Hydraulic system and control method

Abstract

The application discloses a hydraulic system and a control method, comprising: an oil tank; an execution system; a first load-sensitive pump, comprising a first variable pump, a first load-sensitive valve and a first variable cylinder, the first variable pump being connected with the oil tank and the execution system respectively; the input end of the first load-sensitive valve being connected with the first variable pump, the load feedback end of the first load-sensitive valve being connected with the load feedback oil circuit of the execution system, the output end of the first load-sensitive valve being connected with the first variable cylinder, for receiving the load feedback pressure of the execution system and acting on the first variable cylinder to adjust the output flow of the first variable pump, the first load-sensitive pump setting a first load-sensitive pressure; a second load-sensitive pump, the second load-sensitive pump setting a second load-sensitive pressure, the second load-sensitive pressure being greater than the first load-sensitive pressure; and a first on-off control unit, for controlling the on-off or flow direction between the output end of the first load-sensitive pump and the execution system.

Description

Technical Field

[0001] The present invention relates to the technical field of tractor hydraulic systems, and in particular to a hydraulic system. In addition, the present invention also relates to a control method including the hydraulic system. Background Art

[0002] In existing technology, most tractors use a gear pump as their operating oil source. When working in the field, the tractor and gear pump operate at their rated speed. When the working coupler is not operating, the system generates heat through the relief valve or the hydraulic oil is directly returned to the tank by de-energizing the electromagnetic relief valve, causing the entire system to lose pressure. During operation, the working coupler cannot fully utilize the flow generated by the gear pump; excess flow overflows and generates heat, resulting in significant power loss. Due to the tractor's operating characteristics, using a gear pump system presents a significant heat generation issue, necessitating the use of a larger heat sink. However, this heat sink is expensive due to the tractor's inherent structural and field-of-view design requirements.

[0003] To solve the problem of standby power loss, some products in the existing technology reduce the standby pressure by using an open center control multi-way valve. During operation, the system always has flow demand. When the output flow is greater than the actual demand flow, the excess flow will still overflow and generate heat.

[0004] In order to solve the flow demand problem, some products in the existing technology use dual gear pumps in parallel to achieve large flow demand through a set of switching valves. When there is no large flow, one of the gear pumps returns to the oil tank through the pressure relief device. When there is a large flow demand, the switching valve is energized and the two gear pumps output flow at the same time to meet the actual flow usage demand. However, when the output flow is greater than the actual demand flow, the excess flow still overflows and generates heat.

[0005] On the other hand, due to cost considerations, most tractor products only have single-position control for their rear suspension lifting systems, lacking closed-loop control. During operation, increased ground resistance requires manual adjustment, resulting in poor consistency in tillage depth. Force-position sensors are used for control, and the control of position and force parameter ranges is complex, resulting in inconsistent performance across similar products on the market. Summary of the Invention

[0006] The present invention provides a hydraulic system and a control method to solve the technical problems of excess flow overflow, heat generation and large energy loss during the operation of a single-pump or dual-pump parallel hydraulic system used in tractors in the prior art.

[0007] According to one aspect of the present invention, there is provided a hydraulic system for a tractor, comprising:

[0008] Oil tank, used to store and supply hydraulic oil;

[0009] An execution system, configured to be driven by hydraulic oil to execute an action, the execution system comprising a load feedback oil circuit and an oil return oil circuit connected to an oil tank;

[0010] A first load-sensing pump includes a first variable displacement pump, a first load-sensing valve, and a first variable displacement cylinder connected to the first variable displacement pump. The first variable displacement pump is connected to the oil tank and the actuator system, respectively, for supplying hydraulic oil to the actuator system. An input end of the first load-sensing valve is connected to the first variable displacement pump, a load feedback end of the first load-sensing valve is connected to a load feedback oil circuit of the actuator system, and an output end of the first load-sensing valve is connected to the first variable displacement cylinder for receiving load feedback pressure from the actuator system and acting on the first variable displacement cylinder to thereby adjust an output flow of the first variable displacement pump. The first load-sensing pump sets a first load-sensing pressure.

[0011] a second load-sensing pump comprising a second variable displacement pump, a second load-sensing valve, and a second variable displacement cylinder connected to the second variable displacement pump, the second variable displacement pump being connected to the oil tank and the actuator system, respectively, for supplying hydraulic oil to the actuator system; an input end of the second load-sensing valve being connected to the second variable displacement pump, a load feedback end of the second load-sensing valve being connected to a load feedback oil circuit of the actuator system, an output end of the second load-sensing valve being connected to the second variable displacement cylinder for receiving load feedback pressure from the actuator system and acting on the second variable displacement cylinder to thereby adjust an output flow of the second variable displacement pump; the second load-sensing pump setting a second load-sensing pressure, the second load-sensing pressure being greater than the first load-sensing pressure;

[0012] The first on-off control unit is provided between the output end of the first load-sensing pump and the execution system, and is used to control on-off or flow direction between the output end of the first load-sensing pump and the execution system.

[0013] As a further improvement of the above technical solution, the hydraulic system further includes an emergency valve arranged between the output end of the first load-sensing pump and the execution system, and the output end of the second load-sensing pump is connected to the emergency valve.

[0014] As a further improvement of the above technical solution, the hydraulic system also includes a second on-off control unit arranged between the output end of the second load-sensing pump and the execution system, for controlling the on-off or flow direction between the output end of the second load-sensing pump and the execution system.

[0015] As a further improvement of the above technical solution, the execution system includes a low-pressure system, a steering system, a front lifting system and a rear lifting system. The first load-sensitive pump is connected to the rear lifting system via the first input oil circuit, and the second load-sensitive pump is connected to the low-pressure system and the flow priority valve respectively via the main input oil circuit. The priority channel of the flow priority valve is connected to the steering system, and the normal channel of the priority flow valve is connected to the front lifting system and the first input oil circuit respectively.

[0016] As a further improvement of the above technical solution, the execution system also includes a central tie rod cylinder, an accumulator, and a central tie rod main control valve core connected to the central tie rod cylinder. The first input oil circuit also supplies oil to the rodless chamber of the central tie rod cylinder through the central tie rod main control valve core, and the accumulator is connected to the rod chamber of the central tie rod cylinder.

[0017] As a further improvement of the above technical solution, the hydraulic system includes a first shuttle valve, a second shuttle valve, a third shuttle valve and a fourth shuttle valve arranged in the load feedback oil circuit, the load feedback end of the central tie rod cylinder is connected to the first oil inlet of the fourth shuttle valve, the load feedback end of the front lifting system is connected to the second oil inlet of the fourth shuttle valve, the working end of the fourth shuttle valve is connected to the first oil inlet of the first shuttle valve, the load feedback end of the steering system is connected to the first oil inlet of the second shuttle valve, the load feedback end of the front lifting is connected to the first oil inlet of the third shuttle valve, the second oil inlet of the third shuttle valve is connected to the return oil circuit, the working end of the third shuttle valve is connected to the second oil inlet of the second shuttle valve, the working end of the second shuttle valve is connected to the second oil inlet of the first shuttle valve, and the working end of the first shuttle valve is respectively connected to the load feedback end of the first load sensing valve and the load feedback end of the second load sensing valve.

[0018] As a further improvement of the above technical solution, the front lifting system includes a front lowering solenoid valve and a front lifting solenoid valve, and the rear lifting system includes a rear lifting cylinder, a rear lifting main control valve core and a proportional control valve group.

[0019] As a further improvement of the above technical solution, the pressure difference between the second load-sensitive pressure and the first load-sensitive pressure is ≥5 bar.

[0020] According to another aspect of the present invention, a control method is provided, which is applied to the above-mentioned hydraulic system. The hydraulic system also includes a controller, an engine speed sensor electrically connected to the controller, a transmission gear position sensor electrically connected to the controller, a vehicle speed sensor electrically connected to the controller, a steering sensor electrically connected to the controller, a rear suspension position sensor electrically connected to the controller, and a rear suspension position lift CAN electrically connected to the controller. The control method includes:

[0021] Set the plowshare width b, the number of plowshares z, the ground resistance coefficient k, and the plowshare depth H. The controller calculates the theoretical traction force F of the plow based on the plow's traction resistance formula. ll The controller obtains the current gear position signal D through the gearbox gear position sensor s , obtain the engine torque T through the engine speed sensor f , and according to the vehicle tire working diameter R, transmission speed ratio I s Calculate the actual vehicle output traction F s , calculate the current gear D respectively s Upper and lower gear positions D s- With D s+ Output traction force F s- With F s+ , combined with F s Contrast F ll ;

[0022] If F s+ >F s >F ll The controller sends a shift signal and a plowing depth adjustment command, and the rear suspension hydraulic lift CAN performs a lifting action, so that the proportional control valve group is energized, the rear lift main control valve core is actuated, and the load pressure is fed back to the first load-sensing valve and the second load-sensing valve, so that the first load-sensing pump and the second load-sensing pump match the output flow, so that the plowing depth H is matched and adjusted within the range of 0-5% according to the feedback signal from the rear suspension position sensor. After the execution is in place, the proportional control valve group loses power, the load pressure is fed back to the first load-sensing valve and the second load-sensing valve, and the first load-sensing pump and the second load-sensing pump stop outputting flow;

[0023] If F s >F ll , F s+ <F ll , maintain the current state;

[0024] If F s ≤F ll , F s- >F ll The controller sends a shift signal and a plowing depth adjustment instruction, the rear suspension hydraulic lift CAN executes the lifting action, the proportional control valve group is energized, the rear lift main control valve core is actuated, and the load pressure is fed back to the first load sensing valve and the second load sensing valve, so that the first load sensing pump and the second load sensing pump match the output flow, and the plowing depth H is matched and adjusted in the range of 0-5% according to the feedback signal of the rear suspension position sensor. After the execution is in place, the proportional control valve group loses power, the load pressure is fed back to the first load sensing valve and the second load sensing valve, and the first load sensing pump and the second load sensing pump stop outputting flow.

[0025] As a further improvement of the above technical solution, the control method also includes: if the controller detects a reverse gear signal fed back by the transmission sensor, the controller outputs a lifting signal, and the rear suspension hydraulic lifting CAN performs a lifting action; if the controller detects a steering output angle fed back by the steering sensor greater than 20°, the controller outputs a lifting signal, and the rear suspension hydraulic lifting CAN performs a lifting action.

[0026] The present invention has the following beneficial effects:

[0027] When the execution system has a flow demand, the load pressure demand is fed back to the first load sensing valve of the first load sensing pump and the second load sensing valve of the second load sensing pump through the load feedback oil circuit, so that the load feedback pressure acts on the first variable oil cylinder through the first load sensing valve to adjust the output flow of the first variable pump, and acts on the second variable oil cylinder through the second load sensing valve to adjust the output flow of the second variable pump. Since the set second load sensing pressure is greater than the first load sensing pressure, when the output flow of the second load sensing pump meets the flow demand of the execution system, the hydraulic oil pressure output by the second load sensing pump is greater than the hydraulic oil pressure output by the first load sensing pump. The pressure of the second load sensing pump acts on one end of the first on-off control unit through the input oil circuit of the execution system, and the output of the first load sensing pump The end is closed and the first load-sensing pump does not output flow; when the output flow of the second load-sensing pump cannot meet the flow demand of the execution system, the first on-off control unit is turned on, and the second load-sensing pump and the first load-sensing pump jointly output flow, and the combined flow of the two pumps matches the system flow demand; this hydraulic system is set up in parallel with two groups of load-sensing pump groups, and the output oil source is combined to achieve maximum demand supply, and can match the oil supply according to the actual flow demand, reduce system heat, and reduce energy consumption; by setting different load-sensitive pressures, the second load-sensing pump can be automatically matched to supply oil alone or the two pump groups together according to the system load pressure feedback, so that the oil supply flow matches the demand flow, reduces energy consumption loss, and effectively solves the problems of high energy consumption and high system heat when using constant flow pumps or gear pumps.

[0028] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0030] Figure 1 is a connection diagram of a hydraulic system according to a preferred embodiment of the present invention;

[0031] Figure 2This is a schematic diagram of a dual-pump output structure of a preferred embodiment of the present invention;

[0032] Figure 3 1 is a controller connection diagram of a preferred embodiment of the present invention.

[0033] Legend:

[0034] 100, low pressure system; 200, steering system; 300, front lifting system; 400, rear lifting cylinder; 500, central tie rod cylinder; 1, first oil suction filter; 2, first variable displacement pump; 3, first variable displacement cylinder; 4, first load sensing valve; 5, first high pressure filter; 6, first check valve; 7, second oil suction filter; 8, second variable displacement pump; 9, second variable displacement cylinder; 10, second load sensing valve; 11, second high pressure filter; 12, second check valve; 13, first shuttle valve; 14, first relief valve; 15, first pressure reducing relief valve; 16, second shuttle valve; 17, flow priority valve; 18, second relief valve; 19, front lowering solenoid valve; 20, first pressure compensation valve; 21, third shuttle valve; 22, front lifting solenoid valve; 23, third check valve; 24, third relief valve; 25, first proportional control valve Control valve; 26. Second proportional control valve; 29. ​​Fourth relief valve; 30. Second pressure reducing relief valve; 31. Emergency valve; 32. Fourth shuttle valve; 33. Hydraulic lock; 34. Rear lift main control valve core; 35. Second pressure compensation valve; 36. Fourth relief valve; 37. Return oil safety valve; 38. Radiator; 39. Air filter; 40. Hydraulic temperature display; 41. Liquid level switch; 42. Hydraulic oil temperature sensor; 43. Engine speed sensor; 44. Transmission gear position sensor; 45. Vehicle speed sensor; 46. Steering sensor; 47. Rear suspension position sensor; 48. Rear suspension position lift CAN; 49. Controller; P, main input oil circuit; P1, first input oil circuit; P2, second input oil circuit; P3, third input oil circuit; P4, fourth input oil circuit; LS, load feedback oil circuit; T, return oil circuit. DETAILED DESCRIPTION

[0035] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0036] Figure 1 is a connection diagram of a hydraulic system according to a preferred embodiment of the present invention; Figure 2 This is a schematic diagram of a dual-pump output structure of a preferred embodiment of the present invention; Figure 3 1 is a controller connection diagram of a preferred embodiment of the present invention.

[0037] like Figures 1 to 3 As shown, the hydraulic system of this embodiment is applied to a tractor and includes:

[0038] Oil tank, used to store and supply hydraulic oil;

[0039] The execution system is used to execute actions driven by hydraulic oil. The execution system has a load feedback oil circuit LS and an oil return oil circuit T connected to the oil tank;

[0040] A first load-sensing pump includes a first variable displacement pump 2, a first load-sensing valve 4, and a first variable displacement cylinder 3 connected to the first variable displacement pump 2. The first variable displacement pump 2 is connected to the oil tank and the actuator system, respectively, for inputting hydraulic oil to the actuator system. The input end of the first load-sensing valve 4 is connected to the first variable displacement pump 2, the load feedback end of the first load-sensing valve 4 is connected to the load feedback oil circuit LS of the actuator system, and the output end of the first load-sensing valve 4 is connected to the first variable displacement cylinder 3 for receiving the load feedback pressure of the actuator system and acting on the first variable displacement cylinder 3 to thereby adjust the output flow of the first variable displacement pump 2. The first load-sensing pump sets a first load-sensing pressure.

[0041] A second load-sensing pump includes a second variable displacement pump 8, a second load-sensing valve 10, and a second variable displacement cylinder 9 connected to the second variable displacement pump 8. The second variable displacement pump 8 is connected to the oil tank and the actuator system, respectively, for inputting hydraulic oil to the actuator system. The input end of the second load-sensing valve 10 is connected to the second variable displacement pump 8, the load feedback end of the second load-sensing valve 10 is connected to the load feedback oil circuit LS of the actuator system, and the output end of the second load-sensing valve 10 is connected to the second variable displacement cylinder 9 for receiving the load feedback pressure of the actuator system and acting on the second variable displacement cylinder 9 to thereby adjust the output flow of the second variable displacement pump 8. The second load-sensing pump sets a second load-sensing pressure, which is greater than the first load-sensing pressure.

[0042] The first on-off control unit is provided between the output end of the first load-sensing pump and the execution system, and is used to control the on-off or flow direction between the output end of the first load-sensing pump and the execution system.

[0043] The execution system includes a low-pressure system 100, a steering system 200, a front lifting system 300, and a rear lifting system;

[0044] The working principle of this hydraulic system:

[0045] When the execution system has a flow demand, the load pressure demand is fed back to the first load sensing valve 4 of the first load sensing pump and the second load sensing valve 10 of the second load sensing pump through the load feedback oil circuit LS, so that the load feedback pressure acts on the first variable oil cylinder 3 through the first load sensing valve 4 to adjust the output flow of the first variable pump 2, and acts on the second variable oil cylinder 9 through the second load sensing valve 10 to adjust the output flow of the second variable pump 8. Since the set second load sensing pressure is greater than the first load sensing pressure, when the output flow of the second load sensing pump meets the flow demand of the execution system, the hydraulic oil pressure output by the second load sensing pump is greater than the hydraulic oil pressure output by the first load sensing pump. The pressure of the second load sensing pump acts on one end of the first on-off control unit through the input oil circuit of the execution system, and the first load sensing pump The output end of the load-sensitive pump is closed and the first load-sensitive pump does not output flow; when the output flow of the second load-sensitive pump cannot meet the flow demand of the execution system, the first on-off control unit is turned on, and the second load-sensitive pump and the first load-sensitive pump jointly output flow, and the combined flow of the two pumps matches the system flow demand; this hydraulic system is set up in parallel with two groups of load-sensitive pump groups, and the output oil sources are combined to achieve maximum demand supply, and can match the oil supply according to the actual flow demand, reduce system heat, and reduce energy consumption; by setting different load-sensitive pressures, the second load-sensitive pump can be automatically matched to supply oil alone or the two pump groups can be automatically matched to supply oil together according to the system load pressure feedback, so that the oil supply flow matches the demand flow, reduces energy consumption loss, and effectively solves the problems of high energy consumption and high system heat when using constant flow pumps or gear pumps.

[0046] The first on-off control unit is preferably a first one-way valve 6. When a small flow demand occurs, the pressure of the second load-sensing pump is greater than the output pressure of the first load-sensing pump, and the pressure of the second load-sensing pump acts on the first one-way valve 6 to close it. When a large flow demand occurs, the actual demand flow exceeds the rated flow of the second load-sensing pump, and the output pressure of the second load-sensing pump is insufficient to keep the first one-way valve 6 closed. The first load-sensing pump outputs a differential flow under the action of the load-sensing valve and the first variable cylinder 3 regulating the first variable pump 2. The pressure difference between the second load-sensing pressure and the first load-sensing pressure is ≥5 bar.

[0047] It is understandable that the first on-off control unit may also be a solenoid valve with a locking function, which is electrically controlled to be on and off;

[0048] It can be understood that the displacement of the first load sensing pump is greater than the displacement of the second load sensing pump, and the displacement of the second load sensing pump is set to at least meet the requirements of the steering system 200 and the low-pressure system 100;

[0049] In this embodiment, the displacement of the second load-sensing pump is set to meet the needs of the steering system 200, the low-pressure system 100 and the front lifting system 300. The first load-sensing pump is connected to the rear lifting system via the first input oil circuit P1, and the second load-sensing pump is connected to the low-pressure system 100 and the flow priority valve 17 via the main input oil circuit P. The priority channel of the flow priority valve 17 is connected to the steering system 200, and the normal channel of the priority flow valve is connected to the third input oil circuit P3 and the first input oil circuit P1 via the second input oil circuit P2. The third input oil circuit P3 is connected to the front lifting system 300. By setting the flow priority valve 17, the output flow of the second load-sensing pump is preferentially supplied to the steering system 200 and the low-pressure system 100, and the excess flow is used to supply oil to the front lifting system 300, thereby ensuring a stable oil source for the steering system 200 and the low-pressure system 100. At the same time, compared with using a constant-flow pump or a gear pump, the energy consumption is low and the system heat generation is low.

[0050] In this embodiment, the hydraulic system also includes an emergency valve 31 arranged between the output end of the first load-sensing pump and the execution system. The output end of the second load-sensing pump is connected to the emergency channel of the emergency valve 31. When the second load-sensing pump fails and cannot output, the first load-sensing pump supplies oil to the low-pressure system 100 and the steering system 200 through the emergency valve 31 and the main input oil circuit P, ensuring that the steering system 200 and the low-pressure system 100 can still work normally in an emergency state. Compared with the single-pump system, it can effectively solve emergency problems; during emergency oil supply, the first load-sensing pump supplies oil to the low-pressure system 100 and the steering system 200 through the first input oil circuit P1, the fourth input oil circuit P4, and the second input oil circuit P2, and supplies oil to the forward lifting system 300 through the first input oil circuit P1, the fourth input oil circuit P4, and the third input oil circuit P3.

[0051] In this embodiment, the hydraulic system also includes a second on-off control unit arranged between the output end of the second load-sensing pump and the execution system, which is also located between the emergency channel of the emergency valve 31 and the output end of the second load-sensing pump, and is used to control the on-off or flow direction between the output end of the second load-sensing pump and the execution system. It can also be understood that the emergency channel of the emergency valve 31 is connected to the main input oil circuit P; when the first load-sensing pump supplies emergency oil to the main input oil circuit P, the second on-off control unit is used to prevent system impact; the second on-off control unit can be a second one-way valve 12 or a solenoid valve with a locking function.

[0052] In this embodiment, the execution system further includes a central tie rod cylinder 500, an accumulator, and a central tie rod main control valve core connected to the central tie rod cylinder 500. The first input oil circuit P1 also supplies oil to the rodless chamber of the central tie rod cylinder 500 via the central tie rod main control valve core. The accumulator is connected to the rod chamber of the central tie rod cylinder 500. By providing the central tie rod cylinder 500 and the accumulator, the mechanically adjusted central tie rod is improved to a telescopic cylinder coordinated with the accumulator for adjustment. This cushions the instantaneous impact force generated by the plow's swing during a mechanical U-turn, reduces steering control failure caused by vehicle pitching, reduces impact on the rear suspension structure and the rear suspension cylinder, and improves service life.

[0053] In this embodiment, the hydraulic system includes a first shuttle valve 13, a second shuttle valve 16, a third shuttle valve 21, and a fourth shuttle valve 32 provided in the load feedback oil circuit LS. The load feedback terminal of the central tie rod cylinder 500 is connected to the first oil inlet of the fourth shuttle valve 32, the load feedback terminal of the front lifting system 300 is connected to the second oil inlet of the fourth shuttle valve 32, the working end of the fourth shuttle valve 32 is connected to the first oil inlet of the first shuttle valve 13, the load feedback terminal of the steering system 200 is connected to the first oil inlet of the second shuttle valve 16, and the load feedback terminal of the front lifting is connected to the third shuttle valve. The first oil inlet of the valve 21 and the second oil inlet of the third shuttle valve 21 are connected to the return oil circuit T, the working end of the third shuttle valve 21 is connected to the second oil inlet of the second shuttle valve 16, the working end of the second shuttle valve 16 is connected to the second oil inlet of the first shuttle valve 13, and the working end of the first shuttle valve 13 is respectively connected to the load feedback end of the first load sensing valve 4 and the load feedback end of the second load sensing valve 10; by arranging each shuttle valve in the load feedback oil circuit LS to realize load feedback selection, the highest pressure signal is fed back to the first load sensing valve 4 and the second load sensing valve 10.

[0054] In this embodiment, the front lift system 300 includes a front lowering solenoid valve 19 and a front lifting solenoid valve 22 to respectively control the output to control the lifting or lowering of the front lift structure; the rear lift system includes a rear lift cylinder 400, a rear lift main control valve core 34 and a proportional control valve group, including a first proportional control valve 25 and a second proportional control valve 26;

[0055] In this embodiment, a first oil suction filter 1 is provided at the inlet end of the first load-sensitive pump, and a second oil suction filter 7 is provided at the inlet end of the second load-sensitive pump; a first high-pressure filter 5 is provided at the outlet end of the first load-sensitive pump, and a second high-pressure filter 11 is provided at the outlet end of the second load-sensitive pump; the low-pressure system 100 includes a first relief valve 14 and a first pressure-reducing relief valve 15; the front lifting system 300 is provided with a first pressure-compensating valve 20, and the rear lifting system is provided with a second pressure-compensating valve 35 to ensure that the system pressure is stable; a third one-way valve 23 is provided at the output end of the front lifting solenoid valve 22 to achieve pressure maintenance for the front lifting and ensure that the action execution is stable; a second relief valve 18 is provided between the output end of the third one-way valve 23 and the return oil circuit T as a pressure-maintaining safety valve for the front lifting; the rear lifting main control valve core 34 and the rear lifting cylinder A hydraulic lock 33 is provided between 400 for maintaining the pressure of the rear lifting cylinder 400, and a third relief valve 24 is provided between the output end of the hydraulic lock 33 and the return oil circuit T as a pressure-maintaining safety valve for the rear lifting; the hydraulic system is also provided with a second pressure-reducing relief valve 30 to stabilize the pressure of the pilot oil source, and a fourth relief valve 3629 is provided as a pilot oil source safety valve; a radiator 38 is provided on the return oil circuit T to dissipate heat for the hydraulic oil source and maintain the optimal working temperature; the return oil circuit T is provided with a fourth one-way valve in parallel with the radiator 38 as a return oil safety valve 37 to ensure the safety of heat dissipation and oil return; the oil tank is provided with an air filter 39, a hydraulic temperature display 40, a liquid level switch 41 and a hydraulic oil temperature sensor 42. The low liquid level system alarm is realized based on the liquid level switch 41, and the oil temperature monitoring and overheating alarm are realized based on the hydraulic oil temperature sensor 42.

[0056] In this embodiment, the hydraulic system further includes a controller 49, an engine speed sensor 43 electrically connected to the controller 49, a transmission gear position sensor 44 electrically connected to the controller 49, a vehicle speed sensor 45 electrically connected to the controller 49, a steering sensor 46 electrically connected to the controller 49, a rear suspension position sensor 47 electrically connected to the controller 49, and a rear suspension position lift CAN electrically connected to the controller 49;

[0057] On the other hand, this embodiment further provides a control method, which is applied to the above hydraulic system, including:

[0058] When the steering system 200 and the low-pressure system 100 are in operation, the steering system 200 feeds back load pressure via the load feedback oil circuit LS. This pressure is then applied to the first load-sensing valve 4 and the second load-sensing valve 10 via the second shuttle valve 16 and the first shuttle valve 13, regulating the output flow of the first variable cylinder 3 and the second variable cylinder 9. The two variable pumps output flow rates. At this point, the actual required flow rate is less than the rated flow rate of the second variable pump 8. The output pressure acts on the first check valve 6, and its output pressure is greater than the output pressure of the first variable pump 2. This keeps the first check valve 6 closed, and the second load-sensing pump supplies oil to the low-pressure system 100 and the steering system 200.

[0059] When the front lift system 300 and steering system 200 are operating, the operating flow is less than the rated flow of the second variable pump 8. Load feedback is transmitted through the second shuttle valve 16 and the third shuttle valve 21 to select the highest load pressure, which is fed back to the first load sensing valve 4 and the second load sensing valve 10 via the first shuttle valve 13. The two variable cylinders are adjusted, and thus the two variable pumps are regulated. At this time, the actual required flow is less than the rated flow of the second variable pump 8. The output pressure acts on the first check valve 6, and its output pressure is greater than the output pressure of the first variable pump 2, keeping the first check valve 6 closed. The flow is preferentially supplied to the low-pressure system 100 and the steering system 200 via the flow priority valve 17, and the excess flow is supplied to the front lift system 300.

[0060] When the front lifting system 300 and the rear lifting system are working at the same time, the front lifting solenoid valve 22 and the rear lifting main control valve core 34 work at the same time, the actual required flow is greater than the rated flow of the second load-sensing pump, and the load feedback signal selects the highest load pressure through the second shuttle valve 16, the third shuttle valve 21, and the fourth shuttle valve 32, and acts on the first load-sensing valve 4 and the second load-sensing valve 10 through the first shuttle valve 13. The actual required flow is greater than the rated flow of the second variable pump 8, and the flow required by the front lifting system 300 and the steering system 200 is less than the rated flow of the second variable pump 8. The first one-way valve 6 is opened, and the first variable pump 2 outputs flow to supply oil.

[0061] On the other hand, the control method also includes:

[0062] Set the plowshare width b, the number of plowshares z, the ground resistance coefficient k, and the plowshare depth H. The controller calculates the theoretical traction force F of the plow based on the plow's traction resistance formula. ll The controller obtains the current gear position signal D through the gearbox gear position sensor s , obtain the engine torque T through the engine speed sensor f , and according to the vehicle tire working diameter R, transmission speed ratio I s Calculate the actual vehicle output traction F s , calculate the current gear D respectively s Upper and lower gear positions D s- With D s+ Output traction force F s- With F s+ , combined with F s Contrast F ll ,

[0063] If F s+ >F s >F ll, the controller sends a shift signal and a plowing depth adjustment instruction, the rear suspension hydraulic lift CAN performs a lifting action, the proportional control valve group is energized, the rear lift main control valve core is actuated, the load pressure is fed back to the first load sensing valve and the second load sensing valve after selection by the shuttle valve, the first variable oil cylinder and the second variable oil cylinder match the action and adjust the first load sensing pump and the second load sensing pump to match the actual flow demand output flow, so that the plowing depth H is adjusted in the range of 0-5% according to the feedback signal of the rear suspension position sensor, the hydraulic lock is opened, and after the execution is in place, the proportional control valve group loses power, the load pressure is fed back to the first load sensing valve and the second load sensing valve after selection by the shuttle valve, the two variable oil cylinders perform action, and the first load sensing pump and the second load sensing pump stop outputting flow;

[0064] If F s >F ll , F s+ <F ll , maintain the current state, the controller part improves the shift operation, and the plow depth H is not adjusted;

[0065] If F s ≤F ll , F s- >F ll , the controller sends a shift signal and a plowing depth adjustment instruction, the rear suspension hydraulic lift CAN performs a lifting action, the proportional control valve group is energized, the rear lift main control valve core is actuated, and the load pressure is fed back to the first load sensing valve and the second load sensing valve after selection by the shuttle valve. The first variable oil cylinder and the second variable oil cylinder match the action adjustment so that the first load sensing pump and the second load sensing pump match the actual flow demand output flow, so that the plowing depth H is matched and adjusted in the range of 0-5% according to the feedback signal of the rear suspension position sensor, the hydraulic lock is opened, and after execution is in place, the proportional control valve group loses power, and the load pressure is fed back to the first load sensing valve and the second load sensing valve after selection by the shuttle valve. The two variable oil cylinders perform actions to stop the first load sensing pump and the second load sensing pump from outputting flow.

[0066] Furthermore, the control method further includes:

[0067] If the controller detects a reverse gear signal fed back by the transmission sensor, the controller outputs a lifting signal, and the rear suspension hydraulic lifting CAN performs a lifting action; specifically, the controller outputs a lifting signal, and the rear suspension hydraulic lifting CAN performs a lifting action, so that the proportional control valve group is energized, the rear lifting main control valve core is actuated, and the load pressure is fed back to the first load sensing valve and the second load sensing valve after selection by the shuttle valve, and the first variable oil cylinder and the second variable oil cylinder match and adjust the action so that the first load sensing pump and the second load sensing pump match the actual flow demand output flow, so that the plow depth H is matched and adjusted in the range of 0-5% according to the feedback signal of the rear suspension position sensor, and the hydraulic lock is opened; after the rear suspension position sensor detects that the plow is lifted to the highest set position, the proportional control valve group loses power, and the load pressure is fed back to the first load sensing valve and the second load sensing valve after selection by the shuttle valve, and the two variable oil cylinders perform an action so that the first load sensing pump and the second load sensing pump stop outputting flow;

[0068] If the vehicle makes a U-turn, the controller detects that the steering output angle fed back by the steering sensor is greater than 20°, the controller outputs a lifting signal, and the rear suspension hydraulic lifting CAN performs a lifting action; specifically, the controller outputs a lifting signal, the rear suspension hydraulic lifting CAN performs a lifting action, so that the proportional control valve group is energized, the rear lifting main control valve core is actuated, and the load pressure is fed back to the first load sensing valve and the second load sensing valve after selection by the shuttle valve, and the first variable oil cylinder and the second variable oil cylinder match and adjust the action so that the first load sensing pump and the second load sensing pump match the actual flow demand output flow, so that the plow depth H is matched and adjusted in the range of 0-5% according to the feedback signal of the rear suspension position sensor, and the hydraulic lock is opened; after the rear suspension position sensor detects that the plow is lifted to the highest set position, the proportional control valve group loses power, the load pressure is fed back to the first load sensing valve and the second load sensing valve after selection by the shuttle valve, and the two variable oil cylinders perform an action so that the first load sensing pump and the second load sensing pump stop outputting flow;

[0069] Among them, when the vehicle turns around at the end of the field, the plow will have load fluctuations when the vehicle moves forward and backward, and the accumulator will absorb energy and reduce shock, reducing the instantaneous impact force of the rear suspension mechanism and increasing the service life of the rear suspension structure. The balancing valve is used to maintain system pressure when the central tie rod cylinder is not moving, and to keep the cylinder extended smoothly when the central tie rod cylinder is extended to prevent the cylinder from stalling.

[0070] This control method is based on the calculation formula of the plow's traction resistance F ll=k*H*b*z. The theoretical traction resistance is calculated by setting plow parameters, plowing depth parameters, and the ground resistance system. The actual vehicle traction is calculated by obtaining parameters such as engine torque and speed, gear information, vehicle speed, and transmission ratio. The actual traction is compared with the traction resistance of the plow to calculate the actual ground resistance coefficient. The actual traction required by the plow is calculated based on the actual ground resistance system. A working gear or plowing depth adjustment indication signal is given based on the actual traction required by the plow. Closed-loop control is formed in conjunction with various sensors to ensure the tractor is at optimal working efficiency. This solves the problem that a single sensor cannot automatically adjust the plowing depth, and solves the problem that existing mechanical shift tractors cannot accurately match the traction resistance to adjust to the optimal gear.

[0071] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A hydraulic system, applied to a tractor, characterized in that: include: Oil tank, used to store and supply hydraulic oil; An execution system, configured to be driven by hydraulic oil to execute an action, the execution system comprising a load feedback oil circuit and an oil return oil circuit connected to an oil tank; A first load-sensing pump comprises a first variable pump (2), a first load-sensing valve (4), and a first variable oil cylinder (3) connected to the first variable pump (2); the first variable pump (2) is connected to the oil tank and the execution system respectively, and is used to input hydraulic oil to the execution system; the input end of the first load-sensing valve (4) is connected to the first variable pump (2), the load feedback end of the first load-sensing valve (4) is connected to the load feedback oil circuit of the execution system, the output end of the first load-sensing valve (4) is connected to the first variable oil cylinder (3), and is used to receive the load feedback pressure of the execution system and act on the first variable oil cylinder (3) to adjust the output flow of the first variable pump (2); the first load-sensing pump sets a first load-sensing pressure; A second load-sensing pump comprises a second variable pump (8), a second load-sensing valve (10), and a second variable oil cylinder (9) connected to the second variable pump (8); the second variable pump (8) is connected to the oil tank and the execution system respectively, and is used to input hydraulic oil to the execution system; the input end of the second load-sensing valve (10) is connected to the second variable pump (8), the load feedback end of the second load-sensing valve (10) is connected to the load feedback oil circuit of the execution system, the output end of the second load-sensing valve (10) is connected to the second variable oil cylinder (9), and is used to receive the load feedback pressure of the execution system and act on the second variable oil cylinder (9) to adjust the output flow of the second variable pump (8); the second load-sensing pump sets a second load-sensing pressure, and the second load-sensing pressure is greater than the first load-sensing pressure; A first on-off control unit is provided between the output end of the first load-sensing pump and the execution system, and is used to control the on-off or flow direction between the output end of the first load-sensing pump and the execution system; when the output flow of the second load-sensing pump meets the flow requirement of the execution system, the hydraulic oil pressure output by the second load-sensing pump is greater than the hydraulic oil pressure output by the first load-sensing pump, and the pressure of the second load-sensing pump acts on one end of the first on-off control unit through the input oil circuit of the execution system, the output end of the first load-sensing pump is closed, and the first load-sensing pump does not output flow; when the output flow of the second load-sensing pump cannot meet the flow requirement of the execution system, the first on-off control unit is turned on, and the second load-sensing pump and the first load-sensing pump jointly output flow, and the combined flow of the two pumps matches the system flow requirement; The execution system comprises a low-pressure system (100), a steering system (200), a front lifting system (300), and a rear lifting system; the first load-sensing pump is connected to the rear lifting system via a first input oil circuit; the second load-sensing pump is connected to the low-pressure system (100) and a flow priority valve (17) via a main input oil circuit; the priority channel of the flow priority valve (17) is connected to the steering system (200); and the normal channel of the flow priority valve is connected to the front lifting system (300) and the first input oil circuit; The execution system further comprises a central tie rod oil cylinder (500), an accumulator, and a central tie rod main control valve core connected to the central tie rod oil cylinder (500); the first input oil circuit also supplies oil to the rodless chamber of the central tie rod oil cylinder (500) via the central tie rod main control valve core; and the accumulator is connected to the rod chamber of the central tie rod oil cylinder (500); The hydraulic system comprises a first shuttle valve (13), a second shuttle valve (16), a third shuttle valve (21) and a fourth shuttle valve (32) arranged in the load feedback oil circuit; the load feedback terminal of the central tie rod oil cylinder (500) is connected to the first oil inlet of the fourth shuttle valve (32); the load feedback terminal of the front lifting system (300) is connected to the second oil inlet of the fourth shuttle valve (32); the working end of the fourth shuttle valve (32) is connected to the first oil inlet of the first shuttle valve (13); the load feedback terminal of the steering system (200) is connected to the second shuttle valve (32); The first oil inlet of the valve (16) is connected to the first oil inlet of the third shuttle valve (21), the load feedback end of the front lift is connected to the first oil inlet of the third shuttle valve (21), the second oil inlet of the third shuttle valve (21) is connected to the return oil circuit, the working end of the third shuttle valve (21) is connected to the second oil inlet of the second shuttle valve (16), the working end of the second shuttle valve (16) is connected to the second oil inlet of the first shuttle valve (13), and the working end of the first shuttle valve (13) is respectively connected to the load feedback end of the first load sensing valve (4) and the load feedback end of the second load sensing valve (10).

2. The hydraulic system according to claim 1, characterized in that The hydraulic system further comprises an emergency valve (31) arranged between the output end of the first load-sensing pump and the execution system, and the output end of the second load-sensing pump is connected to the emergency valve (31).

3. The hydraulic system according to claim 2, characterized in that The hydraulic system further includes a second on-off control unit disposed between the output end of the second load-sensing pump and the execution system, for controlling on-off or flow direction between the output end of the second load-sensing pump and the execution system.

4. The hydraulic system according to claim 1, characterized in that The front lifting system (300) includes a front lowering solenoid valve (19) and a front lifting solenoid valve (22), and the rear lifting system includes a rear lifting oil cylinder (400), a rear lifting main control valve core (34), and a proportional control valve group.

5. The hydraulic system according to any one of claims 1 to 3, characterized in that: The pressure difference between the second load-sensitive pressure and the first load-sensitive pressure is ≥5 bar.

6. A control method, characterized in that: Applied to the hydraulic system of claim 4, the hydraulic system further comprises a controller, an engine speed sensor electrically connected to the controller, a transmission gear position sensor electrically connected to the controller, a vehicle speed sensor electrically connected to the controller, a steering sensor electrically connected to the controller, a rear suspension position sensor electrically connected to the controller, and a rear suspension position lift CAN electrically connected to the controller, the control method comprising: Set the plowshare width b, the number of plowshares z, the ground resistance coefficient k, and the plowshare depth H. The controller calculates the theoretical traction force of the plow based on the plow's traction resistance formula. , the controller obtains the current gear position signal through the gearbox gear position sensor , obtain the engine torque through the engine speed sensor , and according to the vehicle tire working diameter R, transmission ratio Calculate the actual output traction of the vehicle , calculate the current gear respectively Two gears, upper and lower and Output traction and , combined with contrast ; like > The controller sends a shift signal and a plowing depth adjustment command, and the rear suspension hydraulic lift CAN executes the lifting action, so that the proportional control valve group is energized, the rear lift main control valve core is actuated, and the load pressure is fed back to the first load-sensing valve and the second load-sensing valve, so that the first load-sensing pump and the second load-sensing pump match the output flow, so that the plowing depth H is matched and adjusted within the range of 0-5% according to the feedback signal from the rear suspension position sensor. After the execution is in place, the proportional control valve group loses power, the load pressure is fed back to the first load-sensing valve and the second load-sensing valve, and the first load-sensing pump and the second load-sensing pump stop outputting flow; like > , , maintain the current state; like ≤ , The controller sends a shift signal and a plowing depth adjustment instruction, the rear suspension hydraulic lift CAN executes the lifting action, the proportional control valve group is energized, the rear lift main control valve core is actuated, and the load pressure is fed back to the first load sensing valve and the second load sensing valve, so that the first load sensing pump and the second load sensing pump match the output flow, and the plowing depth H is matched and adjusted in the range of 0-5% according to the feedback signal of the rear suspension position sensor. After the execution is in place, the proportional control valve group loses power, the load pressure is fed back to the first load sensing valve and the second load sensing valve, and the first load sensing pump and the second load sensing pump stop outputting flow.

7. The control method according to claim 6, characterized in that: The control method further includes: If the controller detects a reverse gear signal fed back by the transmission sensor, the controller outputs a lifting signal, and the rear suspension hydraulic lifting CAN performs a lifting action; If the controller detects that the steering output angle fed back by the steering sensor is greater than 20 degrees, the controller outputs a lifting signal, and the rear suspension hydraulic lifting CAN performs a lifting action.

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