Structure and transmission method
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Contrast Dimensions |
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Structural composition |
It consists of a worm (similar to a screw) and a turbine (similar to a gear but with a special tooth shape), the worm is the active part and the turbine is the driven part. |
It is composed of multiple gears, common types include spur gears, helical gears, bevel gears, etc., and can transmit in both directions (the driving part and the driven part are interchangeable). |
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Transmission direction |
It is usually a vertical staggered shaft transmission (the shaft angle is generally 90°), the worm rotates to drive the turbine, and the transmission direction is vertically crossed. |
It can be used for transmission of parallel axes (such as spur gears, helical gears), intersecting axes (such as bevel gears) or staggered axes (such as spiral gears). The transmission direction varies according to the gear type (parallel, intersecting or staggered). |
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Tooth surface contact method |
The tooth surface is in line contact, the contact area is larger, the transmission is smoother, but the friction loss is also greater. |
Spur gears have line contact, while helical gears, bevel gears, etc. have involute meshing, with relatively small contact area and higher transmission efficiency. |
Transmission characteristics
1. Transmission ratio
Turbine worm gear: The transmission ratio is large, and the single-stage transmission ratio is usually 10:1 to 80:1, or even up to 100:1, which is suitable for scenarios that require a large reduction ratio (such as cranes, elevator traction machines).
Gear: The single-stage transmission ratio is generally small (spur gears are usually 1:1 to 10:1, and helical gears can reach about 15:1). Large transmission ratios need to be achieved through multi-stage gear combinations (such as automobile gearboxes).
2. Transmission efficiency
Turbine worm gear: Due to the relative sliding between the tooth surfaces (the worm thread pushes the turbine teeth), the friction loss is large and the efficiency is low (usually 60%~90%, and the efficiency of self-locking worm gears is less than 50%).
Gear: Low friction loss and high efficiency (the efficiency of spur gears is about 90%~98%, and the efficiency of helical gears and planetary gears can reach more than 95%).
3. Self-locking property
Turbine worm: Some worms (such as small lead angle worms) are self-locking (the turbine cannot reverse drive the worm), which is suitable for scenarios that require anti-reversal (such as winches and elevator brakes).
Gears: Generally, there is no self-locking property (except for specially designed ratchet mechanisms), and additional braking devices need to be installed to prevent reversal.
4. Transmission stability and noise
Turbine worm: Line contact transmission and continuous meshing process, small impact, smooth operation, low noise, suitable for precision transmission or high-speed light-load scenarios (such as precision instruments, textile machinery).
Gear: Spur gear transmission has periodic impact and high noise; helical gears and herringbone gears can reduce impact and noise through involute meshing, which is suitable for high-speed and heavy-load scenarios (such as machine tool spindles and aircraft engines).
Typical applications of worm gears
Equipment that requires a large reduction ratio
Such as elevator traction machines (single-stage worm transmission achieves a large reduction ratio, and self-locking ensures safety) and machine tool feed mechanisms (precision control of displacement).
Scenarios where vertical staggered shaft transmission and stability are required
Such as ship steering gear (worm-driven turbine controls steering of rudder surface and reduces vibration), swing mechanism in metallurgical machinery.
Safety scenarios requiring self-locking
Such as winches for construction (prevent heavy objects from sliding down), worm-assisted mechanism in automobile steering system.
Typical applications of gears
High-speed and high-efficiency transmission
Such as automobile gearboxes (multi-stage gear combination realizes speed and torque change, with efficiency of more than 95%), wind turbine gearboxes (transmits high power and is impact-resistant).
Parallel or intersecting shaft transmission
Spur gears are used for simple transmission (such as printer transmission rollers), bevel gears are used for steering transmission (such as automobile differentials), and helical gears are used for high-speed scenarios (such as machine tool spindle boxes).
Precision transmission and indexing mechanisms
Such as clock gears (high-precision meshing ensures accurate timing), indexing heads of CNC machining centers (planetary gears achieve precise indexing).
