阅读说明：本技术 一种液压泵后置式拖拉机电液悬挂系统 (Hydraulic pump postposition type tractor electrohydraulic suspension system ) 是由 徐立友 张伟 刘孟楠 吴静波 闫祥海 李妍颖 韩冰 于 2020-07-22 设计创作，主要内容包括：一种液压泵后置式拖拉机电液悬挂系统,包括动力输入轴、PTO变速装置、悬挂系统变速装置、液压泵、电液溢流阀、压力补偿阀、电液比例换向阀、电液开关阀、梭阀和液压缸；本发明中,悬挂系统变速装置基于拖拉机原动力输入轴增加两对齿轮啮合传动,当拖拉机带悬挂系统农具工作时,动力输入轴为液压泵提供动力；当拖拉机不带悬挂系统农具工作时,液压泵无动力输出。该电液悬挂系统的液压泵具有跟随式转速和恒定转速两种工作模式,可满足拖拉机悬挂多种农机具作业需求。该电液悬挂系统采用电液比例控制,可根据土壤条件的不同切换强压入土与非强压入土工作模式。(An electro-hydraulic suspension system of a tractor with a rear hydraulic pump comprises a power input shaft, a PTO speed change device, a suspension system speed change device, a hydraulic pump, an electro-hydraulic overflow valve, a pressure compensation valve, an electro-hydraulic proportional reversing valve, an electro-hydraulic switch valve, a shuttle valve and a hydraulic cylinder; according to the invention, the speed change device of the suspension system is additionally provided with two pairs of gears for meshing transmission based on the prime power input shaft of the tractor, and when the tractor drives the farm tool of the suspension system to work, the power input shaft provides power for the hydraulic pump; when the tractor works without the farm tool with the suspension system, the hydraulic pump does not have power output. The hydraulic pump of the electro-hydraulic suspension system has two working modes of follow-up rotating speed and constant rotating speed, and can meet the operation requirement of a tractor for suspending various agricultural implements. The electro-hydraulic suspension system adopts electro-hydraulic proportional control, and can switch the working modes of forced penetration and non-forced penetration according to different soil conditions.)

1. The utility model provides a rear-mounted tractor electricity liquid suspension of hydraulic pump, includes vice clutch (1), main clutch (2), derailleur (3), rear axle (5), its characterized in that: the power transmission device also comprises a power input shaft (4), a PTO speed change device (6), a suspension system speed change device (7), a hydraulic pump (14), an electro-hydraulic overflow valve (15), a pressure compensation valve (16), an electro-hydraulic proportional reversing valve (17), an electro-hydraulic switch valve (18), a shuttle valve (19) and a hydraulic cylinder (20); the auxiliary clutch (1) and the main clutch (2) are both connected with an engine, the main clutch (2) is connected with the transmission (3), the auxiliary clutch (1), the power input shaft (4), the PTO speed change device (6) and the power output shaft (13) are sequentially connected, and the suspension system speed change device (7) is connected with the power input shaft (4);

the suspension system speed change gear (7) comprises a hydraulic pump power output shaft first gear (8), a hydraulic pump power output shaft second gear (9), a power input shaft first gear (10) and a power input shaft second gear (11), the suspension system speed change gear (7) is connected with a hydraulic pump power output shaft (12), the power input shaft (4) is connected with the suspension system speed change gear (7) through the suspension system speed change gear (7) for providing power for a hydraulic pump (14), an outlet of the hydraulic pump (14) is connected with a pressure compensator (16), the pressure compensator (16) is connected with an electro-hydraulic proportional reversing valve (17), the electro-hydraulic proportional reversing valve (17), an electro-hydraulic switch valve (18), a shuttle valve (19) and a hydraulic cylinder (20) are sequentially connected, the hydraulic pump (14) is further connected with the electro-hydraulic overflow valve (15), and the electro-hydraulic.

2. The hydraulic pump rear-mounted tractor electrohydraulic suspension system of claim 1, characterized in that: the hydraulic pump (14) has two working modes of follow-up rotation speed and constant rotation speed.

3. The hydraulic pump rear-mounted tractor electrohydraulic suspension system according to claim 2, characterized in that: the power input shaft first gear (10) is meshed with the hydraulic pump power output shaft first gear (8), and the hydraulic pump (14) rotates at a follow-up rotating speed.

4. The hydraulic pump rear-mounted tractor electrohydraulic suspension system according to claim 2, characterized in that: the power input shaft second gear (11) is meshed with the hydraulic pump power output shaft second gear (9), and the hydraulic pump (14) rotates at a constant rotating speed.

5. The hydraulic pump rear-mounted tractor electrohydraulic suspension system of claim 1, characterized in that: the suspension system speed change device (7) is additionally provided with two pairs of gears for meshing transmission based on a prime power input shaft of the tractor, and when the tractor drives the electro-hydraulic suspension system farm tool to work, the power input shaft (4) provides power for the hydraulic pump (14); when the tractor works without the electro-hydraulic suspension system farm tool, the hydraulic pump (14) has no power output.

6. The hydraulic pump rear-mounted tractor electrohydraulic suspension system of claim 5, characterized in that: the speed change device (7) of the suspension system is additionally provided with two pairs of gears for meshing transmission based on a prime power input shaft of a tractor, the transmission ratio of a first gear (10) of the power input shaft and a first gear (8) of a power output shaft of a hydraulic pump is set to be 1, and the transmission ratio of a second gear (11) of the power input shaft and a second gear (9) of the power output shaft of the hydraulic pump is set to be larger than 1.

7. The hydraulic pump rear-mounted tractor electrohydraulic suspension system of claim 1, characterized in that: when the electro-hydraulic suspension system is in an idle state, the power input shaft gear is not meshed with the power output shaft gear of the hydraulic pump, and the hydraulic pump does not have power output, so that power loss caused by idling of the hydraulic pump is avoided; when the electro-hydraulic suspension system is in a working state, the power input shaft gear is meshed with the power output shaft gear of the hydraulic pump, and the hydraulic pump outputs power.

8. The hydraulic pump rear-mounted tractor electrohydraulic suspension system of claim 1, characterized in that: the electro-hydraulic suspension system has two working modes: the hydraulic cylinder (20) of the hydraulic system provides strong pressure for the soil-entering pressure of the agricultural implement and completes non-strong pressure soil-entering depending on the self weight of the agricultural implement.

9. The hydraulic pump rear-mounted tractor electrohydraulic suspension system of claim 1, characterized in that: the electro-hydraulic suspension system adopts electro-hydraulic proportional control, controls the hydraulic cylinder (20) to supply oil in one direction or two directions by controlling the on-off of the electro-hydraulic switch valve (18), and adjusts the lifting speed and the lifting direction of the suspended farm implement by controlling the valve core opening of the electro-hydraulic proportional reversing valve (17) and the hydraulic oil flow direction.

Technical Field

The invention belongs to the technical field of tractors, and relates to a tractor electro-hydraulic suspension system with a rear hydraulic pump.

Background

Under the working conditions of plowing and the like, the engine outputs power at a calibrated power and a rotating speed, when the hydraulic suspension system works, the engine provides power for the hydraulic pump, the hydraulic suspension system realizes lifting of farm tools through movement of the position of a valve core of a reversing valve, and the hydraulic power output cannot meet the requirement of the tractor for hanging various farm tools.

At present, a hydraulic pump is generally arranged on an engine of a tractor produced in China, a hydraulic cylinder is arranged on a rear axle, and a hydraulic pipeline is relatively long. The hydraulic suspension system usually adopts throttling speed regulation, a hydraulic pump is always in a working state after an engine is started, and when the hydraulic suspension system works without an agricultural implement, pressure oil output by the hydraulic pump flows back to a tank through an overflow valve. The hydraulic system has pipeline pressure loss, throttling loss, overflow loss and the like.

When the hydraulic suspension system works and the agricultural implement is not buried, the load is mainly the dead weight of the tractor plough and the connecting equipment thereof; when the agricultural implement is driven into the soil, the agricultural implement is also acted by the soil. The non-forced-pressing soil-entering type lifter enters soil through self weight of the agricultural implement, and the situation that the agricultural implement is difficult to enter the soil can occur under the working condition of hard soil. The strong-pressure soil-entering type lifter can push an agricultural implement to enter soil through the pressure of the oil cylinder, and has the defects of inaccurate positioning, high failure rate and the like in the working process.

Tractor electricity liquid suspension system adopts mechanical control usually, and the mechanical handle drives the push rod mechanism who links to each other with the distributor, and the different positions of main control valve in adjusting the distributor through stirring the mechanical handle realizes the lift of agricultural implement, but mechanical control structure is comparatively complicated, and the regulation precision can receive the lever and contract and expand and the influence of friction.

Disclosure of Invention

In view of the above, in order to solve the defects of the prior art, the invention aims to provide an electrohydraulic suspension system of a tractor with a rear hydraulic pump, which aims to solve the problems that when the existing tractor is not required to output power by the hydraulic suspension system, the hydraulic pump rotates along with an engine to cause energy consumption loss, a non-forced penetration lifter is difficult to penetrate into soil under the condition of hard soil, and the forced penetration lifter has inaccurate positioning, high failure rate and the like. The hydraulic pump has two working modes of following type rotating speed and constant rotating speed, and can meet the operation requirement of a tractor for hanging various agricultural implements. When the farm tool with the suspension system of the tractor works, the power input shaft provides power for the hydraulic pump; when the tractor works without the farm tool with the suspension system, the hydraulic pump does not have power output. The electro-hydraulic suspension system adopts electro-hydraulic proportional control during working, and strong-pressure soil penetration and non-strong-pressure soil penetration working modes are switched according to different soil conditions.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

an electro-hydraulic suspension system of a tractor with a rear hydraulic pump comprises an auxiliary clutch, a main clutch, a transmission, a rear axle, a power input shaft, a PTO speed change device, a suspension system speed change device, a hydraulic pump, an electro-hydraulic overflow valve, a pressure compensation valve, an electro-hydraulic proportional reversing valve, an electro-hydraulic switch valve, a shuttle valve and a hydraulic cylinder; the auxiliary clutch and the main clutch are both connected with the engine, the main clutch is connected with the transmission, the auxiliary clutch, the power input shaft, the PTO speed change device and the power output shaft are sequentially connected, and the suspension system speed change device is connected with the power input shaft;

the suspension system speed change gear comprises a hydraulic pump power output shaft first gear, a hydraulic pump power output shaft second gear, a power input shaft first gear and a power input shaft second gear, the suspension system speed change gear is connected with a hydraulic pump power output shaft, the power input shaft provides power for a hydraulic pump through the suspension system speed change gear, a hydraulic pump outlet is connected with a pressure compensator, the pressure compensator is connected with an electro-hydraulic proportional reversing valve, the electro-hydraulic proportional reversing valve, an electro-hydraulic switch valve, a shuttle valve and a hydraulic cylinder are sequentially connected, the hydraulic pump is further connected with an electro-hydraulic overflow valve, and the electro-hydraulic overflow valve is connected with an oil cylinder.

Further, the hydraulic pump has two working modes of a follow-up rotating speed and a constant rotating speed.

Further, the first gear of the power input shaft is meshed with the first gear of the power output shaft of the hydraulic pump, and the hydraulic pump rotates at a following rotating speed.

Further, the second gear of the power input shaft is meshed with the second gear of the power output shaft of the hydraulic pump, and the hydraulic pump rotates at a constant rotating speed.

Furthermore, the speed change gear of the suspension system is additionally provided with two pairs of gears for meshing transmission based on a prime power input shaft of the tractor, and when the tractor drives the agricultural implement of the electro-hydraulic suspension system to work, the power input shaft provides power for the hydraulic pump; when the tractor works without the electro-hydraulic suspension system farm tool, the hydraulic pump does not have power output.

Furthermore, the speed change device of the suspension system is additionally provided with two pairs of gears for meshing transmission based on a prime power input shaft of the tractor, the transmission ratio of a first gear of the power input shaft to a first gear of a power output shaft of a hydraulic pump is set to be 1, and the transmission ratio of a second gear of the power input shaft to a second gear of the power output shaft of the hydraulic pump is set to be more than 1.

Furthermore, when the electro-hydraulic suspension system is in an idle state, the power input shaft gear is not meshed with the power output shaft gear of the hydraulic pump, and the hydraulic pump does not have power output, so that power loss caused by idling of the hydraulic pump is avoided; when the electro-hydraulic suspension system is in a working state, the power input shaft gear is meshed with the power output shaft gear of the hydraulic pump, and the hydraulic pump outputs power.

Further, the electro-hydraulic suspension system has two working modes: the hydraulic cylinder of the hydraulic system provides strong pressure for the soil-entering pressure of the agricultural implement and non-strong pressure for soil-entering is completed by the self weight of the agricultural implement.

Furthermore, the hydraulic suspension system adopts electro-hydraulic proportional control, controls the hydraulic cylinder to supply oil in a single direction or two directions by controlling the on-off of an electro-hydraulic switch valve, and adjusts the lifting speed and the lifting direction of the suspended farm implement by controlling the opening of a valve core of an electro-hydraulic proportional reversing valve and the flowing direction of hydraulic oil.

The invention has the beneficial effects that:

the invention relates to an electro-hydraulic suspension system of a tractor with a rear hydraulic pump, which aims at solving the problems that when the existing tractor does not need the output power of the hydraulic suspension system, the hydraulic pump rotates along with an engine to cause energy consumption loss, a non-forced-penetration lifter is difficult to penetrate into soil under the condition of hard soil, and the forced-penetration lifter has inaccurate positioning, high failure rate and the like. The hydraulic pump has two working modes of following type rotating speed and constant rotating speed, and can meet the operation requirement of a tractor for hanging various agricultural implements. When the farm tool with the suspension system of the tractor works, the power input shaft provides power for the hydraulic pump; when the tractor works without the farm tool with the suspension system, the hydraulic pump does not have power output. The electro-hydraulic suspension system adopts electro-hydraulic proportional control during working, and strong-pressure soil penetration and non-strong-pressure soil penetration working modes are switched according to different soil conditions.

Compared with the prior art, the hydraulic pump has the advantages that the working power is provided by the power input shaft, the length of an oil pipeline can be reduced, and the on-way loss of a hydraulic system is reduced. Two pairs of gears are additionally arranged on the basis of a prime power input shaft of the tractor for meshing transmission, when a power input shaft gear is meshed with a power output shaft gear of a hydraulic pump, the hydraulic pump outputs power, and the lifting of the agricultural implement is controlled through the oil pressure change of a hydraulic cylinder; when the power input shaft gear is not meshed with the power output shaft gear of the hydraulic pump, the hydraulic pump does not have power output, and power loss caused by rotation of the hydraulic pump along with the power input shaft is avoided, so that the efficiency of a hydraulic system can be improved;

the hydraulic pump of the hydraulic system has two working modes of following type rotating speed and constant rotating speed: the first gear of the power input shaft is meshed with the first gear of the power output shaft of the hydraulic pump, and the hydraulic pump rotates at a following rotating speed; the second gear of the power input shaft is meshed with the second gear of the power output shaft of the hydraulic pump, and the hydraulic pump rotates at a constant rotating speed, so that the operation requirement of a tractor for hanging various agricultural implements is met, and the electro-hydraulic suspension system can be used under the working conditions of multiple working conditions;

the electro-hydraulic suspension system can realize two working modes of forced penetration and non-forced penetration, under the condition of loose soil, the acting force of the hydraulic cylinder can only push the agricultural implement to lift, and the agricultural implement penetrates into the soil by the self weight; under the condition of hard soil, the acting force of the hydraulic cylinder can push the agricultural implement to lift and descend, and the agricultural implement enters the soil by the pressure of the oil cylinder;

the electro-hydraulic suspension system adopts electro-hydraulic proportional control, and the on-off hydraulic cylinder of the electro-hydraulic switch valve is controlled to supply oil in a single direction or in two directions, so that the working modes of forced penetration and non-forced penetration can be switched, and the opening degree of a valve core of the electro-hydraulic proportional reversing valve and the lifting speed and direction of hydraulic oil flowing to the adjustable suspension farm implement are controlled. The invention adopts electro-hydraulic control, has simple structure and easy control, and can meet the operation requirement of the tractor.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a functional block diagram of the present invention;

FIG. 2 is a schematic view of the internal construction of the suspension system transmission of the present invention;

FIG. 3 is a schematic diagram of the hydraulic system of the present invention;

the labels in the figure are: 1. The hydraulic control system comprises an auxiliary clutch, 2, a main clutch, 3, a transmission, 4, a power input shaft, 5, a rear axle, 6, a PTO speed change device, 7, a suspension system speed change device, 8, a hydraulic pump power output shaft first gear, 9, a hydraulic pump power output shaft second gear, 10, a power input shaft first gear, 11, a power input shaft second gear, 12, a hydraulic pump power output shaft, 13, a power output shaft, 14, a hydraulic pump, 15, an electro-hydraulic overflow valve, 16, a pressure compensator, 17, an electro-hydraulic proportional reversing valve, 18, an electro-hydraulic switch valve, 19, a shuttle valve, 20 and a hydraulic cylinder.

Detailed Description

The following specific examples are given to further clarify, complete and detailed the technical solution of the present invention. The present embodiment is a preferred embodiment based on the technical solution of the present invention, but the scope of the present invention is not limited to the following embodiments.

An electrohydraulic suspension system of a hydraulic pump rear-mounted tractor comprises an auxiliary clutch 1, a main clutch 2, a speed changer 3, a rear axle 5, a power input shaft 4, a PTO speed changer 6, a suspension system speed changer 7, a hydraulic pump 14, an electrohydraulic overflow valve 15, a pressure compensation valve 16, an electrohydraulic proportional reversing valve 17, an electrohydraulic switch valve 18, a shuttle valve 19 and a hydraulic cylinder 20; the auxiliary clutch 1 and the main clutch 2 are both connected with an engine, the main clutch 2 is connected with a speed changer 3, the auxiliary clutch 1, a power input shaft 4, a PTO speed change device 6 and a power output shaft 13 are sequentially connected, and the suspension system speed change device 7 is connected with the power input shaft 4;

the suspension system speed change device 7 comprises a hydraulic pump power output shaft first gear 8, a hydraulic pump power output shaft second gear 9, a power input shaft first gear 10 and a power input shaft second gear 11, the suspension system speed change device 7 is connected with a hydraulic pump power output shaft 12, the power input shaft 4 provides power for a hydraulic pump 14 through the suspension system speed change device 7, an outlet of the hydraulic pump 14 is connected with a pressure compensator 16, the pressure compensator 16 is connected with an electro-hydraulic proportional reversing valve 17, the electro-hydraulic proportional reversing valve 17, an electro-hydraulic switch valve 18, a shuttle valve 19 and a hydraulic cylinder 20 are sequentially connected, the hydraulic pump 14 is further connected with an electro-hydraulic overflow valve 15, and the electro-hydraulic overflow valve 15 is connected with the oil cylinder.

Further, the rear axle 5 is connected to the power input shaft 4.

Further, the hydraulic pump 14 has two operation modes of a follow-up type rotation speed and a constant rotation speed.

Further, the power input shaft first gear 10 is meshed with the hydraulic pump power output shaft first gear 8, and the hydraulic pump 14 rotates at a follower rotation speed.

Further, the power input shaft second gear 11 is engaged with the hydraulic pump power output shaft second gear 9, and the hydraulic pump 14 is rotated at a constant rotation speed. The operation requirement of the tractor for suspending various agricultural implements is met, and the electro-hydraulic suspension system can be used for multi-working condition working conditions.

Further, the speed change gear 7 of the suspension system is additionally provided with two pairs of gear meshing transmissions based on a prime power input shaft of the tractor, and when the tractor drives the agricultural implement of the electro-hydraulic suspension system to work, the power input shaft 4 provides power for the hydraulic pump 14; when the tractor works without the electro-hydraulic suspension system farm tool, the hydraulic pump 14 has no power output. Furthermore, the working power of the hydraulic pump 14 is provided by the power input shaft 4, so that the length of an oil pipeline can be reduced, and the loss of a hydraulic system along the way can be reduced. Two pairs of gears are additionally arranged on the basis of the tractor prime power input shaft 4 for meshing transmission, when the electro-hydraulic suspension system does not need to lift farm implements, the gears of the power input shaft 4 are not meshed with the first gear 8 of the power output shaft of the hydraulic pump and the second gear 9 of the power output shaft of the hydraulic pump, and the hydraulic pump 14 does not have power output, so that the power loss caused by the rotation of the hydraulic pump 14 along with the power input shaft 4 is avoided; when the electro-hydraulic suspension system is in a working state, the power input shaft gear is meshed with the power output shaft gear of the hydraulic pump, the hydraulic pump 14 outputs power, and the lifting of the agricultural implement is controlled through the oil pressure change of the hydraulic cylinder 20.

Further, the speed change device 7 of the suspension system is additionally provided with two pairs of gear meshing transmissions based on a prime power input shaft of the tractor, the transmission ratio of the first gear 10 of the power input shaft to the first gear 8 of the power output shaft of the hydraulic pump is set to be 1, and the transmission ratio of the second gear 11 of the power input shaft to the second gear 9 of the power output shaft of the hydraulic pump is set to be larger than 1.

Furthermore, when the electro-hydraulic suspension system is in an idle state, the power input shaft gear is not meshed with the power output shaft gear of the hydraulic pump, and the hydraulic pump does not have power output, so that power loss caused by idling of the hydraulic pump is avoided; when the electro-hydraulic suspension system is in a working state, the power input shaft gear is meshed with the power output shaft gear of the hydraulic pump, and the hydraulic pump outputs power.

Furthermore, the hydraulic suspension system adopts electro-hydraulic proportional control, the hydraulic cylinder 20 is controlled to supply oil in one direction or two directions by controlling the on-off of the electro-hydraulic switch valve 18, and the lifting speed and the lifting direction of the suspended farm implement are regulated by controlling the opening of the valve core of the electro-hydraulic proportional reversing valve 17 and the flowing direction of hydraulic oil.

Further, the electro-hydraulic suspension system has two working modes: the hydraulic cylinder 20 of the hydraulic system provides strong pressure for the soil-entering pressure of the agricultural implement and non-strong pressure for soil-entering is completed by the self weight of the agricultural implement. Under the condition of hard soil, the acting force of the hydraulic cylinder 20 can push the agricultural implement to lift and descend, and the agricultural implement enters the soil by the pressure of the oil cylinder; under the condition of soil loosening operation, the acting force of the hydraulic cylinder 20 can only push the agricultural implement to be lifted, and the agricultural implement enters the soil by means of the self weight.

Under the hard soil working condition, the valve core of the electro-hydraulic switch valve 19 moves to the left position. When the farm tool needs to be lifted, the valve core of the electro-hydraulic proportional directional valve 17 moves to the left position, hydraulic oil of the hydraulic pump 14 flows to a rodless cavity of the hydraulic cylinder through the directional valve, the piston of the hydraulic cylinder 20 is pushed to move rightwards, and the suspension mechanism is driven to realize the lifting of the farm tool; when the farm tool needs to descend, the valve core of the electro-hydraulic proportional directional valve 17 moves to the right, hydraulic oil of the hydraulic pump 14 flows to the rod cavity of the hydraulic cylinder 20 through the electro-hydraulic proportional directional valve 17, the piston of the hydraulic cylinder 20 is pushed to move to the left, and the suspension mechanism is driven to realize the descent of the farm tool; when the farm tool needs to be centered, the valve core of the electro-hydraulic proportional reversing valve 17 moves to the neutral position, hydraulic oil cannot enter the electro-hydraulic proportional reversing valve 17 and returns to the oil tank through the electro-hydraulic overflow valve 15, the hydraulic system maintains pressure, the hydraulic cylinder 20 is locked, and the position of the farm tool is locked. The shuttle valve 18 is used for feeding back the system pressure to the pressure compensator 16, and the pressure compensator 16 keeps the front-back pressure difference of the electro-hydraulic proportional directional valve 17 constant, so that the movement speed of the hydraulic cylinder 20 is relatively stable;

under the condition of soil loosening operation, the valve core of the electro-hydraulic switch valve 19 moves to the right. When the farm tool needs to be lifted, the valve core of the electro-hydraulic proportional directional valve 17 moves to the left position, hydraulic oil of the hydraulic pump 14 flows to the rodless cavity of the hydraulic cylinder 20 through the directional valve, the piston of the hydraulic cylinder 20 is pushed to move rightwards, and the suspension mechanism is driven to realize the lifting of the farm tool; when the farm tool needs to descend, the valve core of the electro-hydraulic proportional reversing valve 17 moves to the right, and the oil in the hydraulic cylinder 20 can return to the oil tank through the electro-hydraulic proportional reversing valve 17 due to the gravity of the farm tool, so that the farm tool descends. When the farm tool needs to be centered, the valve core of the electro-hydraulic proportional reversing valve 17 moves to the neutral position, hydraulic oil cannot enter the electro-hydraulic proportional reversing valve 17 and returns to the oil tank through the electro-hydraulic overflow valve 15, the hydraulic system maintains pressure, the hydraulic cylinder 20 is locked, and the position of the farm tool is locked. The shuttle valve 18 is used for feeding back the system pressure to the pressure compensator 16, and the pressure compensator 16 keeps the pressure difference between the front and the back of the electro-hydraulic proportional directional valve 17 constant, so that the movement speed of the hydraulic cylinder 20 is relatively stable.

In conclusion, the hydraulic pump postposition type tractor electrohydraulic suspension system aims at the problems that when the existing produced tractor does not need the hydraulic suspension system to output power, the hydraulic pump rotates along with the engine to cause energy consumption loss, the non-forced-penetration lifting device is difficult to penetrate into the soil under the hard soil operation condition, the forced-penetration lifting device is inaccurate in positioning, high in failure rate and the like. The hydraulic pump has two working modes of following type rotating speed and constant rotating speed, and can meet the operation requirement of a tractor for hanging various agricultural implements. When the farm tool with the suspension system of the tractor works, the power input shaft provides power for the hydraulic pump; when the tractor works without the farm tool with the suspension system, the hydraulic pump does not have power output. The electro-hydraulic suspension system adopts electro-hydraulic proportional control during working, and strong-pressure soil penetration and non-strong-pressure soil penetration working modes are switched according to different soil conditions.

The principal features, principles and advantages of the invention have been shown and described above. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to explain the principles of the invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the invention as expressed in the following claims. The scope of the invention is defined by the appended claims and equivalents thereof.