Mechanical equipment industrial transmission industry belongs to the accessory industry of construction machinery, which can be roughly divided into gear transmission device, hydraulic transmission device and hydrostatic transmission device.This paper introduces the development trend of gear transmission in construction machinery in China, and takes hydrostatic transmission as an example to introduce its application.
1. Classification of mechanical industrial transmission devices
Mechanical industrial transmission industry belongs to the accessory industry of construction machinery, which can be roughly divided into three categories:
(1) gear transmission
Mainly used in the use of low requirements, low cost of part of the main machine shovel soil transport machinery, engineering lifting machinery, compaction machinery and internal combustion forklift and other products of the transmission, drive axle main transmission and wheel edge reducer, gear transmission according to its structure can be divided into two types of fixed shaft and planetary.The drive axle
It can be divided into rigid, steering and through driving axle according to its function.
(2) hydraulic transmission device
Mainly used for the use and the host performance requirements of soil transport machinery and internal combustion forklift and other products, in which the hydraulic torque converter and power shift transmission as the chassis power transmission in the CVT components, can make the host with good automatic adaptability and operational performance.
(3) hydrostatic transmission device
Mainly used in hydraulic excavator and bulldozer, loader, road machinery, roller and internal combustion forklift and other products and hydrostatic variable speed, steering system and working device, so that the host has good stepless variable speed and operating performance.
2, China's construction machinery gear transmission device development trend
(1) China's mechanical gear transmission technology level is low, with a large space for development.It is necessary to popularize the optimization design method, improve the material and technology of gear, shaft, shell and other key parts, so as to further improve the service life, reduce the weight and reduce the volume.Adopt advanced shift element and shift way, reduce the labor intensity of the driver, shorten the power interruption time, improve the working efficiency of the construction machinery.Domestic has introduced the transmission of advanced design and parts, should be vigorously promoted.
(2) due to the hydraulic torque converter and power shift transmission, the shoveling soil transport machinery has certain automatic adaptation performance, light and smooth shift, good acceleration performance and other advantages, and the production cost is relatively moderate, which has been accepted by most domestic manufacturers.
But, because at present the domestic large and medium-sized tyred type construction machinery has many also USES the big torque ratio the hydraulic transducer and the two-block transmission, produces USES the manual shift way, therefore the work efficiency and the use economy is obviously lower.Have been introduced in the United States CAT company D6D, D7G products such as single stage hydraulic torque converter and the German government and company WG series dynamics shift transmission, and other advanced technology, can effectively improve the efficiency of the engineering machinery operation and use of economy, reduce system calorific value, should be applied in domestic engineering machinery, and then by electric - hydraulic control and electronic control system to replace the manual control system, in order to improve the operating conditions, improve the working efficiency.
Currently, improve the level of domestic hydraulic mechanical drive device of a key issue is the need to accelerate the joint merger and walk, introduce advanced technology, built as early as possible in our country has the world first-class professional technical level of competition ability, only in this way can we achieve hydraulic machinery product specialization, standardization and generalization, make this series of products has exuberant vitality.
(3) promoting the application of self-locking non-slip differential and wet brake in the tyred driving axle of construction machinery is one of the ways to improve the technical level of driving axle products of construction machinery in China.
The self-locking non-slip differential can not only automatically realize the unequal distribution of torque between left and right wheels, so as to make full use of the traction of vehicles, but also can obviously improve the off-road performance and economy of vehicles.Wet brake has high durability and reliability, its service life is 1.5 times higher than the dry brake disc brake, and brake capacity, brake performance is good.It has been widely used in large and medium sized wheeled construction machinery in foreign countries, and should be promoted vigorously.
(4) single power flow steering clutch and brake are generally used in the rear bridge of tracked construction machinery, so that the vehicle has only one turning radius R=B for left and right steering, and the rest turning radius is realized by the skidding of friction components, which not only causes serious power loss, but also reduces the service life of friction components.In order to improve the steering performance and reduce the power loss, the development of power differential steering mechanism similar to CAT D8N bulldozer should be accelerated in China.
Engine power most after input the central main drive variable speed system, another part of the power to the hydraulic pump, motor input the first classical Ⅰ ring gear planetary row.Design power differential steering mechanism should ensure: (1) when the motor speed is not equal to zero, about the same output speed, to ensure the bulldozer has a good straight line running performance.When the speed of the central main transmission is equal to zero, the steering hydraulic motor makes the speed of the output about the same but in the same direction, at this time the bulldozer around its center to achieve in situ steering, that is, R=B/2.(3) because the hydraulic motor can be infinitely variable speed and double and rotation, to achieve the left and right output speed difference stepless precise control, so that the bulldozer steering radius can be stepless adjustment, and smooth steering, improving the performance of the steering, to achieve no power loss.
3. Application of hydrostatic transmission device
Hydrostatic transmission has the advantages of stepless transmission, wide range of speed regulation, constant torque or constant power speed regulation, easy to realize electronic control and so on. It has a good application prospect in construction machinery.But in the shovel transport machinery and lifting machinery as the main drive is rarely used, the main problem is that the quality of domestic hydraulic components, and foreign hydraulic components price is too high, will cause the main cost is too high.
Since the 1990s, Germany linde hydrostatic forklifts and liebherr's hydrostatic bulldozers have been introduced in China, but their share of the domestic market is small.Based on the reality of the domestic construction machinery market, this paper puts forward the following opinions on the promotion and application of hydrostatic transmission in China:
(1) hydrostatic transmission forklifts have been widely used in developed countries. Some domestic warehouses, docks, factories and other departments have higher requirements on the mobility performance (especially low-speed performance) and noise of forklifts, so these departments are becoming domestic users of hydrostatic forklifts.Domestic forklift truck and hydraulic component manufacturers should see the good prospect of hydrostatic forklift truck, and jointly research and develop the hydrostatic forklift truck system suitable for China's national conditions, to provide advanced performance, reliable work, affordable products.It can also adopt the method of joint development with the international hydrostatic component manufacturing company to accelerate the development speed.
(2) small and medium-sized multi-functional construction machinery has been widely used in developed countries due to its multi-functions such as excavation, loading, forklift and lifting.With the development of China's economic construction, especially urban construction, small and medium-sized multi-functional construction machinery will also be promoted and applied in China, and they will undoubtedly first adopt hydrostatic transmission as its main transmission device.Domestic construction machinery enterprises should see the development prospect of small and medium-sized multi-functional construction machinery, and cooperate with domestic and foreign hydrostatic component manufacturers to carry out research and development on them, so as to promote the development of small and medium-sized multi-functional construction machinery in China.
(3) in the domestic large-scale shovel soil transportation and lifting machinery, due to the technical difficulty of supporting hydrostatic and electronic control components, the price is too high, it is difficult to accept among domestic users.Therefore, the research and development of hydrostatic transmission in China should not focus on supporting large shovel and lifting machinery, but should focus on the above two types of construction machinery.