Created on:2021-06-24 14:01

Working principle of hydraulic system of gk400 rubber mixer

Working principle of hydraulic system of gk400 rubber mixer

The hydraulic system of gk400 internal mixer can be roughly divided into four parts: hydraulic pump station, top bolt control, bottom bolt and lock pin control, and hopper control.

① Composition and function of hydraulic pump station the composition of hydraulic pump station of gk400 internal mixer is shown in Figure I.

I.jpg

The combination of variable displacement pump and accumulator is used in the hydraulic pump station, so that the top bolt can obtain a large amount of hydraulic oil in a short time when it acts, and at the same time, the impact or pressure pulsation caused by the action of various hydraulic components in the system can be reduced. When each hydraulic cylinder does not act and the pressure of the accumulator has reached the set value, the pressure relay 10 connected with the accumulator acts and makes the two position four-way valve 16 act. At this time, the variable displacement pump has no flow output, so as to reduce power consumption and heat generation.

In terms of oil temperature regulation and filtration, the pump station adopts the mode of cooler and filter in series, and a small pump is used as the power source to form a circuit independent of the main hydraulic system, so as to continuously remove the impurities in the hydraulic oil, so as to meet the requirements of the closed-loop proportional valve in the upper jack bolt control part for the hydraulic oil, and at the same time, the cooler is not affected by the hydraulic impact.

The pump station is also equipped with a manual pump, which can manually open the lock pin and the lower top bolt for maintenance or when the main pump can not work. The main function of cartridge valve 13 and relief valve 14 and 12 is to protect the whole system from damage due to overload. The function of two position two-way valve 9 is to depressurize the system when it stops working.

② The composition and working principle of the top bolt control part are shown in Figure J. In this part, the most important component is the closed-loop proportional valve. The reason why the pressure of gk400 internal mixer can be stepless adjustable is that the closed-loop proportional valve is used in its system. From the perspective of valve technology, the closed-loop proportional valve is developed from the ordinary proportional valve, but after continuous development and research, the performance of the closed-loop proportional valve has far exceeded that of the ordinary proportional valve, and even can be comparable with the servo valve in some aspects. Compared with ordinary proportional valve, the most important feature of closed-loop proportional valve is that it can achieve zero cover in the middle position. It is this feature that enables it to be used as a control element in the closed-loop regulation loop. The pilot type closed-loop proportional valve is used in the top bolt pressure control system of gk400 internal mixer. The main valve and pilot valve of the valve have displacement sensors. The output signals of the displacement sensor and pressure sensor are compared with the set values of the control board. According to the results of comparison and calculation, the control board sends a signal to the closed-loop proportional valve, which is fed back to the proportional electromagnet of the pilot valve. Therefore, the proportional electromagnet can realize stepless adjustment of the pressure and speed of the top bolt by controlling the opening and direction of the pilot valve.

The working principle of this part is as follows.

When the top bolt moves upward or stays in the upper position, the two position three-way valve 2 is not triggered and is in the left position. At this time, port a of cartridge valve 3 is connected with pressure oil, and the cartridge valve is opened. Although the amount of hydraulic oil required at this time is relatively large, due to the effect of the accumulator and the rapid movement circuit composed of three check valves 5 and hydraulic cylinder 1, the upper jack bolt can rise at a faster speed. On the contrary, when the top bolt moves downward or stays in the lower position, the two position three-way valve 2 is triggered and in the right position to ensure that the top bolt can move downward or float. In this state, although there is no rapid movement loop, the flow rate required for the top bolt to drop is small, so it can also drop rapidly. Therefore, in the rising and falling process of the top bolt, its speed and pressure completely depend on the opening of the closed-loop proportional valve. In addition, in order to prevent accidents, gk400 internal mixer is also equipped with a mechanical buffer device.

③ The composition and working principle of the lower top bolt and lock pin control part are shown in Figure K. In the control part of the lower jack bolt, the pressure reducing valve 8 controls the pressure of the hydraulic cylinder when the lower jack bolt turns over; The reversing direction and opening degree of the pilot proportional valve are proportional controlled by the signal set by the external control board, so as to control the movement speed of the lower top bolt and prevent the impact of the lower top bolt due to the excessive movement; Relief valve 7 is mainly used to protect the hydraulic cylinder from being damaged by overload.

K.jpg

In the lock pin control part, the expansion of the lock pin is controlled by the three position four-way valve 1, and the expansion speed is controlled by the adjustable one-way throttle valve 4. The main function of pressure relief control pilot pressure reducing valve 2 and pilot pressure reducing valve 3 in this part is to protect the lock pin hydraulic cylinder. When the lock pin is extended, the pilot pressure reducing valve 3 works to reduce the oil pressure to the set value of the valve before the lock pin hydraulic cylinder 5 forms a certain pressure; When the lock pin hydraulic cylinder 5 reaches a certain pressure, because the pilot valve of the pilot pressure reducing valve 3 is opened, the valve loses its function. At this time, the pressure relief controls the pilot pressure reducing valve 2 to work and reduces the oil pressure to the set value of the valve.

④ The composition and working principle of the hopper control part are shown in Fig. L. the composition and working principle of this part are similar to the lock pin control part.

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