Work vehicle, system including a work vehicle, and method for controlling a work vehicle

Abstract

An operator seat (5S) is arranged on a floor (5F). A seat suspension (40) is arranged between the floor (5F) and the operator seat (5S) and includes a variable damping element (20) in which a damping force can be switched between at least a first damping force and a second damping force that is greater than the first damping force. A displacement sensor (41) detects a relative displacement of the operator seat (5S) with respect to the floor (5F). A control unit (50) switches the damping force of the variable damping element (20) from the first damping force to the second damping force when a peak value of the relative displacement detected by the displacement sensor (41) is greater than a first predetermined value (PL1).

Description

TECHNICAL AREA

[0001] The disclosure relates to a work vehicle, a system including a work vehicle, and a method for controlling a work vehicle. STATE OF THE ART

[0002] In work vehicles such as hydraulic excavators and wheel loaders, a so-called rigid seat was used, in which an operator's seat (operator's seat) was fixed to the floor of an operator's cabin (cab). However, to improve driving comfort and reduce operator fatigue, a work vehicle was proposed in which a mechanical suspension, air suspension, or similar device was arranged between the operator's seat and the floor.

[0003] Furthermore, there is a work vehicle in which the stiffness level of a damper incorporated in a seat suspension can be adjusted to a multitude of levels according to the operator's wishes. A work vehicle in which the stiffness level of a damper can be adjusted is disclosed in JP 2000-85435 A (Patent Document 1), JP 2000-85436 A (Patent Document 2) and the like. LIST OF COUNTERPOINTS Patent Literature Patent Document 1: JP 2000-85435 A Patent Document 2: JP 2000-85436 A BRIEF DESCRIPTION OF THE INVENTION Technical Problem

[0004] A work vehicle frequently travels on a construction site with a poor surface and often drives over a step while driving. Given this, there is a need to improve driving comfort even in such situations.

[0005] One objective of the present disclosure is to provide a work vehicle, a system including a work vehicle, and a method for controlling a work vehicle that can improve driving comfort during travel. Solution to the problem

[0006] A work vehicle and a system including a work vehicle of the present disclosure each comprise a work device, a floor, an operator's seat, a seat suspension, a displacement sensor, and a control unit. The operator's seat is arranged on the floor. The seat suspension is arranged between the floor and the operator's seat and includes a variable damping element in which a damping force is switchable between at least a first damping force and a second damping force that is greater than the first damping force. The displacement sensor detects a relative displacement of the operator's seat with respect to the floor. The control unit switches the damping force of the variable damping element from the first damping force to the second damping force when a peak value of the relative displacement detected by the displacement sensor is greater than a first predetermined value.

[0007] A method for controlling a work vehicle of the present disclosure is a method for controlling a work vehicle including a work device, a floor, an operator's seat arranged on the floor, a seat suspension arranged between the floor and the operator's seat, which includes a variable damping element in which a damping force is switchable at least between a first damping force and a second damping force which is greater than the first damping force, and a displacement sensor which detects a relative displacement amount of the operator's seat with respect to the floor, and includes the following steps.

[0008] The system detects the relative displacement of the operator's seat with respect to the floor. It determines whether a peak value of the relative displacement detected by the displacement sensor is greater than a first predetermined value. If the peak value is found to be greater than the first predetermined value, the damping force of the variable damping element is switched from the first damping force to the second damping force. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0009] According to the present disclosure, it is possible to achieve a work vehicle, a system including a work vehicle and a method for controlling a work vehicle that can improve driving comfort during the journey. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a side view illustrating a configuration of a wheel loader (an example of a work vehicle) in an embodiment of the present disclosure. Fig. Figure 2 is a diagram illustrating a configuration of a system including a work vehicle in an embodiment of the present disclosure. Fig. Figure 3 is a cross-sectional view illustrating a configuration of a variable damping element incorporated into the system including a work vehicle in the embodiment of the present disclosure. Fig. Figure 4 is a diagram illustrating functional blocks of a control unit that is incorporated into the system, including a work vehicle, in the embodiment of the present disclosure. Fig. 5(A) is a diagram illustrating a state in which the work vehicle is operating, Fig. 5(B) is a diagram illustrating a temporal variation of a relative displacement amount between the floor of an operator's cabin and an operator's seat during travel, Fig. 5(C) is a diagram illustrating a time variation of the acceleration of the floor (the base) of the operator cabin, and Fig. Figure 5(D) is a diagram illustrating a time variation of a command current value applied to the variable damper element. Fig. Figure 6 is a first flowchart showing a method for controlling a work vehicle in an embodiment of the present disclosure. Fig. Figure 7 is a second flowchart showing the method for controlling a work vehicle in the embodiment of the present disclosure. Fig. Figure 8 is a third flowchart showing a method for controlling a work vehicle in the embodiment of the present disclosure. DESCRIPTION OF EXECUTION FORMS

[0010] An embodiment of the present disclosure is described below with reference to the drawings.

[0011] In the description and drawings, identical or corresponding components are designated with identical reference numerals, and duplicate descriptions are not repeated. Furthermore, configurations may be omitted or simplified in the drawings to simplify the description.

[0012] In the following description, "top", "bottom", "front", "back", "left" and "right" refer to directions in relation to an operator seated in a 5S operator seat in a Fig. Cabin 5 is pictured in section 1. Fig. 1 is a forward and reverse direction indicated by Z, the forward direction is indicated by Zf and the reverse direction by Zb. Furthermore, in Fig. 2. An up-and-down direction is marked with Y. Configuration of the work vehicle

[0013] As an example of a work vehicle in the present embodiment, with reference to Fig. Figure 1 describes a configuration of a wheel loader. It should be noted that the work vehicle in the present embodiment is not limited to the wheel loader. The work vehicle in the present embodiment simply needs to be a work vehicle including a work attachment and an operator's seat, and can be a hydraulic excavator, a bulldozer, a motor grader, or the like.

[0014] Fig. Figure 1 is a side view illustrating a configuration of a wheel loader in one embodiment of the present disclosure. As in Fig. As illustrated in Figure 1, the wheel loader 1 in the present embodiment includes a chassis 2 and a working attachment 3. The working attachment 3 is arranged on the chassis 2. The chassis 2 includes a vehicle body frame 10, a pair of front wheels 4, the operator's cab 5, an engine compartment 6, a pair of rear wheels 7, and a steering cylinder 9. The wheel loader 1 performs earthmoving and sand loading operations or the like using the working attachment 3.

[0015] The vehicle body frame 10 is of the so-called articulated type (swivel type) and includes a front frame 11, a rear frame 12, and a coupling shaft section 13. The front frame 11 is arranged in the forward direction Zf of the rear frame 12. The coupling shaft section 13 is provided in the center of the vehicle body frame 10 in the left-and-right direction (vehicle width direction) and rotatably couples the front frame 11 and the rear frame 12 together. The pair of front wheels 4 are mounted to the left and right of the front frame 11. The pair of rear wheels 7 are also mounted to the left and right of the rear frame 12.

[0016] The working device 3 is driven by hydraulic oil from a working device pump, which is omitted from the illustration. The working device 3 includes a boom 14, a bucket 15, a lifting cylinder 16, a bucket cylinder 17, and an angle lever 18. The boom 14 is mounted on the front frame 11. The bucket 15 is mounted at a distal tip end of the boom 14.

[0017] The lifting cylinder 16 and the bucket cylinder 17 are hydraulic cylinders. One end of the lifting cylinder 16 is attached to the front frame 11, and the other end of the lifting cylinder 16 is attached to the boom 14. The boom 14 pivots up and down by extending and retracting the lifting cylinder 16. One end of the bucket cylinder 17 is attached to the front frame 11, and the other end of the bucket cylinder 17 is attached to the bucket 15 via an angle lever 18. The bucket 15 pivots up and down by extending and retracting the bucket cylinder 17.

[0018] The operator's cab 5 is located on the rear frame 12. The cab 5 contains the operator's seat 5S, on which an operator can sit, a steering wheel, a lever for operating the implement 3, various switches, a display device, and the like. The engine compartment 6 is located on the rear frame 12 in the reverse direction Zb of the operator's cab 5 and houses an engine. System configuration including work vehicle

[0019] Next, with reference to Fig. 2 to Fig. 4 describes a configuration of a system that includes the work vehicle in the present embodiment.

[0020] Fig. Figure 2 is a diagram illustrating a configuration of a system including a work vehicle in an embodiment of the present disclosure. Fig. Figure 3 is a cross-sectional view illustrating a configuration of a variable damping element incorporated into the system including a work vehicle in the embodiment of the present disclosure. Fig. Figure 4 is a diagram illustrating functional blocks of a control unit that is incorporated into the system, including a work vehicle, in the embodiment of the present disclosure.

[0021] As in Fig. As illustrated in Figure 2, the system includes a work vehicle, a seat suspension 40, a displacement sensor 41, a current adjustment device 42, an acceleration sensor 43 and a control unit 50.

[0022] The operator cabin 5 encloses a floor 5F. The operator seat 5S is located on the floor 5F of the operator cabin 5. The seat suspension 40 is located between the floor 5F and the operator seat 5S.

[0023] The seat suspension 40 includes a variable damping element 20 and an elastic element 30. The variable damping element 20 absorbs vibrations of the operator seat 5S in the up-and-down direction Y. The variable damping element 20 is configured to change the damping force of the vibrations of the operator seat 5S in the up-and-down direction Y. The damping force in the variable damping element 20 can be switched between at least the first damping force and a second damping force that is greater than the first. One end (for example, a lower end) of the variable damping element 20 is attached to the floor 5F, and the other end (for example, an upper end) is attached to the operator seat 5S.

[0024] The elastic element 30 absorbs vibrations of the operator seat 5S in the up-and-down direction Y that cannot be completely absorbed by the variable damping element 20. The elastic element 30 is configured, for example, as a spring. One end of the elastic element 30 (for example, a lower end) is attached to the floor 5F, and the other end (for example, an upper end) is attached to the operator seat 5S.

[0025] Each end of the variable damping element 20 and the elastic element 30 can be attached directly to the floor 5F or indirectly via a bracket or the like. Furthermore, the other end of the variable damping element 20 and the elastic element 30 can be attached directly to the operator seat 5S or indirectly via a bracket or the like.

[0026] The displacement sensor 41 detects a relative displacement of the operator seat 5S with respect to the floor 5F. For example, the displacement sensor 41 is attached to the floor 5F. The displacement sensor 41 can be attached directly to the floor 5F or indirectly via a bracket or the like. Furthermore, the displacement sensor 41 can, for example, be attached to the operator seat 5S. In such a case, the displacement sensor 41 can be attached directly to the operator seat 5S or indirectly via a bracket or the like.

[0027] The current adjusting device 42 is electrically connected to a coil 25 ( Fig. 3) of the variable damping element 20. The current adjusting device 42 adjusts the amount of current supplied to the coil 25 of the variable damping element 20. For example, the current adjusting device 42 can switch between a state of current supply to the coil 25 of the variable damping element 20 and a state of interrupted current supply.

[0028] The accelerometer 43 detects an acceleration of the ground 5F. For example, the accelerometer 43 is attached to the ground 5F. The accelerometer 43 can be attached directly to the ground 5F or it can be attached indirectly via a bracket or the like.

[0029] The control unit 50 includes a processor, main memory, and storage. The processor is, for example, a central processing unit (CPU). The main memory includes, for example, non-volatile memory such as read-only memory (ROM) and volatile memory such as random-access memory (RAM). The control unit 50 reads a program stored in storage, loads the program into main memory, and executes a predetermined process according to the program.

[0030] The control unit 50 is electrically connected to the displacement sensor 41, the current adjustment device 42, and the acceleration sensor 43. The control unit 50 acquires displacement data detected by the displacement sensor 41. The control unit 50 controls the current adjustment device 42 based on the displacement data detected by the displacement sensor 41. The control unit 50 acquires acceleration data detected by the acceleration sensor 43. The control unit 50 controls the current adjustment device 42 based on the acceleration data detected by the acceleration sensor 43. The control unit 50 controls the current adjustment device 42 to adjust the amount of current applied to the coil 25 of the variable damping element 20. In doing so, the control unit 50 sets the damping force of the variable damping element 20 to at least between the first damping force and the second damping force.

[0031] For example, the first damping force is a damping force of the variable damping element 20 while the current supply to the coil 25 of the variable damping element 20 is interrupted. For example, the second damping force is a damping force of the variable damping element 20 while a current is supplied to the coil of the variable damping element 20.

[0032] The first damping force, however, only needs to be smaller than the second damping force and can be a damping force while a current is supplied to the coil 25 of the variable damping element 20. In such a case, the first damping force is a damping force while a current is supplied, the current being smaller than the current applied to the coil 25 of the variable damping element 20 when the second damping force is detected.

[0033] The floor 5F simply needs to be a base supported by the chassis 2 and can be an element that supports the operator seat 5S via a means of the seat suspension 40.

[0034] It should be noted that the control unit 50 can be mounted on the wheel loader 1 or located remotely from the wheel loader 1. If the control unit 50 is located remotely from the wheel loader 1, it can be wirelessly connected to the position sensor 41, the current adjusting device 42, the acceleration sensor 43, and the like. The control unit 50 can also be housed in a server that is separate from the wheel loader 1.

[0035] As in Fig. As illustrated in Figure 3, the variable damping element 20 includes a cylinder 21, a piston 22, a piston rod 23, a diaphragm 24, the coil 25, a wiring line 26, a magnetorheological fluid 27 and a sealing bearing 28.

[0036] The cylinder 21 has a tubular shape (for example, a cylindrical shape). The piston 22 and the diaphragm 24 are arranged in the tubular interior of the cylinder 21. The piston 22 is displaceable along an axial direction AX of the cylinder 21 while remaining in contact with the inner circumferential surface of the cylinder 21.

[0037] The piston rod 23 comprises a first end section and a second end section, which face each other in the axial direction AX. The first end section of the piston rod 23 is connected to the piston 22 and is positioned inside the cylinder 21. The second end section of the piston rod 23 is positioned outside the cylinder 21. The piston rod 23 is supported by the sealing bearing 28 such that it is movable in the axial direction AX with respect to the cylinder 21.

[0038] The interior of the cylinder 21 is divided by the piston 22 into a first fluid chamber 21A and a second fluid chamber 21B. The piston 22 encloses an annular opening 22a that connects the first fluid chamber 21A and the second fluid chamber 21B. The annular opening 22a penetrates the piston 22 in the axial direction AX.

[0039] Both the first fluid chamber 21A and the second fluid chamber 21B, as well as the annular opening 22a, are filled with the magnetorheological fluid 27. The magnetorheological fluid 27 changes its viscosity according to the strength of a magnetic field acting upon it. For example, the magnetorheological fluid 27 exists in a low-viscosity liquid state when no magnetic field is applied. When a magnetic field is applied, the viscosity increases, and the fluid behaves like a semi-solid. The magnetorheological fluid 27 is, for example, a fluid in which ferromagnetic fine particles with a diameter of 1 µm to 10 µm are uniformly dispersed in a liquid such as oil and water.

[0040] The diaphragm 24 divides the interior of the cylinder 21 into the second fluid chamber 21B and a gas chamber 21C. The gas chamber 21C acts as an accumulator. A free piston can also be used instead of the diaphragm.

[0041] The coil 25 is provided inside the piston 22. The coil 25 is energized to generate a magnetic field, and the magnetic field acts on the magnetorheological fluid 27. The wiring line 26 is electrically connected to the coil 25. The coil 25 is electrically connected to the current-adjusting device 42 via the wiring line 26. This allows the current-adjusting device 42 to adjust the amount of current supplied to the coil 25 via the wiring line 26.

[0042] As in Fig. As illustrated in Figure 4, the control unit 50 includes a displacement information acquisition unit 51, a displacement information determination unit 52, a damping force control unit 53, an acceleration information acquisition unit 54, an acceleration information determination unit 55, and a memory 56. The displacement information acquisition unit 51 acquires a signal indicating the relative displacement of the operator seat 5S with respect to the floor 5F in the up-and-down direction Y, which is detected by the displacement sensor 41.

[0043] The displacement information determination unit 52 detects a peak value of the relative displacement amount detected by the displacement information acquisition unit 51. The displacement information determination unit 52 determines whether the detected peak value of the relative displacement amount is greater than a first predetermined value PL1 ( Fig. 5(B)). When the determination is performed, the displacement information determination unit 52 refers to the first predetermined value PL1 stored in the memory 56. The damping force control unit 53 outputs a command current to control the current adjustment device 42, based on the determination result of the displacement information determination unit 52.

[0044] When the determination result, indicating that the peak value of the relative displacement magnitude is greater than the first predetermined value PL1, is received by the displacement information determination unit 52, the damping force control unit 53 issues a command current to the current setting device 42 to switch the damping force of the variable damping element 20 from the first damping force to the second damping force. If it is thus determined that the peak value of the relative displacement magnitude is greater than the first predetermined value PL1, the control unit 50 switches the damping force of the variable damping element 20 from the first damping force to the second damping force.

[0045] Furthermore, when the displacement information determination unit 52 detects that the peak value of the relative displacement magnitude is equal to or less than the first predetermined value PL1, the damping force control unit 53 outputs a command current to the current adjustment device 42 to maintain the damping force of the variable damping element 20 at the current damping force. In this way, the control unit 50 maintains the damping force of the variable damping element 20 at the current damping force when it is determined that the peak value of the relative displacement magnitude is equal to or less than the first predetermined value PL1.

[0046] Furthermore, the displacement information determination unit 52 determines whether an absolute value of a peak in the recorded relative displacement amount is smaller than a second predetermined value PL2 ( Fig. 5(B)). The second predetermined value PL2 is a value that is smaller than the first predetermined value PL1. When the determination is carried out, the displacement information determination unit 52 refers to the second predetermined value PL2, which is stored in memory 56.

[0047] When the determination result, indicating that the absolute value of the peak of the relative displacement magnitude is less than the second predetermined value PL2, is received by the displacement information determination unit 52, the damping force control unit 53 issues a command current to the current setting device 42 to switch the damping force of the variable damping element 20 from the second damping force to the first damping force. If it is thus determined that the absolute value of the peak of the relative displacement magnitude is less than the second predetermined value PL2, the control unit 50 switches the damping force of the variable damping element 20 from the second damping force to the first damping force.

[0048] The acceleration information acquisition unit 54 acquires a signal indicating the acceleration of the ground 5F in the up-and-down direction Y, as detected by the accelerometer 43. The acceleration information determination unit 55 determines whether an absolute value of a first peak in an acceleration waveform of the ground 5F, acquired by the acceleration information acquisition unit 54, is greater than an absolute value of a second peak immediately preceding the first peak. For example, in Fig. As illustrated in Figure 5(C), the acceleration information determination unit 55 determines whether an absolute value α1 of a first peak PB1 in a ground acceleration waveform 5F is greater than an absolute value α2 of a second peak PB2 immediately preceding the first peak PB1. In this state, the acceleration information determination unit 55 can refer to a ground acceleration waveform 5F stored in the memory 56. The memory 56 can store acceleration information (including acceleration peak values) acquired by the acceleration information determination unit 55.

[0049] The damping force control unit 53 outputs a command current to the current adjustment device 42 to control the damping force of the variable damping element 20, based on the determination result of the acceleration information determination unit 55. When the determination result, indicating that the absolute value of the first peak is greater than the absolute value of the second peak, is received from the acceleration information determination unit 55, the damping force control unit 53 outputs a command current to the current adjustment device 42 to switch the damping force of the variable damping element 20 from the second damping force to the first damping force. If it is thus determined that the absolute value of the first peak is greater than the absolute value of the second peak, the control unit 50 switches the damping force of the variable damping element 20 from the second damping force to the first damping force.

[0050] The current adjusting device 42 sets a current value that is supplied to the coil 25 of the variable damping element 20, based on the command current detected by the damping force control unit 53. For example, if the command current to adjust the variable damping element 20 to the first damping force is detected by the damping force control unit 53, the current adjusting device 42 does not supply any current to the coil 25 of the variable damping element 20 (it interrupts the current supply). Conversely, if the command current to adjust the variable damping element 20 to the second damping force is detected by the damping force control unit 53, the current adjusting device 42 supplies a current to the coil 25 of the variable damping element 20.In this way, the current adjusting device 42 adjusts the damping force of the variable damping element 20 by switching on / off control to supply a current to the coil 25 of the variable damping element 20 or by interrupting the current supply.

[0051] Furthermore, the current-adjusting device 42 can adjust the damping force of the variable damping element 20 by a method other than the on / off control described above. For example, the current-adjusting device 42 can adjust the damping force of the variable damping element 20 by changing (increasing or decreasing) the amount of current supplied to the coil 25 of the variable damping element 20. In particular, when the damping force of the variable damping element 20 is set to the first damping force, control can be carried out such that the amount of current supplied to the coil 25 is reduced. When the damping force of the variable damping element 20 is set to the second damping force, control can be carried out such that the amount of current supplied to the coil 25 is increased. Procedure for controlling the work vehicle

[0052] Next, with reference to Fig. 5 to Fig. 8 a method for controlling a work vehicle in the present embodiment is described, wherein the focus is on a state in which the wheel loader 1, for example, drives over a step while driving.

[0053] Fig. 5(A) is a diagram illustrating a state in which the work vehicle is operating, Fig. 5(B) is a diagram illustrating the temporal variation of a relative displacement amount between the floor of an operator's cabin and an operator's seat during travel. Fig. Figure 5(C) is a diagram illustrating the time variation of the acceleration of the floor (the base) of the operator cabin, and Fig. Figure 5(D) is a diagram illustrating the time variation of a command current value applied to the variable damper element. Fig. 6 to Fig. Figure 8 are flowcharts that show a method for controlling a work vehicle in an embodiment of the present disclosure.

[0054] As in Fig. As illustrated in Figure 5(A), the front wheels 4 of the wheel loader 1 can travel over a step ST while moving forward, and then the rear wheels 7 can travel over the step ST. In such a case, the relative displacement of the operator's seat 5S with respect to the floor 5F of the operator's cab 5 changes in the up-and-down direction Y, as shown in Figure 5(A). Fig. 5(B) illustrates.

[0055] It should be noted that the in Fig. 5(B) illustrated arrow AR1 and arrow AR3 in Fig. 5(C) each represents the time at which the front wheels 4 of the wheel loader 1 pass over step ST. Furthermore, arrow AR2 points in Fig. 5(B) and the AR4 arrow in Fig. 5(C) each indicates a time when the rear wheels 7 of the wheel loader 1 pass over stage ST.

[0056] Furthermore, each of the in Fig. 5(D) illustrated arrows ARA, ARC, and ARD indicate a time when the relative displacement amount reaches each of the peak values ​​PA1, PA2, and PA3, as shown in Fig. 5(B) illustrates this. Furthermore, the information in Fig. Figure 5(D) illustrates arrow ARB at a time when the acceleration of the floor 5F of the operator cabin in the up-and-down direction Y reaches the peak value PB1, as shown in Figure 5(D). Fig. 5(C) illustrates.

[0057] As in Fig. As illustrated in Figure 5(B), the floor 5F of the operator's cab 5 is pushed upwards by the impact when the front wheels 4 of the wheel loader 1 drive over the step ST. This causes the floor 5F to approach the operator's seat 5S via the seat suspension 40, and the operator's seat 5S is displaced relative to the floor 5F in a negative direction. The operator's seat 5S is then returned to its original position by a restoring force of the elastic element 30 ( Fig. 2) separated from the floor 5F and is relatively displaced in the positive direction with respect to the floor 5F. Thereafter, the relative displacement of the operator seat 5S with respect to the floor 5F gradually decreases by repeating the displacement in the negative direction and the displacement in the positive direction.

[0058] When the rear wheels 7 of the wheel loader 1 then drive over the step ST, the floor 5F of the operator's cab 5 is pushed upwards again by the impact. This causes the floor 5F to approach the operator's seat 5S via the seat suspension 40, and the operator's seat 5S is displaced relative to the floor 5F in a negative direction. The operator's seat 5S is then returned to its original position by a restoring force of the elastic element 30 ( Fig. 2) separated from the floor 5F and is relatively displaced in the positive direction with respect to the floor 5F. Thereafter, the relative displacement of the operator seat 5S with respect to the floor 5F gradually decreases by repeating the displacement in the negative direction and the displacement in the positive direction.

[0059] In the present embodiment, the relative displacement of the operator seat 5S with respect to the floor 5F in the up-and-down direction Y is detected by the displacement sensor 41. The displacement sensor 41 outputs a signal to the control unit 50 indicating the detected relative displacement. The displacement information acquisition unit 51 of the control unit 50 acquires the signal indicating the relative displacement of the operator seat 5S and output by the displacement sensor 41 (step S1: Fig. 6) The relative displacement amount forms, for example, a Fig. Figure 5(B) illustrates the waveform. The displacement information acquisition unit 51 outputs a signal indicating the relative displacement magnitude to the displacement information determination unit 52.

[0060] The displacement information determination unit 52 detects a peak in the waveform of the relative displacement magnitude. The displacement information determination unit 52 records a relative displacement magnitude (peak value) of the detected peak (step S2: Fig. 6) The displacement information determination unit 52 determines whether the detected peak value of the relative displacement amount is greater than the first predetermined value PL1 (step S3: Fig. 6).

[0061] If the displacement information determination unit 52 determines that the peak value of the relative displacement amount is greater than the first predetermined value PL1, the displacement information determination unit 52 outputs a signal indicating the determination result to the damping force control unit 53. In such a case, the damping force control unit 53 outputs a command current to the current setting device 42 to switch the damping force of the variable damping element 20 from the first damping force to the second damping force (step S4: Fig. 6) In particular, it controls, as shown by the arrows ARA and ARC in Fig. 5(D) displayed, the damping force control unit 53 the current adjustment device 42, so that, for example, a current is supplied to the coil 25 of the variable damping element 20.

[0062] In this state, as in Fig. As illustrated in Figure 5(B), the control unit 50 switches the damping force of the variable damping element 20 from the first damping force to the second damping force at the time when the relative displacement amount is greater than the first predetermined value PL1 and the relative displacement amount changes from increasing to decreasing (the times indicated by the arrows ARA and ARC).

[0063] The control unit 50 performs a control operation such that the value of the command current applied to the variable damper element 20 is increased along a slope on the time axis from a first current value C0 (for example, 0) to a second current value C1, which is greater than the first current value C0, as shown in Fig. Figure 5(D) illustrates this. In other words, the control unit 50 increases the command current value over a period of time T from the first current value C0 to the second current value C1. The increase of the command current value on the time axis from the first current value C0 to the second current value C1 exhibits a slope.

[0064] The time period T during which the command current value is increased from the first current value C0 to the second current value C1 can, for example, be longer than the time from peak PA1 or peak PA2 to a subsequent (immediately following) peak in the waveform of the relative displacement magnitude. Furthermore, the time period T is preferably constant for each increase of the command current value from the first current value C0 to the second current value C1. The time period T can be changed as required. Additionally, the rate of increase of the command current value from the first current value C0 to the second current value C1 is preferably constant.

[0065] If, on the other hand, the displacement information determination unit 52 is in step S3 in Fig. 6 determines that the peak value of the relative displacement amount is smaller than the first predetermined value PL1; steps S1, S2, and S3 are then executed. Fig. 6 repeated.

[0066] Furthermore, during the in Fig. The control system illustrated in Figure 6 also performs the detection and determination of the acceleration of the ground 5F. Furthermore, the variable damping element 20, in which the second damping force is set during the control system described above, is switched from the second damping force to the first damping force based on the determined acceleration of the ground 5F, as follows.

[0067] The acceleration of the ground 5F (base acceleration) is detected by the accelerometer 43. The accelerometer 43 outputs a signal to the control unit 50 indicating the detected acceleration. The acceleration information acquisition unit 54 of the control unit 50 acquires the signal indicating the acceleration of the ground 5F, which is output by the accelerometer 43 (step S11: Fig. 7) The acceleration of the ground 5F, for example, forms a wave shape that is in Fig. Figure 5(C) illustrates this. The acceleration information acquisition unit 54 outputs a signal indicating the acceleration to the acceleration information determination unit 55.

[0068] The acceleration information determination unit 55 detects a peak (acceleration peak) in the acceleration waveform. The acceleration information determination unit 55 records an absolute value of the acceleration of the detected acceleration peak (step S12: Fig. 7) The acceleration information determination unit 55 determines whether the absolute value of the detected acceleration peak (first peak) is greater than the absolute value of the previous (immediately preceding) acceleration peak (second peak) (step S13: Fig. 7).

[0069] When the acceleration information determination unit 55 determines that the absolute value of the acceleration peak is greater than the absolute value of the previous acceleration peak, the acceleration information determination unit 55 outputs a signal that indicates the determination result to the damping force control unit 53.

[0070] In such a case, the damping force control unit 53 sends a command current to the current setting device 42 to switch the damping force of the variable damping element 20 from the second damping force to the first damping force (step S14: Fig. 7) When the damping force control unit 53 detects the determination result indicating that the absolute value of the acceleration peak is greater than the absolute value of the previous acceleration peak, the current adjusting device 42 is controlled to interrupt the current supply to the coil 25 of the variable damping element 20, as indicated, for example, by arrow ARB in Fig. 5(D) is displayed. It should be noted that the determination for switching the damping force of the variable damping element 20 from the second damping force to the first damping force at the time indicated by the arrow ARB may be a different determination than whether the absolute value of the acceleration peak is greater than the absolute value of the previous acceleration peak. The acceleration information determination unit 55 can perform a control to switch the damping force of the variable damping element 20 from the second damping force to the first damping force, based on a determination result that, for example, indicates that an effective value of the relative displacement magnitude is equal to or greater than a predetermined value.Furthermore, the determination to switch the damping force of the variable damping element 20 from the second damping force to the first damping force at the time indicated by the arrow ARB can be a combination of determining whether the absolute value of the acceleration peak is greater than the absolute value of the previous acceleration peak, and determining that the effective value of the relative displacement amount is equal to or greater than the predetermined value.

[0071] In this way, if the absolute value α1 of the acceleration peak PB1 (first peak) is greater than the absolute value α2 of the previous acceleration peak PB2 (second peak), as for example in Fig. Figure 5(C) illustrates the interruption of the power supply to the coil 25 of the variable damping element 20, as for example in Fig. 5(D) illustrated.

[0072] If, on the other hand, the acceleration information determination unit 55 is in step 13 in Fig. 7 determines that the absolute value of the acceleration peak is equal to or less than the absolute value of the previous acceleration peak; steps S11, S12, and S13 are then executed. Fig. 7 repeated.

[0073] During the in Fig. In the control illustrated in Figure 6, the variable damping element 20, in which the second damping force is set, is switched from the second damping force to the first damping force based on the determination result of the peak value of the relative displacement amount of the operator seat 5S with respect to the floor 5F in the following manner.

[0074] The displacement information acquisition unit 51 of the control unit 50 acquires the signal indicating the relative displacement amount of the operator seat 5S, which is output by the displacement sensor 41 (step S21: Fig. 8) The displacement information acquisition unit 51 outputs a signal indicating the relative displacement amount to the displacement information determination unit 52.

[0075] The displacement information determination unit 52 detects a peak (displacement peak) in a waveform of the relative displacement magnitude. The displacement information determination unit 52 records an absolute value of the relative displacement magnitude of the detected displacement peak (step S22: Fig. 8) The displacement information determination unit 52 determines whether the absolute value of the detected displacement peak is less than the second predetermined value PL2 (step S23: Fig. 8).

[0076] If the displacement information determination unit 52 determines that the absolute value of the displacement peak is less than the second predetermined value PL2, the displacement information determination unit 52 outputs a signal indicating the determination result to the damping force control unit 53. In such a case, the damping force control unit 53 outputs a command current to the current setting device 42 to switch the damping force of the variable damping element 20 from the second damping force to the first damping force (step S24: Fig. 6) In particular, the damping force control unit 53 controls, as indicated by the arrow ARD in Fig. 5(D) indicates the current-setting device 42, for example, to interrupt the current supply to the coil 25 of the variable damping element 20. It should be noted that the determination for switching the damping force of the variable damping element 20 from the second damping force to the first damping force at the time indicated by the arrow ARD may be a different determination than whether the absolute value of the displacement peak is less than the second predetermined value PL2. The displacement information determination unit 52 can perform a control to switch the damping force of the variable damping element 20 from the second damping force to the first damping force, based on a determination result indicating, for example, that an effective value of the relative displacement amount for the last 0.2 seconds (approximately half a wavelength of the suspension vibration) is less than a predetermined value.

[0077] In this way, the control unit 50 controls the current adjusting device 42 so that the power supply to the coil 25 of the variable damping element 20 is interrupted when the absolute value of the peak value is less than the second predetermined value PL2, as in the case of the Fig. 5(B) shown displacement peak PA3, as for example in Fig. 5(D) illustrated.

[0078] If, on the other hand, the displacement information determination unit 52 is in step S23 in Fig. 8 determines that the absolute value of the displacement peak is equal to or greater than the second predetermined value PL2, steps S21, S22 and S23 are executed in Fig. 8 repeated.

[0079] As in Fig. As illustrated in section 5, the control described above is shown in Fig. 6 to Fig. 8 such that a current is supplied to the coil 25 of the variable damping element 20 to achieve an ON state from time ARA, at which the displacement peak PA1 with a peak value greater than the first predetermined value PL1 is detected, until time ARB, at which the acceleration peak PB1 with an absolute value α1 greater than the absolute value α2 of the previous acceleration peak PB2 is detected. Furthermore, from time ARB described above until time ARC, at which the displacement peak PA2 with a peak value greater than the first predetermined value PL1 is detected, the power supply to the coil 25 of the variable damping element 20 is interrupted to achieve an OFF state.Furthermore, from the time ARC described above until the time ARD, at which the displacement peak PA3 with an absolute value less than the second predetermined value PL2 is detected, a current is supplied to the coil 25 of the variable damping element 20 to achieve an on-state. Furthermore, after the time ARD described above, the power supply to the coil 25 of the variable damping element 20 is interrupted to achieve an off-state.

[0080] It should be noted that the above description concerns a case in which the rear wheels 7 cross the step ST on the second pass, and that the second pass could also be a case in which the front wheels 4 cross a different step. Furthermore, the control can be carried out in the same way on the third and all subsequent passes over a step. For example, the sequence when crossing step ST is not limited to front wheels → rear wheels and can be front wheel → front wheel → rear wheel → rear wheel. Furthermore, the above description is for a case in which the wheel loader 1 is moving forward. A control similar to that in a case in which the wheel loader 1 is moving forward can be carried out when the wheel loader 1 is moving in reverse. Effects

[0081] Next, the effects of the present embodiment will be described.

[0082] In the present embodiment, as in Fig. Figure 5(B) illustrates how the damping force of the variable damping element 20 switches from the first damping force to the second damping force when the peak value of the relative displacement detected by the displacement sensor 41 is greater than the first predetermined value PL1. The damping force of the variable damping element 20 is initially set to the first damping force, which is a smaller damping force, until the peak value of the relative displacement exceeds the first predetermined value PL1. This allows the shock to be absorbed more easily. Once the peak value of the relative displacement exceeds the first predetermined value PL1, the damping force of the variable damping element 20 is further switched to the second damping force, which is a larger damping force. This allows vibrations of the operator seat 5S relative to the floor 5F in the up-and-down direction Y to be absorbed quickly.This improves the driving comfort of the wheel loader 1 when driving over a step.

[0083] Furthermore, in the present embodiment, as in Fig. Figure 5(C) illustrates: If it is determined that the absolute value α1 of the first peak PB1 in the acceleration waveform of the ground 5F, detected by the accelerometer 43, is greater than the absolute value α2 of the second peak PB2, which immediately precedes the first peak PB1, the control unit 50 switches the damping force of the variable damping element 20 from the second damping force to the first damping force. This allows the shock generated during the second and subsequent crossings of step ST to be easily mitigated by the variable damping element 20. Furthermore, by focusing on the acceleration as described above, the second or subsequent times at which the wheel crosses step ST can be easily specified.In this way, the first crossing of stage ST is specified by focusing on the relative displacement amount, and the second and subsequent crossings of stage ST can easily be specified by focusing on the acceleration.

[0084] Furthermore, in the present embodiment, as in Fig. Figure 5(B) illustrates how the control unit 50 switches the damping force of the variable damping element 20 from the first damping force to the second damping force when the relative displacement amount detected by the displacement sensor 41 is greater than the first predetermined value PL1 and it is determined that the relative displacement has changed from an increase to a decrease. This allows the damping force to be switched using the peak of the relative displacement amount as a reference.

[0085] Furthermore, in the present embodiment, as in Fig. Figure 5(B) illustrates how the control unit 50 adjusts the damping force of the variable damping element 20 to the first damping force, which is smaller when the absolute value of the peak PA3 of the relative displacement is smaller than the second predetermined value PL2. If the vibration of the operator seat 5S is low, this can reduce the amount of current supplied to the variable damping element 20.

[0086] If the command current value abruptly increases from the first current value to the second current value at the peak of the relative displacement, the convergence of the vibration of the operator seat 5S with respect to the floor 5F is delayed. In view of this, in the present embodiment, as described in Fig. Figure 5(D) illustrates that the value of the command current applied to the variable damping element 20 increases along a slope on the time axis from the first current value to the second current value, which is greater than the first current value. This causes the control unit 50 to switch the damping force of the variable damping element 20 from the first damping force to the second damping force. As a result, the command current value gradually increases from the first current value to the second current value at the peak of the relative displacement, and the vibration of the operator seat 5S with respect to the floor 5F can be quickly compensated.

[0087] Furthermore, the variable damping element 20 in the present embodiment, as shown in Fig. Figure 3 illustrates the magnetorheological fluid 27 and the coil 25, which applies a magnetic field to the magnetorheological fluid 27. This supplies current to the coil 25, and the damping force of the variable damping element 20 can be easily adjusted.

[0088] Furthermore, in the present embodiment, as in Fig. 5(B) and Fig.Figure 5(C) illustrates how the control unit 50 adjusts the variable damping element 20 so that it exhibits the first damping force in a section from the origin to the peak of the waveform of the relative displacement amount detected by the displacement sensor 41, and controls the variable damping element 20 so that it exhibits the second damping force in a section from the peak to the origin of the waveform of the relative displacement amount. This enables shock absorption and rapid vibration convergence, and improves the ride comfort of the wheel loader 1 when driving over a step. Additional remarks

[0089] The embodiment described above includes the following technical ideas. Supplementary Note 1

[0090] A work vehicle with a work tool, the work vehicle including: a floor; an operator seat located on the floor; a seat suspension system located between the floor and the operator's seat, incorporating a variable damping element with a damping force at least switchable between a first damping force and a second damping force that is greater than the first damping force; a displacement sensor that detects the relative displacement of the operator's seat in relation to the floor; and a control unit that switches the damping force of the variable damping element from the first damping force to the second damping force when a peak value of the relative displacement amount detected by the displacement sensor is greater than a first predetermined value. Supplementary Note 2

[0091] The work vehicle as described in supplementary note 1, further including: an accelerometer that detects the acceleration of the ground in the up-and-down direction, wherein The control unit switches the damping force of the variable damping element from the second damping force to the first damping force when an absolute value of a first peak of ground acceleration detected by the accelerometer is greater than an absolute value of a second peak immediately preceding the first peak. Supplementary Note 3

[0092] The work vehicle in accordance with supplementary note 1 or 2, wherein The control unit switches the damping force of the variable damping element from the first damping force to the second damping force when the relative displacement amount detected by the displacement sensor is greater than the first predetermined value and it is determined that the relative displacement amount has changed from an increase to a decrease. Supplementary note 4

[0093] The work vehicle according to one of the supplementary notes 1 to 3, wherein The control unit switches the damping force of the variable damping element from the second damping force to the first damping force when an absolute value of a peak of the relative displacement amount is smaller than a second predetermined value, which is smaller than the first predetermined value. Supplementary note 5

[0094] The work vehicle according to one of the supplementary notes 1 to 4, wherein The control unit switches the damping force of the variable damping element from the first damping force to the second damping force when a value of a command current applied to the variable damping element is increased along a slope on the time axis from a first current value to a second current value that is greater than the first current value. Supplementary Note 6

[0095] The work vehicle according to one of the supplementary notes 1 to 5, wherein The variable damping element includes a magnetorheological fluid and a coil that generates a magnetic field acting on the magnetorheological fluid. Supplementary note 7

[0096] A system consisting of a work vehicle and a work implement, wherein the system includes the work vehicle, including: of a floor; an operator seat located on the floor; a seat suspension arranged between the floor and the operator's seat and including a variable damping element in which a damping force is switchable between at least a first damping force and a second damping force which is greater than the first damping force; a displacement sensor that detects the relative displacement of the operator's seat in relation to the floor; and a control unit that switches the damping force of the variable damping element from the first damping force to the second damping force when a peak value of the relative displacement amount detected by the displacement sensor is greater than a first predetermined value. Supplementary Note 8

[0097] A method for controlling a work vehicle comprising a work implement, a floor, an operator's seat arranged on the floor, a seat suspension arranged between the floor and the operator's seat with a variable damping element in which a damping force is switchable between at least a first damping force and a second damping force which is greater than the first damping force, and a displacement sensor which detects a relative displacement amount of the operator's seat with respect to the floor, wherein the method includes: a step towards capturing a relative displacement amount of the operator's seat in relation to the floor; a step to determine whether a peak value of the relative displacement detected by the displacement sensor is greater than a first predetermined value; and a step to switch the damping force of the variable damping element from the first damping force to the second damping force when it is determined that the peak value is greater than the first predetermined value.

[0098] It is understood that the embodiment disclosed herein is in every respect exemplary and not limiting. The scope of protection of the present invention is defined by the terms of the claims and not by the preceding description and is intended to include all modifications within the scope and meaning that correspond to the content of the claims. Reference symbol list

[0099] 1 Wheel loader, 2 Chassis, 3 Working attachment, 4 Front wheel, 5 Operator's cab, 5F Floor, 5S Operator's seat, 6 Engine compartment, 7 Rear wheel, 9 Steering cylinder, 10 Vehicle body frame, 11 Front frame, 12 Rear frame, 13 Coupling shaft section, 14 Boom, 15 Bucket, 16 Lifting cylinder, 17 Bucket cylinder, 18 Angle lever, 20 Variable damper element, 21 Cylinder, 21A First fluid chamber, 21B Second fluid chamber, 21C Gas chamber, 22 Piston, 22a Annular opening, 23 Piston rod, 24 Diaphragm, 25 Coil, 26 Wiring line, 27 Magnetorheological fluid, 28 Sealing bearing, 30 Elastic element, 40 Seat suspension, 41 Position sensor, 42 Current adjusting device, 43 Acceleration sensor, 50 Control unit, 51 Displacement information acquisition unit, 52 Displacement information determination unit, 53 Damping force control unit, 54 Acceleration information acquisition unit, 55 Acceleration information determination unit, 56 Memory and ST stage QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2000-85435 A

[0003] JP 2000

[0003] JP 85436 A

[0003] JP 2000-85436 A

[0003]

Claims

[1] Work vehicle with a work tool, the work vehicle including: a floor; an operator seat located on the floor; a seat suspension arranged between the floor and the operator's seat and including a variable damping element in which a damping force is switchable between at least a first damping force and a second damping force which is greater than the first damping force; a displacement sensor that detects the relative displacement of the operator's seat in relation to the floor; and a control unit that switches the damping force of the variable damping element from the first damping force to the second damping force when a peak value of the relative displacement amount detected by the displacement sensor is greater than a first predetermined value. [2] Work vehicle according to claim 1, further comprising: an accelerometer that detects an acceleration of the ground in the up-and-down direction, wherein The control unit switches the damping force of the variable damping element from the second damping force to the first damping force when an absolute value of a first peak of ground acceleration detected by the accelerometer is greater than an absolute value of a second peak immediately preceding the first peak. [3] Work vehicle according to claim 1, wherein The control unit switches the damping force of the variable damping element from the first damping force to the second damping force when the relative displacement amount detected by the displacement sensor is greater than the first predetermined value and it is determined that an absolute value of the relative displacement amount has changed from an increase to a decrease. [4] Work vehicle according to claim 1, wherein The control unit switches the damping force of the variable damping element from the second damping force to the first damping force when an absolute value of a peak of the relative displacement amount is smaller than a second predetermined value, which is smaller than the first predetermined value. [5] Work vehicle according to claim 1, wherein The control unit switches the damping force of the variable damping element from the first damping force to the second damping force when a value of a command current applied to the variable damping element is increased along a slope on the time axis from a first current value to a second current value that is greater than the first current value. [6] Work vehicle according to claim 1, wherein The variable damping element includes a magnetorheological fluid and a coil that generates a magnetic field acting on the magnetorheological fluid. [7] System consisting of a work vehicle with a work tool, wherein the system includes the work vehicle, including: of a floor; an operator seat located on the floor; a seat suspension arranged between the floor and the operator's seat and including a variable damping element in which a damping force is switchable between at least a first damping force and a second damping force which is greater than the first damping force; a displacement sensor that detects the relative displacement of the operator's seat in relation to the floor; and a control unit that switches the damping force of the variable damping element from the first damping force to the second damping force when a peak value of the relative displacement amount detected by the displacement sensor is greater than a first predetermined value. [8] Method for controlling a work vehicle comprising a work implement, a floor, an operator's seat arranged on the floor, a seat suspension arranged between the floor and the operator's seat with a variable damping element wherein a damping force is switchable between at least a first damping force and a second damping force which is greater than the first damping force, and a displacement sensor which detects a relative displacement amount of the operator's seat with respect to the floor, wherein the method comprises: a step towards capturing a relative displacement amount of the operator's seat in relation to the floor; a step to determine whether a peak value of the relative displacement detected by the displacement sensor is greater than a first predetermined value; and a step to switch the damping force of the variable damping element from the first damping force to the second damping force when it is determined that the peak value is greater than the first predetermined value.

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