GQZ Technology Knowledge: Improvement Scheme of Motorcycle Steering Bearing Structure
Hot tags: angular contact ball bearing(5)
Current situation and existing problems and angular contact thrust spherical plain bearing.
Abstract: in order to improve the bearing capacity of motorcycle steering bearing and reduce the manufacturing cost, an angular contact thrust spherical plain bearing is studied, which is comprehensively compared with the thrust angular contact ball bearing. It shows that the angular contact thrust spherical plain bearing has advantages in bearing capacity, structure, manufacturing cost and so on.
Key words: Motorcycle; steering bearing; thrust spherical plain bearing; improvement
Motorcycle steering bearing (hereinafter referred to as steering bearing) is a special bearing installed on the frame riser and front fork steering column. The motorcycle steering column is equipped with a limit stop, and the return angle of the steering handle is less than 45 °. The steering bearing only swings and bears the combined axial and radial loads dominated by axial loads. Due to the limitation of the radial size of the frame riser, the load capacity of the steering bearing is large. In order to facilitate the assembly and adjustment of the front fork, the steering bearing should have a certain centering function. There is no lubrication hole at the installation part of the steering bearing, so it is difficult to add grease during daily maintenance, and it is required to have self-lubricating function. In order to adapt to the fierce market competition, the manufacturing cost should also be low.
1. Current situation and existing problems
At present, thrust angular contact ball bearings are widely used in steering bearings. This type of bearings can meet the requirements of swing movement, centering function and general load, but for motorcycles with high load requirements, the bearing capacity is low. Due to the structure and processing technology of the steering bearing, the material utilization rate is low (generally about 40%), there are many processing procedures, and the cost is high; In addition, there is no self-lubricating function, which is difficult to meet the lubrication requirements of long-time driving.
In order to improve the bearing capacity of steering bearings, some motorcycle manufacturers use 32000 series tapered roller bearings. This type of bearing mainly bears radial load and can also bear axial load. Even if it can meet the requirements of axial load, it still has the following shortcomings: (1) it has no centering function, so it has high requirements for the geometric tolerance of motorcycle frame riser; (2) In order to adapt to the outer diameter of the bearing, the radial size of the frame riser needs to be increased, which increases the manufacturing cost; (3) The price is high. The above reasons make it difficult for motorcycle manufacturers to widely adopt. There are also motorcycle manufacturers trying to adopt 31300 series tapered roller bearings, which is also difficult to achieve because of the above reasons.
2. Angular contact thrust spherical plain bearing
Angular contact thrust spherical plain bearing is a kind of contact angle α The bearing with ∈ (30 °, 90 °) spherical sliding support bears the combined axial and radial load dominated by axial load. Under the same outer diameter size, it has large load capacity and is suitable for low-speed swing motion. Because the sliding surface of the bearing is a spherical surface, it can work normally when the coaxiality error between the supporting shaft and the shaft shell hole is large. If the bearing race adopts new composite materials, the bearing will have self-lubricating function.
2.1 Structure comparison
Figures 1 to 4 show the thrust angular contact ball bearings with four typical structures and the corresponding improved angular contact thrust spherical plain bearings widely used by motorcycle manufacturers at present. It can be seen from the figure that without changing the original bearing assembly size and pressure angle, the angular contact thrust spherical plain bearing can meet the dimensional requirements for the installation of motorcycle frame riser and front fork steering column.
2.2 Load comparison and analysis
Calculate the rated axial static load of the steering bearings corresponding to figures 1 to 4 according to GB/T4662-2003 rated static load of rolling bearings and GB/T8567-1997 rated static load of plain bearings. The calculation results show that whether steel / steel friction pair or steel /PTFE friction pair is used, the axial static load rating of angular contact thrust spherical plain bearing is several times that of point contact thrust angular contact ball bearing. There are two points to note here: (1) the groove curvature coefficient of the thrust angular contact ball bearing actually used is designed to be greater than 0.54, so the actual bearing capacity of the steering bearing is smaller than the calculated value; (2) In order to avoid the steel ball falling during the transportation of the assembly line and improve the efficiency of assembly ball filling, some motorcycle manufacturers have changed the full ball structure of the bearing to the structure with cage, which reduces the number of steel balls, so the actual bearing capacity is smaller than the calculated value.
Fig. 1 type 1 comparison diagram
Fig.2 type 2 comparison diagram
Fig.3 type 3 comparison diagram
Figure 4 type 4 comparison diagram
2.3 Process and cost analysis
The angular contact thrust spherical plain bearing has large load capacity and does not need to change the existing structural dimensions of the motorcycle frame riser and the front fork steering column, with good process inheritance; The shape of bearing parts is simple, easy to process, and the manufacturing cost is reduced. Because the articulated bearing has strong centering function, it has good adaptability to the large coaxiality error of the motorcycle frame riser, and reduces the manufacturing cost of the motorcycle frame. With the application of new composite engineering plastics with strong bearing capacity and self-lubricating function, if the race of angular contact thrust spherical plain bearing is injection molded, its features of complete functions, excellent performance, simple structure and low cost will be more prominent.
Based on the analysis of the current use status and existing problems of steering bearings, a steering bearing with angular contact thrust spherical plain bearing structure type is designed, which can meet the requirements of the current steering bearing assembly size and pressure angle, and has advantages in bearing capacity, lubrication, technology and manufacturing cost.
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In angular contact ball bearings the line of action of the load, at the contacts between balls and raceways, forms an angle with the bearings axis. The inner and outer rings are offset to each other and the bearings are particularly suitable for carrying combined radial and axial loads.
Angular contact ball bearings have inner and outer ring raceways that are displaced relative to each other in the direction of the bearing axis. This means that these bearings are designed to accommodate combined loads, i.e. simultaneously acting radial and axial loads.
The axial load carrying capacity of angular contact ball bearings increases as the contact angle increases. The contact angle is defined as the angle between the line joining the points of contact of the ball and the raceways in the radial plane, along which the combined load is transmitted from one raceway to another, and a line perpendicular to the bearing axis