JP7793883B2 - Road machinery - Google Patents

Description

This disclosure relates to road machinery.

Conventionally, an asphalt finisher is known that uses a semiconductor laser projector and a CCD camera attached to the end of the screed to detect the boundary line of the road to be paved, and then extends or retracts the screed to match that boundary line (see Patent Document 1).

This asphalt finisher is configured to extend and retract the screed so that the gap between the end of the screed and the boundary line in the vehicle width direction becomes smaller.

Japanese Patent Application Publication No. 6-294105

However, Patent Document 1 does not mention how to control the expansion and contraction of the screed when laying paving material on curved sections of a road.

Therefore, it is desirable to provide road machinery such as an asphalt finisher that can appropriately control the expansion and contraction of the screed when laying paving material on curved sections of a road.

A road machine according to an embodiment of the present disclosure comprises a tractor, a hopper installed in front of the tractor to receive paving material, a conveyor that feeds the paving material in the hopper to the rear of the tractor, a screw that spreads the paving material fed by the conveyor behind the tractor, a screed that can extend and retract in the vehicle width direction and spreads the paving material spread by the screw behind the screw, and a control device that controls the extension and retraction of the screed, wherein the control device is configured to be able to switch between a first mode in which the extension and retraction of the screed is controlled when the height of a feature that defines the boundary line of a construction area located in front of the screed is higher than the height of the paving material to be spread by the screed, and a second mode in which the extension and retraction of the screed is controlled based on the coordinates of the boundary line in a predetermined coordinate system calculated based on information about the feature .

The above-mentioned road machine can properly control the expansion and contraction of the screed when laying paving material on curved sections of the road.

FIG. 2 is a side view of the asphalt finisher. FIG. 2 is a top view of the asphalt finisher. FIG. 1 is a diagram illustrating an example of the configuration of an operation support system. FIG. 2 is a schematic perspective view of a paving formwork. 10 is a flowchart showing an example of the flow of a goal setting process. 10 is a flowchart illustrating an example of the flow of a control mode selection process. 10A and 10B are top and cross-sectional views of a new pavement being laid by the gradually contracting left rear screed in underlay mode. FIG. 10 is a top view of new pavement being laid by the gradually extending left rear screed in underlayer mode. 10A and 10B are top and cross-sectional views of a new pavement being laid by the left rear screed gradually contracting in surface mode. FIG. 10 is a top view of a new pavement being laid by the gradually extending left rear screed in surface mode.

Figure 1 is a side view of an asphalt finisher 100, which is an example of road machinery according to an embodiment of the present disclosure. Figure 2 is a top view of the asphalt finisher 100. In the illustrated example, the asphalt finisher 100 is a wheel-type asphalt finisher, and is mainly composed of a tractor 1, a hopper 2, and a screed 3. In the following, the direction of the hopper 2 as seen from the tractor 1 (+X direction) is defined as the front, and the direction of the screed 3 as seen from the tractor 1 (-X direction) is defined as the rear.

The tractor 1 is a mechanism for moving the asphalt finisher 100. In the illustrated example, the tractor 1 rotates the rear wheels 5 using a rear-wheel drive hydraulic motor and rotates the front wheels 6 using a front-wheel drive hydraulic motor to move the asphalt finisher 100. The rear-wheel drive hydraulic motor and the front-wheel drive hydraulic motor are rotated by receiving hydraulic oil from a hydraulic pump. However, the front wheels 6 may be driven wheels.

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

The hopper 2 is a mechanism for receiving the paving material PV. In the illustrated example, the hopper 2 is installed in front of the tractor 1 and is configured to be able to open and close in the vehicle width direction (Y-axis direction) using a hopper cylinder. The asphalt finisher 100 typically receives the paving material PV (e.g., asphalt mixture) from the bed of a dump truck when the hopper 2 is fully open. A dump truck is an example of a transport vehicle that transports the paving material PV. Figures 1 and 2 show the hopper 2 in a fully open state. When the paving material PV in the hopper 2 decreases during construction, the operator of the asphalt finisher 100 closes the hopper 2 to collect the paving material PV that was near the inner wall of the hopper 2 in the center of the hopper 2. This is so that the conveyor CV in the center of the hopper 2 can feed the paving material PV to the rear of the tractor 1. The paving material PV fed to the rear of the tractor 1 by the conveyor CV is spread across the width of the vehicle by the screw SC behind the tractor 1 and in front of the screed 3. In the illustrated example, the screw SC is connected to the left extension screw SCL and the right extension screw SCR. For clarity, the paving material PV in the hopper 2 is not shown in Figures 1 and 2; the paving material PV spread by the screw SC is shown with a coarse dot pattern, and the new pavement NP laid and leveled by the screed 3 is shown with a fine dot pattern.

The screed 3 is a mechanism for spreading and leveling the paving material PV. In the illustrated example, the screed 3 includes a front screed 30 and a rear screed 31. The front screed 30 includes a left front screed 30L and a right front screed 30R. The rear screed 31 is a screed that can be extended and retracted in the vehicle width direction and includes a left rear screed 31L and a right rear screed 31R. Specifically, the rear screed 31 is extended and retracted by a screed telescopic cylinder 7 installed within the screed 3. More specifically, the screed telescopic cylinder 7 includes a left screed telescopic cylinder 7L and a right screed telescopic cylinder 7R. The left rear screed 31L is extended and retracted by the left screed telescopic cylinder 7L, and the right rear screed 31R is extended and retracted by the right screed telescopic cylinder 7R.

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 located on the left side of the tractor 1 and a right leveling arm 3AR located on the right side of the tractor 1. An end leveling device may be located at the end of the rear screed 31.

A side plate 41 is attached to the distal end of the rear screed 31. In the illustrated example, a left side plate 41L is attached to the left end of the left rear screed 31L, and a right side plate 41R is attached to the right end of the right rear screed 31R.

Footboards 32 are attached to the rear of the screed 3. Specifically, the footboards 32 are attached to the rear of the screed 3 so that workers can move back and forth in the vehicle width direction behind the screed 3 without stepping on the new pavement NP. In the illustrated example, the footboards 32 include a central footboard 32C attached to the rear of the front screed 30, a left footboard 32L attached to the rear of the left rear screed 31L, and a right footboard 32R attached to the rear of the right rear screed 31R.

A moldboard 42 is attached to the front of the screed 3. The moldboard 42 is configured to adjust the amount of paving material PV retained in front of the screed 3. The paving material PV passes through the gap between the lower end of the moldboard 42 and the roadbed BS and reaches underneath the screed 3. In the illustrated example, the moldboard 42 includes a left moldboard 42L positioned in front of the left rear screed 31L, and a right moldboard 42R positioned in front of the right rear screed 31R.

A screw SC is disposed in front of the moldboard 42, and a retaining plate 43 is disposed in front of the screw SC. Specifically, the retaining plate 43 includes a left retaining plate 43L disposed in front of the left extension screw SCL, and a right retaining plate 43R disposed in front of the right extension screw SCR. Note that the retaining plate 43 may be omitted.

The tractor 1 is equipped with a travel speed sensor S1, a controller 50, an object detection device 51, an on-board display device 52, a steering device 53, and a screed extension/retraction device 54.

The traveling speed sensor S1 is configured to detect the traveling speed of the asphalt finisher 100. In the illustrated example, the traveling speed sensor S1 is a wheel speed sensor, and is configured to detect the rotational angular velocity and rotation angle of the rear wheels 5, and therefore the traveling speed and traveling distance of the asphalt finisher 100.

The controller 50 is a control device that controls the asphalt finisher 100. In the illustrated example, the controller 50 is composed of a microcomputer including a CPU, a volatile memory device, and a non-volatile memory device. 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 a combination of hardware and software.

The object detection device 51 is an example of an information acquisition device that acquires information about the area around the asphalt finisher 100, and is configured to acquire information about features within a predetermined range of the road to be worked on and output the acquired information to the controller 50. In other words, the object detection device 51 is configured to monitor a predetermined range of the road to be worked on. The predetermined range on the road is, for example, an area located forward of the screed 3 and including the road boundary line. In the illustrated example, the predetermined range on the road is an area with a front-to-back and left-to-right width greater than the width of the paving formwork, for example, an area 2 meters square.

The range located forward of the screed 3 includes, for example, the range located forward of the hopper 2, the range located forward of the axle of the front wheels 6, the range located forward of the axle of the rear wheels 5, the range located forward of the screw SC, etc.

The features within the specified range include, for example, the roadbed BS and an object AP located outside the roadbed BS. The object AP is used to determine the widthwise edge position of the pavement to be laid. In the example shown in Figures 1 and 2, the object AP is a paving formwork with a specified thickness (height) and includes a left object APL located on the left side of the asphalt finisher 100 and a right object APR located on the right side of the asphalt finisher 100. Specifically, the left object APL includes a first left object APL1 and a second left object APL2, and the right object APR includes a first right object APR1 and a second right object APR2. The object AP may be an L-shaped gutter block, a curb block, or a cut-out step in an existing pavement. The cut-out step in an existing pavement refers to the step between the surface of the cut portion and the surface of the uncut portion formed when cutting the old pavement to lay a new pavement. The object AP may be a feature with almost no thickness, such as a line drawn on the ground, tape stuck to the ground, or string stretched along the ground. Information about the feature includes, for example, the height of the feature, the color of the surface of the feature, or the reflectance of the surface of the feature. Note that the left object APL is not shown in Figure 1 for clarity.

In the illustrated example, the object detection device 51 is a stereo camera configured to monitor a predetermined range. Note that the object detection device 51 may also be a monocular camera, LIDAR, millimeter-wave radar, laser radar, laser scanner, distance imaging camera, laser range finder, ultrasonic sensor, or a combination thereof configured to monitor a predetermined range.

Furthermore, the stereo camera serving as the object detection device 51 is preferably configured with an automatic exposure adjustment function. This configuration allows the object detection device 51 to acquire information about features within a specified range regardless of day or night, i.e., without the need for special lighting, etc.

In the illustrated example, the object detection device 51 includes a left object detection device 51L installed on the left side of the asphalt finisher 100, and a right object detection device 51R installed on the right side of the asphalt finisher 100.

The left object detection device 51L is configured to monitor the ground to the left of the asphalt finisher 100. In the illustrated example, the left object detection device 51L is a stereo camera that monitors the left monitoring range ZL (the area surrounded by the dashed line in Figure 2) on the ground to the left of the asphalt finisher 100.

The right object detection device 51R is configured to monitor the ground to the right of the asphalt finisher 100. In the illustrated example, the right object detection device 51R is a stereo camera that monitors the right monitoring range ZR (the area surrounded by the dashed line in Figure 2) on the ground to the right of the asphalt finisher 100.

The object detection device 51 may be attached to the asphalt finisher 100 via an attachment member 60. The attachment member 60 is a member used to attach the object detection device 51 to the asphalt finisher 100. In the illustrated example, the attachment member 60 includes a left attachment member 60L and a right attachment member 60R. In the example shown in FIG. 2, the left object detection device 51L is attached to the left front end of the tractor 1 via the left attachment member 60L, and the right object detection device 51R is attached to the right front end of the tractor 1 via the right attachment member 60R. Note that the left object detection device 51L may be attached to another portion of the asphalt finisher 100, such as the left front end of the hopper 2, via the left attachment member 60L. Similarly, the right object detection device 51R may be attached to another portion of the asphalt finisher 100, such as the right front end of the hopper 2, via the right attachment member 60R.

The object detection device 51 may also be configured to monitor the extension and retraction state of the rear screed 31. For example, the object detection device 51 may additionally include a stereo camera configured to monitor the end of the left rear screed 31L and a stereo camera configured to monitor the end of the right rear screed 31R. In this case, the object detection device 51 may be disposed on the screed 3. For example, the object detection device 51 may be disposed on the rear screed 31. Furthermore, if an end leveling device is disposed at the end of the rear screed 31, the object detection device 51 may also be disposed on the end leveling device.

In the example shown in FIG. 2, the object detection device 51 is attached to the mounting member 60 so that it faces vertically downward, but it may also be attached to the mounting member 60 so that it faces in another direction, such as diagonally downward.

In the example shown in Figure 2, the left attachment member 60L is composed of an expandable member TA that can expand and contract in the width direction, and a pivotable member SB that is pivotally connected to the distal end of the expandable member TA. The pivotable member SBa, represented by a dashed line in Figure 2, indicates the state when the pivotable member SB has rotated. The same is true for the right attachment member 60R.

In this way, the mounting member 60 is configured so that the monitoring range of the object detection device 51 can be moved using the expandable member TA and the pivoting member SB. This is to allow it to respond to changes in pavement width, etc. In this case, the controller 50 may be configured to control the rotation of the pivoting member SB so that the object detection device 51 follows the object AP, or may be configured to control the expansion and contraction of the expandable member TA. This allows the controller 50 to ensure that the object AP is continuously included within the monitoring range of the object detection device 51, even if the position of the object AP changes in the vehicle width direction.

The mounting member 60 may be equipped with at least one of a sensor that detects the amount of expansion and contraction of the expandable member TA and a sensor that detects the amount of rotation (rotation angle) of the rotating member SB.

Note that at least one of the telescopic member TA and the rotating member SB may be omitted. For example, the mounting member 60 may be configured to be non-telescopic and non-rotatable. In other words, the mounting member 60 may be a rod-shaped member that is non-telescopic and non-rotatable.

The object detection device 51 may also be attached directly to the asphalt finisher 100 without using the mounting member 60.

The object detection device 51 may also be configured as a single device that can simultaneously monitor the ground on the left side of the asphalt finisher 100 and the ground on the right side of the asphalt finisher 100. Specifically, the object detection device 51 may be configured as a single device that can simultaneously monitor the left object APL and the right object APR. In this case, the object detection device 51 may be attached to the center of the front end of the top surface of the tractor 1.

The asphalt finisher 100 may also be equipped with a steering angle sensor configured to detect the steering angle of the asphalt finisher 100, and a screed extension/contraction amount sensor configured to detect the extension/contraction amount of the rear screed 31.

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

The steering device 53 is configured to steer the asphalt paver 100. In the illustrated example, the steering device 53 is configured to extend and retract 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 hydraulic fluid from the hydraulic pump to the front wheel steering cylinder and the flow rate of hydraulic fluid discharged from the front wheel steering cylinder. The steering electromagnetic control valve is configured to control the flow of hydraulic fluid in and out of the front wheel steering cylinder in response to the rotation of the steering wheel SH (handle) serving as an operating device. Note that the steering electromagnetic control valve may also be configured to control the flow of hydraulic fluid in and out of the front wheel steering cylinder in response to the operation of an input switch, which is an operating device separate from the steering wheel SH, regardless of the movement of the steering wheel SH. Furthermore, the steering electromagnetic control valve may also be configured to control the flow of hydraulic fluid in and out of the front wheel steering cylinder in response to a steering command from the controller 50, regardless of the rotation of the steering wheel SH. In other words, the controller 50 may be configured to automatically steer the asphalt finisher 100 regardless of whether the driver operates the steering wheel SH.

When the asphalt paver 100 is a crawler-type asphalt paver, the steering device 53 is configured to be able to separately control a pair of left and right crawlers. Instead of a steering wheel SH, a crawler-type asphalt paver has a left operating lever, which is an operating device for operating the left crawler, and a right operating lever, which is an operating device for operating the right crawler.

Specifically, the steering device 53 includes a left steering electromagnetic control valve that controls the flow rate of hydraulic oil from the hydraulic pump to the left traveling hydraulic motor that rotates the left crawler, and a right steering electromagnetic control valve that controls the flow rate of hydraulic oil from the hydraulic pump to the right traveling hydraulic motor that rotates the right crawler. The left steering electromagnetic control valve is configured to control the flow of hydraulic oil in and out of the left traveling hydraulic motor in accordance with the amount of operation (tilt angle) of the left operating lever. Similarly, the right steering electromagnetic control valve is configured to control the flow of hydraulic oil in and out of the right traveling hydraulic motor in accordance with the amount of operation (tilt angle) of the right operating lever. The left steering electromagnetic control valve may also be configured to control the flow of hydraulic oil in and out of the left traveling hydraulic motor in accordance with a steering command from the controller 50, regardless of whether the driver operates the left operating lever. Similarly, the right steering electromagnetic control valve may be configured to control the flow of hydraulic oil into and out of the right traveling hydraulic motor in response to a steering command from the controller 50, regardless of whether the driver operates the right operating lever.

The screed extension/retraction device 54 is configured to extend and retract the rear screed 31 in the vehicle width direction (Y-axis direction). In the illustrated example, the screed extension/retraction device 54 is configured to extend and retract the screed telescopic cylinder 7 installed within the screed 3. Specifically, the screed extension/retraction device 54 includes a screed extension/retraction electromagnetic control valve that controls the flow rate of hydraulic oil from the hydraulic pump to the screed telescopic cylinder 7 and the flow rate of hydraulic oil discharged from the screed telescopic cylinder 7. The screed extension/retraction electromagnetic control valve is configured to control the flow of hydraulic oil in and out of the screed telescopic cylinder 7 in response to operation of a telescopic button set (not shown) serving as an operating device provided near the on-board display device 52. The telescopic button set typically includes a left telescopic button set for extending and retracting the left rear screed 31L and a right telescopic button set for extending and retracting the right rear screed 31R. The screed extension/retraction electromagnetic control valve may be configured to control the flow of hydraulic oil in and out of the screed telescopic cylinder 7 in response to an extension/retraction command from the controller 50, regardless of operation of the telescopic button set. In other words, the controller 50 may be configured to automatically extend and retract the rear screed 31 regardless of whether the operator operates the extension/retraction button set.

Specifically, the screed extension/retraction device 54 includes a left telescopic electromagnetic control valve that controls the flow rate of hydraulic oil from the hydraulic pump to the left screed telescopic cylinder 7L for extending and retracting the left rear screed 31L, and a right telescopic electromagnetic control valve that controls the flow rate of hydraulic oil from the hydraulic pump to the right screed telescopic cylinder 7R for extending and retracting the right rear screed 31R. The left telescopic electromagnetic control valve is configured to control the flow of hydraulic oil in and out of the left screed telescopic cylinder 7L in response to the operation of the left telescopic button set. Similarly, the right telescopic electromagnetic control valve is configured to control the flow of hydraulic oil in and out of the right screed telescopic cylinder 7R in response to the operation of the right telescopic button set. The left telescopic electromagnetic control valve may also be configured to control the flow of hydraulic oil in and out of the left screed telescopic cylinder 7L in response to an extension/retraction command from the controller 50, regardless of whether the operator operates the left telescopic button set. Similarly, the right telescopic electromagnetic control valve may be configured to control the flow of hydraulic oil into and out of the right screed telescopic cylinder 7R in response to telescopic commands from the controller 50, regardless of whether the operator operates the right telescopic button set.

Next, with reference to Figure 3, we will explain an example configuration of the operation support system DS installed in the asphalt finisher 100. Figure 3 is a block diagram showing an example configuration of the operation support system DS.

The operation support system DS is mainly composed of a controller 50, a left object detection device 51L, a right object detection device 51R, a driving speed sensor S1, an on-board display device 52, a steering device 53, and a screed extension/retraction device 54.

In the example shown in Figure 3, the controller 50 includes a coordinate calculation unit 50a, a steering control unit 50b, and a screed extension/retraction control unit 50c.

The coordinate calculation unit 50a is configured to calculate coordinates on the boundary line of the construction area based on information about features acquired by the object detection device 51. The guide line GD shown by the thick dashed line in Figure 2 is an example of the boundary line of the road to be constructed, and is a virtual line representing a guide surface. A guide surface is a virtual surface recognized as a surface with which the widthwise edge face of the pavement to be laid should be aligned. In the example shown in Figure 2, the guide line GD includes a left guide line GDL representing the left guide surface with which the left edge face of the new pavement NP should be aligned, and a right guide line GDR representing the right guide surface with which the right edge face of the new pavement NP should be aligned.

Specifically, the coordinate calculation unit 50a calculates coordinates on the guide line GD based on information about the object AP acquired by the object detection device 51. More specifically, the coordinate calculation unit 50a calculates the coordinates of points VL that make up the left guide line GDL based on information about the left object APL acquired by the left object detection device 51L, and calculates the coordinates of points VR that make up the right guide line GDR based on information about the right object APR acquired by the right object detection device 51R.

For example, as shown in FIG. 4, the coordinate calculation unit 50a uses image recognition technology to generate a right guide line GDR so that the virtual line representing the angle (edge) between the left end face LE and the upper end face UE of the right object APR within the right monitoring range ZR of the right object detection device 51R becomes the right guide line GDR. The coordinate calculation unit 50a then calculates the coordinates of the intersection of the generated right guide line GDR and the transverse line TL as the coordinates of point VR. In the example shown in FIG. 4, the transverse line TL is a straight line that is parallel to the vehicle width direction (Y-axis direction) and intersects with the center line (optical axis OA) of the right object detection device 51R. Note that FIG. 4 is a schematic perspective view of a paving formwork serving as the right object APR as seen from behind the asphalt finisher 100, and schematically illustrates the positional relationship between the right object detection device 51R and the right object APR.

For example, the coordinate calculation unit 50a uses a distance image of the right monitoring range ZR generated based on the output of a stereo camera serving as the right object detection device 51R to calculate the coordinates of the pixel including the intersection of the right guide line GDR and the transverse line TL as the coordinates of point VR. The distance image is a data set in which each pixel value of a two-dimensional array of pixels is represented by the distance from the right object detection device 51R.

The coordinate of point VR is a coordinate in a predetermined coordinate system. The predetermined coordinate system is, for example, the World Geodetic System. The World Geodetic System is a three-dimensional Cartesian XYZ coordinate system with its origin at the center of gravity of the Earth, its X axis pointing toward the intersection of the Greenwich Meridian and the equator, its Y axis pointing toward 90 degrees east longitude, and its Z axis pointing toward the North Pole. However, the predetermined coordinate system may also be a local coordinate system with its origin at a predetermined point on the asphalt finisher 100. In other words, the predetermined coordinate system may be a local coordinate system whose origin moves as the asphalt finisher 100 moves. Specifically, the predetermined coordinate system may be, for example, a three-dimensional Cartesian coordinate system with its origin at the center of the asphalt finisher 100. In this case, the center of the asphalt finisher 100 may be, for example, the center of the tractor 1 or the intersection of the axle of the rear wheels 5 and the front-rear axis AX (see Figure 2). The predetermined coordinate system may also be a local coordinate system whose origin does not move even when the asphalt finisher 100 moves. In this case, the local coordinate system may be a coordinate system whose origin is the center point of the asphalt finisher 100 at the start of construction. The predetermined coordinate system may also be a plane rectangular coordinate system such as a surveying plane coordinate system used in a total station or the like.

The coordinate calculation unit 50a may be configured, for example, to extract pixels that make up the distance image and whose difference in value from the pixel to the left is equal to or greater than a predetermined threshold, and to derive a single line as a guide line GD from the arrangement of the extracted pixels. The single line may be a straight line, a curved line, or a combination thereof. Any image recognition technology, such as a Hough transform, may be used to derive the single line.

The coordinate calculation unit 50a may eliminate the influence of variations in the positions of extracted pixels by performing an averaging process. Specifically, such variations may occur in image areas corresponding to the contact points between two paving formworks or irregularities in the cutting steps.

In this example, the predetermined threshold value is a threshold value TH related to the height of the paving formwork. In this case, the coordinate calculation unit 50a can generate, as the right guide line GDR, a virtual line representing the upper left edge of the right object APR, which is a paving formwork having a height H1 equal to or greater than the threshold value TH, as shown in Figure 4.

The threshold value TH may be configured to be set in advance to match the height of the paving formwork that will actually be used. Using a threshold value TH set to match the height of the paving formwork that will actually be used makes it possible to generate guide lines based on the edges of thin paving formwork. Furthermore, using a threshold value TH set to match the height of the paving formwork that will actually be used can prevent the coordinate calculation unit 50a from erroneously generating guide lines based on the shape (edge) of features other than the paving formwork.

Then, the coordinate calculation unit 50a calculates the coordinates of the intersection between the generated right guide line GDR and the transverse line TL as the coordinates of point VR, as shown in Figure 4.

Note that while the above explanation relates to the process of calculating the coordinates of point VR on the right guide line GDR from the distance image for the right monitoring range ZR, it also applies to the process of calculating the coordinates of point VL on the left guide line GDL from the distance image for the left monitoring range ZL.

Furthermore, if the object detection device 51 is a monocular camera, the "distance image" in the above description can be read as "image." In this case, the "pixel value" is represented by color information, etc., rather than distance. The color information may be brightness.

In this way, the coordinate calculation unit 50a continuously calculates and stores the coordinates of points VL and VR. In the illustrated example, the coordinate calculation unit 50a is configured to calculate and store the coordinates of points VL and VR each time the asphalt finisher 100 moves forward a predetermined distance (e.g., 15 cm). The coordinate calculation unit 50a may also be configured to calculate and store the coordinates of points VL and VR each time a predetermined time period has elapsed.

Figure 1 shows how the coordinate calculation unit 50a intermittently calculates and stores the coordinates of point VL. In Figure 1, point VL0 corresponds to point VL derived by the coordinate calculation unit 50a based on the output of the left object detection device 51L at the current time. Point VL1 corresponds to point VL derived by the coordinate calculation unit 50a based on the output of the left object detection device 51L at a point in the past. The same applies to points VL2 to VL4. Point VL11 corresponds to point VL derived by the coordinate calculation unit 50a based on the output of the left object detection device 51L at a point in the future. The same applies to points VL12 to VL14. In other words, at the current time, the coordinate calculation unit 50a has already calculated and stored the coordinate values of point VL0 and points VL1 to VL4.

Like FIG. 1, FIG. 2 also shows how the coordinate calculation unit 50a intermittently calculates and stores the coordinates of points VL and VR. In FIG. 2, point VR0 corresponds to point VR derived by the coordinate calculation unit 50a based on the output of the right object detection device 51R at the current time. The same applies to point VL0. Point VR1 corresponds to point VR derived by the coordinate calculation unit 50a based on the output of the right object detection device 51R at a point in the past. The same applies to points VR2 to VR4. Point VL1 corresponds to point VL derived by the coordinate calculation unit 50a based on the output of the left object detection device 51L at a point in the past. The same applies to points VL2 to VL4. Point VR11 corresponds to point VR derived by the coordinate calculation unit 50a based on the output of the right object detection device 51R at a point in the future. The same applies to points VR12 to VR14. Furthermore, point VL11 corresponds to point VL derived by the coordinate calculation unit 50a based on the output of the left object detection device 51L at a point in the future. The same applies to points VL11 to VL14.

The steering control unit 50b is configured to automatically steer the asphalt finisher 100 regardless of the operation of an operating device such as a travel speed dial. The steering control unit 50b may also be configured to control the travel speed of the asphalt finisher 100 when automatically steering the asphalt finisher 100. The steering control unit 50b may also be omitted.

The screed extension/retraction control unit 50c is configured to automatically extend and retract the left and right extendable rear screed 31, regardless of the operation of an operating device such as an extension/retraction button set. The screed extension/retraction control unit 50c may also be configured to automatically extend and retract the rear screed 31 in accordance with the travel speed and steering angle of the asphalt finisher 100 when the asphalt finisher 100 is automatically steered.

In the illustrated example, the screed extension/retraction control unit 50c generates an extension/retraction command for the screed extension/retraction cylinder 7 based on the coordinates on the boundary line calculated and stored by the coordinate calculation unit 50a. The extension/retraction command may be, for example, a command regarding the extension/retraction speed, a command regarding the extension/retraction amount, or a combination thereof.

Specifically, the screed extension/retraction control unit 50c performs feedforward control of the extension/retraction amount of the rear screed 31. More specifically, the screed extension/retraction control unit 50c extends and retracts the left screed telescopic cylinder 7L so that the coordinates of a predetermined portion of the left rear screed 31L (e.g., the left front end point) match the left target coordinates. The left target coordinates are an example of target coordinates, and are, for example, the coordinates of point VL located closest to the predetermined portion of the left rear screed 31L (e.g., the left front end point). The screed extension/retraction control unit 50c also extends and retracts the right screed telescopic cylinder 7R so that the coordinates of a predetermined portion of the right rear screed 31R (e.g., the right front end point) match the right target coordinates. The right target coordinates are another example of target coordinates, and are, for example, the coordinates of point VR located closest to the predetermined portion of the right rear screed 31R (e.g., the right front end point). Additionally, the screed extension/contraction control unit 50c may be configured to determine the extension/contraction speed according to the travel speed of the asphalt finisher 100 detected by the travel speed sensor S1.

The coordinates of specific portions of the rear screed 31, such as the coordinates of the left front end point of the left rear screed 31L and the coordinates of the right front end point of the right rear screed 31R, can be calculated by the coordinate calculation unit 50a, similar to the coordinates of points VL and VR. Specifically, the coordinate calculation unit 50a can calculate the relative position of the object detection device 51 with respect to the position of a reference point, such as the center point of the tractor 1, based on the amount of extension and contraction of the extension member TA, which positions the object detection device 51. Similarly, the coordinate calculation unit 50a can calculate the relative positions of the left front end point of the left rear screed 31L and the right front end point of the right rear screed 31R with respect to the position of the reference point, based on the amount of extension and contraction of the rear screed 31. Furthermore, the coordinate calculation unit 50a can calculate the relative position of a reference point at a second time point with respect to the position of the reference point at a first time point, based on the outputs of the travel speed sensor S1, steering angle sensor, etc. Therefore, the coordinate calculation unit 50a can calculate the relative positions of points VL, VR, the left front end point of the left rear screed 31L, and the right front end point of the right rear screed 31R at other times relative to the position of the reference point at the first time point.

Next, referring to Figure 5, the process by which the controller 50 sets a target for extending and retracting the rear screed 31 (hereinafter referred to as the "target setting process") will be described. Figure 5 is a flowchart showing an example of the flow of the target setting process. The controller 50 repeatedly executes this target setting process at a predetermined control cycle.

First, the controller 50 acquires vehicle body coordinates (step ST1). The vehicle body coordinates refer to the coordinates of specific parts of the asphalt finisher 100, and include the coordinates of specific parts of the rear screed 31, such as the coordinates of the left front end point of the left rear screed 31L and the coordinates of the right front end point of the right rear screed 31R.

Specifically, the controller 50 stores the center point of the asphalt finisher 100 at a first point in time, such as the start of construction, as the reference point.

During construction, the controller 50 can derive the relative position of the center point of the asphalt finisher 100 and the orientation of the asphalt finisher 100 at any point in time, such as the current time, based on the outputs of the travel speed sensor S1 and the steering angle sensor. Note that the relative position of the center point refers to the relative position of the center point with respect to a reference point. The same applies to the following explanation.

In the illustrated example, the controller 50 can derive the coordinates of the turning center based on the output of the steering angle sensor. Then, based on the coordinates of the turning center and the output of the traveling speed sensor S1, the controller 50 can derive the relative position of the center point of the asphalt finisher 100 and the orientation of the asphalt finisher 100 at any time, such as the current time. The controller 50 may also be configured to derive the travel distance or change in attitude based on the output of an IMU (Inertial Measurement Unit), GNSS (Global Navigation Satellite System), or surveying equipment (not shown) mounted on the asphalt finisher 100. Furthermore, the controller 50 can derive the relative position of a specific portion of the asphalt finisher 100 at any time based on the relative position of the center point and orientation of the asphalt finisher 100 at any time and the known dimensions of each component constituting the asphalt finisher 100. The relative positions of specific parts of the asphalt finisher 100 include the relative position of the left object detection device 51L and the relative position of the right object detection device 51R.

After acquiring the vehicle body coordinates, the controller 50 acquires feature coordinates (step ST2). Feature coordinates refer to the coordinates of features such as objects AP, and include coordinates on the left boundary line of the road to be constructed, and coordinates on the right boundary line of the road to be constructed, etc.

Specifically, the controller 50 can calculate the coordinates of point VL, which is the coordinate on the left boundary line of the road to be worked on, and the coordinates of point VR0, which is the coordinate on the right boundary line of the road to be worked on, based on the relative position of the center point of the asphalt finisher 100 and the orientation of the asphalt finisher 100 at any point in time, and the output of the object detection device 51 at any point in time.

After acquiring the vehicle body coordinates and feature coordinates, the controller 50 sets a target (step ST3). In the illustrated example, the controller 50 calculates a target value for the extension/contraction amount of the rear screed 31.

Specifically, the controller 50 derives the distance (hereinafter referred to as the "first distance") between point VL, which is located closest to and in front of a predetermined portion of the left rear screed 31L (e.g., the left front end point), and the longitudinal axis AX of the asphalt finisher 100, based on the relative position of the center point of the asphalt finisher 100 at the current time and the orientation of the asphalt finisher 100. The controller 50 also derives the distance (hereinafter referred to as the "second distance") between a predetermined portion of the left rear screed 31L (e.g., the left front end point) and the longitudinal axis AX of the asphalt finisher 100, based on the relative position of the center point of the asphalt finisher 100 at the current time and the orientation of the asphalt finisher 100. The controller 50 then sets the difference between the first distance and the second distance as the target extension amount. Specifically, if the first distance is greater than the second distance, the controller 50 sets the difference between the first and second distances as the target expansion amount, and if the first distance is less than the second distance, the controller 50 sets the difference between the first and second distances as the target contraction amount.

The controller 50 also determines the extension/contraction speed based on the distance in the direction of travel between a predetermined location on the left rear screed 31L (e.g., the left front end point) and the point VL closest to it (hereinafter referred to as the "third distance"). Specifically, for the same target extension/contraction amount, the controller 50 increases the extension/contraction speed as the third distance increases.

Alternatively, the controller 50 may predict the position of a predetermined part (e.g., the left front end point) of the left rear screed 31L after a predetermined time (e.g., one second), and derive a line segment connecting the closest point VL in front of the position of the predetermined part after the predetermined time and the closest point VL behind it. The controller 50 may then determine the distance between an interpolation point on that line segment (a point that interpolates two points VL) and the longitudinal axis AX as the first distance.

This configuration allows the controller 50 to grasp the position of the boundary line ahead of the screed 3, allowing the rear screed 31 to extend and retract just enough at the appropriate time. Therefore, the controller 50 can suppress or prevent delays in the extension and retraction of the rear screed 31 when the construction width changes, thereby improving construction accuracy.

With the above-described configuration, the screed extension/retraction control unit 50c can extend or retract the left rear screed 31L so that the coordinates of the left front end point of the left rear screed 31L coincide with the coordinates on the guide line GD when the asphalt finisher 100 has advanced a predetermined distance. In other words, the screed extension/retraction control unit 50c can control the amount of extension/retraction of the left rear screed 31L so that when the distance in the direction of travel between point VL and the left front end point of the left rear screed 31L at any point in time becomes zero, the distance in the vehicle width direction between point VL and the left front end point of the left rear screed 31L also becomes zero.

Similarly, the screed extension/retraction control unit 50c can extend or retract the right rear screed 31R so that, when the asphalt finisher 100 has advanced a predetermined distance, the coordinates of the right front end point of the right rear screed 31R coincide with the coordinates of the nearest point VR located ahead of it. In other words, the screed extension/retraction control unit 50c can control the amount of extension/retraction of the right rear screed 31R so that, when the distance in the direction of travel between point VR and the right front end point of the right rear screed 31R at any point in time becomes zero, the distance in the vehicle width direction between point VR and the right front end point of the right rear screed 31R also becomes zero.

Next, an example of the process by which the controller 50 extends and retracts the screed 3 will be described with reference to Figures 6 to 10. Figure 6 is a flowchart showing an example of the process for selecting a control mode for controlling the extension and retraction of the screed 3 (hereinafter referred to as the "control mode selection process"). In the illustrated example, the controller 50 executes this control mode selection process when construction begins. Specifically, the controller 50 determines whether the screed 3 has been lowered toward the roadbed BS based on the output of a pressure sensor that acquires the hydraulic oil pressure in the lift cylinder 8 (see Figure 1) used to lift the screed 3. More specifically, when the hydraulic oil pressure in the rod-side oil chamber of the lift cylinder 8 falls below a predetermined value, the controller 50 determines that the lift cylinder 8 has extended and the screed 3 has been lowered toward the roadbed BS, and thus determines that construction has begun. Note that the controller 50 may also determine that construction has begun using any other method. The controller 50 may also be configured to execute the control mode selection process at a different timing.

In the illustrated example, the controller 50 has two selectable control modes (first mode and second mode). Note that the controller 50 may have three or more selectable control modes.

The first mode is a control mode used when paving the lower layer (the portion formed below the surface layer) of the new pavement NP, and is also referred to as the "lower layer mode." The second mode is a control mode used when paving the surface layer (upper layer) of the new pavement NP, and is also referred to as the "surface layer mode." When the lower layer mode is selected, the new pavement NP is formed by constructing the lower layer once or multiple times and the surface layer once.

Figure 7 is a diagram of the lower layer of the new pavement NP laid by the left rear screed 31L, which gradually contracts in the lower layer mode. Specifically, the upper diagram in Figure 7 is a top view of the lower layer of the new pavement NP, and the lower diagram in Figure 7 is a diagram of a cross section of the first left object APL1, left side plate 41L, left screed plate SPL, and the lower layer of the new pavement NP, viewed from the -X side, in a plane parallel to the YZ plane including the dashed dotted line L1 shown in the upper diagram in Figure 7.

Figure 8 is a top view of the lower layer of the new pavement NP being laid by the left rear screed 31L, which gradually extends in the lower layer mode.

Figure 9 is a diagram of the surface layer of the new pavement NP laid by the left rear screed 31L, which gradually contracts in surface mode. Specifically, the upper diagram in Figure 9 is a top view of the surface layer of the new pavement NP, and the lower diagram in Figure 9 is a cross-section of the second left object APL2, left side plate 41L, left screed plate SPL, and the lower layer of the new pavement NP, viewed from the -X side, in a plane parallel to the YZ plane including the dashed-dotted line L2 shown in the upper diagram in Figure 9.

Figure 10 is a top view of the surface portion of the new pavement NP being laid by the left rear screed 31L, which gradually extends in surface mode.

In Figures 7 to 10, for clarity, cross patterns are applied to the components that make up the screed 3 (left screed plate SPL of the left rear screed 31L, left footboard 32L, left side plate 41L, left moldboard 42L, and left retaining plate 43L). Also, the main body of the left rear screed 31L is not shown.

As shown in FIG. 6, the controller 50 first determines whether the conditions for executing the first mode are met (step ST11). In the illustrated example, the controller 50 determines that the conditions for executing the first mode are met when a first mode selection button (not shown) serving as an operating device provided near the in-vehicle display device 52 is operated.

The controller 50 may determine whether the execution conditions for the first mode are met based on information about the feature acquired by the object detection device 51. Specifically, as shown in the lower diagram of FIG. 7, the controller 50 may determine that the execution conditions for the first mode are met if it determines that the height (height H11) of the feature (object AP) that defines the boundary line (guide line GD) of the road to be constructed is higher than the height (height H12) of the paving material PV (new pavement NP) to be laid by the screed 3. On the other hand, as shown in the lower diagram of FIG. 9, the controller 50 may determine that the execution conditions for the first mode are not met if it determines that the height (height H11) of the feature (object AP) is equal to or less than the height (height H12) of the paving material PV (new pavement NP).

If it is determined that the conditions for executing the first mode are met (YES in step ST11), the controller 50 selects the first mode (lower layer mode) as the control mode (step ST12). If the first mode (lower layer mode) is selected as the control mode, the controller 50 extends or retracts the screed 3 so that the coordinates of the point at the end of the side plate 41 match the target coordinates.

On the other hand, if it is determined that the conditions for executing the first mode are not met (NO in step ST11), the controller 50 selects the second mode (surface mode) as the control mode (step ST13). If the second mode (surface mode) is selected as the control mode, the controller 50 extends or retracts the screed 3 so that the coordinates of a point at the end of the screed plate SP match the target coordinates.

Here, referring to Figures 7 and 8, we will explain the extension and contraction of the screed 3 when the first mode (lower layer mode) is selected. Figure 7 is a diagram of the lower layer of the new pavement NP laid by the left rear screed 31L, which gradually contracts, and Figure 8 is a diagram of the lower layer of the new pavement NP laid by the left rear screed 31L, which gradually expands.

As shown in the upper diagram of Figure 7, the controller 50 controls the extension and retraction of the left rear screed 31L so that the protruding width of the left rear screed 31L is as large as possible within the range in which the left side plate 41L, which has a predetermined fore-aft width (WD1) in the direction of the fore-aft axis AX of the asphalt finisher 100, does not come into contact with the left object APL (first left object APL1 and second left object APL2). The protruding width of the left rear screed 31L in the first mode refers to the distance in the vehicle width direction between the fore-aft axis AX of the asphalt finisher 100 and the left end of the left side plate 41L.

More specifically, in the first mode (lower layer mode), the controller 50 extends and retracts the left rear screed 31L so that the protruding width of the left side plate 41L is equal to the minimum distance (left paving width) between the fore-and-aft axis AX and the left object APL within the fore-and-aft width (WD1) of the left side plate 41L.

When the left guide line GDL bends to the right as shown in Figure 7, when the front end point of the left side plate 41L reaches a position along the second left object APL2 in the direction of the fore-aft axis AX, the left pavement width within the fore-aft width (WD1) of the left side plate 41L is smallest at the front end of the left side plate 41L. Specifically, the left pavement width W1 at the front end of the left side plate 41L is smaller than the left pavement width at any other part, including the left pavement width W2 at the rear end of the left side plate 41L.

Therefore, the controller 50 contracts the left rear screed 31L so that the coordinates on the left guide line GDL match the coordinates of the left front end point of the left side plate 41L. This is to maximize the protrusion width of the left rear screed 31L while preventing contact between the left side plate 41L and the left object APL.

Specifically, the controller 50 sets the coordinates of point VL11, which is located closest to and forward of the left front end point of the left side plate 41L, as the target coordinates, and contracts the left rear screed 31L so that the target coordinates and the coordinates of the left front end point of the left side plate 41L coincide. Figure 7 shows the state when the target coordinates and the coordinates of the left front end point of the left side plate 41L coincide. Note that point VL11 is a point derived by the coordinate calculation unit 50a based on the output of the left object detection device 51L at a previous point in time.

Furthermore, when the left guide line GDL bends to the left as shown in Figure 8, when the front end point of the left side plate 41L in the direction of the fore-aft axis AX reaches a position along the second left object APL2, the left pavement width within the fore-aft width (WD1) of the left side plate 41L is smallest at the rear end of the left side plate 41L. Specifically, the left pavement width W2 at the rear end of the left side plate 41L is equal to or smaller than the left pavement width at any other part, including the left pavement width W1 at the front end of the left side plate 41L.

Therefore, the controller 50 extends the left rear screed 31L so that the coordinates on the left guide line GDL match the coordinates of the left rear end point of the left side plate 41L. This is to maximize the protrusion width of the left rear screed 31L while preventing contact between the left side plate 41L and the left object APL.

Specifically, the controller 50 sets the coordinates of point VL12, which is located closest to and forward of the left rear end point of the left side plate 41L, as the target coordinates, and extends the left rear screed 31L so that the target coordinates and the coordinates of the left rear end point of the left side plate 41L coincide. Figure 8 shows the state when the target coordinates and the coordinates of the left rear end point of the left side plate 41L coincide. Note that point VL12 is a point derived by the coordinate calculation unit 50a based on the output of the left object detection device 51L at a previous point in time.

Next, referring to Figures 9 and 10, we will explain the extension and contraction of the screed 3 when the second mode (surface mode) is selected. Figure 9 is a diagram of the surface portion of the new pavement NP laid by the left rear screed 31L, which gradually contracts, and Figure 10 is a diagram of the surface portion of the new pavement NP laid by the left rear screed 31L, which gradually expands.

As shown in the upper diagram of Figure 9, the controller 50 controls the extension and retraction of the left rear screed 31L so that the left rear end point of the left screed plate SPL, which has a predetermined fore-and-aft width (WD2) in the direction of the fore-and-aft axis AX of the asphalt finisher 100, coincides with the left object APL (first left object APL1 and second left object APL2) in a top view.

More specifically, in the second mode (surface mode), the controller 50 extends or retracts the left rear screed 31L so that the protruding width of the left rear screed 31L is equal to the maximum distance (left paving width) between the longitudinal axis AX and the left object APL within the longitudinal width (WD2) of the left screed plate SPL. Note that the protruding width of the left rear screed 31L in the second mode refers to the distance in the vehicle width direction between the longitudinal axis AX of the asphalt finisher 100 and the left end of the left screed plate SPL.

When the left guide line GDL bends to the right as shown in Figure 9, when the front end point of the left screed plate SPL in the direction of the fore-aft axis AX reaches a position along the second left object APL2, the left paving width within the fore-aft width (WD2) of the left screed plate SPL is maximum at the rear end of the left screed plate SPL. Specifically, the left paving width W12 at the rear end of the left screed plate SPL is greater than the left paving width at any other part, including the left paving width W11 at the front end of the left screed plate SPL.

Therefore, the controller 50 retracts the left rear screed 31L so that the coordinates on the left guide line GDL match the coordinates of the left rear end point of the left screed plate SPL. This is to align the left guide line GDL with the left end surface of the new pavement NP. In other words, this is to prevent an unpaved area from being formed between the left object APL and the new pavement NP.

Specifically, the controller 50 sets the coordinates of point VL13, which is located closest to and forward of the left rear end point of the left screed plate SPL, as the target coordinates, and contracts the left rear screed 31L so that the target coordinates and the coordinates of the left rear end point of the left screed plate SPL coincide. Figure 9 shows the state when the target coordinates and the coordinates of the left rear end point of the left screed plate SPL coincide. Note that point VL13 is a point derived by the coordinate calculation unit 50a based on the output of the left object detection device 51L at a previous point in time.

Furthermore, when the left guide line GDL bends to the left as shown in Figure 10, when the front end point of the left screed plate SPL in the direction of the fore-aft axis AX reaches a position along the second left object APL2, the left paving width within the fore-aft width (WD2) of the left screed plate SPL is maximum at the front end of the left screed plate SPL. Specifically, the left paving width W11 at the front end of the left screed plate SPL is greater than the left paving width at any other part, including the left paving width W12 at the rear end of the left screed plate SPL.

Therefore, the controller 50 extends the left rear screed 31L so that the coordinates on the left guide line GDL match the coordinates of the left front end point of the left screed plate SPL. This is to align the left guide line GDL with the left end surface of the new pavement NP. In other words, this is to prevent an unpaved area from being formed between the left object APL and the new pavement NP.

Specifically, the controller 50 sets the coordinates of point VL14, which is located closest to and forward of the left front end point of the left screed plate SPL, as the target coordinates, and extends the left rear screed 31L so that the target coordinates and the coordinates of the left front end point of the left screed plate SPL coincide. Figure 10 shows the state when the target coordinates and the coordinates of the left front end point of the left screed plate SPL coincide. Note that point VL14 is a point derived by the coordinate calculation unit 50a based on the output of the left object detection device 51L at a previous point in time.

By appropriately selecting the control mode in this manner, the controller 50 can appropriately extend and retract the screed 3 when laying the lower layer of the new pavement NP and when laying the surface layer of the new pavement NP, regardless of whether the boundary line (guide line GD) is curved or not.

As described above, as shown in Figures 1 and 2, an asphalt finisher 100, which is an example of road machinery according to an embodiment of the present disclosure, comprises a tractor 1, a hopper 2 installed in front of the tractor 1 to receive paving material PV, a conveyor CV that feeds the paving material PV in the hopper 2 to the rear of the tractor 1, a screw SC that spreads the paving material PV fed by the conveyor CV behind the tractor 1, a screed 3 that spreads the paving material PV spread by the screw SC behind the screw SC, and a control device (controller 50) that calculates the coordinates of the boundary line (guide line GD) in a predetermined coordinate system based on information about a feature (object AP) that defines the boundary line (guide line GD) of the construction area located ahead of the screed 3.

In addition, in the asphalt finisher 100, the screed 3 is configured to be extendable and retractable in the vehicle width direction. Therefore, the controller 50 can extend and retract the screed 3 so that the coordinates on the boundary line (guide line GD) match the coordinates of the end of the screed 3.

This configuration allows the controller 50 to recognize a change in the direction of the boundary line (guide line GD) before the screed 3 reaches the section where the direction of the boundary line (guide line GD) changes. Therefore, the controller 50 can appropriately control the amount of extension and contraction of the screed 3 compared to when the controller 50 recognizes that a gap exists between the end of the screed 3 and the boundary line (guide line GD) and then extends or contracts the screed to reduce that gap. In other words, the controller 50 can prevent a gap from forming between the end of the screed 3 and the boundary line (guide line GD).

In the asphalt finisher 100, the controller 50 may also be configured to calculate coordinates on the boundary line (guide line GD) each time the tractor 1 moves forward a predetermined distance. In the example shown in Figure 2, the controller 50 is configured to continuously calculate and store the coordinates of points VL and VR on the boundary line (guide line GD).

This configuration has the advantage of preventing the computational load associated with calculating coordinates from becoming unnecessarily large.

In other words, the controller 50 is configured to extend or retract the screed 3 so that the coordinates on the boundary line (guide line GD) calculated at a first point in time become the target coordinates of the end of the screed 3 at a second point in time that is later than the first point in time.

This configuration allows the controller 50 to recognize a change in the direction of the boundary line (guide line GD) before the screed 3 reaches the point where the direction of the boundary line (guide line GD) changes. Therefore, this configuration has the effect of more appropriately controlling the amount of extension and contraction of the screed 3.

The asphalt finisher 100 may also be equipped with an object detection device 51 that acquires information about features (objects AP) that are located ahead of the screed 3 and define the boundary line (guide line GD) of the road to be worked on. The object detection device 51 may also be located ahead of the screed 3. In the example shown in Figure 2, the object detection device 51 is located ahead of the tractor 1, which is located in front of the screed 3.

This configuration allows the object detection device 51 to obtain information about the portion where the direction of the boundary line (guide line GD) changes (e.g., relative position with respect to the vehicle body (tractor 1), distance image, or image, etc.) before the screed 3 reaches that portion. Therefore, this configuration has the effect of enabling the controller 50 to recognize a change in the direction of the boundary line (guide line GD) before the screed 3 reaches that portion.

As shown in FIG. 2, an asphalt finisher 100, which is an example of road machinery according to an embodiment of the present disclosure, includes a tractor 1, a hopper 2 installed in front of the tractor 1 to receive paving material, a conveyor CV that feeds the paving material PV in the hopper 2 to the rear of the tractor 1, a screw SC that spreads the paving material PV fed by the conveyor CV behind the tractor 1, a screed 3 that can extend and retract in the vehicle width direction and spreads the paving material PV spread by the screw SC behind the screw SC, and a controller 50 that serves as a control device for controlling the extension and retraction of the screed 3. The controller 50 is configured to be able to switch between a first mode (lower layer mode) and a second mode (surface layer mode).

The first mode (lower layer mode) is a control mode that controls the extension and contraction of the screed 3 when the height (height H11) of the feature (object AP) that defines the boundary line (guide line GD) of the road to be constructed is higher than the height (height H12) of the paving material PV (new pavement NP) to be laid by the screed 3, as shown in Figure 7.

The second mode (surface mode) is a control mode that controls the extension and contraction of the screed 3 when the height (height H11) of the feature (object AP) is equal to or less than the height (height H12) of the paving material PV (new pavement NP), as shown in Figure 9.

Specifically, in the first mode (lower layer mode), the controller 50 may be configured to extend and retract the screed 3, which has a predetermined fore-and-aft width (WD1) in the direction of the fore-and-aft axis AX of the asphalt finisher 100, within a range in which the screed 3 does not come into contact with the feature (object AP).

More specifically, in the first mode (lower layer mode), as shown in FIG. 7, the controller 50 may be configured to extend or retract the screed 3 so that the distance in the vehicle width direction between the end of the side plate 41, which has a predetermined fore-aft width (WD1) in the direction of the fore-aft axis AX, and the fore-aft axis AX is equal to the minimum distance in the vehicle width direction between the fore-aft axis AX and the feature (object AP) within that fore-aft width (WD1).

In addition, in the second mode (surface mode), as shown in FIG. 9, the controller 50 may be configured to extend or retract the screed 3 so that the distance in the vehicle width direction between the end of the screed plate SP, which has a predetermined fore-and-aft width (WD2) in the direction of the fore-and-aft axis AX, and the fore-and-aft axis AX is equal to the maximum distance in the vehicle width direction between the fore-and-aft axis AX and the feature (object AP) within that fore-and-aft width (WD2).

Furthermore, as shown in Figures 7 to 10, the controller 50 may be configured to extend or retract the screed 3 so that the coordinates of a specified portion of the screed 3 match target coordinates determined based on the coordinates of a point set on the boundary line (guide line GD).

Specifically, in the first mode (lower layer mode), when paving a road having a portion that curves (concaves) to the right as shown in Figure 7, the controller 50 contracts the left rear screed 31L so that the coordinates of the left front end point of the left side plate 41L match the target coordinates determined based on the coordinates of point VL set on the left guide line GDL.

Furthermore, in the first mode (lower layer mode), when paving a road having a portion that bends (bulges) to the left as shown in Figure 8, the controller 50 extends the left rear screed 31L so that the coordinates of the left rear end point of the left side plate 41L match the target coordinates determined based on the coordinates of point VL set on the left guide line GDL.

In addition, in the second mode (surface mode), when paving a road having a portion that curves (concaves) to the right as shown in Figure 9, the controller 50 contracts the left rear screed 31L so that the coordinates of the left rear end point of the left screed plate SPL of the left rear screed 31L match the target coordinates determined based on the coordinates of point VL set on the left guide line GDL.

In addition, in the second mode (surface mode), when paving a road having a portion that bends (bulges) to the left as shown in Figure 10, the controller 50 extends the left rear screed 31L so that the coordinates of the left front end point of the left screed plate SPL of the left rear screed 31L match the target coordinates determined based on the coordinates of point VL set on the left guide line GDL.

Note that the target coordinates may be the coordinates of a point other than point VL, as long as they are determined based on the coordinates of point VL.

These configurations have the advantage of allowing the screed 3 to expand and contract appropriately, regardless of whether the boundary line (guide line GD) is curved, whether the lower layer of the new pavement NP is being laid or the surface layer of the new pavement NP is being laid. Therefore, these configurations can suppress or prevent delays in the expansion and contraction of the rear screed 31 when the construction width changes, etc., thereby improving construction accuracy.

Preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments. Various modifications or substitutions may be applied to the above-described embodiments without departing from the scope of the present invention. Furthermore, the features described with reference to the above-described embodiments may be combined as appropriate, provided that they are not technically inconsistent.

For example, in the above-described embodiment, the object detection device 51 is configured to acquire information about the feature (object AP) that defines the boundary line (guide line GD) of the construction area located ahead of the screed 3. However, the controller 50 may also be configured to acquire information about the feature (object AP) from design data or the like that is pre-stored in a volatile storage device or non-volatile storage device. In this case, acquisition of information about the feature (object AP) by the object detection device 51 may be omitted.

In addition, in the above-described embodiment, the object detection device 51 is attached to the asphalt finisher 100, but it may also be attached to a moving object other than the asphalt finisher 100, such as a vehicle or a multicopter.

1...Tractor 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 7...Screed telescopic cylinder 7L...Left screed telescopic cylinder 7R...Right screed telescopic cylinder 8...Lift cylinder 30...Front screed 30L...Left front screed 30R...Right front screed 31...Rear screed 31L...Left rear screed 31R...Right rear screed 32...Footplate 32C...Central footplate 32L...Left footplate 32R...Right footplate 41...Side plate 41L...Left side plate 41R...Right side plate 42...Moldboard 42L...Left moldboard 42R...Right moldboard 43...Retaining plate 43L...Left retaining plate 43R...Right retaining plate 50...Controller 50a...Coordinate calculation unit 50b...Steering control unit 50c...Screed extension/retraction control unit 51...Object detection device 51L...Left object detection device 51R...Right object detection device 52...In-vehicle display device 53...Steering device 54...Screed extension/retraction device 60...Mounting member 60L...Left mounting member 60R...Right mounting member 100...Asphalt finisher AP...Object APL...Left object APL1...First left object APL2...Second left object APR...Right object APR1...First right object APR2...Second right object AX...Front/rear axis BS...Roadbed CL...Center line CV...Conveyor DS...Operation support system GD...Guide line GDL...Left guide line GDR...Right guide line NP...Newly constructed pavement PV...Paving material S1...Traveling speed sensor SB, SBa... Rotating member SC... Screw SCL... Left extension screw SCR... Right extension screw SH... Steering wheel SP... Screed plate SPL... Left screed plate TA... Telescopic member ZL... Left monitoring area ZR... Right monitoring area

Claims (3)

A tractor and
a hopper installed in front of the tractor to receive paving material;
a conveyor that feeds the paving material in the hopper to the rear of the tractor;
a screw that spreads the paving material fed by the conveyor behind the tractor;
a screed that can be extended and contracted in the vehicle width direction and that spreads the paving material spread by the screw behind the screw;
A control device for controlling the extension and contraction of the screed,
The control device is configured to be able to switch between a first mode in which the extension and contraction of the screed is controlled when the height of a feature that defines the boundary of the construction area located ahead of the screed is higher than the height of the paving material to be laid by the screed, and a second mode in which the extension and contraction of the screed is controlled when the height of the feature is equal to or less than the height of the paving material ,
The extension and contraction of the screed is controlled based on coordinates on the boundary line in a predetermined coordinate system calculated based on information about the feature .
Road machinery. In the first mode, the control device extends and retracts the screed, which has a predetermined front-to-rear width in the direction of the front-to-rear axis of the road machine, within a range in which the screed does not come into contact with the feature on the ground.
2. A road machine according to claim 1. The control device extends or retracts the screed so that the coordinates of a predetermined portion of the screed coincide with target coordinates determined based on the coordinates of the points set on the boundary line.
3. A road machine according to claim 1 or 2.