Power shift tractor axle housing hydraulic system

Abstract

The application discloses a power shift tractor axle box hydraulic system, comprising: a lifting system oil pump and a filtering system connected with a lubricating circuit and a power shift control circuit; the power shift control circuit is connected with an AMT auxiliary box control circuit and a rear axle and PTO control circuit; the lubricating circuit lubricates a power shift gearbox in the power shift control circuit, an AMT auxiliary box in the AMT auxiliary box control circuit and a wet clutch, a bearing, a gear and a spline in the rear axle and PTO control circuit; the power shift control circuit provides system pressure, controls a power shift clutch and a four-wheel drive clutch to form a gear; the AMT auxiliary box control circuit controls a synchronizer in the AMT auxiliary box to realize gear shifting operation and controls a climbing gear synchronizer to realize climbing gear; and the rear axle and PTO control circuit controls a rear axle differential lock and a PTO gear shift and provides large-flow lubrication when a brake works. The application realizes gear shifting function by controlling different clutch combinations, and power of the power shift tractor is not interrupted during gear shifting.

Description

Technical Field

[0001] This invention belongs to the field of gearbox technology and relates to a hydraulic system for a power shift tractor axle box. Background Technology

[0002] The gearbox is a core component of a tractor, and its performance significantly impacts the tractor's power, operating efficiency, and economy. Traditional tractors use gearboxes with meshing sleeves or synchronizers, achieving gear shifting through complex mechanical transmissions. Most existing tractor gearboxes require power interruption during gear changes, resulting in low shifting efficiency and negatively impacting operational productivity. Summary of the Invention

[0003] The purpose of this invention is to solve the problem that in the prior art, tractor gearboxes often require power to be cut off when shifting gears, resulting in low shifting efficiency, and to provide a hydraulic system for the axle box of a power shift tractor.

[0004] To achieve the above objectives, the present invention employs the following technical solution:

[0005] A hydraulic system for a power shift tractor axle housing includes: a lifting system oil pump and filtration system, a power shift control circuit, an AMT auxiliary gearbox control circuit, a rear axle and PTO control circuit, and a lubrication circuit;

[0006] The lifting system oil pump and filtration system are connected to the lubrication circuit and the power shift control circuit; the lifting system oil pump and filtration system are externally connected to the vehicle lifting system; the lifting system oil pump and filtration system supply oil to the vehicle lifting system; the power shift control circuit is connected to the AMT auxiliary gearbox control circuit and the rear axle and PTO control circuit; the lubrication circuit lubricates the power shift gearbox in the power shift control circuit, the AMT auxiliary gearbox in the AMT auxiliary gearbox control circuit, and the wet clutch, bearings, gears, and splines in the rear axle and PTO control circuit.

[0007] A further improvement of the present invention is that:

[0008] Furthermore, the lifting system oil pump and filtration system includes: a lifting pump, a first coarse filter, a first bypass valve, an oil tank, and a reserved interface; the reserved interface is located on the lifting pump, which is connected to the oil tank, and the reserved interface is externally connected to the vehicle lifting system; the first coarse filter is located on the oil line connecting the lifting pump and the oil tank, and the first bypass valve is located between the lifting pump and the oil tank, and is connected in parallel with the first coarse filter; the first coarse filter filters impurities in the oil in the oil tank; when the first coarse filter is blocked, the oil in the oil tank enters the lifting pump through the first bypass valve, and the lifting pump draws oil from the oil tank and enters the vehicle lifting system through the reserved interface.

[0009] Furthermore, the power shift control circuit includes: a system gear pump, a fine filter, an accumulator, a clutch control valve, a main pressure regulating valve, a clutch control valve, a four-wheel drive clutch control valve, and a reserved interface for the brake booster cylinder; the system gear pump is connected to the oil tank and the accumulator 12 respectively; a fine filter is installed on the oil line between the system gear pump 6 and the accumulator; the inlet of the cold start valve is externally connected to the oil line between the system gear pump and the fine filter; the outlet of the cold start valve is externally connected to the oil tank; the accumulator is connected to the main pressure regulating valve; several clutches are installed between the accumulator and the main pressure regulating valve. The clutch control valve is connected to the oil tank, and several clutch control valves are connected to the main pressure regulating valve. One main pressure regulating valve is connected to the lubrication circuit, and the other is connected in sequence to the clutch control valve, the brake booster cylinder reserved interface, and the four-wheel drive clutch control valve. Both the clutch control valve and the four-wheel drive clutch control valve are externally connected to the oil tank. The brake booster cylinder reserved interface is externally connected to the brake booster cylinder. The outlet branch of the four-wheel drive clutch control valve is set, one of which is connected to the AMT auxiliary gearbox control circuit, and the other is connected to the rear axle and PTO control circuit.

[0010] Furthermore, the system gear pump and accumulator oil circuit are equipped with a sensor and a second bypass valve; the sensor, the second bypass valve and the fine filter are connected in parallel; the sensor monitors whether the fine filter is clogged, and if it is clogged, it will remind the user to replace the fine filter; if it is not replaced in time, when the pressure reaches the set pressure of the second bypass valve, the second bypass valve will open and the oil will directly enter the lubrication circuit.

[0011] Furthermore, the clutch control valve is externally connected to the clutch piston chamber, and the clutch control valve is an electromagnetic proportional pressure reducing valve; the electromagnetic proportional pressure reducing valve is a two-position three-way connecting valve, and the A port of the clutch control valve is connected to the clutch piston chamber; the P port of the clutch control valve is connected to the oil circuit of the accumulator and the main pressure regulating valve; the T port of the clutch control valve is connected to the oil tank; when the clutch control valve is energized, the oil in the oil circuit of the accumulator and the main pressure regulating valve enters the clutch control valve through the P port, and then enters the clutch piston chamber through the A port of the clutch control valve, causing the clutch to engage; when the clutch control valve is de-energized, the oil in the piston chamber returns to the oil tank through the T port of the clutch control valve; the main pressure regulating valve is a valve core type oil drain logic element; both the clutch control valve and the four-wheel drive clutch control valve are externally connected to their respective clutch piston chambers, and the A port of the clutch control valve is connected to the clutch piston chamber of the clutch control valve; the P port of the clutch control valve... The main pressure regulating valve's inlet is connected to the oil inlet; the clutch control valve's T-port is connected to the oil tank; the four-wheel drive clutch control valve's A-port is connected to the clutch piston chamber of the four-wheel drive clutch control valve; the four-wheel drive clutch control valve's P-port is connected to the main pressure regulating valve's inlet; the four-wheel drive clutch control valve's T-port is connected to the oil tank. When the clutch control valve and the four-wheel drive clutch control valve are energized, the oil passing through the main pressure regulating valve's inlet enters the clutch control valve and the four-wheel drive clutch control valve respectively; the oil entering the clutch control valve enters the clutch piston chamber of the clutch control valve through the clutch control valve's A-port; the oil entering the four-wheel drive clutch control valve enters the clutch piston chamber of the four-wheel drive clutch control valve through the four-wheel drive clutch control valve's A-port, disengaging the clutch; when not energized, the oil in the clutch piston chamber of the clutch control valve and the oil in the clutch piston chamber of the clutch control valve return to the oil tank through their respective T-ports.

[0012] Furthermore, the AMT auxiliary gearbox control circuit includes: a shift control valve; one outlet of the four-wheel drive clutch control valve is connected to the inlet of the shift control valve; several synchronizer control valves are sequentially arranged between the four-wheel drive clutch control valve and the shift control valve; the outlets of the shift control valve and the synchronizer control valve are both connected to the oil tank; the P port of the synchronizer control valve is connected to one outlet of the four-wheel drive clutch control valve; the A port of the synchronizer control valve is connected to the shift shaft piston chamber and the selector shaft piston chamber respectively; the shift shaft piston chamber and the selector shaft piston chamber are respectively connected to the synchronizer via shift forks; the T port of the synchronizer control valve is connected to the oil tank.

[0013] The synchronizer control valve includes: a first synchronizer control valve, a second synchronizer control valve, a third synchronizer control valve, and a fourth synchronizer control valve;

[0014] The first synchronizer control valve and the second synchronizer control valve are gear selection valves. Port A of the first synchronizer control valve and the second synchronizer control valve are respectively connected to the piston chamber of the gear selection shaft. The third synchronizer control valve and the fourth synchronizer control valve are gear shifting valves. Port A of the third synchronizer control valve and the fourth synchronizer control valve are respectively connected to the piston chamber of the gear shifting shaft.

[0015] Both the gear selector shaft and the gear shift shaft have 5 gears, of which gears 1 and 2 are low gears; gears 3 and 4 are medium gears; and gear 5 is a high gear.

[0016] When the vehicle starts, the first synchronizer control valve and the second synchronizer control valve are energized simultaneously, and the gear selector shaft is in the middle gear position;

[0017] When the first synchronizer control valve is energized and the second synchronizer control valve is de-energized, the gear selector shaft is in the low gear position.

[0018] When the second synchronizer control valve is energized and the first synchronizer control valve is de-energized, the gear selector shaft is in the high gear position.

[0019] When the vehicle starts, the third synchronizer control valve and the fourth synchronizer control valve are energized simultaneously, and the shift shaft is in the neutral position. When the third synchronizer control valve is energized and the fourth synchronizer control valve is not energized, the vehicle shifts to a lower gear. When the fourth synchronizer control valve is energized and the third synchronizer control valve is not energized, the vehicle shifts to a higher gear.

[0020] When it is necessary to engage first gear, first control the first synchronizer control valve to select the lower gear, and then control the third synchronizer control valve to switch to the lower gear.

[0021] When it is necessary to engage second gear, first control the first synchronizer control valve to select the lower gear, and then control the fourth synchronizer control valve to switch to the higher gear.

[0022] When it is necessary to engage third gear, the gear selector valve does not operate, and the control valve of the third synchronizer is energized to switch to a lower gear.

[0023] When fourth gear is needed, the gear selector valve does not operate, and the control valve of the third synchronizer is energized to switch to a lower gear.

[0024] When it is necessary to engage the fifth gear, first energize the second synchronizer control valve to select the higher gear, and then energize the third synchronizer control valve to switch to the lower gear.

[0025] Furthermore, the gear shift control valve is a two-position four-way valve; the gear shift control valve is connected to the driving gear piston chamber and the gear shift piston chamber respectively; the driving gear piston chamber and the gear shift piston chamber are connected to the synchronizer through the shift fork respectively; when not energized, oil enters the driving gear piston chamber through the gear shift control valve, pushing the shift fork to move the synchronizer to form the driving gear; when energized, oil enters the gear shift piston chamber through the gear shift control valve, pushing the shift fork to move the synchronizer to form the gear shift.

[0026] Furthermore, the rear axle and PTO control circuit includes: a differential lock valve, a PTO main clutch valve, a front axle differential lock control interface, and a PTO shift valve; another outlet of the four-wheel drive clutch control valve is connected in sequence to the differential lock valve, the PTO main clutch valve, and the PTO shift valve. There are several PTO shift valves. The outlets of the differential lock valve, the PTO main clutch valve, and the PTO shift valve are all externally connected to the oil tank 1. The front axle differential lock control interface is located on the differential lock valve.

[0027] The A port of the differential lock valve is connected to the differential lock piston chamber; the P port of the differential lock valve is connected to the other outlet of the four-wheel drive clutch control valve; the T port of the differential lock valve is connected to the oil tank.

[0028] The PTO main clutch valve is externally connected to the PTO clutch piston chamber; the A port of the PTO main clutch valve is connected to the PTO clutch piston chamber; the P port of the PTO main clutch valve is connected to the other outlet of the four-wheel drive clutch control valve; the T port of the PTO main clutch valve is connected to the oil tank.

[0029] The PTO shift valve is connected to the piston chamber of the external PTO shift lever; the A port of the PTO shift valve is connected to the piston chamber of the PTO shift lever; the P port of the PTO shift valve is connected to the other outlet of the four-wheel drive clutch control valve; and the T port of the PTO shift valve is connected to the oil tank.

[0030] Furthermore, the lubrication circuit includes a lubrication gear pump, a second coarse filter, a heat exchanger, a temperature-controlled bypass valve, a lubrication pressure control valve, a brake lubrication shut-off valve, a power shift master gearbox lubrication circuit, an AMT auxiliary gearbox lubrication circuit, a PTO and rear axle lubrication circuit, and a brake lubrication circuit. A second coarse filter and a third bypass valve are installed on the oil line between the system gear pump and the oil tank, and the second coarse filter and the third bypass valve are connected in parallel. The outlet of the second coarse filter is connected to the inlet of the lubrication gear pump, and the outlet of the lubrication gear pump is simultaneously connected to the inlet of the heat exchanger and the inlet of the temperature-controlled bypass valve. The outlet of the heat exchanger is sequentially connected to the outlet of the temperature-controlled bypass valve and the outlet of the main pressure regulating valve. A lubrication pressure control valve and a power shift master gearbox lubrication circuit are installed between the outlet of the heat exchanger and the outlet of the main pressure regulating valve. The power shift master gearbox lubrication circuit is connected to the oil outlet of the main pressure regulating valve. The outlet of the lubrication pressure control valve is sequentially connected to the inlet of the AMT auxiliary gearbox lubrication circuit, the inlet of the PTO and rear axle lubrication circuit, and the inlet of the brake lubrication shut-off valve. The outlet of the brake lubrication shut-off valve is connected to the brake lubrication circuit.

[0031] Furthermore, the lubrication gear pump, system gear pump, and lifting pump are all connected to the same external drive, and the speeds of the lubrication gear pump, system gear pump, and lifting pump are the same.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This invention supplies oil to the entire vehicle lifting system via a lifting system oil pump and filtration system. The lubrication circuit lubricates the power shift transmission in the power shift control circuit, the AMT auxiliary gearbox in the AMT auxiliary gearbox control circuit, and the wet clutches, bearings, gears, and splines in the rear axle and PTO control circuits. The power shift control circuit provides system pressure and controls the power shift clutch and four-wheel drive clutch to form gears. The AMT auxiliary gearbox control circuit controls the synchronizer inside the AMT auxiliary gearbox to achieve gear shifting operations and controls the shift synchronizer to achieve shifting. The rear axle and PTO control circuit controls the rear axle differential lock and PTO shifting, and provides high-flow lubrication when the brakes are engaged. This invention achieves gear shifting functionality through different clutch combinations, ensuring uninterrupted power delivery during gear shifting in the power shift tractor.

[0034] Furthermore, this invention incorporates an accumulator in the system circuit to ensure stable system pressure; the valve core-type oil drain logic element serves as the main pressure regulating valve, ensuring smooth shifting and stable pressure; the clutch control valve employs proportional control, resulting in rapid pressure reduction, smooth gear shifting, and fast pressure release; the coarse and fine filter clogging alarm design and the high-reliability filtration system design ensure stable system operation; the auxiliary hydraulic system uses a shared oil tank design, simplifying the structure; this invention offers advantages such as high operating efficiency, high fuel efficiency, comfortable operation, and low failure rate. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the hydraulic system structure of the power shift tractor axle box of the present invention;

[0037] Figure 2 This is a schematic diagram of the gear selection shaft and gear shift shaft.

[0038] Among them, 1-oil tank; 2-first coarse filter; 3-second coarse filter; 4-lifting pump; 5-lubrication pump; 6-system gear pump; 7-cold start valve; 8-heat exchanger; 9-temperature control bypass valve; 10-fine filter; 11-lubrication pressure control valve; 12-accumulator; 13-first clutch control valve; 14-second clutch control valve; 15-third clutch control valve; 16-fourth clutch control valve; 17-fifth clutch control valve; 18-main pressure regulating valve; 19-power shift master gearbox lubrication circuit; 20-clutch control valve; 21-fourth drive clutch control valve; 22-brake booster cylinder interface; 23-first Synchronizer control valve; 24-Second synchronizer control valve; 25-Third synchronizer control valve; 26-Fourth synchronizer control valve; 27-Gear shift control valve; 28-AMT auxiliary gearbox lubrication circuit; 29-PTO clutch control valve; 30-Differential lock valve; 31-First PTO gear position control valve; 32-Second PTO gear position control valve; 33-Third PTO gear position control valve; 34-Front axle differential lock control interface; 35-Brake lubrication cut-off valve; 36-PTO and rear axle lubrication circuit; 37-Brake lubrication circuit; 38-Reserved interface; 39-First bypass valve; 40-Second bypass valve; 41-Third bypass valve. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0040] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0041] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0042] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0043] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0044] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0045] The present invention will now be described in further detail with reference to the accompanying drawings:

[0046] See Figure 1 and Figure 2 This invention discloses a hydraulic system for a power shift tractor axle housing, comprising: a lifting system oil pump and filtration system, a power shift control circuit, an AMT auxiliary gearbox control circuit, a rear axle and PTO control circuit, and a lubrication circuit;

[0047] The lifting system oil pump and filtration system are connected to the lubrication circuit and the power shift control circuit; the power shift control circuit is connected to the AMT auxiliary gearbox control circuit and the rear axle and PTO control circuit; the lifting system oil pump and filtration system are externally connected to the vehicle lifting system; the lifting system oil pump and filtration system supplies oil to the externally connected vehicle lifting system; the lubrication circuit lubricates the wet clutches, bearings, gears, and splines in the power shift transmission, AMT auxiliary gearbox control circuit, and rear axle and PTO control circuit; the power shift control circuit provides system pressure and controls the power shift clutch and four-wheel drive clutch to form gears; the AMT auxiliary gearbox control circuit controls the synchronizer inside the AMT auxiliary gearbox to achieve gear shifting operation and controls the climb synchronizer to achieve climb gearing; while the rear axle and PTO control circuit controls the rear axle differential lock and PTO shifting, and provides high-flow lubrication when the brakes are engaged.

[0048] The lifting system oil pump and filtration system includes: lifting pump 4, first coarse filter 2, first bypass valve 39, oil tank 1 and reserved interface 38;

[0049] The reserved interface 38 is provided on the lift pump 4, which is connected to the oil tank 1. The reserved interface 38 is externally connected to the vehicle lifting system. The first coarse filter 2 is provided on the oil line connecting the lift pump 4 and the oil tank 1. The first bypass valve 39 is provided between the lift pump 4 and the oil tank 1 and is connected in parallel with the first coarse filter 2. The first coarse filter 2 filters impurities in the oil in the oil tank 1. When the first coarse filter 2 is blocked, the oil in the oil tank 1 enters the lift pump 4 through the first bypass valve 39. The lift pump 4 draws the oil in the oil tank 1 and enters the vehicle lifting system through the reserved interface 38.

[0050] The power shift control circuit includes: system gear pump 6, fine filter 10, accumulator 12, clutch control valve, main pressure regulating valve 18, clutch control valve 20, four-wheel drive clutch control valve 21, and brake booster cylinder reserved interface 22.

[0051] The system gear pump 6 is connected to the oil tank 1 and the accumulator 12 respectively; a fine filter 10 is installed on the oil line between the system gear pump 6 and the accumulator 12; the inlet of the cold start valve 7 is externally connected to the oil line between the system gear pump 6 and the fine filter 10; the outlet of the cold start valve 7 is externally connected to the oil tank 1; the accumulator 12 is connected to the main pressure regulating valve 18; a plurality of clutch control valves are installed between the accumulator 12 and the main pressure regulating valve 18, and all of the plurality of clutch control valves are connected to the oil tank 1. The main pressure regulating valve 18 is connected in two ways: one path is connected to the lubrication circuit, and the other path is sequentially connected to the clutch control valve 20, the brake booster cylinder reserved interface 22, and the four-wheel drive clutch control valve 21. Both the clutch control valve 20 and the four-wheel drive clutch control valve 21 are externally connected to the oil tank 1. The brake booster cylinder reserved interface 22 is externally connected to the brake booster cylinder. The outlet of the four-wheel drive clutch control valve 21 is branched, with one path connected to the AMT auxiliary gearbox control circuit and the other path connected to the rear axle and PTO control circuit.

[0052] A sensor and a second bypass valve 40 are installed on the oil circuit between the system gear pump 6 and the accumulator 12. The sensor, the second bypass valve 40 and the fine filter 10 are connected in parallel. The sensor monitors whether the fine filter 10 is blocked. If it is blocked, it will remind the user to replace the fine filter 10. If it is not replaced in time, when the pressure reaches the set pressure of the second bypass valve 40, the second bypass valve 40 will open and the oil will directly enter the lubrication circuit.

[0053] The clutch control valve is externally connected to the clutch piston chamber. The clutch control valve is an electromagnetic proportional pressure reducing valve. The electromagnetic proportional pressure reducing valve is a two-position three-way connecting valve. The A port of the clutch control valve is connected to the clutch piston chamber. The P port of the clutch control valve is connected to the oil circuit of the accumulator 12 and the main pressure regulating valve 18. The T port of the clutch control valve is connected to the oil tank 1. When the clutch control valve is energized, the oil in the oil circuit of the accumulator 12 and the main pressure regulating valve 18 enters the clutch control valve through the P port, and then enters the clutch piston chamber through the A port of the clutch control valve, so that the clutch is engaged. When the clutch control valve is de-energized, the oil in the piston chamber will return to the oil tank 1 through the T port of the clutch control valve.

[0054] The main pressure regulating valve 18 is a valve core type oil drain logic element; both the clutch control valve 20 and the four-wheel drive clutch control valve 21 are externally connected to their respective clutch piston chambers. The A port of the clutch control valve 20 is connected to its clutch piston chamber; the P port of the clutch control valve 20 is connected to the oil inlet of the main pressure regulating valve 18; the T port of the clutch control valve 20 is connected to the oil tank 1; the A port of the four-wheel drive clutch control valve 21 is connected to its clutch piston chamber; the P port of the four-wheel drive clutch control valve 21 is connected to the oil inlet of the main pressure regulating valve 18; the T port of the four-wheel drive clutch control valve 21 is connected to the oil tank 1; the clutch... When the clutch control valve 20 and the four-wheel drive clutch control valve 21 are energized, the oil passing through the inlet of the main pressure regulating valve 18 enters the clutch control valve 20 and the four-wheel drive clutch control valve 21 respectively; the oil entering the clutch control valve 20 enters the clutch piston chamber of the clutch control valve 20 through port A; the oil entering the four-wheel drive clutch control valve 21 enters the clutch piston chamber of the four-wheel drive clutch control valve 21 through port A, causing the clutch to disengage; when not energized, the oil in the clutch piston chamber of the clutch control valve 21 and the oil in the clutch piston chamber of the clutch control valve 20 return to the oil tank 1 through their respective ports T.

[0055] The AMT auxiliary gearbox control circuit includes: a shift control valve 27; one outlet of the four-wheel drive clutch control valve 21 is connected to the inlet of the shift control valve 27; several synchronizer control valves are sequentially arranged on the four-wheel drive clutch control valve 21 and the shift control valve 27; the outlets of the shift control valve 27 and the synchronizer control valves are both connected to the oil tank 1; the P port of the synchronizer control valve is connected to one outlet of the four-wheel drive clutch control valve 21; the A port of the synchronizer control valve is connected to the shift shaft piston chamber and the selector shaft piston chamber respectively; the shift shaft piston chamber and the selector shaft piston chamber are respectively connected to the synchronizer via shift forks; the T port of the synchronizer control valve is connected to the oil tank 1.

[0056] The gear shift control valve 27 is a two-position four-way valve; the gear shift control valve 27 is connected to the driving gear piston chamber and the gear shift piston chamber respectively; the driving gear piston chamber and the gear shift piston chamber are connected to the synchronizer through the shift fork respectively; when not energized, oil enters the driving gear piston chamber through the gear shift control valve 27, pushing the shift fork to move the synchronizer to form the driving gear; when energized, oil enters the gear shift piston chamber through the gear shift control valve 27, pushing the shift fork to move the synchronizer to form the gear shift.

[0057] The rear axle and PTO control circuit includes: a differential lock valve 30, a PTO main clutch valve 29, and a PTO shift valve; another outlet of the four-wheel drive clutch control valve 21 is sequentially connected to the differential lock valve 30, the PTO main clutch valve 29, and the PTO shift valve, and there are several PTO shift valves. The outlets of the differential lock valve 30, the PTO main clutch valve 29, and the PTO shift valve are all externally connected to the oil tank 1. The front axle differential lock control interface 34 is located on the differential lock valve 30; the front axle differential lock control interface 34 is connected to the front axle.

[0058] The A port of the differential lock valve 30 is connected to the differential lock piston chamber; the P port of the differential lock valve 30 is connected to the other outlet of the four-wheel drive clutch control valve 21; the T port of the differential lock valve 30 is connected to the oil tank 1.

[0059] The PTO main clutch valve 29 is externally connected to the PTO clutch piston chamber; the A port of the PTO main clutch valve 29 is connected to the PTO clutch piston chamber; the P port of the PTO main clutch valve 29 is connected to the other outlet of the four-wheel drive clutch control valve 21; the T port of the PTO main clutch valve 29 is connected to the oil tank 1.

[0060] The PTO shift valve is connected to the piston chamber of the external PTO shift lever; the A port of the PTO shift valve is connected to the piston chamber of the PTO shift valve; the P port of the PTO shift valve is connected to the other outlet of the four-wheel drive clutch control valve 21; and the T port of the PTO shift valve is connected to the oil tank 1.

[0061] The lubrication circuit includes a lubrication gear pump 5, a second coarse filter 3, a heat exchanger 8, a temperature control bypass valve 9, a lubrication pressure control valve 11, a brake lubrication cut-off valve 35, a power shift master gearbox lubrication circuit 19, an AMT auxiliary gearbox lubrication circuit 28, a PTO and rear axle lubrication circuit 36, and a brake lubrication circuit 37. A second coarse filter 3 and a third bypass valve 41 are installed on the oil line between the system gear pump 6 and the oil tank 1, and the second coarse filter 3 and the third bypass valve 41 are connected in parallel. The outlet of the second coarse filter 3 is connected to the inlet of the lubrication gear pump 5, and the outlet of the lubrication gear pump 5 is simultaneously connected to... The inlet of heat exchanger 8 is connected to the inlet of temperature control bypass valve 9, and the outlet of heat exchanger 8 is connected in sequence to the outlet of temperature control bypass valve 9 and the outlet of main pressure regulating valve 18. A lubrication pressure control valve 11 and a power shift master gearbox lubrication circuit 19 are provided between the outlet of heat exchanger 8 and the outlet of main pressure regulating valve 18. The outlet of the lubrication pressure control valve 11 is connected in sequence to the inlet of AMT auxiliary gearbox lubrication circuit 28, the inlet of PTO and rear axle lubrication circuit 36 ​​and the inlet of brake lubrication cut-off valve 35. The outlet of the brake lubrication cut-off valve 35 is connected to brake lubrication 37.

[0062] The lubrication gear pump 5, system gear pump 6, and lifting pump 4 are all externally connected to the same driver, and the speeds of the lubrication gear pump 5, system gear pump 6, and lifting pump 4 are the same. The differential lock valve 30 and the PTO shift valve are on / off solenoid valves, and the PTO main clutch valve 29 is a proportional solenoid valve.

[0063] The tractor power shift gearbox proposed in this invention consists of a six-speed power shift master gearbox, a five-speed AMT auxiliary gearbox, a wet-type braked rear axle, and a three-speed PTO. It realizes control of the power shift clutch, the four-wheel drive / two-wheel drive conversion clutch, the AMT gearbox synchronizer shifting, the hydraulic shifting, the rear axle differential lock clutch, and the PTO master clutch and shift clutch, ensuring forced lubrication of all clutches, synchronizers, brakes, bearings, gears, splines, etc. To achieve the above functions, this invention adopts the following technical solution:

[0064] The system gear pump 6 outlet is equipped with a cold start valve 7, which overflows when the system oil pressure is higher than the set value to protect the hydraulic components in the system. The fine filter 10 is designed with a differential pressure sensor and a second bypass valve 40 connected in parallel. The differential pressure sensor monitors the differential pressure of the fine filter 10. If the differential pressure of the fine filter exceeds the preset value of the differential pressure switch, the system prompts for replacement. The first clutch control valve 13, the second clutch control valve 14, the third clutch control valve 15, the fourth clutch control valve 16, the fifth clutch control valve 17, and the clutch control valve 20 are proportional solenoid valves to ensure precise control of clutch engagement and disengagement. The four-wheel drive clutch control valve 21 is a switching valve. The main pressure regulating valve is a valve core type oil drain logic element to ensure stable main pressure.

[0065] The function of the AMT auxiliary gearbox control circuit is to control the synchronizer inside the AMT auxiliary gearbox to achieve gear shifting operation and control the creeping synchronizer to achieve creeping gear. It includes the first synchronizer control valve 23, the second synchronizer control valve 24, the third synchronizer control valve 25, the fourth synchronizer control valve 26, and the creeping control valve 27. Among them, the first synchronizer control valve 23, the second synchronizer control valve 24, the third synchronizer control valve 25, and the fourth synchronizer control valve 26 are proportional control valves, controlling three-position gear selection and three-position gear shifting. The creeping solenoid valve 27 is a two-position four-way switching valve, and a throttle orifice is set in the oil inlet passage of the piston chamber to reduce gear shifting impact. When not energized, it is in drive gear; when energized, it is in creeping gear.

[0066] The first synchronizer control valve 23 and the second synchronizer control valve 24 are gear selection valves. Port A of the first synchronizer control valve 23 and the second synchronizer control valve 24 are respectively connected to the piston chamber of the gear selection shaft. The third synchronizer control valve 25 and the fourth synchronizer control valve 26 are gear shifting valves. Port A of the third synchronizer control valve 25 and the fourth synchronizer control valve 26 are respectively connected to the piston chamber of the gear shifting shaft.

[0067] Both the gear selector shaft and the gear shift shaft have 5 gears, of which gears 1 and 2 are low gears; gears 3 and 4 are medium gears; and gear 5 is a high gear.

[0068] When the vehicle starts, when the first synchronizer control valve 23 and the second synchronizer control valve 24 are energized simultaneously, the gear selector shaft is in the middle gear position; when the first synchronizer control valve 23 is energized and the second synchronizer control valve 24 is not energized, the gear selector shaft is in the low gear position; when the second synchronizer control valve 24 is energized and the first synchronizer control valve 23 is not energized, the gear selector shaft is in the high gear position.

[0069] When the vehicle starts, the third synchronizer control valve 25 and the fourth synchronizer control valve 26 are energized simultaneously, and the shift shaft is in the neutral position. When the third synchronizer control valve 25 is energized and the fourth synchronizer control valve 26 is not energized, the vehicle shifts to a lower gear. When the fourth synchronizer control valve 26 is energized and the third synchronizer control valve 25 is not energized, the vehicle shifts to a higher gear.

[0070] When it is necessary to engage first gear, first control the first synchronizer control valve 23 to select the lower gear, and then control the third synchronizer control valve 25 to switch to the lower gear.

[0071] When it is necessary to engage second gear, first control the first synchronizer control valve 23 to select the lower gear, and then control the fourth synchronizer control valve 26 to switch to the higher gear.

[0072] When it is necessary to engage the third gear, the gear selector valve does not operate, and the control valve 25 of the third synchronizer is energized to switch to the lower gear.

[0073] When fourth gear is needed, the gear selector valve does not operate, and the third synchronizer control valve 25 is energized to switch to a lower gear.

[0074] When it is necessary to engage the fifth gear, first energize the second synchronizer control valve 24 to select the higher gear, and then energize the third synchronizer control valve 25 to switch to the lower gear.

[0075] The function of the rear axle and PTO control circuit is to control the rear axle differential lock and PTO shifting, and to provide high-flow lubrication when the brakes are working. It includes differential lock valve 30, PTO main clutch valve 29, first PTO gear control valve 31, second PTO gear control valve 32 and third PTO gear control valve 33. Among them, differential lock valve 30, first PTO gear control valve 31, second PTO gear control valve 32 and third PTO gear control valve 33 are switching solenoid valves, and PTO main clutch valve 29 is a proportional solenoid valve.

[0076] The function of the lubrication circuit is to provide forced lubrication for the wet clutches, synchronizers, brakes, bearings, gears, splines, etc. of the power shift master gearbox, AMT auxiliary gearbox, rear axle, and PTO module. This includes lubricating the gear pump 5, coarse filter 3, third bypass valve 41, heat exchanger 8, temperature control bypass valve 9, lubrication pressure control valve 11, brake lubrication cut-off valve 35, power shift master gearbox lubrication circuit 19, AMT auxiliary gearbox lubrication circuit 28, PTO and rear axle lubrication circuit 36, and brake lubrication 37. The temperature control bypass valve opens when the temperature is low, allowing the lubricating oil to bypass the oil cooler and rapidly heat up the system. When the temperature is high, it closes, and the lubricating oil passes through the heat exchanger to ensure the system's lubrication needs. The function of the brake lubrication valve is that when energized, the lubricating oil flows through the throttle orifice to lubricate the brake at a small flow rate. When braking is required, the solenoid valve is de-energized, and the lubricating oil flows through the oil passage to lubricate the brake at a large flow rate.

[0077] The hydraulic system pressure source of the power shift transmission designed in this invention is provided by a lift pump 4, a lubrication pump 5, and a system gear pump 6. These pumps are connected in series and directly driven by the engine. The first coarse filter 2 and the second coarse filter 3 at the oil inlet of the lift pump 4, lubrication pump 5, and system gear pump 6 are responsible for filtering larger contaminants in the system. When the first coarse filter 2 and the second coarse filter 3 are blocked, the first bypass valve 39 and the third bypass valve 41 will open to overflow. The oil outlet of the system gear pump 6 is connected to a fine filter 10. The fine filter 10 is connected in parallel with a differential pressure sensor and a second bypass valve 40. When the differential pressure between the inlet and outlet of the fine filter 10 reaches a set value, the differential pressure sensor alarms. If the differential pressure continues to increase, the second bypass valve 40 will open to overflow. A cold start valve 7 is arranged between the oil outlet of the system gear pump 6 and the fine filter 10. When the system pressure becomes too high due to changes in oil viscosity, exceeding the set value, the cold start valve 7 will open to overflow.

[0078] The outlet of the fine filter 10 is connected to the power shift valve block. The power shift valve block consists of a first clutch control valve 13, a second clutch control valve 14, a third clutch control valve 15, a fourth clutch control valve 16, and a fifth clutch control valve 17, an accumulator 12, and a main pressure regulating valve 18. The accumulator 12, as an energy storage element, maintains stable system pressure when the system flow demand increases due to clutch shifting. The first clutch control valve 13, the second clutch control valve 14, the third clutch control valve 15, the fourth clutch control valve 16, and the fifth clutch control valve 17 are electromagnetic proportional pressure reducing valves. Port A of the first clutch control valve 13, the second clutch control valve 14, the third clutch control valve 15, the fourth clutch control valve 16, and the fifth clutch control valve 17 is connected to the clutch piston chamber they control. The first clutch control valve 13, the second clutch control valve 14, the third clutch control valve 15, the fourth clutch control valve 16, and the fifth clutch control valve 17 are connected to the clutch piston chamber they control. When control valve 16 and fifth clutch control valve 17 are energized, system pressure oil enters their respective piston chambers through first clutch control valve 13, second clutch control valve 14, third clutch control valve 15, fourth clutch control valve 16, and fifth clutch control valve 17, engaging the clutches. When first clutch control valve 13, second clutch control valve 14, third clutch control valve 15, fourth clutch control valve 16, and fifth clutch control valve 17 are de-energized, the oil in their respective piston chambers returns to oil tank 1 through solenoid valve T port. Different gears are achieved through different clutch engagement combinations. A main pressure regulating valve 18 is arranged after the clutch valves to adjust the system pressure for the system pump load. The main pressure regulating valve 18 adopts a valve core type oil drain logic element and is connected in parallel with the main oil circuit. After the system circuit flow meets the requirements, the oil passing through the main pressure regulating valve 18 will flow into the lubrication circuit through port A to meet the lubrication flow requirements and reduce the lubrication pump displacement requirements. The main pressure regulating valve 18 is connected to the oil inlet of another clutch control valve 20 and the four-wheel drive clutch control valve 21. The four-wheel drive clutch control valve 21 is a solenoid valve with port A connected to the piston chamber of the four-wheel drive clutch. When the power is off, the clutch is engaged and the vehicle is in four-wheel drive mode. When the power is on, pressurized oil enters the piston chamber through the solenoid valve to disengage the clutch and the vehicle is in two-wheel drive mode.

[0079] The inlet of the four-wheel drive clutch control valve 21 is connected to the AMT valve block and the rear axle valve block. The AMT valve block consists of a first synchronizer control valve 23, a second synchronizer control valve 24, a third synchronizer control valve 25, a fourth synchronizer control valve 26, and a two-position four-way valve 27 that controls the shift synchronizer. The A ports of the first synchronizer control valve 23, the second synchronizer control valve 24, the third synchronizer control valve 25, and the fourth synchronizer control valve 26 are respectively connected to the piston chambers that control the shift shaft and the selector shaft, which then drive the shift fork to move the synchronizer to achieve the shifting operation. The two-position four-way valve 27 has two outputs, which are respectively connected to the piston chambers that control the driving gear and the shift gear. When not energized, pressurized oil enters the driving gear piston chamber to push the shift fork to move the synchronizer to form the driving gear. When energized, pressurized oil enters the shift gear piston chamber to push the shift fork to move the synchronizer to form the shift gear. The rear axle valve block consists of a PTO clutch control valve 29, a first PTO gear position control valve 31, a second PTO gear position control valve 32, a third PTO gear position control valve 33, and a differential lock valve 30. The PTO clutch control valve 29 is an electromagnetic proportional pressure reducing valve. Port A of the PTO clutch control valve 29 is connected to the PTO clutch piston chamber to control the engagement and disengagement of the PTO clutch. Ports A of the first PTO gear position control valve 31, the second PTO gear position control valve 32, and the third PTO gear position control valve 33 are connected to the PTO shift lever piston chamber. At the same time, pressurized oil enters the piston chamber through the corresponding solenoid valve to push the shift lever to form the corresponding gear. Port A of the differential lock valve is connected to the differential lock piston chamber, and a front axle differential lock interface is reserved.

[0080] The outlet of lubrication pump 5 is connected to heat exchanger 8. Heat exchanger 8 is connected in parallel with a temperature-controlled bypass valve 9. When the temperature is low, the valve opens, allowing lubricating oil to enter the lubrication system directly through the temperature-controlled bypass valve 9 without passing through heat exchanger 8, thus rapidly raising the system temperature. When the temperature is high, the temperature-controlled bypass valve 9 closes, allowing the lubricating oil to pass through heat exchanger 8 to cool the oil and ensure the system's lubrication requirements. The outlet of heat exchanger 8 merges with the outlet of the main pressure regulating valve 18, connecting to the power shift lubrication circuit 19, the AMT auxiliary gearbox lubrication circuit 28, the rear axle and PTO lubrication circuit 36, and the brake lubrication shut-off valve 35. The lubrication shut-off valve is a two-position, two-way valve, with its outlet connected to the brake lubrication circuit 37. A throttle valve is connected in parallel to the shut-off valve. During driving, the shut-off valve closes, and lubricating oil flows through the throttle valve at a small flow rate to lubricate the brakes. During braking, the shut-off valve opens, and lubricating oil flows through the shut-off valve at a large flow rate to lubricate the brakes. A lubrication check valve 11 is connected in parallel to the lubrication circuit to adjust the lubrication system pressure.

[0081] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A hydraulic system for a power shift tractor axle housing, characterized in that, include: Lifting system oil pump and filtration system, power shift control circuit, AMT auxiliary gearbox control circuit, rear axle and PTO control circuit and lubrication circuit; The lifting system oil pump and filtration system are connected to the lubrication circuit and the power shift control circuit; the lifting system oil pump and filtration system are externally connected to the vehicle lifting system; the lifting system oil pump and filtration system supply oil to the vehicle lifting system; the power shift control circuit is connected to the AMT auxiliary gearbox control circuit and the rear axle and PTO control circuit; the lubrication circuit lubricates the power shift gearbox in the power shift control circuit, the AMT auxiliary gearbox in the AMT auxiliary gearbox control circuit, and the wet clutch, bearings, gears, and splines in the rear axle and PTO control circuit; The AMT auxiliary gearbox control circuit includes: a shift control valve (27); one outlet of the four-wheel drive clutch control valve (21) is connected to the inlet of the shift control valve (27); the four-wheel drive clutch control valve (21) and the shift control valve (27) are sequentially provided with a number of synchronizer control valves; the outlet of the shift control valve (27) and the outlet of the synchronizer control valve are both connected to the oil tank (1); the P port of the synchronizer control valve is connected to one outlet of the four-wheel drive clutch control valve (21); the A port of the synchronizer control valve is connected to the shift shaft piston chamber and the selector shaft piston chamber respectively; the shift shaft piston chamber and the selector shaft piston chamber are respectively connected to the synchronizer through a shift fork; the T port of the synchronizer control valve is connected to the oil tank (1). The synchronizer control valves include: a first synchronizer control valve (23), a second synchronizer control valve (24), a third synchronizer control valve (25), and a fourth synchronizer control valve (26). The first synchronizer control valve (23) and the second synchronizer control valve (24) are gear selection valves. The A ports of the first synchronizer control valve (23) and the second synchronizer control valve (24) are respectively connected to the piston chamber of the gear selection shaft. The third synchronizer control valve (25) and the fourth synchronizer control valve (26) are gear shifting valves. The A ports of the third synchronizer control valve (25) and the fourth synchronizer control valve (26) are respectively connected to the piston chamber of the gear shifting shaft. Both the gear selection shaft and the gear shift shaft include 5 gears, of which gears 1 and 2 are low gears; gears 3 and 4 are medium gears; and gear 5 is a high gear. When the vehicle starts, the first synchronizer control valve (23) and the second synchronizer control valve (24) are energized simultaneously, and the gear selector shaft is in the middle gear position; When the first synchronizer control valve (23) is energized and the second synchronizer control valve (24) is not energized, the gear selector shaft is in the low gear position; When the second synchronizer control valve (24) is energized and the first synchronizer control valve (23) is not energized, the gear selector shaft is in the high gear position; When the vehicle starts, the third synchronizer control valve (25) and the fourth synchronizer control valve (26) are energized at the same time, and the shift shaft is in the neutral position. When the third synchronizer control valve (25) is energized and the fourth synchronizer control valve (26) is not energized, the vehicle shifts to a lower gear. When the fourth synchronizer control valve (26) is energized and the third synchronizer control valve (25) is not energized, the vehicle shifts to a higher gear. When it is necessary to engage first gear, first control the first synchronizer control valve (23) to select the lower gear, and then control the third synchronizer control valve (25) to switch to the lower gear. When it is necessary to engage the second gear, first control the first synchronizer control valve (23) to select the lower gear, and then control the fourth synchronizer control valve (26) to switch to the higher gear. When it is necessary to engage the third gear, the gear selection valve does not operate, and the control valve (25) of the third synchronizer is energized to switch to the lower gear. When it is necessary to engage fourth gear, the gear selector valve does not operate, and the control valve (25) of the third synchronizer is energized to switch to a lower gear. When it is necessary to engage the fifth gear, first control the second synchronizer control valve (24) to energize and select the higher gear, and then control the third synchronizer control valve (25) to energize and switch to the lower gear.

2. The hydraulic system for the power shift tractor axle box according to claim 1, characterized in that, The lifting system oil pump and filtration system includes: lifting pump (4), first coarse filter (2), first bypass valve (39), oil tank (1) and reserved interface (38). The reserved interface (38) is set on the lifting pump (4), which is connected to the oil tank (1). The reserved interface (38) is connected to the vehicle lifting system. The first coarse filter (2) is set on the oil line connecting the lifting pump (4) and the oil tank (1). The first bypass valve (39) is set between the lifting pump (4) and the oil tank (1) and is connected in parallel with the first coarse filter (2). The first coarse filter (2) filters impurities in the oil in the oil tank (1). When the first coarse filter (2) is blocked, the oil in the oil tank (1) enters the lifting pump (4) through the first bypass valve (39). The lifting pump (4) draws the oil in the oil tank (1) and enters the vehicle lifting system through the reserved interface (38).

3. The hydraulic system for the power shift tractor axle box according to claim 2, characterized in that, The power shift control circuit includes: system gear pump (6), fine filter (10), accumulator (12), clutch control valve, main pressure regulating valve (18), clutch control valve (20), four-wheel drive clutch control valve (21), and brake booster cylinder reserved interface (22). The system gear pump (6) is connected to the oil tank (1) and the accumulator (12) respectively; a fine filter (10) is installed on the oil line between the system gear pump (6) and the accumulator (12); the inlet of the cold start valve (7) is externally connected to the oil line between the system gear pump (6) and the fine filter (10); the outlet of the cold start valve (7) is externally connected to the oil tank (1); the accumulator (12) is connected to the main pressure regulating valve (18); a plurality of clutch control valves are installed between the accumulator (12) and the main pressure regulating valve (18), and the plurality of clutch control valves are all connected to the oil tank (1). All clutch control valves are connected to the main pressure regulating valve (18). One of the main pressure regulating valves (18) is connected to the lubrication circuit, and the other is connected in sequence to the clutch control valve (20), the brake booster cylinder reserved interface (22), and the four-wheel drive clutch control valve (21). Both the clutch control valve (20) and the four-wheel drive clutch control valve (21) are externally connected to the oil tank (1). The brake booster cylinder reserved interface (22) is externally connected to the brake booster cylinder. The outlet branch of the four-wheel drive clutch control valve (21) is set so that one is connected to the AMT auxiliary gearbox control circuit and the other is connected to the rear axle and PTO control circuit.

4. The hydraulic system for the power shift tractor axle box according to claim 3, characterized in that, The system gear pump (6) and accumulator (12) are equipped with a sensor and a second bypass valve (40) in their oil circuits; the sensor, the second bypass valve (40) and the fine filter (10) are connected in parallel; the sensor monitors whether the fine filter (10) is blocked, and if it is blocked, it will remind the user to replace the fine filter (10); if it is not replaced in time, when the pressure reaches the set pressure of the second bypass valve (40), the second bypass valve (40) will open and the oil will directly enter the lubrication circuit.

5. The hydraulic system for the power shift tractor axle box according to claim 4, characterized in that, The clutch control valve is externally connected to the clutch piston chamber. The clutch control valve is an electromagnetic proportional pressure reducing valve. The electromagnetic proportional pressure reducing valve is a two-position three-way connecting valve. The A port of the clutch control valve is connected to the clutch piston chamber. The P port of the clutch control valve is connected to the oil circuit of the accumulator (12) and the main pressure regulating valve (18). The T port of the clutch control valve is connected to the oil tank (1). When the clutch control valve is energized, the oil in the oil circuit of the accumulator (12) and the main pressure regulating valve (18) enters the clutch control valve through the P port, and then enters the clutch piston chamber through the A port of the clutch control valve, so that the clutch is engaged. When the clutch control valve is de-energized, the oil in the piston chamber will return to the oil tank (1) through the T port of the clutch control valve. The main pressure regulating valve (18) is a valve core type oil drain logic element; the clutch control valve (20) and the four-wheel drive clutch control valve (21) are both externally connected to their respective clutch piston chambers. The A port of the clutch control valve (20) is connected to the clutch piston chamber of the clutch control valve (20); the P port of the clutch control valve (20) is connected to the oil inlet of the main pressure regulating valve (18); the T port of the clutch control valve (20) is connected to the oil tank (1); the A port of the four-wheel drive clutch control valve (21) is connected to the clutch piston chamber of the four-wheel drive clutch control valve (21); the P port of the four-wheel drive clutch control valve (21) is connected to the oil inlet of the main pressure regulating valve (18); the T port of the four-wheel drive clutch control valve (21) is connected to the oil tank (1); When the clutch control valve (20) and the four-wheel drive clutch control valve (21) are energized, the oil passing through the oil inlet of the main pressure regulating valve (18) enters the clutch control valve (20) and the four-wheel drive clutch control valve (21) respectively; the oil entering the clutch control valve (20) enters the clutch piston chamber of the clutch control valve (20) through the A port of the clutch control valve (20); the oil entering the four-wheel drive clutch control valve (21) enters the clutch piston chamber of the four-wheel drive clutch control valve (21) through the A port of the four-wheel drive clutch control valve (21), causing the clutch to disengage; when not energized, the oil in the clutch piston chamber of the four-wheel drive clutch control valve (21) and the oil in the clutch piston chamber of the clutch control valve (20) return to the oil tank (1) through their respective T ports.

6. The hydraulic system for the power shift tractor axle box according to claim 5, characterized in that, The gear shift control valve (27) is a two-position four-way valve; the gear shift control valve (27) is connected to the driving gear piston chamber and the gear shift piston chamber respectively; the driving gear piston chamber and the gear shift piston chamber are connected to the synchronizer through the shift fork respectively; when the power is off, the oil enters the driving gear piston chamber through the gear shift control valve (27) and pushes the shift fork to move the synchronizer to form the driving gear; when the power is on, the oil enters the gear shift piston chamber through the gear shift control valve (27) and pushes the shift fork to move the synchronizer to form the gear shift.

7. The hydraulic system for the power shift tractor axle housing according to claim 6, characterized in that, The rear axle and PTO control circuit includes: a differential lock valve (30), a PTO main clutch valve (29), a front axle differential lock control interface (34), and a PTO shift valve; the other outlet of the four-wheel drive clutch control valve (21) is connected in sequence to the differential lock valve (30), the PTO main clutch valve (29), and the PTO shift valve. There are several PTO shift valves. The outlets of the differential lock valve (30), the PTO main clutch valve (29), and the PTO shift valve are all connected to an external oil tank (1). The front axle differential lock control interface (34) is located on the differential lock valve (30). The A port of the differential lock valve (30) is connected to the differential lock piston chamber; the P port of the differential lock valve (30) is connected to the other outlet of the four-wheel drive clutch control valve (21); the T port of the differential lock valve (30) is connected to the oil tank (1). The PTO main clutch valve (29) is externally connected to the PTO clutch piston chamber; the A port of the PTO main clutch valve (29) is connected to the PTO clutch piston chamber; the P port of the PTO main clutch valve (29) is connected to the other outlet of the four-wheel drive clutch control valve (21); the T port of the PTO main clutch valve (29) is connected to the oil tank (1). The PTO shift valve is connected to the piston chamber of the external PTO shift lever, and the A port of the PTO shift valve is connected to the piston chamber of the PTO shift lever; the P port of the PTO shift valve is connected to the other outlet of the four-wheel drive clutch control valve (21); the T port of the PTO shift valve is connected to the oil tank (1).

8. The hydraulic system for the power shift tractor axle box according to claim 7, characterized in that, The lubrication circuit includes a lubrication gear pump (5), a second coarse filter (3), a heat exchanger (8), a temperature control bypass valve (9), a lubrication pressure control valve (11), a brake lubrication cut-off valve (35), a power shift master gearbox lubrication circuit (19), an AMT auxiliary gearbox lubrication circuit (28), a PTO and rear axle lubrication circuit (36), and a brake lubrication circuit (37). The system gear pump (6) and the oil tank (1) are connected by a second coarse filter (3) and a third bypass valve (41), which are connected in parallel. The outlet of the second coarse filter (3) is connected to the inlet of the lubrication gear pump (5), and the outlet of the lubrication gear pump (5) is also connected to the inlet of the heat exchanger (8). The outlet of the heat exchanger (8) is connected to the outlet of the temperature control bypass valve (9) and the outlet of the main pressure regulating valve (18) in sequence; a lubrication pressure control valve (11) and a power shift master gearbox lubrication circuit (19) are provided between the outlet of the heat exchanger (8) and the outlet of the main pressure regulating valve (18); the power shift master gearbox lubrication circuit (19) is connected to the oil outlet of the main pressure regulating valve (18); the outlet of the lubrication pressure control valve (11) is connected to the inlet of the AMT auxiliary gearbox lubrication circuit (28), the inlet of the PTO and rear axle lubrication circuit (36) and the inlet of the brake lubrication cut-off valve (35) in sequence, and the outlet of the brake lubrication cut-off valve (35) is connected to the brake lubrication circuit (37).

9. The hydraulic system for the power shift tractor axle housing according to claim 8, characterized in that, The lubrication gear pump (5), system gear pump (6) and lifting pump (4) are all connected to the same external driver, and the rotational speeds of the lubrication gear pump (5), system gear pump (6) and lifting pump (4) are the same.

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