Hydraulic driving system of unmanned tractor

Abstract

The invention belongs to the related 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 set 17, a steering metering pump 13, a priority valve 12, a speed regulating valve set 8, a three-position four-way electromagnetic reversing valve set 9, a hydraulic control one-way valve set 10 and a steering hydraulic motor set 11. Hydraulic drive is adopted, power is transmitted through an oil way, a transmission system is simple, stepless speed change can be achieved, speed regulation is convenient, and the tractor can be driven by controlling the opening degree and direction of a valve of a hydraulic element through electric signals; through the arrangement of the load-sensitive proportional multi-way valve and the load-sensitive pump, the problem that the driving capacity is lost due to uneven loads when motors are connected in parallel can be effectively solved, wheels of the tractor can keep rotating synchronously under different load conditions, and the stability and the running performance of the tractor under complex ground conditions are ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field related to hydraulic drive, and more specifically, relates to a hydraulic drive system for an unmanned tractor. Background Art

[0002] Existing research on unmanned tractors mainly relies on traditional tractors, that is, researchers use a certain traditional tractor as a carrier and add auxiliary driving devices, such as adding a cylinder to the brake to simulate the "pedal", so as to use external equipment to simulate manual control of the "accelerator", "brake", "steering wheel", etc. The transmission system in manual mode is used under unmanned driving control, and the transmission link is complex, inefficient, and has low control performance. Unmanned tractors need to be equipped with a drive system that better meets the needs of unmanned driving.

[0003] Compared with mechanical transmission, hydraulic transmission technology has the advantages of stepless speed change and high power density, which can avoid the setback and energy loss of gear switching in mechanical transmission, and can achieve low-speed and high-torque output through pressure regulation, improving the passability on complex terrain. In addition, the high electrification level of hydraulic components provides strong support for the intelligent control of unmanned tractors.

[0004] Therefore, it is urgent to propose an unmanned tractor hydraulic drive system to utilize electrical signals to control hydraulic valve components to achieve stable straight driving and turning driving of the unmanned tractor. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides a hydraulic drive system for an unmanned tractor, thereby solving the technical problem that the existing unmanned tractors rely on the mechanical transmission of traditional tractors.

[0006] To achieve the above object, according to one aspect of the present invention, there is provided an unmanned tractor hydraulic drive system, comprising an engine, a transfer case, a load-sensing pump, a load-sensing proportional multi-way valve, a straight-moving hydraulic motor group, a steering metering pump, a priority valve, a speed regulating valve group, a three-position four-way electromagnetic reversing valve group, a hydraulically controlled one-way valve group, and a steering hydraulic motor group;

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

[0008] The oil outlet of the steering quantitative pump is respectively connected to the oil inlet of the overflow valve and the oil inlet of the priority valve, the first oil outlet of the priority valve is connected to the oil inlet of the N speed regulating valves arranged in parallel in the speed regulating valve group, and the oil outlets of the N speed regulating valves in the speed regulating valve group are respectively connected to the P ports of the N three-position four-way solenoid reversing valves arranged in parallel in the three-position four-way solenoid reversing valve group; the three-position four-way solenoid reversing valve group, the hydraulically controlled one-way valve group, and the steering hydraulic motor group are connected in sequence;

[0009] The oil inlet of the load-sensing pump, the oil inlet of the steering metering pump, the oil outlet of the overflow valve, the N T ports in the three-position four-way electromagnetic reversing valve group, and the M T ports of the load-sensing proportional multi-way valve are all connected to the oil tank.

[0010] Preferably, the straight-moving hydraulic motor group comprises M straight-moving hydraulic motors arranged in parallel, which are connected to the wheels via a planetary reducer, and each wheel is equipped with an independent straight-moving hydraulic motor for driving the tractor to move straight.

[0011] Preferably, the steering hydraulic motor group includes N steering hydraulic motors arranged in parallel, the N steering hydraulic motors control N front wheels, and are used for the rotation of the N front wheels, and the N front wheels are driven by the rotary reducer to complete the adjustment of the direction of the whole machine; the hydraulically controlled one-way valve group includes N hydraulically controlled one-way valves arranged in parallel; preferably, M is set to 4 and N is set to 2.

[0012] Preferably, the N A ports in the three-position four-way solenoid reversing valve group are respectively connected to the N A ports in the hydraulically controlled one-way valve group, and the N B ports in the three-position four-way solenoid reversing valve group are respectively connected to the N B ports in the hydraulically controlled one-way valve group; the N C ports in the hydraulically controlled one-way valve group are respectively connected to the N A ports in the steering hydraulic motor group, and the N D ports in the hydraulically controlled one-way valve group are respectively connected to the N B ports in the steering hydraulic motor group.

[0013] Preferably, a pressure gauge is provided between the steering metering pump and the relief valve for real-time detection of the output pressure of the steering metering pump; 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 reversing valve, the oil inlet of and the oil inlet of the accumulator respectively.

[0015] Preferably, the oil inlet of the steering metering pump is connected to the oil tank through filter 2; the M T ports of the load-sensitive proportional multi-way valve and the N T ports in the three-position four-way solenoid reversing valve group are connected to the oil tank through a condenser and filter 1 in sequence, so as to prevent impurities from entering the system along with the oil and to avoid damage to the hydraulic components due to high temperature.

[0016] Preferably, the three-position four-way solenoid reversing valve has an M-type middle position function. When working 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 working in the middle position, the oil circuit between its P port and T port is connected, and its A port and B port are both cut off; when working 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, the M main valves in the load-sensitive proportional multi-way valve 16 are all O-type neutral position functions. When working in the right position, the oil circuit between the P port and the B port is connected, and the oil circuit between the T port and the A port is connected; when working in the middle position, the P port, T port, A port and B port are all cut off; when working in the left position, the oil circuit between the P port and the A port is connected, and the oil circuit between the T port and the B port is connected.

[0018] In general, compared with the prior art, the above technical solution conceived by the present invention provides an unmanned tractor hydraulic drive system which has the following beneficial effects:

[0019] 1. Compared with the traditional mechanical transmission system, the present invention adopts hydraulic drive and uses oil circuits to transmit power. The transmission system is simple, can achieve stepless speed change, and is convenient for speed regulation. The tractor can be driven by controlling the valve opening and direction of the hydraulic component using electrical signals, which is more in line with the efficiency and accuracy requirements of unmanned driving.

[0020] 2. Compared with the existing hydraulic drive technology, the present invention can effectively overcome the problem of loss of driving ability due to uneven load when motors are connected in parallel through the setting of load-sensitive proportional multi-way valve and load-sensitive pump, and can make the wheels of the tractor 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 maintain the flow rate through each motor consistent through reasonable flow distribution and a stable control mechanism, thereby solving the technical problem of "flow rate giving priority to high load" in traditional hydraulic systems when oil supply is insufficient. The hydraulic drive system of the present invention has good anti-saturation capability. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0023] In all the drawings, the same reference numerals are used to represent the same elements or structures, among which: 1-oil tank; 2-filter one; 3-condenser; 4-overflow valve; 5-pressure gauge; 6-two-position two-way reversing valve; 7-accumulator; 8-speed control valve group; 9-three-position four-way solenoid reversing valve group; 10-hydraulic control one-way valve group; 11-steering hydraulic motor group; 12-priority valve; 13-steering metering pump; 14-filter two; 15-load-sensitive pump; 16-load-sensitive proportional multi-way valve; 17-straight hydraulic motor group. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] Example

[0026] See also Figure 1 , a hydraulic drive system for an unmanned tractor (the tractor is a four-wheel drive two-wheel steering tractor), including an engine, a transfer case, a load-sensitive pump 15, a load-sensitive proportional multi-way valve 16, a straight-moving hydraulic motor group 17, a steering quantitative pump 13, a priority valve 12, a speed regulating valve group 8, a three-position four-way electromagnetic reversing valve group 9, a hydraulically controlled one-way valve group 10, and a steering hydraulic motor group 11;

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

[0028] The oil outlet of the steering metering pump 13 is connected to the oil inlet of the overflow valve 4 and the oil inlet of the priority valve 12 respectively, the first oil outlet of the priority valve 12 is connected to the oil inlet of the two speed regulating valves arranged in parallel in the speed regulating valve group 8, and the oil outlets of the two speed regulating valves in the speed regulating valve group 8 are respectively connected to the P ports of the two three-position four-way electromagnetic reversing valves arranged in parallel in the three-position four-way electromagnetic reversing valve group 9; the three-position four-way electromagnetic reversing valve group 9, the hydraulically controlled one-way valve group 10, and the steering hydraulic motor group 11 are connected in sequence; the speed regulating valve in the speed regulating valve group 8 is integrated with a fixed differential pressure reducing valve and an adjustable flow valve, which is used to control the flow of the steering system to ensure that the passing flow is not affected by the load size, but is only proportional to the opening of the speed regulating valve;

[0029] The oil inlet of the load sensing pump 15 , the oil inlet of the steering metering pump 13 , the oil outlet of the relief valve 14 , the two T ports in the three-position four-way electromagnetic reversing valve group 9 , and the four T ports of the load sensing proportional multi-way valve 16 are all connected to the oil tank 1 .

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

[0031] The steering hydraulic motor group 11 includes two steering hydraulic motors arranged in parallel, preferably bidirectional quantitative cycloidal motors, which control the two front wheels and are used for the rotation of the two front wheels. The two front wheels are driven by a slewing reducer to adjust the direction of the entire machine; the hydraulically controlled one-way valve group 10 includes two hydraulically controlled one-way valves arranged in parallel.

[0032] The two A ports in the three-position four-way electromagnetic reversing valve group 9 are respectively connected to the two A ports in the hydraulic control one-way valve group 10, and the two B ports in the three-position four-way electromagnetic reversing valve group 9 are respectively connected to the two B ports in the hydraulic control one-way valve group 10; the two C ports in the hydraulic control one-way valve group 10 are respectively connected to the two A ports in the steering hydraulic motor group 11, and the two D ports in the hydraulic control one-way valve group 10 are respectively connected to the two B ports in the steering hydraulic motor group 11. The function of the hydraulic control one-way valve in the hydraulic control one-way valve group 10 is to lock the pressure in the steering hydraulic motor when the steering reaches a specified angle to maintain the stability of the steering mechanism.

[0033] A pressure gauge 5 is provided between the steering metering pump 13 and the relief valve 4 for real-time detection of the output pressure of the steering metering pump 13; the relief valve 4 is used to set the maximum pressure of the system circuit, and opens to unload when the pressure exceeds the set pressure to ensure that the oil circuit will not be over-pressurized.

[0034] 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. The oil outlet of the two-position two-way reversing valve 6 is the tractor power output oil port, which is used to connect other non-driven 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 distribute hydraulic oil to the steering hydraulic circuit first. When the steering condition is turned on, the hydraulic demand of the steering system is met first.

[0035] The oil inlet of the steering metering 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 in the three-position four-way electromagnetic reversing valve group 9 are connected to the oil tank 1 through the condenser 3 and the filter 2 in sequence, so as to prevent impurities from entering the system along with the oil and to avoid damage to the hydraulic components due to high temperature.

[0036] The three-position four-way solenoid directional valve has an M-type middle position function. When working 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 working in the middle position, the oil circuit between its P port and T port is connected, and its A port and B port are both blocked; when working 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 model of the load-sensitive proportional multi-way valve 16 is Rexroth M7-22 load-sensitive proportional multi-way valve, which is integrated with four main valves, a pressure compensator, and three shuttle valves; among them, the four main valves are all O-type neutral position functions. When working in the right position, the oil circuit between the P port and the B port is connected, and the oil circuit between the T port and the A port is connected; when working in the middle position, the P port, T port, A port and B port are all cut off; when working in the left position, the oil circuit between the P port and the A port is connected, and the oil circuit between the T port and the B port is connected.

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

[0039] A working process of a driving hydraulic system for an unmanned tractor in this embodiment includes the following steps: the engine transmits power to a load-sensitive pump 15 and a steering metering pump 13 through a transfer case; the load-sensitive pump 15 sucks oil from a fuel tank 1 after being driven, and transmits power to a load-sensitive proportional multi-way valve 16; the load-sensitive proportional multi-way valve 16 then transmits high-pressure oil to a straight hydraulic motor group 17; the steering metering pump 13 sucks oil from a fuel tank 1 after being driven, and the hydraulic oil is filtered through a filter 2 14 in the middle; the high-pressure oil sucked out by the steering metering pump 13 is transmitted to a steering hydraulic motor group 11 after passing through a priority valve 12, a speed regulating valve group 8, a three-position four-way solenoid valve group 9, and a hydraulically controlled one-way valve group 10; the oil after working passes through all T ports of the load-sensitive proportional multi-way valve 16 and the three-position four-way solenoid reversing valve group 9, and is condensed and filtered through a condenser 3 and a filter 2, and then returned to the fuel tank 1.

[0040] Facing the working conditions of straight-line driving on standard roads, driving on slippery or sloped roads, and turning on standard roads, the specific working process of the hydraulic system used for unmanned tractor driving is as follows:

[0041] When driving in a straight line on a standard road, the loads on the four motors in the straight motor group 17 are basically the same. The load signals of the four hydraulic motors in the straight hydraulic motor group 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 shuttle valve 1 in the load-sensitive proportional multi-way valve 16 is introduced into the load-sensitive valve of the load-sensitive pump 8. After being adjusted 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 demand. When the whole machine moves forward or backward, the main valve in the load-sensitive proportional multi-way valve 16 is in the left position or the right position. Adjusting the opening of the main valve can control the speed of the straight hydraulic motor.

[0042] When driving on a slippery or sloped road, the loads on the four motors in the straight-moving motor group 17 are inconsistent. The load signals of the four hydraulic motors in the straight-moving hydraulic motor group 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 the pressure difference before and after the corresponding main valve to be consistent, thereby ensuring that the flow to each straight-moving hydraulic motor in the straight-moving motor group 17 is constant, so that the straight-moving hydraulic motor can maintain the same speed under different load conditions, thereby achieving stable straight-line driving of the tractor under complex ground conditions. In addition, the load signals of the four hydraulic motors in the straight-moving hydraulic motor group 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, the priority valve 12 is energized in the right position and switched to the right position, and the hydraulic oil will be preferentially distributed to the steering hydraulic circuit. The high-pressure oil is adjusted by the speed regulating valve group 8 and the three-position four-way electromagnetic reversing valve group 9 and then 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 of the speed regulating valve in the speed regulating valve group 8, and the turning direction is determined by the four-way electromagnetic reversing valve group 9. When the whole machine turns left, the three-position four-way electromagnetic reversing valve group 9 is energized in the left position, and vice versa, the three-position four-way electromagnetic reversing valve group 9 is energized in the right position.

[0044] It will be easily understood by those skilled in the art that the above description is only 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 in the protection scope of the present invention.

Claims

1. An unmanned tractor hydraulic drive system, characterized in that: It comprises an engine, a transfer case, a load-sensitive pump (15), a load-sensitive proportional multi-way valve (16), a straight-moving hydraulic motor group (17), a steering quantitative pump (13), a priority valve (12), a speed regulating valve group (8), a three-position four-way electromagnetic reversing valve group (9), a hydraulically controlled one-way valve group (10), and a steering hydraulic motor group (11); The engine is connected to the power interface of the load sensing pump (15) and the power interface of the steering quantitative pump (13) through the transfer case; the oil outlet of the load sensing pump (15) is connected to the P port of M main valves arranged in parallel in the load sensing proportional multi-way valve (16); the A port and the B port of the M main valves of the load sensing proportional multi-way valve (16) are connected to the A port and the B port of the M straight-moving hydraulic motors in the straight-moving hydraulic motor group (17); The oil outlet of the steering quantitative pump (13) is respectively connected to the oil inlet of the overflow valve (4) and the oil inlet of the priority valve (12); the first oil outlet of the priority valve (12) is connected to the oil inlet of N speed regulating valves arranged in parallel in the speed regulating valve group (8); the oil outlets of the N speed regulating valves in the speed regulating valve group (8) are respectively connected to the P ports of N three-position four-way electromagnetic reversing valves arranged in parallel in the three-position four-way electromagnetic reversing valve group (9); the three-position four-way electromagnetic reversing valve group (9), the hydraulically controlled one-way 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 steering metering pump (13), the oil outlet of the overflow valve (14), the N T ports in the three-position four-way electromagnetic reversing 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).

2. The unmanned tractor hydraulic drive system according to claim 1, characterized in that: The straight-moving hydraulic motor group (17) comprises M straight-moving hydraulic motors arranged in parallel, which are connected to the wheels via a planetary reducer, and each wheel is equipped with an independent straight-moving hydraulic motor for driving the tractor to move straight.

3. The unmanned tractor hydraulic drive system according to claim 1, characterized in that: The steering hydraulic motor group (11) comprises N steering hydraulic motors arranged in parallel, the N steering hydraulic motors control N front wheels and are used for rotating the N front wheels, and the N front wheels are driven by a rotary reducer to complete the adjustment of the direction of the whole machine; the hydraulically controlled one-way valve group (10) comprises N hydraulically controlled one-way valves arranged in parallel.

4. The unmanned tractor hydraulic drive system according to claim 3, characterized in that: The N A ports in the three-position four-way electromagnetic reversing valve group (9) are respectively connected to the N A ports in the hydraulically controlled one-way valve group (10); the N B ports in the three-position four-way electromagnetic reversing valve group (9) are respectively connected to the N B ports in the hydraulically controlled one-way valve group (10); the N C ports in the hydraulically controlled one-way valve group (10) are respectively connected to the N A ports in the steering hydraulic motor group (11); and the N D ports in the hydraulically controlled one-way valve group (10) are respectively connected to the N B ports in the steering hydraulic motor group (11).

5. The unmanned tractor hydraulic drive system according to claim 1, characterized in that: A pressure gauge (5) is provided between the steering metering pump (13) and the relief valve (4) for real-time detection of the output pressure of the steering metering pump (13); the relief valve (4) is used to set the maximum pressure of the system circuit and is opened to unload when the pressure exceeds the set pressure.

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

7. The unmanned tractor hydraulic drive system according to 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 in the three-position four-way electromagnetic reversing valve group (9) are connected to the oil tank (1) through the condenser (3) and filter 1 (2) in sequence.

8. The unmanned tractor hydraulic drive system according to claim 1, characterized in that: The three-position four-way solenoid reversing valve has an M-type middle position function. When working 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 working in the middle position, the oil circuit between its P port and T port is connected, and its A port and B port are both blocked; when working 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.

9. The unmanned tractor hydraulic drive system according to claim 1, characterized in that: The M main valves in the load-sensitive proportional multi-way valve (16) are all of O-type neutral position function. When working in the right position, the oil path between the P port and the B port is connected, and the oil path between the T port and the A port is connected; when working in the neutral position, the P port, the T port, the A port and the B port are all blocked; when working in the left position, the oil path between the P port and the A port is connected, and the oil path between the T port and the B port is connected.

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