Lifting cylinder bottom valve group, control method thereof and hydraulic system

Abstract

The invention relates to the technical field of electric forklifts, and discloses a lifting cylinder bottom valve group, a control method thereof and a hydraulic system. The lifting cylinder bottom valve group comprises a valve group seat, an oil inlet, an oil outlet and an oil return port are formed in the valve group seat, the oil outlet is communicated with the lifting oil cylinder, and the oil return port is communicated with the hydraulic oil tank; two ends of the first oil duct are respectively communicated with the oil inlet and the oil outlet; two ends of the second oil duct are respectively communicated with the oil outlet and the oil return port; the load holding valve is arranged on the first oil duct and used for switching the flowing direction of hydraulic oil in the first oil duct; and the emergency descending electromagnetic valve is arranged on the second oil channel and is used for being electrified and conducted when the main oil channel breaks down so as to switch a backflow oil channel of the hydraulic oil. The lifting cylinder bottom valve group is high in safety, convenient to install and capable of coping with various working conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of electric forklifts, and in particular to a lifting cylinder bottom valve group, a control method thereof, and a hydraulic system. Background Art

[0002] As an industrial handling vehicle, the lifting performance of an electric forklift directly affects operational efficiency. Currently, the lifting system of an electric forklift is usually driven by hydraulics, and a bottom valve block is installed at the bottom of the lifting cylinder to control the movement characteristics of the cylinder.

[0003] Currently, the cylinder-bottom valve blocks in electric forklifts have a single function. In the event of a main oil line failure (such as a pump failure or pipe rupture), emergency lowering requires an external manual pump or mechanical pressure relief valve. This operation is cumbersome and slow to respond, making it inadequate for emergency situations. Furthermore, most existing valve blocks utilize a split design, requiring external piping to connect the oil supply, return, and control lines. This increases the risk of leakage and is inconvenient for installation in space-constrained equipment. Summary of the Invention

[0004] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a lifting cylinder bottom valve group, a control method thereof, and a hydraulic system. The lifting cylinder bottom valve group has high safety, is easy to install, and can cope with various working conditions.

[0005] In order to achieve the above objectives, the present invention provides a lifting cylinder bottom valve group, which is applied to the lifting cylinder, comprising: A valve block seat, wherein the valve block seat is provided with an oil inlet, an oil outlet, and an oil return port, the oil outlet is connected to the lifting cylinder, and the oil return port is connected to the hydraulic oil tank; a first oil passage, two ends of which are respectively connected to the oil inlet and the oil outlet; a second oil passage, both ends of which are connected to the oil outlet and the oil return port respectively; a load holding valve, provided on the first oil passage, for switching the flow direction of the hydraulic oil in the first oil passage; The emergency lowering solenoid valve is arranged on the second oil channel and is used to be electrically connected to switch the return oil channel of the hydraulic oil when a main oil circuit fails.

[0006] Optionally, the lifting cylinder bottom valve group further includes: a third oil passage, both ends of which are connected to the oil outlet and the oil return port respectively; The overload valve is arranged on the third oil passage and is used to conduct when the load is impacted so that the hydraulic oil can be unloaded and refluxed through the oil return port.

[0007] Optionally, the lifting cylinder bottom valve group further includes a throttle hole, and both ends of the throttle hole are respectively connected to the emergency descent solenoid valve and the oil return port.

[0008] Optionally, the load holding valve and the emergency descent solenoid valve are both configured as two-position, two-way solenoid valves.

[0009] Optionally, the load holding valve, the emergency descent solenoid valve and the overload valve are all arranged on the top of the valve group seat, and the internal oil channels of the load holding valve, the emergency descent solenoid valve and the overload valve are respectively connected to the first oil channel, the second oil channel and the third oil channel.

[0010] Optionally, the lifting cylinder bottom valve group further includes: a first working oil port, connected to the oil outlet; a second working oil port, connected to the oil outlet and the first working oil port respectively; The third working oil port is communicated with the oil inlet and the load holding valve respectively.

[0011] Optionally, the lift cylinder bottom valve group further includes a pressure sensor, and the pressure sensor is arranged on the third working oil port.

[0012] A second aspect of the present invention provides a hydraulic system, comprising: Two lifting cylinders, the output ends of the lifting cylinders are connected to corresponding forks; Two lifting cylinder bottom valve groups as described above, the two lifting cylinder bottom valve groups are respectively arranged at the bottom ends of the two lifting cylinders; A negative swing angle pump, wherein the oil outlet of the negative swing angle pump is respectively connected to the oil inlets of the two lifting cylinder bottom valve groups.

[0013] Optionally, the hydraulic system further includes a joint and a steel pipe connected in sequence, and the two lifting cylinder bottom valve groups are connected to each other through the joint and the steel pipe.

[0014] A third aspect of the present invention provides a method for controlling a cargo fork using the above-mentioned lift cylinder bottom valve assembly, comprising: Get lifting instructions; Control the oil pump to start and pump hydraulic oil into the lift cylinder bottom valve group; Determine whether the load is subjected to impact; When it is determined that the load is subjected to impact, the overload valve is driven to open; Determine whether to obtain the emergency descent instruction; When it is determined that the emergency descent command has been obtained, the emergency descent solenoid valve is driven to open; Get the descent command; Control the load holding valve to the left position to switch the flow direction of the hydraulic oil.

[0015] Through the above technical solution, the valve group seat is integrated with the oil inlet, oil outlet, oil return port and related oil channels, with a compact layout to prevent leakage. The load holding valve on the first oil channel actively controls the flow direction of the hydraulic oil to ensure stable load-bearing of the lifting cylinder when it is stationary or running. The emergency descent solenoid valve configured in the second oil channel can be forced to conduct when the main oil circuit fails, realizing safe pressure relief and controllable descent of the cylinder, thereby improving the stability and safety of the lifting system. It is suitable for hydraulic lifting equipment that requires frequent starting and stopping or long-term pressure maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a structural diagram of a lift cylinder bottom valve group provided by the present invention; Figure 2 This is a schematic diagram of the principle of a lift cylinder bottom valve group provided by the present invention; Figure 3 This is a schematic diagram of the principle of a hydraulic system provided by the present invention; Figure 4 This is a schematic diagram of the installation of a lift cylinder bottom valve group provided by the present invention; Figure 5 This is a schematic diagram of the internal oil circuit of a lift cylinder bottom valve group provided by the present invention.

[0017] Description of Reference Numerals 1. Valve group seat; 11. First oil channel; 111. First branch oil channel; 112. Second branch oil channel; 113. Third branch oil channel; 12. Second oil channel; 121. Fifth branch oil channel; 122. Sixth branch oil channel; 123. Seventh branch oil channel; 124. Eighth branch oil channel; 13. Third oil channel; 131. Fourth branch oil channel; 14. Connector; 2. Load holding valve; 3. Emergency descent solenoid valve; 4. Overload valve; 5. Throttle hole; 6. Pressure sensor; 7. Lifting cylinder; 8. Negative swing pump; 9. Steel pipe; A. Oil inlet; A1. Oil outlet; T. Oil return port; A2. First working oil port; A3. Second working oil port; A4. Third working oil port. DETAILED DESCRIPTION

[0018] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0019] Figure 1 2 is a schematic structural diagram of a lift cylinder bottom valve assembly according to one embodiment of the present invention; Figure 2 Schematic diagram of the principle of the bottom valve group of the lifting cylinder according to one embodiment of the present invention. Figure 1 and Figure 2 In the figure, the lift cylinder bottom valve group may include a valve group seat 1, a first oil channel 11, a second oil channel 12, a load holding valve 2 and an emergency lowering solenoid valve 3.

[0020] Specifically, the valve block seat 1 is provided with an oil inlet A, an oil outlet A1, and an oil return 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 oil return port T is connected to the hydraulic oil tank, used for emergency lowering and overload unloading. The two ends of the first oil channel 11 are connected to the oil inlet A and the oil outlet A1, respectively. The two ends of the second oil channel 12 are connected to the oil outlet A1 and the oil return port T, respectively. The load holding valve 2 is provided in the first oil channel 11 to switch the flow direction of the hydraulic oil in the first oil channel 11. The emergency lowering solenoid valve 3 is provided in the second oil channel 12 to be electrically connected to switch the return path of the hydraulic oil in the event of a main oil circuit failure.

[0021] The lifting cylinder bottom valve assembly provided by the present invention operates as follows: when the high-pressure oil output by the oil pump enters the lifting cylinder 7 through the oil inlet A, the load-holding valve 2, and the oil outlet A1, the fork is lifted; when the load-holding valve 2 electromagnet SV1 is energized, the load-holding valve 2 is in the left working state, and the hydraulic oil flows back to the oil pump through the oil outlet A1, the load-holding valve 2, and the oil inlet A, achieving controlled descent of the fork; when the load-holding valve 2 electromagnet SV1 is de-energized, the load-holding valve 2 is in the right working state, which prevents the hydraulic oil from flowing back, and the fork and load remain in place; when the main oil circuit fails, the emergency descent solenoid valve 3 is energized and opened, and the hydraulic oil flows back to the hydraulic oil tank through the oil outlet A1, the emergency descent solenoid valve 3, and the oil return port T, achieving forced descent of the fork. The lifting cylinder bottom valve assembly is highly safe and can cope with various working conditions. It is suitable for hydraulic lifting equipment such as aerial work platforms and forklifts that require frequent starting and stopping or long-term pressure maintenance.

[0022] In the present invention, the direct connection of the oil return port T to the hydraulic oil tank ensures rapid return of the hydraulic oil on the low-pressure side of the lifting system, reducing back pressure. The oil pump is preferably a negative swing pump 8, which can reduce flow output and energy loss in non-lifting conditions.

[0023] In some embodiments, the lift cylinder bottom valve group further includes a third oil passage 13 and an overload valve 4 .

[0024] Specifically, both 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 provided on the third oil passage 13 for conducting when the load is impacted so that the hydraulic oil can be unloaded and refluxed through the oil return port T.

[0025] In some embodiments, as Figure 5As shown, the first oil channel 11 includes a first branch oil channel 111, a second branch oil channel 112 and a third branch oil channel 113 connected in sequence, the second oil channel 12 includes a fifth branch oil channel 121, a sixth branch oil channel 122, a seventh branch oil channel 123 and an eighth branch oil channel 124 connected in sequence, and the third oil channel 13 includes a fourth branch oil channel 131.

[0026] 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; 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; 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; 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. The fifth branch oil channel 121 is respectively connected to the second branch oil channel 112 and one end of the emergency descent solenoid valve 3; the sixth branch oil channel 122 is respectively connected to the other end of the emergency descent solenoid valve 3 and one end of the throttle hole 5; the seventh branch oil channel 123 is respectively connected to the other end of the throttle hole 5 and one end of the eighth branch oil channel 124; the other end of the eighth branch oil channel 124 is connected to the return oil port T.

[0027] In some embodiments, the lift cylinder bottom valve assembly further includes a throttle orifice 5 , the two ends of which are respectively connected to the emergency descent solenoid valve 3 and the oil return port T. By limiting the flow of hydraulic oil from the second oil passage 12 to the oil return port T, the throttle orifice 5 can slow the pressure relief rate of the lift cylinder 7 during emergency descent, preventing the load from rapidly falling due to rapid hydraulic oil backflow, and ensuring a smooth and controllable descent.

[0028] In some embodiments, the load holding valve 2 and the emergency descent solenoid valve 3 are both configured as two-position, two-way solenoid valves.

[0029] Specifically, the load holding valve 2 shall not be energized in the default state. The load holding valve 2 is in the right working state under the action of the spring. At this time, the hydraulic oil can only flow from the oil inlet A to the oil outlet A1 through the first oil channel 11 to achieve lifting action or load holding. In the load holding stage, the load holding valve 2 is in the right working state to prevent the lifting cylinder 7 from returning oil in the reverse direction, ensuring that the fork and the load stay at the target height and prevent sliding due to their own weight. When it is necessary to descend, the electromagnet SV1 in the load holding valve 2 is energized, so that the load holding valve 2 is in the left working state. At this time, the hydraulic oil in the lifting cylinder 7 can flow back to the oil inlet A through the first oil channel 11, and cooperate with the negative swing angle pump 8 or the multi-way valve to achieve controllable descent.

[0030] The emergency lowering solenoid valve 3, in conjunction with the orifice 5, provides a backup lowering channel in the event of a main oil circuit failure. Under normal operating conditions, it is de-energized, and hydraulic oil does not flow back through the second oil passage 12. In the event of a main oil circuit failure, such as a pipeline rupture or pump failure, the emergency lowering solenoid valve 3 becomes energized, allowing the hydraulic oil in the lift cylinder 7 to slowly release pressure through the oil outlet A1, the emergency lowering solenoid valve 3, the orifice 5, and the oil return port T, allowing the forks to be lowered safely and smoothly to the ground.

[0031] In some embodiments, the overload valve 4 is an adjustable overload valve 4. When the load is impacted, such as by external force or the load is lifted to the top of the mast and causes impact, the overload valve 4 can be opened at high pressure. At this time, the pressure can be unloaded to protect the hydraulic system. When the entire vehicle loses power and the fork needs to be placed on the ground, the overload valve 4 can be manually adjusted at this time, and it can be adjusted down to a pressure lower than the bottom pressure of the lifting cylinder 7 when the load is maintained. Then the hydraulic oil can slowly pass through the overload valve 4 and return to the hydraulic oil tank.

[0032] In some embodiments, the load-holding valve 2, the emergency lowering solenoid valve 3, and the overload valve 4 are all disposed on top of the valve block seat 1, and their internal oil passages are connected to the first oil passage 11, the second oil passage 12, and the third oil passage 13, respectively. The load-holding valve 2, the emergency lowering solenoid valve 3, and the overload valve 4 can be secured to the top of the valve block seat 1 via threads or flanges, forming a modular structure. The oil ports of each valve are interconnected through drilled oil passages within the valve block seat 1, namely, the first oil passage 11, the second oil passage 12, and the third oil passage 13, preventing entanglement of external hoses. This results in a simple structure and comprehensive functionality.

[0033] In some embodiments, the lifting cylinder bottom valve group also includes a first working oil port A2, a second working oil port A3 and a third working oil port A4. Specifically, the first working oil port A2 is connected to the oil outlet A1, the second working oil port A3 is respectively connected to the oil outlet A1 and the first working oil port A2, and the third working oil port A4 is respectively connected to the oil inlet A and the load holding valve 2. The third working oil port A4 is connected to the oil inlet A for installing the pressure sensor 6. The second working oil port A3 is a pressure measuring port. The first working oil ports A2 of the two lifting cylinder bottom valve groups respectively arranged at the bottom ends of the two lifting cylinders 7 are connected to each other to ensure that the two lifting cylinders 7 maintain good synchronization.

[0034] In some embodiments, the lift cylinder bottom valve assembly further includes a pressure sensor 6, which is disposed at the third operating oil port A4. Externally connected to the third operating oil port A4, the pressure sensor 6 continuously monitors changes in the oil pressure within the lift cylinder bottom valve assembly. When the pressure at the oil inlet A falls below a safety threshold, the pressure sensor 6 sends a signal to the vehicle's CPU. Upon receiving the signal from the pressure sensor 6, the CPU de-energizes the load holding valve 2. At this point, the spring forces the load holding valve 2 to the right position, retaining the forks in their original position.

[0035] In summary, the lifting cylinder bottom valve group provided by the present invention is arranged at the bottom end of the lifting cylinder 7, has the advantages of high safety, convenient installation, and comprehensive functions, and can meet the hydraulic control requirements under complex working conditions.

[0036] Specifically, when the hydraulic pipeline suddenly bursts, even if the driver operates it incorrectly, the lift cylinder bottom valve group can immediately cut off the oil circuit under the dual protection of real-time monitoring by the pressure sensor 6 and the closure of the load holding valve 2, thereby stably locking the fork and load in place and eliminating the risk of the load falling.

[0037] Combine Figure 1 and Figure 4 As shown, the lift cylinder bottom valve group adopts a compact modular structure and is integrated into the bottom of the lift cylinder 7 through a standardized interface, eliminating the need for complex external piping arrangements.

[0038] In addition, the lifting cylinder bottom valve group has multiple functions such as load holding, high-pressure unloading, emergency descent, and explosion protection through the coordinated work of various valves.

[0039] On the other hand, the present invention also provides a hydraulic system, such as Figure 3 shown.

[0040] exist Figure 3 In the embodiment, the hydraulic system may include two lifting cylinders 7, two lifting cylinder bottom valve groups as described above, and a negative swing angle pump 8. Specifically, the output end of the lifting cylinder 7 is connected to the corresponding fork for power output of the lifting action. The two lifting cylinder bottom valve groups are respectively arranged at the bottom ends of the two lifting cylinders 7, which are simple and convenient to install. Figure 4 The oil outlet A1 of the negative swing pump 8 is connected to the oil inlet A of the two lift cylinder bottom valve groups respectively to provide high-pressure oil for the hydraulic system.

[0041] Furthermore, the hydraulic system also includes a connector 14 and a steel pipe 9 connected in sequence. The first working oil ports A2 of the two lifting cylinder bottom valve groups are connected to each other through the connector 14 and the steel pipe 9, ensuring 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, thereby preventing the fork from tilting.

[0042] In summary, the specific implementation methods of this hydraulic system under different working conditions are as follows: When performing a lifting operation, the driver issues a lifting command through the operating handle or the control system. After receiving the command, the control system sends a start signal to the motor of the negative swing angle pump 8, causing the negative swing angle pump 8 to start operating and output high-pressure oil according to the command. At this time, the first working oil port A2 of the two lifting cylinder bottom valve groups, respectively provided at the bottom ends of the two lifting cylinders 7, is connected via a steel pipe 9 and a connector 14. The high-pressure oil passes through the oil inlet A and the load holding valve 2 in sequence, reaching the bottom of the lifting cylinder 7. Because the first working oil ports A2 of the two lifting cylinder bottom valve groups are connected, and the first working oil port A2 is connected to the oil outlet A1, the two lifting cylinders 7 can operate synchronously during the lifting process, ensuring the smoothness and accuracy of the lifting action.

[0043] During the lifting process, if the load is impacted by external forces or by impact when it reaches the mast top, pressure sensor 6 will detect an abnormally high pressure increase and send a signal back to the processor. Upon determining the load has been impacted, the processor immediately activates overload valve 4 to open. At this point, hydraulic oil is discharged to the hydraulic tank via outlet A1, third oil channel 13, and return port T, effectively protecting the entire hydraulic system from damage caused by excessive pressure.

[0044] When descending, the operator issues a descending command via the operating handle or the control system. Upon receiving the command, the control system energizes electromagnet SV1 of load-holding valve 2, placing it in the left position. The hydraulic oil in lift cylinder 7 flows through the cylinder bottom and outlet A1, then through first oil channel 11, returning to the oil port of negative swing pump 8. During this process, the flow of hydraulic oil drives the motor of negative swing pump 8, achieving energy recovery and improving the system's energy efficiency.

[0045] When the system receives a load-hold command, the lift cylinder valve block does not execute any commands. Load-hold valve 2 is in its default state, with its solenoid SV1 de-energized and in the right position. Hydraulic oil cannot flow in the reverse direction, and the forks and load remain firmly in the position indicated by the load-hold command, ensuring cargo safety during transport.

[0046] When the driver issues an emergency descent command, for example if the hydraulic system's main oil circuit is damaged and the hydraulic oil cannot return to the hydraulic tank through the main oil circuit, the control system receives the command and energizes electromagnet SV2 of emergency descent solenoid valve 3, placing it in the left position. At this point, the hydraulic oil slowly flows back to the hydraulic tank through the second oil channel 12 and the oil return port T. A throttle orifice 5, located behind the emergency descent solenoid valve 3, limits the flow of hydraulic oil, ensuring a slow descent of the forks and load, and preventing the risk of falling objects due to excessive descent speed.

[0047] When the vehicle loses power and the forks need to be lowered to the ground, the driver can manually adjust the overload valve 4. By gradually reducing the opening of the overload valve 4 until it is less than the bottom pressure of the lift cylinder 7 during load maintenance, the hydraulic oil can pass through the overload valve 4, slowly return to the hydraulic oil tank through the oil outlet A1, the third oil channel 13, and the oil return port T, causing the forks to slowly descend to the ground, ensuring operational safety.

[0048] When a hose bursts, if the driver reacts in time, the operating handle or control system controls the electromagnet SV1 of the load holding valve 2 to lose power, and the load holding valve 2 is in the right working state. The hydraulic oil in the first oil channel 11 cannot flow back to the oil inlet A, and the fork and the load will stay in their original position, preventing the cargo from being damaged by the sudden drop of the fork. If the driver does not react in time and continues to give the descent command, the pressure sensor 6 will feed back the signal to the processor based on the measured pressure information. Based on this signal, the processor forcibly cuts off the power to the electromagnet SV1 of the load holding valve 2, thereby putting the load holding valve 2 in the right working state, and also preventing the hydraulic oil in the first oil channel 11 from flowing back to the oil inlet A, ensuring that the fork and the load stay in their original position and avoiding danger.

[0049] In summary, the hydraulic system, under the action of the lift cylinder bottom valve group, can operate stably and safely under various working conditions, meeting various needs such as fork lifting, lowering, load holding and emergency handling.

[0050] In another aspect, the present invention further provides a method for controlling a cargo fork using the above-mentioned lift cylinder bottom valve assembly. The control method may include: Step 1: Get the lifting command; Step 2: Start the oil pump to pump hydraulic oil into the bottom valve group of the lifting cylinder; Step 3: Determine whether the load is impacted; Step 4: When it is determined that the load is impacted, the overload valve 4 is driven to open; Step 5: Determine whether the emergency descent command is obtained; Step 6: When it is determined that the emergency descent command has been obtained, the emergency descent solenoid valve 3 is driven to open; Step 7: Get the descent command; Step 8: Control the load holding valve 2 to the left position to switch the flow direction of the hydraulic oil.

[0051] The control method of the present invention is based on the lift cylinder bottom valve group to achieve intelligent lifting control of the fork. It can be understood that it can also be combined with sensor detection, electronic control logic and solenoid valves to work together to ensure the safety and stability of the hydraulic system and forklift.

[0052] Specifically, in step 1, a lifting command is obtained. The driver can send a lifting signal via a joystick or button in the cab, or the AGV controller can issue a command. The lifting command is transmitted to the vehicle's CPU via the CAN bus or hardwired.

[0053] In step 2, the oil pump is activated to pump hydraulic oil into the lift cylinder's bottom valve assembly. Upon receiving the lift command, the vehicle's CPU outputs a signal to drive the oil pump motor, regulating the pump's output flow and pressure. Hydraulic oil flows from the pump outlet through the lift cylinder's bottom valve assembly into the rodless chamber of the lift cylinder 7, pushing the piston rod out and raising the forks. In this embodiment, the oil pump can be a negative-swing plunger pump.

[0054] In steps 3 and 4, a determination is made as to whether the load has been impacted. If so, overload valve 4 is actuated to open. This can be determined by installing a pressure sensor 6 to monitor the pressure at oil inlet A in real time. If pressure fluctuations exceed a threshold, an impact is detected. Alternatively, an acceleration sensor can be installed on the forks to detect abnormal vibration signals. The vehicle's CPU compares the sensor data with a preset safety range and triggers overload protection.

[0055] In steps five and six, it is determined whether an emergency descent command has been obtained. When it is determined that an emergency descent command has been obtained, the emergency descent solenoid valve 3 is driven to open. 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 oil inlet A pressure sensor 6 detects a sudden pressure drop 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 position working state, and the hydraulic oil slowly flows back to the hydraulic oil tank through the emergency descent solenoid valve 3, the throttle hole 5 and the return oil port T, thereby achieving a controllable emergency descent.

[0056] In steps 7 and 8, a descending instruction is obtained, and the load holding valve 2 is controlled to be turned on to switch the flow direction of the hydraulic oil. Specifically, the driver can send a descending signal through the joystick / button in the cab. After the vehicle processor CPU receives the descending instruction, it controls the electromagnet SV1 of the load holding valve 2 to be energized, so that the load holding valve 2 is in the left working state. At this time, the hydraulic oil in the lifting cylinder 7 can flow back to the oil port of the negative swing angle pump 8 through the first oil channel 11 and the return oil inlet A. The returning hydraulic oil drives the negative swing angle pump 8 to rotate in the opposite direction, converting the oil pressure energy into mechanical energy, and then generating electricity through the motor to achieve energy recovery.

[0057] 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 technical concept of the present invention, the technical solution of the present invention may be subjected to various simple modifications, including combining the specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not further describe various possible combinations. However, these simple modifications and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

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

2. The lift cylinder bottom valve assembly according to claim 1, characterized in that: The lifting cylinder bottom valve group also includes: A third oil passage (13), both ends of which are respectively connected to the oil outlet (A1) and the oil return port (T); The overload valve (4) is provided on the third oil passage (13) and is used for conducting when the load is impacted so that the hydraulic oil can be unloaded and returned through the oil return port (T).

3. The lift cylinder bottom valve assembly according to claim 1, characterized in that: The lifting cylinder bottom valve group further comprises a throttle hole (5), and both ends of the throttle hole (5) are respectively connected to the emergency lowering solenoid valve (3) and the oil return port (T).

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

5. The lift 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 arranged on the top of the valve group 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 lift cylinder bottom valve assembly according to claim 1, characterized in that: The lifting cylinder bottom valve group also includes: A first working oil port (A2) is connected to the oil outlet (A1); a second working oil port (A3) connected to the oil outlet (A1) and the first working oil port (A2) respectively; The third working oil port (A4) is communicated with the oil inlet (A) and the load holding valve (2) respectively.

7. The lift cylinder bottom valve assembly according to claim 6, characterized in that: The lifting cylinder bottom valve group further includes a pressure sensor (6), and the pressure sensor (6) is arranged on the third working oil port (A4).

8. A hydraulic system, characterized in that: include: Two lifting cylinders (7), wherein the output ends of the lifting cylinders (7) are connected to corresponding forks; Two lifting cylinder bottom valve groups according to any one of claims 1 to 7, wherein the two lifting cylinder bottom valve groups are respectively arranged at the bottom ends of the two lifting cylinders (7); A negative swing angle pump (8), wherein the oil outlet (A1) of the negative swing angle pump (8) is respectively connected to the oil inlet (A) of the two lifting cylinder bottom valve groups.

9. The hydraulic system according to claim 8, characterized in that The hydraulic system further comprises a joint (14) and a steel pipe (9) connected in sequence, and the two lifting cylinder bottom valve groups are connected to each other via the joint (14) and the steel pipe (9).

10. A method for controlling a cargo fork using the lift cylinder bottom valve assembly according to claim 2, characterized in that: include: Get lifting instructions; Control the oil pump to start and pump hydraulic oil into the lift cylinder bottom valve group; Determine whether the load is subjected to impact; When it is determined that the load is subjected to an impact, the overload valve (4) is driven to open; Determine whether to obtain the emergency descent instruction; When it is determined that the emergency descent instruction has been obtained, the emergency descent solenoid valve (3) is driven to open; Get the descent command; The load holding valve (2) is controlled to be energized and open to switch the flow direction of the hydraulic oil.

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