1.The judgment method of rotation direction is the same
The spiral gear drive and the worm drive have the same method to judge the direction of rotation. The so-called direction of rotation refers to the direction of the thread or worm, or the spiral of the turbine, which is wound on the cylindrical surface. Both internal and external threads have left-hand and right-hand winding directions. The winding direction of worm and turbine is no exception, but also left-hand and right-hand. In the mechanical transmission, the right-hand thread is more commonly used, as well as the right-hand worm and the right-hand turbine. In the thread, usually trapezoidal thread is used for transmission. In essence, worm is also a special trapezoid thread, but its pitch is relatively large. Therefore, the spiral gear drive anddrive have the same method to judge the direction of rotation. The specific method is: extend the right hand horizontally to make the palm of the hand upward, keep the direction of the four fingers consistent with that of the thread and worm, and if the direction of the thumb of the right hand is consistent with that of the thread obliquely, then the thread and worm are right-hand thread and right-hand worm. If the direction of the thumb of the right hand is inconsistent with the diagonal direction of the thread, the thread and worm are left-hand thread and left-hand worm.
2.The judgment method of thread moving direction and turbine turning direction is the same
Common application forms of spiral gear drive: (1) the nut is fixed, mainly the screw rotates and moves axially; (2) the screw is fixed, mainly the nut rotates and moves axially; (3) the screw rotates and the nut moves axially. In the form of screw rotation and nut axial movement, both the left and right hand screw rules are used to judge the direction of nut movement and turbine steering in worm gear drive. The meaning of the left and right hand spiral rule is: left hand half clenches with left hand, right hand half clenches with right hand, keep the direction of four fingers consistent with the direction of worm or screw, judge the direction of turbine turning or nut moving through the opposite direction of thumb, and the direction of both is opposite to that of thumb.
3.Same driving conditions
The size of the worm gear teeth, in terms of modulus, is expressed in millimeters. The larger the module is, the larger the gear teeth of worm and turbine are, and the stronger the bearing capacity is accordingly. The size of thread profile is expressed by pitch. The unit of pitch is also mm. The size of pitch is directly proportional to the size of thread profile. Similarly, the larger the pitch, the stronger the bearing capacity. The transmission condition of worm and turbine must meet the meshing of worm and turbine. The condition of spiral gear drive must meet the screw and nut screwing. Only when the pressure angle and modulus of the worm are the same, and when the helix angle of the worm is equal to the helix angle of the worm, the worm can be meshed under the same rotation direction. As the same as worm drive, only when the tooth angle, pitch and direction of screw nut are equal, the screw nut can cooperate to realize the drive.
Spiral gear drive and worm gear drive also have the same point, that is, they have self-locking when the helix angle is small. In screw drive, rotation and movement are produced at the same time. With this feature, the self-locking of screw drive is such a case: no matter how much lifting weight, if the thread does not reverse, the screw will not automatically drop. A common example of the application of thread self-locking is screw jack. Worm gear drive also has self-locking property. The self-locking property of worm gear drive is the case that only worm can be the driving part of worm drive, while turbine can only be the driven part in worm gear drive. The transmission of worm can only be realized by the worm driving the turbine to rotate.
5.Are used as speed reducers
There are many kinds of threads, including single thread, double thread and multi thread. In spiral gear drive, single thread is commonly used. In the process of thread transmission, the nut moves with the rotation of the screw. When the multi thread screw rotates for one turn, the nut will move for a lead. The situation of single screw is different. When the single screw rotates for one turn, the nut can only realize one pitch movement. Because of its large reduction ratio, the spiral gear drive can be used as a reduction mechanism.
In essence, worm is a kind of trapezoidal thread with larger pitch. There are many kinds of worm, such as single line worm, double line worm and multi line worm. In the process of worm and turbine transmission, the turbine rotates with the worm. When the double worm and the multiple worm rotate for one cycle, the turbine can only realize the rotation of two to three teeth. The situation of single worm is different. When the single worm rotates for one circle, the turbine can only complete one tooth rotation. Therefore, the worm drive has a large transmission ratio, so the worm drive can also be used as a reduction mechanism.
6.Good transmission stability, but low efficiency
The spiral gear drive and the turbine drive are relatively stable, but the efficiency is low. Both kinds of transmission belong to vibration free transmission, and this transmission is continuous. Because it is vibration free transmission, there is no noise in the transmission process, and it has good stability. But the friction of two kinds of transmission belongs to sliding friction, so in the process of friction, there is a lot of resistance, which leads to low efficiency of transmission.
7.Same failure mode
In the process of worm gear drive, the sliding speed of the tooth surface is large, which leads to the serious phenomenon of thermal wear. The long-term thermal wear, coupled with the poor lubrication effect, is easy to cause serious wear, and ultimately leads to the failure of worm gear drive. The failure of the spiral gear drive is similar to that of the spiral gear drive. The failure of the spiral gear drive is mainly due to the wear between the thread teeth. In the process of spiral gear transmission, after a long time of wear, the thread will become thinner and the gap between the thread teeth will be increased, which will eventually lead to the failure of thread rotation. Therefore, the failure modes of worm rotation and thread rotation are the same.