Work machine and method for controlling a work machine

Abstract

To provide a working machine capable of easily and properly adjusting the pitch angle of a blade depending on the task.SOLUTION: A controller acquires current terrain data representing a current terrain as a work target. The controller acquires target terrain data representing a target terrain. The controller controls a lift actuator so that the edge of a blade moves according to the target terrain. The controller controls a pitch actuator so that the pitch angle of a blade is changed based on the positional relationship in any two vertical directions of the current terrain corresponding to the current position of the cutting edge, the target terrain corresponding to the current position of the cutting edge, and the current position of the cutting edge.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a work machine and a method for controlling a work machine. [Background technology]

[0002] Some work machines are capable of adjusting the pitch angle of the blade in response to the operation of an operator. For example, the work machine of Patent Document 1 is provided with an operating lever for adjusting the pitch angle of the blade. The operating lever is provided with a switch. When the operating lever is tilted to the right with the switch on, the hydraulic cylinder is controlled so that the blade pitch dumps (tilts forward). When the operating lever is tilted to the left with the switch on, the hydraulic cylinder is controlled so that the blade pitches back (tilts backward). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-252859 Summary of the Invention [Problem to be solved by the invention]

[0004] The pitch angle of the blade affects the workability of excavation or ground leveling. However, the appropriate pitch angle of the blade varies depending on the work content. For example, when the pitch angle is small, i.e., when the blade is tilted backward, the excavation resistance is small and the excavation performance is good, but the soil spills backward and the ground leveling performance is low. Conversely, when the pitch angle is large, i.e., when the blade is tilted forward, the downward penetration force of the blade is large and the ground leveling performance is good, but the excavation resistance is large and the excavation performance is low.

[0005] Therefore, even for a skilled operator, it is not easy to manually and accurately select an appropriate pitch angle depending on the task. An object of the present disclosure is to make it possible to easily and appropriately adjust the blade pitch angle depending on the task in a work machine. [Means for solving the problem]

[0006] A work machine according to one aspect of the present invention includes a vehicle body, a lift frame, a blade, a lift actuator, a pitch actuator, a sensor, and a controller. The lift frame is supported on the vehicle body so as to be rotatable about a lift axis. The blade is supported on the lift frame so as to be rotatable about a pitch axis. The lift actuator lifts the blade up and down about the lift axis. The pitch actuator pitches the blade about the pitch axis. The sensor detects the current position of the cutting edge of the blade.

[0007] The controller acquires current terrain data indicating the current terrain that is the work target. The controller acquires target terrain data indicating the target terrain. The controller controls the lift actuator so that the cutting edge of the blade moves according to the target terrain. The controller controls the pitch actuator so that the pitch angle of the blade is changed based on the positional relationship in the up-down direction between any two of the current terrain corresponding to the current cutting edge position, the target terrain corresponding to the current cutting edge position, and the current cutting edge position.

[0008] A method according to another aspect of the present invention is a method for controlling a work machine. The work machine includes a vehicle body, a lift frame, a blade, a lift actuator, and a pitch actuator. The lift frame is supported on the vehicle body so as to be rotatable about a lift axis. The blade is supported on the lift frame so as to be rotatable about a pitch axis. The lift actuator lifts the blade up and down about the lift axis. The pitch actuator pitches the blade about the pitch axis.

[0009] The method of this embodiment comprises detecting the current cutting edge position of the blade, acquiring current terrain data indicating the current terrain to be worked on, acquiring target terrain data indicating the target terrain, controlling a lift actuator so that the cutting edge of the blade moves in accordance with the target terrain, and controlling a pitch actuator so that the pitch angle of the blade is changed based on the vertical positional relationship between any two of the current terrain corresponding to the current cutting edge position, the target terrain corresponding to the current cutting edge position, and the current cutting edge position. Effect of the Invention

[0010] According to the present invention, the blade pitch angle is changed based on the vertical positional relationship between any two of the current terrain corresponding to the current cutting edge position, the target terrain corresponding to the current cutting edge position, and the current cutting edge position. The vertical positional relationship between any two of the current terrain, the target terrain, and the current cutting edge position differs depending on the work performed by the work machine. Therefore, according to the present invention, the blade pitch angle can be easily and appropriately adjusted in the work machine depending on the work. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a side view showing a work machine according to an embodiment. [Diagram 2] 2 is a block diagram showing the configuration of a drive system and a control system of the work machine. FIG. [Diagram 3] FIG. 13 is a diagram showing a lifting operation of the blade. [Figure 4] FIG. 4 illustrates the pitch movement of the blade. [Diagram 5] 3 is a flowchart showing automatic control of the work machine according to the first embodiment. [Figure 6] FIG. 2 is a diagram showing an example of a current terrain and a target terrain. [Figure 7] FIG. 4 is a diagram showing an example of pitch angle data. [Figure 8] 11A-11C are diagrams illustrating the operation of the blade when the target terrain is located within a predetermined range. [Figure 9] 11A and 11B are diagrams illustrating the operation of the blade when the target terrain is located below a predetermined range. [Figure 10] 11A and 11B are diagrams illustrating the operation of the blade when the target terrain is located above a predetermined range. [Figure 11] 7 is a flowchart showing automatic control of a work machine according to a second embodiment. [Figure 12] 10 is a flowchart showing automatic control of a work machine according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, a work machine according to an embodiment will be described with reference to the drawings. Fig. 1 is a side view showing a work machine 1 according to an embodiment. The work machine 1 according to this embodiment is a bulldozer. The work machine 1 includes a vehicle body 11 and a work implement 12.

[0013] The vehicle body 11 includes a cab 13, an engine compartment 14, and a traveling device 15. A driver's seat (not shown) is disposed in the cab 13. The engine compartment 14 is disposed in front of the cab 13. The traveling device 15 is provided on the lower part of the vehicle body 11. The traveling device 15 includes a pair of left and right tracks 16. Note that only the left track 16 is shown in FIG. 1. The work machine 1 travels as the tracks 16 rotate.

[0014] The work machine 12 is attached to the vehicle body 11. The work machine 12 has a lift frame 17, a blade 18, a lift actuator 19, and a pitch actuator 20. The lift frame 17 is supported on the vehicle body 11 so as to be rotatable about a lift axis X1. The lift axis X1 extends in the lateral direction of the vehicle body 11. The lift frame 17 rotates about the lift axis X1 to perform a lift operation up and down. The lift frame 17 may be attached to the traveling device 15. The lift frame 17 may be disposed inside the traveling device 15, or outside the traveling device 15.

[0015] The blade 18 is disposed in front of the vehicle body 11. The blade 18 is supported to be rotatable about a pitch axis X2 relative to the lift frame 17. The pitch axis X2 extends in the lateral direction of the vehicle body 11. The blade 18 pitches back and forth by rotating about the pitch axis X2. The blade 18 moves up and down in association with the up and down movement of the lift frame 17.

[0016] The lift actuator 19 is connected to the vehicle body 11 and the lift frame 17. The lift actuator 19 is a hydraulic cylinder. When the lift actuator 19 expands and contracts, the lift frame 17 is lifted up and down. When the lift actuator 19 contracts, the blade 18 rises. When the lift actuator 19 expands, the blade 18 descends. The lift actuator 19 may be attached to the blade 18.

[0017] The pitch actuator 20 is connected to the lift frame 17 and the blade 18. The pitch actuator 20 is a hydraulic cylinder. The pitch actuator 20 extends and retracts, causing the blade 18 to pitch forward and backward. The blade 18 pitches about the pitch axis X2, causing a part of the blade 18, for example the upper end, to move forward and backward. The blade 18 tilts forward when the pitch actuator 20 extends. The blade 18 tilts backward when the pitch actuator 20 contracts.

[0018] Fig. 2 is a block diagram showing the configuration of the drive system 2 and control system 3 of the work machine 1. As shown in Fig. 2, the drive system 2 includes an engine 22, a hydraulic pump 23, and a power transmission device 24. The hydraulic pump 23 is driven by the engine 22 and discharges hydraulic oil. The hydraulic oil discharged from the hydraulic pump 23 is supplied to the lift actuator 19 and the pitch actuator 20. Note that, although one hydraulic pump is shown in Fig. 2, multiple hydraulic pumps may be provided.

[0019] The power transmission device 24 transmits the driving force of the engine 22 to the traveling device 15. The power transmission device 24 may be, for example, a hydrostatic transmission (HST). Alternatively, the power transmission device 24 may be, for example, a torque converter or a transmission having a plurality of speed change gears.

[0020] The control system 3 includes a controller 26 and a control valve 27. The controller 26 is programmed to control the work machine 1 based on the acquired data. The controller 26 includes a memory device 28 and a processor 29. The processor 29 includes, for example, a CPU. The memory device 28 includes, for example, a memory and an auxiliary memory device. The memory device 28 may be, for example, a RAM or a ROM. The memory device 28 may be, for example, a semiconductor memory or a hard disk. The memory device 28 is an example of a non-transitory computer-readable recording medium. The memory device 28 stores computer instructions that are executable by the processor 29 and for controlling the work machine 1.

[0021] The control valve 27 is a proportional control valve, and is controlled by a command signal from the controller 26. The control valve 27 is disposed between the hydraulic actuators, such as the lift actuator 19 and the pitch actuator 20, and the hydraulic pump 23. The control valve 27 controls the flow rate of hydraulic oil supplied from the hydraulic pump 23 to the lift actuator 19. The control valve 27 controls the flow rate of hydraulic oil supplied from the hydraulic pump 23 to the pitch actuator 20. The control valve 27 may be a pressure proportional control valve. Alternatively, the control valve 27 may be an electromagnetic proportional control valve.

[0022] The control system 3 includes an operation device 31 and an input device 32. The operation device 31 includes, for example, a lever. Alternatively, the operation device 31 may include a pedal or a switch. An operator can manually operate the traveling of the work machine 1 and the operation of the work implement 12 using the operation device 31. The operation device 31 outputs an operation signal that indicates the operation of the operation device 31. The controller 26 receives the operation signal from the operation device 31.

[0023] The operating device 31 is capable of operating the lift operation of the blade 18. In particular, the operating device 31 is capable of operating the raising and lowering operations of the blade 18. When the operator performs a raising operation on the operating device 31, the controller 26 controls the lift actuator 19 so that the blade 18 rises. When the operator performs a lowering operation on the operating device 31, the controller 26 controls the lift actuator 19 so that the blade 18 descends.

[0024] Fig. 3 is a schematic diagram showing the lifting operation of the work machine 1. In Fig. 3, P0 indicates the current position of the cutting edge of the blade 18. P1 indicates the highest position of the cutting edge of the blade 18. P2 indicates the lowest position of the cutting edge of the blade 18. The work machine 1 can perform a lifting operation of the blade 18 between the highest position P1 and the lowest position P2.

[0025] The operating device 31 is capable of controlling the pitch movement of the blade 18. In particular, the operating device 31 is capable of tilting the blade 18 forward and backward. When the operator tilts the operating device 31 forward, the controller 26 controls the pitch actuator 20 so that the blade 18 tilts forward. When the operator tilts the operating device 31 backward, the controller 26 controls the pitch actuator 20 so that the blade 18 tilts backward.

[0026] 4A to 4C are diagrams showing the pitch angle of the blade 18. As shown in FIG. 4A to FIG. 4C, the pitch angle θ0-θ2 of the blade 18 is the angle between the cutting edge of the blade 18 and the ground contact surface G1 of the crawler belt 16. FIG. 4B shows the pitch angle θ0 of the blade 18 in a standard state (hereinafter referred to as the "standard pitch angle"). FIG. 4A shows the pitch angle θ1 of the blade 18 tilted further forward than the standard state. FIG. 4C shows the pitch angle θ2 of the blade 18 tilted further backward than the standard state. The more the blade 18 tilts forward, the larger the pitch angle. The more the blade 18 tilts backward, the smaller the pitch angle. That is, θ1>θ0>θ2.

[0027] The operating device 31 may be a hydraulic pilot type device. For example, the operating device 31 may output pilot oil pressure according to the operation of the operating device 31. The lift actuator 19 or the pitch actuator 20 may be controlled by controlling the control valve 27 by the pilot oil pressure from the operating device 31. The controller 26 may receive a signal indicating the pilot oil pressure as an operation signal.

[0028] The input device 32 includes, for example, a touch panel. However, the input device 32 may include other devices such as a switch. An operator can use the input device 32 to set a control mode for the pitch angle of the blades 18 by the controller 26. The control modes include a manual mode and an automatic control. In the manual mode, the operator can manually change the pitch angle of the blades 18 using the operation device 31. The automatic control of the pitch angle will be described in detail later.

[0029] As shown in FIG. 2, the control system 3 is equipped with a sensor 33 that detects the current position of the cutting edge of the blade 18 (hereinafter referred to as "cutting edge position P0"). The sensor 33 includes a vehicle body sensor 34, a frame sensor 35, a blade sensor 36, and a position sensor 37. The vehicle body sensor 34 is attached to the vehicle body 11. The vehicle body sensor 34 detects the attitude of the vehicle body 11. The frame sensor 35 is attached to the lift frame 17. The frame sensor 35 detects the attitude of the lift frame 17. The blade sensor 36 is attached to the blade 18. The blade sensor 36 detects the attitude of the blade 18. The position sensor 37 detects the current position of the vehicle body 11.

[0030] The vehicle body sensor 34, the frame sensor 35, and the blade sensor 36 are each an IMU (Inertial Measurement Unit). However, the frame sensor 35 and the blade sensor 36 are not limited to an IMU, and may be other sensors such as an angle sensor or a cylinder stroke sensor.

[0031] The vehicle body sensor 34 detects the front-to-rear angle of the vehicle body 11 with respect to the horizontal (vehicle body pitch angle). The frame sensor 35 detects the rotation angle of the lift frame 17. The blade sensor 36 detects the pitch angle of the blade 18. The vehicle body sensor 34, the frame sensor 35, and the blade sensor 36 each output a detection signal indicating the detected angle.

[0032] The position sensor 37 is, for example, a position sensor of a Global Navigation Satellite System (GNSS) such as a Global Positioning System (GPS). The position sensor 37 includes, for example, a GNSS receiver and an antenna. The position sensor 37 detects the current position of the position sensor 37. The position sensor 37 is arranged on the vehicle body 11. Therefore, the position sensor 37 detects the current position of the vehicle body 11. The current position of the vehicle body 11 is indicated in global coordinates based on the earth. However, the current position of the vehicle body 11 may also be indicated in local coordinates based on the work site where the work machine 1 performs work. The controller 26 acquires a detection signal indicating the current position of the vehicle body 11 from the position sensor 37.

[0033] The controller 26 receives detection signals from the vehicle body sensor 34, the frame sensor 35, the blade sensor 36, and the position sensor 37. The controller 26 stores machine dimension data indicating the dimensions and positional relationship between the vehicle body 11, the lift frame 17, and the blade 18. The controller 26 calculates the cutting edge position P0 of the blade 18 based on the angles detected by the vehicle body sensor 34, the frame sensor 35, and the blade sensor 36, the current position of the vehicle body 11 detected by the position sensor 37, and the machine dimension data.

[0034] The controller 26 automatically controls the work machine 1. Below, a description will be given of the automatic control of the work machine 1 according to the first embodiment, which is executed by the controller 26. Fig. 5 is a flowchart showing the process of automatic control according to the first embodiment.

[0035] 5, in step S101, the controller 26 acquires the current position of the work machine 1. Here, the controller 26 acquires the cutting edge position P0 of the blade 18 described above as the current position of the work machine 1.

[0036] In step S102, the controller 26 acquires current terrain data. The current terrain data indicates the current terrain 50 of the work target. Fig. 6 is a diagram showing an example of the current terrain 50. The current terrain data includes coordinates and altitudes of multiple points on the current terrain 50 located in the traveling direction of the work machine 1. The controller 26 may acquire the current terrain data from an external computer. The controller 26 may acquire updated current terrain data based on the trajectory of the bottom surface of the track 16.

[0037] In step S103, the controller 26 acquires target terrain data. The target terrain data indicates the target terrain 60 relative to the current terrain 50. The target terrain data includes coordinates and altitudes of multiple points on the target terrain 60 located in the traveling direction of the work machine 1. As shown in FIG. 6 , at least a portion of the target terrain 60 is displaced in the vertical direction relative to the current terrain 50. At least a portion of the target terrain 60 may match or approximately match the current terrain 50. At least a portion of the target terrain 60 may be located above the current terrain 50. At least a portion of the target terrain 60 may be located below the current terrain 50.

[0038] The controller 26 may determine the target terrain 60 based on the current terrain 50. For example, the controller 26 may determine the target terrain 60 by displacing the current terrain 50 upward or downward. The controller 26 may determine a trajectory extending at a predetermined angle from a predetermined start position of the work as the target terrain 60. The controller 26 may determine the target terrain 60 based on the capacity or load of the blade 18. The controller 26 may determine the target terrain 60 based on the volume of soil held by the blade 18. Alternatively, the controller 26 may obtain target terrain data from an external computer.

[0039] In step S104, the controller controls the work machine 12 in accordance with the target terrain 60. The controller 26 controls the lift actuator 19 so that the cutting edge of the blade 18 moves in accordance with the target terrain 60. As a result, the blade 18 is lifted up and down so that the cutting edge of the blade 18 moves along the target terrain 60 while the work machine 1 moves forward. Note that the work machine 1 may be moved forward manually by the operator operating the operation device 31. Alternatively, the work machine 1 may be moved forward by automatic control by the controller 26.

[0040] In the work machine 1 according to this embodiment, the controller 26 performs automatic control of the pitch angle while executing automatic control of the height of the blade 18 in accordance with the target terrain 60. In the automatic control of the pitch angle, the controller 26 controls the pitch actuator so that the pitch angle of the blade 18 is changed based on the vertical positional relationship between the current terrain 50 and the target terrain 60. Steps S105 to S107 described below show the process of automatic control of the pitch angle.

[0041] In step S105, the controller 26 acquires the difference in height between the target terrain 60 and the current terrain 50. The controller 26 calculates the difference in height between the target terrain 60 and the current terrain 50 from the target terrain data and the current terrain data.

[0042] In step S106, the controller 26 determines a target pitch angle. In step S107, the controller 26 controls the pitch actuator 20 so that the pitch angle of the blade 18 becomes the target pitch angle.

[0043] In detail, the controller 26 determines the target pitch angle based on the difference in height between the target terrain 60 and the current terrain 50. The controller 26 stores pitch angle data. The pitch angle data defines the relationship between the difference in height between the target terrain 60 and the current terrain 50 and the target pitch angle. The pitch angle data is stored in the controller 26 in the form of, for example, a map. However, the pitch angle data is not limited to a map and may be stored in the controller 26 in another format, such as a mathematical formula.

[0044] The controller 26 determines the target pitch angle from the difference in height between the target terrain 60 and the current terrain 50 by referring to the pitch angle data. Fig. 7 is a diagram showing an example of pitch angle data. In Fig. 7, the solid line shows an example of pitch angle data in this embodiment. In Fig. 7, the two-dot chain line shows the change in pitch angle when automatic control of the pitch angle is not performed. That is, in Fig. 7, the two-dot chain line shows the change in pitch angle when the angle of the blade 18 relative to the lift frame 17 is fixed (hereinafter, referred to as the fixed pitch angle).

[0045] The height difference Hd1 is expressed by the following formula (1). Hd1 = Ht-Ha (1) Ht is the height of the target terrain 60. Ha is the height of the current terrain 50. Therefore, when the height difference Hd1 is greater than 0, it means that the target terrain 60 is located higher than the current terrain 50. When the height difference Hd1 is less than 0, it means that the target terrain 60 is located lower than the current terrain 50. When the height difference Hd1 is 0, it means that the target terrain 60 is at the same height as the current terrain 50.

[0046] In FIG. 7, θmax indicates the maximum pitch angle. In other words, the maximum pitch angle θmax is the limit value of the pitch angle in the forward tilt direction. θmin indicates the minimum pitch angle. In other words, the minimum pitch angle θmin is the limit value of the pitch angle in the backward tilt direction. The standard pitch angle θ0 is a value between the maximum pitch angle θmax and the minimum pitch angle θmin. When fixed, as shown by the two-dot chain line in FIG. 7, the target pitch angle is constant at the standard pitch angle θ0 regardless of the difference in height between the target terrain 60 and the current terrain 50.

[0047] In the pitch angle data, when the height difference is less than or equal to a1 and greater than or equal to -b1, the target pitch angle is the standard pitch angle θ0. Therefore, when the target terrain 60 is located within a predetermined range R0 in the vertical direction including the current terrain 50, the controller 26 sets the target pitch angle to the standard pitch angle θ0. The predetermined range R0 is the range between a position that is a distance a1 above the current terrain 50 and a position that is a distance b1 below the current terrain 50.

[0048] Therefore, as shown in Fig. 8, when the target terrain 60 is located within a predetermined range R0, the controller 26 moves the cutting edge of the blade 18 in accordance with the target terrain 60, causing the work machine 1 to perform ground leveling work. At this time, the controller 26 sets the blade 18 to the standard pitch angle θ0.

[0049] 7, in the pitch angle data, when the height difference is smaller than -b1, the target pitch angle is smaller than the standard pitch angle θ0. Therefore, when the target terrain 60 is located below the predetermined range R0, the controller 26 controls the pitch actuator 20 to tilt the pitch angle of the blade 18 rearward from the standard state.

[0050] Therefore, as shown in Fig. 9, when the target terrain 60 is located below within the predetermined range R0, the controller 26 moves the cutting edge of the blade 18 in accordance with the target terrain 60, causing the work machine 1 to perform excavation work. At this time, the controller 26 tilts the blade 18 rearward more than the standard pitch angle θ0. This reduces the excavation resistance, improving the excavation workability.

[0051] In addition, in the pitch angle data, when the height difference is smaller than -b1, the target pitch angle decreases in response to the decrease in the height difference. Therefore, when the target terrain 60 is located below the predetermined range R0, the controller 26 changes the pitch angle of the blade 18 in the rearward direction in response to an increase in the absolute value of the height difference. In addition, in the pitch angle data, when the height difference is smaller than -b2, the target pitch angle is constant at the minimum pitch angle θmin.

[0052] 7, in the pitch angle data, when the height difference is larger than a1, the target pitch angle is larger than the standard pitch angle θ0. Therefore, when the target terrain 60 is located above the predetermined range R0, the controller 26 controls the pitch actuator 20 so as to tilt the pitch angle of the blade 18 forward from the standard state.

[0053] Therefore, as shown in Fig. 10, when the target terrain 60 is located in the upper part within the predetermined range R0, the controller 26 moves the cutting edge of the blade 18 according to the target terrain 60, and the work machine 1 performs soil transport work. At this time, the controller 26 tilts the blade 18 forward more than the standard pitch angle θ0. This reduces soil spillage from the blade 18, improving workability in soil transport.

[0054] In addition, in the pitch angle data, when the height difference is greater than a1, the target pitch angle increases in response to the increase in the height difference. Therefore, when the target terrain 60 is located above the predetermined range R0, the controller 26 changes the pitch angle of the blade 18 in the forward tilt direction in response to the increase in the absolute value of the height difference. In addition, in the pitch angle data, when the height difference is greater than a2, the target pitch angle is constant at the maximum pitch angle θmax.

[0055] The processes of steps S105 to S106 may be executed after the start of the process of step S104. That is, the controller 26 may change the pitch angle of the blade 18 by automatic control while moving the blade 18 according to the target terrain 60. Alternatively, the processes of steps S105 to S106 may be executed before the start of the process of step S104. That is, the controller 26 may change the pitch angle of the blade 18 by automatic control before moving the blade 18 according to the target terrain 60.

[0056] In the work machine 1 according to this embodiment described above, the pitch angle of the blade 18 is changed based on the vertical positional relationship between the current terrain 50 and the target terrain 60. The vertical positional relationship between the current terrain 50 and the target terrain 60 differs depending on the work performed by the work machine 1. Therefore, in the work machine 1 according to this embodiment, the pitch angle of the blade 18 can be easily and appropriately adjusted depending on the work.

[0057] Next, the automatic control of the pitch angle according to the second embodiment will be described. In the automatic control of the pitch angle according to the second embodiment, the controller 26 controls the pitch actuator 20 so that the pitch angle of the blade 18 is changed based on the vertical positional relationship between the cutting edge position P0 and the current terrain 50. Fig. 11 is a flowchart showing the process of the automatic control according to the second embodiment. In Fig. 11, steps S201-S204 are the same as steps S101-S104 in the first embodiment described above.

[0058] In step S205, the controller 26 acquires the difference in height between the cutting edge position P0 and the current terrain 50. The controller 26 calculates the difference in height between the cutting edge position P0 and the current terrain 50 from the current terrain data and the height of the cutting edge position P0. The difference in height Hd2 is expressed by the following formula (2). Hd2=Hp-Ha (2) Hp is the height of the cutting edge position P0. Ha is the height of the current terrain 50. Therefore, when the height difference Hd2 is greater than 0, it means that the cutting edge position P0 is located above the current terrain 50. When the height difference Hd2 is less than 0, it means that the cutting edge position P0 is located below the current terrain 50. When the height difference Hd2 is 0, it means that the cutting edge position P0 is at the same height as the current terrain 50.

[0059] In step S206, the controller 26 determines a target pitch angle. The controller 26 determines the target pitch angle based on the difference in height between the cutting edge position P0 and the current topography 50. The controller 26 determines the target pitch angle by referring to pitch angle data, as in the first embodiment. In the second embodiment, the pitch angle data specifies the relationship between the difference in height between the cutting edge position P0 and the current topography 50 and the target pitch angle. The pitch angle data in the second embodiment is similar to the pitch angle data in the first embodiment described above, and therefore a detailed description thereof will be omitted.

[0060] In step S207, the controller 26 controls the pitch actuator 20 so that the pitch angle of the blade 18 becomes the target pitch angle. As in Fig. 8, when the cutting edge position P0 is located within a predetermined range R0 in the vertical direction including the current terrain 50, the controller 26 sets the target pitch angle to the standard pitch angle θ0. Therefore, when the cutting edge position P0 is located within the predetermined range R0, the controller 26 moves the cutting edge of the blade 18 in accordance with the target terrain 60, and the work machine 1 performs ground leveling work. At this time, the controller 26 sets the blade 18 to the standard pitch angle θ0.

[0061] 9, when the cutting edge position P0 is located below the predetermined range R0, the controller 26 controls the pitch actuator 20 to tilt the pitch angle of the blade 18 rearward from the standard state. Therefore, when the cutting edge position P0 is located below the predetermined range R0, the controller 26 moves the cutting edge of the blade 18 in accordance with the target topography 60, and the work machine 1 performs excavation work. At this time, the controller 26 tilts the blade 18 rearward more than the standard pitch angle θ0. Furthermore, when the cutting edge position P0 is located below the predetermined range R0, the controller 26 changes the pitch angle of the blade 18 in the rearward direction in accordance with an increase in the absolute value of the height difference.

[0062] 10, when the cutting edge position P0 is located above the predetermined range R0, the controller 26 controls the pitch actuator 20 to tilt the pitch angle of the blade 18 forward more than the standard state. Therefore, the controller 26 moves the cutting edge of the blade 18 in accordance with the target topography 60, and the work machine 1 performs soil moving work. At this time, the controller 26 tilts the blade 18 forward more than the standard pitch angle θ0. Furthermore, when the cutting edge position P0 is located above the predetermined range R0, the controller 26 changes the pitch angle of the blade 18 in the forward tilt direction in accordance with an increase in the absolute value of the height difference.

[0063] The processes in steps S205 to S206 are executed after the process in step S204 is started. That is, the controller 26 changes the pitch angle of the blade 18 by automatic control while moving the blade 18 according to the target topography 60.

[0064] In the automatic pitch angle control according to the second embodiment described above, the pitch angle of the blade 18 is changed based on the vertical positional relationship between the cutting edge position P0 and the current terrain 50. The vertical positional relationship between the cutting edge position P0 and the current terrain 50 differs depending on the work performed by the work machine 1. Therefore, in the work machine 1 according to this embodiment, the pitch angle of the blade 18 can be easily and appropriately adjusted depending on the work.

[0065] Next, automatic control of the pitch angle according to the third embodiment will be described. In the automatic control of the pitch angle according to the third embodiment, the controller 26 controls the pitch actuator 20 so that the pitch angle of the blade 18 is changed based on the vertical positional relationship between the target topography 60 and the blade tip position P0. Fig. 12 is a flowchart showing the process of automatic control according to the third embodiment. In Fig. 12, steps S301-S304 are the same as S101-S104 in the first embodiment described above.

[0066] In step S305, the controller 26 acquires the height difference between the target topography 60 and the cutting edge position P0. The controller 26 calculates the height difference between the target topography 60 and the cutting edge position P0 from the target topography data and the height of the cutting edge position P0. The height difference Hd3 is expressed by the following formula (3). Hd3 = Ht - Hp (3) Ht is the height of the target topography 60. Hp is the height of the cutting edge position P0. Therefore, when the height difference Hd3 is greater than 0, it means that the target topography 60 is located above the cutting edge position P0. When the height difference Hd3 is less than 0, it means that the target topography 60 is located below the cutting edge position P0. When the height difference Hd3 is 0, it means that the target topography 60 is at the same height as the cutting edge position P0.

[0067] In step S306, the controller 26 determines a target pitch angle. The controller 26 determines the target pitch angle based on the difference in height between the target topography 60 and the cutting edge position P0. As in the first embodiment, the controller 26 determines the target pitch angle by referring to the pitch angle data. In the third embodiment, the pitch angle data specifies the relationship between the difference in height between the target topography 60 and the cutting edge position P0 and the target pitch angle. The pitch angle data in the third embodiment is similar to the pitch angle data in the first embodiment described above, and therefore a detailed description thereof will be omitted.

[0068] In step S307, the controller 26 controls the pitch actuator 20 so that the pitch angle of the blade 18 becomes the target pitch angle. As in Fig. 8, when the target terrain 60 is located within a predetermined range R0 in the vertical direction including the blade tip position P0, the controller 26 sets the target pitch angle to the standard pitch angle θ0. Therefore, when the target terrain 60 is located within the predetermined range R0, the controller 26 moves the cutting edge of the blade 18 in accordance with the target terrain 60, causing the work machine 1 to perform ground leveling work. At this time, the controller 26 sets the blade 18 to the standard pitch angle θ0.

[0069] 9, when the target terrain 60 is located below the predetermined range R0, the controller 26 controls the pitch actuator 20 to tilt the pitch angle of the blade 18 rearward from the standard state. Therefore, when the target terrain 60 is located below within the predetermined range R0, the controller 26 moves the cutting edge of the blade 18 in accordance with the target terrain 60, and the work machine 1 performs excavation work. At this time, the controller 26 tilts the blade 18 rearward more than the standard pitch angle θ0. Furthermore, when the target terrain 60 is located below the predetermined range R0, the controller 26 changes the pitch angle of the blade 18 in the rearward direction in accordance with an increase in the absolute value of the height difference.

[0070] As in Fig. 10, when the target terrain 60 is located above the predetermined range R0, the controller 26 controls the pitch actuator 20 to tilt the pitch angle of the blade 18 forward from the standard state. Therefore, the controller 26 moves the cutting edge of the blade 18 in accordance with the target terrain 60, and the work machine 1 performs soil transportation work. At this time, the controller 26 tilts the blade 18 forward from the standard pitch angle θ0. Furthermore, when the target terrain 60 is located above the predetermined range, the controller 26 changes the pitch angle of the blade 18 in the forward tilt direction in response to an increase in the absolute value of the height difference.

[0071] The processes in steps S305 to S306 are executed after the process in step S304 is started. That is, the controller 26 changes the pitch angle of the blade 18 by automatic control while moving the blade 18 according to the target topography 60.

[0072] In the automatic pitch angle control according to the third embodiment described above, the pitch angle of the blade 18 is changed based on the vertical positional relationship between the target terrain 60 and the cutting edge position P0. The vertical positional relationship between the target terrain 60 and the cutting edge position P0 differs depending on the work performed by the work machine 1. Therefore, in the work machine 1 according to this embodiment, the pitch angle of the blade 18 can be easily and appropriately adjusted depending on the work.

[0073] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention.

[0074] The work machine 1 is not limited to a bulldozer, but may be another vehicle such as a wheel loader or a motor grader. The controller 26 may have a plurality of controllers separate from each other. Some of the plurality of controllers may be disposed outside the work machine 1. That is, the work machine 1 may be remotely controllable. The processing by the controller 26 is not limited to that in the above embodiment, and may be modified. Some of the automatic control processing described above may be omitted. Alternatively, some of the processing described above may be modified.

[0075] The lift actuator 19 and the pitch actuator 20 are not limited to hydraulic cylinders. The lift actuator 19 and the pitch actuator 20 may be other actuators such as electric motors. The position sensor 37 is not limited to being disposed in the vehicle body 11, and may be disposed in other parts of the work machine 1. For example, the position sensor 37 may be disposed in the blade 18.

[0076] The pitch angle data is not limited to that in the above embodiment and may be changed. For example, the pitch angle data may define only the relationship between the height difference between excavation work and ground leveling work and the target pitch angle. The pitch angle data may define only the relationship between the height difference between ground leveling work and soil carrying work and the target pitch angle. The pitch angle data may define only the relationship between the height difference between excavation work and soil carrying work and the target pitch angle. Alternatively, the pitch angle data may define the relationship between the height difference in another work and the target pitch angle. [Industrial Applicability]

[0077] According to the present invention, in a work machine, the pitch angle of the blade can be easily and appropriately adjusted depending on the work being performed. [Explanation of symbols]

[0078] 11 Body 17 Lift frame 18 Blades 19 Lift actuator 20 Pitch Actuator 26 Controller 33 Sensors 50 Current Topography 60 Target terrain P0 Blade tip position

Claims

1. The car body and a lift frame supported rotatably about a lift shaft relative to the vehicle body; A blade supported rotatably about a pitch axis relative to the lift frame; a lift actuator that lifts the blade up and down around the lift shaft; a pitch actuator that pitches the blade about the pitch axis; a sensor for detecting a current cutting edge position of the blade; a controller that acquires current terrain data indicating a current terrain that is a work target, acquires target terrain data indicating a target terrain, and controls the lift actuator so that the cutting edge of the blade moves according to the target terrain; Equipped with the controller controls the pitch actuator so that a pitch angle of the blade is changed based on a positional relationship in an up-down direction between any two of the current topography corresponding to the current blade tip position, the target topography corresponding to the current blade tip position, and the current blade tip position. Working machinery.

2. the controller controls the pitch actuator to pitch the blade in a backward tilt direction when the target terrain is located below a predetermined range in a vertical direction including the current terrain.

2. The work machine of claim 1.

3. The controller: Obtaining a height difference between the target terrain and the current terrain; when the target terrain is located below the predetermined range, the pitch angle of the blade is changed in a backward direction in response to an increase in the height difference; 3. A work machine according to claim 2.

4. the controller controls the pitch actuator to pitch the blade in a forward tilt direction when the target terrain is located above a predetermined range in a vertical direction including the current terrain.

2. The work machine of claim 1.

5. The controller: Obtaining a height difference between the target terrain and the current terrain; when the target terrain is located above the predetermined range, the pitch angle of the blade is changed in a forward tilt direction in response to an increase in the height difference; 5. A work machine according to claim 4.

6. the controller controls the pitch actuator to pitch the blade in a backward tilt direction when the target terrain is located below a predetermined range in a vertical direction including the current blade tip position.

2. The work machine of claim 1.

7. The controller: A height difference between the target topography and the current cutting edge position is obtained; when the target terrain is located below the predetermined range, the pitch angle of the blade is changed in a backward direction in response to an increase in the height difference; 7. A work machine according to claim 6.

8. the controller controls the pitch actuator to pitch the blade in a forward tilt direction when the target terrain is located above a predetermined range in a vertical direction including the current blade tip position.

2. The work machine of claim 1.

9. The controller: A height difference between the target topography and the current cutting edge position is obtained; when the target terrain is located above the predetermined range, the pitch angle of the blade is changed in a forward tilt direction in response to an increase in the height difference; 9. A work machine according to claim 8.

10. the controller controls the pitch actuator to pitch the blade in a backward tilt direction when the current blade tip position is located below a predetermined range in a vertical direction including the current topography.

2. The work machine of claim 1.

11. The controller: Obtaining a height difference between the current cutting edge position and the current topography; when the current blade tip position is located below the predetermined range, the pitch angle of the blade is changed in a rearward direction in accordance with an increase in the height difference; 11. A work machine according to claim 10.

12. the controller controls the pitch actuator to pitch the blade in a forward tilt direction when the current blade tip position is located above a predetermined range in a vertical direction including the current topography.

2. The work machine of claim 1.

13. The controller: Obtaining a height difference between the current cutting edge position and the current topography; when the current blade tip position is located above the predetermined range, the pitch angle of the blade is changed in a forward tilt direction in response to an increase in the height difference; 13. A work machine according to claim 12.

14. A method for controlling a work machine including a vehicle body, a lift frame supported rotatably about a lift axis relative to the vehicle body, a blade supported rotatably about a pitch axis relative to the lift frame, a lift actuator that lifts the blade up and down about the lift axis, and a pitch actuator that pitches the blade about the pitch axis, the method comprising: Detecting a current cutting edge position of the blade; Acquiring current terrain data indicating the current terrain that is the target of work; acquiring target terrain data indicative of a target terrain; controlling the lift actuator so that the cutting edge of the blade moves according to the target topography; controlling the pitch actuator so that the pitch angle of the blade is changed based on a positional relationship in the up-down direction between any two of the current topography corresponding to the current cutting edge position, the target topography corresponding to the current cutting edge position, and the current cutting edge position; A method for providing the above.

15. controlling the pitch actuator to pitch the blade in a backward direction when the target terrain is located below a predetermined range in a vertical direction including the current terrain; The method of claim 14 further comprising:

16. controlling the pitch actuator to pitch the blade in a forward tilt direction when the target terrain is located above a predetermined range in a vertical direction including the current terrain; The method of claim 14 further comprising:

17. controlling the pitch actuator so as to pitch the blade in a backward tilt direction when the target terrain is located below a predetermined range in a vertical direction including the current blade tip position; The method of claim 14 further comprising:

18. controlling the pitch actuator so as to pitch the blade in a forward tilt direction when the target terrain is located above a predetermined range in a vertical direction including the current blade tip position; The method of claim 14 further comprising:

19. controlling the pitch actuator so as to pitch the blade in a backward tilt direction when the current blade tip position is located below a predetermined range in a vertical direction including the current topography; The method of claim 14 further comprising:

20. controlling the pitch actuator so as to pitch the blade in a forward tilt direction when the current blade tip position is located above a predetermined range in a vertical direction including the current topography; The method of claim 14 further comprising:

Images