Forklift fork height control method, device and forklift truck

Abstract

The application discloses a pallet fork height control method and device and a pallet truck. The method is applied to the pallet truck, and the pallet truck comprises a vehicle body, a lifting hydraulic system and a pallet fork. The vehicle body is provided with a lifting selection switch and a cargo detection device. The method comprises the following steps: entering an automatic lifting process; in the automatic lifting process, when the lifting selection switch is in a lifting gear state, it is judged whether the cargo detection device detects the cargo at a set height. If yes, the lifting hydraulic system is controlled to stop running. Otherwise, the lifting hydraulic system is controlled to drive the pallet fork to rise after a preset buffer duration. In the automatic lifting process, when the lifting selection switch is in a descending gear state, it is judged whether the cargo detection device detects the cargo at the set height. If yes, the lifting hydraulic system is controlled to drive the pallet fork to descend after the preset buffer duration. Otherwise, the lifting hydraulic system is controlled to stop running. The method can reduce the labor intensity of the workers.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of forklifts, in particular to a forklift truck fork height control method and device and forklift truck. BACKGROUND

[0002] With the rapid development of the logistics industry, pallet trucks are being used more and more widely, and the demand for semi-automatic control for specific industry applications is also increasing.

[0003] In a typical forklift truck, the height of the forks is manually adjusted, which results in a high labor intensity for the workers.

[0004] Therefore, how to reduce the labor intensity of the workers is a technical problem that needs to be solved by those skilled in the art. SUMMARY

[0005] Therefore, the present application aims to provide a forklift truck fork height control method and device that can reduce the labor intensity of the workers. Another object of the present application is to provide a forklift truck that applies the above control method and can reduce the labor intensity of the workers.

[0006] To achieve the above objects, the present application provides the following technical solutions.

[0007] A forklift truck fork height control method is applied to a forklift truck, which includes a vehicle body, a lifting hydraulic system, and forks connected to the output end of the lifting hydraulic system and the vehicle body. The vehicle body is provided with a lifting selection switch and a cargo detection device.

[0008] The control method comprises:

[0009] entering an automatic lifting process;

[0010] In the automatic lifting process, when the lifting selection switch is in a lifting gear position, it is determined whether the cargo detection device detects cargo at a set height. If yes, the lifting hydraulic system is controlled to stop running, otherwise, the lifting hydraulic system is controlled to drive the forks to rise after a preset buffer time.

[0011] In the automatic lifting process, when the lifting selection switch is in a lowering gear position, it is determined whether the cargo detection device detects cargo at the set height. If yes, the lifting hydraulic system is controlled to drive the forks to lower after the preset buffer time, otherwise, the lifting hydraulic system is controlled to stop running.

[0012] Preferably, the control method further comprises:

[0013] determining whether the preset operation of the truck is in a stop state and the truck is in a parking state, and if so, entering the automatic lifting process.

[0014] Preferably, the vehicle body is further provided with limit switches, including a lifting limit switch and a lowering limit switch arranged below the lifting limit switch.

[0015] The control method comprises:

[0016] If at least one of the limit switches detects the forks, the lifting hydraulic system is controlled to stop running.

[0017] Preferably, after the lifting hydraulic system runs continuously for one time, it waits for a preset waiting time, and then determines whether the goods detection device detects goods at the set height.

[0018] Preferably, the control method further comprises:

[0019] If the single continuous running time of the lifting hydraulic system exceeds a preset safety time, the lifting hydraulic system is controlled to stop running.

[0020] Preferably, the control method further comprises:

[0021] After determining that the goods detection device detects goods from the time when the limit switch detects the forks, a running prompt information is sent.

[0022] A truck fork height control device is applied to a truck, the truck comprising a vehicle body, a lifting hydraulic system, and forks connected to the output end of the lifting hydraulic system and the vehicle body, the vehicle body being provided with a lifting selection switch and a goods detection device.

[0023] The control device comprises:

[0024] A lifting module is configured to, in the automatic lifting process, when the lifting selection switch is in a lifting gear, determine whether the goods detection device detects goods at a set height, if so, control the lifting hydraulic system to stop running, otherwise, control the lifting hydraulic system to drive the forks to rise after a preset buffer time.

[0025] A lowering module is configured to, in the automatic lifting process, when the lifting selection switch is in a lowering gear, determine whether the goods detection device detects goods at the set height, if so, control the lifting hydraulic system to drive the forks to lower after the preset buffer time, otherwise, control the lifting hydraulic system to stop running.

[0026] Preferably, the vehicle body is further provided with limit switches, including a lifting limit switch and a lowering limit switch arranged below the lifting limit switch.

[0027] The control device comprises:

[0028] A judging module is configured to judge whether at least one of the limit switches detects the forks, and if so, control the lifting hydraulic system to stop running.

[0029] Preferably, the control device further comprises:

[0030] A safe running module is configured to control the lifting hydraulic system to stop running when a single continuous running duration of the lifting hydraulic system exceeds a preset safe duration.

[0031] A trolley is provided, which applies the control method as described above.

[0032] The trolley fork height control method provided by the application can control the lifting of the forks through the lifting selection switch, and can detect the goods on the forks through the goods detection device, so that the trolley can lift the forks in combination with the goods taking and placing conditions, improve the automation degree of the lifting of the forks, and does not need to manually push the forks to lift, so that the staff does not need to bear the weight of the forks, can effectively reduce the labor intensity of the staff, and improve the use efficiency and safety of the trolley. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only constitute the embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of the provided drawings.

[0034] Figure 1 A circuit diagram of the trolley fork height control provided by the application;

[0035] Figure 2 A structural schematic diagram of the trolley provided by the application;

[0036] Figure 3 A structural diagram of the trolley provided by the application when entering the lifting waiting state;

[0037] Figure 4 A structural diagram of the trolley provided by the application when the upper goods are taken away during the lifting process;

[0038] Figure 5 A structural diagram of the trolley provided by the application when the second layer goods are lifted to the top layer during the lifting process;

[0039] Figure 6 The flow chart of the control method provided by the present application.

[0040] Reference signs:

[0041] Vehicle body 1, fork 2, lifting selection switch 3, lifting gear 31, lowering gear 32, cargo detection device 4, logic controller 5, lifting motor 6, lifting motor contactor 7, coil 71, contact 72, lowering electromagnetic valve 8, lifting limit switch 9, lowering limit switch 10, buzzer 11, indicator light 12, emergency stop switch 13, power supply 14, travel controller 15, start switch 16, fuse 17, travel-related input signal 18, travel-related output signal 19. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of the present application.

[0043] The core of the present application is to provide a forklift fork height control method and device, which can reduce the labor intensity of workers. Another core of the present application is to provide a forklift applying the above control method, which can reduce the labor intensity of workers.

[0044] The forklift fork height control method provided by the present application, please refer to Figures 1 to 5 , applied to a forklift, the forklift comprising a vehicle body 1, a lifting hydraulic system and a fork 2 connected to the output end of the lifting hydraulic system and the vehicle body 1. The inside of the vehicle body 1 is provided with a lifting selection switch 3 and a cargo detection device 4. The forklift fork height control method is realized by a forklift fork height control device applying the method. The forklift fork height control device comprises a logic controller, and the lifting hydraulic system, the lifting selection switch 3 and the cargo detection device 4 are electrically connected to the logic controller.

[0045] The control method comprises:

[0046] S1: entering an automatic lifting process;

[0047] S2: in the automatic lifting process, when the lifting selection switch is in the lifting gear state, it is judged whether the cargo detection device detects the cargo at the set height, if yes, the lifting hydraulic system is controlled to stop running, otherwise, the lifting hydraulic system is controlled to drive the fork to rise after a preset buffer time;

[0048] S3: In the automatic lifting process, when the lifting selection switch is in the descending gear, it is determined whether the goods detection device detects goods at the set height, if yes, the lifting hydraulic system is controlled to lower the forks after a preset buffer time, otherwise, the lifting hydraulic system is controlled to stop running.

[0049] The response to the instruction of the lifting selection switch 3 includes: when the lifting selection switch 3 is in the lifting gear 31, the lifting hydraulic system is controlled to lift the forks 2, and when the lifting selection switch 3 is in the descending gear 32, the lifting hydraulic system is controlled to lower the forks 2.

[0050] The selectable gears of the lifting selection switch 3 include the lifting gear 31 and the descending gear 32 connected in parallel. Specifically, the lifting selection switch 3 includes a lifting button and a descending button. When the lifting button is pressed, the lifting selection switch 3 is in the lifting gear 31, and the lifting subsystem is operated by the logic controller 5, so that the lifting hydraulic system lifts the forks 2. When the descending button is pressed, the lifting selection switch 3 is in the descending gear 32, and the descending subsystem is operated by the logic controller 5, so that the lifting hydraulic system lowers the forks 2.

[0051] The set height is usually the height of taking and placing goods, such as Figures 3 to 5 the lifting process shown in FIG. 6, Figure 3 the top layer of goods is at the height of taking and placing goods, and the goods taking and placing device can take the goods at this height. Specifically, after the goods detection device 4 detects goods at the set height, the goods taking and placing device is controlled to take the goods. After the goods detection device 4 cannot detect goods, it is considered that the goods have been taken away. Then, as shown in Figure 4 the forks 2 are controlled to rise after a preset buffer time. After the goods detection device 4 detects goods at the set height again, the forks stop rising, so that Figure 3 the second layer of goods in FIG. 6 rises to the height of taking and placing goods, and the next taking operation is performed. In the descending process, after the bottom layer of goods is placed on the forks 2, the goods detection device 4 detects goods at the set height. After a preset buffer time, the forks 2 are controlled to descend. After the goods detection device 4 cannot detect goods, the forks stop descending, so as to leave space at the set height for placing the bottom layer of goods.

[0052] The goods detection device 4 is specifically a photoelectric distance measuring switch, preferably a diffuse reflection photoelectric switch, which has good detection effect. The goods detection device 4 is installed on the side of the vehicle body 1 to detect whether there is goods on the uppermost layer of the forks 2. Specifically, when there is goods, the goods detection device 4 outputs a high signal to the logic controller 5, and when there is no goods, the goods detection device 4 outputs a low signal to the logic controller 5. In addition, the logic controller triggers the edge jump signal of the goods detection device 4, which has strong signal recognition and high control reliability.

[0053] The control method provided by the embodiment can control the lifting of the forks through the lifting selection switch 3, and can detect the goods on the forks through the goods detection device 4, so that the trolley can lift the forks 2 in combination with the taking and placing of the goods, the automation degree of lifting the forks 2 is improved, the forks 2 do not need to be manually pushed to lift, the staff does not need to bear the weight of the forks 2, the labor intensity of the staff can be effectively reduced, and the use efficiency and safety of the trolley are improved.

[0054] Further, the control method further comprises: judging whether the preset operation of the trolley is in a stop state and the trolley is in a parking state, and if yes, entering an automatic lifting process.

[0055] In the control device, a starting switch 16 electrically connected between the power supply 14 and the logic controller 5 is included, after the starting switch 16 is closed, the logic controller 5 is powered on to perform the self-checking process, otherwise, the logic controller 5 is powered off.

[0056] The preset operation can be determined according to actual needs, and specifically should include various operations that will interfere with the lifting of the forks 2, or various manual operation instructions. In addition, the logic controller and the vehicle body keep real-time communication, and if any manual operation is triggered during the operation, the automatic lifting process stops and exits the process.

[0057] This step is the self-checking process of the control device, through the setting of the self-checking process, the safety of the lifting operation of the forks 2 can be improved.

[0058] Further, the inside of the vehicle body 1 is also provided with limit switches, the limit switches include a lifting limit switch 9 and a descending limit switch 10 arranged below the lifting limit switch 9. Each limit switch is electrically connected to the logic controller.

[0059] Correspondingly, the control method further comprises: judging whether at least one limit switch detects the forks 2, and if yes, controlling the lifting hydraulic system to stop running.

[0060] Each limit switch positions the forks 2 by detecting a specific position of the forks 2. For example, the lifting limit switch 9 detects the top surface of the forks 2, and the descending limit switch 10 detects the bottom surface of the forks 2. Alternatively, an infrared emitter is arranged on a specific position of the side surface of the forks 2, and the lifting limit switch 9 and the descending limit switch 10 are arranged as receivers cooperating with the infrared emitter, and when the light of the infrared emitter is received, the forks 2 are detected.

[0061] Preferably, the logic controller adopts an electronic working buffer function to make the action of the lifting hydraulic system stop smoothly. In addition, the forks 2 are lowered to be 100 mm higher than the ground, to prevent the foot of the operator from being pressed during the descending operation.

[0062] By setting the limit switch, the limit position of the lifting movement of the fork 2 can be limited, so that the fork 2 can stop moving in time after lifting to the limit position.

[0063] Further, the control method further comprises: after the lifting hydraulic system is continuously operated once, waiting for a preset waiting time length, and then performing the operation of judging whether the goods detection device detects goods at the set height.

[0064] By setting the preset waiting time length, when a single lifting or lowering operation is completed, there is a forced safety time to prevent external operation interference from causing frequent lifting or lowering processes. During the safety time, the logic controller 5 does not respond to the signal of the goods detection device 4, and after the safety time, the signal of the goods detection device 4 is responded again.

[0065] Further, the control method further comprises: when the single continuous operation time length of the lifting hydraulic system exceeds the preset safety time length, controlling the lifting hydraulic system to stop running.

[0066] By setting the preset safety time length, even if the signal of the goods detection device 4 fails, the lifting operation can be smoothly stopped, and the safety of the truck operation can be improved.

[0067] Further, the control method further comprises: issuing a running prompt information from the time when the goods detection device 4 detects the goods to the time when the limit switch detects the fork 2 last time.

[0068] The truck fork height control device further comprises a reminding device electrically connected to the logic controller 5. The reminding device specifically comprises at least one of an indicator light and a buzzer 11. The reminding device can prompt the staff that the fork 2 is about to or is in lifting movement, further improving the safety of the truck use.

[0069] In addition to the above truck fork height control method, the application also provides a truck fork height control device, which applies the above control method, and specifically can provide the control method of any one of the above embodiments.

[0070] The control device is applied to a truck, and the truck comprises a vehicle body, a lifting hydraulic system, and a fork connected to the output end of the lifting hydraulic system and the vehicle body. The vehicle body is provided with a lifting selection switch and a goods detection device.

[0071] The control device comprises:

[0072] The lifting module is configured to determine whether the goods detection device detects goods at the set height in the automatic lifting process when the lifting selection switch is in the lifting gear, and if so, control the lifting hydraulic system to stop running, otherwise, control the lifting hydraulic system to drive the forks to rise after a preset buffer time.

[0073] The lowering module is configured to determine whether the goods detection device detects goods at the set height in the automatic lifting process when the lifting selection switch is in the lowering gear, and if so, control the lifting hydraulic system to drive the forks to lower after the preset buffer time, otherwise, control the lifting hydraulic system to stop running.

[0074] Further, the vehicle body is further provided with limit switches, including a lifting limit switch and a lowering limit switch arranged below the lifting limit switch. Correspondingly, the control device includes a judgment module configured to determine whether at least one of the limit switches detects the forks, and if so, control the lifting hydraulic system to stop running.

[0075] Further, the pallet truck fork height control device further includes a safe running module configured to control the lifting hydraulic system to stop running when the single continuous running time of the lifting hydraulic system exceeds a preset safe time.

[0076] Further, the pallet truck fork height control device further includes a lifting motor contactor 7 electrically connected to the logic controller 5, and the lifting hydraulic system includes a lifting motor 6. After the lifting selection switch 3 is switched to the lifting gear 31, the logic controller 5 turns on the coil 71 of the lifting motor contactor 7 and the power supply 14, so that the contact 72 of the lifting motor contactor 7 is closed to connect the lifting motor 6 and the power supply 14. Through the setting of the lifting motor contactor 7, the on-off control of the lifting motor 6 can be conveniently realized. Specifically, after the lifting motor 6 is powered on, the lifting motor 6 drives the oil pump to supply oil to the hydraulic cylinder to drive the forks 2 to rise.

[0077] Further, the pallet truck fork height control device further includes a lowering solenoid valve 8 electrically connected to the logic controller 5, and the lowering solenoid valve 8 is arranged in the oil discharge circuit of the lifting hydraulic system. After the lifting selection switch 3 is switched to the lowering gear 32, the lowering solenoid valve 8 conducts the oil discharge circuit, so that the hydraulic cylinder returns oil to make the forks 2 descend under the action of gravity.

[0078] Further, the logic controller 5 and the power supply 14 are connected in series with an emergency stop switch 13, and the emergency stop switch 13 can be opened to cut off the power supply of the logic controller 5. When the emergency stop switch 13 is pressed, the operator can quickly cut off the power supply 14 of the logic controller 5, and the lifting hydraulic system will stop running.

[0079] Furthermore, the pallet truck fork height control device also includes a travel controller 15 electrically connected to the logic controller 5, and the travel controller 15 is electrically connected to the travel drive device of the vehicle body 1. The travel controller 15 is used to control the travel drive device that drives the vehicle body 1 forward. Through the electrical connection between the travel controller 15 and the logic controller 5, the logic controller 5 can directly obtain the operating status of the travel drive device to determine whether the vehicle body 1 is in a parked state.

[0080] In addition to the aforementioned method and device for controlling the fork height of the transport vehicle, this invention also provides a transport vehicle that applies a control method, specifically the control method provided in any of the above embodiments. The beneficial effects can be referred to the respective embodiments above. The structure of other parts of the transport vehicle is described in the prior art and will not be repeated here.

[0081] A specific workflow of the transport vehicle provided in this embodiment includes:

[0082] Self-test process: After pressing the start switch 16 and activating the lifting selection switch 3, the logic controller 5 will activate the automatic lifting control program. The indicator light 12 connected in series with the start switch 16 will light up, and the buzzer 11 will sound for 2 seconds to indicate that the control device has been started. The logic controller 5 will activate the automatic control program and enter the self-test step. The automatic lifting process or automatic lowering process will only begin when all manual operation commands of the transport vehicle are in the stop state, the transport vehicle is in the parking state, and the vehicle speed is zero.

[0083] Automatic Lifting Process: When the lifting selector switch 3 is in the lifting position 31, the control device executes the automatic lifting subsystem, and the logic controller 5 enters a waiting process. At this time, if the distance signal from the cargo detection device 4 changes from high to low, the logic controller 5 triggers the buzzer 11 to indicate that the forks 2 are about to lift. After a preset buffer time, the logic controller 5 starts controlling the lifting motor contactor 7. The lifting motor contactor 7 connects the power circuit of the lifting motor 6, causing the lifting motor 6 to lift the forks 2. Simultaneously, the buzzer 11 sounds to alert the operator. When the distance signal from the cargo detection device 4 changes from low to high during the lifting process, it indicates that the forks 2 have reached the predetermined height, and the logic controller 5 stops the lifting motor 6 and the buzzer 11. When the lifting limit switch 9 is detected to be active during the above lifting process, it indicates that the forks 2 have been lifted to the set maximum position, and the logic controller 5 stops the lifting motor 6 and the buzzer 11. To ensure safety and prevent excessive lifting due to malfunction of the cargo detection device 4, the lifting process has a set maximum running time, i.e., a preset safety time. When the preset safety time is reached, the logic controller 5 controls the lifting motor 6 and the buzzer 11 to stop working. After the forks 2 complete a single lifting operation, there is a preset waiting time, which is a forced safety time to prevent frequent execution of the lifting process due to external operational interference. During the preset waiting time, the logic controller 5 does not respond to the signal from the cargo detection device 4, and after the preset waiting time, it re-enters the waiting process.

[0084] Automatic descent function: When the lifting selector switch 3 is in the descent position 32, the control device executes the automatic descent subsystem, and the logic controller 5 enters a waiting process. If the distance signal from the cargo detection device 4 changes from low to high, the logic controller 5 triggers the buzzer 11 to indicate that the forks 2 are about to move. After a preset buffer time, the logic controller 5 starts controlling the descent solenoid valve 8, and the forks 2 begin to descend. Simultaneously, the buzzer 11 alerts the operator. If, during descent, the distance signal from the cargo detection device 4 changes from high to low, it indicates that the forks 2 have descended to the predetermined height. The controller then stops the descent solenoid valve 8 and the buzzer 11, halting the descent. If, during descent, the descent limit switch 10 is activated, the logic controller 5 stops the descent solenoid valve 8 and the buzzer 11, stopping the descent. To ensure safety and prevent the cargo detection device 4 from malfunctioning and causing the descent height to be too low, the descent process has a set maximum running time, i.e., a preset safety time. When the preset safety time is reached, the logic controller 5 controls the descent solenoid valve 8 and the buzzer 11 to stop working. After the forks 2 complete a single descent, there is a preset waiting time, which is a forced safety time to prevent external operational interference from causing frequent execution of the lifting process. During the preset waiting time, the logic controller 5 does not respond to the signal from the cargo detection device 4, and after the preset waiting time, it re-enters the waiting process.

[0085] It should be noted that when an element is referred to as "fixing" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as "connecting" another element, it can be directly connected to the other element or there may be an intervening element. The terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0086] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0087] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0088] The fork height control method, device, and transport vehicle provided by this invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. A method for controlling the height of the forks of a pallet truck, characterized in that, The application is to a transport vehicle, which includes a vehicle body (1), a lifting hydraulic system and forks (2) connected to the output end of the lifting hydraulic system and the vehicle body (1). The vehicle body (1) is provided with a lifting selection switch (3) and a cargo detection device (4). The control method includes: Enter automatic lifting process; In the automatic lifting process, when the lifting selection switch (3) is in the lifting position (31), it is determined whether the cargo detection device (4) has detected cargo at the set height. If so, the lifting hydraulic system is controlled to stop running; otherwise, the lifting hydraulic system is controlled to drive the forks (2) to rise after a preset buffer time. In the automatic lifting process, when the lifting selection switch (3) is in the lowering position (32), it is determined whether the cargo detection device (4) has detected cargo at the set height. If so, the lifting hydraulic system is controlled to drive the fork (2) to descend after the preset buffer time. Otherwise, the lifting hydraulic system is controlled to stop running. During the lifting process, when the cargo detection device (4) detects cargo at a set height, it controls the picking and placing equipment to pick up the cargo. When the cargo detection device (4) fails to detect cargo, it waits for a preset buffer time and then controls the forks (2) to rise until the cargo detection device (4) detects cargo again at the set height. Then the forks (2) stop rising and pick up cargo from the next layer. During the lowering process, after the bottom layer of cargo is placed on the forks (2), the cargo detection device (4) detects cargo at a set height. After a preset buffer time, it controls the forks (2) to descend. When the cargo detection device (4) fails to detect cargo, the forks stop descending so that cargo from the next layer can be placed at the set height. The set height is the picking and placing height. The vehicle body (1) is also provided with a limit switch, which includes a lifting limit switch (9) and a lowering limit switch (10) located below the lifting limit switch (9) to limit the extreme positions of the lifting and lowering movement of the forks (2). It also includes: determining whether at least one of the limit switches detects the fork (2), and if so, controlling the lifting hydraulic system to stop operating; It also includes: determining whether the preset operation of the transport vehicle is a stopped state and the transport vehicle is in a parked state; if so, proceeding to the automatic lifting process. The lifting hydraulic system runs continuously once and waits for a preset waiting time before determining whether the cargo detection device (4) has detected cargo at a set height. It also includes: when the continuous operation time of the lifting hydraulic system exceeds a preset safe time, controlling the lifting hydraulic system to stop operating; It also includes issuing a running prompt message from the moment the cargo detection device (4) detects cargo until the most recent time the limit switch detects the fork (2).

2. A fork height control device for a pallet truck, characterized in that, Applied to a pallet truck, and to the pallet truck fork height control method according to claim 1, the pallet truck includes a vehicle body (1), a lifting hydraulic system and forks (2) connected to the output end of the lifting hydraulic system and the vehicle body (1), and the vehicle body (1) is provided with a lifting selection switch (3) and a cargo detection device (4); The control device includes: The lifting module is used to determine whether the cargo detection device (4) has detected cargo at a set height when the lifting selection switch (3) is in the lifting position (31) during the automatic lifting process. If yes, the lifting hydraulic system is controlled to stop running; otherwise, the lifting hydraulic system is controlled to drive the forks (2) to rise after a preset buffer time. The descent module is used to determine whether the cargo detection device (4) has detected cargo at the set height when the lifting selection switch (3) is in the descent position (32) during the automatic lifting process. If so, the lifting hydraulic system is controlled to drive the fork (2) to descend after the preset buffer time. Otherwise, the lifting hydraulic system is controlled to stop running. During the lifting process, when the cargo detection device (4) detects cargo at a set height, it controls the picking and placing equipment to pick up the cargo. When the cargo detection device (4) fails to detect cargo, it waits for a preset buffer time and then controls the forks (2) to rise until the cargo detection device (4) detects cargo again at the set height. Then the forks (2) stop rising and pick up cargo from the next layer. During the lowering process, after the bottom layer of cargo is placed on the forks (2), the cargo detection device (4) detects cargo at a set height. After a preset buffer time, it controls the forks (2) to descend. When the cargo detection device (4) fails to detect cargo, the forks stop descending so that cargo from the next layer can be placed at the set height. The set height is the picking and placing height. The vehicle body (1) is also provided with a limit switch, which includes a lifting limit switch (9) and a lowering limit switch (10) located below the lifting limit switch (9) to limit the extreme positions of the lifting and lowering movement of the forks (2). The control device includes: The judgment module is used to determine whether at least one of the limit switches detects the fork (2), and if so, controls the lifting hydraulic system to stop running; It also includes a safety operation module, used to control the lifting hydraulic system to stop operating when the duration of a single continuous operation of the lifting hydraulic system exceeds a preset safety time.

3. A transport vehicle, characterized in that, The control method described in claim 1 is applied.

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