Industrial vehicle steering system

Abstract

To provide an industrial truck steering device capable of suppressing affection to actuation of a steering cylinder, according to operation of the steering wheel by hydraulic oil supplied through a circuit for automatic steering.SOLUTION: An industrial truck steering device comprises: a circuit for manual steering for supplying hydraulic oil to a steering cylinder according to operation of the steering wheel; a circuit for automatic steering for supplying the hydraulic oil to the steering cylinder according to a calculation result of automatic drive control; a priority valve for supplying preferentially the hydraulic oil to the circuit for manual steering at a flow rate equal to or greater than a prescribed flow rate for actuating the steering cylinder, and supplying the hydraulic oil to the circuit for automatic steering at a second flow rate being an excessive flow rate obtained by excluding the first flow rate from the hydraulic oil discharged from a hydraulic pump; and supply restriction means for restricting supply of the hydraulic oil to the steering cylinder through the circuit for automatic steering, when detecting operation of the steering wheel by a steering operation detection part.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a steering device for an industrial vehicle. [Background technology]

[0002] BACKGROUND ART Conventionally, as a technique related to a steering device for an industrial vehicle, a vehicle steering control device that selectively switches between a manual steering mode and an automatic steering mode by a hydraulic switching means using a directional control valve is known (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-254801 Summary of the Invention [Problem to be solved by the invention]

[0004] In a steering device for an industrial vehicle that includes a manual steering circuit that supplies hydraulic oil to a steering cylinder in response to steering wheel operation, an automatic steering circuit that supplies hydraulic oil to the steering cylinder in accordance with the results of automatic driving control calculations, and a flow divider valve that divides the hydraulic oil between the manual steering circuit and the automatic steering circuit, it is possible to configure the flow divider valve to supply hydraulic oil discharged from a hydraulic pump to the manual steering circuit at a first flow rate and to supply hydraulic oil to the automatic steering circuit at a second flow rate that is a surplus flow rate of hydraulic oil discharged from the hydraulic pump excluding the first flow rate. In this case, for example, if the steering wheel is operated while hydraulic oil is being supplied to the steering cylinder in accordance with the results of automatic driving control calculations, the hydraulic oil supplied via the automatic steering circuit may affect the operation of the steering cylinder in response to the steering wheel operation.

[0005] The present invention aims to provide a steering device for an industrial vehicle that can suppress the influence of hydraulic oil supplied via an automatic steering circuit on the operation of a steering cylinder in response to the operation of a steering wheel. [Means for solving the problem]

[0006] A steering device for an industrial vehicle according to one aspect of the present invention is a steering device for an industrial vehicle equipped with a hydraulic pump that discharges hydraulic oil, and a steering cylinder that is actuated by the supply of hydraulic oil to steer the steering wheels, and includes a manual steering circuit having a first valve that is opened and closed in response to the operation of the steering wheel, and supplies the hydraulic oil discharged from the hydraulic pump to the steering cylinder via the first valve, an automatic steering circuit having a second valve that is opened and closed in response to the calculation result of automatic driving control, and supplies the hydraulic oil discharged from the hydraulic pump to the steering cylinder via the second valve, and an automatic steering circuit disposed between the hydraulic pump and the first and second valves, and supplies the hydraulic oil to the manual steering circuit. The hydraulic control system is equipped with a flow dividing valve that divides the flow into a manual steering circuit and an automatic steering circuit, and a steering operation detection unit that detects the operation of the steering wheel.The flow dividing valve is a priority valve that supplies hydraulic oil to the manual steering circuit preferentially at a first flow rate that is equal to or greater than a predetermined flow rate for operating the steering cylinder from the hydraulic pump, and supplies hydraulic oil to the automatic steering circuit at a second flow rate that is the surplus flow rate of the hydraulic oil discharged from the hydraulic pump excluding the first flow rate, and further includes a supply limiting means that limits the supply of hydraulic oil to the steering cylinder via the automatic steering circuit when the steering operation detection unit detects the operation of the steering wheel.

[0007] In a steering device for an industrial vehicle according to one aspect of the present invention, the flow divider valve supplies hydraulic oil to the automatic steering circuit at a second flow rate if there is an excess flow rate, even when the steering wheel is operated. The supply of hydraulic oil to the steering cylinder via the automatic steering circuit is limited by the supply limiting means when the steering operation detection unit detects steering wheel operation. As a result, when the steering wheel is operated, operation of the steering cylinder by the hydraulic oil supplied to the automatic steering circuit is limited. Therefore, the steering device for an industrial vehicle according to one aspect of the present invention can prevent the hydraulic oil supplied via the automatic steering circuit from affecting the operation of the steering cylinder in response to steering wheel operation.

[0008] In one embodiment, the supply limiting means includes a shut-off valve provided in the automatic steering circuit and a control unit that controls the shut-off valve based on the detection result of the steering operation detection unit, and when the steering operation detection unit detects the operation of the steering wheel, the control unit may control the shut-off valve so that the hydraulic oil from the hydraulic pump is not supplied to the steering cylinder via the shut-off valve. In this case, when the steering wheel is operated, the hydraulic oil supplied to the automatic steering circuit is blocked by the shut-off valve, thereby limiting the operation of the steering cylinder by the hydraulic oil supplied to the automatic steering circuit.

[0009] In one embodiment, the shutoff valve may be at least one of the second valve and a lock valve provided between the second valve and the steering cylinder. In this case, when the steering operation detection unit detects the operation of the steering wheel, at least one of the second valve and the lock valve can be used to shut off the hydraulic oil supplied to the automatic steering circuit.

[0010] In one embodiment, the supply limiting means includes a shutoff flow rate reducing means provided closer to the hydraulic pump than the shutoff valve in the automatic steering circuit, and the control unit may, when the steering operation detection unit detects steering wheel operation, control the shutoff valve so that hydraulic oil is not supplied to the steering cylinder via the shutoff valve, while controlling the shutoff flow rate reducing means to preliminarily reduce the flow rate of hydraulic oil flowing into the shutoff valve. In this case, when the steering operation detection unit detects steering wheel operation, the shutoff valve is controlled so that the flow rate of hydraulic oil flowing into the shutoff valve is preliminarily reduced, and then the shutoff valve is controlled so that hydraulic oil is not supplied to the steering cylinder. This makes it possible to suppress effects (e.g., shocks) caused by the flow rate of hydraulic oil compared to when the shutoff valve is controlled without reducing the flow rate of hydraulic oil flowing into the shutoff valve.

[0011] In one embodiment, the cutoff flow rate reducing means may include an unloading valve that is provided so as to be able to reduce the pressure on the hydraulic pump side of the cutoff valve in the automatic steering circuit. In this case, the unloading valve can be used to reduce the pressure on the hydraulic pump side of the cutoff valve.

[0012] In one embodiment, the supply limiting means includes an unloading valve capable of reducing the pressure of the hydraulic oil in the automatic steering circuit, and a control unit that controls the unloading valve based on the detection result of the steering operation detection unit, and the control unit may control the unloading valve to reduce the pressure of the hydraulic oil in the automatic steering circuit when the steering operation detection unit detects the operation of the steering wheel. In this case, when the steering wheel is operated, the unloading valve is used to reduce the pressure of the hydraulic oil in the automatic steering circuit, thereby limiting the operation of the steering cylinder by the hydraulic oil supplied to the automatic steering circuit.

[0013] In one embodiment, the steering wheel operation may be a predetermined operation of the steering wheel by an operator of the industrial vehicle, and the steering operation detection unit may detect the predetermined operation when the rotation speed of the steering wheel is equal to or less than a predetermined rotation speed threshold. When the steering wheel is operated, the slower the rotation speed of the steering wheel, the smaller the flow rate of hydraulic oil to the steering cylinder via the manual steering circuit, making it more likely that an excess flow rate will occur. Therefore, by detecting the predetermined operation when the rotation speed of the steering wheel is equal to or less than the rotation speed threshold and limiting the supply of hydraulic oil to the steering cylinder via the automatic steering circuit, it is possible to effectively prevent the hydraulic oil supplied via the automatic steering circuit from affecting the operation of the steering cylinder in response to the steering wheel operation. [Effects of the Invention]

[0014] According to the present invention, it is possible to suppress the influence of hydraulic oil supplied via the automatic steering circuit on the operation of the steering cylinder in response to the operation of the steering wheel. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic configuration diagram of an industrial vehicle to which a steering device for an industrial vehicle according to an embodiment is applied; [Figure 2] FIG. 2 is a schematic circuit diagram showing the configuration of the steering hydraulic circuit of FIG. [Figure 3] FIG. 3 is a hydraulic circuit diagram of an example of the electromagnetic proportional valve of FIG. 2. [Figure 4] 2 is a block diagram showing the functional configuration of a steering device of the industrial vehicle of FIG. 1. FIG. [Figure 5] FIG. 2 is a schematic cross-sectional view taken along the axis of the priority valve of FIG. 1. [Figure 6] FIG. 2 is a schematic cross-sectional view taken along the axis of the priority valve of FIG. 1. [Figure 7] 10 is a timing chart showing the flow rate of hydraulic oil to the steering cylinder when no restriction is imposed by the supply restriction means. [Figure 8]10 is a timing chart showing the flow rate of hydraulic oil to the steering cylinder when the flow rate is restricted by the supply restricting means. [Figure 9] 2 is a flowchart illustrating a supply limiting process of the controller of FIG. 1; [Figure 10] 10 is a flowchart illustrating the steering operation detection process of FIG. 9. [Figure 11] 10 is a flowchart showing another example of the supply limiting process of the controller of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are designated by the same reference numerals, and redundant description will be omitted.

[0017] Fig. 1 is a schematic diagram of an industrial vehicle to which a steering device for an industrial vehicle according to one embodiment is applied. The industrial vehicle 1 shown in Fig. 1 is, for example, an electric towing tractor, and is used to tow containers loaded with cargo at airports, factories, ports, etc.

[0018] The industrial vehicle 1 is configured to be able to execute automatic driving control. Automatic driving is a driving state in which vehicle control is executed to make the industrial vehicle 1 travel automatically in accordance with transport commands from, for example, a traffic control system. The traffic control system is a so-called control system that issues transport commands, monitors operation, and monitors the vehicle status for the industrial vehicle 1. In automatic driving, the vehicle travels automatically without the need for a worker to perform driving operations.

[0019] The autonomous driving here is performed in a predetermined area, for example, including an airport runway, takeoff and landing area, taxiway, apron, control tower, hangar, loading and unloading area, charging station, etc. The industrial vehicle 1 is capable of autonomous driving within the predetermined area, based on a predetermined driving route. In this embodiment, a driving plan is generated that includes automatically steering the industrial vehicle 1 at, for example, intersections, etc., according to the calculation results of the autonomous driving control along the predetermined driving route. Note that the driving route of the industrial vehicle 1 is not fixed and can be changed from the predetermined one. An unfixed driving route means a driving route that can be changed by changing a driving plan generated based on map information, etc., rather than a driving route that is difficult to change once set, such as a driving route of an automated guided vehicle (AGV) that runs along a magnetic tape installed on the road surface.

[0020] [Configuration related to driving and steering of industrial vehicle 1] The industrial vehicle 1 is equipped with FL tire 2 and FR tire 3, which are steerable wheels located at the front of the vehicle body, and RL tire 4 and RR tire 5, which are located at the rear of the vehicle body. The industrial vehicle 1 is equipped with a left travel motor 6 that drives the RL tire 4 and a right travel motor 7 that drives the RR tire 5 as travel motors. The travel motors also function as a braking unit 8 that generates regenerative braking force.

[0021] The left traveling motor 6 and the right traveling motor 7 are AC motors that also function as generators. A left drive unit 6a, which is a speed reducer, is interposed between the left traveling motor 6 and the RL tire 4. A right drive unit 7a, which is also a speed reducer, is interposed between the right traveling motor 7 and the RR tire 5.

[0022] The left traveling motor 6 is electrically connected to the contactor 9 via a left motor driver 6b. The right traveling motor 7 is electrically connected to the contactor 9 via a right motor driver 7b. The left motor driver 6b and the right motor driver 7b each have, for example, an inverter, and are electrically connected to a controller (control unit) 10. In the left motor driver 6b and the right motor driver 7b, the power running and regeneration of the left traveling motor 6 and the right traveling motor 7 are controlled by the controller 10.

[0023] The contactor 9 is electrically connected to the battery B and a hydraulic pump 31 of a steering hydraulic circuit (hydraulic circuit) 30. The contactor 9 is electrically connected to a controller 10, and the power supply from the battery B is controlled by the controller 10.

[0024] Battery B is a power supply source for the left traveling motor 6, the right traveling motor 7, and the hydraulic pump 31. Battery B is formed of, for example, a lead storage battery.

[0025] When the left traveling motor 6 is driven to rotate, the driving force of the left traveling motor 6 is transmitted to the RL tire 4 via the left drive unit 6a, causing the RL tire 4 to rotate. When the industrial vehicle 1 is braking, the left traveling motor 6 operates as a generator due to the rotation of the RL tire 4. When the right traveling motor 7 is driven to rotate, the driving force of the right traveling motor 7 is transmitted to the RR tire 5 via the right drive unit 7a, causing the RR tire 5 to rotate. When the industrial vehicle 1 is braking, the right traveling motor 7 operates as a generator due to the rotation of the RR tire 5.

[0026] The industrial vehicle 1 is equipped with an industrial vehicle steering device 100. The industrial vehicle steering device 100 is configured as a hydraulic power steering system that is actuated by the supply of hydraulic oil to steer the steering wheels. FIG. 2 is a schematic circuit diagram showing the configuration of the steering hydraulic circuit of FIG. 1. As shown in FIG. 2, the industrial vehicle steering device 100 is equipped with a contactor 9, a controller 10, a steering hydraulic circuit 30, a hydraulic pump 31, a steering cylinder 32, and a steering wheel 33. The steering hydraulic circuit 30 is a hydraulic circuit configured with a manual steering circuit 40, an automatic steering circuit 50, and a priority valve 60.

[0027] The hydraulic pump 31 is a hydraulic source that discharges hydraulic oil. The hydraulic pump 31 is installed so that it can pump hydraulic oil stored in a tank 34 to the hydraulic pump circuit 30a. As an example, the hydraulic pump 31 is a constant displacement pump configured so that the amount of hydraulic oil discharged during operation (the amount of discharge at the same rotation speed) is constant. The hydraulic pump 31 is electrically connected to the contactor 9, and the rotation speed of the hydraulic pump 31 is controlled by the controller 10 via the contactor 9, thereby controlling the amount of discharge.

[0028] The steering cylinder 32 is actuated by the supply of hydraulic oil to steer the FL tire 2 and FR tire 3, which are the steered wheels. The steering cylinder 32 has a hydraulic oil supply port 32a to the left cylinder for steering the FL tire 2, and a hydraulic oil supply port 32b to the right cylinder for steering the FR tire 3. The supply port 32a is connected by a hydraulic circuit to one junction 30b of the manual steering circuit 40 and the automatic steering circuit 50. The supply port 32b is connected by a hydraulic circuit to the other junction 30c of the manual steering circuit 40 and the automatic steering circuit 50.

[0029] The manual steering circuit 40 has a PS valve (first valve) 41 that is opened and closed in response to the operation of the steering wheel 33. The manual steering circuit 40 is a hydraulic circuit that supplies hydraulic oil discharged from the hydraulic pump 31 to the steering cylinder 32 via the PS valve 41. The PS valve 41 is a so-called power steering valve.

[0030] The automatic steering circuit 50 has a solenoid proportional valve (second valve) 51 that is opened and closed in accordance with the calculation results of the automatic driving control. The automatic steering circuit 50 is a hydraulic circuit that supplies hydraulic oil discharged from the hydraulic pump 31 to the steering cylinder 32 via the solenoid proportional valve 51. The solenoid proportional valve 51 is a so-called oil control valve. The solenoid proportional valve 51 here is a pilot-type solenoid proportional valve that operates an internal spool 53 (see FIG. 3) using the pressure of hydraulic oil from the hydraulic pump 31 acting on the solenoid proportional valve 51 as a pilot pressure. For example, when the spool 53 is set to a neutral position, the solenoid proportional valve 51 stops supplying hydraulic oil from the hydraulic pump 31 to the steering cylinder 32 via the solenoid proportional valve 51. In other words, the solenoid proportional valve 51 is a shutoff valve provided in the automatic steering circuit 50. The solenoid proportional valve 51 is electrically connected to the controller 10, and its opening and closing (position of the spool 53) is controlled by the controller 10. In the following description, for convenience, the state in which hydraulic oil from the hydraulic pump 31 can be supplied to the steering cylinder 32 via the electromagnetic proportional valve 51 may be expressed as "the electromagnetic proportional valve 51 is open," and the state in which hydraulic oil from the hydraulic pump 31 is not supplied to the steering cylinder 32 via the electromagnetic proportional valve 51 may be expressed as "the electromagnetic proportional valve 51 is closed."

[0031] The priority valve 60 is disposed between the hydraulic pump 31 and the PS valve 41 and solenoid proportional valve 51. The priority valve 60 is a flow dividing valve that divides the hydraulic oil supplied from the hydraulic pump 31 via the hydraulic pump circuit 30a into the manual steering circuit 40 on the PS valve 41 side and the automatic steering circuit 50 on the solenoid proportional valve 51 side. The structure related to the flow division of the priority valve 60 will be described in detail later.

[0032] In the manual steering circuit 40, hydraulic oil from the hydraulic pump circuit 30a flows into the PS valve 41 via the priority valve 60, and is supplied to the junctions 30b and 30c via the PS valve 41, which is opened in response to operation of the steering wheel 33. This causes hydraulic oil to be supplied to the steering cylinder 32, and the FL tire 2 and FR tire 3, which are the steered wheels, are steered in response to operation of the steering wheel 33.

[0033] In the automatic steering circuit 50, hydraulic oil from the hydraulic pump circuit 30a flows into the electromagnetic proportional valve 51 via the priority valve 60, and is supplied to the junctions 30b and 30c via the electromagnetic proportional valve 51, which is opened in accordance with the calculation results of the automatic driving control. As a result, hydraulic oil is supplied to the steering cylinder 32, and the FL tire 2 and FR tire 3, which are the steered wheels, are steered in accordance with the calculation results of the automatic driving control.

[0034] In the automatic steering circuit 50, a lock valve 54 is provided between the solenoid proportional valve 51 and the steering cylinder 32. The lock valve 54 is electrically connected to the controller 10. The opening and closing of the lock valve 54 is controlled by the controller 10. When the lock valve 54 is closed, for example, the hydraulic oil from the hydraulic pump 31 is not supplied to the steering cylinder 32 via the lock valve 54. In other words, the solenoid proportional valve 51 is a shut-off valve provided in the automatic steering circuit 50. The lock valve 54 has better hydraulic oil shut-off properties than the spool 53 of the solenoid proportional valve 51. In the example of FIG. 2, lock valves 54 are provided in both the hydraulic circuit labeled C1 and the hydraulic circuit labeled C2 between the solenoid proportional valve 51 and the steering cylinder 32.

[0035] The electromagnetic proportional valve 51 has an unloading valve 52 that is provided so as to be able to reduce the pressure of the hydraulic oil in the automatic steering circuit 50. The unloading valve 52 is connected to the tank 34 via the return circuit 30d. The unloading valve 52 is electrically connected to the controller 10. The operation of the unloading valve 52 is controlled by the controller 10 (details will be described later).

[0036] Fig. 3 is a hydraulic circuit diagram of an example of the electromagnetic proportional valve of Fig. 2. As shown in Fig. 3, the electromagnetic proportional valve 51 includes an unloading pilot valve 52a and a relief valve 52b that constitute an unloading valve 52, and a spool 53. In the electromagnetic proportional valve 51, hydraulic oil is supplied to the unloading pilot valve 52a, the relief valve 52b, and the spool 53 along a main circuit (solid line in Fig. 3) extending from the symbol P. The symbol P in Fig. 3 corresponds to the symbol P in Fig. 2, and is supplied with hydraulic oil diverted by the priority valve 60.

[0037] When the unloading pilot valve 52a is operated by the controller 10, hydraulic oil is supplied to the relief valve 52b via the unloading pilot valve 52a along the pilot circuit (dashed line in FIG. 3), and pilot pressure acts on the relief valve 52b. This causes the relief valve 52b to operate. Symbol T in FIG. 3 corresponds to symbol T in FIG. 2, and is connected to a return circuit 30d that returns hydraulic oil from the solenoid proportional valve 51 to the tank 34. The hydraulic oil from symbol P flows to symbol T via the relief valve 52b (solid line) and is returned to the tank 34 in accordance with the balance between the hydraulic oil pressure at symbol P, the pressure in the tank 34 and the pressure equivalent to the pressure loss up to the tank 34, and the set pressure of the spring of the relief valve 52b.

[0038] The spool 53 is configured to be able to take three spool positions, for example, positions P1, P2, and P3. When the spool 53 is operated by the controller 10, the spool 53 is moved so that the position of the spool 53 becomes one of positions P1, P2, and P3. Position P1 is a spool position where hydraulic oil from symbol P flows to symbol C1. Position P2 is a spool position where hydraulic oil from symbol P flows to symbol C2. Symbols C1 and C2 in FIG. 3 correspond to symbols C1 and C2 in FIG. 2.

[0039] When the spool position is position P1, hydraulic oil from P passes through spool 53 and flows to C1. The hydraulic oil that passes through C1 passes through junction 30c and is supplied to supply port 32b of steering cylinder 32, is discharged from supply port 32a of steering cylinder 32, and passes through junction 30b to return to C2. The hydraulic oil that passes through C2 passes through spool 53 and flows to T and is returned to tank 34.

[0040] When the spool position is position P2, the hydraulic oil from P passes through the spool 53 and flows to C2. The hydraulic oil that passes through C2 passes through the junction 30b and is supplied to the supply port 32a of the steering cylinder 32, is discharged from the supply port 32b of the steering cylinder 32, and passes through the junction 30c and returns to C1. The hydraulic oil that passes through C1 passes through the spool 53 and flows to T and is returned to the tank 34.

[0041] When the spool position is position P3, the hydraulic oil from symbol P does not flow to symbols C1 or C2. In other words, when the spool position is position P3, the spool 53 is in a neutral state.

[0042] The PS valve 41 is connected to the tank 34 by a return circuit 30e. In the PS valve 41, the hydraulic oil that flows into the PS valve 41 via the priority valve 60, but at a flow rate that exceeds the flow rate supplied to the steering cylinder 32, is returned to the tank 34 via the return circuit 30e. Examples of situations in which this occurs include when the steering wheel 33 is not operated, when the operating speed of the steering wheel 33 is relatively slow, and when the operating speed of the steering wheel 33 decreases transiently.

[0043] [Configuration related to automatic driving control and automatic steering of industrial vehicle 1] FIG. 4 is a block diagram showing the functional configuration of the steering device of the industrial vehicle of FIG. 1. The steering device 100 of the industrial vehicle has a controller 10 that manages steering control and automatic driving control of the industrial vehicle 1. The controller 10 is an electronic control unit having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. The controller 10 realizes various functions by, for example, loading a program recorded in the ROM into the RAM and executing the program loaded into the RAM by the CPU. The controller 10 may detect the voltage of battery B. Note that the controller 10 may be composed of multiple electronic units.

[0044] The controller 10 is connected to a GNSS receiver 21, a surrounding condition sensor 22, a driving information sensor 23, a map database 24, and a steering angle sensor (steering operation detection unit) 25.

[0045] The GNSS receiver 21 receives signals from three or more GNSS satellites to measure the position of the industrial vehicle 1 on a map (for example, the latitude and longitude of the industrial vehicle 1). The GNSS receiver 21 transmits the measured position information of the industrial vehicle 1 to the controller 10.

[0046] The surrounding condition sensor 22 is an on-board detector that detects the conditions around the vehicle. The surrounding condition sensor 22 includes a camera and a LiDAR (Light Detection And Ranging). Image information from the camera is used, for example, for road surface pattern recognition and matching. Obstacle information detected by the LiDAR is used, for example, for danger avoidance of the industrial vehicle 1. The surrounding condition sensor 22 transmits information about the conditions around the industrial vehicle 1 to the controller 10.

[0047] The travel information sensor 23 is a detector that detects the travel state of the industrial vehicle 1. The travel information sensor 23 includes a vehicle speed sensor, an acceleration sensor, and a yaw rate sensor (gyro sensor). The vehicle speed sensor is a detector that detects the speed of the industrial vehicle 1. As the vehicle speed sensor, for example, a speed sensor that is provided in each of the left travel motor 6 and the right travel motor 7 and detects the rotation speed of the left travel motor 6 and the right travel motor 7 is used. The travel information sensor 23 transmits the detected travel information to the controller 10.

[0048] The map database 24 is a database that stores map information. The map database 24 is formed, for example, in a storage device (e.g., an HDD [Hard Disk Drive], etc.) mounted on the industrial vehicle 1. The map information includes information on a predetermined area, such as a runway, takeoff and landing area, taxiway, apron, control tower, hangar, loading and unloading area, charging station, etc. at an airport, such as road position information, road shape information (e.g., curves, type of straight section, curvature of curves, etc.), position information of intersections and branch points, and position information of structures. The map information includes position information of road surface patterns used for position recognition of the industrial vehicle 1. The map database 24 may be formed in a server that can communicate with the industrial vehicle 1.

[0049] The steering angle sensor 25 is a detector that detects the steering angle of the steering wheel 33. The steering angle sensor 25 is provided, for example, on the shaft of the steering wheel 33. The steering angle sensor 25 transmits the detected steering angle information to the controller 10. The steering angle sensor 25 constitutes a steering operation detection unit that detects the operation of the steering wheel 33.

[0050] Next, a description will be given of the functional configuration of the controller 10. The controller 10 has a map information acquisition unit 11, a position information acquisition unit 12, a driving information acquisition unit 13, an automatic driving control unit 14, and a steering hydraulic control unit 15. Note that some of the functions of the controller 10 described below may be executed by a server capable of communicating with the vehicle.

[0051] The map information acquisition unit 11 acquires map information stored in the map database 24. The map information acquisition unit 11 acquires, for example, position information of a road surface pattern used for position recognition of the industrial vehicle 1.

[0052] The position information acquisition unit 12 acquires the position information of the industrial vehicle 1 based on the reception results of the GNSS receiver 21, the detection results of the surrounding condition sensor 22, and the map information of the map database 24. The position information acquisition unit 12 acquires the self-position of the industrial vehicle 1 based on the position information of the road surface pattern included in the map information and the relative position information of the road surface pattern with respect to the industrial vehicle 1 detected by the surrounding condition sensor 22. Note that the position information acquisition unit 12 may estimate the self-position of the industrial vehicle 1 using, for example, a SLAM (Simultaneous Localization And Mapping) method.

[0053] The travel information acquisition unit 13 acquires travel information of the industrial vehicle 1 based on the detection results of the travel information sensor 23. Here, the travel information acquisition unit 13 acquires vehicle speed information of the industrial vehicle 1 based on the detection results of the speed sensors provided on the left travel motor 6 and the right travel motor 7. The travel information acquisition unit 13 may acquire the orientation of the industrial vehicle 1 based on the detection results of the gyro sensor.

[0054] The automatic driving control unit 14 executes automatic driving control, including automatic steering, of the industrial vehicle 1, based on the position information, driving information, and map information. The automatic driving control unit 14 generates a driving plan along a target route based on the position information of the industrial vehicle 1 measured by the GNSS receiver 21, the map information in the map database 24, the surrounding conditions of the industrial vehicle 1 (position of obstacles, etc.) recognized from the detection results of the surrounding condition sensor 22, and the driving state (vehicle speed, yaw rate, etc.) recognized from the detection results of the driving information sensor 23. The target route is set in accordance with a transportation command from the operation management system, etc. The driving plan includes, for example, target steering angles for the FL tires 2 and the FR tires 3. The driving plan may also include a target speed.

[0055] The automatic driving control unit 14 executes automatic driving in accordance with the driving plan. The automatic driving control unit 14 executes automatic driving control to generate the above-mentioned driving plan and calculates whether automatic steering is necessary according to the driving plan. The automatic driving control unit 14 may execute automatic driving control so as to achieve the target speed by sending control signals to the left drive unit 6a and the right drive unit 7a.

[0056] The steering hydraulic control unit 15 controls the opening and closing of the electromagnetic proportional valve 51 in accordance with the calculation result of the automatic driving control by the automatic driving control unit 14. The steering hydraulic control unit 15 sends command signals to the contactor 9 and the electromagnetic proportional valve 51 based on the calculation result of the automatic driving control unit 14 on whether automatic steering is required (the calculation result of the automatic driving control). When automatic driving control is being executed and the calculation result of the automatic driving control is to perform automatic steering, the steering hydraulic control unit 15 controls the opening and closing of the electromagnetic proportional valve 51 so that the turning angles of the FL tires 2 and the FR tires 3 become the target turning angles for automatic steering. For example, when automatic driving control is being executed and the calculation result of the automatic driving control is to not perform automatic steering, or when automatic driving control is not being executed, the electromagnetic proportional valve 51 is controlled to close. The steering hydraulic control unit 15 can obtain the turning angles of the FL tires 2 and the FR tires 3, for example, based on a tire turning angle sensor (not shown).

[0057] The steering hydraulic pressure control unit 15 detects the operation of the steering wheel 33 based on the detection result of the steering angle sensor 25. That is, the steering hydraulic pressure control unit 15 functions as a steering operation detection unit together with the steering angle sensor 25. The function of the steering operation detection unit will be described in detail later.

[0058] [Priority valve flow division structure] The flow division of the priority valve 60 will be described in detail. Figures 5 and 6 are schematic cross-sectional views taken along the axis of the priority valve of Figure 1. As shown in Figures 5 and 6, the priority valve 60 has a valve support chamber 62 formed in a housing 61, a valve element 63 slidably disposed along the inner wall of the valve support chamber 62, and a spring 64 disposed between the inner wall of the valve support chamber 62 and the valve element 63 to bias the valve element 63 in one direction.

[0059] The valve support chamber 62 is formed as a substantially cylindrical cavity. The valve support chamber 62 has a hydraulic pump side opening 62a which is an opening to the hydraulic pump circuit 30a, a manual steering side opening 62b which is an opening to the introduction circuit 40a to the manual steering circuit 40, and an automatic steering side opening 62c which is an opening to the introduction circuit 50a to the automatic steering circuit 50.

[0060] The valve element 63 is disposed between a hydraulic pump side opening 62a and a manual steering side opening 62b in the valve support chamber 62 so as to be slidable along the inner wall of the valve support chamber 62. The valve element 63 divides the valve support chamber 62 into a hydraulic pump side back pressure chamber 65 in which the hydraulic pump side opening 62a is located, and a manual steering side back pressure chamber 66 in which the manual steering side opening 62b is located. The manual steering side back pressure chamber 66 is a back pressure chamber of the valve element 63 located on the side of the introduction circuit 40a. A circuit 30f branching from the hydraulic pump circuit 30a is connected to the hydraulic pump side back pressure chamber 65, and hydraulic oil is supplied from the hydraulic pump 31. In other words, the hydraulic pressure of the hydraulic pump side back pressure chamber 65 is the same as the hydraulic pressure of the hydraulic pump circuit 30a.

[0061] The priority valve 60 here is configured as a priority valve that sets the PS valve 41 side as the priority circuit. The priority valve 60 supplies hydraulic oil preferentially to the manual steering circuit 40 so that the flow rate of hydraulic oil becomes a design flow rate (first flow rate). The design flow rate is a design value of the flow rate of hydraulic oil that is preferentially supplied to the manual steering circuit 40, and is set to, for example, a constant flow rate value equal to or greater than a predetermined flow rate. The predetermined flow rate means the minimum flow rate of hydraulic oil supplied to the steering cylinder 32 that is required for the steering cylinder 32 to operate to steer the front tire 2 and the front tire 3. In other words, the priority valve 60 supplies hydraulic oil preferentially to the manual steering circuit 40 at a flow rate equal to or greater than the predetermined flow rate, thereby enabling the steering cylinder 32 to operate regardless of whether hydraulic oil is diverted to the automatic steering circuit 50.

[0062] The priority valve 60 has an orifice 67 that is provided according to the design flow rate to be preferentially supplied to the PS valve 41 side. The orifice 67 is formed in the valve body 63. The orifice 67 connects a hydraulic pump-side back pressure chamber 65 and a manual steering-side back pressure chamber 66. In the priority valve 60, the manual steering-side opening 62b is formed so as to be located on the opposite side of the orifice 67 from the hydraulic pump-side back pressure chamber 65. Therefore, the hydraulic oil that flows into the hydraulic pump-side back pressure chamber 65 from the hydraulic pump circuit 30a is guided to the manual steering-side back pressure chamber 66 through the orifice 67.

[0063] The flow rate of hydraulic oil passing through the orifice 67 is determined by the hydraulic pressure difference of the hydraulic oil before and after passing through the orifice 67 and the flow path area to the manual steering side opening 62b in the manual steering side back pressure chamber 66. The priority valve 60 of this embodiment is designed so that the flow path area to the manual steering side opening 62b in the manual steering side back pressure chamber 66 changes so that the flow rate of hydraulic oil passing through the orifice 67 remains approximately constant even if the hydraulic pressure difference of the hydraulic oil before and after passing through the orifice 67 changes. In the following description, the communication opening D1 is used as an index of the flow path area to the manual steering side opening 62b in the manual steering side back pressure chamber 66. The communication opening D1 is the dimension along the axial direction of the valve support chamber 62 of the manual steering side communicating flow path 68 that introduces hydraulic oil from the manual steering side back pressure chamber 66 to the introduction circuit 40a.

[0064] When the flow rate of hydraulic oil from the hydraulic pump circuit 30a to the priority valve 60 exceeds the design flow rate, the priority valve 60 supplies the excess hydraulic oil to the automatic steering circuit 50 on the solenoid proportional valve 51 side. In other words, the priority valve 60 preferentially supplies the hydraulic oil discharged from the hydraulic pump 31 to the manual steering circuit 40 at a first flow rate that is equal to or greater than a predetermined flow rate for operating the steering cylinder 32, and also supplies the hydraulic oil to the automatic steering circuit 50 at a second flow rate that is the excess flow rate of the hydraulic oil discharged from the hydraulic pump 31 excluding the first flow rate.

[0065] In the priority valve 60, the automatic steering-side opening 62c is formed so as to be located on the same side of the orifice 67 as the hydraulic pump-side back pressure chamber 65. Therefore, the flow rate of hydraulic oil to the automatic steering circuit 50 is determined mainly by the flow path area to the automatic steering-side opening 62c in the hydraulic pump-side back pressure chamber 65. In the following explanation, the communication opening D2 is used as an index of the flow path area to the automatic steering-side opening 62c in the hydraulic pump-side back pressure chamber 65. The communication opening D2 is the dimension along the axial direction of the valve support chamber 62 of the automatic steering-side communicating flow path 69 that guides hydraulic oil from the hydraulic pump-side back pressure chamber 65 to the introduction circuit 50a.

[0066] The priority valve 60 is configured so that the communication opening degree D2 and the communication opening degree D1 change as the valve element 63 moves along the inner wall of the valve support chamber 62. Specifically, as the valve element 63 moves in the direction in which the spring 64 urges the valve element 63, the communication opening degree D2 of the automatic steering side communication flow path 69 becomes smaller, and the communication opening degree D1 of the manual steering side communication flow path 68 becomes larger.

[0067] Here, the rotation speed of the hydraulic pump 31 is controlled by the steering hydraulic control unit 15 of the controller 10 so as to maintain the flow rate of hydraulic oil in the hydraulic pump circuit 30a even if the open / close state of the PS valve 41 due to manual steering and / or the open / close state of the solenoid proportional valve 51 due to automatic steering changes. When the open / close state of the PS valve 41 due to manual steering and / or the open / close state of the solenoid proportional valve 51 due to automatic steering changes to open, a pressure loss occurs when the hydraulic oil flows into the manual steering circuit 40 and / or the automatic steering circuit 50. In order to pump the hydraulic oil against this pressure loss, the rotation speed of the hydraulic pump 31 increases in an attempt to maintain the flow rate of hydraulic oil in the hydraulic pump circuit 30a, and the hydraulic pressure in the hydraulic pump circuit 30a and the hydraulic pump-side back pressure chamber 65 increases. This increase in hydraulic pressure causes the valve element 63 to move toward the manual steering-side back pressure chamber 66 due to the biasing force of the hydraulic pressure in the hydraulic pump-side back pressure chamber 65.

[0068] For example, Figure 5 corresponds to a state in which neither manual steering nor automatic steering is performed, and both the PS valve 41 and the solenoid proportional valve 51 are closed. Examples of such a state include a case in which automatic driving control is being executed, the calculation result of the automatic driving control indicates that automatic steering will not be performed, and the steering wheel 33 is not being operated, or a case in which automatic driving control is not being executed and the steering wheel 33 is not being operated.

[0069] 5, because the PS valve 41 is closed, hydraulic oil does not flow through the PS valve 41 in the manual steering circuit 40, and no pressure loss occurs due to the flow of hydraulic oil. Similarly, because the solenoid proportional valve 51 is closed, hydraulic oil does not flow through the solenoid proportional valve 51 in the automatic steering circuit 50, and no pressure loss occurs due to the flow of hydraulic oil. In this case, the hydraulic pressure in the hydraulic pump circuit 30a and the hydraulic pump-side back pressure chamber 65 does not increase in accordance with the pressure loss, and therefore no biasing force due to the hydraulic pressure in the hydraulic pump-side back pressure chamber 65 is applied to the valve element 63. Therefore, the valve element 63 does not move toward the manual steering-side back pressure chamber 66, and is biased only by the biasing force of the spring 64 in the direction from the manual steering-side back pressure chamber 66 toward the hydraulic pump-side back pressure chamber 65.

[0070] In this state, the valve element 63 moves so that the biasing forces from both sides of the valve element 63 are balanced, and therefore the hydraulic pressure in the hydraulic pump-side back pressure chamber 65 becomes a pressure that balances the biasing force of the spring 64. The pressure difference between the hydraulic pressure in the hydraulic pump-side back pressure chamber 65 and the hydraulic pressure in the manual steering-side back pressure chamber 66 becomes a predetermined pressure difference corresponding to the biasing force of the spring 64. The flow rate of hydraulic oil passing through the orifice 67 becomes a flow rate according to the predetermined pressure difference corresponding to the biasing force of the spring 64. At this time, because the communication opening D1 is sufficiently large, the flow rate of hydraulic oil passing through the orifice 67 corresponds to the design flow rate supplied to the manual steering circuit 40. Note that in the example of FIG. 5, the priority valve 60 is configured so that the supply of hydraulic oil to the solenoid proportional valve 51 on the automatic steering circuit 50 side is not always completely shut off.

[0071] 6 corresponds to a state in which manual steering is also performed while automatic steering is being performed, and both the PS valve 41 and the solenoid proportional valve 51 are open. An example of such a state is when automatic driving control is being executed, the calculation result of the automatic driving control indicates that automatic steering will be performed, and the steering wheel 33 is being operated.

[0072] 6, because the solenoid proportional valve 51 is open, hydraulic oil flows through the solenoid proportional valve 51 in the automatic steering circuit 50, causing a pressure loss due to the flow of hydraulic oil. Similarly, because the PS valve 41 is open, hydraulic oil flows through the PS valve 41 in the manual steering circuit 40, causing a pressure loss due to the flow of hydraulic oil. Therefore, the hydraulic pressure in the hydraulic pump circuit 30a and the hydraulic pump-side back pressure chamber 65 rises in accordance with the pressure loss, and a biasing force due to the hydraulic pressure in the hydraulic pump-side back pressure chamber 65 is generated on the valve element 63. Then, the biasing force due to the hydraulic pressure in the hydraulic pump-side back pressure chamber 65 moves the valve element 63 toward the manual steering-side back pressure chamber 66, and the communication opening degree D1 of the manual steering-side communicating flow path 68 decreases.

[0073] In this state, the pressure difference between the hydraulic pressure in the hydraulic pump-side back pressure chamber 65 and the hydraulic pressure in the manual steering-side back pressure chamber 66 is larger than the pressure difference in the example of Figure 5, and is larger by an amount corresponding to the pressure loss in addition to the biasing force of the spring 64. Because the pressure difference is larger, the flow rate of hydraulic oil passing through the orifice 67 can be larger than in the example of Figure 5. However, because the communication opening D1 is smaller than in the example of Figure 5, the flow rate of hydraulic oil supplied to the manual steering circuit 40 becomes equivalent to that in the example of Figure 5 and is the design flow rate. The portion of the discharge rate of the hydraulic pump 31 that exceeds the design flow rate is supplied to the automatic steering circuit 50 side as surplus flow rate.

[0074] 5 and 6 so that the valve element 63 is in a balanced position where the sum of the biasing force due to the hydraulic pressure in the manual steering side back pressure chamber 66 and the biasing force due to the spring 64 is in equilibrium with the biasing force due to the hydraulic pressure in the hydraulic pump side back pressure chamber 65. Examples of such a state include a case where automatic driving control is being executed, the calculation result of the automatic driving control is to perform automatic steering, and the steering wheel 33 is not being operated, or a case where automatic driving control is not being executed, and the steering wheel 33 is being operated.

[0075] According to the priority valve 60 configured as described above, even when the solenoid proportional valve 51 is open in accordance with the calculation result of the automatic driving control, hydraulic oil at least at the design flow rate is supplied to the manual steering circuit 40, and therefore the steering cylinder 32 can be operated in response to the operation of the steering wheel 33. Therefore, when automatic steering is being performed under automatic driving control, for example, in a situation where an unexpected obstacle appears and it becomes necessary to avoid it, the steering cylinder 32 is operated in response to the operation of the steering wheel 33 by the operator, and therefore obstacle avoidance by manual steering becomes possible even during automatic steering.

[0076] In the priority valve 60 of this embodiment, the hydraulic oil at a second flow rate, which is an excess flow rate of the hydraulic oil discharged from the hydraulic pump 31 minus the design flow rate (first flow rate) flowing to the manual steering circuit 40, is supplied to the automatic steering circuit 50. Here, assuming that the hydraulic oil at the second flow rate is supplied to the steering cylinder 32 via the automatic steering circuit 50 regardless of whether the steering wheel 33 is operated, for example, it is possible that both the hydraulic oil flowing through the manual steering circuit 40 and the hydraulic oil flowing through the automatic steering circuit 50 are supplied to the steering cylinder 32 simultaneously. Therefore, when the steering wheel 33 is operated, the hydraulic oil supplied to the automatic steering circuit 50 may affect the operation of the steering cylinder 32 in response to the operation of the steering wheel 33. In particular, when the operating speed of the steering wheel 33 is relatively slow, an excess flow rate to the automatic steering circuit 50 is likely to occur, and therefore the effect on the operation of the steering cylinder 32 in response to the operation of the steering wheel 33 may be greater than when the operating speed of the steering wheel 33 is relatively fast.

[0077] Specifically, as an effect on the operation of the steering cylinder 32, for example, if the hydraulic oil flowing through the automatic steering circuit 50 and the hydraulic oil flowing through the manual steering circuit 40 are supplied to the steering cylinder 32 so that they are steering in the same direction, the steered wheels may be steered to a greater extent than the operation of the steering wheel 33. Conversely, if the hydraulic oil flowing through the automatic steering circuit 50 and the hydraulic oil flowing through the manual steering circuit 40 are supplied to the steering cylinder 32 so that they are steering in opposite directions, the steering of the steered wheels by operating the steering wheel 33 may be hindered, resulting in a worsening of the response to the operation (poor efficiency).

[0078] Therefore, the steering device 100 for an industrial vehicle of this embodiment is provided with a supply limiting means that limits the supply of hydraulic oil to the steering cylinder 32 via the automatic steering circuit 50 when the steering hydraulic control unit 15 detects the operation of the steering wheel 33. "When the steering hydraulic control unit 15 detects the operation of the steering wheel 33" corresponds to a case where the hydraulic oil supplied to the automatic steering circuit 50 is likely to affect the operation of the steering cylinder 32 in response to the operation of the steering wheel 33.

[0079] The steering hydraulic control unit 15 detects the operation of the steering wheel 33 based on the detection result of the steering angle sensor 25. In this embodiment, the operation of the steering wheel 33 refers to a predetermined operation of the steering wheel 33 by the operator of the industrial vehicle 1. The predetermined operation refers to the operation of the steering wheel 33 in which the operation of the steering cylinder 32 by the hydraulic oil flowing through the manual steering circuit 40 is easily affected by the hydraulic oil flowing through the automatic steering circuit 50. Note that the detection of the operation of the steering wheel 33 by the steering hydraulic control unit 15 described below may be performed on the condition that automatic driving control is being executed.

[0080] An example of the predetermined operation is an operation of the steering wheel 33 by the operator at a steering speed slower than a certain level. The steering hydraulic control unit 15 detects the predetermined operation when the steering speed of the steering wheel 33 is equal to or lower than a predetermined steering speed threshold, for example, based on the time change in the steering angle (rotation speed) detected by the steering angle sensor 25. The steering speed threshold is a rotation speed threshold for determining whether the operation of the steering wheel 33 by the operator is a predetermined operation. The steering speed threshold can be set in advance, for example, taking into account the surplus flow to the automatic steering circuit 50. As the steering speed of the steering wheel 33 decreases, a smaller amount of the design flow from the priority valve 60 to the PS valve 41 is supplied to the steering cylinder 32 via the manual steering circuit 40, resulting in a larger surplus flow. Therefore, the steering speed threshold may be a steering speed of the steering wheel 33 at which the surplus flow is equal to or greater than a certain amount (e.g., half the design flow).

[0081] An example of the predetermined operation is the operation of the steering wheel 33 by the operator such that the steering direction of the manually steered wheels does not match the direction of the automatic steering. When the steering direction of the manually steered wheels does not match the direction of the automatic steering, supplying hydraulic oil to the steering cylinder 32 via the automatic steering circuit 50 makes it more likely that steering of the wheels by operating the steering wheel 33 will be hindered compared to when the steering direction of the wheels matches the direction of the automatic steering. Therefore, the steering hydraulic control unit 15 may detect the predetermined operation when the steering direction of the manually steered wheels does not match the direction of the automatic steering, for example, based on the change over time in the steering angle (direction of rotation) detected by the steering angle sensor 25.

[0082] As a restriction by the supply restriction means, for example, when the steering hydraulic control unit 15 detects the operation of the steering wheel 33, the controller 10 may control the electromagnetic proportional valve 51 so that the hydraulic oil from the hydraulic pump 31 is not supplied to the steering cylinder 32 via the electromagnetic proportional valve 51 serving as a shut-off valve (for example, so that the spool 53 is neutral). This makes it possible to prevent the hydraulic oil from being supplied to the steering cylinder 32 along the automatic steering circuit 50 via the electromagnetic proportional valve 51 serving as a shut-off valve. In other words, the controller 10 and the electromagnetic proportional valve 51 constitute a supply restriction means that restricts the supply of hydraulic oil to the steering cylinder 32 via the automatic steering circuit 50 when the steering hydraulic control unit 15 detects the operation of the steering wheel 33.

[0083] As another restriction by the supply restriction means, for example, the controller 10 may control the shutoff valve so that hydraulic oil from the hydraulic pump 31 is not supplied to the steering cylinder 32 via the lock valve 54 serving as a shutoff valve (for example, so as to close the lock valve 54) when the steering hydraulic control unit 15 detects the operation of the steering wheel 33. This makes it possible to prevent hydraulic oil from being supplied to the steering cylinder 32 along the automatic steering circuit 50 via the lock valve 54 serving as a shutoff valve. In other words, the controller 10 and the lock valve 54 constitute supply restriction means that restricts the supply of hydraulic oil to the steering cylinder 32 via the automatic steering circuit 50 when the steering hydraulic control unit 15 detects the operation of the steering wheel 33.

[0084] As another restriction by the supply limiting means, the unloading valve 52 of the electromagnetic proportional valve 51 is provided so as to be able to reduce the pressure of the hydraulic oil in the automatic steering circuit 50. Therefore, when a predetermined operation of the steering wheel 33 is detected, the controller 10 may control the unloading valve 52 to return the hydraulic oil to the tank 34 via the return circuit 30d. This reduces the pressure of the hydraulic oil in the automatic steering circuit 50, making it possible to prevent the hydraulic oil from being supplied to the steering cylinder 32 via the automatic steering circuit 50. In this case, the controller 10 and the unloading valve 52 constitute supply limiting means that limits the supply of hydraulic oil to the steering cylinder 32 via the automatic steering circuit 50 when the steering hydraulic control unit 15 detects the operation of the steering wheel 33.

[0085] When restriction is performed by the supply restriction means, if a predetermined operation of the steering wheel 33 is detected, the controller 10 may control the shutoff valve so as not to supply hydraulic oil to the steering cylinder 32 via the shutoff valve, while controlling the unloading valve 52 to reduce in advance the flow rate of hydraulic oil flowing into the shutoff valve. The steering hydraulic control unit 15 operates the unloading valve 52 to return hydraulic oil to the tank 34, for example, before the spool 53 of the electromagnetic proportional valve 51 moves from a position other than the neutral position to the neutral position.

[0086] In this case, the unloading valve 52 constitutes a shutoff flow rate reduction means. The shutoff flow rate reduction means is provided closer to the hydraulic pump 31 than the shutoff valve, and refers to a means for reducing the flow rate of hydraulic oil flowing to the shutoff valve beforehand when shutting off hydraulic oil at the shutoff valve. "More closer to the hydraulic pump 31 than the shutoff valve" means, for example, in the example of the hydraulic circuit of FIG. 3, the unloading valve 52 is provided so that the hydraulic oil flowing into the spool 53 from the point P can be reduced by the operation of the unloading valve 52, and therefore it is closer to the hydraulic pump 31 than the shutoff valve. For example, the position of the unloading valve 52 in the hydraulic circuit of FIG. 3 may be changed, as long as it is located in a position where the hydraulic oil flowing into the spool 53 can be reduced by the operation of the unloading valve 52.

[0087] The shutoff flow rate reduction means prevents a difference in the flow rate of hydraulic oil before and after the shutoff valve shuts off the hydraulic oil. Therefore, compared to controlling the shutoff valve without reducing the flow rate of hydraulic oil flowing into the shutoff valve, it is possible to prevent the occurrence of effects (such as shocks) caused by the flow rate of hydraulic oil. The shutoff valve may be either an electromagnetic proportional valve 51 or a lock valve 54.

[0088] The operation of the supply limiting means will be described with reference to Figures 7 and 8. Figure 7 is a timing chart showing the flow rate of hydraulic oil to the steering cylinder when no limiting action is taken by the supply limiting means. Figure 7 corresponds to a situation in which manual steering is also performed while automatic steering is being performed. In Figure 7, the horizontal axis represents time, and the vertical axis represents the flow rate of hydraulic oil.

[0089] In the example of Figure 7, the flow rate Qa1 represents the flow rate of hydraulic oil supplied to the steering cylinder 32 via the automatic steering circuit 50 when no restriction is imposed by the supply restriction means. The flow rate Qm represents the flow rate of hydraulic oil supplied to the steering cylinder 32 via the manual steering circuit 40 in response to the operation of the steering wheel 33. For simplicity of explanation, it is assumed that the flow rates Qa1 and Qm are smaller than the discharge rate of the hydraulic pump 31, and can each be increased up to a predetermined flow rate Qp that operates the steering cylinder 32.

[0090] In Figure 7, automatic steering has been performed before time t0 in accordance with the calculation results of the automatic driving control, and the solenoid proportional valve 51 is in an open state. Therefore, hydraulic oil is supplied to the steering cylinder 32 via the automatic steering circuit 50 at a flow rate Qa1 equal to the predetermined flow rate Qp. Meanwhile, before time t0, the operator has not started operating the steering wheel 33, so the PS valve 41 is closed. The hydraulic oil at the design flow rate supplied to the manual steering circuit 40 is returned to the tank 34 via the return circuit 30e, so the flow rate Qm is 0 before time t0.

[0091] At time t0, the operator starts operating the steering wheel 33, and the PS valve 41 is further opened while the solenoid proportional valve 51 is open. After time t0, hydraulic oil is supplied to the manual steering circuit 40 side in response to the opening of the PS valve 41, and the flow rate Qm increases.

[0092] In the example of Figure 7, even if the operator starts operating the steering wheel 33 at time t0, hydraulic oil continues to be supplied to the steering cylinder 32 at the flow rate Qa1 via the automatic steering circuit 50 even after time t0. Therefore, there is a risk that the hydraulic oil supplied to the steering cylinder 32 via the automatic steering circuit 50 will affect the operation of the steering cylinder 32 in response to the operation of the steering wheel 33. As an example, in the period from time t0 to t1 when the flow rate Qm is equal to or less than half of the flow rate Qa1, the steering cylinder 32 is likely to operate in accordance with automatic steering rather than manual steering. In this case, steering of the steered wheels by operation of the steering wheel 33 is hindered, resulting in an adverse effect of a worsening response to the operation (deterioration in efficiency).

[0093] Fig. 8 is a timing chart showing the flow rate of hydraulic oil to the steering cylinder when restriction is performed by the supply restriction means. In the example of Fig. 8, flow rate Qa2 represents the flow rate of hydraulic oil supplied to the steering cylinder 32 via the automatic steering circuit 50 when restriction is performed by the supply restriction means. Everything except flow rate Qa2 is the same as Fig. 7.

[0094] In Fig. 8, automatic steering has been performed before time t0 in accordance with the calculation results of the automatic driving control, and the solenoid proportional valve 51 is in an open state, but at time t0, the operator starts operating the steering wheel 33, and restriction is performed by the supply restriction means. As a result, hydraulic oil is no longer supplied to the steering cylinder 32 via the automatic steering circuit 50, and the flow rate Qa2 becomes 0. Therefore, it is possible to prevent the operation of the steering cylinder 32 in response to the operation of the steering wheel 33 from being hindered due to hydraulic oil supplied via the automatic steering circuit 50.

[0095] 8, the unloading valve 52 may be controlled to reduce in advance the flow rate of hydraulic oil flowing into the shutoff valve when a predetermined operation of the steering wheel 33 is detected. Even in this case, since FIG. 8 shows the flow rate of hydraulic oil to the steering cylinder 32, the flow rate may follow a trajectory similar to that of the flow rate Qa2 in FIG.

[0096] However, if the flow rate of the hydraulic oil is not reduced in advance, the flow rate Qa2 of the hydraulic oil will decrease from the predetermined flow rate Qp as a result of the spool 53 of the solenoid proportional valve 51 being set to the neutral position. Therefore, there is a large difference in the flow rate of the hydraulic oil before and after the hydraulic oil is shut off, which may cause a shock to the automatic steering circuit 50.

[0097] In contrast, when the flow rate of hydraulic oil is reduced beforehand and then the hydraulic oil is shut off, the unloading valve 52, which serves as a shutoff flow rate reduction means, returns the hydraulic oil to the tank 34 before the spool 53 of the electromagnetic proportional valve 51 is brought to the neutral position. As a result, the flow rate Qa2 of the hydraulic oil starts to decrease from the predetermined flow rate Qp. Thereafter, by bringing the spool 53 of the electromagnetic proportional valve 51, which serves as a shutoff valve, to the neutral position, the difference in the flow rate of hydraulic oil before and after the hydraulic oil is shut off is suppressed, and shock to the automatic steering circuit 50 is suppressed. The timing for bringing the spool 53 of the electromagnetic proportional valve 51 to the neutral position may be while the flow rate Qa2 of hydraulic oil is decreasing, or may be after the flow rate Qa2 of hydraulic oil has become zero. Note that a lock valve 54 may be used as the shutoff valve.

[0098] [Example of calculation processing by a controller] Next, an example of calculation processing by the controller 10 will be described. Fig. 9 is a flowchart illustrating the supply limiting processing of the controller in Fig. 1. The processing shown in Fig. 9 is executed, for example, while automatic driving control is being performed in the industrial vehicle 1. For example, the processing is executed in a situation where automatic steering is being performed by the automatic driving control and the spool 53 of the solenoid proportional valve 51 is in a position other than the neutral position.

[0099] 9, in S01, the controller 10 detects the operation of the steering wheel 33 using the steering hydraulic control unit 15. Specifically, as the processing of S01, the controller 10 performs a steering operation detection processing exemplified in FIG.

[0100] Fig. 10 is a flowchart illustrating the steering operation detection process of Fig. 9. As shown in Fig. 10, in S11, the controller 10 detects the steering speed of the steering wheel 33 by the steering hydraulic control unit 15. The steering hydraulic control unit 15 detects the steering speed of the steering wheel 33 based on the steering angle detected by the steering angle sensor 25.

[0101] In S12, the controller 10 determines, using the steering hydraulic pressure control unit 15, whether the steering speed of the steering wheel 33 is equal to or less than a predetermined steering speed threshold (rotation speed threshold). If the steering speed of the steering wheel 33 is equal to or less than the steering speed threshold (S12=YES), the controller 10 proceeds to S13. In S13, the controller 10 determines, using the steering hydraulic pressure control unit 15, that a predetermined operation of the steering wheel 33 has been detected. Thereafter, the controller 10 ends the processing in FIG. 10 and proceeds to S02 in FIG. 9.

[0102] On the other hand, if the steering speed of the steering wheel 33 exceeds the steering speed threshold (S12=NO), the controller 10 proceeds to S14. In S14, the controller 10 determines that the steering hydraulic pressure control unit 15 has not detected a predetermined operation of the steering wheel 33. Thereafter, the controller 10 ends the processing in FIG. 10 and proceeds to S02 in FIG. 9.

[0103] Returning to Fig. 9, in S02, the controller 10 determines whether or not the steering hydraulic pressure control unit 15 has detected an operation of the steering wheel 33 (here, a predetermined operation). If the steering hydraulic pressure control unit 15 has determined in S02 that an operation of the steering wheel 33 has been detected (S02 = YES), the controller 10 proceeds to S03. If the steering hydraulic pressure control unit 15 has determined in S02 that an operation of the steering wheel 33 has not been detected (S02 = NO), the controller 10 proceeds to S05.

[0104] In S03, the controller 10 controls the cutoff flow rate reduction means by the steering hydraulic control unit 15 so as to reduce the flow rate of hydraulic oil flowing into the shutoff valve. In this embodiment, in S03, the steering hydraulic control unit 15 controls the unloading valve 52 so as to reduce in advance the flow rate of hydraulic oil flowing into the spool 53 of the electromagnetic proportional valve 51 serving as the shutoff valve. For example, the steering hydraulic control unit 15 operates the unloading valve 52 so as to return the hydraulic oil to the tank 34 before the spool 53 of the electromagnetic proportional valve 51 moves from a position other than the neutral position to the neutral position.

[0105] In S04, the controller 10 controls the shutoff valve via the steering hydraulic pressure control unit 15 so that hydraulic oil is not supplied to the steering cylinder 32 via the shutoff valve. In this embodiment, in S04, the steering hydraulic pressure control unit 15 controls the electromagnetic proportional valve 51, which serves as a shutoff valve, so that hydraulic oil from the hydraulic pump 31 is not supplied to the steering cylinder 32 by setting the spool 53 of the electromagnetic proportional valve 51 as a shutoff valve to a neutral position. Thereafter, the controller 10 ends the processing of FIG. 9.

[0106] In S05, the controller 10 controls the steering hydraulic pressure control unit 15 to supply hydraulic oil to the steering cylinder 32 via the shutoff valve. In this embodiment, in S05, the steering hydraulic pressure control unit 15 controls the electromagnetic proportional valve 51 serving as the shutoff valve to supply hydraulic oil from the hydraulic pump 31 to the steering cylinder 32 by setting the spool 53 of the electromagnetic proportional valve 51 to a position other than the neutral position. Thereafter, the controller 10 ends the processing of FIG. 9.

[0107] [Action and effect] As described above, in the steering device 100 for an industrial vehicle according to this embodiment, the priority valve 60 supplies hydraulic oil to the automatic steering circuit 50 at the second flow rate if there is an excess flow rate, even when the steering wheel 33 is operated. The supply of hydraulic oil to the steering cylinder 32 via the automatic steering circuit 50 is limited by the supply limiting means when the steering operation detection unit detects operation of the steering wheel 33. As a result, when the steering wheel 33 is operated, operation of the steering cylinder 32 by the hydraulic oil supplied to the automatic steering circuit 50 is limited. Therefore, the steering device 100 for an industrial vehicle can prevent the hydraulic oil supplied via the automatic steering circuit 50 from affecting the operation of the steering cylinder 32 in response to operation of the steering wheel 33. In other words, it is possible to prevent the hydraulic oil on the automatic steering side from interfering with steering of the steered wheels due to operation of the steering wheel 33, thereby preventing the effect of a deterioration in response to manual operation (deterioration in efficiency).

[0108] In the industrial vehicle steering device 100, the supply limiting means includes a solenoid proportional valve 51 and a lock valve 54 provided in the automatic steering circuit 50, and a controller 10 that controls at least one of the solenoid proportional valve 51 and the lock valve 54 based on the detection result of the steering angle sensor 25. When the steering hydraulic control unit 15 detects operation of the steering wheel 33, the controller 10 controls at least one of the solenoid proportional valve 51 and the lock valve 54 so as not to supply hydraulic oil from the hydraulic pump 31 to the steering cylinder 32 via at least one of the solenoid proportional valve 51 and the lock valve 54. According to this configuration, when the steering wheel 33 is operated, the hydraulic oil supplied to the automatic steering circuit 50 is blocked by at least one of the solenoid proportional valve 51 and the lock valve 54, thereby limiting operation of the steering cylinder 32 by the hydraulic oil supplied to the automatic steering circuit 50.

[0109] In the steering device 100 for an industrial vehicle, at least one of the electromagnetic proportional valve 51 and the lock valve 54 provided between the electromagnetic proportional valve 51 and the steering cylinder 32 functions as a shutoff valve. According to this configuration, when the steering wheel 33 is operated, the hydraulic oil supplied to the automatic steering circuit 50 can be shut off using at least one of the electromagnetic proportional valve 51 and the lock valve 54.

[0110] In the industrial vehicle steering device 100, the unloading valve 52, which is provided closer to the hydraulic pump 31 than the spool 53 in the automatic steering circuit 50, functions as a supply limiting means. The spool 53 constitutes a shutoff valve, and the unloading valve 52 functions as a shutoff flow rate reducing means. When operation of the steering wheel 33 is detected, the controller 10 controls the unloading valve 52 to reduce the flow rate of hydraulic oil flowing into the spool 53 in advance, and then controls the spool 53 so as not to supply hydraulic oil to the steering cylinder 32 through the spool 53. According to this configuration, when the steering wheel 33 is operated, the flow rate of hydraulic oil flowing into the spool 53 is reduced in advance, and then the spool 53 is controlled so as not to supply hydraulic oil to the steering cylinder 32. This makes it possible to suppress effects (e.g., shocks) caused by the flow rate of hydraulic oil compared to controlling the spool 53 in a state in which the flow rate of hydraulic oil flowing into the spool 53 is not reduced.

[0111] In the steering device 100 for an industrial vehicle, the unloading valve 52, which is provided so as to be able to reduce the pressure on the hydraulic pump 31 side of the shutoff valve in the automatic steering circuit 50, functions as the shutoff flow rate reducing means. According to this configuration, the unloading valve 52 can be used to reduce the pressure on the hydraulic pump 31 side of the shutoff valve.

[0112] In the steering device 100 for an industrial vehicle, the operation of the steering wheel 33 is a predetermined operation of the steering wheel 33 by the operator of the industrial vehicle 1, and the steering operation detection unit detects the predetermined operation when the steering speed of the steering wheel 33 is equal to or less than a predetermined steering speed threshold. When the steering wheel 33 is operated, the slower the rotation speed of the steering wheel 33, the smaller the flow rate of hydraulic oil to the steering cylinder 32 via the manual steering circuit 40, making it more likely that an excess flow rate will occur. Therefore, by detecting the predetermined operation when the steering speed of the steering wheel 33 is equal to or less than the steering speed threshold and restricting the supply of hydraulic oil to the steering cylinder 32 via the automatic steering circuit 50, it is possible to suitably prevent the hydraulic oil supplied via the automatic steering circuit 50 from affecting the operation of the steering cylinder 32 in response to the operation of the steering wheel 33.

[0113] [Variations] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments.

[0114] When the operation of the steering wheel is detected, the controller 10 controls the unloading valve 52 to reduce the flow rate of hydraulic oil flowing into the shutoff valve in advance, but this process may be omitted. In this case, the controller 10 may execute, for example, the process shown in Figure 11 instead of the process shown in Figure 9. Figure 11 is a flowchart showing another example of the supply restriction process of the controller in Figure 1.

[0115] As shown in Fig. 11, in S21, the controller 10 detects the operation of the steering wheel 33 using the steering hydraulic control unit 15. As the processing of S21, the controller 10 specifically performs the steering operation detection processing exemplified in the above-mentioned Fig. 10. A repeated description of the processing in Fig. 10 will be omitted.

[0116] In S22, the controller 10 determines whether or not the steering hydraulic pressure control unit 15 has detected an operation of the steering wheel 33 (here, a predetermined operation). If the controller 10 determines in S22 that an operation of the steering wheel 33 has been detected (S22=YES), the controller 10 proceeds to S23. If the controller 10 determines in S22 that the steering hydraulic pressure control unit 15 has not detected an operation of the steering wheel 33 (S22=NO), the controller 10 proceeds to S24.

[0117] In S23, the controller 10 controls the steering hydraulic control unit 15 to limit the supply of hydraulic oil to the steering cylinder 32 via the automatic steering circuit 50. In this embodiment, in S23, the steering hydraulic control unit 15 controls the solenoid proportional valve 51 so as not to supply hydraulic oil from the hydraulic pump 31 to the steering cylinder 32 via the solenoid proportional valve 51 (for example, to neutralize the spool 53). Alternatively, in S23, the steering hydraulic control unit 15 may control the unloading valve 52 so as to reduce the pressure of the hydraulic oil in the automatic steering circuit 50 (for example, to open the unloading valve 52). This limits the supply of hydraulic oil to the steering cylinder 32 via the automatic steering circuit 50. Thereafter, the controller 10 ends the processing of FIG. 11.

[0118] In S24, the controller 10 does not restrict the supply of hydraulic oil to the steering cylinder 32 via the automatic steering circuit 50, using the steering hydraulic control unit 15. In this embodiment, in S24, the steering hydraulic control unit 15 controls the solenoid proportional valve 51 so that hydraulic oil from the hydraulic pump 31 can be supplied to the steering cylinder 32 via the solenoid proportional valve 51 (for example, so as to allow the spool 53 to move from the neutral position). Alternatively, in S24, the steering hydraulic control unit 15 controls the unloading valve 52 so as not to reduce the pressure of the hydraulic oil in the automatic steering circuit 50 (for example, so as to close the unloading valve 52). This means that the supply of hydraulic oil to the steering cylinder 32 via the automatic steering circuit 50 is not restricted. Thereafter, the controller 10 ends the processing of FIG. 11.

[0119] 11, it is possible to prevent the hydraulic oil supplied via the automatic steering circuit 50 from affecting the operation of the steering cylinder 32 in response to the operation of the steering wheel 33. In other words, it is possible to prevent the hydraulic oil on the automatic steering side from interfering with the steering of the steered wheels by the operation of the steering wheel 33, and it is possible to prevent the effect of a worsening of the response to manual operation (poor efficiency).

[0120] 11 , the unloading valve 52 can also function as supply limiting means because the unloading valve 52 is capable of reducing the pressure of the hydraulic oil in the automatic steering circuit 50. The controller 10 may control the unloading valve 52 based on the detection result of the steering angle sensor 25. The controller 10 may also control the unloading valve 52 to reduce the pressure of the hydraulic oil in the automatic steering circuit 50 when the steering hydraulic control unit 15 detects operation of the steering wheel 33. According to this configuration, when the steering wheel 33 is operated, the unloading valve 52 is used to reduce the pressure of the hydraulic oil in the automatic steering circuit 50, thereby limiting the operation of the steering cylinder 32 by the hydraulic oil supplied to the automatic steering circuit 50.

[0121] The supply limiting means is not limited to the unloading valve 52, the electromagnetic proportional valve 51, and the controller 10 as described above. For example, as a modified example of the unloading means, the controller 10 may control the rotation speed of the (fixed displacement) hydraulic pump 31 as a restriction by the supply limiting means. When the steering hydraulic control unit 15 detects the operation of the steering wheel 33, the controller 10 reduces the rotation speed of the hydraulic pump 31 to reduce the excess flow rate and restrict the supply of hydraulic oil to the steering cylinder 32 via the automatic steering circuit 50. Furthermore, controlling the rotation speed of the fixed displacement hydraulic pump 31 in this manner can also be applied as a modified example of the shutoff flow rate reducing means.

[0122] Alternatively, as another variation of the supply limiting means, the hydraulic pump 31 may be a variable displacement pump configured to be able to change the amount of hydraulic oil discharged during operation. The controller 10 may control the variable displacement pump to reduce the amount of hydraulic oil discharged when the steering hydraulic control unit 15 detects operation of the steering wheel 33. In this case, by controlling the discharge amount of the variable displacement pump during operation as the limitation by the supply limiting means, when the steering hydraulic control unit 15 detects operation of the steering wheel 33, it is possible to reduce the excess flow rate and limit the supply of hydraulic oil to the steering cylinder 32 via the automatic steering circuit 50. Furthermore, controlling the discharge amount of the variable displacement pump in this manner can also be applied as a variation of the shutoff flow rate reduction means.

[0123] In the above embodiment, the steering hydraulic control unit 15 detects the operation of the steering wheel 33 on the condition that automatic driving control is being executed, but the condition does not have to be that automatic driving control is being executed. Even in this case, if, for example, there is residual pressure of hydraulic oil remaining through the automatic steering circuit 50 immediately after automatic driving control changes from being executed to not being executed, the unload valve 52 can reduce the pressure of the hydraulic oil in the automatic steering circuit 50, thereby improving the response of the operation of the steering cylinder 32 in response to the operation of the steering wheel 33 (improving efficiency). Furthermore, by reducing the flow rate of hydraulic oil flowing into the shutoff valve in advance, it is possible to suppress the occurrence of effects (such as shocks) caused by the flow rate of hydraulic oil.

[0124] When controlling the unloading valve 52 to return the hydraulic oil to the tank 34 via the return circuit 30d, the controller 10 may omit controlling the solenoid proportional valve 51 and the lock valve 54 to close. Alternatively, conversely, the controller 10 may limit the supply of hydraulic oil to the steering cylinder 32 via the automatic steering circuit 50 by controlling at least one of the solenoid proportional valve 51 and the lock valve 54 to close. In this case, the unloading valve 52 may be omitted from the steering device 100 for an industrial vehicle. In the example of FIG. 2 , the lock valve 54 is provided in both the hydraulic circuit denoted by reference symbol C1 and the hydraulic circuit denoted by reference symbol C2 between the solenoid proportional valve 51 and the steering cylinder 32, but it may be provided in either one of them. When limiting the supply of hydraulic oil by at least one of the solenoid proportional valve 51 and the lock valve 54, the other may be omitted.

[0125] In the above embodiment, an electric towing tractor as shown in FIG. 1 is exemplified as the industrial vehicle 1, but the present invention is not limited to this, and the industrial vehicle 1 may be, for example, a forklift or other industrial vehicle.

[0126] The configuration for the automatic driving of the industrial vehicle 1 is not limited to the example of the above embodiment. For example, although a LIDAR is used as the surrounding condition sensor 22, another sensor may be used instead.

[0127] At least some of the embodiments and various modified examples described above may be combined in any manner. [Explanation of symbols]

[0128] 1...industrial vehicle, 10...controller (control unit, supply limiting means), 11...map information acquisition unit, 12...position information acquisition unit, 13...traveling information acquisition unit, 14...automatic driving control unit, 15...steering hydraulic control unit (steering operation detection unit), 25...steering angle sensor (steering operation detection unit), 31...hydraulic pump, 32...steering cylinder, 33...steering wheel, 40...manual steering circuit, 41...PS valve (first valve), 50...automatic steering circuit, 51...electromagnetic proportional valve (second valve, supply limiting means, shut-off valve), 52...unload valve (shut-off flow rate reduction means, supply limiting means), 54...lock valve (supply limiting means, shut-off valve), 60...priority valve, 100...steering device of industrial vehicle.

Claims

1. A steering device for an industrial vehicle, comprising: a hydraulic pump that discharges hydraulic oil; and a steering cylinder that is actuated by the supply of the hydraulic oil to steer steering wheels, a manual steering circuit having a first valve that is opened and closed in response to operation of a steering wheel, and that supplies the hydraulic oil discharged from the hydraulic pump to the steering cylinder via the first valve; an automatic steering circuit having a second valve that is opened and closed in accordance with the calculation result of automatic driving control, and that supplies the hydraulic oil discharged from the hydraulic pump to the steering cylinder via the second valve; a dividing valve disposed between the hydraulic pump and the first valve and the second valve, which divides the hydraulic oil into the manual steering circuit and the automatic steering circuit; a steering operation detection unit that detects an operation of the steering wheel; Equipped with the flow dividing valve is a priority valve that supplies the hydraulic oil discharged from the hydraulic pump to the manual steering circuit with a first flow rate that is equal to or greater than a predetermined flow rate for actuating the steering cylinder, and that supplies the hydraulic oil discharged from the hydraulic pump to the automatic steering circuit with a second flow rate that is an excess flow rate obtained by subtracting the first flow rate from the hydraulic oil, A steering device for an industrial vehicle, further comprising a supply limiting means for limiting the supply of hydraulic oil to the steering cylinder via the automatic steering circuit when the steering operation detection unit detects operation of the steering wheel.

2. the supply limiting means includes a shutoff valve provided in the automatic steering circuit, and a control unit that controls the shutoff valve based on a detection result of the steering operation detection unit, 2. The steering device of claim 1, wherein the control unit controls the shut-off valve so that the hydraulic oil from the hydraulic pump is not supplied to the steering cylinder via the shut-off valve when the steering operation detection unit detects operation of the steering wheel.

3. 3. The steering device for an industrial vehicle according to claim 2, wherein the shutoff valve is at least one of the second valve and a lock valve provided between the second valve and the steering cylinder.

4. the supply limiting means includes a shutoff flow rate reducing means provided on the hydraulic pump side of the shutoff valve in the automatic steering circuit, 4. The steering device for an industrial vehicle according to claim 2, wherein the control unit controls the shutoff valve so as not to supply the hydraulic oil to the steering cylinder through the shutoff valve, while controlling the shutoff flow rate reduction means to reduce in advance the flow rate of the hydraulic oil flowing into the shutoff valve, when the steering operation detection unit detects operation of the steering wheel.

5. 5. The steering device for an industrial vehicle according to claim 4, wherein the cutoff flow rate reducing means includes an unloading valve that is provided so as to be able to reduce pressure on the hydraulic pump side of the cutoff valve in the automatic steering circuit.

6. the supply limiting means includes an unloading valve that is provided so as to be able to reduce the pressure of the hydraulic oil in the automatic steering circuit, and a control unit that controls the unloading valve based on a detection result of the steering operation detection unit, 2. The steering device for an industrial vehicle according to claim 1, wherein the control unit controls the unload valve to reduce the pressure of the hydraulic oil in the automatic steering circuit when the steering operation detection unit detects operation of the steering wheel.

7. the operation of the steering wheel is a predetermined operation of the steering wheel by an operator of the industrial vehicle, 7. The steering device for an industrial vehicle according to claim 1, wherein the steering operation detection unit detects the predetermined operation when the rotation speed of the steering wheel is equal to or less than a predetermined rotation speed threshold.

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