Hydraulic control system applied to small agricultural tractor

Abstract

The hydraulic control system applied to the small agricultural tractor comprises a main valve body, a first oil port is formed in the main valve body, the inlet end of the first oil port is connected with an external hydraulic oil system, and the outlet end of the first oil port is connected with a sequence valve used for controlling the pressure of hydraulic oil to be kept at a preset pressure value; the outlet end of the sequence valve is respectively connected with a pressure reducing valve and a priority valve; the outlet end of the pressure reducing valve is connected with a steering valve set, and the steering valve set conducts pressure reduction on the hydraulic oil output by the first oil port through the pressure reducing valve so as to control steering of the small agricultural tractor. The outlet end of the priority valve is respectively connected with a leveling electromagnetic valve and a lifting valve, and the priority valve controls the flow distribution of the hydraulic oil so as to control the automatic leveling and lifting of the rotary tillage accessory on the small agricultural tractor. The steering valve group, the leveling electromagnetic valve and the lifting valve are integrated on one main valve body, so that the steering valve has the characteristics of compact structure and small size, and is suitable for small agricultural tractors.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of small agricultural tractor control equipment, and particularly relates to a hydraulic control system applied to a small agricultural tractor. BACKGROUND

[0002] In the use process of the conventional agricultural tractor with a rotary tillage implement, the rotary tillage implement generally needs to be turned, leveled and lifted to adapt to different working environments, and most of the existing agricultural tractors adopt a multi-piece electric control multi-way valve and multiple hydraulic valve groups to respectively supply oil to a turning valve group, a lifting cylinder and a leveling cylinder, so as to control the turning, leveling and lifting operations of the rotary tillage implement. For a small agricultural tractor, since the tractor has a small size, the space provided for the installation of the control valve group is extremely limited. Therefore, the structure of the existing agricultural tractor that adopts a multi-piece electric control multi-way valve and multiple hydraulic valve groups to respectively supply oil to a turning valve group, a lifting cylinder and a leveling cylinder obviously cannot meet the requirements.

[0003] In view of this, it has become a technical problem to be solved by the technical personnel in the technical field that a hydraulic control system with a compact structure and a small occupied area is developed to be applied to a small agricultural tractor. SUMMARY

[0004] In order to solve the above technical problem, the present application provides a hydraulic control system applied to a small agricultural tractor, comprising:

[0005] a main valve body, a first oil port is arranged on the main valve body, an inlet end of the first oil port is connected with an external hydraulic oil system, and an outlet end of the first oil port is connected with a sequence valve for controlling the input hydraulic oil pressure in the main valve body to be always at a standby pressure value, and an outlet end of the sequence valve is respectively connected with a pressure reducing valve and a priority valve;

[0006] the pressure reducing valve, an outlet end of the pressure reducing valve is connected with a turning valve group, the hydraulic oil pressure output by the first oil port is reduced through the pressure reducing valve, and then the turning level of the small agricultural tractor is controlled based on the sequence valve and the pressure reducing valve;

[0007] the priority valve, an outlet end of the priority valve is respectively connected with a leveling electromagnetic valve and a lifting valve and is used for controlling the priority level of the leveling electromagnetic valve and the lifting valve, and the flow distribution of the hydraulic oil is controlled based on the priority valve, and then the automatic leveling and lifting of the rotary tillage implement on the small agricultural tractor are controlled.

[0008] In some embodiments, an overflow valve is further included, an inlet end of the overflow valve is connected with the outlet end of the first oil port, and an outlet end of the overflow valve is connected with a second oil port arranged on the main valve body, and the second oil port is connected with the external hydraulic oil system.

[0009] In some embodiments, a filter joint is further included, which is arranged between the pressure reducing valve and the steering valve group for filtering the low pressure oil provided by the pressure reducing valve.

[0010] In some embodiments, a first oil path and a second oil path are further included, an inlet end of the first oil path is connected with the leveling solenoid valve, an outlet end of the first oil path is connected with a rodless chamber of the external leveling cylinder, an inlet end of the second oil path is connected with a rod chamber of the external leveling cylinder, an outlet end of the second oil path is connected with the leveling solenoid valve, a first check valve and a check throttle valve are connected in parallel on the second oil path, and the leveling speed of the leveling cylinder is controlled through the check throttle valve.

[0011] In some embodiments, a hydraulic control check valve is further connected on the second oil path, the hydraulic control check valve is connected in series with the first check valve and the check throttle valve, and the first oil path is connected with the hydraulic control check valve for providing pilot oil for the hydraulic control check valve, and the external leveling cylinder is kept stationary when the hydraulic system is not working based on the hydraulic control check valve.

[0012] In some embodiments, a second check valve and an adjustable throttle valve are further included and arranged in parallel, an inlet end of the second check valve is connected with the outlet end of the lift valve, an outlet end of the second check valve is connected with the external lift cylinder, an inlet end of the adjustable throttle valve is connected with the external lift cylinder, and an outlet end of the adjustable throttle valve is connected with the lift valve, and the lowering speed of the rotary tillage implement connected with the lift cylinder is controlled through the second check valve and the adjustable throttle valve.

[0013] In some embodiments, a pressure tap is further included and arranged on the main valve body, the pressure tap is connected between the steering valve group and the pressure reducing valve, and a pressure sensor for detecting the pressure of the low pressure oil output by the pressure reducing valve is connected on the pressure tap.

[0014] In some embodiments, the steering valve group includes a first proportional valve and a second proportional valve connected with the outlet end of the filter joint and arranged in parallel, an outlet end of the first proportional valve is connected with a left clutch of the small agricultural tractor, an outlet end of the second proportional valve is connected with a right clutch of the small agricultural tractor, and the steering of the small agricultural tractor is controlled through the first proportional valve and the second proportional valve.

[0015] In some embodiments, an inclination sensor, a tension sensor and a controller are further included, the inclination sensor is arranged on the rotary tillage implement for detecting the inclination angle of the rotary tillage implement, the tension sensor is arranged on the leveling cylinder for detecting the tension data of the leveling cylinder, and the controller is connected with the inclination sensor, the tension sensor, the lift valve, the leveling solenoid valve and the steering valve group respectively.

[0016] Compared with the prior art, the hydraulic control system provided by the application controls the hydraulic oil pressure in the input main valve body to be the standby pressure value at all times through the sequence valve, thereby ensuring that the steering valve group has priority in the steering level, and meanwhile, the priority valve is used to distribute or control the hydraulic oil flow between the leveling electromagnetic valve and the lifting valve or the priority level of the leveling electromagnetic valve and the lifting valve, thereby controlling the steering, leveling and lifting of the rotary tillage implement on the small agricultural tractor. The hydraulic control system organically integrates the steering valve group, the leveling electromagnetic valve and the lifting valve on a main valve body, provides pressure oil for the steering system, the leveling system and the lifting system through the main valve body, and finally realizes the control of the steering, leveling and lifting of the rotary tillage implement on the small agricultural tractor. Therefore, the hydraulic control system provided by the application has the characteristics of compact structure and small size, and can be applied to the small agricultural tractor on which the rotary tillage implement is installed. BRIEF DESCRIPTION OF DRAWINGS

[0017] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the embodiments. The drawings are for purposes of illustration only and are not considered a limitation of the application. Moreover, in the drawings, like reference numerals designate identical or corresponding parts throughout the several views. In the drawings:

[0018] Figure 1 The working principle diagram of the hydraulic control system applied to the small agricultural tractor in the application is shown,

[0019] Figure 2 The structural schematic diagram of the hydraulic control system applied to the small agricultural tractor in the application is shown,

[0020] Figure 3 is Figure 2 the rear view.

[0021] The reference numerals in the detailed description are as follows:

[0022] 1. main valve body, 2. first oil port, 3. sequence valve, 4. pressure reducing valve, 5. priority valve, 6. steering valve group, 61. first proportional valve, 62. second proportional valve, 7. leveling electromagnetic valve, 8. lifting valve, 9. overflow valve, 10. second oil port, 11. filter joint, 12. first oil path, 13. second oil path, 14. first check valve, 15. check throttle valve, 16. hydraulic control check valve, 17. second check valve, 18. adjustable flow valve, 19. pressure measuring port, 20. pressure sensor, 21. third oil port, 22. fourth oil port, 23. fifth oil port, 24. sixth oil port. DETAILED DESCRIPTION

[0023] In the description of the present application, it needs to be understood that the description of orientation or positional relationship such as "central", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like is based on the orientation or positional relationship shown in the drawings, and is only for facilitating the description of the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application. Therefore, Figure 1 For example, the vertical paper surface is upward as upper, the vertical paper surface is downward as lower, the vertical paper surface is leftward as left, the vertical paper surface is rightward as right, the vertical paper surface is inward as front, and the vertical paper surface is outward as back.

[0024] In addition, when the features limited by "first", "second" appear, it is only for the purpose of description, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features. The features limited by "first", "second" can explicitly or implicitly include at least one of the features limited by "first", "second". When "multiple" appears, it generally means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0025] In the present application, unless otherwise explicitly specified and limited, when the terms such as "mounting", "connecting", "connecting", "fixing" and the like appear, they should be understood in a broad sense. For example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected, it can be directly connected, or it can be indirectly connected through an intermediate medium, it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0026] In the description of the present application, when the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" and the like appear, it means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present description, the illustrative description of the above terms is not necessarily for the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in the present description and the features of the different embodiments or examples without contradiction.

[0027] Please refer to Figures 1-3As shown, the hydraulic control system applied to small agricultural tractor provided by the embodiment of the application comprises:

[0028] A main valve body 1 is provided with a first oil port 2, the inlet end of the first oil port 2 is connected with an external hydraulic oil system, and the outlet end of the first oil port 2 is connected with a sequence valve 3 for controlling the input of the hydraulic oil pressure in the main valve body 1 to be always at a standby pressure value, and the outlet end of the sequence valve 3 is respectively connected with a pressure reducing valve 4 and a priority valve 5;

[0029] The outlet end of the pressure reducing valve 4 is connected with a steering valve group 6, the hydraulic oil pressure output by the first oil port 2 is reduced through the pressure reducing valve 4, and then the steering level priority of the small agricultural tractor is controlled based on the sequence valve 3 and the pressure reducing valve 4;

[0030] The outlet end of the priority valve 5 is respectively connected with a leveling solenoid valve 7 and a lift valve 8 and is used for controlling the priority level of the leveling solenoid valve 7 and the lift valve 8, and simultaneously based on the priority valve 5, the flow distribution of the hydraulic oil is controlled to further control the automatic leveling and lifting of the rotary tillage accessory on the small agricultural tractor.

[0031] In the above embodiment, the external hydraulic oil enters the main valve body 1 from the first oil port 2 and is divided into two paths, and under the action of the sequence valve 3, the pressure of the input hydraulic oil is always at the standby pressure value (in this embodiment, the standby pressure value is 3 MPa, and the hydraulic oil pressure required by the steering valve group 6 is 2.5 MPa, that is, the pressure value after pressure reduction by the pressure reducing valve 4 is 2.5 MPa). One path of the hydraulic oil is delivered to the steering valve group 6 after pressure reduction by the pressure reducing valve 4, and the other path is delivered to the leveling electromagnetic valve 7 and the lifting valve 8 through the priority valve 5. Since the hydraulic oil pressure value at the inlet end of the sequence valve 3 is always at the standby pressure value 3 MPa under the action of the sequence valve 3, and the inlet end of the sequence valve 3 is communicated with the inlet end of the pressure reducing valve 4, when the steering valve group 6 needs to steer, regardless of whether the leveling electromagnetic valve 7 and the lifting valve 8 are actuated, the standby pressure value 3 MPa at the inlet end of the sequence valve 3 is always greater than the pressure value 2.5 MPa required by the steering valve group 6 after pressure reduction by the pressure reducing valve 4. At this time, the response of the steering valve group 6 will not be delayed, that is, the steering valve group 6 has the highest priority level through the sequence valve 3. At the same time, the priority valve 5 can distribute the hydraulic oil input into the priority valve 5 to the leveling electromagnetic valve 7 and the lifting valve 8 according to the actual demand to realize the leveling action and the lifting action of the rotary tillage implement, or preferentially supply oil to the lifting valve 8 to make the lifting action have a higher priority level than the leveling action. When the leveling electromagnetic valve 7 and the lifting valve 8 are not actuated, the hydraulic oil delivered to the leveling electromagnetic valve 7 and the lifting valve 8 through the priority valve 5 will return to the external oil tank. The hydraulic control system provided by the present application organically integrates the steering valve group 6, the leveling electromagnetic valve 7 and the lifting valve 8 on one main valve body 1, and provides pressure oil for the steering system, the leveling system and the lifting system through one main valve body 1, so as to finally realize the control of the steering, leveling and lifting of the rotary tillage implement on the small agricultural tractor. Therefore, the hydraulic control system provided by the present application has the characteristics of compact structure and small size, and can be applied to the small agricultural tractor equipped with the rotary tillage implement.

[0032] It should be noted that the external leveling oil cylinder is connected with the leveling electromagnetic valve 7 through the third oil port 21 and the fourth oil port 22 arranged on the main valve body 1, and the external lifting oil cylinder is connected with the lifting valve 8 through the fifth oil port 23 arranged on the main valve body 1, and the steering valve group 6 is connected with the pressure reducing valve 4 through the sixth oil port 24 arranged on the main valve body 1.

[0033] In some embodiments, an overflow valve 9 is further included, the inlet end of the overflow valve 9 is connected with the outlet end of the first oil port 2, the outlet end of the overflow valve 9 is connected with the second oil port 10 arranged on the main valve body 1, and the second oil port 10 is connected with the external hydraulic oil system.

[0034] In the above embodiment, by arranging the overflow valve 9, the pressure of the hydraulic oil input into the main valve body 1 can be adjusted, so that the pressure of the hydraulic oil input into the main valve body 1 is always stable.

[0035] In some embodiments, a filter joint 11 is further included, which is arranged between the pressure reducing valve 4 and the steering valve group 6 to filter the low pressure oil provided by the pressure reducing valve 4.

[0036] In the above embodiment, the filter joint 11 is arranged to filter the low pressure oil input into the steering valve group 6, so as to avoid the influence of impurities in the low pressure oil on the steering system.

[0037] In some embodiments, a first oil path 12 and a second oil path 13 are further included, the inlet end of the first oil path 12 is connected with the leveling electromagnetic valve 7, the outlet end of the first oil path 12 is connected with the rodless chamber of the external leveling oil cylinder, the inlet end of the second oil path 13 is connected with the rod chamber of the external leveling oil cylinder, the outlet end of the second oil path 13 is connected with the leveling electromagnetic valve 7, and the first one-way valve 14 and the one-way throttle valve 15 are connected in parallel on the second oil path 13, and the leveling speed of the leveling oil cylinder is controlled through the one-way throttle valve 15.

[0038] In the above embodiment, when the leveling electromagnetic valve 7 delivers hydraulic oil to the rodless chamber of the external leveling oil cylinder through the first oil path 12, the external leveling oil cylinder is quickly retracted under the action of the hydraulic oil; when the hydraulic oil in the rod chamber of the external leveling oil cylinder is delivered to the leveling electromagnetic valve 7 through the second oil path 13, at this time, due to the arrangement of the first one-way valve 14, the hydraulic oil can only return to the leveling electromagnetic valve 7 through the one-way throttle valve 15, and the one-way throttle valve 15 can control the flow of the hydraulic oil, so that the extension speed of the external leveling oil cylinder can be controlled through the one-way throttle valve 15, thereby realizing the control of the leveling speed of the leveling oil cylinder.

[0039] In some embodiments, a hydraulic control one-way valve 16 is further connected on the second oil path 13, the hydraulic control one-way valve 16 is connected in series with the first one-way valve 14 and the one-way throttle valve 15, and the first oil path 12 is connected with the hydraulic control one-way valve 16 to provide pilot oil for the hydraulic control one-way valve 16, and the external leveling oil cylinder is kept stationary based on the hydraulic control one-way valve 16 when the hydraulic system is not working.

[0040] In the above embodiment, the hydraulic control one-way valve 16 is arranged on the first oil path 12, which can lock the chamber of the external leveling oil cylinder when the hydraulic system is not working, so as to keep the external leveling oil cylinder in a stationary state.

[0041] In some embodiments, a second one-way valve 17 and an adjustable throttle valve 18 are further included and arranged in parallel, the inlet end of the second one-way valve 17 is connected with the outlet end of the lift valve 8, the outlet end of the second one-way valve 17 is connected with the external lift oil cylinder, the inlet end of the adjustable throttle valve 18 is connected with the external lift oil cylinder, and the outlet end of the adjustable throttle valve 18 is connected with the lift valve 8, so as to control the lowering speed of the rotary tillage implement connected with the lift oil cylinder through the second one-way valve 17 and the adjustable throttle valve 18.

[0042] In the above embodiment, when the lift valve 8 is connected to the external lift cylinder through the second one-way valve 17, hydraulic oil is supplied to the external lift cylinder through the second one-way valve 17, and then the rotary tillage implement connected to the external lift cylinder realizes the lifting action; when the lift valve 8 is connected to the external lift cylinder through the adjustable flow valve 18, hydraulic oil returns to the lift valve 8 through the adjustable flow valve 18, and since the adjustable flow valve 18 can control the flow of hydraulic oil, the adjustable flow valve 18 controls the lowering speed of the rotary tillage implement connected to the lift cylinder by controlling the flow of hydraulic oil.

[0043] In some embodiments, a pressure tapping 19 is further arranged on the main valve body 1, the pressure tapping 19 is connected between the steering valve group 6 and the pressure reducing valve 4, and a pressure sensor 20 for detecting the low-pressure oil pressure output by the pressure reducing valve 4 is connected to the pressure tapping 19.

[0044] In the above embodiment, based on the pressure tapping 19 and the pressure sensor 20, the pressure of the low-pressure oil after the pressure reducing valve 5 is reduced can be monitored in real time, which provides a guarantee for the normal work of the steering valve group 6.

[0045] In some embodiments, the steering valve group 6 includes a first proportional valve 61 and a second proportional valve 62 connected to the outlet end of the filter connector 11 and arranged side by side, the outlet end of the first proportional valve 61 is connected to the left clutch of the small agricultural tractor, the outlet end of the second proportional valve 62 is connected to the right clutch of the small agricultural tractor, and then the steering of the small agricultural tractor is controlled through the first proportional valve 61 and the second proportional valve 62.

[0046] In the above embodiment, by connecting the first proportional valve 61 to the left clutch and the second proportional valve 62 to the right clutch, the steering of the rotary tillage implement on the small agricultural tractor can be realized by controlling the flow of the first proportional valve 61 and the second proportional valve 62. Specifically, when the hydraulic oil delivered to the first proportional valve 61 accounts for 100% and the hydraulic oil delivered to the second proportional valve 62 accounts for 0, since the first proportional valve 61 is connected to the left clutch, at this time, the rotary tillage implement steers left in place; when the hydraulic oil delivered to the first proportional valve 61 accounts for 0 and the hydraulic oil delivered to the second proportional valve 62 accounts for 100%, since the second proportional valve 62 is connected to the right clutch, at this time, the rotary tillage implement steers right in place; when the hydraulic oil delivered to the first proportional valve 61 and the second proportional valve 62 accounts for 50% respectively, at this time, the rotary tillage implement does not perform the steering action; therefore, the more hydraulic oil delivered to which proportional valve, the rotary tillage implement steers in the direction connected to the corresponding proportional valve.

[0047] In some embodiments, further comprising an inclination sensor (not shown in the figure), a pull wire sensor (not shown in the figure) and a controller (not shown in the figure), the inclination sensor is arranged on the rotary tillage tool for detecting the inclination angle of the rotary tillage tool, the pull wire sensor is arranged on the leveling oil cylinder for detecting the tension data of the leveling oil cylinder, and the controller is connected with the inclination sensor, the pull wire sensor, the lift valve 8, the leveling electromagnetic valve 7 and the steering valve group 6 respectively.

[0048] In the above embodiments, the real-time state of the rotary tillage tool can be accurately detected by arranging the inclination sensor, and the tension data of the leveling oil cylinder can be detected in real time by the pull wire sensor, so that the controller can automatically and accurately level the rotary tillage tool according to the detected data and the actual working condition, thereby realizing the automatic leveling of the rotary tillage tool and ensuring the flatness of the farmland after work in various working environments.

[0049] It should be noted that, in order to provide the adjustment accuracy of the lift valve 8, an operating handle can also be arranged on the small agricultural tractor, on the one hand, the operation of the handle is convenient for personnel to operate, and on the other hand, the operating handle can realize the fine adjustment of the lift valve pressure rod, thereby accurately fine adjusting the tillage depth of the rotary tillage tool.

[0050] The above describes in detail the hydraulic control system applied to the small agricultural tractor provided by the present application. In this paper, specific examples are applied to explain the principles and implementation modes of the present application, and the above embodiment is only used to help understand the core idea of the present application. It should be pointed out that, for ordinary skilled persons in the technical field, some improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A hydraulic control system for use on a small agricultural tractor, characterized in that, The utility model relates to a kind of hydraulic control system of small agricultural tractor, including: Main valve body, first oil port is provided on the main valve body, the inlet end of first oil port is connected with external hydraulic oil system, the outlet end of first oil port is connected with the sequence valve for controlling the input hydraulic oil pressure in main valve body always at standby pressure value, the outlet end of sequence valve is connected with pressure reducing valve and priority valve respectively; Pressure reducing valve, the outlet end of pressure reducing valve is connected with steering valve group, the hydraulic oil pressure exported by pressure reducing valve to first oil port is reduced, and then based on sequence valve and pressure reducing valve, the steering level priority of small agricultural tractor is controlled; Priority valve, the outlet end of priority valve is connected with leveling solenoid valve and lift valve respectively and is used to control the priority level of leveling solenoid valve and lift valve, and based on priority valve, the flow distribution of hydraulic oil is controlled, and then the automatic leveling and lifting of rotary tillage accessory on small agricultural tractor are controlled.

2. The hydraulic control system of claim 1, wherein, It also includes an overflow valve, the inlet end of the overflow valve is connected with the outlet end of the first oil port, and the outlet end of the overflow valve is connected with the external hydraulic oil system through the second oil port provided on the main valve body.

3. The hydraulic control system of claim 2, wherein, It also includes a filter joint, which is provided between the pressure reducing valve and the steering valve group for filtering the low-pressure oil provided by the pressure reducing valve.

4. The hydraulic control system of claim 1, wherein, It also includes a first oil path and a second oil path, the inlet end of the first oil path is connected with the leveling solenoid valve, the outlet end of the first oil path is connected with the rodless chamber of the external leveling cylinder, the inlet end of the second oil path is connected with the rod chamber of the external leveling cylinder, the outlet end of the second oil path is connected with the leveling solenoid valve, a first check valve and a check throttle valve are connected in parallel on the second oil path, and the leveling speed of the leveling cylinder is controlled through the check throttle valve.

5. The hydraulic control system of claim 4, wherein, The second oil path also connects a pilot-operated check valve, which is connected in series with the first check valve and the check throttle valve, and the first oil path is connected with the pilot-operated check valve for providing pilot oil for the pilot-operated check valve, based on which the external leveling cylinder remains stationary when the hydraulic system is not working.

6. The hydraulic control system of claim 1, wherein, It also includes a second check valve and an adjustable flow valve arranged in parallel, the inlet end of the second check valve is connected with the outlet end of the lift valve, the outlet end of the second check valve is connected with the external lift cylinder, the inlet end of the adjustable flow valve is connected with the external lift cylinder, and the outlet end of the adjustable flow valve is connected with the lift valve, the lowering speed of the rotary tillage accessory connected with the lift cylinder is controlled through the second check valve and the adjustable flow valve.

7. The hydraulic control system of claim 1, wherein, It also includes a pressure tap provided on the main valve body, which is connected between the steering valve group and the pressure reducing valve, and a pressure sensor is connected to the pressure tap for detecting the low-pressure oil pressure output by the pressure reducing valve.

8. The hydraulic control system of claim 3, wherein, The steering valve group includes a first proportional valve and a second proportional valve connected with the outlet end of the filter joint and arranged in parallel, the outlet end of the first proportional valve is connected with the left clutch of the small agricultural tractor, the outlet end of the second proportional valve is connected with the right clutch of the small agricultural tractor, and then the steering of the small agricultural tractor is controlled through the first proportional valve and the second proportional valve.

9. The hydraulic control system of claim 1, wherein, The application also comprises an inclination sensor arranged on the rotary tillage tool for detecting the inclination angle of the rotary tillage tool, a pull wire sensor arranged on the leveling oil cylinder for detecting the pull force data of the leveling oil cylinder, and a controller connected with the inclination sensor, the pull wire sensor, the lift valve, the leveling electromagnetic valve and the steering valve group respectively.

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