Tractor trailer hydraulic system and tractor

Abstract

The utility model relates to a tractor trailer hydraulic system and a tractor, the tractor trailer hydraulic system comprises an oil tank, a trailer brake system, a steering system and a trailer brake valve, the trailer brake valve is provided with a port CL and a port SL, the trailer brake valve comprises a service brake pilot valve, a parking brake electromagnetic valve, a parking brake pilot valve and a logic valve, the oil tank is simultaneously connected to the steering system and the service brake pilot valve, the trailer brake system is connected to the service brake pilot valve, and the steering system is connected to the parking brake electromagnetic valve and the parking brake pilot valve. The service braking pilot valve is connected to the CL port, the T2 port is connected to the oil tank, the parking braking electromagnetic valve is connected to the parking braking pilot valve and the logic valve, and the parking braking electromagnetic valve is connected to the oil tank. By the adoption of the technical scheme, the technical problems that braking of an existing trailer may fail due to breakage of a pipeline during single-pipeline control, and driving safety and reliability are affected can be solved.

Description

Technical Field

[0001] The utility model relates to the technical field of hydraulic braking, in particular to a hydraulic system for a tractor trailer and a tractor. Background Art

[0002] Generally, a tractor can be matched with trailers of different models. The service brake and parking brake of the tractor and the trailer are both controlled by a single hydraulic control system through a single pipeline. When used for a long time and at a high speed, the aging pipeline and the pipeline joint are prone to rupture and leakage, resulting in the failure of the service brake control of the trailer and affecting the driving safety and reliability. Summary of the Utility Model

[0003] Aiming at the technical problem that the existing trailer brake may fail due to the rupture of the pipeline during single-pipeline control, affecting driving safety and reliability, the utility model provides a hydraulic system for a tractor trailer and a tractor.

[0004] The technical solution for the utility model to solve the above technical problems is as follows:

[0005] On the one hand, the utility model provides a hydraulic system for a tractor trailer, including a fuel tank, a trailer brake system, a steering system, and a trailer brake valve. The trailer brake valve is provided with a CL port for connecting to the service brake system of the trailer and / or the fuel tank, and a SL port for connecting to the parking brake system of the trailer and / or the fuel tank. The trailer brake valve includes a service brake pilot valve, a parking brake solenoid valve, a parking brake pilot valve, and a logic valve. The fuel tank is simultaneously connected to the P port of the steering system and the P1 port of the service brake pilot valve. The trailer brake system is connected to the P2 port of the service brake pilot valve. The T port of the steering system is connected to the P1 port of the parking brake solenoid valve and the P1 port of the parking brake pilot valve. And the T1 port of the service brake pilot valve is connected to the CL port, and the T2 port is connected to the fuel tank. The T1 port of the parking brake solenoid valve is simultaneously connected to the P2 port of the parking brake pilot valve and the P1 port of the logic valve. The T2 port of the parking brake solenoid valve is connected to the fuel tank. The parking brake pilot valve is connected to the SL port, and the T port of the parking brake pilot valve is connected to the fuel tank. The T1 port of the logic valve is connected to the fuel tank. Both two-way interfaces A of the logic valve are connected to the pipeline between the T1 port of the service brake pilot valve and the CL port.

[0006] The beneficial effects of the utility model are as follows: when the CL port pipeline is intact, the oil pressures of the two two-way interfaces A on both sides of the oil cylinder piston below the logic valve are equal, the logic valve moves downward under the action of the upper spring, and the pilot oil of the parking brake pilot valve is maintained; when the CL port pipeline is ruptured, the oil circuit pressure of the two-way interface A on the right side of the oil cylinder below the logic valve is lower than the oil circuit pressure of the two-way interface A on the left side, and the hydraulic oil enters under the oil cylinder piston, causing the logic valve to move upward. At this time, the logic valve oil circuit is connected, and the pilot oil of the parking brake pilot valve flows back to the oil tank through the logic valve, and the pressure is reduced, causing the parking brake pilot valve to move downward under the spring tension, and the SL port is connected to the oil tank through the T port of the parking brake pilot valve, and the parking brake hydraulic oil flows back to the oil tank, and the parking brake is established, thereby completing the emergency braking when the CL port fails, and improving the technical problem that the existing trailer brake may fail due to the rupture of the pipeline during single-line control, affecting the driving safety and reliability.

[0007] On the basis of the above technical solution, the present invention can also be improved as follows.

[0008] Furthermore, the T3 port of the service brake pilot valve is connected to an actuator, and the actuator is connected to the oil tank.

[0009] The beneficial effect of adopting the above further scheme is: during the service braking process, when the main vehicle is not braking, the service brake pilot valve moves upward, and its P1 port is connected to T3. Under the premise of giving priority to the trailer's brake oil, the remaining oil is delivered to the actuator through the T3 port, and the hydraulic oil is directly output to the actuator; when the main vehicle steps on the brake pedal, the brake oil enters the valve block through the P2 port, pushing the service brake pilot valve downward. At this time, the P1 port of the service brake pilot valve is connected to the CL port through the T1 port, and the hydraulic oil is output to the trailer's service brake system for braking.

[0010] Furthermore, the trailer brake system is connected to two pilot oil circuits, and the two pilot oil circuits are simultaneously connected to a three-way valve, and the three-way valve is also connected to the P2 port of the service brake pilot valve.

[0011] The beneficial effect of adopting the above further solution is that the trailer brake system provides brake oil to enter the service brake pilot valve through two pilot oil circuits to provide a hydraulic signal.

[0012] Furthermore, one of the two-way interfaces A of the logic valve is connected to a pipeline between the T1 port of the service brake pilot valve and the CL port, and a throttle valve is connected to the pipeline between the T1 port of the service brake pilot valve and the CL port, and a throttle valve is also connected to the pipeline between the T1 port of the service brake pilot valve and the CL port.

[0013] The beneficial effect of adopting the above further solution is: the flow rate of the corresponding pipeline is controlled by the throttle valve.

[0014] Further, one of the two-way interfaces A of the logic valve is also connected to an oil discharge pipe, and an LS port is formed. The throttle valve is located between the connection of the oil discharge pipe and the logic valve.

[0015] The beneficial effect of adopting the above further solution is that the logic valve can be drained through the LS port to regulate the hydraulic oil volume.

[0016] Further, the oil discharge pipe is also connected to a throttle valve.

[0017] The beneficial effect of adopting the above further solution is that the oil discharge volume at the LS port can be controlled through this throttle valve.

[0018] Further, the tractor-trailer hydraulic system further includes a power source M and two gear pumps both connected to the power source M. One of the gear pumps is installed on the pipeline connecting the fuel tank and the P1 port of the service brake pilot valve, and the other gear pump is installed on the pipeline connecting the fuel tank and the P port of the steering system.

[0019] The beneficial effect of adopting the above further solution is that the power source M provides power for the entire tractor-trailer hydraulic system, and pumps the oil in the fuel tank into the service brake pilot valve and the steering system to achieve steering control and braking control.

[0020] Further, filters are installed on the pipelines where the fuel tank is connected to the two gear pumps.

[0021] The beneficial effect of adopting the above further solution is that the hydraulic oil pumped from the fuel tank into the service brake pilot valve and the steering system is filtered through the filters.

[0022] Further, the pipeline connecting the fuel tank and the P1 port of the service brake pilot valve is connected to the fuel tank through a safety pipe, and a safety valve is connected to the safety pipe.

[0023] The beneficial effect of adopting the above further solution is that the oil volume imported from the fuel tank into the P1 port of the service brake pilot valve is controlled through the safety valve to ensure the safe operation of the equipment.

[0024] On the other hand, the present invention provides a tractor including the above-mentioned tractor-trailer hydraulic system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the schematic diagram of the tractor-trailer hydraulic system of the present invention;

[0026] Figure 2 is the schematic diagram of the trailer brake valve of the tractor-trailer hydraulic system of the present invention;

[0027] Figure 3This is the schematic diagram of the logic valve of the tractor trailer hydraulic system of the present utility model.

[0028] In the attached drawings, the list of components represented by each reference numeral is as follows:

[0029] 1. Fuel tank;

[0030] 2. Trailer braking system; 21. Pilot oil circuit; 22. Three-way valve;

[0031] 3. Steering system;

[0032] 4. Trailer brake valve; 41. Service brake pilot valve; 42. Parking brake solenoid valve; 43. Parking brake pilot valve; 44. Logic valve; 45. Throttle valve;

[0033] 5. Actuator;

[0034] 6. Gear pump;

[0035] 7. Filter;

[0036] 8. Safety valve. Detailed implementation manners

[0037] The principles and features of the present utility model are described below. The examples given are only used to explain the present utility model and are not intended to limit the scope of the present utility model.

[0038] On the one hand, the present utility model provides a tractor trailer hydraulic system, which is specifically described as follows.

[0039] Embodiment 1

[0040] As Figures 1 to 3, a tractor-trailer hydraulic system, comprising an oil tank 1, a trailer braking system 2, a steering system 3 and a trailer brake valve 4. The trailer brake valve 4 is provided with a CL port for connecting to the trailer service braking system and / or the oil tank 1, and is provided with an SL port for connecting to the trailer parking braking system and / or the oil tank 1. The trailer brake valve 4 includes a service braking pilot valve 41, a parking braking solenoid valve 42, a parking braking pilot valve 43 and a logic valve 44. The oil tank 1 is simultaneously connected to the P port of the steering system 3 and the P1 port of the service braking pilot valve 41. The trailer braking system 2 is connected to the P2 port of the service braking pilot valve 41. The T port of the steering system 3 is connected to the P1 port of the parking braking solenoid valve 42 and the P1 port of the parking braking pilot valve 43. And the T1 port of the service braking pilot valve 41 is connected to the CL port, and the T2 port is connected to the oil tank 1. The T1 port of the parking braking solenoid valve 42 is simultaneously connected to the P2 port of the parking braking pilot valve 43 and the P1 port of the logic valve 44. The T2 port of the parking braking solenoid valve 42 is connected to the oil tank 1. The parking braking pilot valve 43 is connected to the SL port, and the T port of the parking braking pilot valve 43 is connected to the oil tank 1. The T1 port of the logic valve 44 is connected to the oil tank 1. Both two-way interfaces A of the logic valve 44 are connected to the pipeline between the T1 port and the CL port of the service braking pilot valve 41.

[0041] The beneficial effect of this embodiment is that when the pipeline of the CL port is intact, the oil pressures at the two two-way interfaces A on both sides of the oil cylinder piston below the logic valve 44 are equal, and the logic valve 44 moves downward under the action of the upper spring, and the pilot oil of the parking braking pilot valve 43 is maintained; when the pipeline of the CL port is broken, the oil pressure of the oil circuit at the right two-way interface A of the oil cylinder below the logic valve 44 is lower than the oil pressure of the oil circuit at the left two-way interface A, and the hydraulic oil enters below the oil cylinder piston, causing the logic valve 44 to move upward. At this time, the oil circuit of the logic valve 44 is connected, and the pilot oil of the parking braking pilot valve 43 flows back to the oil tank 1 through the logic valve 44, and the pressure decreases, causing the parking braking pilot valve 43 to move downward under the action of the spring tension. The SL port is communicated with the oil tank 1 through the T port of the parking braking pilot valve 43, and the parking braking hydraulic oil flows back to the oil tank 1, and the parking braking is established, thereby completing the emergency braking when the CL port fails, and improving the technical problem that the existing trailer braking may fail due to the rupture of the pipeline in single-pipeline control, affecting the driving safety and reliability.

[0042] Among them, the two-way interface A means that it can be used as both an oil inlet and an oil outlet.

[0043] The P port, P1 port and P2 port are all power oil inlets.

[0044] The T port, T1 port, T2 port and T3 port are all oil outlets.

[0045] The CL port is a control port for controlling the access of hydraulic oil to the valve; the SL port is an auxiliary pipeline oil port.

[0046] As a specific control principle of this embodiment: the chassis oil in the oil tank 1 is output, one way directly enters the P1 port of the service brake pilot valve 41 of the trailer brake valve 4 through the pipeline, and the other way is first provided to the hydraulic steering pump of the steering system 3, and its return oil enters the P1 port of the parking brake solenoid valve 42 and the P1 port of the parking brake pilot valve 43 of the trailer brake valve 4 through the pipeline. The brake oil of the trailer brake system 2 is used as a pilot oil circuit and enters the P2 port of the service brake pilot valve 41 of the trailer brake valve 4 through the pipeline to provide a hydraulic signal.

[0047] Parking brake: When the handbrake is released, the parking brake solenoid valve 42 receives the handbrake signal and moves downward, and the hydraulic oil in the oil tank 1 is connected to the pilot oil circuit of the parking brake pilot valve 43, causing it to move downward. The hydraulic oil is output from the SL port through the parking brake pilot valve 43, and the parking brake is released; when the handbrake is pulled up, the parking brake solenoid valve 42 loses its magnetism and moves upward under the push of the spring. The pilot oil of the parking brake pilot valve 43 flows back to the oil tank 1 through the parking brake solenoid valve 42, causing it to move downward under the action of the spring, and the hydraulic oil flows back to the oil tank 1 through the SL port, and the parking brake is established.

[0048] Through the above control method, the system can control the parking brake and driving brake of the trailer through dual-line control. When one line fails, the other line can assist in emergency braking to ensure driving safety.

[0049] On the basis of the above embodiment, the service brake pilot valve 41 further has a T3 port, the T3 port is communicated with the pipeline in which the T1 port is connected to the CL port.

[0050] Example 2

[0051] like Figure 1 and Figure 2 On the basis of Example 1, the T3 port of the service brake pilot valve 41 is connected to the actuator 5, and the actuator 5 is connected to the oil tank 1.

[0052] The beneficial effect of adopting the preferred scheme in the above embodiment is that during the service braking process, when the main vehicle is not braking, the service brake pilot valve 41 moves upward, and its P1 port is connected to T3. Under the premise of giving priority to the trailer's brake oil, the remaining oil is delivered to the actuator 5 through the T3 port, and the hydraulic oil is directly output to the actuator 5; when the main vehicle steps on the brake pedal, the brake oil enters the valve block through the P2 port and pushes the service brake pilot valve 41 downward. At this time, the P1 port of the service brake pilot valve 41 is connected to the CL port through the T1 port, and the hydraulic oil is output to the service brake system of the trailer for braking.

[0053] The actuator 5 may be a multi-way valve, a lifter or other subsequent oil-using equipment.

[0054] Example 3

[0055] As Figure 1 and Figure 2 , on the basis of Embodiments 1 and 2, the trailer braking system 2 is connected with two pilot oil circuits 21, and the two pilot oil circuits 21 are simultaneously connected with a three-way valve 22, and the three-way valve 22 is also connected to the P2 port of the service braking pilot valve 41.

[0056] The beneficial effect of adopting the preferred solution in the above embodiment is that the trailer braking system 2 provides braking oil through the two pilot oil circuits 21 to enter the service braking pilot valve 41 to provide a hydraulic signal.

[0057] On the basis of the above embodiment, two P2 ports are provided on the service braking pilot valve 41 to simultaneously input pilot oil through the two P2 ports.

[0058] Embodiment 4

[0059] As Figure 2 and Figure 3 , on the basis of Embodiments 1-3, one of the two-way interfaces A of the logic valve 44 is connected to a pipeline between the T1 port and the CL port of the service braking pilot valve 41, and a throttle valve 45 is connected to the pipeline, and the pipeline between the T1 port and the CL port of the service braking pilot valve 41 is also connected with a throttle valve 45.

[0060] The beneficial effect of adopting the preferred solution in the above embodiment is to control the flow rate of the corresponding pipeline through the throttle valve 45.

[0061] In the figure, one of the A ports of the logic valve 44 is shown as the left side of the logic valve 44, and the other A port is shown as the right side of the logic valve 44.

[0062] Embodiment 5

[0063] As Figure 2 and Figure 3 , on the basis of Embodiments 1-4, one of the two-way interfaces A of the logic valve 44 is also connected with an oil drain pipe and forms an LS port, and the throttle valve 45 is located between the connection of the oil drain pipe and the logic valve 44.

[0064] The beneficial effect of adopting the preferred solution in the above embodiment is to drain the logic valve 44 through the LS port (oil drain port) to regulate the hydraulic oil volume.

[0065] Embodiment 6

[0066] As Figure 2 and Figure 3 , on the basis of Embodiments 1-5, the oil drain pipe is also connected with a throttle valve 45.

[0067] The beneficial effect of adopting the preferred solution in the above embodiment is to control the oil discharge amount at the LS port through the throttle valve 45.

[0068] Example 7

[0069] As Figure 1 , on the basis of Embodiments 1-6, the tractor-trailer hydraulic system further includes a power source M and two gear pumps 6 both connected to the power source M. One of the gear pumps 6 is installed on the pipeline connecting the fuel tank 1 and the P1 port of the service brake pilot valve 41P1, and the other gear pump 6 is installed on the pipeline connecting the fuel tank 1 and the P port of the steering system 3.

[0070] The beneficial effect of adopting the preferred solution in the above embodiment is that the power source M can provide power for the entire tractor-trailer hydraulic system, and pump the oil in the fuel tank 1 into the service brake pilot valve 41 and the steering system 3 to achieve steering control and braking control.

[0071] Specifically, the gear pump drives the output of two-way chassis oil. One way directly enters the P1 port of the service brake pilot valve 41 of the trailer brake valve 4 through the pipeline, and the other way is first supplied to the hydraulic steering pump of the steering system 3, and its return oil enters the P1 port of the parking brake solenoid valve 42 and the P1 port of the parking brake pilot valve 43 of the trailer brake valve 4 through the pipeline.

[0072] Example 8

[0073] As Figure 1 and Figure 2 , on the basis of Embodiments 1-7, filters 7 are installed on the pipelines connecting the fuel tank 1 to the two gear pumps 6.

[0074] The beneficial effect of adopting the preferred solution in the above embodiment is that the filter 7 can filter the hydraulic oil pumped from the fuel tank 1 into the service brake pilot valve 41 and the steering system 3.

[0075] On the basis of the above embodiment, the fuel tank 1 is connected to the two gear pumps 6 through a three-way valve, and only one filter 7 is provided and is arranged at the inlet end of the filter 7 close to the fuel tank 1.

[0076] As an alternative solution, the fuel tank 1 is connected to the two gear pumps 6 through a three-way valve, and two filters 7 are provided, and the two filters 7 are respectively arranged at the two outlet ends of the filter 7 close to the two gear pumps 6.

[0077] Example 9

[0078] As Figure 1 and Figure 2 , on the basis of Embodiments 1-8, the pipeline connecting the fuel tank 1 and the P1 port of the service brake pilot valve 41 is connected to the fuel tank 1 through a safety pipe, and a safety valve 8 is connected to the safety pipe.

[0079] The beneficial effect of adopting the preferred solution in the above embodiment is that the amount of oil introduced from the fuel tank 1 into the P1 port of the service brake pilot valve 41 can be controlled by the safety valve 8, ensuring the safe operation of the equipment.

[0080] On the other hand, the present invention provides a tractor, which will be specifically described as follows.

[0081] Embodiment 10

[0082] A tractor includes a tractor trailer hydraulic system as described in Embodiments 1-9.

[0083] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0084] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0085] In the present invention, unless otherwise clearly defined and limited, the terms "mounted", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0086] In the present utility model, unless otherwise clearly stipulated and defined, the first feature being "on" or "under" the second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may mean that the first feature is directly above or obliquely above the second feature, or merely indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "below" and "beneath" the second feature may mean that the first feature is directly below or obliquely below the second feature, or merely indicates that the horizontal height of the first feature is less than that of the second feature.

[0087] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present utility model. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0088] Although the embodiments of the present utility model have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present utility model. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present utility model.

Claims

1. A tractor trailer hydraulic system, characterized in that: The invention comprises a fuel tank (1), a trailer brake system (2), a steering system (3) and a trailer brake valve (4); the trailer brake valve (4) is provided with a CL port for connecting to a trailer's service brake system and / or the fuel tank (1), and is provided with an SL port for connecting to a trailer's parking brake system and / or the fuel tank (1); the trailer brake valve (4) comprises a service brake pilot valve (41), a parking brake solenoid valve (42), a parking brake pilot valve (43) and a logic valve (44); the fuel tank (1) is simultaneously connected to the P port of the steering system (3) and the P1 port of the service brake pilot valve (41); the trailer brake system (2) is connected to the P2 port of the service brake pilot valve (41); the T port of the steering system (3) is connected to the P2 port of the parking brake pilot valve (41); the T port of the steering system (3) is connected to the P3 port of the parking brake solenoid valve (42); and the T port of the steering system (3) is connected to the P4 port of the parking brake solenoid valve (42). The P1 port is connected to the P1 port of the parking brake pilot valve (43), and the T1 port of the service brake pilot valve (41) is connected to the CL port, and the T2 port is connected to the oil tank (1). The T1 port of the parking brake solenoid valve (42) is simultaneously connected to the P2 port of the parking brake pilot valve (43) and the P1 port of the logic valve (44). The T2 port of the parking brake solenoid valve (42) is connected to the oil tank (1), the parking brake pilot valve (43) is connected to the SL port, and the T port of the parking brake pilot valve (43) is connected to the oil tank (1). The T1 port of the logic valve (44) is connected to the oil tank (1), and the two bidirectional interfaces A of the logic valve (44) are both connected to the pipeline between the T1 port of the service brake pilot valve (41) and the CL port.

2. A tractor trailer hydraulic system according to claim 1, characterized in that: The T3 port of the service brake pilot valve (41) is connected to an actuator (5), and the actuator (5) is connected to the oil tank (1).

3. A tractor trailer hydraulic system according to claim 1, characterized in that: The trailer brake system (2) is connected to two pilot oil circuits (21), and the two pilot oil circuits (21) are simultaneously connected to a three-way valve (22), and the three-way valve (22) is also connected to the P2 port of the service brake pilot valve (41).

4. A tractor trailer hydraulic system according to claim 1, characterized in that: One of the two-way interfaces A of the logic valve (44) is connected to a pipeline between the T1 port and the CL port of the service brake pilot valve (41), and a throttle valve (45) is connected to the pipeline, and the pipeline between the T1 port and the CL port of the service brake pilot valve (41) is also connected to a throttle valve (45).

5. A tractor trailer hydraulic system according to claim 4, characterized in that: One of the two-way interfaces A of the logic valve (44) is also connected to an oil drain pipe and forms an LS port. The throttle valve (45) is located between the connection of the oil drain pipe and the logic valve (44).

6. A tractor trailer hydraulic system according to claim 5, characterized in that: The oil drain pipe is also connected to a throttle valve (45).

7. A tractor trailer hydraulic system according to any one of claims 1 to 6, characterized in that: The tractor trailer hydraulic system also includes a power source M and two gear pumps (6) both connected to the power source M, wherein one of the gear pumps (6) is installed on a pipeline connecting the oil tank (1) and the P1 port of the service brake pilot valve (41), and the other gear pump (6) is installed on a pipeline connecting the oil tank (1) and the P port of the steering system (3).

8. A tractor trailer hydraulic system according to claim 7, characterized in that: Filters (7) are installed on the pipelines connecting the oil tank (1) to the two gear pumps (6).

9. A tractor trailer hydraulic system according to any one of claims 1 to 6, characterized in that: The pipeline connecting the oil tank (1) and the P1 port of the service brake pilot valve (41) is connected to the oil tank (1) via a safety pipe, and the safety pipe is connected to a safety valve (8).

10. A tractor, characterized in that: Comprising a tractor trailer hydraulic system as described in any one of claims 1-9.

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