Hydraulic drive system for unmanned tractor

Abstract

The present application belongs to the technical field of hydraulic drive, and discloses an unmanned tractor hydraulic drive system, which comprises an engine, a transfer case, a load-sensitive pump 15, a load-sensitive proportional multi-way valve 16, a straight hydraulic motor group 17, a steering constant-displacement pump 13, a priority valve 12, a speed regulating valve group 8, a three-position four-way electromagnetic reversing valve group 9, a hydraulic control check valve group 10, and a steering hydraulic motor group 11. The hydraulic drive is used to transmit power through an oil circuit, and the transmission system is simple, so that stepless speed change can be realized, speed regulation is convenient, and the drive of the tractor can be realized by controlling the valve opening degree and direction of the hydraulic element through an electric signal. Through the setting of the load-sensitive proportional multi-way valve and the load-sensitive pump, the problem of loss of driving ability due to uneven load when the motors are connected in parallel can be effectively overcome, the wheels of the tractor can keep synchronous rotation under different load conditions, and the stability and driving performance of the tractor under complex ground conditions can be ensured.

Description

Technical Field

[0001] This invention belongs to the field of hydraulic drive technology, and more specifically, relates to a hydraulic drive system for an unmanned tractor. Background Technology

[0002] Current research on driverless tractors primarily relies on traditional tractors. Researchers use a conventional tractor as a platform, adding driver assistance devices, such as cylinders to the brakes to simulate pedals, thus using external equipment to mimic manual control of the accelerator, brakes, and steering wheel. However, using the same transmission system in manual mode for driverless control results in complex transmission processes, low efficiency, and poor control performance. Driverless tractors require drive systems that are more suited to the demands of autonomous driving.

[0003] Compared to mechanical transmission, hydraulic transmission technology offers advantages such as continuously variable transmission and high power density. It avoids the jerking and energy loss associated with gear shifting in mechanical transmission and can achieve high torque output at low speeds through pressure regulation, improving traction in complex terrains. Furthermore, the high level of electrification of hydraulic components provides strong support for the intelligent control of unmanned tractors.

[0004] Therefore, there is an urgent need to propose a hydraulic drive system for unmanned tractors, which can use electrical signals to control hydraulic valve components to achieve stable straight-line and turning travel of unmanned tractors. Summary of the Invention

[0005] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a hydraulic drive system for unmanned tractors, thereby solving the technical problem of existing unmanned tractors relying on the mechanical transmission of traditional tractors.

[0006] To achieve the above objectives, according to one aspect of the present invention, an unmanned tractor hydraulic drive system is provided, comprising an engine, a transfer case, a load-sensitive pump, a load-sensitive proportional multi-way valve, a straight-line hydraulic motor assembly, a steering quantitative pump, a priority valve, a speed control valve assembly, a three-position four-way solenoid directional valve assembly, a hydraulically controlled check valve assembly, and a steering hydraulic motor assembly.

[0007] The engine is connected to the power interface of the load-sensitive pump and the power interface of the steering fixed displacement pump through the transfer case; the oil outlet of the load-sensitive pump is connected to the P port of the M parallel main valves in the load-sensitive proportional multi-way valve; the A port and B port of the M main valves of the load-sensitive proportional multi-way valve are connected to the A port and B port of the M straight hydraulic motors in the straight hydraulic motor group.

[0008] The outlet of the steering quantitative pump is connected to the inlet of the overflow valve and the inlet of the priority valve, respectively. The first outlet of the priority valve is connected to the inlet of N parallel speed control valves in the speed control valve group. The outlets of the N speed control valves in the speed control valve group are connected to the P port of the N parallel three-position four-way solenoid directional valves in the three-position four-way solenoid directional valve group, respectively. The three-position four-way solenoid directional valve group, the hydraulic control check valve group, and the steering hydraulic motor group are connected in sequence.

[0009] The oil inlet of the load-sensitive pump, the oil inlet of the directional quantitative pump, the oil outlet of the overflow valve, the N T ports in the three-position four-way solenoid directional valve group, and the M T ports of the load-sensitive proportional multi-way valve are all connected to the oil tank.

[0010] Preferably, the straight-line hydraulic motor assembly includes M straight-line hydraulic motors arranged in parallel, which are connected to the wheels through planetary reducers. Each wheel is equipped with an independent straight-line hydraulic motor for driving the tractor to move straight.

[0011] Preferably, the steering hydraulic motor assembly includes N steering hydraulic motors connected in parallel, and the N steering hydraulic motors control N front wheels for the rotation of the N front wheels. The N front wheels are driven by a rotary reducer to complete the adjustment of the overall machine direction; the hydraulic control check valve assembly includes N hydraulic control check valves connected in parallel; preferably, M is set to 4 and N is set to 2.

[0012] Preferably, the N A ports of the three-position four-way solenoid directional valve group are respectively connected to the N A ports of the hydraulic control check valve group, the N B ports of the three-position four-way solenoid directional valve group are respectively connected to the N B ports of the hydraulic control check valve group; the N C ports of the hydraulic control check valve group are respectively connected to the N A ports of the steering hydraulic motor group, and the N D ports of the hydraulic control check valve group are respectively connected to the N B ports of the steering hydraulic motor group.

[0013] Preferably, a pressure gauge is provided between the steering metering pump and the relief valve to detect the output pressure of the steering metering pump in real time; the relief valve is used to set the maximum pressure of the system circuit, and opens to unload when the pressure exceeds the set pressure.

[0014] Preferably, the second oil outlet of the priority valve is connected to the oil inlet of the two-position two-way directional valve, the oil inlet of the accumulator, and the oil inlet of the accumulator.

[0015] Preferably, the oil inlet of the steering quantitative pump is connected to the oil tank through filter two; the M T ports of the load-sensitive proportional multi-way valve and the N T ports of the three-position four-way solenoid directional valve group are all connected to the oil tank in sequence through the condenser and filter one, in order to prevent impurities from entering the system with the oil and to prevent damage to hydraulic components due to high temperature.

[0016] Preferably, the three-position four-way solenoid directional valve has an M-type neutral position function. When operating in the right position, the oil circuit between its P port and A port is connected, and the oil circuit between its T port and B port is connected. When operating in the neutral position, the oil circuit between its P port and T port is connected, while both its A port and B port are closed. When operating in the left position, the oil circuit between its P port and B port is connected, and the oil circuit between its T port and A port is connected.

[0017] Preferably, all M main valves in the load-sensitive proportional multi-way valve 16 are O-type neutral position valves. When operating in the right position, the oil circuit between its P port and B port is connected, and the oil circuit between its T port and A port is connected. When operating in the neutral position, its P port, T port, A port, and B port are all closed. When operating in the left position, the oil circuit between its P port and A port is connected, and the oil circuit between its T port and B port is connected.

[0018] In summary, compared with the prior art, the hydraulic drive system for an unmanned tractor provided by the present invention has the following advantages:

[0019] 1. Compared with traditional mechanical transmission systems, this invention uses hydraulic drive, which transmits power through oil circuits. The transmission system is simple, can achieve stepless speed change, and is easy to adjust. The tractor can be driven by controlling the valve opening and direction of hydraulic components with electrical signals, which is more in line with the efficiency and precision requirements of unmanned driving.

[0020] 2. Compared with existing hydraulic drive technology, the present invention can effectively overcome the problem of loss of driving capability due to uneven load when motors are connected in parallel by setting load-sensitive proportional multi-way valve and load-sensitive pump. It can enable the tractor wheels to rotate synchronously under different load conditions, ensuring the stability and driving performance of the tractor under complex ground conditions.

[0021] 3. Under high load conditions, the hydraulic drive system of the present invention can keep the flow rate through each motor consistent through reasonable flow distribution and stable control mechanism, which solves the technical problem of "flow rate first meets high load" in traditional hydraulic systems when oil supply is insufficient. The hydraulic drive system of the present invention has good anti-saturation capability. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a hydraulic drive system for an unmanned tractor according to the present invention;

[0023] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1-oil tank; 2-filter one; 3-condenser; 4-relief valve; 5-pressure gauge; 6-two-position two-way directional valve; 7-accumulator; 8-speed control valve assembly; 9-three-position four-way solenoid directional valve assembly; 10-hydraulic control check valve assembly; 11-steering hydraulic motor assembly; 12-priority valve; 13-steering fixed displacement pump; 14-filter two; 15-load-sensitive pump; 16-load-sensitive proportional multi-way valve; 17-straight-line hydraulic motor assembly. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0025] Example

[0026] Please see Figure 1 A hydraulic drive system for an unmanned tractor (the tractor is a four-wheel drive two-wheel steering system) includes an engine, a transfer case, a load-sensitive pump 15, a load-sensitive proportional multi-way valve 16, a straight-line hydraulic motor assembly 17, a steering quantitative pump 13, a priority valve 12, a speed control valve assembly 8, a three-position four-way solenoid directional valve assembly 9, a hydraulically controlled check valve assembly 10, and a steering hydraulic motor assembly 11.

[0027] The engine is connected to the power interface of the load-sensitive pump 15 and the power interface of the steering fixed displacement pump 13 through the transfer case; the oil outlet of the load-sensitive pump 15 is connected to the P port of the four parallel main valves in the load-sensitive proportional multi-way valve 16; the A port and B port of the four main valves of the load-sensitive proportional multi-way valve 16 are connected to the A port and B port of the four straight hydraulic motors in the straight hydraulic motor assembly 17.

[0028] The outlet of the steering quantitative pump 13 is connected to the inlet of the overflow valve 4 and the inlet of the priority valve 12, respectively. The first outlet of the priority valve 12 is connected to the inlet of the two parallel speed control valves in the speed control valve group 8. The outlets of the two speed control valves in the speed control valve group 8 are connected to the P port of the two parallel three-position four-way solenoid directional valves in the three-position four-way solenoid directional valve group 9, respectively. The three-position four-way solenoid directional valve group 9, the hydraulic control check valve group 10, and the steering hydraulic motor group 11 are connected in sequence. The speed control valve in the speed control valve group 8 is integrated with a differential pressure reducing valve and an adjustable flow valve to control the flow rate of the steering system, ensuring that the flow rate is not affected by the load size, but is only proportional to the opening degree of the speed control valve.

[0029] The oil inlet of the load-sensitive pump 15, the oil inlet of the steering fixed displacement pump 13, the oil outlet of the overflow valve 14, the two T ports in the three-position four-way solenoid directional valve group 9, and the four T ports of the load-sensitive proportional multi-way valve 16 are all connected to the oil tank 1.

[0030] The straight-line hydraulic motor assembly 17 includes four straight-line hydraulic motors arranged in parallel, preferably bidirectional quantitative cycloidal motors, which are connected to the wheels through planetary reducers. Each wheel is equipped with an independent straight-line hydraulic motor for driving the tractor to move straight.

[0031] The steering hydraulic motor assembly 11 includes two steering hydraulic motors connected in parallel, preferably bidirectional quantitative cycloidal motors. The two steering hydraulic motors control the two front wheels for rotation of the two front wheels, and the two front wheels are driven by a rotary reducer to complete the adjustment of the overall direction of the machine. The hydraulic control check valve assembly 10 includes two hydraulic control check valves connected in parallel.

[0032] The two A ports of the three-position four-way solenoid directional valve assembly 9 are connected to the two A ports of the hydraulically controlled check valve assembly 10, respectively; the two B ports of the three-position four-way solenoid directional valve assembly 9 are connected to the two B ports of the hydraulically controlled check valve assembly 10, respectively; the two C ports of the hydraulically controlled check valve assembly 10 are connected to the two A ports of the steering hydraulic motor assembly 11, respectively; the two D ports of the hydraulically controlled check valve assembly 10 are connected to the two B ports of the steering hydraulic motor assembly 11, respectively. The function of the hydraulically controlled check valve in the hydraulically controlled check valve assembly 10 is to lock the pressure in the steering hydraulic motor when the steering reaches a specified angle, thereby maintaining the stability of the steering mechanism.

[0033] A pressure gauge 5 is installed between the steering metering pump 13 and the relief valve 4 to detect the output pressure of the steering metering pump 13 in real time; the relief valve 4 is used to set the maximum pressure of the system circuit. When the pressure exceeds the set pressure, it opens to unload and ensure that the oil circuit is not too high.

[0034] The second outlet of the priority valve 12 is connected to the inlet of the two-position two-way directional valve 6 and the inlet of the accumulator 7. The outlet of the two-position two-way directional valve 6 is the tractor power output port, used to connect to other non-driving hydraulic devices. The accumulator 7 is an energy storage device used for system buffering and vibration absorption to improve system stability. The priority valve 12 is used to allocate hydraulic oil to prioritize the supply of hydraulic oil to the steering hydraulic circuit. When the steering condition is activated, the hydraulic demand of the steering system is prioritized.

[0035] The oil inlet of the steering fixed displacement pump 13 is connected to the oil tank 1 through the filter 2 14; the four T ports of the load sensitive proportional multi-way valve 16 and the two T ports of the three-position four-way solenoid directional valve group 9 are connected to the oil tank 1 through the condenser 3 and the filter 1 2 in sequence, in order to prevent impurities from entering the system with the oil and to prevent damage to hydraulic components due to high temperature.

[0036] The three-position four-way solenoid directional valve has an M-type neutral position function. When operating in the right position, the oil circuit between its P port and A port is connected, and the oil circuit between its T port and B port is connected. When operating in the neutral position, the oil circuit between its P port and T port is connected, while both its A port and B port are closed. When operating in the left position, the oil circuit between its P port and B port is connected, and the oil circuit between its T port and A port is connected.

[0037] In this embodiment, the load-sensitive proportional multi-way valve 16 is a Rexroth M7-22 load-sensitive proportional multi-way valve. The load-sensitive proportional multi-way valve 16 is integrated with four main valves, a pressure compensator, and three shuttle valves. The four main valves are all O-type neutral position valves. When operating in the right position, the oil circuit between its P port and B port is connected, and the oil circuit between its T port and A port is connected. When operating in the neutral position, its P port, T port, A port, and B port are all closed. When operating in the left position, the oil circuit between its P port and A port is connected, and the oil circuit between its T port and B port is connected.

[0038] In this embodiment, the load-sensitive pump 15 is a Rexroth A10VO series axial piston variable pump. The load-sensitive pump 15 is integrated with a load-sensitive valve, a pressure shut-off valve, a variable pump, and two variable cylinders. The load-sensitive valve is used to set the pressure difference and control the pressure output of the load-sensitive pump 15. The pressure shut-off valve is used to set the maximum pressure of the load-sensitive pump 15. The displacement of the load-sensitive pump 15 is controlled by the variable cylinders.

[0039] The workflow of a hydraulic system for driving an unmanned tractor in this embodiment includes the following steps: The engine transmits power to the load-sensitive pump 15 and the steering fixed displacement pump 13 through the transfer case. After being driven, the load-sensitive pump 15 draws oil from the oil tank 1 and transmits power to the load-sensitive proportional multi-way valve 16. The load-sensitive proportional multi-way valve 16 then transmits the high-pressure oil to the straight-line hydraulic motor assembly 17. After being driven, the steering fixed displacement pump 13 draws oil from the oil tank 1. The hydraulic oil is filtered by the second filter 14. The high-pressure oil drawn out by the steering fixed displacement pump 13 is transmitted to the steering hydraulic motor assembly 11 after passing through the priority valve 12, the speed control valve assembly 8, the three-position four-way solenoid valve assembly 9, and the hydraulic control check valve assembly 10. After working, the oil returns to the oil tank 1 after being condensed and filtered by the condenser 3 and the first filter 2 through all the T ports of the load-sensitive proportional multi-way valve 16 and the three-position four-way solenoid valve assembly 9.

[0040] The specific working process of the hydraulic system used to drive the unmanned tractor is as follows, when facing conditions such as driving straight on a standard road, driving on a wet or sloping road, and turning on a standard road:

[0041] When traveling straight on a standard road surface, the loads on the four motors in the straight-moving motor assembly 17 are basically the same. The load signals of the four hydraulic motors in the straight-moving hydraulic motor assembly 17 are fed back to the load-sensitive proportional multi-way valve 16. After being collected and processed by the three shuttle valves of the load-sensitive proportional multi-way valve 16, they are introduced into the load-sensitive valve of the load-sensitive pump 8 by the shuttle valve 1 in the load-sensitive proportional multi-way valve 16. After adjustment by the load-sensitive valve, the load-sensitive pump 8 outputs a pressure higher than the fixed value of the load signal, thereby effectively reducing power loss while meeting the load requirements. When the whole machine moves forward or backward, the main valve in the load-sensitive proportional multi-way valve 16 is in the left or right position. Adjusting the opening of the main valve can control the speed of the straight-moving hydraulic motor.

[0042] When driving on wet or sloping surfaces, the loads on the four motors in the straight-line motor assembly 17 are inconsistent. The load signals of the four hydraulic motors in the straight-line hydraulic motor assembly 17 are fed back to the load-sensitive proportional multi-way valve 16. The pressure compensator in the load-sensitive proportional multi-way valve 16 automatically adjusts to make the pressure difference before and after the corresponding main valve consistent, thereby ensuring that the flow to each straight-line hydraulic motor in the straight-line motor assembly 17 remains constant. This allows the straight-line hydraulic motors to maintain the same speed under different load conditions, thus enabling the tractor to travel stably in a straight line under complex terrain conditions. In addition, the load signals of the four hydraulic motors in the straight-line hydraulic motor assembly 17 are fed back to the load-sensitive proportional multi-way valve 16. After being collected and processed by the three shuttle valves of the load-sensitive proportional multi-way valve 16, the maximum load pressure signal is introduced into the load-sensitive valve of the load-sensitive pump 8 by the shuttle valve 1 in the load-sensitive proportional multi-way valve 16. The load-sensitive pump 8 adjusts the output pressure according to the maximum load feedback signal to ensure the power demand.

[0043] When turning on a standard road surface, the priority valve 12 is energized in the right position, switching to the right position, and hydraulic oil will be preferentially distributed to the steering hydraulic circuit. High-pressure oil, after being adjusted by the speed control valve group 8 and the three-position four-way solenoid directional valve group 9, enters the steering hydraulic motor group 10, thereby driving the steering mechanism to complete the steering action. The steering speed is determined by the opening degree of the speed control valve in the speed control valve group 8, and the turning direction is determined by the four-way solenoid directional valve group 9. When the machine turns left, the three-position four-way solenoid directional valve group 9 is energized in the left position; conversely, it is energized in the right position.

[0044] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A hydraulic drive system for an unmanned tractor, characterized in that: Includes engine, transfer case, load-sensitive pump (15), load-sensitive proportional multi-way valve (16), straight-line hydraulic motor assembly (17), steering quantitative pump (13), priority valve (12), speed control valve assembly (8), three-position four-way solenoid directional valve assembly (9), hydraulic control check valve assembly (10), steering hydraulic motor assembly (11). The engine is connected to the power interface of the load-sensitive pump (15) and the power interface of the steering fixed displacement pump (13) through the transfer case; the oil outlet of the load-sensitive pump (15) is connected to the P port of the M parallel main valves in the load-sensitive proportional multi-way valve (16); the A port and B port of the M main valves of the load-sensitive proportional multi-way valve (16) are connected to the A port and B port of the M straight hydraulic motors in the straight hydraulic motor group (17) respectively; The outlet of the steering quantitative pump (13) is connected to the inlet of the overflow valve (4) and the inlet of the priority valve (12), respectively. The first outlet of the priority valve (12) is connected to the inlet of the N parallel speed control valves in the speed control valve group (8). The outlets of the N speed control valves in the speed control valve group (8) are connected to the P port of the N parallel three-position four-way solenoid directional valves in the three-position four-way solenoid directional valve group (9), respectively. The three-position four-way solenoid directional valve group (9), the hydraulic control check valve group (10), and the steering hydraulic motor group (11) are connected in sequence. The oil inlet of the load-sensitive pump (15), the oil inlet of the directional metering pump (13), the oil outlet of the overflow valve (4), the N T ports in the three-position four-way solenoid directional valve group (9), and the M T ports of the load-sensitive proportional multi-way valve (16) are all connected to the oil tank (1). The straight-line hydraulic motor assembly (17) includes M parallel straight-line hydraulic motors, which are connected to the wheels via planetary reducers. Each wheel is equipped with an independent straight-line hydraulic motor for driving the tractor to move straight. The steering hydraulic motor assembly (11) includes N steering hydraulic motors connected in parallel. The N steering hydraulic motors control the N front wheels and are used for the rotation of the N front wheels. The N front wheels are driven by the rotary reducer to complete the adjustment of the overall direction of the machine. The hydraulic control check valve assembly (10) includes N hydraulic control check valves connected in parallel. The N A ports of the three-position four-way solenoid directional valve group (9) are respectively connected to the N A ports of the hydraulic control check valve group (10), the N B ports of the three-position four-way solenoid directional valve group (9) are respectively connected to the N B ports of the hydraulic control check valve group (10), the N C ports of the hydraulic control check valve group (10) are respectively connected to the N A ports of the steering hydraulic motor group (11), and the N D ports of the hydraulic control check valve group (10) are respectively connected to the N B ports of the steering hydraulic motor group (11).

2. The hydraulic drive system for an unmanned tractor as described in claim 1, characterized in that: A pressure gauge (5) is provided between the steering metering pump (13) and the overflow valve (4) to detect the output pressure of the steering metering pump (13) in real time; the overflow valve (4) is used to set the maximum pressure of the system circuit and opens to unload when the pressure exceeds the set pressure.

3. The hydraulic drive system for an unmanned tractor as described in claim 1, characterized in that: The second oil outlet of the priority valve (12) is connected to the oil inlet of the two-position two-way reversing valve (6) and the oil inlet of the accumulator (7), respectively.

4. The hydraulic drive system for an unmanned tractor as described in claim 1, characterized in that: The oil inlet of the steering metering pump (13) is connected to the oil tank (1) through filter 2 (14); the four T ports of the load-sensitive proportional multi-way valve (16) and the two T ports of the three-position four-way solenoid directional valve group (9) are connected to the oil tank (1) in sequence through the condenser (3) and filter 1 (2).

5. The hydraulic drive system for an unmanned tractor as described in claim 1, characterized in that: The three-position four-way solenoid directional valve is a type M-type neutral position valve. When it is in the right position, the oil circuit between its P port and A port is connected, and the oil circuit between its T port and B port is connected. When it is in the neutral position, the oil circuit between its P port and T port is connected, and both its A port and B port are closed. When it is in the left position, the oil circuit between its P port and B port is connected, and the oil circuit between its T port and A port is connected.

6. The hydraulic drive system for an unmanned tractor as described in claim 1, characterized in that: The M main valves in the load-sensitive proportional multi-way valve (16) are all of type O with a neutral position function. When operating in the right position, the oil circuit between its P port and B port is connected, and the oil circuit between its T port and A port is connected. When operating in the neutral position, its P port, T port, A port and B port are all cut off. When operating in the left position, the oil circuit between its P port and A port is connected, and the oil circuit between its T port and B port is connected.

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