The Working principle of Excavator-HaiqinTop Machinery

 

The hydraulic transmission of HaiqinTop excavators is closely linked, and its development is mainly based on the application of hydraulic technology. Its structure is mainly composed of engine, hydraulic system, working device, walking device, and electrical control. Due to the harsh working conditions of excavators, the required actions are very complex, which puts high demands on the design of the hydraulic system. Its hydraulic system is also the most complex in the hydraulic system of construction machinery. Therefore, the analysis and design of excavator hydraulic systems have become an important part of promoting excavators. A single bucket hydraulic excavator is a mechanical equipment that operates on a periodic basis, consisting of three parts: a working device, a rotating device, and a walking device. The working device includes a moving arm, a bucket rod, and various replaceable equipment according to work needs, such as a front shovel, a backhoe, a loading bucket, and a grab bucket. Its typical working cycle is as follows: (1) When the digger excavating in a hard soil city, the main action is usually the action of the bucket rod, and the cutting angle is adjusted by the bucket cylinder to cooperate with the excavation; When digging and overturning in soft soil slopes, the main action is the bucket cylinder; In excavation operations with special requirements, the bucket cylinder, stick cylinder, and boom cylinder are combined to perform the action To ensure that the bucket moves along a specific trajectory. (2) Full bucket lifting and rotary excavation are completed, the bucket cylinder is pushed out, the dynamic intermediate cylinder is raised, and the full bucket is lifted; At the same time, the rotary motor starts and the turntable rotates in the direction of unloading soil. (3) Transfer the unloading turntable to the unloading location Adjust the unloading radius of the rotary table brake arm cylinder The bucket cylinder is retracted and the rotary bucket is unloaded. When there are strict requirements for the unloading position and height The arm kr still needs to cooperate with the action. (4) After uninstallation is complete The turntable rotates in the opposite direction, while the boom cylinder and boom cylinder cooperate to lower the empty bucket into a new excavation position. Single bucket hydraulic excavators are widely used in construction, transportation, water conservancy construction, open-pit mining, and modern military engineering, and are essential main mechanical equipment in various earthwork construction.  

Crawler excavator Transmission system

Single bucket hydraulic excavators are widely used in construction, transportation, water conservancy construction, open-pit mining, and modern military engineering, and are essential main mechanical equipment in various earthwork construction. Fluid transmission includes the following three forms: 1. Hydraulic transmission - a transmission form that uses the pressure energy of liquid to transmit power and motion; 2. Hydraulic transmission - a transmission form that uses the kinetic energy of liquid to transmit power and motion; (such as hydraulic torque converter) 3. Pneumatic transmission - a transmission form that uses the pressure energy of gas to transmit power and motion.  

Excavator power system

According to the external characteristic curve of the diesel engine, it can be seen that the diesel engine is approximately constant torque regulation, and the change in output power is manifested as a change in speed, but the output torque remains basically unchanged. As the throttle opening increases (or decreases), the output power of the diesel engine increases (or decreases). Since the output torque remains basically unchanged, the diesel engine speed also increases (or decreases), that is, different throttle openings correspond to different diesel engine speeds. From this, it can be seen that the purpose of controlling a diesel engine is to regulate the engine speed by controlling the throttle opening. The control devices applied to hydraulic excavator diesel engines include electronic power optimization systems, automatic idle devices, electronic speed controllers, electronic throttle control systems, etc. [1] In addition, with the increasing environmental requirements, modern hydraulic excavator power systems are gradually adopting low emission and noise reduction technologies.  

China excavator Component system

The control of hydraulic pumps is achieved by adjusting their variable swing angle. According to different control forms, it can be divided into three categories: power control system, flow control system, and combination control system. The power control systems include constant power control, total power control, pressure cutoff control, and variable power control; The flow control system includes manual flow control, positive flow control, negative flow control, maximum flow two-stage control, load sensing control, and electrical flow control; The combination control system is a combination control of power control and flow control, which is most commonly used in hydraulic control machines.  

Yanmar excavator Valve control system

The valve control system is essentially a throttling system. On hydraulic excavators, the commonly used valve is a general three position six way multi way valve, which has poor fine adjustment and composite operation performance of the slide valve. Since the 1990s, load sensing control systems have been adopted in hydraulic excavators, which are equipped with pressure compensation valves for both center open and center closed control modes. Compared with traditional hydraulic systems, the main advantages of load sensing control systems in hydraulic excavators using electronic control pressure compensation are: (1) saving energy consumption. Whether using a fixed displacement pump or a variable displacement pump, a portion of the oil always overflows through the overflow valve, wasting energy. By using a load sensing variable system, all the flow of the pump is used for the load, and the pressure of the pump is only 1-3MPa higher than the load pressure. (2) The flow control accuracy is high and is not affected by changes in load pressure. (3) Several actuators can move synchronously or at a certain speed ratio without interfering with each other. The ordinary three position six way valve system uses a parallel oil circuit. When several actuating elements act simultaneously, the oil output from the pump first flows to the low-pressure actuating element and cannot be synchronized. The load sensing control system includes a load sensing control valve and a load sensing control pump (or quantitative pump). 3) The full load sensing control system consists of a load sensing control valve and a load sensing control variable pump. The above-mentioned load sensing control valve only solves the fine-tuning performance and composite operation performance of the slide valve, but does not address the issue of energy conservation. The Rippa excavator system of quantitative pump and load sensing control valve also does not save energy consumption, because when the output flow of the pump exceeds the flow required by the actuating components (hydraulic cylinder and hydraulic motor), the excess oil flows back to the oil tank through the pressure compensation valve (to maintain a constant pressure difference) and becomes thermal energy. Only a fully load sensing control system can solve the problem of energy conservation. 4) Load sensing system with secondary pressure compensation valve [2]

Execution system

The walking automatic two speed system only has this function when the walking speed conversion switch is in the two speed position. At this point, its signal causes the walking two speed solenoid valve to change direction; At the same time, by using a second speed servo cylinder to keep the walking motor in the second speed position, the excavator can travel at high speed. In addition, the control selector valve is also affected by the walking pressure. When there is a heavy load such as uphill, the control selector valve will change direction to the one speed side; The hydraulic unloading is controlled by servo for the second speed, causing the walking motor to automatically switch to the first speed position and increase the driving force. When the excavator is walking on flat ground or downhill, the walking resistance decreases. The control selector valve changes direction again, and the servo cylinder acts on the second speed. The walking motor automatically returns to the second speed position, allowing the control machine to travel at high speed. The mechanism for preventing the rotation and shaking of the turntable is a mechanism that eliminates the shaking of the excavator turntable after it stops rotating. Its working principle is that during the process of stopping the rotation of the turntable, the reverse rotation prevention valve on both sides is subjected to unloading pressure, and the spring is compressed. Due to equal pressure on the left and right sides, the reverse prevention valve cannot change direction. After the rotary motor stops running, the pressure on the B side is higher than that on the A side, which exerts a reaction force on the rotary motor and causes it to shake. At this time, the pressure on the A side is higher than that on the B side, which puts pressure on the reverse rotation prevention valve. Due to the presence of a throttle hole in the valve, there is a time lag, causing the spool valve to move to the right, thereby connecting port A and port B and ensuring equal pressure. Therefore, the turntable only rotates and shakes once. The hydraulic system of the working device control system hydraulic excavator has six actuating components - left and right walking motors, turntable turning motor, boom hydraulic cylinder, arm hydraulic cylinder, and bucket hydraulic cylinder. In order to improve the productivity of excavators and save energy consumption, it is necessary to coordinate the action of the rotary motor and three types of hydraulic cylinders during the excavation and loading process of excavators. The working device control system should have the following three functions: (1) control machine control function. The bucket moves in a straight line or arc along a horizontal plane or at a certain angle to the horizontal plane; Any trajectory motion. (2) Loading mining function. Complete full bucket lifting, turning, and unloading. During this process, it is required that the bucket maintain the angle relative to the ground plane at the beginning of lifting to prevent the material inside the bucket from scattering during the lifting process. (3) Reset control function. After unloading, the bucket is restored to the starting position of excavation through the linkage of four actions: boom, arm, bucket, and rotation.  [1]

control system

a. The mini tracked excavator hydraulic oil temperature control system converts most of the power loss in the hydraulic system into heat, causing an increase in oil temperature. The result not only reduces the efficiency of the hydraulic system, but also accelerates the deterioration of oil quality. For every 9 degrees increase in hydraulic oil temperature above 55 degrees, the service life of the oil will be reduced by half. Therefore, it is advisable to avoid excessively high hydraulic oil temperatures as much as possible. After combining the oil temperature control device with the energy-saving control device, it is in an alarm state. When the device is working, the hot melt type over temperature protector is first set within the reasonable temperature range of the system, and then the magnetic steel type temperature limit switch is closed. Under the control of the self-locking function, the temperature control switch is disconnected. When the temperature of the oil rises to the set temperature of the hot melt over temperature protector, the magnetic steel type temperature limit switch automatically disconnects, and the temperature control switch is closed. At the same time, the temperature control indicator light is on, giving a warning indication. This indicator signal is further controlled by the operation mode selection switch and throttle electronic controller of the electronic energy-saving control module to regulate the throttle opening of the diesel engine. By reducing the diesel engine speed, the flow rate of the hydraulic pump is reduced, and the heat generation of the hydraulic system is controlled to prevent the oil temperature from continuously rising. After the temperature warning is lifted, the magnetic steel type temperature limit switch is activated to eliminate the impact of oil temperature rise on the electronic energy-saving control module, thereby restoring the excavator to normal working condition.  

b. The hydraulic excavator working condition monitoring and fault finding system plays an important role in improving maintenance methods, ensuring safe operation, and eliminating accident hazards. There are two forms of this system: one is a diagnostic computer - a handheld terminal form that plugs into the onboard system, such as Hitachi's Dr. EX fault diagnosis system from Japan; Another type is a randomly installed system, such as the Work Condition Control System (BCS) of the German O&K company, which first uses satellite communication technology to transmit the technical status and fault location of each excavator in operation from an onboard transmitter to a synchronous satellite, and then from the satellite's transponder back to the maintenance management center. The computer screen of the management center displays the real-time operation status of each excavator.  

With the development of the Internet of Things and communication technology, remote monitoring and diagnostic systems are increasingly widely used in modern hydraulic excavators, which can achieve more efficient equipment status monitoring and fault warning, improve equipment maintainability and operational efficiency.  

c. The automatic hydraulic excavator control system utilizes a laser emitter for automatic excavation control. Its basic principle is to set up a rotary laser emitter at the construction site, which can control several excavators to operate on the same required reference surface. A laser receiver is installed on the excavator, which has three light targets - upper, lower, and reference light targets. When the laser beam emitted by the laser emitter precisely hits the reference light target, the working device of the excavator remains on the required ideal working surface for operation. If external factors cause the working device of the excavator to deviate from the ideal working surface, the laser beam will either hit the upper target or the lower target, indicating that the working device has deviated. At this point, the upper or lower light target will convert the light signal into an electronic command signal to drive the diversion valve installed on the excavator to operate, thereby controlling the flow of hydraulic oil and allowing the excavator's working device to return to the desired ideal working surface for operation. The automatic excavation control system using laser emitters can greatly reduce the labor intensity of drivers and achieve better excavation operation quality.  

d. Remote control excavator refers to an excavator that is operated through wired or wireless circuit devices. The general wired remote control distance is 150-300m, and the wireless remote control distance is 1500-2000m. In the remote control device, the displacement of the joystick is converted into voltage, which is then converted into digital value by an A/D converter. The parallel signals of each joystick are converted into series signals, which are transmitted and processed by a wireless motor, and the signals are transmitted to the excavator. The signal received by the excavator is opposite to the action during transmission, converted into a current value, and through an electromagnetic proportional pressure reducing valve, the actuator (hydraulic cylinder or hydraulic motor) is activated. Other actions also rely on receiving wireless signals and using solenoid valves to activate the executing components.  

e. The main features of the hydraulic excavator control system include: (1) adopting an electronic control pressure compensation load sensing hydraulic system. It consists of a load sensing control valve and a load sensing control variable pump, and the output flow of the hydraulic pump is always equal to the flow required by the executing components (hydraulic cylinder, hydraulic motor). (2) Adopting an electronic control power regulation system. This is mainly achieved by setting the power of the engine and hydraulic pump through the computer, determining the throttle opening of the engine and the displacement of the hydraulic pump. In this way, different engine characteristics and hydraulic pump characteristics can be adopted according to the different operating conditions of the excavator, and their characteristic curves are determined by computer software. (3) The control system adopts a combination of manual and electronic control. Due to the changing working conditions and complex operations of excavators, manual control is still indispensable, but electronic control plays an important auxiliary adjustment role. For example, during the entire operation of an excavator, the driver can only operate one handle, and the rest of the actions are automated interlocking movements. But the manual priority principle is adopted, and the automatic control system suspends operation when manually operated. (4) The handheld terminal fault diagnosis system is adopted, which can timely detect and handle the faults that occur in the excavator.  

In addition, the design of human-computer interaction interface is constantly optimized to adapt to different operating environments and habits, aiming to enhance the intuitive operation and user experience.  

f. The cab lifting control system adjusts the hydraulic pump and solenoid valve through an electronic controller to achieve smooth control of the cab lifting speed, aiming to reduce vibration and improve operational comfort, while also helping to extend the service life of equipment.

Writer: Jacky(Haiqinmachinery-Jacky)-Mr Jacky Wang working at HaiqinTop machinery since 2006 year,he have a lot of experience for sales wheel loader/backhoe loader/Telehandler /excavator and he also professional for every kinds of technicals , can give customer good service and Technical Guidance.Also give customers 24 hours service every day.   www.haiqintop.com