Working machine and working machine control method

Abstract

The controller selectively executes a first mode and a second mode. In the second mode, the target traction force of the machine is limited compared to the first mode. In the second mode, the controller reduces the limitation of the target traction force when the acceleration of the machine is less than a predetermined acceleration threshold and determines the target traction force. The controller determines a target speed ratio corresponding to the target traction force. The controller controls the transmission based on the target speed ratio.

Description

Technical Field

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

[0002] As shown in Patent Document 1, in a work machine, a high output mode and a low output mode are sometimes set as control modes of the engine. In the low output mode, the maximum traction force for each vehicle speed is reduced compared to the high output mode. The switching between the low output mode and the high output mode is automatically performed according to the load applied to the work machine. For example, when the work machine is traveling on a steep uphill road, the high output mode is selected. On the other hand, when the work machine is traveling on a flat ground, the low output mode is selected.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: WO2005 / 024208A1 Summary of the invention

[0006] Problems that the invention will solve

[0007] In the above-mentioned working machine, when the load is small, the low output mode is selected. Therefore, on an uphill road with a large inclination, the engine is controlled in the low output mode. As a result, the fuel consumption performance can be improved. However, on flat ground or on an uphill road with a small inclination, the speed or acceleration of the working machine sometimes decreases.

[0008] On the other hand, on flat ground or uphill roads with a small inclination, by canceling the low output mode, the engine output is increased, which can suppress the reduction of the speed or acceleration of the working machine. However, even if the output command to the engine is increased, the actual output of the engine will not increase immediately. Therefore, it is difficult to quickly suppress the reduction of the speed or acceleration of the working machine.

[0009] An object of the present disclosure is to improve fuel consumption performance in a working machine and to quickly suppress a decrease in vehicle speed or acceleration.

[0010] Means for solving problems

[0011] The working machine of the first mode comprises an engine, a transmission, a travel device, a sensor and a controller. The transmission is connected to the engine. The transmission changes the speed ratio steplessly. The travel device is connected to the transmission. The travel device drives the machine. The sensor is a sensor for detecting the acceleration of the machine. The controller selectively executes the first mode and the second mode. In the second mode, the target traction force of the machine is limited compared with the first mode.

[0012] The controller determines the target traction force by reducing the restriction on the target traction force when the acceleration of the machine is smaller than a predetermined acceleration threshold in the second mode. The controller determines a target speed ratio corresponding to the target traction force. The controller controls the transmission based on the target speed ratio.

[0013] The second method is a control method for a working machine. The working machine has an engine, a transmission, and a travel device. The transmission is connected to the engine. The transmission can change the speed ratio steplessly. The travel device is connected to the transmission. The travel device drives the machine. The method includes the following processing.

[0014] The first process is to detect the acceleration of the machine. The second process is to selectively execute the first mode and the second mode. In the second mode, the target traction force of the machine is limited compared to the first mode. The third process is to reduce the restriction on the target traction force and determine the target traction force when the acceleration of the machine is smaller than the specified acceleration threshold in the second mode. The fourth process is to determine the target speed ratio corresponding to the target traction force. The fifth process is to control the transmission based on the target speed ratio.

[0015] Effects of the Invention

[0016] In the present disclosure, by controlling the transmission in the second mode, fuel consumption performance can be improved. In addition, in the second mode, when the acceleration of the machine is smaller than a predetermined acceleration threshold, the restriction on the target traction force is weakened to determine the target traction force. Then, a target speed ratio corresponding to the target traction force is determined, and the transmission is controlled based on the target speed ratio. As a result, a decrease in vehicle speed or acceleration can be quickly suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a side view of the working machine according to the embodiment.

[0018] Figure 2 This is a block diagram showing the configuration of a drive system and a control system of a working machine.

[0019] Figure 3 It is a diagram showing the traction force-vehicle speed characteristics.

[0020] Figure 4 is a block diagram showing a process for controlling an engine.

[0021] Figure 5 is a block diagram showing a process for controlling a transmission.

[0022] Figure 6 This is a diagram showing an example of second mode coefficient data.

[0023] Figure 7 : is a flowchart showing the processing of restriction relaxation control.

[0024] Figure 8 This is a diagram showing an example of acceleration threshold data.

[0025] Fig. 9 This is a diagram showing an example of increase rate data.

[0026] Fig.10 : is a time chart showing the change of parameters when the restriction relaxation control is executed in the second mode. DETAILED DESCRIPTION

[0027] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 1 1 is a side view of a working machine 1 according to an embodiment of the present invention. Figure 1 As shown, the working machine 1 includes a vehicle body 2 and a working device 3 .

[0028] 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 in a manner that allows it to rotate left and right. A hydraulic cylinder 15 is connected to the front vehicle body 2a and the rear vehicle body 2b. The hydraulic cylinder 15 is extended and retracted to allow the front vehicle body 2a to rotate left and right relative to the rear vehicle body 2b.

[0029] The working device 3 is used for excavation and other operations. The working device 3 is mounted on the front vehicle body 2a. The working device 3 includes a boom 11, a bucket 12, and hydraulic cylinders 13 and 14. The boom 11 and the bucket 12 are moved by extending and retracting the hydraulic cylinders 13 and 14.

[0030] Figure 2 1 is a block diagram showing the configuration of the drive system and control system of the working machine 1. Figure 2 As shown, the drive system of the working machine 1 includes an engine 21 , a PTO (Power Take Off) 22 , a transmission 23 , a travel device 24 , and a hydraulic pump 25 .

[0031] The engine 21 is, for example, a diesel engine. The engine 21 is provided with a fuel injection device 26. The fuel injection device 26 controls the output of the engine 21 by adjusting the amount of fuel injected into the cylinder of the engine 21. The PTO 22 distributes the driving force of the engine 21 to the transmission 23 and the hydraulic pump 25. Figure 2 Only one hydraulic pump 25 is shown in the figure. However, two or more hydraulic pumps may be connected to the engine 21 via the PTO 22.

[0032] The transmission 23 is connected to the engine 21. The transmission 23 is a CVT (Continuously Variable Transmission). That is, the transmission 23 can change the speed ratio steplessly. The speed ratio is the ratio of the rotation speed of the input shaft to the rotation speed of the output shaft of the transmission 23. For example, the transmission 23 is an HST (Hydro-Static Transmission). However, the transmission 23 may also be another type of transmission such as an HMT (Hydraulic Mechanical Transmission) or an EMT (Electric Mechanical Transmission).

[0033] The travel device 24 drives the working machine 1. The travel device 24 includes axles 31a, 31b, front wheels 32, and rear wheels 33. The axles 31a, 31b are connected to the transmission 23. The front wheels 32 are provided on the front vehicle body 2a. The rear wheels 33 are provided on the rear vehicle body 2b. The axles 31a, 31b transmit the driving force from the transmission 23 to the front wheels 32 and the rear wheels 33.

[0034] The hydraulic pump 25 is connected to the engine 21 via the PTO 22. The hydraulic pump 25 is driven by the engine 21 to discharge hydraulic oil. The hydraulic oil discharged from the hydraulic pump 25 is supplied to the above-mentioned hydraulic cylinders 13 to 15.

[0035] The control system of the working machine 1 includes an engine sensor 34, a vehicle speed sensor 35, and a pump sensor 36. The engine sensor 34 detects the engine rotation speed. The vehicle speed sensor 35 detects the output rotation speed. The output rotation speed is, for example, the rotation speed of the output shaft of the transmission 23. However, the output rotation speed may also be the rotation speed of other rotating elements located in the transmission 23 or downstream of the transmission 23. The pump sensor 36 detects the discharge pressure of the hydraulic pump 25.

[0036] The control system of the working machine 1 includes a controller 41. The controller 41 controls the working machine 1. The controller 41 receives a signal indicating the engine rotation speed from the engine sensor 34. The controller 41 receives a signal indicating the output rotation speed from the vehicle speed sensor 35. The controller 41 receives a signal indicating the discharge pressure of the hydraulic pump 25 from the pump sensor 36. The controller 41 sends a command signal to the engine 21 and the transmission 23.

[0037] The controller 41 includes a processor 42 and a storage device 43. The processor 42 is, for example, a CPU (central processing unit). Alternatively, it may be a processor different from the processor 42 CPU. The processor 42 executes processing for controlling the working machine 1 according to a program. The storage device 43 includes a non-volatile memory such as a ROM and a volatile memory such as a RAM. The storage device 43 may also include an auxiliary storage device such as a hard disk or an SSD (Solid State Drive). The storage device 43 is an example of a non-transitory computer-readable recording medium. The storage device 43 stores programs and data for controlling the working machine 1.

[0038] The control system of the working machine 1 includes an accelerator operating member 44, a working device operating member 45, and an input device 46. The accelerator operating member 44 can be operated by an operator to control the travel of the working machine 1. The accelerator operating member 44 is, for example, a pedal. However, the accelerator operating member 44 may also be other members such as a lever or a switch.

[0039] The working device operating member 45 can be operated by the operator to control the working device 3. The working device operating member 45 is, for example, a lever. However, the working device operating member 45 can also be other members such as a switch or a pedal. The input device 46 can be operated by the operator to select a control mode of the working machine 1. The input device 46 includes, for example, a touch panel. However, the input device 46 can also include other members such as a mechanical switch.

[0040] The controller 41 receives a signal indicating an accelerator operation amount from the accelerator operation member 44. The accelerator operation amount is the operation amount of the accelerator operation member 44. The controller 41 receives a signal indicating a work implement operation amount from the work implement operation member 45. The work implement operation amount is the operation amount of the work implement operation member 45.

[0041] The controller 41 receives a signal indicating the selection of the control mode from the input device 46. The control mode includes a first mode and a second mode. However, the controller 41 may automatically select the control mode according to the load applied to the working machine 1.

[0042] Figure 3 is a diagram showing the traction force-vehicle speed characteristics of the first mode and the second mode. Figure 3 In FIG. 1 , L1 shows the traction force-vehicle speed characteristics in the first mode. L2 shows the traction force-vehicle speed characteristics in the second mode. The traction force-vehicle speed characteristics indicate the maximum traction force at each vehicle speed. Figure 3As shown, in the second mode, the traction force of the working machine 1 is limited to be smaller than that in the first mode. The controller 41 controls the engine 21 and the transmission 23 according to the control mode selected from the first mode and the second mode.

[0043] Hereinafter, a process for controlling the engine 21 and the transmission 23 executed by the controller 41 will be described. Figure 4 2 is a block diagram showing a process for controlling the engine 21. Figure 4 As shown, in step S101, the controller 41 determines the target traction force. The controller 41 determines the target traction force based on the accelerator operation amount and the output rotation speed. For example, the controller 41 stores the target traction force data D1. The target traction force data D1 specifies the relationship between the vehicle speed V and the target traction force Ft. The target traction force data D1 changes according to the accelerator operation amount. The controller 41 calculates the vehicle speed V according to the output rotation speed. The controller 41 refers to the target traction force data D1 and determines the target traction force Ft according to the accelerator operation amount and the vehicle speed V.

[0044] In step S102, the controller 41 corrects the target traction force. The controller 41 corrects the target traction force by multiplying the traction force coefficient by the target traction force. The traction force coefficient will be described later.

[0045] In step S103, the controller 41 determines the PTO required torque. The controller 41 determines the PTO required torque based on the working device operation amount and the discharge pressure of the hydraulic pump 25. The PTO required torque is the required torque in the device connected to the engine 21 via the PTO22. The PTO required torque includes the required torque in the hydraulic pump 25. For example, the controller 41 determines the required flow rate of the working oil based on the working device operation amount. The controller 41 determines the PTO required torque based on the required flow rate and the discharge pressure. In addition, when more than two hydraulic pumps are connected to the engine 21 via the PTO22, the PTO required torque may also include the required torque in other hydraulic pumps.

[0046] In step S104, the controller 41 determines the required engine power. The required engine power is the required horsepower of the engine 21. The controller 41 determines the required engine power based on the PTO required torque and the target traction force. For example, the controller 41 determines the required engine power based on the sum of the PTO required torque and the target traction force.

[0047] In step S105, the controller 41 determines the target engine rotation speed. The controller 41 determines the target engine rotation speed based on the required engine power. For example, the controller 41 stores target engine rotation speed data D2. The target engine rotation speed data D2 specifies the relationship between the required engine power Pe and the target engine rotation speed Nt. The controller 41 refers to the target engine rotation speed data D2 and determines the target engine rotation speed Nt based on the required engine power Pe.

[0048] The controller 41 determines the command to the fuel injection device 26 based on the target engine rotation speed determined as described above. Thus, the output of the engine 21 is controlled so as to realize the target traction force and the PTO required torque.

[0049] In addition, the controller 41 may determine the target acceleration torque of the engine 21 based on the target engine rotation speed and the current engine rotation speed. The controller 41 may determine the target torque of the engine 21 based on the PTO required torque, the target traction force, and the target acceleration torque. The controller 41 may control the engine 21 based on the target torque of the engine 21.

[0050] Figure 5 2 is a block diagram showing a process for controlling the transmission 23. Figure 5 As shown, in step S201, the controller 41 determines the output acceleration. The output acceleration is, for example, the acceleration of the output shaft of the transmission 23. However, the output acceleration may also be the acceleration of other rotating elements located in the transmission 23 or downstream of the transmission 23. In addition, the output acceleration includes the deceleration of the output shaft of the transmission 23. For example, a negative value of the output acceleration means deceleration. The controller 41 determines the output acceleration of the transmission 23 based on the target traction force and the travel load. For example, the controller 41 calculates the travel load based on the output torque of the transmission 23, the acceleration of the working machine 1, and the weight of the working machine 1.

[0051] In step S202, the controller 41 determines an estimated value of the output rotational speed. The estimated value of the output rotational speed is a value estimated as the output rotational speed after a predetermined time. The predetermined time is determined, for example, based on a control cycle of the processing of the controller 41. The controller 41 determines the estimated value of the output rotational speed based on the current output rotational speed and the output acceleration.

[0052] In step S203, the controller 41 determines the acceleration of the engine 21. The acceleration of the engine 21 is the acceleration of the output shaft of the engine 21. The acceleration of the engine 21 may also be the acceleration of the input shaft of the transmission 23. The controller 41 determines the acceleration of the engine 21 according to the target acceleration torque of the engine 21.

[0053] In step S204, the controller 41 determines an estimated value of the input rotational speed. The input rotational speed is, for example, the rotational speed of the input shaft of the transmission 23. The estimated value of the input rotational speed is a value estimated as the input rotational speed after a predetermined time. The controller 41 determines the estimated value of the input rotational speed based on the current engine rotational speed and the acceleration of the engine 21.

[0054] In step S205, the controller 41 determines a target speed ratio. The controller 41 determines the target speed ratio based on the estimated value of the output rotational speed and the estimated value of the input rotational speed. The target speed ratio is the ratio of the estimated value of the output rotational speed to the estimated value of the input rotational speed.

[0055] The controller 41 determines the instruction to the transmission 23 so that the speed ratio of the transmission 23 becomes the target speed ratio. For example, when the transmission 23 is an HST, the controller 41 determines the target capacity of the hydraulic pump and the hydraulic motor of the HST according to the target speed ratio. When the transmission 23 is an HMT, the controller 41 determines the target torque of the hydraulic motor of the HMT according to the target speed ratio in the same way as the HST. When the transmission 23 is an EMT, the controller 41 determines the target torque of the electric motor of the EMT according to the target speed ratio. Thus, the speed ratio of the transmission 23 is controlled to achieve the target traction force and the target engine rotation speed.

[0056] Next, the process for correcting the target traction force according to the control mode in step S102 will be described. As described above, the controller 41 corrects the target traction force by multiplying the target traction force determined in step S101 by the traction force coefficient. The traction force coefficient changes according to the selected control mode. For example, the traction force coefficient in the first mode is 1. Therefore, the controller 41 does not correct the initial target traction force determined in step S101 and determines it as the target traction force.

[0057] When the second mode is selected, the traction force coefficient in the first mode is a value smaller than 1. Therefore, in the second mode, the target traction force is corrected to be smaller than that in the first mode.

[0058] When the second mode is selected, the controller 41 determines the second mode coefficient according to the vehicle speed as the traction coefficient. The controller 41 stores second mode coefficient data D3. The second mode coefficient data D3 defines the relationship between the vehicle speed and the second mode coefficient. Figure 6 : is a diagram showing an example of the second mode coefficient data D3. Figure 6As shown, in the second mode coefficient data D3, when the vehicle speed is less than V1, the second mode coefficient is C1. C1 is less than 1. In the second mode coefficient data D3, when the vehicle speed is greater than V2, the second mode coefficient is C2. C2 is greater than C1. C2 may also be 1. Alternatively, C2 may also be less than 1. When the vehicle speed is in the range between V1 and V2, the second mode coefficient increases as the vehicle speed increases.

[0059] Therefore, at least when the vehicle speed is smaller than V2, the second mode coefficient is smaller than 1. Therefore, the target traction force is corrected to a value smaller than the initial target traction force determined in step S101. Thus, in the second mode, the target traction force is limited to a smaller value than in the first mode. In particular, when the vehicle is traveling at a low speed in the second mode, the target traction force is limited to a smaller value. Thus, the fuel consumption performance of the working machine 1 can be improved. In addition, the controller 41 increases the traction force coefficient according to the increase in the vehicle speed. Thus, the maximum vehicle speed in the high-speed traveling in the second mode can be made close to the maximum vehicle speed in the first mode.

[0060] In the second mode, the controller 41 executes control (hereinafter referred to as "limit relaxation control") for relaxing the limit on the target traction force according to the acceleration of the working machine 1. The limit relaxation control will be described below. Figure 7 FIG. 4 is a flowchart showing the processing of the restriction relaxation control. Figure 7 As shown, in step S301, the controller 41 obtains the acceleration of the working machine 1. The controller 41 calculates the acceleration of the working machine 1 based on the vehicle speed.

[0061] In step S302, the controller 41 determines the acceleration threshold value. The controller 41 refers to the acceleration threshold value data D4 and determines the acceleration threshold value according to the vehicle speed. Figure 8 2 is a diagram showing an example of the acceleration threshold data D4. The acceleration threshold data D4 specifies the relationship between the vehicle speed and the acceleration threshold. Figure 8 As shown, in the acceleration threshold data D4, when the vehicle speed is below V3, the acceleration threshold is A1. In the acceleration threshold data D4, when the vehicle speed is above V4, the acceleration threshold is A2. A2 is smaller than A1. In the acceleration threshold data D4, when the vehicle speed is between V3 and V4, the acceleration threshold decreases as the vehicle speed increases. Therefore, the controller 41 decreases the acceleration threshold as the vehicle speed increases.

[0062] In step S303, the controller 41 determines whether the first condition is satisfied. The first condition is a condition for relaxing the limitation of the target traction force. The first condition is an AND condition, and includes the following conditions (a1), (b1), and (c1).

[0063] (a1) Accelerator operation amount > first operation threshold

[0064] (b1) The working machine 1 is traveling.

[0065] (c1) Acceleration of the working machine 1 < acceleration threshold

[0066] The first operation threshold is, for example, 100%. However, the first operation threshold may be smaller than 100%. The controller 41 determines whether the working machine 1 is traveling based on the states of the working implement 3 and / or the transmission 23, for example.

[0067] If the first condition is not satisfied in step S303, the process proceeds to step S304. In step S304, the controller 41 determines the second mode coefficient based on the second mode coefficient data D3 as described above. Then, in step S305, the controller 41 determines the second mode coefficient as the traction force coefficient.

[0068] In step S303, when the first condition is satisfied, the process proceeds to step S306. In step S306, the controller 41 determines the increase rate of the traction force coefficient. The controller 41 refers to the increase rate data D5 and determines the increase rate of the traction force coefficient according to the vehicle speed. Fig. 9 2 is a diagram showing an example of the increase rate data D5. In the increase rate data D5, the increase rate of the traction coefficient decreases as the vehicle speed increases.

[0069] In step S307, the controller 41 increases the traction coefficient. The controller 41 gradually increases the traction coefficient at the increase rate of the traction coefficient determined in step S306. Therefore, when the first condition is satisfied in the second mode, the restriction of the target traction force is relaxed, and the target traction force is increased compared to the second mode. However, the controller 41 increases the traction coefficient so as not to exceed 1. In addition, the traction coefficient being 1 means that the target traction force is the same as that in the first mode.

[0070] The controller 41 performs the processing of steps S101 to S105 described above based on the corrected target traction force to determine the target engine rotation speed. Therefore, the controller 41 increases the engine rotation speed compared to the second mode according to the increase in the traction force coefficient. In addition, the controller 41 performs the processing of steps S201 to S205 described above based on the corrected target traction force to determine the target speed ratio. Therefore, the controller 41 increases the target speed ratio according to the increase in the traction force coefficient.

[0071] In step S308, the controller 41 determines whether the second condition is satisfied. The second condition is a condition for releasing the restriction relaxation control and returning the control mode to the normal second mode. The second condition includes the following conditions (a2) and (b2) as OR conditions.

[0072] (a2) Accelerator operation amount < second operation threshold

[0073] (b2) The working machine 1 is in a state other than traveling.

[0074] The second operation threshold value may be the same as or different from the first operation threshold value. The second operation threshold value is, for example, 100%. However, the second operation threshold value may also be less than 100%. A state other than driving is, for example, during excavation or switching between forward and reverse. For example, the controller 41 determines whether the working machine 1 is in a state other than driving based on the state of the working device 3 and / or the transmission 23.

[0075] If the second condition is satisfied in step S308, the process returns to step S304. That is, the control mode returns to the normal second mode. If the second condition is not satisfied, the process returns to step S306.

[0076] In the working machine 1 of the present embodiment described above, by controlling the engine 21 and the transmission 23 in the second mode, it is possible to improve fuel consumption performance. In addition, when the acceleration of the working machine 1 is smaller than the acceleration threshold in the second mode, the restriction on the target traction force is weakened and the target traction force is determined. Then, the engine 21 is controlled based on the target traction force. Thus, it is possible to suppress a decrease in vehicle speed or acceleration. Furthermore, a target speed ratio corresponding to the target traction force is determined, and the transmission 23 is controlled based on the target speed ratio. Thus, it is possible to quickly suppress a decrease in vehicle speed or acceleration.

[0077] For example Fig.10 is a timing chart showing the change of parameters when the restriction relaxation control is executed in the second mode. Fig.10 In the example shown, the first operating threshold is 100%. Fig.10 In the example shown, the change of the parameter when the second mode is selected as the control mode is shown. However, the dotted line Vm1 shows the change of the vehicle speed when the first mode is selected. The solid line Vm2 shows the change of the vehicle speed when the second mode is selected. The dotted line Nm1 shows the change of the engine rotation speed when the first mode is selected. The solid line Nm2 shows the change of the engine rotation speed when the second mode is selected.

[0078] like Fig.10As shown, at time T1, the operator operates the accelerator operating member 44 so that the accelerator operation amount increases from 0% to 100%. As a result, after time T1, the vehicle speed, acceleration, traction and engine rotation speed increase. In addition, the speed ratio decreases as the vehicle speed increases. However, thereafter, the acceleration and traction decrease, and the acceleration becomes smaller than the acceleration threshold from time T2. Therefore, the controller 41 gradually increases the traction coefficient toward the upper limit value 1. As a result, the decrease in acceleration and traction is moderated. In addition, the speed ratio and engine rotation speed are controlled to gradually increase. As a result, the vehicle speed gradually increases and can reach the same vehicle speed as the maximum vehicle speed Vmax in the first mode.

[0079] An embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the invention. The working machine 1 is not limited to a wheel loader, but may be other machines such as a bulldozer or a motor grader.

[0080] The processing for controlling the engine 21 and the transmission 23 is not limited to the above-mentioned processing, and may be changed, omitted, or added. The processing of the restriction relaxation control is not limited to the above-mentioned processing, and may be changed, omitted, or added. The execution order of the processing is not limited to the above-mentioned, and may be changed. The above-mentioned data D1-D5 is not limited to the above-mentioned, and may be changed.

[0081] The first condition is not limited to the above-mentioned conditions, and may be changed, omitted, or added. For example, it may include a case where the braking operation amount of the working machine 1 is smaller than a prescribed first braking threshold. The second condition is not limited to the above-mentioned conditions, and may be changed, omitted, or added. For example, it may include a case where the braking operation amount of the working machine 1 is larger than a prescribed second braking threshold.

[0082] Industrial Applicability

[0083] According to the present disclosure, in a working machine, it is possible to improve fuel consumption performance and quickly suppress a decrease in vehicle speed or acceleration.

[0084] Description of Reference Numerals

[0085] 2a Front body

[0086] 2b Rear body

[0087] 21 Engine

[0088] 23 Transmission

[0089] 24 Traveling device

[0090] 32 Front wheel

[0091] 33 Rear wheel

[0092] 35 Vehicle speed sensor

[0093] 41 Controller

[0094] 44 Accelerator operating parts

Claims

1. A working machine having: engine; A transmission connected to the engine and capable of continuously changing the speed ratio; A travel device connected to the transmission to enable the machine to travel; A sensor for detecting the acceleration of the machine; as well as A controller selectively executes a first mode and a second mode, For the controller, When the first mode is selected, a target traction force is determined. When the second mode is selected, the target tractive force of the machine is limited compared to the first mode. determining a target speed ratio corresponding to the target traction force, and controlling the transmission based on the target speed ratio; In the second mode, when the acceleration of the machine is smaller than a predetermined acceleration threshold, the restriction on the target traction force is weakened to determine the target traction force.

2. The working machine according to claim 1, wherein: The controller determines the target traction force in the second mode by multiplying the target traction force in the first mode by a traction force coefficient. In the second mode, when the acceleration of the machine is smaller than the predetermined acceleration threshold, the traction coefficient is increased.

3. The working machine according to claim 2, wherein: The controller increases the target speed ratio according to an increase in the traction force coefficient.

4. The working machine according to claim 2, wherein: The controller determines an increase rate of the traction force coefficient according to a vehicle speed, and increases the traction force coefficient at the increase rate.

5. The working machine according to claim 4, wherein: The controller reduces the increase rate according to an increase in vehicle speed.

6. The working machine according to claim 2, wherein: The controller determines the traction coefficient according to the vehicle speed.

7. The working machine according to claim 2, wherein: The controller increases the traction coefficient according to an increase in vehicle speed.

8. The working machine according to claim 1, wherein: The controller determines the prescribed acceleration threshold according to the vehicle speed.

9. The working machine according to claim 1, wherein: The controller decreases the prescribed acceleration threshold value according to an increase in vehicle speed.

10. The working machine according to claim 1, wherein: It also has an accelerator operating member that can be operated by an operator. The controller obtains an operation amount of the accelerator operating member, and in the second mode, when the operation amount of the accelerator operating member is greater than a prescribed operation threshold and the acceleration of the machine is less than the prescribed acceleration threshold, reduces the restriction on the target traction force and determines the target traction force, determines a target speed ratio corresponding to the target traction force, and controls the transmission based on the target speed ratio.

11. The working machine according to claim 1, wherein: The controller controls the engine based on the target traction force.

12. The working machine according to any one of claims 1 to 10, wherein: Also available: front body; and The rear vehicle body is connected to the front vehicle body in a manner capable of rotating left and right. The travel device includes front wheels provided on the front vehicle body and rear wheels provided on the rear vehicle body.

13. A control method for a working machine, the working machine comprising: an engine; a transmission connected to the engine and capable of continuously changing a speed ratio; and a travel device connected to the transmission and causing the machine to travel, wherein: The control method of the working machine comprises: Detect mechanical acceleration; selectively executing the first mode and the second mode; determining a target traction force when the first mode is selected, and limiting the target traction force of the machine compared to the first mode when the second mode is selected; determining a target speed ratio corresponding to the target traction force; as well as controlling the transmission based on the target speed ratio; In the second mode, when the acceleration of the machine is smaller than a predetermined acceleration threshold, the restriction on the target traction force is weakened to determine the target traction force.

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