JP7844792B2 - Asphalt finisher - Google Patents

Description

This disclosure relates to an asphalt finisher.

Conventionally, an asphalt finisher is known that comprises a tractor, a hopper installed at the front of the tractor to receive paving material, a conveyor that feeds the paving material from the hopper to the rear of the tractor, a screw that spreads the paving material fed by the conveyor at the rear of the tractor, and a screed that levels the paving material spread by the screw at the rear of the screw (see Patent Document 1).

Asphalt finishers are typically configured to move forward with the center of the road being worked on aligned with the center of the screed.

Japanese Patent Publication No. 2017-160636

However, if the road being paved is curved, the asphalt paver may degrade the quality of the pavement. This is because, when the asphalt paver moves forward with the center of the curved road aligned with the center of the screed, a difference arises between the surface area of the road leveled per unit time by the left rear screed and the surface area leveled per unit time by the right rear screed. Furthermore, a difference also arises between the amount of paving material handled by the left rear screed (left-hand load) and the amount of paving material handled by the right rear screed (right-hand load).

Therefore, there is a need to provide an asphalt finisher that can improve the quality of paving on curved roads.

An asphalt finisher according to an embodiment of the present invention comprises a tractor, a hopper installed on the front side of the tractor for receiving paving material, a conveyor for supplying the paving material received in the hopper to the rear side of the tractor, a screw for spreading the paving material supplied by the conveyor at the rear side of the tractor, a screed for leveling the paving material spread by the screw at the rear side of the screw, and a control device, wherein the control device is configured to generate a target trajectory based on a line that bisects the area of the road surface of the curved portion of the road to be constructed, which is leveled by the screed, and to control the movement of the tractor so that a predetermined point of the asphalt finisher follows the target trajectory.

The aforementioned asphalt finisher can improve the quality of paving on curved roads.

This is a side view of an asphalt finisher according to an embodiment of the present invention. Figure 1 is a top view of the asphalt finisher. This is a diagram showing an example configuration of an automatic steering system. This is a top view of the construction site. This is a top view of the construction site. This is a top view of the construction site. This is a top view of the construction site.

Figure 1 is a side view of an asphalt finisher 100 according to an embodiment of the present invention. Figure 2 is a top view of the asphalt finisher 100. In the illustrated example, the asphalt finisher 100 is a wheeled asphalt finisher and mainly consists of a tractor 1, a hopper 2, and a screed 3. Hereinafter, the direction of the hopper 2 as seen from the tractor 1 (+X direction) is considered the front, and the direction of the screed 3 as seen from the tractor 1 (-X direction) is considered the rear.

The tractor 1 is a mechanism for moving the asphalt finisher 100. In the illustrated example, the tractor 1 moves the asphalt finisher 100 by rotating the rear wheels 5 using a rear-wheel hydraulic motor and rotating the front wheels 6 using a front-wheel hydraulic motor. The rear-wheel and front-wheel hydraulic motors rotate by receiving hydraulic fluid from a hydraulic pump. However, the front wheels 6 may also be driven wheels.

The asphalt finisher 100 may also be a crawler-type asphalt finisher. In this case, the combination of rear wheels 5 and front wheels 6 is replaced by a combination of left crawler and right crawler.

The controller 50 is a control device that controls the asphalt paver 100. In the illustrated example, the controller 50 consists of a microcomputer including a CPU, a volatile memory device, and a non-volatile memory device, and is mounted on the tractor 1. Each function of the controller 50 is realized by the CPU executing a program stored in the non-volatile memory device. However, each function of the controller 50 may be realized not only by software, but also by hardware, or by a combination of hardware and software.

The hopper 2 is a mechanism for receiving paving material. In the illustrated example, the hopper 2 is installed at the front of the tractor 1 and is configured to open and close in the vehicle width direction (Y-axis direction) by a hopper cylinder. The asphalt finisher 100 usually receives paving material (e.g., asphalt mixture) from the bed of a dump truck when the hopper 2 is fully open. A dump truck is an example of a transport vehicle that carries paving material. Figures 1 and 2 show the hopper 2 in the fully open position. When the amount of paving material in the hopper 2 decreases, the hopper 2 is closed, and the paving material that was near the inner wall of the hopper 2 is collected in the center of the hopper 2. This is so that the conveyor CV in the center of the hopper 2 can feed the paving material to the rear of the tractor 1. The paving material fed to the rear of the tractor 1 is spread in the vehicle width direction at the rear of the tractor 1 and in front of the screed 3 by the screw SC. In the illustrated example, the screw SC has extension screws connected to the left and right. Figures 1 and 2 omit the depiction of the paving material inside hopper 2 for clarity. The paving material PV spread by screw SC is shown with a coarse dot pattern, while the newly constructed pavement NP leveled by screed 3 is shown with a fine dot pattern.

The screed 3 is a mechanism for spreading and leveling the paving material PV. In the illustrated example, the screed 3 includes a front screed 30 and a rear screed 31. The front screed 30 includes a left front screed 30L and a right front screed 30R. The rear screed 31 is a screed that can be extended and retracted in the vehicle width direction and includes a left rear screed 31L and a right rear screed 31R. In the illustrated example, the rear screed 31 is extended and retracted in the vehicle width direction by a screed extension cylinder 26. Specifically, the left rear screed 31L is extended and retracted in the vehicle width direction using the left screed extension cylinder 26L, and the right rear screed 31R is extended and retracted in the vehicle width direction using the right screed extension cylinder 26R. The screed 3 is also a floating screed that is towed by the tractor 1 and is connected to the tractor 1 via a leveling arm 3A. The leveling arm 3A includes a left leveling arm 3AL positioned on the left side of the tractor 1 and a right leveling arm 3AR positioned on the right side of the tractor 1.

A mold board 43 is attached to the front of the screed 3. The mold board 43 is configured to adjust the amount of paving material PV that accumulates in front of the screed 3. The paving material PV passes through the gap between the lower end of the mold board 43 and the roadbed BS to reach the area below the screed 3.

In the illustrated example, the tractor 1 is equipped with an information acquisition device 51, an on-board display device 52, a steering device 53, and a screed extension/retraction device 54.

The information acquisition device 51 is configured to acquire information about the road under construction and to output the acquired information to the controller 50. Information about the road under construction includes, for example, the road width, the change in curvature in the transition section (clothoid section), and the curvature in the arc section. In the illustrated example, the information acquisition device 51 includes a forward monitoring device 51F, a rear monitoring device 51B, a driving speed sensor 51S, a positioning device 51P, and a communication device 51T.

The forward monitoring device 51F is configured to monitor the area in front of the asphalt finisher 100. In the illustrated example, the forward monitoring device 51F is a LIDAR that monitors the monitoring range RF in front of the tractor 1 and is mounted on the central part of the tractor 1. The central part of the tractor 1 is, for example, the central part of the front end of the cover that covers the engine compartment at the rear of the hopper 2. However, the forward monitoring device 51F may be mounted on other parts of the asphalt finisher 100 and may consist of multiple LIDARs. When composed of multiple LIDARs, the forward monitoring device 51F can simultaneously monitor multiple non-overlapping monitoring ranges. In this case, the multiple LIDARs may include a right-front LIDAR mounted on the front right side of the tractor 1 and a left-front LIDAR mounted on the front left side of the tractor 1. Furthermore, the LIDARs may be mounted on the tractor 1 via brackets or poles, etc.

The rear monitoring device 51B is configured to monitor the area behind the asphalt paver 100. In the illustrated example, the rear monitoring device 51B is a LIDAR that monitors the monitoring range RB located behind the screed 3, and is mounted on the guide rail 1G, which functions as a handrail. However, the rear monitoring device 51B may also be mounted under the driver's seat 1S, or on other parts of the asphalt paver 100. Furthermore, the rear monitoring device 51B may consist of multiple LIDARs. When composed of multiple LIDARs, the rear monitoring device 51B can simultaneously monitor multiple non-overlapping monitoring ranges. In this case, the multiple LIDARs may include a right rear LIDAR mounted on the right rear end of the tractor 1 and a left rear LIDAR mounted on the left rear end of the tractor 1. The LIDARs may also be mounted on the tractor 1 via brackets or poles.

The information acquisition device 51 may include a side monitoring device configured to monitor the side of the asphalt finisher 100. In this case, the side monitoring device may include a left-side monitoring device and a right-side monitoring device. The left-side monitoring device may, for example, be mounted on the left end of the upper surface of the tractor 1, in front of the rear wheels 5, as a LiDAR that monitors a monitoring range to the left of the tractor 1. The right-side monitoring device may, for example, be mounted on the right end of the upper surface of the tractor 1, in front of the rear wheels 5, as a LiDAR that monitors a monitoring range to the right of the tractor 1.

The LIDAR is configured to measure, for example, the distance between multiple points within the monitoring range and the LIDAR itself. However, at least one of the forward monitoring device 51F and the rear monitoring device 51B may be a monocular camera, stereo camera, millimeter-wave radar, laser radar, laser scanner, depth image camera, or laser rangefinder, etc. The same applies to the side monitoring device. Hereinafter, LIDAR, monocular camera, stereo camera, millimeter-wave radar, laser radar, laser scanner, depth image camera, or laser rangefinder, etc., will be referred to as "LIDAR, etc."

The monitoring range RF of the forward monitoring device 51F preferably includes the roadbed BS and the surface structure AP located outside the roadbed BS. This is to enable the acquisition of information regarding the width of the road under construction. The same applies to the monitoring range of the lateral monitoring device. In the illustrated example, the monitoring range RF has a width greater than the width of the roadbed BS. The surface structure AP is an L-shaped drainage ditch block. The surface structure AP may also be a paving formwork, curb block, or existing pavement, etc.

The monitoring range RB of the rearward monitoring device 51B preferably includes the newly constructed pavement NP and the features AP located outside the newly constructed pavement NP. This is to enable the acquisition of information regarding the width of the newly constructed pavement NP. In the illustrated example, the monitoring range RB has a width greater than the width of the newly constructed pavement NP.

The travel speed sensor 51S is configured to detect the travel speed of the asphalt finisher 100. In the illustrated example, the travel speed sensor 51S is a wheel speed sensor, configured to detect the rotational angular velocity and rotation angle of the rear wheels 5, and consequently, the travel speed and travel distance of the asphalt finisher 100.

The positioning device 51P is configured to measure the position of the asphalt paver 100. In the illustrated example, the positioning device 51P is a GNSS compass and is configured to measure the position and orientation of the asphalt paver 100. The GNSS compass, as shown in Figures 1 and 2, includes a left GNSS receiver 51PL mounted on the upper end of a pole PL extending vertically upward from the rear end of the left leveling arm 3AL, and a right GNSS receiver 51PR mounted on the upper end of a pole PL (invisible) extending vertically upward from the rear end of the right leveling arm 3AR.

However, the positioning device 51P may be a total station. In this case, a reflective prism, which serves as the target for the total station, is attached to the tip of the pole PL. The main unit of the total station, which is installed around the asphalt finisher 100, is connected to the controller 50 via wireless communication. That is, the main unit of the total station transmits information regarding the position of the derived target to the controller 50.

The communication device 51T is configured to enable communication between the asphalt paver 100 and equipment located outside the asphalt paver 100. In the illustrated example, the communication device 51T is installed in front of the driver's seat 1S and is configured to control communication via a mobile communication network, a short-range wireless communication network, or a satellite communication network.

The information acquisition device 51 may include a steering angle sensor configured to detect the steering angle of the asphalt finisher 100, and a pavement width sensor configured to detect the expansion and contraction amount of the rear screed 31 and calculate the pavement width.

Furthermore, the information acquisition device 51 may include a monitoring device installed at the construction site, or a monitoring device attached to an aircraft flying above the asphalt finisher 100. A monitoring device installed at the construction site is, for example, a LiDAR attached to the tip of a pole installed along the road being constructed. A monitoring device attached to an aircraft is, for example, a LiDAR attached to a multirotor (drone) or airship.

The on-board display device 52 is configured to display information related to the asphalt finisher 100. In the illustrated example, the on-board display device 52 is a liquid crystal display installed in front of the driver's seat 1S. However, the on-board display device 52 may also be installed at least one of the left and right ends of the screed 3.

The steering device 53 is configured to control the steering of the asphalt finisher 100. In the illustrated example, the steering device 53 is configured to extend and retract the front wheel steering cylinder, which is installed near the front axle. Specifically, the steering device 53 includes a steering electromagnetic control valve that controls the flow rate of hydraulic fluid from the hydraulic pump to the front wheel steering cylinder, and the flow rate of hydraulic fluid discharged from the front wheel steering cylinder. The steering electromagnetic control valve is configured to control the inflow and outflow of hydraulic fluid in the front wheel steering cylinder in accordance with the rotation of the steering wheel SH (handle) which is the operating device. Furthermore, the steering electromagnetic control valve is configured to control the inflow and outflow of hydraulic fluid in the front wheel steering cylinder independently of the rotation of the steering wheel SH, in response to a control command from the controller 50. In other words, the controller 50 can control the steering of the asphalt finisher 100 regardless of whether or not the operator operates the steering wheel SH.

If the asphalt finisher 100 is a crawler-type asphalt finisher, the steering device 53 is configured to control the left and right pair of crawlers separately. Specifically, the steering device 53 includes a left electromagnetic control valve that controls the flow rate of hydraulic fluid from the hydraulic pump to the left travel hydraulic motor for rotating the left crawler, and a right electromagnetic control valve that controls the flow rate of hydraulic fluid from the hydraulic pump to the right travel hydraulic motor for rotating the right crawler. The left electromagnetic control valve is configured to control the inflow and outflow of hydraulic fluid in the left travel hydraulic motor according to the amount of operation (angle of inclination) of the left operating lever, which is an operating device for operating the left crawler. Furthermore, the left electromagnetic control valve is configured to control the inflow and outflow of hydraulic fluid in the left travel hydraulic motor in response to a control command from the controller 50, regardless of whether the operator operates the left operating lever. Similarly, the right electromagnetic control valve is configured to control the inflow and outflow of hydraulic fluid in the right travel hydraulic motor according to the amount of operation (angle of inclination) of the right operating lever, which is an operating device for operating the right crawler. Furthermore, the right electromagnetic control valve is configured to control the inflow and outflow of hydraulic fluid in the right travel hydraulic motor, regardless of whether the operator operates the right control lever, in response to a control command from the controller 50.

The screed extension/retraction device 54 is configured to extend and retract the rear screed 31. In the illustrated example, the screed extension/retraction device 54 is configured to extend and retract the screed extension/retraction cylinder 26. Specifically, the screed extension/retraction device 54 includes an extension/retraction electromagnetic control valve that controls the flow rate of hydraulic fluid flowing from the hydraulic pump to the screed extension/retraction cylinder 26, and the flow rate of hydraulic fluid discharged from the screed extension/retraction cylinder 26. The extension/retraction electromagnetic control valve is configured to control the inflow and outflow of hydraulic fluid in the screed extension/retraction cylinder 26 in response to the operation of a screed extension/retraction switch (not shown) which acts as an operating device. Furthermore, the extension/retraction electromagnetic control valve is configured to control the inflow and outflow of hydraulic fluid in the screed extension/retraction cylinder 26 in response to a control command from the controller 50, independently of the operation of the screed extension/retraction switch. That is, the controller 50 can control the amount of extension/retraction of the rear screed 31 regardless of whether the operator operates the screed extension/retraction switch.

In the illustrated example, the screed extension/retraction device 54 is configured to independently control the extension/retraction amounts of the left rear screed 31L and the right rear screed 31R. Specifically, the screed extension/retraction device 54 includes a left electromagnetic control valve that controls the flow rate of hydraulic fluid from the hydraulic pump to the left screed extension/retraction cylinder 26L, and a right electromagnetic control valve that controls the flow rate of hydraulic fluid from the hydraulic pump to the right screed extension/retraction cylinder 26R. The left electromagnetic control valve is configured to control the inflow and outflow of hydraulic fluid in the left screed extension/retraction cylinder 26L in response to the operation of the left screed extension/retraction switch, which is an operating device for extending and retracting the left rear screed 31L. Furthermore, the left electromagnetic control valve is configured to control the inflow and outflow of hydraulic fluid in the left screed extension/retraction cylinder 26L in response to a control command from the controller 50, regardless of whether the operator operates the left screed extension/retraction switch. The same applies to the right electromagnetic control valve.

Next, referring to Figure 3, an example configuration of the automatic steering system DS installed on the asphalt finisher 100 will be described. Figure 3 is a block diagram illustrating an example configuration of the automatic steering system DS.

The automatic steering system DS mainly consists of a controller 50, a forward monitoring device 51F, a rearward monitoring device 51B, a driving speed sensor 51S, a positioning device 51P, a communication device 51T, an on-board display device 52, a steering device 53, and a screed extension/retraction device 54, etc.

In the example shown in Figure 3, the controller 50 includes a target calculation unit 50a and a steering control unit 50b as functional blocks.

The target calculation unit 50a is configured to calculate targets used by the steering control unit 50b. The targets used by the steering control unit 50b are, for example, target trajectories, which are the paths that a predetermined point on the asphalt finisher 100 should follow. More precisely, the target trajectory is a one-dimensional array of numerous target positions. Target positions are the points that the predetermined point on the asphalt finisher 100 should reach. Alternatively, the targets used by the steering control unit 50b may be target positions that the predetermined point on the asphalt finisher 100 should reach after a predetermined time has elapsed. The predetermined time is, for example, several milliseconds, tens of milliseconds, hundreds of milliseconds, or several seconds.

The predetermined point is preferably located on the front and rear axes of the tractor 1. Furthermore, the predetermined point is preferably positioned in front of the screed 3. Specifically, the predetermined point is set, for example, at the center, front center, or rear center of the tractor 1, hopper 2, or screed 3.

In the illustrated example, the target calculation unit 50a calculates the target trajectory that a predetermined point in the center of the screed 3 should follow, based on information about the road to be constructed, such as construction data (design data). In this case, the target trajectory is typically calculated before the asphalt finisher 100 starts moving. Therefore, the target trajectory may be calculated on a server or the like installed in a management center outside the asphalt finisher 100 and then transmitted to the controller 50 via communication.

The target calculation unit 50a may calculate a target position as the point that a predetermined point in the center of the screed 3 should reach after a predetermined time has elapsed. In this case, the target position is repeatedly calculated at a predetermined control cycle while the asphalt finisher 100 is running. For example, when the asphalt finisher 100 is running on a straight section of the road to be constructed, the target calculation unit 50a may calculate the center point in the width direction of the road to be constructed, located a predetermined distance ahead of the current position of the predetermined point in the center of the screed 3, based on information acquired by the forward monitoring device 51F, as the target position. The predetermined distance is, for example, a few centimeters or several tens of centimeters. In this case, the target calculation unit 50a can calculate the target position without acquiring design data. However, the target calculation unit 50a may calculate the target position based on design data and information acquired by the forward monitoring device 51F. For example, the target calculation unit 50a may correct the target position calculated based on design data based on information acquired by the forward monitoring device 51F. Furthermore, the target calculation unit 50a may correct the target position using information acquired by the rearward monitoring device 51B.

The steering control unit 50b is configured to automatically control the steering of the asphalt finisher 100, independently of any operation of the control device.

In the illustrated example, the steering control unit 50b outputs a control command to the steering device 53 so that a predetermined point in the center of the screed 3 follows the target trajectory calculated by the target calculation unit 50a. Specifically, the steering control unit 50b derives the current position of the predetermined point in the center of the screed 3 based on the output of the positioning device 51P. If it determines that the predetermined point is deviating to the right from the target trajectory, the steering control unit 50b outputs a control command to the steering device 53 so that the asphalt finisher 100 moves to the left. Similarly, if it determines that the predetermined point is deviating to the left from the target trajectory, the steering control unit 50b outputs a control command to the steering device 53 so that the asphalt finisher 100 moves to the right.

Alternatively, the steering control unit 50b may output a control command to the steering device 53 to position a predetermined point in the center of the screed 3 at the target position calculated by the target calculation unit 50a. In this case, the steering control unit 50b may derive the current position of the predetermined point in the center of the screed 3 based on the output of the positioning device 51P, or it may derive the current position of the predetermined point in the center of the screed 3 based on the output of at least one of the rear-facing monitoring device 51B and the forward-facing monitoring device 51F. In the former case, at least the rear-facing monitoring device 51B and the forward-facing monitoring device 51F may be omitted, and in the latter case, the positioning device 51P may be omitted. However, the steering control unit 50b may derive the current position of the predetermined point in the center of the screed 3 based on the output of the positioning device 51P and at least one of the rear-facing monitoring device 51B and the forward-facing monitoring device 51F.

Next, with reference to Figure 4, an example of the configuration of the function for moving the asphalt finisher 100 along a target trajectory will be described. Figure 4 is a top view of a construction site showing the asphalt finisher 100 passing through the straight section SP1, the curved section LC (left curve), and the straight section SP2 of the road RD to be constructed. The curved section of the road RD to be constructed refers to the part of the road other than the straight section. In Figure 4, asphalt finisher 100a shows the asphalt finisher 100 at the first time point, which is the start of construction. Asphalt finisher 100b shows the asphalt finisher 100 at the second time point, after a predetermined time has elapsed from the first time point. Similarly, asphalt finisher 100c shows the asphalt finisher 100 at a third time point after a predetermined time has elapsed from the second time point; asphalt finisher 100d shows the asphalt finisher 100 at a fourth time point after a predetermined time has elapsed from the third time point; and asphalt finisher 100e shows the asphalt finisher 100 at a fifth time point after a predetermined time has elapsed from the fourth time point. Note that, for clarity, Figure 4 simplifies the tractor 1, front screed 30, left rear screed 31L, and right rear screed 31R of the asphalt finisher 100, while omitting the illustration of the hopper 2.

The target calculation unit 50a of the controller 50 calculates the target trajectory TPS that a predetermined point Q in the center of the front screed 30 should follow at the first time point, which is the start of construction. In the example shown in Figure 4, the predetermined point Q is represented by a triangle, and the target trajectory TPS is represented by a dashed line. The target calculation unit 50a refers to the design data and derives the target trajectory TPS based on the left boundary line LP and the right boundary line RP of the road RD to be constructed. In the example shown in Figure 4, the center line CP of the road RD is represented by a dashed line.

Here, referring to Figures 5 and 6, the target track position (TPS) in the curved section (LC) of the road RD under construction will be explained. Figures 5 and 6 are top views of the curved section (LC) of the road RD under construction, and correspond to enlarged views of a portion of Figure 4. The target track position (TPS) is generated based on a line that bisects the area of the road surface leveled by the screed 3. The road surface area is, for example, the area of the road surface leveled when the asphalt finisher 100 advances a predetermined distance.

In the example shown in Figure 5, the target trajectory TPS is set to divide the area enclosed by the lines connecting points R1, R4, R5, and R8 into two equal parts. That is, the target trajectory TPS is set so that the area of the left portion LZ, enclosed by the lines connecting points R1, R3, R5, and R7, is equal to the area of the right portion RZ, enclosed by the lines connecting points R3, R4, R7, and R8. In Figure 5, for clarity, the left portion LZ is marked with a coarse dot pattern, and the right portion RZ is marked with a fine dot pattern.

Point R0 is the center point of the curvature circle of the curved section LC of the road RD being constructed. Points R1 to R4 are located on the reference line RL (reference line RL1) at time t1, and points R5 to R8 are located on the reference line RL (reference line RL2) at time t2, after a predetermined time has elapsed from time t1.

The reference line RL is the line used as a reference when calculating the areas of the left portion LZ and the right portion RZ, respectively. In the illustrated example, as shown in Figure 4, the reference line RL is a straight line that includes the trailing edge of the left rear screed 31L in a top view. However, the reference line RL may also be a straight line that includes the leading edge of the left rear screed 31L in a top view, a straight line that includes the leading or trailing edge of the right rear screed 31R in a top view, or a line that passes through the leading or trailing edge of the front screed 30 in a top view, etc.

Specifically, points R1 and R5 are on the left boundary line LP of road RD, points R2 and R6 are on the center line CP of road RD, points R3 and R7 are on the target trajectory TPS, and points R4 and R8 are on the right boundary line RP of road RD.

In the example shown in Figure 6, the reference line RL is a polyline that includes the trailing edge lines of the left rear screed 31L and the right rear screed 31R in a top view. Also, in the example shown in Figure 6, the reference line RL at time t1 (reference line RL1) is represented by a thick dotted line, and the reference line RL at time t2 (reference line RL2) is represented by a dashed line. Furthermore, in the example shown in Figure 6, the target trajectory TPS is set such that the area of the left portion LZ, enclosed by the lines connecting points R1, R5, R7, and R9, is equal to the area of the right portion RZ, enclosed by the lines connecting points R3, R4, R8, and R10. Note that points R9 and R10 are points on the target trajectory TPS.

Figures 5 and 6 show that the area of the left portion LZ and the area of the right portion RZ of the road surface leveled during the period from time t1 to time t2 are equal. This relationship also applies to the relationship between the area of the left portion LZ and the area of the right portion RZ of the road surface leveled during other periods, such as the period from time t2 to time t3 (a predetermined time after time t2).

In this embodiment, the target trajectory TPS is generated before construction begins based on information about the road RD to be constructed, such as design data. However, it may also be generated in real time during construction. In this case, the target trajectory TPS may be generated, for example, based on image data output by the forward monitoring device 51F.

In the example shown in Figure 4, the left boundary line LP, the right boundary line RP, the centerline CP, and the target trajectory TPS that the predetermined point Q should follow are all derived as one-dimensional arrays of numerous position coordinates. These position coordinates are, for example, coordinates in a reference coordinate system.

A reference coordinate system is, for example, the World Geodetic System. The World Geodetic System is a three-dimensional orthogonal XYZ coordinate system with its origin at the Earth's center of mass. The X-axis is defined as the axis passing through the intersection of the Greenwich Meridian and the equator and the origin; the Y-axis is defined as the axis passing through the intersection of the 90-degree East longitude meridian and the equator and the origin; and the Z-axis is defined as the axis passing through the North Pole and the origin.

The steering control unit 50b of the controller 50 operates the asphalt finisher 100 so that the actual position coordinates of a predetermined point Q coincide with one of the position coordinates that make up the target trajectory TPS. Specifically, the steering control unit 50b derives the current position of the predetermined point Q in the center of the front screed 30 based on the output of the positioning device 51P. If the position of the predetermined point Q is to the right of the target trajectory TPS, the steering control unit 50b outputs a control command to the steering electromagnetic control valve that makes up the steering device 53, causing a predetermined amount of hydraulic fluid to flow into the bottom oil chamber of the front wheel steering cylinder. As a result, the asphalt finisher 100 moves to the left while moving forward, and the position of the predetermined point Q approaches the target trajectory TPS. Conversely, if the predetermined point Q is located to the left of the target trajectory TPS, the steering control unit 50b outputs a control command to the steering electromagnetic control valve constituting the steering device 53, causing a predetermined amount of hydraulic fluid to flow into the rod-side oil chamber of the front wheel steering cylinder. As a result, the asphalt finisher 100 moves to the right while moving forward, and the position of the predetermined point Q approaches the target trajectory TPS. In this example, the front wheel steering cylinder is configured such that the left steering angle increases as it extends beyond a predetermined length, and the right steering angle increases as it contracts below a predetermined length.

In this way, the controller 50 can position a predetermined point Q, which was at the position of point Qa at the first time point, at point Qb at the second time point, at point Qc at the third time point, at point Qd at the fourth time point, and at point Qe at the fifth time point.

In the example shown in Figure 4, the left rear screed 31L expands and contracts to the left so that its left end face coincides with the left boundary line LP of the road RD, and the right rear screed 31R expands and contracts to the right so that its right end face coincides with the right boundary line RP of the road RD. The left end face of the left rear screed 31L moves along the left boundary line LP, and the right end face of the right rear screed 31R moves along the right boundary line RP. Therefore, even when the controller 50 moves the tractor 1 forward so that a predetermined point Q in the center of the front screed 30 follows the target trajectory TPS, it can match the width of the road RD with the width of the newly constructed pavement NP. In other words, even when the controller 50 moves the tractor 1 forward in the width direction of the road RD, it can match the width of the road RD with the width of the newly constructed pavement NP (the width of the screed 3).

In the illustrated example, the controller 50 outputs a control command to the screed extension/retraction device 54 so that the left end face of the left rear screed 31L coincides with the left boundary line LP of the road RD, and the right end face of the right rear screed 31R coincides with the right boundary line RP of the road RD.

Specifically, the controller 50 is configured to output control commands to the screed extension/retraction device 54 while the asphalt finisher 100 is running, causing the rear screed 31 to extend or retract. For example, if the left end face of the left rear screed 31L is likely to deviate from the left boundary line LP into the road RD, the controller 50 extends the left rear screed 31L to the left. Alternatively, if the right end face of the right rear screed 31R is likely to deviate from the right boundary line RP into the road RD, the controller 50 extends the right rear screed 31R to the right.

Furthermore, in the example shown in Figure 4, the controller 50 controls the steering of the asphalt finisher 100 and the extension and contraction of the rear screed 31 when the asphalt finisher 100 is traveling along the curved section LC of the road RD. However, the controller 50 may also control the steering of the asphalt finisher 100 and the extension and contraction of the rear screed 31 when the asphalt finisher 100 is traveling along the straight section SP of the road RD.

Next, referring to Figure 7, another example of the configuration for the function of moving the asphalt finisher 100 along the target trajectory will be described. Figure 7 is a top view of the construction site showing the asphalt finisher 100 passing through the straight section SP1, the curved section LC (left curve), and the straight section SP2 of the road RD to be constructed, and corresponds to Figure 4.

In Figure 7, asphalt finisher 100a shows the asphalt finisher 100 at the first time point, which is the start of construction. Asphalt finisher 100b shows the asphalt finisher 100 at the second time point, after a predetermined time has elapsed from the first time point. Similarly, asphalt finisher 100c shows the asphalt finisher 100 at the third time point, after a predetermined time has elapsed from the second time point. Asphalt finisher 100d shows the asphalt finisher 100 at the fourth time point, after a predetermined time has elapsed from the third time point. Asphalt finisher 100e shows the asphalt finisher 100 at the fifth time point, after a predetermined time has elapsed from the fourth time point. Note that in Figure 7, for clarity, the tractor 1, front screed 30, left rear screed 31L, and right rear screed 31R of the asphalt finisher 100 are simplified, while the hopper 2 is omitted from the illustration.

The example shown in Figure 7 differs from the examples shown in Figures 4-6 in that it calculates the target trajectory TPT that a predetermined point P at the center of the front end of the tractor 1 should follow, but it is otherwise the same as the examples shown in Figures 4-6.

The target calculation unit 50a of the controller 50 calculates the target trajectory TPT that a predetermined point P at the center of the front end of the tractor 1 should follow at the first time point, which is the start of construction. In the example shown in Figure 7, the predetermined point P is represented by a circle, and the target trajectory TPT is represented by a dashed line.

Specifically, the target calculation unit 50a refers to the design data and derives the target trajectory TPS based on the left boundary line LP and the right boundary line RP of the road RD to be constructed. The target trajectory TPS is the trajectory that a predetermined point Q should follow, as calculated in the examples shown in Figures 4 to 6. In the example shown in Figure 7, the predetermined point Q is represented by a triangle, and the target trajectory TPS is represented by a dashed line. Then, the target calculation unit 50a calculates the target trajectory TPT that a predetermined point P should follow, based on known information such as the distance between the rear wheels 5 and front wheels 6 of the asphalt finisher 100, and the target trajectory TPS.

In the example shown in Figure 7, the left boundary line LP, the right boundary line RP, the centerline CP, the target trajectory TPT that point P should follow, and the target trajectory TPS that point Q should follow are all derived as one-dimensional arrays of numerous position coordinates. These position coordinates are, for example, coordinates in a reference coordinate system.

The steering control unit 50b of the controller 50 operates the asphalt finisher 100 so that the actual position coordinates of a predetermined point P coincide with one of the position coordinates that make up the target trajectory TPT. Specifically, the steering control unit 50b derives the current position of the predetermined point P at the center of the front end of the tractor 1 based on the output of the positioning device 51P. If the position of the predetermined point P is to the right of the target trajectory TPT, the steering control unit 50b outputs a control command to the steering electromagnetic control valve that makes up the steering device 53, causing a predetermined amount of hydraulic fluid to flow into the bottom oil chamber of the front wheel steering cylinder. As a result, the asphalt finisher 100 moves to the left while moving forward, and the position of the predetermined point P approaches the target trajectory TPT. Conversely, if the predetermined point P is located to the left of the target trajectory TPT, the steering control unit 50b outputs a control command to the steering electromagnetic control valve constituting the steering device 53, causing a predetermined amount of hydraulic fluid to flow into the rod-side oil chamber of the front wheel steering cylinder. As a result, the asphalt finisher 100 moves to the right while moving forward, and the position of the predetermined point P approaches the target trajectory TPT.

In this way, the controller 50 can position a predetermined point P, which was at the position of point Pa at the first time point, at point Pb at the second time point, at point Pc at the third time point, at point Pd at the fourth time point, and at point Pe at the fifth time point. As a result, the controller 50 can position a predetermined point Q, which was at the position of point Qa at the first time point, at point Qb at the second time point, at point Qc at the third time point, at point Qd at the fourth time point, and at point Qe at the fifth time point.

In the example shown in Figure 7, the left rear screed 31L expands and contracts to the left so that its left end face coincides with the left boundary line LP of the road RD, and the right rear screed 31R expands and contracts to the right so that its right end face coincides with the right boundary line RP of the road RD. The left end face of the left rear screed 31L moves along the left boundary line LP, and the right end face of the right rear screed 31R moves along the right boundary line RP. Therefore, even when the controller 50 moves the tractor 1 forward so that a predetermined point P at the center of the front end of the tractor 1 follows the target trajectory TPT, the width of the road RD and the width of the newly constructed pavement NP can be matched. In other words, even when the controller 50 moves the tractor 1 forward in the width direction of the road RD, the width of the road RD and the width of the newly constructed pavement NP (width of the screed 3) can be matched.

In the example shown in Figure 7, the controller 50 outputs a control command to the screed extension/retraction device 54 so that the left end face of the left rear screed 31L coincides with the left boundary line LP of the road RD, and the right end face of the right rear screed 31R coincides with the right boundary line RP of the road RD.

Specifically, the controller 50 is configured to output control commands to the screed extension/retraction device 54 while the asphalt finisher 100 is running, causing the rear screed 31 to extend or retract. For example, if the left end face of the left rear screed 31L is likely to deviate from the left boundary line LP into the road RD, the controller 50 extends the left rear screed 31L to the left. Alternatively, if the right end face of the right rear screed 31R is likely to deviate from the right boundary line RP into the road RD, the controller 50 extends the right rear screed 31R to the right.

Furthermore, in the example shown in Figure 7, the controller 50 controls the steering of the asphalt finisher 100 and the extension and contraction of the rear screed 31 when the asphalt finisher 100 is traveling along the curved section LC of the road RD. However, the controller 50 may also control the steering of the asphalt finisher 100 and the extension and contraction of the rear screed 31 when the asphalt finisher 100 is traveling along the straight section SP of the road RD.

As described above, the asphalt finisher 100 according to the embodiment of the present invention comprises a tractor 1, a hopper 2 installed on the front side of the tractor 1 for receiving paving material, a conveyor CV for supplying the paving material received in the hopper 2 to the rear side of the tractor 1, a screw SC for spreading the paving material supplied by the conveyor CV at the rear side of the tractor 1, a screed 3 for leveling the paving material spread by the screw SC at the rear side of the screw SC, and a controller 50 as a control device.

Furthermore, as shown in Figure 4, the controller 50 may be configured to generate a target trajectory TPS based on a line that bisects the area of the road surface leveled by the screed 3, and to control the movement of the tractor 1 so that a predetermined point Q in the center of the front screed 30, which is an example of a predetermined point on the asphalt finisher 100, follows the target trajectory TPS.

Alternatively, as shown in Figure 7, the controller 50 may be configured to generate a target trajectory TPT based on a line that bisects the area of the road surface leveled by the screed 3, and to control the movement of the tractor 1 so that a predetermined point P at the center of the front end of the tractor 1, which is another example of a predetermined point on the asphalt finisher 100, follows the target trajectory TPT. Note that the road surface includes the road surface of the curved portion LC of the road RD to be constructed.

This configuration can improve the paving quality of curved road sections (RD). Even when the asphalt finisher 100 is working on the curved section (LC) of the road section (RD), the surface area of the left section (LZ) and the right section (RZ) can be made the same. Specifically, the amount of left-side gripping by the left rear screed 31L and the amount of right-side gripping by the right rear screed 31R can be made the same, thereby suppressing the influence on steering caused by the difference between the left and right gripping amounts.

Furthermore, the predetermined point on the asphalt finisher 100 used to control its steering is preferably set to be located on the longitudinal axis of the tractor 1 when viewed from above.

Furthermore, the predetermined point of the asphalt finisher 100 is more preferably set in front of the screed 3.

Furthermore, in the example shown in Figure 4, the target trajectory TPS corresponding to the left-curving section (curve section LC) of the road RD is set to the right of the centerline CP, which is the line that bisects the road RD. Similarly, in the example shown in Figure 7, the target trajectory TPT corresponding to the curve section LC is set to the right of the centerline CP. On the other hand, the target trajectory corresponding to the right-curving section of the road RD is set to the left of the centerline CP. Note that the target trajectory corresponding to the straight section of the road RD is typically set on the centerline CP.

Furthermore, the asphalt finisher 100 is configured to extend and retract its screed 3 to match the width of the road RD when passing through the curved section LC of the road RD. Specifically, the asphalt finisher 100 is configured to extend one of the left and right ends of the screed 3 and contract the other when passing through the curved section LC of the road RD. In the example shown in Figure 4 or Figure 7, when the asphalt finisher 100 passes through the curved section LC of the road RD, it extends the left rear screed 31L to the left and contracts the right rear screed 31R to the left.

This configuration allows the screed 3 to automatically adjust to the width of the road RD even when the asphalt paver 100 is moved forward in the width direction of the road RD while navigating the curved section of the road RD being constructed. Therefore, this configuration reduces the burden on the operator of the asphalt paver 100 when paving the curved section of the road RD being constructed.

Preferred embodiments of the present invention have been described above. However, the present invention is not limited to the embodiments described above. Various modifications or substitutions can be applied to the embodiments described above without departing from the scope of the invention. Furthermore, each of the features described with reference to the embodiments described above may be combined as appropriate, as long as they do not conflict technically.

For example, in the above embodiment, the steering device 53 is configured to extend and retract a front wheel steering cylinder installed near the front axle. However, if a hydraulic steering motor is used instead of the front wheel steering cylinder, the steering device 53 may be configured to rotate the hydraulic steering motor. In this case, the steering device 53 includes a steering electromagnetic control valve that controls the flow rate of hydraulic fluid from the hydraulic pump to the hydraulic steering motor. The steering electromagnetic control valve is configured to control the inflow and outflow of hydraulic fluid in the hydraulic steering motor in accordance with the rotation of the steering wheel SH (handle) as an operating device. Alternatively, the steering electromagnetic control valve is configured to control the inflow and outflow of hydraulic fluid in the hydraulic steering motor independently of the rotation of the steering wheel SH, in response to a control command from the controller 50. Alternatively, the steering device 53 may be configured to control an electric motor that automatically rotates the steering wheel SH. In this case, the steering device can automatically control the movement of the asphalt finisher 100 by automatically rotating the steering wheel SH in response to a control command from the controller 50.

1...Tractor 1G...Guide rail 1S...Driver's cab 2...Hopper 3...Screed 3A...Leveling arm 3AL...Left leveling arm 3AR...Right leveling arm 5...Rear wheel 6...Front wheel 26...Screed extension cylinder 30...Front screed 31...Rear screed 43...Mold board 50...Controller 50a...Target calculation unit 50b...Steering control unit 51...Information acquisition device 51B...Rear monitoring device 51F...Forward monitoring device 51P...Positioning device 51PL...Left GNSS receiver 51PR...Right GNSS receiver 51S...Travel speed sensor 51T...Communication device 52...On-board display device 53...Steering device 54...Screed extension device 100, 100a-100e...Asphalt finisher AP...Ground surface BS...Roadbed CP...Centerline CV...Conveyor DS...Automatic Steering System LC...Curve Section LP...Left Boundary Line LZ...Left Section NP...Newly Installed Pavement PL...Pole PV...Pavement Material RD...Road RL, RL1, RL2...Reference Line RP...Right Boundary Line RZ...Right Section SC...Screw SH...Steering Wheel SP, SP1, SP2...Straight Section TPS, TPT...Target Trajectory

Claims (6)

Tractor and,
A hopper installed on the front side of the tractor to receive paving material,
A conveyor that feeds the paving material received in the hopper to the rear of the tractor,
A screw for spreading the paving material supplied by the conveyor at the rear of the tractor,
A screed is used to spread the paving material that has been laid by the screw, and to level the paving material behind the screw.
An asphalt finisher equipped with a control device,
The control device is configured to generate a target trajectory based on a line that bisects the area of the curved portion of the road to be leveled by the screed, and to control the movement of the tractor so that a predetermined point on the asphalt finisher follows the target trajectory.
Asphalt finisher. The predetermined point is located on the front-rear axis of the tractor when viewed from above.
The asphalt finisher according to claim 1. The predetermined point is set in front of the screed.
The asphalt finisher according to claim 2. The target trajectory corresponding to the rightward curve in the aforementioned road is set to the left of the line that bisects the road horizontally.
The target trajectory corresponding to the leftward curve in the aforementioned road is set to the right of the line that bisects the road left and right.
An asphalt finisher according to any one of claims 1 to 3. When passing through the curved portion of the road, the screed is extended and retracted from side to side to match the width of the road.
An asphalt finisher according to any one of claims 1 to 3. When passing the curved portion of the road, one of the left and right ends of the screed is extended and the other is contracted.
The asphalt finisher according to claim 5.