Page 260 - Automotive Engineering Powertrain Chassis System and Vehicle Body
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CH AP TER 9 .1       Steering

































               Fig. 9.1-10 Rack- and- pinion steering by ZF; section through pinion gear, bearing and rod guide. The distance ring 18 is used for setting
               the plays, and the closing screw 16 is tightened against it. The O-ring 19 provides the damping function and prevents rattling noises.

               steering tube (Figs. 8.1-57, 9.1-24 and 9.1-29) making it  machining imprecision, which might occur when the
               easy to connect the two parts together. Using an in-  toothing is being manufactured or the steering rack
               termediate shaft with two joints (Figs. 8.1-49 and 9.1-26)  broached or the pinion gear milled or rolled. The surface
               enables the steering column to bend at this point in an  of the two parts should have a Rockwell hardness of at
               accident.Inthiseventtheentiresteeringgearisturnedwhen  least 55 HRC; the parts are not generally post-ground
               viewed from the side (i.e. around the y-axis).     due to the existence of a balance for the play. Induction-
                 Fig. 9.1-10 is a section showing how, on all rack and  hardenable and annealed steels such as Cf 53, 41 Cr 4
               pinion steering systems, not only can the play between  and others are suitable materials for the steering rack,
               the steering rack and the pinion gear be easily eliminated,  case-hardened steels such as 20 MnCr 5, 20 MoCr 4, for
               but it also adjusts automatically to give the desired  example, are suitable for the pinion gear. In order to
               damping. The pinion gear 21 is carried by the grooved  ensure a good response and feedback of the steering, the
               ball bearing 20; this also absorbs any axial forces. Ingress  frictional forces between guide-bearing 15 and gear rack
               of dirt and dust are prevented by the seal 31 in a threaded  3 must be kept as small as possible.
               ring 43 and the rubber cap 45. The lower end of the  Sealing the steering rack by means of gaiters to the
               pinion gear is supported in the needle bearing 23.  side (Fig. 9.1-9) makes it possible to lubricate them with
                 In a left-hand-drive passenger car or light van, the  grease permanently, and lubrication must be provided


               steering rack 3 is carried on the right by a plastic bearing  through a temperature range of  40 Cto þ80 C. It is
               shell and on the right by guide 15, which presses the  important to note that if one of the gaiters is damaged,
               steering rack against the pinion gear. On a right-hand-drive  the lubricant can escape, leading to the steering becoming
               vehicle this arrangement is reversed. The half-round out-  heavier and, in the worst case, even locking. Gaiters
               line of the guide 15 does not allow radial movement of the  should therefore be checked at every service inspection.
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               steering rack. To stop it from moving off from the pinion  They are also checked at the German TUV (Technischer
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               gear, when subject to high steering wheel moments (which  Uberwachungs Verein) annual vehicle inspection.
               would lead to reduced tooth contact), the underside of the
               guide-bearing 15 is designed as a buffer; when it has moved
               a distance of s   0.12 mm it comes into contact with the  9.1.2.4 Steering gear, manual with
               screw plug 16.                                     centre tie rod take-off
                 Depending on the size of the steering system, coil
               spring 14 has an initial tension force of 0.6–1.0 kN, which  As shown in Figs. 8.1-57 and 9.1-1, and as described in
               is necessary to ensure continuous contact between  Section 9.1.7.3.2, with McPherson struts and strut
               steering rack and pinion gear and to compensate for any  dampers the tie rods must be taken off from the centre if


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