???????As we all know, the front axle of the car is an important part of the car driving system. Today we will discuss the wear of the front axle and main components of the car driving system together:
(1) Automobile front axle fault characteristics
???????Deformation occurs in the vertical direction between the leaf spring seats of the front axle of the car, and most of the two leaf spring seats are upwardly bent, and the middle is bent downward, and the bending is about 4 °; bending deformation occurs in the horizontal direction, and most of the two leaf spring The seat is convex forward, and the convex peak is to the left. Twist deformation along the longitudinal axis of symmetry. Based on the plane of the right leaf spring seat, forward twisting and backward twisting each account for about 50%. The twisting angle of forward twisting is about 6 °; the twisting angle of backward twisting is 8 ° 3 (/ left and right; two kingpins The deformation between the hole axis, and most of the front twist of the pin hole axis, the torsion angle of the right pin hole is generally greater than the left pin hole; the distance between the two main pin hole axis and the longitudinal section of the leaf spring positioning hole axis changes (The part is bent and deformed), the right end is greater than the left end; the inclination angle of the kingpin changes a lot more than 8 °, and most of them are the increase of the camber angle, the increase is 2 ° 20 \-generally the change of the left kingpin hole is greater than that of the right kingpin hole The inclination angle of the kingpin hole increases (that is, the fist-shaped part bends upward), while the inclination angle of the right kingpin hole decreases (that is, the fist-shaped part bends downward); the positioning hole of the leaf spring seat is worn within 1 mm, which is irregular Round pit shape; the main pin hole is generally worn, the two ends of the main pin hole are worn more than the middle, the lower end is worn more than the upper end, the right pin hole is larger than the left pin hole; the forged front shaft of 45 # steel, the cracks are mostly on the right of the left leaf spring seat side.
(2) Cause of failure
???????Front axle damage analysis: vertical and lateral reaction forces produce bending moments in the vertical plane of the front axle, causing the middle of the front axle and the kingpin hole to bend vertically, near the leaf spring seat, near the kingpin hole and front The bending and bending stress of the central section of the shaft are large. When the car turns, the outward reaction force bends the front axis upward; the inner reaction force bends the front axis downward. China ’s traffic regulations stipulate that driving on the right, a small turn radius of the right turn, a large centrifugal force, which causes a large left suspension force and a large ground reaction force, so the bending moment is also large, which causes the left end of the front axle to bend upward Bending upwards than the right end, that is, the inclination angle of the left pin hole increases, and the inclination angle of the right pin hole decreases. The direction of the longitudinal force on the ground is from front to back, bending the vicinity of the kingpin backward. The generated torque twists the axis of the kingpin hole around the longitudinal section of the front shaft, causing the upper end near the kingpin hole to twist forward and backward at the lower end. The vehicle travels to the right and turns more, and when turning right, the speed of the right wheel is less than that of the left wheel, so the right wheel is subjected to a longitudinal force greater than that of the left wheel. The front and middle are twisted, and the right side is larger than the left side. This is also one of the reasons why the wear of the right kingpin hole is greater than that of the left kingpin hole, the axis of the right kingpin hole and the axis of the leaf spring positioning hole (or the symmetry point of the positioning hole) are greater than the left side. Because the vertical bending distance acting on the front axle is greater than the horizontal bending moment, the lateral wear of the kingpin hole and the upper and lower end faces is greater than the longitudinal direction; and due to the large upward force, the lower part of the kingpin hole wears more than the upper part.
The above forces act to bend and deform the front axle, so the distance between the axes of the kingpin holes becomes smaller.
???????The forces acting on the front axle cause the kingpin to twist in two directions in the hole. The front axle kingpin hole is in transitional fit with the kingpin system, and the central wedge-shaped cross pin controls the kingpin's vertical movement and rotation. When the front axle is stressed, the kingpin can only swing with the horizontal pin as the fulcrum. Due to the large swing at both ends, the upper and lower parts of the kingpin hole wear more than the middle. The wear of the flat spring seat plane, positioning holes and bolt bearing holes is mainly due to the relative movement of the leaf spring and the seat, the positioning pin and the bearing hole, and the bolt and the bearing hole when the automobile is in motion after the fastening bolts of the leaf spring are loosened Caused. Due to the complex and changeable forces on vehicles, their wear is irregular. As mentioned earlier, the stress on the front axle is complex and variable, with a large vertical bending moment. When the car brakes, the front axle load increases; when the car passes through the uneven road surface, the front axle is subjected to an impact load, thereby easily causing metal fatigue, and cracks are generated at the place where the bending stress is large.