The vehicle axle (also known as the axle) is connected to the frame (or load-bearing body) through the suspension, and wheels are installed at both ends. Action: It is the suspension, not the axle, that transmits forces and moments between the frame and the axle (wheel). The function of the axle is to bear the load of the car and maintain the normal driving of the car on the road.

type: 

    The axle can be integral, like a huge barbell, and the body is supported by the suspension system at both ends, so the integral axle is usually matched with the non-independent suspension; the axle can also be disconnected, like two Umbrellas are inserted on both sides of the body, and then each supports the body through the suspension system, so the disconnected axle is used with the independent suspension.

According to the different driving methods, the axles are also divided into four types: steering axles, drive axles, steering drive axles and support axles. Among them, the steering axle and the supporting axle belong to the driven axle. Most cars use front rear drive (FR), so the front axle acts as a steering axle and the rear axle acts as a drive axle; while in a front-front drive (FF) car, the front axle becomes the steering drive axle and the rear axle acts as a support axle.

    The structure of the steering axle is basically the same, consisting of two steering knuckles and a beam. If the beam is compared to the body, the steering knuckle is his head swaying from side to side, the neck is what we often call the kingpin, and the wheels are mounted on the steering knuckle, as if wearing a straw hat on his head. However, when driving, the straw hat turns, but the head does not turn. The middle is separated by a bearing, and the head just sways from side to side. The neck - the kingpin is the axis of rotation of the wheel. The axis of this axis is not perpendicular to the ground, and the wheel itself is not vertical. We will discuss it in detail in the wheel positioning section.

    The difference between the steering drive axle and the steering axle is that everything is hollow, the beam becomes the axle housing, and the steering knuckle becomes the steering knuckle housing, because there are more drive shafts inside. This driveshaft becomes two half shafts because it is divided in two by the differential located in the middle of the axle housing. The two straw hats are not simply put on the head, but also directly connected to the two half shafts inside. The half shaft also has one more joint at the "neck" position - a universal joint, so the half shaft has also become two parts, the inner half shaft and the outer half shaft.

    According to the structure of the suspension, the axle can be divided into two types: disconnected and integral. The disconnected axle is a movable joint structure, which is used in conjunction with the independent suspension; the middle of the integral axle is a rigid solid or hollow beam. It is mostly equipped with non-independent suspension. According to the different movement modes of the wheels, the axles can be divided into four types: steering axles, drive axles, steering drive axles and support axles. Among them, the steering axle and the supporting axle belong to the driven axle. In general, the front axle of a car is mostly a steering axle, while the rear axle or the middle and rear axles are mostly drive axles; the front axle of off-road vehicles or most cars is both a steering axle and a drive axle, so it is called a steering drive axle; some single-axle drive axles The middle axle (or rear axle) of the three-axle vehicle (6×2) is the drive axle, then the rear axle (or middle axle) is the supporting axle.

Steering axle:

1) The function uses the swing of the steering knuckle to deflect the wheel to a certain angle to realize the steering of the car; bear the vertical load between the wheel and the frame, the longitudinal road resistance, the braking force and the lateral force and the moment formed by these forces.

2) Key indicators Due to the complex road conditions, the axle needs to have a certain stiffness and strength. The steering wheel has the correct positioning angle and proper steering angle. Minimize steering wheel mass and frictional resistance to transmission parts

3) Composition: front axle, steering knuckle, king pin and wheel hub, etc. Front axle: The cross section is generally I-shaped. In order to improve the torsional strength, there is a thickened part near each end to form a fist shape. There is a through hole in it. The king pin is inserted into this hole, and the middle part is bent downward into a concave shape. , its purpose is to lower the engine position, thereby lowering the center of mass of the car; expanding the driver's field of vision; reducing the angle between the transmission shaft and the transmission output shaft. Steering knuckle: It is the hinge that turns the wheel, it is a fork. The upper and lower forks have two coaxial holes for installing the king pin, and the steering knuckle journal is used to install the wheel. The two ears of the pin hole on the steering knuckle are connected with the fist-shaped parts at both ends of the front axle through the king pin, so that the front wheel can deflect a certain angle around the king pin to turn the car. Kingpin: The function is to articulate the front axle and the steering knuckle, so that the steering knuckle swings around the kingpin to realize the steering of the wheel. A groove is cut in the middle of the kingpin, and the kingpin fixing bolt is used to match the groove on it during installation to fix the kingpin in the fist-shaped hole of the front axle. The king pin and the pin hole on the steering knuckle are in dynamic fit to realize the steering hub: the wheel hub is supported on the journal at the outer end of the steering knuckle through two tapered roller bearings. The tightness of the bearing can be adjusted by adjusting the nut (installed on the outer end of the bearing).

Drive axle:

1. The function of the drive axle transmits the driving force from the engine to the driving wheels to achieve the effect of reducing speed and increasing torque, and at the same time changing the direction of power transmission.

2. The composition of the drive axle consists of the main reducer, the differential, the half shaft and the axle housing.

3. The difference between the installation position and structure of the drive axle of FF and FR FF: the clutch, transmission, main reducer, differential, and drive axle components are all installed in the transmission housing, located in the front of the car, and the power is transmitted to the front wheels . FR: The final reducer, differential, and drive axle components are installed in the drive axle housing, located at the rear of the car, and the power is transmitted to the rear wheels.

Steering drive axle:

1. Function: It has two functions of steering and driving. It not only has the basic components of the general drive axle, but also has the unique king pin of the steering axle.

2. The structure of the steering drive axle not only has the main reducer, differential and half shafts that the general drive axle has, but also has the steering knuckle shell, king pin and wheel hub that the general steering axle has. Compared with the separate drive axle and steering axle, the difference is that the half shaft required for steering is divided into two sections, namely the inner half shaft (connected with the differential) and the outer half shaft (connected with the wheel hub). connection), the two are connected by a constant angular velocity joint. At the same time, the main bridge is also divided into two sections, the upper and lower sections, which are respectively fixed on the spherical bearings of the universal joint. The knuckle journal is made hollow so that the outer half shaft can pass through it. The connecting fork of the steering knuckle is a spherical steering knuckle housing, which not only meets the needs of steering, but also adapts to the force transmission of the steering knuckle. Steering drive axles are widely used in all-wheel drive off-road vehicles

3. The working process of the steering drive axle is driven: the middle of the axle is equipped with a final reducer and a differential. The inner half shaft and the outer half shaft are connected together by a constant angular velocity universal joint, and the end of the outer half shaft is provided with a flower rod, which is engaged with the flange of the half shaft. When the front axle is driven, the torque is transmitted from the final reducer and differential to the inner half shaft, universal joint, outer half shaft and half shaft flange, and finally to the hub to drive the wheel to rotate. Steering: The steering knuckle is bolted together by the steering knuckle journal and the steering knuckle housing. The steering knuckle journal is equipped with two wheel hub bearings to support the wheel hub; the inner hole wall of the steering knuckle journal is press-fitted with a bushing to support the outer half shaft. The upper and lower ends of the steering knuckle shell are respectively equipped with the upper and lower thickened parts of the upper and lower king pins, and are stopped by stop pins. After the grease is injected from the upper and lower oil nozzles, it enters the central oil passage of the king pin respectively, and then comes out from the two side holes and enters between the king pin and the bushing to achieve lubrication. When the car is turning, the steering straight rod pulls the steering knuckle arm to drive the steering knuckle to swing around the king pin, and the steering wheel can be deflected accordingly, thereby realizing the steering of the car.

Support bridge:

    The supporting bridge belongs to the driven bridge. For single-axle-driven three-axle vehicles, the rear axle is designed to support the axle. The axle on the trailer is also the support axle. The rear axle of the front-drive car with the engine also belongs to the support axle.