Patent Description:
In a wheel loader, which is an example of a work machine, an automatic stop system that detects an obstacle behind and automatically stops has been proposed.

For example, in Non-Patent Document <NUM>, a stereo camera is installed in a wheel loader, and a foot brake is activated when an obstacle is recognized while traveling backward.

Non-Patent Document <NUM> "<NPL> Patent publication documents: <CIT>, <CIT>, <CIT>, <CIT>. <CIT> discloses a wheel loader comprising an obstacle detection sensor configured to detect rear of a vehicle body when traveling backward. Further, different states of the vehicle are detected and a controller (calculation unit) is configured to brake the vehicle body based on detection of the obstacle detection sensor. <CIT> discloses a forklift comprising a rear distance sensor configured to detect the rear of a vehicle body when traveling backward. Further, different states of the vehicle are detected and a controller is configured to brake the vehicle body based on detection of the rear distance sensor. <CIT> discloses a vehicle comprising a object detection device configured to detect rear of a vehicle body when traveling backward. The object detection device includes a camera, a radar and a lidar. Further, different states of the vehicle are detected and a processor is configured to brake the vehicle body based on detection of the object detection device. <CIT> discloses a vehicle comprising a rear detection section configured to detect rear of a vehicle body when traveling backward. Further, different states of the vehicle are detected and a controller is configured to brake the vehicle body based on detection of the rear detection section.

However, when working at a construction site, etc., the work machine is often in a relatively unstable state, and in the case of sudden braking is activated when traveling backward in such a state, the work machine may fall down and the work may be interrupted. In construction sites and the like, operators are often aware of surrounding obstacles because they are working carefully, and braking is activated every time an obstacle is detected when traveling backward, which reduces work efficiency.

It is an object of the present invention to provide a work machine and a method for controlling a work machine capable of improving work efficiency.

A work machine according to a first aspect includes a state detection section, a rear detection section, and a controller. The rear detection section detects rear of a vehicle body. The state detection section detects a state of the vehicle body. The controller brakes the vehicle body based on detection of the rear detection section and detection of the state detection section. Further, the vehicle body is an articulate type, and the state of the vehicle body includes an articulate angle.

In a preferred embodiment, the controller is configured to execute braking by automatic brake, suppressing braking force of automatic brake, or stopping automatic brake.

A work machine according to a second aspect comprises a rear detection section configured to detect rear of a vehicle body when traveling backward; a state detection section configured to detect a state of the vehicle body; a controller configured to brake the vehicle body based on detection of the rear detection section and detection of the state detection section, the controller configured to execute braking by automatic brake, suppressing braking force of automatic brake, or stopping automatic brake; and a first notification section configured to notify suppression of the automatic brake or stop of the automatic brake, wherein control of the automatic brake includes notification by the first notification section.

A work machine according to a third aspect comprises a rear detection section configured to detect rear of a vehicle body when traveling backward; a state detection section configured to detect a state of the vehicle body; a controller configured to brake the vehicle body based on detection of the rear detection section and detection of the state detection section; and a second notification section configured to notify that an obstacle is detected behind the vehicle body by the rear detection section.

In a preferred embodiment, the controller is configured to suppress braking force of the automatic brake or stop the automatic brake when detecting an obstacle by the rear detection section in traveling backward, and when determining that the state of the vehicle body detected by the state detection section is a state in which the vehicle body becomes unstable in a case of activating the automatic brake with preset braking force.

A work machine according to a fourth aspect comprises a rear detection section configured to detect rear of a vehicle body when traveling backward; a state detection section configured to detect a state of the vehicle body; a controller configured to brake the vehicle body based on detection of the rear detection section and detection of the state detection section; a service brake; and a brake valve configured to adjust a supply amount of hydraulic fluid to the service brake, wherein the controller is configured to drive the brake valve and use the service brake to execute braking by automatic brake.

In a preferred embodiment, the controller is configured to control to suppress the braking force with the automatic brake by adjusting the brake valve to weaken the braking force of the service brake.

A work machine according to a fifth aspect includes a rear detection section configured to detect rear of a vehicle body when traveling backward; a state detection section configured to detect a state of the vehicle body; a controller configured to brake the vehicle body based on detection of the rear detection section and detection of the state detection section; and a parking brake, wherein the controller is configured to execute braking with the automatic brake by activating the parking brake.

In a preferred embodiment, the work machine includes the vehicle body includes a work implement, and the state of the vehicle body includes a posture of the work implement.

In a preferred embodiment, the work machine includes the vehicle body includes a work implement, and the state of the vehicle body includes a state of a load on the work implement.

In a preferred embodiment, the work machine includes the state of the vehicle body includes inclination of the vehicle body.

A method for controlling a work machine according to a sixth aspect includes a rear detection step, a state detection step, and a control step. The rear detection step detects rear of the vehicle body. The state detection step detects a state of the vehicle body. The control step brakes the vehicle body based on detection result by the rear detection step and detection result by the state detection step. The vehicle body is an articulate type, and the state of the vehicle body includes an articulate angle.

According to the present invention, it is possible to provide a work machine and a method for controlling a work machine capable of improving work efficiency.

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

<FIG> is a schematic view showing a configuration of a wheel loader <NUM> (an example of a work machine) of the present embodiment. The wheel loader <NUM> of the present embodiment includes a vehicle body frame <NUM>, a work implement <NUM>, a pair of front tires <NUM>, a cab <NUM>, an engine room <NUM>, a pair of rear tires <NUM>, and a steering cylinders <NUM> in a vehicle body <NUM>. 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. In <FIG>, 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 loader <NUM> uses work implement <NUM> to perform earth and sand loading work and the like.

The vehicle body frame <NUM> is a so-called articulated type, and includes a front frame <NUM>, a rear frame <NUM>, and a connecting shaft part <NUM>. The front frame <NUM> is arranged in front of the rear frame <NUM>. The connecting shaft part <NUM> is provided at the center in the vehicle width direction, and connects the front frame <NUM> and the rear frame <NUM> so as to be swingable to each other. The pair of front tires <NUM> are attached to the left and right sides of the front frame <NUM>. Further, a pair of rear tires <NUM> are attached to the left and right sides of the rear frame <NUM>.

The work implement <NUM> is driven by a hydraulic fluid from a work implement pump (not illustrated). The work implement <NUM> includes a boom <NUM>, a bucket <NUM>, a lift cylinder <NUM>, and a bucket cylinder <NUM>. The boom <NUM> is attached to the front frame <NUM>. The bucket <NUM> is attached to the tip of the boom <NUM>.

The lift cylinder <NUM> and the bucket cylinder <NUM> are hydraulic cylinders. One end of the lift cylinder <NUM> is attached to the front frame <NUM>, and the other end of the lift cylinder <NUM> is attached to the boom <NUM>. The boom <NUM> swings up and down due to the expansion and contraction of the lift cylinder <NUM>. One end of the bucket cylinder <NUM> is attached to the front frame <NUM>, and the other end of the bucket cylinder <NUM> is attached to the bucket <NUM> via the bell crank <NUM>. As the bucket cylinder <NUM> expands and contracts, the bucket <NUM> swings up and down.

The cab <NUM> is mounted on the rear frame <NUM>, and a handle for steering operation, a lever for operating work implement <NUM>, various display devices, and the like are arranged inside. The engine room <NUM> is located on the rear side of the cab <NUM> and on the rear frame <NUM>, and houses the engine <NUM>.

<FIG> is a block diagram showing a configuration of a control system of the wheel loader <NUM>.

The wheel loader <NUM> includes a drive system <NUM>, a braking system <NUM>, an operation system <NUM>, a notification system <NUM>, a detection system <NUM>, and a controller <NUM> (an example of a controller).

The drive system <NUM> drives the wheel loader <NUM>. The braking system <NUM> brakes while the wheel loader <NUM> is traveling. The operation system <NUM> is operated by the operator. The drive system <NUM> and the braking system <NUM> are activated based on the operation of the operation system <NUM> by the operator. The notification system <NUM> notifies the operator based on the operation of the operation system <NUM> or the detection result by the detection system <NUM>. The detection system <NUM> detects the state of the vehicle body <NUM> and obstacles behind the vehicle body <NUM>. The controller <NUM> operates the drive system <NUM>, the braking system <NUM>, and the notification system <NUM> based on the operator's operation for the operation system <NUM> and the detection by the detection system <NUM>.

The drive system <NUM> includes an engine <NUM>, an HST <NUM>, a transfer <NUM>, an axle <NUM>, the front tires <NUM>, and the rear tires <NUM>.

The engine <NUM> is, for example, a diesel engine, and the driving force generated by the engine <NUM> drives the pump 32a of the HST (Hydro Static Transmission) <NUM>.

The HST <NUM> includes a pump 32a, a motor 32b, and a hydraulic circuit 32c that connects the pump 32a and the motor 32b. The pump 32a is a swash plate type variable displacement pump, and the angle of the swash plate can be changed by a solenoid 32d. The pump 32a is driven by the engine <NUM> to discharge the hydraulic fluid. The discharged hydraulic fluid is sent to the motor 32b through the hydraulic circuit 32c. The motor 32b is a swash plate type pump, and the angle of the swash plate can be changed by a solenoid 32e. The hydraulic circuit 32c includes a first drive circuit 32c1 and a second drive circuit 32c2. Hydraulic fluid is supplied from the pump 32a to the motor 32b via the first drive circuit 32c1, so that the motor 32b is driven in one direction (for example, in the forward direction). Hydraulic fluid is supplied from the pump 32a to the motor 32b via the second drive circuit 32c2, so that the motor 32b is driven in another direction (for example, in the backward direction). The discharge direction of hydraulic fluid to the first drive circuit 32c1 or the second drive circuit 32c2 can be changed by the solenoid 32d.

The transfer <NUM> distributes the output from the engine <NUM> to the front and rear axles <NUM>.

A pair of front tires <NUM> are connected to the front axle <NUM>, and rotate with the distributed output from the engine <NUM>. Further, a pair of rear tires <NUM> are connected to the rear axle <NUM>, and rotate with the distributed output from the engine <NUM>.

The braking system <NUM> includes a brake valve <NUM>, a service brake <NUM>, and a parking brake <NUM>.

The brake valve <NUM> is, for example, an EPC valve (Electric Proportional Control Valve), and the opening degree for the hydraulic fluid sent to the service brake <NUM> can be adjusted.

The service brake <NUM> is provided on the axle <NUM>. The service brake <NUM> is a hydraulic brake. For example, when the opening degree of the brake valve <NUM> is large, the braking force becomes strong, and when the opening degree of the brake valve <NUM> is small, the braking force becomes weak.

As a function of the automatic brake, the brake valve <NUM> is driven by an instruction from the controller <NUM> even when the brake pedal <NUM>, which will be described later, is not operated, and the service brake <NUM> is activated.

The parking brake <NUM> is provided on the transfer <NUM>. As the parking brake <NUM>, 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.

The operation system <NUM> includes an accelerator <NUM>, an FNR lever <NUM>, a parking switch <NUM>, a brake pedal <NUM>, a return switch <NUM>, and an automatic brake release switch <NUM>.

The accelerator <NUM> is provided in the cab <NUM>. The operator operates the accelerator <NUM> to set the throttle opening degree. The accelerator <NUM> generates an opening signal indicating an accelerator operation amount and transmits the signal to the controller <NUM>. The controller <NUM> controls the rotation speed of the engine <NUM> based on the transmitted signal.

When the accelerator <NUM> is turned off, the fuel supply to the engine <NUM> is stopped, the swash plates of the pump 32a and the motor 32b are 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 lever <NUM> is provided in the cab <NUM>. The FNR lever <NUM> can be in a forward, neutral, or reverse position. An operation signal indicating the position of the FNR lever <NUM> is transmitted to the controller <NUM>, and the controller <NUM> controls the solenoid 32d to switch between forward and backward. When the FNR lever <NUM> is in the neutral position, the controller <NUM> controls the solenoids 32d and 32e, and controls the swash plates of the pump 32a and the motor 32b so 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 accelerator <NUM> and the braking force generated by the control of setting the FNR lever <NUM> to the neutral position.

The parking switch <NUM> is provided in the cab <NUM> and can switch the state between on and off, and transmits a signal indicating the state to the controller <NUM>. The controller <NUM> sets the parking brake <NUM> in a braking state or a non-braking state based on the transmitted signal.

The brake pedal <NUM> is provided in the cab <NUM>. The brake pedal <NUM> adjusts the opening degree of the brake valve <NUM>. Further, the brake pedal <NUM> transmits the operation amount to the controller <NUM>.

The return switch <NUM> is operated by an operator to return from the stopped state after the vehicle body <NUM> is stopped by the automatic brake described later.

The automatic brake release switch <NUM> releases the automatic brake function and is set so that the automatic brake function does not work.

The notification system <NUM> includes an alarm device <NUM> (an example of a second notification section), a function OFF notification lamp <NUM> (an example of a first notification section), and an automatic brake activation notification lamp <NUM>.

The alarm device <NUM> gives an alarm to the operator when an obstacle is detected behind the vehicle body <NUM> based on the detection of the rear detection section <NUM> of the detection system <NUM> described later. The alarm device <NUM> may have, for example, a lamp and turn on the lamp. Further, the alarm device <NUM> may 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 lamp <NUM> lights up, for example, to notify the operator when the automatic brake function is suppressed (described later) or stopped at the judgment of the controller <NUM>. Further, the function OFF notification lamp <NUM> lights up, for example, to notify the operator when the automatic brake release switch <NUM> is operated by the operator's judgment and the automatic brake function is in the OFF state. Further, when the function OFF notification lamp <NUM> is turned off, it indicates that the automatic brake function can be activated. Further, the function OFF notification lamp <NUM> does 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 lamp <NUM> notifies the operator that the automatic brake activates, and notifies that the return operation by the return switch <NUM> is necessary. When the return switch <NUM> is operated and the automatic brake is released, the automatic brake activation notification lamp <NUM> turns off.

The automatic brake activation notification lamp <NUM> is 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 system <NUM> can be appropriately selected such as a lamp, a sound, and a monitor.

<FIG> is a block diagram showing the detection system <NUM>.

The detection system <NUM> includes a rear detection section <NUM> and a state detection section <NUM>.

The rear detection section <NUM> detects an obstacle behind the vehicle body <NUM>. The rear detection section <NUM> is attached to the rear end of the vehicle body <NUM> as illustrated in <FIG>, but is not limited to the rear end.

The rear detection section <NUM> includes, 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 section <NUM> is transmitted to the controller <NUM>, and the controller <NUM> can determine that an obstacle exists within a predetermined range when traveling backward. It should be noted that what the rear detection section <NUM> includes is not limited to the millimeter wave radar, and may be, for example, a camera or the like.

The state detection section <NUM> detects the state of the vehicle body <NUM>. The detection by the state detection section <NUM> is performed in order that the controller <NUM> determines whether the state of the vehicle body <NUM> is 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 section <NUM> is performed in order that the controller <NUM> determines whether the state of the vehicle body <NUM> is 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 section <NUM> includes various sensors. The state detection section <NUM> detects, 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> is a view showing that the wheel loader <NUM> is in a work implement posture (first state) such that it is necessary to prevent falling down.

The state detection section <NUM> includes, for example, a boom angle sensor 72a and a speed sensor <NUM> in order to detect the posture (first state) of the work implement. When it is detected that the boom <NUM> is higher than the predetermined threshold value with the boom angle sensor 72a and that the speed in backward traveling is equal to or higher than the predetermined threshold value with the speed sensor <NUM>, the determination section <NUM> of the controller <NUM> determines 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 implement <NUM> may be determined not only by the boom angle sensor 72a but 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> is a view showing that the wheel loader <NUM> is in a loaded state (second state) in which it is necessary to prevent falling down.

The state detection section <NUM> includes the pressure sensor 72b for detecting the pressure of the lift cylinder <NUM>, the boom angle sensor 72a, and a bell crank angle sensor 72d for detecting whether or not the bucket <NUM> is in the tilt state in order to detect the state (second state) of the load. Whether or not the bucket <NUM> is in the tilted state is determined by the length of the bucket cylinder <NUM>. From the boom angle by the boom angle sensor 72a and the bell crank angle by the bell crank angle sensor 72d, the length of the bucket cylinder <NUM> is calculated based on the table stored in advance, and it is possible to detect whether or not the bucket <NUM> is 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 sensor 72b, that the boom <NUM> is raised above a predetermined threshold value, that the bucket <NUM> is in the tilted state, and that the speed in traveling backward is equal to or higher than the predetermined threshold value with the speed sensor <NUM>, the determination section <NUM> of the controller <NUM> determines 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 bucket <NUM> may be used instead of using the bell crank angle sensor 72d, 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> is a view showing that the wheel loader <NUM> is in a state (third state) of an articulate angle such that it is necessary to prevent falling down.

The state detection section <NUM> includes an articulate angle sensor 72e for detecting the articulate angle θ (third state). The articulate angle sensor 72e detects the tilt angle of the front frame <NUM> with respect to the rear frame <NUM>.

When it is detected that the detection value θ is equal to or more than a predetermined angle with the articulate angle sensor 72e, and that the speed in traveling backward is equal to or higher than the predetermined threshold value with the speed sensor <NUM>, the determination section <NUM> of the controller <NUM> determines 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> is a view showing that the state of the road surface condition (fourth state) is such that it is necessary to prevent falling down.

<FIG> shows a state in which the wheel loader <NUM> is arranged on the inclined surface R.

The state detection section <NUM> includes a vehicle body angle sensor 72f. The determination section <NUM> of the controller <NUM> can determine that the wheel loader <NUM> is arranged on the inclined road surface R based on the detection value detected by the vehicle body angle sensor 72f.

When it is detected that the inclination angle is equal to or greater than the predetermined angle with the vehicle body angle sensor 72f and that the speed in traveling backward is equal to or greater than the predetermined threshold value with the speed sensor <NUM>, the determination section <NUM> of the controller <NUM> determines 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 sensor 72f.

The controller <NUM> includes 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 controller <NUM> reads 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 controller <NUM> via the network.

<FIG> is a block diagram showing the configuration of the controller <NUM>.

The controller <NUM> includes a determination section <NUM>, a brake instruction section <NUM>, and a notification instruction section <NUM>. The number of controllers <NUM> is not limited to one, and a plurality of controllers <NUM> may be provided, and the functions of the determination section <NUM>, the brake instruction section <NUM>, and the notification instruction section <NUM> may also be provided separately for the plurality of controllers.

The determination section <NUM> makes a determination regarding the control of the automatic brake. The determination section <NUM> includes an obstacle determination section <NUM> and a state determination section <NUM>.

The obstacle determination section <NUM> determines whether or not there is an obstacle when traveling backward. "Traveling backward" means that the tires are turning backwards. The obstacle determination section <NUM> detects that the vehicle body <NUM> is in the state of traveling backward, for example, by the front tire <NUM> or the rear tire <NUM> rotating backward, or by the FNR lever <NUM> being in the reverse position. The obstacle determination section <NUM> determines that an obstacle exists when receiving the obstacle detection information within a predetermined range from the rear detection section <NUM> of the detection system <NUM> in detecting the state of traveling backward.

The state determination section <NUM> determines whether or not the wheel loader <NUM> is in the states (first state) to (fourth state) illustrated in <FIG>, 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 section <NUM> controls automatic brake based on the determination result of the obstacle determination section <NUM> and the determination result of the state determination section <NUM>. The automatic brake in the present specification is to automatically activate a braking force to the vehicle body <NUM> based on the determination result of the obstacle determination section <NUM> and the determination result of the state determination section <NUM>, and as will be described later, it is not limited to the braking force of the service brake <NUM>.

When the obstacle determination section <NUM> determines that an obstacle exists, and the state determination section <NUM> determines that the state of the vehicle body <NUM> is a state in which it is not necessary to prevent falling down in a case of activating the preset braking force, the brake instruction section <NUM> stops the fuel supply to the engine <NUM> and drives the service brake <NUM> by operating the brake valve <NUM> to stop the vehicle body <NUM>.

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

In the automatic brake with the preset braking force, the vehicle body <NUM> may not be braked by the service brake <NUM> as described above, and the parking brake <NUM> may be operated. In this case, when the obstacle determination section <NUM> determines that the obstacle S exists, and the state determination section <NUM> determines that the state of the vehicle body <NUM> is a state in which it is not necessary to prevent falling down in a case of activating the preset braking force, the brake instruction section <NUM> stops the fuel supply to the engine <NUM>. Then, the brake instruction section <NUM> controls the parking brake <NUM> to brake the vehicle body <NUM>.

Further, when the obstacle determination section <NUM> determines that an obstacle exists, and the state determination section <NUM> determines that the state of the vehicle body <NUM> is a state in which it is not necessary to prevent falling down in a case of activating the weak braking force, the brake instruction section <NUM> stops the fuel supply to the engine <NUM>, sets the opening degree of the brake valve <NUM> to be small, and controls the service brake <NUM> so 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 valve <NUM>, but is also generated when the operator simply turns off the accelerator <NUM>. When the accelerator <NUM> is turned off, the fuel supply to the engine <NUM> is stopped, and the swash plates of the pump 32a and the motor 32b are controlled to serve as traveling resistance, so that the weak braking force is activated.

The brake instruction section <NUM> may activate the weak braking force by controlling like a case in which the operator turns off the accelerator <NUM>.

That is, when the obstacle determination section <NUM> determines that an obstacle exists, and the state determination section <NUM> determines that the state of the vehicle body <NUM> is a state in which it is not necessary to prevent falling down in a case of activating the weak braking force, the brake instruction section <NUM> stops the fuel supply to the engine <NUM>, for example, controls the swash plates of the pump 32a and the motor 32b so 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 lever <NUM> so as to be in the neutral position. Therefore, when the obstacle determination section <NUM> determines that an obstacle exists, and the state determination section <NUM> determines that the state of the vehicle body <NUM> is a state in which it is not necessary to prevent falling down in a case of activating the weak braking force, the brake instruction section <NUM> controls like a case in which the operator operates the FNR lever <NUM> so 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 pump 32a and the motor 32b are 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 section <NUM> determines that an obstacle exists, and the state determination section <NUM> determines that the state of the vehicle body <NUM> is a state in which it is necessary to prevent falling down in a case of activating the weak braking force, the controller <NUM> does not activate the automatic brake.

The notification instruction section <NUM> activates the alarm device <NUM> when the obstacle determination section <NUM> determines that the obstacle S exists.

Further, when the obstacle determination section <NUM> determines that an obstacle exists, and the state determination section <NUM> determines that the state of the vehicle body <NUM> is a state in which it is necessary to prevent falling down in a case of activating the preset braking force, the notification instruction section <NUM> turns on the function OFF notification lamp <NUM> indicating that the function for activating the preset braking force is turned off.

Further, when the return switch <NUM> is operated by the operator after the vehicle body <NUM> is stopped by the automatic brake and the automatic brake is released, the notification instruction section <NUM> turns on the automatic brake activation notification lamp <NUM> for notifying the operator of the release. Further, the notification instruction section <NUM> turns on the function OFF notification lamp <NUM> when the operator operates the automatic brake release switch <NUM> to turn off the function of activating the preset braking force.

Next, the control operation of the wheel loader <NUM> of the present embodiment will be described.

<FIG> is a flow chart showing a control operation regarding to obstacle detection of the wheel loader <NUM> of the present embodiment.

First, in step S10, the obstacle determination section <NUM> of the controller <NUM> determines whether or not an obstacle is detected when the vehicle body <NUM> moves backward. The obstacle determination section <NUM> detects that the vehicle body <NUM> is in the state of moving backward, for example, by the front tire <NUM> or the rear tire <NUM> rotating rearward, or the FNR lever <NUM> being in the reverse position. When the obstacle determination section <NUM> receives the detection information of an obstacle within a predetermined range from the rear detection section <NUM> of the detection system <NUM> in the state of detecting that the backward travel is being performed, the obstacle determination section <NUM> determines that an obstacle exists.

When it is not determined in step S10 that an obstacle exists, the controller <NUM> ends without activating the automatic brake in step S11.

When it is determined in step S10 that an obstacle is exists, in step S12, the state determination section <NUM> determines whether or not it is necessary to prevent falling down in a case of activating the weak braking force.

The state determination section <NUM> acquires the state of the vehicle body <NUM> from the boom angle sensor 72a, the pressure sensor 72b, the bell crank angle sensor 72d, the articulate angle sensor 72e, the vehicle body angle sensor 72f, and the speed sensor <NUM> of the state detection section <NUM>. And the state determination section <NUM> determines whether or not the state of the vehicle body <NUM> corresponds to the above-mentioned (first state) to (fourth state) requiring falling down prevention.

When it is determined in step S12 that the state of the vehicle body <NUM> is a state requiring falling down prevention in a case of activating the weak braking force, the controller <NUM> ends the control without activating the braking force in step S13.

When it is determined in step S12 that the state of the vehicle body <NUM> is a state in which it is not necessary to prevent falling down in the case of activating the weak braking force, the state determination section <NUM> determines whether or not the state of the vehicle body <NUM> is 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 body <NUM> stop before the obstacle S.

When it is determined in step S14 that the state of the vehicle body <NUM> is a state in which it is necessary to prevent falling down in the case of activating the preset braking force, the brake instruction section <NUM> of the controller <NUM> stops the fuel supply to the engine <NUM> and controls the service brake <NUM> so 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 engine <NUM> and controlling the swash plates of the pump 32a and the motor 32b to serve as traveling resistance.

When it is determined in step S14 that the state of the vehicle body <NUM> is a state in which it is not necessary to prevent falling down in the case of activating the preset braking force, the brake instruction section <NUM> of the controller <NUM> stops the fuel supply to the engine <NUM> by releasing the accelerator <NUM> and operates the service brake <NUM> with the preset braking force by operating the brake valve <NUM> in step S16 and the vehicle body <NUM> stops. In this way, the control ends. As described above, the parking brake <NUM> may be operated to generate the preset braking force.

As described above, it is possible to brake the vehicle body <NUM> by 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 S15 and then no obstacle is detected in step S10, the brake is not activated in step S11 and 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 loader <NUM> (an example of a work machine) of the embodiment includes the rear detection section <NUM>, the state detection section <NUM>, and the controller <NUM> (an example of a controller). The rear detection section <NUM> detects the rear of the vehicle body <NUM> when traveling backward. The state detection section <NUM> detects the state of the vehicle body <NUM>. The controller <NUM> brakes the vehicle body <NUM> based on the detection of the state detection section <NUM> and the detection of the rear detection section <NUM>.

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

In the wheel loader <NUM> (an example of a work machine) of the embodiment, the controller <NUM> (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 loader <NUM> (an example of a work machine) of the embodiment further includes the function OFF notification lamp <NUM> (an example of a first notification section). The function OFF notification lamp <NUM> notifies the suppression of automatic brake. The control of the automatic brake includes notification by the function OFF notification lamp <NUM>.

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

The wheel loader <NUM> (an example of a work machine) of the embodiment further includes an alarm device <NUM> (an example of a second notification section). The alarm device <NUM> notifies that the rear detection section <NUM> detects an obstacle S behind the vehicle body <NUM>.

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

In the wheel loader <NUM> (an example of a work machine) of the embodiment, the controller <NUM> (an example of a controller) suppresses the braking force of the automatic brake when detecting an obstacle S by the rear detection section <NUM> in traveling backward, and when determining that the state of the vehicle body <NUM> detected by the state detection section <NUM> is a state in which the vehicle body <NUM> becomes unstable in a case of activating the automatic brake with the preset braking force.

As a result, when the wheel loader <NUM> is in an unstable state, it is possible to suppress the braking force of the automatic brake. Further, when the vehicle body <NUM> is in a stable state, it is possible to brake and stop the vehicle body <NUM> without suppressing the automatic brake function.

The wheel loader <NUM> (an example of a work machine) of the embodiment further includes a service brake <NUM> (an example of a service brake) and a brake valve <NUM>. The brake valve <NUM> can adjust the supply amount of hydraulic fluid to the service brake <NUM>. The controller <NUM> drives the brake valve <NUM> and uses the service brake <NUM> to execute braking by automatic brake.

As a result, it is possible to stop the vehicle body <NUM> when the obstacle S is detected.

The wheel loader <NUM> (an example of a work machine) of the embodiment further includes a parking brake <NUM>. The controller <NUM> (an example of the controller) executes braking by the automatic brake with activating the parking brake <NUM>.

In the wheel loader <NUM> (an example of a work machine) of the embodiment, the vehicle body <NUM> includes the work implement <NUM>. The state of the vehicle body <NUM> includes the posture of work implement <NUM>.

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

In the wheel loader <NUM> (an example of a work machine) of the embodiment, the vehicle body <NUM> includes a work implement <NUM>. The state of the vehicle body <NUM> includes the state of the load on the work implement <NUM>.

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

In the wheel loader <NUM> (an example of a work machine) of the embodiment, the vehicle body <NUM> is the articulate type. The state of the vehicle body includes the articulate angle.

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

In the wheel loader <NUM> (an example of a work machine) of the embodiment, the state of the vehicle body <NUM> includes the inclination of the vehicle body <NUM>.

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

The method for controlling the wheel loader <NUM> (an example of a work machine) of the embodiment includes steps S10 (an example of a rear detection step), steps S12 and S14 (an example of a state detection step), and steps S11, S13, S15, and S16 (an example of a control step). Step S10 detects the rear of the vehicle body <NUM>. Steps S12 and S14 detect the state of the vehicle body <NUM>. Steps S11, S13, S15, and S16 control an automatic brake that automatically brakes the vehicle body <NUM> based on the detection result in step S10 and the detection result in steps S12 and S14.

For example, as illustrated in <FIG>, the weak braking force may not be activated.

In the control flow illustrated in <FIG>, first, in step S20, the obstacle determination section <NUM> of the controller <NUM> determines whether or not an obstacle is detected when the vehicle body <NUM> moves backward.

When it is not determined in step S20 that an obstacle exists, the controller <NUM> ends the control without activating the brake in step S21.

When it is determined in step S20 that an obstacle exists, in step S22, the state determination section <NUM> determines whether or not the state of the vehicle body <NUM> is a state requiring falling down prevention when the preset braking force is activated.

When it is determined in step S22 that the falling down prevention is necessary, the brake instruction section <NUM> of the controller <NUM> does not activate the brake in step S23, and the control ends.

Further, when it is determined in step S22 that the state of the vehicle body <NUM> is not a state requiring falling down prevention, in step S24, the brake instruction section <NUM> of the controller <NUM> operates the brake valve <NUM> to operate the service brake <NUM> with 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 HST <NUM> is used in the drive system <NUM>, but it is not limited to HST, and a torque converter may be used. <FIG> is a block diagram showing a configuration in which the torque converter <NUM> and the transmission <NUM> are provided in the drive system <NUM>. The driving force from the engine <NUM> is transmitted to the transmission <NUM> via the torque converter <NUM>. The transmission <NUM> shifts the rotational driving force of the engine <NUM> transmitted via the torque converter <NUM> and transmits it to the axle <NUM>. The transmission <NUM> is provided with a parking brake <NUM>.

In the case of the torque converter, in order to generate a weak braking force, the opening degree of the brake valve <NUM> may be set small in the same manner as described above. Further, although the braking force is weaker than that of the HST, the accelerator <NUM> may be simply turned off. When generating the preset braking force, the opening degree of the brake valve <NUM> may be increased or the parking brake <NUM> may 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 brake <NUM>, a parking brake <NUM>, and other means for changing the braking force can be appropriately applied.

In the above embodiment, the function OFF notification lamp <NUM> and the alarm device <NUM> are provided, but when the function OFF notification and the alarm notification can be distinguished, the function OFF notification lamp <NUM> may also serve as the alarm device <NUM>.

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.

Claim 1:
A work machine comprising:
a rear detection section (<NUM>) configured to detect rear of a vehicle body (<NUM>) when traveling backward;
a state detection section (<NUM>) configured to detect a state of the vehicle body (<NUM>); and
a controller (<NUM>) configured to brake the vehicle body (<NUM>) based on detection of the rear detection section (<NUM>) and detection of the state detection section (<NUM>),
wherein the vehicle body (<NUM>) is an articulate type, characterised in that
the state of the vehicle body (<NUM>) includes an articulate angle (Θ).