Hydraulic control system of unmanned tractor

Abstract

The utility model discloses a hydraulic control system of an unmanned tractor, which comprises a brake cable and a hydraulic oil circuit formed by connecting a hydraulic pump, a hydraulic steering gear and a hydraulic oil tank, and a control valve block is connected between the hydraulic pump and the hydraulic steering gear. Three working oil ports of the control valve block are respectively communicated with the brake oil cylinder, the energy accumulator and the hydraulic steering gear; a piston rod of the brake oil cylinder is fixedly connected with the brake cable; when the unmanned tractor is parked and braked, hydraulic oil of the brake oil cylinder returns to the hydraulic oil tank through the control valve block, and the piston rod of the hydraulic oil tank contracts to drive the brake inhaul cable to be tensioned to achieve vehicle braking. According to the utility model, the piston rod of the brake oil cylinder can be ensured to retract under the action of the spring force to pull the brake cable under the condition that the vehicle is powered off through the external brake oil cylinder and the negative brake, so that the parking control of the unmanned tractor is realized, and the parking control device is high in universality, safe and reliable.

Description

Technical Field

[0001] This utility model belongs to the field of tractor technology, specifically relating to a hydraulic control system for an unmanned tractor. Background Technology

[0002] With the rapid development of autonomous driving technology, industrial vehicles are also moving towards intelligence. This is especially true in the field of tractor units, whose routes are fixed and whose functions include only steering, braking, and traction. Therefore, using autonomous tractor units can significantly save manpower and resources. Currently, parking brakes on manned tractor units mostly rely on the driver operating a brake lever to pull a brake cable, thereby controlling the brake pads and utilizing friction to achieve parking. This method is simple in structure, stable, and technologically mature, and is therefore widely used in industrial vehicles.

[0003] However, manual parking brake devices cannot meet the braking control requirements of unmanned tractor units. Existing parking brake methods for unmanned tractor units mostly use electromagnetic brakes or electric push rod brakes. While these can achieve braking, they have the following drawbacks: 1. Electromagnetic brakes provide low braking force, suitable for small-tonnage tractor units but not for large-tonnage tractor units; 2. Using electric push rods instead of manually pulling the brake cables will not work in the event of a power outage, causing vehicle loss of control and posing a safety hazard. Furthermore, tractor units weighing over 10 tons mostly use hydraulic steering systems. Therefore, a hydraulic control system with high braking force, integrating steering and braking, high safety and efficiency, and suitable for unmanned tractor units can be provided. Utility Model Content

[0004] To address the shortcomings of existing braking technology in unmanned tractor vehicles, this invention provides a hydraulic control system for parking braking and steering in unmanned tractor vehicles.

[0005] The specific technical solution of this utility model is as follows:

[0006] A hydraulic control system for an unmanned tractor includes a brake cable and a hydraulic circuit formed by a hydraulic pump, a hydraulic steering gear, and a hydraulic oil tank. A control valve block is connected between the hydraulic pump and the hydraulic steering gear. The three working ports of the control valve block are respectively connected to a brake cylinder, an accumulator, and the hydraulic steering gear. The piston rod of the brake cylinder is fixedly connected to the brake cable. When the unmanned tractor brakes, the hydraulic oil in the brake cylinder returns to the hydraulic oil tank through the control valve block, causing the piston rod to contract and tighten the brake cable to achieve vehicle braking.

[0007] In a further embodiment, the control valve block includes a flow divider valve. The inlet of the flow divider valve is connected to a hydraulic pump, and the outlet of the flow divider valve is divided into two paths. The first path is connected to the hydraulic steering gear, and the second path is connected to a first two-position two-way solenoid directional valve and a check valve, respectively. The outlet of the check valve is connected to the brake cylinder, and a second two-position two-way solenoid directional valve and a third two-position two-way solenoid directional valve are connected to the oil path located between the check valve and the brake cylinder, respectively.

[0008] The oil outlets of the first two-position two-way solenoid directional valve and the second two-position two-way solenoid directional valve are both connected to the return port T, and the third two-position two-way solenoid directional valve is connected to the accumulator.

[0009] In a further embodiment, the first and second two-position two-way solenoid directional valves are both normally open solenoid valves, which close the oil circuit when energized and open the oil circuit when de-energized. The third two-position two-way solenoid directional valve is a normally closed solenoid valve, which opens the oil circuit when energized and closes the oil circuit when de-energized.

[0010] The accumulator's oil circuit is connected to a low-pressure detection switch and a high-pressure detection switch to detect its oil pressure; the signal terminals of the low-pressure detection switch and the high-pressure detection switch are respectively connected to the first two-position two-way solenoid directional valve, the second two-position two-way solenoid directional valve, and the third two-position two-way solenoid directional valve.

[0011] In a further embodiment, an overflow valve is connected to the second oil line, and the oil outlet of the overflow valve is connected to the oil return port T.

[0012] In a further embodiment, the brake cylinder includes a cylinder body and a piston rod disposed inside the cylinder body, with a spring sleeved between the piston rod and the cylinder body; the outer end of the piston rod is located outside the cylinder body and is fixedly connected to the brake cable.

[0013] In a further embodiment, a limiting snap ring for limiting the spring is fixed to the outer wall of the piston rod; the outer end of the piston rod is fixedly connected to the brake cable via a hanging bracket.

[0014] In a further embodiment, the return ports of the hydraulic steering gear and control valve block are both connected to the hydraulic oil tank via return oil filters.

[0015] The beneficial effects of this utility model are:

[0016] 1. This utility model achieves parking control of an unmanned tractor by using an external brake cylinder to drive the brake cable, and it has high versatility.

[0017] 2. The negative braking system adopted in this utility model can ensure that when the vehicle is powered off, the piston rod of the brake cylinder retracts under the action of the spring force, thereby pulling the brake cable and automatically putting the vehicle into parking mode, which is safe and reliable.

[0018] 3. The two-position two-way electromagnetic directional valves used in this utility model are all shut-off type, with low leakage; in addition, a single filling of the accumulator can achieve multiple brake releases without the need for multiple fillings, which can improve the service life of the accumulator.

[0019] 4. This utility model supplies oil to the accumulator and hydraulic steering gear simultaneously through a diversion valve, ensuring the independent operation of the steering system. Even if the parking brake fails, the steering function of the unmanned tractor can still be realized, which is highly safe.

[0020] 5. This utility model integrates the steering system and the parking brake system together to achieve hydraulic control, and its integration level is high. Attached Figure Description

[0021] The present invention will now be described in further detail with reference to the accompanying drawings:

[0022] Figure 1 This is a schematic diagram of the hydraulic circuit of this utility model.

[0023] Figure 2 This is a schematic diagram showing the connection between the brake cylinder and the brake cable.

[0024] Figure 3 This is a schematic diagram of the initial state of the brake cylinder.

[0025] Figure 4 This is a schematic diagram showing the extended state of the brake cylinder piston rod.

[0026] Figure 5 This is a diagram showing the parking state after the piston rod of the brake cylinder is connected to the brake cable.

[0027] In the diagram: 1. Hydraulic pump; 2. Control valve block; 21. Diverter valve; 22. Relief valve; 23. First two-position two-way solenoid directional valve; 24. Second two-position two-way solenoid directional valve; 25. Third two-position two-way solenoid directional valve; 26. Check valve; 27. Low-pressure detection switch; 28. High-pressure detection switch.

[0028] 3. Hydraulic steering gear; 4. Accumulator; 5. Brake cylinder; 51. Spring; 52. Piston rod; 53. Limiting circlip; 6. Cable hanger; 7. Brake cable; 8. Hydraulic oil tank; 9. Return oil filter. Detailed Implementation

[0029] The present application will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present application can be combined with each other.

[0030] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," "fixing," and "fixed installation," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0031] like Figure 1-5 As shown, a hydraulic control system for an unmanned tractor includes a brake cable 7, which controls the brake pads by pulling the brake cable, and then uses friction to achieve parking braking. A hydraulic circuit formed by a hydraulic pump 1, a hydraulic steering gear 3, and a hydraulic oil tank 8 is used for steering the unmanned tractor.

[0032] A control valve block 2 is connected between the hydraulic pump 1 and the hydraulic steering gear 3. The oil inlet P of the control valve block 2 is connected to the hydraulic pump 1, and the oil outlet T is connected to the hydraulic oil tank 8. The three working oil ports are respectively connected to the brake cylinder 5, the accumulator 4, and the hydraulic steering gear 3. The piston rod of the brake cylinder 5 is fixedly connected to the brake cable 7. The movement of the brake cable 7 is driven by the extension and retraction of the piston rod of the brake cylinder 5. When the unmanned tractor brakes, the hydraulic oil in the brake cylinder 5 returns to the hydraulic oil tank 8 through the control valve block 2, causing the piston rod to contract and drive the brake cable 7 to tighten, thereby achieving vehicle braking.

[0033] like Figure 1 As shown, the control valve block 2 includes a flow divider valve 21. The inlet of the flow divider valve 21 is connected to the hydraulic pump 1, and the outlet of the flow divider valve 21 is divided into two paths. The first path is connected to the hydraulic steering gear 3, and the second path is connected to the first two-position two-way solenoid directional valve 23 and the check valve 26, respectively. The outlet of the check valve 26 is connected to the brake cylinder 5. The second two-position two-way solenoid directional valve 24 and the third two-position two-way solenoid directional valve 25 are connected to the oil path between the check valve 26 and the brake cylinder 5, respectively.

[0034] The oil outlets of the first two-position two-way solenoid directional valve 23 and the second two-position two-way solenoid directional valve 24 are both connected to the return port T, and the third two-position two-way solenoid directional valve 25 is connected to the accumulator 4.

[0035] In this embodiment, the flow divider valve 21 enables simultaneous oil supply to the accumulator 4 and the hydraulic steering gear 3. By limiting the filling flow rate, it ensures a sufficient supply of hydraulic oil to the steering system of the unmanned tractor, guarantees the normal operation of the hydraulic steering gear 3, and improves the safety of the unmanned tractor.

[0036] When the driverless tractor starts and prepares to move, the hydraulic pump 1 works, inputting the hydraulic oil in the hydraulic oil tank 8 into the valve block 2. After passing through the diversion valve 21, part of the oil flows into the hydraulic steering gear 3 to perform steering work, while the other part of the oil enters the accumulator 4 and the control cylinder 5.

[0037] The first and second position two-way solenoid directional valves 23, 24, and 25 are all shut-off solenoid valves, meaning that the oil circuit is fully opened or fully closed by energizing and de-energizing the electromagnet. They also exhibit low oil leakage, good pressure holding effect, and long pressure maintenance time.

[0038] In this embodiment, the first two-position two-way solenoid directional valve 23 and the second two-position two-way solenoid directional valve 24 are both normally open solenoid valves, which close the oil circuit when energized and open the oil circuit when de-energized. The third two-position two-way solenoid directional valve 25 is a normally closed solenoid valve, which opens the oil circuit when energized and closes the oil circuit when de-energized. When the driverless tractor starts and prepares to move, the first two-position two-way solenoid directional valve 23 and the second two-position two-way solenoid directional valve 24 are energized and close the oil circuit, while the third two-position two-way solenoid directional valve 25 is de-energized and opens the oil circuit. Therefore, as hydraulic oil is continuously input, the pressure of the accumulator 4 and the control cylinder 5 gradually increases, and the control piston rod 52 gradually extends against the spring force, releasing the vehicle's parking brake. When the driverless tractor stops moving and applies the parking brake, the first two-position two-way solenoid directional valve 23, the second two-position two-way solenoid directional valve 24, and the third two-position two-way solenoid directional valve 25 are all de-energized and connected to the oil circuit. The pressurized oil in the accumulator 4 is stored. Due to the presence of the check valve 26, the high-pressure oil in the control cylinder 5 flows back to the hydraulic oil tank 8 through the two-position two-way solenoid directional valve 24. Its piston rod gradually retracts under the action of the spring force, pulling the brake cable 7 to achieve vehicle braking.

[0039] In another embodiment, the accumulator 4 is connected to a low-pressure detection switch 27 and a high-pressure detection switch 28 on its oil circuit to detect its oil pressure; the signal terminals of the low-pressure detection switch 27 and the high-pressure detection switch 28 are respectively connected to the first two-position two-way solenoid valve 23, the second two-position two-way solenoid valve 24, and the third two-position two-way solenoid valve 25 to control their on and off states.

[0040] Specifically, the low-voltage detection switch 27 and the high-voltage detection switch 28 input digital signals to the controller to determine whether the power-on or power-off conditions are met. The controller can be the controller of the control system built into the autonomous vehicle.

[0041] In this embodiment, the pressure required for the piston rod of the control cylinder 5 to fully extend is equal to the minimum pressure value set by the accumulator. The oil pressure of the accumulator is detected by the low-pressure detection switch 27 and the high-pressure detection switch 28, respectively.

[0042] When the vehicle starts, the low-pressure detection switch 27 first checks the pressure of the accumulator 4. If the accumulator pressure is higher than the set value of the low-pressure detection switch 27, it means that the system pressure is sufficient to release the parking brake. The first two-position two-way solenoid valve 23 is de-energized, while the second and third two-position two-way solenoid valves 24 and 25 are energized. The high-pressure oil from the accumulator enters the cylinder 5 through the third two-position two-way solenoid valve 25, pushing the piston rod out and releasing the parking brake. If the accumulator pressure is lower than the set value of the low-pressure detection switch 27, it means that the accumulator pressure is insufficient to release the parking brake, and it needs to be filled with fluid. At this time, the hydraulic pump operates, and the first and second two-position two-way solenoid valves 23 and 24 are energized. The hydraulic oil from the hydraulic pump outlet enters the control cylinder 5, controlling the piston rod 52 to gradually extend against the spring force of the spring 51 (e.g., ...). Figure 4 As shown), the parking brake is released. During the filling process, when the high-pressure detection switch 28 detects that the pressure of the accumulator 4 is higher than the set value of the high-pressure detection switch 28, the first two-position two-way solenoid valve 23 is de-energized, and the oil delivered by the hydraulic pump 1 flows back to the hydraulic oil tank 8 through the first two-position two-way solenoid valve 23, and the accumulator 4 stops filling; the second two-position two-way solenoid valve 24 is energized and the third two-position two-way solenoid valve 25 is de-energized. At this time, the pressure of the control cylinder 5 is equal to the maximum pressure value set by the accumulator, and the parking brake is released.

[0043] When the vehicle needs to be parked, the second two-position two-way solenoid directional valve 24 and the third two-position two-way solenoid directional valve 25 are de-energized, and the first two-position two-way solenoid directional valve 23 is de-energized (pump unloaded). The high-pressure oil in the control cylinder 5 flows back to the hydraulic oil tank 8 through the second two-position two-way solenoid directional valve 24. At the same time, the hydraulic oil in the accumulator is kept at high pressure due to the de-energization of the third two-position two-way solenoid directional valve 25, so that the accumulator can directly supply oil when the vehicle is released from parking, avoiding repeated filling of the accumulator 4 and improving the service life of the accumulator 4.

[0044] An overflow valve 22 is connected to the second oil line, and the oil outlet of the overflow valve 22 is connected to the oil return port T. In this embodiment, the pressure setting value of the overflow valve 22 is slightly higher than the maximum pressure value set by the accumulator 4 to prevent damage caused by continuous liquid filling of the accumulator due to the failure of the pressure detection switch 28 or the first two-position two-way solenoid directional valve 23.

[0045] like Figure 2 As shown, the brake cylinder 5 includes a cylinder body and a piston rod 52 disposed inside the cylinder body. A spring 51 is sleeved between the piston rod 52 and the cylinder body. The outer end of the piston rod 52 is located outside the cylinder body and is fixedly connected to the brake cable 7. A limiting snap ring 53 for limiting the spring 51 is fixedly provided on the outer wall of the piston rod. The outer end of the piston rod 52 is fixedly connected to the brake cable 7 through a cable hanger 6.

[0046] The initial state of piston rod 52 is as follows Figure 3As shown, when there is no external hydraulic oil, the piston rod 52 retracts under the action of the spring 51 (as shown). Figure 5 As shown), the brake cable 6 is tightened, and the parking brake is effective; when hydraulic oil is input, the piston rod 52 will extend against the force of the spring 51 and be limited by the retaining clip 53 (as shown). Figure 4 As shown, the brake cable is released, and the parking brake is released. Therefore, as hydraulic oil is continuously input, when the pressure of the control cylinder 5 gradually increases to the same level as the spring pre-compression force, the piston rod begins to extend until it reaches the limit snap ring 53. At this point, the parking brake is released, and the vehicle can move.

[0047] The return ports of the hydraulic steering gear 3 and the control valve block 2 are both connected to the hydraulic oil tank 8 through the return oil filter 9. That is, in this embodiment, all hydraulic oil must pass through the return oil filter 9 when returning to the hydraulic oil tank, ensuring the cleanliness of the hydraulic oil and improving the service life of the parking brake control device.

[0048] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application shall be within the scope of protection of the claims of this application.

Claims

1. A hydraulic control system for an unmanned tractor, comprising a brake cable (7) and a hydraulic circuit formed by connecting a hydraulic pump (1), a hydraulic steering gear (3), and a hydraulic oil tank (8), characterized in that: A control valve block (2) is connected between the hydraulic pump (1) and the hydraulic steering gear (3). The three working ports of the control valve block (2) are respectively connected to the brake cylinder (5), the accumulator (4), and the hydraulic steering gear (3). The piston rod of the brake cylinder (5) is fixedly connected to the brake cable (7). When the unmanned tractor brakes, the hydraulic oil of the brake cylinder (5) returns to the hydraulic oil tank (8) through the control valve block (2), causing the piston rod to contract and drive the brake cable (7) to tighten to achieve vehicle braking.

2. The hydraulic control system according to claim 1, characterized in that: The control valve block (2) includes a flow divider valve (21). The inlet of the flow divider valve (21) is connected to the hydraulic pump (1). The outlet of the flow divider valve (21) is divided into two paths. The first path is connected to the hydraulic steering gear (3), and the second path is connected to the first two-position two-way solenoid directional valve (23) and the check valve (26). The outlet of the check valve (26) is connected to the brake cylinder (5). The second two-position two-way solenoid directional valve (24) and the third two-position two-way solenoid directional valve (25) are connected to the oil path between the check valve (26) and the brake cylinder (5). The oil outlets of the first two-position two-way solenoid directional valve (23) and the second two-position two-way solenoid directional valve (24) are both connected to the return port T, and the third two-position two-way solenoid directional valve (25) is connected to the accumulator (4).

3. The hydraulic control system according to claim 2, characterized in that: The first two-position two-way solenoid directional valve (23) and the second two-position two-way solenoid directional valve (24) are both normally open solenoid valves, which close the oil circuit when energized and open the oil circuit when de-energized. The third two-position two-way solenoid directional valve (25) is a normally closed solenoid valve, which opens the oil circuit when energized and closes the oil circuit when de-energized.

4. The hydraulic control system according to claim 3, characterized in that: The accumulator (4) is connected to a low-pressure detection switch (27) and a high-pressure detection switch (28) for detecting its oil pressure. The signal terminals of the low-pressure detection switch (27) and the high-pressure detection switch (28) are respectively connected to the first two-position two-way solenoid valve (23), the second two-position two-way solenoid valve (24), and the third two-position two-way solenoid valve (25).

5. The hydraulic control system according to claim 2, characterized in that: An overflow valve (22) is connected to the second oil line, and the oil outlet of the overflow valve (22) is connected to the return port T.

6. The hydraulic control system according to claim 1, characterized in that: The brake cylinder (5) includes a cylinder body and a piston rod (52) located inside the cylinder body. A spring (51) is sleeved between the piston rod (52) and the cylinder body. The outer end of the piston rod (52) is located outside the cylinder body and is fixedly connected to the brake cable (7).

7. The hydraulic control system according to claim 6, characterized in that: The outer wall of the piston rod is fixed with a limiting snap ring (53) for limiting the spring (51); the outer end of the piston rod (52) is fixedly connected to the brake cable (7) through the hanging bracket (6).

8. The hydraulic control system according to claim 1, characterized in that: The return ports of the hydraulic steering gear (3) and the control valve block (2) are both connected to the hydraulic oil tank (8) through the return oil filter (9).

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