Work machine and method for controlling work machine

Abstract

This work machine comprises a vehicle body, a traveling body, a transmission, a traveling motor, a working machine, a lubrication pump, and a controller. The traveling body causes the vehicle body to travel. The transmission is connected to the traveling body. The traveling motor is connected to the transmission. The working machine is operably attached to the vehicle body. The lubrication pump supplies lubricating oil to the transmission. The controller acquires traveling horsepower passing through the transmission. The controller calculates the required lubrication amount of the lubricating oil of the transmission on the basis of the traveling horsepower. The controller controls a discharge amount of the lubrication pump on the basis of the required lubrication amount.

Description

Work machine and method for controlling a work machine

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to work machines and methods for controlling work machines.

[0002] Some work machines are equipped with a lubrication pump for supplying lubricating oil to the transmission. For example, the vehicle disclosed in Patent Document 1 is equipped with an engine, a transmission, a lubrication pump, and a lubricating oil supply passage. The lubricating pump is driven by the engine to discharge lubricating oil. The lubricating oil is supplied to the transmission via the lubricating oil supply passage.

[0003] International Publication No. WO2006 / 009080

[0004] In a work machine, when the traveling horsepower passing through the transmission is high, such as when climbing a slope or traveling at high speeds, the transmission requires a large amount of lubricating oil. Therefore, if a large-capacity lubrication pump is installed in the work machine, the lubrication pump will supply a large amount of lubricating oil to the transmission even when the traveling horsepower is low. This reduces the energy efficiency of the work machine. An object of the present disclosure is to properly lubricate the transmission and improve the energy efficiency of the work machine.

[0005] A work machine according to one aspect of the present disclosure includes a vehicle body, a traveling body, a transmission, a traveling motor, a work implement, a lubrication pump, and a controller. The traveling body causes the vehicle body to travel. The transmission is connected to the traveling body. The traveling motor is connected to the transmission. The work implement is operably attached to the vehicle body. The lubrication pump supplies lubricating oil to the transmission. The controller acquires traveling horsepower passing through the transmission. The controller calculates a required lubrication amount of lubricating oil for the transmission based on the traveling horsepower. The controller controls the discharge amount of the lubrication pump based on the required lubrication amount.

[0006] A method according to another aspect of the present disclosure is a method executed by a controller to control a work machine. The work machine includes a vehicle body, a running body, a transmission, a travel motor, a work implement, and a lubrication pump. The running body drives the vehicle body. The transmission is connected to the running body. The travel motor is connected to the transmission. The work implement is operably attached to the vehicle body. The lubrication pump supplies lubricant to the transmission. The method includes acquiring running horsepower passing through the transmission, calculating a required lubrication amount of lubricant for the transmission based on the running horsepower, and controlling a discharge amount of the lubrication pump based on the required lubrication amount.

[0007] According to the present disclosure, the required lubrication amount of lubricant for the transmission is calculated based on the traveling horsepower. Then, the discharge rate of the lubricant pump is controlled based on the calculated required lubrication amount. Therefore, an appropriate amount of lubricant is supplied to the transmission according to the traveling horsepower without using a large-capacity lubrication pump. This allows the transmission to be properly lubricated and improves the energy efficiency of the work machine.

[0008] Fig. 1 is a side view of a work machine according to an embodiment. Fig. 2 is a block diagram showing the configuration of a drive system of the work machine. Fig. 3 is a block diagram showing the configuration of a control system of the work machine. Fig. 4 is a flowchart showing the processing of lubrication control of a transmission. Fig. 5 is a transition diagram of control modes of a work machine motor. Fig. 6 is a block diagram showing the configuration of a drive system of a work machine according to another embodiment.

[0009] An embodiment of the present invention will now be described with reference to the drawings. Fig. 1 is a side view of a work machine 1 according to the embodiment. The work machine 1 according to this embodiment is a wheel loader. As shown in Fig. 1, the work machine 1 includes a vehicle body 2, a work implement 3, and a running body 4. A driver's cab 5 and a power compartment 6 are arranged in the vehicle body 2. A driver's seat (not shown) and operating devices (described later) are arranged within the driver's cab 5. A part of a drive system (described later) is arranged within the power compartment 6.

[0010] The work implement 3 is used for work such as excavation. The work implement 3 is movably attached to the vehicle body 2. The work implement 3 includes a boom 11, a bucket 12, a boom cylinder 13, and a bucket cylinder 14. The boom cylinder 13 and the bucket cylinder 14 are hydraulic cylinders. The boom 11 moves when the boom cylinder 13 extends and retracts. The bucket 12 moves when the bucket cylinder 14 extends and retracts.

[0011] The running body 4 causes the work machine 1 to travel. Figure 2 is a block diagram showing the configuration of a drive system 8 mounted on the work machine 1. As shown in Figures 1 and 2, the running body 4 includes running wheels 16A, 16B, 17A, and 17B. The running wheels 16A, 16B, 17A, and 17B are rotatably supported by the vehicle body 2.

[0012] As shown in FIG. 2 , the drive system 8 includes a battery 21, a power control circuit 22, a work implement motor 23, and a travel motor 24. The work implement motor 23 and the travel motor 24 are electric motors. The battery 21 supplies power to the work implement motor 23 and the travel motor 24. The power control circuit 22 controls the power supplied to the work implement motor 23 and the travel motor 24. The power control circuit 22 includes, for example, an inverter. The work implement motor 23 generates drive power for driving the work implement 3. The travel motor 24 generates drive power for driving the travel body 4.

[0013] The drive system 8 includes a work implement pump 25 and a control valve 26. The work implement pump 25 is a variable displacement hydraulic pump. The work implement pump 25 is connected to the work implement motor 23. The work implement pump 25 is driven by the work implement motor 23 to supply hydraulic oil to the cylinders 13, 14 described above. The control valve 26 is connected to the work implement pump 25 and the cylinders 13, 14 via a hydraulic circuit. The control valve 26 includes a plurality of valves. The control valve 26 controls the flow rate of hydraulic oil supplied from the work implement pump 25 to the cylinders 13, 14.

[0014] The drive system 8 includes a transmission 27, a front axle 28, and a rear axle 29. The running wheels 16A, 16B are connected to the transmission 27 via the front axle 28. The running wheels 17A, 17B are connected to the transmission 27 via the rear axle 29. The transmission 27 is connected to the traction motor 24. The transmission 27 changes the speed of the driving force from the traction motor 24 and transmits it to the running body 4. The transmission 27 includes a plurality of gears 33-35. The transmission 27 transmits the driving force from the traction motor 24 to the running body 4.

[0015] The drive system 8 includes a lubrication pump 30. The lubrication pump 30 is connected to the work machine motor 23. The lubrication pump 30 is driven by the work machine motor 23 and supplies lubricating oil to the transmission 27. The lubrication pump 30 is a fixed displacement pump such as a gear pump. The lubrication pump 30 discharges lubricating oil at a flow rate that corresponds to the rotational speed of the work machine motor 23. The lubrication pump 30 is connected to the transmission 27 via a lubrication path 31. The lubricating oil discharged from the lubrication pump 30 is supplied to the transmission 27 via the lubrication path 31.

[0016] Figure 3 is a block diagram showing the configuration of a control system 9 for the work machine 1. As shown in Figure 3, the control system 9 includes a controller 40. The controller 40 controls the work machine 1. The controller 40 includes a processor 41 and a storage device 42. The processor 41 is, for example, a CPU (central processing unit). The processor 41 executes processing for controlling the work machine 1 in accordance with a program. The storage device 42 includes non-volatile memory such as ROM and volatile memory such as RAM. The storage device 42 may include storage such as a hard disk or SSD (Solid State Drive). The storage device 42 stores programs and data for controlling the work machine 1.

[0017] The control system 9 includes a travel operation device 43 and a work implement operation device 44. The travel operation device 43 and the work implement operation device 44 can each be manually operated by the operator of the work machine 1. The travel operation device 43 is operated to control the forward movement, reverse movement, and turning of the work machine 1. The travel operation device 43 includes, for example, an accelerator pedal, a steering wheel, and a lever. However, the travel operation device 43 may also include other members such as switches. The travel operation device 43 outputs a signal in response to the operation of the travel operation device 43.

[0018] The work machine operating device 44 is operated to control the work machine 3. The work machine operating device 44 includes, for example, a lever. However, the work machine operating device 44 may also be another member such as a switch or a pedal. The work machine operating device 44 outputs a signal in accordance with the operation of the work machine operating device 44.

[0019] The controller 40 receives signals from the travel operation device 43. The controller 40 acquires a travel operation command for traveling the work machine 1 through the signal from the travel operation device 43. The controller 40 controls the travel motor 24 and the transmission 27 in accordance with the travel operation command. For example, the controller 40 controls the power control circuit 22 to control the rotation speed and output torque of the travel motor 24. The controller 40 controls the transmission 27 to switch the work machine 1 between forward and reverse. The controller 40 controls the transmission 27 to change the gear ratio.

[0020] The control system 9 includes a motor speed sensor 45. The motor speed sensor 45 detects the rotational speed of the travel motor 24. The controller 40 receives a signal indicating the rotational speed of the travel motor 24 from the motor speed sensor 45. The controller 40 obtains the rotational speed of the travel motor 24 from the signal from the travel motor 24.

[0021] The controller 40 receives a signal from the work implement operating device 44. The controller 40 acquires a work operation command for operating the work implement 3 from the signal from the work implement operating device 44. The work operation command includes, for example, the amount of operation of the work implement operating device 44 by the operator. The controller 40 controls the work implement pump 25 and the control valve 26 so that the work implement 3 operates in accordance with the work operation command. The controller 40 controls the work implement motor 23 so that the work implement 3 operates in accordance with the work operation command. For example, the controller 40 determines a target flow rate for the work implement pump 25 in accordance with the amount of operation of the work implement operating device 44. The controller 40 controls the rotational speed of the work implement motor 23 based on the target flow rate of the work implement pump 25.

[0022] Next, we will explain the lubrication control of the transmission 27 in the work machine 1. In this embodiment, the controller 40 controls the rotational speed of the work machine motor 23, thereby controlling the amount of lubricating oil supplied from the lubrication pump 30 to the transmission 27. Figure 4 is a flowchart showing the processing of the lubrication control of the transmission 27.

[0023] 4, in step S101, the controller 40 acquires the traveling horsepower passing through the transmission 27. For example, the controller 40 calculates the traveling horsepower based on the rotation speed and output torque of the traveling motor 24.

[0024] In step S102, the controller 40 calculates the amount of lubrication required for the transmission 27. The amount of lubrication required is the flow rate of lubricating oil per unit time of the transmission 27. The controller 40 calculates the amount of lubrication required based on the running horsepower. For example, the controller 40 determines the amount of lubrication required to increase in accordance with an increase in the running horsepower.

[0025] In step S103, the controller 40 determines a required lubrication rotation speed of the work machine motor 23. The required lubrication rotation speed is the rotation speed of the work machine motor 23 that causes the required amount of lubricating oil to be discharged from the lubrication pump 30. The controller 40 determines the required lubrication rotation speed of the work machine motor 23 based on the required amount of lubrication and the capacity of the lubrication pump 30.

[0026] In step S104, the controller 40 determines the required work rotation speed of the work implement motor 23. The required work rotation speed is the rotation speed of the work implement motor 23 for operating the work implement 3 in accordance with the work operation command. The controller 40 determines the required work rotation speed of the work implement motor 23 based on the work operation command.

[0027] In step S105, the controller 40 determines the control mode of the work implement motor 23. Fig. 5 is a transition diagram of the control modes of the work implement motor 23. As shown in Fig. 5, the control modes of the work implement motor 23 include an idling mode, a work implement mode, and a traveling lubrication mode. The controller 40 determines the control mode of the work implement motor 23 based on the required work rotational speed, the required traveling rotational speed, and the idling rotational speed. The idling rotational speed is the target rotational speed of the work implement motor 23 when idling.

[0028] The control mode of the work implement motor 23 is the idling mode when the system of the work machine 1 is started. If the control mode of the work implement motor 23 is the idling mode, in step S106, the controller 40 determines the idling rotation speed as the target rotation speed of the work implement motor 23.

[0029] 5 , when the control mode is the idling mode and condition 1 is satisfied, the controller 40 changes the control mode from the idling mode to the work machine mode. Condition 1 is that the work required rotational speed is greater than the idling rotational speed and greater than the lubrication required rotational speed. When the control mode of the work machine motor 23 is the work machine mode, the controller 40 determines the work required rotational speed as the target rotational speed of the work machine motor 23 in step S106.

[0030] When the control mode is the work machine mode and condition 2 is satisfied, the controller 40 changes the control mode from the work machine mode to the idling mode. Condition 2 is that the required work rotation speed is equal to or lower than the idling rotation speed, and the required lubrication rotation speed is equal to or lower than the idling rotation speed.

[0031] If condition 3 is satisfied while the control mode is the idling mode, the controller 40 changes the control mode from the idling mode to the traveling lubrication mode. Condition 3 is that the lubrication request rotational speed is greater than the idling rotational speed and is greater than the work request rotational speed. If the control mode of the work implement motor 23 is the traveling lubrication mode, in step S106, the controller 40 determines the lubrication request rotational speed as the target rotational speed of the work implement motor 23.

[0032] When the control mode is the work machine mode and condition 4 is satisfied, the controller 40 changes the control mode from the traveling lubrication mode to the idling mode. Condition 4 is that the required work rotation speed is equal to or lower than the idling rotation speed, and the required lubrication rotation speed is equal to or lower than the idling rotation speed.

[0033] If condition 5 is satisfied when the control mode is the traveling lubrication mode, the controller 40 changes the control mode from the traveling lubrication mode to the work machine mode. Condition 5 is that the work required rotational speed is greater than the idling rotational speed, and the work required rotational speed is greater than the lubrication required rotational speed. If condition 6 is satisfied when the control mode is the work machine mode, the controller 40 changes the control mode from the work machine mode to the traveling lubrication mode. Condition 6 is that the work required rotational speed is smaller than the traveling lubrication rotational speed, and the lubrication required rotational speed is greater than the idling rotational speed.

[0034] In step S107, the controller 40 controls the work machine motor 23. The controller 40 controls the work machine motor 23 based on the target rotation speed. When the control mode of the work machine motor 23 is the idling mode, the controller 40 controls the work machine motor 23 so that the rotation speed of the work machine motor 23 becomes the idling rotation speed.

[0035] When the control mode of the work implement motor 23 is the work mode, the controller 40 controls the work implement motor 23 so that the rotational speed of the work implement motor 23 becomes the rotational speed required for work. Therefore, the controller 40 controls the rotational speed of the work implement motor 23 in accordance with the operation of the work implement operating device 44.

[0036] When the control mode of the work implement motor 23 is the traveling lubrication mode, the controller 40 controls the work implement motor 23 so that the rotational speed of the work implement motor 23 becomes the lubrication required rotational speed. Therefore, the controller 40 controls the rotational speed of the work implement motor 23 in accordance with the traveling horsepower of the transmission 27.

[0037] In the work machine 1 according to the present embodiment described above, the required lubrication amount of lubricating oil for the transmission 27 is calculated based on the traveling horsepower. Then, the rotational speed of the work implement pump 25 is controlled based on the calculated required lubrication amount, thereby controlling the discharge amount of the lubricating pump 30. Therefore, an appropriate amount of lubricating oil is supplied to the transmission 27 in accordance with the traveling horsepower, without using a large-capacity lubricating pump 30. This ensures that the transmission 27 is appropriately lubricated and the electricity consumption of the work implement pump 25 is improved.

[0038] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention.

[0039] The work machine 1 is not limited to a wheel loader, but may be other machines such as a bulldozer, a shovel, or a motor grader. The configuration of the work machine 1 is not limited to that of the above embodiment and may be modified. For example, the running body 4 may include tracks.

[0040] The lubrication pump 30 may be a variable displacement pump. In this case, the controller 40 may determine a target displacement of the variable displacement pump based on the required amount of lubrication. For example, the controller 40 may determine the target displacement based on the rotational speed of the work implement motor 23 and the required amount of lubrication. The controller 40 may control the lubrication pump 30 based on the target displacement. In this case, too, an appropriate amount of lubricating oil is supplied to the transmission 27 in accordance with the traveling horsepower without using a large-capacity lubrication pump 30. This allows the transmission 27 to be appropriately lubricated and improves the electricity consumption of the work implement pump 25.

[0041] The lubricating pump 30 may be driven by a device other than the work machine motor 23. For example, Fig. 6 is a block diagram showing the configuration of a drive system of a work machine 1 according to another embodiment. As shown in Fig. 6, the lubricating pump 30 may be driven by driving force from the travel motor 24.

[0042] The present disclosure provides for proper transmission lubrication and improved energy efficiency in work machines.

[0043] 2: Vehicle body, 3: Work machine, 4: Traveling body, 23: Work machine motor, 24: Traveling motor, 27: Transmission, 30: Lubrication pump, 40: Controller

Claims

1. A work machine comprising: a vehicle body; a running body that runs the vehicle body; a transmission connected to the running body; a travel motor connected to the transmission; a work implement operably attached to the vehicle body; a lubrication pump that supplies lubricating oil to the transmission; and a controller that acquires running horsepower passing through the transmission, calculates a required lubrication amount of lubricating oil for the transmission based on the running horsepower, and controls the discharge amount of the lubrication pump based on the required lubrication amount.

2. The work machine according to claim 1, further comprising a work machine motor that drives the work machine, wherein the lubrication pump is a fixed displacement pump driven by the work machine motor, and wherein the controller determines a target rotation speed of the work machine motor based on the required lubrication amount, and controls the work machine motor based on the target rotation speed.

3. The work machine according to claim 2, wherein the controller: determines a lubrication required rotational speed of the work machine motor based on the required lubrication amount; obtains an operation command to operate the work machine; determines a work required rotational speed of the work machine motor for operating the work machine based on the operation command; if the lubrication required rotational speed is higher than the work required rotational speed, determines a target rotational speed of the work machine motor based on the lubrication required rotational speed; if the work required rotational speed is higher than the lubrication required rotational speed, determines a target rotational speed of the work machine motor based on the work required rotational speed; and controls the work machine motor based on the target rotational speed.

4. The work machine according to claim 2, wherein the controller: acquires a predetermined idling rotation speed of the work machine motor; determines a lubrication required rotation speed of the work machine motor based on the required lubrication amount; if the idling rotation speed is higher than the lubrication required rotation speed, determines a target rotation speed of the work machine motor based on the idling rotation speed; if the lubrication required rotation speed is higher than the idling rotation speed, determines a target rotation speed of the work machine motor based on the lubrication required rotation speed; and controls the work machine motor based on the target rotation speed.

5. The work machine according to claim 2, wherein the controller determines a target rotation speed of the work machine motor based on the capacity of the lubrication pump and the required amount of lubrication.

6. The work machine according to claim 1, further comprising a work machine motor that drives the work machine, wherein the lubrication pump is a variable displacement pump driven by the work machine motor, and wherein the controller determines a target displacement of the variable displacement pump based on the required lubrication amount, and controls the lubrication pump based on the target displacement.

7. A method executed by a controller for controlling a work machine comprising a vehicle body, a running body that runs the vehicle body, a transmission connected to the running body, a travel motor connected to the transmission, a work implement operably attached to the vehicle body, and a lubrication pump that supplies lubricating oil to the transmission, the method comprising: acquiring running horsepower passing through the transmission; calculating a required lubrication amount of lubricating oil for the transmission based on the running horsepower; and controlling the discharge amount of the lubrication pump based on the required lubrication amount.

8. The method according to claim 7, wherein the work machine further comprises a work machine motor that drives the work machine, the lubrication pump being a fixed displacement pump driven by the work machine motor, and the method comprises: determining a target rotation speed of the work machine motor based on the required lubrication amount; and controlling the work machine motor based on the target rotation speed.

9. The method according to claim 8, comprising: determining a required lubrication rotational speed of the work machine motor based on the required lubrication amount; obtaining an operation command to operate the work machine; determining a required work rotational speed of the work machine motor for operating the work machine based on the operation command; if the required lubrication rotational speed is higher than the required work rotational speed, determining a target rotational speed of the work machine motor based on the required lubrication rotational speed; if the required work rotational speed is higher than the required lubrication rotational speed, determining a target rotational speed of the work machine motor based on the required work rotational speed; and controlling the work machine motor based on the target rotational speed.

10. A method according to claim 8, comprising: obtaining a predetermined idling rotation speed of the work machine motor; determining a lubrication request rotation speed of the work machine motor based on the required lubrication amount; if the idling rotation speed is higher than the lubrication request rotation speed, determining a target rotation speed of the work machine motor based on the idling rotation speed; if the lubrication request rotation speed is higher than the idling rotation speed, determining a target rotation speed of the work machine motor based on the lubrication request rotation speed; and controlling the work machine motor based on the target rotation speed.

11. The method according to claim 8, further comprising determining a target rotational speed of the work machine motor based on the displacement of the lubrication pump and the required amount of lubrication.

12. The method according to claim 7, wherein the work machine further comprises a work machine motor that drives the work machine, and the lubrication pump is a variable displacement pump driven by the work machine motor, and the method comprises: determining a target displacement of the variable displacement pump based on the required lubrication amount; and controlling the lubrication pump based on the target displacement.

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