An automatic shift system and a tractor

Abstract

The present invention relates to an automatic shifting system and a tractor. The system includes a pressure oil pipeline, an oil return pipeline, a lubricating oil pipeline, an oil return solenoid valve, a shifting control valve group, and at least two shifting cylinders; the oil inlet of the shifting control valve group is communicated with or disconnected from the pressure oil pipeline, the oil return port of the shifting control valve group is connected to the oil return solenoid valve, and the oil return solenoid valve is respectively communicated with the lubricating oil pipeline or the oil return pipeline; the shifting control valve group also has multiple branch pipes, and each shifting cylinder is respectively connected to two of the branch pipes. The system has the advantages of fast shifting speed, high precision, and simple system structure, etc.

Description

Technical Field

[0001] The present invention relates to the technology of a shifting system, and more particularly, to an automatic shifting system and a tractor. Background Art

[0002] With the continuous improvement of the economic level, users' requirements for the operating comfort and automation degree of tractors are also getting higher and higher, which leads to the fact that the traditional operating mode of a pull rod + flexible shaft can no longer meet the usage requirements. However, for a tractor with an electronically controlled mechanical automatic transmission (AMT), an electronically controlled system controls a shifting actuator to achieve automatic speed change, effectively improving the operating performance and automation level. The electronically controlled system of the AMT is the core to achieve high-quality shifting, mainly realizing clutch control and gear selection; the shifting actuator is a hydraulic component that controls the position of the shift fork to complete synchronizer shifting.

[0003] The existing electronically controlled hydraulic AMT control system uses a three-position four-way valve to control a single extending oil cylinder to achieve gear shifting, and cannot accurately control the neutral gear. Such a structure is prone to problems such as slow shifting response speed and low shifting accuracy; while a control system with high response speed and accuracy often requires complex pipeline and solenoid valve settings. Three to four solenoid valves are often required to control the shifting action of a shifting oil cylinder, which not only increases the cost but also is prone to failures.

[0004] The existing technology often uses a gear pump to supply pressure oil, which has certain power loss, large pressure pulsation, and the higher the speed, the greater the loss.

[0005] In addition, there are also problems in the existing shifting system that the gas in the oil reduces the stiffness and pollutes the system. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an automatic shifting system and a tractor.

[0007] The technical solution of the present invention to solve the above technical problems is as follows:

[0008] The present invention provides an automatic shifting system, including a pressure oil pipeline, a return oil pipeline, a lubricating oil pipeline, a return oil solenoid valve, a shifting control valve group, and at least two shifting oil cylinders; the oil inlet of the shifting control valve group is communicated with or disconnected from the pressure oil pipeline, the oil return port of the shifting control valve group is connected to the return oil solenoid valve, and the return oil solenoid valve is respectively communicated with the lubricating oil pipeline or the return oil pipeline; the shifting control valve group also has multiple branch pipes, and each shifting oil cylinder is respectively connected to two of the branch pipes.

[0009] The beneficial effects of the present invention are as follows. The present invention controls the connection state between the shift control valve group and the lubricating oil pipeline and the oil return pipeline through an oil return solenoid valve, which not only simplifies the pipeline arrangement of the shift system, but also ensures that when the shift cylinder maintains the first state of the gear position, the cooling oil in the lubricating oil pipeline can flow into the shift cylinder, so that the shift cylinder is always filled with oil. In this way, there is a certain pressure in the shift cylinder. In the second state of shifting gears, when the pressure oil enters, the maximum shift pressure can be quickly reached, realizing the rapidity and accuracy of the shifting process.

[0010] The present invention can also be realized through the following technical solutions:

[0011] Further, the shift control valve group includes at least four solenoid valves, each of which is respectively connected to the oil inlet or the oil return port; each solenoid valve is respectively connected to a branch pipe; a piston is arranged in each shift cylinder, and the piston divides the shift cylinder into two cavities, and each cavity is connected to a branch pipe.

[0012] The beneficial effect of adopting the above further technical solution is that each shift system is controlled only by two solenoid valves, further simplifying the system pipeline arrangement.

[0013] Further, each shift cylinder further includes a shift link assembly, the shift link assembly is fixedly connected to the piston, and the piston can drive the shift link assembly to move from one gear position to another gear position; a position sensor is fixedly installed on the shift link assembly; the automatic shift system further includes a shift controller, and the shift controller is electrically connected to each solenoid valve and each position sensor respectively.

[0014] The beneficial effect of adopting the above further technical solution is that by installing a position sensor on the shift link assembly of the shift cylinder, the position where it moves can be sensed; the shift controller is connected to the position sensor and the solenoid valve, and can control the energization and de-energization of the solenoid valve according to the position of the shift link assembly, so as to realize the precise control of the shifting process of the shift cylinder. At the same time, when the moving position deviates, it can be adjusted in time to prevent failures from affecting the operation of the tractor.

[0015] Further, it further includes an oil suction pipeline, a pressure control valve group and a transmission case; one end of the oil suction pipeline is connected to the transmission case, and the other end is connected to the pressure oil pipeline through the pressure control valve group; a variable pump is arranged on the oil suction pipeline; the oil return pipeline is connected to the transmission case.

[0016] The beneficial effect of adopting the above further technical solution is that by using a three-position three-way pressure control valve group to connect the oil suction pipeline and the pressure oil pipeline, the pressure value in the system can be maintained within a certain range, thereby further improving the shifting speed.

[0017] Further, an oil suction filter is provided between the transmission case and the variable pump.

[0018] The beneficial effect of adopting the above further technical solution is that: by using the oil suction filter to filter the oil in the transmission case first, large particle impurities in the oil can be prevented from contaminating the system.

[0019] Further, an accumulator is provided on the pressure oil pipeline, and the accumulator is located between the pressure control valve group and the shift control valve group.

[0020] The beneficial effect of adopting the above further technical solution is that: the accumulator is used to improve the response speed of the shift cylinder and absorb the pressure pulsation in the oil.

[0021] Further, a fine filter is provided on the pressure oil pipeline, and the fine filter is located between the pressure control valve group and the accumulator.

[0022] The beneficial effect of adopting the above further technical solution is that: using the fine filter can further filter out fine contaminants in the oil.

[0023] Further, one end of the lubricating oil pipeline is connected to the oil return solenoid valve, and the other end is connected to the oil suction pipeline. The connection position of the lubricating oil pipeline and the oil suction pipeline is located between the transmission case and the variable pump.

[0024] Further, a lubricating oil cooling pump is provided on the lubricating oil pipeline, and a throttle valve is provided on the lubricating oil pipeline between the lubricating oil cooling pump and the oil return solenoid valve.

[0025] The beneficial effect of adopting the above further technical solution is that: the throttle valve can control the amount of cooling oil entering the shift cylinder.

[0026] The present invention also provides a tractor, including the above automatic shift system. Description of the Drawings

[0027] Figure 1 It is a pipeline layout diagram of the automatic shift system of the present invention;

[0028] Figure 2 It is a pipeline layout diagram of the shift control valve group in the automatic shift system of the present invention.

[0029] In the drawings, the list of components represented by each reference numeral is as follows:

[0030] 1. Lubricating oil cooling system; 2. Priority valve; 3. Oil return solenoid valve; 4. Throttle valve; 5. Power source; 6. Variable pump; 7. Suction filter; 8. Transmission case; 9. Lubricating oil cooling pump; 10. First shift cylinder; 11. First shift shaft; 12. First displacement sensor; 13. First connecting rod; 14. Synchronizer group; 141. First gear position; 142. Second gear position; 143. Third gear position; 144. Fourth gear position; 15. First shift fork; 16. Second shift fork; 17. Second connecting rod; 18. Second shift shaft; 19. Second displacement sensor; 20. Second shift cylinder; 21. Shift controller; 22. Third shift cylinder; 23. Fourth shift cylinder; 24. Shift control valve group; 241. Oil inlet; 242. Oil return port; 243. Solenoid valve; 244. Branch pipe; 25. Accumulator; 26. Other control systems; 27. Fine filter; 28. Pressure control valve group; 29. Multi-way valve control system; 30. Steering system. Detailed implementation mode

[0031] The principles and features of the present invention will be described below in conjunction with the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0032] An automatic shifting system of the present invention includes a pressure oil pipeline, an oil return pipeline, a lubricating oil pipeline, an oil return solenoid valve 3, a shift control valve group 24, and at least two shift cylinders; the oil inlet 241 of the shift control valve group 24 is connected or disconnected from the pressure oil pipeline, the oil return port 242 of the shift control valve group 24 is connected to the oil return solenoid valve 3, and the oil return solenoid valve 3 is respectively connected to the lubricating oil pipeline or the oil return pipeline; the shift control valve group 24 also has a plurality of parallel branch pipes 244, and each shift cylinder is respectively connected to two branch pipes 244; the automatic shifting system has a first state and a second state, and the shift control valve group 24 and the oil return solenoid valve 3 are used to switch between the first state and the second state; the first state is that the oil return solenoid valve 3 is energized, and the oil return port 242 of the shift control valve group 24 is connected to the lubricating oil pipeline; in the first state, the solenoid valve 243 of the shift control valve group 24 cannot be energized, that is, shifting cannot be performed; the second state is that the oil return solenoid valve 3 is de-energized, and the oil return port 242 of the shift control valve group 24 is connected to the oil return pipeline; in the second state, the solenoid valve 243 of the shift control valve group 24 can be energized or de-energized to complete the shifting operation.

[0033] The present invention controls the connection states of the shift cylinder with the pressure oil pipeline, the lubricating oil pipeline, and the oil return pipeline through the oil return solenoid valve 3 and the shift control valve group 24, simplifying the pipeline arrangement of the shift system; in addition, in the first state where the shift cylinder holds the gear position, the cooling oil in the lubricating oil pipeline can flow into the shift cylinder, ensuring that the shift cylinder is always filled with oil. In this way, there is a certain pressure in the shift cylinder. In the second state of shifting gears, when the pressure oil enters, it can quickly reach the maximum shift pressure, achieving a rapid and accurate shifting process.

[0034] The oil supplied to the shift cylinder by the pressure oil pipeline and the lubricating oil pipeline of the present invention has a certain pressure, but the oil pressure in the lubricating oil pipeline is much lower than the minimum shift pressure. In the case where gear holding is required, the shift cylinder will not shift gears; while when shifting gears is needed, the oil supplied to the shift cylinder by the pressure oil pipeline has sufficient pressure to control the shift cylinder to shift gears.

[0035] In the above embodiment, preferably, the shift control valve group 24 includes at least four solenoid valves 243, each solenoid valve 243 is respectively connected to the oil inlet 241 or the oil return port 242; each solenoid valve 243 is respectively connected to an oil outlet branch pipe 244; a piston is provided in each shift cylinder, and the piston divides the shift cylinder into two cavities, and each cavity is connected to a branch pipe 244. In the first state, both cavities of each shift cylinder are connected to the lubricating oil pipeline through an oil outlet branch pipe 244 and a solenoid valve 243; in the second state, each of the above-mentioned cavities of each shift cylinder can be connected to the pressure oil pipeline or the oil return pipeline through an oil outlet branch pipe 244 and a solenoid valve 243; in this way, in the first state, a small amount of cooling oil flows into both cavities of the shift cylinder, and the pressure in the system is much lower than the minimum shift pressure, and the forces on both sides of the piston reach static equilibrium, so that shifting gears will not occur when gear holding is required; while in the second state, the shift cylinder is first connected to the oil return pipeline. After the solenoid valve 243 is powered on, the pressure oil flows into the corresponding cavity of the shift cylinder, causing the shift pressure in the system to quickly reach the maximum shift pressure and start shifting gears. At the same time, after the shifting is completed, the shift cylinder is disconnected from the pressure oil pipeline, and the oil return solenoid valve 3 is quickly powered on, connecting the shift cylinder to the lubricating oil pipeline to ensure that the shift cylinder is filled with oil. However, since the oil pressure is very small, the gear position after shifting is kept stable.

[0036] The automatic shift system of the present invention can control the action of one shift cylinder with only two solenoid valves 243, greatly simplifying the pipeline layout of the control system and the number of control devices, and having the characteristics of simplicity while ensuring a rapid and accurate shifting process.

[0037] The shift cylinder of the present invention includes a shift link assembly. The shift link assembly is fixedly connected to the piston in the shift cylinder and movably connected to the synchronizer group 14. Each shift link assembly has two gears on the synchronizer group 14, and the piston can drive the shift link assembly to move from one gear to another. A position sensor is fixedly installed on the shift link assembly, and the position sensor can sense the position of the shift link assembly.

[0038] The automatic shift system of the present invention further includes a shift controller 21. The shift controller 21 is electrically connected to each solenoid valve 243 and the oil return solenoid valve 3 in the shift control valve group 24 respectively to control the state switching thereof. The shift controller 21 is also electrically connected to the position sensor on the shift link assembly to sense the position information of the shift link assembly and control the specific states of each solenoid valve 243 and the oil return solenoid valve 3 according to the sensed position information. By using the shift controller 21, rapid and precise control of the shift process can be achieved. In addition, when the moving position of the shift link assembly deviates, the shift controller 21 can quickly sense and make real-time adjustment.

[0039] In the above embodiment, preferably, it further includes an oil suction pipeline, a pressure control valve group 28 and a transmission case 8. One end of the oil suction pipeline is communicated with the transmission case 8, and the other end is communicated with the pressure oil pipeline through the pressure control valve group 28. A variable pump 6 is provided on the oil suction pipeline. The oil return pipeline is communicated with the transmission case 8.

[0040] The port where the oil return pipeline is communicated with the transmission case 8 is located below the liquid level of the oil in the transmission case 8 to reduce the air that may be generated when the oil in the oil return pipeline flows back into the transmission case 8, thereby preventing the problem that air may exist when the oil in the transmission case 8 flows into the system again.

[0041] The pressure control valve group 28 includes a pressure valve and a pressure sensing device. Among them, the pressure valve is a three-way three-position valve, which has an open state, a partially open state and a closed state. In the open state and the partially open state, the oil flowing in from the oil suction pipeline flows into the shift control valve group 24, and the inflow stops in the closed state. A pressure sensing pipeline is communicated with the pressure valve, and the pressure sensing pipeline is directly communicated with the transmission case 8. One end of the pressure sensing device is communicated with the pressure oil pipeline, and the other end is communicated with the transmission case 8. In this way, the pressure sensing device can sense the pressure value on the pressure oil pipeline. The pressure sensing device compares the pressure it senses with the spring force on the left side of the pressure valve to switch the pressure valve among the three states. When the pressure value reaches the set value, part of the oil will flow back to the transmission case 8.

[0042] Preferably, the pressure control valve group 28 is also connected to a multi-way valve control system 29 and controls the multi-way valve control system 29, and the multi-way valve control system 29 is connected to other components in the tractor.

[0043] In a preferred embodiment of the present invention, when the shift control valve group 24 is disconnected from the pressure oil pipeline, the pressure oil will leak back to the transmission case 8 through a small amount of leakage on the solenoid valve 243. In this way, in the first state, the pressure on the pressure oil pipeline gradually decreases. As the pressure decreases, under the action of the left spring force, the pressure control valve group 28 switches from the closed state to the partially open state, enabling the pressure on the pressure oil pipeline to rise; in this way, it can ensure that the pressure in the pressure oil pipeline always remains within a certain range, further ensuring the pressure during shifting, thereby improving the shifting speed.

[0044] It should be noted that a small amount of leakage of the shift cylinder in the second state can ensure the formation of a complete oil film on the piston cylindrical surface of the shift cylinder, can greatly improve the response speed of the shift cylinder, and can discharge a small amount of gas in the shift cylinder from the cylinder.

[0045] In the above-mentioned embodiment, preferably, an oil suction filter 7 is provided between the transmission case 8 and the variable pump 6; the oil suction filter 7 can filter the oil in the transmission case 8.

[0046] In the above-mentioned embodiment, preferably, a priority valve 2 is provided between the variable pump 6 and the pressure control valve group 28; the priority valve 2 is connected to the steering system 30 through a pipeline; a small part of the oil supplied by the variable pump 6 is preferentially supplied to the steering system 30 for use through the priority valve 2, and the remaining part is transported to the pressure control valve group 28; the variable pump 6 can supply oil according to the requirements of the steering system 30 and the multi-way valve control system 29, thereby ensuring that each system and device can obtain sufficient oil.

[0047] In the above-mentioned embodiment, preferably, an accumulator 25 is connected to the pressure oil pipeline through a pipeline, and the accumulator 25 is located between the pressure control valve group 28 and the shift control valve group 24; the accumulator 25 is used to improve the response speed of the shift cylinder and absorb the pressure pulsation in the oil.

[0048] In the above-mentioned embodiment, preferably, a fine filter 27 is provided between the shift control valve group 24 and the accumulator 25; the fine filter 27 is used to filter the impurities in the pressure oil entering the shift control valve group 24 to ensure that the cleanliness of the pressure oil meets the system requirements.

[0049] In the above-mentioned embodiment, preferably, other control systems 26 are connected between the fine filter 27 and the accumulator 25 through a pipeline; more preferably, the other control systems 26 may include one or more of a clutch control system and a four-wheel drive, differential, and PTO / PTOB clutch control system.

[0050] In the above-mentioned embodiment, preferably, the lubricating oil pipeline is connected to the oil suction pipeline and the oil return solenoid valve 3, and the connection position between the lubricating oil pipeline and the oil suction pipeline is located between the transmission case 8 and the variable pump 6.

[0051] In the above embodiments, preferably, a lubricating oil cooling pump 9 is provided on the lubricating oil pipeline, and a throttle valve 4 is provided between the lubricating oil cooling pump 9 and the oil return solenoid valve 3; the lubricating oil cooling pump 9 can transport the oil in the transmission case 8 to the lubricating oil cooling system 1 and the oil return solenoid valve 3; the throttle valve 4 can control the flow rate of the oil flowing into the shift cylinder.

[0052] In the above embodiments, preferably, a lubricating oil cooling system 1 is further provided between the lubricating oil cooling pump 9 and the throttle valve 4, and the lubricating oil cooling system 1 is connected to the lubricating oil pipeline through a pipeline.

[0053] In the above embodiments, preferably, both the variable pump 6 and the lubricating oil cooling pump 9 are connected to the power source 5.

[0054] The present invention provides a tractor, including the above automatic shifting system.

[0055] The working process of the automatic shifting system of the present invention will be described below through an embodiment of the present invention, but the automatic shifting system of the present invention is not limited to the specific structure of this embodiment.

[0056] In the automatic shifting system of this embodiment, it includes four shift cylinders, namely the first shift cylinder 10, the second shift cylinder 20, the third shift cylinder 22 and the fourth shift cylinder 23; the shift control valve group 24 includes eight solenoid valves 243, a pipeline communicating with the pressure oil pipeline and a pipeline connecting to the oil return solenoid valve 3, and each solenoid valve 243 can control the cavity in the shift cylinder it is connected to to communicate or disconnect with a pipeline.

[0057] In this embodiment, the first shift cylinder 10 and the second shift cylinder 20 are a group, and the third shift cylinder 22 and the fourth shift cylinder 23 have the same control method as the first shift cylinder 10 and the second shift cylinder 20. Therefore, only the first shift cylinder 10 and the second shift cylinder 20 will be specifically described.

[0058] In this embodiment, the synchronizer group 14 has four gears, namely the first gear position 141, the second gear position 142, the third gear position 143 and the fourth gear position 144; among them, the first shift cylinder 10 corresponds to the first gear position 141 and the third gear position 143, and can be switched between the first gear position 141, the third gear position 143 and the neutral gear position between the two gears, and the second shift cylinder 20 corresponds to the second gear position 142 and the fourth gear position 144, and can be switched between the second gear position 142, the fourth gear position 144 and the neutral gear position between the two gears.

[0059] In this embodiment, the diameter of the left cavity of the piston of the shift oil cylinder is larger than that of the right cavity, and three oil ports are provided on the shift oil cylinder. Among them, the oil port on the left is the first oil port, the oil port on the right is the second oil port, and the oil port in the middle is the third oil port; the first oil port and the second oil port are respectively connected to a solenoid valve 243, and the piston of the shift oil cylinder can move between the first oil port and the second oil port; the third oil ports of the first shift oil cylinder 10 and the second shift oil cylinder 20 are both connected to the transmission case 8 (to make Figure 1 the pipeline layout diagram in clear and simple, the direct connection relationship between the first shift oil cylinder 10 and the second shift oil cylinder 20 and the transmission case 8 is not directly shown, but the device where the middle oil ports of the two are commonly connected in the figure is the transmission case 8, hereby explained).

[0060] The shift link assembly of the first shift oil cylinder 10 includes a piston rod, and the piston rod is sealed and passes through the first shift oil cylinder 10 and can axially move relative to the cylinder block; a piston is provided in the middle of the piston rod. One end of the piston rod is connected to one end of the first link 13 through the first shift shaft 11, the other end of the first link 13 is connected to one end of the first shift fork 15, and the other end of the first shift fork 15 is slidably connected to the synchronizer group 14; a first displacement sensor 12 is fixedly installed on the first shift shaft 11.

[0061] Similarly, the shift link assembly of the second shift oil cylinder 20 also includes a piston rod, and the piston rod is sealed and passes through the first shift oil cylinder 20 and can axially move relative to the cylinder block; a piston is provided in the middle of the piston rod. One end of the piston rod is connected to one end of the second link 17 through the second shift shaft 18, the other end of the second link 17 is connected to one end of the second shift fork 16, and the other end of the second shift fork 16 is slidably connected to the synchronizer group 14; a second displacement sensor 19 is fixedly installed on the second shift shaft 18.

[0062] In the above structure, the displacement sensor is used to ensure that the gear position is at the position required by the shift controller 21. If a certain shift oil cylinder deviates from the required position, the displacement sensor sends the deviation information to the shift controller 21, and the shift controller 21 issues an alarm and controls the tractor not to move.

[0063] The link and the shift shaft are fixed together by elastic pins, and the shift shaft and the shift fork are also connected by elastic pins. The connection method can also be the way of cooperation between the shaft shoulder and the retaining ring.

[0064] The specific working process of this embodiment is as follows:

[0065] Before shifting gears, the system is in the first state. The second shifting oil cylinder 20 is hooked at the second gear position 142 of the synchronizer group 14, and the first shifting oil cylinder 10 is at the neutral gear position between the first gear position 141 and the third gear position 143. At this time, the oil return solenoid valve 3 is in the energized state, and the solenoid valves 243 connected to the first shifting oil cylinder 10 and the second shifting oil cylinder 20 are both in the de-energized state. The two shifting oil cylinders are connected to the lubricating oil pipeline. Under the action of the throttle valve 4, both the left and right chambers of each shifting oil cylinder maintain a low-pressure and small-flow oil supply state; in such an oil supply state, the pressure in the system cannot achieve gear shifting, and the gear states of the shifting oil cylinders remain unchanged.

[0066] When the shift controller 21 determines that the shift requirement is met and it is necessary to shift from the second gear to the first gear, the system enters the second state. At this time, the clutch control system controls the clutch to disengage and disconnect the power of the engine. The shift controller 21 controls the oil return solenoid valve 3 to be de-energized, and controls the solenoid valve 243 connected to the left chamber of the second shifting oil cylinder 20 to be energized and the solenoid valve 243 connected to the right chamber of the second shifting oil cylinder 20 to be de-energized. In this way, the first oil port of the second shifting oil cylinder 20 supplies pressure oil, and the second oil port is depressurized. Under the push of the pressure oil, after the second shifting fork 16 overcomes the shifting resistance, it moves to the right together with the piston rod, the second shifting shaft 18, and the second connecting rod 17. When the moving amount reaches between 2 / 3 of the full stroke to the full stroke of the shift, the second displacement sensor 19 sends a position signal, and the shift controller 21 controls the two solenoid valves 243 to be energized simultaneously; at this time, both the first oil port and the second oil port of the second shifting oil cylinder 20 supply pressure oil. Since the diameter of the left chamber is larger than that of the right chamber, the piston rod, the second shifting shaft 18, the second connecting rod 17, and the second shifting fork 16 of the second shifting oil cylinder 20 continue to move to the right until the synchronizer is in the neutral state.

[0067] After the second shifting oil cylinder 20 is switched to the neutral gear, the second displacement sensor 19 sends a neutral gear in-place signal, and the shift controller 21 controls the two solenoid valves 243 of the second shifting oil cylinder 20 to be de-energized, disconnecting the second shifting oil cylinder 20 from the pressure oil pipeline and connecting it to the oil return pipeline. Both the first oil port and the second oil port of the second shifting oil cylinder 20 are depressurized.

[0068] After the second shift cylinder 20 has completed the switching, the shift controller 21 controls the solenoid valve 243 connected to the right chamber of the first shift cylinder 10 to be energized and the solenoid valve 243 communicating with the left chamber of the first shift cylinder 10 to be de-energized. At this time, the first oil port of the first shift cylinder 10 is depressurized, and the second oil port supplies pressure oil. Under the action of the pressure oil supplied by the second oil port, the piston pushes the first connecting rod 13, the first shift shaft 11, and the first shift fork 15 to move leftward simultaneously until the extreme position on the left side of the first shift cylinder 10, and gear shifting is performed. After the gear shifting is completed, the first displacement sensor 12 issues a signal indicating that the first gear is in place, and the shift controller 21 controls the two solenoid valves 243 connected to the first shift cylinder 10 to be de-energized, and the first oil port and the second oil port of the first shift cylinder 10 are depressurized simultaneously.

[0069] After the gear shifting is completed, the shift controller 21 controls the oil return solenoid valve 3 to be energized, and the lubricating oil pipeline communicates with each shift cylinder, continuing to ensure that the left and right cavities of each shift cylinder maintain a low-pressure oil supply state.

[0070] Meanwhile, the clutch control system controls the clutch to engage, and the power train connects to the power of the engine.

[0071] The automatic shift system of the present invention has the advantages of simple structure, fast shift response speed, and accurate shifting without deviation.

[0072] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "front", "rear", "left", "right", "inner", "outer", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is 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, and therefore should not be construed as a limitation of the present invention.

[0073] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0074] In the present invention, unless otherwise clearly specified or limited, a first feature being "on" or "under" a second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact via an intermediate medium. Moreover, a first feature being "above", "over" and "on top of" a second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the horizontal height of the first feature is higher than that of the second feature. A first feature being "under", "below" and "beneath" a second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the horizontal height of the first feature is less than that of the second feature.

[0075] In the description of the present specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In the present specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of different embodiments or examples.

[0076] In the description of the present invention, it should be noted that, unless otherwise clearly specified or limited, the terms "mounted", "connected" and "coupled" 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 a mechanical connection or an electrical 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.

[0077] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An automatic shifting system, characterized in that, It includes a pressure oil pipeline, a return oil pipeline, a lubricating oil pipeline, a return oil solenoid valve (3), a shift control valve group (24), and at least two shift cylinders; The oil inlet (241) of the shift control valve group (24) is communicated with or disconnected from the pressure oil pipeline. The oil return port (242) of the shift control valve group (24) is connected to the return oil solenoid valve (3), and the return oil solenoid valve (3) is respectively communicated with the lubricating oil pipeline or the return oil pipeline; The shift control valve group (24) also has multiple branch pipes (244), and each shift cylinder is respectively connected to two of the branch pipes (244); The shift control valve group (24) includes at least four shift solenoid valves (243); The automatic shift system also includes a shift controller (21), and the shift controller (21) is electrically connected to each of the shift solenoid valves (243) and the return oil solenoid valve (3); A lubricating oil cooling pump (9) is provided on the lubricating oil pipeline, and a throttle valve (4) is provided on the lubricating oil pipeline between the lubricating oil cooling pump (9) and the return oil solenoid valve (3); When the return oil solenoid valve (3) is in the energized state, under the action of the throttle valve (4), the left and right chambers of each shift cylinder simultaneously maintain a low-pressure and small-flow oil supply state; When the shift controller (21) determines that the shift requirement is met and the system enters the second state, the shift controller (21) controls the return oil solenoid valve (3) to be de-energized; After the shift is completed, the shift controller (21) controls the return oil solenoid valve (3) to be energized, and the lubricating oil pipeline is communicated with each shift cylinder, and continues to ensure that the left and right chambers of each shift cylinder maintain a low-pressure oil supply state.

2. The automatic shifting system according to claim 1, wherein Each shift solenoid valve (243) is respectively communicated with the oil inlet (241) or the oil return port (242); Each shift solenoid valve (243) is respectively connected to one of the branch pipes (244); A piston is provided in each shift cylinder, and the piston divides the shift cylinder into two chambers, and each chamber is communicated with one of the branch pipes (244).

3. The automatic shifting system according to claim 2, characterized in that, Each shift cylinder further includes a shift link assembly, the shift link assembly is fixedly connected to the piston, and the piston can drive the shift link assembly to move from one gear to another gear; A position sensor is fixedly installed on the shift link assembly; The shift controller (21) is electrically connected to each of the position sensors.

4. An automatic shifting system according to any one of claims 1 to 3, characterized in that, It also includes a suction oil pipeline, a pressure control valve group (28), and a transmission case (8); One end of the suction oil pipeline is communicated with the transmission case (8), and the other end is communicated with the pressure oil pipeline through the pressure control valve group (28); A variable pump (6) is provided on the suction oil pipeline; The return oil pipeline is communicated with the transmission case (8).

5. The automatic shifting system according to claim 4, wherein, An oil suction filter (7) is provided between the transmission case (8) and the variable pump (6).

6. The automatic shift system according to claim 4, characterized in that, An accumulator (25) is provided on the pressure oil pipeline, and the accumulator (25) is located between the pressure control valve group (28) and the shift control valve group (24).

7. The automatic shifting system according to claim 6, wherein A fine filter (27) is provided on the pressure oil pipeline, and the fine filter (27) is located between the pressure control valve group (28) and the accumulator (25).

8. The automatic shifting system according to claim 4, characterized in that, One end of the lubricating oil pipeline is communicated with the oil return solenoid valve (3), and the other end is communicated with the oil suction pipeline. The connection position of the lubricating oil pipeline and the oil suction pipeline is located between the transmission case (8) and the variable pump (6).

9. A tractor, characterized in that, It includes the automatic shifting system according to any one of claims 1-8.

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