How Mechanical Steering Gears Work

Mechanical steering gear (manual steering gear) is a mechanism that converts the rotation of the steering wheel into the swing of the steering rocker arm and amplifies the torque according to a certain transmission ratio. The function of the steering gear is to increase torque, reduce speed and change the direction of motion.

The rack and pinion steering gear is composed of driving gear, rack, compression spring, adjusting screw, pressure block and housing and other parts.

The working principle is: the torque and rotation acting on the steering wheel are transmitted to the driving gear through the steering transmission shaft, and the driving gear pushes (pulls) the rack to make it move, and finally drives the left and right tie rods to move, and causes the wheels to deflect Make a turn. The compression spring is compressed on the pressing block, which can eliminate the gear backlash. The pre-tightening force of the compression spring is adjusted with the adjusting bolt.

Because the rack and pinion steering gear has a simple structure, is easy to manufacture, and is convenient to adjust, it is widely used in passenger cars and commercial vehicles with a small load. Worm crank finger pin steering gear consists of worm, finger pin, rocker shaft, adjusting screw, housing and so on. Worm crank pin steering gear is now rarely used.

The spherical worm roller steering gear is composed of a worm, a roller, a crank of a rocker shaft, an adjusting screw, a rocker shaft, a steering gear housing and bearings. According to the number of roller teeth, it is divided into three types: double-tooth type, three-tooth type and single-tooth type.

Structurally, the spherical worm is provided with helical teeth meshing with the teeth on the rollers. The inner hole of the worm is equipped with a worm shaft, the two are fastened as one, and the upper end of the worm shaft is connected with the universal joint drive shaft and the steering wheel through a spline. The upper and lower ends of the worm are supported on the housing with bearings. The roller is supported on the crank part of the rocker arm shaft through the supporting shaft in the roller hole. Needle roller, ball or tapered roller bearings are installed between the support shaft and the rollers. The middle part of the rocker shaft is supported on the housing through sliding bearings or needle bearings, the upper end of the rocker shaft is equipped with adjustment screws, and the lower end is connected with the rocker.

The working principle is as follows: the driver turns the steering wheel, and the worm shaft and the worm integrated with it are driven to rotate through the steering transmission shaft. At the same time, the helical teeth on the worm will push the roller to rotate around the rocker arm shaft, and make the rocker arm linkage, and then push (pull) the straight pull rod to deflect the steering wheel to realize the steering of the car. The rollers can rotate on the support shaft. After the roller is worn, the gap between the teeth of the roller and the worm is eliminated by rotating the adjusting screw. This structure was widely used before the 1960s.

According to different structures, the recirculating ball steering gear is divided into two types: recirculating ball-rack and pinion type and recirculating ball-crank pin type.

①Recirculating ball-rack-and-pinion steering gear. There are two transmission pairs, that is, the screw rod, the steel ball and the nut form the first transmission pair, and the rack on the nut and the tooth fan of the rocker shaft form the second transmission pair. The screw rod in the first transmission pair is combined with a spiral raceway and the inner raceway on the steering nut, and the formed space just accommodates the steel balls that can roll on the raceway. In order to make the steel ball circulate repeatedly, a steel ball guide is installed on the nut. Both ends of the screw are supported on the shell by bearings. The tooth bar on the second transmission pair is made as a straight tooth and meshes with the whole outer cone-shaped tooth sector on the rocker arm shaft. The tooth segment is integrated with the rocker shaft, and is supported in the housing by the bearings at both ends of the shaft. At both ends of the rocker shaft, one end is equipped with an adjusting screw, and the other end is equipped with a rocker arm.

When the recirculating ball-rack-and-pinion steering gear is working, when the torque acting on the steering wheel is transmitted to the steering screw through the steering transmission shaft, the force is transmitted to the steering nut through the steel ball, and the nut moves along the axial direction. Then drive the gear fan through the rack on the steering nut, that is, drive the rocker shaft and the rocker arm to rotate, and push the straight tie rod to turn the steering wheel. Rotating the adjusting screw can make the rocker arm shaft move axially, and can change the meshing interval between the tooth sector and the rack, and it is required to achieve a gapless meshing.

②Recirculating ball-crank pin structure. It is basically similar to the recirculating ball-rack and tooth sector type, only the rack and tooth sector at the second transmission pair are changed to a finger-type structure to cooperate with the steering nut.

Recirculating ball-rack and pinion steering gears are widely used in commercial vehicles.