Work machine

Abstract

The present invention provides a work machine that carries out control such that the cutting edge line of a bucket is parallel or nearly parallel to a target construction surface, in which an improvement in the accuracy of said control can be attained.　An excavator comprises: a bucket; a tilt frame connected to an arm so as to allow rotation about a first axis and supporting the bucket so as to allow rotation about a second axis; a tilt cylinder that rotates the bucket about the second axis; and a control device that controls the tilt cylinder such that a cutting edge line of the bucket is parallel or nearly parallel to a target construction surface. The control device creates a virtual plane bounded by a cutting edge line including a first cutting edge point and a second cutting edge point, a target work line constituting the target construction surface, a first straight line passing through the first cutting edge point and perpendicular to the target work line, and a second straight line passing through the second cutting edge point and perpendicular to the target work line, and controls the tilt cylinder such that the area of the virtual plane becomes smaller.

Description

Work machinery

[0001] The present invention relates to a work machine equipped with a bucket.

[0002] The work machine disclosed in Patent Document 1 includes a bucket, a joint rotatably connected to the arm about the bucket axis and supporting the bucket rotatably about a tilt axis perpendicular to the bucket axis, a tilt cylinder that rotates the bucket about the tilt axis, and a control device that controls the tilt cylinder so that the bucket cutting edge line is parallel to a target design surface. The control device identifies, of multiple polygonal faces that make up the target design surface, the polygonal face that is closest to the bucket cutting edge line, and controls the tilt cylinder so that the bucket cutting edge line is parallel to the identified polygonal face.

[0003] Japanese Patent Application Laid-Open No. 2021-085213

[0004] In Patent Document 1, when the bucket moves due to the rotation of the arm, for example, the target design surface is sequentially switched to the polygonal surface that is closest to the cutting edge line of the bucket among the multiple polygonal surfaces that make up the target design surface. If the difference in angle between the polygonal surface before and after the switch is large, the bucket tilt angle (in other words, the rotation angle around the tilt axis) must be changed abruptly. This increases the bucket tilt angular velocity, which may result in a deterioration in control accuracy.

[0005] The present invention has been made in consideration of the above circumstances, and its object is to provide a work machine that can control the bucket cutting edge line so that it is parallel to or nearly parallel to the target construction surface, thereby improving the control accuracy.

[0006] In order to achieve the above object, the present invention provides a work machine comprising: a bucket; a tilt frame rotatably connected to an arm about a first axis and supporting the bucket rotatably about a second axis perpendicular to the first axis; a tilt cylinder that rotates the bucket about the second axis; and a control device that controls the tilt cylinder so that the cutting edge line of the bucket is parallel to or substantially parallel to a target construction surface, wherein the control device creates an imaginary plane surrounded by the cutting edge line that includes a first cutting edge point and a second cutting edge point that are set in advance; a target work line that is a line where a set plane that includes the cutting edge line and extends in a predetermined direction intersects with the target construction surface; a first straight line that passes through the first cutting edge point and is perpendicular to the target work line; and a second straight line that passes through the second cutting edge point and is perpendicular to the target work line, and controls the tilt cylinder so that the area of ​​the imaginary plane becomes smaller.

[0007] According to the present invention, the cutting edge line of the bucket can be controlled to be parallel to or substantially parallel to the target construction surface, thereby improving the control accuracy.

[0008] FIG. 1 is a side view showing the structure of a work machine in one embodiment of the present invention. FIG. 2 is a view showing the structure of a bucket unit in one embodiment of the present invention. FIG. 3 is a view showing the configuration of a drive device in one embodiment of the present invention. FIG. 4 is a block diagram showing the functional configuration of a control device in one embodiment of the present invention together with related equipment. FIG. 5 is a view showing a specific example of a virtual plane in one embodiment of the present invention. FIG. 6 is a flowchart showing the processing procedure of a control device in one embodiment of the present invention. FIG. 7 is a view showing the relationship between the tilt angle of the bucket and the area of ​​the virtual plane in one embodiment of the present invention. FIG. 8 is a view showing the relationship between the amount of change in the area of ​​the virtual plane and the target angular velocity in one embodiment of the present invention. FIG. 9 is a view showing changes in the attitude of the bucket when the bucket moves in one embodiment of the present invention and a comparative example. FIG. 10 is a view showing changes in the tilt angle and tilt angular velocity when the bucket moves in one embodiment of the present invention and a comparative example.

[0009] An embodiment of the present invention will be described with reference to the drawings.

[0010] Fig. 1 is a side view showing the structure of a work machine according to this embodiment, and Fig. 2 is a view showing the structure of a bucket unit according to this embodiment (more specifically, a view seen from the opening side of the bucket).

[0011] The work machine of this embodiment is a shovel, and includes a travelable running body 1, a rotating body 2 rotatably provided above the running body 1, and a work device 3 connected to the rotating body 2. The running body 1 travels by being driven by left and right traveling motors (not shown). The rotating body 2 rotates by being driven by a swing motor (not shown).

[0012] The working device 3 includes a boom 5 connected to the revolving unit 2 so as to be rotatable about an axis 4A (not shown) in one direction (a direction perpendicular to the plane of the paper in FIG. 1 ), an arm 6 connected to the boom 5 so as to be rotatable about the axis 4B in the one direction, a bucket unit 7 connected to the arm 6 so as to be rotatable about the axis 4C in the one direction, a boom cylinder 8 that rotates the boom 5 about the axis 4A, an arm cylinder 9 that rotates the arm 6 about the axis 4B, and a bucket cylinder 11 connected to the bucket unit 7 via a link 10 and that rotates the bucket unit 7 about the axis 4C.

[0013] The work device 3 includes a detector 12A that detects the rotation angle of the boom 5 about the axis 4A, a detector 12B that detects the rotation angle of the arm 6 about the axis 4B, and a detector 12C that detects the rotation angle of the link 10 and, in turn, the rotation angle of the bucket unit 7 (more specifically, a tilt frame, which will be described later) about the axis 4C. The detectors 12A to 12C are configured, for example, by inertial measurement devices.

[0014] Bucket unit 7 is referred to as a tilt rotator bucket. Bucket unit 7 includes a tilt frame 13 rotatably connected to arm 6 about axis 4C, a rotator frame 14 rotatably connected to tilt frame 13 about axis 4D in a direction orthogonal to axis 4C (a direction parallel to the plane of FIG. 1 and a direction perpendicular to the plane of FIG. 2), a bucket 16 rotatably supported on rotator frame 14 about axis 4E (not shown) in a direction orthogonal to axis 4D (the up-and-down direction in FIG. 2) and having a blade 15, tilt cylinders 17A and 17B that rotate rotator frame 14 (and thus bucket 16) about axis 4D, and a rotator motor 18 (see FIG. 3 described below) that rotates bucket 16 about axis 4E.

[0015] The bucket unit 7 includes a detector 12D that detects the rotation angle of the rotator frame 14 about the axis 4D, and a detector 12E that detects the rotation angle of the bucket 16 about the axis 4E. The detectors 12D and 12E are configured by, for example, inertial measurement units.

[0016] The rotating unit 2 is equipped with a position measurement device 20 (see FIG. 4 described later) that measures the position and orientation of the rotating unit 2 in a global coordinate system based on signals from multiple satellites received by antennas 19A and 19B, and a detector 12F that detects the tilt direction and tilt angle of the rotating unit 2. The detector 12F is configured, for example, by an inertial measurement unit.

[0017] The revolving body 2 includes a cab 21 in which the driver sits, and a machinery room 22 that houses equipment (more specifically, an engine, a pump, a control valve, and the like, which will be described later). A driver's seat (not shown) in which the driver sits is provided inside the cab 21. Left and right travel operation devices (not shown) are provided in front of the driver's seat, which the driver operates in the forward and backward directions with his or her hands or feet to command the operation of the left and right travel motors, respectively.

[0018] On the right side of the driver's seat, there is provided a work operation device 23A (see FIG. 3 described later) that the driver operates by hand in the left-right direction to command the drive of the bucket cylinder 11 and that the driver operates by hand in the front-rear direction to command the drive of the boom cylinder 8. On the left side of the driver's seat, there is provided a work operation device 23B (not shown) that the driver operates by hand in the left-right direction to command the drive of the swing motor and that the driver operates by hand in the front-rear direction to command the drive of the arm cylinder 9.

[0019] A tilt operation device 24 (see FIG. 3 described later) that the driver operates left and right to command the drive of tilt cylinders 17A, 17B is provided on the grip portion of the lever of work operation device 23A. A rotator operation device 25 (see FIG. 3 described later) that the driver operates left and right to command the drive of rotator motor 18 is provided on the grip portion of the lever of work operation device 23B.

[0020] The excavator of this embodiment is equipped with a drive device that drives a plurality of hydraulic actuators (more specifically, the above-mentioned travel motor, swing motor, boom cylinder 8, arm cylinder 9, bucket cylinder 11, tilt cylinders 17A, 17B, and rotator motor 18). Fig. 3 is a diagram showing the configuration of the drive device in this embodiment. Of the configuration related to the drive of the plurality of hydraulic actuators, Fig. 3 shows only the configuration related to the drive of the bucket cylinder 11, tilt cylinders 17A, 17B, and rotator motor 18.

[0021] The drive device of this embodiment includes an engine 26, a main pump 27 and a pilot pump 28 driven by the engine 26, a bucket control valve 29 that controls the flow of pressure oil (specifically, the direction and flow rate) from the main pump 27 to the bucket cylinder 11, a tilt control valve 30 that controls the flow of pressure oil (specifically, the direction and flow rate) from the main pump 27 to the tilt cylinders 17A, 17B, and a tilt control valve 31 that controls the flow of pressure oil (specifically, the direction and flow rate) from the main pump 27 to the rotator motor 18. The bucket control valve 29 includes a rotator control valve 31 that controls the bucket, bucket electromagnetic proportional valves 32A, 32B that generate pilot pressure that operates the bucket control valve 29, tilt electromagnetic proportional valves 33A, 33B that generate pilot pressure that operates the tilt control valve 30, rotator electromagnetic proportional valves 34A, 34B that generate pilot pressure that operates the rotator control valve 31, and a control device 35 that controls the bucket electromagnetic proportional valves 32A, 32B, the tilt electromagnetic proportional valves 33A, 33B, and the rotator electromagnetic proportional valves 34A, 34B. Although not shown in detail, the control device 35 has a processor that executes control according to a program, a memory that stores the program and data, and an interface that performs input and output with other devices.

[0022] The work operation device 23A has a lever that can be operated by the driver and a potentiometer that outputs a first operation signal corresponding to the amount of operation of the lever to the left from the neutral position or a second operation signal corresponding to the amount of operation of the lever to the right from the neutral position.

[0023] When a first operation signal is input from work operating device 23A, control device 35 generates a control signal corresponding to the first operation signal and outputs it to bucket electromagnetic proportional valve 32A. Bucket electromagnetic proportional valve 32A uses the discharge pressure of pilot pump 28 as its source pressure, generates a pilot pressure corresponding to the control signal, and outputs it to bucket control valve 29. As a result, bucket control valve 29 is switched to the switching position on the right side in the figure, and pressure oil from main pump 27 is supplied to the bottom side of bucket cylinder 11 via bucket control valve 29. As a result, bucket cylinder 11 extends.

[0024] When a second operation signal is input from the work operating device 23A, the control device 35 generates a control signal corresponding to the second operation signal and outputs it to the bucket electromagnetic proportional valve 32B. The bucket electromagnetic proportional valve 32B uses the discharge pressure of the pilot pump 28 as its source pressure, generates a pilot pressure corresponding to the control signal, and outputs it to the bucket control valve 29. This switches the bucket control valve 29 to the switching position on the left side in the figure, and pressure oil from the main pump 27 is supplied to the rod side of the bucket cylinder 11 via the bucket control valve 29. As a result, the bucket cylinder 11 retracts and contracts.

[0025] The tilt operation device 24 has a slider that can be operated by the driver and a potentiometer that outputs a third operation signal corresponding to the amount of operation of the slider to the left from the neutral position or a fourth operation signal corresponding to the amount of operation of the slider to the right from the neutral position.

[0026] When the control device 35 receives a third operation signal from the tilt operation device 24, it generates a control signal corresponding to the third operation signal and outputs it to the tilt electromagnetic proportional valve 33A. The tilt electromagnetic proportional valve 33A uses the discharge pressure of the pilot pump 28 as its source pressure, generates a pilot pressure corresponding to the control signal, and outputs it to the tilt control valve 30. This switches the tilt control valve 30 to the switching position on the right side in the figure, and pressure oil from the main pump 27 is supplied to the bottom side of the tilt cylinder 17A and the rod side of the tilt cylinder 17B via the tilt control valve 30. As a result, the tilt cylinder 17A extends, and the tilt cylinder 17B retracts.

[0027] When a fourth operation signal is input from the tilt operation device 24, the control device 35 generates a control signal corresponding to the fourth operation signal and outputs it to the tilt solenoid proportional valve 33B. The tilt solenoid proportional valve 33B uses the discharge pressure of the pilot pump 28 as its source pressure, generates a pilot pressure corresponding to the control signal, and outputs it to the tilt control valve 30. This switches the tilt control valve 30 to the switching position on the left side in the figure, and pressure oil from the main pump 27 is supplied to the rod side of the tilt cylinder 17A and the bottom side of the tilt cylinder 17B via the tilt control valve 30. As a result, the tilt cylinder 17A retracts and the tilt cylinder 17B extends.

[0028] The rotator operating device 25 has a slider that can be operated by the driver and a potentiometer that outputs a fifth operating signal corresponding to the amount of operation of the slider to the left from the neutral position or a sixth operating signal corresponding to the amount of operation of the slider to the right from the neutral position.

[0029] When the control device 35 receives a fifth operation signal from the rotator operation device 25, it generates a control signal corresponding to the fifth operation signal and outputs it to the rotator electromagnetic proportional valve 34A. The rotator electromagnetic proportional valve 34A uses the discharge pressure of the pilot pump 28 as its source pressure, generates a pilot pressure corresponding to the control signal, and outputs it to the rotator control valve 31. This switches the rotator control valve 31 to the switching position on the right side in the figure, and pressure oil from the main pump 27 is supplied to one port of the rotator motor 18 via the rotator control valve 31. As a result, the rotator motor 18 rotates in one direction.

[0030] When the control device 35 receives a sixth operation signal from the rotator operation device 25, it generates a control signal corresponding to the sixth operation signal and outputs it to the rotator electromagnetic proportional valve 34B. The rotator electromagnetic proportional valve 34B uses the discharge pressure of the pilot pump 28 as its source pressure, generates a pilot pressure corresponding to the control signal, and outputs it to the rotator control valve 31. This switches the rotator control valve 31 to the switching position on the left side in the figure, and pressure oil from the main pump 27 is supplied to the other port of the rotator motor 18 via the rotator control valve 31. As a result, the rotator motor 18 rotates in the opposite direction.

[0031] The control device 35 has an automatic control function that controls the tilt electromagnetic proportional valves 33A, 33B and therefore the tilt cylinders 17A, 17B when predetermined conditions are met, regardless of the operation signal from the tilt operation device 24. This automatic control controls the tilt cylinders 17A, 17B so that the cutting edge line L of the bucket 16 (the tip of the blade 15 as shown in FIG. 2) is parallel to or substantially parallel with the target construction surface. Details of this will be explained using FIG. 4. FIG. 4 is a block diagram showing the functional configuration of the control device in this embodiment together with related equipment.

[0032] The control device 35 has, as functional components, a target construction surface acquisition unit 36 ​​, a virtual plane creation unit 37 , an area calculation unit 38 , an area change amount calculation unit 39 , and a control signal generation unit 40 .

[0033] The target construction surface acquisition unit 36 ​​of the control device 35 inputs three-dimensional data of the target construction surface in the global coordinate system from, for example, an external terminal (not shown), and converts the input data into three-dimensional data of the target construction surface in the excavator coordinate system (local coordinate system) based on the position and orientation of the revolving unit 2 measured by the position measurement device 20 and the tilt direction and tilt angle of the revolving unit 2 detected by the detector 12F.

[0034] The virtual plane creation unit 37 of the control device 35 creates a current virtual plane based on the three-dimensional data of the target construction plane acquired by the target construction plane acquisition unit 36 ​​and the detection results of the detectors 12A to 12E. Details of this will be explained using Fig. 5. Fig. 5 is a diagram showing a specific example of a virtual plane in this embodiment.

[0035] The virtual plane creation unit 37 of the control device 35 calculates the positions of cutting edge points P1 and P2 of the bucket 16 in the excavator coordinate system based on the rotation angle of the boom 5 about axis 4A, the rotation angle of the arm 6 about axis 4B, the rotation angle of the tilt frame 13 about axis 4C, the rotation angle of the rotator frame 14 about axis 4D (hereinafter referred to as the tilt angle of the bucket 16), and the rotation angle of the bucket 16 about axis 4E (hereinafter referred to as the rotary angle of the bucket 16) detected by the detectors 12A to 12E, as well as pre-stored dimensional information of the boom 5, arm 6, tilt frame 13, rotator frame 14, and bucket 16. This also obtains the position of the cutting edge line L including the cutting edge points P1 and P2. The cutting edge points P1 and P2 are set in advance to be spaced apart from each other on the cutting edge line L of the bucket 16, and are, for example, at both ends of the cutting edge line L.

[0036] The virtual plane creation unit 37 of the control device 35 calculates the position of the target work line M, which is the line where the target construction surface intersects with a set plane that includes the cutting edge line L of the bucket 16 and extends in a predetermined direction (the vertical direction in this embodiment). The virtual plane creation unit 37 then calculates the positions of a line P1P3 that passes through the cutting edge point P1 and is perpendicular to the target work line M, and a line P2P4 that passes through the cutting edge point P2 and is perpendicular to the target work line M. The virtual plane creation unit 37 then creates a current virtual plane V0 that is surrounded by the cutting edge line L of the bucket 16, the target work line M, the line P1P3, and the line P1P3. The area calculation unit 38 calculates the area A0 of the virtual plane V0.

[0037] In the same manner as described above, the virtual plane creation unit 37 of the control device 35 creates a virtual plane V1 when the tilt angle of the bucket 16 is changed to one side by a predetermined value. The area calculation unit 38 calculates the area A1 of the virtual plane V1, and the area change amount calculation unit 39 calculates the area change amount ΔA1 (=A1-A0) of the virtual plane V1.

[0038] In the same manner as described above, a virtual plane creation unit 37 of the control device 35 creates a virtual plane V2 when the tilt angle of the bucket 16 is changed by a predetermined value to the opposite side (other side). An area calculation unit 38 calculates an area A2 of the virtual plane V2, and an area change amount calculation unit 39 calculates an area change amount ΔA2 (=A2−A0) of the virtual plane V2.

[0039] If automatic control is enabled, the control signal generation unit 40 of the control device 35 generates and outputs a control signal for controlling the tilt cylinders 17A, 17B so as to reduce the area of ​​the virtual plane. In detail, if the area change amount ΔA1 or ΔA2 of the virtual plane calculated by the area change amount calculation unit 39 is negative, a corresponding control signal is generated and output to the corresponding tilt electromagnetic proportional valve.

[0040] If the automatic control is disabled, the control signal generating unit 40 of the control device 35 generates a control signal corresponding to the third or fourth operation signal from the tilt operation device and outputs it to the tilt electromagnetic proportional valve.

[0041] Next, the processing procedure of the control device 35 of this embodiment will be described with reference to Fig. 6. Fig. 6 is a flowchart showing the processing procedure of the control device of this embodiment.

[0042] In step S1, the control device 35 determines whether automatic control is enabled based on whether a predetermined condition is met. For example, if a mode switch (not shown) for switching between enabling and disabling automatic control is provided, the control device 35 determines whether the predetermined condition is met by checking whether the mode switch has been switched to enable automatic control. Alternatively, the control device 35 may calculate the distance between the cutting edge line L of the bucket 16 and the target construction surface and check whether the calculated distance is equal to or less than a predetermined threshold.

[0043] If the predetermined condition is not met in step S1, automatic control is disabled, and the process proceeds to step S2. In step S2, when a third operation signal is input from the tilt operation device 24, the control signal generation unit 40 of the control device 35 calculates a target angular velocity in accordance with the magnitude of the third operation signal, generates a corresponding control signal, and outputs it to the tilt solenoid proportional valve 33A. Alternatively, when a fourth operation signal is input from the tilt operation device 24, the control signal generation unit 40 calculates a target angular velocity in accordance with the magnitude of the fourth operation signal, generates a corresponding control signal, and outputs it to the tilt solenoid proportional valve 33B.

[0044] If a predetermined condition is met in step S1, automatic control is enabled, and the process proceeds to step S3. In step S3, the virtual plane creation unit 37 of the control device 35 creates a current virtual plane V0 (i.e., when the tilt angle is θ0), and the area calculation unit 38 calculates the area A0 of the virtual plane V0.

[0045] Proceeding to step S4, the virtual plane creation unit 37 of the control device 35 creates a virtual plane V1 when the tilt angle of the bucket 16 is changed to one side by a predetermined value (i.e., when the tilt angle is θ1), the area calculation unit 38 calculates the area A1 of the virtual plane V1, and the area change amount calculation unit 39 calculates the area change amount ΔA1 (=A1-A0) of the virtual plane V1.

[0046] Proceeding to step S5, the virtual plane creation unit 37 of the control device 35 creates a virtual plane V2 when the tilt angle of the bucket 16 is changed by a predetermined value to the opposite side (i.e., when the tilt angle is θ2), the area calculation unit 38 calculates the area A2 of the virtual plane V2, and the area change amount calculation unit 39 calculates the area change amount ΔA2 (=A2-A0) of the virtual plane V2.

[0047] Proceeding to step S6, the control signal generating unit 40 of the control device 35 determines whether one of the area change amounts ΔA1 and ΔA2 is negative. For example, if the area change amount ΔA1' (= A1' - A0') is negative and the area change amount ΔA2' (= A2' - A0') is positive, as shown in FIG. 7, proceed to step S7. In step S7, the control signal generating unit 40 of the control device 35 calculates a target angular velocity corresponding to the area change amount ΔA1' on the virtual plane using a function indicating the relationship between the area change amount on the virtual plane and the target angular velocity (see FIG. 8). Then, the control signal generating unit 40 generates a control signal corresponding to the calculated target angular velocity and outputs it to the corresponding tilt solenoid proportional valve 33A. Note that if the area change amount ΔA1 is positive and the area change amount ΔA2 is negative, the control signal generating unit 40 of the control device 35 calculates a target angular velocity corresponding to the area change amount ΔA2 on the virtual plane using the above-mentioned function. Then, a control signal corresponding to the calculated target angular velocity is generated and output to the corresponding tilt electromagnetic proportional valve 33B.

[0048] If one of the area change amounts ΔA1 and ΔA2 is negative, the processing of steps S3, S4, S5, and S7 described above is repeated. As a result, for example, as shown in FIG. 7, the tilt angle of the bucket 16 changes from θ0' to θ0". At this time, in step S6, the area change amount ΔA1" (= A1" - A0") and the area change amount ΔA2" (= A2" - A0") become positive, and the process does not proceed to step S7. In other words, the control signal generation unit 40 of the control device 35 does not output a control signal to the tilt solenoid proportional valves 33A, 33B.

[0049] As described above, the control device 35 of this embodiment creates the cutting edge line L of the bucket 16, the target work line M, the straight line P1P3, and an imaginary plane surrounded by the straight line P1P3, and controls the tilt cylinders 17A and 17B so that the area of ​​the imaginary plane becomes smaller. This makes it possible to control the tilt cylinders 17A and 17B so that the cutting edge line L of the bucket 16 becomes parallel to the target construction surface (in other words, the target work line M) or in a state equivalent to that (more specifically, if the target work line M is a polygonal line, in a state parallel to an approximation of that line).

[0050] The effects of this embodiment will be described in detail with reference to Figures 9A and 9B. Figure 9A is a diagram showing changes in bucket attitude during bucket movement in this embodiment and a comparative example. Figure 9B is a diagram showing changes in tilt angle and tilt angular velocity during bucket movement in this embodiment and a comparative example. Note that Figures 9A and 9B show an example of horizontal movement of bucket 16 due to rotation of rotating body 2.

[0051] Similar to Patent Document 1, the control device of the comparative example identifies, of the multiple polygonal faces that make up the target construction surface, the polygonal face that is the shortest distance from the cutting edge line L of the bucket 16, and controls the tilt cylinders 17A, 17B so that the cutting edge line L of the bucket 16 is parallel to the identified polygonal face. In other words, of the multiple straight lines that make up the target work line M, the straight line that is the shortest distance from the cutting edge line L of the bucket 16 is identified, and controls the tilt cylinders 17A, 17B so that the cutting edge line L of the bucket 16 is parallel to the identified straight line.

[0052] Therefore, as shown in Fig. 9A, when the bucket 16 moves, of the multiple straight lines that make up the target working line M, the straight line that is the shortest distance from the cutting edge line L of the bucket 16 is switched. At this time, if the angle difference between the straight line before and after the switch is large, it is necessary to abruptly change the tilt angle of the bucket 16, as shown in Fig. 9B. Therefore, the tilt angular velocity of the bucket 16 increases, which may result in a deterioration in control accuracy.

[0053] On the other hand, the control device 35 of this embodiment creates an imaginary plane surrounded by the cutting edge line L of the bucket 16, the target working line M, the straight line P1P3, and the straight line P1P3, and controls the tilt cylinders 17A and 17B so that the area of ​​the imaginary plane becomes smaller. Therefore, as shown in Figure 9B, the tilt angle of the bucket 16 can be changed smoothly. Therefore, as shown in Figure 9B, the tilt angular velocity of the bucket 16 becomes smaller, and control accuracy can be improved.

[0054] In the above embodiment, the detector 12A that detects the rotation angle of the boom 5 about the axis 4A has been described as being constituted by an inertial measurement unit (IMU), but this is not a limitation and the detector may be, for example, a stroke sensor that detects the stroke of the boom cylinder 8 that corresponds to the rotation angle of the boom 5 about the axis 4A. In the above embodiment, the detector 12B that detects the rotation angle of the arm 6 about the axis 4B has been described as being constituted by an IMU, but this is not a limitation and the detector may be, for example, a stroke sensor that detects the stroke of the arm cylinder 9 that corresponds to the rotation angle of the arm 6 about the axis 4B. In the above embodiment, the detector 12C that detects the rotation angle of the tilt frame 13 about the axis 4C has been described as being constituted by an IMU, but this is not a limitation and the detector may be, for example, a stroke sensor that detects the stroke of the bucket cylinder 11 that corresponds to the rotation angle of the tilt frame 13 about the axis 4C. Furthermore, in the above embodiment, the detector 12D that detects the rotation angle of the rotator frame 14 about the axis 4D has been described as being configured with an inertial measurement unit, but this is not limiting and the detector 12D may be, for example, a stroke sensor that detects the stroke of the tilt cylinder 17A or 17B that corresponds to the rotation angle of the rotator frame 14 about the axis 4D.

[0055] Furthermore, in the above embodiment, the bucket unit 7 has been described as being what is called a tilt rotator bucket, but this is not limited thereto and may be what is called a tilt bucket. That is, the bucket unit 7 may include a tilt frame 13 rotatably connected to the arm 6 about axis 4C, a bucket 16 rotatably connected to the tilt frame 13 about axis 4D that is perpendicular to axis 4C, and tilt cylinders 17A, 17B that rotate the bucket 16 about axis 4D. Furthermore, in the above embodiment, the bucket unit 7 has been described as being provided with a pair of tilt cylinders 17A, 17B, but this is not limited thereto and may be provided with only one tilt cylinder.

[0056] Furthermore, in the above embodiment, the control device 35 has been described as having an automatic control function for controlling the tilt cylinders 17A, 17B so as to reduce the area of ​​the above-described imaginary plane. However, the control device 35 may also have an automatic control function for controlling the rotator motor 18 so as to reduce the area of ​​the above-described imaginary plane. In this modification, the control device 35 controls the rotator motor 18 in the same manner as the tilt cylinders 17A, 17B. Specifically, the control device 35 calculates the area A3 of the imaginary plane V3 when the rotary angle of the bucket 16 is changed by a predetermined value to one side, and calculates an area change amount ΔA3 (= A3 - A0). The control device 35 also calculates the area A4 of the imaginary plane V4 when the rotary angle of the bucket 16 is changed by a predetermined value to the opposite side (the other side), and calculates an area change amount ΔA4 (= A4 - A0). If one of the area change amounts ΔA3 and ΔA4 is negative, the control device 35 controls the rotator motor 18 so that the rotary angle of the bucket 16 changes in the direction corresponding to the one area change amount.

[0057] In the above embodiment, the predetermined direction in which the setting plane for extracting the target work line M from the target construction surface extends is the vertical direction, but this is not limited to this. The predetermined direction may be the length direction of the blade 15 of the bucket 16, or the direction of the shortest straight line between the blade edge line L of the bucket 16 and the target construction surface.

[0058] Although the above description has been given taking a shovel as an example of an object to which the present invention is applied, the present invention is not limited to this and may be applied to other work machines.

[0059] 4A to 4E Shaft 6 Arm 13 Tilt frame 14 Rotator frame 15 Blade 16 Bucket 17A, 17B Tilt cylinder 18 Rotator motor 35 Control device

Claims

1. A work machine comprising: a bucket; a tilt frame rotatably connected to an arm about a first axis and supporting the bucket rotatably about a second axis perpendicular to the first axis; a tilt cylinder that rotates the bucket about the second axis; and a control device that controls the tilt cylinder so that the cutting edge line of the bucket is parallel to or substantially parallel to a target construction surface, wherein the control device creates an imaginary plane surrounded by the cutting edge line that includes a first cutting edge point and a second cutting edge point that are set in advance, a target work line that is a line where a set plane that includes the cutting edge line and extends in a predetermined direction intersects with the target construction surface, a first straight line that passes through the first cutting edge point and is perpendicular to the target work line, and a second straight line that passes through the second cutting edge point and is perpendicular to the target work line, and controls the tilt cylinder so that the area of ​​the imaginary plane becomes smaller.

2. A work machine as described in claim 1, comprising: a rotator frame connected to the tilt frame so as to be rotatable about the second axis and supporting the bucket so as to be rotatable about a third axis perpendicular to the second axis; and a rotator motor that rotates the bucket about the third axis, wherein the control device controls the rotator motor so as to reduce the area of ​​the imaginary plane.

3. A work machine as described in claim 1, wherein the predetermined direction is one of the vertical direction, the length direction of the bucket blade, and the direction of the shortest straight line between the blade tip line of the bucket and the target construction surface.

4. A work machine as described in claim 1, wherein the control device calculates a first amount of change in the area of ​​the imaginary plane when the rotation angle of the bucket about the second axis is changed by a predetermined value in one direction, calculates a second amount of change in the area of ​​the imaginary plane when the rotation angle of the bucket about the second axis is changed by the predetermined value in the opposite direction, and, when one of the first amount of change and the second amount of change is negative, controls the tilt cylinder so that the direction of change in the rotation angle of the bucket about the second axis corresponds to the one amount of change.

5. A work machine as described in claim 2, wherein the control device calculates a third amount of change in the area of ​​the imaginary plane when the rotation angle of the bucket about the third axis is changed by a predetermined value in one direction, calculates a fourth amount of change in the area of ​​the imaginary plane when the rotation angle of the bucket about the third axis is changed by the predetermined value in the opposite direction, and, when one of the third amount of change and the fourth amount of change is negative, controls the rotator motor so that the direction of change in the rotation angle of the bucket about the third axis corresponds to the one amount of change.

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