System and method for controlling a work machine having a continuously variable transmission

Abstract

To facilitate the shift operation of a continuously variable transmission.SOLUTION: A system according to an aspect of the present disclosure is a system for controlling a work machine having a continuously variable transmission. The system according to this aspect includes a shift operation member and a controller. The shift operation member is operable by an operator. The controller upshifts a virtual gear ratio of the continuously variable transmission at a predetermined increase rate in response to a first upshift operation to the shift operation member. The controller upshifts a virtual gear ratio of the continuously variable transmission to a predetermined preset gear ratio in response to a second upshifting operation to the shifting operation member.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to systems and methods for controlling a work machine having a continuously variable transmission. [Background technology]

[0002] Conventionally, there are known work machines in which the virtual gear ratio of a continuously variable transmission can be shifted by operating an operating member. For example, a bulldozer disclosed in Patent Document 1 is equipped with a shift mode selector switch, a shift-up switch, and a shift-down switch. The shift mode selector switch is operated to switch between a quick shift mode and a continuously variable shift mode.

[0003] In quick shift mode, the controller shifts up one gear when the upshift switch is pressed, and shifts down one gear when the downshift switch is pressed. In continuously variable shift mode, the gears are set more precisely than in quick shift mode. In continuously variable shift mode, the controller shifts up one gear for the duration that the upshift switch is pressed, and shifts down one gear for the duration that the downshift switch is pressed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4956001 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-described work machine, the quick shift mode and the continuously variable shift mode make it easy to change gears in the continuously variable transmission. However, there is a demand for making the gear change operation of the continuously variable transmission even easier. An object of the present disclosure is to make the gear change operation of the continuously variable transmission easier. [Means for solving the problem]

[0006] A system according to one aspect of the present disclosure is a system for controlling a work machine having a continuously variable transmission. The system according to this aspect includes a shift operation member and a controller. The shift operation member is operable by an operator. The controller upshifts a virtual gear ratio of the continuously variable transmission at a predetermined increase rate in response to a first upshift operation to the shift operation member. The controller upshifts the virtual gear ratio of the continuously variable transmission to a predetermined preset gear ratio in response to a second upshift operation to the shift operation member.

[0007] Another aspect of the present disclosure provides a method for controlling a work machine having a continuously variable transmission. The method includes receiving an operation signal indicating an operation of a shift operating member operable by an operator, upshifting a virtual gear ratio of the continuously variable transmission at a predetermined increase rate in response to a first upshift operation of the shift operating member, and upshifting the virtual gear ratio of the continuously variable transmission to a predetermined preset gear ratio in response to a second upshift operation of the shift operating member. [Effects of the Invention]

[0008] According to the present disclosure, a first upshift operation of the shift operation member allows the virtual gear ratio to be finely upshifted at a predetermined rate of increase. Furthermore, a second upshift operation of the shift operation member allows the virtual gear ratio to be quickly upshifted to a predetermined preset gear ratio. This makes it easier to perform gear changes in a continuously variable transmission. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a side view showing a work machine according to an embodiment. [Figure 2] 1 is a block diagram showing the configuration of a drive system and a control system of a work machine. [Figure 3] FIG. [Figure 4]FIG. 4 is a diagram showing an example of set vehicle speed data. [Figure 5] FIG. [Figure 6] FIG. 6 is a diagram illustrating the relationship between the stroke amount of the shift operation member and the operation reaction force. [Figure 7A] FIG. 10 is a diagram showing a change in the shift display when shifting up in the first shift mode. [Figure 7B] FIG. 10 is a diagram showing a change in the shift display when shifting up in the first shift mode. [Figure 7C] FIG. 10 is a diagram showing a change in the shift display when shifting up in the first shift mode. [Figure 8A] FIG. 10 is a diagram showing a change in the shift display when shifting up in the second shift mode. [Figure 8B] FIG. 10 is a diagram showing a change in the shift display when shifting up in the second shift mode. [Figure 8C] FIG. 10 is a diagram showing a change in the shift display when shifting up in the second shift mode. [Figure 9A] FIG. 10 is a diagram showing changes in the shift display when downshifting in the first shift mode. [Figure 9B] FIG. 10 is a diagram showing changes in the shift display when downshifting in the first shift mode. [Figure 9C] FIG. 10 is a diagram showing changes in the shift display when downshifting in the first shift mode. [Figure 10A] FIG. 10 is a diagram showing changes in the shift display when downshifting in the second shift mode. [Figure 10B] FIG. 10 is a diagram showing changes in the shift display when downshifting in the second shift mode. [Figure 10C] FIG. 10 is a diagram showing changes in the shift display when downshifting in the second shift mode. [Figure 11] 10 shows a setting screen for a preset gear ratio. [Figure 12] 10 shows a setting screen for a preset gear ratio. [Figure 13A] FIG. 10 is a diagram showing a change in the shift display when upshifting in the second shift mode after changing the preset gear ratio. [Figure 13B] FIG. 10 is a diagram showing a change in the shift display when upshifting in the second shift mode after changing the preset gear ratio. [Figure 13C] FIG. 10 is a diagram showing a change in the shift display when upshifting in the second shift mode after changing the preset gear ratio. [Figure 14A] FIG. 10 is a diagram showing a change in the shift display when downshifting in the second shift mode after changing the preset gear ratio. [Figure 14B] FIG. 10 is a diagram showing a change in the shift display when downshifting in the second shift mode after changing the preset gear ratio. [Figure 14C] FIG. 10 is a diagram showing a change in the shift display when downshifting in the second shift mode after changing the preset gear ratio. DETAILED DESCRIPTION OF THE INVENTION

[0010] A work machine according to an embodiment will be described below with reference to the drawings. FIG. 1 is a side view showing a work machine 1 according to an embodiment. The work machine 1 according to this embodiment is a bulldozer. The work machine 1 comprises a vehicle body 11 and a work implement 12.

[0011] The vehicle body 11 includes a cab 13 and a traveling device 15. A driver's seat (not shown) is arranged in the cab 13. The traveling device 15 is provided on the lower part of the vehicle body 11. The traveling device 15 includes a pair of left and right tracks 16. Note that only the left track 16 is shown in FIG. 1. The rotation of the tracks 16 causes the work machine 1 to travel.

[0012] The work implement 12 is attached to the vehicle body 11. The work implement 12 has a lift frame 17, a blade 18, and a lift actuator 19. The lift frame 17 is supported so as to be able to rotate up and down relative to the vehicle body 11. The blade 18 is supported by the lift frame 17. The lift actuator 19 is a hydraulic cylinder. The blade 18 moves up and down as the lift actuator 19 extends and retracts.

[0013] Fig. 2 is a block diagram showing the configuration of the drive system 2 and control system 3 of the work machine 1. As shown in Fig. 2, the drive system 2 includes a drive source 22, a hydraulic pump 23, and a continuously variable transmission 24. The drive source 22 includes, for example, an internal combustion engine. The drive source 22 may also include an electric motor. The hydraulic pump 23 is driven by the drive source 22 and discharges hydraulic oil. The hydraulic oil discharged from the hydraulic pump 23 is supplied to the lift actuator 19 via a control valve 25. Although Fig. 2 shows one hydraulic pump 23, multiple hydraulic pumps may be provided.

[0014] The continuously variable transmission 24 transmits the driving force of the drive source 22 to the traveling device 15. The continuously variable transmission 24 is capable of continuously changing the gear ratio. The continuously variable transmission 24 is, for example, an HST (Hydro Static Transmission). The continuously variable transmission 24 includes a hydraulic pump 26 and a hydraulic motor 27. The hydraulic pump 26 is driven by the drive source 22 and discharges hydraulic oil. The hydraulic motor 27 is driven by the hydraulic oil discharged from the hydraulic pump 26. The hydraulic motor 27 is connected to the traveling device 15. The hydraulic motor 27 drives the traveling device 15, causing the work machine 1 to travel. The gear ratio of the continuously variable transmission 24 is continuously and continuously changed continuously.

[0015] The control system 3 includes a controller 30. The controller 30 is programmed to control the work machine 1 based on the acquired data. The controller 30 includes a memory device 31 and a processor 32. The processor 32 includes, for example, a CPU. The memory device 31 includes, for example, a memory and an auxiliary memory device. The memory device 31 may be, for example, a RAM or a ROM. The memory device 31 may be, for example, a semiconductor memory or a hard disk. The memory device 31 stores computer instructions that are executable by the processor 32 and are used to control the work machine 1.

[0016] The control system 3 includes an input device 33 and a display 34. The input device 33 can be operated by an operator to make control settings for the work machine 1. The input device 33 may be a touch screen. Alternatively, the input device 33 may include other devices such as switches. The input device 33 outputs an input signal indicating an operation by the operator to the controller 30. The display 34 displays an image according to an image signal from the controller 30.

[0017] The control system 3 includes a work implement operating device 35 and a travel operating device 36. The work implement operating device 35 can be operated by an operator to operate the work implement 12. The work implement operating device 35 includes, for example, a work implement lever. However, the work implement operating device 35 may include other components such as a switch. The work implement operating device 35 outputs a work command in response to operation by the operator to the controller 30. The controller 30 controls the control valve 25 in response to the work command from the work implement operating device 35 so as to operate the work implement 12. As a result, the work implement 12 moves up and down in response to operation of the work implement operating device 35 by the operator.

[0018] FIG. 3 is a perspective view of the travel operation device 36. As shown in FIG. 3, the travel operation device 36 includes a travel lever 37 and a shift operation member 38. The travel lever 37 can be operated by the operator to control the forward and reverse movement of the work machine 1. The travel operation device 36 outputs a travel command to the controller 30 in response to operation of the travel lever 37 by the operator. In response to the travel command from the travel operation device 36, the controller 30 controls the drive source 22 and the continuously variable transmission 24 so as to cause the work machine 1 to travel. As a result, the work machine 1 moves forward or reverse in response to operation of the travel operation device 36 by the operator. The travel operation device 36 may also include a brake pedal (not shown).

[0019] The shift operating member 38 is operable to change the virtual gear ratio of the continuously variable transmission 24. The travel operation device 36 outputs a gear shift signal in response to operation of the shift operating member 38 by the operator. The controller 30 receives the gear shift signal. The controller 30 changes the virtual gear ratio of the continuously variable transmission 24 among a plurality of virtual gear ratios in response to the gear shift signal from the travel operation device 36. As a result, the continuously variable transmission 24 changes its virtual gear ratio in response to operation of the shift operating member 38 by the operator.

[0020] The virtual gear ratio is a gear ratio set by the controller 30. For example, the controller 30 sets a plurality of virtual gear ratios including 1.0, 2.0, and 3.0. The controller 30 controls the vehicle speed of the work machine 1 according to the virtual gear ratio set by operating the shift operating member 38. For example, FIG. 4 is a diagram showing an example of set vehicle speed data that defines the relationship between the set virtual gear ratio and the vehicle speed of the work machine 1. The set vehicle speed is the vehicle speed obtained at a specified engine speed (e.g., high idle speed) under a specified traveling load state. The specified traveling condition is, for example, a state in which the work machine 1 is traveling on a flat road with hard, compacted soil and no incline, and the work implement 12 is not performing earthwork, towing, or the like. The operator can travel the work machine 1 at a desired vehicle speed by selecting a virtual gear ratio. The controller 30 references the set vehicle speed data and sets the vehicle speed of the work machine 1 based on the set virtual gear ratio. The controller 30 controls the gear ratio of the continuously variable transmission 24 based on the set vehicle speed.

[0021] As shown in FIG. 4, the controller 30 stores a virtual gear ratio that changes at a predetermined rate between 0th gear (neutral) and 3.0th gear. In this embodiment, the predetermined rate is 0.1. For example, the controller 30 stores a plurality of virtual gear ratios that change in increments of 0.1 between 0th gear and 3.0th gear. In this embodiment, the number of virtual gear ratios is 30, ranging from 0.1 to 3.0.

[0022] The controller 30 performs shift control of the virtual gear ratio of the continuously variable transmission 24 in a plurality of modes in response to operation of the shift operating member 38. The plurality of modes include a first shift mode and a second shift mode. In the first shift mode, the controller 30 shifts the virtual gear ratio of the continuously variable transmission 24 at the predetermined change rate (0.1) described above. In the second shift mode, the controller 30 shifts the virtual gear ratio of the continuously variable transmission 24 to a preset gear ratio. The preset gear ratio is a pre-set virtual gear ratio that can be adjusted by an operator operating the input device 33. Note that, as will be described in detail later, in this embodiment, 0.1, 1.0, 2.0, and 3.0 are pre-stored in the controller 30 as initial values ​​of the preset gear ratios.

[0023] The following describes shift control of the virtual gear ratio of the continuously variable transmission 24 in response to operation of the shift operating member 38. FIG. 5 is an enlarged view of the shift operating member 38. The shift operating member 38 is rotatably attached to the travel lever 37. The shift operating member 38 is movable in an upshift direction and a downshift direction from a neutral position N1. The shift operating member 38 is a momentary switch. That is, when not operated, the shift operating member 38 returns to the neutral position N1. As shown in FIG. 3, the shift operating member 38 can be operated with the fingertip (thumb tip) of an operator with their hand on the travel lever 37.

[0024] The shift operating member 38 can be operated between a neutral range, a first range, a second range, a third range, and a fourth range. The neutral range is a range that includes the neutral position N1. The first range is a range in which the stroke amount in the upshift direction is greater than that of the neutral range. The second range is a range in which the stroke amount in the upshift direction is greater than that of the first range. The third range is a range in which the stroke amount in the downshift direction is greater than that of the neutral range. The fourth range is a range in which the stroke amount in the downshift direction is greater than that of the third range.

[0025] The shift operation member 38 is biased by a biasing member (not shown) to generate an actuation reaction force corresponding to the stroke amount. FIG. 6 is a diagram illustrating the relationship between the stroke amount of the shift operation member 38 and the actuation reaction force. As shown in FIG. 6, when the stroke amount of the shift operation member 38 in the upshift direction increases from the neutral range to a first stroke amount S1 within a first range, the actuation reaction force increases at a first increasing rate. When the stroke amount of the shift operation member 38 in the upshift direction increases from the first stroke amount S1 to a second stroke amount S2 within the first range, the actuation reaction force increases at a second increasing rate. The second increasing rate is greater than the first increasing rate. After the stroke amount of the shift operation member 38 in the upshift direction exceeds the second stroke amount S2, the actuation reaction force increases at a third increasing rate. The third increasing rate is smaller than the second increasing rate. The third increasing rate is greater than the first increasing rate.

[0026] Therefore, when the operator operates the shift operation member 38 in the upshift direction, the operator feels a greater resistance due to an increase in the rate of increase in the operation reaction force when the shift operation member 38 is operated from the neutral range to the first range. Then, when the shift operation member 38 is operated beyond the first range to the second range, the operator feels a change in resistance due to a decrease in the rate of increase in the operation reaction force. This allows the operator to easily distinguish between the first range and the second range when operating the shift operation member 38 in the upshift direction.

[0027] Additionally, when the stroke of the shift operation member 38 in the downshift direction is from the neutral range to a third stroke amount S3 within the third range, the operation reaction force increases at a first increasing rate. When the stroke of the shift operation member 38 in the downshift direction is from the third stroke amount S3 to a fourth stroke amount S4 within the third range, the operation reaction force increases at a second increasing rate. After the stroke of the shift operation member 38 in the downshift direction exceeds the fourth stroke amount S4, the operation reaction force increases at a third increasing rate.

[0028] Therefore, when the operator operates the shift operation member 38 in the downshift direction, the operator feels a greater resistance due to an increase in the rate of increase in the operation reaction force when the shift operation member 38 is operated from the neutral range to the third range. Then, when the shift operation member 38 is operated beyond the third range to the fourth range, the operator feels a change in resistance due to a decrease in the rate of increase in the operation reaction force. This allows the operator to easily distinguish between the third range and the fourth range when operating the shift operation member 38 in the downshift direction.

[0029] The controller 30 performs shift control in a first shift mode or a second shift mode depending on the stroke amount of the shift operating member 38. FIGS. 7A to 7C and 8A to 8C are diagrams showing a shift indicator 40 displayed on the display 34 by the controller 30. FIGS. 7A to 7C and 8A to 8C show the shift indicator 40 when traveling forward. As shown in FIGS. 7A to 7C and 8A to 8C, the shift indicator 40 includes preset indicators 41A-41D, a first shift indicator 42, and a second shift indicator 43.

[0030] The preset displays 41A-41D indicate preset gear ratios. The preset gear ratios are virtual gear ratios that can be adjusted by the operator operating the input device 33. In this embodiment, the preset gear ratios include a first preset gear ratio, a second preset gear ratio, a third preset gear ratio, and a fourth preset gear ratio. In this embodiment, the initial values ​​of the first to fourth preset gear ratios are set to 0.1 speed, 1.0 speed, 2.0 speed, and 3.0 speed, respectively. The preset displays 41A-41D include first to fourth preset displays 41A-41D. The first preset display 41A indicates the first preset gear ratio. The second preset display 41B indicates the second preset gear ratio. The third preset display 41C indicates the third preset gear ratio. The fourth preset display 41D indicates the fourth preset gear ratio. 7A to 7C and 8A to 8C, the first preset display 41A indicates 0.1 speed as the initial value of the first preset gear ratio. The second preset display 41B indicates 1.0 speed as the initial value of the second preset gear ratio. The third preset display 41C indicates 2.0 speed as the initial value of the third preset gear ratio. The fourth preset display 41D indicates 3.0 speed as the initial value of the fourth preset gear ratio. In this embodiment, the controller 30 stores four preset gear ratios, but the number of preset gear ratios is not limited to four. The number of preset gear ratios may be more or less than four.

[0031] The first shift indicator 42 and the second shift indicator 43 indicate the current virtual gear ratio of the continuously variable transmission 24. The first shift indicator 42 includes a plurality of indicators 44. Note that in the drawings, only one of the plurality of indicators 44 is given the reference numeral 44, and the reference numerals of the other indicators 44 are omitted.

[0032] One of the indicators 44 indicates a predetermined rate of change of the virtual gear ratio described above. That is, in this embodiment, one of the indicators 44 indicates a rate of change of 0.1 of the virtual gear ratio. The number of indicators 44 corresponds to the number of virtual gear ratios. The first shift indicator 42 indicates the current virtual gear ratio by the number of indicators displayed. The second shift indicator 43 indicates the current virtual gear ratio numerically. In the example shown in FIG. 7A, the current virtual gear ratio is 1.0.

[0033] 7A to 7C show the change in the shift indicator 40 when a gear change is performed in the first shift mode during forward travel. The letter "F" in the displays of FIGS. 7A to 7C indicates forward travel, and "R" is displayed instead of "F" during reverse travel. When the shift operating member 38 is operated from the neutral range to the first range (hereinafter referred to as a first upshift operation), the controller 30 upshifts the virtual gear ratio of the continuously variable transmission 24 at a predetermined rate of increase in the first shift mode. The predetermined rate of increase is equal to the aforementioned rate of change of 0.1. Therefore, when a first upshift operation is performed on the shift operating member 38, the controller 30 increases the virtual gear ratio by 0.1. For example, when the shift operating member 38 returns from the first range to the neutral range after the first upshift operation, the controller 30 upshifts the virtual gear ratio at a predetermined rate of increase. Alternatively, the controller 30 upshifts the virtual gear ratio at a predetermined rate of increase when the shift operating member 38 is held in the first range for a predetermined time after a first upshift operation is performed on the shift operating member 38. The controller 30 increases the indicator 44 displayed on the first shift indicator 42 by one in response to the upshift of the virtual gear ratio.

[0034] For example, as shown in Fig. 7A, when the current virtual gear ratio is 1.0 and a first upshift operation is performed on the shift operation member 38, the controller 30 upshifts the virtual gear ratio to 1.1, as shown in Fig. 7B. When the virtual gear ratio is 1.1 and a first upshift operation is performed on the shift operation member 38, the controller 30 upshifts the virtual gear ratio to 1.2, as shown in Fig. 7C. Similarly, each time the shift operation member 38 is subjected to a first upshift operation, the controller 30 increases the virtual gear ratio by 0.1 until it reaches the maximum virtual gear ratio of 3.0.

[0035] Although not shown, when the virtual gear ratio is between the first preset gear ratio and the second preset gear ratio, the controller 30 similarly increases the virtual gear ratio by 0.1 each time a first upshift operation is performed on the shift operation member 38. Similarly, when the virtual gear ratio is between the third preset gear ratio and the fourth preset gear ratio, the controller 30 similarly increases the virtual gear ratio by 0.1 each time a first upshift operation is performed on the shift operation member 38.

[0036] 8A to 8C show changes in the shift display 40 in the second shift mode. When the shift operating member 38 is operated into the second range (hereinafter referred to as a second upshift operation), the controller 30 upshifts the virtual gear ratio of the continuously variable transmission 24 to a higher preset gear ratio in the second shift mode. The higher preset gear ratio is a preset gear ratio that is closest to the current virtual gear ratio and is greater than the current virtual gear ratio.

[0037] For example, as shown in Fig. 8A, if a second upshift operation is performed on the shift operation member 38 when the current virtual gear ratio is the second preset gear ratio or between the second and third preset gear ratios, the controller 30 upshifts the virtual gear ratio to the third preset gear ratio, which is a higher preset gear ratio, as shown in Fig. 8B. Specifically, as shown in Fig. 8A, if a second upshift operation is performed on the shift operation member 38 when the current virtual gear ratio is 1.2 speed, the controller 30 upshifts the virtual gear ratio to 2.0 speed, as shown in Fig. 8B.

[0038] As shown in Fig. 8B, when a second upshift operation is performed on the shift operation member 38 while the current virtual gear ratio is the third preset gear ratio or between the third and fourth preset gear ratios, the controller 30 upshifts the virtual gear ratio to the fourth preset gear ratio, which is a higher preset gear ratio, as shown in Fig. 8C. Specifically, as shown in Fig. 8B, when a second upshift operation is performed on the shift operation member 38 while the current virtual gear ratio is 2.0, the controller 30 upshifts the virtual gear ratio to 3.0 as shown in Fig. 8C.

[0039] Although not shown, even when the virtual gear ratio is the first preset gear ratio or between the first and second preset gear ratios, if a second upshift operation is performed on the shift operation member 38, the controller 30 will upshift the virtual gear ratio to the second preset gear ratio in the same manner as described above. That is, when the virtual gear ratio is between 0.1 and 0.9 speeds and a second upshift operation is performed on the shift operation member 38, the controller 30 will upshift the virtual gear ratio to 1.0 speed.

[0040] Next, a downshift operation will be described. When the shift operation member 38 is operated from the neutral range to the third range (hereinafter referred to as a first downshift operation), the controller 30 downshifts the virtual gear ratio of the continuously variable transmission 24 at a predetermined rate of decrease in the first shift mode. The predetermined rate of decrease is equal to the rate of change described above. Therefore, when a first downshift operation is performed on the shift operation member 38, the controller 30 decreases the virtual gear ratio by 0.1. For example, the controller 30 downshifts the virtual gear ratio at a predetermined rate of decrease when the shift operation member 38 returns from the third range to the neutral range after a first downshift operation is performed on the shift operation member 38. Alternatively, the controller 30 downshifts the virtual gear ratio at a predetermined rate of decrease when the shift operation member 38 is held in the third range for a predetermined time after a first downshift operation is performed on the shift operation member 38. The controller 30 decreases the indicator displayed on the first shift indicator 42 by one in response to the downshift of the virtual gear ratio.

[0041] For example, as shown in Fig. 9A, when the current virtual gear ratio is 3.0 and a first downshift operation is performed on the shift operation member 38, the controller 30 downshifts the virtual gear ratio to 2.9, as shown in Fig. 9B. When the virtual gear ratio is 2.9 and a first downshift operation is performed on the shift operation member 38 as shown in Fig. 9B, the controller 30 downshifts the virtual gear ratio to 2.8, as shown in Fig. 9C. Similarly, each time the first downshift operation is performed on the shift operation member 38, the controller 30 decreases the virtual gear ratio by 0.1.

[0042] Although not shown, similarly, between the third preset gear ratio and the second preset gear ratio, the controller 30 decreases the virtual gear ratio by 0.1 each time a first downshift operation is performed on the shift operation member 38. Similarly, when the virtual gear ratio is between the second preset gear ratio and the first preset gear ratio, the controller 30 decreases the virtual gear ratio by 0.1 each time a first downshift operation is performed on the shift operation member 38, until the virtual gear ratio reaches 0.1 speed, which is the smallest virtual gear ratio.

[0043] 10A to 10C show changes in the shift display 40 in the second shift mode. When the shift operating member 38 is operated into the fourth range (hereinafter referred to as a second downshift operation), the controller 30 downshifts the virtual gear ratio of the continuously variable transmission 24 to a lower preset gear ratio in the second shift mode. The lower preset gear ratio is a preset gear ratio that is closest to the current virtual gear ratio and is smaller than the current virtual gear ratio.

[0044] For example, as shown in Fig. 10A, if a second downshift operation is performed on the shift operation member 38 when the current virtual gear ratio is the fourth preset gear ratio or between the fourth and third preset gear ratios, the controller 30 downshifts the virtual gear ratio to the third preset gear ratio, which is a lower preset gear ratio, as shown in Fig. 10B. Specifically, as shown in Fig. 10A, if a second downshift operation is performed on the shift operation member 38 when the current virtual gear ratio is 2.8 speed, the controller 30 downshifts the virtual gear ratio to 2.0 speed, as shown in Fig. 10B.

[0045] As shown in Fig. 10B, when a second downshift operation is performed on the shift operation member 38 while the current virtual gear ratio is the third preset gear ratio or between the third preset gear ratio and the second preset gear ratio, the controller 30 downshifts the virtual gear ratio to the second preset gear ratio, which is a lower preset gear ratio, as shown in Fig. 10C. Specifically, as shown in Fig. 10B, when a second downshift operation is performed on the shift operation member 38 while the current virtual gear ratio is 2.0, the controller 30 downshifts the virtual gear ratio to 1.0 as shown in Fig. 10C.

[0046] Although not shown, if a second downshift operation is performed on the shift operation member 38 when the current virtual gear ratio is the second preset gear ratio or between the second preset gear ratio and the first preset gear ratio, the controller 30 downshifts the virtual gear ratio to the first preset gear ratio. That is, if a second downshift operation is performed on the shift operation member 38 when the current virtual gear ratio is between 0.2 and 1.0, the controller 30 downshifts the virtual gear ratio to 0.1. While the shift control during forward travel has been described above, the controller 30 also performs the same shift control during reverse travel.

[0047] As described above, the initial values ​​of the preset gear ratios in the second shift mode are 0.1, 1.0, 2.0, and 3.0, but these values ​​can be changed. That is, the preset gear ratios can be changed by the operator operating the input device 33. Figure 11 is a diagram showing a preset gear ratio setting screen 50. The controller 30 causes the preset gear ratio setting screen 50 to be displayed on the display 34.

[0048] As shown in FIG. 11 , the preset gear ratio setting screen 50 includes a shift range display 51, preset displays 52A-52D, and gear displays 53A-53D. The shift range display 51 shows the entire range of virtual gear ratios of the continuously variable transmission 24. The shift range display 51 includes multiple indicators 54. The number of the multiple indicators 54 corresponds to the number of virtual gear ratios. One of the multiple indicators 54 indicates a predetermined rate of change of the virtual gear ratio described above. That is, in this embodiment, one of the multiple indicators 54 indicates a rate of change of 0.1 of the virtual gear ratio. In this embodiment, 30 indicators 54 are displayed corresponding to the 30 virtual gear ratios.

[0049] Preset displays 52A-52D indicate preset gear ratios. Preset displays 52A-52D are indicated by icons. The position of preset displays 52A-52D relative to shift range display 51 indicates the preset gear ratio that has been set. Preset displays 52A-52D include first to fourth preset displays 52A-52D. First preset display 52A indicates the first preset gear ratio. Second preset display 52B indicates the second preset gear ratio. Third preset display 52C indicates the third preset gear ratio. Fourth preset display 52D indicates the fourth preset gear ratio.

[0050] The preset gear ratios can be changed within a variable range set for each preset gear ratio. In Fig. 11, arrows 55A-55D indicate the variable range set for each preset gear ratio. The operator sets each preset gear ratio by operating input device 33 to move preset indicators 52A-52D on setting screen 50 within variable ranges 55A-55D.

[0051] Gear displays 53A-53D numerically indicate each preset gear ratio that has been set. Gear displays 53A-53D include a first gear display 53A, a second gear display 53B, a third gear display 53C, and a fourth gear display 53D. First gear display 53A numerically indicates the first preset gear ratio. Second gear display 53B numerically indicates the second preset gear ratio. Third gear display 53C numerically indicates the third preset gear ratio. Fourth gear display 53D numerically indicates the fourth preset gear ratio.

[0052] The shift range display 51, preset displays 52A-52D, gear displays 53A-53D, and variable ranges 55A-55D of the preset gear ratio setting screen 50 described above are displays for forward gear. The preset gear ratio setting screen 50 also includes a shift range display 56, preset displays 57A-57D, gear displays 58A-58D, and variable ranges 59A-59D for reverse gear. The shift range display 56, preset displays 57A-57D, gear displays 58A-58D, and variable ranges 59A-59D for reverse gear are similar to the shift range display 51, preset displays 52A-52D, gear displays 53A-53D, and variable ranges 55A-55D for forward gear, respectively, and therefore will not be described in detail again.

[0053] For example, as shown in Fig. 12, the operator operates the input device 33 to move the third preset indicator 52C. In this way, the operator changes the third preset gear ratio. For example, the operator changes the third preset gear ratio from the initial value 2.0 speed shown in Fig. 11 to 1.7 speed shown in Fig. 12. In this case, the position of the third preset indicator 41C in the shift indicator 40 is changed as shown in Figs. 13A to 13C.

[0054] The controller 30 performs shift control in the second shift mode described above based on the changed preset gear ratio. For example, as shown in Fig. 13A, if a second upshift operation is performed on the shift operating member 38 when the current virtual gear ratio is 1.0 or between 1.0 and 1.6, the controller 30 upshifts the virtual gear ratio to 1.7 as shown in Fig. 13B. Also, as shown in Fig. 13C, if a second upshift operation is performed on the shift operating member 38 when the current virtual gear ratio is 1.7 or between 1.7 and 3.0, the controller 30 upshifts the virtual gear ratio to 3.0.

[0055] Similarly, for downshifts, the controller 30 performs shift control in the second shift mode described above based on the changed preset gear ratio. For example, as shown in Fig. 14, if a second downshift operation is performed on the shift operating member 38 when the current virtual gear ratio is 3.0 or between 1.7 and 3.0, the controller 30 downshifts the virtual gear ratio to 1.7 as shown in Fig. 14B. Also, if a second downshift operation is performed on the shift operating member 38 when the current virtual gear ratio is 1.7 or between 1.0 and 1.7, the controller 30 downshifts the virtual gear ratio to 1.0 as shown in Fig. 14C.

[0056] In the work machine 1 according to the present embodiment described above, the virtual gear ratio increases by a predetermined increase rate with a first upshift operation to the shift operation member 38. Therefore, the operator can finely upshift the virtual gear ratio at a predetermined increase rate by repeating the first upshift operation to the shift operation member 38. Furthermore, the virtual gear ratio jumps up to the preset gear ratio with a second upshift operation to the shift operation member 38. Therefore, the operator can quickly upshift to the preset gear ratio with the second upshift operation to the shift operation member 38. This makes it easier to change gears in the continuously variable transmission 24. A first downshift operation to the shift operating member 38 decreases the virtual gear ratio by a predetermined decrease rate. Therefore, by repeating the first downshift operation to the shift operating member 38, the operator can finely downshift the virtual gear ratio at the predetermined decrease rate. Furthermore, a second downshift operation to the shift operating member 38 causes the virtual gear ratio to jump up to the preset gear ratio. Therefore, the operator can quickly downshift to the preset gear ratio by the second downshift operation of the shift operating member 38. This makes it easier to perform gear changes in the continuously variable transmission 24.

[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 gist of the invention.

[0058] The work machine 1 is not limited to a bulldozer, and may be other vehicles such as a wheel loader or motor grader. The work machine 1 may be remotely operable. In that case, the operation devices 35, 36, the input device 33, and the display 34 may be located outside the work machine 1. The work machine 1 may have multiple controllers that are separate from each other. The processing by the controller 30 described above may be distributed and executed by multiple controllers. The continuously variable transmission 24 is not limited to an HST, and may be another transmission such as an HMT (Hydro Mechanical Transmission) or an EMT (Electric-Mechanical Transmission). Alternatively, the continuously variable transmission 24 may be a combination of a generator and an electric motor.

[0059] The structure of the shift operating member 38 is not limited to that of the above embodiment and may be modified. For example, the shift operating member 38 may be slidably attached to the travel lever 37. The shift operating member 38 may also be provided separately from the travel lever 37.

[0060] The shift control processing by the controller 30 is not limited to that of the above embodiment and may be modified. For example, the predetermined rate of change is not limited to 0.1 in the above embodiment and may be modified. The upper limit of the virtual gear ratio of the continuously variable transmission 24 is not limited to 3.0 speed and may be greater than or equal to 3.0 speed. The lower limit of the virtual gear ratio is not limited to 0.1 speed and may be 0.0 speed (i.e., vehicle speed 0). [Industrial Applicability]

[0061] According to the present disclosure, the gear shifting operation of a continuously variable transmission can be easily performed. [Explanation of symbols]

[0062] 1: working machine, 24: continuously variable transmission, 30: controller, 33: input device, 38: shift operation member

Claims

1. 1. A system for controlling a work machine having a continuously variable transmission, comprising: a shift operation member operable by an operator; a controller that upshifts a virtual gear ratio of the continuously variable transmission at a predetermined increase rate in response to a first upshift operation of the shift operation member, and upshifts the virtual gear ratio of the continuously variable transmission to a predetermined preset gear ratio in response to a second upshift operation of the shift operation member; A system comprising:

2. the controller distinguishes between the first up-shifting operation and the second up-shifting operation based on a stroke amount of the shift operating member. The system of claim 1 .

3. the shift operating member is operable between a neutral range, a first range in which the stroke amount is larger than that of the neutral range in a predetermined upshift direction, and a second range in which the stroke amount is larger than that of the first range in the upshift direction, the first upshift operation is an operation of the shift operation member from the neutral range to the first range, The second up-shifting operation is an operation of the shift operating member to the second range. The system of claim 2 .

4. The controller in response to the first upshifting operation of the shift operation member, shifting up a virtual gear ratio of the continuously variable transmission between a first preset gear ratio and a second preset gear ratio at the increasing rate; shifting up a virtual gear ratio of the continuously variable transmission from between the first preset gear ratio and the second preset gear ratio to the second preset gear ratio in response to the second upshift operation of the shift operation member; The system of claim 1 .

5. further comprising an input device operable by an operator; The preset gear ratio can be changed by operating the input device. The system of claim 1 .

6. The controller downshifting a virtual gear ratio of the continuously variable transmission at a predetermined reduction rate in response to a first downshift operation of the shift operation member; shifting down the virtual gear ratio of the continuously variable transmission to the preset gear ratio in response to a second downshift operation of the shift operation member; The system of claim 1 .

7. the controller distinguishes between the first downshift operation and the second downshift operation based on a stroke amount of the shift operation member. The system of claim 6.

8. the shift operating member is operable between a neutral range, a third range in which the stroke amount is larger in a predetermined downshift direction than in the neutral range, and a fourth range in which the stroke amount is larger in the downshift direction than in the third range, the first downshift operation is an operation of the shift operation member from the neutral range to the third range, The second downshift operation is an operation of the shift operation member to the fourth range. The system of claim 7.

9. The controller in response to the first downshifting operation of the shift operation member, downshifting a virtual gear ratio of the continuously variable transmission between a first preset gear ratio and a second preset gear ratio at the reduction rate; shifting down a virtual gear ratio of the continuously variable transmission from between the first preset gear ratio and the second preset gear ratio to the first preset gear ratio in response to the second downshift operation of the shift operation member; The system of claim 6.

10. 1. A method for controlling a work machine having a continuously variable transmission, comprising: receiving an operation signal indicative of an operation on a shift operating member operable by an operator; shifting up a virtual gear ratio of the continuously variable transmission at a predetermined increasing rate in response to a first upshift operation of the shift operation member; shifting up a virtual gear ratio of the continuously variable transmission to a predetermined preset gear ratio in response to a second upshift operation of the shift operation member; A method for providing

11. distinguishing between the first up-shifting operation and the second up-shifting operation based on a stroke amount of the shift operating member, The method of claim 10.

12. the shift operating member is operable between a neutral range, a first range in which the stroke amount is larger than that of the neutral range in a predetermined upshift direction, and a second range in which the stroke amount is larger than that of the first range in the upshift direction, the first upshift operation is an operation of the shift operating member to the first range, The second up-shifting operation is an operation of the shift operating member to the second range. The method of claim 11.

13. shifting up a virtual gear ratio of the continuously variable transmission between a first preset gear ratio and a second preset gear ratio at the increasing rate in response to the first upshift operation of the shift operation member; shifting up a virtual gear ratio of the continuously variable transmission from between the first preset gear ratio and the second preset gear ratio to the second preset gear ratio in response to the second upshift operation of the shift operation member; The method of claim 10 comprising:

14. changing the preset gear ratio in response to an operation on an input device operable by an operator; The method of claim 10.

15. downshifting a virtual gear ratio of the continuously variable transmission at a predetermined reduction rate in response to a first downshift operation of the shift operation member; shifting down a virtual gear ratio of the continuously variable transmission to the preset gear ratio in response to a second downshift operation of the shift operation member; The method of claim 10 comprising:

16. distinguishing between the first downshift operation and the second downshift operation based on a stroke amount of the shift operation member.

16. The method of claim 15.

17. the shift operating member is operable between a neutral range, a third range in which the stroke amount is larger in a predetermined downshift direction than in the neutral range, and a fourth range in which the stroke amount is larger in the downshift direction than in the third range, the first downshift operation is an operation of the shift operating member to the third range, The second downshift operation is an operation of the shift operation member to the fourth range.

17. The method of claim 16.

18. downshifting a virtual gear ratio of the continuously variable transmission between a first preset gear ratio and a second preset gear ratio at the reduction rate in response to the first downshift operation of the shift operation member; downshifting a virtual gear ratio of the continuously variable transmission from between the first preset gear ratio and the second preset gear ratio to the first preset gear ratio in response to the second downshift operation of the shift operating member; The method of claim 15 comprising:

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