8.2. Forward suspension bracket

New steering




Fig. 7.1. Forward suspension bracket: 1 – body longeron; 2 – the bearing beam; 3 – shock-absorber cup; 4 – top cross lever; 5 – rotary fist; 6 – shock-absorber; 7 – a brake disk with a support; 8 – lower cross lever; 9 – twisted spring; 10 – case of a gear lath of steering; 11 – a steering shaft with a gear wheel; 12 – antisplash cover of steering draft; 13 – left steering draft


The design of a forward suspension bracket of the Mercedes E-class car is presented in fig. 7.1. Application of a modern two-lever design allowed to improve comfort, the directing function of a suspension bracket and a povorachivayemost of the car. Each forward wheel has an independent suspension bracket to a body.
Forward suspension bracket on dual cross levers. The similar scheme replaced a damping rack on the previous model. It is applied also on the S-models and the S-class. At this scheme the shock-absorber and a spring are installed separately. Thanks to dual levers shock-absorbers are exempted from function of the direction of forward wheels that allows them to carry out better the main objective — damping of fluctuations.
Cross levers.
The direction of each forward wheel is carried out by two (top and lower) triangular cross levers. The top lever 4 (see fig. 7.1) is connected directly to a body via the big rubber-metal hinge, and the lower lever is fixed on the bearing beam of the 2nd lobby of a suspension bracket.
Lower spherical hinge.
Twisted spring 9 and the shock-absorber 6 lean on a body via the so-called lower spherical hinge which has the changeable characteristic of elasticity, and become firmer with increase of force of damping.
Shock-absorber.
The separate arrangement of the shock-absorber defines accurate behavior of a wheel at working off of road roughnesses. The result of separate provision of a spring and the shock-absorber is swept well up in practice. For example, at the rectilinear movement or a side wind. Mercedes E-class does not deviate on each rutting on the road and deviates from a course at a sudden wind gust only a little.
The rubber elements of a forward suspension bracket counted on the computer with the two-lever scheme (the Latin designation DQ) allow change of the directions of wheels only in certain limits and by that significantly improve stability of behavior of the car when braking and passing turns. Thus, at depreciation corners of disorder and a convergence of wheels significantly do not change that positively affects the characteristic of resistance to swing and wear of tires. Suspension bracket geometry in combination with elastokinematiky the two-lever scheme guarantee the neutral or easily corrected car povorachivayemost that is for ensuring active safety with the immutable principle of Mercedes-Benz when designing the chassis.
Stretcher.
Unlike other automobile Mercedes models the lower cross levers and the steering mechanism of the E-class are fixed on the bearing beam of the forward suspension bracket having the frame form. This so-called stretcher will be tightened in turn to forward longerons of a body and facilitates installation of the engine and a forward suspension bracket at assembly of the car. Besides, it increases protection of passengers at front blow and serves for separation of a running gear from a body. Thus, thanks to a stretcher fluctuations and noise at the movement are less transferred to salon. On the stretcher support of the engine and steering are mounted.
Steering with a gear lath.

Fig. 7.2. Steering: 1 – rotary fist; 2 – right steering draft; 3 – case of a gear lath; 4 – a steering shaft (from two parts); 5 – pump of the hydraulic booster


Novelty in a design is installation of the lower cross levers in the direction forward. Besides, one more modernization was made — rack steering with the hydraulic booster replaced the predny scheme of steering like "screw nut" which did not correspond to the perspective concept of Mercedes-Benz on simplification of a design any more. In a new design of steering (fig. 7.2) there are no bipods, intermediate levers, a plate of rigidity and elements of fastening now. Steering drafts are connected to the steering mechanism without intermediate roundabout elements. The design, thus, provides correct and exact controllability.

Fig. 7.3. Schematical image of a convergence of wheels


Fig. 7.4. Angles of installation of a wheel: And – a corner of a longitudinal inclination; In – a disorder corner; With – a corner of a cross inclination


TECHNICAL DICTIONARY
 Terms of geometry of a suspension bracket
Convergence of wheels. The operated wheels a forward part are reduced to each other more, than back (have as if counter swing) (fig. 7.3). It levels friction force between a paving and a wheel which seeks to send the left wheel to the left side, and right — in right. The convergence interferes with vibration of wheels and unilateral wear of tires. When passing turn the wheel going on internal radius moves in the direction of turn for support of the rotary movement more and experiences big strain from influence of rotary effort, than a wheel of external radius, thus, the corner of a convergence changes on opposite (wheels are reduced by a back part more closely to each other).
Disorder. Defines an inclination of forward wheels in the vertical plane (fig. 7.4, V). Disorder of wheels reduces impact of road roughnesses on steering, reduces effort on a wheel and friction force of wheels about a roadbed.
Corner of a cross inclination of an axis of turn of a wheel. A corner between an axis of turn of a wheel and a vertical (see fig. 7.4, S). If to continue the line of this axis to the earth and to define distance from it to the central point of contact of a wheel with the road, then the running in shoulder turns out. It has to be as it is possible smaller to reduce influence of collateral forces on management. A corner of a cross inclination together with a corner of a longitudinal inclination exert impact that at the turned wheels the car rises a little, and at an otpuskaniye of a steering wheel forward wheels come back to average situation.
Corner of a longitudinal inclination of an axis of turn of a wheel. A corner between an axis of turn of a wheel at a side view and a vertical (fig. 7.4, A). Thanks to a corner of a longitudinal inclination in relation to forward wheels the traction, but not pushing effort is applied. For this reason wheels seek for saving the rectilinear provision.