1. Selection of gear and rack: the modulus is the value indicating the shape and size of the tooth shape of the gear. The bonding transmission can be carried out only when the modulus and pressure angle of the two gears are the same.
M = D / Z, where D is the diameter of the reference circle; Z is the number of teeth. The larger the modulus, the stronger the load capacity.
Common modulus: 0.5, 0.8, 1.0, 1.5, 2.0, 2.5, 3.0; According to the actual application, the load force * radius of reference circle * safety factor shall be less than the allowable transfer force.
Incidentally, the diameter of the reference circle, that is, the diameter of the dividing circle, affects the moving speed. The specific calculation formula is:
w=2 Π n/60
v=wr
Where W is the angular velocity and N is the rotational speed, in R / min; R is the radius of the dividing circle.
In practical application, we usually choose oblique teeth. As for the comparison between straight teeth and oblique teeth, oblique teeth have the following differences:
a. The operation is stable and the noise is low. Because only a part of each tooth surface participates in the meshing process of helical gear, or it is understood that each tooth gradually participates in the meshing and will not produce large vibration, the noise is low.
b. The bearing capacity of helical gears with the same modulus and width is higher than that of spur gears, because the effective tooth width of helical gears is larger in this case.
C. Because there are more meshing contact surfaces, the accuracy of oblique teeth is generally better than that of straight teeth of the same grade.
d. Because the helical gear has left-hand and right-hand rotation, the direction must be determined when cooperating with the rack. Generally, the left-hand gear cooperates with the right-hand rack.
e. Helix angle is a special feature of helical gear. Generally speaking, the helix angle of helical gear we usually refer to refers to the helix angle on the indexing cylindrical surface. The larger the helix angle is, the greater the coincidence degree is, which is more conducive to smooth movement and reduce noise. Everything has two sides. Although increasing the helix angle brings many advantages, the axial force generated during operation also increases. Therefore, the size of the helix angle should depend on the quality requirements and machining accuracy of the work. Generally, it is 8-25. If there are special requirements for noise, it can be taken as a larger value according to the situation.
2. Installation of gear rack: for long-distance transmission, when the rack is installed at the section, it must be installed with the gear gauge. In particular, rack suppliers usually leave two 7 holes at both ends. The purpose is to prevent the rack from moving in the later stage. I didn't use the actual pin holes in practical application, because the rack will be worn, and the accuracy in the later stage can't be reached, so it's difficult to debug. For gear installation, be sure to make a tensioning mechanism.
3. Lubrication and dust prevention of gear rack: during the long-term operation of gear rack, the accidental falling of foreign matters and inadequate lubrication will cause the wear of gear. Therefore, the dust prevention and lubrication of gear rack should be done well. The common dust prevention means is the sheet metal cover. Here, pay attention to the resilience of the sheet metal. The adjacent covers should be connected with the sheet metal, and the appearance of the products designed by ourselves should be at least acceptable. For lubrication, several points should be done: A. select the appropriate oil pump and select the appropriate oil pump according to the type of grease. The gear rack does not need oil at all times. Select different oil injection cycles according to different grease; b. Select the appropriate cotton wheel to avoid tooth profile mismatch;
