A bogie for a railway vehicle with drive motors and reduction units suspended from the chassis

Abstract: The bogie includes a chassis (5) comprising two U-shaped longitudinal members (6) each connected by means of a pin (7) to a structure (8) supporting the axle (9) of a wheel (10). A primary suspension assembly (11) for the bogie is arranged between the chassis (5) and the structure (8). The drive motor (12) for the wheel (10) is mounted on the structure (8) so that its centre of gravity lies substantially on the axis of the pin (7). The structure (8) also carries a speed reducer (20) for transmitting the drive from the motor (12) to the wheel (10).

Description: The present invention relates to a bogie for railway vehicles, including vehicles for light or conventional metropolitan networks. In railway vehicles it is important to reduce that portion of the weight of the bogie which bears directly on the wheels without interposed resilient suspension means, that is, to reduce the non-suspended weight of the bogie. In fact, as this weight increases, the bogie becomes more aggressive towards the tracks, increasing the stresses and vibrations transmitted to the latter when a train passes. This problem is more serious in the case of drive bogies, in which the weight of the bogie itself is increased by the presence of a motor, for example an electric motor, and the transmission required to transmit the drive from the motor to the wheels. Such a transmission normally includes a reduction unit and one or more couplings operable to compensate for relative movements between the motor and the axles. In order to reduce the aggressiveness of the drive bogie towards the track, bogies have been proposed which have their motors entirely suspended from the bogie chassis, but have the weight of the reduction unit bearing on the axle. Other prior art arrangements provide for the reduction unit to be entirely suspended from the bogie chassis. However these arrangements involve a complicated drive transmission between the reduction unit and the axle/wheel assembly. From the document DE-A-2 910 392, a bogie for a tramway vehicles is known, wherein each wheel is mounted on a structure carrying also the motion transmitting gears and the relevant motor. The structure is mounted on the chassis by means of an articulation pin, whereas the motor is mounted on the structure with its rotation axis perpendicular to the axis of the articulation pin. Therefore, a rotation of the structure around the articulation pin causes a corresponding oscillation of the motor, the geras and the motor axis perpendicularly to the articulation pin. The object of the invention is to provide a bogie for railway vehicles which is extremely simple and safe in operation, and eliminates the disadvantages of the prior art listed above. This object is achieved by the bogie for railway vehicles according to the invention, including a rigid chassis, at least two pairs of wheels with each wheel fixed to a corresponding axle, at least one of the wheels being driven by a corresponding drive motor, a structure articulated on the chassis and rotatably mounting the axle of said at least one driven wheel, said structure mounting said motor and transmission means for transmitting drive from the motor to the axle, and primary resilient suspension means between the chassis and the structure, said structure being articulated on the chassis by means of an articulation pin, characterised in that said motor is positioned on said structure with its axis of rotation coincident with the axis of said articulation pin, whereby the centre of gravity of said motor lies on the axis of said articulation pin. Such a bogie achieves the result of carrying the weight of the drive motor, or motors, so that they are entirely suspended while a considerable portion of the weight of the reduction unit is also suspended so that the transmission means do not have to absorb relative movements between the axle and the chassis due to the primary suspension of the bogie. The invention thus simplifies the problem, enabling the motor to be entirely suspended, the reduction unit to be semi-suspended and the drive to be transmitted directly from the motor to the reduction unit and from this to the wheel. In order to provide a clearer understanding of the invention, a preferred embodiment of the bogie is described here, purely by way of example and with the assistance of the appended drawings, in which: Figure 1 is a partial plan view of a railway bogie according to the invention; and Figure 2 is a section taken on the line II-II of Figure 1. With reference to Figure 1, the chassis of a railway bogie is generally indicated 5 and includes a pair of robust symmetrical longitudinal members 6, of inverted-U shape, of which only part of one is visible in the drawings. The longitudinal members 6 are connected to each other by at least two cross-members 4, each of which may be shaped, for example, like a tubular bar. The bogie includes two pairs of wheels 10. One end of a longitudinal member 6 is illustrated schematically in the drawings and a structure 8, commonly known as a "reduction unit" and which acts as a wishbone, is fixed to the said end by means of an articulation pin 7. The structure 8 encloses a speed reducer 20 and houses bearings 14 and 15 carrying an axle 9 on which a wheel 10 is mounted. In the example illustrated, the two wheels 10 are therefore independent. This is particularly useful both for high-speed railway vehicles and for vehicles for city and suburban lines which are often required to travel on tortuous networks. In fact, for high-speed vehicles, the independent wheels 10 avoid the risk of snaking movements caused by the cone angle of the wheel rims and therefore avoid any resulting transverse instability of the bogie. In vehicles for city or suburban lines, which have curves of a small radius, often down to 15 metres, bogies with independent wheels 10 eliminate the anti-steering effect of the axle 9, which is due to the different developments of the inner and outer tracks 13, and therefore any longitudinal slippage between the wheels 10 and tracks 13. In this way, any annoying flats are eliminated from the rolling face of the wheel, thus reducing the need for expensive re-turning of the wheels 10. A brake disc 16 is securely fixed to one end of the axle 9, in the case described the axle 9 inwards of the chassis 5. A brake calliper 17, acting on the disc 16, is carried by the structure 8. The usual primary suspension assembly for the bogie, generally indicated 11, is also fixed to the ends of the longitudinal members 6. The assembly 11 includes, in particular, resilient suspension means of any type, operable to ensure the optimum suspension of the vehicle and acting through a fulcrum 21 on an arm 18 fixed to the structure 8. In addition, a drive motor 12 for the wheel 10 is mounted on the side of the structure 8 (Figure 1), its position being fixed so that its axis of rotation, on which its centre of gravity also lies, coincides with the axis of the pin 7 articulating the chassis 5 to the structure 8. The speed reducer 20 is operable to reduce and transmit the rotation from the shaft of the motor 12 to the axle 9 and thereby to the wheel 10. Therefore the weight of the motor 12 bears only on the primary suspension 11. In addition, the need is eliminated for any devices on the bogie to compensate for any relative movements between the motor 12 and the wheel 10 due to the primary suspension. The advantages of the bogie of the invention over prior art bogies will be apparent from the above description. In fact, as the centre of gravity of the motor 12 lies on the axis of articulation of the structure 8, the weight of the motor 12 does not bear on the axle 9 and therefore its mass does not have to follow the relative movement of the wheel 10 caused by the suspension. In addition, the fact that the geared drive transmission unit is carried by the same structure 8 as that which supports the motor 12, eliminates the need for devices to compensate for relative movements. Finally, the structure 8 is perfectly adapted for the independent drive of each wheel 10 of the bogie, thereby satisfying the requirements of high-speed vehicles and those of suburban vehicles. It is clear that alterations and improvements may be made to the bogie described without departing from the scope of the present invention.

Claims: A bogie for railway vehicles, including a rigid chassis (5), at least two pairs of wheels (10) with each wheel fixed to a corresponding axle (9), at least one of the wheels (10) being driven by a corresponding drive motor (12), a structure (8) articulated on the chassis (5) and rotatably mounting the axle (9) of said at least one driven wheel (10), said structure (8) mounting said motor (12) and transmission means (20) for transmitting drive from the motor (12) to the axle (9), and primary resilient suspension means (11) between the chassis (5) and the structure (8), said structure (8) being articulated on the chassis (5) by means of an articulation pin (7), characterised in that said motor (12) is positioned on said structure (8) with its axis of rotation coincident with the axis of said articulation pin (7), whereby the centre of gravity of said motor (12) lies on the axis of said articulation pin (7). A bogie according to Claim 1, characterised in that the said structure (8) supports an axle (9) on which a corresponding wheel (10) is fixed, the wheels (10) of a pair being driven by independent motors (12).

Inventors: CHIODI GIUSEPPE, CHIODI, GIUSEPPE
Applicants: CHIODI GIUSEPPE, CHIODI, GIUSEPPE
Application year: 1993
Main classification: B61F3
IPC codes: B61F3, B61C9