Wheeled work vehicle

Abstract

To provide a wheel type work vehicle that is able to immediately actuate steering by means of a steering operation lever when runaway occurs while preventing occurrence of steering operation unintended by an operator due to erroneous operation.SOLUTION: A wheel loader including a steering lever 34 and a setting switch 36 including a setting position for validating / invalidating an operation of the steering lever, has a controller 5 that controls actuation of steering cylinders 41, 42. When a vehicle body is in a traveling state, the controller 5 actuates the steering cylinders 41, 42 according to the operation of the steering lever 34 regardless of the setting position of the setting switch 36.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a wheeled work vehicle provided with a plurality of wheels. [Background technology]

[0002] Wheel loaders and other wheeled work vehicles perform work while traveling on roads, requiring frequent steering operations to change the vehicle's direction of travel. Steering operation devices include the typical wheel-type steering operation device located in front of the driver's seat, as well as lever-type steering operation devices located near the armrest in recent years to reduce operator fatigue and allow the operator to operate the steering wheel in a comfortable position with their elbows resting on the armrest. Depending on the specifications of the work vehicle, the driver's cab may be equipped with both wheel-type and lever-type steering devices, or with only one of them.

[0003] Although lever-type steering devices are easier to operate than wheel-type steering devices, they can easily tilt if the operator's clothing or equipment gets caught on the control lever, or if the operator accidentally touches the control lever, which could result in the steering being activated at a time the operator does not expect. Therefore, some work vehicles are equipped with a function to switch the control lever between enabled and disabled to prevent steering activation due to incorrect operation of the control lever.

[0004] For example, Patent Document 1 discloses a work vehicle equipped with a control unit that disables steering operation using the steering lever when a steering lever switch for switching between operating and non-operating states of the steering lever is in the operating position, a seating sensor detects that an operator is not seated in the driver's seat, the vehicle speed is below a predetermined speed, the travel lever is in the neutral position, and the brake pedal is not depressed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-157543 Summary of the Invention [Problem to be solved by the invention]

[0006] Movement of a work vehicle also includes runaway, which is movement unintentional by the operator. Runaway occurs, for example, when a work vehicle is stopped on a steep slope with the parking brake applied and comes into contact with another vehicle, causing the work vehicle to start moving, or when the operator forgets to apply the parking brake, even on a gentle slope, causing the work vehicle to start moving after having been stopped. When a work vehicle runs away like this, the operator needs to immediately apply the steering.

[0007] However, in the work vehicle described in Patent Document 1, because operation with the steering control lever is possible only when various conditions are met, such as the steering lever switch being in the operating position, the seating sensor detecting that an operator is seated in the driver's seat, the vehicle speed being faster than a predetermined speed, the travel lever being in the forward or reverse position, and the brake pedal being depressed, it is difficult to immediately enable operation of the steering control lever if the work vehicle runs away.In particular, if the work vehicle runs away while the steering lever switch is in the inoperable position, the steering control lever cannot be operated at all, and the operator cannot operate the steering with the steering control lever.

[0008] Therefore, an object of the present invention is to provide a wheeled work vehicle that prevents the operator from making unintended steering movements due to erroneous operation, while allowing the operator to immediately operate the steering lever in the event of a runaway. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides a vehicle body provided with a plurality of wheels, a driver's cab provided on the vehicle body, a steering cylinder for steering the plurality of wheels, a hydraulic pump for supplying hydraulic oil to the steering cylinder, a steering control valve for controlling the flow of hydraulic oil discharged from the hydraulic pump and supplied to the steering cylinder, a pilot pump for supplying pilot pressure oil to the steering control valve, a steering lever provided in the driver's cab for steering operation, and an enabling setting for enabling operation of the steering lever to operate the steering cylinder in response to operation of the steering lever. situation and a disable setting that disables the operation of the steering lever and deactivates the steering cylinder. situation and, Set to In a wheeled work vehicle equipped with a setting switch, an electromagnetic control valve that controls pilot pressure oil discharged from the pilot pump and acting on the steering control valve, a controller that controls the electromagnetic control valve, and a vehicle speed sensor that detects the vehicle speed of the vehicle body, the controller determines whether the vehicle body is in a stopped state or a moving state based on the vehicle speed detected by the vehicle speed sensor, and when the vehicle body is determined to be in the stopped state and the setting switch Chi The above enable setting situation When the vehicle body is determined to be in the stopped state, an enabling signal for operating the steering cylinder in response to the operation of the steering lever is output to the electromagnetic control valve, and the setting switch Chi The above-mentioned disable setting situation When the steering lever is operated, a disabling signal that disables the operation of the steering cylinder in response to the operation of the steering lever is output to the electromagnetic control valve, and when it is determined that the vehicle body is in the traveling state, the enabling signal is output to the electromagnetic control valve. [Effects of the Invention]

[0010] According to the present invention, it is possible to prevent unintended steering operations by the operator due to erroneous operation, while enabling the operator to immediately operate the steering lever when the vehicle runs away. Problems, configurations, and effects other than those described above will become clear from the following description of the embodiment. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is an external side view showing an example of the configuration of a wheel loader according to an embodiment of the present invention. [Figure 2] FIG. 2 is a top view showing the wheel loader with the steering wheel turned to the left. [Figure 3] FIG. 2 is a perspective view of the inside of the cab as seen from the rear left side. [Figure 4] FIG. 2 is a perspective view of the inside of the cab as seen from the front right side. [Figure 5] FIG. 1 is a system configuration diagram showing an example of a configuration of a steering drive device. [Figure 6] FIG. 2 is a functional block diagram showing functions of a controller. [Figure 7] 10 is a flowchart showing the flow of processing executed by a controller. [Figure 8] FIG. 4 is a state transition diagram showing state transitions of the steering drive device. DETAILED DESCRIPTION OF THE INVENTION

[0012] Below, as one aspect of a wheeled work vehicle according to an embodiment of the present invention, a wheel loader that performs loading and unloading work, for example, by digging up earth, sand, minerals, etc. and loading them into a loading destination such as a dump truck or hopper, will be described.

[0013] (Overall configuration of wheel loader 1) First, the overall configuration of a wheel loader 1 according to an embodiment of the present invention will be described with reference to FIGS.

[0014] Fig. 1 is an external side view showing an example of the configuration of a wheel loader 1 according to an embodiment of the present invention. Fig. 2 is a top view showing the wheel loader 1 in a state where the steering wheel is turned to the left.

[0015] The wheel loader 1 is an articulated work vehicle that is steered by bending the vehicle body near the center. Specifically, a front frame 1A, which forms the front part of the vehicle body, and a rear frame 1B, which forms the rear part of the vehicle body, are connected by a center joint 10 so that they can rotate freely in the left and right directions, and when the operator performs steering operations, a pair of left and right steering cylinders 41, 42 is actuated, causing the front frame 1A to bend left and right relative to the rear frame 1B.

[0016] In the following explanation, the left side of the vehicle body facing forward will be referred to as the "left direction," and the right side of the operator will be referred to as the "right direction." Figure 2 shows the wheel loader 1 in a state where the steering is turned leftward and the vehicle is turning left. The specific configuration of the steering actuation system will be described later.

[0017] The vehicle body is provided with four wheels 11, two of which are front wheels 11A and are provided on both the left and right sides of the front frame 1A, and the remaining two are rear wheels 11B and are provided on both the left and right sides of the rear frame 1B. Of the four wheels 11, only the front wheel 11A and rear wheel 11B provided on the left side are shown in FIG. 1. There is no particular restriction on the specific number of wheels 11 provided on the vehicle body.

[0018] A working device 2 for carrying out cargo handling work is attached to the front portion of the front frame 1A. The working device 2 has a lift arm 21 attached to the front frame 1A so as to be rotatable in the vertical direction, two lift arm cylinders 22L, 22R that drive the lift arm 21, a bucket 23 attached to the tip of the lift arm 21 so as to be rotatable in the vertical direction, a bucket cylinder 24 that drives the bucket 23, and a bell crank 25 rotatably connected to the lift arm 21 and constituting a link mechanism between the bucket 23 and the bucket cylinder 24.

[0019] The lift arm 21 rotates upward relative to the front frame 1A when the rods 220 of the two lift arm cylinders 22L, 22R extend, and rotates downward relative to the front frame 1A when the rods 220 of the two lift arm cylinders 22L, 22R retract. As shown in Figure 2, the two lift arm cylinders 22L, 22R are arranged side by side at a predetermined distance in the left-right direction of the vehicle body. Note that in Figure 1, both lift arm cylinders 22L, 22R are not shown because they are located in positions hidden by the front wheel 11A provided on the left side.

[0020] The bucket 23 rotates upward relative to the lift arm 21 (tilt operation) when the rod 240 of the bucket cylinder 24 extends, and rotates downward relative to the lift arm 21 (dump operation) when the rod 240 of the bucket cylinder 24 retracts. This enables the bucket 23 to scoop up an object to be worked on and discharge (release) it at the loading destination. The bucket 23 can be replaced with various attachments, such as a blade, and the wheel loader 1 can also perform various operations such as snow removal and earth-dozing in addition to cargo handling operations using the bucket 23.

[0021] The rear frame 1B is provided with a cab 12 in which an operator sits, a machine room 13 that houses various devices required to drive the wheel loader 1, and a counterweight 14 that maintains balance with the work implement 2 so that the vehicle body does not tilt. On the rear frame 1B, the cab 12 is located at the front, the counterweight 14 at the rear, and the machine room 13 between the cab 12 and the counterweight 14.

[0022] In this embodiment, the travel of the vehicle body of the wheel loader 1 is controlled by a torque converter type travel drive device. The travel drive device is configured to include an engine 131, a torque converter 132 connected to the output shaft of the engine 131, and a transmission 133 connected to the output shaft of the torque converter 132.

[0023] The driving force generated by the rotation of the engine 131 is changed in speed by the torque converter 132 and the transmission 133, and then transmitted to each of the four wheels 11 via the propeller shaft 134 and axles 135 (see FIG. 2), thereby causing the wheel loader 1 to travel. Note that in FIG. 1, the engine 131, torque converter 132, transmission 133, and propeller shaft 134 are each indicated by dashed lines.

[0024] (Configuration inside the driver's cab 12) Next, the configuration inside the operator's cab 12 will be described with reference to FIGS.

[0025] Fig. 3 is a perspective view of the inside of the cab 12 as seen from the rear left side, and Fig. 4 is a perspective view of the inside of the cab 12 as seen from the front right side.

[0026] A driver's seat 31 where the operator sits is installed in the center of the driver's cab 12. In front of the driver's seat 31 is a console 32 on which a monitor that displays the running state of the vehicle body and the operating state of the work implement 2, and on which various operation switches are arranged.

[0027] Two work operation levers 33 are provided side by side in the left-right direction on the right side of the driver's seat 31 as operation devices for operating the work implement 2. Each of the two work operation levers 33 is a lever that can be tilted in the front-rear direction.

[0028] One of the two work operation levers 33 corresponds to the lever that operates the lift arm 21, and for example, when the operator tilts one of the work operation levers 33 forward, the lift arm 21 rotates downward relative to the front frame 1A, and when the operator tilts it backward (toward the operator), the lift arm 21 rotates upward relative to the front frame 1A.

[0029] The other of the two work operation levers 33 corresponds to the lever that operates the bucket 23, and for example, when the operator tilts the other work operation lever 33 forward, the bucket 23 performs a dump operation, and when the operator tilts it backward (toward the operator), the bucket 23 performs a tilt operation.

[0030] The operating device for operating the work implement 2 does not necessarily have to be two work operating levers 33; for example, a single work operating lever 33 that can be tilted in two directions, forward / backward and left / right, may be used to operate both the lift arm 21 and the bucket 23.

[0031] A steering lever 34 serving as a steering operation device for steering is provided on the left side of the driver's seat 31. In this embodiment, the steering lever 34 is an electric lever that can be tilted left and right.

[0032] For example, when the operator tilts the steering lever 34 to the left, the wheel loader 1 is steered to the left (turn left) in accordance with the operation signal for left steering output from the steering lever 34. On the other hand, when the operator tilts the steering lever 34 to the right, the wheel loader 1 is steered to the right (turn right) in accordance with the operation signal for right steering output from the steering lever 34. The steering lever 34 does not necessarily have to be an electric lever, and may be a mechanical lever.

[0033] A support base 35 for supporting the left elbow of the operator is provided behind the steering lever 34. The operator can operate the steering lever 34 with his / her left elbow resting on this support base 35.

[0034] 4, a setting switch 36 for enabling or disabling the operation of the steering lever 34 is attached to the front lower side of the support base 35. In this embodiment, the setting switch 36 includes an enable setting position for enabling the operation of the steering lever 34, a disable setting position for disabling the operation of the steering lever 34, and a hold position for holding the enable setting or the disable setting.

[0035] For example, when the operator presses the setting switch 36 forward, the setting switch 36 is set to the enable setting position, and the wheel loader 1 operates the steering in accordance with the operation direction and operation amount (tilt direction and tilt amount) of the steering lever 34. On the other hand, when the operator presses the setting switch 36 rearward (toward the operator), the setting switch 36 is set to the disable setting position, and the steering is not operated.

[0036] The wheel loader 1 uses a lever-type steering operation device (steering lever 34) as the steering operation device, so if the operator's clothing or equipment gets caught on the steering lever 34 or if the operator unconsciously touches the steering lever 34, the loader can easily tip over, making it more susceptible to incorrect operation than with a wheel-type steering operation device.

[0037] Therefore, the wheel loader 1 is provided with a setting switch 36 that sets the operation of the steering lever 34 to valid or invalid, thereby preventing the operator from performing an unintended steering operation due to an erroneous operation of the steering lever 34.

[0038] Furthermore, when the setting switch 36 is in a neutral state where it is not pressed forward or backward, it is in the hold position, and the setting immediately before it was in the hold position is maintained. Note that the setting switch 36 only needs to include at least the enable setting position and the disable setting position, and does not necessarily have to include the hold position.

[0039] The work control lever 33, steering lever 34, and setting switch 36 do not necessarily have to be positioned as shown in Figures 3 and 4, and their positions may be changed depending on the specifications of the cab 12 as long as they are within a range that can be operated by an operator seated in the cab 31.

[0040] (Configuration of steering drive device 4) Next, the configuration of the steering drive device 4 that operates the steering of the wheel loader 1 will be described with reference to FIG.

[0041] FIG. 5 is a system configuration diagram showing an example of the configuration of the steering drive device 4.

[0042] The steering drive device 4 includes a pair of steering cylinders 41, 42 that steer the four wheels 11 (a pair of left and right front wheels 11A and rear wheels 11B), a hydraulic pump 44 that is driven by the engine 131 to supply hydraulic oil to each of the pair of steering cylinders 41, 42, a steering control valve 45 that controls the flow (direction and flow rate) of hydraulic oil discharged from the hydraulic pump 44 and supplied to each of the pair of steering cylinders 41, 42, a pilot pump 46 that is driven by the engine 131 to supply pilot pressure oil to the steering control valve 45, a pair of electromagnetic control valves 47, 48 that control the pilot pressure oil discharged from the pilot pump 46 and acting on the steering control valve 45, and a hydraulic oil tank 49 that stores hydraulic oil.

[0043] The pair of steering cylinders 41, 42 are arranged side by side in the left-right direction of the vehicle body, and connect the front frame 1A and the rear frame 1B. Specifically, the tip ends of the rods 41A, 42A of the pair of steering cylinders 41, 42 are attached to the front frame 1A, and the ends on the bottom chambers 41B, 42B side are attached to the rear frame 1B. In this embodiment, of the pair of steering cylinders 41, 42, the one located on the left side is referred to as the "left steering cylinder 41," and the one located on the right side is referred to as the "right steering cylinder 42."

[0044] The wheel loader 1 steers to the left (turns left) as shown in FIG. 5 when the rod 41A of the left steering cylinder 41 contracts and the rod 42A of the right steering cylinder 42 extends, and steers to the right (turns right) when the rod 41A of the left steering cylinder 41 extends and the rod 42A of the right steering cylinder 42 contracts.

[0045] The steering control valve 45 has a first switching position 45A that turns the wheel loader 1 left, a second switching position 45B that turns the wheel loader 1 right, and a neutral position 45N that moves the wheel loader 1 straight. The first switching position 45A, second switching position 45B, and neutral position 45N are switched among each other by movement of a spool provided inside the steering control valve 45. The first switching position 45A, second switching position 45B, and neutral position 45N are aligned in the movement direction of the spool so that the neutral position 45N is located between the first switching position 45A and the second switching position 45B.

[0046] In the first switching position 45A, the discharge side of the hydraulic pump 44 is connected to the rod chamber 41C of the left steering cylinder 41 and the bottom chamber 42B of the right steering cylinder 42, and the bottom chamber 41B of the left steering cylinder 41 and the rod chamber 42C of the right steering cylinder 42 are connected to the hydraulic oil tank 49.

[0047] Therefore, when the steering control valve 45 is switched to the first switch position 45A, the hydraulic oil discharged from the hydraulic pump 44 flows into the rod chamber 41C of the left steering cylinder 41 and the bottom chamber 42B of the right steering cylinder 42, causing the rod 41A of the left steering cylinder 41 to contract and the rod 42A of the right steering cylinder 42 to extend, causing the wheel loader 1 to turn left.

[0048] In the second switching position 45B, the discharge side of the hydraulic pump 44 is connected to the bottom chamber 41B of the left steering cylinder 41 and the rod chamber 42C of the right steering cylinder 42, and the rod chamber 41C of the left steering cylinder 41 and the bottom chamber 42B of the right steering cylinder 42 are connected to the hydraulic oil tank 49.

[0049] Therefore, when the steering control valve 45 switches to the second switch position 45B, the hydraulic oil discharged from the hydraulic pump 44 flows into the bottom chamber 41B of the left steering cylinder 41 and the rod chamber 42C of the right steering cylinder 42, causing the rod 41A of the left steering cylinder 41 to extend and the rod 42A of the right steering cylinder 42 to contract, causing the wheel loader 1 to turn right.

[0050] In the neutral position 45N, the discharge side of the hydraulic pump 44 is connected to the hydraulic oil tank 49. Therefore, when the steering control valve 45 switches to the neutral position 45N, hydraulic oil is not supplied to the left steering cylinder 41 and the right steering cylinder 42, and the wheel loader 1 moves straight without steering operation.

[0051] The steering control valve 45 switches to the first switching position 45A when the pilot pressure Pi1 acting on the first pilot oil chamber 451 provided on the first switching position 45A side is greater than the pilot pressure Pi2 acting on the second pilot oil chamber 452 provided on the second switching position 45B side (Pi1>Pi2).On the other hand, when the pilot pressure Pi2 acting on the second pilot oil chamber 452 is greater than the pilot pressure Pi1 acting on the first pilot oil chamber 451 (Pi2>Pi1), the steering control valve 45 switches to the second switching position 45B.

[0052] In addition, the steering control valve 45 switches to the neutral position 45N when the pilot pressure Pi1 acting on the first pilot oil chamber 451 and the pilot pressure Pi2 acting on the second pilot oil chamber 452 are the same pressure (Pi1=Pi2) or zero (Pi1=Pi2=0).

[0053] Note that the steering of the wheel loader 1 operates even if the steering control valve 45 is not completely switched to the first switching position 45A or the second switching position 45B, when the internal spool of the steering control valve 45 starts to move toward the first switching position 45A or the second switching position 45B and the hydraulic oil discharged from the hydraulic pump 44 starts to be supplied to the pair of steering cylinders 41, 42.

[0054] The pilot pressure Pi acting on the first pilot oil chamber 451 and the pilot pressure Pi2 acting on the second pilot oil chamber 452 are controlled by a pair of electromagnetic control valves 47, 48. In this embodiment, of the pair of electromagnetic control valves 47, 48, the one that controls the pilot pressure Pi acting on the first pilot oil chamber 451 is referred to as the "first electromagnetic control valve 47," and the one that controls the pilot pressure Pi2 acting on the second pilot oil chamber 452 is referred to as the "second electromagnetic control valve 48." The first electromagnetic control valve 47 and the second electromagnetic control valve 48 are each controlled in accordance with a command signal output from the controller 5.

[0055] The controller 5 is electrically connected to the steering lever 34, the setting switch 36, the vehicle speed sensor 60 mounted on the transmission 133 (shown by dashed lines in Figures 1 and 5) for detecting the vehicle speed, the first electromagnetic control valve 47, and the second electromagnetic control valve 48.

[0056] The controller 5 receives an operation signal output from the steering lever 34, a setting signal output from the setting switch 36, and a vehicle speed signal output from the vehicle speed sensor 60, respectively.

[0057] The operation signal output from the steering lever 34 is a signal based on the operation of the operator, and includes data related to the operation direction and operation amount (tilt direction and tilt amount) of the steering lever 34. If the steering lever 34 is a mechanical lever, the controller 5 receives data output from an operation state sensor that detects the operation direction and operation amount of the steering lever 34, i.e., the operation state of the steering lever 34.

[0058] The setting signal output from the setting switch 36 includes an enabling setting signal relating to an enabling setting position ("ON" shown in FIG. 5) that enables operation of the steering lever 34 and activates the pair of steering cylinders 41, 42 in response to operation of the steering lever 34, and a disabling setting signal relating to a disabling setting position ("LOCK" shown in FIG. 5) that disables operation of the steering lever 34 and deactivates the pair of steering cylinders 41, 42.

[0059] The vehicle speed signal output from the vehicle speed sensor 60 is a data signal related to the vehicle speed detected by the vehicle speed sensor 60. Note that the vehicle speed sensor 60 may be, for example, a rotation speed sensor that detects the rotation speed of a propeller shaft.

[0060] The controller 5 generates command signals for the first electromagnetic control valve 47 and the second electromagnetic control valve 48 based on these input signals, namely, the operation signal from the steering lever 34, the setting signal from the setting switch 36, and the vehicle speed signal from the vehicle speed sensor 60.

[0061] (Controller 5 configuration) Next, the configuration of the controller 5 will be described with reference to FIG.

[0062] FIG. 6 is a functional block diagram showing the functions of the controller 5.

[0063] The controller 5 is configured by interconnecting a CPU, RAM, ROM, HDD, input I / F, and output I / F via a bus. Various operating devices such as the steering lever 34 and setting switch 36, and sensors such as the vehicle speed sensor 60 are connected to the input I / F, and the first electromagnetic control valve 47 and second electromagnetic control valve 48 are connected to the output I / F.

[0064] In such a hardware configuration, the CPU reads out a control program (software) stored on a recording medium such as a ROM, HDD, or optical disk, expands it on RAM, and executes the expanded control program, whereby the control program and hardware work together to realize the functions of the controller 5.

[0065] In this embodiment, the controller 5 is described as a computer configured by a combination of software and hardware, but this is not limiting. For example, as an example of another computer configuration, an integrated circuit that realizes the functions of a control program executed on the wheel loader 1 side may be used.

[0066] The controller 5 includes a data acquisition unit 51 , a determination unit 52 , an elapsed time measurement unit 53 , a command signal output unit 54 , and a storage unit 55 .

[0067] The data acquisition unit 51 acquires an operation signal output from the steering lever 34, a setting signal output from the setting switch 36, and data relating to the vehicle speed detected by the vehicle speed sensor 60 (vehicle speed signal).

[0068] The determination unit 52 includes a setting determination unit 52A, a vehicle body state determination unit 52B, and a lever position determination unit 52C.

[0069] The setting determination unit 52A determines whether the setting position of the setting switch 36 is the enable setting position or the disable setting position, based on the setting signal acquired by the data acquisition unit 51. In other words, the setting determination unit 52A determines whether the setting signal acquired by the data acquisition unit 51 is the enable setting signal or the disable setting signal.

[0070] The vehicle body state determination unit 52B determines whether the vehicle body is in a moving state or not based on the vehicle speed acquired by the data acquisition unit 51. Note that the vehicle body state determination unit 52B does not determine that the vehicle body is in a stopped state only when the vehicle speed detected by the vehicle speed sensor 60 matches 0 (zero), but determines whether the vehicle body is in a stopped state or not within a range that includes a detection error of the vehicle speed sensor 60. A determination threshold for the moving state (or stopped state) of the vehicle body is stored in advance in the storage unit 55.

[0071] The lever position determination unit 52C determines the operation state (tilt direction and tilt amount) of the steering lever 34, i.e., the position to which the steering lever 34 has been tilted by the operator, based on the operation signal acquired by the data acquisition unit 51. In particular, the lever position determination unit 52C determines whether the steering lever 34 is in the neutral position or has been operated to the maximum tilt position.

[0072] Here, the "neutral position" of the steering lever 34 is a position where the hydraulic pump 44 stops supplying hydraulic oil to the pair of steering cylinders 41, 42. Also, the "maximum tilt position" of the steering lever 34 includes a "maximum left tilt position" and a "maximum right tilt position," and is a position where the amount of hydraulic oil supplied from the hydraulic pump 44 to the pair of steering cylinders 41, 42 is a preset maximum amount.

[0073] More specifically, the "maximum left tilt position" is a position where the amount of hydraulic oil supplied from the hydraulic pump 44 to each of the rod chamber 41C of the left steering cylinder 41 and the bottom chamber 42B of the right steering cylinder 42 is set to a preset maximum amount. In other words, when the operator wishes to turn the steering wheel to the maximum left, he or she operates the steering lever 34 to the maximum left tilt position.

[0074] The "right maximum tilt position" is a position where the amount of hydraulic oil supplied from the hydraulic pump 44 to each of the bottom chamber 41B of the left steering cylinder 41 and the rod chamber 42C of the right steering cylinder 42 is set to a preset maximum amount. That is, when the operator wishes to turn the steering wheel to the right as far as possible, he or she operates the steering lever 34 to the right maximum tilt position.

[0075] In addition, the "maximum tilt position" does not necessarily have to be a position at which the maximum amount of hydraulic oil can be supplied from the hydraulic pump 44 to the pair of steering cylinders 41, 42, but may be a position at which the maximum amount of hydraulic oil that can be supplied from the hydraulic pump 44 to the pair of steering cylinders 41, 42 is an amount that is arbitrarily set (a pre-set maximum amount).

[0076] The elapsed time measurement unit 53 measures the time T that has elapsed since the vehicle body state determination unit 52B determined that the vehicle body has stopped, and determines whether the measured time T has exceeded a predetermined time Tth. This "predetermined time Tth" is an arbitrary time (e.g., a time shorter than 10 seconds) that is pre-stored in the storage unit 55, and is set to a time that takes into consideration the possibility that the vehicle body will start moving again after the vehicle body state determination unit 52B determines that the vehicle body is in a stopped state.

[0077] Depending on the judgment result of the judgment unit 52, the command signal output unit 54 outputs an activation signal to activate the pair of steering cylinders 41, 42 in response to the operation of the steering lever 34 or a deactivation signal to deactivate the pair of steering cylinders 41, 42 in response to the operation of the steering lever 34 to the first electromagnetic control valve 47 and the second electromagnetic control valve 48, respectively.

[0078] (Processing within controller 5) Next, a specific flow of processing executed by the controller 5 will be described with reference to FIG.

[0079] FIG. 7 is a flowchart showing the flow of the process executed by the controller 5.

[0080] In the controller 5, first, the setting determination unit 52A determines whether the setting position of the setting switch 36 is the enable setting position or the disable setting position based on the setting signal acquired by the data acquisition unit 51 (step S501). That is, in step S501, it is determined whether the setting switch 36 is in the enable setting or the disable setting.

[0081] If it is determined in step S501 that the setting position of the setting switch 36 is the disabled setting position (step S501 / disabled), the setting determination unit 52A then determines whether the setting position of the setting switch 36 has been switched to the enabled setting position, i.e., whether the setting switch 36 has not been operated to enable the setting and remains in the disabled setting position (step S502).

[0082] If it is determined in step S502 that the setting position of the setting switch 36 has not been switched to the enabled setting position (remains in the disabled setting position) (step S502 / YES), the vehicle body state determination unit 52B determines whether the vehicle body is moving, i.e., whether it is in a traveling state, based on the vehicle speed signal acquired by the data acquisition unit 51 (step S503).

[0083] If it is determined in step S503 that the vehicle body is moving (step S503 / YES), the lever position determination unit 52C determines whether the steering lever 34 is in the neutral position or has been operated to the maximum tilt position (step S504).

[0084] On the other hand, if it is determined in step S502 that the vehicle body is not moving, that is, the vehicle body is in a stopped state (step S503 / NO), the process does not proceed to step S504 until the vehicle body starts moving (enters a running state).

[0085] If it is determined in step S504 that the steering lever 34 is in the neutral position or has been operated to the maximum tilt position (step S504 / YES), the command signal output unit 54 outputs an enable signal to each of the first electromagnetic control valve 47 and the second electromagnetic control valve 48 (step S505). That is, when the steering lever 34 is in the neutral position or has been operated to the maximum tilt position, the controller 5 outputs an enable signal to each of the first electromagnetic control valve 47 and the second electromagnetic control valve 48 even if the setting switch 36 is in the disable setting position.

[0086] On the other hand, if it is determined in step S504 that the steering lever 34 is not in the neutral position and has not been operated to the maximum tilt position (step S504 / NO), the process does not proceed to step S505 until the steering lever 34 returns to the neutral position or is operated to the maximum tilt position.

[0087] Next, the setting determination unit 52A determines, based on the setting signal acquired by the data acquisition unit 51, whether the setting switch 36 has been switched to the enable setting position, i.e., whether an enable setting operation has been performed on the setting switch 36 (step S506).

[0088] If it is determined in step S506 that the setting switch 36 has been switched to the enabling setting position (step S506 / YES), the command signal output unit 54 continues to output an enabling signal to each of the first electromagnetic control valve 47 and the second electromagnetic control valve 48 (step S507).

[0089] Next, the setting determination unit 52A determines, based on the setting signal acquired by the data acquisition unit 51, whether the setting position of the setting switch 36 has been switched to the disabled setting position, i.e., whether a disabled setting operation has been performed on the setting switch 36 (step S508).

[0090] When it is determined in step S508 that the setting position of the setting switch 36 has been switched to the invalidation setting position (step S508 / YES), the vehicle body state determination unit 52B determines whether or not the vehicle body has stopped based on the vehicle speed signal acquired by the data acquisition unit 51 (step S509).

[0091] On the other hand, when it is determined in step S508 that the setting position of the setting switch 36 has not been switched to the invalidation setting position, that is, it remains in the validation setting position (step S508 / NO), the process returns to step S507, and the command signal output unit 54 continues to output the validation signal to the first electromagnetic control valve 47 and the second electromagnetic control valve 48.

[0092] Next, when it is determined in step S509 that the vehicle body has stopped (step S509 / YES), the elapsed time measurement unit 53 measures the time T since the stop of the vehicle body was determined, and determines whether or not the measured time T has elapsed the predetermined time Tth (step S510).

[0093] On the other hand, when it is not determined in step S509 that the vehicle body has stopped, that is, when it is determined that the vehicle body remains in the traveling state (step S509 / NO), the process does not proceed to step S510 until the vehicle body stops.

[0094] Subsequently, when it is determined in step S510 that the measured time T has elapsed the predetermined time Tth (T≧Tth) (step S510 / YES), the command signal output unit 54 outputs an invalidation signal to the first electromagnetic control valve 47 and the second electromagnetic control valve 48, respectively (step S511), and the processing in the controller 5 ends.

[0095] On the other hand, when it is determined in step S510 that the measured time T has not elapsed the predetermined time Tth (T<Tth) (step S510 / NO), the process does not proceed to step S511 until the measured time T has elapsed the predetermined time Tth (T≧Tth).

[0096] If it is determined in step S506 that the setting position of the setting switch 36 has not been switched to the enabled setting position, i.e., remains in the disabled setting position (step S506 / NO), the process proceeds to step S509, where the vehicle body state determination unit 52B determines the state of the vehicle body.

[0097] Also, if it is determined in step S501 that the setting position of the setting switch 36 is the activation setting position (step S501 / activation), the process proceeds to step S508, where the setting determination unit 52A determines whether or not an activation setting operation has been performed on the setting switch 36.

[0098] Also, if it is determined in step S502 that the setting position of the setting switch 36 has been switched to the activation setting position, i.e., that an activation setting operation has been performed on the setting switch 36 (step S502 / NO), the lever position determination unit 52C determines whether the steering lever 34 is in the neutral position (step S512).

[0099] If it is determined in step S512 that the steering lever 34 is in the neutral position (step S512 / YES), the command signal output unit 54 outputs an activation signal to each of the first electromagnetic control valve 47 and the second electromagnetic control valve 48 (step S513), and the process proceeds to step S508.

[0100] On the other hand, if it is determined in step S512 that the steering lever 34 is not in the neutral position (step S512 / NO), the process does not proceed to step S513 until the steering lever 34 is operated to the neutral position.

[0101] (State transition of steering drive device 4) Next, the transition of the state of the steering drive device 4 in accordance with the processing by the controller 5 will be described with reference to FIGS.

[0102] FIG. 8 is a state transition diagram showing the state transition of the steering drive device 4. As shown in FIG.

[0103] First, when the vehicle body is stopped and the setting switch 36 is in the disabled setting position (step S501 / disabled→step S502 / YES), the steering drive device 4 is in the disabled state ST1 in which the steering is not operated.

[0104] When the steering drive device 4 is in the disabled state ST1, if the vehicle body enters a traveling state and it is detected that the steering lever 34 is in the neutral position or has been operated to the maximum tilt position (for example, the amount of operation to the maximum tilt position is detected based on the operation signal output from the steering lever 34), the controller 5 outputs an activation signal to each of the first electromagnetic control valve 47 and the second electromagnetic control valve 48 (step S503 / YES → step S504 / YES → step S505). As a result, the steering drive device 4 transitions to the temporary enabled state ST2 in which the steering is activated regardless of the setting position of the setting switch 36 (arrow X1 shown in FIG. 8).

[0105] In this way, even if the wheel loader 1 goes into a traveling state (runaway occurs) when the steering drive device 4 is in the disabled state ST1, if the controller 5 determines that the steering lever 34 is in the neutral position or has been operated to the maximum tilt position, the steering drive device 4 transitions to the temporary enabled state ST2, and the operator can immediately operate the steering with the steering lever 34 regardless of whether the setting switch 36 is in the enabled setting position or the disabled setting position.

[0106] As a result, in the wheel loader 1, the provision of the setting switch 36 prevents erroneous operation of the steering lever 34, while still making it possible to immediately operate the steering with the steering lever 34 in the event of runaway.

[0107] In this embodiment, the conditions for the steering drive device 4 to transition from the inactive state ST1 to the temporary active state ST2 (the transition conditions from the inactive state ST1 to the temporary active state ST2) include the vehicle body being in a traveling state, the steering lever 34 being in the neutral position, or being operated to the maximum tilt position (the amount of operation to the maximum tilt position being detected), but this is not limited to this, and it is sufficient that the transition condition from the inactive state ST1 to the temporary active state ST2 is at least that the vehicle body is in a traveling state (a runaway has occurred).

[0108] However, by including the steering lever 34 being in the neutral position in the transition conditions from the disabled state ST1 to the temporary enabled state ST2, it is possible to prevent the steering from suddenly operating when the steering drive device 4 transitions to the temporary enabled state ST2.

[0109] Furthermore, by including in the transition conditions from the disabled state ST1 to the temporary enabled state ST2 that the steering lever 34 has been operated to the maximum tilt position (that the amount of operation to the maximum tilt position has been detected), it is possible to confirm the operator's intention to operate the steering in response to the occurrence of runaway, and therefore the controller 5 can more accurately determine that runaway has occurred.

[0110] Subsequently, when the steering drive device 4 is in the temporary valid state ST2, if the setting position of the setting switch 36 is switched to the valid setting position (step S506 / YES), the steering drive device 4 transitions from the temporary valid state ST2 to the valid state ST3 in which the steering is actuated (arrow X2 shown in FIG. 8).

[0111] Next, when the steering drive device 4 is in the enabled state ST3, if the setting position of the setting switch 36 is switched to the disabled setting position (step S508 / YES), the controller 5 outputs a disable signal to each of the first electromagnetic control valve 47 and the second electromagnetic control valve 48 after a predetermined time Tth has elapsed since the vehicle body came to a stop (step S509 / YES → step S510 / YES → step S511).

[0112] That is, when the steering drive device 4 is in the enabled state ST3, simply switching the setting position of the setting switch 36 from the enabled setting position to the disabled setting position does not transition to the disabled state ST1, but instead enters the temporary enabled state ST2 (arrow Y1 shown in FIG. 8). This allows the operator to immediately operate the steering with the steering lever 34, even if the vehicle runs away when the setting position of the setting switch 36 is changed to the disabled setting position.

[0113] Then, when the steering drive device 4 is in the temporary valid state ST2, after the vehicle body has stopped and a predetermined time Tth has elapsed, the steering drive device 4 transitions from the temporary valid state ST2 to the invalid state ST1 (arrow Y2 shown in FIG. 8). That is, when the controller 5 determines that the vehicle body has stopped and there is no possibility that it will return to a running state, the steering drive device 4 is set to the invalid state ST1, thereby making it possible to reliably prevent erroneous operation of the steering lever 34.

[0114] In this embodiment, the condition for the steering drive device 4 to transition from the temporary valid state ST2 to the invalid state ST1 (the transition condition from the temporary valid state ST2 to the invalid state ST1) includes the lapse of a predetermined time Tth since the vehicle body came to a stop, but this is not limiting, and it is sufficient that the transition condition for the temporary valid state ST2 to the invalid state ST1 is at least the lapse of the vehicle body coming to a stop. However, by including the lapse of a predetermined time Tth since the vehicle body came to a stop in the transition condition from the temporary valid state ST2 to the invalid state ST1, it is possible to immediately operate the steering with the steering lever 34 in cases where the vehicle body starts moving immediately after coming to a stop.

[0115] Furthermore, when the steering drive device 4 is in the disabled state ST1, if the setting switch 36 is switched to the enabled setting position and the steering lever 34 is operated to the neutral position (for example, the amount of operation to the neutral position is detected based on the operation signal output from the steering lever 34), the controller 5 outputs an enabling signal to each of the first electromagnetic control valve 47 and the second electromagnetic control valve 48 (step S502 / NO → step S512 / YES → step S513). As a result, the steering drive device 4 transitions from the disabled state ST1 to the enabled state ST3 (arrow X3 shown in FIG. 8).

[0116] In this way, by including the steering lever 34 being in the neutral position as a condition for the steering drive device 4 to transition from the disabled state ST1 to the enabled state ST3, it is possible to prevent the steering from suddenly operating when the steering drive device 4 transitions to the enabled state ST3.

[0117] The above describes an embodiment of the present invention. However, the present invention is not limited to the above embodiment and includes various modifications. For example, the above embodiment has been described in detail to clearly explain the present invention, and is not necessarily limited to an embodiment including all of the described configurations. Furthermore, it is possible to replace part of the configuration of this embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of this embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of this embodiment with other configurations.

[0118] For example, in the above embodiment, a wheel loader 1 was specifically described as an example of one type of wheeled work vehicle, but it does not necessarily have to be a wheel loader 1, and a work vehicle other than a wheel loader 1 may be used as long as it is a wheeled work vehicle equipped with multiple wheels.

[0119] Furthermore, in the above embodiment, the steering lever 34 was an electric operation lever, and therefore the pilot pressure oil was generated by reducing the pressure of the pressure oil discharged from the pilot pump 46 by the first solenoid control valve 47 and the second solenoid control valve 48. However, if the steering lever 34 is a mechanical operation lever, the pilot pressure oil is generated by reducing the pressure of the pressure oil discharged from the pilot pump 46 by the pilot valve. In this case, the first solenoid control valve 47 and the second solenoid control valve 48 control whether or not the pilot pressure oil generated by the pilot valve is applied to the steering control valve 45. [Explanation of symbols]

[0120] 1: Wheel loader (wheeled work vehicle) 5: Controller 11,11A,11B: Wheel 12: Driver's cab 34: Steering lever 36: Setting switch 41: Left steering cylinder (steering cylinder) 42: Right steering cylinder (steering cylinder) 44: Hydraulic pump 45: Steering control valve 46: Pilot pump 47: First electromagnetic control valve (electromagnetic control valve) 48: Second electromagnetic control valve (electromagnetic control valve) 60: Vehicle speed sensor

Claims

1. a vehicle body provided with a plurality of wheels; A driver's cab provided in the vehicle body; a steering cylinder for steering the plurality of wheels; a hydraulic pump that supplies hydraulic oil to the steering cylinder; a steering control valve for controlling the flow of hydraulic oil discharged from the hydraulic pump and supplied to the steering cylinder; a pilot pump that supplies pilot pressure oil to the steering control valve; a steering lever provided in the driver's cab for steering; a setting switch for setting an enabled setting state in which operation of the steering lever is enabled and the steering cylinder is actuated in response to the operation of the steering lever, and a disabled setting state in which operation of the steering lever is disabled and the steering cylinder is not actuated; an electromagnetic control valve for controlling pilot pressure oil discharged from the pilot pump and acting on the steering control valve; a controller for controlling the electromagnetic control valve; a vehicle speed sensor for detecting the vehicle speed of the vehicle body; In a wheeled work vehicle equipped with The controller determining whether the vehicle body is in a stopped state or a moving state based on the vehicle speed detected by the vehicle speed sensor; When it is determined that the vehicle body is in the stopped state and the setting switch is in the enabled setting state, an enable signal for operating the steering cylinder in response to operation of the steering lever is output to the electromagnetic control valve, When it is determined that the vehicle body is in the stopped state and the setting switch is in the disabled setting state, a disable signal is output to the electromagnetic control valve to disable operation of the steering cylinder in response to operation of the steering lever, When it is determined that the vehicle body is in the traveling state, the enabling signal is output to the electromagnetic control valve. A wheeled work vehicle characterized by:

2. A vehicle body provided with a plurality of wheels; A driver's cab provided in the vehicle body; a steering cylinder for steering the plurality of wheels; a hydraulic pump that supplies hydraulic oil to the steering cylinder; a steering control valve for controlling the flow of hydraulic oil discharged from the hydraulic pump and supplied to the steering cylinder; a pilot pump that supplies pilot pressure oil to the steering control valve; a steering lever provided in the driver's cab for steering; a setting switch for setting an enabled setting state in which operation of the steering lever is enabled and the steering cylinder is actuated in response to the operation of the steering lever, and a disabled setting state in which operation of the steering lever is disabled and the steering cylinder is not actuated; an electromagnetic control valve for controlling pilot pressure oil discharged from the pilot pump and acting on the steering control valve; a controller for controlling the electromagnetic control valve; a vehicle speed sensor for detecting the vehicle speed of the vehicle body; In a wheeled work vehicle equipped with The controller determining whether the vehicle body is in a stopped state or a moving state based on the vehicle speed detected by the vehicle speed sensor; When it is determined that the vehicle body is in the stopped state and the setting switch is in the enabled setting state, an enable signal for operating the steering cylinder in response to operation of the steering lever is output to the electromagnetic control valve, When it is determined that the vehicle body is in the stopped state and the setting switch is in the disabled setting state, a disable signal is output to the electromagnetic control valve to disable operation of the steering cylinder in response to operation of the steering lever, When it is determined that the vehicle body is in the traveling state, and the setting switch is in the disabled setting state, and the operation state of the steering lever is a neutral state in which the supply of hydraulic oil from the hydraulic pump to the steering cylinder is stopped, or when it is determined that the vehicle body is in the traveling state, and the setting switch is in the disabled setting state, and the operation state of the steering lever is a maximum tilt state in which the amount of hydraulic oil supplied from the hydraulic pump to the steering cylinder is a preset maximum amount, the enabling signal is output to the electromagnetic control valve, When it is determined that the vehicle body is in the traveling state, the setting switch is in the disable setting state, and the operation state of the steering lever is in an operation state different from the neutral state and the maximum tilt state, the disable signal is output to the electromagnetic control valve. A wheeled work vehicle characterized by:

3. A vehicle body provided with a plurality of wheels; A driver's cab provided in the vehicle body; a steering cylinder for steering the plurality of wheels; a hydraulic pump that supplies hydraulic oil to the steering cylinder; a steering control valve for controlling the flow of hydraulic oil discharged from the hydraulic pump and supplied to the steering cylinder; a pilot pump that supplies pilot pressure oil to the steering control valve; a steering lever provided in the driver's cab for steering; a setting switch for setting an enabled setting state in which operation of the steering lever is enabled and the steering cylinder is actuated in response to the operation of the steering lever, and a disabled setting state in which operation of the steering lever is disabled and the steering cylinder is not actuated; an electromagnetic control valve for controlling pilot pressure oil discharged from the pilot pump and acting on the steering control valve; a controller for controlling the electromagnetic control valve; a vehicle speed sensor for detecting the vehicle speed of the vehicle body; In a wheeled work vehicle equipped with The controller determining whether the vehicle body is in a stopped state or a moving state based on the vehicle speed detected by the vehicle speed sensor; When it is determined that the vehicle body is in the stopped state and the setting switch is in the enabled setting state, an enable signal for operating the steering cylinder in response to operation of the steering lever is output to the electromagnetic control valve, When it is determined that the vehicle body is in the stopped state and the setting switch is in the disabled setting state, a disable signal is output to the electromagnetic control valve to disable operation of the steering cylinder in response to operation of the steering lever, When it is determined that the vehicle body is in the traveling state, the enabling signal is output to the electromagnetic control valve; When the vehicle body is determined to be in the stopped state while the enabling signal is being output to the electromagnetic control valve, and a predetermined time has elapsed with the setting switch in the disabled setting state, the disabling signal is output to the electromagnetic control valve. A wheeled work vehicle characterized by:

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