Asphalt finisher

Abstract

An asphalt finisher (100) comprises: a tractor (1); a hopper (2) installed on the front side of the tractor (1), the hopper receiving paving material; a conveyor (CV) that feeds the paving material inside the hopper (2) to the rear side of the tractor (1); a screw (SC) that spreads out the paving material fed by the conveyor (CV) on the rear side of the tractor; a screed (3) that evens the paving material spread out by the screw (SC) on the rear side of the screw (SC); an information acquisition device (51) that acquires information relating to a road to be constructed; and a controller (50) that controls the movement of the tractor (1) on the basis of a target position (Pf) or (Qf), or of a target trajectory (TPT) decided according to the information acquired by the information acquisition device (51) relating to the road to be constructed.

Description

Technical Field

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

Background Art

[0002] Conventionally, an asphalt finisher is known that includes a tractor, a hopper installed in front of the tractor for receiving paving material, a conveyor for feeding the paving material in the hopper to the rear side of the tractor, a screw for spreading the paving material fed by the conveyor at the rear side of the tractor, and a screed for leveling the paving material spread by the screw at the rear side of the screw (see Patent Document 1).

[0003] The operator of the asphalt finisher usually uses a guide bar (pointer bar) attached to the tractor to drive the asphalt finisher so that the end surface in the width direction of the paving body to be laid extends along the step in the road to be constructed. That is, the operator drives the asphalt finisher while maintaining a state in which the end surface in the width direction of the screed and the step surface formed by the step are substantially parallel. The step in the road to be constructed is, for example, a step between a curb and a roadbed, a step between an existing paving body and a roadbed, a step between a paving formwork and a roadbed, or a step formed when an old paving body is cut.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when the road to be constructed is curved, the driver cannot align the end face in the width direction of the paving body along the step only by using the guide bar. This is because the locus described by a predetermined point at the center of the screed located on the rear side of the tractor bulges outward of the curve without following the locus described by the predetermined point at the center of the tractor.

[0006] In view of the above, it is desirable to provide an asphalt finisher that can appropriately lay a paving body along the road to be constructed.

Means for Solving the Problem

[0007] The asphalt finisher according to an embodiment of the present invention includes a tractor, a hopper installed on the front side of the tractor for receiving a paving material, a conveyor for feeding the paving material in the hopper to the rear side of the tractor, a screw for spreading the paving material fed 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, an information acquisition device for acquiring information on the road to be constructed, and a control device for controlling the movement of the tractor based on a target trajectory determined by the information on the road to be constructed acquired by the information acquisition device. The control device calculates and sets the target trajectory, which is the trajectory that the steering reference point should follow, based on the distance in the front-rear direction between the steering reference point, which is a point pre-associated with the center of the tractor, and the screed, and the center line of the road followed by a predetermined point at the center of the screed, so that the center in the width direction of the road to be constructed coincides with the center in the width direction of the screed when constructing a curved portion of the road to be constructed. When constructing a curved section of a road to be constructed, the control device changes the steering angle so that the steering reference point follows the target trajectory. 。

Effect of the Invention

[0008] By the above means, an asphalt finisher that can appropriately lay a paving body along the road to be constructed is provided.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6A

Figure 6B

Mode for Carrying Out the Invention

[0010] 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 present embodiment, the asphalt finisher 100 is a wheel-type asphalt finisher and mainly includes a tractor 1, a hopper 2, and a screed 3. Hereinafter, the direction of the hopper 2 viewed from the tractor 1 (+X direction) is defined as the front, and the direction of the screed 3 viewed from the tractor 1 (-X direction) is defined as the rear.

[0011] The tractor 1 is a mechanism for moving the asphalt finisher 100. In the present embodiment, the tractor 1 rotates the rear wheels 5 using a hydraulic motor for rear-wheel travel and rotates the front wheels 6 using a hydraulic motor for front-wheel travel to move the asphalt finisher 100. The hydraulic motor for rear-wheel travel and the hydraulic motor for front-wheel travel are rotated by receiving the supply of hydraulic oil from a hydraulic pump. However, the front wheels 6 may be driven wheels.

[0012] The asphalt finisher 100 may be a crawler-type asphalt finisher. In this case, the combination of the rear wheels 5 and the front wheels 6 is replaced with a combination of a left crawler and a right crawler.

[0013] The controller 50 is a control device that controls the asphalt finisher 100. In the present embodiment, the controller 50 is composed of a microcomputer including a CPU, a volatile memory device, a non-volatile memory device, etc., 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.

[0014] The hopper 2 is a mechanism for receiving paving materials. In the present embodiment, the hopper 2 is installed on the front side of the tractor 1 and is configured to be opened and closed in the vehicle width direction (Y-axis direction) by a hopper cylinder. The asphalt finisher 100 usually receives paving materials (for example, an asphalt mixture) from the loading platform of a dump truck when the hopper 2 is in the fully open state. The dump truck is an example of a transport vehicle that transports paving materials. FIGS. 1 and 2 show the hopper 2 in the fully open state. When the paving materials in the hopper 2 decrease, the hopper 2 is closed, and the paving materials near the inner wall of the hopper 2 are collected at the central part of the hopper 2. This is to enable the conveyor CV at the central part of the hopper 2 to feed the paving materials to the rear side of the tractor 1. The paving materials fed to the rear side of the tractor 1 are spread in the vehicle width direction by the screw SC behind the tractor 1 and in front of the screed 3. In the present embodiment, the screw SC is in a state where extension screws are connected to the left and right. FIGS. 1 and 2 omit the illustration of the paving materials in the hopper 2, show the paving materials PV spread by the screw SC in a coarse dot pattern, and show the newly laid pavement NP leveled by the screed 3 in a fine dot pattern.

[0015] The screed 3 is a mechanism for leveling the paving material PV. In this embodiment, 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 expand and contract in the vehicle width direction, and includes a left rear screed 31L and a right rear screed 31R. However, the rear screed 31 may be a fixed-width screed connected to the left and right of the front screed 30. Further, the screed 3 is a floating screed 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 disposed on the left side of the tractor 1 and a right leveling arm 3AR disposed on the right side of the tractor 1.

[0016] A mold board 43 is attached to the front part of the screed 3. The mold board 43 is configured to be able to adjust the amount of the paving material PV staying in front of the screed 3. The paving material PV reaches under the screed 3 through the gap between the lower end of the mold board 43 and the roadbed BS.

[0017] An information acquisition device 51, an in-vehicle display device 52, and a steering device 53 are attached to the tractor 1.

[0018] The information acquisition device 51 is configured to acquire information about the road to be constructed and output the acquired information to the controller 50. The information about the road to be constructed includes, for example, the width of the road, the change in curvature in the relaxation section (clothoid section), and the curvature in the arc section. In this embodiment, 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.

[0019] The front monitoring device 51F is configured to monitor the front of the asphalt finisher 100. In this embodiment, the front monitoring device 51F is a LIDAR that monitors the monitoring range RF in front of the tractor 1 and is attached to the central part of the tractor 1. The central part of the tractor 1 is, for example, the central front part of the cover that covers the engine room behind the hopper 2. However, the front monitoring device 51F may be attached to other parts of the asphalt finisher 100 or may be composed of a plurality of LIDARs. When composed of a plurality of LIDARs, the front monitoring device 51F can simultaneously monitor a plurality of non-overlapping monitoring ranges. In this case, the plurality of LIDARs may include a right front LIDAR attached to the right front side of the front end of the tractor 1 and a left front LIDAR attached to the left front side of the front end of the tractor 1. Also, the LIDAR may be attached to the tractor 1 via a bracket or a pole or the like.

[0020] The rear monitoring device 51B is configured to monitor the rear of the asphalt finisher 100. In this embodiment, the rear monitoring device 51B is a LIDAR that monitors the monitoring range RB behind the screed 3 and is attached to the guide rail 1G that functions as a handrail. However, the rear monitoring device 51B may be attached to the lower part of the driver's seat 1S or may be attached to other parts of the asphalt finisher 100. Also, the rear monitoring device 51B may be composed of a plurality of LIDARs. When composed of a plurality of LIDARs, the rear monitoring device 51B can simultaneously monitor a plurality of non-overlapping monitoring ranges. In this case, the plurality of LIDARs may include a right rear LIDAR attached to the right rear side of the rear end of the tractor 1 and a left rear LIDAR attached to the left rear side of the rear end of the tractor 1. Also, the LIDAR may be attached to the tractor 1 via a bracket or a pole or the like.

[0021] The information acquisition device 51 may include a side monitoring device configured to be able 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 be attached, for example, to the left end of the upper surface of the tractor 1 in front of the rear wheels 5 as a LIDAR that monitors the monitoring range on the left side of the tractor 1. The right side monitoring device may be attached, for example, to the right end of the upper surface of the tractor 1 in front of the rear wheels 5 as a LIDAR that monitors the monitoring range on the right side of the tractor 1.

[0022] The LIDAR is configured to be able to measure, for example, the distances between a large number of 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 lidar, a laser scanner, a distance image camera, or a laser rangefinder, etc. The same applies to the side monitoring device.

[0023] The monitoring range RF of the front monitoring device 51F desirably includes the roadbed BS and the ground object AP outside the roadbed BS. This is to be able to obtain information regarding the width of the road to be constructed. The same applies to the monitoring range of the side monitoring device. In this embodiment, the monitoring range RF has a width larger than the width of the roadbed BS. The ground object AP is an L-shaped side ditch block. The ground object AP may be a paving formwork, a curb block, or an existing paved body, etc.

[0024] The monitoring range RB of the rear monitoring device 51B desirably includes the newly paved body NP and the ground object AP outside the newly paved body NP. This is to be able to obtain information regarding the width of the newly paved body NP. In this embodiment, the monitoring range RB has a width larger than the width of the newly paved body NP.

[0025] The traveling speed sensor 51S is configured to be able to detect the traveling speed of the asphalt finisher 100. In the present embodiment, the traveling speed sensor 51S is a wheel speed sensor and is configured to be able to detect the rotational angular velocity and rotational angle of the rear wheel 5, and thus the traveling speed and traveling distance of the asphalt finisher 100.

[0026] The positioning device 51P is configured to be able to measure the position of the asphalt finisher 100. In the present embodiment, the positioning device 51P is a GNSS compass and is configured to be able to measure the position and attitude of the asphalt finisher 100. The GNSS compass as the positioning device 51P includes a left GNSS receiver 51PL attached to 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 attached to the upper end of a pole PL (invisible) extending vertically upward from the rear end of the right leveling arm 3AR, as shown in FIGS. 1 and 2.

[0027] However, the positioning device 51P may be a total station. In this case, a reflection prism serving as a target of the total station is attached to the tip of the pole PL. The main body of the total station installed around the asphalt finisher 100 is connected to the controller 50 via wireless communication. That is, the main body of the total station transmits information regarding the derived position of the target to the controller 50.

[0028] The communication device 51T is configured to be able to control communication between the asphalt finisher 100 and devices outside the asphalt finisher 100. In the present embodiment, the communication device 51T is installed in front of the driver's seat 1S and is configured to be able to control communication via a mobile communication network, a short-range wireless communication network, a satellite communication network, or the like.

[0029] The information acquisition device 51 may include a steering angle sensor configured to detect the steering angle of the asphalt finisher 100, a paving width sensor configured to detect the expansion and contraction amount of the rear screed 31 and calculate the paving width, and the like.

[0030] Further, the information acquisition device 51 may include a monitoring device installed at the construction site or a monitoring device attached to a flying object flying over the asphalt finisher 100. The monitoring device installed at the construction site is, for example, a LIDAR, a monocular camera, or the like attached to the tip of a pole installed along the road to be constructed. The monitoring device attached to the flying object is, for example, a LIDAR, a monocular camera, or the like attached to a multicopter (drone) or a flying boat.

[0031] The in-vehicle display device 52 is configured to display information about the asphalt finisher 100. In the present embodiment, the in-vehicle display device 52 is a liquid crystal display installed in front of the driver's seat 1S. However, the in-vehicle display device 52 may be installed at at least one of the left and right ends of the screed 3.

[0032] The steering device 53 is configured to control the steering of the asphalt finisher 100. In the present embodiment, the steering device 53 is configured to expand and contract a front-wheel steering cylinder installed near the front axle. Specifically, the steering device 53 includes a steering electromagnetic control valve that controls the flow rate of the 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 control the inflow and outflow of the hydraulic oil in the front-wheel steering cylinder according to the rotation of the steering wheel SH (handle) as an operating device. Further, the steering electromagnetic control valve is configured to control the inflow and outflow of the hydraulic oil in the front-wheel steering cylinder according to 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 whether the driver operates the steering wheel SH.

[0033] When the asphalt finisher 100 is a crawler-type asphalt finisher, the steering device 53 is configured to be able 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 the hydraulic oil flowing from the hydraulic pump to the left traveling hydraulic motor for rotating the left crawler, and a right electromagnetic control valve that controls the flow rate of the hydraulic oil flowing from the hydraulic pump to the right traveling hydraulic motor for rotating the right crawler. The left electromagnetic control valve is configured to be able to control the inflow and outflow of the hydraulic oil in the left traveling hydraulic motor according to the operation amount (tilt angle) of the left operation lever which is an operating device for operating the left crawler. Also, the left electromagnetic control valve is configured to be able to control the inflow and outflow of the hydraulic oil in the left traveling hydraulic motor according to the control command from the controller 50, regardless of whether the left operation lever is operated by the driver. Similarly, the right electromagnetic control valve is configured to be able to control the inflow and outflow of the hydraulic oil in the right traveling hydraulic motor according to the operation amount (tilt angle) of the right operation lever which is an operating device for operating the right crawler. Also, the right electromagnetic control valve is configured to be able to control the inflow and outflow of the hydraulic oil in the right traveling hydraulic motor according to the control command from the controller 50, regardless of whether the right operation lever is operated by the driver.

[0034] Next, referring to FIG. 3, a configuration example of the automatic steering system DS mounted on the asphalt finisher 100 will be described. FIG. 3 is a block diagram showing a configuration example of the automatic steering system DS.

[0035] The automatic steering system DS mainly includes a controller 50, a front monitoring device 51F, a rear monitoring device 51B, a traveling speed sensor 51S, a positioning device 51P, a communication device 51T, an in-vehicle display device 52, and a steering device 53, etc.

[0036] In the example shown in FIG. 3, the controller 50 includes a target calculation unit 50a, a steering control unit 50b, and a display control unit 50c as functional blocks.

[0037] The target calculation unit 50a is configured to calculate a target to be used by the steering control unit 50b. The target to be used by the steering control unit 50b is, for example, a target trajectory as the trajectory that a predetermined point on the asphalt finisher 100 should follow. The predetermined point is a point that is pre-associated with a predetermined part of the asphalt finisher 100 and is also referred to as a steering reference point or a control reference point. However, the predetermined point may be a point that is dynamically associated with a predetermined part of the asphalt finisher 100. Strictly speaking, the target trajectory is a one-dimensional array of a large number of target positions. The target position is a point that the predetermined point on the asphalt finisher 100 should reach. Alternatively, the target to be used by the steering control unit 50b may be a target position as the point 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, several tens of milliseconds, several hundreds of milliseconds, or several seconds.

[0038] In the present embodiment, the target calculation unit 50a calculates, for example, a target trajectory that a predetermined point in the central part of the tractor 1 should follow based on information about the road to be constructed, such as construction design data. In this case, the target trajectory is typically calculated before the running of the asphalt finisher 100 is started. Therefore, the target trajectory may be calculated by a server or the like installed in a management center outside the asphalt finisher 100 and then transmitted to the controller 50 via communication. Note that the predetermined point may be a point set at the center of the front end of the hopper 2 instead of a point set in the central part of the tractor 1. Further, in the case of a wheel-type asphalt finisher, the predetermined point may be a point set at the position of the left front wheel, a point set at the position of the right front wheel, or a point set at the center of the front wheel axle.

[0039] The target calculation unit 50a may calculate a target position as the point to be reached by a predetermined point at the center of the tractor 1 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 traveling. For example, the target calculation unit 50a may calculate, as the target position, the center point in the width direction of the road to be constructed, which is located a predetermined distance ahead of the current position of the predetermined point at the center of the tractor 1, based on the 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 the construction design data. However, the target calculation unit 50a may calculate the target position based on the construction design data and the information acquired by the front monitoring device 51F. For example, the target calculation unit 50a may correct the target position calculated based on the construction design data based on the information acquired by the front monitoring device 51F. Further, the target calculation unit 50a may utilize the information acquired by the rear monitoring device 51B.

[0040] The steering control unit 50b is configured to be able to automatically control the steering of the asphalt finisher 100 regardless of the operation on the operation device.

[0041] In the present embodiment, the steering control unit 50b outputs a control command to the steering device 53 so that the target trajectory calculated by the target calculation unit 50a is followed by a predetermined point at the center of the tractor 1. Specifically, the steering control unit 50b derives the current position of the predetermined point at the center of the tractor 1 based on the output of the positioning device 51P. Then, when it is determined that the predetermined point has deviated 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, when it is determined that the predetermined point has deviated 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.

[0042] Alternatively, the steering control unit 50b may output a control command to the steering device 53 so as to position a predetermined point in the central portion of the tractor 1 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 central portion of the tractor 1 based on the output of the positioning device 51P, or may derive the current position of the predetermined point in the central portion of the tractor 1 based on the output of at least one of the rear monitoring device 51B and the front monitoring device 51F. In the latter case, the positioning device 51P may be omitted.

[0043] Next, with reference to FIG. 4, a function of moving the asphalt finisher 100 along the target trajectory will be described. FIG. 4 is a top view of a construction site showing the asphalt finisher 100 passing through a curved portion (left curve) of a road RD to be constructed. In FIG. 4, the asphalt finisher 100a indicates the asphalt finisher 100 at the first point in time when construction starts. The asphalt finisher 100b indicates the asphalt finisher 100 at the second point in time after a predetermined time has elapsed from the first point in time. Similarly, the asphalt finisher 100c indicates the asphalt finisher 100 at the third point in time after a predetermined time has elapsed from the second point in time, the asphalt finisher 100d indicates the asphalt finisher 100 at the fourth point in time after a predetermined time has elapsed from the third point in time, and the asphalt finisher 100e indicates the asphalt finisher 100 at the fifth point in time after a predetermined time has elapsed from the fourth point in time. Note that FIG. 4 simplifies and shows the tractor 1, the front screed 30, the left rear screed 31L, and the right rear screed 31R of the asphalt finisher 100 for clarity, while omitting the illustration of the hopper 2.

[0044] At the first point in time when construction starts, the target calculation unit 50a of the controller 50 calculates the target trajectory TPT that the predetermined point P at the center of the tractor 1 should follow. In the example shown in FIG. 4, the predetermined point P is represented by "○", and the target trajectory TPT is represented by a dashed-dotted line. The target calculation unit 50a refers to the construction design data and derives the center line CP of the road RD based on the left boundary line LP and the right boundary line RP of the road RD to be constructed. Then, the target calculation unit 50a sets the center line CP as the target trajectory TPS that the predetermined point Q at the center of the front screed 30 should follow. In the example shown in FIG. 4, the predetermined point Q is represented by "△", and the target trajectory TPS is represented by a broken line. Then, based on known information such as the distance between the rear wheel 5 and the front wheel 6 of the asphalt finisher 100 and the target trajectory TPS, the target calculation unit 50a calculates the target trajectory TPT that the predetermined point P should follow.

[0045] In the example shown in FIG. 4, the left boundary line LP, the right boundary line RP, the center line CP of the road RD, the target trajectory TPT that the predetermined point P should follow, and the target trajectory TPS that the predetermined point Q should follow are all derived as one-dimensional arrays of a number of position coordinates. The position coordinates are, for example, coordinates in a reference coordinate system.

[0046] The reference coordinate system is, for example, the World Geodetic System. The World Geodetic System is a three-dimensional orthogonal XYZ coordinate system with the origin at the center of gravity of the earth, the X-axis passing through the intersection of the Greenwich meridian and the equator and the origin, the Y-axis passing through the intersection of the meridian at 90 degrees east longitude and the equator and the origin, and the Z-axis passing through the North Pole and the origin.

[0047] After that, the steering control unit 50b of the controller 50 operates the asphalt finisher 100 so that the actual position coordinates of the predetermined point P match 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 tractor 1 based on the output of the positioning device 51P. When the position of the predetermined point P is located on the right side of the target trajectory TPT, the steering control unit 50b outputs a control command to the steering electromagnetic control valve that constitutes 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 moving forward, and the position of the predetermined point P approaches the target trajectory TPT. Conversely, when the position of the predetermined point P is located on the left side of the target trajectory TPT, the steering control unit 50b outputs a control command to the steering electromagnetic control valve that constitutes 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 moving forward, and the position of the predetermined point P approaches the target trajectory TPT. 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 the predetermined length.

[0048] In this way, the controller 50 can position the 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 the 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.

[0049] In the example shown in FIG. 4, the left rear screed 31L extends to the left such that its left end face coincides with the left boundary line LP of the road RD, and the right rear screed 31R extends to the right such that its right end face coincides with the right boundary line RP of the road RD. Then, 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, the controller 50 can match the width of the road RD with the width of the newly paved body NP by advancing the tractor 1 so that a predetermined point P at the center of the tractor 1 follows the target trajectory TPT.

[0050] The controller 50 may expand and contract the rear screed 31 during the travel of the asphalt finisher 100. For example, when there is a possibility that the left end face of the left rear screed 31L may deviate inward from the left boundary line LP of the road RD, the controller 50 may extend the left rear screed 31L to the left. Alternatively, when there is a possibility that the right end face of the right rear screed 31R may deviate inward from the right boundary line RP of the road RD, the controller 50 may extend the right rear screed 31R to the right.

[0051] Also, in the example shown in FIG. 4, the steering control unit 50b controls the steering of the asphalt finisher 100 when the asphalt finisher 100 is traveling on a curved portion of the road RD, but may also control the steering of the asphalt finisher 100 when the asphalt finisher 100 is traveling on a straight portion of the road RD.

[0052] Next, referring to FIG. 5, a function of moving the asphalt finisher 100 while determining the target position in real time will be described. FIG. 5 is a top view of a construction site showing the asphalt finisher 100 passing through a curved portion of a road RD to be constructed. For clarity, FIG. 5 simplifies and 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 the same manner as FIG. 4, while omitting the illustration of the hopper 2.

[0053] In the example shown in FIG. 5, the target calculation unit 50a of the controller 50 derives the center line CP of the road RD to be constructed based on the information acquired by the front monitoring device 51F. In the example shown in FIG. 5, the center line CP is represented by a dotted line. Specifically, the target calculation unit 50a derives the left boundary line LP and the right boundary line RP of the road RD based on the information acquired by the front monitoring device 51F, and derives the center line CP of the road RD based on the left boundary line LP and the right boundary line RP. The information acquired by the front monitoring device 51F is, for example, the position and orientation of the step between the curb block and the roadbed BS. Further, the target calculation unit 50a derives the current position Pn of the predetermined point P at the center of the tractor 1 and the current position Qn of the predetermined point Q at the center of the front screed 30. Specifically, the target calculation unit 50a derives the current position Pn of the predetermined point P and the current position Qn of the predetermined point Q based on the output of the positioning device 51P. In the example shown in FIG. 5, the predetermined point P is represented by "○", and the predetermined point Q is represented by "△".

[0054] Then, the target calculation unit 50a calculates the target position Pf as the point that the predetermined point P should reach after a predetermined time has elapsed. Specifically, the target calculation unit 50a calculates the target position Qf as the point that the predetermined point Q should reach after a predetermined time has elapsed based on the construction design data and the current position Pn of the predetermined point P, and calculates the target position Pf based on known information such as the distance between the rear wheels 5 and the front wheels 6 of the asphalt finisher 100 and the target position Qf. Both the target position Pf and the target position Qf are derived as position coordinates. The position coordinates are, for example, coordinates in a reference coordinate system. In the example shown in FIG. 5, the target position Pf is represented by "○" shown by a dotted line, and the target position Qf is represented by "△" shown by a dotted line.

[0055] After that, the steering control unit 50b of the controller 50 operates the asphalt finisher 100 so that the position coordinates of the predetermined point P coincide with the position coordinates of the target position Pf. For example, the steering control unit 50b derives the central axis AX of the asphalt finisher 100 based on the output of the positioning device 51P. When the target position Pf is located on the left side of the central axis AX, the steering control unit 50b outputs a control command to the steering electromagnetic control valve that constitutes 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 moving forward, and the position of the predetermined point P approaches the target position Pf. Conversely, when the target position Pf is located on the right side of the central axis AX, the steering control unit 50b outputs a control command to the steering electromagnetic control valve that constitutes 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 moving forward, and the position of the predetermined point P approaches the target position Pf. 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 the predetermined length.

[0056] In this way, the controller 50 can position the predetermined point P at the target position Pf. As a result, the controller 50 can position the predetermined point Q at the target position Qf.

[0057] The steering control unit 50b may operate the asphalt finisher 100 so that the position coordinates of the predetermined point Q coincide with the position coordinates of the target position Qf. Alternatively, the steering control unit 50b may operate the asphalt finisher 100 so that the predetermined point Q approaches the center line CP of the road RD. In this case, the steering control unit 50b determines whether the predetermined point Q is on the center line CP of the road RD, on the right side of the center line CP, or on the left side of the center line CP at each predetermined control cycle. Then, when it is determined that the point is on the right side, the steering control unit 50b moves the asphalt finisher 100 to the left, and when it is determined that the point is on the right side, the steering control unit 50b moves the asphalt finisher 100 to the right.

[0058] In the example shown in FIG. 5, the left rear screen 31L extends to the left such that its left end face coincides with the left boundary line LP of the road RD, and the right rear screen 31R extends to the right such that its right end face coincides with the right boundary line RP of the road RD. Then, the left end face of the left rear screen 31L moves along the left boundary line LP, and the right end face of the right rear screen 31R moves along the right boundary line RP. Therefore, the controller 50 can make the width of the road RD coincide with the width of the newly paved body NP by advancing the tractor 1 so that a predetermined point P at the center of the tractor 1 follows the target position Pf calculated for each predetermined control cycle.

[0059] The controller 50 may expand and contract the rear screen 31 during the travel of the asphalt finisher 100. For example, when there is a possibility that the left end face of the left rear screen 31L may deviate inward from the left boundary line LP of the road RD, the controller 50 may expand the left rear screen 31L to the left. Alternatively, when there is a possibility that the right end face of the right rear screen 31R may deviate inward from the right boundary line RP of the road RD, the controller 50 may expand the right rear screen 31R to the right.

[0060] Also, in the example shown in FIG. 5, the steering control unit 50b controls the steering of the asphalt finisher 100 when the asphalt finisher 100 is traveling on a curved portion of the road RD, but may also control the steering of the asphalt finisher 100 when the asphalt finisher 100 is traveling on a straight portion of the road RD.

[0061] Next, with reference to FIGS. 6A and 6B, the effect of automatically controlling the movement of the asphalt finisher 100 by the steering device 53 will be described. FIGS. 6A and 6B are top views of the construction site showing the asphalt finisher 100 passing through a curved portion of the road RD to be constructed. Specifically, FIG. 6A shows the movement of the asphalt finisher 100 when automatic steering by the steering device 53 is performed. FIG. 6B shows the movement of the asphalt finisher 100 when manual steering is performed so that a predetermined point P at the center of the tractor 1 follows the center line CP of the road RD. In the examples shown in FIGS. 6A and 6B, the predetermined point P at the center of the tractor 1 is represented by "○", and the predetermined point Q at the center of the front screed 30 is represented by "△".

[0062] As shown in FIG. 6B, when manual steering is performed so that the predetermined point P follows the center line CP of the road RD, the predetermined point Q at the center of the front screed 30 follows a locus PS indicated by a two-dot chain line. That is, when the asphalt finisher 100 passes through the curved portion of the road RD, the distance between the front end of the right side surface of the tractor 1 and the right boundary line RP of the road RD changes in a state substantially equal to the distance between the front end of the left side surface of the tractor 1 and the left boundary line LP of the road RD. However, the distance between the front end of the right side surface of the front screed 30 and the right boundary line RP of the road RD changes in a state smaller than the distance between the front end of the left side surface of the front screed 30 and the left boundary line LP of the road RD. Therefore, the paving material is not laid in the area inside the curved portion of the road RD indicated by the dot pattern. On the contrary, the paving material protrudes from the right boundary line RP of the road RD and is laid in the area outside the curved portion of the road RD indicated by the cross pattern.

[0063] Thus, even if the driver of the asphalt finisher 100 moves the asphalt finisher 100 so that the tractor 1 is positioned at the center in the width direction of the road RD when the asphalt finisher 100 passes through the curved portion of the road RD, the screed 3 cannot be positioned at the center in the width direction of the road RD.

[0064] On the other hand, as shown in FIGS. 4 and 6A, when the movement of the asphalt finisher 100 is automatically controlled by the steering device 53 so that a predetermined point P follows the target trajectory TPT, a predetermined point Q at the center of the front screed 30 follows the center line CP of the road RD indicated by the broken line. That is, when the asphalt finisher 100 passes through the curved portion of the road RD, the distance between the front end of the right side surface of the tractor 1 and the right boundary line RP of the road RD changes in a state smaller than the distance between the front end of the left side surface of the tractor 1 and the left boundary line LP of the road RD. However, the distance between the front end of the right side surface of the front screed 30 and the right boundary line RP of the road RD changes in a state substantially equal to the distance between the front end of the left side surface of the front screed 30 and the left boundary line LP of the road RD. Therefore, the paving material is surely laid also in the area inside the curved portion of the road RD, and the paving material does not protrude from the right boundary line RP of the road RD. That is, the asphalt finisher 100 can match the width of the road RD to be constructed and the width of the newly paved body NP even in the curved portion of the road RD.

[0065] As described above, when the asphalt finisher 100 passes through the curved portion of the road RD, the controller 50 can position the screed 3 at the center in the width direction of the road RD in order to move the asphalt finisher 100 so that the tractor 1 approaches the end in the width direction of the road RD.

[0066] As described above, the asphalt finisher 100 according to the embodiment of the present invention includes a tractor 1, a hopper 2 installed in front of the tractor 1 to receive a paving material, a conveyor CV that feeds the paving material in the hopper 2 to the rear side of the tractor 1, a screw SC that spreads the paving material fed by the conveyor CV at the rear side of the tractor 1, a screed 3 that levels the paving material spread by the screw SC at the rear side of the screw SC, an information acquisition device 51 that acquires information on the road to be constructed, and a controller 50 as a control device that controls the movement of the tractor 1 based on the target trajectory TPT or the target position Pf or Qf determined by the information on the road to be constructed acquired by the information acquisition device 51.

[0067] With this configuration, the asphalt finisher 100 can appropriately lay the paving along the road RD to be constructed.

[0068] As shown in FIG. 4 or FIG. 5, when the road RD to be constructed curves to the left, the controller 50 may be configured to set the target trajectory TPT or the target position Pf outside (right side) the center (center line CP) of the road RD to be constructed at the curved portion of the road RD to be constructed. Note that the target trajectory TPT is, for example, the target trajectory that a predetermined point P at the center of the tractor 1 should follow, and the target position Pf is the point that the predetermined point P should reach after a predetermined time has elapsed.

[0069] The controller 50 may be configured to set the target trajectory TPT or the target position Pf so that the center in the width direction of the road RD to be constructed coincides with the center in the width direction of the screed 3. For example, as shown in FIG. 4, the target calculation unit 50a of the controller 50 may be configured to set the target trajectory TPT or the target position Pf so that the trajectory drawn by a predetermined point Q at the center of the front screed 30 coincides with the center line CP of the road RD.

[0070] With this configuration, the controller 50 can match the width of the road RD and the width of the newly installed paving NP even when the asphalt finisher 100 passes not only through the straight portion but also through the curved portion of the road RD.

[0071] The controller 50 may be configured to set the target trajectory TPT or the target position Pf such that at least one of the both end portions of the screed 3 coincides with a ground feature. For example, as shown in FIG. 4, the target calculation unit 50a of the controller 50 may set the target trajectory TPT or the target position Pf such that the left end portion of the screed 3 coincides with the left boundary line LP of the road RD and the right end portion of the screed 3 coincides with the right boundary line RP of the road RD. Alternatively, the target calculation unit 50a of the controller 50 may set the target trajectory TPT or the target position Pf such that the left end portion of the screed 3 coincides with the left boundary line LP of the road RD. Alternatively, the target calculation unit 50a of the controller 50 may set the target trajectory TPT or the target position Pf such that the right end portion of the screed 3 coincides with the right boundary line RP of the road RD.

[0072] Further, the controller 50 may be configured to set the target trajectory TPT or the target position Pf based on the distance in the longitudinal direction between a predetermined point P as a steering reference point and the screed 3. For example, the controller 50 may be configured to set the target trajectory TPT or the target position Pf based on the distance in the longitudinal direction between the predetermined point P and a predetermined point Q at the center of the front screed 30.

[0073] Further, the controller 50 may be configured to set the target trajectory TPS or the target position Qf based on the distance in the longitudinal direction between a predetermined point P as a steering reference point and the screed 3. For example, the controller 50 may be configured to set the target trajectory TPS or the target position Qf based on the distance in the longitudinal direction between the predetermined point P and a predetermined point Q at the center of the front screed 30. Note that the target trajectory TPS is, for example, the target trajectory that the predetermined point Q at the center of the front screed 30 should follow, and the target position Qf is the point that the predetermined point Q should reach after a predetermined time has elapsed.

[0074] In the case of a wheeled asphalt finisher, the controller 50 may be configured to control the movement of the tractor 1 by controlling the steering angle of the front wheels 6, and in the case of a crawler-type asphalt finisher, the controller 50 may be configured to control the movement of the tractor 1 by individually controlling the rotational speeds of the left and right crawlers.

[0075] With this configuration, the controller 50 can appropriately lay the paving material along the road RD to be constructed by automatically controlling the movement of the asphalt finisher 100 regardless of whether the asphalt finisher 100 is a wheeled asphalt finisher or a crawler-type asphalt finisher.

[0076] The controller 50 may be configured to control the movement of the tractor 1 so that the asphalt finisher 100 moves along a preset target trajectory TPT. Specifically, the controller 50 may be configured to control the movement of the tractor 1 so that the asphalt finisher 100 moves along the target trajectory TPT set before the travel of the asphalt finisher 100 is started. However, the controller 50 may be configured to control the movement of the tractor 1 so that the asphalt finisher 100 moves along the target trajectory TPT calculated in real time.

[0077] With this configuration, the controller 50 can easily and surely control the movement of the tractor 1 appropriately.

[0078] The information acquisition device 51 may be an imaging device or a communication device 51T. The imaging device may be a LIDAR, a monocular camera, a stereo camera, a distance image camera, or the like.

[0079] The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments. Various modifications, substitutions, etc. can be applied to the above-described embodiments without departing from the scope of the present invention. Also, each of the features described with reference to the above embodiments may be appropriately combined as long as there is no technical contradiction.

[0080] For example, in the above-described embodiment, the steering device 53 is configured to expand and contract a front-wheel steering cylinder installed near the front axle. However, when a hydraulic steering motor is employed instead of the front-wheel steering cylinder, it 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 the hydraulic oil flowing from the hydraulic pump to the hydraulic steering motor. The steering electromagnetic control valve is configured to control the inflow and outflow of the hydraulic oil in the hydraulic steering motor according to the rotation of the steering wheel SH (handle) as an operating device. Also, the steering electromagnetic control valve is configured to control the inflow and outflow of the hydraulic oil in the hydraulic steering motor independently of the rotation of the steering wheel SH according 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 according to a control command from the controller 50.

[0081] This application claims priority based on Japanese Patent Application No. 2020-056662 filed on March 26, 2020, and the entire contents of this Japanese patent application are incorporated herein by reference.

Description of Reference Numerals

[0082] 1 ··· Tractor 1G ··· Guide rail 1S ··· Driver's seat 2 ··· Hopper 3 ··· Screed 3A ··· Levelling arm 3AL ··· Left levelling arm 3AR ··· Right levelling arm 5 ··· Rear wheel 6 ··· Front wheel 30 ··· Front screed 31 ··· Rear screed 43 ··· Moldboard 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 ··· Travel speed sensor 51T ··· Communication device 52 ··· In-vehicle display device 53 ··· Steering device 100 ··· Asphalt finisher AP ··· Ground feature BS ··· Roadbed CV ··· Conveyor DS ··· Automatic steering system NP ··· Newly constructed pavement PL ··· Pole PV ··· Paving material SC ··· Screw SH ··· Steering wheel

Claims

1. A tractor, a hopper installed on the front side of the tractor for receiving paving materials, a conveyor for feeding the paving materials in the hopper to the rear side of the tractor, a screw for spreading the paving materials fed by the conveyor at the rear side of the tractor, a screed for leveling the paving materials spread by the screw at the rear side of the screw, an information acquisition device for acquiring information about a road to be constructed, and a control device for controlling the movement of the tractor based on a target trajectory determined by the information about the road to be constructed acquired by the information acquisition device, wherein when constructing a curved portion of a road to be constructed, the control device calculates and sets the target trajectory, which is the trajectory that a steering reference point, which is a point pre-associated with the central portion of the tractor, should follow, based on the distance in the front-rear direction between the steering reference point and the screed so that the center in the width direction of the road to be constructed coincides with the center in the width direction of the screed, and the center line of the road followed by a predetermined point at the central portion of the screed, and when constructing a curved portion of a road to be constructed, the control device changes the steering angle so that the steering reference point follows the target trajectory, an asphalt finisher.

2. When constructing a curved portion of a road to be constructed, the control device sets the target trajectory outside the center of the road to be constructed, The asphalt finisher according to Claim 1.

3. The target trajectory is a collection of data in which position coordinates as a number of target positions are arranged continuously, The asphalt finisher according to Claim 1.

4. The control device sets the target trajectory so that at least one of both end portions of the screed coincides with a feature forming a boundary line of a road to be constructed, The asphalt finisher according to Claim 1.

5. When the control device is for a wheel-type asphalt finisher, it controls the movement of the tractor by controlling the steering angle of the front wheels, and when it is for a crawler-type asphalt finisher, it controls the movement of the tractor by individually controlling the rotational speeds of the left crawler and the right crawler, The asphalt finisher according to Claim 1.

6. The control device controls the movement of the tractor so that the asphalt finisher moves along the preset target trajectory, The asphalt finisher according to Claim 1.

7. The information acquisition device is an imaging device or a communication device. The asphalt finisher according to claim 1.

Images