A hydraulic outrigger extension control circuit and control method

Abstract

This invention provides a hydraulic outrigger extension and retraction control circuit and method, including an electronically controlled power unit, a tractor power source, a control valve group, and an outrigger actuator. The control valve group includes a first pilot-operated relief valve and several solenoid directional valves. The first pilot-operated relief valve and the several solenoid directional valves are connected in parallel. The first pilot-operated relief valve is used to control the pressure build-up and unloading of the control valve group. The electronically controlled power unit is connected to the outrigger actuator through the control valve group. The tractor power source is connected to the outrigger actuator. In this invention, the electronically controlled power unit is installed on the semi-trailer and uses a DC power supply to drive the extension and retraction of the outrigger actuator. The tractor power source is installed on the tractor. When the outrigger actuator needs to accelerate its extension and retraction, the hydraulic oil transported by the tractor power source and the hydraulic oil driven by the electronically controlled power unit merge and enter the outrigger actuator together, increasing the flow circulation in the outrigger actuator and making its operation safer and more reliable.

Description

Technical Field

[0001] This invention relates to the field of metallurgical transport vehicle technology, and in particular to a hydraulic outrigger extension control circuit and control method. Background Technology

[0002] The semi-trailer is supported at the rear by an axle and at the front by outriggers. When not in use, the outriggers and axle together support the semi-trailer. There are two types of outrigger structures: one uses articulated outriggers, which are opened when in use, but their height is not adjustable; the other uses height-adjustable outriggers. Height-adjustable outriggers typically employ a mechanical height adjustment device, which is complex and requires manual adjustment. Another type of height-adjustable outrigger often uses a hydraulic cylinder structure. Power sources include those using the tractor unit's power take-off (PTO) and those using an electronically controlled power unit, but a single hydraulic power source has significant shortcomings in terms of reliability and operational efficiency.

[0003] Furthermore, most semi-trailer outriggers or support devices currently used are electro-hydraulic cylinders with independent oil sources. However, the power of the pumps driven by DC power to deliver hydraulic oil is not high. For large-tonnage semi-trailers, especially tank trucks, detaching the semi-trailer from the tractor by extending or retracting the front outriggers is often time-consuming and inefficient. This does not adequately meet the needs of steel mill metallurgical logistics processes. Therefore, improving the extension and retraction speed of hydraulic outriggers, especially the extension speed, and shortening the process time is crucial for large logistics companies to achieve a transportation model where one tractor tows multiple semi-trailers. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a hydraulic outrigger extension and retraction control circuit and control method, which effectively integrates two power sources in a specific way, and solves the problems of low power of DC power-driven pumps for delivering hydraulic oil, long time consumption of hydraulic outriggers during extension and retraction operations, low work efficiency, and low reliability of single power sources in the prior art.

[0005] To achieve the above and other related objectives, the present invention provides a hydraulic outrigger extension and retraction control circuit, including an electronically controlled power unit, a tractor power source, a control valve group, and an outrigger actuator. The control valve group includes a first pilot-operated relief valve and several solenoid directional valves. The first pilot-operated relief valve and the several solenoid directional valves are connected in parallel. The first pilot-operated relief valve is used to control the pressure build-up and unloading of the control valve group. The electronically controlled power unit is connected to the outrigger actuator through the control valve group to realize the slow extension and retraction of the outrigger actuator. The electronically controlled power unit and the tractor power source form a dual power source confluence to realize the accelerated extension or retraction of the outrigger actuator. The tractor power source is connected to the outrigger actuator to realize the retraction and differential extension of the outrigger actuator.

[0006] Preferably, the electronically controlled power unit includes a first motor, a first metering pump, a return oil filter, a breather valve, and a first one-way shut-off valve. The inlet end of the first metering pump is connected to an oil tank, and the outlet end of the first metering pump is connected to the P port of the control valve group through the first one-way shut-off valve. A return oil pipe is provided between the T port of the control valve group and the oil tank, and the return oil filter is installed on the return oil pipe. The breather valve is installed on the oil tank. The first motor drives the first metering pump to work.

[0007] Preferably, the P port of the solenoid directional valve is connected to the P port of the control valve group, and the T port of the solenoid directional valve is connected to the T port of the control valve group; when the solenoid directional valve is in the neutral position, both the A port and the B port of the solenoid directional valve are connected to the T port; the A port of the first pilot-operated relief valve is connected to the P port of the control valve group, and the B port of the first pilot-operated relief valve is connected to the T port of the control valve group.

[0008] Preferably, the outrigger actuator includes a bidirectional hydraulic lock and an outrigger cylinder. The outrigger cylinder includes a rod chamber and a rodless chamber. The A port and B port of the electromagnetic directional valve are connected to the rod chamber and the rodless chamber through the bidirectional hydraulic lock. The outlet end of the first quantitative pump is connected to the outrigger cylinder through a first one-way shut-off valve, a first pilot-operated relief valve, and an electromagnetic directional valve, for driving the extension and retraction of the outrigger cylinder. The hydraulic oil in the outrigger cylinder flows back to the oil tank through the bidirectional hydraulic lock, the electromagnetic directional valve, and the return oil pipe.

[0009] Preferably, the tractor power source includes a second motor, a second fixed displacement pump, a second one-way shut-off valve, a second pilot-operated relief valve, and two first quick connectors. The inlet of the second fixed displacement pump is connected to the oil tank through either of the first quick connectors, and the outlet of the second fixed displacement pump is connected to the outrigger actuator through the other first quick connector. Port A of the second pilot-operated relief valve is connected to the outlet of the second fixed displacement pump, and port B of the second pilot-operated relief valve is connected to the inlet of the second fixed displacement pump. The second one-way shut-off valve is located at the outlet of the second fixed displacement pump, and the second motor drives the second fixed displacement pump to operate.

[0010] Preferably, a third one-way shut-off valve and a second quick connector are also provided between the first quick connector and the outrigger actuator. The second quick connector is connected to the rod chamber or the rodless chamber. The outlet end of the second metering pump is connected to the outrigger cylinder in sequence through the second one-way shut-off valve, the first quick connector, the third one-way shut-off valve, the second quick connector, and the bidirectional hydraulic lock, for driving the extension and retraction of the outrigger cylinder. The hydraulic oil in the outrigger cylinder flows back to the oil tank through the bidirectional hydraulic lock, the solenoid directional valve, and the return oil pipe.

[0011] Preferably, a third one-way shut-off valve and a third quick connector are further provided between the first quick connector and the outrigger actuator. The third quick connector is connected to the rodless chamber or the rod chamber. The outlet end of the second metering pump is connected to the outrigger cylinder in sequence through the second one-way shut-off valve, the first quick connector, the third one-way shut-off valve, the third quick connector, and the bidirectional hydraulic lock, for driving the extension and retraction of the outrigger cylinder. The hydraulic oil in the outrigger cylinder flows back to the oil tank through the bidirectional hydraulic lock, the solenoid directional valve, and the return oil pipe.

[0012] Preferably, a shut-off valve is also provided on the return oil pipe. When the shut-off valve closes the return oil pipe, the hydraulic oil in the rod chamber of the outrigger cylinder can flow back to the rodless chamber of the outrigger cylinder through the bidirectional hydraulic lock and the solenoid directional valve to achieve differential operation.

[0013] Preferably, a high-pressure ball valve is also provided on the pipeline between the bidirectional hydraulic lock and the outrigger cylinder. The high-pressure ball valve is connected to the oil tank, and the bidirectional hydraulic lock is directly connected to the outrigger cylinder body by mechanical means.

[0014] To achieve the above or other objectives, this invention also discloses a control method for a hydraulic outrigger extension control circuit. The method employs the aforementioned hydraulic outrigger extension control circuit. The electrically controlled power unit includes an oil tank. The T-port of the control valve group is connected to the oil tank via a return oil pipe, and a shut-off valve is installed on the return oil pipe. The tractor power source is connected to the outrigger actuator, and several quick-connect couplings are provided between them. These quick-connect couplings are respectively connected to the rod-side chamber and the rodless chamber in the outrigger actuator. The steps are as follows:

[0015] S1: The hydraulic outriggers are slowly extended and retracted via an electronically controlled power unit, especially the extension and retraction of the outriggers after contacting the load: the first pilot-operated relief valve in the control valve group is energized to build up pressure in the control valve group; the solenoid directional valve is energized, one of the solenoid directional valves is connected, and the electronically controlled power unit works to transport hydraulic oil to the solenoid directional valve, and then into the outrigger actuator to complete the extension and retraction of the outrigger actuator. The hydraulic oil in the outrigger actuator flows back to the oil tank of the electronically controlled power unit through the solenoid directional valve.

[0016] S2: The outrigger actuator is accelerated to extend or retract by combining two power sources: the first pilot-operated relief valve in the control valve group is energized to build up pressure in the control valve group; the solenoid directional valve is energized, one of its paths is connected, and the electronic power unit works to transport hydraulic oil to the solenoid directional valve, and then into the outrigger actuator; at the same time, the tractor power source works, and the tractor power source transports hydraulic oil to the rod-side or rodless side of the outrigger actuator without passing through the solenoid directional valve, through several quick connectors. The hydraulic oil driven by the tractor power source merges with the hydraulic oil transported by the electronic power unit, realizing the accelerated extension or retraction of the outrigger actuator. The hydraulic oil in the outrigger actuator flows back to the oil tank in the electronic power unit through the solenoid directional valve.

[0017] S3: Differential extension of the hydraulic outriggers via the tractor's independent hydraulic power source: The tractor's power source is operational, while the electric power unit motor is de-energized, ensuring the return oil is cut off by the shut-off valve installed on the return oil pipe. At this time, the differential connection of the outrigger cylinders is achieved through the neutral position of the solenoid directional valve (A and B are connected to T). When the tractor's power source enters the rodless chamber of the outrigger cylinder, rapid extension is achieved through the differential connection described above (because the return oil from the rod chamber returns to the rodless chamber, flow regeneration is realized). When the shut-off valve is restored, the pilot control port of the bidirectional hydraulic lock on the outrigger cylinder is completely unloaded again, ensuring the safety of the outrigger cylinder lock.

[0018] S4: Through certain logic control and quick-connect oil circuit adjustment (i.e., connecting the second and third quick connectors to the control circuit), the retraction operation of the tractor's power source can also be guaranteed. By changing different quick connector methods, the tractor's power source can be directly introduced into the rod chamber of the outrigger cylinder. The retraction requirement of the outrigger cylinder is completed by energizing the solenoid directional valve and the first pilot-operated relief valve.

[0019] As described above, the hydraulic outrigger extension control circuit and control method of the present invention have the following beneficial effects:

[0020] This invention relates to a hydraulic outrigger extension and retraction control circuit and method, which includes both an electronically controlled power unit and a tractor unit power source. The electronically controlled power unit is mounted on the semi-trailer and uses a DC power supply to drive the extension and retraction of the outrigger actuator. The tractor unit power source is mounted on the tractor and connected to the tractor's power take-off port. When the outrigger actuator needs to accelerate its extension and retraction, the hydraulic oil transported by the tractor unit power source merges with the hydraulic oil driven by the electronically controlled power unit and enters the outrigger actuator together. This increases the flow circulation within the outrigger actuator, improves its extension and retraction speed, meets the requirements of rapid lowering of the semi-trailer outriggers with multi-stage speed selection, and enhances the operational efficiency of the tractor unit handling multiple trailers. Furthermore, the use of both the electronically controlled power unit and the tractor unit power source effectively improves the emergency handling capability for outrigger malfunctions, resulting in safer and more reliable operation. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the hydraulic flow direction of the hydraulic outrigger extension control circuit of the present invention.

[0022] Explanation of reference numerals in the attached figures:

[0023] 1. Tractor power source; 101. Second pilot-operated relief valve; 102. Second fixed displacement pump; 103. Second one-way shut-off valve; 104. First quick connector;

[0024] 2. Electrically controlled power unit; 201. First motor; 202. First quantitative pump; 203. Return oil filter; 204. Breather valve; 205. First one-way shut-off valve;

[0025] 3. Control valve assembly; 301. First pilot-operated relief valve; 302 / 303. Solenoid directional valve;

[0026] 4. Outrigger actuator; 401. Two-way hydraulic lock; 402. High-pressure ball valve; 403. Outrigger cylinder;

[0027] 5. Third quick connector; 6. Second quick connector; 7. Third one-way shut-off valve; 8. Shut-off valve; 9. Return oil pipe. Detailed Implementation

[0028] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0029] It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings of this specification are merely for illustrative purposes to aid those skilled in the art and are not intended to limit the scope of the invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed in this invention. Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0030] like Figure 1 As shown, the present invention provides a hydraulic outrigger extension control circuit, including an electronically controlled power unit 2, a tractor power source 1, a control valve group 3, and an outrigger actuator 4. The control valve group 3 includes a first pilot-operated relief valve 301 and several electromagnetic directional valves 302 / 303. The first pilot-operated relief valve 301 and several electromagnetic directional valves 302 / 303 are connected in parallel. The first pilot-operated relief valve 301 is used to control the pressure build-up and unloading of the control valve group 3. The electronically controlled power unit 2 is connected to the outrigger actuator 4 through the control valve group 3. The tractor power source 1 is connected to the outrigger actuator 4.

[0031] The hydraulic outrigger extension control circuit of this invention includes an electronically controlled power unit 2 and a tractor power source 1. The electronically controlled power unit 2 uses a DC power supply to drive a pump to transport hydraulic oil, while the tractor power source 1 uses the tractor's power take-off to drive the pump to transport hydraulic oil. When the outrigger actuator 4 extends or retracts at normal speed, only the electronically controlled power unit 2 is needed to drive the hydraulic oil. When the outrigger actuator 4 accelerates its extension or retraction, both the tractor power source 1 and the electronically controlled power unit 2 operate. The hydraulic oil driven by the tractor power source 1 and the hydraulic oil driven by the electronically controlled power unit 2 merge and enter the outrigger actuator 4 together, increasing the flow rate in the outrigger actuator 4 and thus accelerating the extension or retraction operation of the outrigger actuator 4.

[0032] Preferred, such as Figure 1As shown, the electronically controlled power unit 2 includes a first motor 201, a first fixed displacement pump 202, a return oil filter 203, a breather valve 204, and a first one-way shut-off valve 205. The inlet end of the first fixed displacement pump 202 is connected to an oil tank, and the outlet end of the first fixed displacement pump 202 is connected to the P port of the control valve group 3 through the first one-way shut-off valve 205. A return oil pipe 9 is provided between the T port of the control valve group 3 and the oil tank, and the return oil filter 203 is installed on the return oil pipe 9. The breather valve 204 is installed on the oil tank. The first motor 201 drives the first fixed displacement pump 202 to work. In this embodiment, when the first motor 201 drives the first fixed displacement pump 202 to work, the first fixed displacement pump 202 transports the hydraulic oil in the oil tank to the P port of the control valve group 3 through the first one-way shut-off valve 205. In this embodiment, the electronically controlled power unit 2 is mounted on the semi-trailer, and the first motor 201 is a DC motor with an output power of less than 3KW. The first fixed displacement pump 202 is a gear pump or vane pump, which has a much smaller displacement than the second fixed displacement pump 102. Generally, it only needs to meet the requirements of slow and stable load support by the outrigger cylinder 403 and rapid retraction of the outriggers.

[0033] Preferred, such as Figure 1 As shown, the P port of the solenoid directional valve 302 / 303 is connected to the P port of the control valve group 3, and the T port of the solenoid directional valve 302 / 303 is connected to the T port of the control valve group 3; when the solenoid directional valve 302 / 303 is in the neutral position, both the A and B ports of the solenoid directional valve 302 / 303 are connected to the T port; the A port of the first pilot-operated relief valve 301 is connected to the P port of the control valve group 3, and the B port of the first pilot-operated relief valve 301 is connected to the T port of the control valve group 3. In this embodiment, as... Figure 1 As shown, the solenoid directional valve 302 / 303 includes two electromagnets, an upper electromagnet and a lower electromagnet. When the upper electromagnet is energized and closed, ports A and T of the solenoid directional valve 302 / 303 are connected, and ports B and P are connected; when the lower electromagnet is energized and closed, ports P and A of the solenoid directional valve 302 / 303 are connected, and ports B and T are connected. The solenoid directional valve 302 / 303 is a three-position four-way solenoid directional valve, and the neutral position of the solenoid directional valve 302 / 303 is Y-type.

[0034] Furthermore, such as Figure 1As shown, in this embodiment, there are two electromagnetic directional valves 302 / 303 and two outrigger actuators 4. Each electromagnetic directional valve 302 / 303 corresponds to one outrigger actuator 4, and both electromagnetic directional valves 302 / 303 are simultaneously connected to the P port and T port of the control valve group 3, thereby ensuring that the hydraulic oil simultaneously drives the two outrigger actuators 4 and ensuring the synchronization of the two outrigger actuators 4. Furthermore, the directional valve group is also provided with ports A1, A2, B1, and B2. Ports A1 and A2 are internally connected to the A port of the electromagnetic directional valve 302 / 303 and externally connected to the rod chambers of the two outrigger cylinders 403. Ports B1 and B2 are internally connected to the B port of the electromagnetic directional valve 302 / 303 and externally connected to the rodless chambers of the two outrigger cylinders 403.

[0035] Preferred, such as Figure 1 As shown, the outrigger actuator 4 includes a bidirectional hydraulic lock 401 and an outrigger cylinder 403. The outrigger cylinder 403 includes a rod chamber and a rodless chamber. Ports A and B of the solenoid directional valves 302 / 303 are connected to the rod chamber and the rodless chamber through the bidirectional hydraulic lock 401. The outlet end of the first quantitative pump 202 is connected to the outrigger cylinder 403 through a first one-way shut-off valve 205, a first pilot-operated relief valve 301, and the solenoid directional valves 302 / 303, for driving the extension and retraction of the outrigger cylinder 403. The hydraulic oil in the outrigger cylinder 403 flows back to the oil tank through the bidirectional hydraulic lock 401, the solenoid directional valves 302 / 303, and the return oil pipe 9. Furthermore, in this embodiment, the bidirectional hydraulic lock 401 is existing technology and includes two one-way valves and two one-way valve pipelines.

[0036] In this embodiment, port A of the electromagnetic directional valve 302 / 303 is connected to the rod chamber of the outrigger cylinder 403, and port B of the electromagnetic directional valve 302 / 303 is connected to the rodless chamber of the outrigger cylinder 403. When port A and port P of the electromagnetic directional valve 302 / 303 are connected, hydraulic oil enters the bidirectional hydraulic lock 401 through port A. Both check valves of the bidirectional hydraulic lock 401 are opened, and hydraulic oil enters the rod chamber through one of the check valves. The hydraulic oil in the rodless chamber flows back to port B of the electromagnetic directional valve 302 / 303 through the gap of the other check valve that has been opened, and then flows to port T through port B and back to the oil tank through the return oil pipe 9, thus completing the retraction of the outrigger cylinder 403. Conversely, when the outrigger cylinder 403 needs to extend, the B and P ports of the solenoid directional valve 302 / 303 are connected, and the hydraulic oil enters the rodless chamber. The hydraulic oil in the rod chamber flows back to the oil tank through the A and T ports of the solenoid directional valve 302 / 303 and the return oil pipe 9.

[0037] Preferred, such as Figure 1As shown, the tractor power source 1 includes a second motor (not shown), a second fixed displacement pump 102, a second one-way shut-off valve 103, a second pilot-operated relief valve 101, and two first quick connectors 104. The inlet of the second fixed displacement pump 102 is connected to the oil tank through either of the first quick connectors 104, and the outlet of the second fixed displacement pump 102 is connected to the outrigger actuator 4 through the other first quick connector 104. Port A of the second pilot-operated relief valve 101 is connected to the outlet of the second fixed displacement pump 102, and port B of the second pilot-operated relief valve 101 is connected to the inlet of the second fixed displacement pump 102. The second one-way shut-off valve 103 is located at the outlet of the second fixed displacement pump 102, and the second motor drives the second fixed displacement pump 102 to work. In this embodiment, the second motor uses the tractor's power take-off port, that is, the tractor's power take-off port is connected to the second fixed displacement pump 102. Power is only output from the power take-off port when the tractor is in neutral; after gearing, the tractor automatically cuts off the power output. The first quick connector 104 connects the oil tank in the electronically controlled power unit 2 to the second fixed displacement pump 102, meaning the second fixed displacement pump 102 draws hydraulic oil from the electronically controlled power unit 2. The first quick connector 104 also allows for quick assembly and disassembly of the tractor's power source 1 and the electronically controlled power unit 2, simplifying operation and improving work efficiency. The second pilot-operated relief valve 101 is used for unloading and pressurizing the tractor's power source 1.

[0038] Furthermore, in this embodiment, when the first quick connector 104 connects the tractor power source 1 and the electronically controlled power unit 2, it also includes auxiliary connection pipelines such as electrically controlled cables and semi-trailer axle brake air circuits.

[0039] Preferred, such as Figure 1 As shown, a third one-way shut-off valve 7, a second quick connector 6, and a third quick connector 5 are also provided between the first quick connector 104 and the outrigger actuator 4.

[0040] In this embodiment, the second quick connector 6 is connected to a branch of the pipeline between port B of the electromagnetic reversing valve 302 / 303 and the rodless chamber. When the hydraulic oil driven by the tractor power source 1 enters the rodless chamber through the second quick connector 6, the hydraulic oil driven by the tractor power source 1 and the hydraulic oil driven by the electronic control power unit 2 merge to accelerate the extension of the outrigger cylinder 403.

[0041] The third quick connector 5 is connected to the branch of the pipeline between port A of the electromagnetic reversing valve 302 / 303 and the rod chamber. When the hydraulic oil driven by the tractor power source 1 enters the rod chamber through the third quick connector 5, the hydraulic oil driven by the tractor power source 1 and the hydraulic oil driven by the electronic control power unit 2 merge to accelerate the retraction of the outrigger cylinder 403.

[0042] Furthermore, when the second quick connector 6 or the third quick connector 5 is connected, the extension and retraction of the outrigger cylinder 403 can also be driven solely by the tractor power source 1. For example, when the outrigger cylinder 403 needs to extend, the second quick connector 6 is connected to the first quick connector 104, and the P port and B port of the solenoid directional valve 302 / 303 are connected. Because there is a first one-way shut-off valve 205 between the control valve group 3 and the first quantitative pump 202, the hydraulic oil driven by the tractor power source 1 can only enter the rodless chamber through the bidirectional hydraulic lock 401. The hydraulic oil in the rod chamber enters the A port of the solenoid directional valve 302 / 303 through the bidirectional hydraulic lock 401, and flows back to the oil tank through the T port and the return oil pipe 9.

[0043] Similarly, when the outrigger cylinder 403 needs to retract, the third quick connector 5 is connected to the first quick connector 104, and the P port of the solenoid directional valve 302 / 303 is connected to the A port. Because there is a first one-way shut-off valve 205 between the control valve group 3 and the first quantitative pump 202, the hydraulic oil driven by the tractor power source 1 can only enter the rod chamber through the bidirectional hydraulic lock 401. The hydraulic oil in the rodless chamber enters the B port of the solenoid directional valve 302 / 303 through the bidirectional hydraulic lock 401, and flows back to the oil tank through the T port and the return oil pipe 9.

[0044] Since the driving force of the tractor power source 1 is greater than the driving force of the first motor 201, the order of the extension and retraction speeds of the outrigger cylinders 403 is: combination of tractor power source 1 and electric control power unit 2 > tractor power source 1 > electric control power unit 2.

[0045] Preferred, such as Figure 1As shown, a shut-off valve 8 is also installed on the return oil pipe 9. When the shut-off valve 8 closes the return oil pipe 9, the hydraulic oil in the rod chamber of the outrigger cylinder 403 flows back to the rodless chamber of the outrigger cylinder 403 through the two-way hydraulic lock 401 and the solenoid directional valves 302 / 303, thereby realizing the accelerated differential extension of the outrigger cylinder 403. In this embodiment, the working condition of the shut-off valve 8 is only applicable when the tractor power source 1 is started alone. When the shut-off valve 8 is working, the return oil pipe 9 is closed. Connect the second quick connector 6 to the first quick connector 104, and position the solenoid directional valves 302 / 303 in the neutral position (i.e., ports A and B are both connected to port T). At this time, the tractor's power source 1 drives hydraulic oil through the first quick connector 104, the second quick connector 6, and the two-way hydraulic lock 401 into the rodless chamber. Meanwhile, the hydraulic oil in the rod chamber enters port A of the solenoid directional valves 302 / 303 through the two-way hydraulic lock 401. Since ports A and B are both connected to port T, and port T is closed by the shut-off valve 8, the hydraulic oil entering port A will enter port B and then re-enter the two-way hydraulic lock 401 into the rodless chamber, thereby accelerating the extension of the outrigger cylinder 403. The outrigger cylinder 403 retracts as follows: First, connect the third quick connector 5 to the pipeline. The tractor's power source 1 drives the hydraulic fluid directly into the rod chamber of the outrigger cylinder 403. To ensure pressure build-up in the rod chamber, the first pilot-operated relief valve 301 must be energized simultaneously. The return oil from the rodless chamber flows through port B to port T of the solenoid directional valve 302 / 303 (YV03 / YV04 are energized), and then through the shut-off valve 8 (de-energized) to open the return oil pipe 9, so that the hydraulic oil in the rodless chamber can flow back to the oil tank through the return oil pipe 9.

[0046] Therefore, the speed order of extension and retraction of outrigger cylinder 403 is: combination of tractor power source 1 and electronic control power unit 2 > tractor power source 1 (shut-off valve 8 starts) > tractor power source 1 (shut-off valve 8 does not start) > electronic control power unit 2.

[0047] Furthermore, in this embodiment, there are two second quick connectors 6 and two third quick connectors 5, used for accelerating the extension and retraction control of the two outrigger actuators 4. The pipes connected to the first quick connector 104 can be connected to the second quick connector 6 or the third quick connector 5 respectively. In this embodiment, when connected to the second quick connector 6, the outrigger cylinder 403 extends; when connected to the third quick connector 5, the outrigger cylinder 403 retracts.

[0048] Preferred, such as Figure 1As shown, a high-pressure ball valve 402 is also installed on the pipeline between the bidirectional hydraulic lock 401 and the outrigger cylinder 403, and the high-pressure ball valve 402 is connected to the oil tank. In this embodiment, when the bidirectional hydraulic lock 401 is jammed, that is, the hydraulic oil in the outrigger cylinder 403 cannot enter or exit, the operator can open the high-pressure ball valve 402 and manually extend or retract the piston rod of the outrigger for emergency handling. Furthermore, the end of the high-pressure ball valve 402 away from the outrigger cylinder 403 is connected to the return oil pipe 9 to discharge the hydraulic oil in the outrigger cylinder 403.

[0049] Furthermore, in this embodiment, the load of the first pilot-operated relief valve 301 when energized is 16 MPa, and the second pilot-operated relief valve 101 is normally open, with a set pressure value sufficient to meet the unloaded extension and retraction requirements of the outrigger cylinder 403. Only in emergency situations, such as a failure of the electrical control system, can the setting be adjusted manually or otherwise to meet temporary emergency needs. The load of the second pilot-operated relief valve 101 when energized is 3 MPa.

[0050] To achieve the above or other objectives, the present invention also discloses a control method for a hydraulic outrigger extension control circuit, employing the aforementioned hydraulic outrigger extension control circuit, with the following steps:

[0051] A1: Initial state of the outrigger actuator 4. The outrigger actuator 4 of an independent semi-trailer should generally be lowered to the ground and, together with the semi-trailer axle, achieve stable support for the vehicle body. At this time, the semi-trailer is waiting to unload or load cargo, and after loading or unloading, it awaits towing by a tractor. At this time, the outrigger cylinder 403 is engaged, and the two-way hydraulic lock 401 maintains pressure to provide support. Some models also use mechanical outriggers for auxiliary support. That is, the initial state of the outrigger actuator 4 is the extended state.

[0052] A2: The tractor unit is connected to the semi-trailer. The tractor unit and the semi-trailer are connected by mechanical devices such as saddles and goosenecks.

[0053] A3: Retraction of outrigger actuator 4. After the tractor unit is connected to the semi-trailer, the outrigger actuator 4 needs to be retracted. Only after it has retracted to its final position can the tractor unit engage gear and move to tow the semi-trailer. The retraction process of the outrigger actuator 4 is as follows: The operator connects the inlet end of the second metering pump 102 to the oil tank through one of the first quick connectors 104, and connects the outlet end of the second metering pump 102 to the third quick connector 5 through the other first quick connector 104.

[0054] The first pilot-operated relief valve 301 and the second pilot-operated relief valve 101 are energized, achieving pressure build-up and starting the first and second fixed displacement pumps 202. This also energizes and closes the lower electromagnets of the solenoid directional valves 302 / 303 (i.e., YV03 and YV04 in the diagram). At this time, the P and A ports of the solenoid directional valves 302 / 303 are connected, and the B and T ports are connected. The first fixed displacement pump 202 pumps hydraulic oil through the first one-way shut-off valve 205 into the P port of the control valve group 3, and then through the solenoid directional valves 302 / 302 / 303... The hydraulic oil from port A of valve 3 and the bidirectional hydraulic lock 401 enters the rod chamber of outrigger cylinder 403. Simultaneously, the second quantitative pump 102 operates, and the hydraulic oil, after passing through the second one-way shut-off valve 103, the first quick connector 104, and the third quick connector 5, merges with the hydraulic oil flowing from port A of solenoid directional valves 302 / 303 and enters the rod chamber of outrigger cylinder 403 together. The hydraulic oil in the rodless chamber enters port B of solenoid directional valves 302 / 303 through the bidirectional hydraulic lock 401 and flows back to the oil tank through port T and return pipe 9. During this process, outrigger cylinder 403 accelerates its retraction.

[0055] A4: After the tractor unit tows the semi-trailer to its destination, the tractor unit brakes, shifts to neutral, and maintains the power take-off port at idle speed. At this time, the second pilot-operated relief valve 101 defaults to low-pressure unloading.

[0056] When it is necessary to separate the tractor and the semi-trailer (the outrigger cylinder 403 needs to extend to support the semi-trailer), connect the outlet end of the second fixed displacement pump 102 to the second quick connector 6. The first pilot-operated relief valve 301 and the second pilot-operated relief valve 101 are energized, pressure is built up, the first fixed displacement pump 202 and the second fixed displacement pump 102 are started, and the upper electromagnets of the solenoid directional valves 302 / 303 are energized and closed (i.e., YV02 and YV05 in the figure). At this time, the P port and B port of the solenoid directional valves 302 / 303 are connected, and the A port and T port are connected. The first fixed displacement pump 202 pumps hydraulic oil through the first one-way shut-off valve 205 into the P port of the control valve group 3, and then through the solenoid directional valves 302 / 302... The hydraulic oil from port B of outrigger 3 and the bidirectional hydraulic lock 401 enters the rodless chamber of outrigger cylinder 403. Simultaneously, the second quantitative pump 102 operates, and the hydraulic oil, after passing through the second one-way shut-off valve 103, the first quick connector 104, and the second quick connector 6, merges with the hydraulic oil flowing from port B of solenoid directional valves 302 / 303 and enters the rodless chamber of outrigger cylinder 403 together. The hydraulic oil in the rod chamber enters port A of solenoid directional valves 302 / 303 through the bidirectional hydraulic lock 401 and flows back to the oil tank through port T and return pipe 9. During this process, outrigger cylinder 403 extends rapidly, providing support for the semi-trailer on the ground.

[0057] A5: Once the semi-trailer has achieved stable support and reached the required height, the operator can separate the tractor's power source 1 and the electronically controlled power unit 2 via the two first quick connectors 104. At this point, the operator can operate the release mechanism to completely separate the tractor from the semi-trailer. The outrigger actuator 4 will then be in the same state as in A1. After the semi-trailer has finished loading and unloading, the steps A1-A5 can be repeated.

[0058] Furthermore, during the retraction of the A3 outrigger, the operator can also drive it using the tractor power source 1 alone, or the electric control power unit 2 alone. They only need to control whether the first motor 201 and the second motor are working, or whether the first pilot-operated overflow valve 301 and the second pilot-operated overflow valve 101 are energized.

[0059] Correspondingly, during the extension of the A4 outriggers, the operator can also drive it using the tractor power source 1 alone, or drive it using the electronically controlled power unit 2 alone. They only need to control whether the first motor 201 and the second motor are working, or whether the first pilot-operated overflow valve 301 and the second pilot-operated overflow valve 101 are energized.

[0060] Alternatively, when driven solely by the tractor power source 1, the shut-off valve 8 can be energized to close the return oil pipe 9, and the solenoid directional valves 302 / 303 can be de-energized. At the same time, the first pilot-operated relief valve 301 is energized to build pressure. When the tractor power source 1 drives, the hydraulic oil enters the rod chamber through the first quick connector 104 and the second quick connector 6. The hydraulic oil in the outrigger cylinder 403 flows back to the solenoid directional valves 302 / 303. Because the return oil pipe 9 is closed, the hydraulic oil re-enters the outrigger cylinder 403 through the solenoid directional valves 302 / 303, thereby realizing the differential extension of the outrigger cylinder 403.

[0061] Furthermore, when the piston rod of the outrigger cylinder 403 is not in contact with the ground and needs to be lowered slowly, in most cases only the electric control power unit 2 needs to be used for driving. At this time, the second pilot-operated overflow valve 101 of the tractor power source 1 is not energized and remains in an unloaded state.

[0062] Furthermore, if the semi-trailer outrigger actuator 4 malfunctions during support or retraction (such as jamming), manual pressure relief can be achieved by opening the high-pressure ball valve 402 to complete the retraction of the outrigger cylinder 403.

[0063] When the control valve group 3 malfunctions, the power supply malfunctions, or the first motor 201 burns out, the first quick connector 104, the second quick connector 6, or the third quick connector 5 can be connected and used in conjunction with the high-pressure ball valve 402 to enable the emergency extension and retraction of the outrigger cylinder 403.

[0064] Additionally, when the outrigger cylinder 403 is in its no-load stroke (the piston rod of the outrigger cylinder 403 is detached from the ground), a cylinder stroke sensor can be used, with timer control as the preferred method. When the no-load stroke ends, the tractor power source 1 is automatically unloaded, the second pilot-operated overflow valve 101 is de-energized, and the load is slowly lifted by the electronically controlled power unit 2 (non-differential motion). As can be seen from the above, multi-stage speed control can be selected for driving the outrigger cylinder 403.

[0065] The hydraulic outrigger extension control circuit and control method disclosed in this invention have the following beneficial effects:

[0066] 1. The present invention is equipped with a tractor power source 1 and an electronically controlled power unit 2, and adopts a dual power source oil supply method, which can accelerate the extension and retraction of the outrigger cylinder 403 according to actual needs.

[0067] 2. The tractor power source 1 in this invention is mainly used to provide the outrigger cylinder 403 with a combined flow of rapid extension and retraction during the unloaded stroke. When the outrigger cylinder 403 is about to contact the ground, the electric control power unit 2 applies pressure separately. Therefore, the electric control power unit 2 mainly provides heavy-load support for the outrigger cylinder 403. In the above way, the semi-trailer and the tractor can be effectively and smoothly separated.

[0068] 3. In this invention, the second quantitative pump 102 shares the same oil tank as the first quantitative pump 202, and the outlet end of the second quantitative pump 102 is directly connected to the outrigger cylinder 403, and is not controlled by the control valve group 3, enabling emergency handling when the control valve group 3 malfunctions. The unloading port of the second pilot-operated relief valve 101 is directly connected to the inlet end of the second quantitative pump 102.

[0069] 4. In this invention, the power source of the second quantitative pump 102 is preferentially connected in parallel with the corresponding pipeline of the electric control power unit 2 of the semi-trailer through the first quick connector 104.

[0070] 5. The present invention is equipped with a shut-off valve 8 on the oil return pipe 9, which can realize the differential connection of the outrigger cylinder 403, thereby further improving the outrigger support speed.

[0071] 6. In this invention, when the semi-trailer is separated from the tractor, the outrigger cylinder 403 is supported by the bidirectional hydraulic lock 401, and the operator can manually unload the outrigger cylinder 403 through the high-pressure ball valve 402.

[0072] 7. The present invention achieves differential connection of outrigger cylinder 403 by connecting a shut-off valve 8 in series on the return oil pipe 9 of control valve group 3; then introduces the combined pressure source of tractor power source 1 to the rodless chamber of outrigger cylinder 403 to accelerate the lowering of outrigger cylinder 403 during idle stroke; and achieves emergency extension and retraction of outrigger cylinder 403 by installing high pressure ball valve 402 on outrigger cylinder 403 and cooperating with second quick connector 6 and third quick connector 5.

[0073] Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0074] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A hydraulic outrigger extension control circuit, characterized in that: The system includes an electric power unit (2), a tractor power source (1), a control valve group (3), and a outrigger actuator (4). The control valve group (3) includes a first pilot-operated relief valve (301) and several electromagnetic directional valves (302 / 303). The first pilot-operated relief valve (301) and several electromagnetic directional valves (302 / 303) are connected in parallel. The first pilot-operated relief valve (301) is used to control the pressure build-up and unloading of the control valve group (3). The electric power unit (2) also includes an oil tank. The T-port of the control valve group (3) is connected to the oil tank through a return oil pipe (9). A shut-off valve (8) is provided on the return oil pipe (9). The tractor power source (1) is connected to the outrigger actuator (4), and several quick connectors are provided between them. The quick connectors are respectively connected to the rod chamber and the rodless chamber in the outrigger actuator (4). The electric power unit (2) is connected to the outrigger actuator (4) through the control valve group (3) to realize the slow extension and retraction of the outrigger actuator (4); specifically: the first pilot relief valve (301) in the control valve group (3) is energized to complete the pressure building of the control valve group (3); the electromagnetic reversing valve (302 / 303) is energized, one of the electromagnetic reversing valves (302 / 303) is connected, the electric power unit (2) works to transport hydraulic oil to the electromagnetic reversing valve (302 / 303), and then enters the outrigger actuator (4) to complete the extension and retraction of the outrigger actuator (4); the hydraulic oil in the outrigger actuator (4) flows back to the oil tank of the electric power unit (2) through the electromagnetic reversing valve (302 / 303); The electronically controlled power unit (2) and the tractor power source (1) form a dual power source confluence to realize the accelerated extension or retraction of the outrigger actuator (4); specifically: the first pilot-operated relief valve (301) in the control valve group (3) is energized to complete the pressure build-up of the control valve group (3); the electromagnetic reversing valves (302 / 303) are energized, one of the electromagnetic reversing valves (302 / 303) is connected, and the electronically controlled power unit (2) works to transport hydraulic oil to the electromagnetic reversing valves (302 / 303), and then enters the outrigger actuator (4). At the same time, the tractor power source (1) works, and the tractor power source (1) transports the hydraulic oil through several quick connectors to the rod chamber or rodless chamber of the outrigger actuator (4) without passing through the electromagnetic reversing valve (302 / 303). The hydraulic oil driven by the tractor power source (1) merges with the hydraulic oil transported by the electronic control power unit (2) to realize the accelerated extension or retraction of the outrigger actuator (4). The hydraulic oil in the outrigger actuator (4) flows back to the oil tank of the electronic control power unit (2) through the electromagnetic reversing valve (302 / 303). The tractor power source (1) is connected to the outrigger actuator (4) to realize the retraction and differential extension of the outrigger actuator (4); specifically: the tractor power source (1) is working, the electronic control power unit (2) is not working, and the shut-off valve (8) cuts off the return oil pipe (9), and the T port of the electromagnetic reversing valve (302 / 303) is closed; the electromagnetic reversing valve (302 / 303) is in the neutral position, and the A port and B port of the electromagnetic reversing valve (302 / 303) are connected to the T port; when the tractor power source (1) drives the hydraulic oil into the rodless chamber in the outrigger actuator (4), the hydraulic oil in the rod chamber flows back to the rodless chamber through the A port and B port of the electromagnetic reversing valve (302 / 303), realizing the differential extension of the outrigger actuator (4); When the tractor power source (1) is working, the hydraulic oil enters the rod chamber of the outrigger actuator (4) under the drive of the tractor power source (1). The first pilot relief valve (301) and several electromagnetic directional valves (302 / 303) are energized to build up pressure to prevent the hydraulic oil in the rod chamber from flowing back to the oil tank for unloading. The hydraulic oil in the rodless chamber of the outrigger actuator (4) flows back to the oil tank of the electric control power unit (2) through the electromagnetic directional valves (302 / 303), thereby realizing the retraction of the outrigger actuator (4).

2. The hydraulic outrigger extension control circuit according to claim 1, characterized in that: The electronically controlled power unit (2) includes a first motor (201), a first metering pump (202), a return oil filter (203), a breather valve (204), and a first one-way shut-off valve (205). The inlet end of the first metering pump (202) is connected to an oil tank, and the outlet end of the first metering pump (202) is connected to the P port of the control valve group (3) through the first one-way shut-off valve (205). A return oil pipe (9) is provided between the T port of the control valve group (3) and the oil tank, and the return oil filter (203) is provided on the return oil pipe (9). The breather valve (204) is provided on the oil tank. The first motor (201) drives the first metering pump (202) to work.

3. The hydraulic outrigger extension control circuit according to claim 2, characterized in that: The P port of the electromagnetic directional valve (302 / 303) is connected to the P port of the control valve group (3), and the T port of the electromagnetic directional valve (302 / 303) is connected to the T port of the control valve group (3); when the electromagnetic directional valve (302 / 303) is in the neutral position, both the A port and the B port of the electromagnetic directional valve (302 / 303) are connected to the T port; the A port of the first pilot-operated relief valve (301) is connected to the P port of the control valve group (3), and the B port of the first pilot-operated relief valve (301) is connected to the T port of the control valve group (3).

4. The hydraulic outrigger extension control circuit according to claim 3, characterized in that: The outrigger actuator (4) includes a bidirectional hydraulic lock (401) and an outrigger cylinder (403). The outrigger cylinder (403) includes a rod chamber and a rodless chamber. The A port and B port of the electromagnetic directional valve (302 / 303) are connected to the rod chamber and the rodless chamber through the bidirectional hydraulic lock (401). The outlet end of the first quantitative pump (202) is connected to the outrigger cylinder (403) through the first one-way shut-off valve (205), the first pilot-operated relief valve (301), and the electromagnetic directional valve (302 / 303) to drive the extension and retraction of the outrigger cylinder (403). The hydraulic oil in the outrigger cylinder (403) flows back to the oil tank through the bidirectional hydraulic lock (401), the electromagnetic directional valve (302 / 303), and the return oil pipe (9).

5. The hydraulic outrigger extension control circuit according to claim 4, characterized in that: The tractor power source (1) includes a second motor, a second fixed displacement pump (102), a second one-way shut-off valve (103), a second pilot-operated overflow valve (101), and a first quick connector (104). There are two first quick connectors (104). The inlet end of the second fixed displacement pump (102) is connected to the oil tank through either of the first quick connectors (104), and the outlet end of the second fixed displacement pump (102) is connected to the outrigger actuator (4) through the other first quick connector (104). Port A of the second pilot-operated overflow valve (101) is connected to the outlet end of the second fixed displacement pump (102), and port B of the second pilot-operated overflow valve (101) is connected to the inlet end of the second fixed displacement pump (102). The second one-way shut-off valve (103) is located on the outlet end of the second fixed displacement pump (102), and the second motor drives the second fixed displacement pump (102) to work.

6. The hydraulic outrigger extension control circuit according to claim 5, characterized in that: A third one-way shut-off valve (7) and a second quick connector (6) are also provided between the first quick connector (104) and the outrigger actuator (4). The second quick connector (6) is connected to the rod chamber or the rodless chamber. The outlet end of the second metering pump (102) is connected to the outrigger cylinder (403) in sequence through the second one-way shut-off valve (103), the first quick connector (104), the third one-way shut-off valve (7), the second quick connector (6), and the two-way hydraulic lock (401) to drive the extension and retraction of the outrigger cylinder (403). The hydraulic oil in the outrigger cylinder (403) flows back to the oil tank through the two-way hydraulic lock (401), the solenoid reversing valve (302 / 303), and the return oil pipe (9).

7. The hydraulic outrigger extension control circuit according to claim 5, characterized in that: A third one-way shut-off valve (7) and a third quick connector (5) are also provided between the first quick connector (104) and the outrigger actuator (4). The third quick connector (5) is connected to the rodless chamber or the rod chamber. The outlet end of the second metering pump (102) is connected to the outrigger cylinder (403) in sequence through the second one-way shut-off valve (103), the first quick connector (104), the third one-way shut-off valve (7), the third quick connector (5), and the two-way hydraulic lock (401) to drive the extension and retraction of the outrigger cylinder (403). The hydraulic oil in the outrigger cylinder (403) flows back to the oil tank through the two-way hydraulic lock (401), the solenoid reversing valve (302 / 303), and the return oil pipe (9).

8. The hydraulic outrigger extension control circuit according to claim 6 or 7, characterized in that: A shut-off valve (8) is also provided on the return oil pipe (9). When the shut-off valve (8) closes the return oil pipe (9), the hydraulic oil in the rod chamber of the outrigger cylinder (403) can flow back to the rodless chamber of the outrigger cylinder (403) through the two-way hydraulic lock (401) and the electromagnetic reversing valve (302 / 303) to achieve differential operation.

9. The hydraulic outrigger extension control circuit according to claim 4, characterized in that: A high-pressure ball valve (402) is also installed on the pipeline between the bidirectional hydraulic lock (401) and the outrigger cylinder (403). The high-pressure ball valve (402) is connected to the oil tank, and the bidirectional hydraulic lock (401) is directly connected to the cylinder body of the outrigger cylinder (403) by mechanical means.

10. A control method for a hydraulic outrigger extension control circuit, employing the hydraulic outrigger extension control circuit as described in any one of claims 1-9, wherein the electronically controlled power unit (2) includes an oil tank, the T-port of the control valve group (3) is connected to the oil tank via a return oil pipe (9), and a shut-off valve (8) is provided on the return oil pipe (9); the tractor power source (1) is connected to the outrigger actuator (4), and a plurality of quick connectors are provided between them, the plurality of quick connectors being respectively connected to the rod-side chamber and the rodless chamber in the outrigger actuator (4); characterized in that: The steps are as follows: S1: The outrigger actuator (4) is slowly extended and retracted through the electric power unit (2); the first pilot relief valve (301) in the control valve group (3) is energized to complete the pressure build-up of the control valve group (3); the solenoid directional valve (302 / 303) is energized, one of the solenoid directional valves (302 / 303) is connected, the electric power unit (2) works to transport hydraulic oil to the solenoid directional valve (302 / 303), and then enters the outrigger actuator (4) to complete the extension and retraction of the outrigger actuator (4); the hydraulic oil in the outrigger actuator (4) flows back to the oil tank of the electric power unit (2) through the solenoid directional valve (302 / 303); S2: The outrigger actuator (4) is accelerated to extend or retract by combining two power sources; the first pilot-operated relief valve (301) in the control valve group (3) is energized to build up pressure in the control valve group (3); the solenoid directional valves (302 / 303) are energized, one of the solenoid directional valves (302 / 303) is connected, and the electric control power unit (2) works to transport hydraulic oil to the solenoid directional valves (302 / 303), and then into the outrigger actuator (4); at the same time, the tractor power source (1) During operation, the tractor power source (1) transports hydraulic oil through several quick connectors to the rod chamber or rodless chamber of the outrigger actuator (4) without passing through the solenoid directional valve (302 / 303). The hydraulic oil driven by the tractor power source (1) merges with the hydraulic oil transported by the electronic power unit (2) to accelerate the extension or retraction of the outrigger actuator (4). The hydraulic oil in the outrigger actuator (4) flows back to the oil tank of the electronic power unit (2) through the solenoid directional valve (302 / 303). S3: The outrigger actuator (4) is differentially extended by the tractor power source (1); the tractor power source (1) is working, the electronic control power unit (2) is not working, and the shut-off valve (8) cuts off the return oil pipe (9), and the T port of the electromagnetic reversing valve (302 / 303) is closed; the electromagnetic reversing valve (302 / 303) is in the neutral position, and the A port and B port of the electromagnetic reversing valve (302 / 303) are connected to the T port; When the tractor power source (1) drives the hydraulic oil into the rodless chamber of the outrigger actuator (4), the hydraulic oil in the rod chamber flows back to the rodless chamber through the A and B ports of the solenoid directional valve (302 / 303), thereby realizing the differential extension of the outrigger actuator (4); S4: The outrigger actuator (4) is retracted by the tractor power source (1); the tractor power source (1) is working, and the hydraulic oil enters the rod chamber of the outrigger actuator (4) under the drive of the tractor power source (1). The first pilot relief valve (301) and several electromagnetic directional valves (302 / 303) are energized to build up pressure to prevent the hydraulic oil in the rod chamber from flowing back to the oil tank for unloading. The hydraulic oil in the rodless chamber of the outrigger actuator (4) flows back to the oil tank of the electric control power unit (2) through the electromagnetic directional valves (302 / 303).

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