Hydraulic control system of industrial vehicle

Abstract

The invention discloses a hydraulic control system for an industrial vehicle. The hydraulic control system comprises a hydraulic oil tank, a hydraulic oil pump, an oil return filter, a hydraulic integrated valve block, a hydraulic power-assisted brake valve, a hydraulic steering gear, an electro-hydraulic proportional multi-way valve, a wheel brake and an execution oil cylinder. An oil outlet of the hydraulic oil pump is connected to an oil inlet of the hydraulic integrated valve block; an oil outlet of the hydraulic integrated valve block is connected to an oil inlet of the hydraulic power-assisted brake valve, an oil inlet of the hydraulic steering gear and an oil inlet of the electro-hydraulic proportional multi-way valve. The hydraulic integrated valve block integrates a steering priority control module, a brake pressure control module and an overflow unloading control module and is used for achieving steering priority oil supply, hydraulic braking and hydraulic system overflow unloading functions. Three functional modules are integrated in the hydraulic integrated valve block, the long-standing technical bottlenecks of steering energy conservation, braking safety and overflow unloading of a large-tonnage forklift are solved at a time, and the core targets of energy conservation, consumption reduction, safety and high efficiency are achieved.

Description

Technical Field

[0001] This invention relates to the field of industrial vehicle technology, and in particular to a hydraulic control system for industrial vehicles. Background Technology

[0002] Currently, with the rapid development of the industrial vehicle industry, customers have increasingly higher requirements for forklift operation comfort, especially the desire for fingertip operation, allowing precise control of lifting and tilting speeds with a simple touch. This not only reduces driver fatigue but also significantly improves the driving experience. However, the hydraulic oil flow of large-tonnage forklifts (5-10 tons) on the market is currently high, and domestic electro-hydraulic proportional multi-way valve technology is not yet mature enough, with most manufacturers still relying on foreign products. Although these imported products can meet some needs, they still have some significant problems, such as the lack of a steering priority valve, which prevents the forklift from achieving optimal energy efficiency during steering; and the lack of a braking circuit, especially in large-tonnage forklifts where the required braking force is high, and manual braking is ineffective, requiring hydraulic braking to ensure safety. In addition, these products often lack an unloading function. Once the load is fully lifted, if the button on the fingertip is not released, the forklift continues to operate under high pressure and high flow, which may not only cause the engine to idle and stop but also lead to overheating of the hydraulic system, thus wasting a lot of energy.

[0003] To address these issues, it is necessary to design a hydraulic control system that integrates steering and braking functions, while also possessing an overflow unloading function. This system aims to meet the energy-saving, consumption-reducing, safe, and efficient requirements of electro-hydraulic proportional forklifts. This design ensures that steering needs are prioritized when required, resulting in lower energy consumption; simultaneously, it provides emergency braking in emergencies such as sudden power outages, ensuring forklift safety. Furthermore, the unloading function releases hydraulic pressure after the load is lifted, preventing the system from operating at high pressure for extended periods, thereby reducing energy consumption and heat generation in the hydraulic system and improving the overall system's energy efficiency and safety. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology. To achieve the above objective, an industrial vehicle hydraulic control system is adopted to solve the problems mentioned in the background technology.

[0005] An industrial vehicle hydraulic control system, comprising: Hydraulic oil tank, hydraulic oil pump, return oil filter, hydraulic integrated valve block, hydraulic power brake valve, hydraulic steering gear, electro-hydraulic proportional multi-way valve, wheel brake, and actuator cylinder; The outlet of the hydraulic oil pump is connected to the inlet of the hydraulic integrated valve block. The oil outlet of the hydraulic integrated valve block is connected to the oil inlet of the hydraulic power-assisted brake valve, the oil inlet of the hydraulic steering gear, and the oil inlet of the electro-hydraulic proportional multi-way valve, respectively. The hydraulic integrated valve block integrates a steering priority control module, a brake pressure control module, and an overflow unloading control module to realize steering priority oil supply, hydraulic braking, and hydraulic system overflow unloading functions.

[0006] As a further embodiment of the present invention, the hydraulic integrated valve block further includes an accumulator, an accumulator low-pressure detection switch, an accumulator high-pressure detection switch, and a system high-pressure detection switch.

[0007] As a further aspect of the present invention: the hydraulic integrated valve block internally integrates: The system includes a first relief valve, a steering priority valve, a first check valve, a second check valve, and a third check valve. The first two-position two-way solenoid directional valve, the second relief valve, and the pressure reducing valve are used for braking control. Two-position two-way directional valve, second two-position two-way solenoid directional valve, and throttle valve for unloading control.

[0008] As a further aspect of the present invention: the hydraulic oil pump includes a first oil pump and a second oil pump connected in parallel, wherein the first oil pump is a dual pump, the main pump outputs oil to the working system, and the auxiliary pump outputs oil to the braking system.

[0009] As a further aspect of the present invention: the hydraulic steering gear is a load-sensing steering gear, and its load pressure is fed back to the steering priority valve of the hydraulic integrated valve block to achieve steering priority oil supply.

[0010] As a further aspect of the present invention: the hydraulic power-assisted brake valve adopts a closed hydraulic system, the brake pressure oil is supplied by the accumulator through the pressure reducing valve, and the accumulator is connected to the auxiliary pump oil circuit through the check valve.

[0011] As a further aspect of the present invention: the execution logic of the overflow unloading control module is as follows: When the system high-pressure detection switch detects that the inlet pressure of the electro-hydraulic proportional multi-way valve has reached the set value, it triggers the two-position two-way solenoid directional valve to open. The oil generates a pressure difference through the throttle valve, which pushes the two-position two-way directional valve to open the unloading oil circuit.

[0012] As a further aspect of the present invention, a shut-off valve connected to the accumulator oil circuit is also included for manually releasing the accumulator pressure.

[0013] Compared with the prior art, the present invention has the following technical advantages: The above technical solution integrates a steering priority control module, a brake pressure control module, and an overflow unloading control module into a hydraulic integrated valve block. This distributes the hydraulic pump output to the hydraulic power-assisted brake valve, the load-sensing steering gear, and the electro-hydraulic proportional multi-way valve, achieving coordinated functions such as dynamic priority oil supply to the steering circuit, independent brake pressure supply to the accumulator, and automatic high-pressure unloading of the hydraulic system. The steering priority module avoids energy waste during non-steering conditions; the overflow unloading module eliminates high-pressure overflow energy consumption and reduces system heat generation; and the brake pressure module provides continuous hydraulic brake assist pressure through the accumulator, supporting emergency braking during power interruption. The integration of these three functional modules into a single valve block simplifies piping layout and improves system response speed and control accuracy. Attached Figure Description

[0014] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the structure of the hydraulic control system according to an embodiment of this application.

[0015] In the diagram: 1. Hydraulic oil tank; 2. First suction filter; 3. Second suction filter; 4. First oil pump; 5. Second oil pump; 6. Return filter; 7. Hydraulic integrated valve block; 8. First relief valve; 9. Steering priority valve; 10. First check valve; 11. Second check valve; 12. Third check valve; 13. First two-position two-way solenoid directional valve; 14. Second relief valve; 15. Pressure reducing valve; 16. Accumulator; 17. Accumulator low-pressure detection switch; 18. Accumulator high-pressure detection switch; 19. Hydraulic power brake valve; 20. Hydraulic steering gear; 21. Electro-hydraulic proportional multi-way valve; 22. Two-position two-way directional valve; 23. Second two-position two-way solenoid directional valve; 24. System high-pressure detection switch; 25. Throttle valve; 26. Wheel brake; 27. Steering cylinder; 28. Lifting cylinder; 29. ​​Tilting cylinder; 30. Attachment cylinder; 31. Shut-off valve. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Please refer to Figure 1 In this embodiment of the invention, an industrial vehicle hydraulic control system includes: Hydraulic oil tank 1, hydraulic oil pump, return oil filter 6, hydraulic integrated valve block 7, hydraulic power brake valve 19, hydraulic steering gear 20, electro-hydraulic proportional multi-way valve 21, wheel brake 26, and actuator cylinder. Specifically, the components include: hydraulic oil tank 1, suction filter 2, suction filter 3, first oil pump 4, second oil pump 5, return oil filter 6, hydraulic integrated valve block 7, accumulator 16, accumulator low-pressure detection switch 17, accumulator high-pressure detection switch 18, closed-loop hydraulic power assist brake valve 19, hydraulic steering gear 20, electro-hydraulic proportional multi-way valve 21, system high-pressure detection switch 24, wheel brake 26, steering cylinder 27, lifting cylinder 28, tilting cylinder 29, and attachment cylinder 30.

[0018] The outlet of the hydraulic oil pump is connected to the inlet of the hydraulic integrated valve block 7. The oil outlet of the hydraulic integrated valve block 7 is connected to the oil inlet of the hydraulic power assist brake valve 19, the oil inlet of the hydraulic steering gear 20, and the oil inlet of the electro-hydraulic proportional multi-way valve 21, respectively. The hydraulic integrated valve block 7 integrates a steering priority control module, a brake pressure control module, and an overflow unloading control module, which are used to realize steering priority oil supply, hydraulic braking, and hydraulic system overflow unloading functions.

[0019] The hydraulic pump outlet is connected to the hydraulic integrated valve block 7 inlet, the hydraulic integrated valve block 7 outlet is connected to the hydraulic power brake valve 19 inlet, the hydraulic integrated valve block 7 outlet is connected to the hydraulic steering gear 20 inlet, and the hydraulic integrated valve block 7 outlet is connected to the electro-hydraulic proportional multi-way valve 21 inlet.

[0020] In this embodiment, the hydraulic integrated valve block 7 also includes an accumulator 16, an accumulator low-pressure detection switch 17, an accumulator high-pressure detection switch 18, and a system high-pressure detection switch 24.

[0021] In this embodiment, the hydraulic integrated valve block 7 integrates the following: First relief valve 8, directional priority valve 9, first check valve 10, second check valve 11, and third check valve 12; The first two-position two-way solenoid directional valve 13, the second relief valve 14, and the pressure reducing valve 15 are used for braking control. Two-position two-way directional valve 22, second two-position two-way solenoid directional valve 23, and throttle valve 25 are used for unloading control.

[0022] In this embodiment, the hydraulic pump includes a first pump 4 and a second pump 5 connected in parallel. The first pump 4 is a dual pump, with the main pump outputting oil to the working system and the auxiliary pump outputting oil to the braking system.

[0023] In this embodiment, the hydraulic steering gear 20 is a load-sensing steering gear, and its load pressure is fed back to the steering priority valve 9 of the hydraulic integrated valve block 7 to achieve steering priority oil supply.

[0024] In this embodiment, the hydraulic power-assisted brake valve 19 adopts a closed hydraulic system. The brake pressure oil is supplied by the accumulator 16 through the pressure reducing valve 15, and the accumulator 16 is connected to the auxiliary pump oil circuit through a check valve.

[0025] The braking system uses a closed hydraulic system, meaning the working circuit is a closed oil circuit. When the brake pedal is not pressed, the pressure oil at the inlet of the brake valve will not enter the brake valve, and the brake valve will not work. When the brake pedal is pressed, the pressure oil enters the wheel brake through the hydraulic power-assisted brake valve, and the forklift is slowed down by friction.

[0026] In this embodiment, the execution logic of the overflow unloading control module is as follows: When the system high pressure detection switch 24 detects that the oil inlet pressure of the electro-hydraulic proportional multi-way valve 21 reaches the set value, it triggers the two-position two-way solenoid directional valve to open. The oil generates a pressure difference through the throttle valve 25, which pushes the two-position two-way directional valve 22 to open the unloading oil circuit.

[0027] In this embodiment, a shut-off valve 31 connected to the oil circuit of the accumulator 16 is also included for manually releasing the pressure of the accumulator 16.

[0028] The hydraulic steering gear 20 is a load-sensing steering gear, meaning that when the steering wheel is not turning, the hydraulic oil will not flow directly from the steering gear inlet back to the oil tank. When turning is required, the precisely measured oil can be supplied to the steering cylinder 27 as needed, which is highly efficient and energy-saving.

[0029] The first oil pump 4 is a dual hydraulic oil pump, with the main pump supplying oil to the working system and the auxiliary pump supplying oil to the braking system.

[0030] The first two-position two-way solenoid directional valve 13 is a normally open solenoid valve; it closes the oil circuit when energized and opens the oil circuit when de-energized. The second two-position two-way solenoid directional valve 23 is a normally closed solenoid valve; it opens the oil circuit when energized and closes the oil circuit when de-energized. The second two-position two-way directional valve 22 is a normally closed directional valve; it closes the oil circuit under the action of spring force and opens the oil circuit when overcoming spring force.

[0031] The accumulator low-voltage detection switch 17, the accumulator high-voltage detection switch 18, and the system high-voltage detection switch 24 can 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 a control system integrated into an industrial vehicle.

[0032] The operation process of the system of this invention is as follows: When the vehicle starts and the first oil pump 4 and the second oil pump 5 operate, the hydraulic oil in the hydraulic oil tank 1 passes through the first suction filter 2 and the second suction filter 3 and is input into the hydraulic integrated valve block 7. The oil output from the main pump in the first oil pump 4 first passes through the steering priority valve 9. When the vehicle does not need to turn, this oil directly merges with the oil output from the second oil pump 5. When the vehicle needs to turn, the P inlet of the hydraulic steering gear 20 is connected to the L or R port of the steering cylinder 27, and the load pressure of the steering cylinder 27 is fed back to the spring chamber of the steering priority valve 9 through the Ls port of the hydraulic integrated valve block 7, pushing the valve core of the steering priority valve 9 to move. The steering priority valve 9 supplies oil to the steering gear through the third check valve 12 to complete the vehicle steering. After the vehicle is turned, the excess hydraulic oil then merges with the oil output from the second oil pump 5.

[0033] Due to the characteristics of the relief valve, the lifting relief pressure is higher than the lifting process pressure, and the set value of the system high-pressure detection switch 24 is equal to the lifting relief pressure. Therefore, if the pressure of the cargo during the lifting process does not reach the set value of the system high-pressure detection switch 24, the second two-position two-way solenoid directional valve 23 is de-energized and closes the oil circuit, and the two-position two-way directional valve 22 closes the oil circuit under the action of spring force. The oil output from the first oil pump 4 and the second oil pump 5 merges and enters the electro-hydraulic proportional multi-way valve 21 through the EF oil port, and then supplies the lifting cylinder 28, tilting cylinder 29 or attachment cylinder 30, and finally flows back to the hydraulic oil tank 1 through the return oil filter 6.

[0034] If the button on the fingertip is not released after the goods have been lifted to the top, the hydraulic system begins to overflow. At this time, the hydraulic system pressure increases. When the high-pressure detection switch 24 detects that the inlet pressure of the electro-hydraulic proportional multi-way valve 21 has reached the set value, it energizes the second two-position two-way solenoid valve 23 to open the oil circuit. A small amount of converging oil flows back to the hydraulic oil tank 1 from the return port T of the hydraulic integrated valve block 7 through the throttle valve 25 and the second two-position two-way solenoid valve 23. The pressure difference generated when the converging oil passes through the throttle valve 25 overcomes the spring force of the two-position two-way directional valve 22 and opens the valve port. The converging oil flows back to the hydraulic oil tank 1 through the two-position two-way directional valve 22. At this time, the dual pumps are unloaded, reducing energy consumption. If the fingertip button is released at this time, the hydraulic system stops overflowing, the second two-position two-way solenoid valve 23 is de-energized and closes the oil circuit, and the two-position two-way directional valve 22 closes the oil circuit under the action of the spring force. The oil enters the electro-hydraulic proportional multi-way valve 21 and flows into the hydraulic oil tank 1.

[0035] The second check valve 11 prevents backflow of oil in the electro-hydraulic proportional multi-way valve 21 when the second two-position two-way solenoid directional valve 23 is energized and connected to the oil circuit, thus preventing the cargo from falling uncontrollably and avoiding damage to the hydraulic pump from impact. The first relief valve 8 prevents excessive resistance to the tires during steering from damaging the steering cylinder 27.

[0036] The specific braking process is as follows: Each time the vehicle starts, the accumulator low-pressure detection switch 17 first checks the pressure in the accumulator 16. When the pressure in the accumulator 16 is detected to be lower than the set value of the accumulator low-pressure detection switch 17, the vehicle issues a low-pressure alarm and stops moving. Then, the first two-position two-way solenoid directional valve 13 is energized to close the oil circuit, and the oil output from the auxiliary pump in the first oil pump 4 first passes through the check valve. Since the hydraulic power brake valve 19 adopts a closed hydraulic system, the oil can only enter the accumulator 16 for filling. The pressure in the accumulator 16 gradually increases. When the pressure exceeds the pressure set value of the accumulator low-pressure detection switch 17, the vehicle low-pressure alarm is lifted, the vehicle is allowed to move, and the accumulator 16 continues to be filled. When the accumulator high-pressure detection switch 18 detects that the pressure in the accumulator 16 has risen to the pressure setting value of the accumulator high-pressure detection switch 18, the first two-position two-way solenoid directional valve 13 is de-energized and connects the oil circuit. The oil output by the auxiliary pump flows directly back to the hydraulic oil tank 1 from the return port T of the hydraulic integrated valve block 7 through the first two-position two-way solenoid directional valve 13. At this time, the auxiliary pump is unloaded, reducing energy consumption. The pressure oil in the accumulator 16 is maintained under the action of the check valve, the hydraulic power assist brake valve 19, and the shut-off valve 31.

[0037] If, during startup, the accumulator low-pressure detection switch 17 detects that the pressure in the accumulator 16 is higher than the set value of the accumulator low-pressure detection switch 17, the first two-position two-way solenoid directional valve 13 is de-energized and connects the oil circuit, and the accumulator 16 does not need to be filled with liquid.

[0038] When the vehicle applies the service brake by pressing the brake pedal, the pressurized oil in the accumulator 16, after passing through the pressure reducing valve 15, forms a constant outlet pressure oil source that enters the hydraulic power-assisted brake valve 19. This oil, combined with the pedal force, generates braking pressure, which then enters the wheel brake 26 through port Br to complete the braking. Subsequent braking actions are also supplied with pressurized oil by the accumulator 16. Even if the vehicle suddenly stops, the pressurized oil in the accumulator 16 can still enter the hydraulic power-assisted brake valve 19 through the pressure reducing valve 15 to complete emergency braking.

[0039] As the number of braking cycles increases, the oil pressure in the accumulator 16 gradually decreases. When the pressure in the accumulator 16 drops to the set value of the accumulator low-pressure detection switch 17, the first and second position two-way solenoid directional valves 13 are energized to close the oil circuit, and the accumulator 16 is refilled until the pressure reaches the set value of the accumulator high-pressure detection switch 18. This method avoids repeated refilling of the accumulator 16 and improves its service life.

[0040] When the vehicle braking system needs maintenance, the shut-off valve 31 can be manually opened first to release the pressurized oil in the accumulator 16 into the hydraulic oil tank 1, so as to avoid high-pressure oil splashing and injuring people when disassembling and assembling parts.

[0041] The pressure setting value of the second overflow valve 14 is slightly higher than the pressure setting value of the high pressure detection switch of the accumulator 16, to prevent damage caused by the continuous filling of the accumulator 16 due to the failure of the high pressure detection switch of the accumulator 16 or the first two-position two-way solenoid directional valve 13.

[0042] In this embodiment, the beneficial effects are: 1. This hydraulic control system enables large-tonnage electro-hydraulic proportional forklifts to have functions such as steering priority, service braking, and overflow unloading. It has a high degree of integration and saves energy and reduces consumption.

[0043] 2. The hydraulic working system and the braking system are independent of each other. The braking system is not disturbed and can be used for emergency braking, which is safe and stable.

[0044] 3. By adjusting the flow rate and pressure, it can meet the needs of forklifts of different tonnages, making it widely applicable.

[0045] 4. It can be applied to both internal combustion engine vehicles and electric vehicles, making it highly versatile.

[0046] 5. The system is simple and efficient, easy to control, and can be easily automated.

[0047] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention. The scope of the invention is defined by the appended claims and their equivalents, all of which should be included within the scope of protection of the invention.

Claims

1. A hydraulic control system for industrial vehicles, characterized in that, It includes a hydraulic oil tank (1), a hydraulic oil pump, a return oil filter (6), a hydraulic integrated valve block (7), a hydraulic power brake valve (19), a hydraulic steering gear (20), an electro-hydraulic proportional multi-way valve (21), a wheel brake (26), and an actuator cylinder; The outlet of the hydraulic oil pump is connected to the inlet of the hydraulic integrated valve block (7); The oil outlet of the hydraulic integrated valve block (7) is connected to the oil inlet of the hydraulic power assist brake valve (19), the oil inlet of the hydraulic steering gear (20), and the oil inlet of the electro-hydraulic proportional multi-way valve (21), respectively. The hydraulic integrated valve block (7) integrates a steering priority control module, a brake pressure control module and an overflow unloading control module, which are used to realize steering priority oil supply, hydraulic braking and hydraulic system overflow unloading functions.

2. The industrial vehicle hydraulic control system according to claim 1, characterized in that, The hydraulic integrated valve block (7) also includes an accumulator (16), an accumulator low-pressure detection switch (17), an accumulator high-pressure detection switch (18), and a system high-pressure detection switch (24).

3. The industrial vehicle hydraulic control system according to claim 1, characterized in that, The hydraulic integrated valve block (7) integrates the following: First relief valve (8), steering priority valve (9), first check valve (10), second check valve (11), and third check valve (12); The first two-position two-way solenoid directional valve (13), the second relief valve (14), and the pressure reducing valve (15) are used for braking control. Two-position two-way directional valve (22), second two-position two-way solenoid directional valve (23), and throttle valve (25) for unloading control.

4. The industrial vehicle hydraulic control system according to claim 1, characterized in that, The hydraulic pump includes a first pump (4) and a second pump (5) connected in parallel. The first pump (4) is a dual pump, with the main pump outputting oil to the working system and the auxiliary pump outputting oil to the braking system.

5. The industrial vehicle hydraulic control system according to claim 1, characterized in that, The hydraulic steering gear (20) is a load-sensing steering gear, and its load pressure is fed back to the steering priority valve (9) of the hydraulic integrated valve block (7) to achieve steering priority oil supply.

6. The industrial vehicle hydraulic control system according to claim 1, characterized in that, The hydraulic power-assisted brake valve (19) adopts a closed hydraulic system. The brake pressure oil is supplied by the accumulator (16) through the pressure reducing valve (15), and the accumulator (16) is connected to the auxiliary pump oil circuit through the check valve (10).

7. The hydraulic control system for industrial vehicles according to claim 2, characterized in that, The execution logic of the overflow unloading control module is as follows: When the system high pressure detection switch (24) detects that the oil inlet pressure of the electro-hydraulic proportional multi-way valve (21) reaches the set value, it triggers the two-position two-way solenoid directional valve (23) to open; The oil generates a pressure difference through the throttle valve (25), which pushes the two-position two-way directional valve (22) to open the unloading oil circuit.

8. The industrial vehicle hydraulic control system according to claim 6, characterized in that, It also includes a shut-off valve (31) connected to the oil circuit of the accumulator (16) for manually releasing the pressure of the accumulator.

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