Work vehicle

Abstract

The present invention can reduce erroneous detection of obstacles and use an obstacle detection and avoidance system if necessary when a work vehicle is climbing a slope.　In a wheel loader 1 equipped with an obstacle detection and avoidance system, a control device 5 determines whether a vehicle body inclination angle α is greater than or equal to a slope determination threshold αth1 with which the state of the vehicle body being on a slope is determined. If determined that the vehicle body inclination angle α is greater than or equal to the slope determination threshold αth1, the control device 5 determines whether the vehicle body location is included in a lower area Z of the slope. If determined that the vehicle body location is included in the lower area Z, the control device 5 disables processing by an obstacle avoidance processing device 4. If determined that the vehicle body location is not included in the lower area Z, the control device 5 enables processing by the obstacle avoidance processing device 4.

Description

Work vehicle

[0001] The present invention relates to a work vehicle equipped with an obstacle detection and avoidance system for detecting obstacles around the vehicle body and avoiding contact.

[0002] In work vehicles such as wheel loaders, in particular, the rear of the vehicle body is difficult for the operator in the cab to visually recognize. Therefore, by using an obstacle detection and avoidance system to monitor the situation behind the vehicle body, it becomes possible to avoid contact with obstacles existing behind the vehicle body during operations such as excavation and loading and during driving.

[0003] However, when applying an obstacle detection and avoidance system to a wheel loader, during a scooping operation (while driving, scooping up earth and sand with a bucket, climbing a slope with the bucket filled and discharging the earth and sand in the bucket to the upper part of the natural ground or to the other side of the natural ground), which is a specific operation of the wheel loader, the vehicle body may tilt, so there is a risk that the obstacle sensor may misdetect the rear ground as an obstacle.

[0004] For example, Patent Document 1 discloses a technique in which when the gradient (tilt angle) of the vehicle body exceeds a predetermined reference gradient, particularly when the gradient of the vehicle body exceeds the predetermined reference gradient and the arm angular velocity of the lift arm is a predetermined angular velocity or more, the notification process based on the detection result of the obstacle sensor is invalidated. [[ID=第十三]] [[ID=第十四]]

[0005] Japanese Patent No. 6757759

[0006] However, in the technique described in Patent Document 1, since the notification process based on the detection result of the obstacle sensor becomes invalid when the gradient of the vehicle body exceeds a predetermined reference gradient, for example, even when it is desired to use the obstacle detection and avoidance system while the wheel loader is climbing a slope, it cannot be used while being invalidated. Further, in the technique described in Patent Document 1, particularly when the gradient of the vehicle body exceeds a predetermined reference gradient and the arm angular velocity of the lift arm is a predetermined angular velocity or more, the notification process based on the detection result of the obstacle sensor becomes invalid. Therefore, for example, when the wheel loader is loading a load at the loading destination while climbing a slope without operating the lift arm, the obstacle sensor may misdetect the rear ground, and the operator will be notified of the misdetection.

[0007] Therefore, the object of the present invention is to provide a work vehicle that can reduce false detection of obstacles when climbing slopes, while also being able to utilize an obstacle detection and avoidance system when necessary.

[0008] To achieve the above objective, the present invention provides a work vehicle comprising: a vehicle body; a vehicle body tilt angle detection device for detecting the tilt angle of the vehicle body; an obstacle detection device for detecting obstacles located behind the vehicle body; an obstacle avoidance processing device that performs at least one of the following: a notification process for notifying the presence of an obstacle and a brake operation process for automatically activating a brake device when an obstacle is detected by the obstacle detection device; and a control device for controlling the obstacle avoidance processing device based on the detection result of the vehicle body tilt angle detection device, wherein the work vehicle comprises a vehicle body position detection device for detecting the position of the vehicle body on a slope, and the control device controls the vehicle body detected by the vehicle body tilt angle detection device The system is characterized by determining whether the inclination angle of the vehicle body is greater than or equal to a slope determination threshold for determining whether the vehicle body is present on the slope, and if it is determined that the inclination angle of the vehicle body is greater than or equal to the slope determination threshold, it is determined whether the position of the vehicle body detected by the vehicle body position detection device is included in the lower region of the slope, which is set within a predetermined distance on the slope starting from the starting point of the vehicle body's entry on the slope, and if it is determined that the position of the vehicle body is included in the lower region, the processing by the obstacle avoidance processing device is disabled, and if it is determined that the position of the vehicle body is not included in the lower region, the processing by the obstacle avoidance processing device is enabled.

[0009] According to the present invention, when climbing a slope, it is possible to reduce false detection of obstacles while utilizing the obstacle detection and avoidance system when necessary. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

[0010] This is an external side view showing an example configuration of a wheel loader according to each embodiment of the present invention. This is a diagram showing the wheel loader performing a hoisting operation. This is a functional block diagram showing the functions of the control device according to the first embodiment. This is a flowchart showing the processing flow executed by the control device according to the first embodiment. This is a diagram showing the movement of the wheel loader when performing a hoisting operation. This is a time chart showing the relationship between the timing of when the obstacle avoidance processing device is enabled and disabled and the status of each parameter in the first embodiment. This is a functional block diagram showing the functions of the control device according to the second embodiment. This is a flowchart showing the processing flow executed by the control device according to the second embodiment. This is a time chart showing the relationship between the timing of when the obstacle avoidance processing device is enabled and disabled and the status of each parameter in the second embodiment.

[0011] Hereinafter, as an example of a work vehicle according to each embodiment of the present invention, a wheel loader used for cargo handling operations will be described.

[0012] <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 Figure 1.

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

[0014] Wheel loader 1 is an articulated work vehicle that is steered by bending its body in the middle near its center. The front frame 1A, which is the front part of the vehicle body, and the rear frame 1B, which is the rear part of the vehicle body, are connected by a center joint 10 so as to be able to rotate in the left and right directions, and the front frame 1A bends in the left and right directions relative to the rear frame 1B. In the following description, the left direction relative to the forward direction of the vehicle body will be referred to as the "left direction," and the right direction relative to the forward direction will be referred to as the "right direction."

[0015] The vehicle body is equipped with four wheels 11. Two wheels 11 are positioned as front wheels 11A on both the left and right sides of the front frame 1A, and the remaining two wheels 11 are positioned as rear wheels 11B on both the left and right sides of the rear frame 1B. Note that in Figure 1, only the left front wheel 11A and rear wheel 11B are shown among the four wheels 11.

[0016] A work device 2 is attached to the front of the front frame 1A for excavating materials such as soil and minerals that make up the ground Y (see Figure 2), and for loading the excavated materials to a loading destination such as the top of the ground Y or a hopper.

[0017] The work device 2 is hydraulically driven and includes a lift arm 21 mounted on 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 mounted on 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 forms a link mechanism between the bucket 23 and the bucket cylinder 24. The two lift arm cylinders 22 are arranged side by side in the left-right direction of the vehicle body, but in Figure 1, only the lift arm cylinder 22 on the left side is shown with a dashed line.

[0018] The lift arm 21 rotates vertically relative to the front frame 1A as hydraulic fluid flows in and out of the two lift arm cylinders 22, causing each rod 22A to extend and retract.

[0019] The bucket 23 rotates vertically relative to the lift arm 21 as hydraulic fluid flows in and out of the bucket cylinder 24, causing the rod 24A to extend and retract. This allows the bucket 23 to scoop up and discharge (excavate and release) the work material, such as soil and minerals.

[0020] 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.

[0021] Wheel loader 1 is equipped with an obstacle detection and avoidance system that detects obstacles behind the vehicle and avoids contact. Note that "obstacles" include not only "objects" such as various devices and other work vehicles besides wheel loader 1 at the work site, but also "animals" such as workers (people) and small birds entering and leaving the work site.

[0022] The obstacle detection and avoidance system consists of an obstacle sensor 30, which acts as an obstacle detection device for detecting obstacles located behind the vehicle, and an obstacle avoidance processing device 4 (see Figure 3), which performs processing to avoid obstacles detected by the obstacle sensor 30.

[0023] The obstacle sensor 30 is, for example, a millimeter-wave radar, a laser beam (three-dimensional laser), or a camera, and is attached to the upper rear end of the counterweight 14.

[0024] The obstacle avoidance processing device 4 performs at least one of the following processes when an obstacle is detected by the obstacle sensor 30: a notification process that alerts the device to the presence of an obstacle, and a brake activation process that automatically activates the brakes. In other words, in the wheel loader 1, if an obstacle is present behind the vehicle, an alarm sounds or the automatic brakes are activated.

[0025] <About the lifting operation> Next, we will explain the "lifting operation," which is a specific operation of wheel loader 1, with reference to Figure 2.

[0026] Figure 2 shows the wheel loader 1 performing a shoveling operation.

[0027] Wheel loader 1 may perform the following operation: it moves forward from a flat area (ground) X towards a natural ground Y, scooping up soil and other materials with the bucket 23, and then climbs the natural ground Y, releasing the soil and other materials in the bucket 23 onto the upper part of the natural ground Y or to the other side of the natural ground Y. This operation is called "scooping up."

[0028] In this shoveling operation, as shown in Figure 2, the body of the wheel loader 1 is tilted. In this state, a flat surface X is located behind the vehicle, causing the obstacle sensor 30 to mistakenly detect the flat surface X as an obstacle. As a result, even though there is no actual obstacle behind the vehicle, the obstacle avoidance processing device 4 executes processing, unnecessarily sounding alarms or activating the automatic brakes, which reduces work efficiency.

[0029] Therefore, the wheel loader 1 is equipped with a control device that controls the obstacle avoidance device 4 according to the inclination angle (gradient) of the vehicle body. The control device will be described below for each embodiment.

[0030] <First Embodiment> The control device 5 according to the first embodiment of the present invention will be described with reference to Figures 3 to 6.

[0031] (Configuration of Control Device 5) First, the configuration of the control device 5 will be explained with reference to Figure 3.

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

[0033] The control device 5 is configured with a CPU, RAM, ROM, HDD, input interface, and output interface all connected to each other via a bus. Various sensors, such as the obstacle sensor 30, IMU 31, and vehicle speed sensor 32, are connected to the input interface, and the obstacle avoidance processing device 4 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, expands it onto RAM, and executes the expanded control program. The control program and hardware then work together to realize the functions of the control device 5.

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

[0036] Here, the IMU 31 is an inertial measurement unit that detects the vehicle body angular velocity and vehicle body acceleration, and outputs the detected vehicle body angular velocity and vehicle body acceleration of the wheel loader 1 to the control device 5.

[0037] Furthermore, the vehicle speed sensor 32 is a vehicle speed detection device that detects the vehicle's speed and outputs the detected vehicle speed to the control device 5. The vehicle speed sensor 32 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.

[0038] The control device 5 calculates the body tilt angle of the wheel loader 1 (the tilt angle α of the vehicle body relative to the flat ground X) based on the vehicle body angular velocity and vehicle body acceleration output from the IMU 31 and the travel speed of the wheel loader 1 output from the vehicle speed sensor 32. Therefore, the IMU 31 and the vehicle speed sensor 32 correspond to one embodiment of a vehicle body tilt angle detection device that detects the tilt angle of the vehicle body.

[0039] It should be noted that the vehicle body tilt angle detection device does not necessarily have to use the IMU 31 and the vehicle speed sensor 32; other devices, such as a tilt sensor that measures the tilt angle of the wheel loader 1 itself, may also be used.

[0040] Furthermore, in this embodiment, the control device 5 calculates the distance traveled by the wheel loader 1 on the slope (a slope of the natural ground Y) based on the travel speed of the wheel loader 1 detected by the vehicle speed sensor 32, and identifies the position of the wheel loader 1 on the slope. Therefore, the vehicle speed sensor 32 also corresponds to one form of a vehicle position detection device that detects the position of the vehicle on the slope.

[0041] Note that the vehicle speed sensor 32 does not necessarily have to be used in the vehicle body position detection device. For example, an obstacle sensor 30 or the like may be used instead. The case where the obstacle sensor 30 is used as one aspect of the vehicle body position detection device will be described in the second embodiment.

[0042] As shown in FIG. 3, the control device 5 includes a data acquisition unit 51, an inclination angle calculation unit 52, a slope entry determination unit 53, a moving distance calculation unit 54, a slope position determination unit 55, a storage unit 56, and a control command unit 57.

[0043] The data acquisition unit 51 acquires an obstacle detection signal detected by the obstacle sensor 30, the vehicle body angular velocity and vehicle body acceleration detected by the IMU 31, and the traveling speed of the vehicle body detected by the vehicle speed sensor 32.

[0044] The inclination angle calculation unit 52 calculates an inclination angle α of the vehicle body with respect to the flat ground X (hereinafter referred to as "vehicle body inclination angle α") based on the vehicle body angular velocity, vehicle body acceleration, and traveling speed of the vehicle body acquired by the data acquisition unit 51. In the present embodiment, the inclination angle calculation unit 52 also calculates a time change rate β of the vehicle body inclination angle α (hereinafter referred to as "inclination angle change rate β").

[0045] When an inclination sensor is used as the vehicle body inclination angle detection device, since the data acquisition unit 51 acquires the data itself related to the vehicle body inclination angle α from the inclination sensor, the inclination angle calculation unit 52 calculates only the inclination angle change rate β.

[0046] The slope entry determination unit 53 determines whether or not the vehicle body inclination angle α calculated by the inclination angle calculation unit 52 is equal to or greater than a slope determination threshold value αth1. This "slope determination threshold value αth1" is a threshold value (inclination angle threshold value) for determining the state where the vehicle body exists on a slope, and is set according to the inclination angle of the natural ground Y with respect to the flat ground X, for example, about 10°.

[0047] In this embodiment, the slope entry determination unit 53 also determines whether or not the rate of change in the inclination angle β immediately before the vehicle body inclination angle α reaches the slope determination threshold value αth1 is equal to or greater than the entry start determination threshold value βth. This "entry start determination threshold value βth" is a value (reference rate of change in the inclination angle) serving as a criterion for determining that the vehicle body has started to enter the slope, and is set, for example, to about 0.5° / sec.

[0048] Further, after the slope entry determination unit 53 determines that the vehicle body inclination angle α calculated by the inclination angle calculation unit 52 is equal to or greater than the slope determination threshold value αth1, it determines whether or not the vehicle body inclination angle α becomes equal to or less than the flat ground determination threshold value αth2. This "flat ground determination threshold value αth2" is a threshold value (inclination angle threshold value) for determining that the vehicle body has entered the flat ground X, that is, the vehicle body has returned from the slope of the natural terrain Y to the flat ground X, and is set according to the inclination angle of the natural terrain Y with respect to the flat ground X.

[0049] The moving distance calculation unit 54 calculates the moving distance L of the vehicle body on the slope based on the traveling speed of the vehicle body acquired by the data acquisition unit 51. This "moving distance L" corresponds to the moving distance of the vehicle body starting from the entry start point of the vehicle body onto the slope. Specifically, the moving distance calculation unit 54 calculates the moving distance L of the vehicle body by integrating the traveling speed of the vehicle body with respect to time (the time from the entry start point of the vehicle body onto the slope to the current location).

[0050] In this embodiment, the moving distance calculation unit 54 sets the time point when the slope entry determination unit 53 determines that the rate of change in the inclination angle β immediately before the vehicle body inclination angle α reaches the slope determination threshold value αth1 is equal to or greater than the entry start determination threshold value βth (β≧βth) as the entry start point of the vehicle body onto the slope, and calculates the moving distance L of the vehicle body.

[0051] In this way, by using the rate of change in the inclination angle β immediately before the vehicle body inclination angle α reaches the slope determination threshold value αth1 to determine the entry start point of the vehicle body onto the slope, compared with the case where the entry of the vehicle body onto the slope is determined only by the vehicle body inclination angle α reaching the slope determination threshold value αth1, the timing at which the vehicle body enters the slope can be accurately determined.

[0052] The slope position determination unit 55 determines whether the vehicle body inclination angle α, calculated by the travel distance calculation unit 54, is less than or equal to the travel distance threshold Lth, when the slope entry determination unit 53 determines that the vehicle body inclination angle α is greater than or equal to the slope determination threshold αth1 (α ≥ αth).

[0053] This "travel distance threshold Lth" is set appropriately according to the distance (detection range) that the obstacle sensor 30 can detect, such as 10m. Therefore, if the slope position determination unit 55 determines that the vehicle's travel distance L is less than or equal to the travel distance threshold Lth (L ≤ Lth), the obstacle sensor 30 will mistakenly detect the flat ground X as an obstacle. On the other hand, if the slope position determination unit 55 determines that the vehicle's travel distance L is longer than the travel distance threshold Lth (L > Lth), the obstacle sensor 30 will not mistakenly detect the flat ground X as an obstacle.

[0054] Here, in a slope of natural ground Y, the area where the obstacle sensor 30 mistakenly detects flat ground X as an obstacle is defined as the "lower region Z". In other words, determining whether the vehicle's travel distance L is less than or equal to the travel distance threshold Lth corresponds to determining whether the vehicle's position is included in the lower region Z of the slope.

[0055] This "lower region Z" refers to the area within a predetermined distance (less than or equal to the travel distance threshold Lth) on the slope, starting from the inclination point of the slope that is the inflection point from the flat ground X to the slope of the natural ground Y (the starting point of the vehicle's entry into the slope). For example, it is set to within 10m (shown by a dashed line in Figure 5). Furthermore, the "lower region Z" is an area where the obstacle sensor 30 may mistakenly detect the flat ground (ground) X, and is set based on the detection performance of the obstacle sensor 30.

[0056] The memory unit 56 is a memory that stores the aforementioned slope determination threshold αth1, flat ground determination threshold αth2, entry start determination threshold βth, and travel distance threshold Lth.

[0057] If the ramp position determination unit 55 determines that the vehicle's travel distance L is less than or equal to the travel distance threshold Lth (L ≤ Lth), that is, that the vehicle's position is included in the lower region Z of the ramp, the control command unit 57 outputs an invalidation command signal to the obstacle avoidance processing device 4 to invalidate the processing performed by the obstacle avoidance processing device 4. Therefore, when the wheel loader 1 is located in the lower region Z of the ramp, even if the obstacle sensor 30 detects an obstacle (flat ground X), no alarm will sound and the automatic brakes will not be activated.

[0058] On the other hand, if the ramp position determination unit 55 determines that the vehicle's travel distance L is longer than the travel distance threshold Lth (L > Lth), that is, that the vehicle's position is not included in the lower region Z of the ramp, the control command unit 57 outputs an effective command signal to the obstacle avoidance processing device 4 to enable processing by the obstacle avoidance processing device 4. Therefore, when the wheel loader 1 has left the lower region Z of the ramp and is located in the middle or upper region of the ramp, if the obstacle sensor 30 detects an obstacle, an alarm will sound or the automatic brakes will be activated.

[0059] <Processing performed by control device 5> Next, the flow of processing performed by control device 5 will be explained with reference to Figure 4.

[0060] Figure 4 is a flowchart showing the processing flow executed by the control device 5 according to the first embodiment.

[0061] In the control device 5, first, the tilt angle calculation unit 52 calculates the vehicle tilt angle α and the tilt angle change rate β based on the vehicle body angular velocity, vehicle body acceleration, and vehicle body travel speed acquired by the data acquisition unit 51 (step S501).

[0062] Next, the slope entry determination unit 53 determines whether the wheel loader 1 has entered the slope based on the vehicle body inclination angle α calculated in step S501 (step S502). Specifically, the slope entry determination unit 53 determines whether the vehicle body inclination angle α calculated in step S501 is greater than or equal to the slope determination threshold αth1.

[0063] If, in step S502, it is determined that the vehicle body inclination angle α is greater than or equal to the slope determination threshold αth1 (α≧αth), that is, that the wheel loader 1 has entered a slope (step S502 / YES), the travel distance calculation unit 54 calculates the travel distance L of the vehicle body on the slope based on the vehicle body's travel speed acquired by the data acquisition unit 51 (step S503).

[0064] On the other hand, if in step S502 the vehicle body tilt angle α is smaller than the slope determination threshold αth1 (α < αth1), that is, if it is determined that the wheel loader 1 has not entered the slope (step S502 / NO), the process returns to step S501 and is repeated.

[0065] In this embodiment, in step S502, the slope entry determination unit 53 also determines whether the rate of change of the inclination angle β immediately before the vehicle body inclination angle α becomes the slope determination threshold αth1 is equal to or greater than the entry start determination threshold βth.

[0066] Then, in step S503, the distance calculation unit 54 determines that the point in step S502 when the rate of change of the inclination angle β immediately before the vehicle body inclination angle α becomes the slope determination threshold αth1 is equal to or greater than the entry start determination threshold βth (β≧βth) is the point at which the vehicle body enters the slope, and calculates the distance the wheel loader 1 has traveled from the entry start point to the current point (= vehicle body travel distance L).

[0067] Next, the ramp position determination unit 55 determines whether the vehicle body's travel distance L calculated in step S503 is less than or equal to the travel distance threshold Lth, that is, whether the vehicle body's position is included in the lower region Z of the ramp (whether the wheel loader 1 is in the lower region Z of the ramp) (step S504).

[0068] If, in step S504, it is determined that the vehicle's travel distance L is less than or equal to the travel distance threshold Lth (L ≤ Lth), that is, that the vehicle's position is included in the lower region Z of the slope (step S504 / YES), the control command unit 57 outputs an invalid command signal to the obstacle avoidance processing device 4 (step S505).

[0069] On the other hand, if in step S504 it is determined that the vehicle's travel distance L is longer than the travel distance threshold Lth (L > Lth), that is, that the vehicle's position is not included in the lower region Z of the slope (step S504 / NO), the control command unit 57 outputs a valid command signal to the obstacle avoidance processing device 4 (step S506).

[0070] Then, after the processing in step S505 and after the processing in step S506, the inclination angle calculation unit 52 again calculates the vehicle inclination angle α based on the vehicle angular velocity, vehicle acceleration, and vehicle speed acquired by the data acquisition unit 51 (step S507).

[0071] Next, the slope entry determination unit 53 determines whether the vehicle body inclination angle α calculated in step S507 is less than or equal to the flat ground determination threshold αth2, that is, whether the vehicle body is located on the slope or not (whether it has left the slope or not) (step S508).

[0072] In step S508, if the vehicle body tilt angle α becomes less than or equal to the level ground determination threshold αth2 (α ≤ αth2), and it is determined that the vehicle body is not located on the slope (has left the slope) (step S508 / YES), the control command unit 57 outputs a valid command signal to the obstacle avoidance processing device 4 (step S509), and the processing in the control device 5 ends.

[0073] Regarding step S508, it is desirable that the slope entry determination unit 53 determines that the vehicle body is not on a slope when, after determining that the vehicle body inclination angle α is greater than or equal to the slope determination threshold αth1, it becomes less than or equal to the flat ground determination threshold αth2 (α≧αth1→α≦αth2) and a predetermined reference time T has elapsed.

[0074] This "reference time T" is set to approximately 1 to 2 minutes, which is sufficient time to exclude from the flat ground determination, for example, when a wheel loader 1 loads a load onto a loading area set up on a flat surface at the top of a hill Y, and then immediately reverses back onto the slope.

[0075] On the other hand, if in step S508 the vehicle body tilt angle α is greater than the level ground determination threshold αth2 (α > αth2), and it is determined that the vehicle body has not left the slope, i.e., the vehicle body is located on the slope (step S508 / NO), the process returns to step S503 and is repeated.

[0076] (Relationship between the movement of the wheel loader 1 and the control timing by the control device 5) Next, the relationship between the movement of the wheel loader 1 during the lifting operation and the obstacle avoidance processing device 4 will be explained by referring to Figures 5 and 6.

[0077] Figure 5 shows the movement of the wheel loader 1 when performing a shoveling operation. Figure 6 is a time chart showing the relationship between the timing at which the obstacle avoidance processing device 4 is enabled and disabled and the status of each parameter in the first embodiment.

[0078] When the wheel loader 1 performs the shoveling operation, it first moves forward toward the ground Y. When the wheel loader 1 is on flat ground X, the vehicle speed (vehicle travel speed), vehicle tilt angle α, and tilt angle change rate β all remain constant (state P1 shown in Figure 5). In this state P1, the obstacle sensor 30 does not mistakenly detect the flat ground X as an obstacle, so the processing by the obstacle avoidance processing device 4 is effective.

[0079] Next, when the wheel loader 1 enters the slope of the natural ground Y, both the vehicle body inclination angle α and the inclination angle change rate β change in the direction of increasing values ​​(state P2 shown in Figure 5). At this time, the control device 5 determines the timing when the inclination angle change rate β has increased as the starting point of entry into the slope and begins calculating the vehicle body's travel distance L.

[0080] Then, the control device 5 determines that the vehicle is on a slope if the vehicle body tilt angle α exceeds the slope determination threshold αth1 (α≧αth1), and disables the processing by the obstacle avoidance processing device 4. In this state P2, the vehicle body's travel distance L is less than or equal to the travel distance threshold Lth (L≦Lth), and the wheel loader 1 is in the lower area Z of the slope. As a result, the obstacle sensor 30 mistakenly detects the flat ground X as an obstacle, and the processing by the obstacle avoidance processing device 4 is disabled.

[0081] Next, as the wheel loader 1 moves down the slope, the rate of change β of the slope angle returns to its original value, and the vehicle body slope angle α remains constant (states P3 and P4 shown in Figure 5). When the vehicle body's travel distance L exceeds the travel distance threshold Lth (L > Lth), the control device 5 determines that the vehicle body has moved away from the lower area Z of the slope and enables the processing by the obstacle avoidance processing device 4.

[0082] When the wheel loader 1 is in state P4, it discharges the soil in the bucket 23 onto the upper part of the ground Y or beyond the ground Y, and then reverses toward the flat ground X. As the wheel loader 1 reverses down the slope (state P5 as shown in Figure 5), and the distance traveled by the vehicle body L becomes less than or equal to the travel distance threshold Lth (L ≤ Lth), the vehicle body's position becomes the lower region Z of the slope, causing the obstacle sensor 30 to mistakenly detect the flat ground X as an obstacle, thus rendering the processing by the obstacle avoidance processing device 4 ineffective.

[0083] Next, as the wheel loader 1 begins to move off the slope, both the vehicle body tilt angle α and the tilt angle change rate β change in the direction of decreasing values ​​(state P6 shown in Figure 5). Then, when the vehicle body tilt angle α becomes less than or equal to the level ground determination threshold αth2 (α ≤ αth2), the control device 5 determines that the vehicle body has moved off the slope and returned to level ground X (state P7 shown in Figure 5), and activates the processing by the obstacle avoidance processing device 4.

[0084] Thus, when the vehicle is in the lower area Z of the slope, the obstacle sensor 30 may mistakenly detect the flat ground X as an obstacle. Therefore, the control device 5 can reduce the false detection of obstacles by the obstacle sensor 30 by disabling the processing by the obstacle avoidance processing device 4.

[0085] On the other hand, when the vehicle body is not in the lower region Z of the slope, that is, when it is in the middle or upper region of the slope, the obstacle sensor 30 will not mistakenly detect the flat ground X as an obstacle. Therefore, the control device 5 enables processing by the obstacle avoidance processing device 4, thereby preventing contact between the wheel loader 1 and obstacles even when climbing a slope.

[0086] As a result, the wheel loader 1 can reduce false detection of obstacles when climbing slopes, and can utilize the obstacle detection and avoidance system when necessary.

[0087] <Second Embodiment> Next, a control device 5A according to the second embodiment of the present invention will be described with reference to Figures 7 to 9. In Figures 7 to 9, components that are common to those described in the first embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0088] Figure 7 is a functional block diagram showing the functions of the control device 5A according to the second embodiment. Figure 8 is a flowchart showing the processing flow executed by the control device 5A according to the second embodiment. Figure 9 is a time chart showing the relationship between the timing at which the obstacle avoidance processing device 4 is enabled and disabled and the status of each parameter in the second embodiment.

[0089] In the control device 5A according to this embodiment, the position of the vehicle on the slope is determined using the obstacle distance LO, which is the distance from the vehicle body to the obstacle detected by the obstacle sensor 30 (including the case of a flat surface X).

[0090] Therefore, in this embodiment, the obstacle sensor 30 also functions as a vehicle position detection device, and not only detects obstacles located behind the vehicle, but also measures the distance from the vehicle to the obstacle (obstacle distance LO).

[0091] As shown in Figure 7, the control device 5A includes a data acquisition unit 51A, an inclination angle calculation unit 52, a slope entry determination unit 53A, a slope position determination unit 55A, a storage unit 56A, a control command unit 57, and a change rate calculation unit 58.

[0092] The data acquisition unit 51A acquires the vehicle angular velocity and acceleration detected by the IMU 31, the vehicle speed detected by the vehicle speed sensor 32, the obstacle distance LO detected by the obstacle sensor 30, and the switching signal (forward or reverse signal) output from the forward / reverse selector switch 33.

[0093] The forward / reverse selector switch 33 is an embodiment of a forward / reverse selector device that switches the vehicle's forward and reverse movement, and is installed in the driver's cab 12. The forward / reverse selector switch 33 has a forward position, a neutral position (stop position), and a reverse position, and outputs a switching signal to the control device 5A corresponding to the position operated by the operator.

[0094] The rate of change calculation unit 58 calculates the rate of change of time γ of the obstacle distance LO acquired by the data acquisition unit 51A (hereinafter referred to as "obstacle rate of change γ"). This obstacle rate of change γ plays a similar role to the rate of change of inclination angle β in the first embodiment and is used to identify the starting point of the wheel loader 1 entering the slope.

[0095] Therefore, in this embodiment, unlike the inclination angle calculation unit 52 in the first embodiment, the inclination angle calculation unit 52A calculates only the vehicle body inclination angle α. Note that if the data acquisition unit 51A acquires data on the vehicle body inclination angle α using an inclination angle sensor or the like, the inclination angle calculation unit 52A becomes unnecessary.

[0096] The slope entry determination unit 53A performs determinations regarding the vehicle body inclination angle α (comparison of vehicle body inclination angle α with slope determination threshold αth1 and comparison of vehicle body inclination angle α with flat ground determination threshold αth2), as well as determinations regarding the obstacle change rate γ.

[0097] First, the slope entry determination unit 53A determines whether the wheel loader 1 is moving forward or backward based on the switching signal (forward or reverse signal) acquired by the data acquisition unit 51. Next, if the slope entry determination unit 53A determines that the wheel loader 1 is moving forward, it determines whether the obstacle change rate γ calculated by the change rate calculation unit 58 is equal to or greater than the entry start determination threshold γth.

[0098] This "entry start determination threshold γth" corresponds to the entry start determination threshold βth in the first embodiment and is a value (reference distance change rate) that serves as a criterion for determining when the vehicle body has started to enter the slope, and is set according to the slope angle of the ground Y (slope) relative to the flat ground X. The slope entry determination unit 53A determines that the point at which the obstacle change rate γ becomes equal to or greater than the entry start determination threshold γth (γ≧γth) is the point at which the vehicle body begins to enter the slope.

[0099] The slope position determination unit 55A determines whether the obstacle distance LO acquired by the data acquisition unit 51 after the vehicle's entry point into the slope is less than or equal to the obstacle distance threshold LOth, when the slope entry determination unit 53 determines that the vehicle's inclination angle α is greater than or equal to the slope determination threshold αth1 (α≧αth).

[0100] This "obstacle distance threshold Lth" corresponds to the travel distance threshold Lth in the first embodiment and is set appropriately according to the distance (detection range) that the obstacle sensor 30 can detect.

[0101] Therefore, when the slope position determination unit 55A determines that the obstacle distance LO is less than or equal to the obstacle distance threshold LOth (LO ≤ LOth), the vehicle's position is included in the lower region Z of the slope. On the other hand, when the slope position determination unit 55A determines that the obstacle distance LO is longer than the obstacle distance threshold LOth (LO > LOth), the vehicle's position is not included in the lower region Z of the slope, that is, it is included in the middle or upper region of the slope.

[0102] The memory unit 56A stores the slope determination threshold αth1, the flat ground determination threshold αth2, the entry start determination threshold γth, and the obstacle distance threshold LOth, respectively.

[0103] As shown in Figure 8, in the control device 5A according to this embodiment, first, the rate of change calculation unit 58 calculates the obstacle change rate γ, which is the rate of change of time of the obstacle distance LO acquired by the data acquisition unit 51 (step S511).

[0104] Next, the slope entry determination unit 53A determines whether the wheel loader 1 has started to enter the slope (step S512). Specifically, in step S512, the slope entry determination unit 53A determines whether the wheel loader 1 is moving forward and whether the obstacle change rate γ calculated in step S511 is equal to or greater than the entry start determination threshold γth.

[0105] If it is determined in step S512 that the wheel loader 1 has started to enter the slope, that is, if the wheel loader 1 is moving forward and the rate of change of the obstacle γ has become greater than or equal to the threshold γth for determining when to enter the slope (γ≧γth) (step S512 / YES), the data acquisition unit 51 acquires the obstacle distance LO measured by the obstacle sensor 30 at that time (step S513).

[0106] On the other hand, if it is not determined in step S512 that the wheel loader 1 has started to enter the slope (step S512 / NO), the process returns to step S511 and is repeated.

[0107] Next, the slope position determination unit 55A determines whether the wheel loader 1 is in the lower area Z of the slope (step S514). Specifically, in step S514, the slope position determination unit 55A determines whether the obstacle distance LO obtained in step S513 is less than or equal to the obstacle distance threshold LOth.

[0108] At this time, the slope entry determination unit 53 has confirmed that the vehicle body inclination angle α is greater than or equal to the slope determination threshold αth1 (α≧αth), meaning that the wheel loader 1 is on a slope.

[0109] In step S514, if it is determined that the obstacle distance LO is less than or equal to the obstacle distance threshold LOth (LO ≤ LOth) and the wheel loader 1 is in the lower region Z of the ramp (step S514 / YES), the control command unit 57 outputs an invalid command signal to the obstacle avoidance processing device 4 (step S515).

[0110] On the other hand, in step S514, if it is determined that the obstacle distance LO is longer than the obstacle distance threshold LOth (LO > LOth) and the wheel loader 1 is not in the lower area Z of the ramp (step S514 / NO), the control command unit 57 outputs a valid command signal to the obstacle avoidance processing device 4 (step S516).

[0111] Then, after the processing in step S515 and after the processing in step S516, the process proceeds to steps S507, S508, and S509, similar to the first embodiment.

[0112] As shown in Figure 9, in this embodiment, when the wheel loader 1 moves forward and enters a slope on the ground Y, the vehicle body tilt angle α changes in the direction of increasing value, and the obstacle change rate γ changes in the direction of decreasing value (state P2 shown in Figure 5). This is because the vehicle body tilts and the vehicle body tilt angle α increases, while on the other hand, the distance from the vehicle body to the flat ground X decreases rapidly due to the tilting of the vehicle body, and the obstacle distance LO measured by the obstacle sensor 30 suddenly decreases.

[0113] The control device 5A determines the point at which the obstacle change rate γ decreases as the starting point for entering the slope, and acquires the obstacle distance LO measured by the obstacle sensor 30 at this time. Then, the control device 5A uses the obstacle distance LO acquired after the vehicle's entry point onto the slope to determine which area of ​​the slope the wheel loader 1 is in.

[0114] Thus, it is also possible to use the obstacle change rate γ to determine the timing of the vehicle's entry into the slope, and the obstacle distance LO to determine the vehicle's position on the slope. In this embodiment as well, the same functions and effects as in the first embodiment are achieved.

[0115] 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.

[0116] For example, in each of the above embodiments, a wheel loader 1 was used as an example of a work vehicle, but the present invention is not limited to this, and can also be applied to other work vehicles that perform work while climbing a slope.

[0117] 1: Wheel loader (work vehicle) 1A: Front frame (vehicle body) 1B: Rear frame (vehicle body) 4: Obstacle avoidance processing device 5: Control device 30: Obstacle sensor (obstacle detection sensor, vehicle body position detection device) 31: IMU (vehicle body tilt angle detection device) 32: Vehicle speed sensor (vehicle body tilt angle detection device, vehicle body position detection device) 33: Forward / reverse switch (forward / reverse switch) α: Vehicle body tilt angle αth1: Slope judgment threshold αth2: Flat ground judgment threshold β: Rate of change of tilt angle βth: Entry start judgment threshold (reference tilt angle change rate) γth: Entry start judgment threshold (reference distance change rate) L: Distance traveled LO: Obstacle distance Lth: Distance traveled threshold LOth: Obstacle distance threshold T: Reference time Z: Lower area

Claims

1. A work vehicle comprising: a vehicle body; a vehicle body tilt angle detection device for detecting the tilt angle of the vehicle body; an obstacle detection device for detecting obstacles located behind the vehicle body; an obstacle avoidance processing device that, when an obstacle is detected by the obstacle detection device, performs at least one of the following: a notification process for notifying the presence of an obstacle and a brake operation process for automatically activating the brake device; and a control device for controlling the obstacle avoidance processing device based on the detection result of the vehicle body tilt angle detection device, wherein the work vehicle has a vehicle body position detection device for detecting the position of the vehicle body on a slope, and the control device determines whether the tilt angle of the vehicle body detected by the vehicle body tilt angle detection device is greater than or equal to a slope determination threshold for determining whether the vehicle body is on the slope, and if it is determined that the tilt angle of the vehicle body is greater than or equal to the slope determination threshold, it determines whether the position of the vehicle body detected by the vehicle body position detection device is included in the lower region of the slope, which is set within a predetermined distance on the slope starting from the starting point of the vehicle body's entry on the slope, A work vehicle characterized in that, if it is determined that the position of the vehicle body is included in the lower region, the processing by the obstacle avoidance processing device is disabled, and if it is determined that the position of the vehicle body is not included in the lower region, the processing by the obstacle avoidance processing device is enabled.

2. A work vehicle according to claim 1, wherein the control device, after disabling the processing by the obstacle avoidance processing device, determines that the vehicle body is not located on the slope and enables the processing by the obstacle avoidance processing device when the level of the vehicle body falls below a level ground determination threshold for determining that the vehicle body has entered a level ground.

3. A work vehicle according to claim 2, wherein the control device determines that the vehicle body is not located on a slope when the inclination angle of the vehicle body is determined to be greater than or equal to the slope determination threshold, and then becomes less than or equal to the flat ground determination threshold, and a predetermined reference time has elapsed.

4. A work vehicle according to claim 1, wherein the vehicle body position detection device is a vehicle speed detection device for detecting the travel speed of the vehicle body, and the control device calculates the distance the vehicle body travels on the slope based on the travel speed of the vehicle body detected by the vehicle speed detection device, determines that the position of the vehicle body is included in the lower region when the calculated distance is less than or equal to a travel distance threshold set according to the detection range of the obstacle detection device, and determines that the position of the vehicle body is not included in the lower region when the calculated distance is longer than the travel distance threshold.

5. A work vehicle according to claim 4, wherein the control device determines the point in time when the rate of change of the inclination angle of the vehicle body immediately before the inclination angle of the vehicle body becomes the slope determination threshold becomes equal to or greater than the reference inclination angle change rate which is the basis for determining the start of entry into the slope, as the point in time when the vehicle body starts to enter the slope, and calculates the distance traveled by the vehicle body from the entry start point as the travel distance based on the vehicle speed detected by the vehicle speed detection device.

6. A work vehicle according to claim 1, wherein the obstacle detection device also functions as the vehicle body position detection device and measures the obstacle distance, which is the distance from the vehicle body to the obstacle; the control device determines that the position of the vehicle body is included in the lower region when the obstacle distance measured by the obstacle detection device is less than or equal to an obstacle distance threshold set according to the detection range of the obstacle detection device; and determines that the position of the vehicle body is not included in the lower region when the obstacle distance measured by the obstacle detection device is longer than the obstacle distance threshold.

7. A work vehicle according to claim 6, comprising: a forward / reverse switching device for switching the forward / reverse movement of the vehicle body; and a vehicle speed detection device for detecting the vehicle body's travel speed, wherein the control device determines whether the vehicle body is moving forward based on the forward or reverse signal output from the forward / reverse switching device and the vehicle body's travel speed detected by the vehicle speed detection device; determines the point at which the vehicle body is moving forward and the rate of change of the obstacle distance measured by the obstacle detection device becomes equal to or greater than a reference distance change rate which is a criterion for determining the start of entry into the slope, is the starting point for the vehicle body's entry into the slope; compares and determines the obstacle distance measured by the obstacle detection device with the obstacle distance threshold starting from the starting point for the vehicle body's entry; and enables or disables the processing by the obstacle avoidance processing device.

Images