Multifunctional steering oil cylinder, hydraulic steering system and steering axle

Abstract

The present invention relates to a multifunctional steering oil cylinder and a hydraulic steering system and a steering axle using the oil cylinder. The oil cylinder comprises a cylinder body, a partition is provided in the cylinder body, a first piston and a second piston are movably provided in the cylinder body, a piston rod is provided on the second piston, a first mounting hole is provided on the partition, a second mounting hole is provided at one end of the cylinder body, the first piston, the partition, and the second piston divide the inner cavity of the cylinder body into a first cavity, a second cavity, a third cavity, and a fourth cavity, a first oil port connected to the first cavity is provided on the cylinder body, a second oil port connected to the second cavity is provided on the cylinder body, a third oil port connected to the third cavity is provided on the cylinder body, and a fourth oil port connected to the fourth cavity is provided on the cylinder body. When the oil cylinder of this structure is equipped with different hydraulic systems, the functions of a hydraulic power steering system and a hydraulic self-steering system can be realized, and the oil cylinder of the same structure can be used for the hydraulic power steering system and the hydraulic self-steering system, thereby saving costs.

Description

Technical Field

[0001] The invention relates to the field of vehicle steering systems, and in particular to a multifunctional steering oil cylinder and a hydraulic steering system and a steering axle using the oil cylinder. Background Art

[0002] The trailer steering axle is divided into two types: power steering and self-steering. The steering axle generally includes a left wheel 1, a right wheel 2, an axle 3 and a cylinder, and also includes a left steering knuckle arm 4, a right steering knuckle arm 5 and a tie rod 6 connecting the left and right steering knuckle arms. Figure 1 and Figure 2 However, the former mostly adopts single-acting cylinder form, and the number of cylinders 7 is two, such as Figure 1 The latter usually adopts a centering locking cylinder 9 or a cylinder structure, such as Figure 2 As shown. According to the above situation, the two steering axles and oil cylinders cannot be used interchangeably. In this way, when other requirements remain unchanged, they need to be produced and managed as two different products, which invisibly increases the product management cost and will also cause more inventory. In addition, the power steering axle needs to install oil cylinders in the left and right positions respectively, which has a complex structure, a heavy weight of the entire axle, and a high cost, and consumes more fuel. In summary, the market is in urgent need of a new oil cylinder and steering axle that can realize both power steering and self-steering, with a simple structure and low cost. Summary of the invention

[0003] The object of the present invention is to provide a multifunctional steering cylinder with strong versatility, which can meet the requirements of power steering and self-steering at the same time; at the same time, the object of the present invention is also to provide a hydraulic steering system using the above-mentioned cylinder; at the same time, the object of the present invention is also to provide a steering axle using the above-mentioned cylinder.

[0004] To achieve the above-mentioned purpose, an oil cylinder of the present invention adopts the following technical scheme: a multifunctional steering oil cylinder, comprising a cylinder body, a partition plate is fixedly arranged in the cylinder body, a first piston is slidingly and sealably arranged on one side of the partition plate in the cylinder body along the axis direction of the cylinder body, a second piston is slidingly and sealably arranged on the other side of the partition plate in the cylinder body along the axis direction of the cylinder body, a piston rod is arranged on the second piston, the piston rod comprises a first piston rod portion located on one side of the second piston and a second piston rod portion located on the other side of the second piston, a first mounting hole for slidingly and sealably installing the first piston rod portion is arranged on the partition plate, and a second mounting hole for slidingly and sealably installing the second piston rod portion is arranged at one end of the cylinder body, The first piston and the piston rod are independently arranged; the first piston and the cylinder body form a first cavity, the first piston, the partition and the cylinder body form a second cavity, the partition, the second piston and the cylinder body form a third cavity, the second piston and the cylinder body form a fourth cavity, the cylinder body is provided with at least one first oil port connected to the first cavity, the cylinder body is provided with at least one second oil port connected to the second cavity, the cylinder body is provided with at least one third oil port connected to the third cavity, and the cylinder body is provided with at least one fourth oil port connected to the fourth cavity; when the cylinder is connected to a hydraulic power-assisting system, the cylinder can realize hydraulic power-assisting, and when the cylinder is connected to a hydraulic self-steering system, the cylinder can realize the functions of forced centering and self-steering.

[0005] A hydraulic steering system of the present invention adopts the following technical scheme: a hydraulic steering system comprises an oil cylinder and a hydraulic system, the oil cylinder comprises a cylinder body, a partition is fixedly arranged in the cylinder body, a first piston is slidingly and sealably arranged on one side of the partition in the cylinder body along the axial direction of the cylinder body, a second piston is slidingly and sealably arranged on the other side of the partition in the cylinder body along the axial direction of the cylinder body, a piston rod is arranged on the second piston, the piston rod comprises a first piston rod part located on one side of the second piston and a second piston rod part located on the other side of the second piston, a first mounting hole for slidingly and sealably installing the first piston rod part is arranged on the partition, a second mounting hole for slidingly and sealably installing the second piston rod part is arranged at one end of the cylinder body, the first piston and the piston rod are independently arranged; the first piston and the cylinder body A first cavity is formed, the first piston, the partition and the cylinder body form a second cavity, the partition, the second piston and the cylinder body form a third cavity, the second piston and the cylinder body form a fourth cavity, the cylinder body is provided with at least one first oil port connected to the first cavity, the cylinder body is provided with at least one second oil port connected to the second cavity, the cylinder body is provided with at least one third oil port connected to the third cavity, and the cylinder body is provided with at least one fourth oil port connected to the fourth cavity; the hydraulic system includes a hydraulic power-assisting system and a hydraulic self-steering system, and the hydraulic systems all include hydraulic pipelines for connecting to corresponding ports on the cylinder body; when the oil cylinder is connected to the hydraulic power-assisting system, it can realize hydraulic power-assisting, and when the oil cylinder is connected to the hydraulic self-steering system, it can realize the functions of forced centering and self-steering.

[0006] The hydraulic system includes a tractor steering cylinder and a tractor hydraulic steering device, the tractor steering cylinder and the tractor hydraulic steering device are connected through a first oil circuit and a second oil circuit to form a circuit, the hydraulic pipeline includes a third oil circuit connected to the third oil port and the first oil circuit, the hydraulic pipeline also includes a fourth oil circuit connected to the fourth oil port and the second oil circuit, a vent plug is provided at the second oil port, and the first oil port is connected to the oil tank.

[0007] The third oil circuit is provided with a first throttle valve, and the fourth oil circuit is provided with a second throttle valve.

[0008] The hydraulic system includes a first reversing valve and a second reversing valve, the hydraulic pipeline includes a fifth oil circuit connecting the first oil port and the first reversing valve, a sixth oil circuit connecting the third oil port and the second reversing valve, and a seventh oil circuit connecting the fourth oil port and the second reversing valve, and a vent plug is provided at the second oil port; the hydraulic pipeline also includes a main oil circuit, an eighth oil circuit connecting the main oil circuit and the first reversing valve, and a ninth oil circuit connecting the main oil circuit and the second reversing valve; the first reversing valve has a first working position connecting the fifth oil circuit and the eighth oil circuit and a second working position connecting the fifth oil circuit and the oil tank, the second reversing valve has a first working position connecting the sixth oil circuit and the seventh oil circuit, and the second reversing valve also has a second working position connecting the seventh oil circuit and the ninth oil circuit while the sixth oil circuit and the oil tank are connected.

[0009] The sixth oil circuit is provided with a third throttle valve.

[0010] A steering axle of the present invention adopts the following technical scheme: a steering axle, including a left wheel, a right wheel and an axle, and also including a left steering knuckle arm, a right steering knuckle arm and a tie rod connecting the left and right steering knuckle arms. The steering axle also includes a hydraulic steering system, and the hydraulic steering system includes an oil cylinder and a hydraulic system. The oil cylinder includes a cylinder body, a partition is fixedly arranged in the cylinder body, a first piston is provided in the cylinder body on one side of the partition along the cylinder axis direction of the cylinder body for sliding sealing, a second piston is provided in the cylinder body on the other side of the partition along the cylinder axis direction for sliding sealing, a piston rod is provided on the second piston, the piston rod includes a first part of the piston rod located on one side of the second piston and a second part of the piston rod located on the other side of the second piston, a first mounting hole for sliding sealing installation of the first part of the piston rod is provided on the partition, a second mounting hole for sliding sealing installation of the second part of the piston rod is provided at one end of the cylinder body, the first piston and the piston rod Independently arranged; the first piston and the cylinder body form a first cavity, the first piston, the partition and the cylinder body form a second cavity, the partition, the second piston and the cylinder body form a third cavity, the second piston and the cylinder body form a fourth cavity, the cylinder body is provided with at least one first oil port connected to the first cavity, the cylinder body is provided with at least one second oil port connected to the second cavity, the cylinder body is provided with at least one third oil port connected to the third cavity, and the cylinder body is provided with at least one fourth oil port connected to the fourth cavity; the hydraulic system includes a hydraulic power-assisting system and a hydraulic self-steering system, and the hydraulic systems all include hydraulic pipelines for connecting to corresponding ports on the cylinder body; when the cylinder is connected to the hydraulic power-assisting system, it can realize hydraulic power-assisting, and when the cylinder is connected to the hydraulic self-steering system, it can realize the functions of forced centering and self-steering; one end of the cylinder is hinged to the axle, and the piston rod is hinged to the tie rod or one of the steering knuckle arms.

[0011] The hydraulic system includes a tractor steering cylinder and a tractor hydraulic steering device, the tractor steering cylinder and the tractor hydraulic steering device are connected through a first oil circuit and a second oil circuit to form a circuit, the hydraulic pipeline includes a third oil circuit connected to the third oil port and the first oil circuit, the hydraulic pipeline also includes a fourth oil circuit connected to the fourth oil port and the second oil circuit, a vent plug is provided at the second oil port, and the first oil port is connected to the oil tank.

[0012] The third oil circuit is provided with a first throttle valve, and the fourth oil circuit is provided with a second throttle valve.

[0013] The hydraulic system includes a first reversing valve and a second reversing valve, the hydraulic pipeline includes a fifth oil circuit connecting the first oil port and the first reversing valve, a sixth oil circuit connecting the third oil port and the second reversing valve, and a seventh oil circuit connecting the fourth oil port and the second reversing valve, and a vent plug is provided at the second oil port; the hydraulic pipeline also includes a main oil circuit, an eighth oil circuit connecting the main oil circuit and the first reversing valve, and a ninth oil circuit connecting the main oil circuit and the second reversing valve; the first reversing valve has a first working position connecting the fifth oil circuit and the eighth oil circuit and a second working position connecting the fifth oil circuit and the oil tank, the second reversing valve has a first working position connecting the sixth oil circuit and the seventh oil circuit, and the second reversing valve also has a second working position connecting the seventh oil circuit and the ninth oil circuit while the sixth oil circuit and the oil tank are connected.

[0014] The beneficial effects of the present invention are as follows: when high-pressure oil is introduced into the third cavity and the fourth cavity returns oil, the high-pressure oil will push the second piston and the piston rod to extend, which can drive the steering knuckle arm to rotate, so that the vehicle can be turned in one direction, and vice versa, so that the vehicle can be turned in another direction. At this time, the function of the hydraulic power steering system is realized. When the first oil port and the fourth cavity are connected to high-pressure oil and the third cavity returns oil, the first piston moves toward the partition, and the first piston and the piston rod also move toward the partition, and remain motionless under the action of the hydraulic oil pressure, that is, the forced centering mode. On the contrary, when the first cavity is connected to the oil tank and the third cavity is connected to the fourth cavity, the axle is in a self-steering state. When the oil cylinder of this structure is equipped with different hydraulic systems, it can realize the functions of the hydraulic power steering system and the hydraulic self-steering system, and has strong versatility. The oil cylinder of the same structure can be used for the hydraulic power steering system and the hydraulic self-steering system, saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of a hydraulic power steering system in the background technology;

[0016] Figure 2 It is a structural schematic diagram of hydraulic self-steering in the background technology;

[0017] Figure 3 It is a structural schematic diagram of a first embodiment of a steering axle of the present invention;

[0018] Figure 4 yes Figure 3 Schematic diagram of the structure of the middle oil cylinder;

[0019] Figure 5 yes Figure 3 The schematic diagram of the structure when the middle oil cylinder realizes the hydraulic power steering system;

[0020] Figure 6 yes Figure 3 Structural diagram of the middle oil cylinder when it realizes the forced centering function;

[0021] Figure 7 yes Figure 3 Structural diagram of the hydraulic self-steering system when the middle oil cylinder realizes it;

[0022] Figure 8 It is a structural schematic diagram of a second embodiment of a steering axle of the present invention. DETAILED DESCRIPTION

[0023] Embodiment 1 of a steering bridge of the present invention is as follows Figure 3-Figure 7 As shown, it includes a left wheel 1, a right wheel 2 and an axle 3, and also includes a left steering knuckle arm 4, a right steering knuckle arm 5 and a tie rod 6 connecting the left and right steering knuckle arms. The steering axle also includes a hydraulic steering system, and the hydraulic steering system includes an oil cylinder 7 and a hydraulic system. The oil cylinder 7 includes a cylinder body 8, in which a partition plate 9 is fixedly arranged, and a first piston 10 is provided in the cylinder body on one side of the partition plate along the cylinder body axis direction in a sliding and sealing manner. A second piston 11 is provided in the cylinder body on the other side of the partition plate along the cylinder body axis direction in a sliding and sealing manner, and a piston rod 12 is provided on the second piston 11. The piston rod 12 includes a first piston rod part 13 located on one side of the second piston and a second piston rod part 14 located on the other side of the second piston. A first mounting hole for sliding and sealing installation of the first piston rod is provided on the partition plate, and a second mounting hole for sliding and sealing installation of the second piston rod is provided at one end of the cylinder body. The first piston 10 and the cylinder body form a first cavity 15, the first piston, the partition and the cylinder body form a second cavity 16, the partition, the second piston and the cylinder body form a third cavity 17, and the second piston and the cylinder body form a fourth cavity 18. The cylinder body is provided with at least one first oil port 19 communicating with the first cavity, the cylinder body is provided with at least one second oil port 20 communicating with the second cavity, the cylinder body is provided with at least one third oil port 21 communicating with the third cavity, and the cylinder body is provided with at least one fourth oil port 22 communicating with the fourth cavity. In this embodiment, the number of the first oil port 19, the second oil port 20, the third oil port 21 and the fourth oil port 22 are all one. In this embodiment, one end of the oil cylinder 7 is hinged to the axle 3, and the piston rod is hinged to the tie rod 7.

[0024] The hydraulic system includes hydraulic lines for communicating with corresponding ports on the cylinder body to realize the hydraulic power steering function and the hydraulic self-steering function. The following will introduce the different functions that can be realized when the oil cylinder cooperates with different hydraulic systems.

[0025] Hydraulic power steering system: Figure 5As shown, at this time, the hydraulic system includes a tractor steering cylinder 23 and a tractor hydraulic steering device 24, and the tractor steering cylinder and the tractor hydraulic steering device are connected through a first oil circuit 25 and a second oil circuit 26 to form a circuit. The tractor steering device and the tractor steering cylinder are both provided by the tractor and are used to control the steering. The hydraulic pipeline includes a third oil circuit 27 connecting the third oil port 21 and the first oil circuit 25, and the hydraulic pipeline also includes a fourth oil circuit 28 connecting the fourth oil port 22 and the second oil circuit 26. A vent plug 30 is provided at the second oil port 20, and the first oil port 19 is connected to the oil tank 29. A first accumulator 32 is provided on the third oil circuit 27, and a second accumulator 34 is provided on the fourth oil circuit 28. The accumulator can play a role of buffering and high-pressure oil source supplement to a certain extent. The function of the vent plug is to connect the atmosphere with the second cavity, and the second cavity can freely adjust the air capacity when the piston rod moves telescopically. A first throttle valve 31 is provided on the third oil circuit 27, and a second throttle valve 33 is provided on the fourth oil circuit 28. The setting of the throttle valve can slow down the flow rate of the oil, form resistance, and play a role in buffering and shock absorption, eliminating the need to separately set a shock absorber on the tie rod in the prior art.

[0026] The principle of the hydraulic power steering function realized by the oil cylinder is as follows: For the convenience of description, the two oil ports of the tractor steering oil cylinder are defined as oil port A and oil port B respectively. Figure 5 As shown. When the tractor steering system supplies high-pressure oil to oil port A, oil port B is connected to the oil return line, and the high-pressure oil also flows into the third cavity through the third oil port. The fourth cavity is connected to the oil return line like oil port B. At this time, the high-pressure oil pushes the piston rod to extend, which can drive the steering knuckle arm to rotate, so that the vehicle can turn to one side. On the contrary, when oil port A is connected to the oil return line and oil port B is connected to the high-pressure oil line, the third cavity is connected to the oil return line and the fourth cavity is connected to the high-pressure line. The high-pressure oil pushes the piston rod to retract, which can drive the steering knuckle arm to rotate, so that the vehicle can turn to the other side. At this time, the function of hydraulic power steering is realized.

[0027] Hydraulic self-steering system: Figure 6 and Figure 7As shown, at this time, the hydraulic system includes a first reversing valve 35 and a second reversing valve 36, and the hydraulic pipeline includes a fifth oil circuit 37 connecting the first oil port 19 and the first reversing valve 35, a sixth oil circuit 38 connecting the third oil port 21 and the second reversing valve 36, and a seventh oil circuit 39 connecting the fourth oil port 22 and the second reversing valve 36. A vent plug is provided at the second oil port. The hydraulic pipeline also includes a main oil circuit 43, an eighth oil circuit 41 connecting the main oil circuit 43 and the first reversing valve 35, and a ninth oil circuit 42 connecting the main oil circuit 43 and the second reversing valve 36. The first reversing valve has a first working position connecting the fifth oil circuit and the eighth oil circuit and a second working position connecting the fifth oil circuit and the oil tank. The second reversing valve has a first working position connecting the sixth oil circuit and the seventh oil circuit, and the second reversing valve also has a second working position connecting the seventh oil circuit and the ninth oil circuit while the sixth oil circuit and the oil tank are connected. A third throttle valve 40 is provided on the sixth oil circuit 38. The first reversing valve is used for switching between forced centering and self-steering modes. The second steering valve is used for opening and closing and reversing the oil circuit between the third cavity and the fourth cavity to extend or retract the piston rod, and can also connect the third cavity and the fourth cavity for automatic steering. The vent plug is connected to the second cavity for free breathing of the second cavity.

[0028] The principle of the hydraulic cylinder to realize the hydraulic power steering function is: when the first reversing valve is in the first working position and the second reversing valve is in the second working position, Figure 6 As shown, the first cavity and the fourth cavity are connected to the high-pressure oil source, and the third cavity is connected to the return oil pipeline. At this time, the first piston moves to the right, and the piston rod retracts. Since the force area of ​​the first piston is larger than that of the second piston, the first piston will move to the right to the partition position and remain motionless under the action of the hydraulic oil pressure, so that the piston rod is in the middle stroke position, which is the so-called forced centering. At this time, the axle is in a straight state. When the first reversing valve is in the second working position and the second reversing valve is in the first working position, as shown in FIG. Figure 7 As shown, the first cavity is connected to the oil return pipeline and is pressure-free, and the third cavity is connected to the fourth cavity. At this time, the axle is in a self-steering state.

[0029] When in use, when the oil cylinder of the above structure is equipped with different hydraulic systems, the functions of the hydraulic power steering system and the hydraulic self-steering system can be realized, and the versatility is strong. The oil cylinder of the same structure can be used for the hydraulic power steering system and the hydraulic self-steering system, saving costs.

[0030] A second embodiment of a steering bridge of the present invention is as follows Figure 7 As shown, the only difference from the first embodiment is the position where the piston rod is hinged. In this embodiment, the piston rod is hinged on the right steering knuckle arm.

[0031] In other embodiments of the present invention, the number of the first oil port, the second oil port, the third oil port and the fourth oil port may also be adjusted according to actual needs. For example, in order to adjust the flow rate, the number of each oil port may be two or more; the piston rod may also be hinged to the left steering knuckle arm; if the use is satisfactory, a throttle valve may not be provided on the hydraulic pipeline; if the use is satisfactory, an accumulator may not be provided on the hydraulic pipeline; a protrusion may be provided on the side of the first piston located in the first cavity, and a groove for accommodating the first part of the piston rod may be provided on the other side of the first piston.

[0032] The embodiment of a multifunctional steering cylinder of the present invention has the same function as the cylinder in each embodiment of the above-mentioned steering axle, and will not be described in detail here.

[0033] An embodiment of a hydraulic steering system of the present invention has the same structure as the hydraulic steering system in the above-mentioned steering axle, and will not be described in detail here.

Claims

1. A multifunctional steering cylinder, comprising a cylinder body, characterized in that: A partition is fixedly arranged in the cylinder body, a first piston is provided in the cylinder body on one side of the partition in a sliding and sealing manner along the cylinder body axis direction, a second piston is provided in the cylinder body on the other side of the partition in a sliding and sealing manner along the cylinder body axis direction, a piston rod is provided on the second piston, the piston rod comprises a first piston rod portion located on one side of the second piston and a second piston rod portion located on the other side of the second piston, a first mounting hole for sliding and sealing installation of the first piston rod portion is provided on the partition, a second mounting hole for sliding and sealing installation of the second piston rod portion is provided at one end of the cylinder body, the first piston and the piston rod are independently arranged; the first piston and the cylinder body A first cavity is formed, the first piston, the partition and the cylinder body form a second cavity, the partition, the second piston and the cylinder body form a third cavity, the second piston and the cylinder body form a fourth cavity, the cylinder body is provided with at least one first oil port connected to the first cavity, the cylinder body is provided with at least one second oil port connected to the second cavity, the cylinder body is provided with at least one third oil port connected to the third cavity, and the cylinder body is provided with at least one fourth oil port connected to the fourth cavity; when the cylinder is connected to a hydraulic power-assisting system, the cylinder can realize hydraulic power-assisting, and when the cylinder is connected to a hydraulic self-steering system, the cylinder can realize the functions of forced centering and self-steering.

2. A hydraulic steering system, comprising a cylinder and a hydraulic system, characterized in that: The oil cylinder comprises a cylinder body, a partition is fixedly arranged in the cylinder body, a first piston is arranged in the cylinder body on one side of the partition in a sliding and sealing manner along the axis of the cylinder body, a second piston is arranged in the cylinder body on the other side of the partition in a sliding and sealing manner along the axis of the cylinder body, a piston rod is arranged on the second piston, the piston rod comprises a first part of the piston rod located on one side of the second piston and a second part of the piston rod located on the other side of the second piston, a first mounting hole for sliding and sealing installation of the first part of the piston rod is arranged on the partition, a second mounting hole for sliding and sealing installation of the second part of the piston rod is arranged at one end of the cylinder body, and the first piston and the piston rod are arranged independently; the first piston and the cylinder body form a first cavity, and the first piston, the partition and the cylinder body form a second cavity. The invention discloses a hydraulic system comprising a hydraulic power-assisting system and a hydraulic self-steering system, and the hydraulic systems both comprise hydraulic pipelines for communicating with corresponding ports on the cylinder body; when the hydraulic cylinder is connected to the hydraulic power-assisting system, the hydraulic power-assisting system can be realized; and when the hydraulic cylinder is connected to the hydraulic self-steering system, the hydraulic power-assisting system can be realized.

3. The hydraulic steering system according to claim 2, characterized in that: The hydraulic system includes a tractor steering cylinder and a tractor hydraulic steering device, the tractor steering cylinder and the tractor hydraulic steering device are connected through a first oil circuit and a second oil circuit to form a circuit, the hydraulic pipeline includes a third oil circuit connected to the third oil port and the first oil circuit, the hydraulic pipeline also includes a fourth oil circuit connected to the fourth oil port and the second oil circuit, a vent plug is provided at the second oil port, and the first oil port is connected to the oil tank.

4. The hydraulic steering system according to claim 3, characterized in that: The third oil circuit is provided with a first throttle valve, and the fourth oil circuit is provided with a second throttle valve.

5. The hydraulic steering system according to claim 2, characterized in that: The hydraulic system includes a first reversing valve and a second reversing valve, the hydraulic pipeline includes a fifth oil circuit connecting the first oil port and the first reversing valve, a sixth oil circuit connecting the third oil port and the second reversing valve, and a seventh oil circuit connecting the fourth oil port and the second reversing valve, and a vent plug is provided at the second oil port; the hydraulic pipeline also includes a main oil circuit, an eighth oil circuit connecting the main oil circuit and the first reversing valve, and a ninth oil circuit connecting the main oil circuit and the second reversing valve; the first reversing valve has a first working position connecting the fifth oil circuit and the eighth oil circuit and a second working position connecting the fifth oil circuit and the oil tank, the second reversing valve has a first working position connecting the sixth oil circuit and the seventh oil circuit, and the second reversing valve also has a second working position connecting the seventh oil circuit and the ninth oil circuit while the sixth oil circuit and the oil tank are connected.

6. The hydraulic steering system according to claim 5, characterized in that: The sixth oil circuit is provided with a third throttle valve.

7. A steering axle, comprising a left wheel, a right wheel and an axle, and also comprising a left steering knuckle arm, a right steering knuckle arm and a tie rod connecting the left and right steering knuckle arms, the steering axle also comprising a hydraulic steering system, the hydraulic steering system comprising an oil cylinder and a hydraulic system, characterized in that: The oil cylinder comprises a cylinder body, a partition is fixedly arranged in the cylinder body, a first piston is slidingly and sealably arranged on one side of the partition in the cylinder body along the axis direction of the cylinder body, a second piston is slidingly and sealably arranged on the other side of the partition in the cylinder body along the axis direction of the cylinder body, a piston rod is arranged on the second piston, the piston rod comprises a first part of the piston rod located on one side of the second piston and a second part of the piston rod located on the other side of the second piston, a first mounting hole for slidingly and sealably installing the first part of the piston rod is arranged on the partition, a second mounting hole for slidingly and sealably installing the second part of the piston rod is arranged at one end of the cylinder body, and the first piston and the piston rod are independently arranged; the first piston and the cylinder body form a first cavity, the first piston, the partition and the cylinder body form a second cavity, the partition, the second piston and the cylinder body form a second cavity. The invention discloses a hydraulic vehicle having three cavities, wherein the second piston and the cylinder body form a fourth cavity, the cylinder body is provided with at least one first oil port connected to the first cavity, the cylinder body is provided with at least one second oil port connected to the second cavity, the cylinder body is provided with at least one third oil port connected to the third cavity, and the cylinder body is provided with at least one fourth oil port connected to the fourth cavity; the hydraulic system comprises a hydraulic power-assisting system and a hydraulic self-steering system, and the hydraulic systems both comprise hydraulic pipelines connected to the corresponding ports on the cylinder body; when the oil cylinder is connected to the hydraulic power-assisting system, it can realize hydraulic power-assisting, and when the oil cylinder is connected to the hydraulic self-steering system, it can realize the functions of forced centering and self-steering; one end of the oil cylinder is hinged to the axle, and the piston rod is hinged to the tie rod or one of the steering knuckle arms.

8. The steering axle according to claim 7, characterized in that: The hydraulic system includes a tractor steering cylinder and a tractor hydraulic steering device, the tractor steering cylinder and the tractor hydraulic steering device are connected through a first oil circuit and a second oil circuit to form a circuit, the hydraulic pipeline includes a third oil circuit connected to the third oil port and the first oil circuit, the hydraulic pipeline also includes a fourth oil circuit connected to the fourth oil port and the second oil circuit, a vent plug is provided at the second oil port, and the first oil port is connected to the oil tank.

9. The steering axle according to claim 8, characterized in that: The third oil circuit is provided with a first throttle valve, and the fourth oil circuit is provided with a second throttle valve.

10. The steering axle according to claim 7, characterized in that: The hydraulic system includes a first reversing valve and a second reversing valve, the hydraulic pipeline includes a fifth oil circuit connecting the first oil port and the first reversing valve, a sixth oil circuit connecting the third oil port and the second reversing valve, and a seventh oil circuit connecting the fourth oil port and the second reversing valve, and a vent plug is provided at the second oil port; the hydraulic pipeline also includes a main oil circuit, a circuit connecting the main oil circuit and The eighth oil circuit of the first reversing valve and the ninth oil circuit connecting the main oil circuit and the second reversing valve; the first reversing valve has a first working position connecting the fifth oil circuit with the eighth oil circuit and a second working position connecting the fifth oil circuit with the oil tank, the second reversing valve has a first working position connecting the sixth oil circuit with the seventh oil circuit, and the second reversing valve also has a second working position connecting the seventh oil circuit with the ninth oil circuit and the sixth oil circuit with the oil tank at the same time.

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