1. Selection of coupling The drive shaft of the hydraulic pump cannot bear radial force and axial force, so it is not allowed to directly install pulleys, gears, and sprockets on the shaft end. Usually, a coupling is used to connect the drive shaft and the pump drive shaft. If due to manufacturing reasons, the coaxiality of the pump and the coupling exceeds the standard, and there is a deviation during assembly, the centrifugal force will increase the deformation of the coupling with the increase of the pump speed, and the large deformation will increase the centrifugal force. A vicious cycle is caused, resulting in vibration and noise, which affects the service life of the pump. In addition, there are other influencing factors such as the coupling pin is loose and not fastened in time, and the rubber ring is worn and not replaced in time. 2. Assembly requirements of the coupling The concentricity error of the two axes of the rigid coupling is ≤0.05mm The concentricity error of the two shafts of the elastic coupling is ≤0.1mm The angular error of the two axes is <1°; The drive shaft and the pump end should keep a distance of 5-10mm;

The main function of the hydraulic oil filter is to filter oil, and various impurities inevitably appear in the hydraulic system. The main sources are: mechanical impurities remaining in the hydraulic system after cleaning, such as scale, casting sand, welding slag, iron filings, paint, paint skin and cotton yarn scraps, etc. Dust that enters the dust ring, etc., impurities generated during the working process, such as fragments formed by the hydraulic action of the seal, metal powder generated by the relative wear of the movement, colloid, asphaltene, carbon residue, etc. generated by the oxidation of the oil. . After the impurities are mixed into the hydraulic oil, with the circulation of the hydraulic oil, they will play a destructive role everywhere, seriously affecting the normal operation of the hydraulic system, such as making the small gap between the relative moving parts in the hydraulic components and the throttle holes and gaps stuck. Dead or blocked; destroy the oil film between relative moving parts, scratch the surface of the gap, increase internal leakage, reduce efficiency, increase heat generation, intensify the chemical action of the oil, and deteriorate the oil. According to production statistics, more than 75% of the failures in the hydraulic system are caused by impurities in the hydraulic oil. Therefore, it is very important to maintain the cleanliness of the oil and prevent the pollution of the oil. Generally, pollutants with a particle size below 10 μm have little effect on the pump, but those with a particle size greater than 10 μm, especially those above 40 μm, have a significant impact on the service life of the pump. The solid pollution particles in the hydraulic oil can easily aggravate the surface wear of the relative moving parts in the pump, so it is necessary to install an oil filter to reduce the degree of oil pollution. Filtration accuracy requirements: 10-15 μm for axial piston pumps, 25 μm for vane pumps, and 40 μm for gear pumps. The pollution wear of the pump can be controlled within the allowable range. High-precision oil filters are increasingly used, which can greatly extend the service life of hydraulic pumps.

A hydraulic pump is a hydraulic component that provides pressurized liquid for hydraulic transmission and is a type of pump. Its function is to convert the mechanical energy of the power machine (such as electric motor and internal combustion engine, etc.) into the pressure energy of the liquid. The figure shows the working principle of a single plunger pump. The cam is rotated by an electric motor. When the cam pushes the plunger to move upward, the sealing volume formed by the plunger and the cylinder decreases, and the oil is squeezed out from the sealing volume and discharged to the required place through the one-way valve. When the cam rotates to the descending part of the curve, the spring forces the plunger downward to form a certain vacuum, and the oil in the oil tank enters the sealed volume under the action of atmospheric pressure. The cam makes the plunger rise and fall continuously, the sealing volume decreases and increases periodically, and the pump continuously absorbs and discharges oil.

The construction machinery market has picked up. In February, the year-on-year decline in domestic sales of excavators in my country narrowed, and the growth rate of exports returned to positive. According to statistics from the China Construction Machinery Industry Association, in February 2023, 26 excavator manufacturers sold 21,450 excavators of various types, a year-on-year decrease of 12.4%, of which 11,492 were domestic units, a year-on-year decrease of 32.6%; exports were 9,958 units, a year-on-year increase of 34%. %. From January to February 2023, the sales volume of excavators was 31,893 units, a year-on-year decrease of 20.4%; of which 14,929 were domestic units, a year-on-year decrease of 41.1%; exports were 16,964 units, a year-on-year increase of 14.9%. The Paper learned that the year-on-year decline in excavator sales in February narrowed by 20.7 percentage points from the previous month, of which the year-on-year decline in domestic sales narrowed by 25.9 percentage points from the previous month, and the year-on-year growth rate of export sales turned from negative to positive. It is worth noting that in the first two months of this year, my country's excavator export sales exceeded domestic sales. Orient Securities Research reported that sales of excavators in February were in line with expectations, and the continued slump in domestic sales year-on-year was related to the short-term impact of the national standard switch and Spring Festival factors. In terms of actual construction, according to data from Komatsu's official website, the operating hours of Komatsu excavators in China in February were 76.4 hours, a year-on-year increase of 61%, ending 11 months of year-on-year decline and a month-on-month increase of 79.8%. From the perspective of other regions in the world, in February, the operating hours of Komatsu excavators in China, North America, and Indonesia all achieved positive year-on-year growth. It is worth noting that among overseas markets, the Southeast Asian market has a large demand for engineering construction, and the number of operating hours has continued to increase year-on-year for more than 24 months. According to Komatsu data, the average monthly operating hours in Southeast Asia in 2022 will be 198 hours, which is 2-4 times that of other regions or countries. Guotai Junan Research Report stated that considering the steady increase in demand for engineering construction in overseas regions such as Southeast Asia and Africa, the products of domestic enterprises are more cost-effective, and the electrification is progressing rapidly, it is expected to accelerate their overseas expansion. The global phenomenon of Chinese manufacturing and supply is obvious, and domestic enterprises are expected to further improve the global market Accounting rate. Domestically, this year's government work report pointed out that 3.8 trillion yuan of new special bonds will be issued in 2023, an increase from the 2022 quota. Superimposed on the acceleration of the issuance of new special bonds in January 2023, it will help the recovery of the infrastructure industry and is expected to stimulate the demand for construction machinery. Orient Securities Research Report stated that with the implementation of the China Securities Regulatory Commission’s adjustment and optimization measures for real estate equity financing, the recovery of infrastructure and real estate is expected to increase, and the bottom-up effect of real estate infrastructure will gradually emerge, which is expected to stimulate a rebound in downstream real estate demand. According to the Zheshang Securities Research Report, based on the 8th year of excavators as the update peak period, domestic excavator update demand will bottom out in 2023, and update demand and exports will dominate, driving the sales of the excavator industry to gradually bottom out. Assuming that the sales of excavators will decline by 5% in 2023, the growth rate of exports will decline, and the annual export growth will be 30%, which can hedge the 30% decline in China. It is expected that the sales of excavators will bottom out in 2023.

Excavator sales were still down year-on-year, but with the improvement of downstream construction, there was an increase month-on-month. A few days ago, the latest data released by the China Construction Machinery Industry Association showed that according to the statistics of major excavator manufacturers, 21,500 excavators of various types were sold in February this year, a year-on-year decrease of 12.4%, and the decline narrowed by about 20 percentage points from the previous month. Compared with January, 11,000 more excavators were sold in February, a month-on-month increase of 1.05 times. In January, the Lunar New Year holiday and other reasons affected the sales of excavators. After the Lantern Festival, the start of work in the downstream market improved, and the construction machinery industry recovered. In February, domestic sales of excavators were 11,500 units, a year-on-year decrease of 32.6%, and a month-on-month increase of 2.34 times; export performance also began to pick up, with a single-month export volume of 9,958 units, a year-on-year increase of 34%, and a month-on-month increase of 42%.

CCTV News: In recent years, more and more Chinese construction machinery has appeared in overseas markets, and the continuous growth of overseas orders also confirms that the innovation of my country's construction machinery industry has been more widely recognized. In the excavator assembly workshop of a construction machinery company in Changsha, Hunan Province, the staff are intensely doing assembly work. The relevant person in charge of the company told the reporter that since the beginning of this year, the sales of excavators in overseas markets have been very hot, among which micro excavators are most popular in European and American markets. At present, most of the products produced on this production line are these 2-ton miniature excavators. In recent years, my country's export of various construction machinery products including excavators has maintained a high growth trend. While actively deploying overseas markets, many companies are also constantly upgrading their products to meet the needs of overseas markets. According to data from the Ministry of Industry and Information Technology, my country has formed 22 major categories of construction machinery products, becoming one of the countries with the most complete product categories and varieties. Among them, the output of major products such as excavators, cranes, and loaders ranks first in the world. According to the statistics of 26 excavator manufacturers by the China Construction Machinery Industry Association, in the first 10 months of 2022, my country exported 89,457 excavators, a year-on-year increase of 67.3%. In addition, in the first 10 months of this year, my country's construction machinery exports amounted to US$36.521 billion, a year-on-year increase of 34.2%.