A Self-Acting Radial Bogie with Independently Rotating Wheels

Transcription

1 Cpyright c 2008 ICCES ICCES, vl.7, n.3, pp A Self-Acting adial Bgie with Independently tating Wheels CHI, Maru 1 ZHANG, Weihua 1 JIANG, Yiping 1 DAI, Huanyun 1 As the independently rtating wheels can individually rtate arund its axle while the axle itself nt rtated, s its axle can be made int cranked axle and thus the flr height f the vehicle can be lwered, therefre the independently rtating wheels are generally adpted in lw-flr light rail vehicles. As knwn, the lngitudinal creep frce plays a key rle in the guidance f wheelset, whereas the independently rtating wheels can t generate lngitudinal creep frces, s it has a pr guidance capability: n the tangent track, the independently rtating wheels usually run t ne side f the track and can t restre the center f the track; n the curved track, the independently rtating wheels have larger attack angle, which usually causes the flange cntact rail. Therefre, the independently rtating wheels nt nly causes serius wheel-rail wear but als increases the risk f derailment. In rder t slve the guidance prblem f independently rtating wheels, a selfacting radial bgie with independently rtating wheels has been put frward in this paper. Its sketch map is shwn in the brken line frame f figure 1. The bgie is made up f tw single-axle bgies linked by a flexible cupled machine, s it als is called as the flexible cupled bgie with independently rtating wheels. Figure 1: the sketch map f flexible cupled bgie with independently rtating wheels Accrding t the cntrastive cnditins f figure 2, the radial capability f the flexible cupled bgie with independently rtating wheels can be intuitively understd. Figure 2(a) shws the tw-axle bgie with independently rtating wheels running n a curved track. Since the N. cñand N. còwheelsets are cnstrained by the same frame, s the N. cñwheelset cme int being a psitive attack angle and 1 State Key Labratry f Tractin Pwer, Suthwest Jiatng University, Chengdu, China Crrespnding address: cmr2000@163.cm

2 142 Cpyright c 2008 ICCES ICCES, vl.7, n.3, pp k (a) Tw-axle bgie (b) Single-axle bgie (c) Flexible cupled bgie Figure 2: Cnditins f the three types f bgie with independently rtating wheels running n curve track N. còwheelset has a negative attack angle n the curved track, which indicates that the N. cñand N. còwheelsets can nt utspread enugh t achieve the radial psitin n the curved track. Figure 2(b) shws the case f single-axle bgie with independently rtating wheels running n a curve track. Since the N. cñand N. còwheelsets are nt cnstrained by the same frame but by the respective car bdies, s the N. cñwheelset cme int being a negative attack angle and N. còwheelset has a psitive attack angle n the curved track, which indicates that the N. cñand N. còwheelsets utspread t much t achieve the radial psitin n the curved track. By further analyses, it is knwn that the reasn why the frnt and rear wheelsets f the tw-axle bgie can nt utspread enugh t achieve the radial psitin n the curved track is that the cnstrain n wheelsets applied by the rigid frame is t great, while that f the tw single-axle bgies utspread t much t achieve the radial psitin n the curved track is the absence f sme necessary cnstrain between the tw wheelsets. Hwever the flexible cupled bgie can make up fr the drawbacks f the frmer tw types f bgies. When a apprpriate cupling stiffness fr the cupled bgie is chsen, the N. cñand N. còwheelsets wuld advisably utspread t achieve the perfect radial psitin n the curved track(shwed in figure 2(c)), which is just the intentin f the flexible cupled bgie with independently rtating wheels put frward in this paper. Hw t chse the apprpriate cupling stiffness fr the flexible cupled bgie with independently rtating wheels? Sme theretical analysis are dne as fllws: Since the primary suspensin stiffness f single-axle bgie is far greater than its secndary suspensin stiffness, therefre in theretical analysis, the frame and the wheelset can be cnsidered as a whle and the yaw mtin equatin f bgie can be written as fllws: [ I Bz ψ Bi +v d ( )] 1 = Mwzi +Mszi +Mczi (1) dt Bi

3 A Self-Acting adial Bgie with Independently tating Wheels 143 Where: i= 1,2,3,4;I Bz dentes the yaw inertia f single-axle bgie; ψ Bi is the yaw angle f single-axle bgie; v is the vehicle running speed; Bi is the radius f curved track; Mwzi is the yaw deflectin trque prduced by the wheel-rail frces; Mszi is the yaw deflectin trque prduced by secndary suspensin frces; Mczi is the yaw deflectin trque prduced by flexible cupled machine. When a train steady-state running n curved track, the left side f the equatin (1) is equal t zer, while n the right side, the yaw deflectin trque Mwzi which mainly generated by the the lngitudinal creep frce is very small and it can be ignred. S the equatin (1) can be written int: Mczi +Mszi = 0 (2) Mszi = 2b 2 s[ψ Bi ψc +( 1) i l ] (3) Mczi =( 1) i k ψ [( 1) i+1 ψ Bi ( 1) i+1 ψ B(i±1) + 2b ] (4) Where: i= 1, 2; dentes the ne side secndary suspensin lngitudinal stiffness; K ψ is the yaw angle stiffness due t the cupled machine; kcx is the ne side lngitudinal cupling stiffness between the frnt and back bgies; bs is half f the secndary suspensin lateral span ; bc is half f the cupled machine lateral span ; l is half f the nminal distance between frnt and back bgies centers; b is half f the cupled bgie wheelbase; is the radius f the circle curve; ψ B is the yaw angle f bgie; ψc is the yaw angle f car bdy. Cnsidering the displacement f the wheelsets and the defrmatin f the suspensins system are far shrter than the length f the nminal distance between frnt and back bgies centers2l, thus the central part f the car bdy is apprximately tangential with the circle curve, i.e.ψc 0. When a train steady-state running n a circle curve track, in rder t let the frnt and rear wheelsets f the cupled bgies achieve radial psitin cmpletely, must haveψ Bi = ψ B(i+1) = 0. S that, based n equatins (2) (4), we can btain: k ψ 2b = 2k sxb 2 s l (5) educes t k ψ = b 2 s l b k sx (6) It is knwn frm the equatin (6) that the cupling stiffness k ψ is nly relatinal with the inherent cnfiguratin parameters (such as l, b, bs, bc) f the train system and the secndary suspensin lngitudinal stiffness, yet irrespective t the external cnditin parameters(such as speed f the train and curve radius f the

4 144 Cpyright c 2008 ICCES ICCES, vl.7, n.3, pp track), which means that as lng as the cupling stiffness k ψ is selected accrding t equatin (6), whatever external cnditin(curve radius and speed)change, the leading and trailing wheelsets f the cupled bgie can run autmatically t radial lcatin by the crdinated peratin f the flexible cupled machine and the secndary suspensin systems f the vehicle. S the cupled bgie is als called as the self-acting radial bgie with independently rtating wheels.

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