Asphalt concrete paver is a high-tech product that integrates machinery, electricity, hydraulics and artificial intelligence. With the vigorous development of high-grade highways and urban roads, asphalt pavers play an important role in road construction, and the requirements for asphalt pavers are getting higher and higher. How to choose an Asphalt concrete paver with superior technical performance, strong reliability, good applicability and good economy is particularly important. First of all, you must have a certain understanding of the basic knowledge of the paver.
Basic mechanical structure and performance analysis
(1) Hydraulic system
The walking steering system, spiral, scraper system and other auxiliary systems of the asphalt concrete paver have undergone a transformation from mechanical transmission to hydraulic transmission. Hydraulic transmission has become the mainstream with its high transmission efficiency, flexible transmission mode, superior control performance and high reliability and low failure rate; the hydraulic system has also undergone a transformation from the initial open-loop system to the closed-loop system. The open-loop system has been gradually replaced by the closed-loop control system due to its defects such as difficulty in stepless speed regulation, scattered components, low efficiency and difficulty in continuous control.
(2) Travel drive mechanism
Large and medium-sized pavers at home and abroad all use crawler travel mechanisms. Crawler travel mechanisms are widely used for their low ground pressure, good adhesion and good paving flatness. In the past, the drive device used a hydraulic motor plus a chain or a reducer combination, but now it uses a hydraulic motor plus a planetary gear reducer, which are matched and driven in the same way. The tire travel mechanism is used on small and medium-sized pavers. It is widely used on low-end pavers due to its high maneuverability and low paving amplitude.
(3) Mechanical, electrical and hydraulic integration
Modern asphalt pavers have developed into advanced equipment that integrates machinery, electronic control, hydraulic transmission and artificial intelligence. Relying on electronic control, they can achieve functions such as constant speed paving, straight line travel, smooth steering, feed ratio control, vibration frequency preselection, floating, lifting, lowering, locking, pressurization, decompression, delay, smooth paving, electrical fault alarm and fault location identification of the ironing device.
(4) Constant speed control system
The instability of the paving speed of the paver is the main factor affecting the smoothness of the paved road surface. The main reasons for the speed instability are:
① Changes in engine speed.
② Changes in the volume ratio of the hydraulic components.
③ Changes in the track slip rate.
All three aspects are related to the sudden change of load during the paving operation. The constant speed of the paver cannot be achieved only by controlling the engine throttle or manually controlling the travel variable pump (which cannot guarantee the precise control of the paving speed). Most modern pavers install speed sensors on the travel hydraulic motors, compare the detected speed signal with the set speed, and then output signals to control the travel variable pump; at the same time, installing a constant power control system is also an effective means to ensure that the engine does not drop in speed when the load suddenly increases, that is, each system automatically distributes power. When the engine drops in speed, the systems with large power consumption of the screw and vibrator automatically adjust the screw speed and vibration frequency to reduce the power of the hydraulic system, avoid speed drops, achieve uniform speed paving, and ensure smoothness.
(5) Automatic leveling control system
The automatic leveling control system can be divided into analog signals and digital signals based on the type of data source. The digital controller not only improves the control accuracy of the system, but also improves the overall performance of the system: such as being able to perform fault alarms, fault diagnosis, and display operating status, etc., and has been widely used. The data collection methods are divided into: contact and non-contact. Contact leveling includes pulling steel fibers and dragging long sliding shoes, which are relatively easy to implement, simple and easy to operate, with low investment, and can achieve limited flatness in the longitudinal direction within the contact range; non-contact leveling includes ultrasonic and laser, which can be highly accurate, highly reliable, and fully compensate for the correction deviation, realizing the networking and intelligent control of the automatic leveling system. The non-contact balance beam with ultrasonic detection technology as the core has mature technology, multiple groups of multi-probe intelligent control systems, a large detection range, high accuracy, and comprehensive compensation for correction deviations. It can alternately use surface datums and line datums to achieve a wide range of flatness control.
(6) Continuous feeding technology
The driving power of the paver feeding system accounts for more than 50% of the total engine power. The matching between feeding volume and productivity affects the flatness of the road surface. In order to achieve continuous and stable feeding under the set paving speed, width and thickness, and ensure the stability of the hydraulic system load, it is necessary to proportionally control the variable pumps and non-contact material levelers used in the left and right scraper feeding systems and the left and right spiral feeding systems to improve the reliability of the transmission system. The spiral distributor in the screed is directly driven by the variable pump at the edge and can rotate forward and reverse, so that the mixed material in the trough can be concentrated to both sides or pushed to one side, without causing the phenomenon of segregation and blocking of materials. The spiral height can be adjusted quickly, and the wings on both sides of the hopper can be controlled separately.
(7) Anti-segregation paving technology
Segregation is a problem that is difficult to solve for large-width paving by pavers. There are four forms of material segregation when the paver paves the road surface: horizontal, vertical, longitudinal strip, and nest-shaped segregation. Among them, horizontal segregation occurs the most and is the most harmful. The corresponding anti-segregation technology can be developed in combination with the structural characteristics of the paver:
① The spiral blade is fully buried in the material feeding method, so that large and small particles can be evenly transported, reducing lateral segregation.
② The spiral height can be adjusted in multiple levels and steplessly, which can continuously stir the paving layer particles again to avoid vertical segregation in the thickness direction.
③ The spiral diameter can be reasonably designed, and the spiral feeding channel can be increased according to the paving thickness to improve the material blocking phenomenon and avoid longitudinal band segregation.
(8) Screwing device structure
The screed plate is a key component of the paver, which is directly related to the quality of the paved road surface. From the structural form, it can be divided into two types: mechanical extension and hydraulic extension; the overall rigidity of the mechanical assembly is high, which is beneficial to improving the smoothness of the paved road surface; from the pre-compaction mechanism, it can be divided into various combinations such as single rammer, double rammer, hydraulic vibration pressure beam, etc., which is the guarantee for the pre-compaction degree to reach more than 90%, and is an essential mechanism for improving the smoothness; when the paver is stopped and restarted, due to the relationship between the ironing plate’s own weight and the material carrying capacity, there will be ironing plate indentation, arm sinking and starting ironing plate climbing, which seriously affects the smoothness of the road surface. Automatically controlled screed plate anti-climbing lock and anti-sinking lock are used on new imported pavers: when the machine is stopped for a short time, the lower chamber of the screed plate lifting cylinder is locked to prevent sinking and causing indentations; when the machine is started, the lower chamber of the screed plate lifting cylinder is locked for a delay, and the lower chamber is opened for floating paving after paving a screed plate width; when the machine is stopped for a long time, the lower chamber of the screed plate lifting cylinder is opened at the same time when the machine is started, and the upper chamber is locked for a delay, and the upper chamber is opened for floating paving after paving a screed plate width, so as to control the screed plate climbing; in addition, intermittent ignition is carried out according to the measured material temperature to keep the screed plate warm.
(9) Digital control technology
Due to the widespread use of electromechanical and hydraulic integration in pavers, the electronic control system has become an important indicator of whether the pavers are advanced or not; the new generation of microcomputer control and CAN system bus design provide space for the expansion of pavers’ functions. For example, the full electronic management system (EPM system), LCD display technology and automatic fault diagnosis system are adopted. The main factors affecting the paving quality of pavers are:
① Whether the paving speed can be constant.
② Whether the material can be continuously transported in an appropriate amount.
③ Whether the material can be spread evenly.
④ Whether the interference between road conditions and materials can be effectively controlled. Pavers of various brands at home and abroad will emphasize that their products are superior to other brands in some aspects. It is necessary to make a suitability analysis from a variety of functional configurations and select a model that meets your actual engineering needs in a targeted manner.
After understanding the basic knowledge of pavers, are you eager to buy one? Why not take a look at our related products?
Click here to visit our web
Click here to visit our alibaba （There are more kinds of products）
You can also contact us directly and we will provide you with the most suitable products according to your needs.
