The speed reducer is achieved by using a motor and a coupling.
There are various structural types of couplings used with speed reducers, such as: cross shaft type, ball cage type, ball fork type, cam type, ball pin type, ball hinge type, ball hinge plunger type, three pin type, three fork type, three ball pin type, hinge rod type, etc. The most commonly used is the cross shaft type, followed by the ball cage type.
A common characteristic of couplings is their large angular compensation. Different types of couplings have varying included angles between their two shafts, typically ranging from ≤5° to 45°. Couplings utilize their mechanism to enable continuous rotation of two shafts that are not on the same axis and have an included angle, reliably transmitting torque and motion. The key features of couplings are their large angular compensation capability, compact structure, and high transmission efficiency. In practical applications, they are categorized into heavy-duty, medium-duty, light-duty, and small-duty types based on the magnitude of the transmitted torque.
A coupling is a mechanical component used to connect two shafts (driving shaft and driven shaft) in different mechanisms, enabling them to rotate together and transmit torque. In high-speed, heavy-load power transmission, some couplings also serve to buffer, dampen vibrations, and improve the dynamic performance of the shaft system. A coupling consists of two halves, which are connected to the driving shaft and the driven shaft respectively. Generally, power machines are mostly connected to working machines by means of couplings.
There are many types of couplings. Based on the relative position of the two connected shafts and how that position changes, they can be classified as follows:
① Fixed coupling
It is mainly used in places where the two shafts need to be strictly aligned and there is no relative displacement during operation. The structure is generally simple and easy to manufacture, and the instantaneous speed of the two shafts is the same. The main types are flange couplings, sleeve couplings, and clamp couplings.
② Removable coupling
Primarily used in situations where two shafts are misaligned or experience relative displacement during operation, couplings can be categorized into rigid movable couplings and flexible movable couplings based on their displacement compensation methods. Rigid movable couplings utilize the mobility of the working parts between the coupling components to compensate for misalignment in one or more directions. Examples include jaw couplings (allowing axial displacement), cross-groove couplings (used to connect two shafts with minimal parallel or angular displacement), couplings (used where two shafts have a large misalignment angle or experience significant angular displacement during operation), gear couplings (allowing combined displacement), and chain couplings (allowing radial displacement). Flexible movable couplings (or simply flexible couplings) utilize the elastic deformation of elastic elements to compensate for misalignment and displacement between the two shafts. These elastic elements also possess buffering and vibration damping properties. Examples include serpentine spring couplings, radial multi-layer leaf spring couplings, elastic ring pin couplings, nylon pin couplings, and rubber sleeve couplings.
Some couplings are already standardized. When selecting one, first choose the appropriate type based on the working requirements, then calculate the torque and speed according to the shaft diameter, and then find the applicable model from the relevant manual. *Perform necessary verification calculations for certain key parts.
I. Coupling Functions
It is used to connect two shafts together. The two shafts cannot be separated while the machine is running. They can only be separated after the machine is stopped and the connection is disassembled.
II. Types of Couplings
The two shafts connected by a coupling may experience changes in their relative positions due to manufacturing and installation errors, deformation under load, and temperature variations, often making perfect alignment impossible. Based on factors such as the presence or absence of elastic elements, the ability to compensate for various relative displacements (i.e., whether the coupling maintains its connection function under relative displacement conditions), and its intended use, couplings can be classified into rigid couplings, flexible couplings, and safety couplings.
Rigid couplings can only transmit motion and torque and do not have other functions, including flange couplings, sleeve couplings, clamp couplings, etc.
Flexible coupling
Flexible couplings without elastic elements can not only transmit motion and torque, but also have different degrees of axial, radial, and angular compensation performance, including gear couplings, chain couplings, slider couplings, diaphragm couplings, etc.
Flexible couplings with elastic elements can transmit motion and torque, have varying degrees of axial, radial, and angular compensation performance, and also have varying degrees of vibration reduction and buffering effects, thus improving the working performance of the transmission system.
This includes various flexible couplings with non-metallic elastic elements and flexible couplings with metallic elastic elements. The structures of these various flexible couplings differ significantly, and their functions in transmission systems also vary. Safety couplings transmit motion and torque, and provide overload protection. Flexible safety couplings also offer varying degrees of compensation capabilities and include pin-type, friction-type, magnetic powder-type, centrifugal-type, and hydraulic-type safety couplings.
III. Selection of Couplings
The selection of couplings mainly considers factors such as the required shaft speed, load size, installation accuracy of the two connected components, smoothness of rotation, and price. By referring to the characteristics of various couplings, a suitable type of coupling can be selected.
When making a specific choice, consider the following points:
1. Due to manufacturing, installation, load deformation, and temperature changes, etc.
After installation and adjustment, it is difficult to maintain strict and precise alignment between the two shafts. There will be some degree of displacement in the x and y directions and a misalignment angle CI. When the radial displacement is large, a sliding block coupling can be selected; for large angular displacements or connections between intersecting shafts, a coupling can be used. When the two shafts generate a large additional relative displacement during operation, a flexible coupling should be selected.
2. The operating speed of the coupling and the magnitude of the resulting centrifugal force.
For high-speed drive shafts, couplings with high balancing accuracy, such as diaphragm couplings, should be selected, rather than sliding block couplings that have eccentricity.
3. The magnitude and nature of the torque to be transmitted, and the requirements for vibration damping function.
For example, gear couplings can be used for high-power, heavy-duty transmissions. For transmissions subjected to severe impact loads or requiring the elimination of torsional vibrations in the shaft system, tire couplings can be used.
The vast majority of couplings are standardized or pre-defined. The designer's task is to select, not to design.
The type of coupling should be selected based on factors such as the magnitude of the transmitted load, the shaft speed, and the installation precision of the two connected components. Referencing the characteristics of various couplings, a suitable type should be chosen.
When making a specific choice, consider the following points:
1) The magnitude and nature of the torque to be transmitted by the gear reducer, as well as the requirements for buffering and vibration reduction functions.
For example, gear couplings can be used for high-power, heavy-duty transmissions; for transmissions subject to severe impact loads or requiring the elimination of torsional vibrations in the shaft system, highly elastic couplings such as tire couplings can be used.
2) The operating speed of the coupling and the magnitude of the resulting centrifugal force.
For high-speed drive shafts, couplings with high balancing accuracy, such as diaphragm couplings, should be selected, rather than sliding block couplings that have eccentricity.
3) The magnitude and direction of the relative displacement between the two axes.
When it is difficult to maintain strict and precise alignment between the two shafts after installation and adjustment, or when the two shafts will generate a large additional relative displacement during operation, a flexible coupling should be selected. For example, when the radial displacement is large, a slider coupling can be selected; when the angular displacement is large, or when connecting two intersecting shafts, a coupling can be selected.
4) The reliability of the coupling and its working environment.
Couplings made of metal components that do not require lubrication are generally more reliable; couplings that require lubrication are more susceptible to performance issues due to the degree of lubrication and may pollute the environment. Couplings containing non-metallic components such as rubber are more sensitive to temperature, corrosive media, and strong light, and are also prone to aging.
5) Manufacturing, installation, maintenance and cost of couplings.
Under the premise of meeting the requirements of ease of use, couplings that are easy to install and disassemble, simple to maintain, and low in cost should be selected. For example, rigid couplings are not only simple in structure but also easy to install and disassemble, and can be used for low-speed, high-rigidity drive shafts. General non-metallic elastic element couplings (such as elastic sleeve pin couplings, elastic pin couplings, and plum blossom-shaped elastic couplings) are widely used in general medium and small power transmissions due to their good comprehensive capabilities.
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