Gearboxes are mechanisms that serve to change the speed of rotation when transmitting rotary motion from one shaft to another. They differ among themselves by the type of transmission: worm gear, gear, hydraulic.
The main types of gearboxes
Helical gearboxes are one of the most popular types of gearboxes that are used in a variety of general industrial equipment. It is important to understand that the wrong gearbox selection results in significant economic losses and damages production. The key is the correspondence of the passport characteristics of the spur gearbox to the real operating conditions. The worm gearbox is characterized by a worm thread profile. This option is most often used to transfer motion between axes crossing each other. Its main advantage is the ability to obtain a large gear ratio. Also, these gearboxes are characterized by smooth running and quiet operation. Worm gearboxes are available in various versions: single-stage, two-stage, with a worm gear located above the wheel, etc. Planetary gearboxes are another popular type of this mechanism, the operation of which is based on the relative position of the electric motor and the output shaft. Their advantages are high efficiency and substantial durability.
Classification of gearboxes by type of speed change
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Automotive transmission is a step speed reducer. There are also gearboxes with smooth, stepless speed change. Such models are called variators. In mechanisms where it is necessary to transform a low angular velocity into a high one, gearboxes are used, which are called multipliers or accelerators.
Where are gearboxes used
Gearboxes find their application in all areas of mechanical engineering without exception, in automation equipment, in the construction of control systems and control devices, in information processing facilities and complex specialized equipment. The gear drive is one of the most common. Often, gearboxes are produced in unified system with an electric drive, such mechanisms are called
One of the most popular components of any industrial machinery is the gearbox. It is this node that is responsible for the stable operation of the transmission mechanism.
The main function of gearboxes is to reduce the transmission torque of electric motors.
Modern gearboxes are of two main types: worm and cylindrical, and differ in the type of mechanical transmission. But today we will focus on the first version of this unit.
One of the most important qualities of a worm gearbox is a high gear ratio (up to 100) and compact dimensions. But as a consequence of the high friction in the transmission mechanism, this type of gearbox is not used in tandem with a high-power engine.
The main transmission mechanism in this system is a worm - a screw, spiraling like a worm, and a gear wheel, which is driven by the worm.
We can say that a worm gearbox serves to convert torque.
Types of worm gearboxes
There are several types of these mechanisms. These include:
- single-stage
- two-stage
- combined gearboxes operating on the basis of a gear-worm gear
As for the rules for caring for these mechanisms, the worm gearbox needs frequent lubrication with viscous compounds. This condition is mandatory in order to increase its efficiency and ensure uninterrupted operation. The lubrication process is carried out manually by immersing the screw and wheels in a special container filled with a lubricant. At this stage, it is very important to correctly determine the level of immersion, which should correspond to the location. The screw itself should be immersed in the bath to the level of the coil.
Application of worm gearboxes
The worm gearbox is able to ensure smooth and absolutely quiet operation of the motors. Due to this quality, its application has become quite widespread in many areas of industry. It can be used in pumps and conveyors, lifts and electric gate drives, etc.
In other words, worm gearboxes are irreplaceable mechanisms where the task of increasing the torque with a simultaneous decrease in the speed of rotation is especially acute, provided that the frequency of switching on is small.
Types of drives and types of gearboxes
The drive of the machine occupies a special position in technology, because without it the mechanical movement of any device is impossible. The rational choice of the drive kinematic scheme and the correct kinematic power calculation largely determines such important requirements for the designed machines, such as an increase in power with the same dimensions, an increase in speed and productivity, an increase in efficiency, as well as a minimum weight and low manufacturing cost.
The most widely used in machines are mechanical drives. Moreover, their design solutions can be very different, so the designer's job is to find the best option that best suits the task at hand. General-purpose mechanical drives of all transmission mechanisms are most widely used in drives of technological and light transport machines. The generalized diagram of a mechanical drive of a working machine includes an engine, a transmission mechanism, a working machine and couplings. And since the angular velocities of the motor shaft and the drive shaft of the working machine, as a rule, are not equal to each other, a gear mechanism consisting of a set of mechanical gears is used for matching in a mechanical drive.
The gear drive is one of the most common types of modern mechanical systems for general industrial applications. The reducer is designed to reduce the angular speed of rotation and increase the torque. Ensuring the required functional parameters and reliability of the machine as a whole largely depends on the performance and resource of gearboxes and geared motors. The wrong gearbox selection can lead to significant economic losses due to unplanned downtime, increased repair costs, etc.
Interestingly, the invention of the multi-stage gearbox is attributed to Archimedes. The discovery of the principle of construction of mechanical gearboxes allowed the inhabitants of his hometown of Syracuse to "force one man" to move the enemy ships pulled ashore.
A modern gearbox is a complete mechanism that is connected to the engine and the working machine by couplings or open mechanical transmissions. The gearbox housing contains gear or worm gears fixedly mounted on the shafts. The shafts are supported by bearings located in the housing seats.
Gearboxes are classified according to the following main features:
Transfer type:
toothed,
worm,
gear-worm);
Number of steps:
single-stage,
two-stage, etc.
Gear type
cylindrical,
conical,
conical-cylindrical, etc.
The relative arrangement of the gearbox shafts in space:
horizontal,
vertical;
Features of the kinematic scheme:
deployed coaxial,
with a bifurcated step, etc.
Most often today, spur gearboxes are used that have high load capacity and efficiency: single-stage, two-stage expanded, bifurcated and coaxial schemes, three-stage expanded and bifurcated schemes. If the arrangement of the machine and the engine requires an orthogonal arrangement of high-speed and low-speed shafts (i.e., the axes of the shafts intersect at an angle of 90 °), then bevel or bevel-cylindrical two-stage and three-stage gearboxes are used.
With the coaxial arrangement of the working machine and the engine, planetary gearboxes * are optimal - the lightest and most compact with large gear ratios. But they cannot be used for precision mechanisms due to the difficulty of sampling gaps. In addition, the inertia of planetary gears is higher than that of cylindrical gears, due to the large moment of inertia of the carrier.
Reducers in which worm gears are used (worm cylindrical, globoid, spiroid, worm-cylindrical and cylindrical-worm gears) can provide a high gear ratio at a low noise level, but have low efficiency and resource. A gearbox and an electric motor are often combined into one sub-assembly called a geared motor. As universal drive elements, these units find their application in virtually all areas of industry. The use of geared motors can significantly simplify and reduce the cost of the drive design, reduce its dimensions, as well as the maintenance costs. The gearboxes are standardized and are serially produced by specialized machine-building plants. And since the needs of industries are very diverse, there are also many types of gearboxes.
The gearbox is a complex mechanism. It consists of worm or gears due to which the shaft of the working mechanism rotates.
Structurally, it consists of a body, which contains elements that transmit motion. These are gear wheels, shafts and others. Sometimes there may be additional devices in the housing to provide chain lubrication or cooling the necessary parts and knots.
Manufacturers produce a large number of units that differ in design and shape.
- cylindrical single-stage. In it, the axes of the driven and driving shaft are parallel;
- conical, in which the intersection of the axes of the shafts occurs;
- worm. In them, the axes in space intersect;
- combined mechanisms that combine gear and worm gears.
Depending on the number of gears, the reducer can be single-stage or multi-stage. This device is widely used by humans in all spheres of their activities.
It is included in the drive of various mechanisms. With its help, the angular speed of the output shaft is reduced. In some cases, the angular velocity must be different.
In order for this to happen, a special switching mechanism and several pairs of toothed rings with different gear ratios are placed in the housing. such a mechanism is known to everyone under the name - gearbox.
Worm gearboxes, advantages and purpose
Individual mechanisms in which the transmission of rotation is carried out in a special way include worm-type products.
They transmit torque using a worm gear. You can also hear the name helical gear.
This is because the main elements are a worm gear and a special screw called a worm.
This screw is really special as the thread profile is trapezoidal. For its manufacture, materials with high strength are used.
There are many varieties of this screw, but the most popular are one-, two-, and four-way products. Lead-in depends on how many thread channels there are on the product.
The worm wheel looks like an ordinary product. But it has a thread fitted to the shape of a worm screw.
For powerful worm gearboxes, the wheel is most often made of various materials. The teeth are most often made of antifriction metal, and cast iron or inexpensive steel is used to make the core.
These units are characterized by high efficiency and are used in those devices where it is necessary to achieve high torque and low angular speed.
This is achieved due to the design of the device. The leading link in the mechanism is the worm. This means that the torque is transmitted to the screw from the engine, after which the output shaft rotates.
Advantages of worm-type aggregates
Before you buy a worm gear, you need to know what advantages it has. Its main advantages include:
- smooth running;
- the noise level is quite low;
- has a self-locking effect;
- using just two elements gives a large gear ratio.
Its disadvantages include a low coefficient useful action, increased wear and due to frictional forces there is a large release of heat. Therefore, most often it is preferable to use such units in cases where the transmission of small capacities is required.
To prevent rapid wear of the device, high accuracy should be observed when assembling and adjusting the mechanism. And to remove excess heat, you will need to install special devices.
Types
There are various types of worm gearboxes that differ in specific criteria. They are subdivided according to:
- from the number of thread starts;
- how the threads are cut. It can be left and right-sided;
- from the shape of the screw. It can be globoid and cylindrical;
- from the shape of the thread profile. It can be convolute, Archimedean and involute;
Gear wheels are of various types. The profile of their teeth can be curved, straight and roller shapes. The latter uses a rotating roller instead of teeth.
These products represent a large group of mechanisms. Them distinctive feature is that the engagement is carried out using a spur gear transmission.
Depending on the distance between the axes of the output and input shafts, they can be coaxial and have parallel shafts.
In turn, the coaxial mechanism can be represented as a cylindrical one, or it can have two or more stages.
Products also differ in the way they are installed. For this purpose, special feet, flanges and nozzles are used.
Advantages of cylindrical models
The advantages of a helical gearbox are undeniable.
- They are distinguished by their high efficiency;
- They have an increased load capacity. They are able, practically without losses, to transmit large powers;
- They are distinguished by high kinematic accuracy;
- They work well both with uneven loads and with any number of starts and stops;
- These products do not have self-locking, so any of them has the ability to turn the output shaft;
- Due to the high efficiency, they heat up very little, as a result, almost all the energy is transferred to the consumer;
- Has good reliability;
- The large number of gear options allows you to select the most suitable gearbox for the required transmission movement.
They also have disadvantages. This is an increased noise level and a low gear ratio. The disadvantages include the lack of reversibility, but this is only if it is necessary that the external load output shaft does not have the ability to turn.
Use of helical gearboxes
With good advantages, cylindrical single-stage, as well as two- and three-stage mechanisms are considered the leader among such devices.
Products have found their application in metal-cutting machines, they are installed in mixers, grinders, rolls and other equipment.
There are practically no restrictions for their use, except for those cases when it would be more expedient to use other types of units.
For example, if there is a need for the mechanism to have a smooth running or an angular arrangement is needed in the drive. Spur gearboxes can be positioned horizontally and vertically.
The most popular is the horizontal installation of the cylinders. In general, the choice depends on how convenient the drive layout is.
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