A ballast hydraulic system and control method thereof

Abstract

A ballast hydraulic system comprises a first hydraulic pump inlet connected to a fuel tank, a first hydraulic pump outlet connected to the first solenoid reversing valve (P) port and the second solenoid reversing valve (P) port, a second solenoid reversing valve (A) port connected to the hydraulically controlled check valve (A) port, a pressure switch disposed between the second solenoid reversing valve (A) port and the hydraulically controlled check valve (A) port, a hydraulically controlled check valve (B) port connected to the rodless chamber of the ballast cylinder, a rod chamber of the ballast cylinder connected to the second solenoid reversing valve (B) port, and a hydraulically controlled check valve (B) port connected to the pilot control port of the hydraulically controlled check valve. The second solenoid reversing valve (T) port is connected to the fuel tank, a first solenoid reversing valve (A) port connected to the variable motor inlet, a variable motor outlet connected to the second hydraulic pump inlet, and a second hydraulic pump outlet connected to the rodless chamber of the ballast cylinder. This design utilizes a variable motor and a fixed displacement pump as pressure regulating elements to achieve rapid, precise, and wide-range continuous pressure regulation with simple and efficient operation.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydraulic testing, and in particular relates to a ballast hydraulic system and a control method thereof, which is suitable for improving the continuously adjustable pressure range and adjustment accuracy of the ballast hydraulic system and is simple to operate. Background Art

[0002] Ballast hydraulic systems are commonly used on ballast test benches to test the compressive strength of test objects. During the hydraulic test, different levels of hydraulic pressure must be applied to the test object, depending on its requirements.

[0003] For example, the utility model of Chinese patent application No. 201920521419.X discloses a comprehensive hydraulic test bench. The device is regulated by controlling the opening of a proportional directional valve in the pressure range of 0.01-0.5 MPa, and by a proportional pressure reducing valve in the pressure range of 0.5 MPa-12 MPa. However, the device still has the following problems:

[0004] 1. Using proportional directional valves and proportional pressure reducing valves as pressure regulating elements has a small continuous pressure regulation range and poor regulation accuracy.

[0005] 2. This device is only a hydraulic system for pressure regulation. During actual testing, it is necessary to first switch to other hydraulic systems to contact the piston rod of the ballast cylinder with the test piece before adjusting the pressure, which is a cumbersome operation. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned problems existing in the prior art and to provide a ballast hydraulic system and a control method thereof which are simple to operate, have a large continuously adjustable pressure range and high adjustment accuracy.

[0007] To achieve the above objectives, the present invention provides the following technical solutions:

[0008] A ballast hydraulic system, comprising a motor, a hydraulic pump, a first electromagnetic reversing valve, a second electromagnetic reversing valve, a hydraulically controlled one-way valve, a variable motor, a quantitative pump, and a pressure switch. The motor is connected to the hydraulic pump in a transmission manner, the oil inlet of the hydraulic pump is connected to the oil tank, the oil outlet of the hydraulic pump is connected to the P port of the first electromagnetic reversing valve and the P port of the second electromagnetic reversing valve, the A port of the second electromagnetic reversing valve is connected to the A port of the hydraulically controlled one-way valve, and the pressure switch is arranged between the A port of the second electromagnetic reversing valve and the Between the A ports of the hydraulically controlled one-way valve, the B port of the hydraulically controlled one-way valve is connected to the rodless chamber of the ballast oil cylinder, the rod chamber of the ballast oil cylinder is connected to the B port of the second solenoid reversing valve, the B port of the second solenoid reversing valve is also connected to the pilot control oil port of the hydraulically controlled one-way valve, the T port of the second solenoid reversing valve is connected to the oil tank, the A port of the first solenoid reversing valve is connected to the oil inlet of the variable motor, the oil outlet of the variable motor is connected to the oil inlet of the metering pump, and the oil outlet of the metering pump is connected to the rodless chamber of the ballast oil cylinder.

[0009] The port A of the first electromagnetic reversing valve is connected to the oil inlet of the variable motor through the pressure reducing valve and the throttle valve in sequence. A first one-way valve is connected in parallel between the oil inlet of the pressure reducing valve and the oil outlet of the throttle valve.

[0010] The first electromagnetic reversing valve is a two-position two-way electromagnetic reversing valve, and the second electromagnetic reversing valve is a three-position four-way electromagnetic reversing valve.

[0011] The oil outlet of the metering pump is communicated with the rodless chamber of the ballast oil cylinder through a second one-way valve.

[0012] A pressure sensor is provided between the rodless cavity of the ballast oil cylinder and the oil outlet of the second one-way valve and the B port of the hydraulically controlled one-way valve.

[0013] The T port of the second electromagnetic reversing valve is connected to the oil tank through the third one-way valve.

[0014] The ballast hydraulic system also includes an electromagnetic overflow unloading valve, the oil inlet of the electromagnetic overflow unloading is connected to the oil outlet of the hydraulic pump, and the oil outlet of the electromagnetic overflow unloading is also connected to the oil outlet of the third one-way valve and the oil tank. The electromagnetic overflow unloading includes a pilot overflow valve and a third electromagnetic reversing valve. The third electromagnetic reversing valve is a two-position two-way electromagnetic reversing valve.

[0015] The oil outlet of the metering pump is also connected to the oil inlet of the third one-way valve through the overflow valve.

[0016] A control method for a ballast hydraulic system, the control method is performed in the following steps:

[0017] S1. Control the first solenoid reversing valve to the right position to disconnect its P port from its A port, and control the second solenoid reversing valve to the left position to connect its P port to its A port, and its B port to its T port. The hydraulic oil output by the hydraulic pump sequentially passes through the P port of the second solenoid reversing valve, the A port of the second solenoid reversing valve, the A port of the hydraulically controlled one-way valve, and the B port of the hydraulically controlled one-way valve before entering the rodless chamber of the ballast cylinder, causing the piston rod of the ballast cylinder to extend rapidly until the piston rod contacts the object being measured. The hydraulic oil in the rod chamber of the ballast cylinder sequentially passes through the B port of the second solenoid reversing valve and the T port of the second solenoid reversing valve before flowing back to the oil tank.

[0018] S2. After the piston rod of the ballast oil cylinder contacts the object to be measured, the pressure of the hydraulic oil gradually increases. When the pressure rises to the set value of the pressure switch, the first electromagnetic reversing valve is controlled to work in the left position so that its P port is connected to the A port, and the second electromagnetic reversing valve is controlled to work in the middle position. The hydraulic oil output by the hydraulic pump passes through the P port of the first electromagnetic reversing valve, the A port of the first electromagnetic reversing valve, the oil inlet of the variable motor, the oil outlet of the variable motor, the oil inlet of the metering pump, and the oil outlet of the metering pump in sequence and then enters the rodless cavity of the ballast oil cylinder. By adjusting the displacement of the variable motor, the test pressure applied to the object to be measured during the ballast test is continuously adjusted.

[0019] The control method further includes step S3, which includes:

[0020] After the test, the first solenoid reversing valve is controlled to work in the right position to disconnect its A port and P port, and the second solenoid reversing valve is controlled to work in the right position to connect its P port and B port, and its A port and T port. The hydraulic oil output by the hydraulic pump passes through the P port of the second solenoid reversing valve and the B port of the second solenoid reversing valve in sequence and then enters the rod chamber of the ballast oil cylinder and the pilot control oil port of the hydraulically controlled one-way valve at the same time. The hydraulic oil in the rodless chamber of the ballast oil cylinder passes through the B port of the hydraulically controlled one-way valve, the A port of the hydraulically controlled one-way valve, the A port of the second solenoid reversing valve, and the T port of the second solenoid reversing valve in sequence and then flows back to the oil tank, causing the piston rod of the ballast oil cylinder to retract quickly.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. A ballast hydraulic system of the present invention includes a motor, a hydraulic pump, a first electromagnetic reversing valve, a second electromagnetic reversing valve, a hydraulically controlled one-way valve, a variable motor, a quantitative pump, and a pressure switch. The working process of the system is as follows: first, the first electromagnetic reversing valve is controlled to work in the right position and the second electromagnetic reversing valve is controlled to work in the left position, and the high-pressure oil output by the hydraulic pump is used to quickly lower the piston of the ballast oil cylinder. After the oil pressure rises after it hits the object to be measured, when the pressure rises to the set value of the pressure switch, the first electromagnetic reversing valve is controlled to work in the left position and the first electromagnetic reversing valve is controlled to work in the middle position. The high-pressure oil output by the hydraulic pump is used to quickly lower the piston of the ballast oil cylinder. The oil pressure causes the variable motor to rotate the metering pump, which then delivers high-pressure oil to the rodless chamber of the ballast oil cylinder. By adjusting the displacement of the variable motor, the output pressure of the metering pump can be continuously adjusted. After the test is completed, the first electromagnetic reversing valve and the second electromagnetic reversing valve are controlled to operate in the right position, causing the ballast oil cylinder piston to retract rapidly. This design, on the one hand, uses the variable motor and metering pump as pressure regulating elements to achieve rapid, precise, and wide-range continuous pressure regulation. On the other hand, a single system can complete the ballast test without switching the hydraulic system, and the operation is simple and efficient. Therefore, the present invention not only achieves rapid, precise, and wide-range continuous pressure regulation, but also is simple to operate and highly efficient.

[0023] 2. In a ballast hydraulic system according to the present invention, port A of a first solenoid reversing valve is connected to the oil inlet of a variable speed motor via a pressure reducing valve and a throttle valve. A first check valve is connected in parallel between the oil inlet of the pressure reducing valve and the oil outlet of the throttle valve. This design adjusts the hydraulic oil flow rate through the throttle valve, thereby adjusting the extension speed of the ballast cylinder piston to meet different testing requirements. Therefore, the present invention can adjust the extension speed of the ballast cylinder piston to meet different testing requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram illustrating the principle of the present invention.

[0025] In the figure, motor 1, hydraulic pump 2, first solenoid reversing valve 3, second solenoid reversing valve 4, hydraulically controlled one-way valve 5, variable motor 6, metering pump 7, pressure switch 8, electromagnetic overflow unloading 9, oil tank 10, ballast cylinder 11, pressure reducing valve 12, throttle valve 13, first one-way valve 14, second one-way valve 15, pressure sensor 16, pilot-operated overflow valve 17, third solenoid reversing valve 18, third one-way valve 19, overflow valve 20. DETAILED DESCRIPTION

[0026] The present invention will be further described below with reference to the accompanying drawings and specific implementation methods.

[0027] See also Figure 1 A ballast hydraulic system includes a motor 1, a hydraulic pump 2, a first electromagnetic reversing valve 3, a second electromagnetic reversing valve 4, a hydraulically controlled one-way valve 5, a variable motor 6, a quantitative pump 7, and a pressure switch 8. The motor 1 is connected to the hydraulic pump 2 in a transmission manner. The oil inlet of the hydraulic pump 2 is connected to the oil tank 10. The oil outlet of the hydraulic pump 2 is connected to the P port of the first electromagnetic reversing valve 3 and the P port of the second electromagnetic reversing valve 4. The A port of the second electromagnetic reversing valve 4 is connected to the A port of the hydraulically controlled one-way valve 5. The pressure switch 8 is arranged at the A port of the second electromagnetic reversing valve 4. Between the A port of the hydraulically controlled one-way valve 5, the B port of the hydraulically controlled one-way valve 5 is connected to the rodless chamber of the ballast cylinder 11, the rod chamber of the ballast cylinder 11 is connected to the B port of the second solenoid reversing valve 4, the B port of the second solenoid reversing valve 4 is also connected to the pilot control oil port of the hydraulically controlled one-way valve 5, the T port of the second solenoid reversing valve 4 is connected to the oil tank 10, the A port of the first solenoid reversing valve 3 is connected to the oil inlet of the variable motor 6, the oil outlet of the variable motor 6 is connected to the oil inlet of the metering pump 7, and the oil outlet of the metering pump 7 is connected to the rodless chamber of the ballast cylinder 11.

[0028] The port A of the first electromagnetic reversing valve 3 is connected to the oil inlet of the variable motor 6 through the pressure reducing valve 12 and the throttle valve 13 in sequence. A first one-way valve 14 is connected in parallel between the oil inlet of the pressure reducing valve 12 and the oil outlet of the throttle valve 13.

[0029] The first electromagnetic reversing valve 3 is a two-position two-way electromagnetic reversing valve, and the second electromagnetic reversing valve 4 is a three-position four-way electromagnetic reversing valve.

[0030] The oil outlet of the metering pump 7 is connected to the rodless chamber of the ballast oil cylinder 11 through the second one-way valve 15 .

[0031] A pressure sensor 16 is provided between the rodless chamber of the ballast oil cylinder 11 and the oil outlet of the second one-way valve 15 and the port B of the hydraulically controlled one-way valve 5 .

[0032] The T port of the second electromagnetic reversing valve 4 is connected to the oil tank 10 through the third one-way valve 19 .

[0033] The ballast hydraulic system also includes an electromagnetic overflow unloading valve 9, the oil inlet of the electromagnetic overflow unloading valve 9 is connected to the oil outlet of the hydraulic pump 2, and the oil outlet of the electromagnetic overflow unloading valve 9 is also connected to the oil outlet of the third one-way valve 19 and the oil tank 10. The electromagnetic overflow unloading valve 9 includes a pilot overflow valve 17 and a third electromagnetic reversing valve 18. The third electromagnetic reversing valve 18 is a two-position two-way electromagnetic reversing valve.

[0034] The oil outlet of the metering pump 7 is also connected to the oil inlet of the third one-way valve 19 through the overflow valve 20.

[0035] A control method for a ballast hydraulic system, the control method is performed in the following steps:

[0036] S1. Control the first solenoid reversing valve 3 to work in the right position so that its P port is disconnected from its A port, and control the second solenoid reversing valve 4 to work in the left position so that its P port is connected to its A port, and its B port is connected to its T port. The hydraulic oil output by the hydraulic pump 2 passes through the P port of the second solenoid reversing valve 4, the A port of the second solenoid reversing valve 4, the A port of the hydraulically controlled one-way valve 5, and the B port of the hydraulically controlled one-way valve 5 in sequence, and then enters the rodless cavity of the ballast cylinder 11, so that the piston rod of the ballast cylinder 11 is quickly extended until the piston rod contacts the object to be measured. The hydraulic oil in the rod cavity of the ballast cylinder 11 passes through the B port of the second solenoid reversing valve 4 and the T port of the second solenoid reversing valve 4 in sequence, and then flows back to the oil tank 10.

[0037] S2. After the piston rod of the ballast cylinder 11 contacts the object to be measured, the pressure of the hydraulic oil gradually increases. When the pressure rises to the set value of the pressure switch 8, the first electromagnetic reversing valve 3 is controlled to work in the left position so that its P port is connected to the A port, and the second electromagnetic reversing valve is controlled to work in the middle position. The hydraulic oil output by the hydraulic pump 2 passes through the P port of the first electromagnetic reversing valve 3, the A port of the first electromagnetic reversing valve 3, the oil inlet of the variable motor 6, the oil outlet of the variable motor 6, the oil inlet of the metering pump 7, and the oil outlet of the metering pump 7 in sequence, and then enters the rodless cavity of the ballast cylinder 11. By adjusting the displacement of the variable motor 6, the test pressure applied to the object to be measured during the ballast test is continuously adjusted.

[0038] The control method further includes step S3, which includes:

[0039] After the test, the first solenoid reversing valve 3 is controlled to work in the right position to disconnect its A port and P port, and the second solenoid reversing valve 4 is controlled to work in the right position to connect its P port and B port, and its A port and T port. The hydraulic oil output by the hydraulic pump 2 passes through the second solenoid reversing valve 4P port and the second solenoid reversing valve 4B port in sequence and then enters the rod chamber of the ballast cylinder 11 and the pilot control oil port of the hydraulically controlled one-way valve at the same time. The hydraulic oil in the rodless chamber of the ballast cylinder 11 passes through the hydraulically controlled one-way valve 5B port, the hydraulically controlled one-way valve 5A port, the second solenoid reversing valve 4A port and the second solenoid reversing valve 4T port in sequence and then flows back to the oil tank 10, causing the piston rod of the ballast cylinder 11 to retract quickly.

[0040] Example 1:

[0041] See also Figure 1 A ballast hydraulic system includes a motor 1, a hydraulic pump 2, a first electromagnetic reversing valve 3, a second electromagnetic reversing valve 4, a hydraulically controlled one-way valve 5, a variable motor 6, a quantitative pump 7, and a pressure switch 8. The motor 1 is connected to the hydraulic pump 2 in a transmission manner. The oil inlet of the hydraulic pump 2 is connected to the oil tank 10. The oil outlet of the hydraulic pump 2 is connected to the P port of the first electromagnetic reversing valve 3 and the P port of the second electromagnetic reversing valve 4. The A port of the second electromagnetic reversing valve 4 is connected to the A port of the hydraulically controlled one-way valve 5. The pressure switch 8 is arranged between the A port of the second electromagnetic reversing valve 4 and the A port of the hydraulically controlled one-way valve 5. The B port of the hydraulically controlled one-way valve 5 is connected to the rodless chamber of the ballast oil cylinder 11. The rod chamber of the ballast oil cylinder 11 is connected to the B port of the second solenoid reversing valve 4, and the B port of the second solenoid reversing valve 4 is also connected to the pilot control oil port of the hydraulically controlled one-way valve 5. The T port of the second solenoid reversing valve 4 is connected to the oil tank 10. The A port of the first solenoid reversing valve 3 is connected to the oil inlet of the variable motor 6, and the oil outlet of the variable motor 6 is connected to the oil inlet of the metering pump 7. The oil outlet of the metering pump 7 is connected to the rodless chamber of the ballast oil cylinder 11. The first solenoid reversing valve 3 is a two-position two-way solenoid reversing valve, and the second solenoid reversing valve 4 is a three-position four-way solenoid reversing valve. The hydraulic pump 2 is a low-pressure and small-displacement pump, which is more energy-efficient as a power source;

[0042] The above-mentioned control method of the ballast hydraulic system is specifically performed according to the following steps:

[0043] S1: DT1 of the first solenoid reversing valve 3 is de-energized. The first solenoid reversing valve 3 works in the right position, and its upper port P is disconnected from its upper port A. At the same time, DT2 of the second solenoid reversing valve 4 is energized and DT3 is de-energized. The second solenoid reversing valve 4 works in the left position, and its upper port P is connected to its upper port A, and its upper port B is connected to its upper port T.

[0044] At this time, the hydraulic oil output by the hydraulic pump 2 passes through the P port of the second electromagnetic reversing valve 4, the A port of the second electromagnetic reversing valve 4, the A port of the hydraulically controlled one-way valve 5, and the B port of the hydraulically controlled one-way valve 5 in sequence, and then enters the rodless chamber of the ballast oil cylinder 11, causing the piston rod of the ballast oil cylinder 11 to extend rapidly until the piston rod contacts the object to be measured. The hydraulic oil in the rod chamber of the ballast oil cylinder 11 passes through the B port of the second electromagnetic reversing valve 4 and the T port of the second electromagnetic reversing valve 4 in sequence, and then flows back to the oil tank 10;

[0045] S2. After the piston rod of the ballast oil cylinder 11 contacts the object to be measured, the pressure of the hydraulic oil gradually increases. When the pressure reaches the set value of the pressure switch 8, DT1 of the first solenoid reversing valve 3 is energized. The first solenoid reversing valve 3 operates in the left position, and its upper port P is connected to the port A. The second solenoid reversing valve 4 is controlled to operate in the middle position.

[0046] At this time, the hydraulic oil output by the hydraulic pump 2 passes through the P port of the first electromagnetic reversing valve 3 and the A port of the first electromagnetic reversing valve 3 in sequence, and then enters the variable motor 6. The variable motor 6 drives the metering pump 7 to rotate, and the hydraulic oil output by the metering pump 7 enters the rodless chamber of the ballast cylinder 11. By adjusting the displacement of the variable motor 6, the test pressure applied to the object under test during the ballast test can be continuously adjusted. Assuming that the output pressure of the metering pump 7 is P2, the oil supply pressure of the variable motor 6 is P1, and A is the displacement ratio of the variable motor 6 to the metering pump 7, then P2=A*P1;

[0047] Step S3: After the test is completed, the first electromagnetic reversing valve 3 DT1 is controlled to be de-energized, and the first electromagnetic reversing valve 3 works in the right position, and the A port and the P port are disconnected; and the second electromagnetic reversing valve 4 DT2 is controlled to be de-energized and DT3 is energized, and the second electromagnetic reversing valve 4 works in the right position, and the P port and the B port are connected, and the A port and the T port are connected;

[0048] At this time, the hydraulic oil output by the hydraulic pump 2 passes through the P port of the second solenoid reversing valve 4 and the B port of the second solenoid reversing valve 4 in sequence, and then enters the rod chamber of the ballast cylinder 11 and the pilot control oil port of the hydraulically controlled one-way valve. The hydraulic oil in the rodless chamber of the ballast cylinder 11 passes through the B port of the hydraulically controlled one-way valve 5, the A port of the hydraulically controlled one-way valve 5, the A port of the second solenoid reversing valve 4, and the T port of the second solenoid reversing valve 4 in sequence, and then flows back to the oil tank 10, and the piston rod of the ballast cylinder 11 retracts rapidly.

[0049] Example 2:

[0050] The difference from Example 1 is that:

[0051] The A port of the first solenoid reversing valve 3 is connected to the oil inlet of the variable motor 6 through the pressure reducing valve 12 and the throttle valve 13 in sequence. A first one-way valve 14 is connected in parallel between the oil inlet of the pressure reducing valve 12 and the oil outlet of the throttle valve 13. The throttle valve 13 is used to adjust the movement speed of the piston of the ballast cylinder 11. The wider the opening of the throttle valve 13, the faster the piston moves.

[0052] Example 3:

[0053] The difference from Example 1 is that:

[0054] The oil outlet of the metering pump 7 is connected to the rodless chamber of the ballast cylinder 11 through the second one-way valve 15. A pressure sensor 16 is provided between the rodless chamber of the ballast cylinder 11 and the oil outlet of the second one-way valve 15 and the B port of the hydraulically controlled one-way valve 5. The pressure sensor 16 is used to provide real-time feedback on the pressure of the rodless chamber of the ballast cylinder 11.

[0055] Example 4:

[0056] The difference from Example 1 is that:

[0057] The T port of the second solenoid reversing valve 4 is connected to the oil tank 10 through the third one-way valve 19. The ballast hydraulic system also includes an electromagnetic overflow unloading valve 9. The oil inlet of the electromagnetic overflow unloading valve 9 is connected to the oil outlet of the hydraulic pump 2. The oil outlet of the electromagnetic overflow unloading valve 9 is simultaneously connected to the oil outlet of the third one-way valve 19 and the oil tank 10. The electromagnetic overflow unloading valve 9 includes a pilot overflow valve 17 and a third solenoid reversing valve 18. The third solenoid reversing valve 18 is a two-position two-way solenoid reversing valve. When DT4 of the third solenoid reversing valve 18 is energized, the electromagnetic overflow unloading valve 9 is in an unloading working state. When DT4 of the third solenoid reversing valve 18 is de-energized, the electromagnetic overflow unloading valve 9 is in an overflow working state.

[0058] Example 5:

[0059] The difference from Example 4 is that:

[0060] The oil outlet of the metering pump 7 is also connected to the oil inlet of the third one-way valve 19 through the relief valve 20, and the maximum output pressure of the metering pump is set by the relief valve 20.

Claims

1. A ballast hydraulic system, characterized by: The ballast hydraulic system comprises a motor (1), a hydraulic pump (2), a first electromagnetic reversing valve (3), a second electromagnetic reversing valve (4), a hydraulically controlled one-way valve (5), a variable motor (6), a quantitative pump (7), and a pressure switch (8). The motor (1) is connected to the hydraulic pump (2) in a transmission manner. The oil inlet of the hydraulic pump (2) is connected to the oil tank (10). The oil outlet of the hydraulic pump (2) is connected to the P port of the first electromagnetic reversing valve (3) and the P port of the second electromagnetic reversing valve (4). The A port of the second electromagnetic reversing valve (4) is connected to the A port of the hydraulically controlled one-way valve (5). The pressure switch (8) is arranged between the A port of the second electromagnetic reversing valve (4) and the The A port of the hydraulically controlled one-way valve (5) is connected to the rodless cavity of the ballast oil cylinder (11), the rod cavity of the ballast oil cylinder (11) is connected to the B port of the second electromagnetic reversing valve (4), the B port of the second electromagnetic reversing valve (4) is also connected to the pilot control oil port of the hydraulically controlled one-way valve (5), the T port of the second electromagnetic reversing valve (4) is connected to the oil tank (10), the A port of the first electromagnetic reversing valve (3) is connected to the oil inlet of the variable motor (6), the oil outlet of the variable motor (6) is connected to the oil inlet of the metering pump (7), and the oil outlet of the metering pump (7) is connected to the rodless cavity of the ballast oil cylinder (11).

2. A ballast hydraulic system according to claim 1, characterized in that: The port A of the first electromagnetic reversing valve (3) is connected to the oil inlet of the variable motor (6) through the pressure reducing valve (12) and the throttle valve (13) in sequence, and a first one-way valve (14) is connected in parallel between the oil inlet of the pressure reducing valve (12) and the oil outlet of the throttle valve (13).

3. A ballast hydraulic system according to claim 1 or 2, characterized in that: The first electromagnetic reversing valve (3) is a two-position two-way electromagnetic reversing valve, and the second electromagnetic reversing valve (4) is a three-position four-way electromagnetic reversing valve.

4. A ballast hydraulic system according to claim 1 or 2, characterized in that: The oil outlet of the metering pump (7) is connected to the rodless chamber of the ballast oil cylinder (11) via a second one-way valve (15).

5. The ballast hydraulic system according to claim 4, characterized in that: A pressure sensor (16) is provided between the rodless chamber of the ballast oil cylinder (11), the oil outlet of the second one-way valve (15), and the B port of the hydraulically controlled one-way valve (5).

6. A ballast hydraulic system according to claim 1 or 2, characterized in that: The T port of the second electromagnetic reversing valve (4) is connected to the oil tank (10) via a third one-way valve (19).

7. The ballast hydraulic system according to claim 6, characterized in that: The ballast hydraulic system further comprises an electromagnetic overflow unloading valve (9), the oil inlet of the electromagnetic overflow unloading valve (9) being connected to the oil outlet of the hydraulic pump (2), and the oil outlet of the electromagnetic overflow unloading valve (9) being connected to the oil outlet of the third one-way valve (19) and the oil tank (10) at the same time. The electromagnetic overflow unloading valve (9) comprises a pilot overflow valve (17) and a third electromagnetic reversing valve (18), and the third electromagnetic reversing valve (18) is a two-position two-way electromagnetic reversing valve.

8. The ballast hydraulic system according to claim 7, characterized in that: The oil outlet of the metering pump (7) is also connected to the oil inlet of the third one-way valve (19) through the overflow valve (20).

9. The method for controlling a ballast hydraulic system according to claim 1, wherein: The control method is carried out in the following steps: S1, control the first electromagnetic reversing valve (3) to work in the right position so that its P port is disconnected from its A port, and control the second electromagnetic reversing valve (4) to work in the left position so that its P port is connected to its A port, and its B port is connected to its T port, the hydraulic oil output by the hydraulic pump (2) passes through the P port of the second electromagnetic reversing valve (4), the A port of the second electromagnetic reversing valve (4), the A port of the hydraulic control check valve (5), and the B port of the hydraulic control check valve (5) in sequence, and then enters the rodless chamber of the ballast oil cylinder (11), so that the piston rod of the ballast oil cylinder (11) is quickly extended until the piston rod contacts the object to be measured, and the hydraulic oil in the rod chamber of the ballast oil cylinder (11) passes through the B port of the second electromagnetic reversing valve (4) and the T port of the second electromagnetic reversing valve (4) in sequence, and then flows back to the oil tank (10); S2. After the piston rod of the ballast oil cylinder (11) contacts the object to be measured, the pressure of the hydraulic oil gradually increases. When the pressure reaches the set value of the pressure switch (8), the first electromagnetic reversing valve (3) is controlled to work in the left position so that its P port is connected to the A port, and the second electromagnetic reversing valve (4) is controlled to work in the middle position. The hydraulic oil output by the hydraulic pump (2) passes through the P port of the first electromagnetic reversing valve (3), the A port of the first electromagnetic reversing valve (3), the oil inlet of the variable motor (6), the oil outlet of the variable motor (6), the oil inlet of the metering pump (7), the oil outlet of the metering pump (7), and then enters the rodless chamber of the ballast oil cylinder (11). By adjusting the displacement of the variable motor (6), the test pressure applied to the object to be measured during the ballast test is continuously adjusted.

10. The control method of a ballast hydraulic system according to claim 9, characterized in that: The control method further includes step S3, which includes: After the test, the first electromagnetic reversing valve (3) is controlled to work in the right position so that its A port is disconnected from its P port, and the second electromagnetic reversing valve (4) is controlled to work in the right position so that its P port is connected to its B port and its A port is connected to its T port. The hydraulic oil output by the hydraulic pump (2) passes through the P port of the second electromagnetic reversing valve (4) and the B port of the second electromagnetic reversing valve (4) in sequence and then enters the rod chamber of the ballast oil cylinder (11) and the pilot control oil port of the hydraulic control check valve at the same time. The hydraulic oil in the rodless chamber of the ballast oil cylinder (11) passes through the B port of the hydraulic control check valve (5), the A port of the hydraulic control check valve (5), the A port of the second electromagnetic reversing valve (4) and the T port of the second electromagnetic reversing valve (4) in sequence and then flows back to the oil tank (10), so that the piston rod of the ballast oil cylinder (11) retracts quickly.

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