I. Basic parameters of worm gear reducer:
Modulus m, pressure angle, worm diameter coefficient q, lead angle, number of worm heads, number of worm gear teeth, top height coefficient (take 1) and top clearance coefficient (take 0.2). Among them, the modulus m and pressure angle refer to the modulus and pressure angle of the worm shaft surface, i.e. the modulus and pressure angle of the worm wheel shaft surface, and they are all standard values; the coefficient of worm diameter q is the ratio of the diameter of the worm indexing circle and its modulus m.
Second, the geometry calculation is basically the same as cylindrical gears, a few issues to note are:
Worm lead angle () is the worm indexing cylinder on the helix of the tangent line and the worm end face between the angle, and the screw helix angle of the relationship between the helix angle of the worm wheel, the larger the transmission efficiency, when smaller than the equivalent friction angle between the meshing teeth, the mechanism of self-locking.
The introduction of worm diameter coefficient q is to limit the number of worm wheel hob, so that the worm indexing circle diameter is standardized m a certain time, q is large, the stiffness and strength of the worm shaft increases accordingly; a certain time, q is small, the lead angle increases, the transmission efficiency increases accordingly.
The recommended values for the number of worm heads are 1, 2, 4 and 6. When taking small values, the transmission ratio is large and self-locking; when taking large values, the transmission efficiency is high.
Unlike cylindrical gearing, the ratio of a worm and worm gear mechanism is not equal to, but rather, the center distance of a worm and worm gear mechanism is not equal to, but rather.
The determination of worm gear steering in worm gear transmission can be based on the direction at the meshing point K, the direction (parallel to the tangent to the helix) and should be perpendicular to the axis of the worm gear to determine the speed vector triangle; can also be used to determine the "right-handed worm gear left-handed grip, left-handed worm gear right-handed grip, the four-finger thumb".
III. Conditions for correct meshing of worm gears and worms
1, the modulus and pressure angle of the worm and worm gear in the middle plane are equal, i.e., the modulus of the end face of the worm gear is equal to the axial modulus of the worm and is a standard value; the pressure angle of the end face of the worm gear should be equal to the pressure angle of the worm gear's axial face and is a standard value, i.e., = = m, = = =.
2, when the staggered angle of the worm gear worm, but also need to ensure that, and worm wheel and worm helix rotation must be the same.
Fourth, the characteristics of worm gear and worm gear mechanism can get a large transmission ratio, than the staggered shaft helical gear mechanism is compact
Linear contact between the meshing tooth surfaces of the two wheels, whose load carrying capacity is much higher than that of the staggered shaft helical gear mechanism.
Worm drive is equivalent to spiral drive, for the multi-tooth mesh transmission, so the transmission is smooth and low noise.
Self-locking. When the lead angle of the worm is smaller than the equivalent friction angle between the teeth of the meshing wheel, the mechanism has a self-locking, can realize the reverse self-locking, that is, can only be driven by the worm wheel, but not by the worm wheel to drive the worm. Such as in its heavy machinery in the use of self-locking worm gear mechanism, its reverse self-locking can play a safety role.
Transmission efficiency is lower, and wear is more serious. Worm gear meshing transmission, the relative sliding speed between the meshing gear teeth is large, so the friction loss is large, low efficiency. On the other hand, the relative sliding speed of the Ambassador's teeth wear serious, serious heat, in order to dissipate heat and reduce wear, often using more expensive friction reduction and anti-wear materials and good lubrication device, and thus higher cost worm axial force.
V. Uses:
Worm gear and worm gear mechanisms are commonly used to transmit motion and power between two staggered shafts. Worm gears and worm shafts are equivalent to gears and racks in their intermediate planes, and worm shafts are similar in shape to screws.