According to whether the transmission ratio of a pair of gear transmission is constant, it can be divided into fixed transmission ratio and variable transmission ratio gear transmission. The gears in the variable transmission ratio gear transmission mechanism are generally non-circular, so it is also called non-circular gear transmission. It is mainly used in some machinery with special requirements. The gears in the fixed transmission ratio gear transmission mechanism are all round, so it is also called circular gear transmission.
There are many types of fixed transmission ratio gear transmission. According to whether the rotation axis of the main and driven wheels are parallel, it can be divided into two types, namely, plane gear transmission and space gear transmission.
2. Classified by tooth profile shapeAccording to the shape of the tooth profile curve, it can be divided into involute gear transmission, cycloid gear transmission, arc gear transmission and parabolic gear transmission. Among them, involute gear transmission is the most widely used.
3. Classified by working conditionsAccording to different working conditions of gear transmission, it can be divided into closed gear transmission, open gear transmission and semi-open gear transmission. In the open gear transmission, the gear teeth are exposed and dust is easy to fall on the tooth surface; in the closed gear transmission, the gear teeth are enclosed in the box, which can ensure good working conditions and is widely used; the half-open gear transmission is more than open gear transmission working conditions Fortunately, the large gear is partially immersed in the pumping pool and has a simple protective cover, but there is still foreign matter intruding.
4. Classified by tooth surface hardnessAccording to the hardness of the tooth surface, it is divided into soft tooth surface gear transmission and hard tooth surface gear transmission. When the tooth surface hardness of the two wheels (or one of them) is less than or equal to 350HBW, it is called soft tooth surface transmission; when the tooth surface hardness of both wheels is both> 350HBW, it is called hard tooth surface transmission. Soft-tooth surface gear transmission is often used for general medium and low-speed gear transmissions that require less precision, and hard-tooth surface gear transmission is often used for gear transmissions that require strong load-bearing capacity and compact structure.
Although there are many types of gear transmission, involute spur gear transmission is the simplest and most basic type.
Selection principle of gear transmission type1) The requirements of the working machinery on the structure and power parameters of the transmission device, such as the size of the transmission device, installation position, power (or torque), speed, efficiency, etc.
2) The performance requirements of the working machinery for the transmission device, such as transmission accuracy, vibration, noise, load characteristics, and working reliability, etc.
3) Installation position, power, speed and load characteristics of power machinery.
4) The rationality, advancement, economy and versatility of the transmission device.
5) Manufacturing equipment conditions, production process level and required production batches.
6) The possibility of using the analogy method to select models, that is, refer to the use conditions and model selection experience of existing or similar machinery.
Generally, for general low-speed gears without special requirements, involute cylindrical gear transmission with parallel shaft structure is used as much as possible, because this type of transmission is relatively simple to manufacture, has strong versatility and low cost. For high-power (or high-torque) low-speed and heavy-duty gear units. Parallel shaft involute gear transmission or circular arc gear transmission with medium or higher gear accuracy can be selected.
Except for high-speed gears that only require low-speed transmission of motion, straight-tooth involute gears can be used. Generally, helical cylindrical gears are required to be used; for high-speed and heavy-duty transmissions, higher-precision helical or double helical gears should be used. Tooth involute gear or arc gear.
For transmission devices that require transmission of intersecting shaft structures, bevel gear transmission should be used. For light-load transmissions with lower speeds, straight or helical bevel gear transmissions can be selected, which is simple to manufacture and lower in cost. For low-speed and heavy-duty situations, curved bevel gears can be used; for higher-speed intersecting shaft transmissions, higher-precision curved bevel gears are used. Generally, the intersecting shaft transmission is widely used in equipment such as automobiles, tractors, machine tools, and metallurgical mines.
High resolution
In order to realize a large-area high-resolution Liquid Crystal Display, it is usually necessary to use low-impedance metal materials, high-performance switching elements, and high-precision processing techniques. Aluminum is the most researched and used material for making TFT buses with low-impedance metals. By solving the problems of easy formation of hillocks, chemical corrosion and oxidation of aluminum, alloy methods (such as Al-Cu, Al-Si, Al-Nd and Al-Ti, etc.) and interlayer methods (such as Mo/Al/Mo) have been reported successively. , Cr/Al/Cr and Ti/Al/Ti, etc.), the alloy method is relatively simple in process, but the material has a higher resistivity. In May 1998, IBM developed a 16.3-inch ultra-high resolution (200ppi) a-Si TFT Display using Al-Nd alloy as the gate electrode, and mass production has been achieved. In April 1999, Toshiba introduced the 20.8-inch 16-SVGA (3, 200 × 2, 400) a-Si TFT-LCD, which can be said to represent the highest level of a-Si TFT-LCD in terms of high resolution and high capacity. .
According to Display Search in the third quarter of 2011, the global flat panel display research report "QuarterlyWorldw ide Flat Pane l Dis play Fore cas t Re port" pointed out that the average pixels per inch (ppi) in large-size LCD panels (>9.1 inches) ) Will grow from 88ppi in 2010 to 98ppi in 2015. The ppi of small and medium-sized LCD panels (<9.0 inches) will grow from 180ppi to 300ppi in the same period. With the rise of smart phones, mobile phones will be the most obvious application product for ppi's growth.
Another important way to realize high-resolution liquid crystal display is to develop LT p-Si TFT technology. The resolution of published p-SiTFT-LCD products is generally around 200ppi. Compared with a-Si TFT-LCD, LT p-Si TFT-LCD has a smaller volume of thin film transistors and storage capacitors. Therefore, it has a larger penetration area per inch, resulting in a brighter display. , And save more power. When the market demands higher ppi, low-temperature polysilicon (LTPS) technology becomes the best choice for manufacturing high-resolution thin-film transistor liquid crystal displays.
Contrast
The control ICs, filters and oriented films used in LCD manufacturing are related to the contrast of the panel. For general users, a contrast ratio of 350:1 is sufficient, but such contrast in the professional field does not satisfy users. Demand. Compared with CRT monitors easily reaching 500:1 or even higher contrast, only high-end LCD monitors can achieve this level. The first-tier LCD monitors on the market, such as Samsung, Asus, LG, etc., can reach a contrast ratio of 1000:1. However, because the contrast is difficult to accurately measure with instruments, you have to go and see it yourself when you pick it.
Tip: Contrast is very important. It can be said that the selection of LCD is a more important indicator than bright spots. When you understand that your customers buy LCDs for entertainment and watching DVDs, you can emphasize that contrast is more important than no dead pixels. We When watching streaming media, the brightness of the source is generally not large, but to see the contrast of light and dark in the scene of the character, the texture change from gray to black hair must be shown by the level of contrast. The 256-level grayscale in the test software In the test, more small gray grids can be seen clearly when looking up, which means that the contrast is better!a
Lcd Display Module,Tft Lcd Screen Display,Display Lcd Enclosure,Tft Display Lvds
ESEN Optoelectronics Technology Co., Ltd, , https://www.esenoptoelectronics.com