When consumers are buying a car, they often adhere to the more and better concepts. They think about the positive role of long-range spatial, and ignore the huge turn radius brought by long axis … … “Discover the problem, solve the problem” as the daily work of the engineer male engineer, naturally cannot let the bad feelings brought by the large turn radius, so the rear wheel steering system is born!
[123 In the urban road, the average width of the lane is about 3.2-3.5 meters. The ordinary B-class car for a car is around 4 meters in the steering wheel, the turning diameter is around 11.6 meters (as shown in the figure above, the turning diameter is turned down). This means that when you kill the steering wheel on the left side, the vehicle will cross the shackles of 3.5 lanes. In other words, when the lane is only satisfied with 4 lanes, the B-class car like the Magotan can complete the head. And if it is replaced with a D-Class D-class for a 5m-bus length of Audi A8L, the turning diameter will reach 12.6 meters directly, and it is necessary to complete the full full full full fullness of the 4 lanes.
Available in real life, it is simple to provide us with 4 lanes. More is the road to two-way dual lanes. At this time, whether it is a B-class car or a D-class car, I am afraid that the two cars can truly turn the head of 180deg;
In fact, the root cause of the vehicle turn diameter is because the car puts the task of the turn to the front wheel, which is equivalent to steering The front of the head is dragging a car that does not turn turns. The birth of the rear wheel steering directly solved the problem of the big car turned strength. When the curve is through the curve, if the front wheel of the vehicle is turned left, the rear wheel will move right toward the right. If you don’t understand, you can imagine the front wheel to turn the right 90deg; after the back wheel is turned 90deg; (as shown in the figure below), the whole trolley can turn around like a gyra!
Of course, the 90deg of the above; examples are just convenient for everyone. Regular production car in real life, the maximum steering angle of the rear wheel is also 10deg; Like the Mercedes-Benz S level, the rear wheel steering angle did 10de; therefore helped the car for 5 meters from the car, and the turn diameter was shortened by nearly 2 meters. Dotted with the flight, this car was only 4 meters 1 small car almost the same 10.8 m turn diameter! Such an exaggerated distance is shortened, enough to prove how immediate results are the actual effect of the rear wheel!
The rear wheel steering except that the turning radius can be greatly shortened at a low speed. It is also possible to make the driver’s operation and the gesture of the driver even more calm after the speed exceeds about 60 km / h. Everyone knows that when the speed of driving the vehicle is high-speed, the driver needs to go to the target lane before the change, but it needs to be slightly oppressed slightly after the change is completed, in order to let the front of the car return parallel to the lane status.
For the car, such a “one left right” direction operation can cause a fast weight transfer, thereby To a certain extent, the balance of the vehicle is somewhat, causing the dynamics of the body in the process of change to relatively unstable.
When the rear wheel steering system can reduce the weight transfer of the body by rotating with the front wheel. As shown in the figure above, the current wheel is turned left, and the rear wheel will turn left. At the same time, due to the change in the variability, the steering angle of the front wheel is usually small, so the rear wheels can basically do the same direction angle with the front wheel. This means that the car tail and the head will be synchronized to complete the change operation, which is equivalent to the whole vehicle is a pan-like. That is when the transformation is completed, the driver does not need to be like a rear wheel to turn the system model, and a small anti-steering wheel allows the front to move back. At the same time, the body also avoids the weight transfer of returning, making the change line movementMore stable, and also greatly enhance the comfort of the occupants in the car.
The birth of the rear wheel steering technology is also derived from the ultimate racing movement. However, it is different from the civilian cars that the rear wheel steering system is in the car, whether it is low speed or high speed, always in the opposite direction of the front wheel, and fundamentally solves the turning problem of the racing. Among them, the first race turned to the race is the 405 Turbo 16, under the blessing of black technology, this car broke the track record of the Pike Peak Mountaineering. However, since this rear wheel is always in opposite direction to the front wheel, it will directly lead to abnormalities at high speed, and the difficulty of driving is extremely difficult, so the rear wheel turns to reduce the effect of the push head, Limited to the racing field.
The rear wheel steering system is currently divided into two types: one is According to the speed of the vehicle, the rear wheel rotation direction is changed according to the speed of the vehicle; the other is the passive shape of the pure mechanical structure.
Active rear wheel steering is realized, in fact, with the front wheel The steering mode is almost the same, so let’s take a look at how the front wheel is turning. When we rotate the steering wheel, the steering column connected to the steering wheel will begin to rotate, which can drive the pinion of the tid of the column to rotate, and then driven by the pinion, the rack of the front wheel steering will be moved by left and right. The front wheel has an angle angle.
The difference in the active rear wheel steering is merely when the front wheel is turned, the driver’s hand rotates the physical rotation drive of the steering wheel. In order to detect the electrical signal driver of the rotation angle of the steering wheel. The reason why the use of electrical signals is used, rather than mechanical structures.One: First, because the front wheel has used the mechanical structure of the steering column, it is sufficient to ensure the safety of the vehicle; Both run logic, so it is more convenient to use electrical signal control. In addition, since the angle of the rear wheel is usually small, the rack of the wheel rotating will also be shorted accordingly.
The passive rear wheel steering, compared to the active operation Many simple. Among them, most of the rear wheel steadow is achieved by increasing the flexible rubber bushing between the suspension and the body. 
, for example, when the vehicle is turned to the left, the force moving backward moves the force to the right back hauspillar, At this time, due to the deformation of the bushing, the wheelbase between the rear suspension and the right front wheel will increase. The rear wheel will present the opposite angle to the front wheel, thereby reducing the head attribute of the vehicle.
Only, the bushing responsible for controlling the angle of the suspension is not imagined. Therefore, it is necessary to reach a certain speed after the passive rear wheel steering, that is, the lateral force is sufficient enough to take effect. For example, a passive rear wheel steering is rich, only when the speed exceeds 60km / h, the rear wheel can present the opposite angle with the front wheel. Therefore, the passive rear wheel steering is compared to the passive, and the passive type does not improve the minimum turn radius at the low speed of the vehicle.
Since the rear wheel steering can greatly reduce the turn radius when the vehicle turns It can also increase the control stability of the vehicle, then this has been born for more than 30 years of technology, why didn’t you spread the household car like a shift dock? The first question is expensive! Compared to a general model only requires a steering machine, there is a model of the active rear wheel steering, and a set of steering machines need to be installed separately in the rear wheelAdding gear rack steering system. Additional parts increase, it is bound to have an impact on the manufacturing cost of the vehicle.
Further, the rear suspension of the vehicle also has to change from the previous fixed, changed to a suspension system that can be rotated. To meet the needs of the rear wheel steering. There is also a premise that satisfying the rear wheel steering needs, it is to increase the rotatable rear suspension to increase two points that can be rotated (one cannot be active). It is equivalent to the post-suspended position, and a cost-high pre-hanging system is copied. Also don’t forget, these more parts are not a one-time consumption, because the active rear wheel steering function of the electric control structure may also increase the cost of the owner’s vehicle due to the problem of failure due to the problem of failure. As for the passive rear wheel steering system, it also causes an increase in the increase in post-maintenance costs because of the multi-flexible bushing.
Furthermore, the method of improving vehicle turn radius In addition to increasing the rear wheel steering system, it can also be left in front of the engine A larger steering angle, thereby reducing the turn radius. Therefore, from a macro perspective, you can draw the following conclusions: small, compact cars can be accepted because the turn radius can be accepted because the turning radius can be accepted; the medium car can pass Longitudinal engine, increase the way the front wheel corner is improved; it is like a large, large sedan, because the turn radius is too large, so the rear wheel steering system is not original standard, which is the original factory (overseas 5 ” Both the bobbin can select the rear wheel steering system). After all, it is basically a luxury brand, and their audience is usually less sensitive to selling prices and post-maintenance costs.
The car acts as a mature product that has been developed more than 100 years, in fact, each The cost of the car is allocated by the model and the pricing is strict. Therefore, under the manufacturing concept of “enough”, it can optimize the driving flexibility in the city, and improve the high-cost rear turn system of high-speed driving stability naturally cannot serve the prolidity, only “It is “the choice of the niche.