ASPHALT ROAD FINISHER

Abstract

 To enhance the quality of pavement of a curved road (RD) . An asphalt finisher (100, 100a, 100b, 100c, 100d, 100e) includes a tractor, a hopper that is provided on a front side of the tractor and that receives a paving material, a conveyor that feeds the paving material received by the hopper to a rear side of the tractor, a screw that spreads the paving material fed by the conveyor on the rear side of the tractor, a screed that levels the paving material spread by the screw on a rear side of the screw, and a controller. The controller is configured to drive the tractor such that a target trajectory (TPS, TPT) is generated based on a line which bisects an area of a road surface leveled by the screed right and left and a predetermined point (Q, P) of the asphalt finisher (100, 100a, 100b, 100c, 100d, 100e) follows the target trajectory (TPS, TPT) . The road surface includes a road surface of a curve portion (LC) of a road (RD) which is a construction target.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

[0001] The present disclosure relates to an asphalt finisher.

Description of Related Art

[0002] In the related art, an asphalt finisher including a tractor, a hopper that is provided on a front side of the tractor and that receives a paving material, a conveyor that feeds the paving material in the hopper to a rear side of the tractor, a screw that spreads the paving material fed by the conveyor on the rear side of the tractor, and a screed that levels the paving material spread by the screw on a rear side of the screw is known (see Japanese Unexamined Patent Publication No. 2017-160636).

[0003] The asphalt finisher is usually configured to advance in a state where the center of a road, which is a construction target, and the center of the screed match each other.

SUMMARY OF THE INVENTION

[0004] However, in a case where the road, which is a construction target, is curved, there is a possibility in which the asphalt finisher decreases the quality of pavement. This is because when the asphalt finisher advances in a state where the center of the curved road and the center of the screed match each other, a difference between the surface area of a road leveled by a left rear screed per unit time and the surface area of a road leveled by a right rear screed per unit time occurs . In addition, this is because there is a difference between the amount of the paving material held by the left rear screed (left holding amount) and the amount of the paving material held by the right rear screed (right holding amount).

[0005] Thus, it is desired to provide an asphalt finisher that can enhance the quality of pavement of the curved road.

[0006] According to an embodiment of the present invention, there is provided an asphalt finisher including a tractor, a hopper that is provided on a front side of the tractor and that receives a paving material, a conveyor that feeds the paving material received by the hopper to a rear side of the tractor, a screw that spreads the paving material fed by the conveyor on the rear side of the tractor, a screed that levels the paving material spread by the screw on a rear side of the screw, and a control device, in which the control device is configured to control a movement of the tractor such that a target trajectory is generated based on a line which bisects an area of a road surface leveled by the screed right and left and a predetermined point of the asphalt finisher follows the target trajectory, and the road surface includes a road surface of a curve portion of a road which is a construction target.

[0007] The asphalt finisher described above can enhance the quality of pavement of the curved road.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] 

Fig. 1 is a side view of an asphalt finisher according to an embodiment of the present invention.

Fig. 2 is a top view of the asphalt finisher of Fig. 1.

Fig. 3 is a diagram showing a configuration example of an automatic steering system.

Fig. 4 is a top view of a construction site.

Fig. 5 is a top view of a construction site.

Fig. 6 is a top view of a construction site.

Fig. 7 is a top view of a construction site.

DETAILED DESCRIPTION OF THE INVENTION

[0009]  Fig. 1 is a side view of an asphalt finisher 100 according to an embodiment of the present invention. Fig. 2 is a top view of the asphalt finisher 100. In the shown example, the asphalt finisher 100 is a wheel type asphalt finisher and is mainly configured by a tractor 1, ahopper 2, anda screed3. Hereinafter, a direction of the hopper 2 viewed from the tractor 1 (+X direction) will be referred to as forward, and a direction of the screed 3 viewed from the tractor 1 (-X direction) will be referred to as rearward.

[0010] The tractor 1 is a mechanism for moving the asphalt finisher 100. In the shown example, the tractor 1 rotates a rear wheel 5 using a rear wheel traveling hydraulic motor and moves the asphalt finisher 100 by rotating a front wheel 6 using a front wheel traveling hydraulic motor. The rear wheel traveling hydraulic motor and the front wheel traveling hydraulic motor rotate by receiving supply of a hydraulic oil from a hydraulic pump. However, the front wheel 6 may be a driven wheel.

[0011] The asphalt finisher 100 may be a crawler type asphalt finisher. In this case, a combination of the rear wheel 5 and the front wheel 6 is replaced with a combination of a left crawler and a right crawler.

[0012] The controller 50 is a control device that controls the asphalt finisher 100. In the shown example, the controller 50 is configured by a microcomputer including a CPU, a volatile storage device, a non-volatile storage device, and the like and is mounted on the tractor 1. Each function of the controller 50 is realized as the CPU executes a program stored in the non-volatile storage device. However, each function of the controller 50 is not only realized by software but may be realized by hardware, or may be realized by a combination of hardware and software.

[0013] The hopper 2 is a mechanism for receiving a paving material. In the shown example, the hopper 2 is provided on a front side of the tractor 1 and is configured to be capable of being opened and closed in a vehicle width direction (Y-axis direction) by a hopper cylinder. The asphalt finisher 100 usually receives a paving material (for example, an asphalt mixture) from a loading platform of a dump truck when the hopper 2 is in a fully open state. The dump truck is an example of a transport vehicle that transports the pavingmaterial. Figs. 1 and2 show that the hopper 2 is in a fully open state. The hopper 2 is closed when the paving material in the hopper 2 decreases, and the paving material near an inner wall of the hopper 2 is collected at a central portion of the hopper 2. This is to enable a conveyor CV which is at the central portion of the hopper 2 to feed the paving material to the rear side of the tractor 1. The paving material fed to the rear side of the tractor 1 is spread in the vehicle width direction on the rear side of the tractor 1 and the front side of the screed 3 by a screw SC. In the shown example, the screw SC is in a state where an extension screw is connected right and left. For the sake of clarity, Figs. 1 and 2 omit showing the paving material in the hopper 2, show a paving material PV spread by the screw SC in a coarse dot pattern, and show a newly constructed pavement body NP leveled by the screed 3 in a fine dot pattern.

[0014] The screed 3 is a mechanism for leveling the paving material PV. In the shown 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 is capable of expanding and contracting in the vehicle width direction and includes a left rear screed 31L and a right rear screed 31R. In the shown example, the rear screed 31 is expanded and contracted in the vehicle width direction by a screed expanding and contracting cylinder 26. Specifically, the left rear screed 31L is expanded and contracted in the vehicle width direction using a left screed expanding and contracting cylinder 26L, and the right rear screed 31R is expanded and contracted in the vehicle width direction using a right screed expanding and contracting cylinder 26R. In addition, the screed 3 is a floating screed pulled 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 disposed on a left side of the tractor 1 and a right leveling arm 3AR disposed on a right side of the tractor 1.

[0015] A mold board 43 is attached to a front portion of the screed 3. The mold board 43 is configured to be capable of adjusting the amount of the paving material PV staying in front of the screed 3. The paving material PV reaches under the screed 3 through a gap between a lower end of the mold board 43 and a roadbed BS.

[0016] In the shown example, an information acquisition device 51, a vehicle-mounted display device 52, a steering device 53, and a screed expanding and contracting device 54 are attached to the tractor 1.

[0017] The information acquisition device 51 is configured to be capable of acquiring information related to a road, which is a construction target, and outputting the acquired information to the controller 50. The information related to the road, which is a construction target, includes, for example, the width of the road, a change in curvature in a relaxation section (crossoid section), and curvature in an arc section. In the shown example, the information acquisition device 51 includes a front monitoring device 51F, a rear monitoring device 51B, a traveling speed sensor 51S, a positioning device 51P, and a communication device 51T.

[0018] The front monitoring device 51F is configured to be capable of monitoring the front of the asphalt finisher 100. In the shown example, the front monitoring device 51F is a LIDAR that monitors a monitoring range RF in front of the tractor 1 and is attached to a central portion of the tractor 1. The central portion of the tractor 1 is, for example, a front end central portion of a cover that covers an engine room on the rear side of the hopper 2. However, the front monitoring device 51F may be attached to other parts of the asphalt finisher 100 or may be configured by a plurality of LIDARs. In a case of being configured by the plurality of LIDARs, the front monitoring device 51F can simultaneously monitor a plurality of monitoring ranges that do not overlap each other. In this case, the plurality of LIDARs may include a right front LIDAR attached to a front end right portion of the tractor 1 and a left front LIDAR attached to a front end left portion of the tractor 1. In addition, the LIDARs may be attached to the tractor 1 via a bracket, a pole, or the like.

[0019] The rear monitoring device 51B is configured to be capable of monitoring the rear of the asphalt finisher 100. In the shown example, the rear monitoring device 51B is a LIDAR that monitors a monitoring range RB behind the screed 3 and is attached to a guide rail 1G functioning as a handrail. However, the rear monitoring device 51B may be attached to a lower portion of a driver's seat 1S or may be attached to other parts of the asphalt finisher 100. In addition, the rear monitoring device 51B may be configured by a plurality of LIDARs. In a case of being configured by the plurality of LIDARs, the rear monitoring device 51B can simultaneously monitor a plurality of monitoring ranges that do not overlap each other. In this case, the plurality of LIDARs may include a right rear LIDAR attached to a rear end right portion of the tractor 1 and a left rear LIDAR attached to a rear end left portion of the tractor 1. In addition, the LIDARs may be attached to the tractor 1 via a bracket, a pole, or the like.

[0020] The information acquisition device 51 may include a side monitoring device configured to be capable of monitoring the side of the asphalt finisher 100. In this case, the side monitoring device may include a left monitoring device and a right monitoring device. The left monitoring device may be attached to a left end portion of an upper surface of the tractor 1 on the front side of the rear wheel 5, for example, as a LIDAR that monitors a monitoring range on the left of the tractor 1. The right monitoring device may be attached to a right end portion of the upper surface of the tractor 1 on the front side of the rear wheel 5, for example, as a LIDAR that monitors a monitoring range on the right of the tractor 1.

[0021] The LIDAR is configured to be capable of measuring, for example, a distance between multiple points within the monitoring range and the LIDAR. However, at least one of the front monitoring device 51F and the rear monitoring device 51B may be a monocular camera, a stereo camera, a millimeter wave radar, a laser radar, a laser scanner, a distance image camera, a laser range finder, or the like. The same applies to the side monitoring device. Hereinafter, a LIDAR, a monocular camera, a stereo camera, a millimeter wave radar, a laser radar, a laser scanner, a distance image camera, a laser range finder, or the like is referred to as a LIDAR or the like.

[0022] The monitoring range RF of the front monitoring device 51F desirably includes the roadbed BS and a feature AP on an outside of the roadbed BS. This is to make information related to the width of the road, which is a construction target, possible to be acquired. The same applies to the monitoring range of the side monitoring device. In the shown example, the monitoring range RF has a width larger than the width of the roadbed BS. The feature AP is an L-shaped side groove block. The feature AP may be a paving mold, a rim stone block, an existing pavement body, or the like.

[0023] The monitoring range RB of the rear monitoring device 51B desirably includes the newly constructed pavement body NP and the feature AP on the outside of the newly constructed pavement body NP. This is to make information related to the width of the newly constructed pavement body NP possible to be acquired. In the shown example, the monitoring range RB has a width larger than the width of the newly constructed pavement body NP.

[0024] The traveling speed sensor 51S is configured to be capable of detecting a traveling speed of the asphalt finisher 100. In the shown example, the traveling speed sensor 51S is a wheel speed sensor and is capable of detecting the rotation angular speed and the rotation angle of the rear wheel 5 and the traveling speed and the traveling distance of the asphalt finisher 100.

[0025] The positioning device 51P is configured to be capable of measuring the position of the asphalt finisher 100. In the shown example, the positioning device 51P is a GNSS compass and is configured to be capable of measuring the position and the posture of the asphalt finisher 100. As shown in Figs. 1 and 2, the GNSS compass, which is the positioning device 51P, includes a left GNSS receiver 51PL that is attached to an upper end of a pole PL extending vertically upward from a rear end portion of the left leveling arm 3AL and a right GNSS receiver 51PR that is attached to the upper end of the pole PL (invisible) extending vertically upward from a rear end portion of the right leveling arm 3AR.

[0026] However, the positioning device 51P may be a total station. In this case, a reflection prism, which is a target of the total station, is attached to a tip of the pole PL. A main body of the total station provided in the surroundings of the asphalt finisher 100 is connected to the controller 50 via wireless communication. That is, the main body of the total station transmits information related to the position of the derived target to the controller 50.

[0027] The communication device 51T is configured to be capable of realizing communication between the asphalt finisher 100 and a device outside the asphalt finisher 100. In the shown example, the communication device 51T is provided in front of the driver's seat 1S and is configured to be capable of controlling communication via a mobile communication network, a short-range wireless communication network, a satellite communication network, or the like.

[0028] The information acquisition device 51 may include a steering angle sensor configured to be capable of detecting the steering angle of the asphalt finisher 100, a pavement width sensor configured to be capable of calculating a pavement width by detecting an expansion and contraction amount of the rear screed 31, and the like.

[0029] In addition, the information acquisition device 51 may include a monitoring device provided at a construction site or a monitoring device attached to an air vehicle flying over the asphalt finisher 100. The monitoring device provided at the construction site is, for example, a LIDAR attached to the tip of the pole provided along the road, which is a construction target, or the like. The monitoring device attached to the air vehicle is, for example, a LIDAR, which is attached to amulticopter (drone), an airship, or the like, or the like.

[0030] The vehicle-mounted display device 52 is configured to be capable of displaying information related to the asphalt finisher 100. In the shown example, the vehicle-mounted display device 52 is a liquid crystal display provided in front of the driver's seat 1S. However, the vehicle-mounted display device 52 may be at least one of a left end portion and a right end portion of the screed 3.

[0031] The steering device 53 is configured to be capable of controlling the steering of the asphalt finisher 100. In the shown example, the steering device 53 is configured to expand and contract a front wheel steering cylinder provided close to a front axle. Specifically, the steering device 53 includes a steering electromagnetic control valve that controls the flow rate of a hydraulic oil flowing from the hydraulic pump to the front wheel steering cylinder and the flow rate of the hydraulic oil discharged from the front wheel steering cylinder. The steering electromagnetic control valve is configured to be capable of controlling the inflow and outflow of the hydraulic oil in the front wheel steering cylinder in accordance with the rotation of a steering wheel SH (handle), which is a manipulation device. In addition, the steering electromagnetic control valve is configured to be capable of controlling the inflow and outflow of the hydraulic oil in the front wheel steering cylinder in accordance with a control command from the controller 50, regardless of the rotation of the steering wheel SH. That is, the controller 50 can control the steering of the asphalt finisher 100 regardless of the presence or absence of an operation of the steering wheel SH by an operator.

[0032] In a case where the asphalt finisher 100 is a crawler type asphalt finisher, the steering device 53 is configured to be capable of controlling each of a pair of right and left crawlers. Specifically, the steering device 53 includes a left electromagnetic control valve that controls the flow rate of a hydraulic oil flowing from the hydraulic pump to a left traveling hydraulic motor for rotating the left crawler and a right electromagnetic control valve that controls the flow rate of a hydraulic oil flowing from the hydraulic pump to a right traveling hydraulic motor for rotating the right crawler. In addition, the left electromagnetic control valve is configured to be capable of controlling inflow and outflow of the hydraulic oil in the left traveling hydraulic motor in accordance with a manipulated variable (inclination angle) of a left operation lever, which is a manipulation device for operating the left crawler. In addition, the left electromagnetic control valve is configured to be capable of controlling inflow and outflow of the hydraulic oil in the left traveling hydraulic motor in accordance with a control command from the controller 50, regardless of the presence or absence of an operation of the left operation lever by the operator. Similarly, the right electromagnetic control valve is configured to be capable of controlling inflow and outflow of the hydraulic oil in the right traveling hydraulic motor in accordance with a manipulated variable (inclination angle) of a right operation lever, which is a manipulation device for operating the right crawler. In addition, the right electromagnetic control valve is configured to be capable of controlling inflow and outflow of the hydraulic oil in the right traveling hydraulic motor in accordance with a control command from the controller 50, regardless of the presence or absence of an operation of the right operation lever by the operator.

[0033] The screed expanding and contracting device 54 is configured to be capable of expanding and contracting the rear screed 31. In the shown example, the screed expanding and contracting device 54 is configured to be capable of expanding and contracting the screed expanding and contracting cylinder 26. Specifically, the screed expanding and contracting device 54 includes an expanding and contracting electromagnetic control valve that controls the flow rate of a hydraulic oil flowing from the hydraulic pump to the screed expanding and contracting cylinder 26 and the flow rate of the hydraulic oil discharged from the screed expanding and contracting cylinder 26. The expanding and contracting electromagnetic control valve is configured to be capable of controlling the inflow and outflow of the hydraulic oil in the screed expanding and contracting cylinder 26 in response to an operation of a screed expanding and contracting switch (not shown), which is a manipulation device. In addition, the expanding and contracting electromagnetic control valve is configured to be capable of controlling the inflow and outflow of the hydraulic oil in the screed expanding and contracting cylinder 26 in accordance with a control command from the controller 50, regardless of the operation of the screed expanding and contracting switch. That is, the controller 50 can control the expansion and contraction amount of the rear screed 31 regardless of the presence or absence of the operation of the screed expanding and contracting switch by the operator.

[0034] In the shown example, the screed expanding and contracting device 54 is configured to be capable of controlling each of the expansion and contraction amounts of the left rear screed 31L and the right rear screed 31R. Specifically, the screed expanding and contracting device 54 includes a left electromagnetic control valve that controls the flow rate of a hydraulic oil flowing from the hydraulic pump to the left screed expanding and contracting cylinder 26L and a right electromagnetic control valve that controls the flow rate of a hydraulic oil flowing from the hydraulic pump to the right screed expanding and contracting cylinder 26R. In addition, the left electromagnetic control valve is configured to be capable of controlling the inflow and outflow of the hydraulic oil in the left screed expanding and contracting cylinder 26L in response to an operation of a left screed expanding and contracting switch, which is a manipulation device for expanding and contracting the left rear screed 31L. In addition, the left electromagnetic control valve is configured to be capable of controlling the inflow and out flow of the hydraulic oil in the left screed expanding and contracting cylinder 26L in accordance with a control command from the controller 50, regardless of the presence or absence of the operation of the left screed expanding and contracting switch by the operator. The same applies to the right electromagnetic control valve.

[0035] Next, a configuration example of an automatic steering system DS mounted on the asphalt finisher 100 will be described with reference to Fig. 3. Fig. 3 is a block diagram showing the configuration example of the automatic steering system DS.

[0036] The automatic steering system DS is mainly configured by the controller 50, the front monitoring device 51F, the rear monitoring device 51B, the traveling speed sensor 51S, the positioning device 51P, the communication device 51T, the vehicle-mounted display device 52, the steering device 53, the screed expanding and contracting device 54, and the like.

[0037] In the example shown in Fig. 3, the controller 50 includes a target calculation unit 50a and a steering control unit 50b, which are functional blocks.

[0038] The target calculation unit 50a is configured to be capable of calculating a target used by the steering control unit 50b. The target used by the steering control unit 50b is, for example, a target trajectory which is a trajectory to be followed by a predetermined point on the asphalt finisher 100. Strictly speaking, the target trajectory is a one-dimensional array of multiple target positions. The target position is a point to be reached by the predetermined point on the asphalt finisher 100. Alternatively, the target used by the steering control unit 50b may be a target position, which is a point to be reached by the predetermined point on the asphalt finisher 100 after a lapse of a predetermined time. The predetermined time is, for example, several milliseconds, several tens of milliseconds, several hundreds of milliseconds, or several seconds.

[0039] The predetermined point is desirably on a front-rear axis of the tractor 1. In addition, the predetermined point is desirably set to be positioned in front of the screed 3. Specifically, the predetermined point is set at, for example, the tractor 1, the hopper 2, or a central portion, a front end central portion, a rear end central portion, or the like of the screed 3.

[0040] In the shown example, the target calculation unit 50a calculates, for example, a target trajectory to be followed by a predetermined point at the central portion of the screed 3 based on information related to the road, which is a construction target, such as construction data (design data) . In this case, the target trajectory is typically calculated before the asphalt finisher 100 starts traveling. For this reason, the target trajectory may be transmitted to the controller 50 via communication after calculating by a server provided at a management center outside the asphalt finisher 100 or the like.

[0041] The target calculation unit 50a may calculate a target position which is a point to be reached by the predetermined point at the central portion of the screed 3 after a lapse of the predetermined time. In this case, the target position is repeatedly calculated in a predetermined control cycle during traveling of the asphalt finisher 100. For example, in a case where the asphalt finisher 100 travels a linear portion of the road, which is a construction target, the target calculation unit 50a may calculate a center point of the road in a width direction, which is a construction target positioned in front of the current position of the predetermined point at the central portion of the screed 3 by a predetermined distance, as a target position, based on information acquired by the front monitoring device 51F. The predetermined distance is, for example, several 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 front monitoring device 51F. For example, the target calculation unit 50a may correct the target position, which is calculated based on the design data, based on the information acquired by the front monitoring device 51F. In addition, the target calculation unit 50a may correct the target position using information acquired by the rear monitoring device 51B.

[0042] The steering control unit 50b is configured to be capable of automatically controlling the steering of the asphalt finisher 100 regardless of an operation of a manipulation device.

[0043] In the shown example, the steering control unit 50b outputs a control command to the steering device 53 such that the predetermined point at the central portion 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 at the central portion of the screed 3 based on an output of the positioning device 51P. Then, in a case where it is determined that the predetermined point deviates to the right from the target trajectory, the steering control unit 50b outputs a control command to the steering device 53 such that the asphalt finisher 100 moves to the left. Similarly, in a case where it is determined that the predetermined point deviates to the left from the target trajectory, the steering control unit 50b outputs a control command to the steering device 53 such that the asphalt finisher 100 moves to the right.

[0044] Alternatively, the steering control unit 50b may output a control command to the steering device 53 such that the predetermined point at the central portion of the screed 3 is positioned 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 at the central portion of the screed 3 based on the output of the positioning device 51P or may derive the current position of the predetermined point at the central portion of the screed 3 based on an output of at least one of the rear monitoring device 51B and the front monitoring device 51F. In a case of the former, at least one of the rear monitoring device 51B and the front monitoring device 51F may be omitted, and in a case of the latter, the positioning device 51P may be omitted. However, the steering control unit 50b may derive the current position of the predetermined point at the central portion of the screed 3 based on the output of the positioning device 51P and the output of at least one of the rear monitoring device 51B and the front monitoring device 51F.

[0045] Next, a configuration example of a function of moving the asphalt finisher 100 along the target trajectory will be described with reference to Fig. 4. Fig. 4 is a top view of a construction site, which shows the asphalt finisher 100 passing through a linear portion SP1, a curve portion LC (left curve), and a linear portion SP2 of a road RD, which is a construction target. The curve portion of the road RD, which is a construction target, means a portion other than a straight portion of the road. In Fig. 4, an asphalt finisher 100a means the asphalt finisher 100 at a first time point when construction starts. An asphalt finisher 100b means the asphalt finisher 100 at a second time point after a predetermined time has elapsed from the first time point. Similarly, an asphalt finisher 100c means the asphalt finisher 100 at a third time point after a predetermined time has elapsed from the second time point, an asphalt finisher 100d means the asphalt finisher 100 at a fourth time point after a predetermined time has elapsed from the third time point, and an asphalt finisher 100e means the asphalt finisher 100 at a fifth time point after a predetermined time has elapsed from the fourth time point. For the sake of clarity, while Fig. 4 shows the tractor 1, the front screed 30, the left rear screed 31L, and the right rear screed 31R of the asphalt finisher 100 in a simplified manner, the hopper 2 is not shown.

[0046] The target calculation unit 50a of the controller 50 calculates a target trajectory TPS to be followed by a predetermined point Q at a central portion of the front screed 30 at the first time point when construction starts. In the example shown in Fig. 4, the predetermined point Q is represented by a triangle, and the target trajectory TPS is represented by a one-dot chain line. The target calculation unit 50a derives the target trajectory TPS based on a left boundary line LP and a right boundary line RP of the road RD, which is a construction target, with reference to design data. In the example shown in Fig. 4, a center line CP of the road RD is represented by a broken line.

[0047] Herein, the target trajectory TPS at the curve portion LC of the road RD, which is a construction target, will be described with reference to Figs. 5 and 6. Figs. 5 and 6 are top views of the curve portion LC of the road RD, which is a construction target, and correspond to a partially enlarged view of Fig. 4. The target trajectory TPS is generated based on a line that bisects the area of the road surface leveled by the screed 3 right and left. The area of the road surface is, for example, the area of the road surface leveled when the asphalt finisher 100 has advanced by a predetermined distance.

[0048] In the example shown in Fig. 5, the target trajectory TPS is set to bisect the area of a portion surrounded by a line connecting a point R1, a point R4, a point R5, and a point R8 to each other right and left. That is, the target trajectory TPS is set such that the area of a left portion LZ surrounded by a line connecting the point R1, a point R3, the point R5, and a point R7 to each other is equal to the area of a right portion RZ surrounded by a line connecting the point R3, the point R4, the point R7, and the point R8 to each other. For the sake of clarity, in Fig. 5, a coarse dot pattern is attached to the left portion LZ, and a fine dot pattern is attached to the right portion RZ.

[0049] A point R0 is a center point of a curvature circle of the curve portion LC of the road RD, which is a construction target, the point R1 to the point R4 are points positioned on a reference line RL (reference line RL1) at time t1, and the point R5 to the point R8 are points positioned on the reference line RL (reference line RL2) at time t2 after a predetermined time has elapsed from the time t1.

[0050] The reference line RL is a reference line when calculating the area of each of the left portion LZ and the right portion RZ. In the shown example, as shown in Fig. 4, the reference line RL is a straight line that includes a rear edge line of the left rear screed 31L when viewed from above. However, the reference line RL may be a straight line that includes a front edge line of the left rear screed 31L when viewed from above, a straight line that includes a front edge line or a rear edge line of the right rear screed 31R when viewed from above, a line passing through a front edge or a rear edge of the front screed 30 when viewed from above, or the like.

[0051] Specifically, the point R1 and the point R5 are points on the left boundary line LP of the road RD, a point R2 and a point R6 are points on the center line CP of the road RD, the point R3 and the point R7 are points on the target trajectory TPS, and the point R4 and the point R8 are points on the right boundary line RP of the road RD.

[0052] In the example shown in Fig. 6, the reference line RL is a bent line that includes the rear edge line of the left rear screed 31L and the rear edge line of the right rear screed 31R when viewed from above. In addition, in the example shown in Fig. 6, the reference line RL (reference line RL1) at the time t1 is represented by a thick dotted line, and the reference line RL (reference line RL2) at the time t2 is represented by a two-dot chain line. In addition, in the example shown in Fig. 6, the target trajectory TPS is set such that the area of the left portion LZ surrounded by a line connecting the point R1, the point R5, the point R7, and a point R9 to each other is equal to the area of the right portion RZ surrounded by a line connecting the point R3, the point R4, the point R8, and a point R10 to each other. The point R9 and the point R10 are points on the target trajectory TPS.

[0053] Figs. 5 and 6 show a relationship in which the area of the left portion LZ and the area of the right portion RZ of the road surface leveled during a period from the time t1 to the time t2 are equal to each other, but this relationship also applies to a 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 a period from the time t2 to time t3 (time after a predetermined time has elapsed from the time t2) .

[0054] In the present embodiment, the target trajectory TPS is generated be fore construction starts based on information related to the road RD, which is a construction target, such as design data, but may 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 front monitoring device 51F.

[0055] In the example shown in Fig. 4, all of the left boundary line LP, the right boundary line RP, and the center line CP of the road RD and the target trajectory TPS to be followed by the predetermined point Q are derived as a one-dimensional array of multiple position coordinates. The position coordinates are, for example, coordinates in a reference coordinate system.

[0056] The reference coordinate system is, for example, the world geodetic system. The world geodetic system is a three-dimensional orthogonal XYZ coordinate system in which the origin is set at the center of gravity of the earth, an axis passing through an intersection point between the Greenwich meridian and the equator and the origin is an X-axis, an axis passing through an intersection point between a meridian of 90 degrees east longitude and the equator and the origin is a Y-axis, and an axis passing through the north pole and the origin is a Z-axis.

[0057] The steering control unit 50b of the controller 50 operates the asphalt finisher 100 such that actual position coordinates of the predetermined point Q match one of position coordinates configuring the target trajectory TPS. Specifically, the steering control unit 50b derives the current position of the predetermined point Q at the central portion of the front screed 30 based on an output of the positioning device 51P. Then, in a case where the position of the predetermined point Q is positioned on the right side of the target trajectory TPS, the steering control unit 50b outputs a control command to the steering electromagnetic control valve configuring the steering device 53 and causes a predetermined amount of hydraulic oil to flow into a bottom-side oil chamber of the front wheel steering cylinder. As a result, the asphalt finisher 100 moves to the left while advancing, and the position of the predetermined point Q approaches the target trajectory TPS. On the contrary, in a case where the position of the predetermined point Q is positioned on the left side of the target trajectory TPS, the steering control unit 50b outputs a control command to the steering electromagnetic control valve configuring the steering device 53 and causes a predetermined amount of hydraulic oil to flow into a rod-side oil chamber of the front wheel steering cylinder. As a result, the asphalt finisher 100 moves to the right while advancing, and the position of the predetermined point Q approaches the target trajectory TPS. In the example, the front wheel steering cylinder is configured such that a left steering angle increases as the front wheel steering cylinder expands beyond a predetermined length and a right steering angle increases as the front wheel steering cylinder contracts below the predetermined length.

[0058] In this manner, the controller 50 can position the predetermined point Q, which is at a position of a point Qa at the first time point, at a point Qb at the second time point, at a point Qc at the third time point, at a point Qd at the fourth time point, and at a point Qe at the fifth time point.

[0059] In the example shown in Fig. 4, the left rear screed 31L is expanded and contracted to the left side such that a left end surface thereof matches the left boundary line LP of the road RD, and the right rear screed 31R is expanded and contracted to the right side such that a right end surface thereof matches the right boundary line RP of the road RD. Then, the left end surface of the left rear screed 31L moves to follow the left boundary line LP, and the right end surface of the right rear screed 31R moves to follow the right boundary line RP. For this reason, even in a case where the tractor 1 is advanced such that the predetermined point Q at the central portion of the front screed 30 follows the target trajectory TPS, the controller 50 can cause the width of the road RD and the width of the newly constructed pavement body NP to match each other. That is, even in a case where the tractor 1 is moved in a width direction of the road RD while being advanced, the controller 50 can cause the width of the road RD and the width of the newly constructed pavement body NP (the width of the screed 3) to match each other.

[0060] In the shown example, the controller 50 outputs a control command to the screed expanding and contracting device 54 such that the left end surface of the left rear screed 31L matches the left boundary line LP of the road RD and such that the right end surface of the right rear screed 31Rmatches the right boundary line RP of the road RD.

[0061] Specifically, the controller 50 is configured to output a control command to the screed expanding and contracting device 54 during traveling of the asphalt finisher 100 and to expand and contract the rear screed 31. For example, the controller 50 expands the left rear screed 31L to the left side in a case where there is a possibility in which the left end surface of the left rear screed 31L deviates to an inside of the road RD from the left boundary line LP. Alternatively, the controller 50 expands the right rear screed 31R to the right side in a case where there is a possibility in which the right end surface of the right rear screed 31R deviates to the inside of the road RD from the right boundary line RP.

[0062] In addition, in the example shown in Fig. 4, the controller 50 may control the steering of the asphalt finisher 100 and the expansion and contraction of the rear screed 31 when the asphalt finisher 100 travels the curve portion LC of the road RD, but may control the steering of the asphalt finisher 100 and the expansion and contraction of the rear screed 31 when the asphalt finisher 100 travels a linear portion SP of the road RD.

[0063] Next, another configuration example of the function of moving the asphalt finisher 100 along the target trajectory will be described with reference to Fig. 7. Fig. 7 is a top view of a construction site, which shows the asphalt finisher 100 passing through the linear portion SP1, the curve portion LC (left curve), and the linear portion SP2 of the road RD, which is a construction target, and corresponds to Fig. 4.

[0064]  In Fig. 7, the asphalt finisher 100a means the asphalt finisher 100 at the first time point when construction starts. The asphalt finisher 100b means the asphalt finisher 100 at the second time point after a predetermined time has elapsed from the first time point. Similarly, the asphalt finisher 100c means the asphalt finisher 100 at the third time point after a predetermined time has elapsed from the second time point, the asphalt finisher 100dmeans the asphalt finisher 100 at the fourth time point after a predetermined time has elapsed from the third time point, and the asphalt finisher 100e means the asphalt finisher 100 at the fifth time point after a predetermined time has elapsed from the fourth time point. For the sake of clarity, while Fig. 7 shows the tractor 1, the front screed 30, the left rear screed 31L, and the right rear screed 31R of the asphalt finisher 100 in a simplified manner, the hopper 2 is not shown.

[0065] The example shown in Fig. 7 is different from the example shown in Figs. 4 to 6, in which the target trajectory TPS to be followed by the predetermined point Q at the central portion of the front screed 30 is calculated, in that a target trajectory TPT to be followed by a predetermined point P at a front end central portion of the tractor 1 is calculated, but is the same as the example shown in Figs. 4 to 6 at other points.

[0066] The target calculation unit 50a of the controller 50 calculates the target trajectory TPT to be followed by the predetermined point P at the front end central portion of the tractor 1 at the first time point when construction starts. In the example shown in Fig. 7, the predetermined point P is represented by a circle, and the target trajectory TPT is represented by a two-dot chain line.

[0067] Specifically, the target calculation unit 50a derives the target trajectory TPS based on the left boundary line LP and the right boundary line RP of the road RD, which is a construction target, with reference to design data. The target trajectory TPS is a trajectory to be followed by the predetermined point Q calculated in the example shown in Figs. 4 to 6. In the example shown in Fig. 7, the predetermined point Q is represented by a triangle, and the target trajectory TPS is represented by a one-dot chain line. Then, the target calculation unit 50a calculates the target trajectory TPT to be followed by the predetermined point P based on known information, such as a distance between the rear wheel 5 and the front wheel 6 of the asphalt finisher 100, and the target trajectory TPS.

[0068] In the example shown in Fig. 7, all of the left boundary line LP, the right boundary line RP, and the center line CP of the road RD, the target trajectory TPT to be followed by the predetermined point P, and the target trajectory TPS to be followed by the predetermined point Q are derived as a one-dimensional array of multiple position coordinates. The position coordinates are, for example, coordinates in a reference coordinate system.

[0069] The steering control unit 50b of the controller 50 operates the asphalt finisher 100 such that actual position coordinates of the predetermined point P match one of position coordinates configuring the target trajectory TPT. Specifically, the steering control unit 50b derives the current position of the predetermined point P at the front end central portion of the tractor 1 based on an output of the positioning device 51P. Then, in a case where the position of the predetermined point P is positioned on the right side of the target trajectory TPT, the steering control unit 50b outputs a control command to the steering electromagnetic control valve configuring the steering device 53 and causes a predetermined amount of hydraulic oil to flow into the bottom-side oil chamber of the front wheel steering cylinder. As a result, the asphalt finisher 100 moves to the left while advancing, and the position of the predetermined point P approaches the target trajectory TPT. On the contrary, in a case where the position of the predetermined point P is positioned on the left side of the target trajectory TPT, the steering control unit 50b outputs a control command to the steering electromagnetic control valve configuring the steering device 53 and causes a predetermined amount of hydraulic oil 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 advancing, and the position of the predetermined point P approaches the target trajectory TPT.

[0070] In this manner, the controller 50 can position the predetermined point P, which is at a position of a point Pa at the first time point, at a point Pb at the second time point, at a point Pc at the third time point, at a point Pd at the fourth time point, and at a point Pe at the fifth time point. As a result, the controller 50 can position the predetermined point Q, which is at a position of the point Qa at the first time point, at the point Qb at the second time point, at the point Qc at the third time point, at the point Qd at the fourth time point, and at the point Qe at the fifth time point.

[0071] In the example shown in Fig. 7, the left rear screed 31L is expanded and contracted to the left side such that the left end surface thereof matches the left boundary line LP of the road RD, and the right rear screed 31R is expanded and contracted to the right side such that the right end surface thereof matches the right boundary line RP of the road RD. Then, the left end surface of the left rear screed 31L moves to follow the left boundary line LP, and the right end surface of the right rear screed 31R moves to follow the right boundary line RP. For this reason, even in a case where the tractor 1 is advanced such that the predetermined point P at the front end central portion of the tractor 1 follows the target trajectory TPT, the controller 50 can cause the width of the road RD and the width of the newly constructed pavement body NP to match each other. That is, even in a case where the tractor 1 is moved in the width direction of the road RD while being advanced, the controller 50 can cause the width of the road RD and the width of the newly constructed pavement body NP (the width of the screed 3) to match each other.

[0072] In the example shown in Fig. 7, the controller 50 outputs a control command to the screed expanding and contracting device 54 such that the left end surface of the left rear screed 31L matches the left boundary line LP of the road RD and such that the right end surface of the right rear screed 31R matches the right boundary line RP of the road RD.

[0073] Specifically, the controller 50 is configured to output a control command to the screed expanding and contracting device 54 during traveling of the asphalt finisher 100 and to expand and contract the rear screed 31. For example, the controller 50 expands the left rear screed 31L to the left side in a case where there is a possibility in which the left end surface of the left rear screed 31L deviates to the inside of the road RD from the left boundary line LP. Alternatively, the controller 50 expands the right rear screed 31R to the right side in a case where there is a possibility in which the right end surface of the right rear screed 31R deviates to the inside of the road RD from the right boundary line RP.

[0074] In addition, in the example shown in Fig. 7, the controller 50 may control the steering of the asphalt finisher 100 and the expansion and contraction of the rear screed 31 when the asphalt finisher 100 travels the curve portion LC of the road RD, but may control the steering of the asphalt finisher 100 and the expansion and contraction of the rear screed 31 when the asphalt finisher 100 travels the linear portion SP of the road RD.

[0075] As described above, the asphalt finisher 100 according to the embodiment of the present invention includes the tractor 1, the hopper 2 that is provided on the front side of the tractor 1 and that receives a paving material, the conveyor CV that feeds the paving material received by the hopper 2 to the rear side of the tractor 1, the screw SC that spreads the paving material fed by the conveyor CV on the rear side of the tractor 1, the screed 3 that levels the paving material spread by the screw SC on the rear side of the screw SC, and the controller 50 that is a control device.

[0076]  In addition, as shown in Fig. 4, the controller 50 may be configured to control the movement of the tractor 1 such that the target trajectory TPS is generated based on the line that bisects the area of the road surface leveled by the screed 3 right and left and the predetermined point Q at the central portion of the front screed 30, which is an example of the predetermined point of the asphalt finisher 100, follows the target trajectory TPS.

[0077] Alternatively, as shown in Fig. 7, the controller 50 may be configured to control the movement of the tractor 1 such that the target trajectory TPT is generated based on the line that bisects the area of the road surface leveled by the screed 3 right and left and the predetermined point P at the front end central portion of the tractor 1, which is another example of the predetermined point of the asphalt finisher 100, follows the target trajectory TPT. The road surface includes a road surface of the curve portion LC of the road RD, which is a construction target.

[0078] The configuration can enhance the quality of pavement of the curved road RD. This is because the surface area of the left portion LZ and the surface area of the right portion RZ can be made the same even in a case where the asphalt finisher 100 constructs the curve portion LC of the road RD, which is a construction target. Specifically, this is because a left holding amount of the left rear screed 31L and a right holding amount of the right rear screed 31R can be made the same and an effect of a difference between the left holding amount and the right holding amount on steering can be suppressed.

[0079] In addition, the predetermined point of the asphalt finisher 100 used when controlling the steering of the asphalt finisher 100 is desirably set to be positioned on the front-rear axis of the tractor 1 when viewed from above.

[0080] In addition, the predetermined point of the asphalt finisher 100 is more desirably set in front of the screed 3.

[0081] In addition, in the example shown in Fig. 4, the target trajectory TPS corresponding to a portion of the road RD which is curved to the left (curve portion LC) is set on the right side of the center line CP which is a line bisecting the road RD right and left. Similarly, in the example shown in Fig. 7, the target trajectory TPT corresponding to the curve portion LC is set on the right side of the center line CP. On the other hand, the target trajectory corresponding to a portion of the road RD which is curved to the right is set on the left side of the center line CP. The target trajectory corresponding to the linear portion of the road RD is typically set on the center line CP.

[0082] In addition, the asphalt finisher 100 is configured to expand and contract the screed 3 right and left in accordance with the width of the road RD when passing through the curve portion LC of the road RD. Specifically, the asphalt finisher 100 is configured to expand one of the left end and the right end of the screed 3 and to contract the other when passing through the curve portion LC of the road RD. In the example shown in Fig. 4 or 7, the asphalt finisher 100 expands the left rear screed 31L to the left and contracts the right rear screed 31R to the left when passing through the curve portion LC of the road RD.

[0083] In the configuration, even when the asphalt finisher 100 is moved in the width direction of the road RD while being advanced at the curve portion of the road RD, which is a construction target, the width of the screed 3 can be automatically adapted to the width of the road RD. For this reason, the configuration has an effect in which a burden of the operator of the asphalt finisher 100 can be reduced when paving the curve portion of the road RD, which is a construction target.

[0084] The preferable embodiment of the present invention has been described hereinbefore. However, the present invention is not limited to the embodiment described above. Various modifications, substitutions, or the like can be applied to the embodiment described above without departing from the scope of the present invention. In addition, each of characteristics described with reference to the embodiment described above may be combined as appropriate insofar as there is no technical inconsistency.

[0085] For example, although the steering device 53 is configured to expand and contract the front wheel steering cylinder provided close to the front axle in the embodiment described above, in a case where a hydraulic steering motor is adopted instead of the front wheel steering cylinder, the hydraulic steering motor maybe configured to be rotated. Inthiscase, the steering device 53 includes a steering electromagnetic control valve that controls the flow rate of a hydraulic oil flowing from the hydraulic pump to the hydraulic steering motor. The steering electromagnetic control valve is configured to be capable of controlling the inflow and outflow of the hydraulic oil in the hydraulic steering motor in accordance with the rotation of the steering wheel SH (handle), which is a manipulation device. In addition, the steering electromagnetic control valve is configured to be capable of controlling the inflow and outflow of the hydraulic oil in the hydraulic steering motor in accordance with a control command from the controller 50, regardless of the rotation of the steering wheel SH. 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 in accordance with a control command from the controller 50 by automatically rotating the steering wheel SH.

Brief Description of the Reference Symbols

[0086] 

1 tractor

1G guide rail

1S driver's seat

2 hopper

3 screed

3A leveling arm

3AL left leveling arm

3AR right leveling arm

5 rear wheel

6 front wheel

26 screed expanding and contracting 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 front monitoring device

51P positioning device

51PL left GNSS receiver

51PR right GNSS receiver

51S traveling speed sensor

51T communication device

52 vehicle-mounted display device

53 steering device

54 screed expanding and contracting device

100, 100a to 100e asphalt finisher

AP feature

BS roadbed

CP center line

CV conveyor

DS automatic steering system

LC curve portion

LP left boundary line

LZ left portion

NP newly constructed pavement body

PL pole

PV paving material

RD road

RL, RL1, RL2 reference line

RP right boundary line

RZ right portion

SC screw

SH steering wheel

SP, SP1, SP2 linear portion

TPS, TPT target trajectory

Claims

1. An asphalt finisher (100, 100a, 100b, 100c, 100d, 100e) comprising:

a tractor (1);

a hopper (2) that is provided on a front side of the tractor (1) and that receives a paving material (PV);

a conveyor (CV) that feeds the paving material (PV) received by the hopper (2) to a rear side of the tractor (1);

a screw (SC) that spreads the paving material (PV) fed by the conveyor (CV) on the rear side of the tractor (1);

a screed (3) that levels the paving material (PV) spread by the screw (SC) on a rear side of the screw (SC); and

a control device (50),

wherein the control device (50) is configured to control a movement of the tractor (1) such that a target trajectory (TPS, TPT) is generated based on a line which bisects an area of a road surface leveled by the screed (3) right and left and a predetermined point (Q, P) of the asphalt finisher (100, 100a, 100b, 100c, 100d, 100e) follows the target trajectory (TPS, TPT) , and

the road surface includes a road surface of a curve portion (LC) of a road (RD) which is a construction target.

2. The asphalt finisher (100, 100a, 100b, 100c, 100d, 100e) according to claim 1,
wherein the predetermined point (Q, P) is on a front-rear axis of the tractor (1) when viewed from above.

3. The asphalt finisher (100, 100a, 100b, 100c, 100d, 100e) according to claim 2,
wherein the predetermined point (Q, P) is set in front of the screed (3).

4. The asphalt finisher (100, 100a, 100b, 100c, 100d, 100e) according to any one of claims 1 to 3,

wherein the target trajectory (TPS, TPT) corresponding to a portion of the road (RD) curved to the right is set on a left side of a line that bisects the road (RD) right and left, and

the target trajectory (TPS, TPT) corresponding to a portion of the road (RD) curved to the left is set on a right side of the line that bisects the road (RD) right and left.

5. The asphalt finisher (100, 100a, 100b, 100c, 100d, 100e) according to any one of claims 1 to 3,
wherein the screed (3) is expanded and contracted right and left in accordance with a width of the road (RD) when passing through the curve portion (LC) of the road (RD).

6. The asphalt finisher (100, 100a, 100b, 100c, 100d, 100e) according to claim 5,
wherein one of a left end and a right end of the screed (3) is expanded and the other is contracted when passing through the curve portion (LC) of the road (RD).

Drawing