Asphalt finisher

Abstract

This invention provides an asphalt finisher that can precisely adjust the width of the screed by extending and retracting the screed extension cylinder at an appropriate extension and retraction speed. [Solution] The asphalt finisher 100 is equipped with a screed 3 that spreads and levels the paving material PV while moving in the laying direction. The asphalt finisher 100 includes a screed extension cylinder 26, a switching valve 34, a screed position sensor 51C, and a controller 50. The controller 50 calculates the target trajectory of the side frame 32 where the side frame 32 is located, and calculates the extension and retraction speed of the screed extension cylinder 26 based on the deviation between the target trajectory of the side frame and the current position of the side frame 32 detected by the screed position sensor 51C. The controller 50 then controls the screed extension and retraction cylinder 26 by switching the switching valve 34 on and off based on the extension and retraction speed.

Description

Technical Field

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

Background Art

[0002] In recent years, an asphalt finisher that automatically controls the width of a screed according to the road surface to which the paving material is to be spread has been developed. If the screed expansion and contraction cylinder performs automatic control at the expansion and contraction speed when manually controlling the width of the screed, the expansion and contraction speed may be too fast. In this case, the accuracy of aligning the width of the screed with the target position may decrease. Conversely, if the asphalt finisher slows down the expansion and contraction speed of the screed expansion and contraction cylinder to improve control accuracy, the operation will become slow when manually operating.

[0003] Therefore, it is conceivable to make the expansion and contraction speed of the width of the screed variable. For example, in Patent Document 1, a detection sensor unit provided on the screed detects a laying boundary portion with the paved surface, and when the outer end of the widener is offset with respect to the laying boundary portion, an asphalt finisher that returns the offset while adjusting the expansion and contraction speed of the widener is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the technique described in Patent Document 1, since the offset is determined by the detection sensor unit provided on the screed, only the situation of the current position (or its vicinity) of the detection sensor unit can be recognized. In this case, it is difficult to accurately adjust the width of the screed to the actual target position at an appropriate speed.

[0006] This disclosure provides an asphalt finisher that can precisely adjust the width of the screed by extending and retracting the screed extension cylinder at an appropriate extension and retraction speed. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, an asphalt finisher is provided which includes a screed for leveling paving material while moving in the laying direction, the screed extension cylinder expands and contracts in accordance with the supply of hydraulic fluid to move a side frame which is the leveling limit of the screed, a switching valve that can switch between supplying hydraulic fluid to the screed extension cylinder (on) and stopping the supply of hydraulic fluid (off), a sensor that detects information relating to the current position of the side frame, and a controller that controls the drive of the switching valve, wherein the controller calculates a side frame target trajectory in which the side frame is located in the laying direction, calculates the extension and contraction speed of the screed extension cylinder based on the deviation between the side frame target trajectory and the current position of the side frame detected by the sensor, and controls the screed extension and contraction cylinder by switching the switching valve on and off based on the extension and contraction speed. [Effects of the Invention]

[0008] According to one embodiment, the width of the screed can be precisely adjusted by extending and retracting the screed extension cylinder at an appropriate extension and retraction speed. [Brief explanation of the drawing]

[0009] [Figure 1] This is a side view of an asphalt finisher according to an embodiment. [Figure 2] This is a plan view of an asphalt finisher. [Figure 3] This is a block diagram showing an example configuration of an automatic steering system. [Figure 4] This is a site plan showing the straight sections, curved sections, and asphalt finishers passing through the straight sections of the road being constructed. [Figure 5]This diagram shows the hydraulic circuit for the right screed extension cylinder. [Figure 6] Figure 6(A) illustrates the supply state of hydraulic fluid by the switching valve. Figure 6(B) is a graph showing the extension and retraction speed of the screed extension cylinder in relation to the duty cycle when hydraulic fluid is supplied. [Figure 7] Figure 7(A) is a plan view showing the operation of extending the right side frame by the right screed telescopic cylinder. Figure 7(B) is a diagram showing the operation of the switching valve when controlling the extension and retraction speed of the right screed telescopic cylinder. Figure 7(C) is a diagram showing the operation of the switching valve when controlling the extension and retraction speed of the right screed telescopic cylinder according to a modified example. [Figure 8] This is a flowchart showing the control method for a screed extension cylinder. [Modes for carrying out the invention]

[0010] The following describes embodiments for implementing this disclosure with reference to the drawings. In each drawing, the same reference numerals are used for identical components, and redundant explanations may be omitted.

[0011] Figure 1 is a side view of the asphalt finisher 100 according to the embodiment. Figure 2 is a top view of the asphalt finisher 100. The asphalt finisher 100 according to the embodiment is a wheeled asphalt finisher and mainly comprises a tractor 1, a hopper 2, and a screed 3. Hereinafter, the direction of the hopper 2 as seen from the tractor 1 (+X direction) will be considered the front, and the direction of the screed 3 as seen from the tractor 1 (-X direction) will be considered the rear.

[0012] Tractor 1 is a mechanism for moving the asphalt finisher 100. Tractor 1 moves the asphalt finisher 100 by rotating the rear wheels 5 using a rear-wheel hydraulic motor and rotating the front wheels 6 using a front-wheel hydraulic motor. The rear-wheel hydraulic motor and the front-wheel hydraulic motor rotate by receiving hydraulic fluid from a hydraulic pump. One of the rear wheels 5 and the front wheels 6 may be a driven wheel. The asphalt finisher 100 may also be a crawler-type asphalt finisher in which the rear wheels 5 and the front wheels 6 are replaced with left and right crawlers.

[0013] The asphalt finisher 100 includes a controller 50, which is a control unit that controls various components. The controller 50 is, for example, a microcomputer including a processor, memory (volatile memory and non-volatile memory, etc.), and an input / output interface, and is mounted on the tractor 1. Each function of the controller 50 is realized by the processor executing a program stored in the non-volatile memory. 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] Hopper 2 is a mechanism for receiving paving material. In the illustrated example, hopper 2 is installed at the front of tractor 1 and opens and closes in the vehicle width direction (Y-axis direction) by a hopper cylinder. The asphalt finisher 100 typically receives paving material (e.g., asphalt mixture) from the bed of a dump truck when hopper 2 is fully open. A dump truck is an example of a transport vehicle for carrying paving material. Figures 1 and 2 illustrate hopper 2 in the fully open state. When the amount of paving material in hopper 2 decreases, hopper 2 is closed, and the paving material that was near the inner wall of hopper 2 is collected in the center of hopper 2. This is so that the conveyor CV in the center of hopper 2 can feed paving material to the rear of tractor 1. The paving material fed to the rear of tractor 1 is spread in the vehicle width direction at the rear of tractor 1 and in front of screed 3 by screw SC. In the illustrated example, screw SC has extension screws connected on both sides. For ease of understanding, Figures 1 and 2 omit the illustration of the paving material inside the hopper 2. Instead, they show the paving material PV spread by the screw SC with a coarse dot pattern, and the newly laid pavement NP leveled by the screed 3 with a fine dot pattern.

[0015] Screed 3 is a mechanism for spreading and leveling the paving material PV. The screed 3 according to this embodiment 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. The rear screed 31 is extended and retracted in the vehicle width direction by a screed extension cylinder 26. Specifically, the left rear screed 31L is extended and retracted in the vehicle width direction using the left screed extension cylinder 26L. The right rear screed 31R is extended and retracted in the vehicle width direction using the right screed extension cylinder 26R. Furthermore, the screed 3 is a floating screed that is towed by the tractor 1 and is connected to the tractor 1 via a leveling arm 3A. The leveling arm 3A includes a left leveling arm 3AL positioned on the left side of the tractor 1 and a right leveling arm 3AR positioned on the right side of the tractor 1.

[0016] A mold board 43 is attached to the front part of the screed 3. The mold board 43 adjusts the amount of 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] A pair of side frames 32 (left side frame 32L and right side frame 32R) that define the spreading limit of the paving material PV are attached to both ends in the width direction of the rear screed 31. The left side frame 32L extends in the front - rear direction with a predetermined length at the left end of the rear screed 31. The left side frame 32L is displaced in the vehicle width direction by the expansion and contraction of the left screed expansion - contraction cylinder 26L. The right side frame 32R extends in the front - rear direction with a predetermined length at the right end of the rear screed 31. The right side frame 32R is displaced in the vehicle width direction by the expansion and contraction of the right screed expansion - contraction cylinder 26R.

[0018] Also, an information acquisition device 51, an in - vehicle display device 52, a steering device 53, and a screed expansion - contraction control device 54 are attached to the tractor 1.

[0019] The information acquisition device 51 acquires information about the road to be constructed and outputs 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 transition section (clothoid section), and the curvature in the arc section, etc. The information acquisition device 51 includes, for example, a front monitoring device 51F, a rear monitoring device 51B, a traveling speed sensor 51S, a positioning device 51P, and a communication device 51T, etc.

[0020] The forward monitoring device 51F acquires information about the external environment in front of the asphalt finisher 100. The forward monitoring device 51F can be a camera or LiDAR that monitors the monitoring range RF in front of the tractor 1. The forward monitoring device 51F is mounted in the center of the tractor 1 (for example, in the front center of the cover that covers the engine compartment at the rear of the hopper 2). However, the forward monitoring device 51F may be mounted in other parts of the asphalt finisher 100. The forward monitoring device 51F may be configured in combination of multiple cameras and multiple LiDARs. For example, the LiDAR may include a right front LiDAR mounted on the front right side of the tractor 1 and a left front LiDAR mounted on the front left side of the tractor 1.

[0021] The rear monitoring device 51B acquires information about the external environment behind the asphalt finisher 100. The rear monitoring device 51B can be equipped with cameras and LiDARs to monitor the monitoring range RB located behind the screed 3. The rear monitoring device 51B is mounted on the guide rail 1G, which functions as a handrail. However, the rear monitoring device 51B may also be mounted under the driver's seat 1S or on other parts of the asphalt finisher 100. The rear monitoring device 51B may also be configured with a combination of multiple cameras and multiple LiDARs. For example, the multiple LiDARs may include a right rear LiDAR mounted on the right rear end of the tractor 1 and a left rear LiDAR mounted on the left rear end of the tractor 1.

[0022] Furthermore, the information acquisition device 51 may include a side monitoring device for monitoring the sides of the asphalt finisher 100. In this case, the side monitoring device comprises a left-side monitoring device and a right-side monitoring device. The left-side monitoring device is, for example, a camera or LiDAR that monitors a monitoring range to the left of the tractor 1, and is mounted on the left end of the top surface of the tractor 1. The right-side monitoring device is, for example, a camera or LiDAR that monitors a monitoring range to the right of the tractor 1, and is mounted on the right end of the top surface of the tractor 1.

[0023] The camera may be either a monocular camera or a stereo camera, and it captures images of the surrounding area to acquire imaging information. The LiDAR measures, for example, the distance between a number of points within the monitoring range and the LiDAR. However, one or both of the forward monitoring device 51F and the rear monitoring device 51B are not limited to cameras or LiDARs, but may also be millimeter-wave radar, laser radar, laser scanners, depth imaging cameras, or laser rangefinders, etc. The same applies to the side monitoring device.

[0024] The forward monitoring device 51F is preferably configured to detect a monitoring range RF that includes the roadbed BS and the features AP located outside the roadbed BS. This is to enable the acquisition of information regarding the width of the road under construction. The same applies to the monitoring range of the lateral monitoring device. In the illustrated example, the monitoring range RF has a width greater than the width of the roadbed BS. Features AP are, for example, paving formwork, L-shaped drainage ditch blocks, curb blocks, or existing pavement.

[0025] The rear-facing monitoring device 51B is preferably configured to detect a monitoring range RB that includes the newly constructed pavement NP and the features AP located outside the newly constructed pavement NP. This is to allow information about the width of the newly constructed pavement NP to be obtained. In the illustrated example, the monitoring range RB has a width greater than the width of the newly constructed pavement NP.

[0026] The travel speed sensor 51S detects the travel speed of the asphalt finisher 100. For example, the travel speed sensor 51S is a wheel speed sensor and is configured to detect the rotational angular velocity and rotation angle of the rear wheels 5, and consequently, the travel speed and travel distance of the asphalt finisher 100.

[0027] The positioning device 51P is configured to measure the position of the asphalt paver 100. For example, the positioning device 51P is a GNSS compass and is configured to measure the position and orientation of the asphalt paver 100. The GNSS compass as the positioning device 51P includes a left GNSS receiver 51PL mounted on pole PL at the rear end of the left leveling arm 3AL and a right GNSS receiver 51PR mounted on pole PL at the rear end of the right leveling arm 3AR.

[0028] However, the positioning device 51P may be a total station. In this case, a reflective prism, which serves as the target for the total station, is attached to the tip of the pole PL. The main body of the total station, which is installed around the asphalt finisher 100, is connected to the controller 50 via wireless communication. That is, the main body of the total station transmits information about the position of the target it has determined to the controller 50.

[0029] The communication device 51T communicates information between the asphalt finisher 100 and equipment located outside the asphalt finisher 100. In the illustrated example, the communication device 51T is installed in front of the driver's seat 1S and is configured to perform communication via a mobile communication network, a short-range wireless communication network, or a satellite communication network.

[0030] Furthermore, the information acquisition device 51 may also include a steering angle sensor 51R (see Figure 3) for detecting the steering angle of the asphalt finisher 100, and a screed position sensor 51C (see Figure 3) for calculating the position of the side frame 32.

[0031] Furthermore, the information acquisition device 51 may include a monitoring device installed at the construction site, or a monitoring device attached to an aircraft flying above the asphalt finisher 100. A monitoring device installed at the construction site is, for example, a camera, LiDAR, etc., attached to the tip of a pole installed along the road being constructed. A monitoring device attached to an aircraft is, for example, a camera, LiDAR, etc., attached to a multicopter (drone) or airship, etc.

[0032] The in-vehicle display device 52 displays information related to the asphalt finisher 100. In this 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 the left end or right end of the screed 3, etc.

[0033] The steering device 53 is a device for steering the asphalt finisher 100. In this embodiment, the steering device 53 extends and retracts a front wheel steering cylinder located 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 controls the inflow and outflow of hydraulic fluid in the front wheel steering cylinder in accordance with the rotation of the steering wheel SH (handle), which is an operating device. Furthermore, the steering electromagnetic control valve is configured to control the inflow and outflow of hydraulic fluid in the front wheel steering cylinder independently of the rotation of the steering wheel SH, in response to a control command from the controller 50. In other words, the controller 50 can automatically control the steering of the asphalt finisher 100 regardless of whether or not the operator operates the steering wheel SH.

[0034] If the asphalt finisher 100 is a crawler-type asphalt finisher, the steering device 53 is configured to control the left and right pairs of crawlers separately. Specifically, the steering device 53 includes a left electromagnetic control valve that controls the flow rate of hydraulic fluid from the hydraulic pump to the left travel hydraulic motor for rotating the left crawler, and a right electromagnetic control valve that controls the flow rate of hydraulic fluid from the hydraulic pump to the right travel hydraulic motor for rotating the right crawler. The left electromagnetic control valve controls the inflow and outflow of hydraulic fluid in the left travel hydraulic motor according to the amount of operation (angle of inclination) of the left operating lever, which is an operating device for operating the left crawler. The left electromagnetic control valve is also configured to control the inflow and outflow of hydraulic fluid in the left travel hydraulic motor in response to a control command from the controller 50, regardless of whether the operator operates the left operating lever. Similarly, the right electromagnetic control valve controls the inflow and outflow of hydraulic fluid in the right travel hydraulic motor according to the amount of operation (angle of inclination) of the right operating lever, which is an operating device for operating the right crawler. Furthermore, the right electromagnetic control valve is configured to control the inflow and outflow of hydraulic fluid in the right travel hydraulic motor, regardless of whether the operator operates the right control lever, in response to a control command from the controller 50.

[0035] The screed extension / retraction control device 54 controls the screed extension / retraction cylinder 26 to extend and retract the rear screed 31. Specifically, the screed 3 is equipped with a control valve unit 33 that controls the flow rate of hydraulic fluid flowing from the hydraulic pump to the screed extension / retraction cylinder 26, and the flow rate of hydraulic fluid discharged from the screed extension / retraction cylinder 26. The screed extension / retraction control device 54 controls the drive of this control valve unit 33.

[0036] The screed extension / retraction control device 54 controls the inflow and outflow of hydraulic fluid in the screed extension / retraction cylinder 26 in response to the on and off operation of the screed extension / retraction switch (not shown), which is an operating device. Furthermore, the screed extension / retraction control device 54 is configured to control the inflow and outflow of hydraulic fluid in the screed extension / retraction cylinder 26 independently of the operation of the screed extension / retraction switch, in response to a control command from the controller 50. In other words, the controller 50 can automatically control the extension / retraction amount of the rear screed 31, regardless of whether the operator operates the screed extension / retraction switch. The control of the screed extension / retraction cylinder 26 will be described in detail later.

[0037] Furthermore, the control valve unit 33 includes a left control valve unit 33L and a right control valve unit 33R, and under the control of the screed extension / retraction control device 54, separately controls the extension / retraction of the left rear screed 31L and the right rear screed 31R. Specifically, the left control valve unit 33L controls the inflow and outflow of hydraulic fluid flowing from the hydraulic pump to the left screed extension / retraction cylinder 26L in response to the operation of the left screed extension / retraction switch (not shown), which is an operating device. In addition, the left control valve unit 33L controls the inflow and outflow of hydraulic fluid flowing from the hydraulic pump to the left screed extension / retraction cylinder 26L in response to a control command from the controller 50, regardless of whether the left screed extension / retraction switch is operated or not. The same applies to the right solenoid control valve.

[0038] Next, an example of the configuration of the automatic steering system DS installed in the asphalt finisher 100 will be explained with reference to Figure 3. Figure 3 is a block diagram showing an example of the configuration of the automatic steering system DS.

[0039] The automatic steering system DS mainly consists of a controller 50, a forward monitoring device 51F, a rear monitoring device 51B, a driving speed sensor 51S, a positioning device 51P, a steering angle sensor 51R, a screed position sensor 51C, a communication device 51T, an on-board display device 52, a steering device 53, and a screed extension / retraction control device 54, etc.

[0040] In the example shown in Figure 3, the controller 50 includes a target calculation unit 50a, a steering control unit 50b, a side frame target trajectory calculation unit 50c, and a screed control unit 50d as functional blocks.

[0041] The target calculation unit 50a calculates the target to be used by the steering control unit 50b. The target used by the steering control unit 50b is, for example, the main target trajectory that a predetermined point on the asphalt finisher 100 should follow. The target trajectory is, strictly speaking, a two-dimensional array of multiple target positions. Alternatively, the target used by the steering control unit 50b may be a target position that the predetermined point on the asphalt finisher 100 should reach after a predetermined time has elapsed. The predetermined time is, for example, several hundred milliseconds, tens of milliseconds, several milliseconds, or several seconds.

[0042] The predetermined point of the asphalt finisher 100 is located on the front and rear axes of the tractor 1, and preferably is set to be located in front of the screed 3. For example, the predetermined point is set in the center, front center, or rear center of the tractor 1, hopper 2, or screed 3. In the embodiment of the asphalt finisher 100, the predetermined point is set in the widthwise center of the screed 3 (front screed 30).

[0043] The target calculation unit 50a calculates the main target trajectory that a predetermined point on the screed 3 should follow, based on information about the road to be constructed, such as construction data (design data). The main target trajectory is typically calculated before the asphalt finisher 100 starts running. Therefore, the main target trajectory may be calculated on a server or the like installed in a management center outside the asphalt finisher 100 and then transmitted to the controller 50 via communication.

[0044] The target calculation unit 50a may calculate the main target position as the point that the predetermined point of the screed 3 should reach after a predetermined time has elapsed. In this case, the main target position is repeatedly calculated at a predetermined control cycle while the asphalt finisher 100 is running. For example, when the asphalt finisher 100 is running on a straight section of the road to be constructed, the target calculation unit 50a may calculate the center point in the width direction of the road to be constructed, located a predetermined distance ahead of the current position of the predetermined point of the screed 3, based on information acquired by the forward monitoring device 51F, as the main target position. The predetermined distance is, for example, several centimeters to several tens of centimeters. The target calculation unit 50a can calculate the main target position without acquiring design data. However, the target calculation unit 50a may calculate the main target position based on design data and information acquired by the forward monitoring device 51F. For example, the target calculation unit 50a may correct the main target position calculated based on design data based on information acquired by the forward monitoring device 51F. Furthermore, the target calculation unit 50a may correct the main target position using information acquired by the rearward monitoring device 51B.

[0045] The steering control unit 50b automatically controls the steering of the asphalt finisher 100 to assist the operator.

[0046] In this embodiment, the steering control unit 50b outputs a control command to the steering device 53 so that a predetermined point on the screed 3 follows the main target trajectory calculated by the target calculation unit 50a. Specifically, the steering control unit 50b calculates the current position of the predetermined point on the screed 3 based on the output of the positioning device 51P. For example, if it is determined that the predetermined point deviates to the right from the main target trajectory, the steering control unit 50b outputs a control command to the steering device 53 so that the tractor 1 moves to the left. Similarly, if it is determined that the predetermined point deviates to the left from the main 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.

[0047] Alternatively, the steering control unit 50b may output a control command to the steering device 53 so that a predetermined point on the screed 3 aligns with 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 on the screed 3 based on the output of the positioning device 51P, or it may derive the current position of the predetermined point on the screed 3 based on the output of at least one of the rearward monitoring device 51B and the forward monitoring device 51F.

[0048] Next, referring to Figure 4, the function of moving the asphalt finisher 100 along the target trajectory will be explained. Figure 4 is a plan view of the construction site showing the asphalt finisher 100 passing through the straight section SP1, the curved section LC (left curve), and the straight section SP2 of the road RD to be constructed. In Figure 4, the asphalt finisher 100 at the first time point, which is the start of construction, is indicated by reference numeral 100a. The asphalt finisher 100 at the second time point, after a predetermined time has elapsed from the first time point, is indicated by reference numeral 100b. Similarly, the asphalt finisher 100 at the third time point, after a predetermined time has elapsed from the second time point, is indicated by reference numeral 100c, the asphalt finisher 100 at the fourth time point, after a predetermined time has elapsed from the third time point, is indicated by reference numeral 100d, and the asphalt finisher 100 at the fifth time point, after a predetermined time has elapsed from the fourth time point, is indicated by reference numeral 100e. Note that Figure 4 shows a simplified representation of the asphalt finisher 100, including the tractor 1, front screed 30, left rear screed 31L, and right rear screed 31R, for clarity.

[0049] The target calculation unit 50a of the controller 50 calculates the main target trajectory TPS that the predetermined point Q of the screed 3 should follow at the first time point, which is the start of construction. In Figure 4, the predetermined point Q is represented by a triangle, and the main target trajectory TPS is represented by a dashed line. For example, the target calculation unit 50a refers to design data and derives the main target trajectory TPS based on the left boundary line and the right boundary line of the road RD to be constructed. Note that in Figure 4, the center line CP of the road RD is shown by a dashed line. The main target trajectory TPS may also be generated based on a line that bisects the area of ​​the road surface leveled by the screed 3. The area of ​​the road surface is, for example, the area of ​​the road surface leveled when the asphalt finisher 100 moves forward a predetermined distance.

[0050] The steering control unit 50b of the controller 50 calculates the current position of a predetermined point Q on the screed 3 based on the output of the positioning device 51P. The steering control unit 50b then operates the asphalt finisher 100 so that the actual position coordinates of the predetermined point Q match one of the position coordinates that make up the main target trajectory TPS. As a result, the steering control unit 50b moves the predetermined point Q, which was at the position of point Qa at the first time point, to point Qb at the second time point, to point Qc at the third time point, to point Qd at the fourth time point, and to point Qe at the fifth time point.

[0051] Furthermore, during the movement of the asphalt finisher 100, the left side frame 32L at the left end of the left rear screed 31L is controlled to move along the left side frame target trajectory LTP calculated by the controller 50. Similarly, the right side frame 32R at the right end of the right rear screed 31R is controlled to move along the right side frame target trajectory RTP calculated by the controller 50.

[0052] Therefore, the side frame target trajectory calculation unit 50c of the controller 50 shown in Figure 3 calculates the left side frame target trajectory LTP and the right side frame target trajectory RTP even when the tractor 1 is advanced so that a predetermined point Q follows the main target trajectory TPS. The left side frame target trajectory LTP is basically calculated as a line corresponding to the left boundary line of the road RD. However, the left side frame target trajectory LTP may be calculated as a line different from the left boundary line depending on the capabilities of the asphalt finisher 100 (e.g., the extension limit and extension speed of the screed 3). Similarly, the right side frame target trajectory RTP is basically calculated as a line corresponding to the right boundary line of the road RD. However, the right side frame target trajectory RTP may also be calculated as a line different from the right boundary line depending on the capabilities of the asphalt finisher 100 (e.g., the extension limit and extension speed of the screed 3).

[0053] The side frame target trajectory calculation unit 50c can calculate the left side frame target trajectory LTP and the right side frame target trajectory RTP based, for example, on construction data acquired in advance and the position of the asphalt finisher 100 measured by the positioning device 51P. In this case, the side frame target trajectory calculation unit 50c may calculate the left side frame target trajectory LTP and the right side frame target trajectory RTP before construction. Alternatively, the side frame target trajectory calculation unit 50c can also calculate the left side frame target trajectory LTP and the right side frame target trajectory RTP during construction based on detection information detected by the forward monitoring device 51F or the side monitoring device. For example, the left side frame target trajectory LTP and the right side frame target trajectory RTP are calculated based on information detected by the forward monitoring device 51F regarding the left and right boundary lines several meters in front of the asphalt finisher 100. Alternatively, the side frame target trajectory calculation unit 50c may calculate the left side frame target trajectory LTP and the right side frame target trajectory RTP using the construction data, the position of the asphalt finisher 100, and the detection information detected by the forward monitoring device 51F or the side monitoring device.

[0054] The screed control unit 50d of the controller 50 outputs control commands to the screed extension / retraction control device 54 based on the left side frame target trajectory LTP and the right side frame target trajectory RTP calculated by the side frame target trajectory calculation unit 50c, thereby controlling the operation of the screed 3. The screed control unit 50d outputs control commands such that the left side frame 32L of the left rear screed 31L matches the left side frame target trajectory LTP, and the right side frame 32R of the right rear screed 31R matches the right side frame target trajectory RTP.

[0055] For example, if there is a risk that the left side frame 32L will deviate inward from the left side frame target trajectory LTP, the left side frame 32L will be extended to the left. Conversely, if there is a risk that the left side frame 32L will deviate outward from the left side frame target trajectory LTP, the left side frame 32L will be shortened to the right. Alternatively, if there is a risk that the right side frame 32R will deviate inward from the right side frame target trajectory RTP, the right side frame 32R will be extended to the right. Conversely, if there is a risk that the right side frame 32R will deviate outward from the right side frame target trajectory RTP, the right side frame 32R will be shortened to the left. This ensures that the side frame target trajectories (left side frame target trajectory LTP, right side frame target trajectory RTP) and the width of the newly constructed pavement NP (width of screed 3) match.

[0056] Next, the specific configuration of the control valve unit 33 will be described. Figure 5 shows the hydraulic circuit for the right screed extension cylinder 26R. In the following, the right control valve unit 33R, which displaces the position of the right side frame 32R as shown in Figure 5, will be used as an example, and the left control valve unit 33L, which is configured similarly to the right control valve unit 33R, will not be described.

[0057] The right control valve unit 33R is installed between the hydraulic pump 25, which is connected to the hydraulic fluid storage tank 24, and the right screed telescopic cylinder 26R. The right control valve unit 33R is also connected to a tank 27 that recovers the hydraulic fluid discharged from the right screed telescopic cylinder 26R. This right control valve unit 33R is equipped with a switching valve 34 and a check valve 35 inside.

[0058] The right screed telescopic cylinder 26R is equipped with a piston rod 262 that divides the internal space of the cylinder body 261 into a base-side oil chamber 261a and a rod-side oil chamber 261b. The right rear screed 31R (see Figure 2) is connected to the piston rod 262. The right screed telescopic cylinder 26R extends the piston rod 262 toward the tip when hydraulic fluid is supplied to the base-side oil chamber 261a from the right control valve unit 33R. As a result, the right side frame 32R of the right rear screed 31R is displaced outward in the width direction of the screed 3. Conversely, the right screed telescopic cylinder 26R shortens the piston rod 262 toward the base end when hydraulic fluid is supplied to the rod-side oil chamber 261b from the right control valve unit 33R. As a result, the right side frame 32R of the right rear screed 31R is displaced inward in the width direction of the screed 3.

[0059] The switching valve 34 of the right control valve unit 33R has the function of selectively supplying hydraulic fluid to the base end oil chamber 261a and the rod end oil chamber 261b of the right screed telescopic cylinder 26R, and the function of stopping the supply of hydraulic fluid. One end of the switching valve 34 is connected to the hydraulic pump 25 via the supply line 251 and to the tank 27 via the discharge line 271. The other end of the switching valve 34 is connected to the first check valve 351 of the check valve 35 via the first line 346 and to the second check valve 352 via the second line 347.

[0060] The supply line 251, discharge line 271, first line 346, and second line 347 are all connected to the body of the switching valve 34, and communicate with three switching paths based on the position of the spool 341 as it moves back and forth within the body. The three switching paths are a supply stop section 343 that stops the supply of hydraulic fluid to the right screed telescopic cylinder 26R, a base end supply section 344 that supplies hydraulic fluid to the base end oil chamber 261a of the right screed telescopic cylinder 26R, and a rod side supply section 345 that supplies hydraulic fluid to the rod side oil chamber 261b of the right screed telescopic cylinder 26R.

[0061] The supply stop unit 343 shuts off the supply line 251 and has an internal path connecting the first line 346 and the second line 347 to the discharge line 271. When the spool 341 is positioned in the supply stop unit 343 by the drive of the electromagnetic coil 342, the switching valve 34 stops the supply of hydraulic fluid from the hydraulic pump 25 and allows excess pressure of the hydraulic fluid to be released through the first line 346 and the second line 347. This stops the supply of hydraulic fluid to the right screed telescopic cylinder 26R and allows the piston rod 262 to maintain its position.

[0062] The base-side supply unit 344 has an internal path that connects the supply line 251 to the first line 346 and the discharge line 271 to the second line 347. When the spool 341 is positioned in the base-side supply unit 344 by the drive of the electromagnetic coil 342, the switching valve 34 can supply hydraulic fluid from the hydraulic pump 25 to the base-side oil chamber 261a and discharge the hydraulic fluid from the rod-side oil chamber 261b to the tank 27. As a result, the piston rod 262 of the right screed telescopic cylinder 26R extends.

[0063] The rod-side supply unit 345 has an internal path that connects the supply line 251 to the second line 347 and the discharge line 271 to the first line 346. When the spool 341 is positioned in the rod-side supply unit 345 by the drive of the electromagnetic coil 342, the switching valve 34 can supply hydraulic fluid from the hydraulic pump 25 to the rod-side oil chamber 261b and discharge the hydraulic fluid from the base-side oil chamber 261a to the tank 27. As a result, the piston rod 262 of the right screed telescopic cylinder 26R is shortened.

[0064] The electromagnetic coil 342 of the switching valve 34 is connected to the screed extension control device 54, and moves the spool 341 based on the power supply from the screed extension control device 54. For example, the switching valve 34 can switch the supply of hydraulic fluid to the base end oil chamber 261a of the right screed extension cylinder 26R (on) and stop the supply (off) by moving the spool 341 between the supply stop section 343 and the base end supply section 344. Alternatively, the switching valve 34 can switch the supply of hydraulic fluid to the rod side oil chamber 261b of the right screed extension cylinder 26R (on) and stop the supply (off) by moving the spool 341 between the supply stop section 343 and the rod side supply section 345.

[0065] The screed extension control device 54 performs PWM (Pulse Width Modulation) control in controlling the screed extension cylinder 26 by switching the supply of hydraulic fluid by the switching valve 34 between on and off at regular intervals. As a result, the switching valve 34 adjusts the flow rate of hydraulic fluid to the right screed extension cylinder 26R, and thus the extension and retraction speed of the right screed extension cylinder 26R can be adjusted.

[0066] Figure 6(A) is a diagram illustrating the supply state of hydraulic fluid by the switching valve 34. Figure 6(B) is a graph showing the extension and retraction speed of the screed extension cylinder 26 in relation to the duty cycle when hydraulic fluid is supplied. In PWM control, the screed extension and retraction control device 54 changes the duty cycle, which is the ratio of the ON time width to the time width of one cycle, based on the target extension and retraction speed of the right screed extension and retraction cylinder 26R.

[0067] Here, as shown in Figure 6(B), when the duty cycle is 100%, the switching valve 34 is always in the ON state. In this case, the switching valve 34 remains open, and the hydraulic fluid is supplied to the right screed telescopic cylinder 26R at its maximum flow rate. Therefore, the extension and retraction speed of the right screed telescopic cylinder 26R is constant at its limit value when the duty cycle is 100%.

[0068] As shown in Figure 6(A), when the duty cycle falls below 100%, the switching valve 34 repeatedly switches on and off, reducing the flow rate of the hydraulic fluid compared to when the duty cycle is 100%. This slows down the extension and retraction speed of the screed telescopic cylinder 26. Furthermore, the smaller the duty cycle, the lower the flow rate of the hydraulic fluid, and thus the slower the extension and retraction speed of the screed telescopic cylinder 26. In this way, the extension and retraction speed of the screed telescopic cylinder 26 can be adjusted to an appropriate speed by controlling the on and off states of the switching valve 34.

[0069] Returning to Figure 5, the check valve 35 of the right control valve unit 33R has the function of preventing backflow in the direction of hydraulic fluid flow switched by the switching valve 34. The check valve 35 is a double check valve that includes a first check valve 351 connected to the first line 346 and a second check valve 352 connected to the second line. The first check valve 351 allows hydraulic fluid supplied from the switching valve 34 to the base end oil chamber 261a to pass through. The second check valve 352 allows hydraulic fluid supplied from the switching valve 34 to the rod side oil chamber 261b to pass through. In addition, the first check valve 351 and the second check valve 352 allow leaked hydraulic fluid from the switching valve 34 to flow to the discharge line 271 when the supply of hydraulic fluid is stopped.

[0070] Furthermore, the right screed extension cylinder 26R is equipped with a screed position sensor 51C that detects the amount of extension or retraction of the piston rod 262. For example, the screed position sensor 51C is located inside or outside the cylinder body 261 and detects the amount of extension or retraction of the piston rod 262 that extends or retracts outward, and transmits this information to the controller 50. Based on the detection information from the screed position sensor 51C, the controller 50 can calculate the current position of the right side frame 32R of the screed 3.

[0071] The controller 50 (screed control unit 50d) then sets the target extension / retraction speed of the screed extension / retraction cylinder 26 based on the deviation (amount of displacement) between the target trajectory RTP of the right side frame and the current position of the right side frame 32R. For example, if the right side frame 32R is displaced from the target trajectory RTP of the right side frame after a small amount of time, the controller calculates the target extension / retraction speed of the right screed extension / retraction cylinder 26R according to the amount of displacement.

[0072] In this case, the screed control unit 50d should calculate the target extension / retraction speed by taking into account the travel speed, steering angle, and control period of the asphalt finisher 100. For example, if the travel speed is high, the target extension / retraction speed of the right screed extension / retraction cylinder 26R should be increased in order to reach the target position (the position where the deviation occurs) of the right side frame target trajectory RTP more quickly. Conversely, if the travel speed is low, the target extension / retraction speed of the right screed extension / retraction cylinder 26R should be decreased in order to reach the target position (the position where the deviation occurs) of the right side frame target trajectory RTP more slowly.

[0073] For example, if the steering angle of the tractor 1 deviates from the main target trajectory and moves towards the right side frame target trajectory RTP, a deviation occurs between the right side frame target trajectory RTP and the right side frame 32R. The screed control unit 50d calculates the extension / retraction speed (shortening speed) of the right screed extension / retraction cylinder 26R based on this deviation. Also, if the steering angle of the tractor 1 deviates from the main target trajectory and moves towards the left side frame target trajectory LTP, a deviation occurs between the right side frame target trajectory RTP and the right side frame 32R. The screed control unit 50d calculates the extension / retraction speed (extension speed) of the right screed extension / retraction cylinder 26R based on this deviation.

[0074] The control cycle used by the screed extension control device 54 to control the switching valve 34 is not particularly limited, but for example, it can be set in units of 1 second. That is, the extension and retraction speed of the right screed extension cylinder 26R can be set by the amount of movement the right screed extension cylinder 26R moves per unit time. For example, if the maximum distance that can be extended and retracted in one second is 5 cm, the extension and retraction speed of the right screed extension cylinder 26R will be 5 cm / second.

[0075] The control cycle may be a preset constant value, or it may be a variable value that changes according to the conditions of the asphalt finisher 100. For example, the control cycle may be shortened when the asphalt finisher 100 is traveling at a high speed, while the control cycle may be lengthened when the asphalt finisher 100 is traveling at a low speed. In this case, the screed control unit 50d calculates the extension and retraction speed of the right screed extension cylinder 26R according to the control cycle.

[0076] Next, the method for setting the extension and retraction speed of the screed extension cylinder 26 relative to the target position (side frame target trajectory) will be explained with reference to Figures 7(A) to 7(C). Figure 7(A) is a plan view showing the operation of extending the right side frame 32R by the right screed extension cylinder 26R. Figure 7(B) is a diagram showing the operation of the switching valve 34 when controlling the extension and retraction speed of the right screed extension cylinder 26R. Figure 7(C) is a diagram showing the operation of the switching valve 34 when controlling the extension and retraction speed of the right screed extension cylinder 26R according to a modified example.

[0077] As described above, the controller 50 of the asphalt finisher 100 can calculate the deviation (amount of displacement) based on the target trajectory RTP of the right side frame and the current position of the right side frame 32R. As shown in Figure 7(A), the deviation between the target trajectory RTP of the right side frame and the current position of the right side frame 32R corresponds to the distance D traveled when the right screed extension cylinder 26R extends the right side frame 32R outward in the width direction.

[0078] As shown in Figure 7(B), this travel distance D may be greater than, for example, the distance that can be moved in 1 second, which is the control cycle of the right screed telescopic cylinder 26R. For example, suppose that the distance da traveled in 1 second (amount of expansion / contraction per unit time) is a maximum of 5 cm (i.e., the limit of the expansion / contraction speed is 5 cm / second), while the travel distance D is 13 cm. In this case, even if the right screed telescopic cylinder 26R is extended at the limit of the expansion / contraction speed, it will take approximately 3 seconds (2.6 seconds). On the other hand, if the screed telescopic cylinder 26 is moved at the limit of the expansion / contraction speed, the speed is high, which increases the possibility that the right side frame 32R cannot be accurately positioned at the target position of the right side frame target trajectory RTP.

[0079] Therefore, the screed control unit 50d of the controller 50 executes control to slow down the extension and retraction speed of the right screed extension cylinder 26R when the right side frame 32R approaches the target position of the right side frame target trajectory RTP. For example, if the travel distance D is 13 cm, the extension and retraction speed is adjusted so that the right side frame 32R is exactly at the target position in 3 seconds (3 control cycles).

[0080] For example, the screed control unit 50d extends the right screed extension cylinder 26R at the limit of its extension speed (5 cm / second) during the first 2 seconds (2 control cycles). At this time, the duty cycle of the switching valve 34 becomes 100%, and the maximum flow rate of hydraulic fluid flows into the oil chamber 261a on the base end side of the right screed extension cylinder 26R. The right screed extension cylinder 26R moves 5 cm per second, with a distance da of movement per second.

[0081] In the following second (the third control cycle), the screed control unit 50d reduces the duty cycle of the switching valve 34 to 60%. As a result, the switching valve 34 supplies the hydraulic fluid, now at 60% of its normal flow rate, to the right screed extension cylinder 26R. The right screed extension cylinder 26R moves the right side frame 32R by slowing down its extension speed. The right screed extension cylinder 26R then moves 3 cm per second, with a distance db of 3 cm. Therefore, at the end of the third control cycle, the right side frame 32R will be precisely aligned with the target position of the right side frame target trajectory RTP.

[0082] In this way, the controller 50 can move the right side frame 32R to the target position with precision by slowing down the extension and retraction speed of the right screed extension cylinder 26R in the vicinity of the target position of the right side frame target trajectory RTP. Moreover, since the time required for the movement of the right side frame 32R is virtually the same, the extension and retraction operation of the right screed extension cylinder 26R can be completed smoothly.

[0083] The method for setting the extension and retraction speed of the screed extension cylinder 26 is not limited to the above, and various modifications are possible. For example, as shown in Figure 7(C), the position (period) for slowing down the extension and retraction speed of the right screed extension cylinder 26R may extend not only to the last control cycle, but also to multiple control cycles including the last control cycle. Figure 7(C) shows an example in which the extension and retraction speed of the right screed extension cylinder 26R is slowed down for the last 2 seconds (the second and third control cycles). In this case, the screed control unit 50d sets the duty cycle for the last 2 seconds to 80%. As a result, the right screed extension cylinder 26R moves 4 cm in distance dc per second, and the right side frame 32R can be precisely aligned with the target position at the end of the last control cycle.

[0084] Alternatively, if the extension and retraction speed of the right screed extension cylinder 26R is to be slowed down over multiple control cycles, the extension and retraction speed may be changed in each control cycle. For example, by setting the duty cycle of the second control cycle to 90% while the duty cycle of the third control cycle to 70%, it is possible to gradually slow down the extension and retraction speed of the right screed extension cylinder 26R.

[0085] The asphalt finisher 100 according to this embodiment is basically configured as described above, and its operation will be explained below. Figure 8 is a flowchart showing the control method for the screed extension cylinder 26. In the control method for the screed extension cylinder 26, the controller 50 sequentially executes, for example, the processing flow of steps S101 to S107 shown in Figure 8.

[0086] The side frame target trajectory calculation unit 50c of the controller 50 first calculates the left side frame target trajectory LTP and the right side frame target trajectory RTP in the control of the screed extension cylinder 26 (step S101). As described above, the left side frame target trajectory LTP and the right side frame target trajectory RTP can be calculated based on the design data and the current position of the asphalt finisher 100 (screed 3) measured by the positioning device 51P. The left side frame target trajectory LTP and the right side frame target trajectory RTP may also be calculated based on detection information from the forward monitoring device 51F or the side monitoring device, or they may be calculated based on the design data, the current position of the screed 3, and detection information from the forward monitoring device 51F and the side monitoring device.

[0087] Next, the screed control unit 50d acquires the current position of the left side frame 32L and the current position of the right side frame 32R based on the detection information from the screed position sensor 51C (step S102). At this time, the screed control unit 50d acquires detection information from the screed position sensor 51C of the left screed extension cylinder 26L and the screed position sensor 51C of the right screed extension cylinder 26R.

[0088] The screed control unit 50d then calculates the amount of deviation of the left side frame 32L relative to the left side frame target trajectory LTP, and the amount of deviation of the right side frame 32R relative to the right side frame target trajectory RTP (step S103). As a result, the controller 50 can obtain the travel distance D of the left side frame 32L and the travel distance D of the right side frame 32R.

[0089] Subsequently, the screed control unit 50d determines whether the displacement of each side frame 32 is greater than or equal to a predetermined threshold (step S104). This threshold should be set to a value that prevents the side frame 32 from being moved unintentionally, for example, by considering the detection error of the current position of the side frame 32. For example, the threshold can be set to any value within the range of approximately 0 cm to 3 cm. If the displacement of all side frames 32 is less than the threshold (step S104: NO), the process proceeds to step S107 without executing steps S105 and S106. On the other hand, if either or both of the displacement amounts of the left side frame 32L and the right side frame 32R are greater than or equal to the threshold (step S104: YES), the process proceeds to step S105.

[0090] In step S105, the screed control unit 50d calculates the extension and retraction speed of the screed extension cylinder 26 that supports the side frame 32 above a threshold (step S105). As described above, the extension and retraction speed of the screed extension cylinder 26 is calculated based on the capacity of the screed extension cylinder 26 (limit value of extension and retraction speed) and the travel distance D (amount of displacement) (see Figures 7(A) to 7(C)). The screed control unit 50d may also calculate (correct) the extension and retraction speed of the screed extension cylinder 26 by taking into account the travel distance D, travel speed, steering angle, control period, etc.

[0091] As a result, the screed control unit 50d extends or retracts the screed extension cylinder 26 to a threshold value or greater based on the calculated extension / retraction speed, thereby positioning the supporting side frame 32 at the target position (step S106). When moving a pair of side frames 32, the screed 3 may move the left screed extension / retraction cylinder 26L and the right screed extension / retraction cylinder 26R simultaneously. Furthermore, when extending or retracting the screed extension / retraction cylinder 26, as described above, the extension / retraction speed of the screed extension / retraction cylinder 26 is slowed down at a position (timing) that approaches the target position. This allows the side frame 32 being extended or retracted to be moved to the target position with high precision.

[0092] The controller 50 then determines whether or not to complete the work of the asphalt finisher 100 (step S107). There are various patterns for determining whether work is complete, such as recognizing that the operator has turned off the automatic control, recognizing that the tractor 1 has stopped moving, or recognizing that the final target position of the target trajectory has been reached. If the controller 50 decides to continue work (step S107: NO), it returns to step S101 and repeats the same process. If the left side frame target trajectory LTP and the right side frame target trajectory RTP are not to be recalculated (corrected), the controller may return to step S102 and repeat the same process.

[0093] On the other hand, when construction is completed (step S107: YES), the controller 50 terminates the control method of the screed extension cylinder 26. At the end of the process, the controller 50 may automatically return the screed extension cylinder 26 to its initial position.

[0094] As described above, the control method for the screed telescopic cylinder 26 allows the side frame 32 of the screed 3 to be moved accurately to the target position by slowing down the extension and retraction speed of the screed telescopic cylinder 26 when it approaches the target position or timing. In particular, the extension and retraction speed of the screed telescopic cylinder 26 can be easily controlled by adjusting the flow rate of the hydraulic fluid supplied to the screed telescopic cylinder 26 by switching the switching valve 34 on and off.

[0095] It should be noted that the asphalt finisher 100 according to this disclosure is not limited to the above-described embodiment and can take various modifications. For example, the asphalt finisher 100 can, of course, set the duty cycle of the screed extension cylinder 26 to less than 100% from the start of extension. In other words, even if there are multiple control cycles depending on the travel distance D, the asphalt finisher 100 may set the duty cycle to less than 100% from the start of extension. Also, if the travel distance D is a multiple of the amount of travel per unit time, the screed control unit 50d does not need to slow down the extension speed of the screed extension cylinder 26. Alternatively, if the travel distance D is a multiple of the amount of travel per unit time, the control cycle may be increased (for example, from 3 seconds to 4 seconds) to slow down the extension speed in multiple control cycles, including the last control cycle.

[0096] <Note> The technical concept and effects of this disclosure, as described in the embodiments above, are described below.

[0097] A first aspect of this disclosure is an asphalt finisher 100 equipped with a screed 3 for leveling paving material PV while moving in the laying direction, comprising: a screed extension cylinder 26 that extends and retracts in accordance with the supply of hydraulic fluid to move a side frame 32 which is the leveling limit of the screed 3; a switching valve 34 that can switch between ON, which is the supply of hydraulic fluid to the screed extension cylinder 26, and OFF, which is the supply of hydraulic fluid; a sensor (screed position sensor 51C) that detects information related to the current position of the side frame 32; and a controller 50 that controls the driving of the switching valve 34, wherein the controller 50 calculates a target trajectory of the side frame where the side frame 32 is located in the laying direction, calculates the extension and retraction speed of the screed extension cylinder 26 based on the deviation between the target trajectory of the side frame and the current position of the side frame 32 detected by the sensor, and controls the screed extension cylinder 26 by switching the switching valve 34 ON and OFF based on the extension and retraction speed.

[0098] As described above, the asphalt finisher 100 can extend and retract the screed extension cylinder 26 at an appropriate extension and retraction speed based on the control of the controller 50. This allows the asphalt finisher 100 to accurately adjust the width of the screed 3 so that the side frame 32 aligns with the side frame target trajectory. In particular, by using the side frame target trajectory, the controller 50 calculates the travel distance and extension and retraction speed of the screed extension cylinder 26 with a sufficient distance to allow the side frame 32 to reach the target position, enabling smooth operation of the screed extension cylinder 26. As a result, the positioning accuracy of the side frame 32 can be improved.

[0099] Furthermore, the controller 50 slows down the extension and retraction speed of the screed extension and retraction cylinder 26 near the target trajectory of the side frame compared to the extension and retraction speed of the screed extension and retraction cylinder 26 when the side frame 32 starts moving from its current position. This allows the asphalt finisher 100 to slow down the extension and retraction speed of the screed extension and retraction cylinder 26 near the target trajectory of the side frame, enabling it to align the side frame 32 with the target trajectory of the side frame with greater precision.

[0100] Furthermore, the controller 50 slows down the extension and retraction speed of the screed extension cylinder 26 as the side frame 32 approaches the side frame target trajectory. This allows the screed extension cylinder 26 to easily follow the side frame target trajectory by slowing down the speed of the side frame 32.

[0101] Furthermore, the extension and retraction speed of the screed extension cylinder 26 is adjusted based on the on and off duty cycle of the switching valve 34, with a constant speed when the duty cycle is 100%. This allows the controller 50 to adjust the extension and retraction speed of the screed extension cylinder 26 using PWM control.

[0102] Furthermore, the controller 50 controls the extension and retraction speed of the screed extension cylinder 26 by a preset amount of movement per unit time. If the amount of movement required for the side frame 32 to reach the side frame target trajectory exceeds the amount of movement per unit time, the controller 50 controls the extension and retraction speed of the screed extension cylinder 26 over multiple unit time intervals. This allows the extension and retraction speed of the screed extension cylinder 26 to be appropriately adjusted even when the amount of movement required for the side frame 32 to reach the side frame target trajectory is large.

[0103] Furthermore, when the controller 50 extends and retracts the screed extension cylinder 26 over multiple unit time periods, it makes the amount of movement per unit time when the side frame 32 moves at the end of the unit time period smaller than the amount of movement per unit time when the side frame 32 starts moving. As a result, even when the screed extension cylinder 26 is extended and retracted over multiple unit time periods (control cycles), the side frame 32 can be positioned accurately while suppressing time delays.

[0104] Furthermore, the controller 50 calculates the target trajectory of the side frame based on either the construction data and the current position information of the asphalt finisher 100, or detection information that detects the external environment of the asphalt finisher 100, or both. This makes it possible for the controller 50 to easily calculate the target trajectory of the side frame 32 that the screed 3 will follow.

[0105] The asphalt finisher 100 according to the embodiments disclosed herein is illustrative and not restrictive in all respects. The embodiments can be modified and improved in various ways without departing from the scope and spirit of the appended claims. The features described in the above embodiments can be combined in any way that is not inconsistent with other configurations. [Explanation of symbols]

[0106] 3 Screede 26 Screed telescopic cylinder 32 Side Frames 34 Switching valve 50 Controllers 51C Scred position sensor 100 Asphalt Finisher PV paving material

Claims

1. An asphalt finisher equipped with a screed for spreading and leveling paving material while moving in the laying direction, A screed extension / retraction cylinder that extends and retracts in conjunction with the supply of hydraulic fluid, thereby moving the side frame which is the limit of the screed's leveling, A switching valve that can switch between "on," which is the supply of hydraulic fluid to the screed extension cylinder, and "off," which is the stop of the supply of hydraulic fluid. A sensor that detects information related to the current position of the side frame, Includes a controller that controls the drive of the switching valve, The controller calculates the target trajectory of the side frame in the laying direction, calculates the extension and retraction speed of the screed extension cylinder based on the deviation between the target trajectory and the current position of the side frame detected by the sensor, and controls the screed extension and retraction cylinder by switching the switching valve on and off based on the extension and retraction speed. Asphalt finisher.

2. The controller slows down the extension and retraction speed of the screed extension and retraction cylinder at a position near the target trajectory of the side frame compared to the extension and retraction speed of the screed extension and retraction cylinder when the side frame starts moving from its current position. The asphalt finisher according to claim 1.

3. The controller slows down the extension and retraction speed of the screed extension cylinder as the side frame approaches the target trajectory of the side frame. The asphalt finisher according to claim 2.

4. The extension and retraction speed of the screed extension cylinder is adjusted based on the on and off duty cycle of the switching valve, with a constant speed when the duty cycle is 100%. The asphalt finisher according to any one of claims 1 to 3.

5. The controller controls the extension and retraction speed of the screed extension cylinder by a preset amount of movement per unit time. If the amount of movement required for the side frame to reach the target trajectory exceeds the amount of movement per unit time, the extension and retraction speed of the screed extension cylinder is controlled over multiple unit time intervals. The asphalt finisher according to any one of claims 1 to 3.

6. The controller, when extending or retracting the screed extension cylinder over a plurality of unit time periods, makes the amount of movement per unit time when the side frame is last moved smaller than the amount of movement per unit time when the side frame starts moving. The asphalt finisher according to claim 5.

7. The controller calculates the side frame target trajectory based on either or both the construction data and the current position information of the asphalt finisher, or the detection information detecting the external environment of the asphalt finisher. The asphalt finisher according to any one of claims 1 to 3.

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