Lifting cylinder bottom valve group, hydraulic system

Abstract

The utility model relates to electric fork truck technical field discloses a lifting cylinder bottom valve group, hydraulic system. Lifting cylinder bottom valve group includes valve group seat, is equipped with oil inlet, oil outlet and oil return on valve group seat, and oil outlet communicates with lifting oil cylinder, and oil return communicates with hydraulic oil tank, first oil channel, both ends respectively with oil inlet, oil outlet intercommunication, second oil channel, both ends respectively with oil outlet, oil return intercommunication, load keeps valve, sets up on first oil channel, is used for switching the flow direction of first oil channel inside hydraulic oil, emergency drop solenoid valve, sets up on second oil channel, is used for when main oil circuit failure electricity conduction to switch the backflow oil circuit of hydraulic oil. The lifting cylinder bottom valve group is high in security, and convenient to install can cope with a variety of working conditions.

Description

Technical Field

[0001] This utility model relates to the field of electric forklift technology, specifically to a lifting cylinder bottom valve assembly and a hydraulic system. Background Technology

[0002] As industrial material handling vehicles, the lifting performance of electric forklifts directly affects operational efficiency. Currently, the lifting system of electric forklifts typically uses hydraulic drive, with a cylinder bottom valve block installed at the bottom of the lifting cylinder to control the movement characteristics of the cylinder.

[0003] Currently, the cylinder bottom valve block of electric forklifts has a single function. When the main oil circuit fails (such as pump damage or pipeline rupture), emergency lowering is achieved by connecting an external manual pump or mechanical pressure relief valve, which is cumbersome and slow to respond, and cannot meet the needs of emergency conditions. Moreover, most existing valve assemblies adopt a split design, and the oil inlet, oil return, and control oil circuits need to be connected through external pipelines, which not only increases the risk of leakage, but also makes it difficult to install equipment with limited space. Utility Model Content

[0004] The purpose of this utility model is to solve at least one of the technical problems existing in the prior art, and to provide a lifting cylinder bottom valve assembly and hydraulic system. This lifting cylinder bottom valve assembly has high safety, is easy to install, and can cope with a variety of working conditions.

[0005] To achieve the above objectives, this utility model provides a lifting cylinder bottom valve assembly, applied to a lifting cylinder, comprising:

[0006] A valve assembly seat is provided with an oil inlet, an oil outlet, and a return oil outlet. The oil outlet is connected to the lifting cylinder, and the return oil outlet is connected to the hydraulic oil tank.

[0007] The first oil passage is connected to the oil inlet and the oil outlet at both ends, respectively;

[0008] The second oil passage is connected to the oil outlet and the oil return port at both ends, respectively;

[0009] A load holding valve is installed on the first oil passage and is used to switch the flow direction of hydraulic oil inside the first oil passage.

[0010] An emergency descent solenoid valve is installed on the second oil passage and is used to switch the return oil passage of the hydraulic oil when the main oil passage fails.

[0011] Optionally, the lifting cylinder bottom valve assembly further includes:

[0012] The third oil passage is connected at both ends to the oil outlet and the oil return port, respectively;

[0013] An overload valve, located on the third oil passage, is used to open when the load is impacted, so that the hydraulic oil can be unloaded and flow back through the return port.

[0014] Optionally, the lifting cylinder bottom valve assembly further includes a throttle orifice, the two ends of which are respectively connected to the emergency lowering solenoid valve and the oil return port.

[0015] Optionally, both the load holding valve and the emergency lowering solenoid valve are configured as two-position two-way solenoid valves.

[0016] Optionally, the load holding valve, the emergency lowering solenoid valve, and the overload valve are all located on the top of the valve assembly seat, and the internal oil passages of the load holding valve, the emergency lowering solenoid valve, and the overload valve are respectively connected to the first oil passage, the second oil passage, and the third oil passage.

[0017] Optionally, the lifting cylinder bottom valve assembly further includes:

[0018] The first working oil port is connected to the oil outlet port;

[0019] The second working oil port is connected to the oil outlet and the first working oil port respectively;

[0020] The third working oil port is connected to both the oil inlet and the load holding valve.

[0021] Optionally, the lifting cylinder bottom valve assembly further includes a pressure sensor, which is disposed on the third working oil port.

[0022] The second aspect of this utility model provides a hydraulic system, comprising:

[0023] Two lifting cylinders, the output end of which is connected to the corresponding fork;

[0024] Two lifting cylinder bottom valve assemblies as described above are respectively located at the bottom ends of the two lifting cylinders.

[0025] A negative swashplate pump, the outlet of which is connected to the inlet of each of the two lifting cylinder bottom valve assemblies.

[0026] Optionally, the hydraulic system further includes a connector and a steel pipe connected in sequence, and the two lifting cylinder bottom valve assemblies are interconnected through the connector and the steel pipe.

[0027] Through the above technical solution, the valve seat integrates the oil inlet, oil outlet, oil return port and related oil passages. The compact layout prevents leakage. The load holding valve on the first oil passage actively controls the flow of hydraulic oil, ensuring that the lifting cylinder can stably bear the load when stationary or running. The emergency descent solenoid valve configured in the second oil passage can be forcibly opened in case of main oil circuit failure, realizing safe pressure relief and controllable descent of the cylinder. This can improve the stability and safety of the lifting system and is suitable for hydraulic lifting equipment that requires frequent start-stop or long-term pressure maintenance. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a lifting cylinder bottom valve assembly provided by this utility model;

[0029] Figure 2 This is a schematic diagram of the principle of a lifting cylinder bottom valve assembly provided by this utility model;

[0030] Figure 3 This is a schematic diagram of a hydraulic system provided by this utility model;

[0031] Figure 4 This is an installation diagram of a lifting cylinder bottom valve assembly provided by this utility model;

[0032] Figure 5 This is a schematic diagram of the internal oil circuit of a lifting cylinder bottom valve assembly provided by this utility model.

[0033] Explanation of reference numerals in the attached figures

[0034] 1. Valve seat; 11. First oil passage; 111. First branch oil passage; 112. Second branch oil passage; 113. Third branch oil passage; 12. Second oil passage; 121. Fifth branch oil passage; 122. Sixth branch oil passage; 123. Seventh branch oil passage; 124. Eighth branch oil passage; 13. Third oil passage; 131. Fourth branch oil passage; 14. Connector; 2. Load holding valve; 3. Emergency lowering solenoid valve; 4. Overload valve; 5. Throttling orifice; 6. Pressure sensor; 7. Lifting cylinder; 8. Negative swing pump; 9. Steel pipe; A. Inlet; A1. Outlet; T. Return port; A2. First working port; A3. Second working port; A4. Third working port. Detailed Implementation

[0035] The specific embodiments of this utility model 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 scope of this utility model.

[0036] Figure 1 This is a schematic diagram of the structure of the lifting cylinder bottom valve assembly according to one embodiment of the present invention; Figure 2 This is a schematic diagram of the lifting cylinder bottom valve assembly according to one embodiment of the present invention. Figure 1 and Figure 2 The lifting cylinder bottom valve assembly may include a valve seat 1, a first oil passage 11, a second oil passage 12, a load holding valve 2, and an emergency lowering solenoid valve 3.

[0037] Specifically, the valve seat 1 is provided with an oil inlet A, an oil outlet A1, and a return oil port T. The oil inlet A can be connected to an oil pump or a multi-way valve, the oil outlet A1 is connected to the lifting cylinder 7, and the return oil port T is connected to the hydraulic oil tank for emergency descent and overload unloading. The two ends of the first oil passage 11 are connected to the oil inlet A and the oil outlet A1, respectively. The two ends of the second oil passage 12 are connected to the oil outlet A1 and the return oil port T, respectively. The load holding valve 2 is provided on the first oil passage 11 to switch the flow direction of the hydraulic oil inside the first oil passage 11. The emergency descent solenoid valve 3 is provided on the second oil passage 12 to be energized and switched to the return oil path of the hydraulic oil when the main oil circuit fails.

[0038] In practical operation, the lifting cylinder bottom valve assembly provided by this utility model allows for the following: when high-pressure oil output from the oil pump enters the lifting cylinder 7 through inlet A, load holding valve 2, and outlet A1, the forks are lifted. When the solenoid SV1 of load holding valve 2 is energized, the load holding valve 2 is in the left-hand working state, and hydraulic oil flows back to the oil pump through outlet A1, load holding valve 2, and inlet A, enabling controlled lowering of the forks. When the solenoid SV1 of load holding valve 2 is de-energized, the load holding valve 2 is in the right-hand working state, preventing hydraulic oil backflow and keeping the forks and load in their original positions. In the event of a main oil circuit failure, the emergency lowering solenoid valve 3 is energized and opens, allowing hydraulic oil to flow back to the hydraulic oil tank through outlet A1, emergency lowering solenoid valve 3, and return port T, enabling forced lowering of the forks. This lifting cylinder bottom valve assembly offers high safety, can handle various working conditions, and is suitable for hydraulic lifting equipment such as aerial work platforms and forklifts that require frequent start-stop or long-term pressure maintenance.

[0039] In this invention, the return port T is directly connected to the hydraulic oil tank, ensuring rapid return of hydraulic oil on the low-pressure side of the lifting system and reducing back pressure. The preferred oil pump is a negative swashplate pump 8, which reduces flow output and energy loss during non-lifting operations.

[0040] In some embodiments, the lifting cylinder bottom valve assembly further includes a third oil passage 13 and an overload valve 4.

[0041] Specifically, the two ends of the third oil passage 13 are connected to the oil outlet A1 and the oil return port T, respectively. The overload valve 4 is installed on the third oil passage 13 and is used to conduct when the load is impacted so that the hydraulic oil can be unloaded and flow back through the oil return port T.

[0042] In some embodiments, such as Figure 5 As shown, the first oil passage 11 includes a first branch oil passage 111, a second branch oil passage 112 and a third branch oil passage 113 connected in sequence. The second oil passage 12 includes a fifth branch oil passage 121, a sixth branch oil passage 122, a seventh branch oil passage 123 and an eighth branch oil passage 124 connected in sequence. The third oil passage 13 includes a fourth branch oil passage 131.

[0043] The first branch oil passage 111 is connected to one end of the load holding valve 2, the oil inlet A, and the third working oil port A4, respectively; the second branch oil passage 112 is connected to the other end of the load holding valve 2 and one end of the third branch oil passage 113, respectively; the other end of the third branch oil passage 113 is connected to the oil outlet A1 and one end of the fourth branch oil passage 131, respectively; one end of the fourth branch oil passage 131 is connected to the oil outlet A1 and the other end of the third branch oil passage 113, and the other end is connected to the overload valve 4.

[0044] The fifth branch oil passage 121 is connected to the second branch oil passage 112 and one end of the emergency descent solenoid valve 3, respectively; the sixth branch oil passage 122 is connected to the other end of the emergency descent solenoid valve 3 and one end of the throttle orifice 5, respectively; the seventh branch oil passage 123 is connected to the other end of the throttle orifice 5 and one end of the eighth branch oil passage 124, respectively; the other end of the eighth branch oil passage 124 is connected to the return oil port T.

[0045] In some embodiments, the lifting cylinder bottom valve assembly further includes a throttle orifice 5, the two ends of which are connected to the emergency lowering solenoid valve 3 and the return port T, respectively. By limiting the flow rate of hydraulic oil from the second oil passage 12 to the return port T, the throttle orifice 5 can slow down the pressure relief rate of the lifting cylinder 7 during emergency lowering, preventing the load from rapidly falling due to the rapid return of hydraulic oil, and ensuring a smooth and controllable lowering process.

[0046] In some embodiments, both the load holding valve 2 and the emergency lowering solenoid valve 3 are configured as two-position two-way solenoid valves.

[0047] Specifically, the load holding valve 2 is not energized in its default state. Under the action of the spring, the load holding valve 2 is in the right-hand working state. At this time, hydraulic oil can only flow from the inlet A to the outlet A1 through the first oil passage 11 to achieve the lifting action or load holding. During the load holding phase, the load holding valve 2 being in the right-hand working state can prevent the lifting cylinder 7 from returning oil in the reverse direction, ensuring that the forks and load remain at the target height and preventing them from sliding down due to their own weight. When it is necessary to lower the load, the electromagnet SV1 in the load holding valve 2 is energized, causing the load holding valve 2 to be in the left-hand working state. At this time, the hydraulic oil in the lifting cylinder 7 can flow back to the inlet A through the first oil passage 11, cooperating with the negative swing pump 8 or the multi-way valve to achieve controlled lowering.

[0048] The emergency lowering solenoid valve 3, in the event of a main oil circuit failure, can cooperate with the throttle orifice 5 to provide a backup lowering channel. Under normal operating conditions, it should not be energized, and hydraulic oil should not flow back through the second oil passage 12. When the main oil circuit fails, such as a pipe rupture or pump failure, the emergency lowering solenoid valve 3 is energized and conducts, and the hydraulic oil in the lifting cylinder 7 is slowly depressurized sequentially through the oil outlet A1, the emergency lowering solenoid valve 3, the throttle orifice 5, and the oil return port T, allowing the forks to be lowered safely and smoothly to the ground.

[0049] In some embodiments, the overload valve 4 is an adjustable overload valve 4. When the load is impacted, such as by an external force or by the load rising to the top of the mast, the overload valve 4 can open under high pressure. At this time, the pressure can be relieved to protect the hydraulic system. When the vehicle loses power and the forks need to be placed on the ground, the overload valve 4 can be manually adjusted until it is reduced to less than the cylinder bottom pressure of the lifting cylinder 7 when the load is held. Then the hydraulic oil can slowly pass through the overload valve 4 and flow back to the hydraulic oil tank.

[0050] In some embodiments, the load holding valve 2, the emergency lowering solenoid valve 3, and the overload valve 4 are all disposed on the top of the valve assembly seat 1, and the internal oil passages of the load holding valve 2, the emergency lowering solenoid valve 3, and the overload valve 4 are respectively connected to the first oil passage 11, the second oil passage 12, and the third oil passage 13. The load holding valve 2, the emergency lowering solenoid valve 3, and the overload valve 4 can be fixed to the top of the valve assembly seat 1 by threads or flanges to form a modular structure. The oil ports of each valve are interconnected through drilled oil passages inside the valve assembly seat 1, namely the first oil passage 11, the second oil passage 12, and the third oil passage 13, avoiding entanglement of external hoses, resulting in a simple structure and complete functions.

[0051] In some embodiments, the lifting cylinder bottom valve assembly further includes a first working port A2, a second working port A3, and a third working port A4. Specifically, the first working port A2 is connected to the oil outlet A1, the second working port A3 is connected to both the oil outlet A1 and the first working port A2, and the third working port A4 is connected to both the oil inlet A and the load holding valve 2.

[0052] The third working port A4 is connected to the inlet port A and is used to install the pressure sensor 6. The second working port A3 is a pressure measuring port. The first working ports A2 of the two lifting cylinder bottom valve groups, which are respectively set at the bottom of the two lifting cylinders 7, are connected to each other so that the two lifting cylinders 7 can maintain good synchronization.

[0053] In some embodiments, the lifting cylinder bottom valve assembly further includes a pressure sensor 6, which is disposed on the third working oil port A4. The pressure sensor 6 is externally connected to the third working oil port A4 and can continuously detect changes in oil pressure in the lifting cylinder bottom valve assembly. When the pressure at the oil inlet A is detected to be lower than a safety threshold, a signal is sent to the vehicle processor CPU. Upon receiving the signal from the pressure sensor 6, the vehicle processor CPU de-energizes the load holding valve 2. At this time, the load holding valve 2 is in the right-hand operating state under the action of the spring, keeping the forks in their original position.

[0054] In summary, the lifting cylinder bottom valve assembly provided by this utility model, located at the bottom of the lifting cylinder 7, has advantages such as high safety, convenient installation, and comprehensive functions, and can meet the hydraulic control requirements under complex working conditions.

[0055] Specifically, when a hydraulic line suddenly bursts, even if the driver misoperates, the lifting cylinder bottom valve group can immediately cut off the oil circuit under the dual protection of real-time monitoring by pressure sensor 6 and locking of load holding valve 2, so as to stably lock the forks and load in their original position and eliminate the risk of load falling.

[0056] Combination Figure 1 and Figure 4 As shown, the lifting cylinder bottom valve assembly adopts a compact modular structure and is integrated into the bottom of the lifting cylinder 7 through a standardized interface, eliminating the need for complex external piping layout.

[0057] In addition, the lifting cylinder bottom valve assembly, with the coordinated operation of various valves, also has multiple functions such as load holding, high-pressure unloading, emergency descent, and explosion protection.

[0058] On the other hand, this utility model also provides a hydraulic system, such as Figure 3 As shown.

[0059] exist Figure 3 The hydraulic system may include two lifting cylinders 7, two lifting cylinder bottom valve assemblies as described above, and a negative sway pump 8. Specifically, the output end of each lifting cylinder 7 is connected to the corresponding fork for power output for lifting action. The two lifting cylinder bottom valve assemblies are respectively located at the bottom ends of the two lifting cylinders 7, making installation simple and convenient. Figure 4 As shown. The outlet A1 of the negative swing pump 8 is connected to the inlet A of the two lifting cylinder bottom valve assemblies, respectively, to provide high-pressure oil to the hydraulic system.

[0060] Furthermore, the hydraulic system also includes a connector 14 and a steel pipe 9 connected in sequence. The first working oil port A2 of the two lifting cylinder bottom valve groups is interconnected through the connector 14 and the steel pipe 9 to ensure the synchronous action of the two lifting cylinders 7, so that the pressure and flow of the two lifting cylinders 7 are balanced during the lifting / lowering process, and to prevent the forks from tilting.

[0061] In summary, the specific implementation methods of this hydraulic system under different working conditions are as follows:

[0062] When lifting is performed, the driver issues a lifting command via the operating handle or control system. Upon receiving the command, the control system sends a start signal to the negative swashplate pump 8 motor, which then begins operation and outputs high-pressure oil according to the command. At this time, the first working ports A2 of the two lifting cylinder bottom valve assemblies, located at the bottom ends of the two lifting cylinders 7, are connected via steel pipe 9 and connector 14. The high-pressure oil passes sequentially through inlet A and load holding valve 2 to reach the bottom of the lifting cylinder 7. Because the first working ports A2 of the two lifting cylinder bottom valve assemblies are connected, and the first working ports A2 are connected to outlet A1, the two lifting cylinders 7 can operate synchronously during the lifting process, ensuring the smoothness and accuracy of the lifting action.

[0063] During the lifting process, if the load is subjected to external impact or if the load is lifted to the top of the gantry and causes an impact, the pressure sensor 6 will detect an abnormal increase in pressure and send a signal back to the processor. After the processor determines that the load has been impacted, it will immediately drive the overload valve 4 to open. At this time, the hydraulic oil is unloaded to the hydraulic oil tank through the oil outlet A1, the third oil passage 13, and the oil return port T, which can effectively protect the entire hydraulic system from damage caused by excessive pressure.

[0064] During the descent, the operator issues a descent command via the control handle or the control system. Upon receiving the command, the control system energizes the solenoid SV1 of the load holding valve 2, placing the load holding valve 2 in the left-hand operating position. The hydraulic oil in the lifting cylinder 7 flows through the cylinder bottom and outlet A1, through the first oil passage 11, and back to the port of the negative swashplate pump 8. During this process, the flow of hydraulic oil drives the motor of the negative swashplate pump 8, achieving energy recovery and improving the system's energy efficiency.

[0065] When the system receives a load holding command, the lifting cylinder bottom valve assembly does not execute any commands. At this time, the load holding valve 2 is in the default state, that is, its solenoid SV1 is de-energized, the load holding valve 2 is in the right-hand working state, the hydraulic oil cannot flow backward, and the forks and load will remain stably in the position where the load holding command was received, ensuring the safety of the goods during transportation.

[0066] When the driver issues an emergency descent command, such as when the main hydraulic circuit is damaged and hydraulic oil cannot return to the hydraulic tank, the control system receives the command and energizes the electromagnet SV2 of the emergency descent solenoid valve 3, placing the emergency descent solenoid valve 3 in the left-hand operating position. At this time, the hydraulic oil flows slowly back to the hydraulic tank through the second oil passage 12 and the return port T. The throttle orifice 5 is located after the emergency descent solenoid valve 3 to limit the flow of hydraulic oil, ensuring that the forks and load can descend slowly and avoiding the risk of falling objects due to excessive descent speed.

[0067] When the vehicle loses power and the forks need to be lowered back to the ground, the operator can manually adjust the overload valve 4. By gradually reducing the opening of the overload valve 4 until it is less than the cylinder bottom pressure of the lifting cylinder 7 when the load is held, hydraulic oil can slowly flow back to the hydraulic oil tank through the overload valve 4, through the oil outlet A1, the third oil passage 13, and the oil return port T, causing the forks to slowly descend to the ground, ensuring operational safety.

[0068] In the event of a hose rupture, if the driver reacts promptly, the operating handle or control system will de-energize the solenoid SV1 of the load holding valve 2, placing the load holding valve 2 in the right-hand position. This prevents the hydraulic oil in the first oil passage 11 from flowing back to the inlet A, keeping the forks and load in their original positions and preventing damage to the cargo from a sudden fork descent. If the driver fails to react promptly and continues to issue a descent command, the pressure sensor 6 will send a signal to the processor based on the measured pressure information. The processor will then forcibly de-energize the solenoid SV1 of the load holding valve 2, placing the load holding valve 2 in the right-hand position. This again prevents the hydraulic oil in the first oil passage 11 from flowing back to the inlet A, ensuring the forks and load remain in their original positions and preventing any danger.

[0069] In summary, this hydraulic system, under the action of the lifting cylinder bottom valve assembly, can operate stably and safely under various working conditions, meeting multiple needs such as lifting and lowering of forks, load holding, and emergency handling.

[0070] Furthermore, this utility model also provides a control method for controlling the forks using the aforementioned lifting cylinder bottom valve assembly, which may include:

[0071] Step 1: Obtain the lifting command;

[0072] Step 2: Control the oil pump to start, so as to pump hydraulic oil into the lifting cylinder bottom valve assembly;

[0073] Step 3: Determine if the load has been impacted;

[0074] Step 4: If it is determined that the load is under impact, drive the overload valve 4 to open;

[0075] Step 5: Determine if an emergency descent command has been received;

[0076] Step Six: Upon determining that an emergency descent command has been received, activate emergency descent solenoid valve 3 to open;

[0077] Step 7: Obtain the descent command;

[0078] Step 8: Control the load holding valve 2 to be in the left position to switch the direction of hydraulic oil flow.

[0079] The control method of this utility model is based on the lifting cylinder bottom valve group to realize intelligent lifting control of the forks. It can be understood that it can also be combined with sensor detection, electronic control logic and solenoid valve to ensure the safety and stability of the hydraulic system and forklift.

[0080] Specifically, in step one, a lifting command is obtained. This can be achieved by the driver sending a lifting signal via a joystick / button in the cab, or by the AGV controller issuing a command. The lifting command is transmitted to the vehicle's CPU via the CAN bus or hardwired connection.

[0081] In step two, the oil pump is started to pump hydraulic oil into the lifting cylinder bottom valve assembly. Upon receiving the lifting command, the vehicle's CPU outputs a signal to drive the oil pump motor, adjusting the pump's output flow and pressure. The hydraulic oil flows from the pump outlet through the lifting cylinder bottom valve assembly into the rodless chamber of the lifting cylinder 7, pushing the piston rod out and raising the forks. In this invention, the oil pump can be a negative-angle plunger pump.

[0082] In steps three and four, it is determined whether the load has been subjected to an impact. If an impact is detected, the overload valve 4 is activated. The impact can be determined by using a pressure sensor 6 to monitor the pressure at the oil inlet A in real time. If the pressure fluctuation exceeds a threshold, an impact can be identified. Alternatively, an acceleration sensor can be installed on the forks to detect abnormal vibration signals. The vehicle's CPU then triggers overload protection by comparing the sensor data with a preset safety range.

[0083] In steps five and six, it is determined whether an emergency descent command has been received. If an emergency descent command has been received, the emergency descent solenoid valve 3 is opened. Specifically, when the main oil circuit fails, the hydraulic oil cannot flow back. At this time, the driver can press the emergency stop button to issue a command, or the pressure sensor 6 at the oil inlet A detects a sudden drop in pressure and issues a command. The vehicle processor CPU receives the command and controls the electromagnet SV2 of the emergency descent solenoid valve 3 to be energized. After SV2 is energized, the emergency descent solenoid valve 3 is in the left-hand working state, and the hydraulic oil slowly flows back to the hydraulic oil tank through the emergency descent solenoid valve 3, the throttle orifice 5, and the return port T, realizing a controllable emergency descent.

[0084] In steps 7 and 8, a descent command is obtained, and the load holding valve 2 is opened to switch the direction of hydraulic oil flow. Specifically, the driver can send a descent signal through the control lever / button in the cab. After receiving the descent command, the vehicle processor CPU controls the electromagnet SV1 of the load holding valve 2 to be energized, so that the load holding valve 2 is in the left-hand working state. At this time, the hydraulic oil in the lifting cylinder 7 can flow back to the port of the negative swing pump 8 through the first oil passage 11 and the return oil inlet A. The returning hydraulic oil drives the negative swing pump 8 to rotate in the opposite direction, converting the oil pressure energy into mechanical energy, and then generating electricity through the motor to realize energy recovery.

[0085] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings; however, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including the combination of various specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. However, these simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A lifting cylinder bottom valve assembly, applied to a lifting cylinder (7), characterized in that, include: Valve assembly seat (1), the valve assembly seat (1) is provided with an oil inlet (A), an oil outlet (A1) and an oil return port (T), the oil outlet (A1) is connected to the lifting cylinder (7) and the oil return port (T) is connected to the hydraulic oil tank; The first oil passage (11) is connected at both ends to the oil inlet (A) and the oil outlet (A1), respectively; The second oil passage (12) is connected at both ends to the oil outlet (A1) and the oil return port (T), respectively; A load holding valve (2) is installed on the first oil passage (11) to switch the flow direction of hydraulic oil inside the first oil passage (11); An emergency descent solenoid valve (3) is installed on the second oil passage (12) and is used to switch the return oil passage of the hydraulic oil when the main oil passage fails.

2. The lifting cylinder bottom valve assembly according to claim 1, characterized in that, The lifting cylinder bottom valve assembly also includes: The third oil passage (13) is connected at both ends to the oil outlet (A1) and the oil return port (T); An overload valve (4) is provided on the third oil passage (13) for opening when the load is impacted so that the hydraulic oil is unloaded and flows back through the return port (T).

3. The lifting cylinder bottom valve assembly according to claim 1, characterized in that, The lifting cylinder bottom valve group also includes a throttle orifice (5), the two ends of which are connected to the emergency lowering solenoid valve (3) and the oil return port (T), respectively.

4. The lifting cylinder bottom valve assembly according to claim 1, characterized in that, Both the load holding valve (2) and the emergency descent solenoid valve (3) are configured as two-position two-way solenoid valves.

5. The lifting cylinder bottom valve assembly according to claim 2, characterized in that, The load holding valve (2), the emergency descent solenoid valve (3), and the overload valve (4) are all located on the top of the valve assembly seat (1), and the internal oil passages of the load holding valve (2), the emergency descent solenoid valve (3), and the overload valve (4) are respectively connected to the first oil passage (11), the second oil passage (12), and the third oil passage (13).

6. The lifting cylinder bottom valve assembly according to claim 1, characterized in that, The lifting cylinder bottom valve assembly also includes: The first working oil port (A2) is connected to the oil outlet (A1); The second working oil port (A3) is connected to the oil outlet (A1) and the first working oil port (A2) respectively; The third working oil port (A4) is connected to the oil inlet (A) and the load holding valve (2) respectively.

7. The lifting cylinder bottom valve assembly according to claim 6, characterized in that, The lifting cylinder bottom valve assembly also includes a pressure sensor (6), which is located on the third working port (A4).

8. A hydraulic system, characterized in that, include: Two lifting cylinders (7), the output end of which is connected to the corresponding fork; Two lifting cylinder bottom valve assemblies as described in any one of claims 1-7, wherein the two lifting cylinder bottom valve assemblies are respectively disposed at the bottom ends of the two lifting cylinders (7); The negative swashplate pump (8) has its outlet (A1) connected to the inlet (A) of the two lifting cylinder bottom valve groups.

9. The hydraulic system according to claim 8, characterized in that, The hydraulic system also includes a connector (14) and a steel pipe (9) connected in sequence, and the two lifting cylinder bottom valve groups are interconnected through the connector (14) and the steel pipe (9).

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