阅读说明：本技术 一种自动换挡系统及拖拉机 (Automatic gear shifting system and tractor ) 是由 申屠军阳 付颜红 乔康 于 2021-09-07 设计创作，主要内容包括：本发明涉及一种自动换挡系统及拖拉机。该系统包括压力油管路、回油管路、润滑油管路、回油电磁阀、换挡控制阀组以及至少两个换挡油缸；所述换挡控制阀组的进油口与所述压力油管路连通或断开,所述换挡控制阀组的回油口与所述回油电磁阀连接,所述回油电磁阀分别与所述润滑油管路或所述回油管路连通；所述换挡控制阀组还具多条分支管,每个所述换挡油缸分别与两条所述分支管连接。该系统具有换挡过程速度快、精确度高、系统结构简单等优点。(The invention relates to an automatic gear shifting system and a tractor. The system comprises a pressure oil pipeline, an oil return pipeline, a lubricating oil pipeline, an oil return electromagnetic valve, a gear shifting control valve group and at least two gear shifting oil cylinders; an oil inlet of the gear shifting control valve group is communicated or disconnected with the pressure oil pipeline, an oil return port of the gear shifting control valve group is connected with the oil return electromagnetic valve, and the oil return electromagnetic valve is respectively communicated with the lubricating oil pipeline or the oil return pipeline; the gear shifting control valve group is also provided with a plurality of branch pipes, and each gear shifting oil cylinder is respectively connected with two branch pipes. The system has the advantages of high speed of the gear shifting process, high accuracy, simple system structure and the like.)

1. An automatic gear shifting system is characterized by comprising a pressure oil pipeline, an oil return pipeline, a lubricating oil pipeline, an oil return electromagnetic valve (3), a gear shifting control valve group (24) and at least two gear shifting oil cylinders;

an oil inlet (241) of the gear shifting control valve group (24) is communicated or disconnected with the pressure oil pipeline, an oil return port (242) of the gear shifting control valve group (24) is connected with the oil return electromagnetic valve (3), and the oil return electromagnetic valve (3) is respectively communicated with the lubricating oil pipeline or the oil return pipeline; the gear shifting control valve group (24) is further provided with a plurality of branch pipes (244), and each gear shifting oil cylinder is respectively connected with the two branch pipes (244).

2. An automatic gear shifting system according to claim 1, characterized in that said shift control valve group (24) comprises at least four solenoid valves (243), each of said solenoid valves (243) being in communication with said oil inlet (241) or said oil return (242), respectively; each electromagnetic valve (243) is respectively connected with one branch pipe (244);

and a piston is arranged in each gear shifting oil cylinder, the piston divides the gear shifting oil cylinder into two cavities, and each cavity is communicated with one branch pipe (244).

3. The automatic shifting system of claim 2, wherein each of the shift cylinders further comprises a shift link assembly, the shift link assembly being fixedly coupled to the piston, the piston moving the shift link assembly from one gear to another gear;

a position sensor is fixedly arranged on the gear shifting connecting rod assembly;

the automatic gear shifting system further comprises a gear shifting controller (21), and the gear shifting controller (21) is electrically connected with each electromagnetic valve (243) and each position sensor respectively.

4. An automatic gear shift system according to any one of claims 1 to 3, characterized by further comprising an oil suction line, 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 of the oil suction pipeline is communicated with the pressure oil pipeline through the pressure control valve group (28); the oil suction pipeline is provided with a variable pump (6);

the oil return pipeline is communicated with the transmission case (8).

5. An automatic gear shift system according to claim 4, characterized in that an oil suction filter (7) is provided between the transmission case (8) and the variable displacement pump (6).

6. An automatic gear shift system according to claim 4, characterized in that an accumulator (25) is arranged on the pressure oil line, the accumulator (25) being located between the pressure control valve block (28) and the shift control valve block (24).

7. An automatic gear shift system according to claim 6, characterized in that a fine filter (27) is arranged in the pressure oil line, said fine filter (27) being located between the pressure control valve block (28) and the accumulator (25).

8. An automatic gear shift system according to claim 4, characterized in that one end of the lubricating oil line is connected to the oil return solenoid valve (3) and the other end is connected to the oil suction line, and the connecting position of the lubricating oil line and the oil suction line is between the transmission case (8) and the variable displacement pump (6).

9. An automatic gear shift system according to claim 8, characterized in that a lubricant cooling pump (9) is provided on the lubricant line, and a throttle valve (4) is provided on the lubricant line between the lubricant cooling pump (9) and the oil return solenoid valve (3).

10. A tractor characterized by comprising an automatic gear shift system according to any one of claims 1 to 9.

Technical Field

The invention relates to the technology of gear shifting systems, in particular to an automatic gear shifting system and a tractor.

Background

Along with the continuous improvement of the economic level, the requirements of users on the operation comfort and the automation degree of the tractor are higher and higher, so that the traditional operation mode of the pull rod and the flexible shaft cannot meet the use requirements. However, an electric control mechanical automatic transmission (AMT) for the tractor realizes automatic speed change by controlling a gear shifting actuating mechanism through an electric control system, and effectively improves the operating performance and the automation level. An AMT electric control system is the core for realizing high-quality gear shifting and mainly realizes clutch control and gear selection; the gear shifting executing mechanism is a hydraulic element which controls the position of a shifting fork to complete gear shifting of a synchronizer.

The conventional electric control hydraulic AMT control system adopts a three-position four-way valve to control a single extending oil cylinder to realize gear shifting, can not realize accurate control of neutral gear, and easily has the problems of low gear shifting response speed and low gear shifting accuracy due to the structure; the control system with high response speed and high accuracy usually needs complicated pipelines and electromagnetic valves, and one gear shifting oil cylinder usually needs three to four electromagnetic valves to control gear shifting actions, so that the cost is increased, and faults are easy to occur.

In the prior art, pressure oil is supplied by a gear pump, certain power loss exists, pressure pulsation is large, and the loss is larger when the rotating speed is higher.

In addition, the gear shifting system in the prior art also has the problems that gas exists in oil to cause rigidity reduction and system pollution.

Disclosure of Invention

The invention aims to solve the technical problem of providing an automatic gear shifting system and a tractor.

The technical scheme for solving the technical problems is as follows:

the invention provides an automatic gear shifting system which comprises a pressure oil pipeline, an oil return pipeline, a lubricating oil pipeline, an oil return electromagnetic valve, a gear shifting control valve group and at least two gear shifting oil cylinders, wherein the pressure oil pipeline is connected with the oil return pipeline; an oil inlet of the gear shifting control valve group is communicated or disconnected with the pressure oil pipeline, an oil return port of the gear shifting control valve group is connected with the oil return electromagnetic valve, and the oil return electromagnetic valve is respectively communicated with the lubricating oil pipeline or the oil return pipeline; the gear shifting control valve group is also provided with a plurality of branch pipes, and each gear shifting oil cylinder is respectively connected with two branch pipes.

The invention has the advantages that the connection state of the gear shifting control valve group, the lubricating oil pipeline and the oil return pipeline is controlled by the oil return electromagnetic valve, so that the pipeline arrangement of a gear shifting system is simplified, and meanwhile, the cooling oil in the lubricating oil pipeline can flow into the gear shifting oil cylinder to enable the gear shifting oil cylinder to be filled with the oil all the time when the gear shifting oil cylinder keeps a gear position in a first state, so that the gear shifting oil cylinder has certain pressure, and the maximum gear shifting pressure can be quickly reached after the pressure oil enters in a second state for gear shifting, and the gear shifting process is quick and accurate.

The invention can also be realized by the following technical scheme:

further, the gear shifting control valve group comprises at least four electromagnetic valves, and each electromagnetic valve is respectively communicated with the oil inlet or the oil return port; each electromagnetic valve is respectively connected with one branch pipe; and a piston is arranged in each gear shifting oil cylinder, the piston divides the gear shifting oil cylinder into two cavities, and each cavity is communicated with one branch pipe.

The beneficial effect of adopting the further technical scheme is that: each gear shifting system is controlled by only two solenoid valves, and the system pipeline arrangement is further simplified.

Furthermore, each gear shifting oil cylinder also comprises a gear shifting connecting rod assembly, the gear shifting connecting rod assembly is fixedly connected with the piston, and the piston can drive the gear shifting connecting rod assembly to move from one gear to the other gear; a position sensor is fixedly arranged on the gear shifting connecting rod assembly; the automatic gear shifting system further comprises a gear shifting controller, and the gear shifting controller is electrically connected with each electromagnetic valve and each position sensor respectively.

The beneficial effect of adopting the further technical scheme is that: the shifting position of the shifting oil cylinder can be sensed by mounting a position sensor on a shifting connecting rod assembly of the shifting oil cylinder; the gear shifting controller is connected with the position sensor and the electromagnetic valve, and can control the power on and power off of the electromagnetic valve according to the position of the gear shifting connecting rod assembly, so that the gear shifting process of the gear shifting oil cylinder can be accurately controlled, and meanwhile, when the shifting position deviates, the gear shifting controller can be timely adjusted, and the tractor is prevented from being influenced by faults.

Further, the device also comprises an oil suction pipeline, a pressure control valve group and a transmission case; one end of the oil suction pipeline is communicated with the transmission case, and the other end of the oil suction pipeline is communicated with the pressure oil pipeline through the pressure control valve group; the oil suction pipeline is provided with a variable pump; the oil return pipeline is communicated with the transmission case.

The beneficial effect of adopting the further technical scheme is that: the three-position three-way pressure control valve set is adopted to communicate the oil suction pipeline and the pressure oil pipeline, so that the pressure value in the system can be kept within a certain range, and the gear shifting speed is further improved.

Further, an oil absorption filter is arranged between the transmission case and the variable pump.

The beneficial effect of adopting the further technical scheme is that: the oil suction filter is adopted to filter oil in the transmission case, so that the system can be prevented from being polluted by large-particle impurities in the oil.

Furthermore, an energy accumulator is arranged on the pressure oil pipeline and is positioned between the pressure control valve group and the gear shifting control valve group.

The beneficial effect of adopting the further technical scheme is that: the energy accumulator is used for improving the response speed of the gear shifting oil cylinder and absorbing pressure pulsation in oil.

Furthermore, a fine filter is arranged on the pressure oil pipeline and is positioned between the pressure control valve bank and the energy accumulator.

The beneficial effect of adopting the further technical scheme is that: fine pollutants in the oil can be further filtered by adopting the fine filter.

Furthermore, one end of the lubricating oil pipeline is communicated with the oil return electromagnetic valve, the other end of the lubricating oil pipeline is communicated with the oil suction pipeline, and the communication position of the lubricating oil pipeline and the oil suction pipeline is located between the transmission case and the variable displacement pump.

Further, be equipped with the lubricating oil cooling pump on the lubricated oil pipe way, the lubricating oil cooling pump with between the oil return solenoid valve be equipped with the choke valve on the lubricated oil pipe way.

The beneficial effect of adopting the further technical scheme is that: the throttle valve can control the oil mass that the cooling oil got into the hydro-cylinder of shifting.

The invention also provides a tractor comprising the automatic gear shifting system.

Drawings

FIG. 1 is a piping layout of the automatic shifting system of the present invention;

fig. 2 is a piping layout diagram of a shift control valve assembly in the automatic shift system of the present invention.

In the drawings, the components represented by the respective reference numerals are listed below:

1. a lubricating oil cooling system; 2. a priority valve; 3. an oil return electromagnetic valve; 4. a throttle valve; 5. a power source; 6. a variable displacement pump; 7. an oil absorption filter; 8. a transmission case; 9. a lubricating oil cooling pump; 10. a first shift cylinder; 11. a first shift shaft; 12. a first displacement sensor; 13. a first link; 14. a synchronizer group; 141. a first gear position; 142. a second gear position; 143. a third gear position; 144. a fourth gear position; 15. a first shift fork; 16. a second shift fork; 17. a second link; 18. a second shift shaft; 19. a second displacement sensor; 20. a second shift cylinder; 21. a shift controller; 22. a third shift cylinder; 23. a fourth shift cylinder; 24. a shift control valve group; 241. an oil inlet; 242. an oil return port; 243. an electromagnetic valve; 244. a branch pipe; 25. an accumulator; 26. other control systems; 27. a fine filter; 28. a pressure control valve group; 29. a multi-way valve control system; 30. a steering system.

Detailed Description

The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.

The invention relates to an automatic gear shifting system which comprises a pressure oil pipeline, an oil return pipeline, a lubricating oil pipeline, an oil return electromagnetic valve 3, a gear shifting control valve group 24 and at least two gear shifting oil cylinders, wherein the pressure oil pipeline is connected with the oil return pipeline through a pipeline; an oil inlet 241 of the gear shifting control valve group 24 is communicated or disconnected with a pressure oil pipeline, an oil return port 242 of the gear shifting control valve group 24 is connected with an oil return electromagnetic valve 3, and the oil return electromagnetic valve 3 is respectively communicated with a lubricating oil pipeline or an oil return pipeline; the shift control valve assembly 24 further has a plurality of branch pipes 244 connected in parallel, and each shift cylinder is connected to two branch pipes 244 respectively; the automatic gear shifting system has a first state and a second state, and the gear shifting control valve group 24 and the oil return electromagnetic valve 3 are used for switching the first state and the second state; in the first state, the oil return electromagnetic valve 3 is powered on, and the oil return port 242 of the gear shift control valve group 24 is connected with the lubricating oil pipeline; in the first state, solenoid valve 243 of shift control valve group 24 cannot be energized, i.e., shifting is not possible; in the second state, the oil return solenoid valve 3 is powered off, and the oil return port 242 of the gear shift control valve group 24 is connected with an oil return pipeline; in the second state, solenoid valve 243 of shift control valve assembly 24 may be energized or de-energized to complete the shifting action.

According to the invention, the connection state of the gear shifting oil cylinder with the pressure oil pipeline, the lubricating oil pipeline and the oil return pipeline is controlled through the oil return electromagnetic valve 3 and the gear shifting control valve group 24, so that the pipeline arrangement of a gear shifting system is simplified; in addition, under the first state that the gear shifting oil cylinder keeps a gear, cooling oil in the lubricating oil pipeline can flow into the gear shifting oil cylinder to enable the gear shifting oil cylinder to be filled with oil all the time, so that the gear shifting oil cylinder has certain pressure, and under the second state that gear shifting is carried out, the pressure oil can quickly reach the maximum gear shifting pressure after entering, and the gear shifting process is quick and accurate.

According to the invention, oil liquid input to the gear shifting oil cylinder by the pressure oil pipeline and the lubricating oil pipeline has certain pressure, but the oil liquid pressure in the lubricating oil pipeline is far lower than the minimum gear shifting pressure, and the gear shifting oil cylinder cannot shift gears under the condition of maintaining gears; when gear shifting is needed, the oil supplied to the gear shifting oil cylinder by the pressure oil pipeline has enough pressure, and the gear shifting oil cylinder can be controlled to shift gears.

In the above embodiment, preferably, the shift control valve assembly 24 includes at least four solenoid valves 243, and each solenoid valve 243 is respectively communicated with the oil inlet 241 or the oil return 242; each solenoid valve 243 is connected with one oil outlet branch pipe 244; a piston is arranged in each gear shifting oil cylinder, the piston divides the gear shifting oil cylinder into two cavities, and each cavity is communicated with one branch pipe 244. In the first state, two cavities of each shift cylinder are communicated with the lubricating oil pipeline through a branch pipe 244 and an electromagnetic valve 243; in the second state, each cavity of each shift cylinder can be communicated with the pressure oil pipeline or the oil return pipeline through a branch pipe 244 and an electromagnetic valve 243; therefore, in the first state, a small amount of cooling oil flows into the two cavities of the gear shifting oil cylinder, the pressure in the system is far lower than the minimum gear shifting pressure, and the two sides of the piston are stressed to achieve static balance so that gear shifting cannot be carried out under the condition that gears are required to be kept; in the second state, the shifting cylinder is firstly communicated with the oil return pipeline, after the electromagnetic valve 243 is powered on, pressure oil flows into the cavity of the corresponding shifting cylinder, so that the shifting pressure in the system rapidly reaches the maximum shifting pressure, shifting is started, meanwhile, after the shifting is finished, the shifting cylinder is disconnected from the pressure oil pipeline, the oil return electromagnetic valve 3 is rapidly powered on, the shifting cylinder is communicated with the lubricating oil pipeline, the shifting cylinder is fully filled with oil, but the oil pressure is very small, so that the shifted gear is kept stable.

The automatic gear shifting system can control the action of one gear shifting oil cylinder only by the two electromagnetic valves 243, greatly simplifies the pipeline arrangement of the control system and the number of control devices, and has the characteristic of simplicity under the condition of ensuring the gear shifting process to be rapid and accurate.

The gear shifting oil cylinder comprises a gear shifting connecting rod component, wherein the gear shifting connecting rod component is fixedly connected with a piston in the gear shifting oil cylinder and movably connected with a synchronizer group 14; each shifting connection assembly has two gears on the synchronizer group 14, and the piston can drive the shifting connection rod assembly to move from one gear to the other gear; a position sensor is fixedly arranged on the gear shifting connecting rod assembly and can sense the position of the gear shifting connecting rod assembly.

The automatic gear shifting system of the invention also comprises a gear shifting controller 21, wherein the gear shifting controller 21 is respectively electrically connected with each electromagnetic valve 243 and the oil return electromagnetic valve 3 in the gear shifting control valve group 24 so as to control the state switching of the electromagnetic valves; the shift controller 21 is also electrically connected to a position sensor on the shift connection assembly, so as to sense the position information of the shift connection 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 adopting the gear shifting controller 21, the gear shifting process can be controlled quickly and accurately; in addition, the shift controller 21 can quickly sense and make real-time adjustments when the shift linkage assembly is misaligned.

In the above embodiment, preferably, the oil suction pipe, the pressure control valve group 28 and the transmission case 8 are further included; one end of the oil suction pipeline is communicated with the transmission case 8, and the other end of the oil suction pipeline is communicated with the pressure oil pipeline through a pressure control valve group 28; the oil suction pipeline is provided with a variable pump 6; the oil return line is communicated with the transmission case 8.

The port of the oil return pipeline communicated with the transmission box 8 is positioned below the liquid level of oil in the transmission box 8, so that air possibly generated when the oil in the oil return pipeline flows back into the transmission box 8 is reduced, and the problem that air possibly exists when the oil in the transmission box 8 flows into the system again is solved.

The pressure control valve set 28 comprises a pressure valve and a pressure sensing device, wherein the pressure valve is a three-way three-position valve and has an opening state, a partially opening state and a closing state; in the open state and in the partially open state, the oil entering from the oil suction line flows into the shift control valve block 24, and stops flowing in the closed state. A pressure sensing pipeline is communicated with the pressure valve and 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 of the pressure sensing device is communicated with the transmission case 8, so that the pressure sensing device can sense the pressure value on the pressure oil pipeline. The pressure sensing device compares the sensed pressure with the left spring force of the pressure valve, so that the pressure valve is switched among three states, and when the pressure value reaches a set value, part of oil flows back to the transmission case 8.

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

In a preferred embodiment of the present invention, when the shift control valve assembly 24 is disconnected from the pressure oil line, the pressure oil will leak back to the transmission case 8 through a small amount of the solenoid valve 243, so that the pressure on the pressure oil line gradually decreases in the first state, and as the pressure decreases, the pressure control valve assembly 28 is switched from the closed state to the partially open state under the action of the left spring force, so that the pressure on the pressure oil line can rise; therefore, the pressure in the pressure oil pipeline can be always kept in a certain range, the pressure during gear shifting is further ensured, and the gear shifting speed is improved.

It should be noted that a small amount of leakage of the shift cylinder in the second state can ensure that the cylindrical surface of the piston of the shift cylinder forms a complete oil film, the response speed of the shift cylinder can be greatly improved, and a small amount of gas in the shift cylinder can be discharged out of the cylinder.

In the above embodiment, preferably, an oil suction filter 7 is arranged between the transmission case 8 and the variable displacement pump 6; the oil suction filter 7 can filter oil in the transmission case 8.

In the above embodiment, preferably, a priority valve 2 is provided between the variable displacement pump 6 and the pressure control valve group 28, and the priority valve 2 is connected to the steering system 30 through a pipeline; a small part of oil supplied by the variable pump 6 is preferentially supplied to a steering system 30 through the priority valve 2, and the rest part of oil is conveyed to the pressure control valve group 28; the variable displacement pump 6 can supply oil according to the requirements of the steering system 30 and the multi-way valve control system 29, so that all systems and devices can obtain enough oil.

In the above embodiment, preferably, the pressure oil pipeline is connected to the accumulator 25 through a pipeline, and the accumulator 25 is located between the pressure control valve set 28 and the shift control valve set 24; the accumulator 25 is used to increase the response speed of the shift cylinder and absorb pressure pulsation in the oil.

In the above embodiment, preferably, a fine filter 27 is disposed between the shift control valve set 24 and the accumulator 25; the fine filter 27 is used for filtering impurities of the pressure oil entering the gear shifting control valve group 24, and the cleanliness of the pressure oil is ensured to meet the system requirement.

In the above embodiment, preferably, the fine filter 27 and the accumulator 25 are communicated with another control system 26 through a pipeline; further preferably, the other control systems 26 may include one or more of a clutch control system and a four-drive, differential, and PTO/PTOB clutch control system.

In the above embodiment, preferably, the lubricating oil pipeline is communicated with the oil suction pipeline and the oil return electromagnetic valve 3, and a communication position of the lubricating oil pipeline and the oil suction pipeline is located between the transmission case 8 and the variable displacement pump 6.

In the above embodiment, preferably, the lubricating oil pipeline is provided with a lubricating oil cooling pump 9, and a throttle valve 4 is arranged between the lubricating oil cooling pump 9 and the oil return electromagnetic valve 3; the lubricating oil cooling pump 9 can convey oil in the transmission case 8 to the lubricating oil cooling system 1 and the oil return electromagnetic valve 3; the throttle valve 4 can control the flow rate of the oil flowing into the shift cylinder.

In the above embodiment, preferably, the 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 and the lubricating oil pipeline are communicated through a pipeline.

In the above embodiment, it is preferable that both the variable displacement pump 6 and the lubricating oil cooling pump 9 are connected to the power source 5.

The invention provides a tractor which comprises the automatic gear shifting system.

The operation of the automatic shifting system of the present invention will be described below by way of an embodiment of the present invention, but the automatic shifting system of the present invention is not limited to the specific structure of the embodiment.

The automatic gear shifting system of the present embodiment includes four gear shifting cylinders, which are a first gear shifting cylinder 10, a second gear shifting cylinder 20, a third gear shifting cylinder 22, and a fourth gear shifting cylinder 23; the shift control valve group 24 comprises eight electromagnetic valves 243, a pipeline communicated with the pressure oil pipeline and a pipeline connected with the oil return electromagnetic valve 3, and each electromagnetic valve 243 can control a cavity in a shift oil cylinder connected with the electromagnetic valve to be communicated or disconnected with one pipeline.

In this embodiment, the first shift cylinder 10 and the second shift cylinder 20 are a set, and the third shift cylinder 22 and the fourth shift cylinder 23 have the same control manner as the first shift cylinder 10 and the second shift cylinder 20, and therefore, only the first shift cylinder 10 and the second shift cylinder 20 will be specifically described.

In this embodiment, the synchronizer group 14 has four gears, which are a first gear position 141, a second gear position 142, a third gear position 143, and a fourth gear position 144; 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 a neutral gear 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 between the two gears.

In the embodiment, the diameter of a left cavity of a piston of the gear shifting oil cylinder is larger than that of a right cavity, and three oil ports are formed in the gear shifting oil cylinder, wherein the oil port on the left side is a first oil port, the oil port on the right side is a second oil port, and the oil port in the middle is a third oil port; the first oil port and the second oil port are respectively connected with an electromagnetic valve 243, and a piston of the shift cylinder can move between the first oil port and the second oil port; the third oil ports of the first shift cylinder 10 and the second shift cylinder 20 are both communicated with the transmission case 8 (for the purpose of simplifying and clarity the pipeline layout in fig. 1, the direct communication relationship between the first shift cylinder 10 and the transmission case 8 and the second shift cylinder 20 are not directly shown, but the device in which the intermediate oil ports of the two are communicated together is the transmission case 8, and thus the description is given here).

The gear shifting connecting rod assembly of the first gear shifting oil cylinder 10 comprises a piston rod, and the piston rod is hermetically arranged on the first gear shifting oil cylinder 10 in a penetrating mode and can axially move relative to the cylinder body; the middle part of the piston rod is provided with a piston. One end of the piston rod is connected with one end of a first connecting rod 13 through a first gear shifting shaft 11, the other end of the first connecting rod 13 is connected with one end of a first gear shifting fork 15, and the other end of the first gear shifting fork 15 is slidably connected with a synchronizer group 14; a first displacement sensor 12 is fixedly mounted on the first shift shaft 11.

Similarly, the shift link assembly of the second shift cylinder 20 also includes a piston rod, and the piston rod is hermetically inserted into the first shift cylinder 20 and can axially move relative to the cylinder body; the middle part of the piston rod is provided with a piston. One end of the piston rod is connected with one end of a second connecting rod 17 through a second shift shaft 18, the other end of the second connecting rod 17 is connected with one end of a second shift fork 16, and the other end of the second shift fork 16 is slidably connected with the synchronizer group 14; a second displacement sensor 19 is fixedly mounted on the second shift shaft 18.

In the structure, the displacement sensor is used for ensuring that the gears are located at the position required by the gear shifting controller 21, if a certain gear shifting oil cylinder deviates from the required position, the displacement sensor sends deviation information to the gear shifting controller 21, and the gear shifting controller 21 gives an alarm and controls the tractor to be incapable of walking.

The connecting rod and the gear shifting shaft are fixed together through the elastic pin, the gear shifting shaft and the gear shifting fork are also connected together through the elastic pin, and the connecting mode can also be a mode that a shaft shoulder is matched with the check ring.

The specific working process of this embodiment is as follows:

before the gear shift, the system is in the first state, the second shift cylinder 20 is engaged in the second gear position 142 of the synchronizer group 14, and the first shift cylinder 10 is in the neutral gear between the first gear position 141 and the third gear position 143. At this time, the oil return electromagnetic valve 3 is in a power-on state, the electromagnetic valves 243 connected to the first shift oil cylinder 10 and the second shift oil cylinder 20 are in a power-off state, the two shift oil cylinders are communicated with the lubricating oil pipeline, and under the action of the throttle valve 4, the left cavity and the right cavity of each shift oil cylinder are simultaneously kept in a low-pressure small-flow oil supply state; under the oil supply state, the pressure in the system can not realize gear shifting, and the gear state of each gear shifting oil cylinder is unchanged.

When the shift controller 21 determines that the shift request is satisfied and a shift from second gear to first gear is required, the system enters the second state. At this time, the clutch control system controls the clutch to be disengaged, and disconnects the power of the engine. The gear shifting controller 21 controls the oil return electromagnetic valve 3 to be powered off, and controls the electromagnetic valve 243 communicated with the left cavity of the second gear shifting cylinder 20 to be powered on and the electromagnetic valve 243 communicated with the right cavity of the second gear shifting cylinder 20 to be powered off, so that the first oil port of the second gear shifting cylinder 20 is supplied with pressure oil, the second oil port is decompressed, under the pushing of the pressure oil, the second gear shifting fork 16, after overcoming the gear shifting resistance, moves rightwards together with the piston rod, the second gear shifting shaft 18 and the second connecting rod 17, when the movement amount reaches between the full stroke and the full stroke of the gear shifting 2/3, the second displacement sensor 19 sends a position signal, and the gear shifting controller 21 controls the two electromagnetic valves 243 to be powered on simultaneously; at this time, the first oil port and the second oil port of the second shift cylinder 20 are simultaneously supplied with pressure oil, and because the diameter of the left cavity is larger than that of the right cavity, the piston rod of the second shift cylinder 20, the second shift shaft 18, the second connecting rod 17 and the second shift fork 16 continue to move rightward until the synchronizer is in a neutral state.

When the second shift cylinder 20 is switched to the neutral position, the second displacement sensor 19 sends a neutral position signal, the shift controller 21 controls the two electromagnetic valves 243 of the second shift cylinder 20 to be powered off, so that the second shift cylinder 20 is disconnected from the pressure oil pipeline and communicated with the oil return pipeline, and the first oil port and the second oil port of the second shift cylinder 20 are simultaneously depressurized.

After the second shifting cylinder 20 is switched, the shifting controller 21 controls the electromagnetic valve 243 connected with the right cavity of the first shifting cylinder 10 to be powered on, and the electromagnetic valve 243 communicated with the left cavity of the first shifting cylinder 10 to be powered off, at this time, the first oil port of the first shifting cylinder 10 is decompressed, the second oil port is supplied with pressure oil, and the piston pushes the first connecting rod 13, the first shifting shaft 11 and the first shifting fork 15 to move leftwards at the same time under the action of the pressure oil provided by the second oil port until the left limit position of the first shifting cylinder 10 is reached, and the shifting is engaged; after the gear is engaged, the first displacement sensor 12 sends a first gear in-place signal, the gear shift controller 21 controls the two electromagnetic valves 243 connected with the first gear shift cylinder 10 to lose power, and the first oil port and the second oil port of the first gear shift cylinder 10 release pressure simultaneously.

After gear shifting is completed, the gear shifting controller 21 controls the oil return electromagnetic valve 3 to be electrified, the lubricating oil pipeline is communicated with each gear shifting oil cylinder, and the left cavity and the right cavity of each gear shifting oil cylinder are continuously guaranteed to be in a low-pressure oil supply state.

Meanwhile, the clutch control system controls the clutch to be combined, and the transmission system is connected with the power of the engine.

The automatic gear shifting system has the advantages of simple structure, high gear shifting response speed and accuracy in gear shifting, and is not easy to deviate.

In the description of the present invention, it should be noted that the terms "front", "rear", "left", "right", "inner", "outer", "axial", "radial", "circumferential", etc., indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.