The main feature of harmonic reducer is elastic deformation and small tooth shape. Therefore, the deformation must be controlled within the range of design requirements, and beyond the control range will cause the failure of the transmission device. In the power transmission, the control of elastic deformation is more important, and the tooth skipping phenomenon often occurs, which is also the key factor that the bearing capacity of many harmonic reducer transmission devices cannot be improved. Once the phenomenon of tooth skipping occurs, if measures are not taken in time, the transmission device will be damaged quickly.
The essence of tooth skipping problem is that in the system composed of rigid wheel, flexible wheel and generator, the radial meshing force will be generated in the teeth when the external load is applied. The rigid wheel, the flexible wheel and the generator are mutually supported, and each of them produces a certain amount of deformation. When the relative deformation between the rigid wheel and the flexible wheel exceeds the height of the gear teeth, the tooth skipping phenomenon occurs under the action of the tangential component force. When the load is large, the violent impact will produce a huge noise and damage the teeth.
There are three keys to controlling deformation. One is to control the load, so as not to overload unrestricted due to the large bearing capacity of harmonic drive; One is to strengthen the support; the other is to design the rigidity of relevant structures to avoid excessive deformation. Due to the complexity of the problem, it is difficult to obtain some simple and general calculation formulas. The following methods and measures can be adopted in the specific design.
1. The lack of radial stiffness of the rigid wheel is the key factor to cause tooth skipping. Under the condition of large load, the rigid wheel with poor radial stiffness will deform like the flexible wheel, which greatly reduces the bearing capacity. The radial deformation of the rigid wheel can be roughly estimated by referring to the radial deformation of the ring in the elastic force.
2. The support stiffness of the generator to the flexible wheel is also an important factor affecting the tooth skipping phenomenon. The test shows that when using the double contact wave generator, since there are only two fulcrums of the flexible wheel, it is difficult to control the deformation of the flexible wheel after the load is carried out, and the phenomenon of jump occurs when the load is small. When the four contact wave generator is used, the flexible wheel has four support points, and the support points are close to the action point of the external load, so the bearing capacity is improved. When the Thin-walled bearing generator is used, the control of deformation state is further improved, but the bearing capacity can be greatly improved due to the limit filling angle of the bearing. Under the condition of large load, the disc type wave generator can be used as the generator, which has a large control over the deformation of the flexible wheel. In particular, it is convenient to process and change the design parameters. The bearing used is also a standard bearing, so it has good processability.
3. Increasing the wave height within the allowable range is also an important means to solve the tooth skipping phenomenon. When the tooth skipping phenomenon occurs, the method of increasing the wave height is also an important means to repair, and the effect is relatively significant.
4. In the process of design, processing and installation, unilateral deviation will cause tooth skipping. When using the disc generator, special attention shall be paid to the symmetry of the eccentric shaft, otherwise it will cause the single side tooth to be loaded and cause tooth skipping.
5. In the structural design, the thickness of the anti bending ring can also be appropriately increased to control the deformation of the flexible wheel. In addition, reasonable tooth clearance and tooth crest correction should also be controlled during design.
The above is all about the key factors that can not improve the bearing capacity of the harmonic reducer drive device today. I hope it will be helpful for you to use this equipment in the future.
