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The open system means that the hydraulic pump sucks oil from the tank, supplies oil to the hydraulic motor (or hydraulic cylinder) through the reversing valve to drive the working mechanism, and the hydraulic motor returns oil and then returns to the tank through the reversing valve. Install a relief valve at the pump outlet. This system has a simple structure. The oil after work flows back to the tank, and the tank can play a role in dissipating heat and precipitating impurities. However, since the oil is often in contact with air, it is easy for air to penetrate into the system. A back pressure valve should be installed on the oil line, which will cause additional energy loss and increase the oil temperature.
The open system uses a quantitative pump or a one-way variable pump. In order to avoid the phenomenon of vacuuming in the pump, for hydraulic pumps with poor self-priming ability, the operating speed is usually limited to 75% of the rated speed, or an auxiliary filling pump is added. Pump. The reversal of the working mechanism relies on the reversing valve. During the reversal, in addition to the hydraulic impact, the inertial energy of the moving parts will be converted into heat energy, causing the oil to heat up. However, due to its simple structure, the open system is still used by most cranes.
The winch hydraulic system consists of motor rotation, speed limiter, clutch-brake and free-fall hook circuits. The working principle is as follows.
The motor rotating circuit part consists of a variable hydraulic motor, a back pressure valve, a relief valve and a directional control valve.
When the motor is wound up, P, the pump pressure oil is controlled by the direction
When the motor is rolled down, P, the pressure oil of the pump passes through the directional control valve to the motor. At the same time, the hydraulic control opens the balance valve and connects the oil return line. The hydraulic oil discharged from the motor returns to the oil tank through the balance valve and directional control valve.
1).Characteristics of closed hydraulic system
The closed system means that the oil inlet pipe of the hydraulic pump is directly connected to the oil return pipe of the actuator. The working fluid performs a closed cycle in the system pipeline. The structure is compact, there are fewer opportunities for contact with air, the air is not easy to penetrate, and the transmission is smooth. The speed change and reversal of the working mechanism are realized by adjusting the variable mechanism of the pump or motor, which avoids the hydraulic impact and energy loss of the open system reversal. However, the conditions for oil heat dissipation and filtration are worse than those of the open type. In order to compensate for system leakage, a small-capacity replenishing pump is usually required for oil replenishment and heat dissipation, so this system is actually a semi-closed system.
Generally speaking, if a double-acting single-piston rod hydraulic cylinder is used as the actuator in a closed system, the power utilization rate will decrease due to the different flow rates in the large and small chambers. Therefore, the actuator in a closed hydraulic system is generally a hydraulic cylinder. motor.
2). Working principle of winch closed hydraulic system
The Yangtze 80t truck crane hoists a speed regulating circuit composed of a variable pump and a variable motor. Position 1 is a bidirectional variable pump to realize speed regulation and reversal of the hydraulic motor, and position 2 is a bidirectional variable motor. Since the displacement of the hydraulic pump and motor can be changed, the speed regulation range of the circuit can be expanded. This speed regulation circuit is actually a combination of the two speed regulation circuits mentioned above. When adjusting the speed of the hydraulic motor from low to high, the displacement of the motor should be fixed at the maximum value during the low-speed stage, and the displacement of the variable pump should be adjusted to gradually increase from small to large. At this time, the speed of the hydraulic motor also changes from low to high. It gradually increases until the pump displacement reaches the maximum value. The adjustment at this stage is constant torque adjustment, and the speed adjustment range is R,. In the high-speed stage, the displacement of the variable pump should be fixed at the maximum displacement position, and the displacement of the variable motor should be adjusted from large to small. The motor speed will continue to increase until it reaches the maximum allowable speed. The adjustment at this stage It is a constant power adjustment, and the speed adjustment range is R2. This adjustment sequence can meet the requirements of most machines to maintain a large torque when running at low speed and output a large power when running at high speed. Its total speed regulation range is R=R1·R2.
Please feel free to contactus Parts Sea engineers or sales for help if you have no parts No.
tse@partssea.com | sales@partssea.com
The open system means that the hydraulic pump sucks oil from the tank, supplies oil to the hydraulic motor (or hydraulic cylinder) through the reversing valve to drive the working mechanism, and the hydraulic motor returns oil and then returns to the tank through the reversing valve. Install a relief valve at the pump outlet. This system has a simple structure. The oil after work flows back to the tank, and the tank can play a role in dissipating heat and precipitating impurities. However, since the oil is often in contact with air, it is easy for air to penetrate into the system. A back pressure valve should be installed on the oil line, which will cause additional energy loss and increase the oil temperature.
The open system uses a quantitative pump or a one-way variable pump. In order to avoid the phenomenon of vacuuming in the pump, for hydraulic pumps with poor self-priming ability, the operating speed is usually limited to 75% of the rated speed, or an auxiliary filling pump is added. Pump. The reversal of the working mechanism relies on the reversing valve. During the reversal, in addition to the hydraulic impact, the inertial energy of the moving parts will be converted into heat energy, causing the oil to heat up. However, due to its simple structure, the open system is still used by most cranes.
The winch hydraulic system consists of motor rotation, speed limiter, clutch-brake and free-fall hook circuits. The working principle is as follows.
The motor rotating circuit part consists of a variable hydraulic motor, a back pressure valve, a relief valve and a directional control valve.
When the motor is wound up, P, the pump pressure oil is controlled by the direction
When the motor is rolled down, P, the pressure oil of the pump passes through the directional control valve to the motor. At the same time, the hydraulic control opens the balance valve and connects the oil return line. The hydraulic oil discharged from the motor returns to the oil tank through the balance valve and directional control valve.
1).Characteristics of closed hydraulic system
The closed system means that the oil inlet pipe of the hydraulic pump is directly connected to the oil return pipe of the actuator. The working fluid performs a closed cycle in the system pipeline. The structure is compact, there are fewer opportunities for contact with air, the air is not easy to penetrate, and the transmission is smooth. The speed change and reversal of the working mechanism are realized by adjusting the variable mechanism of the pump or motor, which avoids the hydraulic impact and energy loss of the open system reversal. However, the conditions for oil heat dissipation and filtration are worse than those of the open type. In order to compensate for system leakage, a small-capacity replenishing pump is usually required for oil replenishment and heat dissipation, so this system is actually a semi-closed system.
Generally speaking, if a double-acting single-piston rod hydraulic cylinder is used as the actuator in a closed system, the power utilization rate will decrease due to the different flow rates in the large and small chambers. Therefore, the actuator in a closed hydraulic system is generally a hydraulic cylinder. motor.
2). Working principle of winch closed hydraulic system
The Yangtze 80t truck crane hoists a speed regulating circuit composed of a variable pump and a variable motor. Position 1 is a bidirectional variable pump to realize speed regulation and reversal of the hydraulic motor, and position 2 is a bidirectional variable motor. Since the displacement of the hydraulic pump and motor can be changed, the speed regulation range of the circuit can be expanded. This speed regulation circuit is actually a combination of the two speed regulation circuits mentioned above. When adjusting the speed of the hydraulic motor from low to high, the displacement of the motor should be fixed at the maximum value during the low-speed stage, and the displacement of the variable pump should be adjusted to gradually increase from small to large. At this time, the speed of the hydraulic motor also changes from low to high. It gradually increases until the pump displacement reaches the maximum value. The adjustment at this stage is constant torque adjustment, and the speed adjustment range is R,. In the high-speed stage, the displacement of the variable pump should be fixed at the maximum displacement position, and the displacement of the variable motor should be adjusted from large to small. The motor speed will continue to increase until it reaches the maximum allowable speed. The adjustment at this stage It is a constant power adjustment, and the speed adjustment range is R2. This adjustment sequence can meet the requirements of most machines to maintain a large torque when running at low speed and output a large power when running at high speed. Its total speed regulation range is R=R1·R2.