The types of power transmission mainly include direct drive, gear transmission, chain drive and synchronous belt drive. These methods are widely used in various application scenarios. For example, in an automotive power transmission system, the power generated by the engine is transferred to the driving wheels through components such as the clutch, transmission, universal joint and transmission shaft, facilitating the movement of the vehicle.
Furthermore, all-electric vehicles powered by renewable energy employ a direct drive mechanism where the engine directly drives the wheels, converting electrical energy into power. This method is characterized by its efficiency and speed.
Wireless power transmission is a unique type of power transmission method. It uses radio waves to send energy from a power plant to a specific receiving device, converting it into electricity for use. Although this method is mainly used in specific scenarios such as wireless charging, it demonstrates the diversity and innovation of power transmission technology.
In the field of aviation, the power transmission system is a crucial component of aircraft engine design. The technical characteristics and application research of this system are of vital importance for improving the performance of aircraft engines.
Types of power transmission
| Type of power transmission | Description | Benefits | Disadvantages |
|---|---|---|---|
| Mechanical Transmission | It uses mechanical parts such as couplings, chains, sprockets, belts and pulleys. Includes gear, worm gear, belt, chain and gear train transmission. | Accurate and efficient, ideal for short-distance transmission, high reliability and long service life. | High manufacturing and installation costs, not suitable for long-distance transmission, no overload protection. |
| Electric drive | It uses electric motors to convert electrical energy into mechanical energy for machines and vehicles. | High precision, energy saving, precise control, environmentally friendly, reduced noise and cost saving. | – |
| Pneumatic Transmission | Employs compressed gas to transmit energy or information, suitable for harsh environments. | Fast action, quick response, low maintenance, clean environment, economical and automatic overload protection. | Affected by air compressibility, low working pressure, significant noise during high-speed exhaust, slower than electronic signals. |
| Hydraulic Transmission | Uses liquid as a medium to transmit energy and control. | Compact, allows continuous adjustments, fast response, easy integration with electrical control, safe and reliable. | Potential oil leaks, not completely incompressible, losses during oil flow, difficulties under extreme temperatures, require high precision in manufacturing. |
The table above summarizes the main aspects of each type of energy transmission, highlighting their main characteristics, benefits and limitations.
1. Mechanical transmission methods
(1) What is mechanical power transmission?
Mechanical energy transmission refers to products used to move mechanical parts, not to supply electrical energy. These products include couplings, chains and sprockets, belts and pulleys, and transmission components.
The mechanical transmission system is a crucial part of the machine tool. It is mainly driven by a ball screw, which is integrated into the moving shaft during the transmission process.
The machine tool is powered by a motor. The purpose of mechanical transmission is to transmit movement and force.
Commonly used mechanical transmission types include gear transmission, worm gear transmission, belt transmission, chain transmission and gear train.
The role of mechanical transmission is to transmit movement and force.
(2) Types of mechanical power transmission
The most common mechanical power transmission mainly includes: gear drive, turbo vortex drive, belt drive, chain drive, gear train, etc.
01. Gear drive
Gear transmission is the most commonly used transmission type in mechanical transmission.
It offers precise, efficient, compact, reliable and long-lasting transmission.
There are several different types of reducers classified based on various standards.
Benefits:
- Compact structure, ideal for transmission over short distances.
- Compatible with a wide range of speeds and peripheral powers.
- The transmission rate is accurate, stable and efficient.
- High reliability and long service life.
- Capable of transmitting motion and force between parallel axes, axes that intersect at any angle, and staggered axes at any angle.
Disadvantages:
- High manufacturing and installation precision and high cost;
- Not suitable for long-distance transmission between two axles;
- No overload protection.
02. Turbo Vortex Unit
Suitable for movement and power between two axes with vertical and non-intersecting spaces.
Benefits:
- Large gear ratio;
- The structure is compact.
Disadvantages:
- Large axial force
- Easy to heat
- Low efficiency
- One-way transmission only.
The main parameters of the turbine drive are:
- Module
- pressure angle
- Helical gear indexing circle
- Worm Indexing Circle
- Lead course
- Helical gear number
- Number of worm heads
- Transmission rate
03. Belt drive
A belt drive is a mechanical transmission system that uses a flexible belt, tensioned on pulleys, to transmit motion or power.
Belt drive typically consists of a driving wheel, a drive wheel, and an endless belt that is tensioned between the two wheels.
1) When the rotation direction of two axes is parallel, it is called open motion concept, center distance and wrap angle.
2) Belts can be divided into three categories based on cross-sectional shape: flat belt, V-belt and special belt.
3) The focus of its applications includes:
- the calculation of the transmission ratio;
- the calculation of belt tension analysis;
- the permissible power of the single V-belt.
Pros and cons of belt driving:
Benefits:
- Applicable to transmission with large center distance between the two shafts, the belt has good flexibility, can mitigate impact and absorb vibration;
- Slip during overload to avoid damage to other parts;
- Simple structure and low cost.
Disadvantages:
- The external dimensions of the transmission are large;
- The tensioning device is necessary;
- Due to slippage, a fixed gear ratio cannot be guaranteed;
- The belt has a short service life;
- Transmission efficiency is low.
04. Chain transmission
Chain drive is a mechanical transmission system that transmits motion and power from a sprocket with a specialized tooth shape to a driven sprocket with a similar tooth shape via a chain.
Including:
- active chain
- driven chain
- circular current
Benefits:
Chain drives have many advantages compared to belt drives,
- Inelastic slipping and sliding resulting in a precise medium gear ratio
- Reliable operation and high efficiency
- Large transmission power with strong overload capacity and small transmission size under the same working conditions
- Low voltage requirement and small pressure acting on the shaft
- Ability to work in aggressive environments, such as high temperatures, humidity, dust and pollution.
Compared to gear transmission, chain transmission featured:
- Low manufacturing and installation requirements;
- When the center distance is large, the transmission structure is simple;
- The instantaneous chain speed and instantaneous transmission ratio are not constant and the transmission is less stable.
Disadvantages:
The main disadvantages of chain drive are:
- Can only be used for transmission between two parallel shafts
- High cost
- Easy to use, easy to stretch, low transmission stability
- Additional dynamic loads, vibration, shock and noise are generated during operation
- It should not be used in a fast reverse gear.
05. Gear Train
A transmission system comprising more than two gears is called a gear train. Gear transmission can be classified into two types: common gear transmission and planetary gear transmission.
A planetary gear is a gear that undergoes rotational and axial movement within the gear train.
Gear train can be divided into two categories: fixed shaft train and epicyclic train.
The gear ratio of the train, which is the relationship between the angular velocity (or rotational speed) of the input shaft and the output shaft, is calculated by dividing the product of the number of teeth of all follower gears in each gear pair gears by the number of teeth of all driving gears.
In an epicyclic gear train, the planetary gear, which undergoes rotational and axial motion, is contrasted with the center gear or sun gear, which has a fixed axial position.
The gear ratio of the epicyclic gear train cannot be calculated directly and requires the use of the relative motion method (or inversion method) to convert the epicyclic gear train into a hypothetical fixed-shaft gear train.
Gear train characteristics include:
- Suitable for transmission between two distant axles;
- Can be used as transmission to achieve variable speed transmission;
- A higher gear ratio can be obtained;
- Achieve movement synthesis and decomposition.
2. Electric drive methods
Electric drive refers to the use of electric motors to convert electrical energy into mechanical energy to drive various types of production machines, transportation vehicles, and other items that require movement in daily life.
Benefits:
High precision: Servo motors are used as power sources, and the simple and efficient transmission mechanism consisting of ball screws and timing belts results in a repeatability error of 0.01%. This transmission method is used in bending machines.
Energy savings: Energy released during the deceleration phase of the work cycle can be converted back into electrical energy, reducing operating costs and requiring only 25% of the equipment power required for hydraulic drives.
Precise control: With the support of high-precision sensors, measuring devices and computer technology, precise control can be achieved according to set parameters, far exceeding the control accuracy of other control methods.
Environmental Protection: Lower energy consumption and optimized performance result in reduced pollution and noise, providing better environmental protection for the factory.
Reduced noise: Operating noise is less than 70 decibels, about 2/3 of the noise produced by a hydraulically driven injection molding machine.
Cost Savings: The cost of hydraulic oil and associated maintenance is eliminated and there is no need for hard or soft pipes, hydraulic oil cooling or reduced cooling water costs.
3. Pneumatic transmission methods
Pneumatic transmission uses compressed gas as the working medium and transmits energy or information through gas pressure.
Benefits:
Since air is the working medium in pneumatic transmission, it is relatively easy to obtain. The used air can be conveniently discharged to the atmosphere, eliminating the need for a recovered fuel tank and piping, as in hydraulic transmission.
Furthermore, the air's viscosity being very low (about one ten thousandth of that of hydraulic oil), it results in minimal losses and allows for easy concentration of gas supply and long distance transportation. Leaks in pneumatic systems also do not cause as much environmental pollution as hydraulic drives.
Compared to hydraulic transmission, pneumatic transmission offers fast action, quick response, low maintenance, clean working medium and no deterioration of the medium.
Furthermore, it has good adaptability to harsh working environments such as flammable, explosive, dusty, strong magnetic, radiation and vibration conditions, making it superior to hydraulic, electronic and electrical control systems.
Lastly, pneumatic transmission is economical and has automatic overload protection capability.
Disadvantages:
The stability of the working speed is affected by the compressibility of the air. However, the use of a gas-liquid connecting device provides satisfactory results.
Due to the low working pressure, generally 0.31 MPa, and the need to keep the structure size small, the total output force should not exceed 10 to 40 kN.
The high-speed exhaust generates significant noise, so a muffler is added to mitigate this.
The transmission speed of gas signals in pneumatic devices is slower than the speed of electrons and light within the speed of sound.
As a result, pneumatic control systems should not be used in complex circuits with numerous stages.
4. Hydraulic transmission methods
Hydraulic transmission is a method of transmitting power and control through the use of liquid as the working medium.
Benefits:
From a structural point of view, the four transmission modes have a force-compressed output power per unit weight and size and a large moment of inertia ratio.
However, hydraulic transmission has a smaller volume when transmitting the same power, is lightweight, has low inertia, has a compact structure and flexible layout.
In terms of performance, the hydraulic transmission allows continuous adjustments of speed, torque and power with a fast response time and a wide speed range of up to 100:1 to 2,000:1.
Control and adjustment are relatively simple, making it convenient to operate and labor-saving.
Furthermore, it is easy to integrate with electrical control and computer systems for automation.
In terms of use and maintenance, hydraulic components have good self-lubricating properties, are easy to protect against overload and maintain pressure, and are safe and reliable. Components are also easily standardized and generalized.
Hydraulic technology is known for its safety and reliability, and its plasticity and variability provide great flexibility in production, allowing easy changes and adjustments in the production process.
Furthermore, hydraulic components are relatively inexpensive and widely adaptable.
The combination of hydraulic technology with new technologies such as microcomputer control is becoming a trend in the world and constitutes “machine-electrical-hydraulic-light” integration, facilitating digitalization.
Everything has two sides, there are advantages and disadvantages. Hydraulic drives are no exception:
Disadvantages:
The relative movement of the surfaces in the hydraulic transmission leads to inevitable oil leaks, and the oil is not completely incompressible.
This can result in the lack of a tight gear ratio and make it unsuitable for use in machine tool drive chains such as threaded gears.
There are losses such as along loss, local loss and leakage during oil flow, leading to low transmission efficiency, making it unsuitable for long-distance transmission.
Hydraulic transmission faces difficulties under high and low temperature conditions.
To prevent oil leaks and meet performance requirements, hydraulic components need to be manufactured with high precision, which can create difficulties in use and maintenance.
Diagnosing failures in hydraulic systems can be challenging, especially in areas where hydraulic technology is not widely used. This often hinders the wider promotion and application of hydraulic technology.
Maintaining hydraulic equipment requires a certain level of experience and training hydraulic technicians takes more time.
What are the advantages and limitations of gear drive, chain drive and synchronous belt drive in modern industry?
The advantages and limitations of gear transmission, chain transmission and synchronous belt transmission in modern industry are as follows:
The main advantages of gear drive include: constant and highly stable instantaneous transmission rate, reliable structure, low noise, high power transmission efficiency, wide speed range, ability to achieve large transmission rate, compact structure and long life useful. Furthermore, gear drive is suitable for transmissions where the center distance between the two shafts is large, with good flexibility to cushion impacts and absorb vibrations; slipping when overloaded prevents damage to other parts, with simple structure and low cost.
The limitations of gear drive include: high environmental requirements, good lubrication conditions are required, it is not suitable for transmission between two shafts with a lot of dust or long distance, and high precision in manufacturing and installation is required.
The advantage of chain drive lies in its systematic analysis and description in its design, including the structure, principle, design calculation and tensioning aspects of various belt drives (flat belt drive, V-belt drive, belt drive narrow V, multi-wedge belt drive, synchronous belt drive, etc.).
Synchronous belt drive combines the advantages of chain, gear and triangle belt and is gaining attention with the development of the industry. Its characteristics include smooth transmission, high transmission efficiency and good product heat resistance.
Gear drive is widely used in modern industry for its high efficiency, high stability, suitability for large transmission rates and long service life, but it requires a higher environment and is not suitable for dusty or long distance applications. The specific pros and cons of chain drive and synchronous belt drive need to be analyzed based on the specific design and application scenario, but they all reflect modern industry's demand for efficient and stable transmission methods.
