System and method for controlling motor grader

Abstract

This system includes a left lift operation member, a right lift operation member, and a controller. The left lift operation member is operated to raise and lower a blade by a left lift cylinder. The right lift operation member is operated to raise and lower the blade by a right lift cylinder. The controller can receive a signal corresponding to the operation of the left lift operation member and a signal corresponding to the operation of the right lift operation member. The controller executes automatic blade raising control for raising the blade to a predetermined target raising position by controlling the left lift cylinder and the right lift cylinder when the left lift operation member or the right lift operation member has returned to a neutral position after being operated to raise the blade for a predetermined first duration or longer during backward traveling of the vehicle body.

Description

System and method for controlling a motor grader

[0001] The present disclosure relates to a system and method for controlling a motor grader.

[0002] The motor grader includes a blade, a left lift cylinder, a right lift cylinder, a left lift operating member, and a right lift operating member. The left lift cylinder and the right lift cylinder raise and lower the blade. The left lift operating member and the right lift operating member are each operated by the left lift cylinder to raise and lower the blade.

[0003] Japanese Patent Application Laid-Open No. 2021-054269

[0004] A motor grader may perform operations in which the blade is positioned near the ground, the motor grader moves forward to perform leveling or grading work, then raises the blade and moves backward, and then moves forward again to repeat the leveling or grading work. In such cases, after switching the direction of travel from forward to reverse, the operator must continue to operate two operating members, the left lift operating member and the right lift operating member, to simultaneously raise the blade. This makes it difficult to simultaneously perform other operations, such as steering. An object of the present disclosure is to improve the operability of a motor grader.

[0005] A system according to one aspect of the present disclosure is a system for controlling a motor grader. The motor grader includes a vehicle body, a work machine, a left lift cylinder, and a right lift cylinder. The vehicle body includes running wheels. The work machine includes a blade. The work machine is operably connected to the vehicle body. The left lift cylinder is connected to the work machine and raises and lowers the blade. The right lift cylinder is connected to the work machine and raises and lowers the blade. The system includes a left lift operating member, a right lift operating member, and a controller. The left lift operating member is operated by the left lift cylinder to raise and lower the blade. The right lift operating member is operated by the right lift cylinder to raise and lower the blade. The controller is capable of receiving a signal corresponding to operation of the left lift operating member and a signal corresponding to operation of the right lift operating member. When the vehicle body is moving backward and the left lift operating member or the right lift operating member returns to the neutral position after being operated to raise the blade for a predetermined first duration or longer, the controller controls the left lift cylinder and the right lift cylinder to execute automatic blade raising control to raise the blade to a predetermined target raised position.

[0006] A method according to another aspect of the present disclosure is a method for controlling a motor grader. The motor grader includes a vehicle body, a work implement, a left lift cylinder, and a right lift cylinder. The vehicle body includes running wheels. The work implement includes a blade. The work implement is operably connected to the vehicle body. The left lift cylinder is connected to the work implement and raises and lowers the blade. The right lift cylinder is connected to the work implement and raises and lowers the blade. The method includes receiving a signal in response to operation of a left lift operating member operated by the left lift cylinder to raise and lower the blade, and receiving a signal in response to operation of a right lift operating member operated by the right lift cylinder to raise and lower the blade. When the left lift operating member or the right lift operating member returns to a neutral position after being operated to raise the blade for a predetermined first duration or longer while the vehicle body is moving backward, controlling the left lift cylinder and the right lift cylinder to execute automatic blade raising control to raise the blade to a predetermined target raised position.

[0007] According to the present disclosure, when the vehicle body is moving backward, the operator raises the left lift operating member or the right lift operating member for a first duration or longer and then returns it to the neutral position. This causes the automatic blade raising control to automatically raise the blade to the target raised position. This makes other operations, such as steering, easier, and improves the operability of the motor grader.

[0008] 1 is a perspective view of a motor grader according to an embodiment; FIG. 2 is a side view of the motor grader; FIG. 3 is a schematic diagram showing a drive system of the motor grader; FIG. 4 is a schematic diagram showing a control system of the motor grader; FIG. 5 is a top view showing the articulating operation of the motor grader; FIG. 6 is a top view showing the articulating operation of the motor grader; FIG. 7 is a side view of the motor grader showing the pitch angle of the blade relative to the vehicle body; FIG. 8 is a top view of the motor grader showing the rotation angle of the blade; FIG. 9 is a flowchart showing the processing of automatic blade raising control; FIG. 10 is a diagram showing the operation of the lift operating member and the control of the blade when traveling backward; FIG. 11 is a diagram showing the operation of the lift operating member and the control of the blade when traveling backward; FIG. 12 is a flowchart showing the processing of automatic blade lowering control; FIG. 13 is a diagram showing the operation of the lift operating member and the control of the blade when traveling forward; FIG. 14 is a diagram showing the operation of the lift operating member and the control of the blade when traveling forward; FIG. 15 is a diagram showing the operation of the lift operating member and the control of the blade when traveling forward; FIG. 16 is a flowchart showing the processing of lift cylinder control in automatic blade control; FIG. 17 is a diagram showing an example of spool stroke-actual pitch angle data.

[0009] An embodiment of the present disclosure will now be described with reference to the drawings. Fig. 1 is a perspective view of a motor grader 1 according to the embodiment. Fig. 2 is a side view of the motor grader 1. As shown in Fig. 1, the motor grader 1 includes a vehicle body 2, a plurality of running wheels 3A, 3B, 4A-4D, and a work implement 5. The vehicle body 2 includes a front frame 11, a rear frame 12, a cab 13, and a power compartment 14. The plurality of running wheels 3A, 3B, 4A-4D include front wheels 3A, 3B, and rear wheels 4A-4D.

[0010] The rear frame 12 is connected to the front frame 11. The front frame 11 can be articulated left and right relative to the rear frame 12. A cab 13 and a power compartment 14 are disposed on the rear frame 12. A driver's seat (not shown) is disposed in the cab 13. The power compartment 14 is disposed behind the cab 13. The front frame 11 extends forward from the rear frame 12. Front wheels 3A, 3B are attached to the front frame 11. Rear wheels 4A-4D are attached to the rear frame 12.

[0011] The work implement 5 is operably connected to the vehicle body 2. The work implement 5 includes a support member 15 and a blade 16. The support member 15 is movably connected to the vehicle body 2. The support member 15 supports the blade 16. The support member 15 includes a draw bar 17 and a circle 18. The draw bar 17 is disposed below the front frame 11.

[0012] The drawbar 17 is connected to a front portion 19 of the front frame 11. The drawbar 17 extends rearward from the front portion 19 of the front frame 11. The drawbar 17 is supported relative to the front frame 11 so as to be swingable at least in the up-down direction and the left-right direction of the vehicle body 2. For example, the front portion 19 includes a ball joint. The drawbar 17 is rotatably connected to the front frame 11 via the ball joint.

[0013] The circle 18 is connected to the rear of the drawbar 17. The circle 18 is supported rotatably relative to the drawbar 17. The blade 16 is connected to the circle 18. The blade 16 is supported by the drawbar 17 via the circle 18. As shown in FIG. 2 , the blade 16 is supported by the circle 18 rotatably around a tilt shaft 21. The tilt shaft 21 extends in the left-right direction.

[0014] The motor grader 1 is equipped with a plurality of actuators 22-26 for changing the attitude of the work implement 5. The plurality of actuators 22-26 includes a plurality of hydraulic cylinders 22-25. The plurality of hydraulic cylinders 22-25 are connected to the work implement 5. The plurality of hydraulic cylinders 22-25 extend and retract by hydraulic pressure. By extending and retracting, the plurality of hydraulic cylinders 22-25 change the attitude of the work implement 5 relative to the vehicle body 2. In the following description, the extension and retraction of the hydraulic cylinders is referred to as a "stroke operation."

[0015] In detail, the multiple hydraulic cylinders 22-25 include a left lift cylinder 22, a right lift cylinder 23, a drawbar shift cylinder 24, and a blade tilt cylinder 25. The left lift cylinder 22 and the right lift cylinder 23 are arranged apart from each other in the left-right direction. The left lift cylinder 22 and the right lift cylinder 23 are connected to the drawbar 17. The left lift cylinder 22 and the right lift cylinder 23 are connected to the front frame 11 via a lifter bracket 29. The stroke operation of the left lift cylinder 22 and the right lift cylinder 23 causes the drawbar 17 to swing up and down. As a result, the blade 16 moves up and down.

[0016] The drawbar shift cylinder 24 is connected to the drawbar 17 and the front frame 11. The drawbar shift cylinder 24 is connected to the front frame 11 via a lifter bracket 29. The drawbar shift cylinder 24 extends obliquely downward from the front frame 11 toward the drawbar 17. The stroke movement of the drawbar shift cylinder 24 causes the drawbar 17 to swing left and right. The blade tilt cylinder 25 is connected to the circle 18 and the blade 16. The stroke movement of the blade tilt cylinder 25 causes the blade 16 to rotate around the tilt axis 21.

[0017] The multiple actuators 22-26 include a rotary actuator 26. The rotary actuator 26 is connected to the draw bar 17 and the circle 18. The rotary actuator 26 rotates the circle 18 relative to the draw bar 17. This causes the blade 16 to rotate around a rotation axis extending in the vertical direction.

[0018] Figure 3 is a schematic diagram showing the configuration of the drive system of the motor grader 1. Figure 4 is a schematic diagram showing the configuration of the control system of the motor grader 1. As shown in Figure 3, the motor grader 1 includes a drive source 31, a hydraulic pump 32, a power transmission device 33, and a work equipment valve 34. The drive source 31 is, for example, an internal combustion engine. Alternatively, the drive source 31 may be an electric motor or a hybrid of an internal combustion engine and an electric motor. The hydraulic pump 32 is driven by the drive source 31 to discharge hydraulic oil.

[0019] The work implement valve 34 is connected to the hydraulic pump 32 and the plurality of hydraulic cylinders 22-25 via a hydraulic circuit. The work implement valve 34 includes a plurality of valves connected to the plurality of hydraulic cylinders 22-25, respectively. The work implement valve 34 controls the flow rate of hydraulic oil supplied from the hydraulic pump 32 to the plurality of hydraulic cylinders 22-25. The work implement valve 34 is, for example, an electromagnetic proportional control valve. Alternatively, the work implement valve 34 may be a hydraulic pilot type proportional control valve.

[0020] The rotary actuator 26 is a hydraulic motor. The work equipment valve 34 is connected to the hydraulic pump 32 and the rotary actuator 26 via a hydraulic circuit. The work equipment valve 34 controls the flow rate of hydraulic oil supplied from the hydraulic pump 32 to the rotary actuator 26. Alternatively, the rotary actuator 26 may be an electric motor.

[0021] The power transmission device 33 transmits the driving force from the drive source 31 to the rear wheels 4A-4D. The power transmission device 33 may include a torque converter and / or a plurality of speed change gears. Alternatively, the power transmission device 33 may be another transmission such as a hydraulic static transmission (HST) or a hydraulic mechanical transmission (HMT).

[0022] The motor grader 1 includes a steering cylinder 35 and a steering valve 36. The steering cylinder 35 is a hydraulic cylinder. The steering cylinder 35 expands and contracts using hydraulic oil from the hydraulic pump 32. The expansion and contraction of the steering cylinder 35 steers the front wheels 3A, 3B to the left and right.

[0023] The steering valve 36 is connected to the hydraulic pump 32 and the steering cylinder 35 via a hydraulic circuit. The steering valve 36 controls the flow rate of hydraulic oil supplied from the hydraulic pump 32 to the steering cylinder 35. The steering valve 36 is an electromagnetic control valve. Alternatively, the steering valve 36 may be a hydraulic pilot type control valve.

[0024] The motor grader 1 is equipped with articulation cylinders 37A, 37B and an articulation valve 38. The articulation valve 38 is a hydraulic cylinder. The articulation valve 38 expands and contracts using hydraulic oil from the hydraulic pump 32. As shown by the two-dot chain lines in Figures 5 and 6 , the articulation cylinders 37A, 37B expand and contract, causing the front frame 11 to articulate left and right relative to the rear frame 12.

[0025] The articulate valve 38 is connected to the hydraulic pump 32 and the articulate cylinders 37A, 37B via a hydraulic circuit. The articulate valve 38 controls the flow rate of hydraulic oil supplied from the hydraulic pump 32 to the articulate cylinders 37A, 37B. The articulate valve 38 is an electromagnetic control valve. Alternatively, the articulate valve 38 may be a hydraulic pilot type control valve.

[0026] As shown in Fig. 4, the motor grader 1 includes a controller 40. The controller 40 includes a storage device 401 and a processor 402. The processor 402 is, for example, a CPU, and executes a program for controlling the motor grader 1. The storage device 401 includes memories such as RAM and ROM, and auxiliary storage devices such as an SSD or HDD. The storage device 401 stores programs and data for controlling the motor grader 1.

[0027] The motor grader 1 includes an accelerator operating member 41, an FNR switching member 42, a steering operating member 43, and an articulating operating member 44. The accelerator operating member 41 can be operated by an operator to travel the motor grader 1. The accelerator operating member 41 includes, for example, an accelerator pedal. Alternatively, the accelerator operating member 41 may be another member such as a switch or a lever. The accelerator operating member 41 outputs a signal to the controller 40 in response to operation of the accelerator operating member 41 by the operator. The controller 40 controls the drive source 31 and the power transmission device 33 in response to operation of the accelerator operating member 41, thereby traveling the motor grader 1.

[0028] The FNR switching member 42 can be operated by an operator to switch the motor grader 1 between forward and reverse. The FNR switching member 42 can be operated between a neutral position, a forward position, and a reverse position. The FNR switching member 42 includes, for example, a switch. Alternatively, the FNR switching member 42 may be another member such as a lever. The FNR switching member 42 outputs a signal to the controller 40 in response to the operator's operation of the FNR switching member 42. The controller 40 controls the power transmission device 33 in response to the operation of the FNR switching member 42, thereby switching the motor grader 1 between forward and reverse.

[0029] The steering operation member 43 can be operated by an operator to steer the front wheels 3A, 3B left and right. The steering operation member 43 is a lever such as a joystick. Alternatively, the steering operation member 43 may be a member other than a lever, such as a steering wheel. The steering operation member 43 outputs a signal corresponding to the operation of the steering operation member 43 to the controller 40. The controller 40 controls the steering cylinder 35 in accordance with the operation of the steering operation member 43, thereby steering the front wheels 3A, 3B left and right.

[0030] The articulation operation member 44 can be operated by an operator to articulate the front frame 11 left and right relative to the rear frame 12. The articulation operation member 44 is a lever. Alternatively, the articulation operation member 44 may be another member such as a switch. The articulation operation member 44 outputs a signal corresponding to the operation of the articulation operation member 44 to the controller 40. The controller 40 controls the articulation cylinders 37A, 37B in accordance with the operation of the articulation operation member 44, thereby articulating the front frame 11 left and right relative to the rear frame 12.

[0031] The motor grader 1 includes a left lift operation member 45 and a right lift operation member 46. The left lift operation member 45 and the right lift operation member 46 are, for example, levers. Alternatively, the left lift operation member 45 and the right lift operation member 46 may be other members such as switches.

[0032] The left lift operating member 45 is operated by the operator to raise and lower the blade 16 by the left lift cylinder 22. The right lift operating member 46 is operated by the operator to raise and lower the blade 16 by the right lift cylinder 23. The left lift operating member 45 and the right lift operating member 46 can each be operated to a blade-up position, a neutral position, and a blade-down position. The left lift operating member 45 and the right lift operating member 46 each output a signal to the controller 40 in accordance with the operation of each operating member 45, 46 by the operator.

[0033] The controller 40 controls the left lift cylinder 22 in response to the operation of the left lift operation member 45, thereby raising and lowering the left end of the blade 16. Specifically, when the left lift operation member 45 is operated to the blade-up position, the controller 40 controls the left lift cylinder 22 to raise the left end of the blade 16 at a speed corresponding to the amount of operation of the left lift operation member 45. When the left lift operation member 45 is operated to the blade-down position, the controller 40 controls the left lift cylinder 22 to lower the left end of the blade 16 at a speed corresponding to the amount of operation of the left lift operation member 45.

[0034] The controller 40 raises and lowers the right end of the blade 16 in response to the operation of the right lift operation member 46. Specifically, when the right lift operation member 46 is operated to the blade-up position, the controller 40 controls the right lift cylinder 23 to raise the right end of the blade 16 at a speed corresponding to the amount of operation of the right lift operation member 46. When the right lift operation member 46 is operated to the blade-down position, the controller 40 controls the right lift cylinder 23 to lower the right end of the blade 16 at a speed corresponding to the amount of operation of the right lift operation member 46.

[0035] The motor grader 1 includes a drawbar shift operating member 47, a rotation operating member 48, and a blade tilt operating member 49. The drawbar shift operating member 47, the rotation operating member 48, and the blade tilt operating member 49 are, for example, levers. Alternatively, the drawbar shift operating member 47, the rotation operating member 48, and the blade tilt operating member 49 may be other members such as switches.

[0036] The drawbar shift operating member 47 is operated by the operator to swing the drawbar 17 left and right. The rotation operating member 48 is operated by the operator to rotate the circle 18 relative to the drawbar 17. The blade tilt operating member 49 is operated by the operator to rotate the blade 16 around the tilt axis 21. The drawbar shift operating member 47, the rotation operating member 48, and the blade tilt operating member 49 each output a signal to the controller 40 in response to the operation of each operating member 43-46 by the operator.

[0037] The controller 40 controls the drawbar shift cylinder 24 in response to operation of the drawbar shift operating member 47, thereby swinging the drawbar 17 left and right. The controller 40 controls the rotation actuator 26 in response to operation of the rotation operating member 48, thereby rotating the circle 18. The controller 40 controls the blade tilt cylinder 25 in response to operation of the blade tilt operating member 49, thereby rotating the blade 16 around the tilt axis 21.

[0038] The motor grader 1 includes a first attitude sensor 51 and a second attitude sensor 52. The first attitude sensor 51 detects the attitude of the vehicle body 2. The second attitude sensor 52 detects the attitude of the work implement 5. The first attitude sensor 51 and the second attitude sensor 52 are, for example, inertial measurement units (IMUs). As shown in FIG. 1 , the first attitude sensor 51 is attached to the front frame 11. The first attitude sensor 51 detects the pitch angle and roll angle of the vehicle body 2 with respect to the horizontal direction. The first attitude sensor 51 outputs signals indicating the pitch angle and roll angle of the vehicle body 2 with respect to the horizontal direction to the controller 40.

[0039] The second attitude sensor 52 is attached to the drawbar 17. The second attitude sensor 52 detects the pitch angle and roll angle of the drawbar 17 with respect to the horizontal direction. The second attitude sensor 52 outputs signals indicating the pitch angle and roll angle of the drawbar 17 with respect to the horizontal direction to the controller 40. The controller 40 calculates the pitch angle θ1 of the drawbar 17 with respect to the car body 2 shown in FIG. 7 based on the pitch angle of the car body 2 detected by the first attitude sensor 51 and the pitch angle of the drawbar 17 detected by the second attitude sensor 52.

[0040] The motor grader 1 includes a rotation angle sensor 53 and an articulate angle sensor 54. The rotation angle sensor 53 detects the rotation angle θ2 of the blade 16 relative to the drawbar 17 shown in Fig. 8. The rotation angle sensor 53 outputs a signal indicating the rotation angle θ2 of the blade 16 relative to the drawbar 17 to the controller 40.

[0041] The articulation angle sensor 54 detects the articulation angle θ3 of the front frame 11 with respect to the rear frame 12 shown in Figures 5 and 6. The articulation angle sensor 54 outputs a signal indicating the articulation angle θ3 of the front frame 11 with respect to the rear frame 12 to the controller 40.

[0042] The motor grader 1 includes an input device 55. The input device 55 can be operated by an operator to set the control of the motor grader 1. The input device 55 includes, for example, a touch panel. Alternatively, the input device 55 may include an operating member such as a switch or a button. The input device 55 outputs a signal indicating an input to the input device 55 by the operator to the controller 40.

[0043] The motor grader 1 includes an automatic blade control mode switching member 56. The mode switching member 56 is, for example, a switch. However, the mode switching member 56 may be another member such as a lever or a touch panel. The mode switching member 56 is operated by an operator to switch the automatic blade control mode. The automatic blade control includes automatic blade raising control and automatic blade lowering control.

[0044] In the automatic blade-raising control, when the left lift operating member 45 or the right lift operating member 46 returns to the neutral position after being operated to raise the blade for a predetermined first duration or longer while the vehicle body 2 is moving backward, the controller 40 controls the left lift cylinder 22 and the right lift cylinder 23 to raise the blade 16 to a predetermined target raised position. In the automatic blade-lowering control, when the left lift operating member 45 or the right lift operating member 46 returns to the neutral position after being operated to lower the blade for a predetermined second duration or longer while the vehicle body 2 is moving forward, the controller 40 controls the left lift cylinder 22 and the right lift cylinder 23 to lower the blade 16 to a predetermined target lowered position.

[0045] The mode switching member 56 outputs a signal to the controller 40 in response to the operation of the mode switching member 56. The controller 40 switches the automatic blade control mode between an off mode, a first mode, and a second mode in response to the operation of the mode switching member 56. In the off mode, the controller 40 disables both the automatic blade raising control and the automatic blade lowering control. In the first mode, the controller 40 enables both the automatic blade raising control and the automatic blade lowering control. In the second mode, the controller 40 enables the automatic blade raising control and disables the automatic blade lowering control. The automatic blade raising control and the automatic blade lowering control will be described below.

[0046] 9 is a flowchart showing the automatic blade raising control process. As shown in FIG. 9, in step S101, the controller 40 acquires data from the sensors. The controller 40 acquires data detected by the first attitude sensor 51, the second attitude sensor 52, the rotation angle sensor 53, and the articulation angle sensor 54.

[0047] In step S102, the controller 40 determines whether the vehicle body 2 is moving backward. As shown in Fig. 10A, the controller 40 determines that the vehicle body 2 is moving backward when the FNR switching member 42 is in the reverse position R. If the controller 40 determines that the vehicle body 2 is moving backward, the process proceeds to step S103.

[0048] In step S103, the controller 40 determines whether the left lift operating member 45 or the right lift operating member 46 is being operated to raise the blade. As shown in Fig. 10A, when the left lift operating member 45 or the right lift operating member 46 is in the blade-raising position U1, the controller 40 determines that the left lift operating member 45 or the right lift operating member 46 is being operated to raise the blade. When the left lift operating member 45 or the right lift operating member 46 is being operated to raise the blade, the process proceeds to step S104.

[0049] In step S104, the controller 40 raises the blade 16 in response to the operation of the lift operation members 45, 46. For example, when the left lift operation member 45 is operated to raise the blade, the left end of the blade 16 is raised in response to the operation of the left lift operation member 45. When the right lift operation member 46 is operated to raise the blade, the right end of the blade 16 is raised in response to the operation of the right lift operation member 46. When both the left lift operation member 45 and the right lift operation member 46 are operated to raise the blade, both the left and right ends of the blade 16 are raised in response to the operation of the left lift operation member 45 and the right lift operation member 46.

[0050] In step S105, the controller 40 determines whether the duration T1 after the start of the blade raising operation is equal to or greater than the first duration Th1. If the duration T1 after the start of the blade raising operation is equal to or greater than the first duration Th1, the process proceeds to step S106.

[0051] In step S106, the controller 40 determines whether the lift operation members 45, 46 have returned to the neutral position. As shown in Fig. 10B, if the lift operation members 45, 46 have returned to the neutral position N1, the process proceeds to step S107.

[0052] In step S107, the controller 40 determines whether the attitude of the work implement 5 is a predetermined risk attitude. The predetermined risk attitude indicates an attitude in which there is a risk that the blade 16 will interfere with the vehicle body 2 due to automatic blade raising control. The controller 40 determines that the attitude of the work implement 5 is a predetermined risk attitude, for example, when the roll angle of the drawbar 17 or the pitch angle θ1 of the blade 16 relative to the vehicle body 2 is equal to or greater than a predetermined threshold. Alternatively, the controller 40 may determine whether the attitude of the work implement 5 is a predetermined risk attitude based on the rotation angle θ2 or articulation angle θ3 degrees of the blade 16.

[0053] Alternatively, the predetermined risk posture may be a posture in which the blade 16 does not rise or fall perpendicular to the ground. For example, the controller 40 may determine that the posture of the work machine 5 is a predetermined risk posture when the left and right lift cylinders 22, 23 are significantly tilted from the vertical. If the posture of the work machine 5 is a predetermined risk posture, the controller 40 prohibits the automatic blade raising control. If the posture of the work machine 5 is not a predetermined risk posture, the processing proceeds to step S108. Note that if the controller 40 determines that the posture of the work machine 5 is a predetermined risk posture, it may prohibit the automatic blade raising control and issue an alarm to notify the operator of this.

[0054] In step S108, the controller 40 performs automatic blade-raising control to raise the blade 16 toward the target raised position. As shown in Fig. 10B, in the automatic blade-raising control, the controller 40 automatically raises the blade 16 even if the lift operating members 45, 46 are returned to the neutral position N1.

[0055] The controller 40 sets and stores a target ascent position in advance in response to an operation on the input device 55 by the operator. The target ascent position can be selected from a plurality of height levels. The plurality of height levels includes, for example, a high level and a low level. However, the plurality of height levels may include three or more levels. The controller 40 determines a height corresponding to the set height level as the target ascent position.

[0056] In step S109, the controller 40 determines whether the blade 16 has reached the target raised position. The controller 40 determines that the blade 16 has reached the target raised position when the cutting edge of the blade 16 has reached the target raised position. If the blade 16 has reached the target raised position, the controller 40 stops the raising of the blade 16 in step S110. As a result, the blade 16 stops at the target raised position, as shown in FIG. 10C .

[0057] If the left lift operating member 45 or the right lift operating member 46 is operated to lower the blade during the automatic blade raising control, the controller 40 cancels the automatic blade raising control. That is, the controller 40 stops the raising of the blade 16 and returns to the process from step S101.

[0058] Furthermore, if the left lift operating member 45 or the right lift operating member 46 is operated to raise the blade during the automatic blade raising control, the controller 40 temporarily suspends the automatic blade raising control. After that, if the left lift operating member 45 or the right lift operating member 46 returns to the neutral position N1, the controller 40 resumes the automatic blade raising control. That is, the controller 40 resumes the processing from step S108 onwards.

[0059] Next, the automatic blade lowering control will be described. Fig. 11 is a flowchart showing the process of the automatic blade lowering control. As shown in Fig. 11, in step S201, similar to step S101, the controller 40 acquires data from the sensor.

[0060] In step S202, the controller 40 determines whether the vehicle body 2 is moving forward. As shown in Fig. 12A, the controller 40 determines that the vehicle body 2 is moving forward when the FNR switching member 42 is in the forward position F. If the controller 40 determines that the vehicle body 2 is moving forward, the process proceeds to step S203.

[0061] In step S203, the controller 40 determines whether the left lift operating member 45 or the right lift operating member 46 is being operated to lower the blade. As shown in Fig. 12A, when the left lift operating member 45 or the right lift operating member 46 is in the blade lowering position D1, the controller 40 determines that the left lift operating member 45 or the right lift operating member 46 is being operated to lower the blade. When the left lift operating member 45 or the right lift operating member 46 is being operated to lower the blade, the process proceeds to step S204.

[0062] In step S204, the controller 40 lowers the blade 16 in response to the operation of the lift operation members 45, 46. For example, when the left lift operation member 45 is operated to lower the blade, the left end of the blade 16 is lowered in response to the operation of the left lift operation member 45. When the right lift operation member 46 is operated to lower the blade, the right end of the blade 16 is lowered in response to the operation of the right lift operation member 46. When both the left lift operation member 45 and the right lift operation member 46 are operated to lower the blade, both the left and right ends of the blade 16 are lowered in response to the operation of the left lift operation member 45 and the right lift operation member 46.

[0063] In step S205, the controller 40 determines whether the duration T2 after the start of the blade lowering operation is equal to or greater than a second duration Th2. The second duration Th2 may be the same as the first duration Th1. Alternatively, the second duration Th2 may be different from the first duration Th1. If the duration T2 after the start of the blade lowering operation is equal to or greater than the second duration Th2, the process proceeds to step S206.

[0064] In step S206, the controller 40 determines whether the lift operation members 45, 46 have returned to the neutral position N1. As shown in Fig. 12B, if the lift operation members 45, 46 have returned to the neutral position N1, the process proceeds to step S207.

[0065] In step S207, the controller 40 determines whether the attitude of the work implement 5 is a predetermined risk attitude. The predetermined risk attitude indicates an attitude in which there is a risk that the blade 16 will interfere with the vehicle body 2 due to the automatic blade lowering control. The predetermined risk attitude in the automatic blade lowering control may be the same as the predetermined risk attitude in the automatic blade raising control, or may be different. If the attitude of the work implement 5 is a predetermined risk attitude, the controller 40 prohibits the automatic blade lowering control. If the attitude of the work implement 5 is not a predetermined risk attitude, the processing proceeds to step S208.

[0066] In step S208, the controller 40 performs automatic blade lowering control to raise the blade 16 toward the target lowered position. As shown in Fig. 12B, in the automatic blade lowering control, the controller 40 automatically lowers the blade 16 even if the lift operating members 45, 46 are returned to the neutral position N1.

[0067] The controller 40 preliminarily sets and stores a target lowering position in response to an operator's operation of the input device 55. The target lowering position can be set more precisely than the target raised position. The target lowering position can be set arbitrarily. For example, the target position can be set by numerically inputting the target position into the input device 55. Alternatively, the operator can operate the lift operating member to position the blade 16 at a desired height, and then operate the input device 55 (for example, by pressing a setting button), causing the controller 40 to determine the height of the blade 16 at that time as the target lowering position.

[0068] In step S209, the controller 40 determines whether the blade 16 has reached the target lowered position. The controller 40 determines that the blade 16 has reached the target lowered position when the cutting edge of the blade 16 has reached the target lowered position. If the blade 16 has reached the target lowered position, the controller 40 stops the descent of the blade 16 in step S210. As a result, the blade 16 stops at the target lowered position, as shown in FIG. 12C .

[0069] If the left lift operating member 45 or the right lift operating member 46 is operated to raise the blade during the automatic blade lowering control, the controller 40 cancels the automatic blade lowering control. That is, the controller 40 stops the lowering of the blade 16 and returns to the processing from step S201.

[0070] Furthermore, if the left lift operating member 45 or the right lift operating member 46 is operated to lower the blade during the automatic blade lowering control, the controller 40 temporarily suspends the automatic blade lowering control. After that, if the left lift operating member 45 or the right lift operating member 46 returns to the neutral position N1, the controller 40 resumes the automatic blade lowering control. That is, the controller 40 resumes the processing from step S208 onwards.

[0071] Next, the control of the lift cylinders 22, 23 in the automatic blade control will be described. Figure 13 is a flowchart showing the process of controlling the lift cylinders 22, 23 in the automatic blade control. As shown in Figure 13, in step S301, the controller 40 acquires the actual pitch angle of the blade 16 relative to the vehicle body 2. The controller 40 acquires the above-mentioned pitch angle θ1 of the drawbar 17 relative to the vehicle body 2 as the actual pitch angle of the blade 16.

[0072] In step S302, the controller 40 acquires the target pitch angle of the blade 16 relative to the vehicle body 2. In the automatic blade-raising control, the controller 40 calculates the pitch angle of the blade 16 corresponding to the target raised position as the target pitch angle of the blade 16. In the automatic blade-lowering control, the controller 40 calculates the pitch angle of the blade 16 corresponding to the target lowered position as the target pitch angle of the blade 16.

[0073] In step S303, the controller 40 determines a spool stroke command. The spool stroke command is a command value for the spool stroke of the work implement valve 34 for controlling the lift cylinders 22, 23. The controller 40 stores spool stroke-actual pitch angle data. The spool stroke-actual pitch angle data is data that defines the relationship between the spool stroke command and the actual pitch angle of the blade 16. The spool stroke-actual pitch angle data will be described later.

[0074] In step S304, the controller 40 controls the work implement valve 34 based on the spool stroke command. As a result, in the automatic blade-raising control, the lift cylinders 22, 23 are controlled so that the blade 16 rises at a speed corresponding to the spool stroke command. In the automatic blade-lowering control, the lift cylinders 22, 23 are controlled so that the blade 16 descends at a speed corresponding to the spool stroke command.

[0075] 14 is a diagram showing an example of spool stroke-actual pitch angle data. In FIG. 14, L1 shows spool stroke-actual pitch angle data under automatic blade-up control. L2 shows spool stroke-actual pitch angle data under automatic blade-down control.

[0076] A positive value of the spool stroke command indicates that the work equipment valve 34 is controlled to retract the lift cylinders 22, 23, i.e., to raise the blade 16. A negative value of the spool stroke command indicates that the work equipment valve 34 is controlled to extend the lift cylinders 22, 23, i.e., to lower the blade 16.

[0077] The larger the absolute value of the spool stroke command, the faster the stroke speed of the lift cylinders 22, 23. In other words, the larger the absolute value of the spool stroke command, the faster the rate of change of the actual pitch angle of the blade 16, and the faster the lifting and lowering speed of the blade 16. Conversely, the smaller the absolute value of the spool stroke command, the slower the rate of change of the actual pitch angle of the blade 16, and the slower the lifting and lowering speed of the blade 16.

[0078] Furthermore, the actual pitch angle decreases as the blade 16 rises. In automatic blade raising control, as shown in the spool stroke-actual pitch angle data L1, the controller 40 sets the spool stroke command to the first command value S1A until the actual pitch angle decreases and reaches the actual pitch angle A1 at the deceleration start point P1. During the period from the actual pitch angle A1 at the deceleration start point until the actual pitch angle reaches the target pitch angle A2 corresponding to the target raised position, the controller 40 decreases the spool stroke command to the second command value S2A as the actual pitch angle decreases. In other words, the controller 40 slows down the rate of change of the actual pitch angle, i.e., the raising speed of the blade 16, as the blade 16 rises.

[0079] Conversely, the actual pitch angle increases as the blade 16 descends. In the automatic blade lowering control, as shown in the spool stroke-actual pitch angle data L2, the controller 40 sets the spool stroke command to the third command value S1B until the actual pitch angle increases and reaches the actual pitch angle B1 at the deceleration start point P2. During the period from the actual pitch angle B1 at the deceleration start point P2 to the target pitch angle B2 corresponding to the target lowering position, the controller 40 increases the spool stroke command to the fourth command value S2B as the actual pitch angle increases. In other words, the controller 40 slows down the rate of change of the actual pitch angle, i.e., the descent speed of the blade 16, as the blade 16 descends.

[0080] In step S109 of the automatic blade-raising control described above, the controller 40 determines that the blade 16 has reached the target raised position when the actual pitch angle reaches the target pitch angle A2. In step S209 of the automatic blade-lowering control, the controller 40 determines that the blade 16 has reached the target lowered position when the actual pitch angle reaches the target pitch angle B2.

[0081] According to the motor grader 1 according to the present embodiment described above, when the vehicle body 2 is moving backward, the operator can raise the left lift operating member 45 or the right lift operating member 46 for at least the first duration Th1 and then return it to the neutral position. This causes the automatic blade raising control to automatically raise the blade 16 to the target raised position. This makes other operations, such as steering, easier, and improves the operability of the motor grader 1.

[0082] When the vehicle body 2 is moving forward, the operator can lower the left lift operating member 45 or the right lift operating member 46 for at least the second duration Th2 and then return it to the neutral position. This causes the automatic blade lowering control to automatically lower the blade 16 to the target lowering position. This makes other operations, such as steering, easier, and improves the operability of the motor grader 1.

[0083] The rate of change of the actual pitch angle of the blades 16 is controlled in accordance with the actual pitch angle. Specifically, the rate of change of the actual pitch angle of the blades 16 is fast until the actual pitch angle of the blades 16 reaches the actual pitch angle of the deceleration start point, and then decelerates after the deceleration start point until the actual pitch angle of the blades 16 reaches the target pitch angle. This allows the blades 16 to be raised to the target raised position quickly and accurately.

[0084] 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.

[0085] The motor grader 1 may be remotely operable. In this case, the above-described operating members and the controller 40 may be disposed outside the motor grader 1.

[0086] The automatic blade control process is not limited to that of the above embodiment and may be modified. For example, in the automatic blade lowering control, the controller 40 may store the height of the blade 16 when the vehicle body 2 is switched from forward to reverse as the target lowering position. Alternatively, the target lowering position may be selectable from a plurality of height levels.

[0087] The controller 40 may cancel the automatic blade-raising control even when the left lift operating member 45 or the right lift operating member 46 is operated to raise the blade during the automatic blade-raising control. The controller 40 may also cancel the automatic blade-lowering control even when the left lift operating member 45 or the right lift operating member 46 is operated to lower the blade during the automatic blade-lowering control.

[0088] According to the present disclosure, the operability of a motor grader can be improved.

[0089] 2: Vehicle body, 3A, 3B, 4A-4D: Traveling wheels, 5: Work equipment, 16: Blade, 22: Left lift cylinder, 23: Right lift cylinder, 40: Controller, 45: Left lift operating member, 46: Right lift operating member, 51: First attitude sensor, 52: Second attitude sensor, 55: Input device

Claims

1. A system for controlling a motor grader, the motor grader including: a vehicle body including running wheels; a work machine including a blade and operably connected to the vehicle body; a left lift cylinder connected to the work machine and raising and lowering the blade; and a right lift cylinder connected to the work machine and raising and lowering the blade; the system comprises: a left lift operating member operated to raise and lower the blade by the left lift cylinder; a right lift operating member operated to raise and lower the blade by the right lift cylinder; and a controller capable of receiving a signal corresponding to the operation of the left lift operating member and a signal corresponding to the operation of the right lift operating member, the controller controlling the left lift cylinder and the right lift cylinder to perform automatic blade raising control to raise the blade to a predetermined target raised position when the left lift operating member or the right lift operating member returns to a neutral position after being operated to raise the blade for a predetermined first duration or more when the vehicle body is moving backwards.

2. The system according to claim 1, further comprising an input device operable by an operator, wherein the controller sets the target lifted position in response to an operation on the input device.

3. The system according to claim 1, further comprising a sensor for detecting the attitude of the work machine, wherein the controller prohibits the automatic blade raising control when the attitude of the work machine is a predetermined risk attitude.

4. The system according to claim 1, wherein the controller cancels the automatic blade raising control when the left lift operating member or the right lift operating member is operated to lower the blade during the automatic blade raising control.

5. The system described in claim 1, wherein the controller temporarily suspends the automatic blade raising control when the left lift operating member or the right lift operating member is operated to raise the blade during the automatic blade raising control, and resumes the automatic blade raising control when the left lift operating member or the right lift operating member returns to a neutral position.

6. The system described in claim 1, wherein when the left lift operating member or the right lift operating member returns to a neutral position after being operated to lower the blade for a predetermined second duration or longer while the vehicle body is moving forward, the controller controls the left lift cylinder and the right lift cylinder to execute automatic blade lowering control to lower the blade to a predetermined target lowering position.

7. The system according to claim 6, wherein the controller cancels the automatic blade lowering control when the left lift operating member or the right lift operating member is operated to raise the blade during the automatic blade lowering control.

8. The system described in claim 6, wherein the controller temporarily suspends the automatic blade lowering control when the left lift operating member or the right lift operating member is operated to lower the blade during the automatic blade lowering control, and resumes the automatic blade lowering control when the left lift operating member or the right lift operating member returns to a neutral position.

9. The system according to claim 6, further comprising an input device operable by an operator, wherein the controller sets the target ascending position and the target descending position in response to an operation on the input device, and the target descending position can be set more precisely than the target ascending position.

10. The system of claim 9, wherein the target elevation position is selectable from a plurality of height levels.

11. The system according to claim 9, wherein the target lowered position can be arbitrarily set.

12. The system according to claim 6, wherein the controller stores the height of the blade when the vehicle body is switched from forward to reverse as the target lowered position.

13. A method for controlling a motor grader, the motor grader including: a vehicle body including running wheels; a work machine including a blade and operably connected to the vehicle body; a left lift cylinder connected to the work machine and raising and lowering the blade; and a right lift cylinder connected to the work machine and raising and lowering the blade, the method comprising: receiving a signal in response to operation of a left lift operating member operated to raise and lower the blade by the left lift cylinder; receiving a signal in response to operation of a right lift operating member operated to raise and lower the blade by the right lift cylinder; and executing automatic blade raising control to raise the blade to a predetermined target raised position by controlling the left lift cylinder and the right lift cylinder when the left lift operating member or the right lift operating member returns to a neutral position after being operated to raise the blade for a predetermined first duration or longer while the vehicle body is moving in reverse.

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