Application and Advantages of Axial Piston Variable Motor A6VM in Coal Mine Equipment

In modern coal mining operations, hydraulic axial piston motors are core power components, and their performance directly determines the working efficiency and reliability of coal mining machinery. The A6VM series axial piston variable motors have become the preferred drive solution for high-end coal mining equipment at home and abroad due to their excellent power density , wide speed regulation range and outstanding durability . This article will comprehensively analyze the technical characteristics of the A6VM series motors, deeply explore their application scenarios in key coal mining equipment such as coal mining machines, tunneling machines, and scraper conveyors, systematically explain their energy-saving advantages compared to traditional motors, and provide scientific selection and maintenance recommendations. Finally, it looks forward to the development prospects of this technology in the construction of intelligent mines.

Introduction: Core requirements of hydraulic systems for coal mine equipment

As an important component of the global energy structure, the mining efficiency and safety of coal have always been the focus of the industry. With the increasing depth of coal mining and the increasingly complex operating environment, higher requirements are placed on coal mining machinery and equipment - high power output , precise speed regulation , high reliability and energy saving and environmental protection have become the four core indicators of modern coal mining equipment. In this context, the hydraulic transmission system has become the preferred power transmission method for various types of coal mining machinery due to its advantages such as high power density, flexible layout and strong impact resistance.

As a key actuator of the hydraulic system, the performance of the hydraulic axial piston motor directly affects the performance of the whole machine. Traditional quantitative motors often face problems such as narrow speed regulation range, low efficiency, and frequent maintenance under harsh working conditions in coal mines, which seriously restricts the full performance of the equipment. The A6VM series axial piston variable motors perfectly solve these pain points through innovative helical axis design and advanced control technology, providing efficient and reliable power solutions for coal mine equipment.

This article will introduce the technical principles and product characteristics of the A6VM series motors, analyze in detail their typical applications in various types of coal mining equipment, demonstrate their energy-saving advantages through comparative data, and provide a practical selection and maintenance guide. Finally, it will look forward to their development prospects in smart mines, providing a comprehensive reference for coal mining equipment manufacturers, users and technicians.

Rexroth A6VM series axial piston variable motor technology analysis

Product Series Overview and Basic Parameters

high-pressure variable motor product line designed for heavy-duty conditions , covering a specification range of 28 to 1000, which can meet the needs of coal mining equipment of different power levels. This series adopts a modular design concept and can be divided into two categories according to the nominal pressure: the nominal pressure of motors with specifications of 28 to 200 is 400bar, and the peak pressure can reach 450bar; while the nominal pressure of products with specifications of 250 to 1000 is 350bar, and the peak pressure is 400bar. This high-pressure design enables the A6VM series to output greater torque at the same volume, which is particularly suitable for coal mining machinery applications with limited space but high power requirements.

Displacement range is another significant advantage of the A6VM series, its stepless variable characteristics allow the displacement to be continuously adjusted within the range of Vg max to Vg min (=0). Taking the A6VM140 model as an example, the maximum displacement can reach 171.8cm³ and the minimum displacement can be adjusted to 0. This wide adjustment range enables a single motor to adapt to the needs of various operating conditions of coal mining equipment, greatly simplifying the transmission system design. In terms of speed characteristics, the nominal speed range of this series of motors under Vg max conditions is 2500-4450rpm (depending on different specifications), and the maximum speed can reach 8400rpm at minimum displacement, demonstrating excellent high-speed performance .

Core structure and working principle

The A6VM series adopts an axial conical plunger rotor group with a slanted axis design . This structure has higher power density and longer service life than the traditional slanted plate design. Its core components include cylinder body, plunger, valve plate, slanted axis and variable mechanism, etc. All friction pairs are optimized and equipped with high-quality bearing systems to ensure stable performance in the harsh environment of coal mines.

working principle , when high-pressure oil enters the plunger cavity through the distribution plate, it pushes the plunger to move axially. Due to the certain inclination of the inclined axis, the linear motion of the plunger is converted into the rotational motion of the main shaft. By adjusting the inclination of the inclined axis, the motor displacement can be changed to achieve stepless adjustment of the output speed and torque. The unique variable mechanism design of the A6VM series makes it respond quickly and has high control accuracy, and can match the changing load requirements of coal mine equipment in real time.

It is worth mentioning that the A6VM motor adopts a bidirectional rotation design, which can easily achieve forward and reverse switching. This feature is particularly important in coal mining equipment that requires frequent reversing (such as the cutting head of a roadheader). At the same time, the symmetrical design of its internal structure ensures performance consistency under forward and reverse working conditions, avoiding the problem of reverse performance degradation caused by the unidirectional design of traditional motors.

Highlight technical features and advantages

A6VM series hydraulic axial piston motors have many technical advantages in coal mine applications:

High power density is one of the most notable features of the A6VM series. By optimizing the hydraulic flow path and using high-strength materials, this series of motors achieves extremely high torque output in a compact size. Taking the A6VM200 model as an example, it can output up to 1550Nm of torque at nominal pressure and weighs only 78kg. This excellent power-to-weight ratio makes it an ideal choice for coal mining equipment with limited space.

The wide control range enables the A6VM to meet the dual requirements of high speed and high torque of coal mining equipment. In coal mining operations, equipment often needs to frequently switch between low-speed and high-torque conditions (such as cutting hard coal) and high-speed and low-torque conditions (such as rapid shifting). Traditional fixed-displacement motors need to use complex gearboxes to achieve this requirement, while the A6VM variable-displacement motor can achieve this requirement simply by adjusting the displacement, greatly simplifying the transmission system and improving reliability.

Excellent starting characteristics and low moment of inertia enable the A6VM series to perform well under the frequent start-stop conditions of coal mining equipment. Coal mining machinery often needs to start instantly and withstand sudden loads. Traditional motors are prone to problems such as difficulty in starting or excessive impact. A6VM significantly reduces the starting friction torque by optimizing the plunger structure and bearing system. At the same time, it has a small moment of inertia and a fast response speed, ensuring the smooth starting of the equipment under heavy load conditions.

The rugged and durable design makes the A6VM particularly suitable for the harsh environment of coal mines. Its housing is made of high-strength cast iron, the key friction pairs are specially treated, and the bearing system is reinforced to resist the dust, moisture and vibration in the coal mine environment. Practical applications have shown that with proper maintenance, the service life of the A6VM motor in coal mine equipment can reach 1.5-2 times that of traditional motors, greatly reducing equipment downtime and maintenance costs.

Table: Comparison of technical parameters of some models of Rexroth A6VM series

Analysis of Typical Applications of A6VM in Coal Mine Equipment

Coal mining machine drive system

As the core equipment of modern fully mechanized mining face, the performance of coal mining machine directly affects the production efficiency and safety of coal mines. With its high torque output and precise speed regulation capability, A6VM series hydraulic axial piston motor has become the ideal drive choice for the traction and cutting parts of high-end coal mining machine.

In the shearer traction system, the A6VM motor is usually used in conjunction with a reducer to drive the shearer to move along the working face. The complexity of coal mine geological conditions requires the traction system to be able to adjust speed and torque in real time according to load changes. The stepless variable characteristics of the A6VM enable the shearer to automatically reduce speed and increase torque under hard coal conditions, and increase speed and productivity under soft coal conditions. Actual application data shows that the shearer traction system using the A6VM motor is 15%-20% more efficient than the traditional quantitative motor solution, especially in the working face where the coal seam thickness varies greatly, its adaptive advantage is more obvious.

The cutting section drive has more stringent requirements on the motor, which needs to withstand strong impact loads and frequent forward and reverse rotation. The high power density design of the A6VM series enables it to provide sufficient torque to drive the cutting drum in a limited space. Its sturdy bearing system and optimized plunger group can effectively absorb the vibration and impact during the cutting process. A comparative test in a large coal mine showed that the cutting section of the coal mining machine using the A6VM160 motor worked continuously for 800 hours without failure under hard coal conditions, while similar competing motors required maintenance every 500 hours on average.

Application of key parts of tunnel boring machine

Coal mine roadheaders face more complex working conditions and need to meet the dual requirements of efficient rock breaking and precise positioning . The A6VM series motors have excellent performance in the cutting head, loading mechanism and travel mechanism of the roadheader.

The cutting head drive is the core function of the tunnel boring machine, which requires the motor to provide continuous and stable high torque output . The A6VM107 and A6VM140 models are often used for the cutting drive of medium-sized tunnel boring machines. Their wide speed regulation range allows operators to adjust the cutting speed in real time according to the hardness of the rock formation, which not only protects the cutting teeth but also improves the footage efficiency. Especially when encountering faults or hard rocks, the motor can automatically reduce the speed and increase the torque to avoid equipment overload and shutdown. Application data of a coal tunneling project shows that the tunnel boring machine using the A6VM motor has a 40% lower failure rate and a 25% increase in monthly footage than the traditional electric drive solution.

In the traveling mechanism of the roadheader, the low-speed stability and precise control characteristics of the A6VM motor are fully utilized. The conditions of coal mine tunnels are complex, requiring the roadheader to be able to perform millimeter-level precise positioning. The A6VM can achieve ultra-low-speed stable operation of 0.1r/min through a closed-loop control system, fully meeting the precise positioning requirements. At the same time, its fast response characteristics enable operators to adjust the position of the roadheader in a timely manner to ensure the quality of the roadway forming.

Scraper conveyor and hydraulic support system

Scraper conveyor is a key equipment for coal transportation in coal mine working face, and its drive system needs to operate continuously at high load . A6VM series motors perform well in the head and tail drive of heavy-duty scraper conveyors, especially large displacement models such as A6VM200 and A6VM250, which can provide sufficient starting torque to overcome the resistance of full-load starting.

Compared with traditional motor drives, scraper conveyors using A6VM hydraulic axial piston motors have three major advantages: First, the overload protection performance is good. When the conveyor chain is stuck, the increased pressure in the hydraulic system will automatically reduce the motor speed to avoid equipment damage; second, the power distribution is flexible. When multiple motors are driven, the power of each drive point can be automatically balanced; third, the soft start feature significantly reduces chain impact and extends the service life of the equipment. The application practice in a mine with a capacity of tens of millions of tons shows that the chain life of the hydraulically driven scraper conveyor is more than 30% longer than that of the electric drive, and the annual maintenance cost is reduced by about 150,000 yuan.

In the hydraulic support system, the A6VM motor is mainly used for the rapid frame movement function. Modern fully mechanized mining faces require that the support can move quickly with the coal mining machine. Traditional quantitative motors are difficult to balance the pushing speed and positioning accuracy. The A6VM variable motor can achieve a perfect combination of high-speed frame movement and precise positioning through displacement adjustment, significantly improving the working face advancement efficiency. Monitoring data shows that the support system using the A6VM motor has a 20% higher frame moving speed than the traditional solution, and the positioning accuracy can reach ±10mm, which fully meets the requirements of the automated work surface.

Other coal mine auxiliary equipment applications

In addition to the above core equipment, A6VM series hydraulic axial piston motors are also widely used in various types of coal mine auxiliary equipment. For coal mine drilling rigs, small and medium-displacement models such as A6VM55 and A6VM80 provide ideal rotational power. Their high-speed performance meets the drilling requirements of different rock formations, while variable control enables automatic parameter adjustment during the drilling process.

The hydraulic drive pump group of the coal mine drainage system also often uses the A6VM motor as the power source. The hydrological conditions in coal mines are complex, the discharge volume varies greatly, and traditional fixed-speed pump sets are inefficient. The A6VM variable motor driven pump can adjust the pump speed in real time according to the water level changes, maintain the best working efficiency, and achieve significant energy saving effect. The renovation case of a coal mine central water pumping station showed that after adopting the hydraulic variable system, the annual electricity saving reached 450,000 kWh, and the investment payback period was less than 2 years.

In addition, A6VM motors are also used in coal mine overhead passenger devices , crushers , loading stations and other equipment, and their reliability and adaptability have been widely recognized by coal mine users. With the improvement of coal mine automation and intelligence, the precise control characteristics of A6VM series motors will play a greater role and provide high-quality power solutions for intelligent mine construction.

Table: Typical application configurations of A6VM series in different coal mine equipment

Energy-saving advantages and technical and economic analysis of A6VM variable motor

Energy consumption comparison with traditional fixed displacement motors

As a high-energy-consuming industry, improving equipment energy efficiency in coal mining is directly related to production costs and carbon emissions. Rexroth A6VM series hydraulic axial piston motors use advanced variable technology to achieve significant energy saving effects compared to traditional fixed displacement motors, which are mainly reflected in the following aspects:

Load adaptive regulation is the core energy-saving mechanism of A6VM. The load conditions of coal mining equipment vary greatly. The efficiency of traditional fixed displacement motors drops sharply at partial loads. However, the A6VM can adjust the displacement to keep the motor operating in the high-efficiency range. Taking the coal mining machine traction system as an example, when the load decreases, the A6VM automatically increases the displacement and reduces the speed to keep the working pressure in the high-efficiency area, while the fixed-speed motor causes the pressure to drop and the efficiency to decrease. Actual measured data show that under typical working conditions, the average efficiency of the A6VM variable system is 18%-25% higher than that of the quantitative system, and the annual electricity savings can reach tens of thousands of kWh.

No overflow loss is another important energy saving point. Coal mine equipment often requires different speed and torque combinations. The traditional system adjusts the flow through the proportional valve throttling, which causes the high-pressure oil to overflow through the overflow valve, resulting in energy waste. The A6VM adopts the volumetric speed regulation principle and adjusts the speed by changing the motor displacement. The system flow is accurately matched with the load demand, and the throttling and overflow losses are basically eliminated. The modification case of a coal mine scraper conveyor shows that after adopting the A6VM variable system, the hydraulic oil temperature is reduced by an average of 15-20℃, and the energy consumption of the cooling system is reduced by 40%, which fully proves its energy saving effect.

power matching function enables the A6VM system to dynamically adjust the output power according to actual working conditions. The power requirements of coal mining equipment vary greatly in different working stages. For example, a roadheader requires high power when cutting, but only low power when positioning. The A6VM system monitors load changes through sensors and adjusts motor displacement and system pressure in real time to avoid energy waste caused by "a big horse pulling a small cart". Statistics show that this intelligent power matching can reduce the energy consumption of the entire machine by 20%-30%. Against the backdrop of rising energy prices, this advantage has significant economic value.

Comprehensive comparison with electric drive systems

hydraulic axial piston motors shows unique advantages under special working conditions in coal mines :

overload capacity , the A6VM motor has a natural advantage. The overload capacity of the electric motor is usually no more than 1.5 times the rated value, and the duration is short, while the hydraulic motor can easily withstand 2-2.5 times the instantaneous overload, which is crucial for coal mining equipment that bears impact loads. For example, when the coal mining machine encounters hard coal gangue, the A6VM system can automatically increase the pressure and torque to avoid equipment shutdown, while the electric motor may trigger a protective shutdown, affecting production efficiency.

Explosion-proof safety is the primary consideration for coal mine equipment. The hydraulic system is inherently safe, with no risk of electric sparks, and is particularly suitable for high-gas mine environments. The A6VM motor adopts a fully enclosed design with a protection level of up to IP67, which fully meets the dust and water requirements of the harsh environment of coal mines. In contrast, explosion-proof motors are large in size, high in cost, and complex to maintain, and do not have advantages under some working conditions.

system flexibility , hydraulic drive has irreplaceable value. The A6VM system transmits power through pipelines, has a flexible layout, and is easy to achieve multi-drive point synchronization and power distribution, which is particularly suitable for equipment such as long-distance scraper conveyors. However, electric drive requires an independent motor and control system for each drive point, which requires large investment and complex control. A comparative test of a large coal mine showed that at a working surface above 300 meters, the total cost of ownership of a hydraulically driven scraper conveyor is 15%-20% lower than that of an electric drive.

Life cycle cost analysis

From a long-term operational perspective, the A6VM hydraulic axial piston motor system has superior economic efficiency, which is mainly reflected in the following aspects:

initial investment , the cost of high-end hydraulic systems is comparable to that of explosion-proof motor drives, but considering that hydraulic systems can simplify mechanical transmission components (such as reducers, clutches, etc.), the overall cost is often more competitive. Especially for high-power equipment, the power density advantage of hydraulic systems makes them more valuable in the space-constrained underground coal mine environment.

Operating energy costs are a major part of life cycle costs. As mentioned earlier, the A6VM variable system can save 15%-25% energy compared to traditional hydraulic systems and 10%-15% energy compared to fixed-speed motor drives. Taking a medium-sized coal mining face that consumes 2 million kWh of electricity per year as an example, the use of the A6VM system can save 200,000 to 500,000 kWh of electricity per year, equivalent to an electricity bill of about 100,000 to 250,000 yuan (calculated at 0.5 yuan per kWh), with significant economic benefits.

maintenance costs , the A6VM series has significantly reduced maintenance frequency and costs thanks to its rugged design and long life . Statistics show that under the same operating conditions, the overhaul interval of the A6VM motor is 1.5-2 times that of ordinary motors, and spare parts consumption is reduced by more than 30%. In addition, the modular design of the hydraulic system makes on-site maintenance more convenient and reduces equipment downtime.

The indirect economic benefits brought by the improvement of production efficiency are even more considerable. The rapid response and precise control of the A6VM system enable coal mining equipment to operate at optimal parameters, improving mining efficiency and resource recovery rate. Multiple application cases have shown that the efficiency of coal mining machines using the A6VM hydraulic system has increased by 10%-15%, and the monthly footage of tunneling machines has increased by 20%-25%. These hidden benefits often far exceed the direct energy-saving benefits.

Table: Comparison of the full life cycle costs of the A6VM hydraulic system and alternative technologies (taking coal mining machine as an example)

Note: The data in the table are the industry average, and the specific values vary depending on mine conditions and equipment configuration

A6VM Motor Selection and Maintenance Guide

Scientific selection methods and key parameters

Correct selection is the prerequisite for ensuring that the hydraulic axial piston motor performs optimally in coal mining equipment. There are many models in the A6VM series, which need to be scientifically selected according to specific application conditions, mainly considering the following parameters:

Displacement selection is basic work and needs to be calculated based on the maximum torque and working pressure required by the equipment . The formula is: displacement Vg=(2π×T)/(Δp×ηm), where T is the load torque (Nm), Δp is the working pressure difference (bar), and ηm is the mechanical efficiency (usually 0.9-0.95). Coal mining equipment often faces sudden loads, and it is recommended to leave a torque margin of 10%-15%. For example, the maximum load torque of a certain roadheader cutting head is 950Nm, and the system working pressure is 350bar. It is calculated that Vg≈(2×3.14×950)/(350×0.93)≈183cm³, so it is more appropriate to choose the A6VM200 model (Vg max=216.5cm³).

The speed range must meet both the minimum and maximum speed requirements of the equipment. The A6VM series can reach the highest speed at the minimum displacement, and provides maximum torque but the lowest speed at the maximum displacement. When selecting a model, it is necessary to check whether the motor speed at Vg max meets the low-speed requirements of the equipment, and whether the speed at Vg min meets the high-speed requirements. It is particularly important to note that coal mining equipment works under low-speed and high-torque conditions for a long time. It is necessary to ensure that the efficiency curve of the selected model under this condition is relatively flat to avoid overheating caused by a sharp drop in efficiency.

control mode depends on the degree of automation of the equipment. A6VM provides a variety of control options: HD type is hydraulic proportional control, suitable for most coal mining equipment; EP type is electric proportional control, which is easy to connect to the automation system; EZ type has a neutral switch, which is suitable for occasions where precise position control is required. For modern intelligent mining equipment, it is recommended to choose EP or EZ type to facilitate remote monitoring and intelligent adjustment. For example, a smart coal mining machine project uses the A6VM200EP2D/63W2 motor, which is connected to the control system through the CAN bus to achieve automatic optimization of cutting parameters.

The installation interface and shaft extension form must match the mechanical structure of the equipment. The A6VM series provides a variety of flange and shaft extension options, including ISO, SAE standards and special customized interfaces. Coal mining equipment is often exposed to strong vibrations. It is recommended to use SAE flange interfaces with better rigidity and use them with shock-absorbing supports. The shaft extension form needs to consider the torque transmission requirements. It is recommended to use spline shafts for large torque occasions, and flat key shafts for small and medium torques.

System Configuration Key Points and Precautions

the A6VM hydraulic axial piston motor is inseparable from reasonable system configuration. In coal mine applications, special attention should be paid to the following points:

Oil cleanliness is a key factor affecting the life of A6VM. Coal mines are dusty, so the hydraulic system must be equipped with high-precision filters. It is recommended to set a 10μm filter with β≥75 in the oil inlet and a 20μm filter with β≥75 in the oil return. Practical experience shows that oil contamination causes more than 70% of A6VM motor failures, so it must be taken seriously. For high-dust coal mine underground environments, consider adding an offline filtration system to regularly finely filter the oil in the tank.

the oil drain line is often overlooked but is crucial. A6VM requires that the housing oil drain back pressure does not exceed 0.5 bar, and the oil drain pipe should return directly to the oil tank and be inserted below the oil level. Due to space limitations, coal mining equipment often uses multiple motors to share one oil drain line, which can easily lead to excessive back pressure and oil seal damage. It is recommended to set up a separate oil drain pipe for each A6VM motor, or use a common pipe with a large enough diameter (at least the same diameter as the motor oil drain port). The improvement case of a mining tunneling machine shows that after optimizing the oil drain line, the bearing life of the A6VM motor was extended by 3 times.

the cooling system needs to be calculated and determined based on the actual heat generation. The total efficiency of A6VM can reach more than 90% when working in the high-efficiency zone, but the efficiency may drop to about 80% under low-speed and high-torque conditions, and 10%-20% of the power will be converted into heat. The ambient temperature underground in coal mines is high and the heat dissipation conditions are poor, so a cooler of sufficient capacity must be configured. It is recommended to install an oil temperature sensor for real-time monitoring. When the oil temperature exceeds 65°C, an alarm should be issued, and when it exceeds 70°C, the machine should be shut down for inspection. Practical experience shows that good temperature control can extend the maintenance interval of A6VM motors by 30%-50%.

Anti-vibration measures are particularly important for coal mining equipment. Although the A6VM has a sturdy and durable design, long-term strong vibration will still affect its life. It is recommended to use shock-absorbing supports during installation, and all connecting pipes should use flexible hose transitions to avoid rigid connections. Especially for high-frequency vibration parts such as the cutting part of the coal mining machine, it is possible to consider adding a hydraulic accumulator to absorb pressure pulsations. Monitoring data from a coal mine showed that perfect anti-vibration measures reduced the failure rate of the A6VM motor in a strong vibration environment by 60%.

Maintenance Best Practices

Scientific maintenance can maximize the service life of the A6VM hydraulic axial piston motor . The maintenance points in the coal mine environment include:

Daily inspection items should include: oil level, oil temperature, oil quality; motor housing temperature (should not exceed 80℃); abnormal noise or vibration; leakage at each connection. It is recommended to adopt the four-step method of "look, listen, touch, and measure": look at the color and foam of the oil; listen to whether the running sound is uniform; touch the housing temperature to see if it is abnormal; and measure whether the system pressure and flow are normal. It is best to conduct a quick inspection of coal mine equipment every shift and record key parameters to facilitate the discovery of early signs of failure.

of regular maintenance should be determined according to the actual working conditions. It is generally recommended to replace the return oil filter every 500 working hours; take samples to test the oil contamination and moisture content every 2000 hours; and conduct a comprehensive inspection of the internal wear of the motor every 4000 hours. The underground environment of coal mines is harsh, and the maintenance cycle can be appropriately shortened. During maintenance, special attention should be paid to the wear of key friction pairs such as plungers, distribution plates, and bearings, and parts that exceed the allowable value should be replaced in time. The maintenance experience of a large coal mine shows that insisting on preventive maintenance can extend the overhaul interval of the A6VM motor to more than 10,000 hours.

Fault diagnosis requires systematic thinking. Common faults of A6VM include: difficulty in starting (possibly due to excessive oil viscosity or system air intake); insufficient output torque (possibly due to excessive internal leakage or insufficient control pressure); abnormal noise (possibly due to bearing damage or plunger jamming). During diagnosis, a comprehensive analysis of multiple parameters such as pressure, flow, and temperature should be conducted to avoid misjudgment. For example, possible reasons for excessive motor temperature include: improper oil viscosity, insufficient cooling, excessive internal leakage, overload operation, etc., which need to be checked one by one. It is recommended that coal mining enterprises be equipped with basic hydraulic testing equipment, such as pressure gauges, flow meters, infrared thermometers, etc., to improve the efficiency of fault diagnosis.

Spare parts management is crucial to reducing downtime. Coal mines have high requirements for production continuity. It is recommended to stock the following A6VM key spare parts: shaft seal assembly, plunger shoe assembly, distributor plate, bearing kit. Spare parts should be stored in a clean and dry environment, and the dimensional accuracy and surface quality should be checked before installation. Special reminder: accessories of different models of A6VM cannot be mixed. Even parts with similar appearance may have slight differences. Forced use will lead to early failure. The lesson of a coal mine shows that the use of non-original accessories shortens the average life of the A6VM motor by 40%.

Table: Recommended maintenance cycle for A6VM motors in coal mine environments

Note: The maintenance cycle in the table is a general recommendation and should be adjusted according to actual working conditions and equipment manufacturer's recommendations.

The development prospects of A6VM technology under the trend of intelligent mining

Integration and application of digital technology

With the accelerated advancement of smart mine construction, hydraulic axial piston motors are transforming from simple power elements to intelligent actuators. The A6VM series provides an ideal platform for the digital upgrade of coal mining equipment by integrating sensors and communication interfaces. The new generation of A6VM EPR motors have built-in pressure, temperature and speed sensors, which can monitor the working status in real time and transmit data to the control system through the CAN bus or IO-Link interface. This intelligent monitoring function enables equipment managers to remotely grasp the health status of the motor, realize predictive maintenance, and avoid production interruptions caused by sudden failures.

digital twin technology in the A6VM system are broad. By building a virtual model of the motor and synchronizing the operating data of the physical motor in real time, the performance under various working conditions can be simulated and predicted in the digital space. Coal mining companies can use this technology to optimize equipment operating parameters, simulate the best cutting strategies under different geological conditions, and even predict the remaining life of key components. For example, a test mine connected the digital twin model of the A6VM200 motor to the mine's central control system and successfully achieved adaptive adjustment of the cutting power, reducing energy consumption per ton of coal by 12%.

Automatic control is the core requirement of smart mines. The combination of the A6VM series and electro-hydraulic proportional technology provides precise actuators for coal mining equipment. By programming and controlling the motor displacement and rotation direction, advanced functions such as automatic height adjustment of the coal mining machine and automatic positioning of the tunneling machine can be realized. In particular, the neutral position switch (NLS) equipped with the A6VM EZ motor can accurately detect the position of the inclined axis and provide feedback signals for closed-loop control. Practice has shown that the drum height control accuracy of the coal mining machine using the A6VM intelligent control can reach ±2cm, far exceeding the level of manual operation.

Continuous innovation of energy-saving technology

Under the "dual carbon" goal, the energy-saving and consumption-reduction requirements for coal mining equipment are constantly increasing, and the innovation of the A6VM series in energy efficiency will continue to deepen:

The hybrid power system provides a new energy-saving idea for coal mine hydraulic equipment. Combining the A6VM motor with flywheel energy storage or supercapacitor can provide auxiliary power when the load changes suddenly, reducing the peak power demand of the main pump. This system is particularly suitable for equipment with large load fluctuations such as tunneling machines. It can reduce the installed power by 15%-20% and improve the dynamic response speed. A certain model of hybrid tunneling machine uses an A6VM140 motor and a 50kJ flywheel energy storage device, which reduces the cutting peak power by 25% and the energy recovery efficiency reaches 35%.

Variable speed pump control system is another important development direction. The traditional constant pressure variable pump system still has throttling loss under partial load, while the variable speed system that uses a variable frequency motor to drive the pump and the A6VM motor can achieve more accurate flow matching . This system controls the flow by adjusting the pump speed instead of throttling, which can theoretically eliminate all throttling losses. Field test data shows that the variable speed pump control system saves 10%-15% energy compared to the traditional load-sensitive system and 30%-40% energy compared to the fixed-displacement pump system, representing the future direction of hydraulic transmission technology.

.

Energy recovery technology has special value in coal mining equipment. When the A6VM motor works as a pump, it can convert the gravitational potential energy of the equipment when it is braked or lowered into hydraulic energy for storage and utilization. For example, when the coal mining machine is towed down or the hydraulic support is lowered, some energy can be recovered. The advanced energy recovery system uses the A6VM motor in combination with the accumulator, and the recovery efficiency can reach more than 60%. Statistics from a certain test mine show that after the comprehensive application of various energy-saving technologies, the total energy consumption of the working face equipment has been reduced by 25%-30%, saving more than one million yuan in electricity bills annually.

Advances in materials and manufacturing processes

A6VM hydraulic axial piston motor is inseparable from the innovation of materials and manufacturing technology:

friction pair materials have significantly extended motor life. The new composite material sliding shoe and coated distributor plate improve the wear resistance of A6VM in the high dust environment of coal mines by more than 50%. In particular, the key friction pairs using diamond-like carbon (DLC) coating have a friction coefficient as low as 0.05-0.08, which greatly reduces starting torque and mechanical losses. A comparative test in a coal mine showed that the A6VM motor using new materials reduced temperature rise by 10-15°C under the same operating conditions and extended its expected life by 8,000 working hours.

bearing technology have increased the load-bearing capacity of the A6VM. The new generation of hybrid ceramic bearings (steel rings with ceramic balls) have excellent corrosion resistance in the wet environment of coal mines, while allowing higher speeds and longer lubrication intervals. The preloaded bearing group optimized for shock loads can effectively absorb the vibration energy during cutting operations and protect the internal structure of the motor. Practical applications show that the failure rate of the A6VM motor using the new bearing under heavy load conditions is reduced by more than 40%.

Additive manufacturing technology provides new possibilities for the optimized design of the A6VM. 3D printing can manufacture complex flow channels and lightweight structures that are difficult to achieve with traditional processes, further improving power density and efficiency. Chinese companies have begun to experiment with the use of selective laser melting (SLM) technology to manufacture certain key components of the A6VM, such as cylinders with optimized oil channel shapes. Test data shows that this design increases the volumetric efficiency of the motor by 2%-3%, which can bring considerable energy-saving benefits in long-term operation.

Role in green mine construction

The green transformation of the coal mining industry has created new application space for A6VM technology:

Fully electric drive hydraulic system is the future trend of coal mining equipment. Combining A6VM motor with electric cylinder, electric control valve and other components can build a completely leak-free "green hydraulic" system. This system uses biodegradable hydraulic oil, which will not pollute the mine environment even if it leaks. At present, Chinese companies are developing an improved version of A6VM specifically for electric hydraulic systems, using special sealing materials and surface treatment to ensure compatibility with environmentally friendly oils.

Noise control technology makes A6VM more suitable for modern mines with high requirements for working environment. By optimizing the number of plungers and the timing of flow distribution, the noise level of the new generation A6VM is 3-5dB lower than that of traditional products. Combined with external mufflers and shock-absorbing brackets, the underground sound environment can be further improved. Measured data shows that the sound pressure level of the A6VM system with a full set of noise reduction measures does not exceed 75dB at 1 meter, which greatly improves the working conditions of miners.

The long-life design reduces waste generation and conforms to the concept of circular economy. The modular design of the A6VM series makes more than 90% of the materials recyclable, and key wear parts can be replaced individually without scrapping the entire machine. Rexroth has also established a complete remanufacturing system. After professional repair, the performance of old motors can be restored to more than 95% of new ones, while the cost is only 60%-70% of new ones. The practice of a mining group shows that the use of remanufactured A6VM motors saves 30% of procurement costs annually and reduces 50 tons of hydraulic waste.

As the construction of smart green mines is further promoted, the A6VM series hydraulic axial piston motors will continue to innovate, providing strong power while meeting the diversified needs of the coal mining industry for high efficiency , energy saving, intelligent control and environmental friendliness , becoming an indispensable core component in the modernization of coal mining equipment. Coal mining companies should pay close attention to these technological development trends and upgrade equipment in a timely manner to maintain market competitiveness and achieve sustainable development goals.