Engineering vehicles are an important component of the machinery industry, playing a crucial role in urban construction, transportation, energy extraction, offshore development, agricultural water conservancy, and national defense construction, providing advanced construction equipment and means for modernization. However, with global energy shortages and environmental pollution issues, some developed countries have announced bans on the sale of fuel vehicles, and China's Ministry of Industry and Information Technology has also put a comprehensive ban on the sale of fuel vehicles on the agenda.

Electric cylinders now have the characteristics of high speed, high efficiency, high power, high reliability, and high integration, and maintenance costs are less than one tenth of hydraulic cylinders. After the electric actuation modification of the construction vehicle, it can effectively avoid the loss of service life and efficiency caused by the original hydraulic cylinder running, emitting, dripping, leaking, and grade change impact, and improve the service life and energy utilization rate of the construction vehicle.

In the context of Industry 4.0, servo electric cylinders are more conducive to achieving the integration of automation and informatization due to their closed-loop control, high precision, high response, and high rigidity. The electric actuation system of construction vehicles will be widely used in the field of construction machinery in the future.

Reliability analysis from a perspective

The system composition of hydraulic cylinders is relatively complex, including hydraulic pipelines, hydraulic pumps, hydraulic valves, cylinder bodies, etc. The stroke of hydraulic cylinders is controlled by proximity switch signals received through solenoid valves, and their position locking is controlled by locking valves. If there is oil leakage in the hydraulic system, the stroke accuracy and position maintenance accuracy of hydraulic cylinders will decrease.

The composition of the electric cylinder system is simpler than that of the hydraulic cylinder. The motor and cylinder body are integrated together, and with the controller and cables, the structure is simple and compact; The stroke of the electric cylinder is controlled by a proximity switch, and the highly reliable proximity switch controls the expansion and contraction of the electric cylinder, ensuring reliable stroke control; The extension of the electric cylinder is controlled by the rotation of the electric motor, and the rotation of the motor is precisely controlled by the controller, so that the electric cylinder can stop and lock at any position within any stroke (screw self-locking, motor brake), and the position locking is reliable.

Testing perspective analysis

The difficulty in diagnosing faults in hydraulic systems is currently a challenge in the industry, mainly due to the complex selection of pressure testing points, which also leads to difficulties in testing and repairing hydraulic systems.

When designing the testability of electric cylinders, it is important to choose appropriate testing methods and techniques, divide product units reasonably, and set up testing points to facilitate debugging and maintenance.

Analysis from the perspective of maintainability

The maintenance of hydraulic cylinders is divided into inspection and maintenance of seals, inspection and maintenance of cylinder barrels, inspection and maintenance of piston rods/guide sleeves, and inspection and maintenance of buffer valves.

Electric cylinder is a design that integrates the motor, reducer, gearbox, and cylinder body, making it easy to isolate and troubleshoot faults in the event of an electric cylinder failure. At the same time, due to its high integration, few components, low failure points, and low probability of maintenance, routine grease injection maintenance is basically required.

Analysis from a security perspective

In daily work, safety accidents often occur in hydraulic systems, resulting in minor injuries or fatalities, severe injuries or even serious damage to the workplace.

For electric cylinders, when the drive detects that the current is greater than the set value during operation, it will issue an alarm and stop working. The corresponding alarm information will be displayed on the digital tube of the drive, and the alarm information will be fed back to the upper computer. Electric cylinders have position locking and current limiting functions. In the event of a power outage during operation, the electric cylinder will self lock; Open current limiting when the electric cylinder malfunctions to ensure the safety of the load and cylinder.

Analysis from the perspective of security

The viscosity of hydraulic oil in hydraulic cylinders is easily affected by external temperature. When the hydraulic cylinder is in a low-temperature environment, the viscosity of the hydraulic oil increases, the gap between hydraulic oil molecules decreases, resulting in an increase in hydraulic oil friction and a decrease in hydraulic cylinder efficiency; When the hydraulic cylinder operates under sand and dust conditions, if sand and dust enter the hydraulic system, it will reduce the service life of hydraulic valves, hydraulic pumps, and hydraulic pipelines.

Electric cylinders are mainly composed of mechanical transmission mechanisms such as motors, reducers, and cylinder bodies. They have a simple and compact structure, and the impact of environmental temperature changes on the operation of electric cylinders is small. The working temperature range of electric cylinders is usually -40~80 degrees Celsius. When designing electric cylinders, motors, reducers, and drivers that meet high and low temperature working performance are selected. The lubrication of structural components uses lubricating grease that adapts to high and low temperatures, making the electric cylinder have good temperature adaptability; The installation surface of the electric cylinder is sealed with rubber or copper foil, and the protruding end face of the push rod is treated with a sealed dust ring for waterproofing and dust prevention, so the electric cylinder can operate reliably in water and sand dust conditions.

Analysis from the perspective of lifespan

Due to the fact that all power, transmission, and execution components of electric cylinders are mechanical transmission structures, their lifespan can be estimated through L10 lifespan calculation and dynamic rated load. However, the lifespan of hydraulic cylinders is closely related to external conditions such as environmental temperature, making it difficult to accurately calculate. According to market research, the service life of hydraulic systems is generally 12000 hours, which is calculated to be about 4 years based on a 12 hour working system. The service life of electric cylinders can be calculated and designed in advance according to actual needs, and the theoretical service life is greater than that of hydraulic cylinders. However, as a weak component of electric cylinders, bearings have an average trouble free usage time of about 1000 hours, which is lower than the trouble free usage time of components such as valves, pipelines, and hydraulic oil in hydraulic cylinders. Therefore, electric cylinders are more suitable for construction vehicles with larger working intervals, such as car cranes, dump trucks, and bulldozers.

Conventional electric cylinder

The commonly used structural forms of electric cylinders are: direct connection, folding, right angle, etc. Different structural forms of electric cylinders can be selected according to the limitations of installation space.

Synchronous belt electric cylinder

The synchronous belt driven electric cylinder has the following performance characteristics: 1) accurate transmission, no sliding during operation, and a constant transmission ratio; 2) Smooth transmission, with buffering and damping capabilities, and low noise; 3) The synchronous belt transmission efficiency is high, reaching 0.98, and the energy-saving effect is significant; 4) The speed ratio range is large, generally up to 10 (considering the size of the gearbox, the speed ratio of the gear transmission electric cylinder is generally 1-1.5), the linear speed can reach 50mm/s, and it has a large power transmission range of several watts to several kilowatts; 5) It can be used for long-distance transmission, and the maximum center distance of synchronous belt driven electric cylinder transmission can reach 10m or more.

High frequency electric cylinder

The high-frequency electric cylinder adopts a spiral mechanism to convert the cylinder barrel limit into linear motion. The input shaft of the electric cylinder rotates once, and the electric cylinder can travel back and forth for one stroke, with high-frequency characteristics. The power output of high-frequency electric cylinders and diesel hammer pile drivers is based on the crank connecting rod mechanism. The input shaft drives the crankshaft to rotate once, and the load can travel back and forth for one stroke. The power input of high-frequency electric cylinders is different. High frequency electric cylinders drive the crankshaft to rotate through an electric motor, causing the piston (push rod) to make reciprocating motion. Combining the performance characteristics of high-frequency electric cylinders with the functions of pile drivers, high-frequency electric cylinders can be applied to pile drivers.

Telescopic rotary electric cylinder

Rotary drilling rig is a comprehensive drilling rig that has the characteristics of fast drilling speed, low pollution, and strong maneuverability. When the rotary drilling rig is working, the power device of the drilling rig provides torque to the drill rod, and the pressure device provides pressure to the drill rod. The drill bit rotates to break the soil along the edge, and the soil along the edge is loaded into the drill bit and unloaded externally. The telescopic rotary electric cylinder is an electric cylinder that can move back and forth while also rotating 360 ° freely. Connect the push rod of the telescopic rotary electric cylinder to the drill bit to complete the function of rotary drilling.

Buffer electric cylinder

The front of the bulldozer is equipped with a large metal bulldozer blade. When in use, the hydraulic cylinder above the bulldozer extends to lower the bulldozer blade, and it moves forward to cut and push mud, sand, stones, etc. The position and angle of the bulldozer blade can be adjusted. It has the characteristics of flexible operation and easy rotation. During the operation of a bulldozer, the bulldozer blade is prone to biased loads, which can affect the lifespan of the actuator. The instantaneous impact load of the buffer type electric cylinder is reduced during the starting and impact processes. The buffer type electric cylinder is used on bulldozers as an actuator for lifting bulldozers, and its service life is effectively improved compared to hydraulic cylinders.

Due to its closed-loop control, high precision, high response, and high rigidity, servo electric cylinders are more conducive to achieving the integration of automation and informatization. The electric actuation system of construction vehicles will be widely used in the field of construction machinery in the future.