve (5) can slide. The sleeve has a larger-diameter portion (12) which is adapted to fit over the outer surface of that part of the locating element (1) which projects through the corresponding locating hole in order to facilitate the centring and insertion of the screw (3) in the threaded hole in the locating element (1).

Description: The present invention relates to a device for fixing to the floor of a motor-vehicle body having at least one hole formed therein, by screwing from above, a mechanical part which has previously been brought up to the floor from below. A tendency has developed recently in in the art to preassemble the mechanical units of a motor vehicle, usually by mounting the various parts on preassembly subframes, and then to mount the subframes carrying the preassembled units on the motor vehicle body by means of automatic equipment. An example of this mode of production which relates to a rear suspension unit mounted on the floor of the motor-vehicle body from below, is described in the prior Italian Patent Application Nb. 68092-A/88, corresponding to EP-A-0 373 125, published 13.06.90, and filed by the same Applicant and designating the same inventor as the present Application. In this mode of production, the preassembled unit is fixed under the floor of the motor vehicle body by screwing from below with the aid of automatic screwing devices. Because of the particular shape and size of the structure to be fixed, however, some of the fixing points of the preassembled unit may have to be screwed to the body from above, that is, from inside the-motor-vehicle body, instead of from below, and this may be difficult to carry out with automatic equipment. Moreover, the mechanical parts are sometimes mounted on box elements forming part of the body and this can make them even more difficult to fix,taking into account the need to avoid the risk of deformation or local weakening of the box element. taking into account the need to avoid the risk of deformation or local weakening of the box element. The European patent application EP-A-0 298 929, of the same Applicant, illustrates a device for fixing a mechanical part to the floor of a motor-vehicle. The device comprises a tubular element having two flanges on its ends. One of the flanges is brought in contact with the outer surface of the floor so that the tubular element is coaxial with a hole provided in the floor. A bolt inserted into the tubular element projects through the hole in the floor and is screwed to a nut inserted from the above of the floor to tighten the assembly. German patent DE-B-1 185 866 discloses a device of the known type wherein a bolt inserted from the above into a hole in a floor is screwed to a nut engaging a mechanical part which has been brought up to the floor from below. In order to resolve all the aforesaid problems simply, the subject of the present invention is a device of the type indicated above, whose features are set forth in the characterising portion of Claim 1. The fixing device preferably includes a resilient ring which is fitted on the shank of the screw to prevent the accidental disengagement of the screw from the sleeve. Further characteristics and advantages will become clear from the description which follows with reference to the appended drawings, provided by way of non-limiting example, in which: Figure 1 shows in section a detail of the mechanical part to be fixed, provided with a locating element engaged in a corresponding locating hole in part of the floor of a motor-vehicle body, Figure 2 is a sectional view of the fixing device according to the invention, and Figure 3 is a sectional view showing the mechanical part mounted on the floor of the motor-vehicle body by means of the device of Figure 2. In the drawings, a mechanical part 7 (for example, an element with a cross member on which a rear suspension unit has been preassembled - see the Applicant's patent Application No. 68092-A/88 and corresponding EP-A-0 373 125) is to be brought up to the floor 2 of the motor-vehicle body from below and fixed to the floor by screwing from above. The part 7 carries at least one locating element 1 which, in the embodiment illustrated, is constituted by a locating peg with a body which is inserted through a hole 7' in the part 7 and a head which is fixed to the part 7 by welding 9. When the part 7 is mounted under the floor 2 of the body, the portion of the locating element 1 which projects from the part 7 engages a locating hole 2' formed in the floor 2. The free end of the locating element 1 which projects above the floor 2 - still with reference to the particular embodiment shown - has a circumferential chamfer 1'. Figure 3 shows the portion of the floor 2 to which the part 7 is to be fixed in greater detail. As can be seen, in the embodiment shown, the part 7 is fixed to the lower wall of a box element. The fixing device according to the invention, generally indicated 8, (see also Figure 2) includes a screw 3 with a threaded end portion 3a terminating in a conical point 3b. The threaded portion 3a is intended to be screwed into the threaded hole 1a in the locating element 1. A sleeve, indicated 5, has a first, smaller-diameter portion 11 mounted slidably on the unthreaded part of the shank of the screw 3 and a second, larger-diameter portion 12 (the diameters of the two portions are indicated d and D respectively in the drawings). The head 3' of the screw 3 abuts the free end surface of the smaller-diameter portion 11 of the sleeve 5 with the interposition of a washer 4. The shank of the screw 3 also has a circumferential groove 3c in which a resilient split ring 6 is fitted to prevent the accidental disengagement of the screw 3 from the sleeve 5. Figure 3 clearly shows the operating principle of the device 8 according to the invention: after the mechanical part 7 has been positioned adjacent the box element 2 from below by the insertion of the locating element 1 in the locating hole 2', the device 8 is fitted into the cavity of the body element 2 from above by being passed through a hole 2a (Figure 3) in the upper wall of the box element. The larger-diameter portion 12 of the sleeve 5 fits over the outer surface of that part of the locating element 1 which projects through the hole 2' so as to facilitate the centring and insertion of the screw 3 in the threaded hole in the locating element 1. The chamfer 1' of the locating element facilitates the fitting of the sleeve 5 over it. At the same time, the conical point 3b of the screw facilitates its fitting in the threaded hole 1a. The device according to the invention is particularly suitable for fixing mechanical parts to box elements which form parts of motor-vehicle bodies, as shown in Figure 3, but its use is not of course limited exclusively to box parts. Another characteristic of the solution according to the invention is that the same locating elements 1 as are normally used for the mounting of preassembled subassemblies are also used as engagement elements for fixing screws. The fixing achieved by the device according to the invention provides a good distribution of the loading of the bolts between the connected elements by virtue of the wide annular coupling surface between the larger-diameter portion of the sleeve 5 and the fixed parts. Moreover, good resilience under tension is achieved by virtue of the overall length of the screw.

Claims: A device for fixing to the floor (2) of a motor-vehicle body having at least one hole (2') formed therein, by screwing from the above, a mechanical part (7) which has previously been brought up to the floor from below, characterised in that it comprises, in combination: a locating element (1) adapted to engage said at least one hole (2') formed in the body, the locating element (1) being constituted by a peg with a head which is intended to be welded to the mechanical part (7) to be fixed, the locating element (1) further having a threaded hole (1a); a screw (3) adapted to engage the threaded hole (1a) in the locating element (1) and having a head (3'); and a sleeve (5) having a first, smaller-diameter portion (11) mounted slidably on the screw (3) with the head (3') of the screw (3) bearing on its end, and a second, larger-diameter portion (12) adapted to fit over the outer surface of that part of the locating element (1) which, in the mounted condition. results in projecting through the hole (2') in the body (2), so as to facilitate the centring and insertion of the screw (3) in the threaded hole (1a) in the locating element (1). A fixing device according to Claim 1, characterised in that it includes a resilient ring (6) which is fitted onto the shank of the screw (3) to prevent the accidental disengagement of the screw (3) from the sleeve (5). A fixing device according to Claim 1, characterised in that the locating element (1) has a circumferential chamfer at the end opposite to its head for facilitating the fitting of the larger-diameter portion (12) of the sleeve (5). A fixing device according to Claim 1, characterised in that a washer (4) is interposed between the head (3') of the screw and the end surface of the smaller-diameter portion (11) of the sleeve (5).

Inventors: CAMUFFO SERGIO, CAMUFFO, SERGIO
Applicants: FIAT AUTO SPA, FIAT AUTO S.P.A.
Application year: 1990
Main classification: F16B5
IPC codes: F16B5, F16B35, F16B37, B62D27