Lifting system and method with unloading function for tractor

Abstract

The invention provides a lifting system with an unloading function for a tractor and a method. A lifting system with an unloading function for a tractor comprises a hydraulic three-point suspension system and an unloading valve, and the unloading valve is connected with the hydraulic three-point suspension system. By adding the unloading valve, the unloading function is achieved, the lifting force is steplessly adjustable, and the pressure of the machine tool on crops or the ground can be adjusted according to needs.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic three-point hitch systems, and particularly to a lifting system and method with unloading function for tractors. Background Art

[0002] The tractor hydraulic three-point hitch system is one of the core technologies of modern agricultural machinery. It realizes the rapid connection, lifting and depth control of agricultural implements through hydraulic power, significantly improving the operation efficiency and mechanization level. The evolution of tractor hydraulic three-point hitch technology from mechanical levers to intelligent electro-hydraulic systems has promoted the development of agricultural mechanization. In the future, with the popularization of electrification, autonomous driving and precision agriculture, the hitch technology will further break through in the direction of high efficiency, intelligence and lightweight, becoming the core execution component of smart agriculture.

[0003] Currently, the general hydraulic three-point hitch has four functions: floating, lifting, forced lowering and lowering by its own weight. These four functions are all realized through the lifting cylinder control valve. Throughout the process, the implement is always in a lifting motion state under the action of the three-point hitch mechanical link until the cylinder stroke ends or the implement load is too heavy for the lifting action to stop. For the operating conditions of some implements, such as mowing profiling implements and snow removal implements, they need to minimize the pressure of the implement's own weight on the operating object or the ground during operation, and at the same time the implement cannot be in a lifting motion state. At this time, the three-point hitch system needs to provide an upward force to offset part of the implement's own gravity, and this force can also be adjusted according to the different weights of the implements. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a lifting system and method with unloading function for tractors in view of the deficiencies of the prior art.

[0005] The technical solution of the present invention to solve the above technical problem is as follows: A lifting system with unloading function for tractors, comprising: a hydraulic three-point hitch system and an unloading valve, the unloading valve is connected to the hydraulic three-point hitch system.

[0006] The beneficial effect of adopting the technical solution of the present invention is: By adding an unloading valve, the unloading function is realized, so that the lifting force is steplessly adjustable, and the pressure of the implement on the crop or the ground can be adjusted according to needs.

[0007] Further, the hydraulic three-point hitch system is a fixed-displacement system or a variable-displacement system.

[0008] The beneficial effect of adopting the above further technical solution is: The hydraulic three-point hitch system is a fixed-displacement system or a variable-displacement system, which is convenient to select the type of hydraulic three-point hitch system according to actual needs and improves applicability.

[0009] Further, when the hydraulic three-point hitch system is a fixed-displacement system, the hydraulic three-point hitch system includes: a hydraulic oil tank, a fixed-displacement pump, a left lift cylinder, a lift cylinder control valve, and a right lift cylinder. The fixed-displacement pump is connected to the hydraulic oil tank through a pipeline. The rodless cavity of the left lift cylinder is connected to the rodless cavity of the right lift cylinder through a pipeline. The rod end cavity of the left lift cylinder is connected to the rod end cavity of the right lift cylinder through a pipeline. The first end of the lift cylinder control valve is connected to the fixed-displacement pump through a pipeline. The second end of the lift cylinder control valve is connected to the pipeline between the rod end cavities of the left lift cylinder and the right lift cylinder through a pipeline. The third end of the lift cylinder control valve is connected to the pipeline between the rodless cavities of the left lift cylinder and the right lift cylinder through a pipeline. The fourth end of the lift cylinder control valve is connected to the hydraulic oil tank through a pipeline. When the hydraulic three-point hitch system is a variable-displacement system, the hydraulic three-point hitch system includes: a hydraulic oil tank, a variable-displacement pump, a left lift cylinder, a lift cylinder control valve, and a right lift cylinder. The variable-displacement pump is connected to the hydraulic oil tank through a pipeline. The rodless cavity of the left lift cylinder is connected to the rodless cavity of the right lift cylinder through a pipeline. The rod end cavity of the left lift cylinder is connected to the rod end cavity of the right lift cylinder through a pipeline. The first end and the second end of the lift cylinder control valve are respectively connected to the variable-displacement pump through pipelines. The third end of the lift cylinder control valve is connected to the pipeline between the rod end cavities of the left lift cylinder and the right lift cylinder through a pipeline. The fourth end of the lift cylinder control valve is connected to the pipeline between the rodless cavities of the left lift cylinder and the right lift cylinder through a pipeline. The fifth end of the lift cylinder control valve is connected to the hydraulic oil tank through a pipeline.

[0010] The beneficial effect of adopting the above further technical solution is that the hydraulic three-point hitch system can be a fixed-displacement system or a variable-displacement system, which is convenient to select the type of the hydraulic three-point hitch system according to actual needs and improves the applicability.

[0011] Further, when the hydraulic three-point hitch system is a fixed-displacement system or a variable-displacement system, the unloading valve is installed on the pipeline between the lift cylinder control valve and the rodless cavity of the left lift cylinder, and a proportional pressure reducing valve is installed in the unloading valve.

[0012] The beneficial effect of adopting the above further technical solution is that it is realized by using an electro-hydraulic proportional pressure reducing valve. This solution is applicable to both fixed-displacement systems and variable-displacement systems. The proportional pressure reducing valve in the unloading valve can be adjusted timely according to the required unloading force, and the greater the current, the greater the unloading force.

[0013] Further, the unloading valve includes: a two-position three-way electromagnetic directional control valve, a first two-position two-way electromagnetic directional control valve, and a second two-position two-way electromagnetic directional control valve. The two-position three-way electromagnetic directional control valve is connected to the lifting cylinder control valve, the first two-position two-way electromagnetic directional control valve, and the proportional pressure reducing valve through pipelines respectively. The proportional pressure reducing valve is connected to the second two-position two-way electromagnetic directional control valve through a pipeline. Both the first two-position two-way electromagnetic directional control valve and the second two-position two-way electromagnetic directional control valve are connected to the rodless cavity of the left lifting cylinder through pipelines.

[0014] The beneficial effect of adopting the above further technical solution is: It is realized by using an electro-hydraulic proportional pressure reducing valve. This solution is applicable to both fixed-displacement systems and variable-displacement systems. The proportional pressure reducing valve in the unloading valve can be adjusted timely according to the required unloading force. The greater the current, the greater the unloading force.

[0015] Further, when the hydraulic three-point hitch system is a fixed-displacement system or a variable-displacement system, the unloading valve is respectively connected to the hydraulic oil tank and the pipelines between the lifting cylinder control valve and the rodless cavity of the left lifting cylinder through pipelines. An overflow valve is installed in the unloading valve.

[0016] The beneficial effect of adopting the above further technical solution is: It is realized by using an electro-hydraulic proportional overflow valve. This solution is applicable to both fixed-displacement systems and variable-displacement systems. The overflow valve in the unloading valve can be adjusted timely according to the required unloading force. The smaller the current, the greater the unloading force.

[0017] Further, a third two-position two-way electromagnetic directional control valve is installed in the unloading valve. The overflow valve is respectively connected to the hydraulic oil tank and the third two-position two-way electromagnetic directional control valve through pipelines. The third two-position two-way electromagnetic directional control valve is connected to the pipelines between the lifting cylinder control valve and the rodless cavity of the left lifting cylinder through a pipeline.

[0018] The beneficial effect of adopting the above further technical solution is: It is realized by using an electro-hydraulic proportional overflow valve. This solution is applicable to both fixed-displacement systems and variable-displacement systems. The overflow valve in the unloading valve can be adjusted timely according to the required unloading force. The smaller the current, the greater the unloading force.

[0019] Further, when the hydraulic three-point hitch system is a variable-displacement system, both ends of the unloading valve are respectively connected to the hydraulic oil tank and the pipelines between the second end of the lifting cylinder control valve and the variable pump through pipelines. The unloading valve is an electro-hydraulic proportional overflow valve.

[0020] The beneficial effect of adopting the above further technical solution is: It is realized by using an electro-hydraulic proportional overflow valve. This solution is applicable to variable-displacement systems. The unloading valve is an electro-hydraulic proportional overflow valve, which can be adjusted timely according to the required unloading force. The smaller the current, the greater the unloading force.

[0021] In addition, the present invention also provides a lifting method with unloading function for a tractor. Based on the above-mentioned lifting system with unloading function for a tractor, the lifting method with unloading function for a tractor includes: realizing the unloading function of the hydraulic three-point suspension system through an unloading valve.

[0022] The beneficial effect of adopting the technical solution of the present invention is: by adding an unloading valve, an unloading function is realized, so that the lifting force is steplessly adjustable, and the pressure of the machine on the crop or the ground can be adjusted as needed.

[0023] Furthermore, the steps of realizing the unloading function of the hydraulic three-point suspension system through the unloading valve include: controlling the lifting cylinder control valve to be in the lifting position, and controlling the two-position three-way solenoid reversing valve, the first two-position two-way solenoid reversing valve, the second two-position two-way solenoid reversing valve and the proportional pressure reducing valve to be energized to realize the unloading function of the hydraulic three-point suspension system; or, controlling the lifting cylinder control valve to be in the lifting position, and controlling the third two-position two-way solenoid reversing valve and the overflow valve to be energized to realize the unloading function of the hydraulic three-point suspension system; or, controlling the lifting cylinder control valve to be in the lifting position, and controlling the electric proportional overflow valve to be energized to realize the unloading function of the hydraulic three-point suspension system.

[0024] The beneficial effects of adopting the above further technical solution are: it is realized by adopting an electric proportional pressure reducing valve, which is applicable to quantitative systems and variable systems, wherein the proportional pressure reducing valve in the unloading valve can be adjusted in time according to the required unloading force, and the greater the current, the greater the unloading force. Or it is realized by adopting an electric proportional relief valve, which is applicable to quantitative systems and variable systems, wherein the relief valve in the unloading valve can be adjusted in time according to the required unloading force, and the smaller the current, the greater the unloading force. Or it is realized by adopting an electric proportional relief valve, which is applicable to variable systems, and the unloading valve is an electric proportional relief valve, which can be adjusted in time according to the required unloading force, and the smaller the current, the greater the unloading force.

[0025] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is one of the structural schematic diagrams of a lifting system with unloading function for a tractor provided in an embodiment of the present invention.

[0027] Figure 2 The second structural schematic diagram of the lifting system with unloading function for a tractor provided in an embodiment of the present invention.

[0028] Figure 3 The third structural schematic diagram of the lifting system with unloading function for a tractor provided in an embodiment of the present invention.

[0029] Figure 4This is the fourth structural schematic diagram of the lifting system with unloading function for tractors provided by the embodiments of the present invention.

[0030] Figure 5 This is the fifth structural schematic diagram of the lifting system with unloading function for tractors provided by the embodiments of the present invention.

[0031] Explanation of the reference numerals in the drawings: 1. Hydraulic oil tank; 2. Fixed displacement pump; 3. Left lifting cylinder; 4. Lifting cylinder control valve; 5. Right lifting cylinder; 6. Unloading valve; 7. Variable displacement pump; 8. Proportional pressure reducing valve; 9. Two-position three-way electromagnetic directional valve; 10. First two-position two-way electromagnetic directional valve; 11. Second two-position two-way electromagnetic directional valve; 12. Relief valve; 13. Third two-position two-way electromagnetic directional valve. Detailed implementation manners

[0032] The principles and features of the present invention will be described below with reference to the accompanying drawings. The illustrated embodiments are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0033] As Figures 1 to 5 shown, the embodiments of the present invention provide a lifting system with unloading function for tractors, including: a hydraulic three-point hitch system and an unloading valve 6, and the unloading valve 6 is connected to the hydraulic three-point hitch system.

[0034] The beneficial effects of adopting the technical solution of the present invention are: by adding an unloading valve, the unloading function is realized, so that the lifting force is steplessly adjustable, and the pressure of the implement on the crop or the ground can be adjusted according to needs.

[0035] As Figures 1 to 5 shown, further, the hydraulic three-point hitch system is a fixed displacement system or a variable displacement system.

[0036] The beneficial effects of adopting the above further technical solution are: the hydraulic three-point hitch system is a fixed displacement system or a variable displacement system, which is convenient to select the type of the hydraulic three-point hitch system according to actual needs and improves the applicability.

[0037] As Figures 1 to 5As shown, further, when the hydraulic three-point suspension system is a quantitative system, the hydraulic three-point suspension system includes: a hydraulic oil tank 1, a quantitative pump 2, a left lifting cylinder 3, a lifting cylinder control valve 4 and a right lifting cylinder 5, the quantitative pump 2 is connected to the hydraulic oil tank 1 through a pipeline, the rodless chamber of the left lifting cylinder 3 is connected to the rodless chamber of the right lifting cylinder 5 through a pipeline, the rod chamber of the left lifting cylinder 3 is connected to the rod chamber of the right lifting cylinder 5 through a pipeline, the first end of the lifting cylinder control valve 4 is connected to the quantitative pump 2 through a pipeline, the second end of the lifting cylinder control valve 4 is connected to the pipeline between the rod chamber of the left lifting cylinder 3 and the rod chamber of the right lifting cylinder 5 through a pipeline, the third end of the lifting cylinder control valve 4 is connected to the pipeline between the rodless chamber of the left lifting cylinder 3 and the rodless chamber of the right lifting cylinder 5 through a pipeline, and the fourth end of the lifting cylinder control valve 4 is connected to the hydraulic oil tank 1 through a pipeline. When the hydraulic three-point suspension system is a variable system, the hydraulic three-point suspension system includes: a hydraulic oil tank 1, a variable pump 7, a left lifting cylinder 3, a lifting cylinder control valve 4 and a right lifting cylinder 5, the variable pump 7 is connected to the hydraulic oil tank 1 through a pipeline, the rodless chamber of the left lifting cylinder 3 is connected to the rodless chamber of the right lifting cylinder 5 through a pipeline, the rod chamber of the left lifting cylinder 3 is connected to the rod chamber of the right lifting cylinder 5 through a pipeline, the first end and the second end of the lifting cylinder control valve 4 are respectively connected to the variable pump 7 through a pipeline, the third end of the lifting cylinder control valve 4 is connected to the pipeline between the rod chamber of the left lifting cylinder 3 and the rod chamber of the right lifting cylinder 5 through a pipeline, the fourth end of the lifting cylinder control valve 4 is connected to the rodless chamber of the left lifting cylinder 3 and the rodless chamber of the right lifting cylinder 5 through a pipeline, and the fifth end of the lifting cylinder control valve 4 is connected to the hydraulic oil tank 1 through a pipeline.

[0038] The beneficial effect of adopting the above further technical solution is that the hydraulic three-point suspension system is a quantitative system or a variable system, which makes it easy to select the type of the hydraulic three-point suspension system according to actual needs, thereby improving applicability.

[0039] like Figure 1 and Figure 2 As shown, further, when the hydraulic three-point suspension system is a quantitative system or a variable system, the unloading valve 6 is installed on the pipeline between the lifting cylinder control valve 4 and the rodless chamber of the left lifting cylinder 3, and a proportional pressure reducing valve 8 is installed in the unloading valve 6.

[0040] The beneficial effect of adopting the above further technical solution is: it is realized by adopting an electric proportional pressure reducing valve. This solution is applicable to quantitative systems and variable systems. The proportional pressure reducing valve in the unloading valve can be adjusted in time according to the required unloading force. The greater the current, the greater the unloading force.

[0041] Among them, the proportional pressure reducing valve 8 can be a two-position three-way electromagnetic reversing valve.

[0042] Such as Figure 1 and Figure 2 As shown, further, the unloading valve 6 includes: a two-position three-way electromagnetic reversing valve 9, a first two-position two-way electromagnetic reversing valve 10, and a second two-position two-way electromagnetic reversing valve 11. The two-position three-way electromagnetic reversing valve 9 is respectively connected to the lifting oil cylinder control valve 4, the first two-position two-way electromagnetic reversing valve 10, and the proportional pressure reducing valve 8 through pipelines. The proportional pressure reducing valve 8 is connected to the second two-position two-way electromagnetic reversing valve 11 through a pipeline. Both the first two-position two-way electromagnetic reversing valve 10 and the second two-position two-way electromagnetic reversing valve 11 are connected to the rodless cavity of the left lifting oil cylinder 3 through pipelines.

[0043] The beneficial effect of adopting the above further technical solution is: It is realized by using an electro-hydraulic proportional pressure reducing valve. This solution is applicable to both fixed-displacement systems and variable-displacement systems. Among them, the proportional pressure reducing valve in the unloading valve can be adjusted in a timely manner according to the required unloading force. The greater the current, the greater the unloading force.

[0044] Such as Figure 3 and Figure 4 As shown, further, when the hydraulic three-point hitch system is a fixed-displacement system or a variable-displacement system, the unloading valve 6 is respectively connected to the hydraulic oil tank 1 and the pipeline between the lifting oil cylinder control valve 4 and the rodless cavity of the left lifting oil cylinder 3 through pipelines. An overflow valve 12 is installed in the unloading valve 6.

[0045] The beneficial effect of adopting the above further technical solution is: It is realized by using an electro-hydraulic proportional overflow valve. This solution is applicable to both fixed-displacement systems and variable-displacement systems. Among them, the overflow valve in the unloading valve can be adjusted in a timely manner according to the required unloading force. The smaller the current, the greater the unloading force.

[0046] Such as Figure 3 and Figure 4 As shown, further, a third two-position two-way electromagnetic reversing valve 13 is installed in the unloading valve 6. The overflow valve 12 is respectively connected to the hydraulic oil tank 1 and the third two-position two-way electromagnetic reversing valve 13 through pipelines. The third two-position two-way electromagnetic reversing valve 13 is connected to the pipeline between the lifting oil cylinder control valve 4 and the rodless cavity of the left lifting oil cylinder 3 through a pipeline.

[0047] The beneficial effect of adopting the above further technical solution is: It is realized by using an electro-hydraulic proportional overflow valve. This solution is applicable to both fixed-displacement systems and variable-displacement systems. Among them, the overflow valve in the unloading valve can be adjusted in a timely manner according to the required unloading force. The smaller the current, the greater the unloading force.

[0048] Such as Figure 5As shown, further, when the hydraulic three-point hitch system is a variable system, both ends of the unloading valve 6 are connected through pipelines to the hydraulic oil tank 1 and the pipeline between the second end of the lift cylinder control valve 4 and the variable pump 7 respectively, and the unloading valve 6 is an electro-hydraulic proportional relief valve.

[0049] The beneficial effect of adopting the above further technical solution is: It is realized by using an electro-hydraulic proportional relief valve. This solution is applicable to variable systems. The unloading valve is an electro-hydraulic proportional relief valve, which can be adjusted timely according to the required unloading force. The smaller the current, the greater the unloading force.

[0050] In addition, the present invention also provides a lifting method for a tractor with an unloading function. Based on the above-mentioned lifting system for a tractor with an unloading function, the lifting method for a tractor with an unloading function includes: realizing the unloading function of the hydraulic three-point hitch system through the unloading valve.

[0051] The beneficial effect of adopting the technical solution of the present invention is: By adding an unloading valve, the unloading function is realized, so that the lifting force can be adjusted steplessly, and the pressure of the implement on the crop or the ground can be adjusted according to needs.

[0052] Further, the step of realizing the unloading function of the hydraulic three-point hitch system through the unloading valve includes: controlling the lift cylinder control valve to be in the lift position, and controlling the two-position three-way solenoid directional valve, the first two-position two-way solenoid directional valve, the second two-position two-way solenoid directional valve and the proportional pressure reducing valve to be energized to realize the unloading function of the hydraulic three-point hitch system; or, controlling the lift cylinder control valve to be in the lift position, and controlling the third two-position two-way solenoid directional valve and the relief valve to be energized to realize the unloading function of the hydraulic three-point hitch system; or, controlling the lift cylinder control valve to be in the lift position, and controlling the electro-hydraulic proportional relief valve to be energized to realize the unloading function of the hydraulic three-point hitch system.

[0053] The beneficial effect of adopting the above further technical solution is: It is realized by using an electro-hydraulic proportional pressure reducing valve. This solution is applicable to both fixed-displacement systems and variable systems. Among them, the proportional pressure reducing valve in the unloading valve can be adjusted timely according to the required unloading force. The greater the current, the greater the unloading force. Or it is realized by using an electro-hydraulic proportional relief valve. This solution is applicable to both fixed-displacement systems and variable systems. Among them, the relief valve in the unloading valve can be adjusted timely according to the required unloading force. The smaller the current, the greater the unloading force. Or it is realized by using an electro-hydraulic proportional relief valve. This solution is applicable to variable systems. The unloading valve is an electro-hydraulic proportional relief valve, which can be adjusted timely according to the required unloading force. The smaller the current, the greater the unloading force.

[0054] Among them, the first oil port of the two-position three-way electromagnetic reversing valve 9 is connected to the lifting cylinder control valve 4 through a pipeline. The second oil port of the two-position three-way electromagnetic reversing valve 9 is connected to the first oil port of the first two-position two-way electromagnetic reversing valve 10. The second oil port of the first two-position two-way electromagnetic reversing valve 10 is connected to the rodless cavity of the left lifting cylinder 3 through a pipeline. The third oil port of the two-position three-way electromagnetic reversing valve 9 is connected to the first oil port of the proportional pressure reducing valve 8 through a pipeline. The second oil port of the proportional pressure reducing valve 8 is connected to the first oil port of the second two-position two-way electromagnetic reversing valve 11 through a pipeline. The second oil port of the second two-position two-way electromagnetic reversing valve 11 is connected to the second oil port of the first two-position two-way electromagnetic reversing valve 10 through a pipeline.

[0055] When the two-position three-way electromagnetic reversing valve 9 is energized, the first oil port of the two-position three-way electromagnetic reversing valve 9 is communicated with the third oil port of the two-position three-way electromagnetic reversing valve 9, and the first oil port of the two-position three-way electromagnetic reversing valve 9 is disconnected from the second oil port of the two-position three-way electromagnetic reversing valve 9. When the two-position three-way electromagnetic reversing valve 9 is de-energized, the first oil port of the two-position three-way electromagnetic reversing valve 9 is disconnected from the third oil port of the two-position three-way electromagnetic reversing valve 9, and the first oil port of the two-position three-way electromagnetic reversing valve 9 is communicated with the second oil port of the two-position three-way electromagnetic reversing valve 9.

[0056] When the proportional pressure reducing valve 8 is energized, the first oil port of the proportional pressure reducing valve 8 is communicated with the second oil port of the proportional pressure reducing valve 8. When the proportional pressure reducing valve 8 is de-energized, the first oil port of the proportional pressure reducing valve 8 is disconnected from the second oil port of the proportional pressure reducing valve 8.

[0057] When the first two-position two-way electromagnetic reversing valve 10 is energized, the first oil port and the second oil port of the first two-position two-way electromagnetic reversing valve 10 are disconnected. When the first two-position two-way electromagnetic reversing valve 10 is de-energized, the first oil port and the second oil port of the first two-position two-way electromagnetic reversing valve 10 are communicated.

[0058] When the second two-position two-way electromagnetic reversing valve 11 is energized, the first oil port and the second oil port of the second two-position two-way electromagnetic reversing valve 11 are communicated. When the second two-position two-way electromagnetic reversing valve 11 is de-energized, the first oil port and the second oil port of the second two-position two-way electromagnetic reversing valve 11 are disconnected.

[0059] The first oil port of the third two-position two-way electromagnetic reversing valve 13 is connected to the rodless cavity of the left lifting cylinder 3 through a pipeline. The second oil port of the third two-position two-way electromagnetic reversing valve 13 is connected to the first oil port of the relief valve 12 through a pipeline. The second oil port of the relief valve 12 is connected to the hydraulic oil tank 1.

[0060] When the third two-position two-way electromagnetic reversing valve 13 is energized, the first oil port of the third two-position two-way electromagnetic reversing valve 13 is connected with the second oil port of the third two-position two-way electromagnetic reversing valve 13. When the third two-position two-way electromagnetic reversing valve 13 is de-energized, the first oil port of the third two-position two-way electromagnetic reversing valve 13 is disconnected from the second oil port of the third two-position two-way electromagnetic reversing valve 13.

[0061] When the relief valve 12 is powered, the first oil port of the relief valve 12 is connected to the second oil port of the relief valve 12. When the relief valve 12 is powered off, the first oil port of the relief valve 12 is disconnected from the second oil port of the relief valve 12.

[0062] The first oil port of the electric proportional relief valve is connected to the pipeline between the variable pump 7 and the lifting cylinder control valve 4 through a pipeline, and the second oil port of the electric proportional relief valve is connected to the hydraulic oil tank 1 through a pipeline.

[0063] When the electric proportional relief valve is energized, the first oil port of the electric proportional relief valve is connected with the second oil port of the electric proportional relief valve. When the electric proportional relief valve is de-energized, the first oil port of the electric proportional relief valve is disconnected from the second oil port of the electric proportional relief valve.

[0064] There are two control modes for the hydraulic three-point suspension on the tractor, namely, a quantitative system and a variable system. The embodiments of the present invention will adopt different schemes to realize the unloading function, which will be introduced respectively below.

[0065] Solution 1: Use electric proportional pressure reducing valve to achieve this. This solution is applicable to quantitative system and variable system, such as Figure 1 Quantitative system, Figure 2 Variable system. The specific control logic is shown in the following table, where the proportional pressure reducing valve Y4 in the unloading valve 6 can be adjusted in time according to the required unloading force, and the greater the current, the greater the unloading force.

[0066] Control logic: Solution 2: Use an electric proportional relief valve to achieve this. This solution is applicable to both quantitative and variable systems, such as Figure 3 Quantitative system, Figure 4 Variable system. The specific control logic is shown in the following table, where the overflow valve Y2 in the unloading valve 6 can be adjusted in time according to the required unloading force. The smaller the current, the greater the unloading force.

[0067] Control logic: Solution 3: Use electric proportional relief valve to achieve this. This solution is suitable for variable systems. Figure 5 In the variable system, the unloading valve 6 is an electric proportional relief valve, which can be adjusted in time according to the required unloading force. The smaller the current, the greater the unloading force.

[0068] Without the unloading valve 6, the maximum lifting force provided by the tractor's three-point hitch to the implement is fixed. During the operation of the implement, it is not allowed for the lift valve (lift cylinder control valve) to be in the lifting state. In this case, the self-weight of the implement will act entirely on the crop or the ground, and for some working conditions, it will not meet the usage requirements. If the unloading valve 6 is added, the lifting force can be adjusted steplessly, so that the pressure of the implement on the crop or the ground can be adjusted according to needs.

[0069] Those of ordinary skill in the art can understand that all or part of the steps of implementing the above method embodiments can be completed by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it performs the steps including the above method embodiments; and the aforementioned storage medium includes various media such as ROM, RAM, magnetic disks, or optical discs that can store program codes.

[0070] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lifting system with unloading function for a tractor, characterized in that, Comprising: A hydraulic three-point hitch system and a relief valve (6), the relief valve (6) being connected to the hydraulic three-point hitch system.

2. The lifting system with unloading function for a tractor according to claim 1, characterized in that, The hydraulic three-point hitch system is a fixed-displacement system or a variable-displacement system.

3. The lifting system with unloading function for a tractor according to claim 2, characterized in that, When the hydraulic three-point hitch system is a fixed-displacement system, the hydraulic three-point hitch system comprises: a hydraulic oil tank (1), a fixed-displacement pump (2), a left lift cylinder (3), a lift cylinder control valve (4), and a right lift cylinder (5). The fixed-displacement pump (2) is connected to the hydraulic oil tank (1) through a pipeline. The rodless cavity of the left lift cylinder (3) is connected to the rodless cavity of the right lift cylinder (5) through a pipeline. The rod end cavity of the left lift cylinder (3) is connected to the rod end cavity of the right lift cylinder (5) through a pipeline. The first end of the lift cylinder control valve (4) is connected to the fixed-displacement pump (2) through a pipeline. The second end of the lift cylinder control valve (4) is connected to the pipeline between the rod end cavities of the left lift cylinder (3) and the right lift cylinder (5) through a pipeline. The third end of the lift cylinder control valve (4) is connected to the pipeline between the rodless cavities of the left lift cylinder (3) and the right lift cylinder (5) through a pipeline. The fourth end of the lift cylinder control valve (4) is connected to the hydraulic oil tank (1) through a pipeline. When the hydraulic three-point hitch system is a variable-displacement system, the hydraulic three-point hitch system comprises: a hydraulic oil tank (1), a variable-displacement pump (7), a left lift cylinder (3), a lift cylinder control valve (4), and a right lift cylinder (5). The variable-displacement pump (7) is connected to the hydraulic oil tank (1) through a pipeline. The rodless cavity of the left lift cylinder (3) is connected to the rodless cavity of the right lift cylinder (5) through a pipeline. The rod end cavity of the left lift cylinder (3) is connected to the rod end cavity of the right lift cylinder (5) through a pipeline. The first end and the second end of the lift cylinder control valve (4) are respectively connected to the variable-displacement pump (7) through pipelines. The third end of the lift cylinder control valve (4) is connected to the pipeline between the rod end cavities of the left lift cylinder (3) and the right lift cylinder (5) through a pipeline. The fourth end of the lift cylinder control valve (4) is connected to the pipeline between the rodless cavities of the left lift cylinder (3) and the right lift cylinder (5) through a pipeline. The fifth end of the lift cylinder control valve (4) is connected to the hydraulic oil tank (1) through a pipeline.

4. The lifting system with unloading function for a tractor according to claim 3, characterized in that, When the hydraulic three-point hitch system is a fixed-displacement system or a variable-displacement system, the relief valve (6) is installed on the pipeline between the lift cylinder control valve (4) and the rodless cavity of the left lift cylinder (3), and a proportional pressure reducing valve is installed in the relief valve (6).

5. A lifting system with unloading function for a tractor according to claim 4, characterized in that, The unloading valve (6) includes: a two-position three-way electromagnetic directional control valve, a first two-position two-way electromagnetic directional control valve, and a second two-position two-way electromagnetic directional control valve. The two-position three-way electromagnetic directional control valve is respectively connected to the lifting cylinder control valve (4), the first two-position two-way electromagnetic directional control valve, and the proportional pressure reducing valve through pipelines. The proportional pressure reducing valve is connected to the second two-position two-way electromagnetic directional control valve through a pipeline. Both the first two-position two-way electromagnetic directional control valve and the second two-position two-way electromagnetic directional control valve are connected to the rodless cavity of the left lifting cylinder (3) through pipelines.

6. The lifting system with unloading function for a tractor according to claim 3, characterized in that, When the hydraulic three-point hitch system is a fixed-displacement system or a variable-displacement system, the unloading valve (6) is respectively connected to the hydraulic oil tank (1), and the pipeline between the lifting cylinder control valve (4) and the rodless cavity of the left lifting cylinder (3) through pipelines. An overflow valve is installed in the unloading valve (6).

7. A lifting system with unloading function for a tractor according to claim 6, characterized in that, A third two-position two-way electromagnetic directional control valve is installed in the unloading valve (6). The overflow valve is respectively connected to the hydraulic oil tank (1) and the third two-position two-way electromagnetic directional control valve through pipelines. The third two-position two-way electromagnetic directional control valve is connected to the pipeline between the lifting cylinder control valve (4) and the rodless cavity of the left lifting cylinder (3) through a pipeline.

8. The lifting system with unloading function for a tractor according to claim 3, characterized in that, When the hydraulic three-point hitch system is a variable-displacement system, both ends of the unloading valve (6) are respectively connected to the hydraulic oil tank (1), and the pipeline between the second end of the lifting cylinder control valve (4) and the variable pump (7) through pipelines. The unloading valve (6) is an electro-hydraulic proportional overflow valve.

9. A lifting method with unloading function for a tractor, characterized in that, Based on the lifting system with unloading function for a tractor according to any one of the above claims 1 to 8, the lifting method with unloading function for a tractor includes: realizing the unloading function of the hydraulic three-point hitch system through the unloading valve.

10. A lifting method with unloading function for a tractor according to claim 9, characterized in that, The steps of realizing the unloading function of the hydraulic three-point hitch system through the unloading valve include: controlling the lifting cylinder control valve to be in the lifting position, and controlling the two-position three-way electromagnetic directional control valve, the first two-position two-way electromagnetic directional control valve, the second two-position two-way electromagnetic directional control valve, and the proportional pressure reducing valve to be energized to realize the unloading function of the hydraulic three-point hitch system; or, controlling the lifting cylinder control valve to be in the lifting position, and controlling the third two-position two-way electromagnetic directional control valve and the overflow valve to be energized to realize the unloading function of the hydraulic three-point hitch system; or, controlling the lifting cylinder control valve to be in the lifting position, and controlling the electro-hydraulic proportional overflow valve to be energized to realize the unloading function of the hydraulic three-point hitch system.

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