During the driving process, a car often needs to change its direction. This requires a system for controlling the car's [http://www.hbjndf.com/] driving direction —— the car [http://www.hbjndf.com/] steering system. Depending on the type of steering energy used, the car [http://www.hbjndf.com/] steering system can be divided into two major categories: mechanical steering systems and power steering systems. The mechanical steering system consists of three main parts: the steering control mechanism, the steering gear, and the steering transmission mechanism. When the driver turns the steering wheel, through the steering shaft, steering universal joint, and steering drive shaft, the torque is input into the steering gear. After being amplified by the steering gear, the torque is transmitted to the steering rocker arm, steering tie rod, and steering knuckle arm, causing the left steering knuckle to rotate around the kingpin. At the same time, the left trapezoidal arm drives the steering cross rod, which makes the right steering knuckle rotate around the kingpin in the same direction, thus enabling both wheels on the left and right steering joints to turn simultaneously, achieving the car’s steering function.
The steering control mechanism is composed of components such as the steering wheel, steering shaft, and steering universal joint. The steering wheel, also known as the steering disc, usually has 2-3 spokes. The hub has round holes and key slots, and it is fixed onto the conical end of the steering shaft using keys and nuts. The steering wheel is equipped with a horn button.
The steering shaft is mostly made of seamless steel pipe. Its upper part is supported within the steering column using bearings or bearing sets, while its lower part is supported in the bearing inside the lower fixed bracket. A spring is installed below the bearing to automatically eliminate the axial clearance between the steering column and the steering shaft. The lower end of the steering shaft is connected to the steering universal joint. The lower end of the steering column is press-fitted into the hole of the lower fixed bracket, which is fixed to the bottom plate of the cab using two bolts. The upper end of the steering column is fixed to the instrument panel at the front of the cab through the upper bracket. On the left side below the steering wheel, there are signal light and headlight switch levers as well as lighting switches. On the right side below the steering wheel, there are emergency signal light levers, windshield wipers, and washer levers. The horn button is located in the center of the steering wheel.
In the event of a collision, the safety steering column allows the upper and lower flanges to disengage from their pin holes, limiting the rearward movement of the steering wheel and steering column, effectively protecting the driver’s safety.
### Structure of the Steering Gear
The function of the steering gear is to increase the steering torque transmitted from the steering wheel to the steering wheels and to change the direction of force transmission. There are many types of steering gears. According to their structural forms, they can be classified into recirculating ball, worm crank pin, spherical worm roller, worm gear, rack and pinion, etc. Based on the transmission of force within the steering gear, they can be categorized into reversible, irreversible, and limited reversible types.
#### 1. Structure of Recirculating Ball Steering Gear
A recirculating ball steering gear generally consists of two sets of transmission pairs: one set is the thread transmission pair, and the other set is the rack and pinion transmission pair or slider crank pin transmission pair.
The steering screw is supported in the housing by two thrust ball bearings. The pre-tightness of the bearings can be adjusted using adjustment shims. The lower plane of the steering nut is machined into a rack, which meshes with the pinion portion of the inner end of the steering rocker arm shaft. Therefore, the steering nut serves as both the driven component of the first-level transmission pair and the active component of the second-level transmission pair (rack and pinion transmission pair).
To reduce friction between the steering screw and the nut, their threads do not directly contact each other. Instead, numerous steel balls are placed between them to achieve rolling friction. Spiral grooves with a nearly semi-circular cross-section are machined on the outer cylindrical surface of the steering screw and the inner cylindrical surface of the steering nut, forming a spiral channel with a nearly circular cross-section when combined. The side of the nut has two pairs of round holes through which steel balls can be inserted into the spiral channel. Two steel ball guide tubes are mounted outside the nut, with each tube's ends inserted into a pair of round holes on the side of the nut, forming two closed tubular channels that contain a certain number of steel balls.
The lower plane of the steering nut is cut with inclined equal-thickness teeth that mesh with the pinion. The pinion is integrally formed with the pinion shaft and is supported by needle bearings. When the steering screw rotates, the steering nut moves left and right along the steering screw via the steel balls, driving the pinion to rotate around its axis.
#### 2. Structure of Worm Crank Pin Steering Gear
The transmission pair of the worm crank pin steering gear is the worm and the pin. Depending on the number of pins, it can be divided into single-pin and double-pin types. The steering worm has a trapezoidal thread and is supported in the steering gear housing by two turning shafts. An adjustment plug is installed on the lower cover of the housing to adjust the pre-tightness of the bearings. The steering worm meshes with two conical pins. The pins are supported on the crank of the steering rocker arm by double-row tapered roller bearings without inner raceways, allowing the rollers to directly contact the pin necks. Mounting the pins on the roller bearings reduces wear between the worm and the pins and improves transmission efficiency, making steering easier.
The steering rocker arm shaft and the crank are integrally formed and are supported in the housing by bearing sets. The outer end is equipped with a self-sealing oil seal to prevent oil leakage. The ends of the steering rocker arm shaft have markings that should align with the graduations on the steering rocker arm during assembly.
#### 3. Structure of Rack and Pinion Steering Gear
The rack and pinion steering gear consists of a pair of gears and a rack. The steering gear housing is made of a steel pipe with fittings pressed onto both ends and is fixed to the frame using two studs. The steering gear is vertically installed in the right fitting of the housing. The upper end of the steering gear is connected to the flexible universal joint on the steering shaft via a spline. The steering rack, which meshes with the steering gear, is horizontally arranged. A compression spring presses the rack tightly against the gear through a pressure block to ensure gap-free operation, with the preload of the spring adjusted by an adjusting screw. A connecting fork is mounted on the left end of the rack, which connects to the steering transmission mechanism. To avoid unbalanced air pressure in the dust cover when the rack moves, a dust cover vent pipe connects the chambers of the dust covers on both sides.
### Maintenance of the Steering Gear
#### 1. Maintenance of the Steering Gear
##### (1) Cleaning and Inspection of the Steering Gear
- **Cleaning and External Inspection**: Ensure the steering gear is securely fixed and shows no signs of oil leakage.
- **Inspection of Steering Wheel Free Play**: Place the vehicle in a straight-line position and attach the scale dial and pointer of the free-play checker to the steering column tube and the steering wheel respectively. Turn the steering wheel left and right; the angle that the steering wheel can turn without the steering wheels moving is the free play of the steering wheel. Excessive free play will make steering heavy, difficult to operate, and accelerate wear. Too much free play will reduce the sensitivity of the steering wheels, affecting driving safety. The free play of the steering wheel should not exceed 15~30 degrees; otherwise, adjustments are necessary.
##### (2) Adjustment of the Steering Gear
- **Adjustment of Free Play in Recirculating Ball Steering Gear**: Loosen the locknut on the adjustment bolt of the rocker arm shaft and turn the adjustment bolt until the free play meets the specified range (±15°), then lock the adjustment bolt.
**Note**: During adjustment, the steering must be securely fixed, the universal joint must not be loose, the joints of the steering tie rods must have normal clearances, and the clearances of the hub bearings and steering knuckles must be normal. Excessive axial clearance in the steering gear shaft can also cause excessive free play in the steering wheel, which can be adjusted by the adjusting nut.
- **Adjustment of Double-Pin Steering Gear**
- **Adjustment of Pre-Tightness of Planar Thrust Bearings for Steering Worm**: Before installing the rocker arm shaft into the housing, loosen the locknut and use a hex wrench to tighten the adjustment plug for the steering worm bearing at the bottom cover of the steering gear until it bottoms out, then back off 1/8~1/4 turn to give the steering worm a pre-tightening torque of 1.0~1.7 N·m at the input end, then lock it.
- **Adjustment of Pre-Tightness of Pin Bearings**: Clean the pin bearings and inject a small amount of lubricating oil into the bearing raceway. After installing the pin bearings into the bearing holes of the rocker arm shaft, adjust them using the pin adjusting nut so that they turn freely and have no axial clearance in the bearing. Flip up one or two teeth of the stop washer to make it snug against the flat side of the nut, then lock the nut. Adjust the pre-tightness of the pin bearings.
- **Adjustment of Steering Wheel Free Play**: Rotate the steering wheel to place the steering gear in the middle meshing position (vehicle straight-line position). Loosen the locknut of the adjustment screw on the steering rocker arm shaft and adjust the meshing clearance between the steering worm and the rocker pin. Tighten the adjustment screw all the way down, then back off about 1/8 turn. Finally, tighten the locknut and apply a small amount of sealant to the exposed part of the adjustment screw.
##### (3) Securing and Lubrication of the Steering Gear
- **Securing**:
- Secure the fixing bolts and nuts of the steering gear side cover, top cover, and bottom cover. The tightening torque for the upper and lower cover nuts is 30~40 N·m, and for the side cover, M10 is 30~40 N·m, and M14 is 70~100 N·m.
- Secure the connecting bolts and nuts of the steering gear to the frame, steering column tube, and universal joint fork lock pin. The tightening torque for the universal joint fork fixing bolts is 32~42 N·m for the Jiefang CA1092 type vehicle and 29~50 N·m for the Dongfeng EQ1092 type vehicle.
- Secure the fixing nuts of the steering transmission shaft and steering wheel.
- **Lubrication**:
- Check the steering gear lubricating oil every 8000 km and add lubricating oil as needed. In summer, the oil level should be flush with the lower edge of the oil filler hole, and in winter, it should not be less than 10 mm below the lower edge of the oil filler hole.
- Change the lubricating oil every 4800 km. Clean the steering gear and refill with new lubricating oil. The capacity should meet the specified standard: 0.9 L (GL-3 gear oil) for the Jiefang CA1092 type vehicle and 1.1 L (90 or 85W/90 gear oil) for the Dongfeng EQ1092 type vehicle.
- Lubricate the steering transmission shaft every 2000 km. Use a grease gun to inject grease until some new grease squeezes out at the sliding spline tail.
Hubei Jiangnan Dongfeng Special Automobile Co., Ltd. is a designated production factory by the National Development and Reform Commission, the only fire truck production qualification manufacturer in the special automobile capital by the Ministry of Public Security Fire Bureau, and a supporting modification plant of Dongfeng Automobile Company. The main products produced and sold include fire trucks [file:///D:/Program%20Files/信鸽博客群发专家/editor/网站/hbzycar/xiaofang/xiaofang.html], road clearance vehicles, aerial work platforms, wing-opening box transport vehicles, water sprinklers, fuel tankers, chemical liquid transport vehicles, refrigerated vehicles, blasting materials transport vehicles, flatbed transport vehicles, suction sewage vehicles, high-pressure cleaning vehicles, garbage trucks, road sweepers, dump trucks, crane-equipped transport vehicles [file:///D:/Program%20Files/信鸽博客群发专家/editor/网站/hbzycar/qinzhang/qinzhang.html], etc., hundreds of varieties. All models have been listed in the national announcement directory and have obtained ISO9001-2000 quality management system certification, and the products have passed CCC certification.
Phone: 18671079388 0710-3328659 3328629 (Fax)
Website: http://www.hbjndf.com[http://www.hbjndf.com/]
E-mail: [email protected]
Related Articles: How to better save lubricating oil for your beloved car 18671079388 Understand oil tankers well 18671079366