Abstract:
A drive bogie includes axles, a chassis and a device for driving each axle, including a motor, a reduction gearbox and a transmission coupling between the motor and the reduction gearbox, with a support mechanism being provided to allow the vehicle to support the drive device. The support mechanism for supporting the drive device comprises a suspension for suspending the reduction gearbox from the body of the vehicle, the suspension being articulated to the reduction gearbox or to the body, a device for articulating the motor to the chassis of the bogie about a roughly horizontal axis, and a device for connecting the motor to the reduction gearbox, the connecting device being articulated both to the motor and to the reduction gearbox. Thus, most of the mass of the reduction gearbox and of the motor is suspended vertically from the body of the vehicle.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a drive bogie for a rail vehicle and to a rail vehicle equipped with at least one such bogie. 
     Customarily, a drive bogie comprises axles resting on the rails of the track and supporting a chassis, with the interposition of a suspension known as the primary suspension. The body of the railway vehicle rests on the chassis of this bogie, with the interposition of a suspension known as the secondary suspension. 
     Each drive bogie is fitted with means for driving each axle, which means comprise at least one motor and at least one reduction gearbox equipped with a wheel for driving the corresponding axle. There are also means allowing the railway vehicle to support the motors and the reduction gearboxes. 
     It is advantageous to have the mass of the drive means supported by a mechanical part of the vehicle which is as suspended as possible. This plays a part in reducing the loadings exerted on the rails by the drive bogie and makes it possible to increase the speed of the railway vehicle. From this standpoint it is preferable to have the masses of the motors and of the reduction gearboxes supported by the body of the vehicle and, failing that, by the chassis of the bogie, the solution of having the axles support these masses being the most unfavorable solution. 
     Incidentally, the body of the vehicle, the chassis of the bogie and the axles are free to move with respect to one another. Now, as the drive wheel of the reduction gearbox has to be secured to the axle, the higher up the members from which the motor and the reduction gearbox are suspended, the more complex will be the transmission between the suspended motor and this drive wheel fixed to the axle. 
     A compromise has therefore to be found between suspending these masses solely from the axle, which is simple to implement but which allows only low speeds, and suspending the masses from the body, which allows high speeds but which is complex in technical terms. 
     A first solution consists in suspending a geared motor unit from the body of the vehicle and in installing an additional reduction gearbox on the axle, these two reduction gearboxes being connected by a constant-velocity joint. This solution does, however, have drawbacks in that it is necessary to use two separate reduction gearboxes. What is more, the use of a constant-velocity joint, which is particularly expensive, leads to high costs. 
     An alternative solution has been proposed. It consists in suspending the reduction gearbox from the chassis of the bogie, at the opposite end to the axle. Incidentally, the motor is fixed permanently to the chassis, the reduction gearbox and the motor usually interacting via a curved-tooth coupling. 
     This arrangement, although relatively advantageous in terms of cost, does have other drawbacks. Specifically, the masses of the motor and of the reduction gearbox are supported not by the body of the vehicle but by the chassis of the bogie, which means that the axles exert relatively high loads on the rails. What is more, mounting the motor permanently on the chassis leads to the emergence of high mechanical loadings exerted on this chassis. 
     SUMMARY OF THE INVENTION 
     In order to alleviate the various drawbacks of the prior art as mentioned hereinabove, the invention proposes to produce a railway vehicle drive bogie in which the masses of the motors and of the reduction gearboxes are supported, to a large extent, by the body of the vehicle, via a low number of mechanical parts which have a simple structure and are inexpensive. 
     To this end, the subject of the this invention is a drive bogie for a rail vehicle, intended to support a body of the said vehicle, the said drive bogie comprising axles resting on rails, a chassis resting on the said axles and means for driving each axle, including a motor, a reduction gearbox and means of transmission between the motor and the reduction gearbox, means being provided to allow the vehicle to support the drive means, characterized in that the said means for supporting drive means comprise means for suspending the reduction gearbox or the motor from the body of the vehicle, these means being articulated to the reduction gearbox or to the motor, and to the body, means for articulating the motor to the chassis of the bogie about a roughly horizontal axis, and means for connecting the motor to the reduction gearbox, these means being articulated both to the motor and to the reduction gearbox. 
     According to other features of the invention: 
     when viewed from the side, the point of articulation of the reduction gearbox or of the motor to the suspension means lies between the center of gravity of the reduction gearbox and the center of gravity of the motor; 
     the moment exerted by the reduction gearbox on the said articulation point is approximately equal to the moment exerted by the motor on this articulation point; 
     when viewed from above, the reduction gearbox and the motor are transversely offset with respect to each other, the point of articulation of the suspension means to the reduction gearbox or to the motor being located between the center of gravity of the reduction gearbox and the center of gravity of the motor; 
     the means for suspending the reduction gearbox or the motor from the body of the vehicle are articulated to the reduction gearbox or to the motor, and to the body, at least about a horizontal axis; 
     the suspension means comprise an approximately straight connection rod stretching roughly vertically between the reduction gearbox and the body of the vehicle; 
     the means of articulation of the motor to the chassis comprise two arms secured to the housing of the motor, these arms being articulated to the chassis about the said horizontal axis; 
     the means for connecting the motor to the reduction gearbox are articulated to the motor and to the reduction gearbox at least about a horizontal axis; 
     the means for connecting the motor to the reduction gearbox comprise a link rod which, when viewed from the side, is in the shape of a C, the two ends of this link rod, one of them articulated to the motor and the other to the reduction gearbox, being located roughly one below the other; 
     the means of transmission between the motor and the reduction gearbox comprise a curved-tooth coupling; 
     the reduction gearbox comprises a driven wheel driven by the motor, a drive wheel secured to the axle and an intermediate wheel. 
     Another subject of the invention is a railway vehicle comprising at least one drive bogie and a body resting on the or each drive bogie, characterized in that the or each drive bogie is as defined hereinabove. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described hereafter with reference to the appended drawings which are given merely by way of non-limiting examples, and in which: 
     FIG. 1 is a diagrammatic view illustrating the distribution of mass of a drive bogie belonging to a railway vehicle according to the invention; 
     FIG. 2 is a perspective view of part of the drive bogie of FIG. 1; 
     FIGS. 3 and 4 are views respectively from the side and from above, to a larger scale, of the drive bogie of FIG. 1; and 
     FIG. 5 is a view similar to FIG. 3, illustrating an alternative form of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 diagrammatically depicts a railway vehicle denoted overall by the reference  2 . This vehicle is equipped with a number of bogies, just one of which,  4 , is illustrated in this figure. This bogie comprises two axles  6 , resting on rails  8  and supporting a chassis  10  with the interposition of a primary suspension denoted by the references  12 . The railway vehicle is also equipped with a body  14 , depicted partially, resting on the chassis  10  of the bogie  4  with the interposition of a secondary suspension  16 . 
     Each axle  6  is equipped with a corresponding drive assembly. Only the drive assembly of the left-hand axle, in FIG. 1, will be described in what follows, it being understood that the two drive assemblies are symmetric with respect to a transverse central axis of the bogie. Each drive assembly comprises a reduction gearbox denoted overall by the reference  18 , which is equipped with three gearwheels  20 ,  22 ,  24  illustrated in FIGS. 3 and 4. The wheel  20 , secured to the axle, is a wheel for driving the latter, while the wheel  24  is a driven wheel driven by a motor, as will be explained in what follows, the wheel  22  being an intermediate wheel. 
     These wheels,  20 ,  22 ,  24 , which are arranged one behind the other in the direction of forward travel F of the railway vehicle are housed in a box  26  which is formed with two half-elements, in the conventional way. The box  26  pivots about the axis of the axle  6 , the drive wheel  20  is secured to the axle whereas the other two wheels  22  and  24  are borne by the box. The three axes of the wheels  20 ,  22 ,  24  are arranged in a plane which is slightly inclined to the horizontal, but may be arranged differently according to the layout of the bogie. 
     The box  26  has a projection  28  extending transversely, arranged towards the rear end of this box  26  away from the axle  6 . A connecting rod  30  stretching roughly vertically, is mounted on spherical bearings both on the projection  28  of the box  26  and in a yoke  32  with which a cross member  34  of the body  14  is provided (FIG.  4 ). This connecting rod is depicted only in part in FIG.  2 . 
     Each drive assembly also comprises a motor, denoted overall by the reference  36 . This motor, which is powered by electrical means, not depicted, is housed in an approximately parallelepipedal housing  38 . This motor, which is transversely offset with respect to the reduction gearbox  18 , faces the opposite end of this reduction gearbox to the axle  6 . For reasons of clarity, the motor is not depicted in FIG.  2  and has been depicted in chain line in FIG.  3 . 
     The housing  38  is articulated, about a horizontal axis, to a cross member  40  of the chassis  10  of the bogie  4 . For this purpose, the housing  38  is secured to two arms  42 ,  44  articulated to yokes  46  with which the cross member  40  is equipped. The first arm  42  stretches longitudinally while the other arm  44  stretches obliquely, it being understood that the arms  42 ,  44  may be parallel. 
     The rotational movement of the motor is transmitted to the driven wheel  24  by a curved-tooth coupling  48  of a conventional type. 
     At its opposite end to the axle  6 , the box  26  is equipped with a flange  50  which projects both upwards and towards the motor. The latter, at its lower part, has a snout  52  which projects towards the reduction gearbox and comes vertically in line with the flange  50 . The flange  50  and the snout  52  are located one on each side of the driven wheel  24 . A link rod  54  is mounted, in spherical bearings, via its two ends, on the flange  50  and on the snout  52 , respectively. When viewed from the side this link rod is in the shape of a C and stretches near to the coupling  48 , on the opposite side thereof to the axle  6 . This link rod allows the motor to be articulated to the reduction gearbox. Advantageously, the flange  50  and the snout  52  are arranged in such a way as to be aligned with the axis of the driven wheel  24 , although a slight misalignment is acceptable. 
     As shown by FIG. 2, the chassis  10  of the bogie  4  is provided, on the opposite side of the axle  6  to the motor  36 , that is to say at its front end, with a tubular cross member  56  equipped with a linkage, not depicted, for disc brakes. This linkage is able to collaborate with discs  58  secured to the axle  6  and visible in FIG.  4 . 
     Referring again to FIG. 1, the center of gravity g of the reduction gearbox and the center of gravity g′ of the motor  36  are located, when viewed from the side, one on each side of the projection  28  which constitutes the point of articulation of the reduction gearbox  18  to the connecting rod  30 , and therefore to the body  14 . Furthermore, the moment exerted by the reduction gearbox on this projection  28  is approximately equal to the moment exerted by the motor  36  on this same projection. In other words, the product of the mass m of the reduction gearbox and the distance d separating the center of gravity g from the projection  28  when viewed from the side is approximately equal to the product of the mass M of the motor and the distance d′ separating, when viewed from the side, the projection  28  from the point of articulation of the motor to the reduction gearbox, namely the flange  50 . 
     As also shown in FIG. 4, the centers of gravity g, g′ are arranged, when viewed from above, one on each side of the projection  28  so that the latter lies pretty much at the center of inertia of the system formed by the motor and the reduction gearbox. 
     In service, the relative displacements transversely and in curves of the body with respect to the axle are compensated for by means of the suspension connecting rod  30  which is mounted in spherical bearings at both ends. The relative displacements of the axle with respect to the chassis of the bogie are compensated for on the one hand by the arms  42 ,  44 , which have a small transverse travel and, on the other hand, by the connecting link rod  54 , which is mounted in spherical bearings at both ends. The reduction gearbox  18  is connected in terms of translation to the axle  6  which bears it. 
     FIG. 5 depicts an alternative form of the invention, in which the box  26  has a parting line P extending obliquely, so as to define two box elements  26 ′,  26 ″. The first element  26 ′ extends only near to the axle  6  and the wheel  20 , while the second element  26 ″, suspended by the connecting rod  30 , covers the wheels  22  and  24 . It is thus possible to remove the first element  26 ′ so as to remove the axle and its wheel  20  without having to operate on the wheels  22  and  24 , which remain suspended from the connecting rod  30 . 
     In the embodiments described hereinabove, the reduction gearbox  18  is suspended from the body of the vehicle, the motor being articulated on the one hand to the chassis of the bogie, and on the other hand, to the reduction gearbox. It is also conceivable to suspend the motor from the body, using a connecting rod similar to the connecting rod  30  depicted. In this case, the motor is also articulated to the chassis of the bogie and the reduction gearbox is suspended only from the motor, without being suspended directly from the body. 
     The invention makes it possible to achieve the aforementioned objectives. Specifically, it allows a significant part of the mass of the motor and of the reduction gearbox to be suspended vertically from the body. In this respect it should be noted that although the reduction gearbox and the motor are connected respectively to the axle and to the chassis of the bogie, they exert only light loads on these elements. Furthermore, the invention involves a very low number of mechanical parts because just one connecting rod allows the reduction gearbox to be suspended from the body, whereas another single link rod provides the mutual articulation between the motor and the reduction gearbox. These mechanical parts are robust, of simple design and of low cost. 
     The arrangement according to the invention generates very little transverse movement between the reduction gearbox and the motor. This guarantees optimum operation of the coupling that provides the transmission between this motor and this reduction gearbox and allows the mass of these elements to be reduced. Given that the reduction gearbox is longitudinally offset with respect to the axle, it is possible to place the braking discs on this axle, within the space which is thus available. 
     Arranging the centers of gravity of the motor and of the reduction gearbox respectively one on either side, when viewed from the side (FIGS.  1  and  3 ), of the point of articulation of the connecting rod for suspending the reduction gearbox, or the motor, from the body, is advantageous. This is because a configuration of this kind allows the moments exerted on this point of articulation both by the motor and by the reduction gearbox to compensate for each other. From this standpoint, it is particularly advantageous for these moments to cancel each other out, when the products of the masses of the reduction gearbox and of the motor, respectively, and the length of the corresponding lever arms are equal. 
     The fact that the center of gravity of the reduction gearbox and of the motor are arranged, when viewed from above (FIG.  4 ), one on either side of the point of articulation of the connecting rod for suspending the reduction gearbox or the motor is also advantageous. This gives the assembly formed by this motor and this reduction gearbox excellent stability in so far as this point of articulation is located pretty much at the center of inertia of this assembly.