RAIL VEHICLE HAVING INCREASED SIDE-WIND STABILITY

[0001]The invention relates to a rail vehicle as claimed in the preamble of claim 1, according to which a rail vehicle is known for which a direction of travel is specified and which has a leading bogie at the front end of the rail vehicle in the direction of travel and a trailing bogie at the end of the rail vehicle facing counter the direction of travel, wherein the leading bogie and the trailing bogie are each equipped with an anti-roll support (stabilizer).

[0002]High-speed trains in particular are characterized by long, aerodynamically optimized and particularly lightweight car bodies. The aerodynamic characteristics combined with the lightweight construction, particularly in the case of end cars, makes them highly sensitive to side winds.

[0003]This problem can also occur with regional trains, especially if they are designed as double-decker vehicles which are by their very nature sensitive to side winds.

[0004]Proceeding therefrom, the object of the invention is to improve the design of a rail vehicle of the abovementioned type, used in particular as the leading end car of a multiple unit, so as to achieve increased side-wind stability for the rail vehicle.

[0005]This object is achieved by a rail vehicle having the features as claimed in claim 1.

[0006]Accordingly, the rail vehicle described in the introduction is characterized in that different roll stiffnesses are selected for the anti-roll stabilizers of the leading bogie and trailing bogie such that, when the rail vehicle is subjected to side wind, unequal wheel unloading on the leading and trailing bogie is counteracted.

[0007]The technical measures set forth in claim 1 are based on the insight that side wind acting on the rail vehicle results in differing degrees of wheel unloading on the front and rear bogie. The anti-roll stabilizers of the leading and trailing bogies are designed to ensure that these differences in wheel unloading are less pronounced than they would be if both bogies were designed to have the same roll stiffness. Consequently, the anti-roll stabilizers of the leading and trailing bogie are asymmetrically designed, i.e. they have differing roll stiffnesses that minimize differences in the wheel unloadings of the leading and trailing bogie.

[0008]The roll stiffnesses of the anti-roll stabilizers of the leading and trailing bogie are preferably selected such that wheel unloadings on the leading and trailing bogie are minimal when the rail vehicle is subjected to side wind. In this way, the effects of side wind on the running characteristics of the rail vehicle in side-wind conditions are minimized. The leading bogie and the trailing bogie can in particular be designed as internally mounted bogies.

[0009]The ratio of the roll stiffnesses of the anti-roll stabilizers of the leading and trailing bogie depends on the extent to which the wheel unloading between leading and trailing bogie is unequal when the vehicle is subject to lateral forces, e.g. a gust of wind. For example, if the relative wheel unloading on the leading bogie during a wind gust is 90% and on the trailing bogie 70%, a larger redistribution is required than e.g. if the relative wheel unloading were 90% at the front and 85% at the rear. The redistribution also depends on the aerodynamic properties (aerodynamic yaw or pitch moment and the longitudinal position of the rail vehicle's center of gravity). The unequal distribution of wheel unloading between the leading and trailing bogie is relatively constant over the speed of the rail vehicle, so that the redistribution between the leading and trailing bogie, achieved by means of the different roll stiffnesses, is effective over the entire speed range of the vehicle. In practice, the roll stiffness will be optimized for the speed at which the rail vehicle, particularly when deployed as the leading end car of a train, is most critically affected by side wind.

[0010]The roll stiffness of the anti-roll stabilizer of the leading bogie is preferably lower than the roll stiffness of the anti-roll stabilizer of the trailing bogie. This measure is based on the insight that the leading bogie is more critical than the trailing bogie in respect of its wheel unloading due to side winds. In particular, it can be observed that a critical average wheel unloading of 90% is achieved on the leading bogie at significantly lower wind speeds than on the trailing bogie. The reasons for this observation will be discussed in more detail below.

[0011]In principle, the anti-roll stabilizers with different roll stiffnesses can be either primary anti-roll stabilizers (disposed between the wheelsets and the bogie frame) or secondary anti-roll stabilizers. However, the anti-roll stabilizers of the leading and trailing bogies are preferably designed as secondary anti-roll stabilizers in each case, disposed between the car body of the rail vehicle and a respective bogie, particularly on the bogie frame thereof. To implement the invention, secondary anti-roll stabilizers are preferred, because stiffening of primary anti-roll stabilizers of both wheelsets on a two-axle bogie would restrict the relative twisting of the wheelsets, which can adversely affect the rail vehicle's running characteristics. This negative effect associated with the stiffening of anti-roll stabilizers does not occur in the same way if secondary anti-roll stabilizers are used.

[0012]In a preferred embodiment, the different roll stiffnesses of the anti-roll stabilizers of the leading or trailing bogie can be achieved by using torsion bars with different torsional stiffnesses for the anti-roll stabilizers of the leading and trailing bogie. Alternatively, the different roll stiffnesses of the anti-roll stabilizers of the leading and trailing bogie can also be achieved by using levers of different lengths between the torsion bar and the bogie frame in the anti-roll stabilizers.

[0013]The overall roll stiffness of the anti-roll stabilizers of the leading and trailing bogie preferably corresponds to an overall roll stiffness of the leading and trailing bogie having identical roll stiffnesses when the effect of side wind on the rail vehicle is taken into account. The advantage of this is that the rail vehicle's tilt coefficient (roll angle of the car body of the rail vehicle relative to the wheelsets in relation to the roll angle of the wheelsets; defined in EN 14363) remains unchanged compared to a rail vehicle that has not been improved in respect of its side-wind stability in the manner described here. The required overall roll stiffness is derived from the loading gauge to be maintained. The car body may only roll to the extent that the available loading gauge is not infringed.

[0014]Exemplary embodiments of the invention will now be explained in more detail with reference to the accompanying drawings in which:

[0015]FIG. 1 shows a perspective view of a car body of a rail vehicle

[0016]FIG. 2 shows a perspective view of a leading bogie of the rail vehicle according to FIG. 1,

[0017]FIG. 3 show a perspective view of a trailing bogie of the rail vehicle according to FIG. 1, 6

[0018]FIG. 4 shows a side view of the leading bogie of the rail vehicle of FIG. 1,

[0019]FIG. 5 shows a top view of the bogie according to FIG. 4,

[0020]FIG. 6 shows a perspective view of part of an antiroll stabilizer of one of the bogies of the rail vehicle according to FIGS. 1 and

[0021]FIG. 7 shows a perspective view of a lever arm of the anti-roll stabilizer of FIG. 6.

[0022]As an example of a rail vehicle with improved side-wind stability, FIG. 1 shows a front/leading end car of a multiple unit, said car comprising a car body 1, a leading bogie and a trailing bogie 3, wherein both bogies are designed as internally mounted bogies. FIG. 1 also shows the forces and moments acting on the car body 1 that are generated when the car body 1 is subjected to side wind, e.g. a lateral gust. A lateral force FW, y acts at the height of the top of the rail and thus produces a moment about the wheel-rail contact points of the bogies 2, 3.

[0023]The wind gust also produces a roll moment MW, x (rotation about the vehicle's longitudinal axis). This roll moment MW, x causes unloading on the windward-side wheels of the bogies 2, 3.

[0024]The rail vehicle's direction of travel is indicated by an arrow R.

[0025]In addition, a vertical force FW, z resulting from the application of side wind causes lifting of the car body 1 and, associated therewith, additional unloading of all the wheels of the bogies 2, 3. As well as the lifting described above (vertical force FW, z) and the roll moment MW, x, the wind acting laterally on the car body 1 also causes a significant moment MW, z about the vertical axis of the car body 1. This yaw moment MW, z acting on the car body 1 must be balanced by a force couple FMz, h and FMz, v at a connection between the car body 1 and the bogies 2, 3, cf. FIGS. 2 and 3. This force couple causes additional wheel unloading on the leading bogie 2 and reduced wheel unloading on the trailing bogie 3. This in turn means that the leading bogie 2 is more critical in terms of wheel unloading than the trailing bogie 3. A critical average wheel unloading of 90% is achieved on the leading bogie at significantly lower wind speeds than on the trailing bogie 3.

[0026]The bogies 2 and 3 have different roll stiffnesses in order to achieve improved side-wind stability of the car body 1. This will be explained in more detail below.

[0027]The bogies 2, 3 are each equipped with an anti-roll stabilizer 4, 5. The stiffness of the anti-roll stabilizer 4 of the leading bogie 2 differs from the stiffness of the antiroll stabilizer 5 of the trailing bogie 3 in being less than that of the anti-roll stabilizer 5 of the trailing bogie 3.

[0028]The design and operation of the anti-roll stabilizers 4, 5 will now be explained in more detail with reference to FIGS. 4 and 5. The anti-roll stabilizers 4, 5 are so-called secondary anti-roll stabilizers, which are articulated on one side to the car body 1 of the rail vehicle and on the other side to a bogie frame 6 of the bogie 2.

[0029]FIGS. 4 and 5 show, by way of example, the leading bogie whose anti-roll stabilizer 4 basically operates in the same way as the anti-roll stabilizer 5 of the trailing bogie 3. As will be explained later, measures have been taken solely to achieve different roll stiffnesses of the antiroll stabilizers 4 and 5, with the basic design of the anti-roll stabilizers 4, 5 remaining unchanged.

[0030]The anti-roll stabilizer 4 has a torsion bar 7, said torsion bar 7 being rotationally mounted on the car body, namely by means of two rotary bearings 8 which are attached to the underside of the car body 1. By means of horizontal lever arms 9 and vertical lever arms 10, the torsion bar 7 is articulated to the bogie frame 6 via a bogie-side bearing 11.

[0031]In the event of uniform compression of secondary springs 12 of the car body 1 on both sides of the vehicle, the torsion bar 7 rotates within the bearings 8, and no moment is generated. However, if a rolling motion of the car body 1 occurs, i.e. rotation of the car body 1 about its longitudinal axis, uneven compression arises on both sides of the car body 1. This causes the torsion bar 7 to twist, thereby counteracting the rolling motion of the car body 1.

[0032]FIG. 6 illustrates the forces FWa,l and FWa,r acting on the car body 1 that support the roll moment on the car body. This roll moment MW can be calculated via

$\begin{array}{cc}{M}_W={\phi }_W{c}_T\frac{w^2}{l^2}& \left(1\right)\end{array}$

where C_T is the torsional stiffness of the torsion bar 7 and φ_w is the roll angle of the car body 1. It is assumed that the car body 1 is torsionally stiff, so that the roll angle φ_w is the same on both bogies 2, 3. By modifying the torsional stiffness Cr, different roll moments can be achieved on the leading and trailing bogie. Due to a higher roll 6 stiffness on the rear anti-roll stabilizer 5 than on the front anti-roll stabilizer 4, the roll moment MW, x, see FIG. 1, is supported more strongly on the trailing bogie 3. Wheel unloading is redistributed from the leading bogie to the trailing bogie 3, while the total unloading of all the windward-side wheels of the bogies 2, 3 remains the same. The stiffness of the anti-roll stabilizers 4, 5 is adjusted so that the wheel unloading on the leading and trailing bogie is the same and both bogies 2, 3 are therefore used optimally to increase the side-wind stability of the car body 1.

[0033]In order not to change the tilt coefficient of the car body 1, the roll stiffness of the anti-roll stabilizers 4, 5 is modified so that the overall roll stiffness C_ges of the car body 1 remains constant. The following must therefore apply:

$\begin{array}{cc}{c}_{\mathrm{ges}}=\frac{4c^{+}+2c^{*}}{2c^{+}{c}^{*}}=\frac{2c_1^{+}+c_1^{*}}{2c_1^{+}{c}_1^{*}}+\frac{2c_2^{+}+c_2^{*}}{2c_2^{+}{c}_2^{*}}=\mathrm{const}.& \left(2\right)\end{array}$$\mathrm{with}$$\begin{array}{cc}{c}^{+}=c_{T,\mathrm{Prim}}\frac{w_{\mathrm{prim}}^2}{l_{\mathrm{prim}}^2}& \left(3\right)\end{array}$$\begin{array}{cc}{c}^{*}=C_{T,\sec }\frac{w_{\sec }^2}{l_{\sec }^2}& \left(3\right)\end{array}$

[0034]Starting from equal roll stiffnesses of the anti-roll stabilizers 4, 5, the roll stiffness of the anti-roll stabilizer of the leading bogie 2, for example, is reduced in order to increase the side-wind stability of the car body 1. As per equation 2 above, the roll stiffness of the trailing bogie 3 can be increased so that the tilt coefficient remains unchanged.

[0035]In one embodiment, a required increase or decrease in torsional stiffness for one of the torsion bars 7 can be achieved by increasing or decreasing the diameter of the relevant torsion bar 7.

[0036]An alternative option for increasing or decreasing the roll stiffness of the anti-roll stabilizers 4, 5 is to have a shorter or longer lever length 1 for the levers 9. This is explained with reference to FIG. 7.

[0037]Shortening or lengthening the lever length 1 is an effective method of modifying the roll stiffness of the antiroll stabilizers 4 and 5, as the lever length 1 is a quadratic function of the roll stiffness. In addition, when combined with the lifting of the car body 1, an additional positive effect arises:

[0038]The roll stiffnesses according to equations 2 and 3 assume small deflections of the anti-roll stabilizers 4, 5 about their neutral positions. However, in the event of strong side-wind gusts, the car body 1 is lifted by the uplift force FW, z, cf. FIG. 1, resulting in larger deflections of the secondary anti-roll stabilizers 4 and 5 of the bogies 2 and 3.

[0039]In the case of a car body 1 lifted by height h, a supporting force Fw acts on the torsion bar 7 over the lever length l_eff with

$\begin{array}{cc}{l}_{\mathrm{eff}}=\sqrt{l^2-h^2}.& \left(4\right)\end{array}$

[0040]This increases the roll stiffness according to equations 2 and 3. With the same lifting on the leading and trailing bogie 2, 3 and different lever lengths l (longer lever on the leading bogie, shorter lever on the trailing bogie), the roll stiffness on the trailing bogie 3 in the lifted state of the car body 1 increases more strongly than at the front. This supports the effect to be achieved, namely the redistribution of the wheel unloading on the leading bogie and on the trailing bogie 3 under side-wind conditions. As a result, the difference in the roll stiffnesses of the anti-roll stabilizers 4, 5 in the non-lifted state of the car body 1 is less than with the previously described modification of the roll stiffness via the diameter of the torsion bars 7.