A working machine and a method for controlling the working machine.

Abstract

To obtain stable braking force in a work machine, no matter whether inertia braking force becomes insufficient or varies.SOLUTION: A work machine is provided with a driving source, a transmission, a running device, a brake device and a controller. The transmission is connected to the driving source. The running device is connected to the transmission and causes the work machine to run. The brake device brakes the running device. The controller obtains a braking command for braking the work machine. The controller determines target braking force at the time when the work machine runs by inertia, on the basis of the braking command. The controller determines auxiliary braking force in such a manner that target braking force can be obtained by inertia braking force from the transmission and the auxiliary braking force by the brake device. The controller determines whether the transmission is in an excessive rotating state. When determining that the transmission is in the excessive rotating state, the controller increases the auxiliary braking force.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a working machine and a method for controlling the working machine.

Background Art

[0002] Some working machines have a transmission. When the operator is not operating the accelerator pedal, a braking force acts on the working machine due to the inertial braking force from the transmission. For example, the working machine of Patent Document 1 has a HST (Hydro Static Transmission). The HST includes a hydraulic pump and a hydraulic motor. In the HST, an inertial braking force is generated due to the internal loads of the hydraulic pump, the hydraulic motor, and the engine. The operator adjusts the vehicle speed of the working machine by utilizing such an inertial braking force.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, there is a limit to the inertial braking force from the transmission. Therefore, for example, when going downhill, the inertial braking force from the transmission may be insufficient for the required braking force. Also, the inertial braking force may change depending on the state of the transmission. Therefore, it is difficult to stably adjust the vehicle speed of the working machine by the inertial braking force. The object of the present disclosure is to obtain a stable braking force in a working machine regardless of the insufficiency or variation of the inertial braking force.

Means for Solving the Problems

[0005] A work machine according to one aspect of this disclosure comprises a drive source, a transmission, a travel unit, a brake unit, and a controller. The transmission is connected to the drive source. The travel unit is connected to the transmission and moves the work machine. The brake unit brakes the travel unit. The controller receives a braking command to brake the work machine. Based on the braking command, the controller determines a target braking force during the inertial travel of the work machine. The controller determines an auxiliary braking force such that the target braking force is obtained by the inertial braking force from the transmission and the auxiliary braking force from the brake unit. The controller determines whether the transmission is in an over-rotation state. If the controller determines that the transmission is in an over-rotation state, it increases the auxiliary braking force.

[0006] Another aspect of the present disclosure relates to a method for controlling a work machine. The work machine comprises a drive source, a transmission, a travel unit, and a brake device. The transmission is connected to the drive source. The travel unit is connected to the transmission and drives the work machine. The brake device brakes the travel unit. The method comprises obtaining a braking command for braking the work machine, determining a target braking force during the inertial travel of the work machine based on the braking command, determining an auxiliary braking force such that the target braking force is obtained by the inertial braking force from the transmission and the auxiliary braking force from the brake device, determining whether the transmission is in an over-rotation state, and, if it is determined that the transmission is in an over-rotation state, increasing the auxiliary braking force. [Effects of the Invention]

[0007] According to this disclosure, the auxiliary braking force is determined so that the target braking force is obtained by combining the inertial braking force from the transmission and the auxiliary braking force from the brake device. Therefore, if the inertial braking force is insufficient to meet the target braking force, the braking force from the brake device compensates for the deficiency. Furthermore, even if the inertial braking force fluctuates, a stable braking force is obtained because the target braking force is determined. As a result, a stable braking force is obtained in the work machine regardless of insufficient or fluctuating inertial braking force. In addition, if it is determined that the transmission is in an over-rotating state, the auxiliary braking force is increased. As a result, for example, when descending a slope, if the target braking force set by the braking command is insufficient to meet the required braking force, the auxiliary braking force is increased, thereby decelerating the work machine. [Brief explanation of the drawing]

[0008] [Figure 1] This is a side view of the work machine according to the embodiment. [Figure 2] This is a block diagram showing the configuration of a working machine. [Figure 3] This figure shows an example of the driving force characteristics of a work machine. [Figure 4] This diagram shows the configuration of the hydraulic circuit for driving the brake system. [Figure 5] This is a flowchart showing the process of automatic braking control. [Figure 6] This figure shows an example of a target braking force for the first level. [Figure 7] This figure shows an example of a target braking force for the second level. [Figure 8] This figure shows an example of a target braking force for the third level. [Figure 9] This figure shows an example of braking force when the transmission is over-revving. [Figure 10] This flowchart shows the process of automatic brake control related to a modified example. [Figure 11] This figure shows an example of braking force when the transmission is over-revving in an automatic brake control system according to a modified example. [Modes for carrying out the invention]

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Figure 1 is a side view of a work machine 1 according to the embodiment. Figure 2 is a block diagram showing the configuration of the work machine 1. In this embodiment, the work machine 1 is a wheel loader. As shown in Figure 1, the work machine 1 comprises a vehicle body 2 and a work machine 3.

[0010] The vehicle body 2 includes a front vehicle body 2a and a rear vehicle body 2b. The rear vehicle body 2b is connected to the front vehicle body 2a so as to be able to pivot left and right. A hydraulic cylinder 15 is connected to the front vehicle body 2a and the rear vehicle body 2b. By extending and retracting the hydraulic cylinder 15, the front vehicle body 2a pivots left and right relative to the rear vehicle body 2b.

[0011] The work implement 3 is used for excavation and other operations. The work implement 3 is movably mounted to the front vehicle body 2a. The work implement 3 includes a boom 11, a bucket 12, and hydraulic cylinders 13 and 14. The boom 11 and bucket 12 move as the hydraulic cylinders 13 and 14 extend and retract.

[0012] As shown in Figure 2, the work machine 1 includes a drive source 21, a transmission 24, and a travel device 25. The drive source 21 is, for example, a diesel engine. The drive source 21 is equipped with a fuel injector 30. The fuel injector 30 controls the output of the drive source 21 by adjusting the amount of fuel injected into the cylinder of the drive source 21.

[0013] The transmission 24 is connected to the drive source 21. The transmission 24 transmits the driving force from the drive source 21 to the traveling device 25. For example, the transmission 24 is an HST and includes a hydraulic pump 38 and a hydraulic motor 39. The transmission 24 can change the gear ratio continuously by controlling the respective capacities of the hydraulic pump 38 and the hydraulic motor 39. The transmission 24 includes a clutch 40. The clutch 40 can be switched between an engaged state and a disengaged state. The transmission 24 transmits the driving force to the traveling device 25 when the clutch 40 is in the engaged state. The transmission 24 blocks the driving force to the traveling device 25 when the clutch 40 is in the disengaged state.

[0014] However, the transmission 24 may be another type of transmission such as an EMT (Electric Mechanical Transmission) or an HMT (Hydraulic Mechanical Transmission). Alternatively, the transmission 24 may be a transmission including a torque converter and a plurality of transmission gears.

[0015] The traveling device 25 is mounted on the vehicle body 2 and drives the vehicle body 2 to travel by being driven by the driving force from the drive source 21. The traveling device 25 includes axles 26, 27, front wheels 28A, 28B, and rear wheels 28C, 28D. The axles 26, 27 are connected to the transmission 24. The front wheels 28A, 28B are provided on the front vehicle body 2a. The rear wheels 28C, 28D are provided on the rear vehicle body 2b. The axle 26 transmits the driving force from the transmission 24 to the front wheels 28A, 28B. The axle 27 transmits the driving force from the transmission 24 to the rear wheels 28C, 28D.

[0016] The work machine 1 includes a PTO (Power Take Off) 31, a work implement pump 32, and a control valve 33. The PTO 31 distributes the driving force of the drive source 21 to the transmission 24 and the work implement pump 32. In FIG. 2, only one work implement pump 32 is illustrated. However, two or more hydraulic pumps may be connected to the drive source 21 via the PTO 31.

[0017] The work implement pump 32 is connected to the drive source 21 via the PTO 31. The work implement pump 32 is a hydraulic pump. The work implement pump 32 is driven by the drive source 21 and discharges hydraulic oil. The hydraulic oil discharged from the work implement pump 32 is supplied to the hydraulic cylinders 13 - 15 described above. The control valve 33 controls the flow rate of the hydraulic oil supplied from the work implement pump 32 to the hydraulic cylinders 13 - 15. The control valve 33 is, for example, an electromagnetic proportional control valve and is controlled according to the input electrical signal. Alternatively, the control valve 33 may be a pressure proportional control valve and may be controlled according to the input pilot pressure.

[0018] The work machine 1 includes a brake pump 36 and brake devices 37A - 37D. The brake devices 37A - 37D are hydraulic brakes. The brake pump 36 is driven by the drive source 21 and discharges hydraulic oil. The hydraulic oil discharged from the brake pump 36 is supplied to the brake devices 37A - 37D. The brake devices 37A - 37D drive the traveling device 25 by being driven by hydraulic oil to brake it. The brake devices 37A - 37D are, for example, wet multi - plate brakes. Specifically, the brake devices 37A - 37D include front brakes 37A, 37B and rear brakes 37C, 37D. The front brakes 37A, 37B brake the front wheels 28A, 28B. The rear brakes 37C, 37D brake the rear wheels 28C, 28D.

[0019] The work machine 1 includes an engine sensor 34 and a vehicle speed sensor 35. The engine sensor 34 detects the engine rotational speed. The vehicle speed sensor 35 detects the vehicle speed. The vehicle speed sensor 35 detects, for example, the output rotational speed of the travel device 25 as the vehicle speed. The output rotational speed of the travel device 25 corresponds to the vehicle speed of the work machine 1. The output rotational speed of the travel device 25 is, for example, the rotational speed of the output shaft of the transmission 24. However, the output rotational speed may be the rotational speed of other rotating elements located within or downstream of the transmission 24.

[0020] The working machine 1 includes a controller 41. The controller 41 includes a processor such as a CPU (central processing unit) and storage devices such as RAM and ROM. The controller 41 may also include an auxiliary storage device such as a hard disk or an SSD (Solid State Drive). The controller 41 stores programs and data for controlling the working machine 1. The controller 41 executes processes for controlling the working machine 1 according to the stored programs and data.

[0021] The controller 41 receives a signal from the engine sensor 34 indicating the engine rotation speed. The controller 41 also receives a signal from the vehicle speed sensor 35 indicating the output rotation speed.

[0022] The controller 41 controls the output of the drive source 21 by sending a command signal to the drive source 21. The controller 41 switches the forward gear and reverse gear of the transmission 24 by sending a command signal to the transmission 24. The controller 41 controls the gear ratio of the transmission 24 by sending a command signal to the transmission 24. The controller 41 switches the clutch 40 between the engaged and disengaged states by sending a command signal to the transmission 24. The controller 41 controls the implement 3 by sending command signals to the implement pump 32 and the control valve 33.

[0023] The work machine 1 includes an FR operating member 42, an accelerator operating member 43, a work machine operating member 44, a brake operating member 45, and a setting device 46. The FR operating member 42 is operable by the operator to switch between forward and reverse movement of the work machine 1. The FR operating member 42 can be operated from a neutral position to a forward position and a reverse position. The FR operating member 42 is, for example, a lever. However, the FR operating member 42 may be other members such as a switch or a pedal.

[0024] The accelerator operating member 43 is operable by the operator to control the vehicle speed of the work machine 1. The accelerator operating member 43 is, for example, a pedal. However, the accelerator operating member 43 may be other components such as a lever or a switch. The work machine operating member 44 is operable by the operator to control the work machine 3. The work machine operating member 44 is, for example, a lever. However, the work machine operating member 44 may be other components such as a switch or a pedal.

[0025] The controller 41 receives a signal from the FR operating member 42 indicating the operating position of the FR operating member 42. The controller 41 switches between the forward and reverse gears of the transmission 24 according to the signal from the FR operating member 42. The controller 41 receives a signal from the accelerator operating member 43 indicating the amount of accelerator operation. The amount of accelerator operation is the amount of operation of the accelerator operating member 43.

[0026] Figure 3 shows the driving force characteristics of the work machine 1. In Figure 3, the solid line F1 shows the driving force characteristics when the accelerator pedal is pressed 100%. In Figure 3, the dashed line F2 shows the driving force characteristics when the accelerator pedal is pressed 0%. The controller 41 controls the drive source 21 and the transmission 24 according to the accelerator pedal input and vehicle speed so that the driving force characteristics shown in Figure 3 are obtained.

[0027] As shown in Figure 3, the driving force includes both positive and negative values. The positive driving force represents the positive driving force that propels the work machine 1. The negative driving force represents the negative driving force that brakes the work machine 1, i.e., the inertial braking force from the transmission 24. The inertial braking force is the so-called engine brake, and is the braking force due to the internal loads of the transmission 24 and the drive source 21.

[0028] The brake operating member 45 is operable by an operator to drive the brake devices 37A-37D. The brake operating member 45 is, for example, a pedal. However, the brake operating member 45 may be other components such as a lever or a switch. In response to the operation of the brake operating member 45, the hydraulic pressure of the hydraulic fluid supplied to the brake devices 37A-37D is controlled. As a result, the brake devices 37A-37D generate a braking force in proportion to the amount the brake operating member 45 is operated.

[0029] Figure 4 shows a hydraulic circuit 50 for driving the brake devices 37A-37D. As shown in Figure 4, the hydraulic circuit 50 includes a flow divider valve 51, a first flow path 52, a second flow path 53, a third flow path 54, an automatic brake valve 55, a manual brake valve 56, and a shuttle valve 57. The flow divider valve 51 divides the hydraulic fluid from the brake pump 36 into the second flow path 53 and the third flow path 54. The first flow path 52 is connected to the second flow path 53.

[0030] The automatic brake valve 55 is electrically connected to the controller 41. The automatic brake valve 55 is, for example, a solenoid valve and is electrically controlled in response to a command signal from the controller 41. The automatic brake valve 55 changes the hydraulic pressure (hereinafter referred to as the first hydraulic pressure) supplied from the automatic brake valve 55 to the brake devices 37A-37D via the first passage 52 in response to a command signal from the controller 41.

[0031] The manual brake valve 56 is connected to the brake operating member 45. The manual brake valve 56 is mechanically connected to the brake operating member 45 via a link member such as a spring. The manual brake valve 56 is connected to a second passage 53 and a third passage 54. The manual brake valve 56 changes the hydraulic pressure (hereinafter referred to as the second hydraulic pressure) supplied from the manual brake valve 56 to the brake devices 37A-37D via the second passage 53 and the third passage 54, according to the amount of operation of the brake operating member 45.

[0032] The shuttle valve 57 is connected to the first passage 52, the second passage 53, and the third passage 54. The shuttle valve 57 selectively supplies the first hydraulic pressure from the automatic brake valve 55 and the second hydraulic pressure from the manual brake valve 56 to the brake devices 37A-37D. Specifically, the shuttle valve 57 supplies the larger of the first and second hydraulic pressures to the brake devices 37A-37D. Therefore, for example, if the first hydraulic pressure generated by the operator's operation of the brake operating member 45 is greater than the second hydraulic pressure generated by the command signal from the controller 41, the first hydraulic pressure is supplied to the brake devices 37A-37D. As a result, the braking force of the brake devices 37A-37D is controlled according to the amount of operation of the operator's brake operating member 45.

[0033] Conversely, if the second hydraulic pressure generated by the command signal from the controller 41 is greater than the first hydraulic pressure generated by the operator's operation of the brake operating member 45, the second hydraulic pressure is supplied to the brake devices 37A-37D. As a result, the braking force of the brake devices 37A-37D is controlled in accordance with the command signal from the controller 41.

[0034] In the work machine 1 according to this embodiment, the controller 41 performs automatic brake control to automatically control the braking force during inertial travel of the work machine 1. Inertial travel of the work machine 1 means the state in which the work machine 1 is traveling by inertia when the accelerator operating member 43 and the brake operating member 45 are not operated. The setting device 46 is operable by the operator to set the target braking force during inertial travel in the automatic brake control. The setting device 46 is, for example, a dial-type switch. However, the setting device may be other devices such as a slide-type switch, a push-button switch, or a touch panel. The setting device 46 outputs a braking command indicating the target braking force in response to the operator's operation.

[0035] The target braking force is expressed in multiple levels. These levels may include, for example, a first level, a second level, and a third level. The first level has the largest target braking force, and the third level has the smallest target braking force. The second level's target braking force is somewhere between the first and second levels.

[0036] Figure 5 is a flowchart of the automatic brake control process. As shown in Figure 5, in step S101, the controller 41 acquires a braking command. The controller 41 acquires a braking command indicating the target braking force set by the operator using the setting device 46.

[0037] In step S102, the controller 41 determines the target braking force. The controller 41 determines the target braking force based on the braking command from the setting device 46. In step S103, the controller 41 acquires transmission information. The transmission information indicates the status of the transmission 24. The transmission information includes, for example, the gear ratio of the transmission 24. The transmission information includes the vehicle speed. If the transmission 24 is an HST, the transmission information may also include the capacity of the hydraulic pump and the capacity of the hydraulic motor. If the transmission 24 includes multiple gears, the transmission information may also include the gear ratios of the gears.

[0038] In step S104, the controller 41 calculates the inertial braking force from the transmission 24. Based on the transmission information described above, the controller 41 calculates the inertial braking force from the transmission 24.

[0039] In step S105, the controller 41 determines the auxiliary braking force. The controller 41 determines the auxiliary braking force so that the target braking force can be obtained by combining the inertial braking force from the transmission 24 and the auxiliary braking force from the brake devices 37A-37D. The controller 41 determines the auxiliary braking force to be a braking force equivalent to the difference between the target braking force and the inertial braking force.

[0040] In step S106, the controller 41 controls the automatic brake valve 55. The controller 41 calculates the target brake hydraulic pressure for the brake devices 37A-37D, which corresponds to the auxiliary braking force. The controller 41 controls the opening degree of the automatic brake valve 55 so that the target brake hydraulic pressure is supplied to the brake devices 37A-37D.

[0041] In step S107, the controller 41 determines whether the transmission 24 is in a first over-rotation state. The controller 41 determines that the transmission 24 is in a first over-rotation state if the vehicle speed is equal to or greater than a first threshold. If the controller 41 determines that the transmission 24 is in a first over-rotation state, the process proceeds to step S108. In step S108, the controller 41 increases the auxiliary braking force. For example, the controller 41 increases the auxiliary braking force up to the maximum braking force of the brake devices 37A-37D. Alternatively, the controller 41 may increase the auxiliary braking force in stages.

[0042] In step S109, the controller 41 determines whether the transmission 24 is in a second over-revving state. The controller 41 determines that the transmission 24 is in a second over-revving state if the vehicle speed is greater than or equal to a second threshold. The second threshold is greater than the first threshold. If the controller 41 determines that the transmission 24 is in a second over-revving state, the process proceeds to step S110.

[0043] In step S110, the controller 41 switches the clutch 40 to the disengaged state. This interrupts the transmission of driving force from the running gear 25 to the transmission 24. The second threshold is determined from the standpoint of protecting the transmission 24 from over-revving. The second threshold is determined, for example, based on the maximum permissible kinetic speed of the transmission 24's hydraulic motor, hydraulic pump, or engine. The first threshold is smaller than the second threshold. The first threshold is determined from the standpoint of preventing the transmission 24 from entering a second over-revving state.

[0044] For example, in Figure 6, L1 shows an example of a target braking force for the first level. In Figure 7, L2 shows an example of a target braking force for the second level. In Figure 8, L3 shows an example of a target braking force for the third level. Data showing the relationship between the target braking forces L1-L3 for the first to third levels and the vehicle speed is stored in the controller 41.

[0045] As shown in Figure 6, when the setting device 46 sets a first level as the target braking force, the controller 41 determines a target braking force L1 according to the vehicle speed. In Figure 6, L0 represents the inertial braking force from the transmission 24 during coasting. The controller 41 calculates the inertial braking force L0 from the transmission information. The controller 41 calculates the target brake hydraulic pressure of the brake devices 37A-37D so as to generate an auxiliary braking force equivalent to the difference dF between the target braking force L1 and the inertial braking force L0. The controller 41 controls the opening degree of the automatic brake valve 55 so that the target brake hydraulic pressure is supplied to the brake devices 37A-37D. As a result, even if the inertial braking force L0 is insufficient for the first level target braking force L1, the auxiliary braking force from the brake devices 37A-37D compensates for it, and a braking force according to the first level target braking force L1 is obtained.

[0046] As shown in Figure 7, the target braking force L2 for the second level is smaller than the target braking force L1 for the first level. When the setting device 46 sets the second level as the target braking force, the controller 41 determines the target braking force L2 according to the vehicle speed. Subsequently, as in the case where the first level is set, the controller 41 calculates the target brake hydraulic pressure of the brake devices 37A-37D to generate an auxiliary braking force equivalent to the difference between the target braking force L2 and the inertial braking force L0, and controls the opening degree of the automatic brake valve 55 according to the target brake hydraulic pressure.

[0047] As shown in Figure 8, the target braking force L3 for the third level is smaller than the target braking force L2 for the second level. When the setting device 46 sets the third level as the target braking force, the controller 41 determines the target braking force L3 according to the vehicle speed. Subsequently, as in the case where the first level is set, the controller 41 calculates the target brake hydraulic pressure of the brake devices 37A-37D to generate an auxiliary braking force equivalent to the difference between the target braking force L3 and the inertial braking force L0, and controls the opening degree of the automatic brake valve 55 according to the target brake hydraulic pressure.

[0048] As described above, the braking force during coasting can be changed by changing the target braking force using the setting device 46. Therefore, when the work machine 1 travels down the same downhill slope, the vehicle speed at which the work machine 1 stabilizes during coasting can be changed. Furthermore, even on downhill slopes where coasting cannot be achieved solely by the inertial braking force from the transmission 24, the machine can travel at a constant vehicle speed. Note that coasting refers to the state in which the work machine 1 travels at a constant speed during coasting.

[0049] For example, as shown in Figures 6 to 8, when the work machine 1 is traveling down a certain slope, the braking force that balances the force accelerating the work machine 1 (hereinafter referred to as statically determinate braking force) is A1. If the inertial braking force L0 from the transmission 24 is smaller than the statically determinate braking force A1, the work machine 1 cannot be statically determinated by the inertial braking force from the transmission 24 alone.

[0050] Therefore, as shown in Figure 6, by setting the target braking force to level 1 using the setting device 46, a braking force equivalent to the target braking force L1 of level 1 can be obtained. As a result, at the vehicle speed V1 where the target braking force L1 balances the static braking force A1, the work machine 1 can travel at a constant speed.

[0051] As shown in Figure 7, by setting the target braking force to level 2 using the setting device 46, a braking force equivalent to the target braking force L2 of level 2 can be obtained. As a result, at the vehicle speed V2 where the target braking force L2 balances the static braking force A1, the work machine 1 can travel at a constant speed.

[0052] Furthermore, as shown in Figure 8, by setting the target braking force to level 3 using the setting device 46, a braking force equivalent to the target braking force L3 of level 3 can be obtained. As a result, at the vehicle speed V3 where the target braking force L3 balances the static braking force A1, the work machine 1 can travel at a constant speed. In this way, when the work machine 1 travels down the same downhill slope, the operator can change the vehicle speed at which the work machine 1 stabilizes during coasting by changing the target braking force using the setting device 46.

[0053] When the work machine 1 travels down a steep slope, the static braking force A2 may be greater than the target braking force L2 set by the operator, as shown in Figure 9. In this case, the work machine 1 cannot be statically controlled with the target braking force L2, and the vehicle speed increases. If the vehicle speed continues to increase, the transmission 24 may become over-revved, potentially damaging the transmission 24.

[0054] In the work machine according to this embodiment, when the vehicle speed exceeds a first threshold B1, the controller 41 increases the auxiliary braking force of the brake devices 37A-37D. As a result, as shown in Figure 9, a braking force C1 greater than the static braking force A2 is obtained, causing the work machine 1 to decelerate. Furthermore, the first threshold B1 for increasing the auxiliary braking force is smaller than the second threshold B2 at which the clutch 40 is switched to a disengaged state. Therefore, by increasing the auxiliary braking force before the clutch 40 becomes disengaged, the work machine 1 can be decelerated. This prevents the work machine 1 from becoming immobile.

[0055] In the work machine 1 according to this embodiment described above, the braking force by the brake devices 37A-37D is controlled based on the difference between the target braking force and the inertial braking force. Therefore, if the inertial braking force is insufficient compared to the target braking force, the braking force by the brake devices 37A-37D can compensate for the deficiency. Furthermore, even if the inertial braking force fluctuates, a stable braking force can be obtained because the target braking force is determined. As a result, a stable braking force can be obtained in the work machine 1 regardless of insufficient or fluctuating inertial braking force.

[0056] Furthermore, if it is determined that the transmission 24 is in a first over-rotation state, the auxiliary braking force is increased. As a result, for example, when descending a slope, if the target braking force set by the braking command is insufficient to provide the necessary braking force, the auxiliary braking force is increased, thereby decelerating the work machine 1.

[0057] 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 spirit of the invention.

[0058] The work machine 1 is not limited to a wheel loader; it may be another machine such as a bulldozer or a motor grader. The work machine 1 may be operable remotely. In that case, the FR operating member 42, accelerator operating member 43, work machine operating member 44, brake operating member 45, and setting device 46 may be located outside the work machine 1.

[0059] The drive source 21 is not limited to an engine and may include an electric motor. The controller 41 may be composed of multiple controllers. The control processing of the work machine 1 described above may be distributed and executed by multiple controllers.

[0060] The automatic braking control process is not limited to that of the embodiments described above and may be modified. For example, the number of target braking force levels is not limited to three. The number of target braking force levels may be more than three or less than three. The target braking force may also be expressed as a numerical value of braking force.

[0061] Figure 10 is a flowchart showing the process of automatic brake control according to a modified example. In Figure 10, steps S201 to S206 are the same as steps S101 to S106 in the embodiment described above. In step S207, the controller 41 determines whether the transmission 24 is in an over-revving state. The controller 41 determines that the transmission 24 is in an over-revving state if the vehicle speed is equal to or greater than the second threshold B2 described above. If the controller 41 determines that the transmission 24 is in an over-revving state, the process proceeds to step S208.

[0062] In step S208, the controller 41 switches the clutch 40 to the disengaged state. Also, in step S209, the controller 41 increases the auxiliary braking force. That is, as shown in Figure 11, the controller 41 increases the auxiliary braking force when the vehicle speed is greater than or equal to the second threshold B2 at which the clutch 40 is switched to the disengaged state. As a result, with the transmission of driving force from the transmission 24 to the running gear 25 interrupted, the work machine 1 can be decelerated by the braking force C2 from the brake devices 37A-37D. [Industrial applicability]

[0063] According to this disclosure, a stable braking force can be obtained in a work machine regardless of insufficient or fluctuating inertial braking force. [Explanation of Symbols]

[0064] 21: Power source 24: Transmission 25: Running gear 37A: Brake system 41: Controller 45: Brake operating member 46: Setting device 55: Automatic brake valve 56: Manual brake valve 57: Shuttle valve

Claims

1. It is a work machine, Power source and A transmission connected to the aforementioned drive source, A traveling device connected to the aforementioned transmission for driving the aforementioned work machine, A braking device for braking the aforementioned running gear, Controller and Equipped with, The aforementioned controller, A braking command is obtained to brake the aforementioned work machine, Based on the braking command, the target braking force during the inertial movement of the work machine is determined. The auxiliary braking force is determined such that the target braking force is obtained by the inertial braking force from the transmission and the auxiliary braking force from the brake device. Determine whether the transmission is in an over-revving state. If the transmission determines that it is in the over-rotation state, it increases the auxiliary braking force. Agricultural machinery.

2. The aforementioned controller, The vehicle speed of the aforementioned work machine is acquired, When the vehicle speed is above a first threshold, it is determined that the transmission is in an over-rotating state, and the auxiliary braking force is increased. The work machine according to claim 1.

3. The transmission includes a clutch that can be switched between an engaged state and an engaged state. The transmission transmits driving force to the running gear when the clutch is engaged, and disconnects the driving force to the running gear when the clutch is disengaged. The aforementioned controller, When the vehicle speed is equal to or greater than the first threshold, the system determines that the transmission is in a first over-rotation state and increases the auxiliary braking force. When the vehicle speed is greater than or equal to a second threshold greater than the first threshold, the system determines that the transmission is in a second over-rotation state and switches the clutch to the disengaged state. The work machine according to claim 1.

4. The transmission includes a clutch that can be switched between an engaged state and an engaged state. The transmission is such that the clutch transmits driving force to the running gear when engaged, and the clutch disconnects the driving force to the running gear when disengaged. The aforementioned controller, If the vehicle speed is above a predetermined threshold, the system determines that the transmission is in an over-revving state and switches the clutch to the disengaged state. When the vehicle speed is equal to or greater than the predetermined threshold, the auxiliary braking force is increased. The work machine according to claim 1.

5. The aforementioned controller, The system acquires transmission information indicating the state of the transmission. Based on the transmission information, the inertial braking force from the transmission is calculated. Based on the difference between the target braking force and the inertial braking force, the auxiliary braking force by the braking device is determined. The work machine according to claim 1.

6. The system further includes a setting device that can be operated by an operator to set the target braking force, The controller acquires the braking command in response to the operation of the setting device. The work machine according to claim 1.

7. The aforementioned brake device is a hydraulic brake, The system further includes an automatic brake valve that changes the first hydraulic pressure supplied to the brake device when controlled by the aforementioned controller, The controller controls the automatic brake valve to change the first hydraulic pressure supplied to the brake device according to the difference between the target braking force and the inertial braking force. The working machine according to claim 5.

8. A brake operating member that can be operated by an operator to adjust the braking force of the aforementioned brake device, A manual brake valve that changes the second hydraulic pressure supplied to the brake device in response to the operation of the brake operating member, A shuttle valve that selectively supplies the first hydraulic pressure from the automatic brake valve and the second hydraulic pressure from the manual brake valve to the brake device, The work machine according to claim 7, further comprising:

9. The shuttle valve supplies the larger of the first hydraulic pressure and the second hydraulic pressure to the brake device. The working machine according to claim 8.

10. A method for controlling a work machine comprising a drive source, a transmission connected to the drive source, a travel device connected to the transmission for moving the work machine, and a brake device for braking the travel device, To obtain a braking command for braking the aforementioned work machine, Based on the braking command, the target braking force during the inertial movement of the work machine is determined, The auxiliary braking force is determined such that the target braking force is obtained by the inertial braking force from the transmission and the auxiliary braking force from the brake device. To determine whether the transmission is in an over-revving state, If the transmission determines that it is in the over-rotation state, the auxiliary braking force is increased. A method for providing this.

11. To obtain the vehicle speed of the aforementioned work machine, When the vehicle speed is equal to or greater than a first threshold, it is determined that the transmission is in an over-rotating state, and the auxiliary braking force is increased. The method according to claim 10, comprising:

12. The transmission includes a clutch that can be switched between an engaged state and an engaged state. The transmission transmits driving force to the running gear when the clutch is engaged, and disconnects the driving force to the running gear when the clutch is disengaged. When the vehicle speed is equal to or greater than a first threshold, the system determines that the transmission is in a first over-rotation state and increases the auxiliary braking force. When the vehicle speed is greater than or equal to a second threshold greater than the first threshold, the transmission is determined to be in a second over-rotation state, and the clutch is switched to the disengaged state. The method according to claim 10, comprising:

13. The transmission includes a clutch that can be switched between an engaged state and an engaged state. The transmission transmits driving force to the running gear when the clutch is engaged, and disconnects the driving force to the running gear when the clutch is disengaged. When the vehicle speed exceeds a predetermined threshold, the system determines that the transmission is in an over-revving state and switches the clutch to the disengaged state. When the vehicle speed is equal to or greater than the predetermined threshold, the auxiliary braking force is increased. The method according to claim 10, comprising:

14. To obtain transmission information indicating the state of the aforementioned transmission, Calculating the inertial braking force from the transmission based on the transmission information, The auxiliary braking force by the braking device is determined based on the difference between the target braking force and the inertial braking force. The method according to claim 10, comprising:

15. To set the target braking force, the operator can operate a setting device to obtain the braking command corresponding to the operation of the setting device. The method according to claim 10, comprising:

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