Improved technology for articulated frame of ZL40/ZL50 loader

1. The raising of the question

The front and rear frames of the ZL40/ZL50 wheel loader produced by Linyi Construction Machinery Co., Ltd. adopt a hinged structure (see Figure 1). The structural difference of the upper hinge part is that the upper hinge part (axial direction) is floating positioning, while the lower hinge part (axial direction) is positioned through a spacer sleeve. Due to the large force on the hinge pin during the operation of the loader, poor lubrication conditions, and the influence of the accuracy of the end face of the hinge hole of the rear frame, it was damaged. For this reason, we have made improvements.

Defects of the original hinged structure

When the rear frame is subjected to boring machine hole processing on the T612 boring machine, due to the limitations of the equipment processing conditions, the φ end face needs to be feed in 2 to 3 times radially along the hole (each time the tool is manually adjusted). Due to the long extension of the boring bar, the large cutting force of the basic construction, and the influence of manual feed errors and other factors, This leads to the processed ends being different and the notched edges being denied to form a conical surface. As shown in Figure 2. In this way, the thickness dimension of 40°-0.1 at both ends may not be fully guaranteed. Therefore, during assembly, there will be a gap between the positioning surface and the outer ring of the spherical plain bearing. In addition, there is a gap between the rings. In addition, if the thickness dimensions of both end faces exceed the upper limit of the tolerance, there will be a gap between the outer ring of the spherical plain bearing and the end face of the flange. The existence of any kind of gap will change the force state of the spherical plain bearing, affecting its service life. In severe cases, it may cause the spherical plain bearing to crack, especially when the loader is in operation, it can lead to the overall axial movement of the rear frame. This changes the force state of the hinge pin and accelerates its wear.

(2) The axial positioning of the lower hinge pin is achieved by connecting the pad 7 with the bolt 9. However, after long-term use, it has been verified that this positioning is not very reliable. Due to the harsh working environment of the loader, especially under overload conditions, the hinge pin not only bears a large radial force but also a certain axial force and shear force, which can easily cause the bolt to loosen This leads to axial positioning failure.

3 Improvements

The improved hinge structure is shown in Figure 3. It has mainly been improved in the following three aspects.

The positioning method of the spherical plain bearing has been changed. Flange 3 is fixed and connected to the upper hinge plate of the frame through bolts 11. The phenomenon of relative up and down movement between the rear frame and the closing bearing occurs due to the difficulty in ensuring the size of the scraping surface between the connecting plate 6 and the lower part of the rear frame, eliminating the gap between the outer ring of the spherical plain bearing and the carbonyl surface of the flange.

(2) Extend the uniform joint pin, process the lower end into a thread, and accordingly configure the slotted nut 8. After tightening the slotted nut, fix it with the split pin 9 to prevent loosening. This way, the occurrence of faults such as the fracture of the spherical plain bearing and the breakage of the joint pin caused by the axial movement of the hinge pin due to the loosening of the bolts in the original structure is avoided.

(3) During assembly, based on the actual measurement conditions, add an adjusting gasket between the flange and the upper end face of the hinge hole. The specific measures are as follows: During assembly, after fastening the connecting plate to the end face of the rear frame hinge hole through bolts, insert the spherical joint bearing into the hinge hole to ensure that the outer ring end face of the spherical joint bearing is fully angular with the connecting plate. Then, measure the distance h2 from the upper end face of the outer ring of the spherical joint bearing to the upper end face of the rear frame hinge hole. Based on the difference Δh=(Δh=h2h1), select and adjust the thickness of the gasket. Keep the assembly clearance within a certain range, which ensures the assembly accuracy.

4 Effects

Since the use of the improved hinge structure, there have been no more faults such as hinge pins twisting and breaking or spherical plain bearings cracking.

This structural form is not only applicable to the hinge connection of the front and rear frames of loaders, but also to other types of construction machinery.