Road Paver With Control Unit For Determining The Weight And/Or The Center Of Gravity And/Or The Width Of The Screed And Corresponding Method

Abstract

The present invention relates to a road paver with a drive, a bunker, a material conveying device, a screed comprising a tamping device and an electric heating device on the screed and/or on the tamping device, wherein a control unit is provided, which is configured in such a manner that it determines, by means of a measurable electrical operating parameter of the electrical heating device on the screed and/or on the tamping device, the weight and/or the center of gravity and/or the width of the screed transversely to the working direction of the screed. The present invention further relates to a method for determining a width and/or a weight and/or a center of gravity of a screed of a road paver, comprising the steps: measuring an electrical variable of a heating device, in particular a heating power, a heating resistance or a power consumption of the heating device; calculating the weight and/or the center of gravity and/or the width of the screed transversely to the working direction of the screed by means of the electrical operating variable.

Claims

1. A road paver with a drive, a bunker, a material conveying device, a screed and an electric heating device on said screed and/or a tamping device, wherein a control unit is provided which is configured to determine a weight and/or a center of gravity and/or a width of the screed transversely to a working direction of the screed in response to a measurable electrical operating parameter of the electric heating device on the screed and/or on the tamping device.

2. The road paver according to claim 1, wherein the at least one electrical operating parameter is a heating resistance of the screed and/or of the tamping device or a heating power received by the screed and/or the tamping device or a power consumption on the screed and/or the tamping device.

3. The road paver according to claim 1, wherein the screed and/or the stamping device has a variable size, which can be varied in particular by providing at least one add-on part.

4. The road paver according to claim 1, wherein a measuring device is provided for measuring a heating power on the screed and/or on the tamping device, for measuring a resistance on the screed and/or on the tamping device and/or for measuring a power consumption on the screed and/or on the tamping device.

5. The road paver according to claim 1, wherein a hydraulic control arrangement is provided for controlling at least two actuating cylinders which are spaced apart from one another transversely with respect to the working direction, wherein the actuation cylinders are each connected at least indirectly on one side with a frame of the road paver and on the other side with the screed of the road paver, wherein the screed can be subjected to a load pressure and/or a relief pressure via the actuating cylinders, and wherein the control unit is configured to determine a desired load pressure and/or a relief pressure from the determined weight and/or center of gravity and/or width of the screed transversely to the direction of operation of the screed.

6. The road paver according to claim 5, wherein the load pressure and/or the relief pressure can be adjusted by the control unit as a function of a defined operating state of the road paver, wherein the defined operating state includes a downtime of the road paver, an ascent of the road paver or an inclined position of the road paver.

7. The road paver according to claim 6, wherein the control arrangement applies a relief pressure to the at least two actuation cylinders in the defined operating state of a downtime, an ascent or an inclined position.

8. The road paver according to claim 6, wherein a device for determining a cylinder force of the at least two actuation cylinders is provided, which indirectly determines the relief pressure required in the defined operating state of the road paver via of a calculation of the mass of the screed and the center of gravity of the screed transversely to a working direction of the road paver.

9. The road paver according to claim 8, wherein the device for determining the cylinder force determines the mass and the center of gravity of the screed on the basis of a measured heating power or a measured resistance or a measured power consumption.

10. The road paver according to claim 8, wherein the device for determining the cylinder force further takes into account a hydraulic extension width of the screed, a speed of the road paver and/or a transverse and longitudinal inclination of the road paver to calculate the required cylinder force in order to provide the necessary relief pressure in the defined operating state of the road paver.

11. The road paver according to claim 5, wherein the control arrangement controls a first actuating cylinder and a second actuating cylinder of the screed in order to provide the required relief pressure.

12. The road paver according to claim 1, wherein the control unit is configured for adapting an operating parameter of a drive control and/or of a material flow control and/or of a heating control as a function of the determined weight and/or of the determined center of gravity and/or the determined width of the screed transversely to the working direction of the screed.

13. The road paver according to claim 1, wherein the control unit is configured for determining a paving volume considering the known paving height and the determined width of the screed transversely to the direction of operation of the screed.

14. A method for determining a width and/or a weight and/or a center of gravity of a screed of a road paver claim 1, comprising the steps: measuring an electric operating variable of a heating device; and calculating the weight and/or the center of gravity and/or the width of the screed transversely to the operating direction of the screed from the electric operating variable.

15. The method according to claim 14, wherein the method further comprises the step of controlling a relief pressure and/or a load pressure of the at least two actuating cylinders which are spaced apart from one another transversely to the working direction and are each connected on one side to a frame of the road paver and on the other side to a screed of the road paver, wherein the screed can be subjected to a load pressure or a relief pressure via the actuating cylinders and a target value for a load pressure and/or a relief pressure necessary in a defined operating state of the road paver and corresponding to the calculated weight and/or the center of gravity position of the screed is determined.

16. The method according to claim 14, wherein the method further comprises a step of detecting an actual value of a load pressure and/or a relief pressure.

17. The method according to claim 14, wherein the method further comprises the step of controlling the at least two actuation cylinders for generating a load pressure and/or a relief pressure required for a defined operating state, and wherein the defined operating state comprises a downtime of the road paver, an ascent of the road paver or an inclined position of the road paver.

18. The method according to claim 14, wherein the method comprises the adaptation of an operating parameter of a drive control and/or a material flow control and/or a heating control.

19. The method according to claim 14, wherein the method comprises the determination of a paving volume considering a known paving height.

20. The method according to claim 14, wherein the electric operating variable comprises a heating power, a heating resistance or a power consumption of the heating device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In the following, the present invention is described in greater detail by means of the Figures, which are schematic in nature:

[0027] FIG. 1 shows a side view of a road paver with a screed;

[0028] FIG. 2 shows a side view of a screed of a road paver, the screed comprising a heating device;

[0029] FIG. 3 shows a schematic view of a screed of a road paver;

[0030] FIGS. 4A-4D show schematic views of different screed configurations; and

[0031] FIG. 5 shows a flow diagram for the schematic representation of the sequence of the method in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0032] FIG. 1 shows a side view of a road paver 1 with a machine frame 34 (also referred to as frame 34), a material bunker 31 (also referred to as bunker 31), a drive 30, which is usually a diesel combustion engine, a material conveying device 32, which transports material from the bunker 31 through the road paver 1 against the working direction “a” towards the rear and a transverse conveying device 33, for example, a cross-feed screw, which distributes the material to be paved over the entire paving width. In addition, the road paver 1 includes a screed 2, which is attached to a tractor part of the road paver 1 via holding arms 3. The screed 2 is mounted in a height-adjustable manner on the road paver 1 and can be raised, lowered or held in any desired position by means of two double-acting hydraulic cylinders 4, only one of which is visible here. The holding arms 3 are height-adjustable via a leveling cylinder 5 in order to set the angle of incidence of the screed 2. The hydraulic cylinders 4 are connected in an articulated manner to the frame of the road paver 1 on the piston side, i.e., to the cylinder housing. On the piston rod side, the hydraulic cylinders 4 are connected in an articulated manner to the screed 2. On account of its own weight, the screed 2 generates the weight force F.sub.B (FIG. 3), which is directed vertically downwards. In the position shown, the screed 2 is lifted in accordance with the defined operating state, here during a downtime of the road paver 1, so that the screed 2 does not exert any force on the ground and the screed 2 is prevented from sinking into the ground. In this operating state, a corresponding relief pressure is exerted on the hydraulic cylinders 4. If, on the other hand, the ground is processed, i.e., the road paver 1 is in operation and deposits a layer of bituminous paving material of the desired layer thickness on the ground U, the screed 2 is lowered so that it applies a force on the ground. For this purpose, the relief pressure in the hydraulic cylinders 4 is lowered correspondingly. Moreover, it is also possible to apply a load pressure via the hydraulic cylinders 4. In this case, therefore, forces greater than the pure weight force of the paving screed are exerted on the ground to be paved by way of the screed.

[0033] FIG. 2 shows a side view of a screed 2 with a tamping strip or tamping device 8 and a smoothing plate 9 arranged behind it in the working direction a, as well as a supporting housing 10 with an excitation device 11. The tamping device 8 is adjustable vertically in the direction of the arrow “b” and thus performs a tamping movement in the direction of the arrow “b” during the paving operation. In its front region, the tamping device 8 has a guide surface (entry slope 12) extending obliquely in the working direction “a”, followed by a tamping surface 23 extending horizontally. The smoothing plate 9 is connected to the tamping strip. Above the smoothing plate 9, an excitation device 11 is arranged, via which a vibratory movement can be induced in the screed 2. The smoothing plate 9 has an underside 19, which slides over the material to be paved during operation and smoothes it. The smoothing plate 9 and the region with the inlet slope 12 are provided with heating devices 18, which can be configured, e.g., as heating layers (a first heating layer, an insulation layer and a metallic heating layer), which are applied, e.g., by thermal spraying, in particular by plasma spraying or HVOF, successively to the smoothing plate 9 and/or tamping device 8. However, other embodiments of electrical heating devices for heating the screed 2 and/or tamping device 8 can also be implemented, such as, e.g., heating rods. It is also possible to configure the tamping device 8 entirely without a heating device or the screed 2 without a tamping device.

[0034] In accordance with the present invention, the width, the weight and/or the center of gravity of the paving screed 2 can be determined by measuring an electrical operating parameter of the electrical heating device. This shall be described further in the following figures.

[0035] FIG. 3 shows a schematic view of the screed 2, here with an uneven weight distribution. The screed 2 includes a basic or main screed 6 and two screed extensions 7, 7′, which can be extended individually and hydraulically via positioning cylinders 10, 10′. In addition, additional screeds, configured as rigid add-on parts 13, 13′, 13″, 13′″, can be attached to the screed extensions 7, 7′ for broadening the working width, if required. The actuating cylinders, which are configured as double-acting hydraulic cylinders 4, 4′, are each connected in an articulated manner to one side of the basic screed 6, each at an equal distance from the axis of symmetry 15. If the screed 2 is widened symmetrically, the overall center of gravity of the screed 2 lies on the line of symmetry 15. In this case, the cylinders 4, 4′ would be supplied with the same load pressure and relief pressure. However, there are paving situations in which an asymmetrical broadening of the screed 2 is required, as shown FIG. 3. In this case, the overall center of gravity 16 of the screed 2 shifts to the right by a length 17 so that the line of action of the weight force FB of the screed 2 is shifted by the length 17 from the axis of symmetry 15.

[0036] The hydraulic cylinders 4, 4′ are actuated independently of one another in the case of a non-uniform distribution of weight due to an asymmetrical screed broadening so that overall a uniform, even distribution and compression of the material is achieved. For example, the right cylinder 4′ could raise the right side of the base screed 6 slightly in order to counteract a slope due to the displacement of the center of gravity 16. However, it is also conceivable to press the left side of the basic screed 6 on the material to be laid by means of the left cylinder 4 or to carry out both measures simultaneously. However, in order to determine the pressure to be applied on the left and right cylinders 4, 4′, i.e., the load pressure or the relief pressure, it is necessary to determine both the mass of the screed 2 and the exact position or displacement of the overall center of gravity 16. According to one embodiment of the present invention, this occurs via the hydraulic control arrangement 14 and/or the control unit 20, which determines the desired load pressure and/or the relief pressure to be applied on the hydraulic cylinders 4, 4′ indirectly via at least one electric operating parameter of an electric heating device 18 (see FIG. 2), which can be measured on the screed 2 and/or on a tamping device 8. In particular, the at least one electrical operating parameter is a heating resistance of the screed 2 and/or of the tamping device 8 or the heating power received by the screed 2 and/or the tamping device 8 or the power consumption on the screed 2 and/or the tamping device 8. The load pressure and/or the relief pressure can be set by the control unit 20 as a function of a defined operating state of the road paver 1. The defined operating state in which a relief pressure is applied to the hydraulic cylinders 4, 4′ comprises a downtime of the road paver, an ascent or an inclined position. In this case, the hydraulic cylinders 4, 4′ are subjected, as required, either to the same relief pressure or to two different relief pressures, for example, in the case of an inclined position and/or an asymmetrical distribution of the mass of the screed 2 with the add-on parts 13, 13′, 13″, 13′″.

[0037] In order to determine the heating power, the resistance at the screed 2 and/or at the tamping device 8 (see FIG. 2), and/or the power consumption at the screed 2 and/or at the tamping device 8, different measuring devices are provided, which are designated here schematically by the reference numeral 21. Likewise, a device 22 is provided for determining the cylinder force of the hydraulic cylinders 4, 4′, which device 22 indirectly determines the relief pressure required in the defined operating state of the road paver 1 by calculating the mass of the screed 2 and the overall center of gravity 16 of the screed 2 from the above-described electrical operating parameters.

[0038] FIGS. 4A-4D show various configurations of the screed 2, specifically different attachment sizes and mass distributions of the screed 2 transversely to the direction of travel or working direction “a”. The force vector F1 acts on the basic screed 6 and the force vectors F2, F3, F4, F5 and F6 act on the respective centers of gravity of the attachments. As can be seen in FIG. 4A, a situation is shown here in which the left width extension 7 of the screed 2 is extended further than the right width extension 7′ (y>x), which causes a displacement of the overall center of gravity of the screed 2. The situation shown in FIG. 4B basically proceeds from the situation shown in FIG. 4A, but add-on parts 13, 13′, 13″ are additionally provided on the screed 2, namely a single add-on part 13 on the left side of the screed 2 and two further add-on parts 13′, 13″ on the right side of the screed 2, which leads to a further displacement of the center of gravity. FIG. 4C shows a situation, which starts out again from the situation shown in FIG. 4A, but in contrast to FIG. 4C, the add-on parts 13, 13′ of equal size are provided on either side of the axis of symmetry 15 of the screed 2. In this case as well, the center of gravity is shifted due to the different extension widths of the right and left screed width extensions 7, 7′. Finally, FIG. 4D shows a situation in which the arrangement shown in FIG. 4B is guided in an inclined position. The uniform load pressure or relief pressure of the screed is achieved by adjusting the respective forces on the right and left hydraulic cylinders 4, 4′. The adjustment of these forces is effected by applying appropriate pressure to the actuation cylinders. For all the situations illustrated, it is therefore necessary to determine the mass of the screed, i.e., including all width extensions 7, 7′ and add-on parts 13, 13′, 13″ and, in particular, in view of the asymmetric mass distributions, also the distances of the add-on parts with respect to the axis of symmetry 15, in order to determine indirectly the forces F1-F6 acting downwards and the required load pressure or relief pressure to be applied to the hydraulic cylinders 4, 4′, as already described above.

[0039] The determination in accordance with one embodiment of the present invention begins here. With the enlargement of the paving width, the heating surface of the overall screed also increases, as does the consumption of electrical heating energy. If an electrical operating parameter proportional to the electrical heating energy is now determined, the total width of the screed 2 can be inferred. If, for example, the mass of the add-on parts 13, 13′ and 13″ is known, the heating power of the overall arrangement, e.g., as a function of the number of add-on elements 13, 13′ and 13″, and ultimately the total weight of the screed arrangement can be determined. For ascertaining the center of gravity, it is useful if the electrical operating parameter in question, e.g., the heating power, is determined separately at the sides of the basic screed in order to be able to draw conclusions here about a weight distribution at the sides. Further data advantageously taken into account by the control unit 20 are parameters such as the hydraulic extension width of the add-on screeds 7, 7′, the speed and/or the transverse and/or longitudinal inclination of the road paver 1, etc. It is then possible to determine the required adjusting force, whether for a load pressure or a relief pressure, on the right and left actuating cylinders 4, 4′.

[0040] Overall, an automatic calculation of the required pressure for the actuating cylinders 4, 4′ is thus possible with the system described above, as is an automatic adaptation of the entire system to different extension situations and/or overall configurations of the screed 2. In addition, or alternatively, a display of the required pressure—or at least of whether the required pressure has already been reached, has yet to be reached or has been exceeded—can also be provided. For this purpose, a display device 24, e.g., a display screen, is provided on the screed 2 itself and/or in the operating platform of the road paver 1, the display device 24 also being controlled by the control unit 20. As an alternative to the automatic adaptation of the entire system, the adjustment of the actuation cylinders 4, 4′ can also occur by means of manual entries until the target values determined by control unit 20 have been reached.

[0041] FIG. 5 shows a flow diagram for the schematic representation of the sequence of the method in accordance with one embodiment of the present invention. It includes the following steps. In a first step S1 of the present example, a heating device 18 for heating the screed 2 and/or the tamping device 8 is switched on, although this step is optional. An electrical operating variable of the heating device 18, in particular a heating power, a heating resistance or a power consumption of the heating device 18, is then measured in a next step S2. In step S3, the width, the weight and/or the center of gravity transversely to the working direction “a” of the screed 2 is calculated via the electrical operating variable. The calculated values can be used to control a plurality of operating parameters of the road paver 1. In step S5, for example, a target value for a load pressure and/or relief pressure necessary in a defined operating state of the road paver 1 and corresponding to the calculated weight and/or the center of gravity of the screed 2, can be determined. Furthermore, the method includes a step S6 for detecting an actual value of the load pressure and/or the relief pressure.

[0042] While the present invention has been illustrated by description of various embodiments and while those embodiments have been described in considerable detail, it is not the intention of Applicants to restrict or in any way limit the scope of the appended claims to such details. Additional advantages and modifications will readily appear to those skilled in the art. The present invention in its broader aspects is therefore not limited to the specific details and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of Applicant's invention.