Micro-flow hydraulic transmission system and control method thereof

Abstract

The application discloses a micro-flow hydraulic transmission system and a control method thereof, which comprises a first oil path, a second oil path, a first electromagnetic reversing valve, a second electromagnetic reversing valve, a cylinder and an oil tank; the first oil path is connected with the oil tank, and an oil outlet end of the first oil path is communicated with a P7 port of the first electromagnetic reversing valve; the second oil path is connected with the oil tank, and an oil outlet end of the second oil path is communicated with a T5 port of the first electromagnetic reversing valve; an outlet A4 of the first electromagnetic reversing valve is communicated with an inlet P8 of the second electromagnetic reversing valve, an outlet B4 of the first electromagnetic reversing valve and a back oil port T6 of the second electromagnetic reversing valve are communicated with the oil tank, an outlet A5 of the second electromagnetic reversing valve is communicated with an inlet A6 of the cylinder, and an outlet B5 of the second electromagnetic reversing valve is communicated with an inlet B6 of the cylinder; a first hydraulic motor is arranged on the first oil path, a second hydraulic motor is arranged on the second oil path, and a rotor of the first hydraulic motor is coupled with a rotor of the second hydraulic motor; the micro-flow stable control can be realized, the structure is simple, the high pressure resistance is good, and the cost is low.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydraulic transmission, in particular to a micro-flow hydraulic transmission system. In addition, the present application also relates to a control method comprising the above-mentioned micro-flow hydraulic transmission system. BACKGROUND

[0002] With the continuous development of hydraulic technology, the control accuracy of hydraulic systems is increasingly required in some machine tooling equipment, robot control and aerospace applications or experimental tests. The control of physical parameters such as displacement and speed of the hydraulic system is actually realized by controlling the flow of the hydraulic system, and the control accuracy depends on the minimum flow that the hydraulic system can control. Therefore, the control of small flow determines the control accuracy of part of the high-precision hydraulic system.

[0003] The existing small flow control method generally adopts the form of a fixed displacement pump + a servo motor. This structure can achieve the control of a certain small flow. However, since the fixed displacement pump has a minimum stable speed requirement, it cannot achieve the stable control of a small flow at a speed of several tens of r / min. Moreover, in the case of high pressure, the volumetric efficiency is low, and the flow is even more unstable at low speed. There is also a method of using a magnetic material to make a throttle hole, changing the area of the throttle hole by changing the magnetic field, thereby achieving the control of a small flow. For example, Chinese patent CN 109718731B. The material of the throttle hole is complex, the control is difficult, and it is not resistant to high pressure, which is difficult to apply to the control of small flow of the hydraulic system. SUMMARY

[0004] The present application provides a micro-flow hydraulic transmission system and a control method thereof to solve the technical problem that the existing micro-flow hydraulic transmission system is difficult to control a small flow.

[0005] According to one aspect of the present application, a micro-flow hydraulic transmission system is provided, comprising a first oil path for providing large flow pressure oil, a second oil path for providing small flow pressure oil, a first electromagnetic directional valve, a second electromagnetic directional valve, a cylinder and an oil tank; the oil inlet end of the first oil path is connected with the oil tank, and the oil outlet end of the first oil path is in communication with the P7 port of the first electromagnetic directional valve; the oil inlet end of the second oil path is connected with the oil tank, and the oil outlet end of the second oil path is in communication with the T5 port of the first electromagnetic directional valve; the outlet A4 of the first electromagnetic directional valve is in communication with the inlet P8 of the second electromagnetic directional valve, the outlet B4 of the first electromagnetic directional valve and the oil return port T6 of the second electromagnetic directional valve are in communication with the oil tank, the outlet A5 of the second electromagnetic directional valve is in communication with the inlet A6 of the cylinder, and the outlet B5 of the second electromagnetic directional valve is in communication with the inlet B6 of the cylinder; a first hydraulic motor is arranged on the first oil path, a second hydraulic motor is arranged on the second oil path, and the rotor of the first hydraulic motor is coupled with the rotor of the second hydraulic motor.

[0006] Further, a large flow pump and a proportional speed regulating valve are arranged on the first oil path, the suction port S1 of the large flow pump is connected with the oil tank, the outlet P1 of the large flow pump is communicated with the inlet A1 of the proportional speed regulating valve, the outlet B1 of the proportional speed regulating valve is communicated with the inlet A2 of the first hydraulic motor, the outlet B2 of the first hydraulic motor is communicated with the P7 port of the first electromagnetic reversing valve; a small flow pump is arranged on the second oil path, the suction port S2 of the small flow pump is communicated with the oil tank, the outlet P2 of the small flow pump is communicated with the inlet A3 of the second hydraulic motor, the outlet B3 of the second hydraulic motor is communicated with the T5 port of the first electromagnetic reversing valve; the displacement V1 of the first hydraulic motor is greater than the displacement V2 of the second hydraulic motor.

[0007] Further, the rotor of the first hydraulic motor is coupled with the rotor of the second hydraulic motor through a speed reducer.

[0008] Further, a large flow pump and a proportional speed regulating valve are arranged on the first oil path, the suction port S1 of the large flow pump is connected with the oil tank, the outlet P1 of the large flow pump is communicated with the inlet A1 of the proportional speed regulating valve, the outlet B1 of the proportional speed regulating valve is communicated with the inlet A2 of the first hydraulic motor, the outlet B2 of the first hydraulic motor is communicated with the P7 port of the first electromagnetic reversing valve; a small flow pump is arranged on the second oil path, the suction port S2 of the small flow pump is communicated with the oil tank, the outlet P2 of the small flow pump is communicated with the inlet A3 of the second hydraulic motor, the outlet B3 of the second hydraulic motor is communicated with the T5 port of the first electromagnetic reversing valve; the displacement V1 of the first hydraulic motor is greater than the displacement V2 of the second hydraulic motor.

[0009] Further, the pressure oil flow at the outlet end of the first oil path is V3, the pressure oil flow at the outlet end of the second oil path is V4, and the range of V3:V4 is 10:1-1000:1.

[0010] Further, the first oil path further comprises a first proportional overflow valve, the outlet T1 of the first proportional overflow valve is communicated with the oil tank, and the inlet P3 of the first proportional overflow valve is communicated with the outlet P1 of the large flow pump; the second oil path further comprises a second proportional overflow valve, the inlet P6 of the second proportional overflow valve is communicated with the outlet P2 of the small flow pump, and the outlet T4 of the second proportional overflow valve is communicated with the oil tank.

[0011] Further, the pressure setting value of the second proportional overflow valve is the load pressure value of the oil cylinder, and the ratio of the pressure setting value of the second proportional overflow valve to the pressure setting value of the first proportional overflow valve is equal to V1:V2.

[0012] Further, the first oil circuit further comprises a first safety valve, an inlet P4 of the first safety valve being communicated with an outlet P1 of the large-flow pump, and an outlet T2 of the first safety valve being communicated with the oil tank; and the second oil circuit further comprises a second safety valve, an inlet P5 of the second safety valve being communicated with an outlet P2 of the small-flow pump, and an outlet T3 of the second safety valve being communicated with the oil tank.

[0013] Further, the maximum load pressure of the first proportional overflow valve and the second proportional overflow valve is 30 Mpa, and the pressure setting of the first safety valve and the second safety valve is 32±0.5 Mpa.

[0014] According to another aspect of the present application, a control method of the micro-flow hydraulic transmission system is also provided, which comprises the micro-flow hydraulic transmission system described above,

[0015] When the micro-flow hydraulic transmission system requires large flow and the oil cylinder is extended, the large-flow pump and the small-flow pump are started, the first electromagnetic reversing valve is in the left position, and the second electromagnetic reversing valve is in the right position, the first oil circuit is S1-P1-A1-B1-A2-B2-P7-A4, the second oil circuit is S2-P2-A3-B3-T5-A4, the pressure oil of the first oil circuit and the pressure oil of the second oil circuit are combined at A4, the combined pressure oil circuit is A4-P8-A5-A6, the oil return circuit is B6-B5-T6-oil tank, the flow after combination is adjusted by adjusting the proportional speed valve, and the large-stroke control of the oil cylinder is completed.

[0016] When the micro-flow hydraulic transmission system requires micro-flow and the oil cylinder is extended, the large-flow pump and the small-flow pump are started, the first electromagnetic reversing valve is in the right position, and the second electromagnetic reversing valve is in the right position, the large-flow oil circuit is S1-P1-A1-B1-A2-B2-P7-B4-oil tank, the micro-flow oil circuit is S2-P2-A3-B3-T5-A4-P8-A5-A6, the oil return circuit is B6-B5-T6-oil tank, the flow of the first hydraulic motor is controlled by the proportional speed valve, the micro-flow control of the second hydraulic motor is realized in proportion, and the high-precision micro-motion control of the oil cylinder is completed.

[0017] The present application has the following beneficial effects:

[0018] The micro-flow hydraulic transmission system of the application is driven by the first hydraulic motor to drive the second hydraulic motor, the large-flow pressure oil provided by the first oil path and the small-flow pressure oil provided by the second oil path can be combined through the outlet A4 of the first electromagnetic reversing valve, the combined pressure oil enters the inlet P8 of the second electromagnetic reversing valve, and then enters the oil cylinder 12 through A5 / B5 of the second electromagnetic reversing valve, so as to realize the large-stroke driving of the oil cylinder; the large-flow pressure oil provided by the first oil path enters the mailbox through the outlet B4 of the first electromagnetic reversing valve, the small-flow pressure oil provided by the second oil path enters the inlet P8 of the second electromagnetic reversing valve through the outlet A4 of the first electromagnetic reversing valve, and then enters the oil cylinder through A5 / B5 of the second electromagnetic reversing valve, so as to realize the high-precision micro-motion control of the oil cylinder; by adjusting the flow ratio of the first oil path and the second oil path, the stable adjustment of different micro-flow levels can be realized, the flow adjustment of the full-flow domain starting from 0L / min can be realized, so as to improve the control precision of the hydraulic transmission system, the structure is simple, the cost is low, the high pressure resistance is good, and the application range is wide.

[0019] In addition to the purposes, features and advantages described above, the application has other purposes, features and advantages. The application will be further described below with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0020] The drawings that form a part of this application are used to provide a further understanding of the application, the illustrative embodiments of the application and their descriptions serve to explain the application, and do not constitute an improper limitation on the application. In the drawings:

[0021] Figure 1 is a structure schematic view of the micro-flow hydraulic transmission system of the preferred embodiment of the application.

[0022] LEGEND:

[0023] 1, large-flow pump; 2, small-flow pump; 3, first proportional overflow valve; 4, first safety valve; 5, second safety valve; 6, second proportional overflow valve; 7, proportional speed regulating valve; 8, first hydraulic motor; 9, second hydraulic motor; 10, first electromagnetic reversing valve; 11, second electromagnetic reversing valve; 12, oil cylinder; 13, oil tank. DETAILED DESCRIPTION

[0024] The embodiments of the application will be described in detail below with reference to the drawings, but the application can be implemented in various different ways limited and covered by the following description.

[0025] As Figure 1As shown, the micro-flow hydraulic transmission system of the embodiment includes a first oil path for providing large-flow pressure oil, a second oil path for providing small-flow pressure oil, a first electromagnetic reversing valve 10, a second electromagnetic reversing valve 11, a cylinder 12, and an oil tank 13; the oil inlet end of the first oil path is connected with the oil tank 13, and the oil outlet end of the first oil path is in communication with the P7 port of the first electromagnetic reversing valve 10; the oil inlet end of the second oil path is connected with the oil tank 13, and the oil outlet end of the second oil path is in communication with the T5 port of the first electromagnetic reversing valve 10; the outlet A4 of the first electromagnetic reversing valve 10 is in communication with the inlet P8 of the second electromagnetic reversing valve 11, the outlet B4 of the first electromagnetic reversing valve 10 and the oil return port T6 of the second electromagnetic reversing valve 11 are in communication with the oil tank 13, the outlet A5 of the second electromagnetic reversing valve 11 is in communication with the inlet A6 of the cylinder 12, and the outlet B5 of the second electromagnetic reversing valve 11 is in communication with the inlet B6 of the cylinder 12; a first hydraulic motor 8 is arranged on the first oil path, and a second hydraulic motor 9 is arranged on the second oil path, and the rotor of the first hydraulic motor 8 is coupled with the rotor of the second hydraulic motor 9.

[0026] The micro-flow hydraulic transmission system of the embodiment drives the second hydraulic motor 9 to rotate by the first hydraulic motor 8, the large-flow pressure oil provided by the first oil path and the small-flow pressure oil provided by the second oil path can be combined through the outlet A4 of the first electromagnetic reversing valve 10, the combined pressure oil enters the inlet P8 of the second electromagnetic reversing valve 11, and then enters the cylinder 12 through A5 / B5 of the second electromagnetic reversing valve 11, so as to realize the large-stroke driving of the cylinder 12; the large-flow pressure oil provided by the first oil path enters the mailbox through the outlet B4 of the first electromagnetic reversing valve 10, the small-flow pressure oil provided by the second oil path enters the inlet P8 of the second electromagnetic reversing valve 11 through the outlet A4 of the first electromagnetic reversing valve 10, and then enters the cylinder 12 through A5 / B5 of the second electromagnetic reversing valve 11, so as to realize the high-precision micro-motion control of the cylinder 12; by adjusting the flow ratio of the first oil path and the second oil path, stable adjustment of different micro-flow levels can be realized, and flow adjustment in the full-flow domain starting from 0L / min can be realized, so as to improve the control precision of the hydraulic transmission system, and the structure is simple, the cost is low, the high pressure resistance is good, and the application range is wide.

[0027] In the embodiment, the first oil circuit is further provided with a large flow pump 1 and a proportional speed regulating valve 7, the suction port S1 of the large flow pump 1 is connected with the oil tank 13, the outlet P1 of the large flow pump 1 is communicated with the inlet A1 of the proportional speed regulating valve 7, the outlet B1 of the proportional speed regulating valve 7 is communicated with the inlet A2 of the first hydraulic motor 8, and the outlet B2 of the first hydraulic motor 8 is communicated with the P7 port of the first electromagnetic reversing valve 10; the second oil circuit is further provided with a small flow pump 2, the suction port S2 of the small flow pump 2 is communicated with the oil tank 13, the outlet P2 of the small flow pump 2 is communicated with the inlet A3 of the second hydraulic motor 9, and the outlet B3 of the second hydraulic motor 9 is communicated with the T5 port of the first electromagnetic reversing valve 10; the displacement V1 of the first hydraulic motor 8 is greater than the displacement V2 of the second hydraulic motor 9, and the rotors of the first hydraulic motor 8 and the second hydraulic motor 9 are coupled through a shaft coupling; the proportional speed regulating valve 7 is used to achieve the flow regulation of the full flow range starting from 0L / min, and the displacement ratio of the first hydraulic motor 8 and the second hydraulic motor 9 is adjusted, so that the flow ratio of the first oil circuit and the second oil circuit can be adjusted, and the structure is simple and the cost is low.

[0028] In the embodiment, the rotors of the first hydraulic motor 8 and the second hydraulic motor 9 are coupled through a speed reducer, compared with the coupling through the shaft coupling, in the case that the rotation speed of the first hydraulic motor 8 is the same, the displacement of the second hydraulic motor 9 is smaller, so that the minimum flow of the second oil circuit is reduced, the displacement ratio of the first hydraulic motor 8 and the second hydraulic motor 9 can be further increased, and the precision of the micro-control of the oil cylinder 12 is improved.

[0029] In the embodiment, the first oil circuit is further provided with a large flow pump 1 and a proportional speed regulating valve 7, the suction port S1 of the large flow pump 1 is connected with the oil tank 13, the outlet P1 of the large flow pump 1 is communicated with the inlet A1 of the proportional speed regulating valve 7, the outlet B1 of the proportional speed regulating valve 7 is communicated with the inlet A2 of the first hydraulic motor 8, and the outlet B2 of the first hydraulic motor 8 is communicated with the P7 port of the first electromagnetic reversing valve 10; the second oil circuit is further provided with a small flow pump 2, the suction port S2 of the small flow pump 2 is communicated with the oil tank 13, the outlet P2 of the small flow pump 2 is communicated with the inlet A3 of the second hydraulic motor 9, and the outlet B3 of the second hydraulic motor 9 is communicated with the T5 port of the first electromagnetic reversing valve 10; the displacement V1 of the first hydraulic motor 8 is greater than the displacement V2 of the second hydraulic motor 9, and the rotors of the first hydraulic motor 8 and the second hydraulic motor 9 are coupled through a shaft coupling; the proportional speed regulating valve 7 is used to achieve the flow regulation of the full flow range starting from 0L / min, and the displacement ratio of the first hydraulic motor 8 and the second hydraulic motor 9 is adjusted, so that the flow ratio of the first oil circuit and the second oil circuit can be adjusted, and the structure is simple and the cost is low.

[0030] In the embodiment, the pressure oil flow at the oil outlet of the first oil circuit is V3, the pressure oil flow at the oil outlet of the second oil circuit is V4, and the ratio of V3:V4 is 10:1-1000:1. When the displacement V1 of the first hydraulic motor 8 is greater than the displacement V2 of the second hydraulic motor 9, the rotor of the first hydraulic motor 8 is coaxially connected to the rotor of the second hydraulic motor 9 through a shaft coupling, and when V1:V2=20:1 and the displacement of the first hydraulic motor 8 is 1 L / min, the displacement of the second hydraulic motor 9 is 0.05 L / min, at this time, V3:V4=20:1, and the flow of the micro-control of the system lifting cylinder 12 is 0.05 L / min. It can be understood that if the rotor of the first hydraulic motor 8 is connected to the rotor of the second hydraulic motor 9 through a speed reducer, then the displacement of the second hydraulic motor 9 is 0.05 L / min divided by the speed reduction ratio. When the displacement V1 of the first hydraulic motor 8 is equal to the displacement V2 of the second hydraulic motor 9, the flow of the first oil circuit is 1 L / min, and the flow of the second oil circuit is 0.05 L / min, then V3:V4=20:1, and the speed reduction ratio of the speed reducer is 20:1.

[0031] In the embodiment, the first oil circuit further comprises a first proportional relief valve 3, the outlet T1 of the first proportional relief valve 3 is communicated with the oil tank 13, and the inlet P3 of the first proportional relief valve 3 is communicated with the outlet P1 of the large-flow pump 1; the second oil circuit further comprises a second proportional relief valve 6, the inlet P6 of the second proportional relief valve 6 is communicated with the outlet P2 of the small-flow pump 2, and the outlet T4 of the second proportional relief valve 6 is communicated with the oil tank 13, which can accurately control the pressure of the first oil circuit and the second oil circuit and ensure the stable operation of the micro-flow hydraulic transmission system.

[0032] In the embodiment, the pressure setting of the first proportional relief valve 3 is set according to the displacement ratio of the two motors, which needs to ensure that the first hydraulic motor 8 can drive the second hydraulic motor 9, the pressure setting value of the second proportional relief valve 6 is the load pressure value of the cylinder 12, and the ratio of the pressure setting value of the second proportional relief valve 6 to the pressure setting value of the first proportional relief valve 3 is equal to V1:V2, at this time, the heat generation can be reduced, thereby reducing the energy consumption of the micro-flow hydraulic transmission system.

[0033] In the embodiment, the first oil circuit further comprises a first safety valve 4, the inlet P4 of the first safety valve 4 is communicated with the outlet P1 of the large-flow pump 1, and the outlet T2 of the first safety valve 4 is communicated with the oil tank 13; the second oil circuit further comprises a second safety valve 5, the inlet P5 of the second safety valve 5 is communicated with the outlet P2 of the small-flow pump 2, and the outlet T3 of the second safety valve 5 is communicated with the oil tank 13, which can release excess pressure and avoid damage to the first hydraulic motor 8 and the second hydraulic motor 9.

[0034] In the embodiment, the maximum load pressure of the first proportional relief valve 3 and the second proportional relief valve 6 is 30Mpa, and the pressure of the first safety valve 4 and the second safety valve 5 is set to 32±0.5Mpa.

[0035] A control method of the micro-flow hydraulic transmission system,

[0036] When the micro-flow hydraulic transmission system needs large flow and the oil cylinder 12 is extended, the large-flow pump 1 and the small-flow pump 2 are started, the first electromagnetic reversing valve 10 is in the left position, the second electromagnetic reversing valve 11 is in the right position, the first oil path is S1-P1-A1-B1-A2-B2-P7-A4, the second oil path is S2-P2-A3-B3-T5-A4, the pressure oil of the first oil path and the pressure oil of the second oil path are combined at A4, the combined pressure oil path is A4-P8-A5-A6, the oil return path is B6-B5-T6-tank 13, the flow after combination is adjusted by adjusting the proportional speed regulating valve 7, and the large-stroke control of the oil cylinder 12 is completed.

[0037] When the micro-flow hydraulic transmission system needs micro flow and the oil cylinder 12 is extended, the large-flow pump 1 and the small-flow pump 2 are started, the first electromagnetic reversing valve 10 is in the right position, the second electromagnetic reversing valve 11 is in the right position, the large-flow oil path is S1-P1-A1-B1-A2-B2-P7-B4-tank 13, the micro-flow oil path is S2-P2-A3-B3-T5-A4-P8-A5-A6, the oil return path is B6-B5-T6-tank 13, the flow of the first hydraulic motor 8 is controlled by the proportional speed regulating valve 7, so that the micro-flow control of the second hydraulic motor 9 is realized in proportion, and the high-precision micro-motion control of the oil cylinder 12 is completed.

[0038] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A micro-flow hydraulic transmission system, characterized in that, it comprises a first oil circuit for providing large-flow pressure oil, a second oil circuit for providing small-flow pressure oil, a first electromagnetic reversing valve (10), a second electromagnetic reversing valve (11), a cylinder (12), and an oil tank (13); an oil inlet end of the first oil circuit is connected with the oil tank (13), and an oil outlet end of the first oil circuit is in communication with a P7 port of the first electromagnetic reversing valve (10); an oil inlet end of the second oil circuit is connected with the oil tank (13), and an oil outlet end of the second oil circuit is in communication with a T5 port of the first electromagnetic reversing valve (10); an outlet A4 of the first electromagnetic reversing valve (10) is in communication with an inlet P8 of the second electromagnetic reversing valve (11), an outlet B4 of the first electromagnetic reversing valve (10), a back oil port T6 of the second electromagnetic reversing valve (11) are in communication with the oil tank (13), an outlet A5 of the second electromagnetic reversing valve (11) is in communication with an inlet A6 of the cylinder (12), and an outlet B5 of the second electromagnetic reversing valve (11) is in communication with an inlet B6 of the cylinder (12); a first hydraulic motor (8) is arranged on the first oil circuit, and a second hydraulic motor (9) is arranged on the second oil circuit, a rotor of the first hydraulic motor (8) is coupled with a rotor of the second hydraulic motor (9); a large-flow pump (1) and a proportional speed regulating valve (7) are further arranged on the first oil circuit, an oil suction port S1 of the large-flow pump (1) is connected with the oil tank (13), an outlet P1 of the large-flow pump (1) is in communication with an inlet A1 of the proportional speed regulating valve (7), an outlet B1 of the proportional speed regulating valve (7) is in communication with an inlet A2 of the first hydraulic motor (8), and an outlet B2 of the first hydraulic motor (8) is in communication with the P7 port of the first electromagnetic reversing valve (10); a small-flow pump (2) is further arranged on the second oil circuit, an oil suction port S2 of the small-flow pump (2) is in communication with the oil tank (13), an outlet P2 of the small-flow pump (2) is in communication with an inlet A3 of the second hydraulic motor (9), and an outlet B3 of the second hydraulic motor (9) is in communication with the T5 port of the first electromagnetic reversing valve (10). 2.The micro-flow hydraulic transmission system according to claim 1, characterized in that, a displacement V1 of the first hydraulic motor (8) is greater than a displacement V2 of the second hydraulic motor (9). 3.The micro-flow hydraulic transmission system according to claim 2, characterized in that, the rotor of the first hydraulic motor (8) is coupled with the rotor of the second hydraulic motor (9) through a speed reducer. 4.The micro-flow hydraulic transmission system according to claim 1, characterized in that, the displacement V1 of the first hydraulic motor (8) is equal to the displacement V2 of the second hydraulic motor (9), and the rotor of the first hydraulic motor (8) is coupled with the rotor of the second hydraulic motor (9) through a speed reducer. 5.The micro-flow hydraulic transmission system according to any one of claims 1 to 4, characterized in that, The pressure oil flow at the outlet end of the first oil path is V3, the pressure oil flow at the outlet end of the second oil path is V4, and the ratio of V3:V4 is 10:1-1000:

1. 6.The micro-flow hydraulic transmission system according to claim 5, characterized in that, The first oil path further comprises a first proportional relief valve (3), the outlet T1 of the first proportional relief valve (3) is communicated with the oil tank (13), and the inlet P3 of the first proportional relief valve (3) is communicated with the outlet P1 of the large-flow pump (1); the second oil path further comprises a second proportional relief valve (6), the inlet P6 of the second proportional relief valve (6) is communicated with the outlet P2 of the small-flow pump (2), and the outlet T4 of the second proportional relief valve (6) is communicated with the oil tank (13). 7.The micro-flow hydraulic transmission system according to claim 6, characterized in that, The pressure setting value of the second proportional relief valve (6) is the load pressure value of the oil cylinder (12), and the ratio of the pressure setting value of the second proportional relief valve (6) to the pressure setting value of the first proportional relief valve (3) is equal to the ratio of the displacement V1 of the first hydraulic motor (8) to the displacement V2 of the second hydraulic motor (9). 8.The micro-flow hydraulic transmission system according to claim 7, characterized in that, The first oil path further comprises a first safety valve (4), the inlet P4 of the first safety valve (4) is communicated with the outlet P1 of the large-flow pump (1), and the outlet T2 of the first safety valve (4) is communicated with the oil tank (13); the second oil path further comprises a second safety valve (5), the inlet P5 of the second safety valve (5) is communicated with the outlet P2 of the small-flow pump (2), and the outlet T3 of the second safety valve (5) is communicated with the oil tank (13). 9.The micro-flow hydraulic transmission system according to claim 8, characterized in that, The maximum load pressure of the first proportional relief valve (3) and the second proportional relief valve (6) is 30 MPa, and the pressure setting of the first safety valve (4) and the second safety valve (5) is 32±0.5 MPa.

10. A control method of a micro-flow hydraulic transmission system, characterized by, The micro-flow hydraulic transmission system according to any one of claims 1-9, When the micro-flow hydraulic transmission system needs large flow and the oil cylinder (12) is extended, the large-flow pump (1) and the small-flow pump (2) are started, the first electromagnetic reversing valve (10) is in the left position, and the second electromagnetic reversing valve (11) is in the right position, the first oil path is S1-P1-A1-B1-A2-B2-P7-A4, the second oil path is S2-P2-A3-B3-T5-A4, the pressure oil of the first oil path and the pressure oil of the second oil path are combined at A4, the combined pressure oil path is A4-P8-A5-A6, the return oil path is B6-B5-T6-oil tank (13), the flow after combination is adjusted by adjusting the proportional speed regulating valve (7), and the large stroke control of the oil cylinder (12) is completed. The micro-flow hydraulic transmission system requires micro-flow, when the oil cylinder (12) extends, the large-flow pump (1) and the small-flow pump (2) are started, the first electromagnetic reversing valve (10) is in the right position, the second electromagnetic reversing valve (11) is in the right position, the large-flow oil way is: S1-P1-A1-B1-A2-B2-P7-B4-tank (13); the micro-flow is the oil way: S2-P2-A3-B3-T5-A4-P8-A5-A6, the back oil way is: B6-B5-T6-tank (13), the flow of the first hydraulic motor (8) is controlled through the proportional speed regulating valve (7), so that the micro-flow control of the second hydraulic motor (9) is realized in proportion, and the high-precision micro-motion control of the oil cylinder (12) is completed.

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