Road paver with heating element for a screed

Abstract

A road paver comprises a generator, a control device and a screed, the screed comprising a basic screed and being suited to be modified, by selectively attaching or detaching broadening parts, from a first to at least a second, different screed configuration. The basic screed and the broadening parts each comprise one compacting unit and one electric heating element to be supplied with power from the generator for heating the compacting unit to prevent the laying material from adhering to the compacting unit and to finish a high-quality road pavement. The control device is configured to individually switch on or off each one of the two resistance wire windings of the heating element of the basic screed depending on the screed configuration determined by the control device to distribute electrical power generated by the generator to the individual resistance wire windings.

Claims

1. A road paver comprising: a generator; a control device; and a screed comprising a basic screed that is modifiable, by selectively attaching or detaching broadening parts, from a first to at least a second, different screed configuration, the basic screed and the broadening parts each comprising a compacting unit and at least one electric heating element that can be supplied with power by the generator for heating the compacting unit, each heating element comprising at least two resistance wire windings; wherein the control device is configured to determine a screed configuration assumed by the screed based on presence, if any, of broadening parts in addition to the basic screed, and to individually switch on or off each one of the resistance wire windings of the at least one heating element of the basic screed, depending on the screed configuration determined by the control device, to distribute electrical power generated by the generator to the individual resistance wire windings.

2. The road paver according to claim 1 wherein each of the heating elements is designed modularly and is detachably attached to a portion of the screed.

3. The road paver according to claim 1 wherein the control device is configured to individually switch on or off each one of the resistance wire windings of the broadening parts depending on the screed configuration.

4. The road paver according to claim 1 wherein the resistance wire windings of each heating element are designed to output different heating powers.

5. The road paver according to claim 1 wherein the control device is configured to automatically determine the screed configuration.

6. The road paver according to claim 1 wherein the control device is configured to detect the screed configuration by means of a weight sensor or an ID tag.

7. The road paver according to claim 1 further comprising a Power Line Communication (PLC) base module, and wherein the screed comprises one or several PLC modules, and the control device and/or the PLC base module are configured to detect design of the screed by evaluating the PLC modules by PLC.

8. The road paver according to claim 1 wherein for each resistance wire winding of the at least one heating element of the basic screed, a switching relay is provided for switching on or off the resistance wire winding.

9. The road paver according to claim 8 wherein the control device is configured to control each switching relay via a power line by means of Power Line Communication.

10. The road paver according to claim 1, wherein for each resistance wire winding of the heating elements, a switching relay integrated in a heating element monitoring module is provided for switching on or off the resistance wire winding.

11. The road paver according to claim 10 wherein the control device is configured to control each switching relay via a power line by means of Power Line Communication.

12. The road paver according to claim 10 wherein a separate power line and a separate control line are connected to each switching relay of a heating element, and the control device is configured to control the switching relay via the separate control line.

13. The road paver according to claim 1 wherein the basic screed and/or the broadening parts comprise two or more heating elements each, and wherein each of the heating elements comprises at least two resistance wire windings.

14. The road paver according to claim 1 wherein the generator is configured to be operated at variable speeds so that the power of the generator is increased with an increased speed.

15. The road paver according to claim 14 wherein, depending on the setting of an operating mode of the road paver, a maximum generator speed can be pre-set, and the resistance wire windings can be switched on and off by the control device depending on a maximally available generator power.

16. The road paver according to claim 1 wherein the control device is configured to vary heating power of the heating elements depending on a pre-set timed program or switching pattern.

17. The road paver according to claim 1 wherein the control device is configured to process signals from sensors which measure winding temperature, winding resistance, speed or voltage output and thus load of the generator, and to adapt heating power of the heating elements to prevent the generator from being overloaded.

18. A method for heating compacting units of a screed of a road paver comprising a basic screed by means of one or more electric heating elements, wherein the heating elements each comprise at least two resistance wire windings and are provided with power from a generator, and wherein a control device controls the heating of the compacting units, the method comprising: determining, by the control device, a screed configuration assumed by the screed based on presence, if any, of broadening parts in addition to the basic screed; determining, by the control device, a maximally possible electrical power of the generator; and switching on or off individual resistance wire windings, by the control device, depending on at least the screed configuration and pre-set parameters to distribute electrical power generated by the generator to the individual resistance wire windings.

19. The method according to claim 18 wherein the control device automatically determines the screed configuration.

20. The method according to claim 18 wherein a switching relay is assigned to one resistance wire winding of one of the one or more heating elements, and the method further comprises switching on or off the one resistance wire winding by the control device via a power line by Power Line Communication.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic view of an exemplified embodiment of a road paver with a heatable screed according to the disclosure;

(2) FIG. 2 shows a schematic view of an exemplified embodiment of a road paver with a heatable screed according to the disclosure in a first screed configuration comprising a basic screed;

(3) FIG. 3 shows a schematic view of an exemplified embodiment of a road paver with a heatable screed according to the disclosure in a second screed configuration comprising a basic screed and two broadening parts;

(4) FIG. 4 shows a schematic view of an exemplified embodiment of a road paver with a heatable screed which includes a left and a right broadening part and comprises several heating elements;

(5) FIG. 5 shows a schematic detailed view of a PLC module and a heating element of a heatable screed; and

(6) FIG. 6 shows a schematic view of the most important steps of the method, controlled by the control device.

(7) Corresponding components are always provided with the same reference numerals in the figures.

DETAILED DESCRIPTION

(8) FIG. 1 shows an exemplified embodiment of a road paver 1 according to the disclosure in a schematic view with a heatable screed 3 and a tractor 5. Screeds 3 of different types may be exchangeably attached to the tractor 5 via a fastening mechanism. At the bottom side of the screed 3, there is a compacting unit 7 which turns the laying material into a plane and firm road pavement. A weight sensor 8, which is attached to the suspension of the screed 3 at the tractor 5, may serve to determine the screed configuration by means of known weight values of the different models of the screed 3.

(9) FIG. 2 shows a schematic view of an exemplified embodiment of a road paver 1 with a heatable screed 3 according to the disclosure in a first screed configuration comprising a basic screed 9. Two power lines 25 lead from the tractor 5 to the basic screed 9 and essentially serve to supply the screed heating with power and are, due to their dual design, already suited for supplying additional broadening parts. Depending on the required electrical power, one single power line 25 would also be possible and sufficient. The shown first screed configuration already has a sufficient width for the desired field of employment.

(10) FIG. 3 shows a schematic view of an exemplified embodiment of a road paver 1 with a heatable screed 3 according to the disclosure in a second screed configuration, comprising a basic screed 9 and left and right broadening parts 11, 13. This second screed configuration serves to finish, i.e., asphalt, broader roads or areas than in FIG. 2. The broadening parts 11, 13 may be detachably arranged at the basic screed 9 as supplementary elements and may be connected with the basic screed 9 via mechanical and/or hydraulic and/or electrical connections 10. To represent the connections 10, a distance between the basic screed 9 and the broadening parts 11, 13 is shown in the drawing. The broadening parts 11, 13 are actually arranged flush at the basic screed 9 since the road pavement must be formed without any irregularities or ribs. This would occur if there were distances between the broadening parts 11, 13 and the basic screed 9. The broadening parts 11, 13 may also be telescopic elements which are arranged at the basic screed 9 and are completely or partially extensible laterally therefrom.

(11) FIG. 4 shows a schematic view of the components and their connection of an exemplified embodiment of a road paver 1 with a heatable screed 3. The road paver 1 comprises the tractor 5 and the screed 3 which comprises a basic screed 9 and here, by way of example, a left and a right 11, 13 broadening part. The control device 15, a Power Line Communication (PLC) base module 17, and a control panel 21, which the operator uses on the control platform of the road paver 1 to control the screed heating, are typically mounted on the tractor 5. Moreover, the tractor 5 comprises a battery 19 which provides a voltage supply of, for example, 24V and is used to start a primary drive, typically a diesel engine, or to supply the electronic components when the engine is switched off. A generator G is driven by the engine and generates the electrical power for heating the screed 3. Moreover, a contactor 23 is provided for securing the electronic components.

(12) As is shown in the representation, the power lines 25 are used to supply the heating elements 27, and the control signals of the PLC base module 17 are coupled into the power lines 25. Here, a variation is shown in which two power lines 25 lead away from the contactor 23 and thus from the generator G to supply one half each of the screed 3 with power. If the dimensioning is suited, however, only one single power line 25, which leads from the contactor 23 on the tractor 5 to the screed 3 and is distributed to the heating elements 27 on the screed 3, is also possible. The heating elements 27 are connected to the power lines 25 via a PLC module 29. The PLC module 29 receives the signals for switching on and off the resistance wire windings of the heating elements 27 from the control device 15 or the PLC base module 17 and thereby switches a switching relay 31 (FIG. 5) for opening and closing the power supply of the respective resistance wire winding. In addition to the control panel 21, a second control panel 35 may also be present at the screed 3 to permit control directly at the screed 3.

(13) The screed configuration may be determined by the control device 15, for example, by a weight sensor 8 which measures the weight of the screed 3 at its suspension at the tractor 5. As an alternative or in addition, an ID tag 37, which is attached each at the basic screed 9 and the broadening parts 11, 13, may be read out from the control device 15. Here, the weight sensor 8 or the ID tag 37 is connected with the control device 15 and/or the PLC base module 17 by a cable, or its data may be read out via radio communication (e.g., by RFID). The PLC module 29, too, may contain the specific information on the type and design of the screed 3, and the data record may be read out by the control device 15 or the PLC base module 17. The PLC module 29 and the ID tag 37 are here not only present on the basic screed 9, but also on broadening parts 11, 13 which are connected to the basic screed 9 via mechanical and/or hydraulic and/or electric connections 10. If no PLC technique is employed, an additional control line 26 may be arranged which connects the control device 15 with the switching relay 31 (FIG. 5) and transmits the control signal.

(14) Furthermore, a sensor 43 may be attached to the generator G to monitor its operating state and load, e.g., by measuring the winding temperature, the speed or the output voltage.

(15) FIG. 5 shows a detailed schematic view of a PLC module 29 and a heating element 27 of a heatable screed 3. If the heating of the screed 3 is PLC-controlled, the electric current and the control signal reach the switching relay 31 via the power line 25, the switching relay being connected to the power line 25 in such a way that due to the control signal, the switching relay 31 establishes or interrupts the current flow to the heating element 27. Each switching relay 31 switches one of, in this case, two resistance wire windings 41 of the heating element 27 and is connected with the resistance wire winding 41 by one further power line 25 each. The supply line from the generator G to the switching relay 31 or the PLC modules 29 may be effected, if the line dimensions are selected in a suitable manner, by one single power line 25 which is divided in front of the PLC modules 29 towards them. Equally, more than two power lines 25 are conceivable. The electronic circuit within the PLC modules 29 is configured to process the control signals destined for the respective PLC module 29 as is generally known from data transmission. Separate power lines 25 lead from the switching relay 31 or the PLC modules 29 to the individual resistance wire windings 41. Here, an LED light 33 may be inserted to indicate the working state of the resistance wire winding 41. Additionally, the switching relay 31 may be integrated in a heating element monitoring module 32 which provides additional functions for monitoring the screed heating. Preferably, the heating elements 27 are designed modularly, i.e., they are formed to be detachable as a module including their resistance wire windings and are dimensionally stable. The resistance wire windings 41 may be encapsulated in a heat-conducting material.

(16) If no PLC communication is employed, an additional control line 26 may be arranged and transmit the control signal to the switching relay 31.

(17) FIG. 6 shows a schematic view of the most important steps of the method 50 for heating compacting units 7 of a screed 3, controlled by the control device 15. In step 51, the control device 15 determines the screed configuration, for example by means of the weight sensor 8. Thus, e.g., a basic screed 9 may have a known weight of 2.0 t, and two broadening parts 11, 13 of 0.8 t each. Since the weights are specific for the individual screed types, the control device 15 may determine their configurations and heating power data. As an alternative, the screed data are stored in electronic storage units, the ID tags 37, and may be read out by the control device 15. As an alternative, the screed data may also be stored in storage units of the PLC modules 29 or are entered by the operator via an interface.

(18) Then, a further step 53 follows in which the maximally possible electrical power of the generator G is determined by the control device 15. In the process, the selection of the operating mode, e.g., Eco or Power, is considered in which the maximally available power is limited by limiting, in the operating mode Eco, the speed of the generator G to a maximum value, or by allowing, in the operating mode Power, the technically possible maximum power of the generator G.

(19) Subsequently, the control device 15 distributes, in step 55, electrical power generated by the generator G to the resistance wire windings 41 by switching them on or off. As was already mentioned above, one has to distinguish between a maximum electrical power available for heating the screed 3 and a maximum generator power, since the generator G typically also feeds other electric consumers with power. The switching on and off of the resistance wire windings 41 may also be done in a clocked manner, i.e., the individual resistance wire windings 41 are provided with electric energy alternatingly, according to a previously calculated switching pattern.

(20) Starting from the above represented embodiments of a road paver 1 with a heatable screed 3, many modifications thereof are possible. For example, the screed 3 may comprise, apart from the compacting units 7, such as tampers, screed plates or pressing strips, other compacting units 7. Equally, the road paver 1 may also comprise screeds 3 of a fixed working width. The heating elements 27 may be designed differently, as required, where the resistance wire windings 41 may have different shapes and sizes. Modifications of the power and voltage supply and the control device 15 are possible in many variations. For example, the power supply may be designed in direct or alternating current technique.