Patent ID: 12209390

DESCRIPTION OF EMBODIMENTS

A wheel loader as an example of the work machine according to the present disclosure will be described below with reference to the drawings.

(Overview of Wheel Loader)

FIG.1is a schematic view showing a configuration of a wheel loader10(an example of a work machine) of the present embodiment. The wheel loader10of the present embodiment includes a vehicle body frame2, a work implement3, a pair of front tires4, a cab5, an engine room6, a pair of rear tires7, and a steering cylinder9in a vehicle body1. In the following description, “front”, “rear”, “right”, “left”, “top”, and “bottom” indicate directions based on the state of looking forward from the driver's seat. In addition, “vehicle width direction” and “left-right direction” are synonymous. InFIG.1, the front-rear direction is indicated by X, the front direction is indicated by Xf, and the rear direction is indicated by Xb.

The wheel loader10uses work implement3to perform earth and sand loading work and the like.

The vehicle body frame2is a so-called articulated type, and includes a front frame11, a rear frame12, and a connecting shaft part13. The front frame11is arranged in front of the rear frame12. The connecting shaft part13is provided at the center in the vehicle width direction, and connects the front frame11and the rear frame12so as to be swingable to each other. The pair of front tires4are attached to the left and right sides of the front frame11. Further, a pair of rear tires7are attached to the left and right sides of the rear frame12.

The work implement3is driven by a hydraulic fluid from a work implement pump (not illustrated). The work implement3includes a boom14, a bucket15, a lift cylinder16, and a bucket cylinder17. The boom14is attached to the front frame11. The bucket15is attached to the tip of the boom14.

The lift cylinder16and the bucket cylinder17are hydraulic cylinders. One end of the lift cylinder16is attached to the front frame11, and the other end of the lift cylinder16is attached to the boom14. The boom14swings up and down due to the expansion and contraction of the lift cylinder16. One end of the bucket cylinder17is attached to the front frame11, and the other end of the bucket cylinder17is attached to the bucket15via the bell crank18. As the bucket cylinder17expands and contracts, the bucket15swings up and down.

The cab5is mounted on the rear frame12, and a handle for a steering operation, a lever for operating the work implement3, various display devices, and the like are arranged inside. The engine room6is located on the rear side of the cab5and on the rear frame12, and houses the engine31.

FIG.2is a block diagram showing a configuration of a control system of the wheel loader10.

The wheel loader10includes a drive system21, a braking system22, an operation system23, a notification system24, a detection system25, and a controller26(an example of a controller).

The drive system21drives the wheel loader10. The braking system22brakes while the wheel loader10is traveling. The operation system23is operated by the operator. The drive system21and the braking system22are activated based on the operation of the operation system23by the operator. The notification system24notifies the operator based on the operation of the operation system23or the detection result by the detection system25. The detection system25detects the state of the vehicle body1and obstacles behind the vehicle body1. The controller26operates the drive system21, the braking system22, and the notification system24based on the operator's operation for the operation system23and the detection by the detection system25.

(Drive System21)

The drive system21includes an engine31, an HST32, a transfer33, an axle34, the front tires4, and the rear tires7.

The engine31is, for example, a diesel engine, and the driving force generated by the engine31drives the pump32aof the HST (Hydro Static Transmission)32.

The HST32includes a pump32a, a motor32b, and a hydraulic circuit32cthat connects the pump32aand the motor32b. The pump32ais a swash plate type variable displacement pump, and the angle of the swash plate can be changed by a solenoid32d. The pump32ais driven by the engine31to discharge the hydraulic fluid. The discharged hydraulic fluid is sent to the motor32bthrough the hydraulic circuit32c. The motor32bis a swash plate type pump, and the angle of the swash plate can be changed by a solenoid32e. The hydraulic circuit32cincludes a first drive circuit32c1and a second drive circuit32c2. Hydraulic fluid is supplied from the pump32ato the motor32bvia the first drive circuit32c1, so that the motor32bis driven in one direction (for example, in the forward direction). Hydraulic fluid is supplied from the pump32ato the motor32bvia the second drive circuit32c2, so that the motor32bis driven in another direction (for example, in the backward direction). The discharge direction of hydraulic fluid to the first drive circuit32c1or the second drive circuit32c2can be changed by the solenoid32d.

The transfer33distributes the output from the engine31to the front and rear axles34.

A pair of front tires4are connected to the front axle34, and rotate with the distributed output from the engine31. Further, a pair of rear tires7are connected to the rear axle34, and rotate with the distributed output from the engine31.

(Brake System22)

The braking system22includes a brake valve41, a service brake42, and a parking brake43.

The brake valve41is, for example, an EPC valve (Electric Proportional Control Valve), and the opening degree for the hydraulic fluid sent to the service brake42can be adjusted.

The service brake42is provided on the axle34. The service brake42is a hydraulic brake. For example, when the opening degree of the brake valve41is large, the braking force becomes strong, and when the opening degree of the brake valve41is small, the braking force becomes weak.

As a function of the automatic brake, the brake valve41is driven by an instruction from the controller26even when the brake pedal54, which will be described later, is not operated, and the service brake42is activated.

The parking brake43is provided on the transfer33. As the parking brake43, for example, a wet multi-stage brake that can switch between a braking state and a non-braking state, a disc brake, and the like can be used.

(Operation System23)

The operation system23includes an accelerator51, an FNR lever52, a parking switch53, a brake pedal54, a return switch55, and an automatic brake release switch56.

The accelerator51is provided in the cab5. The operator operates the accelerator51to set the throttle opening degree. The accelerator51generates an opening signal indicating an accelerator operation amount and transmits the signal to the controller26. The controller26controls the rotation speed of the engine31based on the transmitted signal.

When the accelerator51is turned off, the fuel supply to the engine31is stopped, the swash plates of the pump32aand the motor32bare controlled to serve as traveling resistance, and the internal inertia acts, so that the braking force (weak braking force, which will be described later) is generated.

The FNR lever52is provided in the cab5. The FNR lever52can be in a forward, neutral, or reverse position. An operation signal indicating the position of the FNR lever52is transmitted to the controller26, and the controller26controls the solenoid32dto switch between forward and backward. When the FNR lever52is in the neutral position, the controller26controls the solenoids32dand32e, and controls the swash plates of the pump32aand the motor32bso as to have traveling resistance. As a result, the internal inertia works, so that a braking force (weak braking force, which will be described later) is generated.

The automatic brake also includes the braking force generated by the control of turning off the accelerator51and the braking force generated by the control of setting the FNR lever52to the neutral position.

The parking switch53is provided in the cab5and can switch the state between on and off, and transmits a signal indicating the state to the controller26. The controller26sets the parking brake43in a braking state or a non-braking state based on the transmitted signal.

The brake pedal54is provided in the cab5. The brake pedal54adjusts the opening degree of the brake valve41. Further, the brake pedal54transmits the operation amount to the controller26.

The return switch55is operated by an operator to return from the stopped state after the vehicle body1is stopped by the automatic brake described later.

The automatic brake release switch56releases the automatic brake function and is set so that the automatic brake function does not work.

(Notification System24)

The notification system24includes an alarm device61(an example of a second notification section), a function OFF notification lamp62(an example of a first notification section), and an automatic brake activation notification lamp63.

The alarm device61gives an alarm to the operator when an obstacle is detected behind the vehicle body1based on the detection of the rear detection section71of the detection system25described later. The alarm device61may have, for example, a lamp and turn on the lamp. Further, the alarm device61may have a speaker and sound a sound, not limited to the lamp. Further, the alarm may be displayed on a display panel such as a monitor.

The function OFF notification lamp62lights up, for example, to notify the operator when the automatic brake function is suppressed (described later) or stopped at the judgment of the controller26. Further, the function OFF notification lamp62lights up, for example, to notify the operator when the automatic brake release switch56is operated by the operator's judgment and the automatic brake function is in the OFF state. Further, when the function OFF notification lamp62is turned off, it indicates that the automatic brake function can be activated. Further, the function OFF notification lamp62does not have to be limited to the lamp, and may make a sound. Further, the notification may be displayed on a display panel such as a monitor.

The automatic brake activation notification lamp63notifies the operator that the automatic brake activates, and notifies that the return operation by the return switch55is necessary. When the return switch55is operated and the automatic brake is released, the automatic brake activation notification lamp63turns off.

The automatic brake activation notification lamp63is not limited to the lamp, and may make a sound. Further, the notification may be displayed on a display panel such as a monitor.

As described above, the means for notifying the operator of information by the notification system24can be appropriately selected such as a lamp, a sound, and a monitor.

(Detection System25)

FIG.3Ais a block diagram showing the detection system25.

The detection system25includes a rear detection section71and a state detection section72.

The rear detection section71detects an obstacle behind the vehicle body1. The rear detection section71is attached to the rear end of the vehicle body1as illustrated inFIG.1, but is not limited to the rear end.

The rear detection section71includes, for example, a millimeter wave radar. A receiving antenna detects how the millimeter-wave band radio waves emitted from a transmitting antenna are reflected on a surface of an obstacle and returned, and the distance to the object can be measured. The detection result by the state detection section72is transmitted to the controller26, and the controller26can determine that an obstacle exists within a predetermined range when traveling backward. It should be noted that what the rear detection section71includes is not limited to the millimeter wave radar, and may be, for example, a camera or the like.

The state detection section72detects the state of the vehicle body1. The detection by the state detection section72is performed in order that the controller26determines whether the state of the vehicle body1is a state requiring falling down prevention (an example of a state in which a vehicle body becomes unstable) or a state in which it is possible to stop without requiring falling down prevention when the automatic brake is activated with the preset braking force of the preset strength while traveling backward.

Further, the detection by the state detection section72is performed in order that the controller26determines whether the state of the vehicle body1is a state requiring falling down prevention (an example of a state in which a vehicle body becomes unstable) or a state in which it is possible to stop without requiring falling down prevention when the automatic brake is activated with a braking force weaker than the preset braking force of the preset strength while traveling backward.

The state detection section72includes various sensors. The state detection section72detects, for example, (first state) work implement posture, (second state) load state, (third state) articulate angle as an example of the posture of the vehicle body, (fourth state) the road surface condition, and speed.

FIG.4is a view showing that the wheel loader10is in a work implement posture (first state) such that it is necessary to prevent falling down.

The state detection section72includes, for example, a boom angle sensor72aand a speed sensor72gin order to detect the posture (first state) of the work implement. When it is detected that the boom14is higher than the predetermined threshold value with the boom angle sensor72aand that the speed in backward traveling is equal to or higher than the predetermined threshold value with the speed sensor72g, the determination section81of the controller26determines that it is necessary to prevent the vehicle from falling down due to braking with the preset braking force or the weak braking force. The posture of work implement3may be determined not only by the boom angle sensor72abut also by providing a camera and performing image analysis. It is preferable to appropriately change the predetermined threshold value used for the determination between braking with the preset braking force and braking with a weak braking force. This also applies to (second state), (third state), and (fourth state), which will be described later.

FIG.5is a view showing that the wheel loader10is in a loaded state (second state) in which it is necessary to prevent falling down.

The state detection section72includes the pressure sensor72bfor detecting the pressure of the lift cylinder16, the boom angle sensor72a, and a bell crank angle sensor72dfor detecting whether or not the bucket15is in the tilt state in order to detect the state (second state) of the load. Whether or not the bucket15is in the tilted state is determined by the length of the bucket cylinder17. From the boom angle by the boom angle sensor72aand the bell crank angle by the bell crank angle sensor72d, the length of the bucket cylinder17is calculated based on the table stored in advance, and it is possible to detect whether or not the bucket15is in the tilted state.

When it is detected that a load W is loaded with equal to or greater than a predetermined value with the pressure sensor72b, that the boom14is raised above a predetermined threshold value, that the bucket15is in the tilted state, and that the speed in traveling backward is equal to or higher than the predetermined threshold value with the speed sensor72g, the determination section81of the controller26determines that it is necessary to prevent the vehicle from falling down due to braking with the preset braking force or the weak braking force. In addition, in order to detect the tilt state, a sensor (proximity sensor or the like) capable of detecting the position of the work implement such as the bucket15may be used instead of using the bell crank angle sensor72d, and it is possible to set the sensor arbitrarily. Further, in order to detect the state of the load, a camera may be provided to perform image analysis.

FIG.6is a view showing that the wheel loader10is in a state (third state) of an articulate angle such that it is necessary to prevent falling down.

The state detection section72includes an articulate angle sensor72efor detecting the articulate angle θ (third state). The articulate angle sensor72edetects the tilt angle of the front frame11with respect to the rear frame12.

When it is detected that the detection value θ is equal to or more than a predetermined angle with the articulate angle sensor72e, and that the speed in traveling backward is equal to or higher than the predetermined threshold value with the speed sensor72g, the determination section81of the controller26determines that it is necessary to prevent the vehicle from falling down due to braking with the preset braking force or the weak braking force.

FIG.7is a view showing that the state of the road surface condition (fourth state) is such that it is necessary to prevent falling down.

FIG.7shows a state in which the wheel loader10is arranged on the inclined surface R.

The state detection section72includes a vehicle body angle sensor72f. The determination section81of the controller26can determine that the wheel loader10is arranged on the inclined road surface R based on the detection value detected by the vehicle body angle sensor72f.

When it is detected that the inclination angle is equal to or greater than the predetermined angle with the vehicle body angle sensor72fand that the speed in traveling backward is equal to or greater than the predetermined threshold value with the speed sensor72g, the determination section81of the controller26determines that it is necessary to prevent the vehicle from falling down due to braking with the preset braking force or the weak braking force. An IMU (Inertial Measurement Unit) may be used instead of the vehicle body angle sensor72f.

(Controller26)

The controller26includes a processor such as a CPU (Central Processing Unit), a main memory including a non-volatile memory, such as a ROM (Read Only Memory), and a volatile memory, such as a RAM (Random Access Memory), and a storage. The controller26reads the program stored in the storage, expands the program on the main memory, and executes a predetermined process according to the program. The program may be delivered to the controller26via the network.

FIG.3Bis a block diagram showing the configuration of the controller26.

The controller26includes a determination section81, a brake instruction section82, and a notification instruction section83. The number of controllers26is not limited to one, and a plurality of controllers26may be provided, and the functions of the determination section81, the brake instruction section82, and the notification instruction section83may also be provided separately for the plurality of controllers.

The determination section81makes a determination regarding the control of the automatic brake. The determination section81includes an obstacle determination section84and a state determination section85.

The obstacle determination section84determines whether or not there is an obstacle when traveling backward. “Traveling backward” means that the tires are turning backwards. The obstacle determination section84detects that the vehicle body1is in the state of traveling backward, for example, by the front tire4or the rear tire7rotating backward, or by the FNR lever52being in the reverse position. The obstacle determination section84determines that an obstacle exists when receiving the obstacle detection information within a predetermined range from the rear detection section71of the detection system25in detecting the state of traveling backward.

The state determination section85determines whether or not the wheel loader10is in the states (first state to fourth state) illustrated inFIGS.4to7, and determines whether or not it is necessary to prevent falling down when braking with the preset braking force or the weak braking force is activated in traveling backward based on the speed.

The brake instruction section82controls automatic brake based on the determination result of the obstacle determination section84and the determination result of the state determination section85. The automatic brake in the present specification is to automatically activate a braking force to the vehicle body1based on the determination result of the obstacle determination section84and the determination result of the state determination section85, and as will be described later, it is not limited to the braking force of the service brake42.

When the obstacle determination section84determines that an obstacle exists, and the state determination section85determines that the state of the vehicle body1is a state in which it is not necessary to prevent falling down in a case of activating the preset braking force, the brake instruction section82stops the fuel supply to the engine31and drives the service brake42by operating the brake valve41to stop the vehicle body1.

FIG.8is a view showing a state in which the obstacle S is detected when traveling backward and the vehicle body1is stopped. When the state of the vehicle body1is stable and it is not necessary to prevent falling down in case where a preset braking force (which can be said to be a braking force) causing the vehicle body1to stop in front of the obstacle S is activated by operating the service brake42, it is possible to stop the vehicle body1by activating the preset brake force with the service brake42. At this time, the opening degree of the brake valve41is set large in order to activate the preset braking force that stops the vehicle body1in front of the obstacle S. InFIG.8, the stopped vehicle body1is indicated by a chain double-dashed line.

In the automatic brake with the preset braking force, the vehicle body1may not be braked by the service brake42as described above, and the parking brake43may be operated. In this case, when the obstacle determination section84determines that the obstacle S exists, and the state determination section85determines that the state of the vehicle body1is a state in which it is not necessary to prevent falling down in a case of activating the preset braking force, the brake instruction section82stops the fuel supply to the engine31. Then, the brake instruction section82controls the parking brake43to brake the vehicle body1.

Further, when the obstacle determination section84determines that an obstacle exists, and the state determination section85determines that the state of the vehicle body1is a state in which it is not necessary to prevent falling down in a case of activating the weak braking force, the brake instruction section82stops the fuel supply to the engine31, sets the opening degree of the brake valve41to be small, and controls the service brake42so that a weak braking force is activated. Here, the weak braking force is set smaller than the preset braking force. Activating the weak braking force corresponds to an example of suppressing the braking force of the automatic brake.

The weak braking force is not limited to being generated by adjusting the opening degree of the brake valve41, but is also generated when the operator simply turns off the accelerator51. When the accelerator51is turned off, the fuel supply to the engine31is stopped, and the swash plates of the pump32aand the motor32bare controlled to serve as traveling resistance, so that the weak braking force is activated.

The brake instruction section82may activate the weak braking force by controlling like a case in which the operator turns off the accelerator51.

That is, when the obstacle determination section84determines that an obstacle exists, and the state determination section85determines that the state of the vehicle body1is a state in which it is not necessary to prevent falling down in a case of activating the weak braking force, the brake instruction section82stops the fuel supply to the engine31, for example, controls the swash plates of the pump32aand the motor32bso as to serve as a traveling resistance, and activates the weak braking force.

The weak braking force is also activated by the operator operating the FNR lever52so as to be in the neutral position. Therefore, when the obstacle determination section84determines that an obstacle exists, and the state determination section85determines that the state of the vehicle body1is a state in which it is not necessary to prevent falling down in a case of activating the weak braking force, the brake instruction section82controls like a case in which the operator operates the FNR lever52so as to be in the neutral position without executing the control of activating the preset braking force. As a result, the swash plates of the pump32aand the motor32bare controlled to serve as traveling resistance, and a weak braking force is exerted. Since it is possible to apply such a weak braking force, the posture can be stabilized even in an unstable state.

Further, when the obstacle determination section84determines that an obstacle exists, and the state determination section85determines that the state of the vehicle body1is a state in which it is necessary to prevent falling down in a case of activating the weak braking force, the controller26does not activate the automatic brake.

The notification instruction section83activates the alarm device61when the obstacle determination section84determines that the obstacle S exists.

Further, when the obstacle determination section84determines that an obstacle exists, and the state determination section85determines that the state of the vehicle body1is a state in which it is necessary to prevent falling down in a case of activating the preset braking force, the notification instruction section83turns on the function OFF notification lamp62indicating that the function for activating the preset braking force is turned off.

Further, when the return switch55is operated by the operator after the vehicle body1is stopped by the automatic brake and the automatic brake is released, the notification instruction section83turns on the automatic brake activation notification lamp63for notifying the operator of the release. Further, the notification instruction section83turns on the function OFF notification lamp62when the operator operates the automatic brake release switch56to turn off the function of activating the preset braking force.

<Operation>

Next, the control operation of the wheel loader10of the present embodiment will be described.

FIG.9is a flow chart showing a control operation regarding to obstacle detection of the wheel loader10of the present embodiment.

First, in step S10, the obstacle determination section84of the controller26determines whether or not an obstacle is detected when the vehicle body1moves backward. The obstacle determination section84detects that the vehicle body1is in the state of moving backward, for example, by the front tire4or the rear tire7rotating rearward, or the FNR lever52being in the reverse position. When the obstacle determination section84receives the detection information of an obstacle within a predetermined range from the rear detection section71of the detection system25in the state of detecting that the backward travel is being performed, the obstacle determination section84determines that an obstacle exists.

When it is not determined in step S10that an obstacle exists, the controller26ends without activating the automatic brake in step S11.

When it is determined in step S10that an obstacle is exists, in step S12, the state determination section85determines whether or not it is necessary to prevent falling down in a case of activating the weak braking force.

The state determination section85acquires the state of the vehicle body1from the boom angle sensor72a, the pressure sensor72b, the bell crank angle sensor72d, the articulate angle sensor72e, the vehicle body angle sensor72f, and the speed sensor72gof the state detection section72. And the state determination section85determines whether or not the state of the vehicle body1corresponds to the above-mentioned first state to fourth state requiring falling down prevention.

When it is determined in step S12that the state of the vehicle body1is a state requiring falling down prevention in a case of activating the weak braking force, the controller26ends the control without activating the braking force in step S13.

When it is determined in step S12that the state of the vehicle body1is a state in which it is not necessary to prevent falling down in the case of activating the weak braking force, the state determination section85determines whether or not the state of the vehicle body1is the state requiring falling down prevention in the case of activating the preset braking force. The preset braking force is the above-mentioned strong braking force that is capable of making the vehicle body1stop before the obstacle S.

When it is determined in step S14that the state of the vehicle body1is a state in which it is necessary to prevent falling down in the case of activating the preset braking force, the brake instruction section82of the controller26stops the fuel supply to the engine31and controls the service brake42so as to activate the weak braking force by setting the opening degree of the brake valve to be small in step S15, and the control ends. As described above, the weak braking force may be generated by stopping the fuel supply to the engine31and controlling the swash plates of the pump32aand the motor32bto serve as traveling resistance.

When it is determined in step S14that the state of the vehicle body1is a state in which it is not necessary to prevent falling down in the case of activating the preset braking force, the brake instruction section82of the controller26stops the fuel supply to the engine31by releasing the accelerator51and operates the service brake42with the preset braking force by operating the brake valve41in step S16and the vehicle body1stops. In this way, the control ends. As described above, the parking brake43may be operated to generate the preset braking force.

As described above, it is possible to brake the vehicle body1by activating the preset braking force or the weak braking force within the range where it is not necessary to prevent falling down.

Further, for example, when the control is started again after the control ends by activating the brake with the weak braking force in step S15and then no obstacle is detected in step S10, the brake is not activated in step S11and activating the weak braking force is stopped. In this way, even when there are no obstacles in the middle of traveling backward, it is possible to control the automatic brake appropriately. The same applies when an obstacle appears in the middle of traveling backward.

The wheel loader10(an example of a work machine) of the embodiment includes the rear detection section71, the state detection section72, and the controller26(an example of a controller). The rear detection section71detects the rear of the vehicle body1when traveling backward. The state detection section72detects the state of the vehicle body1. The controller26brakes the vehicle body1based on the detection of the state detection section72and the detection of the rear detection section71.

As a result, the control of the automatic brake can be changed depending on the state of the vehicle body1and the detection result at the rear. For example, when the vehicle body1is unstable due to an operator loading a load or the like, the control of the automatic brake can be suppressed. Further, when the vehicle body1is stable and it is not necessary to prevent falling down, it is possible to brake and stop the vehicle body1by the automatic brake.

In the wheel loader10(an example of a work machine) of the embodiment, the controller26(an example of a controller) executes braking by automatic brake or control of suppressing the braking force of the automatic brake.

Thereby, for example, when the work machine is unstable, it is possible to suppress the braking of the automatic control section.

The wheel loader10(an example of a work machine) of the embodiment further includes the function OFF notification lamp62(an example of a first notification section). The function OFF notification lamp62notifies the suppression of automatic brake. The control of the automatic brake includes notification by the function OFF notification lamp62.

As a result, it is possible to notify the operator that braking by the automatic brake is suppressed.

The wheel loader10(an example of a work machine) of the embodiment further includes an alarm device61(an example of a second notification section). The alarm device61notifies that the rear detection section71detects an obstacle S behind the vehicle body1.

Thereby, it is possible to notify the operator that the obstacle S has been detected.

In the wheel loader10(an example of a work machine) of the embodiment, the controller26(an example of a controller) suppresses the braking force of the automatic brake when detecting an obstacle S by the rear detection section71in traveling backward, and when determining that the state of the vehicle body1detected by the state detection section72is a state in which the vehicle body1becomes unstable in a case of activating the automatic brake with the preset braking force.

As a result, when the wheel loader10is in an unstable state, it is possible to suppress the braking force of the automatic brake. Further, when the vehicle body1is in a stable state, it is possible to brake and stop the vehicle body1without suppressing the automatic brake function.

The wheel loader10(an example of a work machine) of the embodiment further includes a service brake42(an example of a service brake) and a brake valve41. The brake valve41can adjust the supply amount of hydraulic fluid to the service brake42. The controller26drives the brake valve41and uses the service brake42to execute braking by automatic brake.

As a result, it is possible to stop the vehicle body1when the obstacle S is detected.

The wheel loader10(an example of a work machine) of the embodiment further includes a parking brake43. The controller26(an example of the controller) executes braking by the automatic brake with activating the parking brake43.

As a result, it is possible to stop the vehicle body1when the obstacle S is detected.

In the wheel loader10(an example of a work machine) of the embodiment, the vehicle body1includes the work implement3. The state of the vehicle body1includes the posture of work implement3.

As a result, it is possible to detect that the vehicle body1is in an unstable state in which it is necessary to prevent falling down when the vehicle body1is braked with the preset braking force due to the posture of the work implement3.

In the wheel loader10(an example of a work machine) of the embodiment, the vehicle body1includes a work implement3. The state of the vehicle body1includes the state of the load on the work implement3.

As a result, it is possible to detect that the vehicle body1is in an unstable state in which it is necessary to prevent falling down when the vehicle body1is braked with the preset braking force due to the posture and load of work implement3.

In the wheel loader10(an example of a work machine) of the embodiment, the vehicle body1is the articulate type. The state of the vehicle body includes the articulate angle.

As a result, it is possible to detect that the vehicle body1is in an unstable state in which it is necessary to prevent falling down when the vehicle body1is braked with the preset braking force due to the articulation angle.

In the wheel loader10(an example of a work machine) of the embodiment, the state of the vehicle body1includes the inclination of the vehicle body1.

As a result, it is possible to detect that the vehicle body1is in an unstable state in which it is necessary to prevent falling down when the vehicle body1is braked with the preset braking force due to the inclination of the ground or the like.

The method for controlling the wheel loader10(an example of a work machine) of the embodiment includes steps S10(an example of a rear detection step), steps S12and S14(an example of a state detection step), and steps S11, S13, S15, and S16(an example of a control step). Step S10detects the rear of the vehicle body1. Steps S12and S14detect the state of the vehicle body1. Steps S11, S13, S15, and S16control an automatic brake that automatically brakes the vehicle body1based on the detection result in step S10and the detection result in steps S12and S14.

As a result, the control of the automatic brake can be changed depending on the state of the vehicle body1and the detection result at the rear. For example, when the vehicle body1is unstable due to an operator loading a load or the like, the control of the automatic brake can be suppressed. Further, when the vehicle body1is stable and it is not necessary to prevent falling down, it is possible to brake and stop the vehicle body1by the automatic brake.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the invention.

In the above embodiment, in step S12, it is determined whether or not it is necessary to prevent falling down by activating the weak braking force, and when it is not necessary, further, in step S14, it is determined whether or not it is necessary to prevent falling down by activating the preset braking force, but it is not limited to this.

For example, as illustrated inFIG.10, the weak braking force may not be activated.

In the control flow illustrated inFIG.10, first, in step S20, the obstacle determination section84of the controller26determines whether or not an obstacle is detected when the vehicle body1moves backward.

When it is not determined in step S20that an obstacle exists, the controller26ends the control without activating the brake in step S21.

When it is determined in step S20that an obstacle exists, in step S22, the state determination section85determines whether or not the state of the vehicle body1is a state requiring falling down prevention when the preset braking force is activated.

When it is determined in step S22that the falling down prevention is necessary, the brake instruction section82of the controller26does not activate the brake in step S23, and the control ends.

Further, when it is determined in step S22that the state of the vehicle body1is not a state requiring falling down prevention, in step S24, the brake instruction section82of the controller26operates the brake valve41to operate the service brake42with the preset braking force, and the control ends.

In step S22, the weak brake may be activated instead of not activating the brake.

In the above embodiment, the HST32is used in the drive system21, but it is not limited to HST, and a torque converter may be used.FIG.11is a block diagram showing a configuration in which the torque converter132and the transmission133are provided in the drive system21. The driving force from the engine31is transmitted to the transmission133via the Torque converter132. The transmission133shifts the rotational driving force of the engine31transmitted via the torque converter132and transmits it to the axle34. The transmission133is provided with a parking brake43.

In the case of the torque converter, in order to generate a weak braking force, the opening degree of the brake valve41may be set small in the same manner as described above. Further, although the braking force is weaker than that of the HST, the accelerator51may be simply turned off. When generating the preset braking force, the opening degree of the brake valve41may be increased or the parking brake43may be used as in the above embodiment.

Further, not limited to HST, HMT (Hydro Mechanical Transmission) may be used.

For the control of the braking force, a service brake42, a parking brake43, and other means for changing the braking force can be appropriately applied.

In the above embodiment, the function OFF notification lamp62and the alarm device61are provided, but when the function OFF notification and the alarm notification can be distinguished, the function OFF notification lamp62may also serve as the alarm device61.

The wheel loader of the above embodiment may be operated by an operator on board, or may be operated unattended.

In the above embodiment, the wheel loader has been described as an example of the work machine, but it may not be limited to the wheel loader, and a hydraulic excavator or the like may be used.

The work machine and the method for controlling the work machine of the present invention exert an effect capable of improving work efficiency and is useful as a wheel loader or the like.