Analysis on Key Technologies of the hottest all te

The birthplace of all terrain crane is Germany. "Technology first, quality first" is the core value of German manufacturing industry, showing its enthusiastic pursuit of product technology and quality

the strength of American grove company is cross-country tire crane and truck crane. In the 1980s, European all terrain cranes developed in full swing, gradually squeezing grove out of the European market. After several studies, grove bought Coles, an old British enterprise, in 1983, in an attempt to use Coles as a bridgehead to re-enter the European market. Grove invested heavily in the development of all terrain cranes and produced them in the UK. Although the products developed to 300t, they still failed to get enough share of the European market. After learning from the bitter experience, grove realized that Germany's all terrain crane was unshakable in the European market, so he used the power of capital to acquire Germany's Krupp wheel crane company in 1999, which truly became one of the three pillars in the all terrain crane market

Germany has become the de facto overlord of all terrain cranes, and the technology it uses on all terrain cranes has also become a crownless standard. This paper analyzes the main key technologies of all terrain crane from three aspects: chassis design technology, boom manufacturing technology and can bus control technology

chassis design technology

the key of chassis design technology is the design of hydro pneumatic suspension system and multi axle steering system, which are unique technologies of all terrain cranes. Next, the hydro pneumatic suspension system is discussed

the necessary condition of multi axle chassis of hydro pneumatic suspension system can not only play the role of multi axle balance, but also increase the roll stiffness of the whole machine, overcome the brake forward tilt, adjust the frame height and lock the suspension. The hydro pneumatic suspension system is composed of hydro pneumatic spring and flow distribution system. The hydro pneumatic spring uses gas as the elastic element and introduces oil as the intermediate medium between the gas and the piston; The flow distribution system uses the flow of oil to balance the axle load, damp the vibration, and adjust the height of the car body. Hydro pneumatic suspension system has the following advantages

enhance the pressure bearing capacity

the hydro pneumatic spring takes the steel cylinder accumulator as the elastic element, which can withstand high pressure, usually up to 20MPa, so it is small in size and light in weight. When used for heavy axle load, the mass is more than 50% lighter than that of leaf spring

improve the ride comfort

the hydro pneumatic spring can obtain a good elastic characteristic curve and low natural frequency, so the ride comfort and comfort of the vehicle are much better than that of the leaf spring suspension, and the impact of the vehicle on the ground is reduced. The variable stiffness elastic characteristic curve of hydro pneumatic suspension can prevent suspension breakdown, which is very important for off-road driving

effectively balance the axle load

the hydro pneumatic suspension system can connect the hydro pneumatic spring cylinders of different axles through the connection of pipelines to balance the axle load

increase the roll stiffness of the whole machine

when the vehicle rotates, tighten the diameter of the test pressure plate 1 Φ At 150 turns, due to the centrifugal force, the center of gravity shifts, so the whole vehicle tilts significantly. The hydro pneumatic suspension system connects the left and right hydro pneumatic springs in series, which can greatly enhance the roll stiffness of the whole vehicle. The ideal roll stiffness can be obtained by selecting the optimal ratio of large and small cavity area of hydro pneumatic suspension hydraulic cylinder. Similarly, if the front and rear hydro pneumatic spring cylinders are connected in series, the longitudinal stiffness of the whole machine can be improved and the phenomenon of braking nodding can be overcome

in addition, the hydro pneumatic suspension system can play a damping role (i.e. vibration reduction role) by adjusting the oil flow, and can also adjust the body height and lock the suspension. The latter is very useful in the lifting operation of wheeled cranes

to manufacture all terrain cranes, it is necessary to develop hydro pneumatic suspension system; It can also be said that there is no all terrain crane without hydro pneumatic suspension system. The design of the chassis of the all terrain crane should be carried out by the crane factory itself, rather than relying on the ready-made chassis provided by the professional automobile factory. The reasons are as follows

different mechanisms

the key technology of all terrain crane is hydro pneumatic suspension mechanism and its corresponding system. This is a proprietary technology, which is not used in trucks, so the automobile factory will not invest in the research of this technology

the operating conditions and design methods are different.

the operating conditions of the crane chassis are always full load, but the driving mileage is far lower than that of trucks. Therefore, there are great differences between them in design methods and computer principles, especially in the chassis of large tonnage cranes. For example, in automobile design, the damage form of transmission gear is pitting corrosion, so the design computer is mainly fatigue load; In the design of crane chassis, the damage form of transmission gear is fracture, so the design calculation is mainly based on the bending resistance of gear teeth

the production mode is different from the batch production.

the production mode of the automotive industry is a typical single variety batch production, and even the trucks in small batches are all in 10000 units. The production mode of cranes is multi variety and small batch, and one model of products often only produces 100 sets. Therefore, it is very difficult for automobile factories to supply products in batches according to crane factories

it is worth mentioning Grove's mega track sliding column hydro pneumatic independent suspension system. Independent suspension is superior to the overall suspension in terms of driving comfort, operating stability and off-road trafficability, so it is widely used in cars, off-road vehicles and armored personnel carriers. However, due to the complexity of its structure, few civil trucks use this structure except for Tatra. The most commonly used independent suspension is the strut swing arm suspension, also known as Mike 6. The universal material testing machine has many different fixed screw Pherson suspension. It was developed by Earle s MacPherson, an engineer of General Motors in 1947, inspired by the aircraft landing gear, and named after him. The advantages of this suspension are simple structure and compact layout. The piston rod of the shock absorber is also used as the steering kingpin. When the wheel jumps, it moves along the axis of the kingpin. The front wheel positioning changes little, and it has good driving stability. Compared with other independent suspensions, it has no other tie rods, which increases the internal space between the two wheels and brings convenience to the layout of the engine and other components

when the wheels equipped with McPherson suspension jump, the steering kingpin swings slightly, and the front wheel deflection angle changes. The sliding column suspension (also known as candle suspension), which is very similar to McPherson suspension, can avoid this disadvantage. When the wheels of candle suspension jump, the kingpin angle and wheel alignment angle remain unchanged, which is very beneficial to the handling and stability of the vehicle. This advantage is inferior to other forms of independent suspension. Compared with other independent suspensions, the change of track width during wheel runout is also small. The sliding column hydro pneumatic suspension has the advantages of small volume, light weight and simple overall layout, so it is widely used on heavy dump trucks with more than 32t

in 1988, after analyzing the advantages and disadvantages of various suspensions and studying the structural characteristics of various hydro pneumatic suspensions such as off-road vehicles, dump trucks and aircraft landing gears, Krupp wheel crane company of Germany decisively invested 2million marks and took 20000 man hours to successfully develop a sliding column independent hydro pneumatic suspension, which was applied to bridge all ground cranes, As the only crane chassis that has passed the cross-country road test of the German tank car test field, it is called a new technology across the century. This may be one of the reasons why grove bought Krupp. Liebherr and Demag adopt the traditional design of whole bridge suspension

boom manufacturing technology

in order to improve the lifting performance of the crane, the most direct way is to reduce the quality of the boom. In order to achieve this goal, we must first have advanced boom design theory and design a boom with high stiffness and light weight. At present, the boom section shape of all terrain cranes in Germany is all oval. Secondly, high-strength steel should be used. Foreign cranes generally use steel above 960mpa. In order to reduce the weight of some 100t cranes, weldox1100 steel produced by SSAB in Sweden, which is only 4mm thick, is even used on the boom to carry out the operation board according to the actual utilization. SSAB is currently developing 1300mpa ultra-high strength steel plate

such a high steel plate not only has very high welding requirements, but also is very difficult to form. Generally, the rebound angle of steel plate is only 1 °. If you bend a 90 ° bend, you need to bend the steel plate to 89 °. When you bend a 90 ° bend, you need to bend the steel plate to 65 °

the design of elliptical section jib requires the most advanced mechanical theory and powerful computer. When I visited Liebherr factory in terms of supply and demand, I was shocked by the huge section boom. The length of the 7-section boom of the 500t LTM 1500 all terrain crane when fully extended is 84m, and the section height of the basic boom is 1.65m. People who are not tall can pass through the boom barrel by bending over. In this way, the arm barrel with large section is welded by four steel plates. For example, the arm barrel of the third section is 14.5m long, and the upper cover plate is a plate, which is bent by two 90 ° bends; The lower cover plate is welded by three steel plates, which are 8.6MM thick, 8m long, 9.5mm thick and 4.5m long respectively; 10mm thick and 2m long, each plate is bent 30 times, and the cross-section shape is approximate to ellipse. Then three steel plates are welded together, and then welded with the upper cover plate to form the whole arm barrel. Although the thickness of the three lower cover plates is different, after 30 bends respectively, they are perfectly connected, which is really a huge steel art. A total of 24 steel plates are used for the boom barrel of the 7-section boom, with a minimum thickness of 6mm and a maximum thickness of 12mm

it is precisely because of the complexity of the manufacturing of the elliptical section boom that it is difficult for the crane manufacturer to master the processing technology of the boom, with low equipment utilization and high manufacturing cost. Therefore, Liebherr, Demag, grove and other telescopic boom crane manufacturers have completely abandoned the manufacturing of elliptical section jibs and outsourced them to professional manufacturers. The most famous professional manufacturer of boom is vlassenroot company in Belgium, which is called "Belgian boy" in the industry. Vlassenroot, located in the suburbs of Brussels, was founded in 1926 and now specializes in cutting, bending and welding all kinds of telescopic booms. The company has two 5-axis CNC laser cutting machines, 4kw laser, which can cut 30m × 7m, steel plate with maximum thickness of 20mm and various welding grooves; There are 12 bending machines, with the maximum bending length of 24m (960) t and the maximum pressure of 4000t (15m). These machines work 24 hours a day, 7 days a week, consume 11000t of steel a year, and produce 20% of the crane jibs in the world. Users benefit crane manufacturers in Bohai, Demag, grove, TADANO, Kato, ppm, link belt, Luna and other countries in the world. Vlassenroot only manufactures the jib according to the user's drawings, provides the jib assembly or sets the boom barrel of a set of jibs together for delivery

can bus control system

the electrical control system of traditional cranes is one-to-one control, the control is direct and unique, and the analog signal flows in the wire. With the increasingly complex electrical system of cranes, especially the use of a large number of ECU (electric control unit), one-to-one communication is almost impossible. Can bus control system effectively solves this problem

can (control area network) is the application and development of computer network technology in the field of modern control technology. With the improvement of intelligent components, engine, transmission, hydraulic pump/motor, electro-hydraulic control