Work vehicle

Abstract

To provide a work vehicle capable of switching between a forward travel and a rearward travel to travel in accordance with an operator's intention even when a changeover switch is operated incorrectly during travel.SOLUTION: A wheel loader 1 is provided with: an operation lever 34A for forward and rearward travel and an operation switch 34B for forward and rearward travel; a changeover switch 39 for outputting a changeover signal between an effective command for making the operation switch 34B for forward and rearward travel in an effective state and an ineffective command for making it in an ineffective state; and a controller 5 for controlling the forward and rearward travel of a vehicle, and further comprises a vehicle speed sensor 40 for detecting the travel state of the vehicle, wherein the controller 5 maintains a second operation signal output from the operation switch 34B for forward and rearward travel as effective when the changeover signal output form the changeover switch 39 is switched from the effective command to the ineffective command while the vehicle is travelling, and controls the forward and rearward travel of the vehicle based on a first operation signal output from the operation lever 34A for forward and rearward travel and the second operation signal output from the operation switch 34B for forward and rearward travel.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a work vehicle provided with a forward and reverse operation device near the driver's seat.

Background Art

[0002] In work vehicles such as wheel loaders, a forward and reverse operation device for moving the vehicle body forward, backward, and stopping is provided in the driver's cab, and its shape and installation location vary depending on the vehicle specifications. In addition, there may be cases where a plurality of forward and reverse operation devices are provided at different locations in the driver's cab. Further, in order to prevent malfunction caused by the operator accidentally touching the forward and reverse operation device, there may be a changeover switch that can switch the forward and reverse operation device between an effective state and an ineffective state.

[0003] For example, Patent Document 1 discloses a work machine including a forward and reverse lever device (first forward and reverse operation device) disposed on the steering wheel side, a forward and reverse switch device (second forward and reverse operation device) disposed on the work machine lever side for operating a work machine (working device), and a changeover switch for instructing switching to an effective state in which forward and reverse switching control is performed by the forward and reverse switch device or an ineffective state in which forward and reverse switching control is not performed by the forward and reverse switch device.

[0004] In this work machine, the forward and reverse switching control by the forward and reverse lever device is always in an effective state, while the forward and reverse switching control by the forward and reverse switch device is in an effective state only when the changeover switch instructs switching to an effective state in which forward and reverse switching control is performed by the forward and reverse switch device and the forward and reverse lever device indicates neutral. This prevents inadvertent running operations of the work machine due to unintentional operation of the forward and reverse switch device by the operator.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the working machine described in Patent Document 1, if the changeover switch is accidentally operated to a position indicating an invalid state in which the forward / backward switching control by the forward / backward switch device is not performed during traveling, the forward / backward switching control by the forward / backward switch device becomes invalid. In this case, when it is desired to quickly switch between forward and backward, even if the operator operates the forward / backward switch device arranged immediately near at hand, it is ineffective, so a situation occurs where the forward / backward cannot be switched as intended by the operator.

[0007] Therefore, an object of the present invention is to provide a work vehicle capable of traveling by switching between forward and backward as intended by the operator even when the changeover switch is accidentally operated during traveling.

Means for Solving the Problems

[0008] In order to achieve the above object, the present invention provides a first forward and reverse operation device and a second forward and reverse operation device provided in the driver's cab for operating the forward and reverse movement of the vehicle body, a switching device provided in the driver's cab for outputting a switching signal for switching between an enable command for enabling the second forward and reverse operation device and a disable command for disabling the second forward and reverse operation device, a switching signal output from the switching device, a first operation signal output from the first forward and reverse operation device, and a second operation signal output from the second forward and reverse operation device, and a controller for controlling the forward and reverse movement of the vehicle body based on the above signals. In the work vehicle, a running state detection device for detecting the running state of the vehicle body is provided. The controller determines whether the vehicle body is running or stopped based on the running state detected by the running state detection device. When the switching signal output from the switching device is switched from the enable command to the disable command while the vehicle body is running, the second forward and reverse operation device is maintained in the enabled state, and the forward and reverse movement of the vehicle body is controlled based on the first operation signal output from the first forward and reverse operation device and the second operation signal output from the second forward and reverse operation device.

Effects of the Invention

[0009] According to the present invention, even when the switching switch is accidentally operated during running, the vehicle can be switched between forward and reverse as intended by the operator and run. Problems, configurations, and effects other than those described above will be clarified by the description of the following embodiments.

Brief Description of the Drawings

[0010]

Figure 1

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Embodiments for Carrying Out the Invention

[0011] Hereinafter, as an aspect of the work vehicle according to each embodiment of the present invention, for example, a wheel loader that performs a loading operation of excavating earth and sand, minerals, etc. and loading them into a loading destination such as a dump truck or a hopper will be described.

[0012] <Overall Configuration of Wheel Loader 1> First, the overall configuration of the wheel loader 1 will be described with reference to FIG. 1.

[0013] FIG. 1 is an external side view showing a configuration example of the wheel loader 1 according to each embodiment of the present invention.

[0014] The wheel loader 1 is an articulated work vehicle that is steered by the body folding in the middle near the center. Specifically, a front frame 1A that is the front part of the body and a rear frame 1B that is the rear part of the body are connected to be rotatable in the left - right direction by a center joint 10, and the front frame 1A bends in the left - right direction with respect to the rear frame 1B. In the following description, among the left - right directions of the body, the left - hand side of the operator facing the forward direction is defined as the "left direction", and the right - hand side of the operator is defined as the "right direction".

[0015] Four wheels 11 are provided on the body. Two wheels 11 are provided as front wheels 11A on both the left and right sides of the front frame 1A, and the remaining two wheels 11 are provided as rear wheels 11B on both the left and right sides of the rear frame 1B, respectively. In FIG. 1, only the front wheel 11A and the rear wheel 11B provided on the left side among the four wheels 11 are shown. Note that there is no particular limitation on the specific number of the plurality of wheels 11 provided on the body.

[0016] A working device 2 for carrying out loading and unloading work is attached to the front part of the front frame 1A. The working device 2 includes a lift arm 21 that is attached to the front frame 1A so as to be rotatable in the vertical direction, two lift arm cylinders 22 that drive the lift arm 21, a bucket 23 that is 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 that is rotatably connected to the lift arm 21 and constitutes a link mechanism between the bucket 23 and the bucket cylinder 24.

[0017] The lift arm 21 rotates upward with respect to the front frame 1A when the rods 220 of the two lift arm cylinders 22 extend, and rotates downward with respect to the front frame 1A when the rods 220 of the two lift arm cylinders 22 contract. In FIG. 1, only the lift arm cylinder 22 arranged on the left side among the two lift arm cylinders 22 is shown by a dashed line.

[0018] The bucket 23 rotates upward with respect to the lift arm 21 as the rod 240 of the bucket cylinder 24 extends (tilt operation), and rotates downward with respect to the lift arm 21 as the rod 240 of the bucket cylinder 24 contracts (dump operation). As a result, the bucket 23 can scoop up loads such as earth and sand, minerals, etc. and discharge (dump) them to the loading destination. Note that the bucket 23 can be replaced with various attachments such as a blade, etc. The wheel loader 1 can perform various operations such as snow removal work and earth-pushing work in addition to the handling work using the bucket 23.

[0019] The rear frame 1B is provided with a driver's cab 12 where the operator rides, a machine room 13 that houses various devices necessary for driving the wheel loader 1 inside, and a counterweight 14 for maintaining the balance with the working device 2 so that the vehicle body does not tip over. In the rear frame 1B, the driver's cab 12 is arranged at the front, the counterweight 14 is arranged at the rear, and the machine room 13 is arranged between the driver's cab 12 and the counterweight 14.

[0020] The traveling of the vehicle body of this wheel loader 1 is controlled by a torque converter type traveling drive device. The torque converter type traveling drive device includes an engine, a torque converter connected to the output shaft of the engine, and a transmission connected to the output shaft of the torque converter.

[0021] In the torque converter type traveling drive control, first, when the operator steps on the accelerator pedal provided in the driver's cab 12, the engine rotates according to the amount of depression, and as the engine rotates, the input shaft of the torque converter (hereinafter referred to as "torcon") connected to the output shaft of the engine rotates. When the input shaft of the torcon rotates, the output shaft of the torcon rotates through the oil inside the torcon, and the output torque from the torcon is shifted by the transmission and then transmitted to the four wheels 11 respectively. Thereby, the wheel loader 1 travels.

[0022] When the operator wants to stop or decelerate the wheel loader 1, he steps on the brake pedal provided inside the cab 12. Then, according to the amount of depression of the brake pedal, the clutches for forward and reverse of the transmission are controlled, and the transmission of the driving force to the four wheels 11 is cut off. As a result, the wheel loader 1 stops or decelerates.

[0023] Note that the traveling drive device of the wheel loader 1 does not necessarily have to be a torque converter type, and other drive systems such as an HST (Hydraulic Static Transmission) type may be used.

[0024] <First Embodiment> Subsequently, the first embodiment of the present invention will be described with reference to FIGS. 2 to 6.

[0025] (Internal Configuration of Cab 12) First, the internal configuration of the cab 12 will be described with reference to FIG. 2.

[0026] FIG. 2 shows an example of the internal configuration of the cab 12 according to the first embodiment, and is a view of the inside of the cab 12 as seen from the ceiling side.

[0027] Inside the cab 12, there are a driver's seat 31 arranged in the center, a steering wheel 32 arranged in front of the driver's seat 31 for switching the traveling direction of the vehicle body left and right, a support column 33 extending upward from the floor to support the steering wheel 32, a forward and reverse operation lever 34A as a first forward and reverse operation device protruding leftward from the support column 33 for switching the traveling direction of the vehicle body forward and backward, a monitor 35 as a display device for displaying the traveling state of the vehicle body, etc., a first work operation lever 36A and a second work operation lever 36B for operating the work device 2.

[0028] The steering wheel 32 is an aspect of the steering operation device. The vehicle body turns left when the operator operates the steering wheel 32 in the left direction (counterclockwise), and turns right when the operator operates the steering wheel 32 in the right direction (clockwise).

[0029] The forward and backward operation lever 34A has a forward position F for moving the vehicle body forward, a backward position R for moving the vehicle body backward, and a neutral position N for cutting off the driving force to the four wheels 11. These forward position F, backward position R, and neutral position N are arranged in the order of backward position R, neutral position N, and forward position F from the side of the driver's seat 31, for example, as shown in FIG. 2.

[0030] The monitor 35 is assembled at the center of the front console 37 installed in front of the steering wheel 32. Various switches and buttons are attached to both the left and right sides of the monitor 35.

[0031] Both the first work operation lever 36A and the second work operation lever 36B are single-axis levers that can be operated along the front-rear direction of the cab 12, and are arranged side by side in the left-right direction at the front part on the side console 38 installed on the right side of the driver's seat 31. When the operator tilts the first work operation lever 36A arranged on the left side (the driver's seat 31 side) in the front-rear direction, the bucket 23 moves in the vertical direction with respect to the lift arm 21. On the other hand, when the operator tilts the second work operation lever 36B arranged on the right side in the front-rear direction, the lift arm 21 moves in the vertical direction with respect to the front frame 1A.

[0032] On the side console 38, in addition to the first work operation lever 36A and the second work operation lever 36B, there is a forward and backward operation switch 34B as a second forward and backward operation device for switching the forward and backward traveling directions of the vehicle body, and a switch unit 390 including a changeover switch 39 as a changeover device for switching the forward and backward operation switch 34B between an effective state and an ineffective state, and a right armrest 31R for supporting the right arm of the operator.

[0033] The forward / backward operation switch 34B, similar to the forward / backward operation lever 34A, has a forward position F for moving the vehicle body forward, a reverse position R for moving the vehicle body backward, and a neutral position N for cutting off the driving force to the four wheels 11. That is, in this embodiment, two different forward / backward operation devices (the first forward / backward operation device and the second forward / backward operation device) are provided in the cab 12, and the operator can selectively use the forward / backward operation lever 34A and the forward / backward operation switch 34B according to their preferences and the situation. Note that the control states of the forward / backward operation lever 34A and the forward / backward operation switch 34B are displayed on the monitor 35.

[0034] The forward / backward operation switch 34B is disposed on the right side of the first working operation lever 36A and the second working operation lever 36B. The first working operation lever 36A, the second working operation lever 36B, and the forward / backward operation switch 34B are located on the side console 38 in front of the right armrest 31R. As a result, the operator can operate the first working operation lever 36A, the second working operation lever 36B, and the forward / backward operation switch 34B with the right arm placed on the right armrest 31R.

[0035] Thus, since the forward / backward operation switch 34B is located very close to the operator's hand, the operability is good. However, on the other hand, there is a possibility that the operator may accidentally touch it when operating the first working operation lever 36A or the second working operation lever 36B. On the other hand, when the operator touches the forward / backward operation lever 34A, an action of stretching the hand forward is required. Therefore, the forward / backward operation switch 34B is more likely to be misoperated than the forward / backward operation lever 34A.

[0036] Therefore, a changeover switch 39 is provided in the cab 12 (on the side console 38 in this embodiment) to suppress the occurrence of misoperation of the forward / backward operation switch 34B. This changeover switch 39 outputs an enable command for enabling the forward / backward operation switch 34B and a disable command for disabling it as switching signals to a controller 5 described later.

[0037] The forward / backward operation lever 34A, the forward / backward operation switch 34B, and the changeover switch 39 are each electrically connected to the controller 5. The controller 5 controls the forward and backward movement of the vehicle body based on a first operation signal output from the forward / backward operation lever 34A, a second operation signal output from the forward / backward operation switch 34B, and a changeover signal output from the changeover switch 39.

[0038] (Functional configuration of the controller 5) Next, the functional configuration of the controller 5 will be described with reference to FIG. 3.

[0039] FIG. 3 is a functional block diagram showing the functions of the controller 5 according to the first embodiment.

[0040] The controller 5 is configured such that a CPU, a RAM, a ROM, an HDD, an input I / F, and an output I / F are connected to each other via a bus. Various operating devices such as the forward / backward operation lever 34A, the forward / backward operation switch 34B, and the changeover switch 39, and sensors such as the vehicle speed sensor 40 as a traveling state detection device for detecting the traveling state of the vehicle body are connected to the input I / F, and a forward-side solenoid valve 41 for controlling a forward clutch, a backward-side solenoid valve 42 for controlling a backward clutch, and a monitor 35 are connected to the output I / F.

[0041] In such a hardware configuration, the CPU reads out a control program (software) stored in a recording medium such as a ROM, an HDD, or an optical disk and expands it on the RAM, and by executing the expanded control program, the control program and the hardware cooperate to realize the functions of the controller 5.

[0042] Note that in the present embodiment, the controller 5 is described as a computer configured by a combination of software and hardware. However, the present invention is not limited to this. For example, as an example of the configuration of another computer, an integrated circuit that realizes the functions of the control program executed on the side of the wheel loader 1 may be used.

[0043] The controller 5 includes a data acquisition unit 51, a switching determination unit 52, a vehicle body state determination unit 53, a storage unit 53A, a valid / invalid determination unit 54, a traveling direction determination unit 55, and a signal output unit 56.

[0044] The data acquisition unit 51 respectively acquires a first operation signal output from the forward / backward operation lever 34A, a second operation signal output from the forward / backward operation switch 34B, a switching signal output from the changeover switch 39, and data regarding the vehicle speed output from the vehicle speed sensor 40.

[0045] The switching determination unit 52 determines whether the switching signal acquired by the data acquisition unit 51 is a valid command or an invalid command. Further, the switching determination unit 52 also determines whether the switching signal output from the changeover switch 39 has been switched from one command to another command (from a valid command to an invalid command, or from an invalid command to a valid command).

[0046] When it is determined by the switching determination unit 52 that the switching signal output from the changeover switch 39 has been switched from a valid command to an invalid command, the vehicle body state determination unit 53 determines whether the vehicle body is traveling or stopped based on the vehicle speed V acquired by the data acquisition unit 51. Specifically, the vehicle body state determination unit 53 compares the vehicle speed V acquired by the data acquisition unit 51 with a predetermined threshold value Vth.

[0047] The "predetermined threshold value Vth" corresponds to the vehicle speed when the wheel loader 1 (vehicle body) stops, and is a value that takes into account not only 0 km / h but also the error range of the vehicle speed sensor 40, and is stored in advance in the storage unit 53A.

[0048] When it is determined by the valid / invalid determination unit 54 that the switching signal output from the changeover switch 39 has been switched from an invalid command to a valid command, the valid / invalid determination unit 54 validates the second operation signal from the forward / backward operation switch 34B acquired by the data acquisition unit 51 (validates the forward / backward operation switch 34B).

[0049] Furthermore, when the switching determination unit 52 determines that the switching signal output from the changeover switch 39 has been switched from a valid command to an invalid command, and the vehicle body state determination unit 53 determines that the vehicle speed V is greater than a predetermined threshold value Vth (V>Vth), that is, the vehicle body is moving, the valid / invalid determination unit 54 enables the second operation signal from the forward / reverse operation switch 34B if the current second operation signal is valid (maintains the valid state of the forward / reverse operation switch 34B).

[0050] In addition, if the switching determination unit 52 determines that the switching signal output from the changeover switch 39 is an invalid command, and the vehicle body state determination unit 53 determines that the vehicle speed V is equal to or less than a predetermined threshold value Vth (V≦Vth), that is, that the vehicle body is stopped, the valid / invalid determination unit 54 invalidates the second operation signal from the forward / reverse operation switch 34B acquired by the data acquisition unit 51 (invalidates the forward / reverse operation switch 34B).

[0051] When the validity / invalidity determination unit 54 determines to validate the second operation signal from the forward / reverse operation switch 34B, the traveling direction determination unit 55 determines whether the vehicle body will move forward or backward based on the most recent operation signal among the operation signals (first operation signal and second operation signal) acquired by the data acquisition unit 51. In other words, when the forward / reverse operation switch 34B is in the valid state, the controller 5 controls the forward / reverse movement of the vehicle body based on the operation signal of the forward / reverse operation lever 34A or the forward / reverse operation switch 34B, whichever was last operated.

[0052] Specifically, when the data acquisition unit 51 acquires the second operation signal after the first operation signal, the traveling direction determination unit 55 determines whether the vehicle body will move forward or backward based on the second operation signal, i.e., in response to the operation of the forward / reverse operation switch 34B. On the other hand, when the data acquisition unit 51 acquires the first operation signal after the second operation signal, the traveling direction determination unit 55 determines whether the vehicle body will move forward or backward (forward, backward, or stopped) based on the first operation signal, i.e., in response to the operation of the forward / reverse operation lever 34A.

[0053] Further, when the forward / backward direction determination unit 55 determines that the second operation signal from the forward / backward operation switch 34B is to be invalidated in the valid / invalid determination unit 54, it determines the forward / backward movement (forward movement, backward movement, or stop) of the vehicle body based on the first operation signal from the forward / backward operation lever 34A acquired by the data acquisition unit 51.

[0054] The signal output unit 56 outputs control signals corresponding to the traveling state (forward movement, backward movement, or stop) of the vehicle body determined by the forward / backward direction determination unit 55 to the forward electromagnetic valve 41 and the backward electromagnetic valve 42, respectively.

[0055] Further, when the signal output unit 56 determines that the switching signal output from the changeover switch 39 in the changeover determination unit 52 is a valid command and determines in the valid / invalid determination unit 54 to validate the second operation signal from the forward / backward operation switch 34B, it outputs a first valid display signal to the monitor 35.

[0056] This "first valid display signal" is a valid display signal that indicates that both the forward / backward operation lever 34A and the forward / backward operation switch 34B are valid because the switching signal output from the changeover switch 39 is a valid command.

[0057] On the other hand, when the signal output unit 56 determines that the switching signal output from the changeover switch 39 in the changeover determination unit 52 is an invalid command, but determines in the vehicle body state determination unit 53 that the vehicle body is traveling and determines in the valid / invalid determination unit 54 to validate the second operation signal from the forward / backward operation switch 34B, it outputs a second valid display signal different from the first valid display signal to the monitor 35.

[0058] This "second valid display signal" is a valid display signal that indicates that although the switching signal output from the changeover switch 39 has been switched from a valid command to an invalid command, both the forward / reverse operation lever 34A and the forward / reverse operation switch 34B are valid because the vehicle body is in motion. Therefore, although it is common for both the first valid display signal and the second valid display signal to indicate that both the forward / reverse operation lever 34A and the forward / reverse operation switch 34B are valid, the conditions for such indication are different.

[0059] And when the signal output unit 56 determines that the switching signal output from the changeover switch 39 in the switching determination unit 52 is an invalid command, and the vehicle body state determination unit 53 determines that the vehicle body has stopped, and the valid / invalid determination unit 54 determines to invalidate the second operation signal from the forward / reverse operation switch 34B, the signal output unit 56 outputs an invalid display signal to the monitor 35.

[0060] This "invalid display signal" is a display signal that indicates that the forward / reverse operation switch 34B is invalid (only the forward / reverse operation lever 34A is valid) because the switching signal output from the changeover switch 39 is an invalid command while the vehicle body is stopped.

[0061] Here, FIG. 4 is a diagram showing an example of the display on the monitor 35.

[0062] The first display D01 shown at the left end of FIG. 4 is the display content of the monitor 35 when the first valid display signal is output from the signal output unit 56 to the monitor 35. The first display D01 includes a forward mark 351 with the letter "F" written in a white upward arrow, a reverse mark 352 with the letter "R" written in a white downward arrow, a lever valid mark 353 which is an effective mark of the forward / reverse operation lever 34A indicated by a leftward arrow arranged between the forward mark 351 and the reverse mark 352, and a switch valid mark 354 which is an effective mark of the forward / reverse operation switch 34B indicated in a triangular shape on the opposite side of the lever valid mark 353.

[0063] The second display D02 shown in the center of FIG. 4 is the display content of the monitor 35 when a second valid display signal is output from the signal output unit 56 to the monitor 35. Similar to the first display D01, the second display D02 is composed of a forward mark 351, a reverse mark 352, a lever valid mark 353, and a switch valid mark 354. However, different from the first display D01, the background of the second display D02 lights up or blinks yellow, for example. In FIG. 4, the difference from the first display D01 in the second display D02 is shown in sandy areas.

[0064] The third display D03 shown at the right end of FIG. 4 is the display content of the monitor 35 when an invalid display signal is output from the signal output unit 56 to the monitor 35. The third display D03 is composed of a forward mark 351, a reverse mark 352, and a lever valid mark 353. In the third display D03, since the forward / backward operation switch 34B is invalid, the switch valid mark 354 is not displayed.

[0065] In this way, since the monitor 35 displays the first display D01 based on the first valid display signal, the second valid display signal based on the second valid display signal, and the third display D03 based on the invalid display signal, respectively, the operator can immediately confirm the states of the forward / backward operation lever 34A and the forward / backward operation switch 34B by looking at the display of the monitor 35.

[0066] (Processing in the controller 5) Next, the specific processing flow executed by the controller 5 will be described with reference to FIG. 5.

[0067] FIG. 5 is a flowchart showing the processing flow executed by the controller 5 according to the first embodiment.

[0068] In the controller 5, first, the data acquisition unit 51 acquires the first operation signal output from the forward / reverse operation lever 34A, the second operation signal output from the forward / reverse operation switch 34B, and the switching signal output from the changeover switch 39 (step S501).

[0069] Next, the switching determination unit 52 determines whether the switching signal acquired in step S501 is a valid command or an invalid command (step S502).

[0070] If it is determined in step S502 that the switching signal output from the selector switch 39 is a valid command (step S502 / valid command), the validity / invalidation determination unit 54 validates the second operation signal from the forward / reverse operation switch 34B acquired in step S501 (step S503). Subsequently, the signal output unit 56 outputs a first valid display signal related to the first display D01 to the monitor 35 (step S504).

[0071] Next, the traveling direction determination unit 55 determines whether the vehicle body is to travel forward or backward based on the latest operation signal of the first operation signal and the second operation signal acquired in step S501 (step S505). Then, the signal output unit 56 outputs control signals according to the traveling state of the vehicle body (forward, reverse, or stop) determined in step S505 to the forward solenoid valve 41 and the reverse solenoid valve 42, respectively (step S506). Thereafter, the controller 5 returns to step S501 and repeats each process.

[0072] Also, if it is determined in step S502 that the switching signal output from the changeover switch 39 is an invalid command (step S502 / invalid command), the data acquisition unit 51 acquires the vehicle speed V detected by the vehicle speed sensor 40 (step S507).

[0073] Next, the vehicle body state determination unit 53 determines whether or not the vehicle speed V acquired in step S507 is equal to or less than a predetermined threshold value Vth, that is, whether or not the vehicle body is stopped (step S508).

[0074] If it is determined in step S508 that the vehicle speed V is greater than a predetermined threshold value Vth (V>Vth), that is, that the vehicle body is moving (step S508 / NO), and if the current second operation signal is valid (step S500 / valid), the validity / invalidation determination unit 54 keeps the second operation signal from the forward / reverse operation switch 34B valid (maintains the valid state of the forward / reverse operation switch 34B) (step S509).

[0075] Next, the signal output unit 56 outputs a second effective display signal related to the second display D02 to the monitor 35 (step S510), and the process proceeds to step S505.

[0076] On the other hand, if it is determined in step S508 that the vehicle speed V is equal to or less than the predetermined threshold value Vth (V≦Vth), that is, that the vehicle body is stopped (step S508 / YES), the validity / invalidity determination unit 54 invalidates the second operation signal from the forward / reverse operation switch 34B acquired in step S501 (step S511).

[0077] Note that even if it is determined in step S508 that the vehicle body is moving and the current second operation signal is invalid in step S500 (step S500 / invalid), the process proceeds to step S511.

[0078] Subsequently, the signal output unit 56 outputs an invalid display signal related to the third display D03 to the monitor 35 (step S512).

[0079] Next, the traveling direction determination unit 55 determines whether the vehicle body is to travel forward or backward based on the first operation signal from the forward / reverse operation lever 34A acquired in step S501 (step S513). Then, the signal output unit 56 outputs control signals according to the traveling state of the vehicle body (forward, reverse, or stop) determined in step S513 to the forward solenoid valve 41 and the reverse solenoid valve 42, respectively (step S506).

[0080] In this way, even when the switching signal output from the changeover switch 39 is switched from a valid command to an invalid command, for example, due to an incorrect operation, while the vehicle body is running, the controller 5 maintains the valid state of the forward / backward operation switch 34B until the vehicle body stops. On the other hand, when the vehicle body is stopped and the switching signal output from the changeover switch 39 is switched from a valid command to an invalid command, the controller 5 then maintains the invalid state of the forward / backward operation switch 34B even when the vehicle body starts running thereafter.

[0081] Also, when the switching signal output from the changeover switch 39 is switched from an invalid command to a valid command, regardless of whether the vehicle body is running or stopped, the forward / backward operation switch 34B is set to the valid state.

[0082] Note that in the flowchart shown in FIG. 5, after the signal output unit 56 outputs each display signal to the monitor 35 (steps S504, S510, S512), the forward / backward direction determination unit 55 determines the forward / backward movement of the vehicle body (steps S505, S513). However, it is not necessarily required that the processing be executed in this order. These processes may be executed in the order reverse to that shown in FIG. 5 or in parallel.

[0083] Here, the specific states of each device when the processing in the controller 5 is executed will be described with reference to FIG. 6.

[0084] FIG. 6 is a table showing the transition of the state of the vehicle body and the display on the monitor 35 when the changeover switch 39, the forward / backward operation lever 34A, and the forward / backward operation switch 34B are each operated.

[0085] As shown in Nos. 1 to 3 in the table of Fig. 6, when the state (position) of the changeover switch 39 is valid (valid position), regardless of whether the vehicle body is running (for example, V = 5 km / h) or stopped (for example, V = 0 km / h), both the first operation signal from the forward / backward operation lever 34A and the second operation signal from the forward / backward operation switch 34B are valid. Therefore, based on the latest operation signal input to the controller 5, the state (travel content) of the vehicle body is determined, and the first display D01 is displayed on the monitor 35.

[0086] In Nos. 2 and 3 in the table of Fig. 6, while the forward / backward operation lever 34A is operated to the neutral position N, the forward / backward operation switch 34B is operated to the forward position F. In this case, when the second operation signal from the forward / backward operation switch 34B is input to the controller 5 after the first operation signal from the forward / backward operation lever 34A, the vehicle body moves forward (F) according to the second operation signal from the forward / backward operation switch 34B.

[0087] Next, as shown in Nos. 4 and 5 in the table of Fig. 6, when the state (position) of the changeover switch 39 is invalid (invalid position) and the vehicle body is running (for example, V = 5 km / h), similar to Nos. 1 to 3, both the first operation signal from the forward / backward operation lever 34A and the second operation signal from the forward / backward operation switch 34B are valid. Therefore, based on the latest operation signal input to the controller 5, the state (travel content) of the vehicle body is determined. However, the second display D02 is displayed on the monitor 35.

[0088] In No. 4 in the table of Fig. 6, similar to Nos. 2 and 3, while the forward / backward operation lever 34A is operated to the neutral position N, the forward / backward operation switch 34B is operated to the forward position F. In this case, when the second operation signal from the forward / backward operation switch 34B is input to the controller 5 after the first operation signal from the forward / backward operation lever 34A, the vehicle body moves forward (F) according to the second operation signal from the forward / backward operation switch 34B.

[0089] And, as shown in Nos. 6 to 8 in the table of FIG. 6, when the state of the changeover switch 39 is invalid and the vehicle body is stopped (for example, V = 0 km / h), the second operation signal from the forward / backward operation switch 34B becomes invalid. Therefore, based on the first operation signal from the forward / backward operation lever 34A, the state (travel content) of the vehicle body is determined, and a third display D03 is displayed on the monitor 35.

[0090] In No. 7 in the table of FIG. 6, while the forward / backward operation lever 34A is operated to the neutral position N, the forward / backward operation switch 34B is operated to the forward position F. In this case, the vehicle body stops (N) according to the first operation signal from the forward / backward operation lever 34A. Also, in No. 8 in the table of FIG. 6, while the forward / backward operation lever 34A is operated to the reverse position R, the forward / backward operation switch 34B is operated to the forward position F. In this case, the vehicle body reverses (R) according to the first operation signal from the forward / backward operation lever 34A.

[0091] Thus, even when the state of the changeover switch 39 is invalidly operated, when the vehicle body is traveling, the second operation signal output from the forward / backward operation switch 34B becomes valid. Therefore, when the operator wants to quickly switch between forward and backward or stop, the operator can operate the traveling direction of the vehicle body using the forward / backward operation switch 34B arranged close at hand.

[0092] On the other hand, when the changeover switch 39 is invalidly operated and the vehicle body is stopped, since it is difficult to assume a situation where the operator wants to quickly switch between forward and backward, in this case, by invalidating the second operation signal output from the forward / backward operation switch 34B, it is possible to prevent the vehicle from traveling unintentionally due to an accidental operation of the forward / backward operation switch 34B.

[0093] Furthermore, in the present embodiment, when both the first operation signal from the forward / backward operation lever 34A and the second operation signal from the forward / backward operation switch 34B are valid, the forward / backward movement of the vehicle body is determined based on the latest operation signal input to the controller 5. Therefore, it is possible to control the forward / backward movement of the vehicle body more in accordance with the operator's intention.

[0094] As described above, in this wheel loader 1, even when the changeover switch 39 is erroneously operated during the running of the vehicle body, it is possible to switch the forward / backward movement and run as intended by the operator.

[0095] <Second Embodiment> Next, the controller 5A according to the second embodiment of the present invention will be described with reference to FIGS. 7 and 8. In FIGS. 7 and 8, components common to those described for the controller 5 according to the first embodiment are denoted by the same reference numerals, and their descriptions are omitted.

[0096] FIG. 7 is a functional block diagram showing the functions of the controller 5A according to the second embodiment. FIG. 8 is a flowchart showing the flow of processing executed by the controller 5A according to the second embodiment.

[0097] The controller 5A according to the present embodiment includes a data acquisition unit 51A, a changeover determination unit 52, an operation presence / absence determination unit 57, a valid / invalid determination unit 54A, a traveling direction determination unit 55, and a signal output unit 56. Since the functional configurations of the changeover determination unit 52, the traveling direction determination unit 55, and the signal output unit 56 in the controller 5A are the same as those in the controller 5 according to the first embodiment, their descriptions will be omitted below.

[0098] The data acquisition unit 51A acquires the first operation signal output from the forward / backward operation lever 34A, the second operation signal output from the forward / backward operation switch 34B, and the changeover signal output from the changeover switch 39, respectively.

[0099] When the operation presence / absence determination unit 57 determines that the switching signal output from the changeover switch 39 in the switching determination unit 52 is an invalid command (step S502 / invalid command), it determines whether the forward / backward operation lever 34A has been operated, that is, whether the data acquisition unit 51A has acquired the first operation signal from the forward / backward operation lever 34A (steps S514 and S514A).

[0100] When the valid / invalid determination unit 54A determines that the switching signal output from the changeover switch 39 in the switching determination unit 52 is a valid command (step S502 / valid command), it enables the second operation signal from the forward / backward operation switch 34B acquired by the data acquisition unit 51 in the same manner as the processing in the valid / invalid determination unit 54 of the controller 5 according to the first embodiment (step S503).

[0101] Further, when the valid / invalid determination unit 54A determines that the switching signal output from the changeover switch 39 in the switching determination unit 52 is an invalid command (step S502 / invalid command), and when the operation presence / absence determination unit 57 determines that the forward / backward operation lever 34A has not been operated (step S514A / NO), if the current second operation signal is valid (step S500 / valid), it enables the second operation signal from the forward / backward operation switch 34B (maintaining the valid state of the forward / backward operation switch 34B).

[0102] On the other hand, when the valid / invalid determination unit 54A determines that the switching signal output from the changeover switch 39 in the switching determination unit 52 is an invalid command (step S502 / invalid command), and even when the operation presence / absence determination unit 57 determines that the forward / backward operation lever 34A has not been operated (step S514A / NO), if the current second operation signal is invalid (step S500 / invalid), it proceeds to step S511 to invalidate the second operation signal from the forward / backward operation switch 3dB).

[0103] Further, when the forward / backward operation determination unit 54A determines that the forward / backward operation lever 34A has been operated in the presence / absence of operation determination unit 57 (step S514A / YES), it invalidates the second operation signal from the forward / backward operation switch 34B (step S511).

[0104] That is, in the present embodiment, the controller 5A determines the validity or invalidity of the second operation signal from the forward / backward operation switch 34B based on the presence or absence of operation of the forward / backward operation lever 34A. When the switching signal output from the changeover switch 39 is switched from a valid command to an invalid command and the forward / backward operation lever 34A is operated, it indicates the operator's intention not to perform an operation using the forward / backward operation switch 34B. Therefore, regardless of whether the vehicle body is running or not, there is no problem in invalidating the second operation signal from the forward / backward operation switch 34B.

[0105] Conversely, even when the switching signal output from the changeover switch 39 is switched from a valid command to an invalid command, if the forward / backward operation lever 34A is not operated, there is a possibility that the operator may suddenly operate the forward / backward operation switch 34B. Therefore, in this case, it is necessary to keep the second operation signal from the forward / backward operation switch 34B valid.

[0106] In this way, instead of determining the state of the vehicle body (running or stopped), the controller 5A may determine the presence or absence of operation of the forward / backward operation lever 34A and determine the validity or invalidity of the second operation signal from the forward / backward operation switch 34B based on the determination result. Even in this case, the same operations and effects as those in the first embodiment are achieved.

[0107] <Third Embodiment> Next, the wheel loader 1 according to the third embodiment of the present invention will be described with reference to FIGS. 9 to 11. In FIGS. 9 to 11, components common to those described for the wheel loader 1 according to the first embodiment are denoted by the same reference numerals and their description is omitted.

[0108] FIG. 9 shows a configuration example inside the cab 12 according to the third embodiment, and is a view of the inside of the cab 12 as seen from the ceiling side. FIG. 10 is an enlarged view showing the joystick lever 6 in FIG. 9.

[0109] In the present embodiment, as shown in FIG. 9, the cab 12 is provided with a joystick lever 6 for switching the traveling direction of the vehicle body. As shown in FIG. 10, the joystick lever 6 is provided with a steering operation unit 61 for switching the left and right traveling directions of the vehicle body, and a switch-type forward / backward operation unit 62 for switching the forward and backward traveling directions of the vehicle body.

[0110] That is, in the present embodiment, the steering operation unit 61 is provided on the joystick lever 6 instead of the steering wheel 32 in the first and second embodiments, and the forward / backward operation unit 62 is provided on the joystick lever 6 instead of the forward / backward operation levers 34A and the forward / backward operation switch 34B in the first and second embodiments.

[0111] Note that the wheel loader 1 was provided with two forward / backward operation devices (the forward / backward operation lever 34A and the forward / backward operation switch 34B) in the first and second embodiments, but is provided with only one forward / backward operation device (the forward / backward operation unit 62) in the present embodiment.

[0112] As shown in FIG. 9, the joystick lever 6 is attached to the tip (front end) of the left armrest 31L of the driver's seat 31, whereby the operator can operate the steering operation unit 61 and the forward / backward operation unit 62 with the left arm placed on the left armrest 31L.

[0113] The vehicle body turns left when the operator tilts the steering operation unit 61 to the left, and turns right when the operator tilts the steering operation unit 61 to the right. In FIG. 10, the tilting direction of the steering operation unit 61 is indicated by an arrow.

[0114] The forward / backward operation unit 62 has three positions: a forward position F, a backward position R, and a neutral position N, similar to the forward / backward operation lever 34A and the forward / backward operation switch 34B in the first embodiment.

[0115] Also, similar to the forward / backward operation switch 34B in the first embodiment, the forward / backward operation unit 62 is a switch type and is located very close to the operator's hand, so it has good operability but is prone to accidental operation. Therefore, also in this embodiment, as a switching device for switching the forward / backward operation unit 62 between an effective state and an ineffective state, a changeover switch 39 is provided on the side console 38.

[0116] Next, the processing within the controller 5 according to this embodiment will be described with reference to FIG. 11. Note that since the functional components of the controller 5 according to this embodiment are the same as those of the controller 5 according to the first embodiment (see FIG. 3), the same reference numerals will be used for description below.

[0117] FIG. 11 is a flowchart showing the flow of processing executed by the controller 5 according to the third embodiment.

[0118] In the controller 5 according to this embodiment, first, the data acquisition unit 51 acquires the operation signal output from the forward / backward operation unit 62 and the switching signal output from the changeover switch 39, respectively (step S501B).

[0119] Next, the switching determination unit 52 determines whether the switching signal output from the changeover switch 39 is a valid command or an invalid command based on the switching signal from the changeover switch 39 acquired in step S501B (step S502).

[0120] If it is determined in step S502 that the switching signal output from the changeover switch 39 is a valid command (step S502 / valid command), the valid / invalid determination unit 54 validates the operation signal from the forward / reverse operation unit 62 acquired in step S501B (step S503), and the signal output unit 56 outputs a first valid display signal to the monitor 35 (step S504).

[0121] Next, the traveling direction determination unit 55 determines whether the vehicle body is to travel forward or backward based on the operation signal from the forward / backward operation unit 62 acquired in step S501B (step S515). Then, the signal output unit 56 outputs control signals according to the traveling state of the vehicle body (forward, reverse, or stop) determined in step S515 to the forward solenoid valve 41 and the reverse solenoid valve 42, respectively (step S506).

[0122] Also, if it is determined in step S502 that the switching signal output from the changeover switch 39 is an invalid command (step S502 / invalid command), the vehicle body state determination unit 53 determines the running state (stopped state) of the vehicle body based on the vehicle speed V acquired in step S507 (step S508).

[0123] If it is determined in step S508 that the vehicle body is stopped (V≦Vth) (step S508 / YES), the validity / invalidity determination unit 54 invalidates the operation signal from the forward / reverse operation unit 62 acquired in step S501B (step S511).

[0124] Next, the signal output unit 56 outputs an invalid display signal to the monitor 35 (step S512). Subsequently, the controller 5 holds the current forward / reverse movement of the vehicle body (step S516), and the process proceeds to step S506.

[0125] In this embodiment, the only forward / reverse operation device for operating the forward and reverse movement of the vehicle body is the forward / reverse operation unit 62, so the vehicle body cannot switch between forward and reverse movement unless the switching signal output from the changeover switch 39 switches from an invalid command to an valid command (step S502 / valid command).

[0126] On the other hand, if it is determined in step S508 that the vehicle body is moving (V > Vth) (step S508 / NO), and if the operation signal from the current forward / reverse operation unit 62 is valid (step S500 / valid), the valid / invalid determination unit 54 maintains the valid state of the forward / reverse operation unit 62 (step S509). After the signal output unit 56 outputs a second valid display signal to the monitor 35 (step S510), the process proceeds to step S515.

[0127] Note that if it is determined in step S508 that the vehicle body is moving (V > Vth) (step S508 / NO), and if the operation signal from the current forward / reverse operation unit 62 is invalid (step S500 / invalid), the process proceeds to step S511.

[0128] Thus, even when a plurality of forward / reverse operation devices are not provided in the cab 12, the present invention can be applied, and the same operations and effects as those in the first embodiment are achieved.

[0129] <Fourth Embodiment> Next, the wheel loader 1 according to the fourth embodiment of the present invention will be described with reference to FIGS. 12 and 13. In FIGS. 12 and 13, the same reference numerals are given to the components common to those described for the wheel loader 1 according to the first and third embodiments, and the description thereof is omitted.

[0130] FIG. 12 shows an example of the internal configuration of the cab 12 according to the fourth embodiment, and is a view of the inside of the cab 12 as seen from the ceiling side.

[0131] In the present embodiment, similar to the third embodiment, a joystick lever 6 provided with a steering operation unit 61 and a forward / reverse operation unit 62 is attached to the tip (front end) of the left armrest 31L of the driver's seat 31.

[0132] As in the first embodiment, a forward / reverse operation switch 34B is provided on the side console 38 to the right of the first work operation lever 36A and the second work operation lever 36B. The switch unit 390 of the side console 38 includes a first selector switch 39A that switches the forward / reverse operation unit 62 between an enabled state and an disabled state, and a second selector switch 39B that switches the forward / reverse operation switch 34B between an enabled state and an disabled state.

[0133] That is, in this embodiment, the wheel loader 1 is equipped with two forward / reverse operation devices (forward / reverse operation unit 62 and forward / reverse operation switch 34B) and two changeover devices (first changeover switch 39A and second changeover switch 39B).

[0134] Since both the forward / reverse operation unit 62 and the forward / reverse operation switch 34B are switch-type and located very close to the operator, making them prone to erroneous operation, a first change-over switch 39A is provided in the driver's cab 12 as a change-over device corresponding to the forward / reverse operation unit 62, and a second change-over switch 39B is provided in the driver's cab 12 as a change-over device corresponding to the forward / reverse operation switch 34B.

[0135] Next, processing within the controller 5 according to this embodiment will be described with reference to Fig. 13. Note that the functional components of the controller 5 according to this embodiment are the same as those of the controller 5 according to the first embodiment (see Fig. 3), and therefore will be denoted by the same reference numerals in the following description.

[0136] FIG. 13 is a flowchart showing the flow of processing executed by the controller 5 according to the fourth embodiment.

[0137] In the controller 5 according to the present embodiment, first, the data acquisition unit 51 acquires the second operation signal output from the forward and reverse operation switch 34B, the third operation signal output from the forward and reverse operation unit 62 (corresponding to the "operation signal output from the forward and reverse operation unit 62" in the third embodiment), the first switching signal output from the first switching switch 39A, and the second switching signal output from the second switching switch 39B, respectively (step S521).

[0138] Next, the switching determination unit 52 determines whether the switching signal output from the first switching switch 39A is a valid command or an invalid command based on the first switching signal from the first switching switch 39A acquired in step S521 (step S522).

[0139] If it is determined in step S522 that the switching signal output from the first switching switch 39A is a valid command (step S522 / valid command), subsequently, the switching determination unit 52 determines whether the switching signal output from the second switching switch 39B is a valid command or an invalid command based on the second switching signal from the second switching switch 39B acquired in step S521 (step S523).

[0140] If it is determined in step S523 that the switching signal output from the second switching switch 39B is a valid command (step S523 / valid command), the valid / invalid determination unit 54 validates the second operation signal from the forward and reverse operation switch 34B and the third operation signal from the forward and reverse operation unit 62 acquired in step S521, respectively (step S524). Subsequently, the signal output unit 56 outputs a first valid display signal to the monitor 35 (step S525).

[0141] Next, the traveling direction determination unit 55 determines the forward and backward movement of the vehicle body based on the latest operation signal among the second operation signal and the third operation signal acquired in step S521 (step S526). Then, the signal output unit 56 outputs control signals corresponding to the traveling content (forward movement, backward movement, or stop) of the vehicle body determined in step S526 to the forward electromagnetic valve 41 and the backward electromagnetic valve 42, respectively (step S527).

[0142] Also, when it is determined in step S523 that the switching signal output from the second changeover switch 39B is an invalid command (step S523 / invalid command), the data acquisition unit 51 acquires the vehicle speed V detected by the vehicle speed sensor 40 (step S531). Subsequently, the vehicle body state determination unit 53 determines whether the vehicle body is stopped based on the vehicle speed V acquired in step S531 (step S532).

[0143] When it is determined in step S532 that the vehicle body is stopped (step S532 / YES), the validity determination unit 54 invalidates the second operation signal from the forward / backward operation switch 34B acquired in step S521 (step S533).

[0144] Subsequently, the signal output unit 56 outputs a first invalid display signal to the monitor 35 (step S534). This "first invalid display signal" is an invalid display signal related to the display indicating that the second operation signal from the forward / backward operation switch 34B among the second operation signal from the forward / backward operation switch 34B and the third operation signal from the forward / backward operation unit 62 is invalid (the third operation signal from the forward / backward operation unit 62 is valid).

[0145] Next, the traveling direction determination unit 55 determines the forward and backward movement of the vehicle body based on the third operation signal from the forward / backward operation unit 62 acquired in step S521 (step S535), and the processing in the controller 5 proceeds to step S527.

[0146] On the other hand, when it is determined in step S532 that the vehicle body is traveling (step S532 / NO), the valid / invalid determination unit 54 enables both the second operation signal from the forward / backward operation switch 34B and the third operation signal from the forward / backward operation unit 62 acquired in step S521 (step S536). Subsequently, the signal output unit 56 outputs a second valid display signal to the monitor 35 (step S537), and the processing in the controller 5 proceeds to step S526.

[0147] Also, when it is determined in step S522 that the switching signal output from the first changeover switch 39A is an invalid command (step S522 / invalid command), the data acquisition unit 51 acquires the vehicle speed V detected by the vehicle speed sensor 40 (step S541). Subsequently, the vehicle body state determination unit 53 determines whether the vehicle body is stopped based on the vehicle speed V acquired in step S541 (step S542).

[0148] When it is determined in step S542 that the vehicle body is stopped (step S542 / YES), the valid / invalid determination unit 54 invalidates the third operation signal from the forward / backward operation unit 62 acquired in step S521 (step S543).

[0149] Subsequently, the signal output unit 56 outputs a second invalid display signal to the monitor 35 (step S544). This "second invalid display signal" is an invalid display signal related to the display indicating that the third operation signal from the forward / backward operation unit 62 is invalid (the second operation signal from the forward / backward operation switch 34B is valid) among the second operation signal from the forward / backward operation switch 34B and the third operation signal from the forward / backward operation unit 62.

[0150] Next, the forward / backward direction determination unit 55 determines the forward / backward movement of the vehicle body based on the second operation signal from the forward / backward operation switch 34B acquired in step S521 (step S545), and the processing in the controller 5 proceeds to step S527.

[0151] On the other hand, when it is determined in step S542 that the vehicle body is moving (step S542 / NO), the processing in the controller 5 proceeds to step S536 and step S537.

[0152] As described above, even when a plurality of forward / backward operation devices (forward / backward operation switch 34B and forward / backward operation unit 62) are provided in the cab 12 and changeover switches (first changeover switch 39A and second changeover switch 39B) are provided corresponding to each forward / backward operation device, the present invention can be applied, and the same operations and effects as those in the first embodiment are achieved.

[0153] In FIG. 13, when the changeover signal output from the first changeover switch 39A is an invalid command (step S522 / invalid command), the valid / invalid determination unit 54 determines the validity or invalidity of the third operation signal from the forward / backward operation unit 62 based on the state of the vehicle body (steps S542, S543, S536). However, the present invention is not limited to this. Similar to the second embodiment, the validity or invalidity of the third operation signal from the forward / backward operation unit 62 may be determined based on whether or not the forward / backward operation switch 34B, which is the other forward / backward operation device, is operated. The same applies when the changeover signal output from the second changeover switch 39B is an invalid command (step S523 / invalid command).

[0154] The embodiments of the present invention have been described above. It should be noted that the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Also, a part of the configuration of this embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of this embodiment. Furthermore, for a part of the configuration of this embodiment, addition, deletion, or replacement with other configurations is possible.

[0155] For example, in each of the above embodiments, the changeover switches 39, 39A, and 39B were provided corresponding to the switch-type forward and reverse operation devices. However, the present invention is not limited to this, and they may be provided corresponding to the lever-type forward and reverse operation devices.

[0156] Also, in each of the above embodiments, as one aspect of the forward and reverse operation device, the switch-type and lever-type ones were described. However, there is no particular limitation on the operation form of the forward and reverse operation device.

[0157] Also, in each of the above embodiments, as one aspect of the changeover device, the switch-type one was described. However, there is no particular limitation on the changeover means of the changeover device.

[0158] Also, in each of the above embodiments, the wheel loader 1 was described as an example of one aspect of the work vehicle. However, the present invention is not limited to this, and other work vehicles capable of moving forward and backward may also be used.

Explanation of Reference Numerals

[0159] 1: Wheel loader (work vehicle) 5, 5A: Controller 12: Cab 34A: Forward and reverse operation lever (first forward and reverse operation device) 34B: Forward and reverse operation switch (second forward and reverse operation device) 39: Changeover switch (changeover device) 39A: First changeover switch (changeover device) 39B: Second changeover switch (changeover device) 40: Vehicle speed sensor (travel state detection device) 62: Forward and reverse operation unit (forward and reverse operation device)

Claims

1. A first forward / backward operation device and a second forward / backward operation device provided in the driver's cab for operating the forward and backward movement of the vehicle body, A switching device provided in the driver's cab that outputs, as a switching signal, an enable command to enable the second forward / backward operation device and a disable command to disable it, Based on the switching signal output from the switching device, the first operation signal output from the first forward / backward operation device, and the second operation signal output from the second forward / backward operation device, a controller for controlling the forward and backward movement of the vehicle body, In a work vehicle equipped with, It has a traveling state detection device for detecting the traveling state of the vehicle body, The controller, Determines whether the vehicle body is traveling or stopped based on the traveling state detected by the traveling state detection device, When the switching signal output from the switching device is switched from the enable command to the disable command while the vehicle body is traveling, the second forward / backward operation device is maintained in the enabled state, and the forward and backward movement of the vehicle body is controlled based on the first operation signal output from the first forward / backward operation device and the second operation signal output from the second forward / backward operation device A work vehicle characterized by this.

2. In the work vehicle according to Claim 1, The controller, When it is determined that the vehicle body has stopped after the switching signal output from the switching device is switched from the enable command to the disable command while the vehicle body is traveling, the second forward / backward operation device is set to the disabled state, and the forward and backward movement of the vehicle body is controlled based on the first operation signal output from the first forward / backward operation device A work vehicle characterized by this.

3. In the work vehicle according to Claim 1, The controller, When the second forward / backward operation device is in the enabled state, the forward and backward movement of the vehicle body is controlled based on the operation signal of the forward / backward operation device that was operated last among the first forward / backward operation device and the second forward / backward operation device A work vehicle characterized by this.

4. In the work vehicle according to Claim 1, It further includes a display device for displaying the control states of the first forward / backward operation device and the second forward / backward operation device by the controller, The controller, When the switching signal output from the switching device is the enable command, it outputs a first enable display signal related to the display indicating that all of the first forward / backward operation device and the second forward / backward operation device are enabled to the display device, When the switching signal output from the switching device is switched from the valid command to the invalid command while the vehicle body is running, a second valid display signal different from the first valid display signal, which is a display indicating that all of the first forward / backward operation device and the second forward / backward operation device are valid, is output to the display device. When the switching signal output from the switching device is the invalid command while the vehicle body is stopped, an invalid display signal related to the display indicating that the second forward / backward operation device is invalid is output to the display device. A work vehicle characterized by the above.

5. A first forward / backward operation device and a second forward / backward operation device provided in the driver's cab for operating the forward and backward movement of the vehicle body, A switching device provided in the driver's cab that outputs, as a switching signal, a valid command for putting the second forward / backward operation device in an effective state and an invalid command for putting it in an invalid state, A controller that controls the forward and backward movement of the vehicle body based on the switching signal output from the switching device, the first operation signal output from the first forward / backward operation device, and the second operation signal output from the second forward / backward operation device. In a work vehicle equipped with: The controller is: When the switching signal output from the switching device is switched from the valid command to the invalid command, the second forward / backward operation device is kept in the effective state until the first forward / backward operation device is operated, and the forward and backward movement of the vehicle body is controlled based on the first operation signal output from the first forward / backward operation device and the second operation signal output from the second forward / backward operation device. When the switching signal output from the switching device is the invalid command and the first forward / backward operation device is operated, the second forward / backward operation device is put in the invalid state and the forward and backward movement of the vehicle body is controlled based on the first operation signal output from the first forward / backward operation device. A work vehicle characterized by the above.

6. A forward / backward operation device provided in the driver's cab for operating the forward and backward movement of the vehicle body, A switching device provided in the driver's cab that outputs, as a switching signal, a valid command for putting the forward / backward operation device in an effective state and an invalid command for putting it in an invalid state, A controller that controls the forward and backward movement of the vehicle body based on the switching signal output from the switching device and the operation signal output from the forward / backward operation device. In a work vehicle equipped with: It has a traveling state detection device for detecting the traveling state of the vehicle body. The controller is: Based on the running state of the vehicle body detected by the running state detection device, it is determined whether the vehicle body is running or stopped. When the switching signal output from the switching device is switched from the valid command to the invalid command during the running of the vehicle body, the forward and reverse operation device is maintained in the valid state. A work vehicle characterized by the above.

7. In the work vehicle according to claim 6, The controller, When it is determined that the vehicle body has stopped after the switching signal output from the switching device is switched from the valid command to the invalid command during the running of the vehicle body, the forward and reverse operation device is set to the invalid state. A work vehicle characterized by the above.

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