CN214304670U - Hydraulic discharging system - Google Patents

Abstract

The embodiment of the specification provides a hydraulic pressure unloading system. The hydraulic pressure system of unloading is used for self-discharging semitrailer, specifically includes: a main oil supply pipeline and a main oil return pipeline; the unloading assembly is arranged between the main oil supply pipeline and the main oil return pipeline and is configured for unloading materials on the self-unloading semitrailer; and the buffer assembly is arranged between the main oil supply pipeline and the main oil return pipeline, is connected with the discharging assembly in parallel and is configured to adjust the pressure of the hydraulic discharging system to different preset values. Through setting up with the parallelly connected buffer unit of subassembly of unloading utilizes buffer unit to realize the pressure to the different default in the hydraulic pressure system of unloading for the pressure of system can enough satisfy the demand that increases to highly compressed fast, can satisfy the requirement of slow off-load through stepping step-by-step depressurization again, finally realizes the even running of hydraulic pressure system of unloading, improves the stability and the security of self-discharging semitrailer unloading in-process, improves self-discharging semitrailer's wholeness ability.

Description

Hydraulic discharging system

Technical Field

The embodiment of the specification relates to the technical field of mechanical manufacturing, in particular to a hydraulic discharging system.

Background

The self-unloading semi-trailer is also called as tip lorry or engineering truck, and is composed of automobile chassis, hydraulic lifting mechanism, power take-off device and cargo compartment. In civil engineering, the combined operation of an excavator, a loader, a belt conveyor and the like is commonly carried out to form a loading, transporting and unloading production line for loading, unloading and transporting earthwork, gravel and loose materials, thereby improving the production efficiency and reducing the cost. Because the dump semitrailer is easy to roll over to cause accidents and personal injuries, the dump semitrailer is gradually replaced by an integrated vehicle-mounted conveying belt. However, the hydraulic system in the existing discharging device is difficult to meet the requirements of quick start and stable operation, and the requirements of safe and efficient discharging are difficult to meet.

SUMMERY OF THE UTILITY MODEL

In view of the above, a first object of one or more embodiments of the present disclosure is to provide a hydraulic discharging system to solve the technical drawbacks of the prior art.

In view of the above, in a first aspect, one or more embodiments of the present specification provide a hydraulic unloading system for a dump semi-trailer, including:

a main oil supply pipeline and a main oil return pipeline;

the unloading assembly is arranged between the main oil supply pipeline and the main oil return pipeline and is configured for unloading materials on the self-unloading semitrailer; and

the buffer assembly is arranged between the main oil supply pipeline and the main oil return pipeline, is connected with the discharging assembly in parallel and is configured to adjust the pressure of the hydraulic discharging system to different preset values.

Further, the discharge assembly includes a conveyor belt drive unit, the conveyor belt drive unit including:

the motor is configured for driving the conveying belt to move; and

the first reversing valve comprises a first pressure oil port, a first oil return port and two first working oil ports and is configured to adjust the working state of the motor; the two first working oil ports are respectively connected with two ends of the motor; the first pressure oil port is communicated with the main oil supply pipeline; the first oil return port is communicated with the main oil return pipeline.

Further, the subassembly of unloading still includes the chamber door unit that opens and shuts, the chamber door unit that opens and shuts includes:

a first hydraulic cylinder configured to control an open/close state of the door; and

the second reversing valve comprises a second pressure oil port, a second oil return port and two second working oil ports and is configured to control the working state of the first hydraulic cylinder; the two second working oil ports are respectively connected with two ends of the first hydraulic cylinder; the second pressure oil port is communicated with the main oil supply pipeline; and the second oil return port is communicated with the main oil return pipeline.

Further, the box door opening and closing unit further comprises a throttle valve, and the throttle valve is arranged between the second reversing valve and the first hydraulic cylinder.

Further, the buffer assembly includes:

the buffer two-way cartridge valve comprises an oil inlet end, an oil return end and a control cavity, and is configured in such a way that the oil inlet end is communicated with the main oil supply pipeline and the oil return end is communicated with the main oil return pipeline;

the first overflow valve is configured to have an oil inlet end communicated with the control cavity and an oil return end communicated with the main oil return pipeline;

the third reversing valve comprises a third pressure oil port, a third oil return port and two third working oil ports, the third pressure oil port is communicated with the control cavity, and the third oil return port is communicated with the main oil return pipeline; and

the second overflow valve is configured to have an oil inlet end communicated with the control cavity and an oil return end communicated with the third working oil port; the second overflow valve and the first overflow valve have different overflow pressures; the third reversing valve can adjust the working states of the first overflow valve and the second overflow valve.

Further, the third reversing valve is selected from an H-shaped three-position four-way reversing valve.

Further, the hydraulic system also comprises a second hydraulic cylinder and a pressure valve group; wherein the content of the first and second substances,

the second hydraulic cylinder is configured to provide back pressure for the dump semi-trailer and is arranged to be communicated with the upstream end of the main oil return pipeline through a back pressure branch;

the pressure valve group is arranged on the main oil return pipeline and is configured to adjust the pressure of the upstream end of the main oil return pipeline.

Further, the pressure valve group comprises a pressure two-way cartridge valve and a third overflow valve;

the oil inlet end of the pressure two-way cartridge valve is connected with the upstream end of the main oil return pipeline, and the oil return end of the pressure two-way cartridge valve is connected with the downstream end of the main oil return pipeline; and the control cavity of the pressure two-way cartridge valve is communicated with the downstream end of the main oil return pipeline through a third overflow valve.

Furthermore, the device also comprises an oil return branch and a one-way valve;

the oil return branch is connected with the third overflow valve in parallel, and the one-way valve is arranged on the oil return branch; and the relief pressure of the third relief valve is smaller than the relief pressures of the second relief valve and the first relief valve.

Further, the first overflow valve, the second overflow valve and the third overflow valve are independently selected from a pilot type overflow valve or a direct type overflow valve.

As can be seen from the above, according to the hydraulic unloading system for the dump semi-trailer provided in one or more embodiments of the present specification, by providing the buffering component connected in parallel with the unloading component, the buffering component is utilized to realize that the pressure in the hydraulic unloading system reaches different preset values, so that the pressure of the system can meet the requirement of rapidly increasing to a high pressure, and can also meet the requirement of slowly unloading through gradually reducing the pressure, and finally, the smooth operation of the hydraulic unloading system is realized, so that the stability and the safety of the dump semi-trailer in the unloading process are improved, and the overall performance of the dump semi-trailer is improved.

Drawings

In order to more clearly illustrate one or more embodiments or prior art solutions of the present specification, the drawings that are needed in the description of the embodiments or prior art will be briefly described below, and it is obvious that the drawings in the following description are only one or more embodiments of the present specification, and that other drawings may be obtained by those skilled in the art without inventive effort from these drawings.

Fig. 1 is a schematic structural diagram of a hydraulic discharging system provided in one or more embodiments of the present disclosure;

FIG. 2 is a schematic structural diagram of another hydraulic discharge system provided in one or more embodiments of the present disclosure;

FIG. 3 is a schematic structural diagram of another hydraulic unloading system provided in one or more embodiments of the present disclosure;

fig. 4 is a flowchart illustrating a control method according to one or more embodiments of the present disclosure.

Detailed Description

For the purpose of promoting a better understanding of the objects, aspects and advantages of the present disclosure, reference is made to the following detailed description taken in conjunction with the accompanying drawings.

It is to be noted that unless otherwise defined, technical or scientific terms used in one or more embodiments of the present specification should have the ordinary meaning as understood by those of ordinary skill in the art to which this disclosure belongs. The use of "first," "second," and similar terms in one or more embodiments of the specification is not intended to indicate any order, quantity, or importance, but rather is used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.

Based on the technical defects of the unloading system of the dump semi-trailer in the prior art, in a first aspect, one or more embodiments of the present specification provide a hydraulic unloading system for a dump semi-trailer.

Specifically, referring to fig. 1, the hydraulic discharging system includes: a main oil supply line 100 and a main oil return line 200; a dump assembly 300 disposed between the main supply line and the main return line and configured to dump material on the dump semi-trailer; and a buffering assembly 400 disposed between the main oil supply line 100 and the main oil return line 200 and connected in parallel with the discharging assembly 300, and configured to adjust the pressure of the hydraulic discharging system to different preset values.

It should be noted that the discharging assembly 300 and the buffering assembly 400 may be communicated with the main oil supply pipeline 100 through an oil supply branch, and communicated with the main oil return pipeline 200 through an oil return branch. Here, the specific arrangement manner of the oil supply branch and the oil return branch is not particularly limited. The technical personnel in the field can carry out reasonable arrangement according to the position relation of the discharging component 300, the buffering component 400 and the oil tank.

According to the embodiment, the buffering assembly connected with the unloading assembly in parallel is arranged, and the buffering assembly is utilized to realize that the pressure in the hydraulic unloading system reaches different preset values, so that the pressure of the system can meet the requirement of rapid increase to high pressure, and can meet the requirement of slow unloading through gradual pressure reduction, and finally the stable operation of the hydraulic unloading system is realized, thereby improving the stability and safety of the unloading process of the self-unloading semitrailer and improving the overall performance of the self-unloading semitrailer.

It should be understood that the discharge assembly 300 may have a variety of configurations and is not particularly limited thereto.

As an alternative embodiment, the unloading assembly 300 includes a hydraulic cylinder, and the position of the container of the dump truck semi-trailer is changed by lifting the hydraulic cylinder, so as to realize unloading of the materials.

As another alternative, the discharge assembly 300 may be used to discharge material by controlling the movement of the conveyor belt on board the vehicle.

Optionally, as shown in fig. 2, the discharge assembly comprises a conveyor belt drive unit comprising:

a motor 301 configured to move the conveyor belt; and

a first direction valve 302 including a first pressure port, a first return port, and two first working ports, and configured to adjust a working state of the motor 301; the two first working oil ports are respectively connected with two ends of the motor; the first pressure oil port is communicated with the main oil supply pipeline 100; the first oil return port is communicated with the main oil return pipeline 200.

It should be understood that the specific arrangement of the conveyor belt is not limited herein. Those skilled in the art will appreciate that the belt drive units of the embodiments of the present disclosure have a wide range of applicability and are not limited to a particular belt structure. The specific connection relationship between the motor 301 and the conveying belt can also be set reasonably according to the structure of the conveying belt, and is not limited specifically.

Illustratively, the first directional valve 302 is a three-position, four-way valve to switch between forward and reverse rotation and stop of the motor 301. Optionally, the first direction valve 302 is an O-type three-position four-way valve. Specifically, when the first direction changing valve 302 is in the neutral position, the motor 301 and the oil path are disconnected, and the motor 301 is in a stopped state; when the first direction valve 302 is in the left position or the right position, the motor 301 is in the forward rotation state or the reverse rotation state. The corresponding relationship between the left and right positions and the forward and reverse rotation of the motor 301 is not specifically limited herein. Optionally, the first directional valve 302 is an electro-hydraulic valve.

It will be appreciated by those skilled in the art that other types of directional valves may be used with the embodiments of the present disclosure as long as they function to accommodate the motor operating conditions. And is not particularly limited herein.

The unloading assembly of this description embodiment, through the uninstallation of motor and first switching-over valve realization material, have strong, the simple structure's of controllability advantage.

During the unloading process, the box door of the container is usually required to be opened so as to facilitate the unloading of the materials.

Based on this, please refer to fig. 2, in one or more embodiments of the present disclosure, the discharging assembly further includes a box door opening and closing unit, and the box door opening and closing unit includes:

a first hydraulic cylinder 303 configured to control an open/close state of the door; and

a second direction valve 304 including a second pressure port P, a second return port T, and two second working ports A, B, and configured to control an operating state of the first hydraulic cylinder 303; the two second working oil ports A, B are respectively connected with two ends of the first hydraulic cylinder 303; the second pressure port P is communicated with the main oil supply pipeline 100; the second oil return port T is communicated with the main oil return pipeline 200.

Illustratively, the second reversing valve 304 is an O-type three-position, four-way solenoid valve. When the O-shaped three-position four-way electromagnetic valve is positioned at the middle position, no oil body enters or exits the first hydraulic cylinder 303, and the position is fixed; when the oil pump is located at the straight-through position, the second pressure oil port P is communicated with the second working oil port A, and the second working oil port B is communicated with the second oil return port T; and when the oil return port is positioned at the cross position, the second pressure oil port P is communicated with the second working oil port B, and the second working oil port A is communicated with the second oil return port T.

Optionally, the second working oil port a is communicated with a rodless cavity of the first hydraulic cylinder 303; the second working oil port B communicates with the rod chamber of the first hydraulic cylinder 303.

Based on this, the position of the piston in the first hydraulic cylinder 303 can be adjusted by adjusting the position of the second directional control valve 304, so that the working state of the first hydraulic cylinder 303 can be effectively controlled, automation can be conveniently realized, and the workload of workers can be reduced.

It should be noted that, by using an appropriate circuit structure, control of the first and second reversing valves can be realized, which facilitates realization of automatic control. The specific circuit configuration is not particularly limited.

As an alternative embodiment, the box door opening and closing unit further includes a throttle valve 305, and the throttle valve 305 is disposed between the second direction changing valve 304 and the first hydraulic cylinder 303. Optionally, the throttle valve 305 is selected from a stack of dual one-way throttle valves. By using the throttle valve 305 in combination with the second directional valve 304, the flow of the oil into and out of the first hydraulic cylinder 303 can be better controlled, and the operation thereof can be more stable.

The specific structure of the cushion assembly is further described below. Still referring to fig. 2, in one or more embodiments of the present disclosure, the buffer assembly includes:

the buffering two-way cartridge valve 401 comprises an oil inlet end, an oil return end and a control cavity, and is configured such that the oil inlet end is communicated with the main oil supply pipeline 100, and the oil return end is communicated with the main oil return pipeline 200;

a first overflow valve 402, configured to have an oil inlet end communicated with the control chamber and an oil return end communicated with the main oil return pipeline 200;

a third directional control valve 404 including a third pressure port P, a third oil return port T and two third working ports A, B, and configured such that the third pressure port P communicates with the control chamber, and the third oil return port T communicates with the main oil return line 200; and

a second overflow valve 403, configured such that an oil inlet end communicates with the control chamber and an oil return end communicates with the third working port (B); wherein the relief pressure of second relief valve 403 is different from that of first relief valve 402; the third direction changing valve 404 can adjust the operating states of the first relief valve 402 and the second relief valve 403.

Alternatively, the relief pressure of first relief valve 402 is greater than the relief pressure of second relief valve 403. For example, the relief pressure of the first relief valve 402 is 28MPa, and the relief pressure of the second relief valve 403 is 10 MPa. Those skilled in the art will appreciate that the relief pressure for the two relief valves may be appropriately set based on the operating power requirements of the dump assembly, and the above is merely exemplary.

It can be seen that the damping assembly of the embodiment of the present specification controls the pressure in the system by providing a damping two-way cartridge 401, two relief valves 402, 403 with different relief pressures, and a directional valve 404. Based on the overflow valve 402 with high overflow pressure, the pressure in the system can be quickly increased, and the low overflow pressure overflow valve 403 is used, so that the system pressure can be reduced from high pressure to low pressure to realize slow unloading, the sudden change of the speed of the unloading assembly caused by the abrupt change of the pressure in the system is avoided, and the safety and the operation stability of the liquid unloading system can be effectively improved. Based on the buffering two-way cartridge valve, the process of reducing the system pressure is smoother, and the stability is further improved.

As an alternative embodiment, the third reversing valve 404 is selected from an H-type three-position, four-way reversing valve. Here, when the third direction changing valve 404 is located at the neutral position, the control chamber is directly communicated with the main oil return pipeline 200, and at this time, both overflow valves do not work; when the third reversing valve 404 is located at the direct-current position, the third working fluid port B is communicated with the main oil return pipeline 200, and at this time, the second overflow valve 403 is in a working state; when the third directional valve 404 is located at the cross position, the third working port B is communicated with the third pressure port P, and at this time, the first overflow valve 402 is in a working state. It can be seen that, the technical scheme provided by the embodiment of the specification utilizes a reversing valve to realize the adjustment of the buffer assembly through ingenious pipeline design, and has the advantages of simple structure and high efficiency.

Optionally, the third directional valve 404 is selected from solenoid valves.

Further, the working principle and working process of the damping assembly are explained as follows with reference to fig. 2.

The system hydraulic oil flows to the control cavity through the central small hole of the buffering two-way cartridge valve 401, a third pressure oil port P of the third reversing valve is controlled to be communicated with a third working oil port B, the third working oil port B is communicated with an oil return end of a second overflow valve, and the oil way is stopped; the control cavity is communicated with a main oil return pipeline 200 through a first overflow valve 402; the control cavity maintains high pressure, the pressure is adjusted through the first overflow valve 402, the pressure meets the working size of the discharging assembly, and the high-speed operation of the discharging assembly is guaranteed. It should be noted that, by using the first direction valve 302 and the second direction valve 304, the discharging assembly in a specific working state can be adjusted, and is not limited in particular here.

When the unloading assembly runs to the end position, the third oil return port T of the third reversing valve 404 is controlled to be communicated with the third working oil port B, so that the oil return end of the second overflow valve 403 is communicated with the main oil return pipeline 200, and because the overflow pressure of the second overflow valve 403 is lower than that of the first overflow valve 402, the pressure of the control cavity is gradually reduced to the set pressure of the second overflow valve 403, the speed of the unloading assembly is reduced, and the stable running of the unloading assembly can still be guaranteed.

And finally, controlling the third reversing valve 404 to be in a neutral position, and communicating the third pressure port P with the third oil return port T, that is, the control cavity is directly communicated with the main oil return pipeline 200, so that the pressure of the control cavity disappears, and the system is unloaded.

By the mode, the stable and reliable rapid pressurization and slow unloading process is realized, no impact and vibration is caused, and the technological action of the unloading assembly during high-speed operation and buffering is realized.

Under the condition of poor road conditions, the dump semi-trailer is easy to vibrate due to the jolt of the road, so that the impact of parts (such as the collision between a container and a chassis) is caused, the dump semi-trailer is abraded, and even the dump semi-trailer is turned over under severe conditions.

Therefore, referring to fig. 2, in one or more embodiments of the present disclosure, a second hydraulic cylinder 503 and a pressure valve set are further included. The discharging assembly and the buffering assembly are connected with the pressure valve bank in series. The second hydraulic cylinder 503 is configured to provide back pressure to the dump trailer and is configured to communicate with an upstream end of the main return line through a back pressure branch (not shown); the pressure valve group is arranged on the main oil return pipeline and is configured to adjust the pressure of the upstream end of the main oil return pipeline.

Such technical scheme, hydraulic pressure through hydraulic system production provides the backpressure to self-discharging semitrailer (for example packing box), increases the relative stability between self-discharging semitrailer part to prevent that self-discharging semitrailer from improving vehicle stability because of the not good vibrations of road conditions, avoid taking place to turn on one's side. Optionally, the back pressure is a pressure towards the dump semi-trailer contact surface. Here, the contact surface may be, for example, a road surface.

It should be noted that, in some embodiments, when the pressure valve set provides hydraulic pressure for the second hydraulic cylinder 503 for a long time, the pressure threshold of the pressure valve set is smaller than the minimum pressure required for the operation of the discharging assembly, so as to facilitate the normal start and stop of the discharging assembly.

In some alternative embodiments, the pressure valve group comprises a pressure two-way cartridge valve 501 and a third overflow valve 502; the oil inlet end of the pressure two-way cartridge valve 501 is connected with the upstream end 201 of the main oil return pipeline 200, and the oil return end of the pressure two-way cartridge valve is connected with the downstream end 202 of the main oil return pipeline; the control chamber of the pressure two-way cartridge valve 501 is communicated with the downstream end 202 of the main oil return pipeline through a third overflow valve 502 (refer to fig. 3). Through the matching of the pressure two-way cartridge valve 501 and the third overflow valve 502, the pressure adjustment of the upstream end 201 of the main oil return pipeline can be realized, and the back pressure is provided for the second hydraulic cylinder 503.

In some optional embodiments, please refer to fig. 3, further comprising an oil return branch 504 and a check valve 503; the oil return branch 504 is connected in parallel with the third overflow valve 502, and the check valve 503 is arranged on the oil return branch 504; the relief pressure of third relief valve 502 is lower than the relief pressures of second relief valve 403 and first relief valve 402.

In some alternative embodiments, damping members are provided on the lines entering first relief valve 402, second relief valve 403 and third relief valve 502 to improve the stability of the system. Alternatively, the first relief valve 402 and the second relief valve 403 may share one damping member.

In some alternative embodiments, first relief valve 402, second relief valve 403, and third relief valve 502 are each independently selected from a pilot relief valve or a direct relief valve.

Through the arrangement of the oil return branch 504 and the check valve 503, the pressure of the whole hydraulic discharging system can be reduced to zero from the overflow pressure of the third overflow valve 502, and further multi-stage adjustment of the system pressure is realized. After the system pressure is reduced from the relief pressure of the high-pressure relief valve (e.g., first relief valve 402) to the relief pressure of the low-pressure relief valve (e.g., second relief valve 402) in the cushion assembly, the system pressure is further slowly relieved by third relief valve 502, and the system pressure is prevented from being abruptly reduced to zero. After the check valve 503 is opened, the system pressure is reduced to zero by the relief pressure of the third relief valve. Compare in the simple buffering subassembly that uses, the hydraulic pressure of the hydraulic pressure system of unloading of this embodiment can carry out more levels's regulation, is favorable to improving the stability of system.

It should be noted that, a person skilled in the art selects whether to provide the second hydraulic cylinder, and this is not particularly limited.

It should be understood that the dump semi-trailer is not usually in the transport condition and the discharge condition at the same time, that is, the dump semi-trailer is in the transport condition or in the discharge condition. Thus, when the system includes the return branch 404 and the check valve 503, the pressure valve set can provide both the adjustment of the pressure to the discharge assembly and the back pressure to the second hydraulic cylinder 503. Optionally, the relief pressure of the third relief valve 502 is greater than the minimum pressure required for operation of the dump assembly. When the self-discharging semitrailer is in a discharging working condition, the pressure valve bank is matched with the discharging assembly to work by controlling the opening and closing of the one-way valve; when the dump semitrailer is in a transportation working condition, the check valve of the pressure valve group is closed to be matched with the second hydraulic cylinder 503 to work, so that greater back pressure can be provided, and the stability of the dump semitrailer can be kept more favorably.

In a second aspect, one or more embodiments of the present disclosure further provide a method for controlling a hydraulic dump system as described in any of the preceding. As shown in fig. 4, the control method specifically includes:

step S601: and under the transportation working condition, the one-way valve is controlled to be closed, so that the pressure valve group provides back pressure for the second hydraulic cylinder.

Step S602: under the unloading working condition, the working state of the buffer assembly and the opening and closing state of the one-way valve are controlled, so that the pressure in the hydraulic unloading system is adjusted to meet the requirement of the unloading assembly.

For example, when the discharging assembly needs high pressure, a first overflow valve in the buffering assembly is in a working state; when the unloading assembly needs medium pressure, a second overflow valve in the buffering assembly is in a working state; when the discharging assembly needs low pressure, the third overflow valve is in a working state.

The method of the above embodiment is based on the corresponding hydraulic discharging system in any of the foregoing embodiments, and has the beneficial effects of the corresponding system embodiment, which are not described herein again.

Those of ordinary skill in the art will understand that: the discussion of any embodiment above is meant to be exemplary only, and is not intended to intimate that the scope of the disclosure, including the claims, is limited to these examples; within the spirit of the present disclosure, features from the above embodiments or from different embodiments may also be combined, steps may be implemented in any order, and there are many other variations of different aspects of one or more embodiments of the present description as described above, which are not provided in detail for the sake of brevity.

While the present disclosure has been described in conjunction with specific embodiments thereof, many alternatives, modifications, and variations of these embodiments will be apparent to those of ordinary skill in the art in light of the foregoing description.

It is intended that the one or more embodiments of the present specification embrace all such alternatives, modifications and variations as fall within the broad scope of the appended claims. Therefore, any omissions, modifications, substitutions, improvements, and the like that may be made without departing from the spirit and principles of one or more embodiments of the present disclosure are intended to be included within the scope of the present disclosure.

Claims (10)

1. A hydraulic unloading system for a self-unloading semitrailer, comprising:

a main oil supply pipeline and a main oil return pipeline;

the unloading assembly is arranged between the main oil supply pipeline and the main oil return pipeline and is configured for unloading materials on the self-unloading semitrailer; and

the buffer assembly is arranged between the main oil supply pipeline and the main oil return pipeline, is connected with the discharging assembly in parallel and is configured to adjust the pressure of the hydraulic discharging system to different preset values.

2. The hydraulic discharge system of claim 1 wherein the discharge assembly comprises a belt drive unit comprising:

the motor is configured for driving the conveying belt to move; and

the first reversing valve comprises a first pressure oil port, a first oil return port and two first working oil ports and is configured to adjust the working state of the motor; the two first working oil ports are respectively connected with two ends of the motor; the first pressure oil port is communicated with the main oil supply pipeline; the first oil return port is communicated with the main oil return pipeline.

3. The hydraulic discharge system of claim 2, wherein the discharge assembly further comprises a bin door opening and closing unit, the bin door opening and closing unit comprising:

a first hydraulic cylinder configured to control an open/close state of the door; and

the second reversing valve comprises a second pressure oil port, a second oil return port and two second working oil ports and is configured to control the working state of the first hydraulic cylinder; the two second working oil ports are respectively connected with two ends of the first hydraulic cylinder; the second pressure oil port is communicated with the main oil supply pipeline; and the second oil return port is communicated with the main oil return pipeline.

4. The hydraulic discharge system according to claim 3, wherein the door opening and closing unit further comprises a throttle valve provided between the second direction valve and the first hydraulic cylinder.

5. The hydraulic discharge system of claim 1, wherein the buffer assembly comprises:

the buffer two-way cartridge valve comprises an oil inlet end, an oil return end and a control cavity, and is configured in such a way that the oil inlet end is communicated with the main oil supply pipeline and the oil return end is communicated with the main oil return pipeline;

the first overflow valve is configured to have an oil inlet end communicated with the control cavity and an oil return end communicated with the main oil return pipeline;

the third reversing valve comprises a third pressure oil port, a third oil return port and two third working oil ports, the third pressure oil port is communicated with the control cavity, and the third oil return port is communicated with the main oil return pipeline; and

the second overflow valve is configured to have an oil inlet end communicated with the control cavity and an oil return end communicated with the third working oil port; the second overflow valve and the first overflow valve have different overflow pressures; the third reversing valve can adjust the working states of the first overflow valve and the second overflow valve.

6. The hydraulic discharge system of claim 5 wherein the third reversing valve is selected from an H-type three-position four-way reversing valve.

7. The hydraulic discharge system of claim 5, further comprising a second hydraulic cylinder and a pressure valve set; wherein the content of the first and second substances,

the second hydraulic cylinder is configured to provide back pressure for the dump semi-trailer and is arranged to be communicated with the upstream end of the main oil return pipeline through a back pressure branch;

the pressure valve group is arranged on the main oil return pipeline and is configured to adjust the pressure of the upstream end of the main oil return pipeline.

8. The hydraulic dump system of claim 7 wherein the pressure valve bank comprises a pressure two-way cartridge valve and a third excess flow valve;

the oil inlet end of the pressure two-way cartridge valve is connected with the upstream end of the main oil return pipeline, and the oil return end of the pressure two-way cartridge valve is connected with the downstream end of the main oil return pipeline; and the control cavity of the pressure two-way cartridge valve is communicated with the downstream end of the main oil return pipeline through a third overflow valve.

9. The hydraulic discharge system of claim 8 further comprising an oil return branch and a check valve;

the oil return branch is connected with the third overflow valve in parallel, and the one-way valve is arranged on the oil return branch; and the relief pressure of the third relief valve is smaller than the relief pressures of the second relief valve and the first relief valve.

10. The hydraulic dump system of claim 8, wherein the first, second, and third relief valves are each independently selected from a pilot relief valve or a direct relief valve.

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