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I. The pain point of no-load energy consumption brought by quantitative hydraulic pumps
Traditional construction machinery heavily relies on fixed displacement hydraulic pumps, which are driven by motors. Whenever the motor rotates, the pump continuously outputs a fixed volume of hydraulic oil. When the joystick is in the neutral position without any lifting or bucket-closing actions, the hydraulic oil does not enter the cylinders to perform work and instead flows back to the oil tank through the overflow valve. During the return flow of oil, pressure energy is converted into heat energy, which not only wastes battery power but also causes the hydraulic system to heat up. For fuel-powered loaders, engine idle fuel consumption is relatively limited, and this issue is often overlooked. Electric loaders have limited electric energy storage, and continuous no-load power consumption directly depletes the battery. In yard operations, there are often waiting periods for trucks to be in position, material piles to be organized, and shift changes to be completed, with each wait lasting for more than ten minutes. The cumulative no-load power consumption over multiple waiting periods is considerable. In addition to power consumption, overflow heating brings about a chain of problems: the temperature of the hydraulic oil rises, accelerating the aging of the hydraulic oil and seals; high temperatures can be transmitted to surrounding components, increasing the burden on the overall cooling system. With the fixed displacement pump solution, as long as the motor rotates, overflow losses are continuously generated, regardless of whether hydraulic action is required.
II. Operating principle of variable hydraulic system: oil supply on demand, low output in non-action state
The variable hydraulic pump equipped on Jining Xinghang can automatically adjust its output flow according to system requirements. When the joystick is in the neutral position and there is no demand for hydraulic action, the pump automatically reduces its displacement, outputting an extremely low flow rate with almost no oil overflow. This significantly reduces power consumption under no-load conditions and decreases standby power consumption. When the operator pulls the joystick, the main control valve opens, and the system detects a pressure demand. The variable pump quickly increases its displacement, outputting sufficient flow to drive the boom and bucket to complete the action. The variable pump achieves flow self-adaptation through pressure feedback, delivering as much oil as needed, eliminating meaningless overflow losses. The energy consumption of the hydraulic system dynamically changes according to operational requirements. During the no-load standby phase, the motor load drops significantly, resulting in a notable reduction in power consumption. Compared to fixed displacement pump models, it exhibits outstanding energy-saving advantages in scenarios such as intermittent operations and waiting for unloading.
III. Collaborative optimization of variable hydraulic system and electric drive and control
The variable hydraulic pump does not work independently but is interconnected with the vehicle's VCU electronic control system. The system collects hydraulic pressure and handle operation signals in real time, predicts operational needs, and adjusts the pump displacement in advance. When it detects that a heavy-load shoveling condition is imminent, the pump displacement is increased in advance to ensure fast action response; during the no-load standby phase, a small displacement output is maintained to reduce motor load. The electro-hydraulic collaborative calibration optimizes the response logic of the variable pump, avoiding sluggish action caused by lagging displacement adjustment. Some low-end variable pump models have slow pump displacement adjustment after handle operation, resulting in delayed action response. Jining Xinghang ensures rapid switching of variable pump displacement through electronic control tuning, providing a crisp operating feel without action lag issues, while balancing energy conservation and operational response speed. Additionally, the system incorporates built-in pressure protection. When the hydraulic system pressure reaches the upper limit, the variable pump automatically reduces its displacement to achieve pressure limitation, reduce overflow impact, lower hydraulic pipeline impact load, and protect hydraulic components.
IV. Energy consumption and performance under multiple operating conditions
Under continuous high-intensity shoveling conditions, the variable displacement pump can deliver a large flow rate, ensuring sufficient flow for the combined lifting and bucket retracting actions, without compromising operational performance. In scenarios such as intermittent standby, waiting for unloading, and empty-load transfer, the variable displacement pump reduces its displacement, thereby cutting down on empty-load energy consumption. In factory yard operations, there are numerous periods of waiting and intermittent work throughout the day. Over time, this results in a significant energy-saving effect, extending the operational duration after a single charge. Simultaneously, hydraulic heating is improved, with a substantial reduction in overflow heat generation. This slows down the rise in hydraulic oil temperature, reducing the aging rate of hydraulic oil and seals at high temperatures. Consequently, the hydraulic oil replacement cycle is extended, the probability of seal leakage due to high-temperature aging is reduced, and maintenance workload is decreased.
V. Precautions for operation and maintenance of variable hydraulic system
The variable hydraulic pump structure is more precise than the fixed displacement pump and requires higher cleanliness of the hydraulic oil. Impurities entering the pump body can wear down the internal flow distribution structure, causing the variable mechanism to become stuck and affecting the displacement adjustment performance. Therefore, during use, it is necessary to replace the hydraulic filter element periodically and use qualified hydraulic oil to avoid oil contamination. During routine inspections, pay attention to whether the hydraulic system has any abnormal noise or abnormal heating. If the variable mechanism becomes stuck, the pump will maintain high displacement output, losing its energy-saving effect. Jining Xinghang provides corresponding maintenance guidelines to guide users in managing oil cleanliness and ensuring long-term stable operation of the variable hydraulic system. Many users are concerned about the difficulty of maintaining variable pumps. However, under standardized maintenance, the entire system can work stably for a long time, saving electricity costs and reducing wear and tear on hydraulic components, which over the long term offsets maintenance costs.
Conclusion
Continuous power consumption under no-load conditions is an inherent weakness of fixed displacement hydraulic pump models in intermittent operation scenarios. On electric loaders, power loss directly affects operational endurance. Jining Xinghang electric loaders are equipped with a variable displacement hydraulic system, which enables on-demand hydraulic flow supply. When the joystick is in the neutral position, the pump displacement is reduced, eliminating ineffective power consumption caused by overflow and reducing heat generation in the hydraulic system. In factory yard conditions where unloading is pending and operations are intermittent, this effectively reduces no-load energy consumption, extends the operational duration per charge, reduces the thermal load on the hydraulic system, and delays the aging of hydraulic components. The variable displacement hydraulic system, coupled with native electric drive and electronic control collaborative calibration, balances energy-saving effects with shoveling action response performance, and is an important design to enhance the overall economic efficiency of electric loaders.
