Lifting hydraulic system and forklift

Abstract

The invention belongs to the technical field of hydraulic pressure, and particularly relates to a lifting hydraulic system and a forklift. A hydraulic oil tank; the left lifting oil cylinder and the right lifting oil cylinder are each provided with a rodless cavity and a rod cavity, the two rodless cavities communicate with the oil supply way, the two rod cavities communicate with the hydraulic oil tank, and buffer air cavity assemblies are arranged in piston rods of the left lifting oil cylinder and the right lifting oil cylinder correspondingly; the buffer air pressure difference of the two buffer air cavity assemblies is a first preset air pressure value, and the buffer air pressure in the two buffer air cavity assemblies is larger than the rated pressure of the rodless cavity. By the adoption of the lifting hydraulic system, the risk of oil leakage caused by an external energy accumulator structure is avoided, meanwhile, the weight of the forklift is reduced, and the requirement for light weight of the forklift is met.

Description

Technical Field

[0001] This invention belongs to the field of hydraulic technology, specifically relating to a lifting hydraulic system and a forklift. Background Technology

[0002] The lifting hydraulic system of a forklift is a crucial component for enabling forklift handling, loading, and unloading operations. During lifting, loading, unloading, and stacking operations, the lifting cylinders of the lifting hydraulic system bear the entire weight of the goods. Therefore, the lifting cylinders affect the overall stability and safety of the forklift.

[0003] In lifting hydraulic systems, traditional forklifts often use accumulators for cushioning. For example, an accumulator is installed outside the lifting cylinder, connected to the hydraulic fluid inside the cylinder, to prevent abnormal increases in oil pressure. However, external accumulators not only pose a risk of oil leakage, but also further increase the weight of the forklift, making it difficult to meet the lightweight requirements of some models. Summary of the Invention

[0004] The purpose of this invention is to provide a lifting hydraulic system and a forklift to solve the technical problem in the prior art where the lifting cylinder of the forklift is equipped with an external accumulator, which leads to a high risk of oil leakage and additional weight.

[0005] To achieve the above objectives, the present invention provides a lifting hydraulic system for use in forklifts, the lifting hydraulic system comprising: Oil supply circuit; Hydraulic oil tank; The left and right lifting cylinders each have a rodless chamber and a rod chamber. Both rodless chambers are connected to the oil supply circuit, and both rod chambers are connected to the hydraulic oil tank. Both piston rods of the left and right lifting cylinders are equipped with buffer air chamber assemblies. The buffer air pressure difference between the two buffer air chamber assemblies is a first preset air pressure value. The buffer air pressure in both buffer air chamber assemblies is greater than the rated pressure of the rodless chamber.

[0006] In some embodiments, buffer chambers are provided in the piston rods of both the left and right lifting cylinders along the axial direction of the rod body, and air inlets are provided on the piston rods. The buffer pressure difference between the two buffer chambers is a preset value. Each of the two buffer air chamber assemblies includes: a first piston, which is movably disposed in the buffer chamber and divides the buffer chamber into a buffer air chamber and an oil chamber along the axial direction, and the oil chamber is connected to the rodless chamber; and an air inlet switch, which is installed at the air inlet and used to switch the connection between the buffer air chamber and the outside.

[0007] In some embodiments, the lifting hydraulic system further includes: a pressure sensor disposed in the buffer air chamber and used to detect the pressure in the buffer air chamber; a pressure regulating component connected to both air inlets, the pressure regulating component being used to regulate the gas pressure in the buffer air chamber; and a control unit electrically connected to both the pressure sensor and the pressure regulating component, the control unit being configured to adjust the buffer air pressure in the buffer air chamber according to a preset control strategy.

[0008] In some embodiments, the lifting hydraulic system further includes a stroke detection unit disposed in the buffer chamber and used to detect the stroke of the first piston and send a stroke signal to the control unit.

[0009] In some implementations, the control unit is configured to: acquire stroke signals in real time; and, if it is determined that the stroke of the first piston continues to exceed a preset time period at the limit stroke position, control the air pressure regulating component to inflate the buffer air chamber to fill it with a preset amount of gas medium.

[0010] In some embodiments, the control unit is further configured to: acquire pressure signals and stroke signals detected by the pressure sensor in real time; and control the air pressure regulating component to perform an air intake operation when the pressure in the buffer air chamber is greater than a second preset air pressure value and the first piston is in the initial position, so that the air pressure in the buffer air chamber is lower than a third preset air pressure value, wherein the second preset air pressure value is greater than the third preset air pressure value, and the third preset air pressure value is greater than the rated pressure of the rodless chamber.

[0011] In some embodiments, the lifting hydraulic system also includes an alarm element, and the control unit is further configured to: acquire pressure signals detected by pressure sensors in real time; and control the alarm element to activate an alarm when it is determined that the pressure in the buffer air chamber is lower than the rated pressure of the rodless chamber.

[0012] In some embodiments, the oil chamber and the rodless chamber are connected by a buffer channel, and both buffer chamber assemblies also include a buffer switch disposed in the buffer channel, which is used to switch the oil chamber and the rodless chamber on and off.

[0013] In some embodiments, the lifting hydraulic system further includes: a speed limiting valve, located on the oil supply line and used to limit the lifting speed of the lifting cylinder; and a shut-off valve, located on the connecting oil line between the rod chamber of the left lifting cylinder and the rod chamber of the right lifting cylinder, the shut-off valve being used to open or close the connecting oil line.

[0014] A second aspect of the present invention provides a forklift including the above-described lifting hydraulic system.

[0015] In the aforementioned technical solution, the lifting hydraulic system includes an oil supply circuit, a hydraulic oil tank, a left lifting cylinder, and a right lifting cylinder. Both the left and right lifting cylinders have buffer air chamber assemblies in their piston rods. These buffer air chamber assemblies achieve a buffering effect, eliminating the need for an external accumulator and avoiding the risk of oil leakage. Simultaneously, they reduce the weight of the forklift, meeting the requirements for lightweight forklifts. Furthermore, the buffer air pressure difference between the two buffer air chamber assemblies is a first preset air pressure value. The buffer air pressure within both assemblies is greater than the rated pressure of the rodless chamber. Using different buffer air pressures allows for adaptation to the lifting needs of the forklift under various working conditions, improving the stability and adaptability of the lifting hydraulic system.

[0016] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. Those skilled in the art can obtain other drawings based on the structures shown in these drawings without any inventive effort. In the drawings: Figure 1 A hydraulic schematic diagram of a lifting hydraulic system provided according to an embodiment of the present invention; Figure 2 This is a cross-sectional schematic diagram of the left or right lifting cylinder provided according to an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures L1 fuel supply circuit 10 Hydraulic oil tank 20. Left lifting cylinder 21 First Piston 22 Inflation switch 23 Buffer Channel 24 Rodless chamber working port 25 Rod chamber working oil port 26 cylinder barrel 27 Piston Assembly 28 rods 29. Rod-shaped cavity 30 Right lifting cylinder 40 Speed ​​limiting valve 50 Shut-off valve Detailed Implementation The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0019] The lifting hydraulic system and forklift according to the present invention are described below with reference to the accompanying drawings. Figure 1 The diagram shown is a hydraulic schematic of a lifting hydraulic system provided according to an embodiment of the present invention; as follows: Figure 2 The diagram shown is a cross-sectional schematic of the left lifting cylinder 20 or the right lifting cylinder 30 provided according to an embodiment of the present invention. The lifting hydraulic system provided in this embodiment of the present invention includes: Fuel supply line L1; Hydraulic oil tank 10; The left lifting cylinder 20 and the right lifting cylinder 30 each have a rodless chamber and a rod chamber 29. Both rodless chambers are connected to the oil supply circuit L1, and both rod chambers 29 are connected to the hydraulic oil tank 10. Both piston rods of the left lifting cylinder 20 and the right lifting cylinder 30 are equipped with buffer air chamber assemblies. The buffer air pressure difference between the two buffer air chamber assemblies is a first preset air pressure value. The buffer air pressure in both buffer air chamber assemblies is greater than the rated pressure of the rodless chamber.

[0020] In existing technologies, forklift lifting cylinders mostly use external accumulators for buffering. While this design can alleviate the problem of abnormally high hydraulic pressure to some extent, it has many drawbacks. External accumulators not only increase the risk of oil leaks—if a leak occurs, it will directly affect the normal operation of the forklift and may even cause a safety accident—but the additional accumulator undoubtedly increases the overall weight of the forklift. This is particularly problematic for lightweight small forklift designs, which impose strict weight restrictions. The presence of an external accumulator further hinders the improvement of forklift performance.

[0021] To address the aforementioned problems, this invention proposes a lifting hydraulic system. In this embodiment, a buffer air chamber assembly is incorporated into the piston rods of the left lifting cylinder 20 and the right lifting cylinder 30, achieving internal integration of the buffering effect and eliminating the need for an external accumulator. Specifically, the buffer air chamber assembly in this invention cleverly utilizes the interaction between gas pressure and liquid pressure to provide buffer protection for the lifting cylinders. Gas is compressible; when the lifting cylinder bears the weight of the load, causing the hydraulic pressure to rise, the gas within the buffer air chamber is compressed, absorbing some of the pressure energy, thereby effectively preventing abnormal increases in hydraulic pressure. Simultaneously, since the buffer air chamber assembly is located inside the piston rod, there is no risk of oil leakage, significantly improving the stability and safety of forklift operation.

[0022] Furthermore, in this embodiment of the invention, the pressure difference between the two buffer air chamber assemblies is a first preset air pressure value, and the buffer air pressure in both buffer air chamber assemblies is greater than the rated pressure of the rodless chamber. This design allows the lifting hydraulic system to automatically adjust the air pressure in the buffer air chambers according to the lifting requirements of the forklift under different working conditions, thereby improving the stability and adaptability of the lifting hydraulic system. For example, the buffer air pressure of the left buffer air chamber assembly is slightly greater than that of the right buffer air chamber assembly. When the forklift is carrying a heavy load, the left buffer air chamber assembly can provide greater buffering force to prevent damage to the lifting cylinder due to excessive pressure; while when the forklift is carrying a light load, the right buffer air chamber assembly can provide less buffering force to avoid unnecessary energy loss.

[0023] Specifically, such as Figure 2 As shown, the lifting cylinder also includes a rodless chamber working port 24 located at the bottom end of the cylinder barrel 26 and a rod chamber working port 25 opened on the top side wall of the cylinder barrel 26.

[0024] In one embodiment, such as Figure 2 As shown, both the left lifting cylinder 20 and the right lifting cylinder 30 have buffer chambers along the axial direction of the piston rod 28. An air inlet is located on the piston rod. The pressure difference between the two buffer chambers is a preset value. Each buffer chamber assembly includes a first piston 21 and an air inlet switch 22. The first piston 21 is movably disposed within the buffer chamber, dividing it axially into a buffer air chamber and an oil chamber. The oil chamber communicates with the rodless chamber. The air inlet switch 22 is installed at the air inlet to connect or disconnect the buffer air chamber from the outside environment. When the forklift lifts goods and the hydraulic pressure gradually increases, the first piston 21 moves towards the buffer air chamber under pressure, compressing the gas within. The compressed gas generates a reaction force, buffering the increase in hydraulic pressure and preventing abnormal pressure rise from damaging the lifting cylinder. The air inlet switch 22 plays a crucial role in controlling the gas exchange between the buffer air chamber and the outside environment. When it is necessary to inflate or deflate the buffer air chamber, the air chamber can be easily connected or disconnected from the outside by operating the air inflation switch 22, thereby adjusting the air pressure in the buffer air chamber to meet the buffering requirements of the forklift lifting hydraulic system under different working conditions.

[0025] In one embodiment, the lifting hydraulic system further includes a pressure sensor (not shown), a pressure regulating component (not shown), and a control unit (not shown). The pressure sensor is disposed in the buffer air chamber and is used to detect the pressure within the buffer air chamber. The pressure regulating component is connected to both inflation ports and is used to regulate the gas pressure within the buffer air chamber. The control unit is electrically connected to both the pressure sensor and the pressure regulating component, and is configured to adjust the buffer air pressure within the buffer air chamber according to a preset control strategy. The pressure sensor can monitor the pressure changes within the buffer air chamber in real time and transmit the pressure signal to the control unit. After receiving the pressure signal, the control unit issues a command to the pressure regulating component according to the preset control strategy. The pressure regulating component, according to the command, inflates or deflates the buffer air chamber through its connection to the two inflation ports, thereby precisely regulating the gas pressure within the buffer air chamber. This intelligent pressure regulating method enables the lifting hydraulic system to automatically adjust the air pressure within the buffer air chamber according to actual working conditions, ensuring that the forklift remains stable and safe during lifting. Simultaneously, the design of the pressure regulating component also fully considers the ease of operation and reliability, further improving the performance of the entire lifting hydraulic system.

[0026] In one embodiment, the lifting hydraulic system further includes a stroke detection unit (not shown in the figure), which is disposed in the buffer chamber and used to detect the stroke of the first piston 21 and send a stroke signal to the control unit. The stroke detection unit can accurately monitor the movement distance of the first piston 21 in the buffer chamber and transmit this stroke signal to the control unit in real time. After receiving the stroke signal, the control unit can further analyze whether the stroke of the first piston 21 is within the normal range. For example, if the stroke of the first piston 21 is continuously at the limit stroke position, it may mean that the air pressure in the buffer chamber is insufficient and cannot effectively buffer the increase in oil pressure. At this time, the control unit will react quickly and control the air pressure regulating component to fill the buffer chamber with air, filling it with a preset amount of gas medium to ensure that the buffer chamber can continue to perform its normal buffering function and prevent the lifting cylinder from being damaged due to abnormal pressure. This real-time monitoring and intelligent adjustment mechanism for the stroke of the first piston 21 greatly improves the reliability and safety of the lifting hydraulic system and ensures the stable operation of the forklift under various complex working conditions.

[0027] Specifically, the left lifting cylinder 20 and right lifting cylinder 30 provided in this embodiment of the invention both include a cylinder barrel 26, a piston assembly 27, a rod 28, and a first piston 21. The cylinder barrel 26 has a receiving space, and the piston assembly 27 is movably inserted into the receiving space. The piston assembly 27 divides the receiving space into a rod chamber 29 and a rodless chamber. One end of the rod 28 is connected to the piston assembly 27, and the other end extends outside the receiving space. A buffer chamber is formed in the rod 28 along the axial direction of the cylinder barrel 26. The first piston 21 is movably disposed in the buffer chamber, dividing the buffer chamber into a buffer gas chamber and an oil chamber. The buffer gas chamber contains a gaseous medium, and the oil chamber contains hydraulic oil and communicates with the rodless chamber. When the hydraulic oil pressure in the rodless chamber rises abnormally, the hydraulic oil in the rodless chamber enters the oil chamber through the communication, pushing the first piston 21 to move in the buffer chamber, compressing or expanding the gaseous medium in the buffer gas chamber. The compressibility of the gaseous medium is used to absorb the hydraulic shock energy, effectively suppressing the impact of pressure changes on the hydraulic system. This built-in buffer structure not only avoids the risk of seal failure that may occur with external accumulators, but also reduces the overall weight of the cylinder through integrated design.

[0028] In one embodiment, an air inlet is provided on the side wall of the rod 28. The air inlet connects the buffer air chamber to the outside gas. The lifting cylinder also includes an air inlet switch 22, which is located in the air inlet and used to open and close the air inlet. This design allows the pressure of the gaseous medium in the buffer air chamber to be adjusted according to the actual working conditions. When it is necessary to enhance the buffering effect, gaseous medium can be added to the buffer air chamber through the air inlet to increase its initial pressure; when it is necessary to reduce the buffering strength, some gaseous medium can be released through the air inlet. The air inlet switch 22 can precisely control the amount of gaseous medium entering and leaving the chamber, ensuring that the pressure in the buffer air chamber remains stable within the set range, thereby ensuring that the lifting cylinder can provide reliable buffering performance under different loads and working conditions.

[0029] In one embodiment, multiple limiting members (not shown in the figure) are provided on the inner wall of the buffer chamber to limit the stroke of the first piston 21. By providing limiting members, the first piston 21 can be prevented from moving beyond a predetermined range within the buffer chamber, thereby avoiding damage to the buffer air chamber and oil chamber, and ensuring the stability and reliability of the lifting cylinder. Furthermore, the limiting members can be configured as detachable connections, allowing the position of the limiting members to be adjusted according to actual buffering needs, thus changing the stroke range of the first piston 21 to adapt to different working scenarios and load requirements. In a specific embodiment, the limiting members are divided into a first limiting member and a second limiting member. The first limiting member is used to limit the first piston 21 to the initial buffer position, and the second limiting member is used to limit the second piston to the extreme buffer position. When the first limiting member is in the initial buffer position, the buffer air chamber and oil chamber are in a relatively stable state and can perform their buffering function normally. When the first piston 21 moves towards the buffer air chamber under the action of hydraulic pressure until it contacts the second limiting member and reaches the limit buffer position, it indicates that the gas in the buffer air chamber has been fully compressed. At this point, the limiting member prevents the first piston 21 from continuing to move and damaging the buffer air chamber and oil chamber. Moreover, this detachable limiting member design provides more possibilities for the flexibility and adaptability of the lifting hydraulic system.

[0030] In one embodiment, the control unit is configured to: acquire stroke signals in real time; and, upon determining that the stroke of the first piston 21 remains at its limit position for an extended period of time, control the pneumatic pressure regulating component to inflate the buffer chamber with a preset amount of gas medium. This configuration allows the control unit to accurately monitor the real-time status of the first piston 21. When the stroke of the first piston 21 remains at its limit position for an extended period of time, this often indicates that the air pressure in the buffer chamber may not be able to effectively cope with the increased hydraulic pressure under the current operating conditions. At this time, the control unit quickly takes action, controlling the pneumatic pressure regulating component to initiate the inflation procedure, infusing the buffer chamber with a preset amount of gas medium. This process is not only fast but also precise, enabling timely restoration of the buffer chamber's buffering capacity and ensuring that the lifting cylinder is not damaged due to abnormal pressure when bearing the weight of the cargo. Simultaneously, the pre-set amount of gas medium inflation avoids over-inflation or under-inflation, further improving the stability and reliability of the lifting hydraulic system.

[0031] In one embodiment, the control unit is further configured to: acquire pressure signals detected by a pressure sensor in real time; and, when the pressure in the buffer air chamber is greater than a second preset air pressure value and the first piston 21 is in its initial position, control the air pressure regulating component to perform a suction operation to lower the air pressure in the buffer air chamber below a third preset air pressure value, wherein the second preset air pressure value is greater than the third preset air pressure value, and the third preset air pressure value is greater than the rated pressure of the rodless chamber. When the pressure in the buffer air chamber is greater than the second preset air pressure value and the first piston 21 is in its initial position, this indicates that the air pressure in the buffer air chamber may be too high. During subsequent lifting of the forklift, if a lighter load is encountered, it may be difficult to compress the high-pressure gas in the buffer air chamber, potentially leading to poor buffering performance. At this time, the control unit quickly makes a judgment based on the real-time acquired pressure signal and controls the air pressure regulating component to perform a suction operation. Through the suction operation, the air pressure in the buffer air chamber is reduced to the third preset air pressure value, which ensures that the buffer air chamber can still play an effective buffering role during subsequent lifting while avoiding energy loss due to excessive air pressure. This intelligent air pressure regulation mechanism allows the lifting hydraulic system to flexibly adjust the air pressure in the buffer air chamber according to actual working conditions, thereby improving the operating efficiency and stability of the forklift.

[0032] In one embodiment, the gaseous medium in the buffer chamber is an inert gas. Inert gases are chemically stable and do not readily react with other substances. Using an inert gas as the gaseous medium in the buffer chamber effectively avoids performance degradation or damage caused by chemical reactions between the gaseous medium and the inner wall of the buffer chamber or other components, thus extending the service life of the lifting cylinder. Simultaneously, inert gases also possess good compressibility and elasticity, enabling them to quickly return to their original shape after absorbing hydraulic impact energy, ensuring the stability and reliability of the buffering effect. In a specific embodiment, the gaseous medium is argon or nitrogen.

[0033] In one embodiment, the lifting hydraulic system also includes an alarm device (not shown in the figure), and the control unit is further configured to: acquire the pressure signal detected by the pressure sensor in real time; and control the alarm device to activate an alarm when it is determined that the pressure in the buffer air chamber is lower than the rated pressure of the rodless chamber. When the pressure in the buffer air chamber is lower than the rated pressure of the rodless chamber, it means that the buffer air chamber may not be able to perform its buffering function properly. During the lifting of goods by the forklift, the risk of abnormally high hydraulic pressure will increase significantly, which may damage the lifting cylinder and affect the normal operation of the forklift. At this time, after acquiring this pressure signal detected by the pressure sensor in real time, the control unit will react quickly and control the alarm device to activate an alarm. The alarm device can take various forms, such as a sharp alarm sound from an audible alarm or a flashing bright light from a visual alarm, to attract the operator's attention. Upon receiving an alarm signal, operators can promptly inspect and repair the lifting hydraulic system, identifying potential causes of abnormal pressure within the buffer air chamber. This includes checking for malfunctions in the air pressure regulating components and blockages in the air inlet. By doing so, the normal function of the buffer air chamber can be restored in a timely manner, ensuring the stable operation of the forklift lifting hydraulic system and preventing more serious safety accidents or equipment damage caused by untimely handling of faults. This significantly improves the safety and reliability of forklift operation.

[0034] In one embodiment, the oil chamber and the rodless chamber are connected via a buffer channel 23. Both buffer chamber assemblies also include a buffer switch, disposed within the buffer channel 23, used to connect and disconnect the oil chamber and the rodless chamber. The buffer switch provides a more flexible and precise buffer control method for the lifting hydraulic system. At different stages of forklift lifting, the connection or disconnection between the oil chamber and the rodless chamber can be easily controlled by operating the buffer switch according to actual needs. When a greater buffering effect is required from the lifting cylinder, the buffer switch is opened, connecting the oil chamber and the rodless chamber, allowing the oil to flow freely between them. This allows the buffer chamber assembly to better absorb and disperse oil pressure, enhancing the buffering effect. Conversely, under certain specific conditions, such as when the forklift is carrying lighter loads and does not require greater buffering force, the buffer switch is closed, cutting off the connection between the oil chamber and the rodless chamber. This reduces unnecessary energy loss and improves the working efficiency of the lifting hydraulic system.

[0035] In one embodiment, the lifting hydraulic system further includes a speed limiting valve 40 and a shut-off valve 50. The speed limiting valve 40 is located on the oil supply circuit L1 and is used to limit the lifting speed of the lifting cylinder. The shut-off valve 50 is located on the connecting oil circuit between the rodless chamber of the left lifting cylinder 20 and the rodless chamber of the right lifting cylinder 30, and is used to open and close the connecting oil circuit. The speed limiting valve 40 plays a crucial role in the oil supply circuit L1, as it can precisely limit the lifting speed of the lifting cylinder. During the lifting or lowering of goods by the forklift, if the speed is too fast, it may cause the goods to sway, reduce the stability of the forklift, or even cause a safety accident. The speed limiting valve 40, by regulating the flow of hydraulic fluid, controls the lifting speed of the lifting cylinder within a safe and reasonable range, ensuring that the forklift can operate smoothly under various working conditions. For example, when the forklift lifts heavy loads, the speed limiting valve 40 automatically reduces the hydraulic flow and lowers the lifting speed to prevent the forklift from tipping over due to excessive speed. Similarly, when the forklift lowers loads, the speed limiting valve 40 also functions to prevent excessive descent speed and impact damage. The shut-off valve 50 is located on the connecting oil line between the rodless chamber of the left lifting cylinder 20 and the rodless chamber of the right lifting cylinder 30. Its function is to open and close the connecting oil line. In some special working conditions, such as when a single lifting cylinder needs maintenance or adjustment, operating the shut-off valve 50 can cut off the hydraulic flow between the rodless chambers of the left lifting cylinder 20 and the right lifting cylinder 30. This allows the operator to perform operations on one lifting cylinder independently without affecting the normal operation of the other, greatly improving the convenience and safety of maintenance and adjustment work. Meanwhile, during forklift operation, if an abnormality occurs in one side of the lifting cylinder, such as leakage, the shut-off valve 50 can quickly cut off the connecting oil circuit to prevent the abnormality from spreading and affecting the other side of the lifting cylinder, thus ensuring the overall stability and reliability of the lifting hydraulic system.

[0036] In one embodiment, a forklift is provided, including the lifting hydraulic system described above.

[0037] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0038] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," 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 connection that allows communication between them; 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, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0039] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0040] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A lifting hydraulic system, characterized in that, Applied to forklifts, the lifting hydraulic system includes: Fuel supply line (L1); Hydraulic oil tank (10); The left lifting cylinder (20) and the right lifting cylinder (30) each have a rodless chamber and a rod chamber (29). Both rodless chambers are connected to the oil supply circuit (L1), and both rod chambers (29) are connected to the hydraulic oil tank (10). Both piston rods of the left lifting cylinder (20) and the right lifting cylinder (30) are provided with buffer air chamber assemblies. The buffer air pressure difference between the two buffer air chamber assemblies is a first preset air pressure value. The buffer air pressure in both buffer air chamber assemblies is greater than the rated pressure of the rodless chamber.

2. The lifting hydraulic system according to claim 1, characterized in that, Both the left lifting cylinder (20) and the right lifting cylinder (30) have buffer chambers along the axial direction of the rod body (28) inside their piston rods. The piston rods have air inlets. The buffer pressure difference between the two buffer chambers is a preset value. Both buffer chamber assemblies include: The first piston (21) is movably disposed in the buffer chamber and divides the buffer chamber into a buffer gas chamber and an oil chamber along the axial direction. The oil chamber is connected to the rodless chamber. An inflation switch (22) is installed at the inflation port to switch the buffer air chamber on and off from the outside.

3. The lifting hydraulic system according to claim 2, characterized in that, The lifting hydraulic system also includes: A pressure sensor is disposed in the buffer air chamber and is used to detect the pressure inside the buffer air chamber; A pressure regulating component is connected to both of the two air inlets, and the pressure regulating component is used to regulate the gas pressure in the buffer air chamber; The control unit is electrically connected to both the pressure sensor and the air pressure regulating component, and is configured to adjust the buffer air pressure in the buffer air chamber according to a preset control strategy.

4. The lifting hydraulic system according to claim 3, characterized in that, The lifting hydraulic system also includes: The stroke detection unit is electrically connected to the control unit. The stroke detection unit is disposed in the buffer chamber and is used to detect the stroke of the first piston (21) and send a stroke signal to the control unit.

5. The lifting hydraulic system according to claim 4, characterized in that, The control unit is configured to: The travel signal is acquired in real time; If it is determined that the stroke of the first piston (21) continues to exceed the preset time period at the limit stroke position, the air pressure regulating component is controlled to fill the buffer air chamber with air to fill the preset amount of gas medium.

6. The lifting hydraulic system according to claim 4, characterized in that, The control unit is also configured to: The pressure signal and the stroke signal detected by the pressure sensor are acquired in real time. When the pressure in the buffer air chamber is greater than the second preset air pressure value and the first piston (21) is in the initial position, the air pressure regulating component is controlled to perform an air intake operation so that the air pressure in the buffer air chamber is lower than the third preset air pressure value, wherein the second preset air pressure value is greater than the third preset air pressure value and the third preset air pressure value is greater than the rated pressure of the rodless chamber.

7. The lifting hydraulic system according to claim 4, characterized in that, The lifting hydraulic system also includes an alarm device, and the control unit is further configured to: Real-time acquisition of the pressure signal detected by the pressure sensor; If the pressure in the buffer chamber is determined to be lower than the rated pressure of the rodless chamber, the alarm device is controlled to activate the alarm.

8. The lifting hydraulic system according to claim 2, characterized in that, The oil chamber and the rodless chamber are connected by a buffer channel (23), and both buffer chamber assemblies further include: A buffer switch is provided in the buffer channel (23) and is used to switch the oil chamber and the rodless chamber on and off.

9. The lifting hydraulic system according to any one of claims 1 to 8, characterized in that, The lifting hydraulic system also includes: A speed limiting valve (40) is provided on the oil supply line (L1) and is used to limit the lifting speed of the lifting cylinder; A shut-off valve (50) is provided on the connecting oil line between the rodless chamber of the left lifting cylinder (20) and the rodless chamber of the right lifting cylinder (30). The shut-off valve (50) is used to switch the connecting oil line on and off.

10. A forklift, characterized in that, The lifting hydraulic system includes any one of claims 1 to 9.

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