Road paver with compaction control

Abstract

A road paver comprises a paving screed, wherein the paving screed comprises a tamper, and the road paver further comprises a GNSS receiver and a material conveyor. In addition, the road paver comprises an electronic control system, which comprises a memory and a data processor, wherein digital construction data, in particular a target height profile of a road surface to be paved, a target layer thickness of paving material and, if necessary, a height profile of a roadbase are stored in the memory. The control system is configured to automatically control compaction performance of the paving screed as a function of the target layer thickness in order to pave the paving material for the respective local coordinate point of the road paver determined by the GNSS receiver.

Claims

1. A road paver comprising: a paving screed including a tamper; a GNSS receiver; a material conveyor; and an electronic control system comprising a memory and a data processor, wherein in the memory digital construction data are stored including a target layer thickness of paving material and a pre-compaction degree that depends on the target layer thickness for a respective local coordinate point, and the control system is configured to automatically control compaction performance of the paving screed as a function of the target layer thickness in order to pave the paving material with the pre-compaction degree for the respective local coordinate point of the road paver determined with the GNSS receiver.

2. The road paver according to claim 1, wherein the digital construction data further comprise a target height profile of a road surface to be produced.

3. The road paver according to claim 1, wherein the control system is configured to automatically adjust the compaction performance of the paving screed by controlling paving speed.

4. The road paver according to claim 1, wherein the digital construction data further comprise a height profile of a roadbase on which the paving material is to be paved.

5. The road paver according to claim 1, wherein the paving screed comprises a screed plate and/or a pressure bar, and the control system is configured to automatically adjust the compaction performance of the paving screed by controlling vibration frequency and/or amplitude of the screed plate and/or pressure of the pressure bar.

6. The road paver according to claim 1, further comprising a sensor for measuring an actual layer thickness of paving material, wherein the control system is configured to calculate a deviation of the actual layer thickness from the target layer thickness.

7. The road paver according to claim 1, wherein the control system is configured to automatically adjust the compaction performance of the paving screed by controlling tamper frequency and/or tamper stroke of the tamper.

8. A method for operating a road paver, the method comprising: storing digital construction data in a memory of an electronic control system, wherein the digital construction data includes a target height profile of a road surface to be produced, a target layer thickness of a paving material for local coordinate points of a roadbase, and a respective pre-compaction degree depending on the target layer thickness; and paving of the paving material, wherein a current position of the road paver is determined by means of a GNSS receiver and the electronic control system automatically controls compaction performance of a paving screed of the road paver as a function of the target layer thickness in order to pave the paving material at the respective pre-compaction degree depending on the target layer thickness.

9. The method according to claim 8, wherein the paving of the paving material comprises detecting an actual layer thickness of the paving material by a sensor, calculating a difference between the actual layer thickness and the target layer thickness, and automatically controlling the road paver to minimize the difference.

10. The method according to claim 8, wherein the paving screed comprises a tamper, and the electronic control system automatically adjusts the compaction performance of the paving screed by controlling tamper frequency and/or tamper stroke of the tamper.

11. The method according to claim 8, wherein the paving screed comprises a screed plate and/or a pressure bar, and the control system automatically adjusts the compaction performance of the paving screed by controlling vibration frequency and/or amplitude of the screed plate and/or pressure of the pressure bar.

12. The method according to claim 8, wherein the control system automatically adjusts the compaction performance of the paving screed by controlling paving speed.

13. The method according to claim 8, wherein the digital construction data comprising the height profile of the roadbase is transferred at a beginning of the method from an external data processing system to the memory of the electronic control system by means of a radio or cable connection.

14. The method according to claim 8, wherein by means of an external data processing system the compaction performance is calculated as a function of the target layer thickness and/or the compaction performance is assigned to a local point as a function of the target layer thickness and data is then transferred to the memory of the electronic control system.

15. The method according to claim 8, wherein by means of the electronic control system the compaction performance is calculated as a function of the target layer thickness and/or the compaction performance is assigned to a local coordinate point as a function of the target layer thickness.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, embodiments of the disclosure are described in more detail using the Figures.

(2) FIG. 1 shows a schematic side view of a road paver;

(3) FIG. 2 shows a three-dimensional view of construction data;

(4) FIG. 3 shows a schematic view of screed compaction of paving material on a level roadbase;

(5) FIG. 4 shows a schematic view of roller compaction of paving material on level roadbase;

(6) FIG. 5 shows the graphic representation of the change in compaction degree of the paving screed as a function of layer thickness at constant rolling dimension;

(7) FIG. 6 shows a schematic view of screed compaction of paving material on an irregular roadbase; and

(8) FIG. 7 shows a schematic view of roller compaction of paving material on an irregular roadbase.

(9) Components corresponding to each other are marked with the same reference numerals in the Figures.

DETAILED DESCRIPTION

(10) FIG. 1 shows a schematic side view of a road paver 1, wherein in a lower area in a sectional view a hopper 3 with paving material 5 is shown, and the paving material 5 is conveyed by a material conveyor 7 through a tunnel 9 to the rear in front of a paving screed 11, where it is evenly distributed by an auger 12. The road paver 1 also includes a GNSS receiver 13 which is connected to an electronic control system 15. The electronic control system 15 comprises a memory 17 and a data processor 19. The paving screed 11 comprises a tamper 21, a screed plate 23, and a pressure bar 25, wherein a plurality of these components may also be present. The paving material 5 is pre-compacted by means of the paving screed 11 and paved on a roadbase 27 as road surface 28 with a layer thickness d.sub.B, which in ideal operation corresponds to the target layer thickness d.sub.S, wherein the target layer thickness d.sub.S is higher by one rolling dimension s than the desired final layer thickness d.sub.E, which is present after post-compaction by a roller. A sensor 29, which can be attached to the paving screed 11 or to the chassis of the road paver 1, is used to measure the actual layer thickness d.sub.I of the paving material 5. The sensor 29 can also be attached in such a way that it measures the actual layer thickness d.sub.I while paving, thus enabling the paving screed 11 to be readjusted. An external data processing system 31, e.g., a laptop computer, may be provided for transmitting and receiving construction data, by means of a radio link via antennas 33 on the road paver 1 and on the data processing system 31, wherein the antennas 33 may also be suitable for receiving satellite signals for position determination, or via a cable connection 35.

(11) FIG. 2 shows a three-dimensional view of digital construction data 37. The roadbase 27 has a height profile 39, which includes height data for individual local coordinate points 41. This height profile 39 may have been obtained from a previous surface scan using an external vehicle. However, it is also possible that a scanning device is attached to the road paver 1 itself and the surface scan is carried out for a part of the roadbase 27 further forward in the direction of travel, while paving material 5 is already being paved in a rear part based on the digital construction data 37 already obtained. The data of the height profile 39 of the roadbase 27 are enriched with the data of a target height profile 43 of the road pavement 28 to be paved. In accordance with the elevations and depressions of the height profile 39 of the roadbase 27, the different target layer thicknesses d.sub.S are thus stored for the respective local coordinate points 41. The number of data points or local coordinate points 41, for which roadbase and road surface data are stored, can vary depending on the technical specifications for data collection and processing, for example the accuracy of the GNSS, and thus represents a form of “resolution.” It is also conceivable that the processing of the digital construction data 37 includes algorithms that distinguish areas with frequent and/or more severe irregularities in the roadbase 27 from areas with little change and proportionally adjust the number of data points, thereby maintaining a high information density on the one hand and reducing the data volume on the other. The position of the data points 41 in the grid can be influenced by a sensor position. The digital construction data 37 includes further data, which were calculated in particular on the basis of the measured data, such as the height profile 39 of the roadbase 27, such as a desired compaction degree per local coordinate point 41.

(12) FIG. 3 shows a schematic view of screed compaction of paving material 5 on a level roadbase 27. The paving material 5 is deposited by the material conveyor 7 and auger 12 in front of the paving screed 11 with a bulk density ρ.sub.S. The paving screed 11, which is pulled by the road paver 1 in direction of travel F, compacts the paving material 5 to a screed density ρ.sub.B and a layer thickness d.sub.B equal to the target layer thickness d.sub.S for screed paving, thus paving the road surface 28. In the case of a level roadbase 27, the paving screed 11 can be used without any major changes to the paving parameters once set.

(13) FIG. 4 shows a schematic view of the roller compaction of paving material 5 or the road surface 28 paved by the paving screed 11 on a level roadbase 27. The layer thickness d.sub.B is reduced by the rolling dimension s to the final layer thickness d.sub.E for which the roller 45 performs one or more runs. The density of the pavement material 5 increases to the rolling density pw. Accordingly, a compaction degree can be specified for paving screed 11 and roller 45:

(14) $\mathrm{Compaction}\mathrm{degree}{k}_B\mathrm{of}\mathrm{paving}\mathrm{screed}=k_B=\frac{{\rho }_B}{{\rho }_M}*100\%\mathrm{Compaction}\mathrm{degree}{k}_W\mathrm{of}\mathrm{roller}=k_W=\frac{{\rho }_W}{{\rho }_M}*100\%$

(15) Here, ρ.sub.M is the density of the Marshall test specimen, which is produced with a compaction device under laboratory conditions. The density ρ.sub.M essentially corresponds to the maximum density of the paving material 5, i.e., the compaction degree k.sub.B, k.sub.W indicates the percentage of the maximum density ρ.sub.M to which the paving material 5 is brought by the respective machine, paving screed 11 or roller 45.

(16) FIG. 5 shows the graphical representation of the change in compaction k.sub.B as a function of layer thickness d.sub.B of the paving screed 11 at constant rolling dimension s according to equation 1, which is derived as follows:

(17) It applies generally:

(18) $\rho =\frac{m}{V}=\frac{m}{b*x*d}$

(19) with m, b, x=const. and m=mass, b=width, x=length in driving direction and d=layer thickness of the considered section of the road surface 28.

(20) Further applies thus:

(21) $k=\frac{{\rho }_1}{{\rho }_2}=\frac{d_1}{d_2}$

(22) It follows that, assuming that after final compaction of the road surface by the roller, the material density ρ.sub.W corresponds approximately to the Marshall density ρ.sub.M for the compaction degree k.sub.B of the road surface

(23) $k_B=\frac{{\rho }_B}{{\rho }_W}=\frac{{\rho }_B}{{\rho }_M}=\frac{d_W}{d_B}\mathrm{with}{\rho }_W\approx {\rho }_M$
With
rolling dimension s=d.sub.B−d.sub.W.fwdarw.d.sub.W=d.sub.B−s
follows:

(24) $\begin{array}{cc}{k}_B=\frac{d_B-s}{d_B}& \mathrm{Equation}1\end{array}$

(25) As the layer thickness d.sub.B is predetermined and varies due to the irregularities of the roadbase 27, the compaction degree k.sub.B must be adjusted according to FIG. 5 in order to obtain the same rolling dimension s for all layer thicknesses d.sub.B, i.e., to remain on the corresponding functional curve (s=10 mm, 20 mm, 30 mm) in FIG. 5.

(26) FIG. 6 shows a schematic view of screed compaction of paving material 5 on irregular roadbase 27. The layer thicknesses d.sub.B1 and d.sub.B2 are specified to obtain a level road pavement 28 at a desired level. The rolling dimension s, by which the height of the road surface 28 is reduced by the rolling compaction, is purposefully taken into account. The respective compaction degrees k.sub.B1 and k.sub.B2 are calculated according to equation 1. The electronic control system 15 is capable of controlling the compaction performance of paving screed 11 by activating one or a plurality of the compaction units 21, 23, 25, thus producing the respective calculated degree of compaction k.sub.B at the point known from the three-dimensional construction data 37. The compaction ratio k.sub.B and thus the density ρ.sub.B depending on the layer thickness d.sub.B is paved in order to achieve a uniform rolling dimension s everywhere during subsequent post-compaction by roller 45.

(27) FIG. 7 shows a schematic view of the roller compaction of paving material 5 on irregular roadbase 27. The rolling dimension s is the same everywhere due to the adapted compaction degrees k.sub.B1, k.sub.B2. The road surface 28, which has already been paved by paving screed 11, is thus compacted by roller 45 while maintaining the longitudinal levelness. After roller compaction, the road surface 28 has a uniform density ρ.sub.W, a uniform compaction degree k.sub.W and a final layer thickness d.sub.E that varies in accordance with the roadbase 27.