Work vehicles

Abstract

In confined work areas, this system makes it possible to avoid collisions with objects surrounding the vehicle while maintaining work efficiency. [Solution] In a wheel loader 1 in which the steering device 100 is automatically controlled by controllers 5, 5A, the device includes a bending angle sensor 35 for detecting the bending angle θ of the vehicle body, a front distance sensor 33 for detecting the front distance LF, which is the distance between an object W1 located on one side of the vehicle body and the front frame 1A, and a rear distance sensor 34 for detecting the rear distance LR, which is the distance between the object W1 and the rear frame 1B. Controllers 5, 5A calculate the difference between the front distance LF and the rear distance LR, and based on the difference and the bending angle θ, determine whether the vehicle body is approaching or moving away from the object W1. Based on the determination result, they output a steering signal to the steering device 100 to steer the vehicle body so that it travels alongside the object W1 while maintaining a predetermined distance from the object W1.

Description

Technical Field

[0001] The present invention relates to an articulated work vehicle.

Background Art

[0002] In work vehicles such as wheel loaders, in order to avoid collisions with obstacles existing around the vehicle body, a technique of detecting obstacles using an obstacle sensor such as a camera or a radar and automatically operating a braking device is known.

[0003] ]>For example, in Patent Document 1, an area from the vehicle body to an obstacle is divided into three areas, a first area, a second area, and a third area, in the order of increasing distance from the obstacle. When an obstacle is detected in the first area, which is the area closest to the vehicle body, a wheel loader that automatically operates a braking device to stop the vehicle body is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the wheel loader described in Patent Document 1, for example, when working in a narrow work site such as an excavation site surrounded by walls, every time a wall is detected, the braking device operates and the vehicle body stops frequently, which hinders the work and reduces the work efficiency.

[0006] Therefore, an object of the present invention is to provide a work vehicle that can avoid collisions with objects existing around the vehicle body while not reducing work efficiency in a narrow work site.

Means for Solving the Problems

[0007] To achieve the above objective, the present invention provides a work vehicle comprising: a vehicle body provided with a plurality of wheels, the front and rear portions of which are connected so as to bend in the vehicle width direction; a work device attached to the vehicle body; a steering device for steering the plurality of wheels; and a controller for controlling the steering device, wherein the work vehicle comprises: a bending angle detection device for detecting the bending angle of the vehicle body; a front distance detection device attached to one side in the vehicle width direction of the front portion of the vehicle body for detecting the front distance which is the distance between an object located on the one side of the vehicle body and the front portion of the vehicle body; and a device attached to one side of the rear portion of the vehicle body for detecting the object The controller comprises a front distance detection device that detects a rear distance which is the distance between the front distance detected by the front distance detection device and the rear distance detected by the rear distance detection device, and determines whether the vehicle body is approaching the object or moving away from the object based on the calculated difference and the bending angle detected by the bending angle detection device, and outputs a steering signal to the steering device that steers the vehicle body to travel alongside the object while maintaining a predetermined distance from the object based on the determination result. [Effects of the Invention]

[0008] According to the present invention, it is possible to avoid collisions with objects surrounding the vehicle body in a confined work area without reducing work efficiency. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments. [Brief explanation of the drawing]

[0009] [Figure 1] This is an external side view showing one example of the configuration of a wheel loader according to each embodiment of the present invention. [Figure 2] Figure 1 is a top view of the wheel loader, seen from above. [Figure 3] This is a functional block diagram showing the functions of the controller according to the first embodiment. [Figure 4]It is a flowchart showing the overall processing flow executed by the controller according to the first embodiment. [Figure 5] It is a flowchart showing the processing flow during reverse travel among the processes executed by the controller according to the first embodiment. [Figure 6] It is a diagram showing the state of steering of the wheel loader when LF < LR. [Figure 7] It is a diagram showing the state of steering of the wheel loader when LF > LR. [Figure 8] It is a schematic diagram showing the state of steering of the wheel loader according to the second embodiment. [Figure 9] It is a functional block diagram showing the functions of the controller according to the second embodiment. [Figure 10] It is a flowchart showing the processing flow executed by the controller according to the second embodiment.

Modes for Carrying Out the Invention

[0010] Hereinafter, as an aspect of the work vehicle according to each embodiment of the present invention, a wheel loader that performs a loading and unloading operation will be described as an example.

[0011] <Configuration of Wheel Loader 1> First, the configuration of the wheel loader 1 according to each embodiment of the present invention will be described with reference to FIGS. 1 and 2.

[0012] FIG. 1 is an external side view showing a configuration example of the wheel loader 1 according to each embodiment of the present invention. FIG. 2 is a top view of the wheel loader 1 shown in FIG. 1 as viewed from above.

[0013] The wheel loader 1 is an articulated work vehicle that is steered by the body being bent near the center. The front frame 1A that is the front part of the body and the rear frame 1B that is the rear part of the body are connected by a center pin 10 so as to be rotatable in the vehicle width direction, and the front frame 1A bends in the vehicle width direction with respect to the rear frame 1B.

[0014] In the following description, in the vehicle width direction of the vehicle body, the left side direction with respect to the forward direction is defined as the "left direction", and the right side direction with respect to the forward direction is defined as the "right direction".

[0015] The vehicle body is provided with four wheels 11. Two wheels 11 are provided as front wheels 11A on the left and right sides of the front frame 1A, and the remaining two wheels 11 are provided as rear wheels 11B on the left and right sides of the rear frame 1B, respectively. In FIG. 1, only the left front wheel 11A and the rear wheel 11B among the four wheels 11 are shown.

[0016] At the front part of the front frame 1A, a working device 2 for performing a loading and unloading operation of excavating earth and sand, minerals, etc. and loading them into a loading destination such as a dump truck or a hopper is attached.

[0017] The working device 2 is hydraulically driven and includes a lift arm 21 rotatably attached to the front frame 1A in the vertical direction, two lift arm cylinders (not shown) for driving the lift arm 21, a bucket 22 rotatably attached to the tip of the lift arm 21 in the vertical direction, a bucket cylinder 22A for driving the bucket 22, and a bell crank 23 rotatably connected to the lift arm 21 to form a link mechanism between the bucket 22 and the bucket cylinder 22A.

[0018] The lift arm 21 rotates in the vertical direction with respect to the front frame 1A by the inflow and outflow of hydraulic oil to and from two lift arm cylinders arranged side by side in the vehicle width direction and the expansion and contraction of each rod.

[0019] A lift arm angle sensor 31 for detecting a lift arm angle α, which is the angle of the lift arm 21 with respect to the front frame 1A, is attached to the base of the lift arm 21 (the attachment part to the front frame 1A).

[0020] The bucket 22 rotates vertically relative to the lift arm 21 as hydraulic fluid flows in and out of the bucket cylinder 22A, causing the rod to extend and retract. This allows the bucket 22 to scoop up and discharge (excavate and release) soil, minerals, and other materials.

[0021] A bucket angle sensor 32 is attached to the bell crank 23 to detect the bucket angle β, which is the angle of the bucket 22 relative to the lift arm 21.

[0022] The lift arm angle sensor 31 and the bucket angle sensor 32 are one embodiment of a posture detection device for detecting the posture of the work device 2. Note that the posture detection device does not necessarily have to be an angle sensor; it could also be, for example, a sensor for detecting the extension and retraction length of the rods of each cylinder.

[0023] The rear frame 1B is provided with a driver's cab 12 where the operator sits, a machine room 13 that houses various equipment necessary for driving the wheel loader 1, and a counterweight 14 that maintains balance with the work device 2 to prevent the vehicle body from tilting. In the rear frame 1B, the driver's cab 12 is located at the front, the counterweight 14 is located at the rear, and the machine room 13 is located between the driver's cab 12 and the counterweight 14.

[0024] As shown in Figures 1 and 2, the wheel loader 1 has a front distance sensor 33, which is a front distance detection device that detects the distance between the front frame 1A and an object such as a wall or fence located on one side of the vehicle body in the vehicle width direction (one of the left and right directions in Figures 1 and 2), and a rear distance sensor 34, which is a rear distance detection device that detects the distance between the rear frame 1B and the object, and is mounted on one side of the vehicle body in the vehicle width direction (the left side in Figures 1 and 2).

[0025] The front distance sensor 33 and the rear distance sensor 34 are, for example, millimeter-wave radar, laser light (three-dimensional laser), and cameras, respectively, and are mounted on the left side of the vehicle body in Figures 1 and 2. More specifically, the front distance sensor 33 is located at the base of the headlight 15, which is on the left side of the front frame 1A, and the rear distance sensor 34 is located at the base of the taillight 16, which is on the left side of the rear frame 1B.

[0026] It is desirable that the front distance sensor 33 and the rear distance sensor 34 be located as far apart as possible in the longitudinal direction of the vehicle body. If the front distance sensor 33 and the rear distance sensor 34 were located close together in the longitudinal direction of the vehicle body (for example, near the center pin 10), the front distance LF detected by the front distance sensor 33 and the rear distance LR detected by the rear distance sensor 34 would be similar values, making it difficult to accurately determine the relationship between the position of the front frame 1A relative to the object and the position of the rear frame 1B relative to the object.

[0027] In Figures 1 and 2, the front distance sensor 33 and the rear distance sensor 34 are mounted on the left side of the vehicle body, but are not limited to this; they may also be mounted on the right side of the vehicle body, or on both the left and right sides of the vehicle body. In other words, the front distance sensor 33 and the rear distance sensor 34 only need to be mounted so that their detection area includes at least a portion of the vehicle body where an object is assumed to exist.

[0028] Furthermore, as shown in Figure 1, the wheel loader 1 has a bending angle sensor 35, which acts as a bending angle detection device for detecting the bending angle θ of the vehicle body, mounted near the center pin 10. The bending angle θ of the vehicle body corresponds to the relative angle between the front frame 1A and the rear frame 1B. When the bending angle θ is 0° (θ=0°), the front frame 1A and the rear frame 1B are in a straight state. On the other hand, when the bending angle θ is a positive or negative value (θ>0° or θ<0°), the front frame 1A is bent in the vehicle width direction relative to the rear frame 1B.

[0029] In this wheel loader 1, the steering device 100 (see Figure 3) that steers the four wheels 11 is controlled not only by the operator's manual operation but also automatically by a controller. For example, when the wheel loader 1 is working in a narrow work site such as an excavation site surrounded by walls or fences, the steering device 100 is controlled to prevent the vehicle from colliding with the surrounding walls or fences (automatic steering control). The controller that controls the steering device 100 will be described below for each embodiment.

[0030] <First Embodiment> The controller 5 according to the first embodiment will be described with reference to Figures 3 to 7.

[0031] (Controller 5 configuration) First, the configuration of controller 5 will be explained with reference to Figure 3.

[0032] Figure 3 is a functional block diagram showing the functions of the controller 5 according to the first embodiment.

[0033] Controller 5 is configured with a CPU, RAM, ROM, HDD, input interface, and output interface connected to each other via a bus. Various sensors such as a lift arm angle sensor 31, a bucket angle sensor 32, a front distance sensor 33, a rear distance sensor 34, a bending angle sensor 35, and a vehicle speed sensor 43, as well as various switches such as a forward / reverse selector switch 41 and a selection switch 42, are connected to the input interface, and the steering device 100 is connected to the output interface.

[0034] In this hardware configuration, the CPU reads the control program (software) stored on a recording medium such as ROM, HDD, or optical disc, loads it onto RAM, and executes the loaded control program. The control program and hardware then work together to realize the functions of the controller 5.

[0035] In this embodiment, the configuration of the controller 5 is described as a combination of software and hardware, but it is not limited to this, and it may also be configured using an integrated circuit that realizes the functions of the control program executed on the wheel loader 1.

[0036] Here, the vehicle speed sensor 43 is a vehicle speed detection device that detects the vehicle's speed and outputs the detected vehicle speed to the controller 5. The vehicle speed sensor 43 may include, for example, a sensor that detects the rotational speed of the wheels 11 or a sensor that detects the amount the accelerator pedal is pressed.

[0037] The forward / reverse selector switch 41 is a forward / reverse selector device for switching the forward / reverse movement of the vehicle body, and has a forward position for moving the vehicle body forward, a reverse position for moving the vehicle body backward, and a neutral position for stopping the vehicle body. The forward / reverse selector switch 41 is installed in the driver's cab 12 (see Figures 1 and 2), and when the operator performs a switching operation, it outputs a switching signal to the controller 5.

[0038] The selection switch 42 is a selection device for selecting whether or not to perform automatic steering control by the controller 5. The selection switch 42 is located inside the driver's cab 12, and when operated to the ON position by the operator, it outputs a selection signal (ON signal) to the controller 5 indicating that automatic steering control should be performed.

[0039] The controller 5 includes a data acquisition unit 51, a control execution determination unit 52, a work state determination unit 53, a distance determination unit 54, a bending state determination unit 55, and a steering control unit 56.

[0040] The data acquisition unit 51 acquires the forward / reverse switching signal output from the forward / reverse switching switch 41, the selection signal output from the selection switch 42, the lift arm angle α detected by the lift arm angle sensor 31, the bucket angle β detected by the bucket angle sensor 32, the front distance LF detected by the front distance sensor 33, the rear distance LR detected by the rear distance sensor 34, the bending angle θ of the vehicle body detected by the bending angle sensor 35, and the vehicle body's travel speed detected by the vehicle speed sensor 43.

[0041] The control execution determination unit 52 determines whether or not to execute automatic steering control by the controller 5 based on the selection signal acquired by the data acquisition unit 51. Specifically, if the data acquisition unit 51 acquires a selection signal (on signal) indicating that automatic steering control should be performed, the control execution determination unit 52 determines that automatic steering control by the controller 5 should be performed. If the data acquisition unit 51 acquires a selection signal (off signal) indicating that automatic steering control should not be performed, the control execution determination unit 52 determines that automatic steering control by the controller 5 should not be performed.

[0042] The work state determination unit 53 determines the work state of the wheel loader 1 when the control execution determination unit 52 determines that the controller 5 should start automatic control of the steering device 100. Specifically, the work state determination unit 53 determines the posture of the work device 2 based on the lift arm angle α and bucket angle β acquired by the data acquisition unit 51, and also determines the driving state of the vehicle based on the forward / reverse switching signal and the vehicle's driving speed acquired by the data acquisition unit 51.

[0043] The distance determination unit 54 calculates the difference between the front distance LF and the rear distance LR obtained by the data acquisition unit 51, and compares the magnitude relationship between the distance from the previous frame 1A to the object and the distance from the next frame 1B to the object.

[0044] The bending state determination unit 55 determines the bending state of the vehicle body based on the bending angle θ acquired by the data acquisition unit 51. Specifically, if the bending angle θ is 0° (θ=0°), the vehicle body is straight and not bent. If the bending angle θ is not 0° (θ≠0°), that is, if the bending angle θ is a positive value (θ>0°) or a negative value (θ<0°), the vehicle body is bent in either the vehicle width direction (left or right).

[0045] The steering control unit 56 determines whether the vehicle body is approaching the object based on the difference between the front distance LF and the rear distance LR calculated by the distance determination unit 54, and the bending state of the vehicle body determined by the bending state determination unit 55. If the steering control unit 56 determines that the vehicle body is approaching the object, it outputs a steering signal to the steering device 100 to steer the vehicle body so that it travels alongside the object at a predetermined distance away from it.

[0046] For example, the steering control unit 56 outputs a steering signal to the steering device 100 to steer the vehicle to the right if it determines that the vehicle is moving forward and approaching a wall located on the left side, and to steer the vehicle to the left if it determines that the vehicle is moving forward and moving too far away from the wall on the left side (for example, approaching a wall located on the right side).

[0047] In this embodiment, the steering control unit 56 outputs a steering signal to the steering device 100 to steer the vehicle body in the direction away from the object when the difference between the front distance LF and the rear distance LR calculated by the distance determination unit 54 is a positive value (|LF-LR|>0), that is, when the front distance LF and the rear distance LR are not equal (LF≠LR).

[0048] Subsequently, if the difference between the front distance LF and the rear distance LR calculated by the distance determination unit 54 becomes zero (|LF-LR|=0), that is, if the front distance LF and the rear distance LR become equal (LF=LR), the steering control unit 56 outputs a return signal to the steering device 100 that steers in the opposite direction to the steering signal until the bending angle θ detected by the bending angle sensor 35 reaches 0 (zero) (θ=0°).

[0049] Furthermore, in this embodiment, prior to the steering control unit 56 outputting a steering signal to the steering device 100 to steer the vehicle body away from an object, if the difference between the front distance LF and the rear distance LR calculated by the distance determination unit 54 is zero (|LF-LR|=0), that is, if the front distance LF and the rear distance LR are equal (LF=LR), the bending state determination unit 55 determines whether or not the bending angle θ detected by the bending angle sensor 35 is 0°.

[0050] Then, if the bending state determination unit 55 determines that the bending angle θ is not 0° (θ≠0°), the steering control unit 56 outputs a signal to the steering device 100 to steer in the opposite direction to the bending direction of the vehicle body. In this case, the vehicle body is bent so that the front frame 1A and the rear frame 1B are approaching the center (center pin 10), and the distance from the front frame 1A to the object and the distance from the rear frame 1B to the object are equal. Therefore, the controller 5 controls the vehicle body to return to a straight state by outputting a signal to the steering device 100 to steer in the opposite direction to the bending direction of the vehicle body.

[0051] Furthermore, in this embodiment, when the working state determination unit 53 determines that the working device 2 is in a transporting position, the steering control unit 56 outputs a steering signal to the steering device 100 to steer the vehicle body away from the object.

[0052] Here, "transportation posture" refers to the posture when transporting the load to a loading destination such as a dump truck or hopper. Specifically, it is the posture in which the lift arm 21 is positioned at a height set based on the minimum ground clearance of the wheel loader 1, and the bucket 22 is in its most rearward-tilted position.

[0053] In this way, automatic steering control by the controller 5 is performed only when the work device 2 is in a transport position, that is, when the wheel loader 1 is performing load transport work. On the other hand, in operations where there is a low possibility of the vehicle body colliding with surrounding objects, such as excavation work, automatic steering control by the controller 5 is not performed, thereby preventing a decrease in work efficiency.

[0054] (Processing executed by controller 5) Next, the processing flow executed by controller 5 will be explained with reference to Figures 4 and 5.

[0055] Figure 4 is a flowchart showing the overall processing flow performed by the controller 5 according to the first embodiment. Figure 5 is a flowchart showing the processing flow performed by the controller 5 according to the first embodiment when the vehicle is driving in reverse.

[0056] As shown in Figure 4, in the controller 5, first, the control execution determination unit 52 determines whether or not to execute automatic steering control by the controller 5 based on the selection signal acquired by the data acquisition unit 51 (step S501).

[0057] If, in step S501, it is determined that automatic steering control by the controller 5 will be performed (step S501 / YES), that is, if the selection switch 42 is turned ON and an ON signal is acquired by the data acquisition unit 51, the data acquisition unit 51 acquires the lift arm angle α detected by the lift arm angle sensor 31 and the bucket angle β detected by the bucket angle sensor 32, respectively (step S502).

[0058] On the other hand, if it is determined in step S501 that automatic steering control by the controller 5 will not be performed (step S501 / NO), that is, if the selection switch 42 is turned off and an off signal is acquired by the data acquisition unit 51, the processing in the controller 5 ends.

[0059] Next, the work state determination unit 53 determines whether the work device 2 is in a transport position based on the lift arm angle α and bucket angle β obtained in step S502 (step S503).

[0060] If it is determined in step S503 that the work device 2 is in a transport position (step S503 / YES), the data acquisition unit 51 acquires the front distance LF detected by the front distance sensor 33 and the rear distance LR detected by the rear distance sensor 34 (step S504).

[0061] On the other hand, in this embodiment, if it is determined in step S503 that the work device 2 is not in a transport position (step S503 / NO), the processing in the controller 5 ends.

[0062] Next, the distance determination unit 54 determines whether the front distance LF and the rear distance LR obtained in step S504 are not equal, that is, whether the difference between the front distance LF and the rear distance LR is not zero (step S505).

[0063] If, in step S505, it is determined that the front distance LF and the rear distance LR are not equal (LF≠LR), that is, the difference between the front distance LF and the rear distance LR is not zero (|LF-LR|≠0) (step S505 / YES), the work state determination unit 53 determines whether the vehicle is moving forward or not based on the forward / reverse switching signal and the vehicle's travel speed acquired by the data acquisition unit 51 (step S506).

[0064] When it is determined in step S506 that the vehicle body is moving forward (step S506 / YES), the distance determination unit 54 determines whether the front distance LF is shorter than the rear distance LR (step S507).

[0065] When it is determined in step S507 that the front distance LF is shorter than the rear distance LR (LF < LR) (step S507 / YES), the steering control unit 56 outputs a right steering signal for steering the vehicle body to the right to the steering device 100 (step S508).

[0066] Here, FIG. 6 is a diagram showing the state of steering of the wheel loader 1 when LF < LR.

[0067] As shown in FIG. 6, the case where the front distance LF is shorter than the rear distance LR (LF < LR) indicates that the vehicle body is approaching an object W1 existing on the left side while moving forward. In this case, by controlling the controller 5 to steer the vehicle body to the right, the wheel loader 1 can continue the work without approaching (colliding) with the object W1 too much.

[0068] As shown in FIG. 4, subsequently, the distance determination unit 54 determines whether the front distance LF and the rear distance LR acquired by the data acquisition unit 51 are equal (step S509).

[0069] When it is determined in step S509 that the front distance LF and the rear distance LR are equal (LF = LR) (step S509 / YES), the steering control unit 56 outputs a left steering signal for steering the vehicle body to the left (a return signal for steering in the opposite direction to the steering signal for avoiding collision with an object) to the steering device 100 (step S510).

[0070] As shown in Figure 6, the wheel loader 1 is steered to the right, away from object W1, by the process in step S508. However, if the steering continues in this direction, there is a possibility that the vehicle will move too far away from object W1 (and collide with another object W2, for example, a wall located to the right of the vehicle). Therefore, by turning back to the left, it is possible to keep the vehicle running parallel to object W1.

[0071] On the other hand, as shown in Figure 4, if it is determined in step S509 that the front distance LF and the rear distance LR are not equal (LF≠LR), the process does not proceed to the next step S510 until the front distance LF and the rear distance LR become equal.

[0072] Next, the bending state determination unit 55 determines whether the bending angle θ acquired by the data acquisition unit 51 has reached 0°, that is, whether the vehicle body has become straight (step S511).

[0073] If it is determined in step S511 that the bending angle θ has reached 0° (θ=0°), that is, if the vehicle body is running parallel to object W1 (step S511 / YES), the process returns to step S501 and is repeated.

[0074] On the other hand, if it is determined in step S511 that the bending angle θ has not reached 0° (θ≠0°), that is, if the vehicle body is not running parallel to object W1 (step S511 / NO), the process returns to step S510.

[0075] Furthermore, if it is determined in step S507 that the front distance LF is not shorter than the rear distance LR, that is, that the front distance LF is longer than the rear distance LR (LF > LR) (step S507 / NO), the steering control unit 56 outputs a left steering signal to the steering device 100 to steer the vehicle body to the left (step S512).

[0076] Here, Figure 7 shows the steering of wheel loader 1 when LF > LR.

[0077] As shown in Figure 7, when the front distance LF is longer than the rear distance LR (LF > LR), it indicates that the vehicle is moving away from object W1 as it moves forward, and is approaching another object W2 located to the right. In this case, the controller 5 controls the vehicle to steer to the left, allowing the wheel loader 1 to continue its work without getting too close to (colliding with) the other object W2.

[0078] Next, as shown in Figure 4, the distance determination unit 54 determines whether the front distance LF and the rear distance LR obtained by the data acquisition unit 51 are equal, similar to step S509 (step S513).

[0079] If it is determined in step S513 that the front distance LF and the rear distance LR are equal (LF=LR) (step S513 / YES), the steering control unit 56 outputs a right steering signal to the steering device 100 to steer the vehicle to the right (a return signal that steers in the opposite direction to the steering signal used to avoid collision with an object) (step S514).

[0080] As shown in Figure 7, the wheel loader 1 is steered to the left, which is the direction towards object W1, by the process in step S512. However, if the steering continues in this direction, there is a possibility that the vehicle will move too far away from other objects W2 (and collide with object W1, for example, the wall located on the left side of the vehicle). By steering back to the right, it becomes possible to keep the vehicle running parallel to the other objects W2.

[0081] On the other hand, as shown in Figure 4, if it is determined in step S513 that the front distance LF and the rear distance LR are not equal (LF≠LR) (step S513 / NO), the process does not proceed to the next step S514 until the front distance LF and the rear distance LR become equal.

[0082] Next, the bending state determination unit 55 determines, similar to step S511, whether the bending angle θ acquired by the data acquisition unit 51 has reached 0°, that is, whether the vehicle body has become straight (step S515).

[0083] If it is determined in step S515 that the bending angle θ has reached 0° (θ=0°), that is, if the vehicle body is running parallel to the other object W2 (step S515 / YES), the process returns to step S501 and is repeated.

[0084] On the other hand, if it is determined in step S515 that the bending angle θ has not reached 0° (θ≠0°), that is, if the vehicle body is not running parallel to the other object W2 (step S515 / NO), the process returns to step S514.

[0085] Furthermore, if it is determined in step S505 that the front distance LF and the rear distance LR are equal (LF=LR) (step S505 / NO), the bending state determination unit 55 determines whether the bending angle θ acquired by the data acquisition unit 51 is not 0°, that is, whether the vehicle body is bending or not (step S516).

[0086] If, in step S516, it is determined that the bending angle θ is not 0° (θ≠0°), that is, that the vehicle body is bent (step S516 / YES), then the bending state determination unit 55 subsequently determines whether or not the vehicle body is bent to the right (step S517).

[0087] On the other hand, if it is determined in step S516 that the bending angle θ is 0° (θ=0°), that is, the vehicle body is not bent and is in a straight state (step S516 / NO), the process returns to step S505.

[0088] Next, if it is determined in step S517 that the vehicle body is bending to the right (step S517 / YES), the steering control unit 56 outputs a left steering signal to steer the vehicle body to the left (step S518), and then returns to step S517.

[0089] On the other hand, if it is determined in step S517 that the vehicle body is not bent to the right, that is, if it is determined that the vehicle body is bent to the left (step S517 / NO), the steering control unit 56 outputs a right steering signal for steering the vehicle body to the right (step S519), and then returns to step S517.

[0090] Also, if it is determined in step S506 that the vehicle body is not moving forward (step S506 / NO), the working state determination unit 53 determines whether the vehicle body is moving backward (step S520).

[0091] If it is determined in step S520 that the vehicle body is not moving backward (step S520 / NO), the processing in the controller 5 ends.

[0092] On the other hand, if it is determined in step S520 that the vehicle body is moving backward (step S520 / YES), as shown in FIG. 5, the distance determination unit 54 determines whether the front distance LF is shorter than the rear distance LR in the same manner as in step S507 (step S521).

[0093] [[ID=ID=18]]If it is determined in step S521 that the front distance LF is shorter than the rear distance LR (LF < LR) (step S521 / YES), the steering control unit 56 outputs a left steering signal for steering the vehicle body to the left to the steering device 100 (step S522).

[0094] The case where the front distance LF is shorter than the rear distance LR (LF < LR) indicates that the vehicle body is approaching another object W2 existing on the right side while moving backward. In this case, by controlling the controller 5 to steer the vehicle body to the left, the wheel loader 1 can continue the work without approaching (colliding) with the other object W2 too much.

[0095] Next, the distance determination unit 54 determines whether the front distance LF and the rear distance LR obtained by the data acquisition unit 51 are equal (step S523).

[0096] If it is determined in step S523 that the front distance LF and the rear distance LR are equal (LF=LR) (step S523 / YES), the steering control unit 56 outputs a right steering signal to the steering device 100 (a return signal that steers in the opposite direction to the steering signal used to avoid collision with an object) to steer the vehicle to the right (step S524).

[0097] As a result of the process in step S522, the wheel loader 1 is steered to the left, away from the other object W2. However, if the steering continues in this direction, there is a possibility that the vehicle will move too far away from the other object W2 (and collide with object W1, for example, a wall located on the left side of the vehicle). Therefore, by turning back to the right, it becomes possible to keep the vehicle running parallel to the other object W2.

[0098] On the other hand, if it is determined in step S523 that the front distance LF and the rear distance LR are not equal (LF≠LR) (step S523 / NO), the process does not proceed to the next step S524 until the front distance LF and the rear distance LR become equal.

[0099] Next, the bending state determination unit 55 determines whether the bending angle θ acquired by the data acquisition unit 51 has reached 0°, that is, whether the vehicle body has become straight (step S525).

[0100] If it is determined in step S525 that the bending angle θ has reached 0° (θ=0°), that is, if the vehicle body is running parallel to the other object W2 (step S525 / YES), the process returns to step S501 and is repeated.

[0101] On the other hand, if it is determined in step S525 that the bending angle θ has not reached 0° (θ≠0°), that is, if the vehicle body is not running parallel to the other object W2 (step S525 / NO), the process returns to step S524.

[0102] Furthermore, if it is determined in step S521 that the front distance LF is not shorter than the rear distance LR, that is, that the front distance LF is longer than the rear distance LR (LF > LR) (step S521 / NO), the steering control unit 56 outputs a right steering signal to the steering device 100 to steer the vehicle to the right (step S526).

[0103] When the front distance LF is longer than the rear distance LR (LF > LR), it indicates that the vehicle is moving backward and approaching object W1 located on the left side. In this case, the controller 5 controls the vehicle to steer to the right, allowing the wheel loader 1 to continue its work without getting too close to (colliding with) object W1.

[0104] Next, the distance determination unit 54 determines, similar to step S523, whether the front distance LF and the rear distance LR obtained by the data acquisition unit 51 are equal (step S527).

[0105] If it is determined in step S527 that the front distance LF and the rear distance LR are equal (LF=LR) (step S527 / YES), the steering control unit 56 outputs a left steering signal (a return signal that steers in the opposite direction to the steering signal used to avoid collision with an object) to the steering device 100 (step S528). This makes it possible for the wheel loader 1 to run parallel to the object W1 on its left side.

[0106] On the other hand, if it is determined in step S527 that the front distance LF and the rear distance LR are not equal (LF≠LR) (step S527 / NO), the process does not proceed to the next step S528 until the front distance LF and the rear distance LR become equal.

[0107] Next, the bending state determination unit 55 determines, similar to step S525, whether the bending angle θ acquired by the data acquisition unit 51 has reached 0°, that is, whether the vehicle body has become straight (step S529).

[0108] If it is determined in step S529 that the bending angle θ has reached 0° (θ=0°), that is, if the vehicle body is running parallel to object W1 (step S529 / YES), the process returns to step S501 and is repeated.

[0109] On the other hand, if it is determined in step S529 that the bending angle θ has not reached 0° (θ≠0°), that is, if the vehicle body is not running parallel to object W1 (step S529 / NO), the process returns to step S528.

[0110] In this way, the controller 5 determines the distance relationship between the vehicle body and objects in its surroundings, and if it determines that the vehicle body is approaching an object, it controls the steering device 100 to steer the vehicle body away from the object. This makes it possible to avoid collisions with walls or fences while maintaining work efficiency, for example, in a narrow work site surrounded by objects such as walls or fences (see Figures 6 and 7).

[0111] <Second Embodiment> Next, a controller 5A according to the second embodiment of the present invention will be described with reference to Figures 8 to 10. In Figures 8 to 10, components that are common to those described in the first embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0112] Figure 8 is a schematic diagram showing the steering of the wheel loader 1 according to the second embodiment. Figure 9 is a functional block diagram showing the functions of the controller 5A according to the second embodiment. Figure 10 is a flowchart showing the processing flow executed by the controller 5A according to the second embodiment.

[0113] As shown in FIG. 9, the controller 5A according to this embodiment includes a data acquisition unit 51, a control execution determination unit 52, a working state determination unit 53, a distance determination unit 54A, a bending state determination unit 55A, a steering control unit 56A, and in addition, a relative angle calculation unit 57, a steering angle calculation unit 58, and a storage unit 59.

[0114] When the distance determination unit 54A determines that the front distance LF acquired by the data acquisition unit 51 is shorter than the rear distance LR (LF < LR), it further determines whether the front distance LF is less than or equal to the minimum front distance LFmin.

[0115] This "minimum front distance LFmin" is a threshold value set based on the front distance LF when the vehicle body will collide if it approaches the object W1 any further, as shown in FIG. 8, and is stored in the storage unit 59.

[0116] The relative angle calculation unit 57 calculates the relative angle γ between the vehicle body and the object based on the front distance LF and the rear distance LR acquired by the data acquisition unit 51. This "relative angle γ" refers to the angle formed by the vehicle body and the object W1, for example, when the wheel loader 1 approaches an object W1 existing on the left side of the vehicle body while moving forward, as shown in FIG. 8.

[0117] The steering angle calculation unit 58 calculates the upper limit value θlim of the steering angle of the vehicle body (hereinafter referred to as the "upper limit steering angle θlim") based on the relative angle γ calculated by the relative angle calculation unit 57. This "upper limit steering angle θlim" is an angle that changes according to the current bending angle θ of the vehicle body (the bending angle θ detected by the bending angle sensor 35 at the time of calculation by the steering angle calculation unit 58), and is not the rated value in the wheel loader 1.

[0118] The bending state determination unit 55A determines whether the bending angle θ acquired by the data acquisition unit 51 has reached the upper limit steering angle θlim calculated by the steering angle calculation unit 58.

[0119] When the distance determination unit 54A determines that the front distance LF is less than or equal to the minimum front distance LFmin (LF≦LFlim), the steering control unit 56A outputs a steering signal to the steering device 100 so that the bending angle θ reaches the upper limit steering angle θlim at a predetermined angular velocity.

[0120] When the bending angle θ reaches the upper limit steering angle θlim (θ = θlim), the steering control unit 56A outputs a return signal to the steering device 100 so that the bending angle θ becomes 0° (so that the vehicle body is in a straight state) at a predetermined angular velocity.

[0121] As shown in FIG. 10, in the controller 5A, when it is determined in step S505 that the front distance LF and the rear distance LR are not equal (LF≠LR) (step S505 / YES), the relative angle calculation unit 57 calculates the relative angle γ between the vehicle body and the object based on the front distance LF and the rear distance LR obtained in step S504 (step S531).

[0122] On the other hand, when it is determined in step S505 that the front distance LF and the rear distance LR are equal (LF = LR) (step S505 / NO), the process corresponding to the processes from step S516 to step S519 shown in FIG. 4 (the process in the case of LF = LR) is performed (step S530A).

[0123] Next, the steering angle calculation unit 58 calculates the upper limit steering angle θlim based on the relative angle γ calculated in step S531 (step S532).

[0124] Subsequently, the process proceeds to step S506 and step S507. When it is determined in step S507 that the front distance LF is shorter than the rear distance LR (LF < LR) (step S507 / YES), the distance determination unit 54A determines whether the front distance LF is less than or equal to the minimum front distance LFmin (step S533).

[0125] On the other hand, if it is determined in step S507 that the front distance LF is longer than the rear distance LR (LF>LR) (step S507 / NO), the process corresponding to the process in steps S512 to S515 shown in Figure 4 (processing in the case of LF>LR) is performed (step S530B).

[0126] Next, if it is determined in step S533 that the front distance LF is less than or equal to the minimum front distance LFmin (LF ≤ LFlim) (step S533 / YES), the steering control unit 56A outputs a right steering signal to the steering device 100 so that the bending angle θ reaches the upper limit steering angle θlim calculated in step S532 at a predetermined angular velocity (step S508A).

[0127] Then, the bending state determination unit 55A determines whether the bending angle θ acquired by the data acquisition unit 51 has reached the upper limit steering angle θlim calculated in step S532 (step S534).

[0128] If it is determined in step S534 that the bending angle θ has reached the upper limit steering angle θlim (θ=θlim) (step S534 / YES), the steering control unit 56A outputs a left steering signal to the steering device 100 so that the bending angle θ becomes 0° at a predetermined angular velocity (step S510A), and proceeds to step S511.

[0129] On the other hand, if it is determined in step S534 that the bending angle θ has not reached the upper limit steering angle θlim (θ≠θlim), the process will not proceed to the next step S510A until the bending angle θ reaches the upper limit steering angle θlim.

[0130] Furthermore, if it is determined in step S520 that the vehicle is moving in reverse (step S520 / YES), the process corresponding to the flow shown in Figure 5 (processing during reverse driving) is performed (step S530C).

[0131] In this embodiment as well, the same effects and benefits as those in the first embodiment are achieved.

[0132] The embodiments of the present invention have been described above. It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail for the purpose of clearly illustrating the present invention, and are not necessarily limited to those having all the described configurations. Furthermore, it is possible to replace parts of the configuration of each embodiment with the configuration of other embodiments, and it is also possible to add configurations from other embodiments to the configuration of each embodiment. Moreover, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations.

[0133] For example, in each of the above embodiments, a wheel loader 1 was used as an example of a work vehicle, but the invention is not limited to this, and other work vehicles may also be used.

[0134] Furthermore, in each of the above embodiments, object W1 (the wall on the left side of the vehicle body) is referred to as "object" and other object W2 (the wall on the right side of the vehicle body) is referred to as "other object," but the embodiment is not limited to this, and other object W2 may be referred to as "object" and object W1 as "other object." [Explanation of symbols]

[0135] 1: Wheel loader (work vehicle) 1A: Front frame (front part of the vehicle) 1B: Rear frame (rear of the vehicle) 5.5A: Controller 11,11A,11B: Wheel 31: Lift arm angle sensor (attitude detection device) 32: Bucket angle sensor (attitude detection device) 33: Front distance sensor (front distance detection device) 34: Rear distance sensor (rear distance detection device) 42: Selection switch (selection device) 100: Steering system LF: Front distance LR: Rear distance W1:Object W2: Other objects γ: relative angle θ: bending angle θlim: Upper limit of steering angle

Claims

1. A vehicle body with multiple wheels, and whose front and rear sections are connected in a way that allows it to bend in the width direction, A work device attached to the vehicle body, A steering device for steering the aforementioned multiple wheels, A controller that controls the steering device, In a work vehicle equipped with, A bending angle detection device for detecting the bending angle of the vehicle body, A front distance detection device is attached to one side in the vehicle width direction at the front of the vehicle body and detects the front distance, which is the distance between an object located on that side of the vehicle body and the front of the vehicle body. A rear distance detection device is attached to one side of the rear of the vehicle body and detects the rear distance, which is the distance between the object and the rear of the vehicle body. It has, The aforementioned controller, The difference between the front distance detected by the front distance detection device and the rear distance detected by the rear distance detection device is calculated. Based on the calculated difference and the bending angle detected by the bending angle detection device, it is determined whether the vehicle body is approaching the object or moving away from the object. Based on the determination result, a steering signal is output to the steering device to steer the vehicle body so that it travels alongside the object while maintaining a predetermined distance from the object. A work vehicle characterized by the following features.

2. In the work vehicle described in claim 1, The aforementioned controller, If the calculated difference is a positive value, the steering signal is output to the steering device. Subsequently, if the difference becomes zero and it is determined that the front distance and the rear distance are equal, a return signal is output to the steering device to steer in the opposite direction to the steering signal until the bending angle detected by the bending angle detection device reaches zero. A work vehicle characterized by the following features.

3. In the work vehicle described in claim 2, Based on the front distance detected by the front distance detection device and the rear distance detected by the rear distance detection device, the relative angle between the vehicle body and the object is calculated. Based on the calculated relative angle, the upper limit of the steering angle of the vehicle body is calculated. Based on the determination result, the steering signal is output to the steering device such that the bending angle reaches the upper limit at a predetermined angular velocity. If it is determined that the front distance and the rear distance are equal, the steering device outputs a return signal so that the bending angle reaches zero at a predetermined angular velocity. A work vehicle characterized by the following features.

4. In the work vehicle described in claim 1, The aforementioned controller, If the calculated difference is zero and it is determined that the front distance and the rear distance are equal, then it is determined whether the bending angle detected by the bending angle detection device is zero. If it is determined that the bending angle is not zero, a signal is output to steer the vehicle in the opposite direction to the bending direction of the vehicle body. A work vehicle characterized by the following features.

5. In the work vehicle described in claim 1, The device further includes a posture detection device for detecting the posture of the work device, The aforementioned controller, The posture detection device determines whether the posture of the work device detected is the transport posture, which is the posture when transporting the load to the loading destination. When the posture of the work device is the transport posture, the steering signal is output to the steering device based on the determination result. A work vehicle characterized by the following features.

6. In the work vehicle described in claim 1, The controller further includes a selection device for selecting whether or not to perform automatic steering control, which involves outputting the steering signal to the steering device, based on the determination result. The aforementioned controller, When a selection signal indicating that the automatic steering control should be performed is output from the selection device, the automatic steering control should be performed. A work vehicle characterized by the following features.

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