Hydraulic system of small square bundle bundling and collecting machine

Abstract

The invention relates to the technical field of bale collecting equipment, in particular to a hydraulic system of a small square bale bundling and collecting machine. The main hydraulic system comprises a plunger variable pump, a high-pressure filter and an electric proportional multi-way valve; the plunger variable pump adopts a plunger variable pump with pressure cut-off and load sensitive functions, and the electric proportional multi-way valve is a load sensitive electric proportional multi-way valve; the plunger variable pump is powered by a power shaft of a tractor; an oil inlet of the electric proportional multi-way valve is connected with a pressure oil port of the plunger variable pump through the high-pressure filter, and the high-pressure filter filters rolling oil. A control oil return port of the electric proportional multi-way valve is connected with the oil tank, and a load pressure feedback signal output port is connected with a feedback oil port of the plunger variable pump; the electric proportional multi-way valve comprises a multi-union reversing valve which is connected with an actuator to form hydraulic loops with different functions. The hydraulic system has the advantages of being high in output efficiency, saving fuel oil, reducing oil consumption, reducing heating of the hydraulic system, prolonging the service life of hydraulic elements and reducing pollution.

Description

Technical Field

[0001] The present invention relates to the technical field of bale collection equipment, and particularly to a hydraulic system for a small square bale baling and bundling machine. Background Art

[0002] Small square bale forage is a forage bale with a regular cuboid shape after being mechanically baled, and is mainly used for feed storage and transportation in animal husbandry. The small square bale forage is about 30 - 40 cm (width) × 40 - 50 cm (height) × 70 - 100 cm (length), and the weight of a single bale is usually 15 - 30 kg, which is convenient for manual handling. The manual handling cost is low, no special machinery is required, it is suitable for small pastures or decentralized transportation (such as by truck or tractor), has good ventilation, and has a relatively low risk of mildew during short - term storage.

[0003] At present, the application areas of small square bale baling and bundling machines in China are mainly concentrated in the northern regions of the corn - growing areas. Small square bale forage is suitable for large neighboring pastures; it is convenient for handling, loading and unloading, and for feeding at the back end; it solves the problem of loading; it solves the cost of the back - end loading and unloading links; it solves the problems of difficult hiring and high cost due to the aging of the farming population.

[0004] However, at the present stage, the hydraulic system of small square bale baling and bundling machines has the following defects and deficiencies. On the premise of ensuring the best use performance of the equipment, it is still a technical problem urgently to be solved in this field to utilize the maximum fuel efficiency, reduce the heat generation phenomenon and carbon emissions during the equipment operation, so as to achieve energy conservation and emission reduction. Summary of the Invention

[0005] In order to solve the above - mentioned technical problems, the present invention provides a hydraulic system for a small square bale baling and bundling machine, which has the advantages of high output efficiency, fuel saving, reduced oil consumption, reduced heat generation of the hydraulic system, increased service life of hydraulic components and reduced pollution.

[0006] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0007] A hydraulic system for a small square bale baling and bundling machine includes a main hydraulic system and an auxiliary hydraulic system. The main hydraulic system includes a piston variable pump, a high - pressure filter and an electro - proportional multi - way valve; the piston variable pump is a piston variable pump with pressure cut - off and load - sensing functions, and the electro - proportional multi - way valve is a load - sensing electro - proportional multi - way valve; the piston variable pump is powered by the power shaft of a tractor; the oil inlet of the electro - proportional multi - way valve is connected to the pressure oil port of the piston variable pump through a high - pressure filter, and the high - pressure filter filters impurities in the oil; the control oil return port of the electro - proportional multi - way valve is connected to the fuel tank, and the load pressure feedback signal output port is connected to the feedback oil port of the piston variable pump; the electro - proportional multi - way valve includes multiple multi - way directional control valves, which are connected to actuators to form hydraulic circuits with different functions.

[0008] Furthermore, the transmission shaft of the plunger variable pump is connected to the power shaft of the tractor and is powered by the power shaft of the tractor; the oil suction port of the plunger variable pump draws oil from the hydraulic oil tank on the chassis assembly, and the pressure oil is provided to the electric proportional multi-way valve through a high-pressure filter; the load-sensitive circuit control oil is fed back from the electric proportional multi-way valve to the plunger variable pump; the oil drain port of the plunger variable pump is separately connected back to the hydraulic oil tank to drain the oil.

[0009] Furthermore, the main hydraulic system also includes an accumulator, a first lifting motor, a second lifting motor, a transmission motor, a back pressure maintaining valve, a lower box cover cylinder, an upper box cover cylinder, a throttle valve, a bale pushing cylinder, a needle threading motor, a hydraulically controlled one-way valve, a bale pressing cylinder, a diverter block, a pressure sensor, a transition block, a one-way sequence valve, a lifting cylinder, a tensioning cylinder and an inlet cylinder.

[0010] Furthermore, the first reversing valve of the electric proportional multi-way valve is connected in series with the first lifting motor, the second lifting motor and the transmission motor; the first lifting motor, the second lifting motor and the transmission motor are all cycloidal motors with bypass solenoid valves, and the rotation and stopping of the first lifting motor, the second lifting motor and the transmission motor are controlled respectively by the power gain and loss of the electromagnet.

[0011] Furthermore, the second reversing valve of the electric proportional multi-way valve is connected to the back pressure holding valve, which is divided into three routes through the back pressure holding valve and respectively connected to the lower box cover cylinder, the upper box cover cylinder, and the bundle pushing cylinder. The logical action sequence of the three groups of hydraulic circuits is guaranteed by the back pressure holding valve and the throttle valve.

[0012] Furthermore, the third reversing valve of the electric proportional multi-way valve is connected to the needle threading motor.

[0013] Furthermore, after the fourth reversing valve of the electric proportional multi-way valve is connected to the hydraulically controlled one-way valve, it is connected to the baling cylinder through the hydraulically controlled one-way valve.

[0014] Furthermore, the fifth reversing valve of the electric proportional multi-way valve is connected to the shunt block, which divides into four circuits, one of which is connected to the pressure sensor, two of which are connected to the lifting cylinder, one of which is connected to the one-way sequence valve, and the outlet of the one-way sequence valve is connected to the tensioning cylinder. The fifth reversing valve of the electric proportional multi-way valve is connected to the transition block, which divides into three circuits, one of which is connected to the tensioning cylinder and two of which are connected to the lifting cylinder.

[0015] Furthermore, the sixth reversing valve of the electric proportional multi-way valve is connected to the inlet oil cylinder.

[0016] Furthermore, the auxiliary hydraulic system is powered by a valve group provided by the tractor, including a lifting cylinder, a guard plate cylinder, a one-way throttle valve, a relief valve, a throttle valve and a one-way sequence valve.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The variable displacement piston pump of the present invention is a piston pump with pressure cut-off and load-sensitive functions. The load-sensitive valve is a displacement differential regulating valve of the pump, which maintains a pressure difference of 22 bar between the oil pressure at the oil outlet of the pump and the oil pressure of the maximum load actuator, and adaptively adjusts the displacement of the pump to keep the output flow rate always maintained at the flow rate required for the actuator to move, and is not affected by the load of the actuator and the speed of the power unit. The actuator always moves at the set speed curve; when the system pressure reaches 22MPa, the pressure cut-off valve reduces the displacement of the pump to the minimum, and only maintains the leakage of the system itself, so as to realize the high-pressure and zero-output state of the hydraulic system during the movement of each actuator and the switching process; at the same time, when the baler is in the standby state, the hydraulic system maintains a low-pressure and zero-output state.

[0019] The electric proportional multi-way valve is an electric proportional pilot control with LS valve front pressure compensation function. The pressure compensator is set with a 6bar pressure difference. The electric proportional multi-way valve can adapt to the load pressure and reduce the system pressure to just maintain a 6bar pressure difference between the inlet and outlet of the reversing valve core. The flow output to the actuator has nothing to do with the system and load pressure, but only with the size of the valve core opening.

[0020] The hydraulic system of the present invention uses a load-sensitive variable pump and an electric proportional multi-way valve to form a load-sensitive system. The load-sensitive system detects load pressure, flow and power change signals by sensing, and feeds back to the hydraulic system to achieve energy-saving control, flow and speed control, simultaneous action and prime mover power matching.

[0021] The invention has the advantages of high output efficiency, fuel saving and reduced fuel consumption, reduced heating of the hydraulic system, increased service life of hydraulic components and reduced pollution.

[0022] 2. The hydraulic logic composed of the one-way throttle valve and the one-way sequence valve in the hydraulic system of the present invention can realize that when starting work, the guard plate cylinder will extend only after the lifting cylinder is lowered into place; after the work is completed, the lifting cylinder will be retracted after the guard plate cylinder is retracted. This system does not work during the operation of the baler, and this system is simple to control and has a small flow rate. The requirements can be met by using the valve group provided by the tractor. The complex pipeline installation of the multi-way valve part is reduced, which is convenient for pipe layout design, and can also reduce design costs and simplify control logic.

[0023] 3. The electro-hydraulic proportional multi-way valve of the present invention is divided into six reversing units. The actions of each unit are controlled by proportional electro-magnets, and the hydraulic oil flow required for the actions of each unit is provided. The action sequence of each actuator in each unit is ensured by an auxiliary valve group. The back-pressure holding valve and the throttle valve achieve the action sequence when pushing the bale out of the baler. The upper box cover cylinder is opened first, and the bale pushing cylinder pushes the bale outwards. When the pressure at the lower box cover cylinder reaches 6 MPa, the sequence valve opens to discharge the bale. After the discharge is completed, the upper box cover cylinder and the bale pushing cylinder are reset first, and the lower box cover cylinder is reset later to complete the entire set of logical actions. The throttle valve is directly installed on the back-pressure holding valve to reduce unnecessary pipelines. The one-way sequence valve ensures that the tensioning cylinder will not release until the lifting cylinder has been lowered in place. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the main hydraulic system of the present invention.

[0025] Figure 2 It is a schematic diagram of the auxiliary hydraulic system of the present invention.

[0026] Reference signs in the figures: 13, piston variable pump; 14, high-pressure filter; 15, electro-hydraulic proportional multi-way valve; 16, accumulator; 17, cycloidal motor; 18, back-pressure holding valve; 19, lower box cover cylinder; 20, upper box cover cylinder; 21, throttle valve; 22, bale pushing cylinder; 23, threading motor; 24, hydraulic control one-way valve; 25, baling cylinder; 26, manifold block; 27, pressure sensor; 28, transition block; 29, one-way sequence valve; 30, lifting cylinder; 31, tensioning cylinder; 32, guiding cylinder; 33, lifting cylinder; 34, guard plate cylinder; 35, one-way throttle valve; 36, relief valve. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.

[0028] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] The following further describes the specific embodiments of the present invention with reference to the drawings:

[0030] As Figure 1 、 Figure 2 shown, a hydraulic system for a small square bale baling and bundling machine includes two parts: a main hydraulic system and an auxiliary hydraulic system.

[0031] As Figure 1 shown, the first part is the main hydraulic system powered by the power shaft of a tractor, which is also the core part of the present invention. The main hydraulic system includes a piston variable pump 13 with pressure cut-off and load-sensing functions, a high-pressure filter 14, an LS load-sensing electro-hydraulic proportional multi-way valve 15, an accumulator 16, a cycloidal motor 17 with a bypass solenoid valve, a back-pressure holding valve 18, a lower box cover cylinder 19, an upper box cover cylinder 20, a throttle valve 21, a bale pushing cylinder 22, a needle-piercing motor 23, a hydraulic control check valve 24, a bale pressing cylinder 25, a manifold block 26, a pressure sensor 27, a transition block 28, a one-way sequence valve 29, a lifting cylinder 30, a tensioning cylinder 31, and a guiding cylinder 32.

[0032] The direct spline of the drive shaft of the piston variable pump 13 is connected to the power shaft of the tractor through a dividing box, powered by the tractor power shaft. The suction port of the pump sucks oil from the hydraulic oil tank on the chassis assembly. The pressure oil is supplied to the electro-hydraulic proportional multi-way valve 15 through the high-pressure filter. The load-sensing circuit control oil is fed back from the electro-hydraulic proportional multi-way valve 15 to the piston variable pump 13, and the drain port of the piston variable pump 13 is separately connected back to the hydraulic oil tank for draining.

[0033] The high-pressure filter 14 is connected between the piston variable pump 13 and the electro-hydraulic proportional multi-way valve 15, and the high-pressure filter 14 filters impurities in the oil.

[0034] The oil inlet port P of the electric proportional multi-way valve 15 is connected to the pressure oil port of the plunger variable pump 13 through the high-pressure filter 14, the T port is connected to the oil tank, and the LS port is connected to the feedback oil port of the plunger variable pump 13. In this embodiment, the electric proportional multi-way valve 15 includes a total of 6 reversing links connected to the actuator to form hydraulic circuits with different functions.

[0035] The first link A1 and B1 of the electric proportional multi-way valve 15 are connected in series with three identical cycloidal motors 17 with bypass solenoid valves, including the first lifting motor, the second lifting motor and the conveying motor. The rotation and stop of the first lifting motor, the second lifting motor and the conveying motor can be controlled respectively by the electromagnet gaining and losing power.

[0036] After the second link A2 and B2 of the electric proportional multi-way valve 15 are connected to the back pressure holding valve 18, the flow is then divided into three paths through the back pressure holding valve 18 and respectively connected to the lower box cover cylinder 19, the upper box cover cylinder 20 and the bundle pushing cylinder 22. The logical action sequence of the three groups of hydraulic circuits is guaranteed by the back pressure holding valve 18 and the throttle valve 21.

[0037] The third link A3 and B3 of the electric proportional multi-way valve 15 are connected to the needle threading motor 23 .

[0038] After the fourth link A4 and B4 of the electric proportional multi-way valve 15 are connected to the hydraulically controlled one-way valve 24 , they are connected to the baling cylinder 25 through the hydraulically controlled one-way valve 24 .

[0039] The fifth link A5 of the electric proportional multi-way valve 15 is connected to the diverter block 26, and the diverter block 26 divides into four circuits, one of which is connected to the pressure sensor 27, two are connected to the lifting cylinder 30, and one is connected to the one-way sequence valve 29. The outlet of the one-way sequence valve 29 is connected to the tensioning cylinder 34.

[0040] The fifth link B5 of the electric proportional multi-way valve 15 is connected to the transition block 28 , and the transition block 28 is divided into three circuits, one of which is connected to the tensioning cylinder 31 , and two of which are connected to the lifting cylinder 30 .

[0041] The sixth link A6 and B6 of the electric proportional multi-way valve 15 are connected to the inlet oil cylinder 32 .

[0042] like Figure 2 As shown, the second part is the auxiliary hydraulic system responsible for the lifting and lowering of the pickup device and the extension and retraction of the guard plate, which is powered by the valve group of the tractor. The auxiliary hydraulic system includes a lifting cylinder 33, a guard plate cylinder 34, a one-way throttle valve 35, a relief valve 36, a throttle valve 21 and a one-way sequence valve 29.

[0043] A stream of oil is led out from the valve block on the tractor, tentatively called port A, and is divided into three oil circuits. One circuit is connected to the rod chamber of the lifting cylinder, one circuit returns oil from port B through the overflow valve 36 and the one-way throttle valve 35, and one circuit is connected to the rod chamber of the guard plate cylinder through the one-way sequence valve 29 and the throttle valve 21. Another stream of oil is also divided into three oil circuits through port B and the one-way throttle valve 35. One circuit is connected to the drain port of the overflow valve 36, one circuit is connected to the rodless chamber of the guard plate cylinder 34, and the last circuit is connected to the rodless chamber of the lifting cylinder 33 through the one-way throttle valve 35.

[0044] The working principle and process of the present invention are as follows:

[0045] The components of the baler that include hydraulic actuators are: the pick-up device, which includes the first lifting motor, the second lifting motor, the lifting cylinder 33 and the guard plate cylinder 34; the horizontal transmission device, which includes the transmission motor; the bale discharging device, which includes two identical lower box cover cylinders 19 and the compressing cylinder 25; the bale storage device, which includes two identical upper box cover cylinders 20 and the bale pushing cylinder 22; the knotter assembly device, which includes the threading motor 23; the bale lifting device, which includes two identical lifting cylinders 30; the tensioning device, which includes the tensioning cylinder 31; and the bale guiding device, which includes the guiding cylinder 32.

[0046] During the working process of the baler, when the bale touches the pick-up device, the lifting motors drive two lifting chains respectively to convey the bale to the chassis and wait for conveyance. When there is no bale at the horizontal push plate mechanism in the chassis, the transmission motor of the horizontal transmission device drives the chain to convey the bale to the horizontal push plate mechanism. The guiding cylinder 32 pushes the bale into the box body of the chassis. When the second bale is pushed in, the compressing cylinder 25 is loosened, and the lifting cylinder 30 lifts the bale to the bale storage device and moves up one layer. After moving in place, the compressing cylinder 25 compresses the bale, and the lifting cylinder 30 resets to prepare for the next bale lifting. When the bale storage device cycles up to full load, the tensioning cylinder 31 clamps the bale to the pressure set by the pressure sensor 27, and the threading motor 23 drives the knotter assembly device to tie the bale in the bale storage device. After tying, the upper box cover cylinder 20 and the lower box cover cylinder 19 open the rear door of the bale discharging device, and the bale pushing cylinder 22 pushes the bale out of the baler. When the photoelectric switch detects that the whole bale has left the warehouse door, the bale pushing cylinder 22 resets, and the upper box cover cylinder 20 and the lower box cover cylinder 19 close the rear door, completing one cycle of work.

[0047] When the baler finishes working, the lifting cylinder 33 retracts the pick-up device as a whole to the highest point to prevent collision and reduce the floor area. The guard plate cylinder 34 retracts the guard plate of the pick-up device, serving the purposes of preventing collision, reducing the floor area and facilitating transportation.

[0048] Compared with the prior art, the auxiliary hydraulic system of the present invention has at least the following beneficial effects and advantages: the hydraulic logic composed of the one-way throttle valve 35 and the one-way sequence valve 29 in the auxiliary hydraulic system can realize that when starting work, the guard plate cylinder 34 will not extend until the lifting cylinder 33 is lowered into place; after the work is completed, the lifting cylinder 33 will not be retracted until the guard plate cylinder 34 is completely retracted. This system does not work during the operation of the baler, and this system is simple to control and has a small flow rate. The requirements can be met by using the valve group provided by the tractor. The complex pipeline installation of the multi-way valve part is reduced, which is convenient for the pipe layout design, and at the same time, the design cost can be reduced and the control logic can be simplified.

[0049] Compared with the prior art, the main hydraulic system of the present invention has at least the following beneficial effects and advantages: the main system divides the electric proportional multi-way valve 15 into six-way reversing links according to the working conditions, controls the action of each link through a proportional solenoid and provides the hydraulic oil flow required for the action of each link, and the action sequence of each actuator in each link is guaranteed by the auxiliary valve group.

[0050] The back pressure holding valve 18 and the throttle valve 21 realize the action sequence when pushing the bale out of the baler. The upper cover cylinder 20 opens first, and the bale pushing cylinder 22 pushes the bale outward. When the pressure at the lower cover cylinder 19 reaches 6MPa, the sequence valve opens to unload the bale. After unloading, the upper cover cylinder 20 and the bale pushing cylinder 22 are reset first, and the lower cover cylinder 19 is reset later, completing the whole set of logical actions. The throttle valve 21 is directly installed on the back pressure holding valve 18 to reduce unnecessary piping.

[0051] The one-way sequence valve 29 ensures that the tensioning cylinder 31 will be released only after the lifting cylinder 30 is lowered into place.

[0052] The plunger variable pump 13 of the hydraulic system of the present invention is a plunger pump with pressure cut-off and load-sensitive functions. The load-sensitive valve is a displacement differential regulating valve of the pump, which maintains a pressure difference of 22 bar between the oil pressure at the oil outlet of the pump and the oil pressure of the maximum load actuator, and adaptively adjusts the displacement of the pump to keep the output flow rate always maintained at the flow rate required for the actuator to move, and is not affected by the load of the actuator and the speed of the power unit. The actuator always moves at the set speed curve; when the system pressure reaches 22MPa, the pressure cut-off valve reduces the pump displacement to the minimum, and only maintains the leakage of the system itself, so as to realize the high-pressure and zero-output state of the hydraulic system during the movement and switching of each actuator; at the same time, when the baler is in standby mode, the hydraulic system maintains a low-pressure and zero-output state. The selected plunger variable pump 13 has the characteristics of sensitive response and fast response.

[0053] The electro-hydraulic proportional multi-way valve 15 of the hydraulic system of the present invention is electro-hydraulic proportional pilot control, with the LS valve front pressure compensation function. The pressure compensator is set with a pressure difference of 6 bar. The electro-hydraulic proportional multi-way valve 15 can adapt to the load pressure, reduce the system pressure to exactly maintain a pressure difference of 6 bar at both ends of the inlet and outlet of the reversing spool. The flow rate output to the actuator is independent of the system and load pressures and is only related to the opening size of the spool.

[0054] The hydraulic system of the present invention uses a load-sensing piston variable pump 13 and an electro-hydraulic proportional multi-way valve 15 to form a load-sensing system. By sensing and detecting the load pressure, flow rate, and power change signals, it feeds back to the hydraulic system to achieve energy-saving control, flow rate and speed control, simultaneous operation, and prime mover power matching. The present invention has the advantages of high output efficiency, fuel saving and reduced fuel consumption, reduced heat generation of the hydraulic system, increased service life of hydraulic components, and reduced pollution.

[0055] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered within the protection scope of the present invention.

Claims

1. A hydraulic system for a small square bale baling and bundling machine, comprising a main hydraulic system and an auxiliary hydraulic system, characterized in that: The main hydraulic system includes a plunger variable pump, a high-pressure filter and an electric proportional multi-way valve; The plunger variable pump adopts a plunger variable pump with pressure cut-off and load-sensing functions, and the electric proportional multi-way valve is a load-sensitive electric proportional multi-way valve; The plunger variable displacement pump is powered by the tractor power shaft; The oil inlet of the electric proportional multi-way valve is connected to the pressure oil port of the plunger variable pump through a high-pressure filter, and the high-pressure filter filters impurities in the oil; The electric proportional multi-way valve control oil return port is connected to the oil tank, and the load pressure feedback signal output port is connected to the plunger variable pump feedback oil port; the electric proportional multi-way valve includes a multi-link reversing valve, which is connected to the actuator to form hydraulic circuits with different functions.

2. The hydraulic system of a small square bale baling and bundling machine according to claim 1, characterized in that: The transmission shaft of the plunger variable displacement pump is connected to the power shaft of the tractor and is powered by the power shaft of the tractor; The oil suction port of the plunger variable pump draws oil from the hydraulic oil tank on the chassis assembly, and the pressure oil is supplied to the electric proportional multi-way valve through the high-pressure filter; The load sensing circuit controls the oil to be fed back from the electric proportional multi-way valve to the plunger variable pump; The oil drain port of the piston variable pump is connected back to the hydraulic oil tank to drain the oil.

3. The hydraulic system of a small square bale baling and bundling machine according to claim 1, characterized in that: The main hydraulic system also includes an accumulator, a first lifting motor, a second lifting motor, a transmission motor, a back pressure maintaining valve, a lower box cover cylinder, an upper box cover cylinder, a throttle valve, a bale pushing cylinder, a needle threading motor, a hydraulically controlled one-way valve, a bale pressing cylinder, a diverter block, a pressure sensor, a transition block, a one-way sequence valve, a lifting cylinder, a tensioning cylinder and an inlet cylinder.

4. The hydraulic system of a small square bale baling and bundling machine according to claim 3, characterized in that: The first reversing valve of the electric proportional multi-way valve is connected in series with the first lifting motor, the second lifting motor and the transmission motor; the first lifting motor, the second lifting motor and the transmission motor are all cycloidal motors with bypass solenoid valves, and the rotation and stopping of the first lifting motor, the second lifting motor and the transmission motor are controlled respectively by the power gain and loss of the electromagnet.

5. The hydraulic system of a small square bale baling and bundling machine according to claim 3, characterized in that: The second reversing valve of the electric proportional multi-way valve is connected to the back pressure holding valve, which is divided into three ways through the back pressure holding valve and respectively connected to the lower box cover cylinder, the upper box cover cylinder, and the bundle pushing cylinder. The logical action sequence of the three groups of hydraulic circuits is guaranteed by the back pressure holding valve and the throttle valve.

6. The hydraulic system of a small square bale baling and bundling machine according to claim 3, characterized in that: The third reversing valve of the electric proportional multi-way valve is connected to the needle threading motor.

7. The hydraulic system of a small square bale baling and bundling machine according to claim 3, characterized in that: After the fourth reversing valve of the electric proportional multi-way valve is connected to the hydraulically controlled one-way valve, it is connected to the baling oil cylinder through the hydraulically controlled one-way valve.

8. The hydraulic system of a small square bale baling and bundling machine according to claim 3, characterized in that: The fifth reversing valve of the electric proportional multi-way valve is connected to the shunt block, which divides four circuits, one of which is connected to the pressure sensor, two of which are connected to the lifting cylinder, and one of which is connected to the one-way sequence valve. The outlet of the one-way sequence valve is connected to the tensioning cylinder. The fifth reversing valve of the electric proportional multi-way valve is connected to the transition block, and the transition block divides into three circuits, one of which is connected to the tensioning cylinder and the other two are connected to the lifting cylinder.

9. The hydraulic system of a small square bale baling and bundling machine according to claim 3, characterized in that: The sixth directional control valve of the electric proportional multi-way valve is connected to the inlet oil cylinder.

10. The hydraulic system of a small square bale baling and bundling machine according to claim 1, characterized in that: The auxiliary hydraulic system is powered by a valve group provided by the tractor, and includes a lifting cylinder, a guard plate cylinder, a one-way throttle valve, a relief valve, a throttle valve and a one-way sequence valve.

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