Industrial vehicle steering system

Abstract

To provide an industrial truck steering device which can cause a hydraulic circuit to function so as to achieve manual steering even when automatic steering is possible.SOLUTION: An industrial truck steering device 100 comprises: a hydraulic pump 31; a steering cylinder 32; a circuit 40 for manual steering, which supplies hydraulic oil which is discharged from a hydraulic pump 31 through a PS valve 41 which is opened / closed according to an operation of a steering wheel 33, to the steering cylinder 32; a circuit 50 for automatic steering for supplying the hydraulic oil discharged from the hydraulic pump 31 via an electromagnetic proportional valve 51 which is opened / closed according to a calculation result of the automatic drive control, to the steering cylinder 32; and a priority valve 60 which is provided between the hydraulic pump 31 and the PS valve 41 and the electromagnetic proportional valve 51, distributes the hydraulic oil to the circuit 40 for manual steering and the circuit 50 for automatic steering, and preferentially supplies the hydraulic oil to the circuit 40 for manual steering, at a flow rate equal to or greater than a prescribed flow rate for actuating the steering cylinder 32.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] 2. Description of the Related 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 the above-mentioned conventional vehicle steering control device, in the manual steering mode, hydraulic pressure is equally supplied to both of the pair of hydraulic chambers, and the device operates as a hydraulic reaction type power steering device. In the automatic steering mode, hydraulic pressure is supplied to one of the hydraulic chambers according to the steering direction by switching control of the directional control valve, and automatic steering is performed. In such a configuration, since the manual steering mode and the automatic steering mode are selectively switched by switching the directional control valve, it may be difficult to make the hydraulic circuit function in response to manual steering by the operator in the automatic steering mode, for example.

[0005] An object of the present invention is to provide a steering device for an industrial vehicle that can cause a hydraulic circuit to function so as to enable manual steering even when automatic steering is possible. [Means for solving the problem]

[0006] A steering device for an industrial vehicle according to one embodiment 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 operates by the supply of hydraulic oil to steer the steering wheels, and is equipped with a manual steering circuit having a first valve that is opened and closed in response to the operation of the steering wheel, and supplies 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 results of automatic driving control, and supplies hydraulic oil discharged from the hydraulic pump to the steering cylinder via the second valve, and a diversion valve that is arranged between the hydraulic pump and the first and second valves, and diverts the hydraulic oil to the manual steering circuit and the automatic steering circuit, and the diversion valve is a priority valve that preferentially supplies hydraulic oil to the manual steering circuit at a flow rate equal to or greater than a predetermined flow rate that operates the steering cylinder.

[0007] In a steering device for an industrial vehicle according to one aspect of the present invention, hydraulic oil is divided into a manual steering circuit and an automatic steering circuit by a flow dividing valve. The flow dividing valve is a priority valve that preferentially supplies hydraulic oil to the manual steering circuit at a flow rate equal to or greater than a predetermined flow rate for operating the steering cylinder. As a result, even if the second valve is opened according to the calculation result of the automatic driving control, at least a predetermined flow rate of hydraulic oil is supplied to the manual steering circuit, so that the steering cylinder can be operated in response to the operation of the steering wheel. Therefore, according to the steering device for an industrial vehicle according to one aspect of the present invention, it is possible to make the hydraulic circuit function so that manual steering is possible even in a state in which automatic steering is possible.

[0008] In one embodiment, the steering device of the industrial vehicle may further include an unloading means for lowering the pressure of the hydraulic oil from the hydraulic pump acting on the second valve when a predetermined automatic steering non-operation condition for suspending the supply of hydraulic oil through the second valve is satisfied, compared to when the automatic steering non-operation condition is not satisfied. In this case, for example, when the flow dividing valve is configured so that the supply of hydraulic oil to the second valve is not always completely cut off, assuming that the excess flow rate of hydraulic oil supplied to the automatic steering circuit side is not returned to the tank, the pressure of the hydraulic oil from the hydraulic pump always acts on the second valve, and an unnecessary load is applied to the hydraulic pump. Therefore, by using the unloading means to lower the pressure of the hydraulic oil from the hydraulic pump acting on the second valve when the automatic steering non-operation condition is satisfied, it is possible to suppress the application of an unnecessary load to the hydraulic pump. As a result, it is possible to suppress the shortening of the operating time of the steering device of the industrial vehicle due to the application of an unnecessary load to the hydraulic pump.

[0009] In one embodiment, the unloading means includes a control unit that determines whether an automatic steering non-operation condition is satisfied based on information regarding execution or non-execution of automatic driving control or vehicle speed information of the industrial vehicle, and an unloading valve that is provided to be able to reduce the pressure of hydraulic oil from the hydraulic pump acting on the second valve based on the determination result of the control unit, and when the control unit determines that the automatic steering non-operation condition is satisfied, the control unit may control the unloading valve to reduce the pressure of hydraulic oil from the hydraulic pump acting on the second valve. In this case, by controlling the unloading valve based on the determination result of the control unit, it is possible to reduce the pressure of hydraulic oil from the hydraulic pump acting on the second valve when the automatic steering non-operation condition is satisfied.

[0010] In one embodiment, the unloading means includes a control unit that determines whether an automatic steering non-operation condition is satisfied based on information on whether automatic driving control is being performed or not or vehicle speed information of the industrial vehicle, and a variable displacement pump that is a hydraulic pump configured to be able to change the amount of hydraulic oil discharged during operation based on the determination result of the control unit, and the control unit may control the variable displacement pump to reduce the amount of hydraulic oil discharged when it determines that the automatic steering non-operation condition is satisfied. In this case, by controlling the amount of hydraulic oil discharged during operation of the variable displacement pump based on the determination result of the control unit, it is possible to reduce the pressure of hydraulic oil from the variable displacement pump acting on the second valve when the automatic steering non-operation condition is satisfied.

[0011] In one embodiment, the control unit may determine that the automatic steering non-operation condition is satisfied when the state of the switch for switching between execution and non-execution of the automatic driving control is in the state where the automatic driving control is not executed, based on a signal from the switch. In this case, it is possible to suppress unnecessary load from being applied to the hydraulic pump in a state where the automatic driving control is not executed and automatic steering is not performed.

[0012] In one embodiment, the control unit may determine whether the industrial vehicle has been stopped for a predetermined time based on the vehicle speed information of the industrial vehicle, and determine that the automatic steering non-operation condition is satisfied when it is determined that the industrial vehicle has been stopped for a predetermined time. In this case, it is possible to suppress unnecessary load from being applied to the hydraulic pump when the industrial vehicle has been stopped for a predetermined time. Effect of the Invention

[0013] According to the present invention, the hydraulic circuit can be made to function so as to enable manual steering even when automatic steering is possible. [Brief description of the drawings]

[0014] [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; [Diagram 2]FIG. 2 is a schematic circuit diagram showing the configuration of the steering hydraulic circuit of FIG. [Diagram 3] 2 is a block diagram showing a functional configuration of a steering device of the industrial vehicle shown in FIG. 1. [Figure 4] FIG. 2 is a schematic cross-sectional view taken along the axis of the priority valve of FIG. 1. [Diagram 5] FIG. 2 is a schematic cross-sectional view taken along the axis of the priority valve of FIG. 1. [Figure 6] 2 is a flowchart illustrating an unload process of the controller of FIG. 1; [Figure 7] 7 is a flowchart illustrating the process of determining whether an automatic steering non-operating condition exists in FIG. 6; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment 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 duplicated explanations will be omitted.

[0016] Fig. 1 is a schematic diagram of an industrial vehicle to which a steering device for an industrial vehicle according to an 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.

[0017] The industrial vehicle 1 is configured to be able to execute automatic driving control. Automatic driving is an operating state in which vehicle control is executed to automatically drive the industrial vehicle 1 according to a transport command from, for example, a traffic management system. The traffic management system is a so-called control system that issues transport commands, monitors the operation, and monitors the vehicle status of the industrial vehicle 1. In automatic driving, the vehicle runs automatically without the need for a worker to perform driving operations.

[0018] The automatic driving here is performed in a predetermined area including, for example, a runway, takeoff and landing area, taxiway, apron, control tower, hangar, loading and unloading area, charging area, etc. at an airport. The industrial vehicle 1 can automatically drive a predetermined driving route within the predetermined area. In this embodiment, a driving plan is generated that includes automatically steering the industrial vehicle 1 according to the calculation result of the automatic driving control at, for example, an intersection, etc., on 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. The unfixed driving route means a driving route that can be changed by changing the driving plan generated based on map information, etc., rather than a driving route that is difficult to change once set, such as an automated guided vehicle (AGV) that runs along a magnetic tape installed on the road surface.

[0019] [Configuration related to driving and steering of the industrial vehicle 1] The industrial vehicle 1 is equipped with FL tires 2 and FR tires 3, which are steerable wheels disposed at the front of the vehicle body, and RL tires 4 and RR tires 5 disposed at the rear of the vehicle body. The industrial vehicle 1 is equipped with, as travel motors, a left travel motor 6 that drives the RL tire 4, and a right travel motor 7 that drives the RR tire 5. The travel motors also function as a braking unit 8 that generates regenerative braking force.

[0020] 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 reduction gear, is interposed between the left traveling motor 6 and the RL tire 4. A right drive unit 7a, which is a reduction gear, is interposed between the right traveling motor 7 and the RR tire 5.

[0021] 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.

[0022] 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 of the battery B is controlled by the controller 10.

[0023] The battery B is a power supply source for the left traveling motor 6, the right traveling motor 7, and the hydraulic pump 31. The battery B is formed of, for example, a lead storage battery.

[0024] 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 braked, 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 braked, the right traveling motor 7 operates as a generator due to the rotation of the RR tire 5.

[0025] 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 operates by supplying 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.

[0026] The hydraulic pump 31 is a hydraulic source that discharges hydraulic oil. The hydraulic pump 31 is installed so as to be able to 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 discharge amount of hydraulic oil during operation (discharge amount 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 discharge amount.

[0027] The steering cylinder 32 is actuated by the supply of hydraulic oil to steer the FL tire 2 and the 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 to one of the junctions 30b of the manual steering circuit 40 and the automatic steering circuit 50 by a hydraulic circuit. The supply port 32b is connected to the other of the junctions 30c of the manual steering circuit 40 and the automatic steering circuit 50 by a hydraulic circuit.

[0028] 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.

[0029] The automatic steering circuit 50 has an electromagnetic proportional valve (second valve) 51 that is opened and closed in accordance with the calculation result 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 electromagnetic proportional valve 51. The electromagnetic proportional valve 51 is a so-called oil control valve. The electromagnetic proportional valve 51 here is a pilot-type electromagnetic proportional valve that operates an internal spool (not shown) using the pressure of the hydraulic oil from the hydraulic pump 31 acting on the electromagnetic proportional valve 51 as a pilot pressure. The electromagnetic proportional valve 51 is electrically connected to the controller 10, and its opening and closing is controlled by the controller 10.

[0030] The priority valve 60 is disposed between the hydraulic pump 31 and the PS valve 41 and between the hydraulic pump 31 and the 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 relating to the flow division of the priority valve 60 will be described in detail later.

[0031] 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 that is opened in response to the 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 the operation of the steering wheel 33.

[0032] 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 that is opened according to the calculation results of the automatic driving control. 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 according to the calculation results of the automatic driving control.

[0033] The solenoid proportional valve 51 has an unloading valve 52 that is provided so as to be able to reduce the pressure of the hydraulic oil from the hydraulic pump 31 acting on the solenoid proportional valve 51. The unloading valve 52 is connected to the tank 34 by the return circuit 30d. The unloading valve 52 is electrically connected to the controller 10. As will be described later, when the controller 10 determines that the automatic steering non-operation condition is satisfied based on the determination result of the controller 10, the unloading valve 52 returns the hydraulic oil to the tank 34 via the return circuit 30d, thereby reducing the pressure of the hydraulic oil from the hydraulic pump 31 acting on the solenoid proportional valve 51 (i.e., pilot pressure).

[0034] 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 and that exceeds the flow rate supplied to the steering cylinder 32 is returned to the tank 34 via the return circuit 30e. Examples of such situations 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.

[0035] [Configuration related to automatic driving control and automatic steering of industrial vehicle 1] FIG. 3 is a block diagram showing the functional configuration of the steering device of the industrial vehicle in 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. In the controller 10, for example, a program recorded in the ROM is loaded into the RAM, and the program loaded into the RAM is executed by the CPU, thereby realizing various functions. The controller 10 may detect the voltage of the battery B. The controller 10 may be composed of a plurality of electronic units.

[0036] 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 changeover switch (switch) 25.

[0037] 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.

[0038] 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). The image information of the camera is used for, for example, road surface pattern recognition and matching. The obstacle information detected by the LiDAR is used for, for example, 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.

[0039] 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 provided in each of the left traveling motor 6 and the right traveling motor 7 that detects the rotation speed of the left traveling motor 6 and the right traveling motor 7 is used. The travel information sensor 23 transmits the detected travel information to the controller 10.

[0040] The map database 24 is a database that stores map information. The map database 24 is formed, for example, in a storage device (for example, a hard disk drive (HDD) or the like) mounted on the industrial vehicle 1. The map information includes, for example, information on a specific area including a runway, takeoff and landing area, taxiway, apron, control tower, hangar, loading and unloading area, charging area, etc. at an airport, such as road position information, road shape information (for example, curves, types of straight sections, curvature of curves, etc.), intersection and branch point position information, and structure position information. The map information includes position information of a road surface pattern 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.

[0041] The changeover switch 25 is a switch for switching between execution and non-execution of automatic driving control. Depending on the operation position of the changeover switch 25, the changeover switch 25 can be in either a state of execution of automatic driving control or a state of non-execution of automatic driving control. The changeover switch 25 outputs a signal according to the state of the changeover switch 25 to the controller 10.

[0042] 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.

[0043] The map information acquiring unit 11 acquires map information stored in the map database 24. The map information acquiring unit 11 acquires, for example, position information of a road surface pattern used for position recognition of the industrial vehicle 1.

[0044] The position information acquiring unit 12 acquires the position information of the industrial vehicle 1 based on the reception result of the GNSS receiver 21, the detection result of the surrounding condition sensor 22, and the map information of the map database 24. The position information acquiring 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 acquiring unit 12 may estimate the self-position of the industrial vehicle 1 using, for example, a SLAM [Simultaneous Localization And Mapping] method.

[0045] The travel information acquisition unit 13 acquires travel information of the industrial vehicle 1 based on the detection result of the travel information sensor 23. The travel information acquisition unit 13 here acquires vehicle speed information of the industrial vehicle 1 based on the detection result of the speed sensors provided on each of 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 result of the gyro sensor.

[0046] 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, map information, and the state of the changeover switch 25. 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 of the map database 24, the surrounding conditions (position of obstacles, etc.) of the industrial vehicle 1 recognized from the detection results of the surrounding conditions 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 according to a transportation command of the operation management system. The driving plan includes, for example, target turning angles of the FL tires 2 and the FR tires 3. The driving plan may also include a target speed.

[0047] The automatic driving control unit 14 executes automatic driving according to the driving plan. When a signal corresponding to the execution state of automatic driving control is input from the changeover switch 25, the automatic driving control unit 14 executes automatic driving control to generate the above-mentioned driving plan, and calculates whether automatic steering is required according to the driving plan. When a signal indicating that automatic driving control is not to be executed is input from the changeover switch 25, the automatic driving control unit 14 does not execute automatic driving control (non-execution of automatic driving control). The automatic driving control unit 14 may execute automatic driving control so as to realize the target speed by sending control signals to the left drive unit 6a and the right drive unit 7a.

[0048] The steering hydraulic control unit 15 controls the opening and closing of the electromagnetic proportional valve 51 according to the calculation result of the automatic driving control by the automatic driving control unit 14. The steering hydraulic control unit 15 transmits a command signal 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 (calculation result of automatic driving control). When automatic driving control is being executed and the calculation result of the automatic driving control is that automatic steering is to be performed, 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 tire 2 and the FR tire 3 become the target turning angles of the automatic steering. For example, when automatic driving control is being executed and the calculation result of the automatic driving control is that automatic steering is not to be performed, and when automatic driving control is not being executed, the electromagnetic proportional valve 51 is controlled to close. The steering hydraulic control unit 15 can acquire the turning angles of the FL tire 2 and the FR tire 3 based on, for example, a tire turning angle sensor (not shown).

[0049] [Structure regarding flow division of priority valve] The flow division of the priority valve 60 will be specifically described. Figures 4 and 5 are schematic cross-sectional views along the axis of the priority valve of Figure 1. As shown in Figures 4 and 5, the priority valve 60 has a valve support chamber 62 formed in a housing 61, a valve body 63 arranged slidably along the inner wall of the valve support chamber 62, and a spring 64 arranged between the inner wall of the valve support chamber 62 and the valve body 63 to bias the valve body 63 in one direction.

[0050] The valve support chamber 62 is formed as a cavity having a substantially cylindrical shape. The valve support chamber 62 has a hydraulic pump side opening 62a which is an opening of the hydraulic pump circuit 30a, a manual steering side opening 62b which is an opening of the introduction circuit 40a to the manual steering circuit 40, and an automatic steering side opening 62c which is an opening of the introduction circuit 50a to the automatic steering circuit 50.

[0051] The valve body 63 is disposed between the hydraulic pump side opening 62a and the 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 body 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 body 63 located on the side of the introduction circuit 40a. The hydraulic pump side back pressure chamber 65 is connected to a circuit 30f branched from the hydraulic pump circuit 30a, and is supplied with hydraulic oil 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.

[0052] The priority valve 60 here is configured as a priority valve with 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 the hydraulic oil becomes the design flow rate. The design flow rate is a design value of the flow rate of hydraulic oil preferentially supplied to the manual steering circuit 40, and is set to a constant flow rate value equal to or higher than a predetermined flow rate, for example. The predetermined flow rate means the minimum supply flow rate of hydraulic oil to the steering cylinder 32 required for the steering cylinder 32 to operate to steer the FL tire 2 and the FR tire 3. In other words, the priority valve 60 enables the operation of the steering cylinder 32 regardless of whether or not the hydraulic oil is diverted to the automatic steering circuit 50 by preferentially supplying hydraulic oil to the manual steering circuit 40 at a flow rate equal to or higher than the predetermined flow rate.

[0053] The priority valve 60 has an orifice 67 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 to the hydraulic pump side back pressure chamber 65. Therefore, the hydraulic oil that flows from the hydraulic pump circuit 30a into the hydraulic pump side back pressure chamber 65 is guided to the manual steering side back pressure chamber 66 through the orifice 67.

[0054] The flow rate of the 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 the hydraulic oil passing through the orifice 67 is 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 degree 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 degree D1 is a dimension along the axial direction of the valve support chamber 62 of the manual steering side communication flow path 68 that introduces the hydraulic oil from the manual steering side back pressure chamber 66 to the introduction circuit 40a.

[0055] 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 surplus hydraulic oil to the automatic steering circuit 50 on the solenoid proportional valve 51 side. In the priority valve 60, the automatic steering side opening 62c is formed to be located on the same side as the hydraulic pump side back pressure chamber 65 with respect to the orifice 67. Therefore, the flow rate of hydraulic oil to the automatic steering circuit 50 is mainly determined by the flow path area to the automatic steering side opening 62c in the hydraulic pump side back pressure chamber 65. In the following description, the communication opening degree 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 degree D2 is the dimension along the axial direction of the valve support chamber 62 of the automatic steering side communication flow path 69 that guides hydraulic oil from the hydraulic pump side back pressure chamber 65 to the introduction circuit 50a.

[0056] The priority valve 60 is configured so that the communication opening degree D2 and the communication opening degree D1 change as a result of the valve element 63 moving along the inner wall of the valve support chamber 62. Specifically, as the valve element 63 moves in the biasing direction of the valve element 63 by the spring 64, the communication opening degree D2 of the automatic steering side communication passage 69 becomes smaller and the communication opening degree D1 of the manual steering side communication passage 68 becomes larger.

[0057] 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 the 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 electromagnetic 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 electromagnetic 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. When the rotation speed of the hydraulic pump 31 increases in an attempt to maintain the flow rate of the hydraulic oil in the hydraulic pump circuit 30a in order to pump the hydraulic oil against this pressure loss, the hydraulic pressure in the hydraulic pump circuit 30a and the hydraulic pump side back pressure chamber 65 increases. Due to this increase in hydraulic pressure, the valve body 63 moves 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.

[0058] For example, Fig. 4 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.

[0059] In the example of Fig. 4, since the PS valve 41 is closed, the 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 the hydraulic oil. Similarly, since the solenoid proportional valve 51 is closed, the 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 the 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 according to the pressure loss, so the valve body 63 is not subjected to a biasing force due to the hydraulic pressure in the hydraulic pump side back pressure chamber 65. Therefore, the valve body 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.

[0060] In this state, the valve body 63 moves so that the biasing forces from both sides of the valve body 63 are balanced, so that 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 the 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, since the communication opening degree D1 is sufficiently large, the flow rate of the hydraulic oil passing through the orifice 67 corresponds to the design flow rate supplied to the manual steering circuit 40. In the example of FIG. 4, 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 cut off.

[0061] 5 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 is to perform automatic steering, and the steering wheel 33 is being operated.

[0062] In the example of Fig. 5, since the solenoid proportional valve 51 is open, hydraulic oil flows through the solenoid proportional valve 51 in the automatic steering circuit 50, and a pressure loss occurs due to the flow of hydraulic oil. Similarly, since the PS valve 41 is open, hydraulic oil flows through the PS valve 41 in the manual steering circuit 40, and a pressure loss occurs 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 increases according to the pressure loss, and a biasing force due to the hydraulic pressure of the hydraulic pump side back pressure chamber 65 is generated on the valve body 63. Then, the valve body 63 moves toward the manual steering side back pressure chamber 66 due to the biasing force due to the hydraulic pressure of the hydraulic pump side back pressure chamber 65, and the communication opening degree D1 of the manual steering side communication flow path 68 becomes smaller.

[0063] 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 4, and is larger by an amount corresponding to the pressure loss in addition to the biasing force of the spring 64. Since the pressure difference is larger, the flow rate of the hydraulic oil passing through the orifice 67 can be larger than the example of Figure 4. However, since the communication opening degree D1 is smaller than the example of Figure 4, the flow rate of the hydraulic oil supplied to the manual steering circuit 40 becomes equivalent to the example of Figure 4 and becomes 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 a surplus flow rate.

[0064] When either the PS valve 41 or the solenoid proportional valve 51 is open, the position of the valve body 63 is, for example, between Figures 4 and 5 so that 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 a balanced position 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.

[0065] According to the priority valve 60 configured as described above, even when the electromagnetic proportional valve 51 is open according to the calculation result of the automatic driving control, at least the designed flow rate of hydraulic oil is supplied to the manual steering circuit 40, so that the steering cylinder 32 can be operated in response to the operation of the steering wheel 33. Therefore, when the automatic driving control is being executed and automatic steering is being performed, for example, in a situation where an unexpected obstacle appears and it becomes necessary to avoid the obstacle, the steering cylinder 32 is operated in response to the operation of the steering wheel 33 by the operator, so that obstacle avoidance by manual steering is possible even during automatic steering.

[0066] Incidentally, in the priority valve 60 as in this embodiment, the surplus flow rate of hydraulic oil exceeding the design flow rate flowing to the manual steering circuit 40 is supplied to the automatic steering circuit 50. When the electromagnetic proportional valve 51 is closed in the automatic steering circuit 50, the hydraulic oil does not flow through the electromagnetic proportional valve 51 in the automatic steering circuit 50. If it is assumed that the surplus flow rate of hydraulic oil supplied to the automatic steering circuit 50 is not returned to the tank 34, the hydraulic oil remains in the automatic steering circuit 50, and the pressure (pilot pressure) of the hydraulic oil from the hydraulic pump 31 acting on the electromagnetic proportional valve 51 becomes high. As a result, the driving energy (electricity in this case) of the hydraulic pump 31 becomes excessively large, and there is a risk that the operating time of the steering device 100 of the industrial vehicle will be shortened.

[0067] Therefore, in the steering device 100 for an industrial vehicle of this embodiment, the steering hydraulic control unit 15 judges whether or not the automatic steering non-operation condition is satisfied. The unloading valve 52 is provided so as to be able to reduce the pressure of the hydraulic oil acting on the solenoid proportional valve 51 based on the judgment result of the steering hydraulic control unit 15. When it is judged that the automatic steering non-operation condition is satisfied, the steering hydraulic control unit 15 controls the unloading valve 52 to reduce the pressure of the hydraulic oil acting on the solenoid proportional valve 51. In other words, the controller 10 and the unloading valve 52 constitute an unloading means for reducing the pressure of the hydraulic oil from the hydraulic pump 31 acting on the solenoid proportional valve 51.

[0068] The automatic steering non-operation condition is a predetermined condition for determining whether or not to halt the supply of hydraulic oil via the electromagnetic proportional valve 51. The automatic steering non-operation condition can be a condition based on information regarding execution or non-execution of automatic driving control, or vehicle speed information of the industrial vehicle 1.

[0069] More specifically, the steering hydraulic control unit 15 may determine, based on a signal from the changeover switch 25, that the automatic steering non-operation condition is satisfied when the state of the changeover switch 25 indicates that automatic driving control is not being executed.

[0070] Alternatively, the steering hydraulic control unit 15 may determine whether the industrial vehicle 1 has been stopped continuously for a predetermined time based on the vehicle speed information of the industrial vehicle 1, and may determine that the automatic steering non-operation condition is satisfied when it is determined that the industrial vehicle 1 has been stopped continuously for the predetermined time. The steering hydraulic control unit 15 may determine that the industrial vehicle 1 has been stopped continuously for a predetermined time when the vehicle speed of the industrial vehicle 1 has been equal to or lower than a predetermined stopping vehicle speed threshold for a predetermined time. The stopping vehicle speed threshold and the predetermined time are not particularly limited, but may be, for example, several km / h and several minutes, assuming a situation in which the industrial vehicle 1 is left stopped.

[0071] The automatic steering non-operation condition is not limited to the above specific example. For example, the steering hydraulic control unit 15 may determine that the automatic steering non-operation condition is satisfied when a configuration for performing automatic driving (for example, any one of the GNSS receiver 21, the surrounding situation sensor 22, the driving information sensor 23, the map database 24, and the changeover switch 25) is malfunctioning.

[0072] According to the above-described unloading means, when the automatic steering non-operation conditions are satisfied, the pressure of the hydraulic oil from the hydraulic pump 31 acting on the electromagnetic proportional valve 51 can be reduced compared to when the automatic steering non-operation conditions are not satisfied.

[0073] [An example of calculation processing by a controller] Next, an example of the calculation process by the controller 10 will be described. Fig. 6 is a flow chart illustrating an example of the unload process of the controller in Fig. 1. The process shown in Fig. 6 is executed, for example, when the main power supply of the industrial vehicle 1 is turned on and power supply to the hydraulic pump 31 is possible.

[0074] 6, in S01, the controller 10 determines whether or not an automatic steering non-operation condition is satisfied by the steering hydraulic control unit 15. Specifically, as the processing in S01, the controller 10 performs a process of determining whether or not the automatic steering non-operation condition is satisfied, as exemplified in FIG.

[0075] Fig. 7 is a flowchart illustrating the process of determining whether the automatic steering is inoperative in Fig. 6. As shown in Fig. 7, in S11, the controller 10 receives a signal from the changeover switch 25 via the steering hydraulic control unit 15. The steering hydraulic control unit 15 receives a signal from the changeover switch 25 according to the state of the changeover switch 25.

[0076] In S12, the controller 10 determines whether or not the automatic driving control is not being executed by the steering hydraulic control unit 15. For example, based on a signal from the changeover switch 25, when the state of the changeover switch 25 indicates that the automatic driving control is not being executed, the controller 10 determines that the automatic driving control is not being executed.

[0077] If the state of the changeover switch 25 is a state in which the automatic driving control is not executed (S12=YES), the controller 10 proceeds to S16 described below. If the state of the changeover switch 25 is a state in which the automatic driving control is executed (S12=NO), the controller 10 proceeds to S13.

[0078] In S13, the controller 10 acquires vehicle speed information by the travel information acquisition unit 13. The travel information acquisition unit 13 acquires vehicle speed information of the industrial vehicle 1 based on the detection results of the travel information sensor 23 (e.g., the rotation speed of the left travel motor 6 and the rotation speed of the right travel motor 7).

[0079] In S14, the controller 10 determines, by the steering hydraulic control unit 15, whether or not the industrial vehicle 1 has been stopped for a predetermined time. For example, based on vehicle speed information, the steering hydraulic control unit 15 determines that the industrial vehicle 1 has been stopped for a predetermined time when the vehicle speed of the industrial vehicle 1 has been below a predetermined stopping vehicle speed threshold for a predetermined time. When the steering hydraulic control unit 15 determines that the industrial vehicle 1 has been stopped for a predetermined time (S14=YES), the process proceeds to S16 described below. When the steering hydraulic control unit 15 determines that the industrial vehicle 1 has not been stopped for a predetermined time (S14=NO), the process proceeds to S15.

[0080] In S15, the controller 10 determines that the automatic steering non-operation condition is not satisfied by the steering hydraulic control unit 15. On the other hand, in S16, the controller 10 determines that the automatic steering non-operation condition is satisfied by the steering hydraulic control unit 15. After that, the controller 10 ends the processing in FIG. 7 and proceeds to S02 in FIG. 6.

[0081] 6, if the steering hydraulic control unit 15 determines in S02 that the automatic steering non-operation condition is satisfied (S02=YES), the controller 10 proceeds to S04, which will be described later. If the steering hydraulic control unit 15 determines in S02 that the automatic steering non-operation condition is not satisfied (S02=NO), the controller 10 proceeds to S03.

[0082] In S03, the controller 10 sets the hydraulic pressure (pilot pressure) acting on the solenoid proportional valve 51 as the first pressure by the steering hydraulic control unit 15. The first pressure is the pressure of the hydraulic oil when the surplus flow rate of the hydraulic oil supplied to the automatic steering circuit 50 side is not returned to the tank 34. In this embodiment, in S03, the steering hydraulic control unit 15 controls the pressure of the hydraulic oil acting on the solenoid proportional valve 51 so as not to be reduced by the unloading valve 52 (for example, to close the unloading valve 52). As a result, the hydraulic pressure (pilot pressure) acting on the solenoid proportional valve 51 becomes the first pressure. Thereafter, the controller 10 ends the processing of FIG. 6 and repeats the processing of FIG. 6 after a predetermined calculation period.

[0083] In S04, the controller 10 sets the hydraulic pressure (pilot pressure) acting on the solenoid proportional valve 51 to a second pressure lower than the first pressure by the steering hydraulic control unit 15. The second pressure is the pressure of the hydraulic oil when the surplus flow rate of the hydraulic oil supplied to the automatic steering circuit 50 side is returned to the tank 34. In this embodiment, the steering hydraulic control unit 15 controls the unloading valve 52 so as to reduce the pressure of the hydraulic oil acting on the solenoid proportional valve 51 (for example, to open the unloading valve 52) compared to when it is determined in S04 that the automatic steering non-operation condition is not satisfied (S02=NO). As a result, the hydraulic pressure (pilot pressure) acting on the solenoid proportional valve 51 becomes the second pressure. After that, the controller 10 ends the process of FIG. 6 and repeats the process of FIG. 6 after a predetermined calculation period.

[0084] [Action and Effects] As described above, in the steering device 100 for an industrial vehicle according to this embodiment, the hydraulic oil is divided into the manual steering circuit 40 and the automatic steering circuit 50 by the priority valve 60, and is preferentially supplied to the manual steering circuit 40 at a flow rate equal to or greater than the predetermined flow rate for operating the steering cylinder 32. As a result, even if the solenoid proportional valve 51 is in a state where it is opened according to the calculation result of the automatic driving control, at least the predetermined flow rate of hydraulic oil is supplied to the manual steering circuit 40, so that the steering cylinder 32 can be operated in response to the operation of the steering wheel 33. Therefore, according to the steering device 100 for an industrial vehicle, it is possible to make the steering hydraulic circuit 30 function so that manual steering is possible even in a state where automatic steering is possible.

[0085] For example, in a configuration in which the manual steering circuit 40 and the automatic steering circuit 50 are divided by a lock valve that operates in response to an electric signal instead of the priority valve 60, and an electric signal is sent to the lock valve using a spare battery, if the spare battery fails, the lock valve cannot be operated and manual steering is also impossible. In contrast, according to the steering device 100 for an industrial vehicle using the priority valve 60 as in this embodiment, the hydraulic oil can be mechanically supplied to the manual steering circuit 40 at a design flow rate even without a power source such as the spare battery, so that by mechanically connecting the steering wheel 33 and the PS valve 41, it is possible to avoid manual steering being impossible due to the failure of the power source for division. In addition, since the configuration of a power source such as the spare battery can be omitted, an increase in the number of parts can be suppressed.

[0086] The steering device 100 for the industrial vehicle further includes an unloading means for lowering the pressure of the hydraulic oil from the hydraulic pump 31 acting on the electromagnetic proportional valve 51 when a predetermined automatic steering non-operation condition for suspending the supply of hydraulic oil via the electromagnetic proportional valve 51 is satisfied, compared to when the automatic steering non-operation condition is not satisfied. As a result, when the priority valve 60 is configured so that the supply of hydraulic oil to the electromagnetic proportional valve 51 is not always completely cut off, assuming a configuration in which the surplus flow rate of hydraulic oil supplied to the automatic steering circuit 50 side is not returned to the tank 34, the pressure of the hydraulic oil from the hydraulic pump 31 always acts on the electromagnetic proportional valve 51, and an unnecessary load is applied to the hydraulic pump 31. Therefore, by using the unloading means to lower the pressure of the hydraulic oil from the hydraulic pump 31 acting on the electromagnetic proportional valve 51 when the automatic steering non-operation condition is satisfied, it is possible to suppress the application of an unnecessary load to the hydraulic pump 31. As a result, it is possible to suppress a reduction in the operating time of the steering device 100 of the industrial vehicle caused by unnecessary load being applied to the hydraulic pump 31. In addition, by reducing the load on the hydraulic pump 31, the temperature of the hydraulic oil is less likely to rise, and overheating of the hydraulic pump 31 and the hydraulic oil is less likely to occur, for example, in a high-temperature environment. In addition, it is possible to employ a hydraulic pump 31 with a relatively low heat resistance.

[0087] In the steering device 100 for an industrial vehicle, the unloading means includes a controller 10 that determines whether an automatic steering non-operation condition is satisfied based on information on whether automatic driving control is executed or not, or vehicle speed information of the industrial vehicle 1, and an unloading valve 52 that is provided so as to be able to reduce the pressure of the hydraulic oil from the hydraulic pump 31 acting on the solenoid proportional valve 51 based on the determination result of the controller 10. When it is determined that the automatic steering non-operation condition is satisfied, the controller 10 controls the unloading valve 52 so as to reduce the pressure of the hydraulic oil from the hydraulic pump 31 acting on the solenoid proportional valve 51. Thus, by controlling the unloading valve 52 based on the determination result of the controller 10, it is possible to reduce the pressure of the hydraulic oil from the hydraulic pump 31 acting on the solenoid proportional valve 51 when the automatic steering non-operation condition is satisfied.

[0088] In the steering device 100 of the industrial vehicle, the controller 10 determines that the automatic steering non-operation condition is satisfied when the changeover switch 25, which switches between execution and non-execution of automatic driving control, is in the state where automatic driving control is not executed, based on a signal from the changeover switch 25. This makes it possible to prevent unnecessary load from being applied to the hydraulic pump 31 in a state where automatic driving control is not executed and automatic steering is not performed.

[0089] In the steering device 100 for an industrial vehicle, the controller 10 determines whether the industrial vehicle 1 has been stopped continuously for a predetermined time based on the vehicle speed information of the industrial vehicle 1, and determines that the automatic steering non-operation condition is satisfied when it is determined that the industrial vehicle 1 has been stopped continuously for the predetermined time. This makes it possible to prevent unnecessary load from being applied to the hydraulic pump 31 when the industrial vehicle 1 has been stopped continuously for the predetermined time.

[0090] [Variations] Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment.

[0091] The unloading means is not limited to the unloading valve 52 and the controller 10 that controls the unloading valve 52 as described above. For example, as a modified example of the unloading means, the controller 10 may control the rotation speed of the (fixed capacity) hydraulic pump 31 based on the determination result of the controller 10. When the automatic steering non-operating condition is satisfied, the controller 10 can reduce the pressure of the hydraulic oil from the hydraulic pump 31 acting on the solenoid proportional valve 51 by reducing the rotation speed of the hydraulic pump 31.

[0092] Alternatively, as another modified example of the unloading 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, and the controller 10 may control the variable displacement pump to reduce the amount of hydraulic oil discharged when it is determined that the automatic steering non-operation condition is satisfied. In this case, by controlling the discharge amount during operation of the variable displacement pump based on the determination result of the controller 10, it is possible to reduce the pressure of the hydraulic oil from the variable displacement pump acting on the solenoid proportional valve 51 when the automatic steering non-operation condition is satisfied.

[0093] In the above embodiment, the steering device 100 for the industrial vehicle is provided with an unloading means, but the unloading means may be omitted. In this case, as in the example of Fig. 4, the priority valve 60 is configured so that the supply of hydraulic oil to the electromagnetic proportional valve 51 on the automatic steering circuit 50 side is not always completely cut off, but a dividing valve configured to be completely cut off may be used. By completely cutting off the supply of hydraulic oil to the electromagnetic proportional valve 51, a decrease in the pressure of the hydraulic oil (pilot pressure) from the hydraulic pump 31 acting on the electromagnetic proportional valve 51 can be expected compared to the case where the supply is not completely cut off.

[0094] 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, another industrial vehicle such as a forklift.

[0095] 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.

[0096] At least some of the embodiments and various modified examples described above may be combined in any desired manner. [Explanation of symbols]

[0097] 1...industrial vehicle, 10...controller (control unit), 11...map information acquisition unit, 12...location information acquisition unit, 13...driving information acquisition unit, 14...automatic driving control unit, 15...steering hydraulic control unit, 25...changeover switch (switch), 30...steering hydraulic circuit (hydraulic circuit), 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), 52...unload 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 a steering wheel, a manual steering circuit having a first valve that is opened and closed in response to an 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 according to a 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, dividing the hydraulic oil into the manual steering circuit and the automatic steering circuit; Equipped with the flow dividing valve is a priority valve that preferentially supplies the hydraulic oil to the manual steering circuit at a flow rate equal to or greater than a predetermined flow rate for operating the steering cylinder, A steering device for an industrial vehicle, further comprising an unloading means for reducing the pressure of the hydraulic oil from the hydraulic pump acting on the second valve when a predetermined automatic steering non-operation condition for suspending the supply of the hydraulic oil via the second valve is satisfied, compared to when the automatic steering non-operation condition is not satisfied.

2. The unloading means includes: A control unit that determines whether the automatic steering non-operation condition is satisfied based on information regarding execution or non-execution of the automatic driving control or vehicle speed information of the industrial vehicle; and an unloading valve that is provided to be able to reduce a pressure of the hydraulic oil from the hydraulic pump acting on the second valve based on a determination result of the control unit; having 2. The steering device for an industrial vehicle according to claim 1, wherein the control unit controls the unloading valve so as to reduce the pressure of the hydraulic oil from the hydraulic pump acting on the second valve when it determines that the automatic steering non-operation condition is satisfied.

3. The unloading means includes: A control unit that determines whether the automatic steering non-operation condition is satisfied based on information regarding execution or non-execution of the automatic driving control or vehicle speed information of the industrial vehicle; and a variable displacement pump that is the hydraulic pump configured to change the discharge amount of the hydraulic oil during operation based on a determination result of the control unit; having 3. The steering device for an industrial vehicle according to claim 1, wherein the control unit controls the variable displacement pump to reduce a discharge amount of the hydraulic oil when it is determined that the automatic steering non-operation condition is satisfied.

4. 4. The steering device of an industrial vehicle as described in claim 2 or 3, wherein the control unit determines that the automatic steering non-operation condition is satisfied when the state of the switch for switching between execution or non-execution of the automatic driving control is in a state in which the automatic driving control is not executed, based on a signal from the switch.

5. The control unit determines whether the industrial vehicle has been stopped continuously for a predetermined time based on vehicle speed information of the industrial vehicle, and determines that the automatic steering non-operation condition is satisfied when it determines that the industrial vehicle has been stopped continuously for the predetermined time.

Images