Hydraulic system for controlling lower pressure of single seeding machine, hydraulic system and seeding machine

Abstract

The utility model relates to a seeding machine single body down pressure control hydraulic system, a hydraulic system and a seeding machine, and the seeding machine single body down pressure control hydraulic system comprises a tractor main control valve, a pressure valve, a proportional valve and a piston rod which is used for connecting an oil cylinder of a seeding machine single body, an oil outlet 1a of the tractor main control valve is communicated with a two-way oil port 3a and a pilot oil port 3b of the pressure valve and an oil inlet 5a of the proportional valve at the same time, an oil outlet 5b and a two-way oil port 5c of the proportional valve are communicated with a rodless cavity 8a of the oil cylinder at the same time, and a rod cavity 8b of the oil cylinder is communicated with a two-way oil port 3c of the pressure valve. And an oil outlet 5d of the proportional valve is communicated with an oil return port 1b of the tractor main control valve. According to the utility model, the technical problem that the seeding accuracy is difficult to guarantee as the seeding pressure of the existing seeding machine monomer cannot be effectively adjusted according to the hardness of soil can be solved.

Description

Technical Field

[0001] This utility model relates to the technical field of individual control equipment for seeders, and in particular to a hydraulic system for controlling the downward pressure of an individual seeder, a hydraulic system, and a seeder. Background Technology

[0002] When multiple seeders simultaneously sow crops, the accuracy of the seeder's penetration depth directly affects crop emergence and yield. However, in current technology, the simultaneous descent of multiple seeders in rows to complete the sowing of rows of crops typically involves using lifting equipment to control the simultaneous ascent of multiple seeders, followed by their descent under gravity to complete the sowing. This mechanical gravity-based insertion method cannot effectively adjust the sowing pressure according to soil hardness, making it difficult to guarantee sowing accuracy. Utility Model Content

[0003] This invention addresses the technical problem that existing single-unit seeders cannot effectively adjust the planting pressure according to soil hardness, making it difficult to guarantee planting accuracy. It provides a hydraulic system for controlling the single-unit pressure of a seeder, a hydraulic system, and a seeder.

[0004] The technical solution of this utility model to solve the above-mentioned technical problems is as follows:

[0005] This utility model discloses a hydraulic system for controlling the pressure of a single planter unit, including a tractor main control valve, a pressure valve, a proportional valve, and a piston rod for connecting the planter unit to a hydraulic cylinder. The tractor main control valve has an oil outlet 1a and an oil return port 1b. The pressure valve has a bidirectional oil port 3a, a pilot oil port 3b, and a bidirectional oil port 3c. The proportional valve has an oil inlet 5a, an oil outlet 5b, a bidirectional oil port 5c, and an oil outlet 5d. The proportional valve can be switched to its bidirectional oil port 3a and its bidirectional oil port 3d. The oil outlet 1a of the tractor main control valve is connected to the oil port 3c or its oil outlet 5d and bidirectional oil port 3c. The oil outlet 1a of the tractor main control valve is simultaneously connected to the bidirectional oil port 3a and pilot oil port 3b of the pressure valve and the oil inlet 5a of the proportional valve. The oil outlet 5b and bidirectional oil port 5c of the proportional valve are simultaneously connected to the rodless chamber 8a of the cylinder. The rod chamber 8b of the cylinder is connected to the bidirectional oil port 3c of the pressure valve. The oil outlet 5d of the proportional valve is connected to the return oil port 1b of the tractor main control valve.

[0006] The beneficial effects of this utility model are as follows: When the piston rod of the hydraulic cylinder extends, it drives the seeder unit to press down, realizing the sowing operation. During this process, the proportional valve is energized. By operating the tractor's main control valve, the pressure oil reaches the pressure valve and forces the pressure valve to switch, making it open. At the same time, the pressure oil reaches the proportional valve and then reaches the rodless chamber 8a of the hydraulic cylinder. The piston rod of the hydraulic cylinder begins to move. The oil in the rod chamber 8b of the hydraulic cylinder returns to the rodless chamber 8a of the hydraulic cylinder after passing through the pressure valve, thereby realizing the rapid movement of the hydraulic cylinder. Thus, through this hydraulic system, the amount of pressure oil is controlled by the tractor's main control valve, realizing the precise control function of the downward pressure of the seeder unit. This improves the technical problem that the downward pressure of the existing seeder unit cannot be effectively adjusted according to the hardness of the soil, making it difficult to guarantee the sowing accuracy.

[0007] Based on the above technical solution, the present invention can be further improved as follows.

[0008] Furthermore, it also includes a solenoid valve, which has a bidirectional oil port 6a and a bidirectional oil port 6b. The oil outlet 5b and the bidirectional oil port 5c of the proportional valve are simultaneously connected to the bidirectional oil port 6a of the solenoid valve, and the bidirectional oil port 6b of the solenoid valve is connected to the rodless chamber 8a of the hydraulic cylinder.

[0009] The beneficial effects of adopting the above-mentioned further solution are: by setting up a solenoid valve to control the on / off state, flow regulation and direction control of the oil circuit in which it is located.

[0010] Furthermore, it also includes a safety valve having a bidirectional oil port 7a and a bidirectional oil port 7b. The bidirectional oil port 7a of the safety valve is simultaneously connected to the bidirectional oil port 3c of the pressure valve and the rod chamber 8b of the cylinder, and the bidirectional oil port 7b of the safety valve is simultaneously connected to the bidirectional oil port 6b of the solenoid valve and the rodless chamber 8a of the cylinder.

[0011] The beneficial effects of adopting the above-mentioned further scheme are as follows: when the oil pressure in the oil circuit connected to the bidirectional oil port 3c of the pressure valve and the rod chamber 8b of the cylinder, or the oil circuit pressure in the oil circuit connected to the bidirectional oil port 6b of the solenoid valve and the rodless chamber 8a of the cylinder exceeds the set value, it will automatically start, and the pressure oil in the two oil circuits will be circulated through the safety valve to release the excess pressure and protect the equipment and personnel safety. When the oil circuit pressure is lower than the set value, the safety valve will close.

[0012] Furthermore, it also includes an accumulator, which is simultaneously connected to the bidirectional oil port 3c of the pressure valve and the rod chamber 8b of the oil cylinder.

[0013] The beneficial effects of adopting the above-mentioned further scheme are: to store and release energy in the hydraulic system through the accumulator for purposes such as compensating for leakage, absorbing pulsations, maintaining constant pressure, and serving as an auxiliary power source. Specifically, when the piston rod of the oil cylinder extends or retracts, pressurized oil fills the accumulator.

[0014] Furthermore, it also includes a pressure reducing valve, which has an oil inlet 2a and an oil outlet 2b. The oil inlet 2a of the pressure reducing valve is connected to the oil outlet 1a of the tractor main control valve, and the oil outlet 2b of the pressure reducing valve is simultaneously connected to the bidirectional oil outlet 3a and the pilot oil outlet 3b of the pressure valve, as well as the oil inlet 5a of the proportional valve.

[0015] The beneficial effect of adopting the above-mentioned further solution is that the high oil pressure output from the oil outlet 1a of the tractor main control valve is reduced and stabilized to a suitable oil pressure through the pressure reducing valve, and the hydraulic pressure of the stabilized pressure is output to the bidirectional oil outlet 3a, the pilot oil outlet 3b of the pressure valve and the oil inlet 5a of the proportional valve.

[0016] Furthermore, the pressure reducing valve also has an oil outlet 2c and an oil outlet 2d, both of which are connected to the return oil port 1b of the tractor main control valve.

[0017] The beneficial effect of adopting the above-mentioned further solution is that by using a pressure reducing valve to directly return a portion of the pressure oil discharged from the oil outlet 1a of the tractor's main control valve to the tractor's main control valve, the pressure oil of the entire planter's individual pressure control hydraulic system can be regulated.

[0018] Furthermore, the pressure valve also has an oil drain port 3d, which is connected to the oil return port 1b of the tractor main control valve.

[0019] The beneficial effect of adopting the above-mentioned further solution is that by directly returning a portion of the pressure oil in the system to the tractor's main control valve through the oil drain port 3d of the pressure valve, the pressure oil of the hydraulic system for controlling the pressure of the entire seeder unit can be regulated.

[0020] Furthermore, at least two hydraulic cylinders are provided, and the oil outlet 5b and bidirectional oil port 5c of the proportional valve are simultaneously connected to the rodless chamber 8a of each hydraulic cylinder, and the rod chamber 8b of each hydraulic cylinder is simultaneously connected to the bidirectional oil port 3c of the pressure valve.

[0021] The beneficial effect of adopting the above-mentioned further solution is that it can simultaneously control the hydraulic system of multiple seeders, thereby improving seeding efficiency.

[0022] This utility model also discloses a hydraulic system, including the aforementioned hydraulic system for controlling the downpressure of a single seeder.

[0023] This utility model also discloses a seeder, including the aforementioned hydraulic system. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the hydraulic system for controlling the single-unit downward pressure of the seeder according to this utility model;

[0025] Figure 2 This is a schematic diagram of the hydraulic cylinder piston rod of this utility model when it is in the extended state.

[0026] Figure 3 This is a schematic diagram of the hydraulic cylinder piston rod in the retracted state according to this utility model.

[0027] Figure 4 This is a schematic diagram of the hydraulic cylinder of this utility model when it is in the locked state.

[0028] The attached diagram lists the components represented by each number as follows:

[0029] 1. Tractor main control valve; 2. Pressure reducing valve; 3. Pressure valve; 4. Accumulator; 5. Proportional valve; 6. Solenoid valve; 7. Safety valve; 8. Hydraulic cylinder. Detailed Implementation

[0030] The principles and features of this utility model are described below with reference to the accompanying drawings. The examples given are only for explaining this utility model and are not intended to limit the scope of this utility model.

[0031] Example 1

[0032] like Figures 1 to 4 This utility model discloses a hydraulic system for controlling the pressure of a single seeder unit, including a tractor main control valve 1, a pressure valve 3, a proportional valve 5, and a piston rod for connecting the seeder unit to a cylinder 8. The tractor main control valve 1 has an oil outlet 1a and an oil return port 1b. The pressure valve 3 has a bidirectional oil port 3a, a pilot oil port 3b, and a bidirectional oil port 3c. The proportional valve 5 has an oil inlet 5a, an oil outlet 5b, a bidirectional oil port 5c, and an oil outlet 5d. The proportional valve 5 can be switched to its bidirectional oil... Port 3a and bidirectional oil port 3c are connected, or its oil outlet 5d and bidirectional oil port 3c are connected. The oil outlet 1a of the tractor main control valve 1 is simultaneously connected to the bidirectional oil port 3a, pilot oil port 3b of the pressure valve 3, and the oil inlet 5a of the proportional valve 5. The oil outlet 5b and bidirectional oil port 5c of the proportional valve 5 are simultaneously connected to the rodless chamber 8a of the cylinder 8. The rod chamber 8b of the cylinder 8 is connected to the bidirectional oil port 3c of the pressure valve 3. The oil outlet 5d of the proportional valve 5 is connected to the return oil port 1b of the tractor main control valve 1.

[0033] The beneficial effects of this embodiment are as follows: When the piston rod of the hydraulic cylinder 8 extends, it drives the seeder unit to press down, realizing the sowing operation. During this process, the proportional valve 5 is energized. By operating the tractor main control valve 1, the pressure oil reaches the pressure valve 3 and forces the pressure valve 3 to switch direction, making it open. At the same time, the pressure oil reaches the proportional valve 5, and after passing through the proportional valve 5, it reaches the rodless chamber 8a of the hydraulic cylinder 8. The piston rod of the hydraulic cylinder 8 begins to move. The oil in the rod chamber 8b of the hydraulic cylinder 8 returns to the rodless chamber 8a of the hydraulic cylinder 8 after passing through the pressure valve 3, thereby realizing the rapid movement of the hydraulic cylinder 8. Thus, through this hydraulic system, the amount of pressure oil is controlled by the tractor main control valve 1, realizing the precise control function of the downward pressure of the seeder unit. This improves the technical problem that the downward pressure of the existing seeder unit cannot be effectively adjusted according to the hardness of the soil, making it difficult to guarantee the sowing accuracy.

[0034] When the piston rod of cylinder 8 retracts, the proportional valve 5 is not energized. By operating the tractor main control valve 1, the pressurized oil reaches the pressure valve 3 and forces the pressure valve 3 to switch, making it open. The pressurized oil reaches the rod chamber 8b of cylinder 8 from the bidirectional oil port 3c of pressure valve 3. At the same time, the piston rod of cylinder 8 begins to move. The oil in the rodless chamber 8a of cylinder 8 passes through the proportional valve 5 and returns to the oil tank from the return oil port 1b of the tractor main control valve 1.

[0035] When the hydraulic cylinder 8 is in the locked state, the main control valve 1 of the operating tractor is in the neutral position, the proportional valve 5 is not energized, the pressure valve 3 is closed, the oil in the rodless chamber 8a and the rod chamber 8b of the hydraulic cylinder 8 does not change, the hydraulic cylinder 8 is in the locked state and remains stationary.

[0036] Based on the above embodiment, the main control valve 1 of the tractor is communicatively connected to the instrument panel in the tractor's cab so that the driver can control it from the cab.

[0037] The pressure valve 3 has an oil chamber and a control chamber. A check valve is installed in the control chamber, and the pilot port 3b of the pressure valve 3 is connected to its oil chamber. For example... Figure 2 and Figure 3 When the piston rod of cylinder 8 extends and retracts, pressurized oil enters the oil chamber through the pilot port 3b of pressure valve 3, causing pressure valve 3 to switch. Both the bidirectional ports 3a and 3c of pressure valve 3 are connected to the oil chamber, realizing the input and output of oil. Figure 4 When the cylinder 8 is locked, the pressure oil no longer enters the oil chamber through the pilot port 3b of the pressure valve 3, the pressure valve 3 is closed, and both the bidirectional ports 3a and 3c of the pressure valve 3 are connected to the control chamber.

[0038] Example 2

[0039] like Figures 1 to 4Based on Embodiment 1, the hydraulic system for controlling the single-unit pressure of a seeder described in this utility model further includes a solenoid valve 6. The solenoid valve 6 has a bidirectional oil port 6a and a bidirectional oil port 6b. The oil outlet 5b and the bidirectional oil port 5c of the proportional valve 5 are simultaneously connected to the bidirectional oil port 6a of the solenoid valve 6. The bidirectional oil port 6b of the solenoid valve 6 is connected to the rodless chamber 8a of the oil cylinder 8.

[0040] The beneficial effect of adopting the preferred solution in the above embodiments is that the on / off state, flow rate regulation and direction control of the oil circuit are controlled by setting the solenoid valve 6.

[0041] Both pressure valve 3 and solenoid valve 6 have built-in check valves.

[0042] Specifically, when the piston rod of the hydraulic cylinder 8 is extended or retracted, the solenoid valve 6 is not energized. However, when the hydraulic cylinder 8 is locked, the solenoid valve 6 is energized, so that the hydraulic cylinder 8 is simultaneously locked through the pressure valve 3 and the check valve built into the solenoid valve 6.

[0043] When the piston rod of the hydraulic cylinder 8 extends, the pressurized oil passes through the proportional valve 5 and enters the solenoid valve 6, and is output from the bidirectional oil port 6b of the solenoid valve 6 to the rodless chamber 8a of the hydraulic cylinder 8; when the piston rod of the hydraulic cylinder 8 retracts, the pressurized oil in the rodless chamber 8a of the hydraulic cylinder 8 passes through the bidirectional oil port 6b of the solenoid valve 6 and enters the solenoid valve 6, and is output from the bidirectional oil port 6a of the solenoid valve 6 to the proportional valve 5.

[0044] The solenoid valve 6 has an oil chamber and a control chamber, and a one-way valve is installed in the control chamber. For example... Figure 2 and Figure 3 When the piston rod of the hydraulic cylinder 8 is extended or retracted, the solenoid valve 6 is not energized. At this time, both the bidirectional oil port 6a and the bidirectional oil port 6b of the solenoid valve 6 are connected to the oil chamber of the solenoid valve 6. When the hydraulic cylinder 8 is locked, the solenoid valve 6 is energized, and both the bidirectional oil port 6a and the bidirectional oil port 6b of the solenoid valve 6 are connected to the control chamber of the solenoid valve 6, so that the hydraulic cylinder 8 is simultaneously locked through the pressure valve 3 and the one-way valve built into the solenoid valve 6.

[0045] Example 3

[0046] like Figures 1 to 4 Based on embodiments 1 and 2, the hydraulic system for controlling the single-unit pressure of a seeder described in the utility model further includes a safety valve 7. The safety valve 7 has a bidirectional oil port 7a and a bidirectional oil port 7b. The bidirectional oil port 7a of the safety valve 7 is simultaneously connected to the bidirectional oil port 3c of the pressure valve 3 and the rod chamber 8b of the cylinder 8. The bidirectional oil port 7b of the safety valve 7 is simultaneously connected to the bidirectional oil port 6b of the solenoid valve 6 and the rodless chamber 8a of the cylinder 8.

[0047] The beneficial effect of adopting the preferred scheme in the above embodiments is that when the oil pressure in the oil circuit connected to the bidirectional oil port 3c of the pressure valve 3 and the rod chamber 8b of the cylinder 8, or the oil circuit pressure connected to the bidirectional oil port 6b of the solenoid valve 6 and the rodless chamber 8a of the cylinder 8, exceeds the set value, the safety valve 7 is automatically activated. The bidirectional oil ports 7a and 7b of the safety valve 7 are connected, and the pressure oil in the two oil circuits is circulated through the safety valve 7 to release excess pressure and protect the safety of equipment and personnel. When the oil circuit pressure is lower than the set value, the safety valve 7 is closed.

[0048] Example 4

[0049] like Figures 1 to 4 Based on embodiments 1-3, the hydraulic system for controlling the single-unit pressure of a seeder described in the utility model also includes an accumulator 4, which is simultaneously connected to the bidirectional oil port 3c of the pressure valve 3 and the rod chamber 8b of the oil cylinder 8.

[0050] The beneficial effect of adopting the preferred solution in the above embodiments is that the energy in the hydraulic system is stored and released through the accumulator 4 for purposes such as compensating for leakage, absorbing pulsations, maintaining constant pressure, and serving as an auxiliary power source. Specifically, when the piston rod of the oil cylinder 8 extends or retracts, the pressurized oil fills the accumulator 4.

[0051] Example 5

[0052] like Figures 1 to 4 Based on embodiments 1-4, the hydraulic system for controlling the single-unit pressure of a seeder described in the utility model further includes a pressure reducing valve 2. The pressure reducing valve 2 has an oil inlet 2a and an oil outlet 2b. The oil inlet 2a of the pressure reducing valve 2 is connected to the oil outlet 1a of the tractor main control valve 1, and the oil outlet 2b of the pressure reducing valve 2 is simultaneously connected to the bidirectional oil outlet 3a of the pressure valve 3, the pilot oil outlet 3b, and the oil inlet 5a of the proportional valve 5.

[0053] The beneficial effect of adopting the preferred solution in the above embodiments is that the high oil pressure output from the oil outlet 1a of the tractor main control valve 1 is reduced and stabilized to a suitable oil pressure by the pressure reducing valve 2, and the hydraulic pressure of the stabilized pressure is output to the bidirectional oil outlet 3a, the pilot oil outlet 3b and the oil inlet 5a of the pressure valve 3 and the proportional valve 5.

[0054] Example 6

[0055] like Figures 1 to 4 Based on embodiments 1-5, pressure reducing valve 2 also has an oil outlet 2c and an oil outlet 2d, and both the oil outlet 2c and the oil outlet 2d of pressure reducing valve 2 are connected to the return oil outlet 1b of the tractor main control valve 1.

[0056] The beneficial effect of adopting the preferred solution in the above embodiments is that the pressure reducing valve 2 directly returns a portion of the pressure oil discharged from the oil outlet 1a of the tractor main control valve 1 to the tractor main control valve 1, thereby realizing the regulation of the pressure oil of the hydraulic system for controlling the pressure of the entire seeder unit.

[0057] Example 7

[0058] like Figures 1 to 4 Based on embodiments 1-6, pressure valve 3 also has an oil drain port 3d, which is connected to the oil return port 1b of the tractor main control valve 1.

[0059] The beneficial effect of adopting the preferred solution in the above embodiments is that a portion of the pressure oil in the system is directly returned to the tractor main control valve 1 through the oil drain port 3d of the pressure valve 3, thereby realizing the adjustment of the pressure oil of the hydraulic system for controlling the pressure of the entire seeder unit.

[0060] Example 8

[0061] like Figures 1 to 4 Based on embodiments 1-7, the hydraulic cylinder 8 is provided with at least two oil outlets 5b and bidirectional oil outlets 5c of the proportional valve 5, which are simultaneously connected to the rodless chamber 8a of each hydraulic cylinder 8, and the rod chamber 8b of each hydraulic cylinder 8 is simultaneously connected to the bidirectional oil outlet 3c of the pressure valve 3.

[0062] The advantage of adopting the preferred solution in the above embodiments is that it can simultaneously control the hydraulic system of multiple seeders, thereby improving seeding efficiency.

[0063] Example 9

[0064] This utility model also discloses a hydraulic system, including the single-unit pressure control hydraulic system for the seeder as described in Examples 1-8.

[0065] Example 10

[0066] This utility model also discloses a seeder, including the hydraulic system described in Example 9.

[0067] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0068] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this utility model, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0069] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0070] In this utility model, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0071] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0072] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A hydraulic system for controlling the downpressure of a single planter, characterized in that, The system includes a tractor main control valve (1), a pressure valve (3), a proportional valve (5), and a piston rod for connecting a hydraulic cylinder (8) to a single planter unit. The tractor main control valve (1) has an oil outlet 1a and an oil return port 1b. The pressure valve (3) has a bidirectional oil port 3a, a pilot oil port 3b, and a bidirectional oil port 3c. The proportional valve (5) has an oil inlet 5a, an oil outlet 5b, a bidirectional oil port 5c, and an oil outlet 5d. The proportional valve (5) can be switched to have its bidirectional oil ports 3a and 3c connected or its oil outlet 5d connected. The oil outlet 1a of the tractor main control valve (1) is connected to the bidirectional oil outlet 3a and pilot oil outlet 3b of the pressure valve (3) and the oil inlet 5a of the proportional valve (5). The oil outlet 5b and bidirectional oil outlet 5c of the proportional valve (5) are connected to the rodless chamber 8a of the cylinder (8). The rod chamber 8b of the cylinder (8) is connected to the bidirectional oil outlet 3c of the pressure valve (3). The oil outlet 5d of the proportional valve (5) is connected to the return oil outlet 1b of the tractor main control valve (1).

2. The hydraulic system for controlling the single-unit downward pressure of a seeder according to claim 1, characterized in that, It also includes a solenoid valve (6), which has a bidirectional oil port 6a and a bidirectional oil port 6b. The oil outlet 5b and the bidirectional oil port 5c of the proportional valve (5) are simultaneously connected to the bidirectional oil port 6a of the solenoid valve (6), and the bidirectional oil port 6b of the solenoid valve (6) is connected to the rodless chamber 8a of the oil cylinder (8).

3. The hydraulic system for controlling the single-unit downward pressure of a seeder according to claim 2, characterized in that, It also includes a safety valve (7), which has a bidirectional oil port 7a and a bidirectional oil port 7b. The bidirectional oil port 7a of the safety valve (7) is simultaneously connected to the bidirectional oil port 3c of the pressure valve (3) and the rod chamber 8b of the cylinder (8). The bidirectional oil port 7b of the safety valve (7) is simultaneously connected to the bidirectional oil port 6b of the solenoid valve (6) and the rodless chamber 8a of the cylinder (8).

4. The hydraulic system for controlling the single-unit downward pressure of a seeder according to claim 1, characterized in that, It also includes an accumulator (4), which is simultaneously connected to the bidirectional oil port 3c of the pressure valve (3) and the rod chamber 8b of the cylinder (8).

5. The hydraulic system for controlling the single-unit downward pressure of a seeder according to claim 1, characterized in that, It also includes a pressure reducing valve (2), which has an oil inlet 2a and an oil outlet 2b. The oil inlet 2a of the pressure reducing valve (2) is connected to the oil outlet 1a of the tractor main control valve (1), and the oil outlet 2b of the pressure reducing valve (2) is simultaneously connected to the bidirectional oil outlet 3a and the pilot oil outlet 3b of the pressure valve (3) and the oil inlet 5a of the proportional valve (5).

6. The hydraulic system for controlling the single-unit downward pressure of a seeder according to claim 5, characterized in that, The pressure reducing valve (2) also has an oil outlet 2c and an oil outlet 2d, and the oil outlet 2c and the oil outlet 2d of the pressure reducing valve (2) are both connected to the return oil outlet 1b of the tractor main control valve (1).

7. The hydraulic system for controlling the single-unit downward pressure of a seeder according to claim 1, characterized in that, The pressure valve (3) also has an oil drain port 3d, which is connected to the oil return port 1b of the tractor main control valve (1).

8. A single-unit downward pressure control hydraulic system for a seeder according to any one of claims 1-7, characterized in that, At least two oil cylinders (8) are provided. The oil outlet 5b and the bidirectional oil port 5c of the proportional valve (5) are simultaneously connected to the rodless chamber 8a of each oil cylinder (8), and the rod chamber 8b of each oil cylinder (8) is simultaneously connected to the bidirectional oil port 3c of the pressure valve (3).

9. A hydraulic system, characterized in that, Includes the individual downpressure control hydraulic system for the seeder as described in any one of claims 1-8.

10. A seeder, characterized in that, Includes the hydraulic system as described in claim 9.

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