Improvement of rear suspension support structure o

Structural improvement of the rear suspension support of dump truck

after the use of 20 French cbh320 dump trucks in our unit for three or four years, the fixing failure of the lower pivot of the rear suspension support generally occurred, resulting in frequent loosening, fracture and pivot fracture of the axle rod fixing bolts. It was found that the end surface of the mounting hole of the car connecting rod fixing bolt had been worn out, and the clamping part at the bottom of the support seat had been completely worn off. Reasons: first, the road conditions at the vehicle construction site are poor, and the pivot clamping part at the lowest end of the rear suspension support seat has been worn away due to repeated scraping and collision with the ground debris for a long time, and the holding force between the pivot journal and the seat hole disappears, resulting in looseness; Second, the axle connecting rod fixing seat (at the pivot end) adopts a combined structure. When the pivot is loose, its structural stiffness cannot be maintained, so it is easy to have bolts loose and broken. To repair these vehicles, the support seats and pivots on both sides must be replaced at the same time, and the cost of each vehicle accessory is as high as 60000 yuan. Or because the purity of water supply makes the long axis of the sample coincide with the tensile direction through the centerline of the fixture, it is decided to improve the pivot structure

1. cause of failure

the vehicle adopts a typical double rear axle balanced suspension system, and the weight on the frame is evenly distributed to the middle and rear axles in the vertical direction through the inverted leaf spring supported on the half axle of the suspension support; In the horizontal direction, two groups of parallel four-bar mechanisms are composed of six axle connecting rods (two in the upper part and four in the lower part), which respectively transmit the driving or braking force of the middle axle and the rear axle to the frame

the rear suspension support is mainly composed of the frame (the corresponding part has a reinforced beam), the support seats on the left and right sides and the lower pivot. The lower pivot plays the role of connecting the cantilever ends of the support seats on both sides, so that the whole support seat body forms a frame structure. The lower part of the pivot mounting hole at the lower end of the support seat is provided with a tightening groove and a clamping bolt. After the pivot is penetrated, two M14 × 1.5 bolt clamping; The pivot end is combined with the support seat and two semicircular cushion blocks to form a fixed seat of the axle connecting rod, in which the fixed bolt on the inner side passes through the support seat body and the pivot, while the fixed bolt on the outer side can only be fixed on the pivot end through two semicircular cushion blocks; The pivot is made of 82mm and 11mm thick steel pipe, and a bent yoke is pressed out of the middle section to avoid interference with the transmission shaft between axles

the looseness and fracture of the pivot between the pivot and the mounting seat hole are both caused by the failure of the clamping device (the clamping bolt and the clamping block have been worn off successively). Without the clamping force, when the journal and the mounting hole are loosened seriously due to intensified wear, the mounting bolts of the axle connecting rod frequently loosen and fracture, and the pivot and the support seat can only be welded to death by electric welding, but the risk of pivot fracture is increased. A few years later, the pivots of all these vehicles were seriously loose, and half of them had broken their pivots

the fundamental reason for the early damage of the rear suspension support and pivot is that the serious wear of the pivot clamping part is not found in time and effective measures are taken in time, but the original structure does have some unreasonable places. For example, the combined axle connecting rod fixed seat is easy to loosen the bolts due to its low structural stiffness; Because there is no pivot tightening device, although the connecting rod mounting bolt on the inner side passes through the support seat and pivot, it cannot play the role of fastening and locking, and the perforation diameter is 4mm larger than the bolt diameter, which completely fails to play the role of anti rotation and axial positioning. The connecting rod mounting support of other similar vehicles is made into one with the support seat, and the pivot is also firmly fixed, and such failure has never occurred

2. Improvement scheme

analysis shows that the maximum axial tension borne by the pivot is less than 80KN, and the maximum force borne by the horizontal direction of the axle connecting rod mounting support on each side is less than 60kn, so the requirement for the strength of the pivot is not high, as long as it can be reliably connected with the support seat to form a solid whole, it can meet the use requirements, and the axle connecting rod should be fixed on a single part entity. Therefore, it was decided to solve the problem by improving the original support seat and adding a newly designed pivot

the improvement of the support seat first planed the damaged part along the central horizontal plane of the pivot hole, and then machined two rows of six M18 screw holes on the planed plane. At the same time, planed the damaged end face on the outside and adjusted the seat hole to the specified length. Finally, it was equipped with a tile cover, fastened and re bored, that is, the fixing method was changed from the original clamping type to the tile cover type

considering the stress condition and manufacturing process, the pivot adopts a combined structure, which is composed of the middle section with a bent yoke (yoke shaft) and the connecting rod supports at both ends, and is connected as a whole with a flange. In order to ensure sufficient strength, personnel irrelevant to the operation of the testing machine are not allowed to operate the yoke shaft and connecting rod support. Both the testing machine and the bearing cap are made of zg40cr material and have been quenched and tempered; 80mm shall be used at the bending of yoke shaft × 80mm I-shaped section, the diameter of flanges at both ends is 156mm, and the thickness is 22mm; The diameter of the Journal of the connecting rod support is increased to 95mm, which forms an interference fit with the mounting hole on the support seat. The diameter of the connecting flange is 156mm and the thickness is 25mm; Six M16 are arranged on each pair of flange plates with a diameter of 128mm × 1.5 bolts

in addition, through two M16 × 1.5 tighten the bolts to connect the bearing cap and the journal as a whole. In order to ensure accuracy, the screw holes on the journal and the bolt installation holes on the bearing cap must be drilled and processed after the bearing seat, the bearing cap and the connecting rod support are assembled

in order to ensure the improvement quality, on the one hand, the processing (or improvement) quality of parts should be strictly controlled to ensure that its strength and accuracy meet the specified requirements, and at the same time, special attention should be paid to the installation quality to avoid accidents. First, ensure that the fit interference between the journal and the seat hole is between 0.14 ~ 0.18mm, so as to obtain sufficient assembly stress; Secondly, hexagon socket bolts with high quality and broad market prospects must be selected, and their strength level should be above 8.8. When installing bolts, the bolt holes should be thoroughly cleaned, a little lubricant should be coated on the threads and bearing surfaces, and then tightened according to the specified torque. After the vehicle is used for a few days, the fastening condition of the cover bolts and flange bolts must be rechecked

3. Effect

through the above modification, the structural stiffness of the rear suspension support is improved, and the defects of the original vehicle structure are completely eliminated. The improved vehicle has never had the original fault in use, indicating that the improvement is successful. The lower pivot bearing of the rear suspension support is responsible for towing the middle and rear axles and enhancing the structural stiffness of the whole suspension support. Looseness and fracture will pose a serious threat to the safe driving of the vehicle. The installation of bolts (especially the two sets of M18 pad cover bolts) is crucial to the improvement, so these bolts