大学生方程式赛车转向系统设计外文翻译资料

4．Steering

4.1 Steering system

4.1.1 Requirements

On passenger cars, the driver must select the steering wheel angle to keep deviation from the desired course low. However, there is no definite functional relationship between the turning angle of the steering wheel made by the driver and the change in driving direction, because the correlation of the following is not linear (Fig. 4.2):

bull; turns of the steering wheel; bull; alteration of steer angle at the front wheels; bull; development of lateral tyre forces; bull; alteration of driving direction.

This results from elastic compliance in the components of the chassis. To move a vehicle, the driver must continually adjust the relationship between turning the steering wheel and the alteration in the direction of travel. To do so, the driver

Fig. 4.1 Damper strut front axle of a VW Polo (up to 1994) with lsquo;steering gearrsquo;, long tie rods and a lsquo;sliding clutchrsquo; on the steering tube; the end of the tube is stuck onto the pinion gear and fixed with a clamp. The steering arms, which consist of two half shells and point backwards, are welded to the damper strut outer tube. An lsquo;additional weightrsquo; (harmonic damper) sits on the longer right drive shaft to damp vibrations. The anti-roll bar carries the lower control arm. To give acceptable ground clearance, the back of it was designed to be higher than the fixing points on the control arms. The virtual pitch axis is therefore in front of the axle and the vehicles front end is drawn downwards when the brakes are applied (Figs 3.142 and 3.143).

will monitor a wealth of information, going far beyond the visual perceptive faculty (visible deviation from desired direction). These factors would include for example, the roll inclination of the body, the feeling of being held steady in the seat (transverse acceleration) and the self-centring torque the driver will feel through the steering wheel. The most important information the driver receives comes via the steering moment or torque which provides him with feedback on the forces acting on the wheels.

Fig. 4.2 Delayed, easily manageable response of the right front wheel when the steering wheel is turned by 100° in 0.2 s, known as step steering input. A slip angle of af asymp; 7° on both front tyres is generated in this test. The smaller angle ar on the rear axle, which later increases, is also entered. Throughout the measurement period it is smaller than af (x-axis), i.e. the model studied by Mercedes Benz understeers and is therefore easy to handle.

Fig. 4.3 Synchronous steering A-bar on the front suspension of a left-hand drive passenger car or light van; on the right-hand drive vehicle, the steering gear is on the other side. The steering arm (3) and the pitman arm (4) rotate in the same direction. The tie rods (2) are fixed to these arms.

Fig. 4.4 Rack and pinion steering with the steering linkage lsquo;trianglersquo; behind the front axle. The spigots of the inner tie rod joints 7 are fixed to the ends of the steering rack 8 and the outside ones to the steering arms 3 (see also Figs 1.40 and 1.54).

It is therefore the job of the steering system to convert the steering wheel angle into as clear a relationship as possible to the steering angle of the wheels and to convey feedback about the vehiclersquo;s state of movement back to the steering wheel. This passes on the actuating moment applied by the driver, via the steering column to the steering gear 1 (Fig. 4.3) which converts it into pulling forces on one side and pushing forces on the other, these being transferred to the steering arms 3 via the tie rods 2. These are fixed on both sides to the steering knuckles and cause a turning movement until the required steering angle has been reached. Rotation is around the steering axis EG (Fig. 3.103), also called kingpin inclination, pivot or steering rotation axis (Fig. 1.3).

4.1.2 Steering system on independent wheel suspensions

If the steering gear is of a type employing a rotational movement, i.e. the axes of the meshing parts (screw shaft 4 and nut 5, Fig. 4.15) are at an angle of 90° to one another, on independent wheel suspensions, the insides of the tie rods are connected on one side to the pitman arm 4 of the gear and the other to the idler arm 5 (Fig. 4.3). As shown in Figs 4.12 and 4.36 to 4.38, parts 4 and 5 are connected by the intermediate rod 6. In the case of steering gears, which operate using a shift movement (rack and pinion steering), it is most economical to fix the inner tie rod joints 7 to the ends of the steering rack 8 (Fig. 4.4).

4.1.3 Steering system on rigid axles

Rack and pinion steering systems are not suitable for steering the wheels on rigid front axles, as the axles move in a longitudinal direction during wheel travel as a result of the sliding-block guide. The resulting undesirable relative movement between wheels and steering gear cause unintended steering movements. Therefore only steering gears with a rotational movement are used. The intermediate lever 5 sits on the steering knuckle (Fig. 4.5). The intermediate rod 6links the steering knuckle and the pitman arm 4. When the wheels are turned to the left, the rod is subject to tension and turns both wheels simultaneously, whereas when they are turned to the right, part 6 is subject to compression. A single tie rod connects the wheels via the steering arm.

Fig. 4.5 On rigid axles, apart from the two steering arms 3, only the tie rod 2, the idler arm 5 and the drag link 6 are needed to steer the wheels. If leaf springs are used to carry the axle, they must be aligned precisely in the longitudinal direction, and lie vertical to the lever 5 when the vehicle is moving in a straight line. Steering arm angle is an essential factor in the relationship between the outer and the inner curve steering angles.

However, on f

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The Automotive Chassis:

Engineering Principles

4．Steering

4.1 Steering system

4.1.1 Requirements

On passenger cars, the driver must select the steering wheel angle to keep deviation from the desired course low. However, there is no definite functional relationship between the turning angle of the steering wheel made by the driver and the change in driving direction, because the correlation of the following is not linear (Fig. 4.2):

bull; turns of the steering wheel; bull; alteration of steer angle at the front wheels; bull; development of lateral tyre forces; bull; alteration of driving direction.

This results from elastic compliance in the components of the chassis. To move a vehicle, the driver must continually adjust the relationship between turning the steering wheel and the alteration in the direction of travel. To do so, the driver

Fig. 4.1 Damper strut front axle of a VW Polo (up to 1994) with lsquo;steering gearrsquo;, long tie rods and a lsquo;sliding clutchrsquo; on the steering tube; the end of the tube is stuck onto the pinion gear and fixed with a clamp. The steering arms, which consist of two half shells and point backwards, are welded to the damper strut outer tube. An lsquo;additional weightrsquo; (harmonic damper) sits on the longer right drive shaft to damp vibrations. The anti-roll bar carries the lower control arm. To give acceptable ground clearance, the back of it was designed to be higher than the fixing points on the control arms. The virtual pitch axis is therefore in front of the axle and the vehicles front end is drawn downwards when the brakes are applied (Figs 3.142 and 3.143).

will monitor a wealth of information, going far beyond the visual perceptive faculty (visible deviation from desired direction). These factors would include for example, the roll inclination of the body, the feeling of being held steady in the seat (transverse acceleration) and the self-centring torque the driver will feel through the steering wheel. The most important information the driver receives comes via the steering moment or torque which provides him with feedback on the forces acting on the wheels.

Fig. 4.2 Delayed, easily manageable response of the right front wheel when the steering wheel is turned by 100° in 0.2 s, known as step steering input. A slip angle of af asymp; 7° on both front tyres is generated in this test. The smaller angle ar on the rear axle, which later increases, is also entered. Throughout the measurement period it is smaller than af (x-axis), i.e. the model studied by Mercedes Benz understeers and is therefore easy to handle.

Fig. 4.3 Synchronous steering A-bar on the front suspension of a left-hand drive passenger car or light van; on the right-hand drive vehicle, the steering gear is on the other side. The steering arm (3) and the pitman arm (4) rotate in the same direction. The tie rods (2) are fixed to these arms.

Fig. 4.4 Rack and pinion steering with the steering linkage lsquo;trianglersquo; behind the front axle. The spigots of the inner tie rod joints 7 are fixed to the ends of the steering rack 8 and the outside ones to the steering arms 3 (see also Figs 1.40 and 1.54).

It is therefore the job of the steering system to convert the steering wheel angle into as clear a relationship as possible to the steering angle of the wheels and to convey feedback about the vehiclersquo;s state of movement back to the steering wheel. This passes on the actuating moment applied by the driver, via the steering column to the steering gear 1 (Fig. 4.3) which converts it into pulling forces on one side and pushing forces on the other, these being transferred to the steering arms 3 via the tie rods 2. These are fixed on both sides to the steering knuckles and cause a turning movement until the required steering angle has been reached. Rotation is around the steering axis EG (Fig. 3.103), also called kingpin inclination, pivot or steering rotation axis (Fig. 1.3).

4.1.2 Steering system on independent wheel suspensions

If the steering gear is of a type employing a rotational movement, i.e. the axes of the meshing parts (screw shaft 4 and nut 5, Fig. 4.15) are at an angle of 90° to one another, on independent wheel suspensions, the insides of the tie rods are connected on one side to the pitman arm 4 of the gear and the other to the idler arm 5 (Fig. 4.3). As shown in Figs 4.12 and 4.36 to 4.38, parts 4 and 5 are connected by the intermediate rod 6. In the case of steering gears, which operate using a shift movement (rack and pinion steering), it is most economical to fix the inner tie rod joints 7 to the ends of the steering rack 8 (Fig. 4.4).

4.1.3 Steering system on rigid axles

Rack and pinion steering systems are not suitable for steering the wheels on rigid front axles, as the axles move in a longitudinal direction during wheel travel as a result of the sliding-block guide. The resulting undesirable relative movement between wheels and steering gear cause unintended steering movements. Therefore only steering gears with a rotational movement are used. The intermediate lever 5 sits on the steering knuckle (Fig. 4.5). The intermediate rod 6links the steering knuckle and the pitman arm 4. When the wheels are turned to the left, the rod is subject to tension and turns both wheels simultaneously, whereas when they are turned to the right, part 6 is subject to compression. A single tie rod connects the wheels via the steering arm.

Fig. 4.5 On rigid axles, apart from the two steering arms 3, only the tie rod 2, the idler arm 5 and the drag link 6 are needed to steer the wheels. If leaf springs are used to carry the axle, they must be aligned precisely in the longitudinal direction, and lie vertical to the lever 5 when the vehicle is moving in a straight line. Steering arm angle is an essential factor in

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