Road finishing machine and screed leveling method

Abstract

To provide a road finishing machine having a leveling system that forms a more precise flat pavement layer.SOLUTION: A road finishing machine 1 is a screed 4 for forming a pavement layer on a roadbed 3 and includes: a screed with a traction arm 5 that is height adjustable and connected to the road finishing machine via a leveling cylinder 7 at a front traction point 6; at least one measurement means 10 that makes at least one distance measurement; recording means; a control system; and closed loop control means operatively coupled to accommodate leveling cylinder settings. The control system is configured to: calculate a correction value in response to at least one distance measurement to the roadbed and / or reference 11 taken at a measurement point 14 located in front of a screed front end 9 in the laying direction; store the correction value in the recording means at least temporarily; and calculate a leveling target value for the measurement point in consideration of the stored correction value while continuing the laying work.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a road finishing machine according to the preamble of claim 1. Furthermore, the present invention relates to a method according to independent method claim 16. [Background technology]

[0002] German Patent Application Publication No. 19647150, German Utility Model No. 29619831, and German Patent No. 10025474 disclose leveling systems for screeds in road finishing machines. These leveling systems have a towing point control loop that takes into account the difference between the towing arm inclination detected by an inclination sensor and a target inclination value for the towing arm. The target inclination value is calculated based on height monitoring performed in the trailing edge region of the screed. In height monitoring, the target inclination value is determined by measuring the distance to a reference in the trailing edge region of the screed and comparing it with the target distance. In these devices, unevenness of the subgrade ahead of the screed is only inaccurately or not at all taken into account during the leveling process.

[0003] In the above implementation, the use of tilt sensors is particularly problematic because they are sensitive to unevenness and vibrations in the roadbed during construction, which can adversely affect leveling adjustment. Furthermore, the above-mentioned tow point control loop requires a great deal of effort for open and closed loop control, since control at the tow point is performed simultaneously with height monitoring.

[0004] DE 10025462 A1 discloses a road finishing machine with a layer thickness measuring device in the rear end region of the screed for measuring the thickness of the applied pavement layer. To measure the laid layer thickness at the rear end of the screed, a height signal from a sensor that is fixedly arranged on the screed / tractor arm combination and detects the height relative to the subgrade, and an inclination signal from an inclination sensor that is also arranged on the screed / tractor arm combination, are used.

[0005] German Patent Application No. DE 112009001767 A1 discloses a road finishing machine with a control system for leveling the screed. The control system has a first sensor located on the front side of the road finishing machine, in front of the material bunker, for detecting the height relative to the subgrade. The control system also has a second sensor for detecting the height of the traction point in front of the screed arm relative to the subgrade. Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is to provide a road finisher equipped with a leveling system which reliably improves the leveling of the screed of the road finisher by means of simple technical means suitable for practical use, and which is particularly suitable for forming more precisely flat pavement layers. It is also an object of the present invention to provide a method for leveling the screed of a road finisher which enables the formation of a flatter pavement layer. [Means for solving the problem]

[0007] This object is achieved by a road finishing machine according to claim 1. This object is also achieved by a method according to claim 16.

[0008] Advantageous developments of the invention are set out in the respective dependent claims.

[0009] The road finishing machine according to the invention comprises a screed for forming a paving layer on a subsoil along which the road finishing machine moves in a laying direction over a laying section. The screed is mounted so as to be adjustable in height and has a pulling arm attached to the road finishing machine at a front pulling point via leveling cylinders. The road finishing machine according to the invention further comprises measuring means for taking distance measurements, memory means, a control system and closed-loop control means operatively connected to adapt the settings of the leveling cylinders.

[0010] According to the invention, the control unit is configured to calculate a correction value in response to at least one distance measurement of the measuring means relative to the subgrade and / or a reference, said at least one distance measurement being performed at a measuring point located in front of the front end of the screed in the laying direction. The correction value preferably reproduces the irregularities (unevenness) detected at the measuring point as the difference between the foundation and the actual subgrade with unevenness. Furthermore, the control unit is configured to at least temporarily store the correction value in the storage means, calculate a leveling target value for the measuring point taking the stored correction value into account while continuing the laying operation, and control the leveling cylinder of the screed using the leveling target value when the front end of the screed reaches the measuring point.

[0011] This allows the closed-loop control means to intentionally react to the detected subgrade irregularities at a later point in the laying run, i.e., when the front end of the towed screed reaches the measurement point where the correction value detects the irregularities in the subgrade. The determination of the correction value for detecting the subgrade irregularities prior to the actual closed-loop control operation is based on a simple height measurement technique that can be easily used in road finishing machines. Furthermore, the present invention has the advantage of not requiring an inclination sensor, so the leveling system according to the present invention has a more robust structure suitable for construction sites. Furthermore, in the present invention, the measuring means is located in front of the screed and is less affected by the screed's vibration movement, so the distance measured by the measuring means can be more accurately taken into account in the screed leveling. Furthermore, the present invention provides an inexpensive solution that can be easily installed and retrofitted to road finishing machines. In the present invention, the closed-loop control means reacts to the detected irregularities at the measurement point only when the front end of the screed reaches the measurement point, allowing for better correction of the leveling cylinder's reaction time, thereby achieving a pavement layer with high flatness.

[0012] Preferably, the measuring means is attached to the towing arm of the screed, so that the movements of the towing arm, in particular its raising and lowering, can be taken into account in the distance measurement. In particular, the measuring means can accurately detect unevenness of the subgrade in front of the working area of ​​the screed at the towing arm on the side of the road finisher, i.e. immediately next to the running gear, and / or measure the distance relative to a reference provided along the subgrade on the side of the screed, for example a guide wire stretched on the side of the road finisher. Instead of a guide wire, a tensioned rope, a curbstone and / or an already formed paving layer can also be used as reference.

[0013] According to a variant, a measuring means can be attached to the tractor of the road finisher, the measurements of which can optionally be taken into account together with the measurements of further measuring means arranged on the towing arm or on the screed in order to adjust for a specific screed height.

[0014] In a particularly advantageous variant, the measuring means is arranged near the front of the towing arm at the towing point, which allows distance measurements to the subgrade and / or reference to be made in the immediate vicinity of the levelling cylinder, i.e. without being significantly influenced by the tilt of the towing arm, and allows for accurate levelling of the screed.

[0015] Preferably, the measuring means is rotatably mounted on the towing arm, in particular at or at least in the immediate vicinity of the towing point at the front of the towing arm. This allows the measuring means to maintain equilibrium, or at least to automatically return to equilibrium, independently of changes in the tilt of the towing arm controlled during the leveling process. This means that the measuring means does not follow changes in the tilt of the towing arm. This means that the height measurement by the measuring means is not affected by changes in the tilt of the towing arm, and only detects changes in distance to the roadbed and / or reference.

[0016] In one variant, the towing arm is formed with a linear guide for the measuring means, along which the measuring means is adjustably arranged in the laying direction, so that the distance between the measuring means and the front end of the screed can be adjusted. The measuring means can be rotatably mounted on the linear guide in order to ignore changes in the inclination of the towing arm.

[0017] According to one embodiment of the present invention, the measuring means comprises at least one first sensor for measuring the distance relative to a reference and at least one second sensor for measuring the distance relative to the roadbed. These two height measurements are taken into account in calculating the correction value so that irregularities in the roadbed can be detected. In one variant, the measuring means comprises a sensor adapted to detect both the distance relative to the roadbed and the distance relative to the reference. This can be, for example, a radar sensor.

[0018] Preferably, the first and second sensors are positioned at equal distances from the front end of the screed in the laying direction. This allows the two sensors to perform height measurements at the same measuring point in the laying direction, and based on these measurements, unevenness at the measuring point can be accurately detected as a deviation from the foundation. In this variant, two distance measurements are performed at the same point in front of the screed, one relative to the subgrade and the other relative to the reference, and a correction value for this measuring point is determined based on these measurements.

[0019] The first and / or second sensor is preferably in the form of an optical or acoustic sensor, for example a laser or ultrasonic sensor. The height measurement can be performed by runtime measurement, phase position measurement, and / or laser triangulation.

[0020] The determined correction value can be visualized in the road finishing machine, for example using a display on the screed control platform, as an indication of the detected unevenness in the subgrade compared to an averaged subsoil course (base), where the correction factor can indicate slight and relatively large unevennesses with different colors.

[0021] Advantageously, the control system is configured to determine a correction value for the measurement point by subtracting the distance to the reference measured by the first sensor from the distance to the subgrade measured at the measurement point by the second sensor, and further subtracting the height of the predetermined reference to the foundation. The correction value calculated by the control system for the measurement point using this formula accurately reproduces irregularities that deviate from the foundation, i.e. bumps and depressions in the subgrade.

[0022] Preferably, the control system is configured to form the difference between a preset desired basic leveling value and a stored correction value in an intermediate step for deriving a desired leveling value for the measurement point, i.e. for forming a target value for the distance to the sensor reference. The desired basic leveling value provides a guidance value for the open-loop and closed-loop control functions, based on which the screed is towed assuming a uniform and flat subgrade, i.e. a virtual subgrade without irregularities. The correction value serves to adapt the desired basic leveling value if the measuring means actually detects an irregularity in the subgrade, so that a more accurate leveling target value adapted to the irregularity can be calculated for the measurement point. This allows the detected irregularities to be optimally compensated for.

[0023] In an advantageous development, the control system is configured to calculate a leveling target value from the difference between a preset basic leveling target value and the stored correction value minus the distance to the reference actually measured by the measuring means, which leveling target value is presented as an input variable to the closed-loop control means, on the basis of which the level cylinder can be controlled to level the screed.

[0024] According to one embodiment, the measurement means comprises a plurality of sensors for measuring distances to the subgrade and / or datum, and the control system is configured to form a respective average value based on a plurality of simultaneously performed distance measurements to the subgrade and / or datum, on which a correction value is based. Averaging a plurality of distance measurements to the subgrade and / or datum to determine the correction value forms a filter function that causes the closed-loop control means to react to irregularities in a pseudo-damped manner during the laying operation, thereby allowing for smoother transitions in screed levelling.

[0025] In one development of the invention, the control system is configured to multiply the calculated correction value by a correction factor depending on the screed geometry. Besides or instead of the screed geometry, the correction factor can also take into account, for example, the screed weight and / or at least operational parameters set and / or detected during screed operation, such as the tamping speed and / or the screed heating power. Furthermore, the correction factor can also take into account the density of the subgrade through which the road finisher is moving during laying. This allows for the flexibility of the subgrade to be taken into account during screed leveling, so that irregularities can be corrected by the screed movement as needed. In one embodiment, the correction factor takes into account the current laying temperature of the formed pavement layer, measured behind the screed.

[0026] Preferably, the road finishing machine has at least one path measuring means for detecting the covered distance of the front end of the screed, and when the screed travel distance detected by the path measuring means corresponds to the distance between the measuring means and the front end of the screed, calculation of the levelling target value can be initiated in the control system, so that the closed-loop control means can carry out locally accurate levelling of the screed at the right time and at the right place, i.e. at the measuring point, based on the correction value determined there, so that unevenness measured at the measuring point can be reliably compensated for.

[0027] It is particularly advantageous if the control system is configured to continuously calculate correction values ​​while the road finishing machine is laying the section to be laid, to store the correction values ​​for each measurement point, and to use the stored correction values ​​to determine the adapted target leveling value, thereby ensuring that the closed-loop control means can react to all irregularities in the subgrade along the section to be laid and to produce a smooth pavement layer over the entire section to be laid.

[0028] Preferably, the control system is configured to determine the correction values ​​using a subsoil data model based on GPS data. In a variant, the subsoil data model based on GPS data can be stored in a web-based application, in particular a cloud-based application, of the control system in order to provide the road finishing machine, in particular the control system provided on the road finishing machine, with updated geo-subsoil basic data along the section to be laid.

[0029] According to one embodiment of the present invention, the control system is configured to calculate the correction value taking into account the actual position of the leveling cylinder piston at the measurement point. The piston position may, for example, be represented by the piston extension path, which can be detected in particular by the measurement means. In this way, it is possible to determine the unevenness of the roadbed even if the measurement means only measures the distance to a reference or a tensioned guide wire, but not to the roadbed. The detection of the leveling cylinder piston position can be replaced by measuring the distance to the roadbed. This is advantageous for certain types of roadbed, in particular porous roadbed surfaces.

[0030] It is conceivable that the control system is configured to determine a correction value for the measurement point by subtracting the structural height between the bottom of the running gear of the road finishing machine and the traction point of the levelling cylinder in the retracted state from the sum of the distance to the reference measured by the first sensor at the measurement point, the height of the reference relative to the base, the distance of the measuring means to the traction point height, and the extension distance of the levelling cylinder set by the piston position.

[0031] The invention also relates to a method for levelling the screed of a road finishing machine, in which a control system of the road finishing machine calculates a correction value in response to at least one distance measurement made by measuring means provided on the road finishing machine at a measurement point located in front of the front end of the screed in the laying direction relative to the subgrade and / or a reference, at least temporarily stores said correction value in storage means, calculates a target levelling value for the measurement point taking into account the stored correction value during the laying operation, and controls at least one levelling cylinder of the screed using said target levelling value when the front end of the screed reaches the measurement point.

[0032] Preferably, the measuring means performs at least two distance measurements at the measuring point in front of the screed to determine the correction value, i.e., one relative to a reference point and one relative to the subgrade, so that any irregularities in the subgrade present at the measuring point can be accurately determined locally as deviations from the foundation and accurately used for levelling the screed.

[0033] The leveling system according to the invention and the leveling method according to the invention can be carried out on both sides of the road finishing machine, and therefore the embodiments described above in relation to the invention can be employed on both sides of the road finishing machine.

[0034] Embodiments of the present invention will now be described in more detail with reference to the following figures. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 shows a road finishing machine for applying a paving layer to a roadbed. [Figure 2] 5 is a schematic extract of a screed of a road finishing machine equipped with measuring means according to a variant of the invention; FIG. [Figure 3] FIG. 10 is a schematic extract of a screed fitted with measuring means according to another variant of the invention; [Figure 4] FIG. 4 is a schematic diagram of a control loop according to the invention for carrying out levelling of the screed of FIGS. 2 and 3; [Figure 5] FIG. 10 is a schematic extract of a screed fitted with measuring means according to a further variant of the invention; [Figure 6] FIG. 6 is a schematic diagram of a control loop for leveling of the screed according to the variant of FIG. 5; DETAILED DESCRIPTION OF THE INVENTION

[0036] In the figures, identical components are always provided with the same reference numerals.

[0037] Figure 1 shows a road finisher 1 which moves over a subgrade 3 in a laying direction R during a laying run and forms a paving layer 2 on the subgrade 3. The road finisher 1 has a height-adjustable screed 4 for (pre-)compacting the paving layer 2. The screed 4 is attached to a towing arm 5 which is connected at a front pull point 6 to a levelling cylinder 7 mounted on a tractor 22 of the road finisher 1. The towing arm 5 acts as a lever which varies the angle of attack of the screed 4 depending on the displacement of the levelling cylinder, in particular to compensate for unevenness 8 of the subgrade 3.

[0038] Figure 2 shows a schematic representation of the screed 4, the towing arm 5 and the levelling cylinder 7. A measuring means 10 is arranged on the towing arm 5 between the front end 9 of the screed and the front towing point 6. The measuring means 10 is configured to perform at least one distance measurement relative to the subgrade 3 and / or a reference 11. According to Figure 2, the reference 11 is provided as a guide wire and is positioned at an average height h above the subgrade 3. 11 The datums 11 are attached to the sides of the road finisher 1 and provide a levelling function for the screed 4, as will be explained in more detail below.

[0039] In Figure 2, the measuring means 10 comprises a first sensor 12 which measures the distance y1 relative to a reference and a second sensor 13 which measures the distance y2 relative to the subgrade 3. Preferably, the first and second sensors 12, 13 are located at equal distances x9 from the front end 9 of the screed 4 in the laying direction R. Thus, at the measuring point 14 according to Figure 2, two distance measurements are made: one for the distance y1 and one for the distance y2.

[0040] 2 further shows that the measuring means 10 is able to detect an unevenness 8 of the subgrade 3 at a measuring point 14 directly below the measuring means 10 by means of two sensors 12, 13. The unevenness 8 indicates a difference from the foundation P. In order to compensate for the unevenness 8 of FIG. 2, a corresponding leveling of the screed 4 is carried out during the continuation of the laying work in the laying direction R, when the front end 9 of the screed 4 reaches directly above the unevenness 8, i.e. at the measuring point 14. In other words, the leveling system according to the variant of the invention shown in FIG. 2 responds to the unevenness 8 detected at the measuring point 14 by the measuring means 10 when the front end 9 of the screed 4 has passed the distance x9 shown in FIG. 2.

[0041] Figure 3 shows a variant of the mounting of the measuring means 10 in Figure 2. The arrangement in Figure 3 differs from that in Figure 2 in that the measuring means 10 is arranged directly at the front towing point 6. In this position, which is also the front end of the towing arm 5, the distances y1, y2 detected by the two sensors 12, 13 can be particularly advantageously employed to compensate for unevenness 8 in the leveling of the screed 4 to form a smooth paving layer 2, since at this point the height of the towing point 6 can be accurately detected without any leveling displacement of the screed 4 being added to it.

[0042] Figure 4 shows a schematic representation of a levelling system 15. The levelling system 15 can use the height measurements detected in Figures 2 and 3 to level the screed 4 to compensate for unevenness 8 in the subgrade 3.

[0043] The leveling system 15 comprises a storage means 16, a control system 17 and a closed-loop control means 18 operatively connected to adapt the settings of the leveling cylinders 7. According to Fig. 4, the distances y1, y2 measured by the sensors 12, 13 are transmitted to the control system 17. The control system 17 determines a set height h, which is the height of the datum 11 relative to the base P, based on the measured distances y1, y2. 11 The correction value K can be determined taking into consideration the above.

[0044] The control system 17 of FIG. 4 subtracts the distance y1 measured by the first sensor 12 to the reference 11 from the distance y2 measured by the second sensor 13 at the measurement point 14 to the roadbed 3, and further subtracts the predetermined height h of the reference 11 from the distance y1 measured by the first sensor 12 to the reference 11. 11 Furthermore, the control system 17 may be configured to continuously store in the storage means 16 the correction values ​​K determined for each measuring point 14 during the laying operation in the laying travel direction R over the laying section, so that each correction value K can be used for levelling the screed 4 when the front end 9 of the screed 4 reaches the corresponding measuring point 14 in the laying section.

[0045] FIG. 4 further shows the current laying speed V of the road finishing machine 1. E can be displayed to the control system 17 by the speed sensor 19. The laying speed V E may be used to determine the distance x9. According to Figure 4, a path measuring means 20 for the levelling system 15 may be provided which is connected to the levelling system 15 or which is a functionally independent unit. The path measuring means 20 detects the distance x9 or the travel section of the front end 9 of the screed 4 when the road finishing machine 1 moves towards the front in the laying direction R during the laying run.

[0046] FIG. 4 further shows the preset basic target value y 1-Basis is transmitted to the control system 17. Furthermore, a correction factor c, which may depend on the geometry of the screed 4, may be stored in the control system 17.

[0047] The control system 17 of FIG. 4 is configured to determine, for each stored correction value K, the path of movement, i.e. the section of movement, traversed by the screed 4, in particular its front end 9, from the time of storage. As soon as the section of movement corresponds to the distance x9, the control system 17 adjusts the correction value K to the basic target leveling value y 1-BasisOptionally, the correction value K may be multiplied by a correction coefficient c.

[0048] Leveling basic target value y 1-Basis can be set manually by the operator on the control panel of the road finishing machine, so that the target height of the screed 4 can be adjusted accordingly for the laying operation. The height of the screed 4 can be determined manually by the operator or measured by a layer thickness sensor (not shown).

[0049] FIG. 4 further illustrates the leveling target value y determined for the measurement point 14. 1-Soll is transmitted to the closed-loop control means 18 after taking into account the correction value K by the control system 17. Furthermore, the measured distance y1 is transmitted to the closed-loop control means 18. The closed-loop control means 18 calculates the leveling target value y 1-Soll and the distance y1 actually measured at the measuring point 14, the control variable u to be sent to the actuator 21 is calculated. The actuator 21 is, for example, a hydraulically driven component, and determines the extension distance s7 of the leveling cylinder 7, thereby adjusting the height h6 of the towing point to raise the screed 4, in particular the rear end of the screed, to the target height h bo It can be positioned at.

[0050] 5 basically shows the configuration of FIG. 3, and the measuring means 10 according to FIG. 5 includes only a first sensor 12 that measures the distance y1 relative to the reference 11. According to the configuration of FIG. 5, the correction value K can be calculated mainly by the distance y1 and the extension distance s7 of the leveling cylinder 7. The correction value K for the unevenness 8 detected by the measuring means 10 is calculated by the distance y1 and the height h relative to the reference 11. 11 and the distance h of the first sensor 12 to the front traction point 6. s The sum of the extension distance s7 of the leveling cylinder 7 and the extension distance s7 of the leveling cylinder 7 is the structural height h of the front traction point 6 relative to the bottom surface F of the traveling device when the leveling cylinder 7 is retracted. zp It can be calculated by subtracting

[0051] 6 shows a schematic diagram of a leveling system 15' having the configuration shown in FIG. 5. Here, the measured distance y1 and the detected extension distance s7 of the leveling cylinder 7 are continuously transmitted to a control system 17, and based on these, a correction value K is calculated for each measurement point 14 in the laying section and stored in a memory means 16. The correction value K is calculated by subtracting the height h of the leveling cylinder 7 in the retracted state from the sum of the above-mentioned values. zp The basic target value y of leveling stored in the control system 17 can be calculated by subtracting 1-Soll The leveling target value y is calculated by subtracting the correction value K from 1-Soll is transmitted as an input quantity to the closed-loop control means 18 at the latest when the front end 9 of the screed 4 arrives at the measuring point 14 for measuring the distance y1, and the closed-loop control means 18 calculates the calculated target leveling value y 1-Soll and the measured distance y1, the control amount u of the actuator 21 that adjusts the leveling cylinder 7 to level the screed 4 is determined.

Claims

1. A road finishing machine (1), comprising: A screed (4) for forming a paving layer (2) on a subgrade (3) along a laying section moved by a road finishing machine (1) in a laying direction (R), the screed (4) being height adjustable and having a towing arm (5) attached to the road finishing machine (1) at a front towing point (6) via leveling cylinders (7), at least one measuring means (10) for performing at least one distance measurement, memory means (16), a control system (17), and closed-loop control means (18) operatively connected to adapt the settings of the leveling cylinders (7), The control system (17) calculates a correction value (K) in response to at least one distance measurement relative to the subgrade (3) and / or a reference (11) made at a measurement point (14) located in front of the front end (9) of the screed (4) in the laying direction (R), stores the correction value (K) at least temporarily in the storage means (17), and calculates a leveling target value (y ) for the measurement point (14) while continuing the laying operation, taking into account the stored correction value (K). １－Ｓｏｌｌ ) and wherein when the front end (9) of the screed (4) reaches the measuring point (14), the leveling cylinder (7) of the screed (4) is controlled based on the leveling target value.

2. 2. Road finishing machine according to claim 1, characterized in that the measuring means (10) are attached to the towing arm (5) of the screed (4).

3. 3. Road finishing machine according to claim 1 or 2, characterized in that the measuring means (10) are arranged in the vicinity of the towing point (6) of the towing arm (5).

4. The measuring means (10) measures the distance (y １ ) and a distance (y ２ 4. A road finishing machine according to claim 1, further comprising at least one second sensor (13) for measuring the rotational speed of the road.

5. The first sensor (12) and the second sensor (13) are positioned at equal distances (x) from the front end (9) of the screed (4) in the laying direction (R). ９ 5. A road finishing machine according to claim 4, characterized in that it is located at

6. The control system (17) controls the distance (y ２ ) to the reference (11) measured by the first sensor (12), １ 6. A road finishing machine according to claim 4 or 5, characterized in that it is configured to determine the correction value (K) for the measurement point (14) by subtracting a predetermined value (h11) of the reference (11) from the roadbed (3) and further by subtracting a predetermined height (h11) of the reference (11) from the roadbed (3).

7. The control system (17) adjusts the preset basic leveling target value (y １－Ｂａｓｉｓ ) and the stored correction value (K) to obtain the leveling target value (y １－Ｓｏｌｌ 7. A road finishing machine according to any one of the preceding claims 4 to 6, characterized in that it is arranged to derive a

8. The control system (17) controls the preset basic leveling target value (y １－Ｂａｓｉｓ ) and the stored correction value (K), the distance (y ) to the reference (11) actually measured by the measuring means (10) is calculated. １ ) to obtain the leveling target value (y １－Ｓｏｌｌ 8. A road finishing machine according to claim 7, configured to calculate:

9. The measuring means (10) measures the distance (y) relative to the roadbed (3) and / or the reference (11). １ , y ２ ) and the control system (17) measures multiple distance measurements (y ) relative to the roadbed (3) and / or the reference (11) made simultaneously. １ , y ２ 9. A road finishing machine according to claim 1, which is configured to form a respective average value on the basis of which the correction value (K) is determined, based on the respective average values ​​of the respective ...

10. 10. A road finishing machine according to any one of claims 1 to 9, characterized in that the control system (17) is configured to multiply the calculated correction value (K) by a correction factor (c) depending on the shape of the screed (4).

11. The road finishing machine (1) comprises at least one path measuring means (20) for detecting the travel distance of the front end (9) of the screed (4), and the travel distance of the screed (4) detected by the path measuring means (20) is determined by the distance (x) between the measuring means (10) and the front end (9) of the screed (4). ９ ), the control system (17) determines the leveling target value (y １－Ｓｏｌｌ 11. A road finishing machine according to claim 1, wherein the calculation of the distance .gtoreq.1 is initiated.

12. The control system (17) continuously calculates and stores correction values ​​(K) while the road finishing machine (1) is running along the construction section, and adjusts the adapted leveling target value (y) using each stored correction value (K). １－Ｓｏｌｌ 12. A road finishing machine according to any one of claims 1 to 11, characterized in that it is arranged to determine

13. 13. A road finishing machine according to any one of claims 1 to 12, characterized in that the control system (17) is configured to determine the correction value (K) using a data model of the roadbed based on GPS data.

14. 14. Road finishing machine according to any one of claims 1 to 13, characterized in that the control system (17) is configured to calculate the correction value (K) taking into account the piston position of the levelling cylinder (7) actually set at the measuring point (14).

15. 15. A road finishing machine according to any one of claims 1 to 14, characterized in that the measuring means (10) is attached to a tractor (22) of the road finishing machine (1) and its measurements can be taken into account together with measurements of further measuring means arranged on the towing arm or on the screed in order to adjust a specific screed height.

16. A method for leveling a screed (4) of a road finishing machine (1), comprising: A control system (17) of the road finishing machine (1) calculates a correction value (K) in response to at least one distance measurement made by a measuring means (10) provided on the road finishing machine (1) at a measuring point (14) located in front of the front end (9) of the screed (4) in the laying direction (R) relative to the subgrade (3) and / or a reference (11), stores said correction value (K) at least temporarily in a storage means (16), and calculates a leveling target value (y) for said measuring point (14) taking into account said stored correction value (K) while continuing the laying operation. １－Ｓｏｌｌ ) and when the front end (9) of the screed (4) reaches the measuring point (14), at least one leveling cylinder (7) of the screed (4) is controlled based on the leveling target value.

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