Patent Abstract:
An anti-vibration device “D” having a shank ( 10 ) fixed to a structure (S) and a mass ( 4 ) retained on the shank ( 10 ) that is pressed by a spring ( 8 ) against the structure (S) with a predetermined force. The spring ( 8 ) increases the friction forces between the structure (S) and the mass ( 4 ) to deaden vibrations of the structure (S).

Full Description:
The present invention relates mainly to an anti-vibration device and to a structure comprising such a device, the structure in particular being a disk brake or a drum brake. 
     BACKGROUND OF THE INVENTION 
     In the automotive field, the comfort of the passengers of a motor vehicle is a major concern, this concern manifesting itself in a fight against noise, particularly the operating noise of the various parts that make up a motor vehicle. The braking device, particularly the brakes, disk brakes and/or drum brakes, positioned at the wheels are sources of noise. Because of their arrangement and the way in which they are stressed, they are very sensitive to motor vehicle vibration. The brakes are liable to start to vibrate and to generate rather a loud noise, and because of the frequency of braking actions this carries the risk of becoming a major annoyance. 
     Document FR 0 202 442 discloses an anti-vibration device comprising a mass slideably mounted along a screw screwed into the structure liable to vibrate and a spring mounted to provide reaction between one end of the screw and the mass and exerting a determined force on the mass so as to press the mass against the structure. As a result, when the mass starts to move, it rubs against the surface of the structure and deadens the vibrations. The mass is mounted with clearance around the screw. This device is satisfactory although its effectiveness could usefully be improved. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to offer a vibration-deadening device that is highly effective and simple in design. 
     Another object of the present invention is to offer a structure, particularly a motor vehicle brake, that is silent and provides good driving safety. 
     These objects are achieved by an anti-vibration device comprising a mass, an element for fixing the mass to a structure the potential vibrations of which need to be damped, a means for adjusting the force with which the mass rubs against the structure and means for causing the mass to collaborate in friction with the fixing means. 
     In other words, as the fixing means is an element entirely separate from the structure and fixed rigidly thereto, the present invention uses the fixing means as part of the structure in order to increase the amount of contact between the mass and the structure, thus increasing the friction forces between the structure and the mass. Vibrations are dissipated through the structure more quickly. 
     The main subject of the present invention is an anti-vibration device able to be fixed to a structure, comprising a means of fixing the said device to the said structure, a mass and a means able to press the said mass against the structure with a predetermined force, characterized in that it also comprises means intended to increase the friction forces between the fixing means and the mass. 
     Another subject of the present invention is an anti-vibration device, characterized in that the mass is mounted around the fixing means and in that the means intended to increase the friction forces between the fixing means and the mass comprise at least one pair of opposing surfaces borne one by the mass and one by the fixing means. 
     Another subject of the present invention is a device, characterized in that the said surfaces are formed by a screw thread formed on the fixing means and by a tapped thread formed in the mass. 
     Another subject of the present invention is a device, characterized in that the means applying a predetermined force to the mass to bring it into contact with the structure is an elastic means. 
     Another subject of the present invention is an anti-vibration device, characterized in that the elastic means is a helical spring. 
     Another subject of the present invention is an anti-vibration device, characterized in that the fixing means is a screw screwed by a first end into the said structure and equipped at a second, opposite, longitudinal end, with a head, and in that the helical spring is mounted to provide reaction between the nut and the mass. 
     Another subject of the present invention is an anti-vibration device, characterized in that the screw comprises a threaded shank, the head being formed of a nut mounted at the second longitudinal end, so that the load on the spring can be adjusted. 
     Another subject of the present invention is a motor vehicle brake comprising a body, a means of pressing at least one friction pad against an element made to rotate by the wheel of the motor vehicle, an anti-vibration device fixed on the body, characterized in that the anti-vibration device is a device according to the invention. 
     Another subject of the present invention is a brake, characterized in that the brake is a disk brake, in that the element made to rotate is a brake disk and in that the anti-vibration device is fixed to a carrier and/or a caliper of the disk brake. 
     Another subject of the present invention is a brake, characterized in that the brake is a drum brake, in that the element made to rotate is a drum and in that the anti-vibration device is fixed to the plate. 
     The present invention will be better understood with the aid of the description which will follow and of the attached figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view in axial section of one exemplary embodiment of an anti-vibration device according to the present invention; 
         FIG. 2  is a detailed view of  FIG. 1 ; 
         FIG. 3  is an overall view of a disk brake equipped with a device according to the present invention; and 
         FIG. 4  is an overall view of a drum brake equipped with a device according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows an anti-vibration device D according to the present invention comprising a fixing means  2  for fixing it to a structure S, a mass  4  kept in contact with a surface L of the structure S by a pressing means  8  mounted to provide reaction between the fixing means  2  and the mass  4 . 
     In the example depicted, the fixing means is a shank  10  provided with a screw thread  11  along its entire length. The shank  10  is intended to be screwed via a first longitudinal end  12  into a tapped hole  14  in the structure S. A nut  16  is screwed onto a second longitudinal end  18  of the shank  10 , the opposite end to the first end. The nut is advantageously prevented from turning for example by an adhesive, to prevent it from becoming detached from the shank. 
     Of course, provision could be made for the shank  10  to be bonded or welded to the structure. 
     In the example depicted, the mass  4  is of annular shape pierced with a passage  20  so that the mass  4  can be mounted around the shank  10 . According to the present invention, the device comprises means for increasing the friction forces between the shank of the fixing means and the mass. The means intended to increase the friction forces between the fixing means and the mass comprise at least one pair of opposing surfaces intended to come into contact with one another, one surface of the pair being borne by the mass and the other surface of the pair being borne by the fixing means. In the example depicted, the pairs of surfaces are formed by a tapped thread  21  and the screw thread  11  of the fixing means. 
       FIG. 2  shows the screw thread  11  comprising a first helical surface  22  and a second helical surface  24  which face a third and fourth  26 ,  28  helical surface forming the tapped thread  21 , respectively. The first pair of surfaces comprises the first surface  22  and the third surface  26  and the second pair comprises the second surface  24  and the fourth surface  28 . 
     As the shank  10  is rigidly fixed to the structure S, it is also set in vibration when the structure vibrates and the collaboration between the shank  10  and the mass  4  has the effect of reducing the vibrations of the structure S. 
     Of course, other means for causing the shank and the mass to collaborate in friction may be envisaged, for example a mass comprising a stepped passage  20  collaborating with a stepped shank  10 . 
     An advantage of the present invention is that it allows the force exerted by the spring on the mass to be adjusted and therefore allows the anti-vibration device to be tailored to suit the resonant frequencies of the structure since the distance between the nut and the surface of the structure can be adjusted because of the screw-fastening. 
     Provision could be made to use a screw in place of the threaded shank/nut assembly, although the ease of tuning the device for frequency would then be lost. 
     The anti-vibration device according to the present invention is advantageously used to limit the vibrations of a motor vehicle brake. 
       FIG. 3  shows an example of a disk brake according to the present invention, comprising a caliper  30  able to slide via guide pins  34 ,  36  with respect to a carrier  32  mounted fixedly on a stub axle of a motor vehicle. A piston slideably mounted in the caliper and actuated for example by a pressurized hydraulic fluid is intended to move at least a first friction means towards a first face of a brake disk, a second friction means being moved against a second face of the disk through the sliding of the caliper relative to the carrier. 
     The anti-vibration device D according to the present invention is mounted for example on the caliper and/or on the carrier, advantageously on the parts experiencing the greatest-amplitude vibrations, for example on the nose of the caliper. In  FIG. 3 , the device schematically depicted is mounted on the nose of the caliper. 
     The anti-vibration device is, for example fixed to one end of a guide pin. 
     Of course, the present invention is just as applicable to a so-called fixed disk brake, comprising at least two pistons positioned one on each side of the brake disk. 
       FIG. 4  shows a drum brake according to the present invention comprising a plate  40  equipped with a brake cylinder  42  able to move first and second shoes  44 ,  46 , provided with linings, towards a drum (not depicted) secured to the wheel of the motor vehicle; the wheel cylinder is for example actuated by a pressurized hydraulic fluid. 
     The anti-vibration device D according to the present invention is, in the example depicted, fixed to the plate. 
     Of course, several anti-vibration devices according to the present invention may be provided for one and the same system that needs to be damped. 
     Of course, the device according to the present invention applies to any type of structure requiring the damping of vibrations to which it is subjected, for example a machine tool. 
     The present invention applies particularly to motor vehicle braking systems.

Technology Classification (CPC): 5