CN117212268A - Hydraulic system of four-quadrant working closed pump driven single-rod double-acting piston hydraulic cylinder and control method thereof - Google Patents

Abstract

A hydraulic system of a four-quadrant working closed-circuit pump driving a single-rod double-acting piston hydraulic cylinder and a control method thereof. When the system of the present invention works in the I and II quadrants, an open constant pressure variable pump is used to replenish the oil return port of the closed pump, so that the flow rate of the oil return port of the closed pump is the same as the flow rate of the oil outlet, ensuring that the closed pump is closed. The pump works normally. The oil supply flow is the oil supply flow required by the system, without throttling loss or overflow loss. When working in quadrants III and IV, a relief valve is used to drain the oil from the rodless cavity of the hydraulic cylinder to the oil tank, so that the flow rate of the oil return port of the closed pump is the same as the flow rate of the oil outlet, ensuring the normal operation of the closed pump. The oil drain flow is the oil drain flow required by the system, without any throttling loss. Use a pressure transmitter to detect the pressure of the rodless cavity and rod cavity of the hydraulic cylinder, calculate the size of the load and judge the direction of the load, and combine the movement direction of the piston rod to judge and switch the working quadrant. The detection is accurate, the switching is rapid, and the impact is Small, smooth operation.

Description

Hydraulic system of four-quadrant closed-circuit pump driven single-rod double-acting piston hydraulic cylinder system and its control methods

Technical field

The invention relates to the technical field of hydraulic transmission of mechanical equipment, and is mainly used in the driving mechanism of a four-quadrant closed pump-driven single-rod double-acting piston hydraulic cylinder on the equipment.

Background technique

Single-rod double-acting piston hydraulic cylinders are widely used in various mechanical equipment to drive the movement of the mechanism by controlling the expansion and contraction direction and speed of the piston rod of the hydraulic cylinder.

The hydraulic cylinder is a single-rod double-acting piston cylinder, and the hydraulic speed regulating circuit method is usually:

The open valve-controlled throttling and speed regulating circuit uses a quantitative pump to supply oil, and cooperates with the on-off reversing valve and throttle valve, or the proportional reversing valve to achieve reversing and throttling speed regulation, with overflow loss and throttling loss;

The open valve-controlled volumetric throttling and speed regulating circuit uses a constant pressure variable pump to supply oil, and cooperates with the on-off reversing valve and throttle valve, or the proportional reversing valve to achieve reversing and throttling speed regulation, with throttling losses.

The open pump-controlled volume speed regulating circuit uses a variable pump to regulate speed and cooperates with the on-off reversing valve to achieve reversal without overflow loss or throttling loss.

With the above speed regulation method, the piston rod can only drive a load with an action direction opposite to the piston rod movement direction (pressure when the piston rod extends, tension when the piston rod retracts). If you need to drive a load with the same direction as the piston rod movement direction, Load (tension when the piston rod extends, compression when the piston rod retracts), a balance valve or a throttle valve must be connected to the oil line of the hydraulic cylinder. The balance valve or throttle valve will cause throttling loss and heat, and the balance valve will work The vibration is relatively large. To change the direction of movement of the mechanism, it is necessary to switch the reversing valve position. During the switching process, the reversing valve must pass through the middle position, and the action will have pauses, delays, and impacts.

Because the flow rate of the inlet and outlet of the closed pump must be the same, it usually drives a double-rod double-acting piston hydraulic cylinder (referred to as a double-rod hydraulic cylinder). The effective area of the two chambers of the piston is the same, and the flow rate of the two chambers is the same. The oil outlet and return port of the closed pump are directly connected to the oil ports of the two chambers of the hydraulic cylinder. There is no reversing valve in the middle, which avoids local loss of the reversing valve. When the system is working normally, there is no overflow loss or throttling loss, and the system efficiency is high. The closed pump can continuously change the flow size and flow direction by changing the displacement. When switching directions, the flow rate changes from large to small to zero, and then changes from small to large in the other direction. There is no commutation delay or impact, and the drive control is accurate. sensitive. If it is necessary to drive a load that acts in the same direction as the piston rod (the piston rod is stretched when it extends and is compressed when it retracts), the hydraulic cylinder will drive the closed pump in reverse, and the closed pump will drive the motor or engine in reverse. , realize anti-drag braking, and for some motor systems, anti-drag braking can also be used to generate electricity to reduce energy consumption.

The double-rod hydraulic cylinder has two-way rods, takes up a lot of space, and has high manufacturing costs. In practical applications, usually the mechanism only needs to use a single-rod double-acting piston hydraulic cylinder (single-rod hydraulic cylinder for short). The effective areas of the rod cavity and the rodless cavity of the single-rod hydraulic cylinder are different. At the same piston rod movement speed, the corresponding flow rate of the rod cavity is smaller than the flow rate of the rodless cavity. Due to unbalanced flow, closed pumps and single-rod hydraulic cylinders cannot be directly connected. According to the direction of movement of the piston rod and the direction of the load, the working condition of the hydraulic cylinder can be divided into four quadrants. If a closed pump is required to drive a single-rod hydraulic cylinder, it is necessary to solve the problem of oil replenishment of the closed pump and oil draining of the hydraulic cylinder according to the movement direction of the piston rod when the hydraulic cylinder is working in four quadrants. During the movement of the piston rod in the same direction, the load direction will change. The system needs to detect and judge the change in the load direction in real time and switch to the corresponding quadrant to ensure normal operation of the system.

Existing technical documents involving closed-circuit pump-driven single-rod hydraulic cylinders only analyze the working conditions of a single quadrant, and do not provide a complete, specific and implementable four-quadrant-operated closed-circuit pump-driven single-rod piston hydraulic cylinder hydraulic system. and control methods for switching quadrant work.

Contents of the invention

The invention provides a hydraulic system in which a four-quadrant working closed-type pump drives a single-rod double-acting piston hydraulic cylinder.

The technical solution adopted by the present invention is:

The hydraulic system includes a main pump 1, a charge pump 2, a hydraulic cylinder 3, a first reversing valve 4, a first relief valve 5, a second relief valve 6, a second reversing valve 7, and a third reversing valve. Valve 8, third relief valve 9, fourth relief valve 10, first pressure transmitter 11, second pressure transmitter 12.

The main pump 1 is a closed swash plate electric proportional bidirectional variable pump, including proportional electromagnets m1 and m2 that control displacement. When m1 is powered on, the swash plate deflects forward, and oil is discharged from port A of main pump 1 and returned to port B. When m2 is powered on, the swash plate deflects in the opposite direction, and port B of main pump 1 discharges oil and returns oil to port A. The flow rate is proportional to the current size of the proportional electromagnets m1 and m2, and the flow rate at the oil outlet is the same as the flow rate at the oil return port.

Charge pump 2 is an open swash plate constant pressure variable pump. The pressure at outlet P is always the same as the pressure at pressure control port X. The flow rate provided by outlet P is the flow rate required by the system.

Hydraulic cylinder 3 is a single-rod double-acting piston hydraulic cylinder used to drive the load. The area of the rod cavity is A2, the area of the rodless cavity is A1, and the area ratio coefficient

The first reversing valve 4 is a two-position four-way electromagnetic reversing valve, including an electromagnet m3.

The first relief valve 5 is a direct-acting relief valve with a small flow rate. The set pressure is Pbmax, which is determined by overcoming the maximum reverse load when the piston rod extends.

The second relief valve 6 is a direct-acting relief valve with a small flow rate. The set pressure is Pbmin, which is determined according to the minimum oil supply pressure of the system (generally 2.5Mpa).

The second reversing valve 7 is a two-position electro-hydraulic reversing valve and includes an electromagnet m4.

The third reversing valve 8 is a three-position four-way electro-hydraulic reversing valve, including electromagnets m5 and m6.

The third relief valve 9 is a pilot-operated relief valve with a large flow rate. The set pressure is Pxmax, which is determined by overcoming the maximum forward load when the piston rod retracts.

The fourth relief valve 10 is a large-flow pilot-operated relief valve, and the set pressure is Pxmax, which is determined according to the minimum oil drain pressure of the system (generally 2.5Mpa).

The first pressure transmitter 11 detects the rod chamber pressure P2 of the hydraulic cylinder 3 .

The second pressure transmitter 12 detects the rodless chamber pressure P1 of the hydraulic cylinder 3 .

Port B of the main pump 1 is connected to port B of the hydraulic cylinder 3 , the first pressure transmitter 11 , and port A of the second reversing valve 7 . Port A of the main pump 1 is connected to port A of the hydraulic cylinder 3 , the second pressure transmitter 12 , and port P of the third reversing valve 8 .

Port A of the first reversing valve 4 is connected to port P of the first relief valve 5, port B of the first reversing valve 4 is connected to port P of the second relief valve 6, port P of the first reversing valve 4 is connected to X port of charge pump 2.

The P port of the variable charge pump 2 is connected to the P port of the second reversing valve 7 .

Port A of the third reversing valve 8 is connected to port P of the third relief valve 9 , and port B of the third reversing valve 8 is connected to port P of the fourth relief valve 10 .

The S port of the charge pump 2, the T port of the first reversing valve 4, the T port of the third reversing valve 8, the T port of the first relief valve 5, the T port of the second relief valve 6, and the third relief valve. The T port of the flow valve 9 and the T port of the fourth relief valve 10 are connected to the oil tank.

When m3 is powered off, the P port of the second relief valve 6 is connected to the X port of the charge pump 2. When m3 is powered on, the P port of the first relief valve 5 is connected to the X port of the charge pump 2. When m4 is powered on, port P of charge pump 2 is connected to port B of main pump 1. When m5 is powered on, port P of the fourth relief valve 10 is connected to port A of the main pump 1. When m6 is powered on, the P port of the third relief valve 9 is connected to the A port of the main pump 1.

The schematic diagram of the hydraulic system is shown in Figure 1.

The effects and benefits of the present invention are:

When working in the I and II quadrants, an open constant pressure variable pump is used to replenish the oil return port of the closed pump, so that the flow rate of the oil return port of the closed pump is the same as the flow rate of the oil outlet, ensuring the normal operation of the closed pump. The oil supply flow is the oil supply flow required by the system, without throttling loss or overflow loss.

When working in the III and IV quadrants, a relief valve is used to drain the oil from the rodless cavity of the hydraulic cylinder to the oil tank, so that the flow rate of the return port of the closed pump is the same as the flow rate of the oil outlet, ensuring the normal operation of the closed pump. . The oil drain flow is the oil drain flow required by the system, without any throttling loss.

Use a pressure transmitter to detect the pressure of the rodless cavity and rod cavity of the hydraulic cylinder, calculate the load size and determine the load direction, and combine the movement direction of the piston rod to judge and switch the working quadrant. The detection is accurate, the switching is rapid, and the impact is small. ,Running smoothly.

Description of the drawings

Figure 1 is the schematic diagram of the hydraulic system.

Figure 2 is a schematic diagram of the four-quadrant operation of the hydraulic cylinder.

Figure 3 is the electromagnet action table for the four-quadrant operation of the hydraulic cylinder.

Figure 4 is a schematic diagram of the hydraulic principle when the hydraulic cylinder stops working.

Figure 5 is a schematic diagram of the working hydraulic principle of the first quadrant of the hydraulic cylinder.

Figure 6 is a schematic diagram of the working hydraulic principle of the second quadrant of the hydraulic cylinder.

Figure 7 is a schematic diagram of the working hydraulic principle of the third quadrant of the hydraulic cylinder.

Figure 8 is a schematic diagram of the working hydraulic principle of the fourth quadrant of the hydraulic cylinder.

The figure includes: 1 main pump, 2 oil charge pump, 3 hydraulic cylinder, 4 first reversing valve, 5 first relief valve, 6 second relief valve, 7 second reversing valve, 8 third reversing valve , 9 third relief valve, 10 fourth relief valve, 11 first pressure transmitter, 12 second pressure transmitter.

Detailed ways

The specific embodiments of the present invention will be described in detail below with reference to the technical solutions and drawings.

As shown in Figure 2, when the hydraulic cylinder is working, the piston rod extends as forward movement (denoted as V+), the piston rod retracts as reverse motion (denoted as V-), and the load presses the piston rod as forward load (denoted as V-). is F+), and the load pulling the piston rod is a reverse load (expressed as F-), which constitutes the four working quadrants of the hydraulic cylinder. The I and II quadrants are forward motion. During the movement, if the load direction changes, it will switch between the I and II quadrants. Quadrants III and IV are reverse movements. During the movement, if the load direction changes, it will switch between quadrants III and IV.

As shown in Figure 3, when the hydraulic system is working, the electromagnet is powered on and off under various working conditions. + means power is on, - means power is off. m1 and m2 are proportional electromagnets, and the rest are switching electromagnets.

When the hydraulic cylinder stops: As shown in Figure 4, all electromagnets are powered off, the swash plate of main pump 1 returns to the zero position, zero displacement, port A and port B of main pump 1 have zero flow, and hydraulic cylinder 3 stops operating.

Quadrant I of the hydraulic cylinder works: As shown in Figure 5, the electromagnets m1 and m4 are energized, the outflow flow from port A of the main pump 1 is Q, enters the rodless chamber of the hydraulic cylinder 3, the piston rod extends, and the flow rate outflows from the rod chamber is kQ, and the inflow flow rate at port B of main pump 1 is Q, then the oil charge flow rate provided by charge pump 2 to port B of main pump 1 is (1-k)Q. The P port of the second relief valve 6 is connected to the pressure control port X of the charge pump 2, then the pump port pressure of the charge pump 2, that is, the rod chamber pressure of the hydraulic cylinder 3, is stabilized at Pbmin. According to the force balance on the piston rod, in this quadrant, F=P1·A1-P2·A2=P1·A1-Pbmin·A2≥0, where P1 is the rodless chamber pressure of hydraulic cylinder 3, and A1 is the pressure of hydraulic cylinder 3. The effective area of the rodless cavity, P2 is the rod cavity pressure of hydraulic cylinder 3, A2 is the effective area of the rod cavity of hydraulic cylinder 3, If F<0, switch to quadrant II. Summary of the working principle of quadrant I: The rodless cavity pressure P1 of the hydraulic cylinder 3 overcomes the forward load F, the rod cavity pressure P2 is maintained at the minimum oil supply pressure Pbmin, and at the same time, port B of the main pump 1 is supplied with oil.

The operation of the second quadrant of the hydraulic cylinder: As shown in Figure 6, the electromagnets m1, m3 and m4 are energized, the outflow flow from port A of the main pump 1 is Q, and enters the rodless cavity of the hydraulic cylinder 3. The piston rod extends and the rod cavity The outflow flow rate is kQ, and the inflow flow rate at port B of main pump 1 is Q. Then the oil charge flow rate provided by charge pump 2 to port B of main pump 1 is (1-k)Q. The P port of the first relief valve 5 is connected to the pressure control port X of the charge pump 2, then the pump port pressure of the charge pump 2, that is, the rod chamber pressure of the hydraulic cylinder 3, is stabilized at Pbmax. According to the force balance on the piston rod, in this quadrant, F=P1·A1-P2·A2=P1·A1-Pbmax·A2<0. If F≥0, switch to quadrant I. Summary of the working principle of Quadrant II: Increase and maintain the rod chamber pressure P2 of the hydraulic cylinder 3 to Pbmax to overcome the reverse load F, and at the same time replenish port B of the main pump 1 with oil. The maximum reverse load that can be overcome in this quadrant is F=-P2·A2=-Pbmax·A2, at this time P1=0.

The work of the third quadrant of the hydraulic cylinder: As shown in Figure 7, the electromagnets m2 and m5 are energized, the outflow flow from port B of the main pump 1 is Q, enters the rod cavity of the hydraulic cylinder 3, the piston rod retracts, and the flow rate out of the rodless cavity for The inflow flow rate from port A of the main pump 1 is Q, then the drain flow rate from port A of the hydraulic cylinder 3 to the tank through port P of the fourth relief valve 10 is/> The pressure of port A of the main pump 1, that is, the rodless cavity of the hydraulic cylinder 3, is stable at Pxmin. According to the force balance on the piston rod, in this quadrant, F=P1·A1-P2·A2=Pxmin·A1-P2·A2≤0. If F>0, switch to quadrant IV. Summary of the working principle of Quadrant III: The rod cavity pressure P2 of the hydraulic cylinder 3 overcomes the reverse load F, the rodless cavity pressure P1 is maintained at the minimum oil drain pressure Pxmin, and oil is drained to port A of the hydraulic cylinder 3 at the same time.

The IV quadrant of the hydraulic cylinder works: As shown in Figure 8, the electromagnets m2 and m6 are energized, the outflow flow from port B of the main pump 1 is Q, enters the rod cavity of the hydraulic cylinder 3, the piston rod retracts, and the flow rate out of the rodless cavity for The inflow flow rate from port A of the main pump 1 is Q, then the drain flow rate from port A of the hydraulic cylinder 3 to the tank through port P of the third relief valve 9 is/> The pressure of port A of the main pump 1, that is, the rodless cavity of the hydraulic cylinder 3, is stable at Pxmax. According to the force balance on the piston rod, F=P1·A1-P2·A2=Pxmax·A1-P2·A2>0. If F≤0, switch to quadrant III. Summary of the working principle of Quadrant IV: Increase and maintain the rodless chamber pressure P1 of hydraulic cylinder 3 to Pxmax to overcome the forward load F, and at the same time drain oil from port A of hydraulic cylinder 3. The maximum forward load that can be overcome in this quadrant is F=P1·A1=Pxmax·A1, at this time P2=0.

Claims (7)

1. A hydraulic system of a four-quadrant closed pump driving a single-rod double-acting piston hydraulic cylinder, characterized in that the hydraulic system includes a main pump (1), a charge pump (2), a hydraulic cylinder (3), The first directional valve (4), the first relief valve (5), the second relief valve (6), the second directional valve (7), the third directional valve (8), the third relief valve (9), fourth relief valve (10), first pressure transmitter (11), second pressure transmitter (12); The main pump (1) is a closed swash plate electric proportional two-way variable pump, including proportional electromagnets m1 and m2 that control the displacement; the charge pump (2) is an open swash plate constant pressure variable pump; the hydraulic cylinder (3) is a single Rod double-acting piston hydraulic cylinder; the first reversing valve (4) is a two-position four-way electromagnetic reversing valve, including an electromagnet m3; the first relief valve (5) is a small flow direct-acting relief valve. The set pressure is Pbmax; the second relief valve (6) is a small flow direct-acting relief valve, and the set pressure is Pbmin; the second reversing valve (7) is a two-position, two-way electro-hydraulic reversing valve, including Electromagnet m4; the third reversing valve (8) is a three-position four-way electro-hydraulic reversing valve, including electromagnets m5 and m6; the third relief valve (9) is a large-flow pilot-operated relief valve that adjusts the pressure is Pxmax; the fourth relief valve (10) is a large flow pilot relief valve, and the set pressure is Pxmin; the first pressure transmitter (11) detects the rod chamber pressure P2 of the hydraulic cylinder (3); The second pressure transmitter (12) detects the rodless cavity pressure P1 of the hydraulic cylinder (3); Port B of the main pump (1) is connected to port B of the hydraulic cylinder (3), the first pressure transmitter (11), and port A of the second reversing valve (7); port A of the main pump (1) is connected to the hydraulic pressure Port A of the cylinder (3), the second pressure transmitter (12), and port P of the third reversing valve (8); Port A of the first reversing valve (4) is connected to the first relief valve (5) The P port of the first reversing valve (4) is connected to the P port of the second relief valve (6), and the P port of the first reversing valve (4) is connected to the X port of the charge pump (2); The P port of the oil variable pump (2) is connected to the P port of the second reversing valve (7); the A port of the third reversing valve (8) is connected to the P port of the third relief valve (9). The B port of the valve (8) is connected to the P port of the fourth relief valve (10); the S port of the charge pump (2), the T port of the first reversing valve (4), and the third reversing valve (8) T port, T port of the first relief valve (5), T port of the second relief valve (6), T port of the third relief valve (9), T port of the fourth relief valve (10) Connect the fuel tank. 2. The hydraulic system of a four-quadrant closed pump driven single-rod double-acting piston hydraulic cylinder according to claim 1, characterized in that when m3 is powered off, the P port of the second relief valve (6) is connected to the The X port of the charge pump (2) is connected; when m3 is powered on, the P port of the first relief valve (5) is connected with the X port of the charge pump (2); when m4 is powered on, the P port of the charge pump (2) is connected with the main Port B of the pump (1) is connected; when m5 is powered on, port P of the fourth relief valve (10) is connected with port A of the main pump (1); when m6 is powered on, port P of the third relief valve (9) Connected to port A of the main pump (1). 3. The control method of the hydraulic system of the four-quadrant working closed pump driving the single-rod double-acting piston hydraulic cylinder according to claim 1 or 2, characterized in that all electromagnets are powered off and the main pump (1) has zero discharge. The flow rate of port A and port B of the main pump (1) is zero, and the hydraulic cylinder stops moving. 4. The control method of the hydraulic system of the closed-type pump driven single-rod double-acting piston hydraulic cylinder operating in four quadrants according to claim 1, characterized in that the first quadrant of the hydraulic cylinder operates, and the electromagnets m1 and m4 are energized, The outflow flow rate from port A of the main pump (1) is Q, and it enters the rodless cavity of the hydraulic cylinder (3). The piston rod extends, and the outflow flow rate from the rod cavity is kQ. The flow rate from the charge pump (2) to B of the main pump (1) The oil supply flow rate at the port is (1-k)Q; the rod cavity pressure of the hydraulic cylinder (3) is Pbmin, and the load on the piston rod is F=P1·A1-Pbmin·A2≥0; if F<0, switch Go to Quadrant II to work; where, P1 is the rodless cavity pressure of the hydraulic cylinder (3), A1 is the effective area of the rodless cavity of the hydraulic cylinder (3), P2 is the rodless cavity pressure of the hydraulic cylinder (3), and A2 is The effective area of the rod cavity of the hydraulic cylinder (3), 5. The control method of the hydraulic system of the four-quadrant closed pump-driven single-rod double-acting piston hydraulic cylinder according to claim 1, characterized in that the hydraulic cylinder operates in the II quadrant, and the electromagnets m1, m3 and m4 When the power is turned on, the outflow flow rate from port A of the main pump (1) is Q, which enters the rodless cavity of the hydraulic cylinder (3). The piston rod extends, and the outflow flow rate from the rod cavity is kQ. The flow rate from the charge pump (2) to the main pump (1) The oil supply flow rate at port B is (1-k)Q; the rod cavity pressure of the hydraulic cylinder (3) is Pbmax, and the load on the piston rod is F＝P1·A1-Pbmax·A2<0; if F≥0, Then switch to Quadrant I to work. 6. The control method of the hydraulic system of the four-quadrant closed pump-driven single-rod double-acting piston hydraulic cylinder according to claim 1, characterized in that the hydraulic cylinder operates in the III quadrant, and the electromagnets m2 and m5 are energized, The outflow flow rate from port B of the main pump (1) is Q, and enters the rod cavity of the hydraulic cylinder (3). The piston rod retracts, and the outflow flow rate from the rodless cavity is The drain flow rate from port A of the hydraulic cylinder (3) to the oil tank through port P of the fourth relief valve (10) is/> The rodless chamber pressure of the hydraulic cylinder (3) is Pxmin, and the load on the piston rod is F=Pxmin·A1-P2·A2≤0; if F>0, switch to the IV quadrant to work. 7. The control method of the hydraulic system of the four-quadrant closed pump-driven single-rod double-acting piston hydraulic cylinder according to claim 1, characterized in that the IV quadrant of the hydraulic cylinder operates, and the electromagnets m2 and m6 are energized, The outflow flow rate from port B of the main pump (1) is Q, and enters the rod cavity of the hydraulic cylinder 3. The piston rod retracts, and the outflow flow rate from the rodless cavity is The drain flow rate from port A of the hydraulic cylinder (3) to the oil tank through port P of the third relief valve (9) is/> The rodless chamber pressure of the hydraulic cylinder (3) is Pxmax, and the load on the piston rod is F=Pxmax·A1-P2·A2>0; if F≤0, switch to the third quadrant to work.