The application of hydraulic transmission is common, but the characteristics of the hydraulic transmission itself and the heat generated by the engineering hydraulic system are usually insufficient by the heat dissipation of the fuel tank, components and the surface of the pipe. However, ensuring the effective control of the hydraulic oil temperature is the basic premise of the normal operation of the system, so the dedicated cooling device and the corresponding cooling circuit are essential in the hydraulic system of most construction machinery. Below Dalan Hydraulics to share the four methods of cooling the hydraulic system:
1. The oil passing through the cooler is part of the system returning oil, and the amount of heat dissipation depends on the size of the orifice.
1 corresponds to a certain temperature and a certain flow of oil return, the smaller the orifice, the greater the heat dissipation flow, and vice versa.
The diameter of the 2 orifices is not determined by a single factor and must be considered together. Related factors are: power loss of the system, target control range of oil temperature, and constraints on the back pressure of the system.
The finalization of the 3 orifice sizes should be a result based on experimental and ambient temperature statistics.
4 The main disadvantage of this scheme is that the thermal equilibrium temperature of the hydraulic system varies widely with changes in ambient temperature and operating conditions, which affects the stability of the working efficiency and the service life of the medium.
2. Use the control system to supply heat to the oil pump.
1 When the accumulator reaches the preset pressure, the force of the liquid control end of the two-position two-way valve is greater than the force of the spring end, and the two-position two-way valve is shifted, and the pump oil is cooled by the cooler.
2 When the accumulator pressure drops to the preset lower limit, the spring force is greater than the hydraulic pressure, the two-position two-way valve switches to the position shown, and the pump supplies oil to the accumulator.
3Because in the actual working conditions of most construction machinery, the accumulation time of the accumulator of the control system is not long, especially for non-hydrostatic transmission engineering machinery, the operating frequency of the pilot valve is lower during walking and transportation. The control system oil supply pump is in an idling state, and a certain amount of no-load energy loss is caused by the pressure drop of the pipeline. Therefore, the scheme can not only effectively utilize the control oil pump to achieve heat dissipation, but also the two-way two-way valve has the unloading effect.
4 For the small and medium-sized mechanical control oil pump displacement can generally meet the requirements of heat dissipation, for large-scale machinery or medium-sized machinery that does not meet the requirements of heat dissipation, the pump displacement can be appropriately increased. Because there are many factors affecting the heat dissipation effect, the calculated displacement of the pump can only be used as the basis for the preliminary selection. Finally, it must be determined through experiments.
3. Hydraulic servo control type cooling system.
1 The cooler is forced to accelerate heat exchange by a dedicated fan, the fan is driven by a motor, the motor is supplied by a variable pump, and the output of the variable pump is controlled by the oil temperature. The pressure regulating valve pressure of the pressure relief pilot control changes with the oil temperature, so that the displacement of the variable pump is controlled by feedback.
2 When the oil temperature rises, the pump displacement controlled by the pressure regulating valve increases, the motor speed increases, and the fan is driven to accelerate heat exchange, so that the oil temperature drops. When the oil temperature drops, the fan speed slows down.
3 Because there is a dedicated fan to enhance the heat exchange of the cooler, the heat dissipation efficiency is significantly improved, and because the fan speed changes with the oil temperature, the oil temperature can be controlled within a small fluctuation range, which is beneficial to the normal use of the medium. Due to the variable pump and servo control, the cost of components is relatively high.
4. Electronically controlled cooling system.
1 When the system oil temperature exceeds the preset upper limit, the solenoid valve is changed position, the pump oil supply drives the fan to accelerate heat exchange through the motor, and when the oil temperature drops to the preset lower limit, the solenoid valve is switched to the position shown, the motor is cut off. The fan stops rotating.
2 Due to the rapid development of sensor technology, microelectronics technology and digital hydraulic components, digital real-time dynamic control of hydraulic oil temperature is feasible and valuable in both theory and practice.
3 This kind of scheme is beneficial to control the oil temperature to a smaller fluctuation range, reduce the leakage caused by the large temperature rise and fall, and prolong the service life of the medium, the hose and the seal, thereby improving the efficiency and stability of the system and even the whole machine. Reliability. In addition, a similar electronically controlled cooling system is also beneficial to the realization of intelligent control of the whole machine.
The above-mentioned schemes have certain typicality. Different schemes have advantages and disadvantages in theory, but in practical applications, specific problems must be analyzed.
----- Editor-in-Chief: Dalan Oil Pump Motor 02-Procurement Consultant
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