A new hydraulic impactor with independent stepless

2022-09-19
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A new type of hydraulic impactor with independent stepless regulation control

Abstract Based on the analysis of the current hydraulic impactor, this paper proposes a new type of impactor with pressure feedback independent stepless regulation energy and impact frequency, and expounds its structure and working principle. The new hydraulic impactor can meet the needs of various working conditions, reduce energy consumption and improve work efficiency

key words: hydraulic impactor stepless adjustment of impact energy impact frequency

1 current situation and improvement ways of hydraulic impactor

at present, the hydraulic impactor bucket produced by many manufacturers in the world has the function of adjusting impact energy to meet the crushing requirements of rocks with different sizes and hardness. Different from general hydraulic machinery, the load of hydraulic impactor is the inertia force of piston movement. Therefore, changing the flow provided to the hydraulic impactor can change the working pressure and impact energy of the hydraulic impactor. However, because the impact power is directly proportional to the cube of the flow and inversely proportional to the piston stroke, in order to ensure the normal operation of the hydraulic system motor, the purpose of changing the impact energy and impact frequency of the hydraulic impactor is generally achieved by changing the piston motion stroke while changing the flow. The scheme of changing the piston stroke of the hydraulic impactor is called the shift scheme

the stroke adjustment of various hydraulic impactors at home and abroad is graded. Generally, there are only two to three gears, and it is very inconvenient to adjust the stroke. Therefore, when the hydraulic impactor is working, the stroke remains unchanged, unless it meets a large number of large rocks and needs to change the impact energy. It must be pointed out that due to the limitation of structural size, the stroke of the impactor cannot be large, and the impact frequency of the hydraulic impactor cannot be designed very low

according to the theory of rock crushing, there is a minimum energy requirement for rock crushing. When the impact energy is lower than the required minimum impact energy, the rock cannot be broken. In order to crush rocks with different block sizes and hardness, when the stroke is unchanged and the impact energy is to be increased, the impact pressure must be increased, so the impact frequency will also increase, and the impact power will increase a lot. Because the impact energy and impact power of hydraulic impactor using the principle of stroke feedback change synchronously in the adjustment process, when the impact energy increases, the impact power also increases, which requires increasing the installed capacity

the solution to this problem is to break the relationship between pressure and flow, so that the impact pressure and oil supply flow can be adjusted and controlled independently and steplessly, so that the impact energy and impact frequency can be adjusted and controlled independently and steplessly. That is, the impact energy of the control impactor is adjusted by adjusting the working pressure of the control impact system. When the impact pressure is high, the impact energy is very large; When the impact pressure is low, the impact energy is small. The impact frequency of the hydraulic impactor is adjusted and controlled by adjusting the output flow of the oil supply pump. When the oil supply flow is large, the impact frequency is very high; The impact frequency is low when the oil supply flow is small. In this way, the impact energy can be adjusted to a large extent, and the impact frequency can be reduced to a very low level, so that the impact power will not increase much. Selecting the impact energy and the appropriate impact frequency according to the crushing phenomenon can improve the efficiency, reduce the model of the supporting chassis of the hydraulic crusher, and reduce the cost, which is conducive to the promotion and application of the hydraulic crusher

2 new another literature review 8 years after operation structure and working principle of the type impactor

the new hydraulic lithotriptor adopts the working mode of pressure feedback control principle, breaking through the traditional stroke feedback control principle of hydraulic impactor and the purpose of independent stepless regulation of oil supply flow to control the working performance parameters of hydraulic lithotriptor impactor. Its structure and working principle can have many types. The following analysis and research is a main structure type and its working principle

(1) structure

as shown in Figure 1, the impactor adopts the rear chamber control type with normal pressure in the front chamber and alternating high and low pressure in the rear chamber. The impact piston 1 and the cylinder block 2 form four chambers, namely, the normal pressure front chamber a with oil hole I, the normal low pressure chamber B with stroke feedback signal hole II and oil hole III, the variable pressure rear chamber C with IV and the closed nitrogen chamber 3. The normal high-pressure chamber a in the front of the cylinder block is connected with the normal high-pressure chamber e of the oil distribution valve and the high-pressure oil source P output by the oil supply pump through I and the oil circuit, and the high-pressure accumulator 5 is set on the oil source channel. The oil hole II is connected with the normal and low pressure chamber g of the oil distribution valve and the oil return O by the oil circuit, and the oil return accumulator 6 is set on the oil return channel. At the end of the stroke, piston end face B passes over oil hole II, and oil chamber B connects hole II and hole III. The rear chamber C at the rear of the cylinder block is connected with the pressure transformation chamber F of the oil distribution valve through the oil hole IV and the oil circuit

the oil distribution valve adopts the cone valve form and the optimized unequal valve opening technology, and the valve opening is small during the return trip; The valve opening is large during stroke. The push valve chamber D is connected with the pressure control cone valve 7 through the oil circuit to control the on-off of the high-pressure oil source P. The opening pressure of cone valve 7 is determined by the control oil pressure px. The left and right vertebral column shoulders of the valve core 8 alternately control the on-off of the constant high pressure chamber E and the variable pressure chamber F of the oil distribution valve and the constant low pressure chamber g and the variable pressure chamber F of the oil distribution valve. When the chamber e is connected with the chamber F, the chamber G is blocked with the chamber F, and when the chamber e is blocked with the chamber F, the chamber G is connected with the chamber F. The effective area of the valve core D cavity is larger than that of the H cavity, and the push valve h is connected with the high-pressure oil source P through the oil circuit

Figure 1 Structure and working principle diagram of the new hydraulic impactor

(a) return start state (b) stroke start state

1 impact piston 2 cylinder body 3 nitrogen chamber 4 pickaxe 5 accumulator 6 oil return accumulator 7 cone valve 8 spool 9 valve body

(2) working principle

a return

figure 1A shows that the piston has completed an impact, the valve has been reversed, and the whole system is in the return start state. At this time, the push valve chamber D of the oil distribution valve has been connected with the return oil o through the oil holes II and III, while the push valve is always connected with the high-pressure oil source P through the oil circuit and the hole in the center of the valve core, and the valve core chamber is at the left end of the figure under the action of high-pressure oil for 8h. The high-pressure oil p is connected with the front chamber a of the piston through the high-pressure chamber E and oil hole I of the valve body, and the rear chamber C is connected with the return oil through the oil hole IV through the variable pressure chamber F and low-pressure chamber g of the valve body; Therefore, under the action of the pressure oil in the front chamber, the piston 1 starts to return to the right, compresses the nitrogen chamber 3 at the same time, and the high-pressure accumulator 5 is filled with oil. With the increase of return, the compression of nitrogen chamber 3 increases, its pressure increases, and the system pressure also increases; When the pressure rises to the opening pressure of the pressure control cone valve 7, the cone valve 7 opens, and the high-pressure oil enters the push valve chamber D. because the acting area of chamber D is greater than that of chamber h, the valve core quickly makes a return reversing movement to the right under the action of pressure difference, and the control variable pressure chamber F of the valve body is connected with the high-pressure chamber E. In this way, the front and rear cavities of the piston are connected with the high-pressure oil to form a differential connection, and the acceleration stage of the piston return stroke ends. Although the action area of the rear chamber of the piston is larger than that of the front chamber and the effect of nitrogen pressure, at this time, the piston will continue to move to the right due to inertia, but make deceleration movement until the speed is zero, and complete the whole return action. From the above description, it can be seen that the piston return actually includes two stages: return acceleration and return deceleration

b stroke

the return stroke of the piston is over, which is ready for the stroke. The whole oil circuit state at the beginning of the stroke is shown in Figure 1b. Like the return deceleration stage, the valve element 8 is still in the right position under the action of the oil pressure difference, and the front and rear cavities of the piston are connected with high-pressure oil to maintain differential connection. Impact piston 1 accelerates to the left under the action of pressure oil pressure difference and nitrogen expansion to start stroke. At the late stage of stroke acceleration, the speed is very high, which requires a large oil flow, the system pressure decreases, and a large amount of oil discharged from the high-pressure accumulator is added to the rear chamber. When the piston end face B crosses the stroke reversing feedback signal hole II, the push valve chamber D communicates with the return oil through oil holes II and III, and the maximum needle force value is lost; High pressure, at the same time, the pressure control cone valve 7 is closed, and the valve core quickly makes a stroke reversing movement to the left under the action of high-pressure oil in chamber h. then the piston 1 impacts the pickaxe 4, and the stroke ends. End of stroke. The impactor returns to the initial return state and starts the next cycle of return movement again

from the above working principle, it can be seen that the pressure control cone valve can control the impact pressure P of the system. When other parameters of the hydraulic impactor are determined, the control oil pressure PX can be adjusted steplessly, and the cone valve control pressure can change steplessly, so the impact energy of the hydraulic impactor may also change steplessly. When the pressure is high, the impact energy is large, and when the pressure is low, the impact energy efficiency is high. Through stepless regulation and control of the flow of the oil supply pump to the impact system, the impact frequency of the hydraulic impactor can be steplessly adjusted and controlled. When the flow is large, the impact frequency is high, and when the flow is small, the impact frequency is low. Its important feature is that the regulation and control of the two can be carried out synchronously or independently, so that the impact frequency can be adjusted very low and the impact energy can be adjusted to a large extent. The method of making full use of the installed capacity is to thicken the viscosity of the oil to meet the needs of various working conditions

in addition, if PX is adjusted too much and the system pressure increases during return, but the pressure control cone valve 7 cannot be opened, the piston still returns. When the piston end face a crosses the signal hole II, the pressure oil will enter the push valve chamber D through the front chamber a and oil holes I and II, so that the valve core will make a return reversing movement to the right. In this way, the impact pressure of the system is too high, the impact stroke is too long, and the impact energy is too large to damage the machine

the impactor adopts a new type of oil distribution valve. The valve port adopts the form of conical valve port, and the seal adopts the combination of conical and cylindrical seal. When the valve core moves in place and stands still, the valve port is sealed by a combination of conical seal and cylindrical seal. When the valve core reverses, it is sealed by cylindrical seal. However, the valve core stays still for a long time, the oil leakage of conical seal is almost zero, and the movement time of the valve core is short, so the oil leakage of the valve port is very small in the whole working process. In addition, the flow coefficient of the cone valve port is large, and the pressure loss of the oil flowing through the valve port is small. In addition, the new oil distribution valve also adopts the optimized unequal valve opening technology, that is, the hydraulic impactor requires a large flow during the stroke, the valve core makes its opening amount large when it is in the right position, the hydraulic impactor requires a small flow during the return stroke, and the valve core makes its opening amount small when it is in the left position. Make full use of the movement stroke of the valve core, reduce the movement stroke of the valve core, and reduce the energy loss of the reversing movement, which will greatly reduce the energy loss of the oil distribution valve. Once the valve is opened during the return reversing, the area of the valve core push valve increases rapidly, the valve core moves in place quickly, and there is a hydraulic oil cushion cushion to prevent the collision and damage of the valve core movement

this control principle makes the piston stroke longer when the impact system pressure is higher, and the piston stroke shorter when the impact system pressure is lower. It is completely different from the control principle of constant power multi gear hydraulic rock drill impactor, which has long stroke, low impact system pressure, short stroke and high impact system pressure

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