Multi-way directional valve for tractor

Abstract

The application discloses a multi-way reversing valve for a tractor, which comprises a connected inlet-return valve body, a four-position six-way reversing valve and two or more three-position six-way reversing valves, the inlet-return valve body is provided with a total oil inlet, a total oil return and a safety valve, the oil inlets of the reversing valves are connected with the total oil inlet, and the oil returns of the reversing valves are connected with the total oil return; a mechanical lock is arranged in the oil outlet of a working oil outlet of the four-position six-way reversing valve; the spool of the four-position six-way reversing valve is provided with a positioning reset mechanism; the application can not only prevent the static settlement of a lifting mechanism, improve the operation comfort and the controllability of micro-motion, but also can automatically return to a middle unloading state when the system pressure is overpressure, so as to reduce the energy consumption, protect the equipment safety, realize the descent of other accessories when there is no power, improve the safety and facilitate the maintenance.

Description

TECHNICAL FIELD

[0001] The present application relates to a multi-way directional valve, in particular a multi-way directional valve for a hydraulic system of a large tractor. BACKGROUND

[0002] The large tractor is a multi-purpose, high-efficiency and flexible agricultural machinery, and the hydraulic system drives corresponding attachments to perform operations such as portal lifting, soil loosening, plowing and harvesting. Currently, the safety and comfort of the large tractor are increasingly required, which puts forward new requirements for the multi-way valve in the hydraulic system of the main machine. The existing four-position six-way directional valve for driving the lifting mechanism can realize the functions of portal lifting, mid-position, lowering and floating. However, under the condition of a large load, a small amount of oil backflow occurs, which leads to the static settlement of the lifting mechanism, affects the safety, and the operating force is large when the spool valve is shifted. In particular, when the system pressure is overpressure, the spool valve is difficult to return to the mid-position unloading state, which not only increases the energy consumption, but also reduces the comfort and micro-control of the directional process, and increases the labor intensity of the operator. The existing hydraulic system suddenly stops oil due to failure, at which time the attachments and other actuators driven by other directional valves remain in the working position, i.e. the hydraulic system has no power oil supply, and the actuators remain in the air and cannot be lowered, which is dangerous and inconvenient for maintenance and other operations. SUMMARY

[0003] The purpose of the present application is to overcome the above-mentioned deficiencies of the prior art, and to provide a multi-way directional valve for a tractor, which can not only prevent the static settlement of the lifting mechanism, improve the comfort and micro-control of the operation, but also automatically return the spool valve to the mid-position unloading state when the system pressure is overpressure, which can reduce the energy consumption, protect the safety of the equipment, and also realize the lowering of other attachments when there is no power, thereby improving the safety and facilitating maintenance.

[0004] In order to achieve the above-mentioned purpose, the multi-way directional valve for tractor comprises a connected inlet and return valve body, a four-position six-way directional valve and two or more three-position six-way directional valves, the inlet and return valve body is provided with a total oil inlet, a total oil return and a safety valve, the oil inlet of each directional valve is connected with the total oil inlet, and the oil return of each directional valve is connected with the total oil return; characterized in that a mechanical lock is arranged in the oil outlet of a working oil port of the four-position six-way directional valve, the mechanical lock comprises a valve sleeve fixedly connected in the oil outlet, a limiting seat fixedly arranged in the inner hole of the valve sleeve, a large spool valve slidingly arranged in the inner hole of the valve sleeve in front of the limiting seat, a limiting screw plug fixedly arranged in the inner hole of the valve sleeve in rear of the limiting seat, the valve sleeve is provided with a plurality of front radial holes for connecting the inner hole in front of the limiting seat with the oil outlet and a plurality of rear radial holes for connecting the inner hole in rear of the limiting seat with the oil outlet, an outer reset spring is arranged between the large spool valve and the limiting seat, and the limiting screw plug is provided with a plurality of axial through holes; the inner hole of the large spool valve is fixedly connected with an inner screw plug, the inner screw plug is provided with an inner hole, a small valve core is slidingly arranged in the inner hole of the large spool valve in front of the inner screw plug, an inner reset spring is arranged between the small valve core and the inner screw plug, the large spool valve is provided with a radial damping hole for connecting the inner hole and the outer circle in rear of the small valve core, the inner side of the small valve core is provided with a top rod slidingly passing through the valve body, the inner end of the top rod is in contact with a sliding valve, the sliding valve is provided with a conical surface matched with the inner end of the top rod, and the working oil port and the inner end of the oil outlet are connected through an oil hole; the sliding valve of the four-position six-way directional valve is provided with a positioning reset mechanism, which comprises an end cover fixedly connected with the valve body and a connecting sleeve fixedly connected with one end of the sliding valve, the connecting sleeve is provided with an axial stepped hole and a plurality of radial holes located on the same radial, the front end of a positioning column is fixedly connected with the end of the inner hole of the connecting sleeve, a step is fixedly arranged on the outer circle of the end of the positioning column, a front spring seat and a rear spring seat are sleeved on the outer circle of the positioning column between the step and the end of the connecting sleeve and slidingly arranged, a reset spring is arranged between the front spring seat and the rear spring seat; the front end of the positioning column is provided with a stepped hole, a follower column is slidingly arranged in the connecting sleeve in front of the positioning column, the follower column is provided with a stepped hole in the inner, a positioning spring is arranged between the positioning column and the follower column, the front end of the outer circle of the follower column is provided with a conical surface, a steel ball is arranged in each radial hole, the conical surface is located on the inner side of each steel ball in the radial, and the diameters of the steel balls are all greater than the depth of the radial hole; a positioning sleeve is fixedly arranged in the end cover on the outer side of all the steel balls in the radial, and the inner circle of the positioning sleeve is provided with four positioning grooves in the radial;

[0005] In use, the four-position six-way directional valve drives the corresponding lifting oil cylinder, the steel ball is positioned in different positioning grooves by operating the sliding valve, the functions of lifting, mid-positioning, lowering and floating of the portal frame can be realized, the mechanical lock can prevent the oil in the lifting oil cylinder from flowing back after lifting back to the mid-position, so that the static settlement of the lifting mechanism is prevented, the positive unlocking is realized during lifting, the reverse unlocking is realized during lowering, the area difference between the front side sealing surface of the large spool valve and the pressure surface of the rear cavity of the large spool valve and the pressure difference between the front and rear cavities of the large spool valve can easily push the sliding valve to realize the reverse unlocking, and the operation comfort and the micro-motion controllability are improved;

[0006] As a further improvement of the present application, a plunger is also slidably arranged in the connecting sleeve in front of the follower column, a blind hole is arranged at the rear end of the plunger, a pressure regulating spring is arranged between the positioning column and the plunger, a push rod is slidably arranged in the connecting sleeve in front of the plunger, a load pressure feedback oil passage is arranged in the spool and communicates with the oil inlet in the valve body, and the front end of the push rod is located in the load pressure feedback oil passage; the positioning reset mechanism is a positioning overpressure recoil reset valve, when the load pressure is overpressure, the push rod is forced to push the plunger, the follower column moves backward, the steel ball is not supported by the follower column and automatically enters the connecting sleeve, the spool is released from the restraint of the steel ball and automatically returns to the neutral position under the action of the reset spring to unload, the energy consumption can be reduced, and the equipment safety is protected;

[0007] As a further improvement of the present application, a stepped adjusting rod is slidably arranged in the stepped hole of the positioning column, the pressure regulating spring is sleeved on the front section of the adjusting rod, the end face of the stepped hole of the positioning column is located at the rear side of the adjusting rod, a pressure regulating screw is arranged at the rear side of the adjusting rod, and a gasket and a locking nut are arranged on the pressure regulating screw at the rear side of the positioning column; the opening pressure of the automatic reset of the spool can be adjusted through the pressure regulating screw;

[0008] As a further improvement of the present application, the middle two recesses of the four positioning recesses are connected through a sliding groove; in the descending position, the manual operation mode must be maintained, and after the operating handle is released, the spool returns to the neutral position under the action of the reset spring, the needs of specific operation modes are met, and the safety is improved;

[0009] As a further improvement of the present application, at least one working oil port of the three-position six-way reversing valve is connected with the oil return port through a single-acting oil cylinder switching valve, the single-acting oil cylinder switching valve comprises a switching valve sleeve fixedly connected to the valve body, an adjusting valve rod connected to the switching valve sleeve through threads, and a locking nut connected to the rear end of the adjusting valve rod, the front end of the adjusting valve rod is arranged in an oil passage connecting the working oil port and the oil return port, and a sealing ring is arranged on the outer circle of the front end of the adjusting valve rod; when the working system suddenly stops oil supply due to failure, that is, the hydraulic system has no power oil supply, and the actuator is still in the working position and stays in the air, at this time, the adjusting valve rod is adjusted to connect the working oil port and the oil return port, and then the spool is operated to connect the other working oil port and the oil return port, so that the two cavities of the actuator oil cylinder are in an unloading state, and the actuator can be lowered under the action of its own gravity and external force, and the implement can also be lowered by operating the reversing valve when there is no power, so that the safety is improved and the maintenance is facilitated;

[0010] As a further improvement of the present application, a bridge valve body is further arranged, a bridge oil port is arranged in the bridge valve body, and the total oil inlet, the middle passage unloading oil inlets and outlets of the reversing valves and the bridge oil port are sequentially connected; when the reversing valves are in the neutral position, the oil source can be provided for other valve groups of the main machine hydraulic system;

[0011] In summary, the present application can prevent static settlement of the lifting mechanism, improve the steering comfort and micro-motion controllability, and when the system pressure is overpressure, the slide valve automatically returns to the mid unloading state, which can reduce energy consumption, protect the equipment safety, and also can realize the descent of other accessories when there is no power, improve the safety, and facilitate the maintenance. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 The hydraulic principle diagram of the embodiment of the present application.

[0013] Figure 2 The top view of the embodiment of the present application.

[0014] Figure 3 The Figure 2 The partial sectional view of the four-position six-way reversing valve.

[0015] Figure 4 The Figure 3 The front view of the positioning sleeve.

[0016] Figure 5 The Figure 2 The partial sectional view of the three-position six-way reversing valve.

[0017] Figure 6 The Figure 3 The schematic view in the lifting position.

[0018] Figure 7 The Figure 3 The schematic view in the descending position.

[0019] Figure 8 The Figure 3 The schematic view in the floating position.

[0020] Figure 9 The schematic view of the single-acting and double-acting cylinder conversion valve in the three-position six-way reversing valve in the open state. DETAILED DESCRIPTION

[0021] The present application will be further described in detail below with reference to the drawings.

[0022] As Figures 1 to 5The tractor multi-way directional valve of the embodiment shown, comprising in turn the inlet and return valve body 1, four-position six-way directional valve 2, three three-position six-way directional valves 3, 4, 5 and bridge valve body 6, the inlet and return valve body 1 is provided with a total oil inlet P, a total oil return T and a safety valve 7, each directional valve 2 to 5 includes a valve body, a spool, an oil inlet, an oil return, a middle passage unloading oil inlet P0, a working oil port A, a working oil port B and a middle passage unloading oil outlet P1, the oil inlet of each directional valve 2 to 5 is connected with the total oil inlet P, the oil return of each directional valve 2 to 5 is connected with the total oil return T, the bridge oil port P2 is provided in the bridge valve body 6, the total oil inlet P, the middle passage unloading oil inlet P0 and the middle passage unloading oil outlet P1 of each directional valve 2 to 5 and the bridge oil port P2 are connected in turn;

[0023] The oil outlet 8 of the working oil port A of the four-position six-way directional valve 2 is provided with a mechanical lock 57, the mechanical lock 57 includes a valve sleeve 9 fixed in the oil outlet 8 by threads, a limiting seat 10 fixed in the inner hole of the valve sleeve 9, a large spool valve 11 slidingly arranged in the inner hole of the valve sleeve 9 in front of the limiting seat 10, a limiting screw plug 12 fixed in the inner hole of the valve sleeve 9 behind the limiting seat 10 by threads, the valve sleeve 9 is provided with a plurality of front radial holes 13 communicating the inner hole in front of the limiting seat 10 with the oil outlet 8 and a plurality of rear radial holes 14 communicating the inner hole behind the limiting seat 10 with the oil outlet 8, an outer return spring 15 is arranged between the large spool valve 11 and the limiting seat 10, the limiting screw plug 12 is provided with a plurality of axial through holes 16; the inner hole of the large spool valve 11 is fixed with an inner screw plug 17 by threads, the inner screw plug 17 is provided with an inner hole 58, a small spool 18 is slidingly arranged in the inner hole of the large spool valve 11 in front of the inner screw plug 17, an inner return spring 19 is arranged between the small spool 18 and the inner screw plug 17, the large spool valve 11 is provided with a radial damping hole 20 located behind the small spool 18, communicating the inner hole and the outer circle thereof, the inner side of the small spool 18 is provided with a top rod 21 slidingly passing through a valve body 22, the inner end of the top rod 21 is in contact with a spool 23, the spool 23 is provided with a conical surface 24 matched with the inner end of the top rod 21, the working oil port A and the inner end of the oil outlet 8 are connected by an oil hole 25;

[0024] The spool valve 23 of the four-position six-way directional valve 2 is provided with a positioning overpressure recoil reset valve 26, which comprises an end cover 27 fixedly connected with the valve body 22, a connecting sleeve 28 fixedly connected with one end of the spool valve 23 by screwing, the connecting sleeve 28 is provided with an axial stepped hole and a plurality of radial holes located in the same radial direction, a steel ball 29 is arranged in each radial hole, a front end of a positioning column 30 is fixedly connected with the end of the inner hole of the connecting sleeve 28 by screwing, the end of the positioning column 30 is integrally provided with a step, a front spring seat 31 and a rear spring seat 32 are sleeved on the outer circle of the positioning column 30 between the step and the end of the connecting sleeve 28, and a reset spring 33 is arranged between the front spring seat 31 and the rear spring seat 32; a stepped hole is arranged in the front end of the positioning column 30, a stepped adjusting rod 34 is slidably arranged in the stepped hole, the end face of the stepped hole of the positioning column 30 is located at the rear side of the adjusting rod 34, a pressure regulating screw 35 is arranged at the rear side of the adjusting rod 34, a gasket 36 and a locking nut 37 are arranged on the pressure regulating screw 35 at the rear side of the positioning column 30, a follower column 38 and a plunger 39 are sequentially slidably arranged in the connecting sleeve 28 at the front side of the positioning column 30, a stepped hole is arranged in the follower column 38, a blind hole is arranged at the rear end of the plunger 39, a pressure regulating spring 40 is arranged between the positioning column 30 and the plunger 39, the pressure regulating spring 40 is sleeved on the front section of the adjusting rod 34, a positioning spring 41 is arranged between the positioning column 30 and the follower column 38, a conical surface 42 is arranged on the front end outer circle of the follower column 38, the conical surface 42 is located at the radial inner side of each steel ball 29, and the diameters of the steel balls 29 are all greater than the depth of the radial hole; a push rod 43 is slidably arranged in the connecting sleeve 28 at the front side of the plunger 39, a load pressure feedback oil path 44 is arranged in the spool valve 23 and communicates with the oil inlet P in the valve body, and the front end of the push rod 43 is located in the load pressure feedback oil path 44; a positioning sleeve 45 is fixedly arranged in the end cover 27 at the radial outer side of the steel ball 29, four positioning grooves 46-49 are arranged on the inner circle of the positioning sleeve 45 along the axial direction, and the middle two grooves 47 and 48 are connected through a sliding groove 50;

[0025] The working oil ports B of the three three-position six-way directional valves 3, 4 and 5 are all connected with the oil return ports T through single-acting oil cylinder switching valves 51, the single-acting oil cylinder switching valve 51 comprises a switching valve sleeve 53 fixedly connected with the valve body 52 by screwing, an adjusting valve rod 54 connected with the switching valve sleeve 53 by screwing, and a locking nut 55 connected with the rear end of the adjusting valve rod 54 by screwing, the front end of the adjusting valve rod 54 is arranged in the oil passing hole connecting the working oil port B and the oil return port T, and a sealing ring 56 is arranged on the outer circle of the front end of the adjusting valve rod 54;

[0026] In use, the four-position six-way directional valve 2 drives the corresponding lifting oil cylinder, the spool valve 23 is operated by the handle, the steel balls 29 are positioned in different positioning grooves, and the functions of lifting, mid-positioning, lowering and floating of the gantry can be realized, and the specific working process is as follows.

[0027] 1. Lifting position

[0028] When the handle is moved inward, the spool valve 23 moves to the corresponding stroke, and the spool valve 23 is in the position from the middle to the lifting position. At this time, the mechanical lock 57 is in the positive unlocking position, and the spool valve 23 is in the positioning state, as shown in Figure 6 The process is as follows:

[0029] (1) Positive unlocking: first move the spool valve 23 so that the oil inlet P is connected with the working oil port A in the valve body 22, and the pressure oil enters the front cavity d of the large spool valve 11, pushes away the large spool valve 11 to overcome the action force of the outer return spring 15, and the pressure oil passes through the front radial hole 13 of the valve sleeve 9, the annular cavity of the oil outlet 8 outside the valve sleeve 9, the rear radial hole 14 of the valve sleeve 9, and then reaches the rear cavity n of the limiting seat 10, and then enters the inner hole of the valve sleeve 9 through the axial through hole 16 of the limiting plug 12, and then enters the lifting oil cylinder to start the lifting action;

[0030] (2) Positioning: continue to move the spool valve 23 to overcome the action force of the return spring 33, and after the spool valve 23 moves to the corresponding stroke, the steel ball 29 is positioned in the positioning groove 46 of the positioning sleeve 45 under the action of the positioning spring 41. The positioning force can overcome the force value of the return spring 33. At this time, the handle is released, the spool valve 23 is in the positioning state, the hydraulic system continuously supplies oil to the lifting oil cylinder, and the lifting oil cylinder is in the continuous working state;

[0031] (3) Overpressure reset: when in the lifting position, the oil inlet P is connected with the working oil port A in the valve body 22, and the A cavity pressure (i.e. the load pressure) oil passes through the load pressure feedback oil way 44 in the spool valve 23 to introduce the load pressure signal to the front cavity of the push rod 43. After the push rod 43 is forced, it acts on the rear plunger 39. When the hydraulic pressure value of the front cavity of the push rod 43 is greater than the setting force value of the pressure adjusting spring 40 in the rear cavity of the plunger 39 and the force value of the positioning spring 41, the plunger 39 moves backward and transmits the force to the follow-up column 38. The follow-up column 38 moves backward, the steel ball 29 is in a free state without the support of the follow-up column 38, and the spool valve 23 starts to move backward under the action of the return spring 33. The steel ball 29 automatically enters the connecting sleeve 28 along the radial hole. The spool valve 23 is free from the restraint of the steel ball 29, automatically returns to the middle position under the action of the return spring 33, and is unloaded. The energy consumption can be reduced, and the safety of the equipment can be protected;

[0032] After lifting to the position, the spool valve 23 returns to the middle position (as shown in Figure 3 , the steel ball 29 is positioned in the positioning groove 47 of the positioning sleeve 45), and the mechanical lock 57 is closed. The oil in the lifting oil cylinder can be prevented from flowing back, so that the static settlement of the lifting mechanism is prevented;

[0033] 2, Lowering position

[0034] As shown in Figure 7As shown, when the control handle is moved outward from the neutral or lifting position, the slide valve 23 overcomes the force of the return spring 33, causing the slide valve 23 to move within the inner hole of the reversing valve body 22. The steel ball 29 is located in the slide groove 50 or the positioning groove 48. The conical surface 24 of the slide valve 23 pushes the push rod 21 to open the small valve core 18 in the opposite direction. At the same time, the working oil port A and the return oil port T are connected, performing reverse unlocking: the oil from the actuator cylinder first reaches the rear end of the inner hole of the valve sleeve 9, and then passes through the rear radial hole 14. The oil flows through the axial through-hole 16, the rear cavity n of the limiting seat 10, the annular cavity of the oil outlet 8 outside the valve sleeve 9, and the front radial hole 13 to reach the front cavity d of the large cone valve 11. Then, it enters the inner hole of the large cone valve 11 through the radial damping hole 20. At this time, the oil flows from the inner hole of the large cone valve 11 into the front cavity d of the large cone valve 11, and then enters the return port T through the working oil port A. Due to the flow of the oil, a pressure difference is generated when it flows through the radial damping hole 20 on the large cone valve 11. The pressure in the rear cavity of the large cone valve 11... The hydraulic oil connects to the low-pressure return chamber through the open gap of the small valve core 18, thus also becoming a low-pressure chamber, achieving pilot unlocking. Since the rear chamber of the large cone valve 11 is a low-pressure chamber, there is an area difference between the sealing surface of the large cone valve 11 and the valve sleeve 9 and the large-diameter surface of the rear chamber of the large cone valve 11. Because the rear chamber of the large cone valve 11 is already at low pressure, the thrust generated by this area difference causes the large cone valve 11 to open backward, achieving differential pressure unlocking. The front chamber of the large cone valve 11 communicates with the front radial hole 13; that is, achieving... The pilot valve core 18 is opened by the pilot differential pressure, which opens the pilot differential pressure unlock of the large cone valve 11. This allows the slide valve 23 to be easily pushed to achieve reverse unlocking, improving operating comfort and micro-motion controllability. The inner hole 58 of the inner screw plug 17 can be used to drain oil from the rear chamber of the large cone valve 11 when unlocking and to enter oil when locking. In the descending position, manual operation must be maintained. After releasing the operating handle, the slide valve 23 returns to the neutral position under the action of the return spring 33, meeting the needs of specific operating modes and improving safety.

[0035] 3. Floating position

[0036] like Figure 8 As shown, when the control handle moves the slide valve 23 outward, overcoming the force of the return spring 33, after the slide valve 23 moves the corresponding stroke, the steel ball 29 is positioned in the positioning groove 49 under the action of the positioning spring 41. This positioning force can overcome the force of the return spring 33. At this time, the control handle is released, and the slide valve 23 is in the positioning state. The two working ports A and B of the floating position are connected and the pressure is equal. At this time, the lifting mechanism is always in the follow-up state, which can realize the floating adjustment tillage depth control mode. The floating position needs to be returned to the middle position by the control handle being returned to the lower position and then returning to the middle position under the action of the return spring 33.

[0037] The four-position six-way directional valve 2 is a Q-type four-position valve, without changing the original operating mode, without external hydraulic lock, solving the problem of static settlement and large operating force of the lifting mechanism of the tractor, improving the comfort and controllability of the operation; At the same time, the end cover 27 integrates a four-position positioning overpressure recoil reset valve 26, without external oil source, through the load feedback oil pressure to push the spool 23 to reset automatically, to protect the equipment safety when overpressure, energy saving, simplify the system pipeline, at the same time, reduce the labor intensity of the operator; By adjusting the compression amount of the pressure adjusting screw 35 to adjust the compression amount of the pressure adjusting spring 40, the reset pressure can be adjusted, and after adjustment, it can be locked by the locking nut 37 to prevent pressure change;

[0038] When the working system suddenly breaks down due to failure, i.e. no power oil is provided for the hydraulic system, and the three three-position six-way directional valves 3, 4 and 5 drive the actuator to stay in the working position in the air, as shown in the figure, at this time, adjust the adjusting valve rod 54, rely on the oil passage hole 61 to make the working oil port B and the return oil port T communicate, and then operate the spool 59 to make the other working oil port A and the return oil port T also communicate, so that the two cavities of the actuator oil cylinder are in unloading state, and the actuator can be lowered under the action of its own gravity and external force, and the tool can also be lowered by operating the directional valve when there is no power, improving safety and facilitating maintenance; Figure 9

[0039] When each directional valve 2 to 5 is in the middle position, the bridge oil port P2 of the bridge valve body 6 can provide oil source for other valve groups of the main machine hydraulic system.​

Claims

1. A multi-way directional valve for tractor, comprising a connected inlet and return valve body, a four-position six-way directional valve and two or more three-position six-way directional valves, the inlet and return valve body is provided with a total inlet port, a total return port and a safety valve, the inlet port of each directional valve is connected with the total inlet port, and the return port of each directional valve is connected with the total return port; characterized in that A mechanical lock is arranged in an oil outlet of a working oil port of a four-position six-way directional valve, the mechanical lock comprising a valve sleeve fixedly arranged in the oil outlet, a limiting seat fixedly arranged in an inner hole of the valve sleeve, a large spool valve slidingly arranged in the inner hole of the valve sleeve in front of the limiting seat, a limiting screw fixedly arranged in the inner hole of the valve sleeve in back of the limiting seat, the valve sleeve being provided with a plurality of front radial holes communicating the inner hole in front of the limiting seat with the oil outlet and a plurality of back radial holes communicating the inner hole in back of the limiting seat with the oil outlet, an outer reset spring being arranged between the large spool valve and the limiting seat, the limiting screw being provided with a plurality of axial through holes; an inner screw is fixedly arranged in an inner hole of the large spool valve, the inner screw being provided with an inner hole, a small spool valve slidingly arranged in the inner hole of the large spool valve in front of the inner screw, an inner reset spring being arranged between the small spool valve and the inner screw, the large spool valve being provided with a radial damping hole communicating the inner hole and an outer circle in back of the small spool valve, a top rod slidingly passing through the valve body being arranged in the inner side of the small spool valve, an inner end of the top rod being in contact with a spool valve, the spool valve being provided with a conical surface matched with the inner end of the top rod, the working oil port being connected with the inner end of the oil outlet through an oil hole.

2. The multi-way directional valve for a tractor according to claim 1, characterized by: The spool valve of the four-position six-way directional valve is provided with a positioning reset mechanism, the positioning reset mechanism comprising an end cover fixedly connected with the valve body and a connecting sleeve fixedly connected with one end of the spool valve, the connecting sleeve being provided with an axial stepped hole and a plurality of radial holes in the same radial direction, a front end of a positioning column being fixedly connected with a terminal end of the inner hole of the connecting sleeve, a step being fixedly arranged on an outer circle of the terminal end of the positioning column, a front spring seat and a back spring seat being sleeved on the outer circle of the terminal end of the positioning column in sliding manner, a reset spring being arranged between the front spring seat and the back spring seat; a stepped hole being arranged in the front end of the positioning column, a follower column slidingly arranged in the connecting sleeve in front of the positioning column, a stepped hole being arranged in the follower column, a positioning spring being arranged between the positioning column and the follower column, a conical surface being arranged on an outer circle of a front end of the follower column, a steel ball being arranged in each radial hole, the conical surface being located in the radial inner side of each steel ball, the diameter of each steel ball being greater than the depth of the radial hole; a positioning sleeve being fixedly arranged in the end cover in radial outer side of all the steel balls, four positioning grooves being arranged on an inner circle of the positioning sleeve in axial direction.

3. The multi-way directional valve for a tractor according to claim 2, characterized by: A plunger is further slidingly arranged in the connecting sleeve in front of the follower column, a blind hole being arranged on a back end of the plunger, an adjusting spring being arranged between the positioning column and the plunger, a push rod slidingly arranged in the connecting sleeve in front of the plunger, a load pressure feedback oil path being arranged in the spool valve and communicating with an oil inlet of the valve body, a front end of the push rod being located in the load pressure feedback oil path.

4. The multi-way directional valve for a tractor according to any one of claims 1 to 3, characterized in that: An adjusting rod with a step is slidingly arranged in the stepped hole of the positioning column, the adjusting spring being sleeved on a front section of the adjusting rod, an end face of the stepped hole of the positioning column being located in back of the adjusting rod, an adjusting screw being arranged in back of the positioning column, a gasket and a locking nut being arranged on the adjusting screw in back of the positioning column.

5. The multi-way directional valve for a tractor according to claim 4, characterized by: The middle two grooves of the four positioning grooves are connected through a sliding groove. A working oil port of at least one three-position six-way directional valve is connected with a return oil port of the valve through a single / dual-acting oil cylinder switching valve, the single / dual-acting oil cylinder switching valve comprising a switching valve sleeve fixedly connected with a valve body, an adjusting valve rod threadedly connected with the switching valve sleeve, a locking nut connected with a back end of the adjusting valve rod, a front end of the adjusting valve rod being arranged in an oil passing hole connecting the working oil port and the return oil port, a sealing ring being arranged on an outer circle of the front end of the adjusting valve rod.

6. The multi-way directional valve for a tractor according to claim 5, characterized by: The bridge valve body is connected with the bridge valve body, and the bridge oil port, the total oil inlet, the middle through unloading oil inlet and the middle through unloading oil outlet of each reversing valve, and the bridge oil port are sequentially connected.

Images