Work machine and method for controlling work machine

Abstract

This work machine is provided with an engine, a transmission, a travel device, a vehicle speed sensor, a hydraulic brake, an oil temperature sensor, and a controller. The controller acquires a travel command for controlling the travel of the work machine. The controller acquires a vehicle speed. The controller determines a target driving force based on a travel command and a vehicle speed. The target driving force includes a positive driving force for causing the work machine to travel and a negative driving force for braking the work machine. The controller controls the engine and the transmission such that a target driving force is obtained. The controller obtains the oil temperature. The controller determines an assist braking force for assisting the braking force by the hydraulic brake on the basis of the oil temperature. The controller determines a target driving force such that an assist braking force is obtained.

Description

Technical Field

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

[0002] Among work machines, some are equipped with hydraulic brakes. For example, in the work machine of Patent Document 1, the hydraulic oil supplied to the hydraulic brake is controlled according to the operation amount of the brake pedal. Thereby, the braking force based on the hydraulic brake is controlled.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent No. 5412011 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] Work machines are sometimes used in harsh environments, which impose a large burden on the brakes. For example, due to a large number of brake applications per unit time, long continuous operation time, heavy weight of the work machine, etc., a large burden is imposed on the brakes. Therefore, the hydraulic oil is likely to become hot. An object of the present disclosure is to suppress overheating of the hydraulic oil of the hydraulic brake in a work machine.

[0008] Means for Solving the Problems

[0009] A work machine according to an aspect of the present disclosure includes: an engine, a transmission, a traveling device, a vehicle speed sensor, a hydraulic brake, an oil temperature sensor, and a controller. The transmission is connected to the engine. The traveling device is connected to the transmission and travels the work machine. The vehicle speed sensor detects the vehicle speed. The hydraulic brake brakes the traveling device by being driven by hydraulic oil. The oil temperature sensor detects the oil temperature of the hydraulic oil.

[0010] The controller acquires a travel command for controlling the travel of the work machine. The controller acquires the vehicle speed. The controller determines a target driving force based on the travel command and the vehicle speed. The target driving force includes a positive driving force for traveling the work machine and a negative driving force for braking the work machine. The controller controls the engine and the transmission so as to obtain the target driving force. The controller acquires the oil temperature. The controller determines an auxiliary braking force for assisting the braking force based on the hydraulic brake based on the oil temperature. The controller determines the target driving force so as to obtain the auxiliary braking force.

[0011] Another method according to the present disclosure is a method for controlling a work machine. The work machine includes: an engine, a transmission, a traveling device, and a hydraulic brake. The transmission is connected to the engine. The traveling device is connected to the transmission and causes the work machine to travel. The hydraulic brake is driven by hydraulic oil to brake the traveling device.

[0012] The method includes: obtaining a travel command for controlling the travel of the work machine; obtaining a vehicle speed; determining a target driving force based on the travel command and the vehicle speed, the target driving force including a positive driving force for causing the work machine to travel and a negative driving force for braking the work machine; controlling the engine and the transmission to obtain the target driving force; obtaining the oil temperature of the hydraulic oil; determining an auxiliary braking force for assisting the braking force based on the hydraulic brake based on the oil temperature; and determining the target driving force to obtain the auxiliary braking force.

[0013] Effects of the Invention

[0014] According to the present disclosure, the auxiliary braking force is determined based on the oil temperature of the hydraulic brake. The braking force based on the hydraulic brake is assisted by the auxiliary braking force, thereby suppressing heat generation in the hydraulic brake. In addition, the auxiliary braking force is obtained by the negative driving force based on the engine and the transmission, that is, by the engine brake. Therefore, overheating of the hydraulic oil in the hydraulic brake can be suppressed. Description of the Drawings

[0015] Figure 1 is a side view of the work machine according to the embodiment.

[0016] Figure 2 is a block diagram showing the structure of the work machine.

[0017] Figure 3 is a block diagram showing the process for controlling the engine.

[0018] Figure 4 is a diagram showing an example of driving force data.

[0019] Figure 5 is a diagram showing driving force data based on brake assist control.

[0020] Figure 6 is a flowchart showing the process of brake assist control.

[0021] Figure 7 is a diagram showing an example of auxiliary brake data.

[0022] Figure 8 is a diagram showing the relationship between the brake operation amount and the braking force in brake assist control.

[0023] Figure 9 This is a diagram showing the auxiliary braking data related to the first modified example.

[0024] Figure 10 This is a diagram showing the auxiliary braking data related to the second modified example. Detailed implementation mode

[0025] Hereinafter, an embodiment of the present disclosure will be described with reference to the accompanying drawings. Figure 1 This is a side view of the work machine 1 according to the embodiment. Figure 2 This is a block diagram showing the structure of the work machine 1. In the present embodiment, the work machine 1 is a wheel loader. As Figure 1 shown, the work machine 1 includes a vehicle body 2 and a working machine 3.

[0026] The vehicle body 2 includes a front vehicle body 2a and a rear vehicle body 2b. The rear vehicle body 2b is rotatably connected to the front vehicle body 2a in the left-right direction. A hydraulic cylinder 15 is connected to the front vehicle body 2a and the rear vehicle body 2b. The hydraulic cylinder 15 expands and contracts, so that the front vehicle body 2a rotates to the left and right with respect to the rear vehicle body 2b.

[0027] The working machine 3 is used for operations such as excavation. The working machine 3 is movably mounted relative to the front vehicle body 2a. The working machine 3 includes a boom 11, a bucket 12, and hydraulic cylinders 13 and 14. The boom 11 and the bucket 12 are moved by the expansion and contraction of the hydraulic cylinders 13 and 14.

[0028] As Figure 2 shown, the work machine 1 includes an engine 21, a transmission 24, and a traveling device 25. The engine 21 is, for example, a diesel engine. A fuel injection device 30 is provided in the engine 21. The fuel injection device 30 controls the output of the engine 21 by adjusting the amount of fuel injected into the cylinder of the engine 21.

[0029] The transmission 24 is connected to the engine 21. The transmission 24 transmits the driving force from the engine 21 to the traveling device 25. For example, the transmission 24 is an HMT (Hydraulic Mechanical Transmission). The HMT includes a planetary gear mechanism, a hydraulic pump / motor, and a clutch. The HMT can change the speed ratio steplessly by controlling the capacity of the hydraulic pump / motor.

[0030] However, the transmission 24 can also be other types of transmissions such as an EMT (Electric Mechanical Transmission) or an HST (Hydro-Static Transmission). Alternatively, the transmission 24 can also be a transmission that includes a torque converter and multiple transmission gears.

[0031] The traveling device 25 is mounted on the vehicle body 2 and is driven by the driving force from the engine 21, thereby causing the vehicle body 2 to travel. The traveling device 25 includes axles 26, 27, front wheels 28A, 28B, rear wheels 28C, 28D. The axles 26, 27 are connected to the transmission 24. The front wheels 28A, 28B are provided on the front vehicle body 2a. The rear wheels 28C, 28D are provided on the rear vehicle body 2b. The axle 26 transmits the driving force from the transmission 24 to the front wheels 28A, 28B. The axle 27 transmits the driving force from the transmission 24 to the rear wheels 28C, 28D.

[0032] The work machine 1 includes a PTO (Power Take Off) 31, a work machine pump 32, and a control valve 33. The PTO 31 distributes the driving force of the engine 21 to the transmission 24 and the work machine pump 32. Additionally, in Figure 2 , only one work machine pump 32 is illustrated. However, two or more hydraulic pumps can also be connected to the engine 21 via the PTO 31.

[0033] The work machine pump 32 is connected to the engine 21 via the PTO 31. The work machine pump 32 is a hydraulic pump. The work machine pump 32 is driven by the engine 21 and discharges hydraulic oil. The hydraulic oil discharged from the work machine pump 32 is supplied to the above-mentioned hydraulic cylinders 13 - 15. The control valve 33 controls the flow rate of the hydraulic oil supplied from the work machine pump 32 to the hydraulic cylinders 13 - 15. The control valve 33 is, for example, an electromagnetic proportional control valve and is controlled according to the input electrical signal. Alternatively, the control valve 33 can also be a pressure proportional control valve and is controlled according to the input pilot pressure.

[0034] The work machine 1 includes a brake pump 36 and hydraulic brakes 37A - 37D. The brake pump 36 is driven by the engine 21 and discharges hydraulic oil. The hydraulic oil discharged from the brake pump 36 is supplied to the hydraulic brakes 37A - 37D. The hydraulic brakes 37A - 37D are driven by the hydraulic oil, thereby braking the traveling device 25. The hydraulic brakes 37A - 37D are, for example, wet multi-disc brakes. Specifically, the hydraulic brakes 37A - 37D include front brakes 37A, 37B and rear brakes 37C, 37D. The front brakes 37A, 37B brake the front wheels 28A, 28B. The rear brakes 37C, 37D brake the rear wheels 28C, 28D.

[0035] The work machine 1 includes an engine sensor 34 and a vehicle speed sensor 35. The engine sensor 34 detects the engine speed. The vehicle speed sensor 35 detects the vehicle speed. The vehicle speed sensor 35 detects, for example, the output speed of the traveling device 25 as the vehicle speed. The output speed of the traveling device 25 corresponds to the vehicle speed of the work machine 1. The output speed of the traveling device 25 is, for example, the rotational speed of the output shaft of the transmission 24. However, the output speed may also be the rotational speed of other rotating elements within the transmission 24 or downstream of the transmission 24.

[0036] The work machine 1 includes a first oil temperature sensor 39 and a second oil temperature sensor 40. The first oil temperature sensor 39 and the second oil temperature sensor 40 detect the temperature of the hydraulic oil used to drive the hydraulic brakes 37A - 37D (hereinafter referred to as the brake oil temperature). The first oil temperature sensor 39 detects the brake oil temperature of the front brakes 37A, 37B. The second oil temperature sensor 40 detects the brake oil temperature of the rear brakes 37C, 37D.

[0037] The work machine 1 includes a controller 41. The controller 41 includes a processor such as a CPU (Central Processing Unit), and storage devices such as a RAM and a ROM. The controller 41 may also include an auxiliary storage device such as a hard disk or an SSD (Solid State Drive). The controller 41 stores programs and data for controlling the work machine 1. The controller 41 executes processing for controlling the work machine 1 based on the stored programs and data.

[0038] The controller 41 receives a signal representing the engine speed from the engine sensor 34. The controller 41 receives a signal representing the output speed from the vehicle speed sensor 35. The controller 41 receives signals representing the brake oil temperatures of the hydraulic brakes 37A - 37D from the oil temperature sensors 39, 40. The controller 41 receives a signal representing the brake oil temperatures of the front brakes 37A, 37B from the first oil temperature sensor 39. The controller 41 receives a signal representing the brake oil temperatures of the rear brakes 37C, 37D from the second oil temperature sensor 40.

[0039] The controller 41 controls the output of the engine 21 by sending a command signal to the engine 21. The controller 41 switches the forward and reverse gears of the transmission 24 by sending a command signal to the transmission 24. The controller 41 controls the speed ratio of the transmission 24 by sending a command signal to the transmission 24. The controller 41 controls the work machine 3 by sending command signals to the work machine pump 32 and the control valve 33.

[0040] The work machine 1 includes an FR operation member 42, an accelerator operation member 43, a work machine operation member 44, a brake operation member 45, and an input device 46. The FR operation member 42 can be operated by the operator to switch the forward and reverse of the work machine 1. The FR operation member 42 can be operated from the neutral position to the forward position and the reverse position. The FR operation member 42 is, for example, a lever. However, the FR operation member 42 can also be other components such as a switch or a pedal.

[0041] The accelerator operation member 43 can be operated by the operator to control the vehicle speed of the work machine 1. The accelerator operation member 43 is, for example, a pedal. However, the accelerator operation member 43 can also be other components such as a lever or a switch. The work machine operation member 44 can be operated by the operator to control the work machine 3. The work machine operation member 44 is, for example, a lever. However, the work machine operation member 44 can also be other components such as a switch or a pedal.

[0042] The brake operation member 45 can be operated by the operator to drive the hydraulic brakes 37A - 37D. The brake operation member 45 is, for example, a pedal. However, the brake operation member 45 can also be other components such as a lever or a switch. According to the operation of the brake operation member 45, the hydraulic pressure of the hydraulic oil supplied to the hydraulic brakes 37A - 37D is controlled. Thus, the hydraulic brakes 37A - 37D generate braking force according to the operation amount of the brake operation member 45.

[0043] The input device 46 can be operated by the operator to set the control of the work machine 1. For example, the input device 46 makes settings for the work machine 1 according to the operator's operation. The input device 46 includes, for example, a touch panel. However, the input device 46 may also include other components such as a mechanical switch.

[0044] The controller 41 receives a signal representing the operation position of the FR operation member 42 from the FR operation member 42. The controller 41 switches the forward and reverse gears of the transmission 24 according to the signal from the FR operation member 42. The controller 41 receives a signal representing the accelerator operation amount from the accelerator operation member 43. The accelerator operation amount is the operation amount of the accelerator operation member 43.

[0045] The controller 41 receives a signal representing the brake operation amount from the brake operation member 45. The brake operation amount is the operation amount of the brake operation member 45. The controller 41 receives a signal representing the work machine operation amount from the work machine operation member 44. The work machine operation amount is the operation amount of the work machine operation member 44. The controller 41 receives a signal representing the setting of the work machine 1 from the input device 46.

[0046] Next, the process for controlling the engine 21 executed by the controller 41 will be described. Figure 3 It is a block diagram showing the process for controlling the engine 21.

[0047] As Figure 3 shown, in step S101, the controller 41 determines the target driving force. The target driving force is the driving force required for the traveling device 25 to make the work machine 1 travel. The controller 41 acquires a travel command and a vehicle speed for controlling the travel of the work machine 1. The controller 41 determines the target driving force according to the travel command and the vehicle speed.

[0048] Specifically, the controller 41 acquires the accelerator operation amount as the travel command. The controller 41 stores driving force data D1. The driving force data D1 defines the relationship of the target driving force (Ft) of the work machine 1 with respect to the vehicle speed (V) and the accelerator operation amount (A1). The controller 41 refers to the driving force data D1 and determines the target driving force (Ft) according to the vehicle speed (V) and the accelerator operation amount (A1).

[0049] Figure 4 It is a diagram showing an example of the driving force data D1. Figure 4 In it, the solid line L1 shows the driving force data in the case where the accelerator operation amount is 100%. Figure 4 In it, the dashed line L2 shows the driving force data in the case where the accelerator operation amount is 0%. The driving force data D1 changes in such a way that the target driving force for the vehicle speed increases as the accelerator operation amount increases.

[0050] As Figure 4 shown, the target driving force includes positive and negative values. The target driving force with a positive value represents the positive driving force for driving the work machine 1. The target driving force with a negative value represents the negative driving force for braking the work machine 1, that is, the braking force based on the engine brake. For example, as shown in the driving force data L2, when the accelerator operation amount is 0% and the vehicle speed is greater than V1, the controller 41 causes the braking force based on the engine brake to occur.

[0051] In step S102, the controller 41 determines the target output torque and the target rotational speed of the engine 21. The controller 41 determines the target output torque (T) and the target rotational speed (N) of the engine 21 according to the target driving force and the vehicle speed. For example, the controller 41 stores the target matching data D2. The target matching data D2 defines the relationship between the target output torque (T) and the target rotational speed (N) of the engine 21. The controller 41 calculates the target output horsepower of the engine 21 according to the target driving force and the vehicle speed. The controller 41 determines the target output torque (T) and the target rotational speed (N) of the engine 21 according to the intersection point M1 of the line P1 representing the target output horsepower and the line representing the target matching data D2.

[0052] In step S103, the controller 41 determines the engine command. The controller 41 determines the throttle command for the fuel injection device 30 as the engine command according to the target output torque (T) of the engine 21 determined as described above. Thus, the output of the engine 21 is controlled to achieve the target output torque (T).

[0053] In step S104, the controller 41 determines the target speed ratio of the transmission. The controller 41 determines the target speed ratio of the transmission according to the target rotational speed (N) of the engine 21 and the vehicle speed. The speed ratio of the transmission represents the ratio of the output rotational speed to the input rotational speed of the transmission.

[0054] In step S105, the controller 41 determines the transmission command. The controller 41 determines the transmission command so as to obtain the target speed ratio in the transmission. For example, when the transmission is an HMT, the transmission command includes the capacity command for the hydraulic pump / motor and the command for the clutch. As described above, by controlling the engine 21 and the transmission 24, as Figure 4 shown, in the work machine 1, the target driving force corresponding to the vehicle speed and the accelerator operation amount is obtained.

[0055] In the construction machine 1 according to the present embodiment, when the brake operation member 45 is operated, the controller 41 executes brake assist control for assisting the braking force based on the hydraulic brakes 37A - 37D. In the brake assist control, when the brake operation member 45 is being operated, the braking force based on the engine brake is increased to assist the braking force based on the hydraulic brakes 37A - 37D.

[0056] Figure 5 It is a diagram showing the driving force data D1 based on the brake assist control. When the accelerator operation amount is 0% as described above and the brake assist control is not performed, the target driving force is determined by the driving force data L2. That is, when both the accelerator operation amount and the brake operation amount are 0%, the target driving force is determined by the driving force data L2.

[0057] Figure 5 In it, the dashed line L3 represents the driving force data D1 based on the brake assist control when the accelerator operation amount is 0%. That is, the driving force data L3 represents the driving force data D1 when the accelerator operation amount is 0% and the brake operation amount is greater than 0%. As Figure 5 shown, compared with the driving force data L2 in the case where the brake assist control is not performed, in the driving force data L3 based on the brake assist control, the braking force based on the engine brake increases by the amount of the assist braking force Fa. Hereinafter, the process of the brake assist control executed by the controller 41 will be described.

[0058] Figure 6 It is a flowchart showing the process of the brake assist control. As Figure 6 shown, in step S201, the controller 41 acquires a brake command for braking the construction machine 1. The controller 41 acquires the brake operation amount as the brake command.

[0059] In step S202, the controller 41 acquires the brake oil temperature. In addition, for ease of explanation, here, it is assumed that the controller 41 acquires the brake oil temperatures of the front brakes 37A, 37B. However, the controller 41 may also acquire the brake oil temperatures of the rear brakes 37C, 37D.

[0060] In step S203, the controller 41 determines the assist braking force based on the brake command and the brake oil temperature. That is, the controller 41 determines the assist braking force based on the brake operation amount and the brake oil temperature. As described above, the assist braking force is the braking force of the engine brake for assisting the braking force based on the hydraulic brakes 37A - 37D. The detailed determination method of the assist braking force will be described later.

[0061] In step S204, the controller 41 determines the target driving force. The controller 41 determines the target driving force so as to obtain the auxiliary braking force. The controller 41 determines the target driving force according to the driving force data L3 based on the braking assistance control described above, whereby the auxiliary braking force is generated.

[0062] Next, the method for determining the auxiliary braking force will be described. The controller 41 stores the auxiliary braking data D3. The auxiliary braking data D3 defines the relationship of the auxiliary braking force with respect to the brake operation amount and the brake oil temperature. The controller 41 refers to the auxiliary braking data D3 and determines the auxiliary braking force according to the brake operation amount and the brake oil temperature.

[0063] Figure 7 is a diagram showing an example of the auxiliary braking data D3. In the auxiliary braking data D3, the auxiliary braking force increases as the brake operation amount increases. As Figure 7 shown, the auxiliary braking data D3 includes the first braking force data L11 and the second braking force data L12.

[0064] The first braking force data L11 is used when the brake oil temperature is within a specified normal range. In the first braking force data L11, before the brake operation amount reaches the first threshold value Tb1, the auxiliary braking force that increases as the brake operation amount increases is defined. In the first braking force data L11, when the brake operation amount is equal to or greater than the first threshold value Tb1, a fixed auxiliary braking force is defined regardless of the increase in the brake operation amount.

[0065] The second braking force data L12 is used when the brake oil temperature is within a specified high temperature range higher than the normal range. The second braking force data L12 defines an auxiliary braking force greater than the first braking force data L11. Therefore, the controller 41 increases the auxiliary braking force as the brake oil temperature increases. In the second braking force data L12, before the brake operation amount reaches the second threshold value Tb2, the auxiliary braking force that increases as the brake operation amount increases is defined. In the second braking force data L12, when the brake operation amount is equal to or greater than the second threshold value Tb2, a fixed auxiliary braking force is defined regardless of the increase in the brake operation amount. The second threshold value Tb2 is less than the first threshold value Tb1.

[0066] For example, when the brake oil temperature is equal to or lower than the specified first temperature threshold value, the controller 41 determines the auxiliary braking force based on the first braking force data L11 according to the brake operation amount. When the brake oil temperature becomes greater than the first temperature threshold value, the controller 41 determines the auxiliary braking force based on the second braking force data L12 according to the brake operation amount.

[0067] When the brake oil temperature changes from a temperature higher than the first temperature threshold to a temperature equal to or lower than the specified second temperature threshold, the controller 41 determines the auxiliary braking force based on the first braking force data L11 according to the brake operation amount. The second temperature threshold is less than the first temperature threshold. Alternatively, the second temperature threshold may be the same as the first temperature threshold.

[0068] In addition, when switching between the first braking force data L11 and the second braking force data L12 according to the change in the brake oil temperature, the controller 41 may also set a limit on the change amount per unit time for the difference between the first braking force data L11 and the second braking force data L12. Thereby, when switching between the first braking force data L11 and the second braking force data L12, a sudden change in the auxiliary braking force is suppressed.

[0069] Figure 8 It is a diagram showing the relationship between the brake operation amount and the braking force in the brake assist control. Figure 8 In [the figure], the double-dashed line L21 represents the relationship between the brake operation amount and the braking force based on the hydraulic brakes 37A - 37D. As shown by the double-dashed line L21, when the brake operation amount is equal to or less than the threshold value Tb0, regardless of the brake operation amount, the braking force based on the hydraulic brakes 37A - 37D is 0. That is, the range where the brake operation amount is equal to or less than the threshold value Tb0 becomes the clearance area where the hydraulic brakes 37A - 37D do not operate. When the brake operation amount is greater than the threshold value Tb0, the braking force based on the hydraulic brakes 37A - 37D increases according to the increase in the brake operation amount.

[0070] Figure 8 In [the figure], the dashed line L22 represents the relationship between the brake operation amount and the auxiliary braking force. When the brake oil temperature is within the above-mentioned normal range. In accordance with Figure 7 the first braking force data L11 shown [in the figure], the auxiliary braking force increases according to the brake operation amount. When the brake oil temperature is within the above-mentioned high-temperature range, in accordance with Figure 7 the second braking force data L12 shown [in the figure], the auxiliary braking force increases according to the brake operation amount. Even in the clearance area of the hydraulic brakes 37A - 37D, the auxiliary braking force increases according to the increase in the brake operation amount. That is, the threshold values Tb1 and Tb2 of the above-mentioned auxiliary braking data D3 are also greater than the threshold value Tb0 of the clearance area of the hydraulic brakes 37A - 37D.

[0071] Figure 8 In [the figure], the solid line L23 represents the total braking force of the braking force based on the hydraulic brakes 37A - 37D and the auxiliary braking force. As shown by the solid line L23, a higher braking force is obtained by the auxiliary braking force than the braking force (L21) based only on the hydraulic brakes 37A - 37D.

[0072] In the construction machine 1 according to the embodiment described above, the auxiliary braking force is determined based on the brake oil temperature of the hydraulic brakes 37A - 37D. The braking force based on the hydraulic brakes 37A - 37D is assisted by the auxiliary braking force, whereby the heat generation in the hydraulic brakes 37A - 37D is suppressed. In addition, the auxiliary braking force is obtained by the negative driving force based on the engine 21 and the transmission 24, that is, by the engine brake. Therefore, while suppressing the increase in cost, the overheating of the hydraulic oil in the hydraulic brakes 37A - 37D is suppressed.

[0073] As described above, one embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the invention.

[0074] The construction machine 1 is not limited to a wheel loader, and may be other machines such as a bulldozer or a motor grader. The construction machine 1 may also be remotely operable. In this case, the FR operation member 42, the accelerator operation member 43, the work implement operation member 44, the brake operation member 45, and the input device 46 may also be arranged outside the construction machine 1.

[0075] The controller 41 may also be composed of a plurality of controllers. The processing of the control of the above-described construction machine 1 may also be executed by dispersing it among a plurality of controllers. The control method of the engine 21 is not limited to the above-described embodiment, and may also be changed.

[0076] The processing of the brake assist control is not limited to the above-described embodiment, and may also be changed. For example, the travel command is not limited to the accelerator operation amount, and may also be determined by automatic control based on the controller 41. The brake command is not limited to the brake operation amount, and may also be determined by automatic control based on the controller 41. The controller 41 may also change the drive force data L2 according to the oil temperature.

[0077] The auxiliary brake data D3 is not limited to the above-described embodiment, and may also be changed. For example, the number of braking force data included in the auxiliary brake data D3 is not limited to 2, and may be more than 2. Figure 9 It is a diagram showing the auxiliary brake data D3 according to the first modification. As Figure 9 shown, the auxiliary brake data D3 includes a plurality of braking force data L31 - L35 more than 2. The controller 41 may also switch the plurality of braking force data L31 - L35 according to the brake oil temperature.

[0078] Specifically, the auxiliary braking data D3 related to the first modification example includes the first to fifth braking force data L31 - L35. In the order of the first to fifth braking force data L31 - L35, the corresponding temperature range of the brake oil temperature becomes higher. For example, the first braking force data L31 corresponds to the lowest temperature range. The fifth braking force data L35 corresponds to the highest temperature range. As the corresponding temperature range rises, the threshold values Tb1 - Tb5 of the brake operation amount for each braking force data L31 - L35 become smaller. For example, the first threshold value Tb1 of the first braking force data L31 is the largest, and the fifth threshold value Tb5 of the fifth braking force data L35 is the smallest.

[0079] Alternatively, the controller 41 can also calculate, through arithmetic operations, the braking force data between the first braking force data L11 and the second braking force data L12 in the above-described embodiment. For example, Figure 10 FIG. is a diagram showing the auxiliary braking data D3 related to the second modification example. As Figure 10 shown, the controller 41 can also calculate the third threshold value Tb3 based on the brake oil temperature, and determine any braking force data L13 between the first braking force data L11 and the second braking force data L12 based on the third threshold value Tb3. For example, the controller 41 can also calculate the third threshold value Tb3 through proportional calculation based on the first threshold value Tb1, the second threshold value Tb2, and the brake oil temperature.

[0080] Industrial Applicability

[0081] According to the present disclosure, overheating of the hydraulic oil of the hydraulic brake can be suppressed in the work machine.

[0082] Symbol Explanation

[0083] 1: Work machine

[0084] 21: Engine

[0085] 24: Transmission

[0086] 25: Travel device

[0087] 35: Vehicle speed sensor

[0088] 37A - 37D: Hydraulic brake

[0089] 39, 40: Oil temperature sensor

[0090] 41: Controller

[0091] 45: Brake operation member.

Claims

1. An operating machine, comprising: An engine; A transmission connected to the engine; A traveling device connected to the transmission and causing the operating machine to travel; A vehicle speed sensor for detecting the vehicle speed; A hydraulic brake for braking the traveling device by being driven by hydraulic oil; An oil temperature sensor for detecting the oil temperature of the hydraulic oil; And A controller, The controller Obtains a travel command for controlling the travel of the operating machine; Obtains the vehicle speed; Determines a target driving force based on the travel command and the vehicle speed, the target driving force including a positive driving force for causing the operating machine to travel and a negative driving force for braking the operating machine; Controls the engine and the transmission so as to obtain the target driving force; Obtains the oil temperature; Determines an auxiliary braking force for assisting the braking force based on the hydraulic brake based on the oil temperature; and Determines the target driving force so as to obtain the auxiliary braking force.

2. The operating machine according to claim 1, Wherein, The controller increases the auxiliary braking force as the oil temperature increases.

3. The operating machine according to claim 1, Wherein, The controller Obtains a braking command for controlling the braking of the operating machine; and Determines the auxiliary braking force according to the braking command.

4. The operating machine according to claim 3, Wherein, The controller When the oil temperature is within a first temperature range, determines the auxiliary braking force according to the braking command based on first braking force data that defines the relationship between the braking command and the auxiliary braking force; And When the oil temperature is within a second temperature range higher than the first temperature range, determines the auxiliary braking force according to the braking command based on second braking force data that defines the relationship between the braking command and the auxiliary braking force, The second braking force data defines a higher auxiliary braking force than the first braking force data.

5. The operating machine according to claim 4, Wherein, In the first braking force data, before the braking command reaches a first threshold value, the auxiliary braking force that increases according to the increase of the braking command is defined, and when the braking command is above the first threshold value, a fixed auxiliary braking force is defined regardless of the increase of the braking command, In the second braking force data, before the braking command reaches a second threshold value, the auxiliary braking force that increases according to the increase of the braking command is defined, and when the braking command is above the second threshold value, a fixed auxiliary braking force is defined regardless of the increase of the braking command, The second threshold value is less than the first threshold value.

6. The operating machine according to claim 3, Wherein, The operating machine further includes: a brake operation member that can be operated by an operator, The hydraulic brake generates a braking force according to the operation amount of the brake operation member, The controller obtains the operation amount of the brake operation member as the braking command.

7. A method for controlling a work machine, wherein the work machine includes: an engine, a transmission connected to the engine, a traveling device connected to the transmission and for traveling the work machine, and a hydraulic brake that is driven by hydraulic oil to brake the traveling device; the method comprises: obtaining a travel command for controlling the travel of the work machine; obtaining the vehicle speed; determining a target driving force based on the travel command and the vehicle speed, the target driving force including a positive driving force for traveling the work machine and a negative driving force for braking the work machine; controlling the engine and the transmission to obtain the target driving force; obtaining the oil temperature of the hydraulic oil; determining an auxiliary braking force for assisting the braking force based on the hydraulic brake based on the oil temperature; and determining the target driving force to obtain the auxiliary braking force.

8. The method according to claim 7, wherein, the method comprises: increasing the auxiliary braking force as the oil temperature increases.

9. The method according to claim 7, wherein, the method comprises: obtaining a braking command for controlling the braking of the work machine; and determining the auxiliary braking force according to the braking command.

10. The method according to claim 9, comprises: when the oil temperature is within a first temperature range, determining the auxiliary braking force according to the braking command based on first braking force data that defines the relationship between the braking command and the auxiliary braking force; and when the oil temperature is within a second temperature range higher than the first temperature range, determining the auxiliary braking force according to the braking command based on second braking force data that defines the relationship between the braking command and the auxiliary braking force, wherein the second braking force data defines a higher auxiliary braking force than the first braking force data.

11. The method according to claim 10, wherein, in the first braking force data, before the braking command reaches a first threshold value, the auxiliary braking force that increases as the braking command increases is defined, and when the braking command is greater than or equal to the first threshold value, a fixed auxiliary braking force is defined regardless of the increase in the braking command, in the second braking force data, before the braking command reaches a second threshold value, the auxiliary braking force that increases as the braking command increases is defined, and when the braking command is greater than or equal to the second threshold value, a fixed auxiliary braking force is defined regardless of the increase in the braking command, wherein the second threshold value is less than the first threshold value.

12. The method according to claim 9, wherein, the hydraulic brake generates a braking force according to an operation amount of a brake operation member that can be operated by an operator, the method comprises: obtaining the operation amount of the brake operation member as the braking command.

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