JP7533352B2 - Driving support device - Google Patents

Description

The present invention relates to a driving assistance device.

As a conventional driving support device, for example, the technology described in Patent Document 1 is known. The driving support device described in Patent Document 1 calculates a predicted course of a vehicle such as a forklift based on the steering angle and vehicle speed, and compares the predicted course with a predicted course captured by a camera to determine road conditions in the direction of vehicle travel. If there is an abnormality in the road conditions, it notifies the driver or the like of the abnormality in the road conditions with a warning light or warning sound.

JP 2016-143399 A

However, the above-mentioned conventional technology does not specifically detect slopes. When an industrial vehicle such as a forklift enters a slope, the vehicle's running may become unstable depending on its condition.

The object of the present invention is to provide a driving support device that can stabilize the driving of industrial vehicles on slopes.

One aspect of the present invention is a driving assistance device that provides driving assistance to an industrial vehicle having left and right wheels, the device comprising: a gradient detection unit that detects the gradient of a road on which the industrial vehicle is traveling; an angle calculation unit that calculates a roll angle and a pitch angle of the industrial vehicle based on the gradient of the road detected by the gradient detection unit; a slope entry determination unit that determines whether the industrial vehicle has entered a slope based on the roll angle and the pitch angle of the industrial vehicle calculated by the angle calculation unit; and a vehicle speed limiting processing unit that executes a process to limit the vehicle speed of the industrial vehicle when the slope entry determination unit determines that the industrial vehicle has entered a slope.

In such a driving assistance device, the gradient of the road on which the industrial vehicle is traveling is detected, and the roll angle and pitch angle of the industrial vehicle are calculated based on the gradient of the road. Then, based on the roll angle and pitch angle of the industrial vehicle, it is determined whether the industrial vehicle has entered a slope. Then, if it is determined that the industrial vehicle has entered a slope, a process is executed to limit the speed of the industrial vehicle. Therefore, when the industrial vehicle enters a slope, the speed of the industrial vehicle is limited. This stabilizes the driving of the industrial vehicle on a slope.

The driving support device may further include a warning unit that issues a warning that the industrial vehicle has entered a slope when the slope entry judgment unit determines that the industrial vehicle has entered a slope, and the vehicle speed limiting processing unit may execute a process to limit the vehicle speed of the industrial vehicle after the warning unit issues a warning that the industrial vehicle has entered a slope. In such a configuration, when the industrial vehicle enters a slope, a warning is issued to that effect, so that the driver of the industrial vehicle is urged to pay attention. Therefore, this is particularly effective when executing a process to limit the vehicle speed of the industrial vehicle through driving operations by the driver.

The slope entry determination unit may determine that the industrial vehicle has entered a slope when the amount of change in the roll angle or pitch angle is equal to or greater than a predetermined threshold. In this configuration, the simple process of comparing the amount of change in the roll angle and pitch angle of the industrial vehicle with the thresholds makes it easy to determine whether the industrial vehicle has entered a slope.

The driving support device may further include an unstable state avoidance processing unit that, after executing processing to limit the speed of the industrial vehicle by the vehicle speed limit processing unit, determines whether there is a gradient in the roll direction for the industrial vehicle, and executes processing to avoid a state in which the driving of the industrial vehicle becomes unstable depending on whether there is a gradient in the roll direction. In such a configuration, the driving of the industrial vehicle on a slope is stabilized regardless of whether there is a gradient in the roll direction for the industrial vehicle.

The industrial vehicle is a forklift equipped with liftable forks for holding cargo, and the unstable state avoidance processing unit may execute processing to lower the forks with the forklift stopped when the forklift is moving forward down a slope or when the forklift is moving backward up a slope when there is no gradient in the roll direction relative to the forklift. In this configuration, when the forklift is moving forward down a slope or when the forklift is moving backward up a slope, the forks are lowered with the forklift stopped. This increases the stability of the forklift, and thus stabilizes its movement on slopes.

The forklift may be equipped with a lift cylinder that raises and lowers the forks and a tilt cylinder that tilts the forks, and the unstable state avoidance processing unit may execute processing to drive the lift cylinder to lower the forks and drive the tilt cylinder to tilt the forks backwards while the forklift is stopped. In this configuration, when the forklift is moving forward down a slope or when the forklift is moving backward up a slope, the forks are lowered and tilted backwards while the forklift is stopped. This further increases the stability of the forklift, making the forklift's travel on slopes even more stable.

When there is a gradient in the roll direction for the industrial vehicle, the unstable state avoidance processing unit may execute a process to steer the industrial vehicle so that the industrial vehicle turns while traveling in a direction that brings the roll angle of the industrial vehicle closer to zero. In such a configuration, when the roll angle of the industrial vehicle becomes zero, the industrial vehicle travels straight up the slope, so that the industrial vehicle exits the slope while ensuring the stability of the industrial vehicle. This further stabilizes the travel of the industrial vehicle on the slope.

The industrial vehicle is a forklift equipped with liftable forks for holding cargo, and the unstable state avoidance processing unit may execute a process to lower the forks with the forklift stopped when the forklift is moving forward down a slope or when the forklift is moving backward up a slope, and then execute a process to steer the forklift so that the forklift turns while moving in a direction that brings the roll angle of the forklift closer to zero. In this configuration, when the forklift is moving forward down a slope or when the forklift is moving backward up a slope, the forks are lowered with the forklift stopped. This increases the stability of the forklift, and thus stabilizes its movement on slopes.

The driving support device further includes a load estimation unit that estimates the ground load of the left and right wheels, and the unstable state avoidance processing unit may execute a process to lower the forklift while stopping the forklift if the ground load of either the left or right wheels estimated by the load estimation unit is equal to or less than a predetermined value when the forklift is moving forward up a slope or moving backward down a slope, and then execute a process to steer the forklift so that the forklift turns while traveling in a direction that approaches zero. In this configuration, when the forklift is moving forward up a slope or moving backward down a slope, if the ground load of either the left or right wheels is low, the forklift stops traveling and lowers, thereby increasing the stability of the forklift. On the other hand, if the ground load of all the left and right wheels is high, the fork is not lowered, and the forklift immediately transitions to a turning operation.

The forklift is equipped with a lift cylinder that raises and lowers the forks and a tilt cylinder that tilts the forks, and the unstable state avoidance processing unit may execute a process of driving the lift cylinder to lower the forks and driving the tilt cylinder to tilt the forks backwards while the forklift is stopped, and then execute a process of steering the forklift so that it turns while traveling in a direction in which the roll angle of the forklift approaches zero. In this configuration, while the forklift is stopped, the forks are lowered and tilted backwards. This further increases the stability of the forklift, making the forklift's travel on slopes even more stable.

The driving assistance device may further include a center of gravity detection unit that detects the center of gravity of the forklift, and the load estimation unit may estimate the ground loads of the left and right wheels based on the gradient of the driving path detected by the gradient detection unit and the center of gravity of the forklift detected by the center of gravity detection unit. In this configuration, the center of gravity of the forklift is used to estimate the ground loads of the left and right wheels, so that the ground loads of the left and right wheels can be estimated with high accuracy.

The left and right wheels are driven to rotate independently by different drive sources, and the unstable state avoidance processing unit executes a process to steer the forklift so that it turns while traveling in a direction that brings the roll angle of the forklift closer to zero, and may also control the drive sources so that the torque of the left and right wheels on the side opposite the turning side is greater than the torque of the wheel on the turning side. In this configuration, even if the maximum steering angle of the forklift is small, the turning operation of the forklift due to steering is assisted by changing the torque of the left and right wheels, so that the roll angle of the forklift approaches zero sufficiently.

The present invention makes it possible to stabilize the operation of industrial vehicles on slopes.

1 is a side view showing a forklift, which is an industrial vehicle equipped with a travel assistance device according to an embodiment of the present invention. 1 is a block diagram illustrating a schematic configuration of a driving assistance device according to an embodiment of the present invention; FIG. 2 is a conceptual diagram showing a roll angle and a pitch angle of a forklift. FIG. 2 is a perspective view showing an example of a slope. 3 is a flowchart showing details of a procedure of a slope entry determination process executed by a slope entry determination unit shown in FIG. 2 . 3 is a flowchart showing a procedure of an unstable state avoidance process executed by an unstable state avoidance processing unit shown in FIG. 2 . 7 is a flowchart showing details of the procedure of the unstable state avoidance process for when there is no roll gradient shown in FIG. 6 . 1 is a conceptual diagram showing the relationship between the height position of the forks and the position of the center of gravity in the front-rear direction of the forklift truck. FIG. 7 is a flowchart showing details of the procedure of the unstable state avoidance process when a roll gradient is present, shown in FIG. 6 . FIG. 2 is a plan view showing a forklift truck moving forward from an upper flat road onto a slope and then descending the slope. FIG. 2 is a plan view showing a forklift truck reversing from a lower flat road onto a slope and climbing the slope. FIG. 2 is a plan view showing a forklift truck moving forward from a lower flat road onto a slope and climbing the slope. FIG. 2 is a plan view showing a forklift truck reversing from an upper flat road onto a slope and descending the slope. 1 is a table showing turning patterns of a forklift on a slope. FIG. 11 is a block diagram illustrating a schematic configuration of a driving assistance device according to another embodiment of the present invention. FIG. 2 is a conceptual diagram showing how the rear wheels of a forklift are steered. 16 is a flowchart showing details of a procedure of unstable state avoidance processing for when there is no roll gradient, which is executed by the unstable state avoidance processing unit shown in FIG. 15 . 16 is a flowchart showing details of a procedure of unstable state avoidance processing when a roll gradient is present, which is executed by the unstable state avoidance processing unit shown in FIG. 15 . 20 is a flowchart showing a modified example of the procedure of the unstable state avoidance process when a roll gradient is present, shown in FIG. 18 . FIG. 1 is a conceptual diagram showing how the torque of the left front wheel increases as the rear wheels of a forklift are steered.

Embodiments of the present invention will be described in detail below with reference to the drawings. In the drawings, identical or equivalent elements are given the same reference numerals, and duplicate descriptions will be omitted.

Figure 1 is a side view showing a forklift, which is an industrial vehicle equipped with a travel assistance device according to one embodiment of the present invention. In Figure 1, the forklift 1 according to this embodiment is a battery-powered forklift. The forklift 1 is equipped with a travel device 2 and a loading device 3 that is disposed in front of the travel device 2 and is used to lift and lower cargo W.

The traveling device 2 has a vehicle body 4, two front wheels 5 (left and right drive wheels) located at the front of the vehicle body 4, two rear wheels 6 (left and right steerable wheels) located at the rear of the vehicle body 4, two traveling motors 7 (see FIG. 2) that independently rotate and drive the left and right front wheels 5, a loading motor 9 that rotates and drives a hydraulic pump (not shown) of a hydraulic drive unit 8 (see FIG. 2) described later, and a battery 10 that supplies power to the traveling motors 7 and loading motors 9. The front wheels 5 and rear wheels 6 are the wheels of the forklift 1. The traveling motor 7 is the drive source for the front wheels 5.

The loading and unloading device 3 has a mast 11 erected at the front end of the vehicle body 4, a pair of left and right forks 13 that are attached to the mast 11 via lift brackets 12 and can be raised and lowered to hold cargo W, a lift cylinder 14 that raises and lowers the forks 13, and a tilt cylinder 15 that tilts the forks 13 via the mast 11. The lift cylinder 14 and tilt cylinder 15 are driven by a hydraulic drive unit 8 (see Figure 2).

Figure 2 is a block diagram showing the schematic configuration of a driving assistance device according to one embodiment of the present invention. In Figure 2, the driving assistance device 20 according to this embodiment is mounted on a forklift 1. The driving assistance device 20 provides driving assistance when the forklift 1 is driven manually by the driver.

The driving support device 20 includes a pressure sensor 21, a lift sensor 22, a tilt angle sensor 23, an inclination angle sensor 24, an acceleration sensor 25, an angular velocity sensor 26, a traveling direction sensor 27, an electronic control unit 30 (ECU: Electronic Control Unit), a warning device 28, a display device 29, the driving motor 7, and the hydraulic drive unit 8.

The pressure sensor 21 is a sensor that detects the pressure of the lift cylinder 14. The lift height sensor 22 is a sensor that detects the height position of the forks 13. The tilt angle sensor 23 is a sensor that detects the tilt angle of the mast 11. The tilt angle sensor 24 is a sensor that detects the tilt angle of the forklift 1. The acceleration sensor 25 is a sensor that detects the acceleration of the forklift 1. The angular velocity sensor 26 is a sensor that detects the angular velocity of the forklift 1. The traveling direction sensor 27 is a sensor that detects the traveling direction of the forklift 1.

The electronic control unit 30 is composed of a CPU, RAM, ROM, an input/output interface, etc. The electronic control unit 30 inputs the detection values of the pressure sensor 21, the lift sensor 22, the tilt angle sensor 23, the inclination angle sensor 24, the acceleration sensor 25, the angular velocity sensor 26, and the traveling direction sensor 27, executes predetermined processing, and controls the warning device 28, the display device 29, the traveling motor 7, and the hydraulic drive unit 8.

The warning device 28 generates a warning sound related to the driving support. The display device 29 displays a screen and a warning related to the driving support. The warning device 28 and the display device 29 may be configured as a single device.

Although not specifically shown, the hydraulic drive unit 8 has a hydraulic pump that supplies hydraulic oil to the lift cylinder 14 and the tilt cylinder 15, a lift valve arranged between the hydraulic pump and the lift cylinder 14, and a tilt valve arranged between the hydraulic pump and the tilt cylinder 15.

The electronic control unit 30 has a center of gravity detection unit 31, a gradient detection unit 32, an angle calculation unit 33, a slope entry determination unit 34, a warning processing unit 35, a vehicle speed limit processing unit 36, a ground load estimation unit 37, and an unstable state avoidance processing unit 38.

The center of gravity detection unit 31 detects the center of gravity of the forklift 1 based on the detection values of the pressure sensor 21, the lifting height sensor 22, and the tilt angle sensor 23, and data related to the dimensions, weight, etc. of each component part of the forklift 1. At this time, the center of gravity detection unit 31 detects the position of the center of gravity in the front-rear, left-right, and up-down directions of the forklift 1. Note that the center of gravity detection unit 31 may detect the center of gravity of the forklift 1 using sensors other than the pressure sensor 21, the lifting height sensor 22, and the tilt angle sensor 23.

The gradient detection unit 32 detects the gradient of the runway 40 (see FIG. 4) on which the forklift 1 is traveling based on the detection value of the inclination angle sensor 24. The gradient of the runway 40 is the degree of inclination of the runway 40 with respect to the horizontal plane. The gradient detection unit 32 may detect the gradient of the runway 40 based on the detection values of the acceleration sensor 25 and the angular velocity sensor 26, or may detect the gradient of the runway 40 using a sensor other than the inclination angle sensor 24, the acceleration sensor 25, and the angular velocity sensor.

The angle calculation unit 33 calculates the roll angle and pitch angle of the forklift 1 based on the gradient of the travel path 40 detected by the gradient detection unit 32. The roll angle of the forklift 1 is the rotation angle in the left-right direction of the forklift 1, as shown in FIG. 3(a). In other words, the roll angle of the forklift 1 is the rotation angle around an axis (X-axis) parallel to the front-rear direction of the forklift 1. The pitch angle of the forklift 1 is the rotation angle in the front-rear direction of the forklift 1, as shown in FIG. 3(b). In other words, the pitch angle of the forklift 1 is the rotation angle around an axis (Y-axis) parallel to the left-right direction of the forklift 1.

The slope entry determination unit 34 determines whether the forklift 1 has entered a slope 41 (see FIG. 4) based on the roll angle and pitch angle of the forklift 1 calculated by the angle calculation unit 33.

The patterns in which the forklift 1 enters the slope 41 include a pattern in which the forklift 1 enters the slope 41 from the upper flat road 42 by moving forward, a pattern in which the forklift 1 enters the slope 41 from the upper flat road 42 by moving backward, a pattern in which the forklift 1 enters the slope 41 from the lower flat road 43 by moving forward, and a pattern in which the forklift 1 enters the slope 41 from the lower flat road 43 by moving backward.

Figure 5 is a flowchart showing the details of the procedure for the slope entry judgment process executed by the slope entry judgment unit 34. In Figure 5, the slope entry judgment unit 34 first obtains data on the roll angle and pitch angle of the forklift 1 calculated by the angle calculation unit 33 (step S101).

Then, the slope entry determination unit 34 determines whether the amount of change in the roll angle or pitch angle is equal to or greater than a predetermined threshold (step S102). If the slope entry determination unit 34 determines that the amount of change in the roll angle or pitch angle is equal to or greater than the threshold, it determines that the forklift 1 has entered the slope 41 (step S103). If the slope entry determination unit 34 determines that neither the amount of change in the roll angle nor the pitch angle is equal to or greater than the threshold, it determines that the forklift 1 has not entered the slope 41 (step S104).

Returning to FIG. 2, when the slope entry determination unit 34 determines that the forklift 1 has entered the slope 41, the warning processing unit 35 controls the warning device 28 and the display device 29 to issue a warning that the forklift 1 has entered the slope 41. This allows the driver of the forklift 1 to know that the forklift 1 has entered the slope 41 through the warning device 28 and the display device 29.

At this time, the warning processing unit 35 controls the warning device 28 to generate a warning sound, and controls the display device 29 to display a warning and the roll angle and pitch angle on the screen. The warning processing unit 35 cooperates with the warning device 28 and the display device 29 to constitute a warning unit.

The speed limiting processor 36 executes processing to limit the speed of the forklift 1 after the warning processor 35 issues a warning that the forklift 1 has entered the slope 41. The speed limiting processor 36 controls the display 29 to display guidance to the driver to limit the speed of the forklift 1 together with audio guidance. This causes the driver to stop operating the accelerator and apply the brakes when he sees the screen display on the display 29.

The ground load estimation unit 37 estimates the ground loads of the left and right front wheels 5 and the left and right rear wheels 6 based on the center of gravity of the forklift 1 detected by the center of gravity detection unit 31, the gradient of the travel path 40 detected by the gradient detection unit 32, and the detection values of the acceleration sensor 25 and the angular velocity sensor 26.

After the unstable state avoidance processing unit 38 executes processing to limit the vehicle speed of the forklift 1 using the vehicle speed limit processing unit 36, it determines whether or not there is a gradient in the roll direction for the forklift 1 using the gradient detection unit 32, and executes processing to avoid a state in which the forklift 1 becomes unstable in its travel depending on the presence or absence of a gradient in the roll direction. At this time, the unstable state avoidance processing unit 38 controls the display 29 to display guidance together with audio guidance to avoid a state in which the forklift 1 becomes unstable in its travel. A state in which the forklift 1 becomes unstable in its travel is a state in which there is a possibility that the forklift 1 may tip over.

Figure 6 is a flowchart showing the steps of the unstable state avoidance process executed by the unstable state avoidance processing unit 38. In Figure 6, the unstable state avoidance processing unit 38 first obtains data on the roll angle and pitch angle of the forklift 1 calculated by the angle calculation unit 33 (step S111).

Then, the unstable state avoidance processing unit 38 judges whether or not there is no gradient in the roll direction for the forklift 1 based on the roll angle of the forklift 1 (step S112). Note that a state in which there is no gradient in the roll direction for the forklift 1 is a state in which the roll angle of the forklift 1 is equal to or less than a predetermined value close to 0 degrees.

When the unstable state avoidance processing unit 38 determines that there is no gradient in the roll direction for the forklift 1, it means that there is a gradient only in the pitch direction for the forklift 1, and executes unstable state avoidance processing for no roll gradient (step S113).

When the unstable state avoidance processing unit 38 determines that there is a gradient in the roll direction for the forklift 1, it means that there is a gradient in both the roll direction and the pitch direction for the forklift 1, and executes unstable state avoidance processing for when there is a roll gradient (step S114).

Figure 7 is a flowchart showing the details of the procedure for the unstable state avoidance process when there is no roll gradient. Below, using Figure 7, we will explain the procedure for the unstable state avoidance process when there is no roll gradient, and also explain the operation for avoiding an unstable state when there is no gradient in the roll direction for the forklift 1.

In FIG. 7, the unstable state avoidance processing unit 38 first determines whether the forklift 1 is moving forward and descending the slope 41, or whether the forklift 1 is moving backward and ascending the slope 41, based on the detection values of the acceleration sensor 25 and the travel direction sensor 27 (step S121).

When the forklift 1 is moving forward and descending the slope 41, and when the forklift 1 is moving backward and ascending the slope 41, as shown in FIG. 8, the higher the position of the forks 13, the further forward the center of gravity G of the forklift 1 is. In this case, if the center of gravity G of the forklift 1 is located forward of the front wheels 5, the forklift 1 becomes more likely to wobble, and the forklift 1 may become unstable when traveling. Furthermore, if the forks 13 are tilted forward in this state, the forklift 1 becomes even more likely to wobble.

When the unstable state avoidance processing unit 38 determines that the forklift 1 is moving forward down a slope or moving backward up a slope, it issues an operation instruction to temporarily stop the forklift 1 (step S122). Specifically, the unstable state avoidance processing unit 38 controls the display unit 29 to display a screen display for the driver to operate the brakes, for example. The driver then sees the screen display on the display unit 29 and applies the brakes. This causes the forklift 1 to stop.

Then, the unstable state avoidance processing unit 38 issues an operation instruction to lower the forks 13 and tilt the forks 13 backward (step S123). Specifically, the unstable state avoidance processing unit 38 controls the display 29 to display a screen that causes the driver to operate the lift operation lever (not shown) to lower and tilt the tilt operation lever (not shown) backward, for example. The driver then looks at the screen display on the display 29 and operates the lift operation lever to lower and tilt the tilt operation lever backward. As a result, the forks 13 reach the lowest position by the lift cylinder 14, and the forks 13 reach the rearward tilt position by the tilt cylinder 15.

Then, the unstable state avoidance processing unit 38 issues an operation instruction to resume the travel of the forklift 1 (step S124). Specifically, the unstable state avoidance processing unit 38 controls the display unit 29 to display a screen to prompt the driver to operate the accelerator, for example. The driver then sees the screen display on the display unit 29 and steps on the accelerator. As a result, if the forklift 1 enters the slope 41 in a forward motion, the forklift 1 moves forward again to go down the slope 41. If the forklift 1 enters the slope 41 in a reverse motion, the forklift 1 moves backward again to go up the slope 41.

When the unstable state avoidance processing unit 38 determines in step S121 that the forklift 1 is neither moving forward and descending the slope 41 nor moving backward and ascending the slope 41, it does not execute steps S122 to S124. As a result, when the forklift 1 is moving forward and ascending the slope 41 or when the forklift 1 is moving backward and descending the slope 41, no operation instruction is issued to lower the forks 13 and tilt the forks 13 backward, and the forklift 1 continues to travel up the slope 41.

Figure 9 is a flowchart showing the details of the procedure for the unstable state avoidance process when there is a roll gradient. Below, using Figure 9, we will explain the procedure for the unstable state avoidance process when there is a roll gradient, and also explain the operation for avoiding an unstable state when there is a gradient in the roll direction for the forklift 1.

In FIG. 9, the unstable state avoidance processing unit 38 first determines whether the forklift 1 is moving forward and descending the slope 41, or whether the forklift 1 is moving backward and ascending the slope 41, based on the detection values of the acceleration sensor 25 and the travel direction sensor 27 (step S131).

When the unstable state avoidance processing unit 38 determines that the forklift 1 is moving forward and descending the slope 41, or that the forklift 1 is moving backward and ascending the slope 41, it issues an operation instruction to temporarily stop the forklift 1, similar to step S122 above (step S132). As a result, the driver applies the brakes, and the forklift 1 stops.

Then, the unstable state avoidance processing unit 38 issues an operation instruction to lower the forks 13 and tilt the forks 13 backward, similar to step S123 above (step S133). As a result, the driver operates the lift operation lever and the tilt operation lever, and the forks 13 reach the lowest position and the backward tilt position.

Next, the unstable state avoidance processing unit 38 sets limit values (maximum values) for the vehicle speed and steering angle when the forklift 1 turns (step S134). The limit value for the vehicle speed is, for example, an extremely slow speed. The limit value for the steering angle is, for example, an angle that prevents a sharp turn.

Then, the unstable state avoidance processing unit 38 issues a steering command to turn the forklift 1 while traveling in a direction that brings the roll angle of the forklift 1 closer to zero according to the limit values of the vehicle speed and steering angle (step S135). Specifically, the unstable state avoidance processing unit 38 controls the display unit 29 to display, for example, the turning direction, the traveling direction, the steering angle, and the like on a screen. The driver then performs steering operation while looking at the screen display on the display unit 29. As a result, the forklift 1 turns while traveling at a slow speed.

As shown in FIG. 10, when the forklift 1 advances from the upper flat road 42 onto the slope 41 and then descends the slope 41, if the forklift 1 turns while moving forward, the forklift 1 is more likely to wobble than if the forklift 1 turns while moving backward.

Specifically, as shown in FIG. 10(a), when the right front wheel 5 is lower than the left front wheel 5 and the forklift 1 turns to the right while moving forward, the forklift 1 is more likely to wobble than when the forklift 1 turns while moving backward. As shown in FIG. 10(b), when the left front wheel 5 is lower than the right front wheel 5 and the forklift 1 turns to the left while moving forward, the forklift 1 is more likely to wobble than when the forklift 1 turns while moving backward.

Therefore, as shown in FIG. 10(a), when the right front wheel 5 is lower than the left front wheel 5, the unstable state avoidance processing unit 38 issues a steering command to make a left turn while the forklift 1 is moving backwards (see No. 1 in FIG. 14). As shown in FIG. 10(b), when the left front wheel 5 is lower than the right front wheel 5, the unstable state avoidance processing unit 38 issues a steering command to make a right turn while the forklift 1 is moving backwards (see No. 2 in FIG. 14).

In addition, as shown in FIG. 11, when the forklift 1 reverses from the lower flat road 43 onto the slope 41 and then ascends the slope 41, if the forklift 1 turns while reversing, the forklift 1 is more likely to wobble than if the forklift 1 turns while moving forward.

Specifically, as shown in FIG. 11(a), when the right rear wheel 6 is lower than the left rear wheel 6 and the forklift 1 turns left while moving backwards, the forklift 1 is more likely to wobble than when the forklift 1 turns forward. As shown in FIG. 11(b), when the left rear wheel 6 is lower than the right rear wheel 6 and the forklift 1 turns right while moving backwards, the forklift 1 is more likely to wobble than when the forklift 1 turns forward.

Therefore, as shown in FIG. 11(a), when the right rear wheel 6 is lower than the left rear wheel 6, the unstable state avoidance processing unit 38 issues a steering command to make a right turn while moving the forklift 1 forward (see No. 3 in FIG. 14). As shown in FIG. 11(b), when the left rear wheel 6 is lower than the right rear wheel 6, the unstable state avoidance processing unit 38 issues a steering command to make a left turn while moving the forklift 1 forward (see No. 4 in FIG. 14).

Returning to FIG. 9, after executing step S135, the unstable state avoidance processing unit 38 determines whether the roll angle of the forklift 1 is approximately 0 degrees (step S136). The unstable state avoidance processing unit 38 continues to execute step S135 until the roll angle of the forklift 1 becomes approximately 0 degrees. Note that a state in which the roll angle is approximately 0 degrees means a state in which the roll angle is equal to or less than a predetermined value close to 0 degrees, and also includes a state in which the roll angle is exactly 0 degrees.

When the unstable state avoidance processing unit 38 determines that the roll angle of the forklift 1 is approximately 0 degrees, it notifies the user that the steering angle of the forklift 1 is 0 degrees (step S137). Specifically, the unstable state avoidance processing unit 38 controls the display unit 29 to display on the screen that the steering angle of the forklift 1 is 0 degrees. The driver then looks at the screen display on the display unit 29 and operates the steering wheel to return to its original position.

Then, the unstable state avoidance processing unit 38 issues an operation instruction to make the forklift 1 travel straight ahead (step S138). Specifically, the unstable state avoidance processing unit 38 controls the display unit 29 to display a screen to make the driver operate the accelerator, for example. The driver then sees the screen display on the display unit 29 and steps on the accelerator. As a result, if the forklift 1 enters the slope 41 in a forward motion, the forklift 1 moves forward again to go down the slope 41. If the forklift 1 enters the slope 41 in a reverse motion, the forklift 1 moves backward again to go up the slope 41.

When the unstable state avoidance processing unit 38 determines in step S131 that the forklift 1 is neither moving forward down the slope 41 nor moving backward up the slope 41, it acquires data on the ground loads of the left and right front wheels 5 and the left and right rear wheels 6 estimated by the ground load estimation unit 37 (step S139).

Then, the unstable state avoidance processing unit 38 judges whether the ground contact load of either the left or right front wheels 5 or the left or right rear wheels 6 is equal to or less than a predetermined specified value (step S140). When the unstable state avoidance processing unit 38 judges that the ground contact load of either the left or right front wheels 5 or the left or right rear wheels 6 is equal to or less than the specified value, it issues an operation instruction to temporarily stop the forklift 1, similar to step S132 above (step S141). As a result, the driver applies the brakes, and the forklift 1 stops.

Then, the unstable state avoidance processing unit 38 issues an operation instruction to lower the forks 13 and tilt the forks 13 backward (step S142), similar to step S133 described above. As a result, the forks 13 reach the lowest position and the backward tilt position when the driver operates the lift operation lever and the tilt operation lever.

Next, the unstable state avoidance processing unit 38 sets limit values (maximum values) for the vehicle speed and steering angle when the forklift 1 turns, similar to step S134 above (step S143).

Then, the unstable state avoidance processing unit 38 issues a steering command to turn the forklift 1 while traveling in a direction that brings the roll angle of the forklift 1 closer to zero according to the limit values of the vehicle speed and steering angle (step S144). Specifically, the unstable state avoidance processing unit 38 controls the display unit 29 to display, for example, the turning direction, the traveling direction, the steering angle, and the like on a screen. The driver then performs steering operation while looking at the screen display on the display unit 29. As a result, the forklift 1 turns while traveling at a slow speed.

As shown in FIG. 12, when the forklift 1 advances from the lower flat road 43 onto the slope 41 and ascends the slope 41, if the forks 13 are lowered and tilted backward, the forklift 1 is less likely to wobble even if it turns while moving forward.

Therefore, as shown in FIG. 12(a), when the left front wheel 5 is lower than the right front wheel 5, the unstable state avoidance processing unit 38 issues a steering command to make a right turn while moving forward with the forklift 1 (see No. 5 in FIG. 14). As shown in FIG. 12(b), when the right front wheel 5 is lower than the left front wheel 5, the unstable state avoidance processing unit 38 issues a steering command to make a left turn while moving forward with the forklift 1 (see No. 6 in FIG. 14).

In addition, as shown in FIG. 13, when the forklift 1 reverses from the upper flat road 42 onto the slope 41 and descends the slope 41, if the forks 13 are lowered and tilted backward, the forklift 1 is less likely to wobble even if it turns while reversing.

Then, as shown in FIG. 13(a), when the left rear wheel 6 is lower than the right rear wheel 6, the unstable state avoidance processing unit 38 issues a steering command to make a left turn while the forklift 1 is moving backwards (see No. 7 in FIG. 14). As shown in FIG. 13(b), when the right rear wheel 6 is lower than the left rear wheel 6, the unstable state avoidance processing unit 38 issues a steering command to make a right turn while the forklift 1 is moving backwards (see No. 8 in FIG. 14).

Returning to FIG. 9, after executing step S144, the unstable state avoidance processing unit 38 determines whether the roll angle of the forklift 1 is approximately 0 degrees (step S145). The unstable state avoidance processing unit 38 continues to execute step S144 until the roll angle of the forklift 1 becomes approximately 0 degrees.

When the unstable state avoidance processing unit 38 determines that the roll angle of the forklift 1 is approximately 0 degrees, it notifies the driver that the steering angle of the forklift 1 is 0 degrees (step S146), similar to step S137 above. The driver then looks at the screen display on the display 29 and operates the steering wheel to return to its original position.

Then, the unstable state avoidance processing unit 38 issues an operation instruction to make the forklift 1 travel straight ahead, similar to step S138 above (step S147). The driver then looks at the screen display on the display 29 and depresses the accelerator. As a result, when the forklift 1 enters the slope 41 in a forward direction, the forklift 1 moves forward again to climb the slope 41. When the forklift 1 enters the slope 41 in a reverse direction, the forklift 1 moves backward again to descend the slope 41.

When the unstable state avoidance processing unit 38 determines in step S140 that the ground contact loads of the left and right front wheels 5 and the left and right rear wheels 6 are all higher than the specified value, it does not execute steps S141 and S142, but executes steps S143 to S147. As a result, when the forklift 1 enters the slope 41 in a forward motion, the forklift 1 ascends the slope 41 without stopping. When the forklift 1 enters the slope 41 in a reverse motion, the forklift 1 descends the slope 41 without stopping.

As described above, in this embodiment, the gradient of the road 40 on which the forklift 1 is traveling is detected, and the roll angle and pitch angle of the forklift 1 are calculated based on the gradient of the road 40. Then, based on the roll angle and pitch angle of the forklift 1, it is determined whether the forklift 1 has entered the slope 41. Then, when it is determined that the forklift 1 has entered the slope 41, a process is executed to limit the vehicle speed of the forklift 1. Therefore, when the forklift 1 enters the slope 41, the vehicle speed of the forklift 1 is limited. This stabilizes the travel of the forklift 1 on the slope 41.

In addition, in this embodiment, when the forklift 1 enters the slope 41, a warning to that effect is issued, so that the driver of the forklift 1 is urged to pay attention. Therefore, the process of limiting the vehicle speed of the forklift 1 is effectively executed by the driver's driving operation.

In addition, in this embodiment, when the amount of change in the roll angle or pitch angle of the forklift 1 is equal to or greater than a threshold, it is determined that the forklift 1 has entered the slope 41. In this way, the simple process of comparing the amount of change in the roll angle or pitch angle with the threshold makes it easy to determine whether the forklift 1 has entered the slope 41.

In addition, in this embodiment, it is determined whether there is a gradient in the roll direction for the forklift 1, and depending on the presence or absence of a gradient in the roll direction, a process is executed to avoid a state in which the travel of the forklift 1 becomes unstable. Therefore, regardless of the presence or absence of a gradient in the roll direction for the forklift 1, the travel of the forklift 1 on the slope 41 is stabilized.

In addition, in this embodiment, when there is no gradient in the roll direction for the forklift 1, when the forklift 1 moves forward down the slope 41 or when the forklift 1 moves backward up the slope 41, the forks 13 are lowered while the forklift 1 is stopped. This increases the stability of the forklift 1, and further stabilizes the forklift 1's travel on the slope 41.

In addition, in this embodiment, when there is no gradient in the roll direction for the forklift 1, when the forklift 1 moves forward down the slope 41 or when the forklift 1 moves backward up the slope 41, the forks 13 move downward and tilt backward while the forklift 1 is stopped. This further increases the stability of the forklift 1, making the forklift 1's travel on the slope 41 even more stable.

In addition, in this embodiment, when there is a gradient in the roll direction for the forklift 1, a process is executed to steer the forklift 1 so that the forklift 1 turns while traveling in a direction in which the roll angle of the forklift 1 approaches zero. Therefore, when the roll angle of the forklift 1 becomes zero, the forklift 1 travels straight up the slope 41, and the forklift 1 exits the slope 41 while ensuring the stability of the forklift 1. This further stabilizes the travel of the forklift 1 on the slope 41.

In addition, in this embodiment, when there is a gradient in the roll direction of the forklift 1, when the forklift 1 moves forward down the slope 41 or when the forklift 1 moves backward up the slope 41, the forks 13 are lowered while the forklift 1 is stopped. This increases the stability of the forklift 1, making the forklift 1's travel on the slope 41 even more stable.

In addition, in this embodiment, when there is a gradient in the roll direction with respect to the forklift 1, and the forklift 1 is moving forward up the slope 41 or moving backward down the slope 41, if the ground load of any of the left and right front wheels 5 and the left and right rear wheels 6 is low, the forklift 1 stops traveling and the forks 13 lower, increasing the stability of the forklift 1. On the other hand, if the ground loads of all of the left and right front wheels 5 and the left and right rear wheels 6 are high, the fork 13 is not lowered, and the forklift 1 immediately transitions to a turning operation.

In addition, in this embodiment, when the forklift 1 is moving forward up the slope 41 or when the forklift 1 is moving backward down the slope 41, if the ground contact load of either the left or right front wheels 5 or the left or right rear wheels 6 is low, the forks 13 are lowered and tilted backwards while the forklift 1 is stopped. This further increases the stability of the forklift 1, making the forklift 1's travel on the slope 41 even more stable.

In addition, in this embodiment, the center of gravity of the forklift 1 is used to estimate the ground loads of the left and right front wheels 5 and the left and right rear wheels 6, so that the ground loads of the left and right front wheels 5 and the left and right rear wheels 6 can be estimated with high accuracy.

Figure 15 is a block diagram showing the schematic configuration of a driving support device according to another embodiment of the present invention. In Figure 15, the driving support device 20A of this embodiment provides driving support when driving a forklift 1 by automatic driving. In addition to the configuration of the driving support device 20 in the above embodiment, the driving support device 20A includes a steering motor 50. As shown in Figure 16, the steering motor 50 is a motor that steers the left and right rear wheels 6.

The electronic control unit 30 of the driving support device 20A has an unstable state avoidance processing unit 38A instead of the unstable state avoidance processing unit 38 in the above embodiment. The unstable state avoidance processing unit 38A controls the driving motor 7, the hydraulic drive unit 8, and the steering motor 50 to execute processing to avoid a state in which the driving of the forklift 1 becomes unstable.

Figure 17 is a flowchart showing details of the procedure for the unstable state avoidance process when there is no roll gradient executed by the unstable state avoidance processing unit 38A, and corresponds to Figure 7. Below, using Figure 17, the procedure for the unstable state avoidance process when there is no roll gradient will be explained, while also explaining the operation for avoiding an unstable state when there is no gradient in the roll direction for the forklift 1.

In FIG. 17, when the unstable state avoidance processing unit 38A determines in step S121 that the forklift 1 is moving forward and descending the slope 41, or that the forklift 1 is moving backward and ascending the slope 41, it controls the travel motor 7 to temporarily stop the forklift 1 (step S122A). This causes the forklift 1 to automatically stop.

Then, the unstable state avoidance processing unit 38A controls the lift valve (not shown) of the hydraulic drive unit 8 to lower the fork 13, and controls the tilt valve (not shown) of the hydraulic drive unit 8 to tilt the fork 13 backward (step S123A). As a result, the lift cylinder 14 and tilt cylinder 15 are automatically driven, and the fork 13 reaches the lowest position and the backward tilt position.

Then, the unstable state avoidance processing unit 38A controls the travel motor 7 to resume travel of the forklift 1 (step S124A). As a result, when the forklift 1 enters the slope 41 in a forward direction, the forklift 1 automatically moves forward again to descend the slope 41. When the forklift 1 enters the slope 41 in a reverse direction, the forklift 1 automatically moves backward again to ascend the slope 41.

When the unstable state avoidance processing unit 38A determines in step S121 that the forklift 1 is neither moving forward down the slope 41 nor moving backward up the slope 41, the unstable state avoidance processing unit 38A does not execute steps S122A to S124A described above.

Figure 18 is a flowchart showing details of the unstable state avoidance process when there is a roll gradient executed by the unstable state avoidance processing unit 38A, and corresponds to Figure 9. Below, the procedure of the unstable state avoidance process when there is a roll gradient will be explained using Figure 18, and the operation of avoiding an unstable state when there is a gradient in the roll direction for the forklift 1 will be explained.

In FIG. 18, when the unstable state avoidance processing unit 38A determines in step S131 that the forklift 1 is moving forward and descending the slope 41, or that the forklift 1 is moving backward and ascending the slope 41, it controls the travel motor 7 to temporarily stop the forklift 1, similar to step S122A described above (step S132A). This causes the forklift 1 to automatically stop.

Then, the unstable state avoidance processing unit 38A controls the lift valve of the hydraulic drive unit 8 to lower the fork 13, as in step S123A above, and controls the tilt valve of the hydraulic drive unit 8 to tilt the fork 13 backward (step S133A). As a result, the fork 13 automatically reaches the lowest position and the backward tilt position.

Then, the unstable state avoidance processing unit 38A controls the travel motor 7 and the steering motor 50 so that the forklift 1 turns while traveling in a direction in which the roll angle of the forklift 1 approaches zero, according to the vehicle speed and steering angle limit values set in step S134 (step S135A).

As shown in FIG. 10(a), when the forklift 1 is moving forward and descending the slope 41, if the right front wheel 5 is lower than the left front wheel 5, the unstable state avoidance processing unit 38A controls the travel motor 7 and steering motor 50 so that the forklift 1 turns left while moving backwards (see No. 1 in FIG. 14). As shown in FIG. 10(b), when the forklift 1 is moving forward and descending the slope 41, if the left front wheel 5 is lower than the right front wheel 5, the unstable state avoidance processing unit 38A controls the travel motor 7 and steering motor 50 so that the forklift 1 turns right while moving backwards (see No. 2 in FIG. 14).

As shown in FIG. 11(a), when the forklift 1 is going up a slope 41 in reverse and the right rear wheel 6 is lower than the left rear wheel 6, the unstable state avoidance processing unit 38A controls the travel motor 7 and steering motor 50 so that the forklift 1 turns right while moving forward (see No. 3 in FIG. 14). As shown in FIG. 11(b), when the forklift 1 is going up a slope 41 in reverse and the left rear wheel 6 is lower than the right rear wheel 6, the unstable state avoidance processing unit 38A controls the travel motor 7 and steering motor 50 so that the forklift 1 turns left while moving forward (see No. 4 in FIG. 14).

After executing step S135A, if the unstable state avoidance processing unit 38A determines in step S136 that the roll angle of the forklift 1 is approximately 0 degrees, it controls the travel motor 7 to make the forklift 1 travel straight (step S138A). As a result, if the forklift 1 enters the slope 41 in a forward motion, the forklift 1 automatically travels forward again to go down the slope 41. If the forklift 1 enters the slope 41 in a reverse motion, the forklift 1 automatically travels backward again to go up the slope 41.

When the unstable state avoidance processing unit 38A determines in step S131 that the forklift 1 is neither moving forward down the slope 41 nor moving backward up the slope 41, it executes steps S139 and S140 described above. When the unstable state avoidance processing unit 38A determines that the ground contact load of either the left or right front wheels 5 or the left or right rear wheels 6 is equal to or less than a specified value, it controls the travel motor 7 to temporarily stop the forklift 1, as in step S132A described above (step S141A). This causes the forklift 1 to automatically stop.

Then, the unstable state avoidance processing unit 38A controls the lift valve of the hydraulic drive unit 8 so that the fork 13 descends, as in step S133A above, and controls the tilt valve of the hydraulic drive unit 8 so that the fork 13 tilts backward (step S142A). As a result, the fork 13 automatically reaches the lowest position and the backward tilt position.

Then, the unstable state avoidance processing unit 38A controls the travel motor 7 and the steering motor 50 so that the forklift 1 turns while traveling in a direction in which the roll angle of the forklift 1 approaches zero, according to the vehicle speed and steering angle limit values set in step S143 (step S144A).

As shown in FIG. 12(a), when the forklift 1 is moving forward and climbing a slope 41, if the left front wheel 5 is lower than the right front wheel 5, the unstable state avoidance processing unit 38A controls the travel motor 7 and steering motor 50 so that the forklift 1 turns right while moving forward (see No. 5 in FIG. 14). As shown in FIG. 12(b), when the forklift 1 is moving forward and climbing a slope 41, if the right front wheel 5 is lower than the left front wheel 5, the unstable state avoidance processing unit 38A controls the travel motor 7 and steering motor 50 so that the forklift 1 turns left while moving forward (see No. 6 in FIG. 14).

As shown in FIG. 13(a), when the forklift 1 is going down a slope 41 in reverse and the left rear wheel 6 is lower than the right rear wheel 6, the unstable state avoidance processing unit 38A controls the travel motor 7 and steering motor 50 so that the forklift 1 turns left while going backward (see No. 7 in FIG. 14). As shown in FIG. 13(b), when the forklift 1 is going down a slope 41 in reverse and the right rear wheel 6 is lower than the left rear wheel 6, the unstable state avoidance processing unit 38A controls the travel motor 7 and steering motor 50 so that the forklift 1 turns right while going backward (see No. 8 in FIG. 14).

After executing step S144A, if the unstable state avoidance processing unit 38A determines in step S145 that the roll angle of the forklift 1 is approximately 0 degrees, it controls the travel motor 7 to make the forklift 1 travel straight (step S147A). As a result, if the forklift 1 enters the slope 41 in a forward motion, the forklift 1 automatically travels forward again to climb the slope 41. If the forklift 1 enters the slope 41 in a reverse motion, the forklift 1 automatically travels backward again to descend the slope 41.

When the unstable state avoidance processing unit 38A determines in step S140 that the ground contact loads of the left and right front wheels 5 and the left and right rear wheels 6 are all higher than the specified value, it executes the above steps S143 to 147A without executing the above steps S141A and 142A.

In this embodiment, when the forklift 1 enters the slope 41, a process to limit the vehicle speed of the forklift 1 is automatically performed. This reduces the burden on the driver of the driving operation and stabilizes the travel of the forklift 1 on the slope 41.

Figure 19 is a flow chart showing a modified example of the procedure of the unstable state avoidance process when there is a roll gradient, which is executed by the unstable state avoidance processing unit 38A shown in Figure 18. In Figure 19, the unstable state avoidance processing unit 38A controls the travel motor 7 and the steering motor 50 so that the forklift 1 turns while traveling in a direction in which the roll angle of the forklift 1 approaches zero, according to the vehicle speed and steering angle limit values set in step S134, and also controls the travel motor 7 so that the torque of the front wheel 5 on the opposite side to the turning side is greater than the torque of the front wheel 5 on the turning side (step S151).

At this time, the unstable state avoidance processing unit 38A controls the rotation direction of the travel motor 7 according to the traveling direction of the forklift 1, and controls the rotation speed (torque) of the travel motor 7 and the rotation direction of the steering motor 50 according to the turning direction of the forklift 1.

Specifically, when turning the forklift 1 to the right, the unstable state avoidance processing unit 38A controls the rotation direction of the steering motor 50 to steer the left and right rear wheels 6 to the right as shown in FIG. 20, and controls the rotation speed of the traveling motor 7 so that the torque of the left front wheel 5 is greater than the torque of the right front wheel 5. When turning the forklift 1 to the left, the unstable state avoidance processing unit 38A controls the rotation direction of the steering motor 50 to steer the left and right rear wheels 6 to the left, and controls the rotation speed of the traveling motor 7 so that the torque of the right front wheel 5 is greater than the torque of the left front wheel 5.

The unstable state avoidance processing unit 38A also controls the travel motor 7 and steering motor 50 so that the forklift 1 turns while traveling in a direction in which the roll angle of the forklift 1 approaches zero according to the vehicle speed and steering angle limit values set in step S143, and controls the travel motor 7 so that the torque of the front wheel 5 on the opposite side to the turning side is greater than the torque of the front wheel 5 on the turning side (step S152). The method of controlling the travel motor 7 and steering motor 50 is the same as in step S151 above.

In this modified example, even if the steering angle limit value (maximum value) of the forklift 1 is small, the turning operation of the forklift 1 caused by steering is assisted by changing the torque of the left and right front wheels 5, so that the roll angle of the forklift 1 approaches zero sufficiently.

The present invention is not limited to the above embodiment. For example, in the above embodiment, when the forklift 1 advances on the slope 41 and descends the slope 41, the forklift 1 turns while moving backward, and then the forklift 1 advances to exit the slope 41, and when the forklift 1 advances on the slope 41 and ascends the slope 41, the forklift 1 turns while moving forward, and then the forklift 1 advances to exit the slope 41, but the present invention is not limited to such a form. When the forklift 1 advances on the slope 41 and descends the slope 41, the forklift 1 turns while moving backward, and then the forklift 1 advances to exit the slope 41, and when the forklift 1 advances on the slope 41 and ascends the slope 41, the forklift 1 turns while moving forward, and then the forklift 1 advances to exit the slope 41.

In the above embodiment, when the forklift 1 is moving forward and descending the slope 41, the forklift 1 is turned while moving backward, and when the forklift 1 is moving backward and ascending the slope 41, the forklift 1 is turned while moving forward, but this is not limited to the above embodiment. For example, if the ground loads of the left and right front wheels 5 and the left and right rear wheels 6 are all higher than a predetermined specified value, the forklift 1 may be turned while moving forward even when the forklift 1 is moving forward and descending the slope 41, and may be turned while moving backward even when the forklift 1 is moving backward and ascending the slope 41.

In the above embodiment, it is determined that the forklift 1 has entered the slope 41 when the change in the roll angle or pitch angle of the forklift 1 is equal to or greater than a threshold value. However, this is not a particular form of determination, and it may be possible to determine whether the forklift 1 has entered the slope 41 using, for example, the inclination angle sensor 24 and the acceleration sensor 25, etc.

In addition, in the above embodiment, driving assistance is provided when the forklift 1 is driven manually by the driver, or when the forklift 1 is driven automatically, but the present invention is not limited to this form, and some of the driving assistance processing may be performed by the driver's manual driving, and other driving assistance processing may be performed by automatic driving.

In addition, the above embodiment is applied to a battery-powered forklift 1 in which the front wheels 5, which are the drive wheels, are rotated by a travel motor 7, but the present invention can also be applied to an engine-powered forklift in which the drive wheels are rotated by an engine.

In addition, the above embodiment is applied to a forklift 1 equipped with forks 13 that hold cargo W, but the present invention can also be applied to other industrial vehicles, such as crane trucks, whose running conditions can become unstable when entering a slope.

1...Forklift (industrial vehicle), 5...Front wheels (wheels), 6...Rear wheels (wheels), 7...Travel motor (drive source), 13...Fork, 14...Lift cylinder, 15...Tilt cylinder, 20, 20A...Travel support device, 28...Warning device (warning section), 29...Display (warning section), 31...Center of gravity detection section, 32...Gradient detection section, 33...Angle calculation section, 34...Slope entry determination section, 35...Warning processing section (warning section), 36...Vehicle speed limit processing section, 37...Track load estimation section, 38, 38A...Unstable state avoidance processing section, 40...Travel path, 41...Slope.

Claims (11)

A driving assistance device that assists driving of an industrial vehicle having left and right wheels,
A gradient detection unit that detects a gradient of a road on which the industrial vehicle is traveling;
an angle calculation unit that calculates a roll angle and a pitch angle of the industrial vehicle based on the gradient of the travel path detected by the gradient detection unit;
a slope entry determination unit that determines whether the industrial vehicle has entered a slope based on the roll angle and the pitch angle of the industrial vehicle calculated by the angle calculation unit;
a vehicle speed limiting processing unit that executes a process of limiting a vehicle speed of the industrial vehicle when the slope entry determination unit determines that the industrial vehicle has entered a slope ;
a driving assistance device comprising: an unstable state avoidance processing unit that, after the vehicle speed limiting processing unit has executed a process to limit the speed of the industrial vehicle, determines whether or not there is a gradient in a roll direction for the industrial vehicle, and executes a process to avoid a state in which the driving of the industrial vehicle becomes unstable depending on whether or not there is a gradient in the roll direction . a warning unit that issues a warning that the industrial vehicle has entered a slope when the slope entry determination unit determines that the industrial vehicle has entered a slope,
2. The driving support device according to claim 1, wherein the vehicle speed restriction processing unit executes processing for restricting the vehicle speed of the industrial vehicle after the warning unit issues a warning that the industrial vehicle has entered a slope. The driving support device according to claim 1 or 2, wherein the slope entry determination unit determines that the industrial vehicle has entered a slope when the amount of change in the roll angle or the pitch angle is equal to or greater than a predetermined threshold value. The industrial vehicle is a forklift equipped with liftable forks for holding loads,
4. The driving support device according to claim 1, wherein the unstable state avoidance processing unit executes a process to lower the forks while the forklift is stopped when the forklift is moving forward down a slope or when the forklift is moving backward up a slope when there is no gradient in a roll direction with respect to the forklift. The forklift includes a lift cylinder for raising and lowering the forks and a tilt cylinder for tilting the forks,
5. The travel support device according to claim 4, wherein the unstable state avoidance processing unit executes processing for driving the lift cylinder to lower the forks and driving the tilt cylinder to tilt the forks backward while the forklift is stopped. The driving support device according to any one of claims 1 to 3, wherein the unstable state avoidance processing unit executes a process for steering the industrial vehicle so that the industrial vehicle turns while traveling in a direction in which the roll angle of the industrial vehicle approaches zero when there is a gradient in the roll direction for the industrial vehicle. The industrial vehicle is a forklift equipped with liftable forks for holding loads,
7. The driving support device according to claim 6, wherein the unstable state avoidance processing unit executes a process for lowering the forks while stopping the forklift when the forklift is moving forward down a slope or when the forklift is moving backward up a slope, and then executes a process for steering the forklift so that it turns while traveling in a direction that approaches zero with a roll angle of the forklift. A load estimating unit is further provided for estimating ground loads of the left and right wheels,
8. A driving assistance device according to claim 7, wherein the unstable state avoidance processing unit executes a process to lower the forks while the forklift is stopped if the ground contact load of either the left or right wheel estimated by the load estimating unit is equal to or smaller than a predetermined specified value when the forklift is moving forward up a slope or when the forklift is moving backward down a slope, and then executes a process to steer the forklift so that the forklift turns while traveling in a direction such that a roll angle of the forklift approaches zero . The forklift includes a lift cylinder for raising and lowering the forks and a tilt cylinder for tilting the forks,
9. A driving support device according to claim 7 or 8, wherein the unstable state avoidance processing unit, while the forklift is stopped, executes a process of driving the lift cylinder to lower the forks and driving the tilt cylinder to tilt the forks backward, and then executes a process of steering the forklift so that it turns while traveling in a direction in which a roll angle of the forklift approaches zero . A center of gravity detection unit that detects the center of gravity of the forklift is further provided.
9. The driving support device according to claim 8, wherein the load estimation unit estimates ground contact loads of the left and right wheels based on a gradient of the driving path detected by the gradient detection unit and a center of gravity of the forklift detected by the center of gravity detection unit. The left and right wheels are independently rotated by two drive sources,
The unstable state avoidance processing unit executes a process for steering the industrial vehicle so that the industrial vehicle turns while traveling in a direction in which the roll angle of the industrial vehicle approaches zero, and controls the drive source so that the torque of the wheel on the opposite side to the turning side of the left and right wheels is greater than the torque of the wheel on the turning side.

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