A tractor front lift selection control valve and a tractor hydraulic system

Abstract

The present application relates to a tractor front lifting selection control valve and a tractor hydraulic system, belonging to the field of tractors. It comprises a front lifting selection control valve, a front lifting oil cylinder and a multi-way reversing valve. The two ends of the front lifting selection control valve are respectively in bidirectional communication with the front lifting oil cylinder and the multi-way reversing valve, for locking the front lifting oil cylinder, or making the front lifting oil cylinder extend through hydraulic oil, or making the front lifting oil cylinder extend through the gravity of the front suspension implement, or making the front lifting oil cylinder retract through hydraulic oil. The present application is conducive to making the tractor front suspension implement have the locking function, the double-acting mode of making the front lifting oil cylinder extend and retract through hydraulic oil, and the single-acting mode of making the front lifting oil cylinder extend through the gravity of the front suspension implement and retract through hydraulic oil, thereby improving the adaptability of the front suspension implement under different use conditions.

Description

Technical Field

[0001] This invention relates to the field of tractors, and more particularly to a tractor front lift selection control valve and a tractor hydraulic system. Background Technology

[0002] As an important component of agricultural machinery and engineering equipment, the tractor's suspension lifting system is the core device for raising, lowering, and adjusting the depth of implements (such as plows, harrows, seeders, and mowers). Tractors typically have two types of suspension systems: a front suspension system and a rear suspension system. The front suspension system is installed at the front of the tractor and is mainly used for raising and adjusting the position of implements; while the rear suspension system is installed at the rear of the tractor and is also used for raising and adjusting implements. The core working principle of both is that the driver operates a multi-way valve handle in the cab, which controls the movement of the front and rear lifting cylinders, thereby driving the suspension rods to control the raising or lowering of the implements.

[0003] Conventional tractors are generally equipped with only a rear suspension system. In order to meet more types of agricultural implements and higher operational requirements, some tractors have been equipped with a front suspension system. This flexibility makes the tractor more applicable in different agricultural scenarios. However, the current control method of the front suspension is relatively simple, relying only on a multi-way valve to connect the lifting cylinder. The extension or retraction of the cylinder is achieved by switching the function position of the multi-way valve. This method is not adaptable to different operating conditions of the implements. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a tractor front lift selection control valve and a tractor hydraulic system to solve the above-mentioned problem.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A tractor front lift selection control valve, comprising: a front lift selection control valve, a front lift cylinder, and a multi-way reversing valve, wherein the two ends of the front lift selection control valve are bidirectionally connected to the front lift cylinder and the multi-way reversing valve, respectively, for locking the front lift cylinder, or extending the front lift cylinder by hydraulic oil, or extending the front lift cylinder by the gravity of the front suspension implement, or retracting the front lift cylinder by hydraulic oil.

[0006] The beneficial effects of this invention are: it facilitates the use of locking functions in the front suspension mechanism of tractors, a dual-action mode in which the front lifting cylinder extends and retracts via hydraulic oil, and a single-action mode in which the front lifting cylinder extends via gravity and retracts via hydraulic oil, thereby improving the adaptability of the front suspension mechanism under different operating conditions.

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

[0008] Furthermore, the front lift selection control valve includes a first control valve and a second control valve. The valve core of the first control valve is fixedly connected to the valve core of the second control valve. Both the first control valve and the second control valve are two-position two-way valve bodies. Both the first valve position of the first control valve and the first valve position of the second control valve are provided with a straight-through passage. Both the second valve position of the first control valve and the second valve position of the second control valve are open circuits. The first control valve is provided with an electromagnet, and the second control valve is provided with a return spring, which is used to synchronize the switching of the first control valve and the second control valve after the electromagnet of the first control valve is energized or de-energized.

[0009] The beneficial effect of adopting the above-mentioned further scheme is that it facilitates the synchronous switching of the first control valve and the second control valve after the first control valve is energized or de-energized.

[0010] Furthermore, the second valve position of the first control valve and the second valve position of the second control valve are both connected to the multi-way directional valve, which is used to lock the front lifting cylinder.

[0011] The beneficial effect of adopting the above-mentioned further solution is that it helps to realize the locking function of the front lifting cylinder.

[0012] Furthermore, the multi-way directional valve is a three-position four-way solenoid valve. Its first valve position has two intersecting first and second passages, and its third valve position has two parallel third and fourth passages. One end of the first passage and one end of the second passage are respectively connected to one end of the first valve position of the first control valve and one end of the first valve position of the second control valve, or one end of the third passage and one end of the fourth passage are respectively connected to one end of the first valve position of the first control valve and one end of the first valve position of the second control valve.

[0013] The beneficial effect of adopting the above-mentioned further solution is that it facilitates the flow of hydraulic oil to the rodless or rod-shaped chamber of the front lifting cylinder, thereby realizing the extension or retraction of the front lifting cylinder.

[0014] Furthermore, it also includes a hydraulic oil tank and a working pump, the input end of the working pump being connected to the hydraulic oil tank, the other end of the first passage and the other end of the second passage being connected to the output end of the hydraulic oil tank and the working pump respectively, or the other end of the third passage and the other end of the fourth passage being connected to the output end of the working pump and the hydraulic oil tank respectively.

[0015] The beneficial effect of adopting the above-mentioned further solution is that the working pump is conducive to pumping the hydraulic oil in the hydraulic oil tank to the downstream hydraulic transmission components.

[0016] Furthermore, it also includes an overflow valve, one end of which is connected to the pipeline connecting the multi-way directional valve and the working pump, and the other end of which is connected to the hydraulic oil tank.

[0017] The beneficial effect of adopting the above-mentioned further solution is that the overflow valve helps protect the multi-way directional valve.

[0018] Furthermore, the front lifting selection control valve also includes a third control valve and a one-way throttle valve. The other end of the first valve position of the first control valve is connected to one end of the one-way throttle valve, and the other end of the one-way throttle valve is connected to the rod chamber of the front lifting cylinder. The other end of the first valve position of the second control valve is connected to the rodless chamber of the front lifting cylinder, which is used to extend the front lifting cylinder by means of hydraulic oil. Alternatively, the other end of the first valve position of the second control valve is connected to the third control valve, which is used to extend the front lifting cylinder by means of the gravity of the front suspension device.

[0019] The beneficial effect of adopting the above-mentioned further solution is that it facilitates the extension of the front lifting cylinder by means of hydraulic oil or by means of the gravity of the front suspension mechanism.

[0020] Furthermore, the third control valve is a two-position two-way solenoid valve, with a straight-through passage in its first valve position. The other end of the first valve position of the second control valve is connected to one end of the first valve position of the third control valve, and the other end of the first valve position of the third control valve is connected to one end of the one-way throttle valve.

[0021] The beneficial effect of adopting the above-mentioned further scheme is that the third control valve, by switching valve positions and cooperating with the first control valve, the second control valve and the multi-way directional valve, facilitates the switching between double-acting mode, single-acting mode and lock-up mode.

[0022] Furthermore, a check valve is provided between the third control valve and the one-way throttle valve to allow hydraulic oil to flow from the third control valve to the one-way throttle valve.

[0023] The beneficial effect of adopting the above-mentioned further solution is that the check valve is advantageous in single-acting mode so that the hydraulic oil flowing out of the first control valve preferentially enters the third control valve instead of entering the front lifting cylinder.

[0024] The technical solution of the present invention also includes a tractor hydraulic system, comprising the aforementioned tractor front lifting selection control valve. Attached Figure Description

[0025] Figure 1 This is a hydraulic transmission diagram provided in Embodiment 1 of the present invention; Figure 2 This is a hydraulic transmission diagram provided in Embodiment 2 of the present invention; Figure 3This is a hydraulic transmission diagram provided in Embodiment 2 of the present invention; Figure 4 This is a hydraulic transmission diagram provided in Embodiment 3 of the present invention; Figure 5 This is a hydraulic transmission diagram provided in Embodiment 3 of the present invention; Figure 6 This is a schematic diagram of a multi-way directional valve provided in an embodiment of the present invention.

[0026] The attached diagram lists the components represented by each number as follows: 1. Front lift selection control valve; 2. Front lift cylinder; 3. Multi-way directional valve; 4. Working pump; 5. Hydraulic oil tank; 6. Relief valve; 11. First control valve; 12. Second control valve; 13. Third control valve; 14. One-way throttle valve; 15. One-way valve; 31. First passage; 32. Second passage; 33. Third passage; 34. Fourth passage. Detailed Implementation

[0027] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0028] Example 1.

[0029] This embodiment is used to lock the front lifting cylinder 2.

[0030] like Figure 1 As shown, this embodiment provides a tractor front lift selection control valve, including: a front lift selection control valve 1, a front lift cylinder 2, a multi-way directional valve 3, a working pump 4, a hydraulic oil tank 5, and an overflow valve 6. The front lift selection control valve 1 includes: a first control valve 11, a second control valve 12, a third control valve 13, a one-way throttle valve 14, and a one-way valve 15. The valve core of the first control valve 11 is fixedly connected to the valve core of the second control valve 12. Both the first control valve 11 and the second control valve 12 are two-position two-way valve bodies. Both the first valve position of the first control valve 11 and the first valve position of the second control valve 12 are provided with a straight passage. Both the second valve position of the first control valve 11 and the second valve position of the second control valve 12 are open circuits. The first control valve 11 is provided with an electromagnet, and the second control valve 12 is provided with a return spring, which is used to make the first control valve 11 and the second control valve 12 switch synchronously after the electromagnet of the first control valve 11 is energized or de-energized. The multi-way directional valve 3 is a three-position four-way solenoid valve. Its first valve position has two intersecting first passages 31 and second passages 32, its third valve position has two parallel third passages 33 and fourth passages 34, and its second valve position is a disconnected circuit. The third control valve 13 is a two-position two-way solenoid valve, with a straight-through passage in its first valve position and a closed circuit in its second valve position; The input end of the working pump 4 is connected to the hydraulic oil tank 5, and its output end is connected to the first port of the second valve position of the multi-way directional valve 3. The second port of the second valve position of the multi-way directional valve 3 is connected to the hydraulic oil tank 5. One end of the relief valve 6 is connected to the pipeline connecting the multi-way directional valve 3 and the working pump 4, and the other end is connected to the hydraulic oil tank 5. The third port of the second valve position of the multi-way directional valve 3 is connected to one end of the second valve position of the first control valve 11, and the fourth port of the second valve position of the multi-way directional valve 3 is connected to one end of the second valve position of the second control valve 12. The other end of the second valve position of the second control valve 12 is connected to one end of the second valve position of the third control valve 13 and the rodless chamber of the front lifting cylinder 2. The other end of the second valve position of the third control valve 13 is connected to one end of the one-way throttle valve 14. One end of the one-way throttle valve 14 is connected to the other end of the second valve position of the first control valve 11. A one-way valve 15 is provided between the third control valve 13 and the one-way throttle valve 14 to allow hydraulic oil to flow from the third control valve 13 to the one-way throttle valve 14. The other end of the one-way throttle valve 14 is connected to the rod chamber of the front lifting cylinder 2.

[0031] The working principle of this embodiment is as follows: When the first control valve 11 and the third control valve 13 are not energized, and the valve cores of the first control valve 11, the second control valve 12 and the third control valve 13 are all in the second valve position, regardless of whether the multi-way directional valve 3 is energized or not, and regardless of which valve position the valve core of the multi-way directional valve 3 is in, the hydraulic oil in the hydraulic oil tank 5 will not enter the downstream hydraulic equipment from the first control valve 11 and the second control valve 12.

[0032] This working condition is applicable to the transportation of front-suspension implements by tractors, ensuring that the front-suspension implements are locked in position and will not fall due to bumps. When switched to the locking mode, it can also prevent the driver from accidentally touching the operating handle of the multi-way reversing valve 3 during the driving of the front-suspension implement, which would cause the front lifting cylinder 2 to move and thus lead to a safety accident.

[0033] Example 2.

[0034] This embodiment is a dual-action mode, in which the front lifting cylinder 2 is extended by hydraulic oil and retracted by hydraulic oil.

[0035] like Figure 2 and Figure 3As shown, this embodiment provides a tractor front lift selection control valve, including: a front lift selection control valve 1, a front lift cylinder 2, a multi-way directional valve 3, a working pump 4, a hydraulic oil tank 5, and an overflow valve 6. The front lift selection control valve 1 includes: a first control valve 11, a second control valve 12, a third control valve 13, a one-way throttle valve 14, and a one-way valve 15. The valve core of the first control valve 11 is fixedly connected to the valve core of the second control valve 12. Both the first control valve 11 and the second control valve 12 are two-position two-way valve bodies. Both the first valve position of the first control valve 11 and the first valve position of the second control valve 12 are provided with a straight passage. Both the second valve position of the first control valve 11 and the second valve position of the second control valve 12 are open circuits. The first control valve 11 is provided with an electromagnet, and the second control valve 12 is provided with a return spring, which is used to make the first control valve 11 and the second control valve 12 switch synchronously after the electromagnet of the first control valve 11 is energized or de-energized. The multi-way directional valve 3 is a three-position four-way solenoid valve. Its first valve position has two intersecting first passages 31 and second passages 32, its third valve position has two parallel third passages 33 and fourth passages 34, and its second valve position is a disconnected circuit. The third control valve 13 is a two-position two-way solenoid valve, with a straight-through passage in its first valve position and a closed circuit in its second valve position; The input end of the working pump 4 is connected to the hydraulic oil tank 5, and its output end is connected to the first or third valve position of the multi-way directional valve 3. The first or third valve position of the multi-way directional valve 3 is connected to the hydraulic oil tank 5. One end of the relief valve 6 is connected to the pipeline connecting the multi-way directional valve 3 and the working pump 4, and the other end is connected to the hydraulic oil tank 5. The first or third valve position of the multi-way directional valve 3 is connected to one end of the first valve position of the first control valve 11 and one end of the first valve position of the second control valve 12. The other end of the valve position is connected to one end of the second valve position of the third control valve 13 and the rodless chamber of the front lifting cylinder 2. The other end of the second valve position of the third control valve 13 is connected to one end of the one-way throttle valve 14. One end of the one-way throttle valve 14 is connected to the other end of the first valve position of the first control valve 11. A one-way valve 15 is provided between the third control valve 13 and the one-way throttle valve 14 to allow hydraulic oil to flow from the third control valve 13 to the one-way throttle valve 14. The other end of the one-way throttle valve 14 is connected to the rod chamber of the front lifting cylinder 2.

[0036] The working principle of this embodiment is as follows: like Figure 2As shown, both the first control valve 11 and the second control valve 12 are energized, so that the valve cores of the first control valve 11 and the second control valve 12 are in the first valve position. The third control valve 13 is not energized, so that the valve core of the third control valve 13 is in the second valve position. One of the electromagnets of the multi-way directional valve 3 is energized, so that the valve core of the multi-way directional valve 3 is in the first valve position. At this time, one end of the first passage 31 and one end of the second passage 32 are respectively connected to one end of the first valve position of the first control valve 11 and one end of the first valve position of the second control valve 12. The other end of the first passage 31 and the other end of the second passage 32 are respectively connected to the output end of the hydraulic oil tank 5 and the working pump 4. When the working pump 4 is started, the hydraulic oil in the hydraulic oil tank 5 is pumped sequentially through the second passage 32 in the first valve position of the multi-way directional valve 3 and the passage in the first valve position of the second control valve 12 to the rodless chamber of the front lifting cylinder 2, so that the front lifting cylinder 2 extends and the front suspension device is lowered. In this embodiment, the lowering of the front suspension device is achieved by hydraulic oil, that is, the front lifting cylinder 2 can generate a downward pressure, which is suitable for front suspension devices that require downward pressure during operation. like Figure 3 As shown, both the first control valve 11 and the second control valve 12 are energized, so that the valve cores of the first control valve 11 and the second control valve 12 are in the first valve position. The third control valve 13 is not energized, so that the valve core of the third control valve 13 is in the second valve position. The other electromagnet of the multi-way directional valve 3 is energized, so that the valve core of the multi-way directional valve 3 is in the third valve position. At this time, one end of the third passage 33 and one end of the fourth passage 34 are respectively connected to one end of the first valve position of the first control valve 11 and one end of the first valve position of the second control valve 12. The other end of the third passage 33 and the other end of the fourth passage 34 are respectively connected to the output end of the working pump 4 and the hydraulic oil tank 5. When the working pump 4 is started, the hydraulic oil in the hydraulic oil tank 5 is pumped sequentially through the third passage 33 in the third valve position of the multi-way directional valve 3, the passage in the first valve position of the first control valve 11, and the one-way throttle valve 14 to the rod chamber of the front lifting cylinder 2, so that the front lifting cylinder 2 retracts and the front suspension implement rises.

[0037] Example 3.

[0038] This embodiment is a single-action mode. In this mode, the front lifting cylinder 2 is extended by the gravity of the front suspension mechanism and retracted by hydraulic oil.

[0039] like Figure 4 and Figure 5As shown, this embodiment provides a tractor front lift selection control valve, including: a front lift selection control valve 1, a front lift cylinder 2, a multi-way directional valve 3, a working pump 4, a hydraulic oil tank 5, and an overflow valve 6. The front lift selection control valve 1 includes: a first control valve 11, a second control valve 12, a third control valve 13, a one-way throttle valve 14, and a one-way valve 15. The valve core of the first control valve 11 is fixedly connected to the valve core of the second control valve 12. Both the first control valve 11 and the second control valve 12 are two-position two-way valve bodies. Both the first valve position of the first control valve 11 and the first valve position of the second control valve 12 are provided with a straight passage. Both the second valve position of the first control valve 11 and the second valve position of the second control valve 12 are open circuits. The first control valve 11 is provided with an electromagnet, and the second control valve 12 is provided with a return spring, which is used to make the first control valve 11 and the second control valve 12 switch synchronously after the electromagnet of the first control valve 11 is energized or de-energized. The multi-way directional valve 3 is a three-position four-way solenoid valve. Its first valve position has two intersecting first passages 31 and second passages 32, its third valve position has two parallel third passages 33 and fourth passages 34, and its second valve position is a disconnected circuit. The third control valve 13 is a two-position two-way solenoid valve, with a straight-through passage in its first valve position and a closed circuit in its second valve position; The input end of the working pump 4 is connected to the hydraulic oil tank 5, and its output end is connected to the first or third valve position of the multi-way directional valve 3. The first or third valve position of the multi-way directional valve 3 is connected to the hydraulic oil tank 5. One end of the relief valve 6 is connected to the pipeline connecting the multi-way directional valve 3 and the working pump 4, and the other end is connected to the hydraulic oil tank 5. The first or third valve position of the multi-way directional valve 3 is connected to one end of the first valve position of the first control valve 11 and one end of the first valve position of the second control valve 12. The other end of the valve position is connected to one end of the first valve position of the third control valve 13 and the rodless chamber of the front lifting cylinder 2. The other end of the first valve position of the third control valve 13 is connected to one end of the one-way throttle valve 14. One end of the one-way throttle valve 14 is connected to the other end of the first valve position of the first control valve 11. A one-way valve 15 is provided between the third control valve 13 and the one-way throttle valve 14 to allow hydraulic oil to flow from the third control valve 13 to the one-way throttle valve 14. The other end of the one-way throttle valve 14 is connected to the rod chamber of the front lifting cylinder 2.

[0040] The working principle of this embodiment is as follows: like Figure 4As shown, both the first control valve 11 and the second control valve 12 are energized, so that the valve cores of the first control valve 11 and the second control valve 12 are in the first valve position. The third control valve 13 is energized, so that the valve core of the third control valve 13 is in the first valve position. One of the electromagnets of the multi-way directional valve 3 is energized, so that the valve core of the multi-way directional valve 3 is in the first valve position. At this time, one end of the first passage 31 and one end of the second passage 32 are respectively connected to one end of the first valve position of the first control valve 11 and one end of the first valve position of the second control valve 12. The other end of the first passage 31 and the other end of the second passage 32 are respectively connected to the output end of the hydraulic oil tank 5 and the working pump 4. When the working pump 4 is started, the hydraulic oil in the hydraulic oil tank 5 is pumped through the second passage 32 in the first valve position of the multi-way directional valve 3 to the first valve position of the second control valve 12. Since the opening pressure of the check valve 15 is much smaller than the pressure that pushes the front lifting cylinder 2 to extend, the hydraulic oil flowing out from the first valve position of the second control valve 12 will flow back to the hydraulic oil tank 5 through the check valve 15, the passage in the first valve position of the first control valve 11, and the first passage 31 in the first valve position of the multi-way directional valve 3 in sequence. Only a very small portion, or even none, of the hydraulic oil enters the front lifting cylinder 2. In the rodless cavity, the front lifting cylinder 2 cannot extend due to hydraulic oil. Instead, it can only extend due to the gravity of the front suspension device, which is fixedly connected to the output shaft of the front lifting cylinder 2, thereby causing the front suspension device to descend. In this embodiment, the descent of the front suspension device is achieved by the gravity of the front suspension device. This is suitable for some front suspension devices, such as front suspension lawnmowers. When the front suspension device is in contact with the ground in the working state, it should not be subjected to additional downward pressure in addition to its own weight. This allows the front suspension device to freely adjust its up and down position according to the terrain conditions or load changes to maintain the best contact between the front suspension device and the ground. Furthermore, in this embodiment, since the hydraulic oil in the rod chamber of the front lifting cylinder 2 will eventually flow back to the hydraulic oil tank 5 through the throttling channel of the one-way throttle valve 14, the passage in the first valve position of the first control valve 11, and the first passage 31 in the first valve position of the multi-way directional valve 3, the extension speed of the front lifting cylinder 2 can be adjusted by adjusting the opening of the valve core of the one-way throttle valve 14, thereby adjusting the descent speed of the front suspension device. like Figure 5As shown, both the first control valve 11 and the second control valve 12 are energized, so that the valve cores of the first control valve 11 and the second control valve 12 are in the first valve position. The third control valve 13 is energized, so that the valve core of the third control valve 13 is in the first valve position. The other electromagnet of the multi-way directional valve 3 is energized, so that the valve core of the multi-way directional valve 3 is in the third valve position. At this time, one end of the third passage 33 and one end of the fourth passage 34 are respectively connected to one end of the first valve position of the first control valve 11 and one end of the first valve position of the second control valve 12. The other end of the third passage 33 and the other end of the fourth passage 34 are respectively connected to the output end of the working pump 4 and the hydraulic oil tank 5. When the working pump 4 is started, the hydraulic oil in the hydraulic oil tank 5 is pumped sequentially through the third passage 33 in the third valve position of the multi-way directional valve 3, the passage in the first valve position of the first control valve 11, and the one-way throttle valve 14 to the rod chamber of the front lifting cylinder 2, so that the front lifting cylinder 2 retracts and the front suspension implement rises.

[0041] Example 4.

[0042] This embodiment provides a tractor hydraulic system, including the tractor front lift selection control valve described in Embodiments 1 to 3 above.

[0043] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention 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. Therefore, they should not be construed as limitations on this invention.

[0044] 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 technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0045] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," 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 invention according to the specific circumstances.

[0046] In this invention, 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," "over," and "on top" of 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.

[0047] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are 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.

[0048] 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 tractor front lift selection control valve, characterized in that, include: The front lifting selection control valve (1), the front lifting cylinder (2), and the multi-way directional valve (3) are configured to lock the front lifting cylinder (2), extend the front lifting cylinder (2) by means of hydraulic oil, extend the front lifting cylinder (2) by means of the gravity of the front suspension device, or retract the front lifting cylinder (2) by means of hydraulic oil.

2. The tractor front lift selection control valve according to claim 1, characterized in that, The front lift selection control valve (1) includes a first control valve (11) and a second control valve (12). The valve core of the first control valve (11) is fixedly connected to the valve core of the second control valve (12). Both the first control valve (11) and the second control valve (12) are two-position two-way valve bodies. Both the first valve position of the first control valve (11) and the first valve position of the second control valve (12) are provided with a straight passage. Both the second valve position of the first control valve (11) and the second valve position of the second control valve (12) are open circuits. The first control valve (11) is provided with an electromagnet, and the second control valve (12) is provided with a reset spring, which is used to make the first control valve (11) and the second control valve (12) switch synchronously after the electromagnet of the first control valve (11) is energized or de-energized.

3. The tractor front lift selection control valve according to claim 2, characterized in that, The second valve position of the first control valve (11) and the second valve position of the second control valve (12) are both connected to the multi-way directional valve (3) to lock the front lifting cylinder (2).

4. The tractor front lift selection control valve according to claim 2, characterized in that, The multi-way directional valve (3) is a three-position four-way solenoid valve. Its first valve position has two intersecting first passages (31) and second passages (32), and its third valve position has two parallel third passages (33) and fourth passages (34). One end of the first passage (31) and one end of the second passage (32) are respectively connected to one end of the first valve position of the first control valve (11) and one end of the first valve position of the second control valve (12), or one end of the third passage (33) and one end of the fourth passage (34) are respectively connected to one end of the first valve position of the first control valve (11) and one end of the first valve position of the second control valve (12).

5. The tractor front lift selection control valve according to claim 4, characterized in that, It also includes a hydraulic oil tank (5) and a working pump (4), the input end of the working pump (4) is connected to the hydraulic oil tank (5), the other end of the first passage (31) and the other end of the second passage (32) are respectively connected to the output end of the hydraulic oil tank (5) and the working pump (4), or the other end of the third passage (33) and the other end of the fourth passage (34) are respectively connected to the output end of the working pump (4) and the hydraulic oil tank (5).

6. The tractor front lift selection control valve according to claim 5, characterized in that, It also includes an overflow valve (6), one end of which is connected to the pipeline connecting the multi-way directional valve (3) and the working pump (4), and the other end of which is connected to the hydraulic oil tank (5).

7. The tractor front lift selection control valve according to claim 2, characterized in that, The front lifting selection control valve (1) further includes a third control valve (13) and a one-way throttle valve (14). The other end of the first control valve (11) in the first valve position is connected to one end of the one-way throttle valve (14). The other end of the one-way throttle valve (14) is connected to the rod chamber of the front lifting cylinder (2). The other end of the first valve position of the second control valve (12) is connected to the rodless chamber of the front lifting cylinder (2). It is used to extend the front lifting cylinder (2) by means of hydraulic oil. Alternatively, the other end of the first valve position of the second control valve (12) is connected to the third control valve (13). It is used to extend the front lifting cylinder (2) by means of the gravity of the front suspension mechanism.

8. The tractor front lift selection control valve according to claim 7, characterized in that, The third control valve (13) is a two-position two-way solenoid valve. Its first valve position has a straight passage. The other end of the first valve position of the second control valve (12) is connected to one end of the first valve position of the third control valve (13). The other end of the first valve position of the third control valve (13) is connected to one end of the one-way throttle valve (14).

9. The tractor front lift selection control valve according to claim 7, characterized in that, A check valve (15) is provided between the third control valve (13) and the one-way throttle valve (14) for allowing hydraulic oil to flow from the third control valve (13) to the one-way throttle valve (14).

10. A tractor hydraulic system, characterized in that, Includes the tractor front lift selection control valve as described in any one of claims 1-9.

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