Road milling machine and method for controlling a road milling machine

Abstract

A self-propelled road milling machine includes a plurality of height sensors and a controller configured to determine a cross slope of the roadway being milled. Wherein in a first leveling mode at least two sensors are longitudinally aligned and laterally spaced on one side of the milling machine, closet to the center of the road. The controller using sensor signals to adjust the cross slope of the milling drum to be parallel to the cross slope of the roadway adjacent the milling machine. Wherein in a second leveling mode the sensors are on opposite sides of the milling drum.

Claims

1. A road milling machine, comprising: a machine frame on which a milling drum is arranged; at least one running gear on a left side of the road milling machine in the working direction and at least one running gear on a right side of the road milling machine in the working direction; lifting devices respectively corresponding to each of said running gears and upon which the machine frame is supported, wherein one or more of a height and an inclination of the machine frame is adjustable with respect to a driving surface by actuating of the lifting devices; a first distance measuring device configured to measure a first distance between at least one associated reference point and the driving surface; a second distance measuring device configured to measure a second distance between at least one associated reference point and the driving surface; a controller configured to compare a first distance value corresponding to the first measured distance to a first prespecified distance value, to compare a second distance value corresponding to the second measured distance to a second prespecified distance value, and to generate control signals for one or more of the lifting devices according to respective deviations therefrom; wherein in a first levelling mode for a track section on an outer side of the driving surface: the respective reference points of the first and second distance measuring devices are each located on a first side of the milling drum closest to a centre of the driving surface, wherein the reference point of the second distance measuring device lies at a lateral distance extending from the reference point of the first distance measuring device and away from the milling drum; the controller is configured, according to a deviation of the first distance value from the prespecified distance value, to generate control signals for the at least one lifting device corresponding to the first side of the milling drum, and the controller is configured, according to a deviation of the second distance value from the prespecified distance value, to generate control signals for the at least one lifting device corresponding to an opposing second side of the milling drum.

2. The road milling machine of claim 1, wherein in a second levelling mode for a track section on an inner side of the driving surface: the first distance measuring device is configured such that its reference point lies on the left side of the milling drum in the working direction, the second distance measuring device is configured such that its reference point lies on the right side of the milling drum in the working direction, and the reference point of the second distance measuring device lies at a lateral distance from the reference point of the first distance measuring device on the right side of the reference point of the first distance measuring device.

3. The road milling machine of claim 2, wherein the controller, for the second levelling mode, is configured such that the at least one lifting device corresponding to the at least one running gear on the left side in the working direction is retracted if the first distance value is greater than the prespecified distance value, the at least one lifting device corresponding to the at least one running gear on the left side in the working direction is extended if the first distance value is less than the prespecified distance value, the at least one lifting device corresponding to the at least one running gear on the right side in the working direction is retracted if the second distance value is greater than the prespecified distance value, and the at least one lifting device corresponding to the at least one running gear on the right side in the working direction is extended if the second distance value is less than the prespecified distance value.

4. The road milling machine of claim 1, wherein: the first and second distance measuring devices are configured such that their reference points lie on the left side of the milling drum in the working direction, the reference point of the second distance measuring device lies at a lateral distance from the reference point of the first distance measuring device on the left side of the reference point of the first distance measuring device, and the controller, for the first levelling mode, is configured according to the deviation of the first distance value from the prespecified distance value, to generate control signals for the at least one lifting device corresponding to the at least one running gear on the left side in the working direction, and according to the deviation of the second distance value from the prespecified distance value, to generate control signals for the at least one lifting device corresponding to the at least one running gear on the right side in the working direction.

5. The road milling machine of claim 4, wherein the controller is configured, for the first levelling mode, such that the at least one lifting device corresponding to the at least one running gear on the left side in the working direction is retracted if the first distance value is greater than the prespecified distance value, the at least one lifting device corresponding to the at least one running gear on the left side in the working direction is extended if the first distance value is less than the prespecified distance value, the at least one lifting device corresponding to the at least one running gear on the right side in the working direction is extended if the second distance value is greater than the prespecified distance value, and the at least one lifting device corresponding to the at least one running gear on the right side in the working direction is retracted if the second distance value is less than the prespecified distance value.

6. The road milling machine of claim 1, wherein: the first and second distance measuring devices are configured such that their reference points lie on the right side of the milling drum in the working direction, the reference point of the second distance measuring device lies at a lateral distance from the reference point of the first distance measuring device on the right side of the reference point of the first distance measuring device, and the controller, for the first levelling mode, is configured according to the deviation of the first distance value from the prespecified distance value, to generate control signals for the at least one lifting device corresponding to the at least one running gear on the right side in the working direction, and according to the deviation of the second distance value from the prespecified distance value, to generate control signals for the at least one lifting device corresponding to the at least one running gear on the left side in the working direction.

7. The road milling machine of claim 6, wherein the controller, for the first levelling mode, is configured such that the at least one lifting device corresponding to the at least one running gear on the right side in the working direction is retracted if the first distance value is greater than the prespecified distance value, the at least one lifting device corresponding to the at least one running gear on the right side in the working direction is extended if the first distance value is less than the prespecified distance value, the at least one lifting device corresponding to the at least one running gear on the left side in the working direction is extended if the second distance value is greater than the prespecified distance value, and the at least one lifting device corresponding to the at least one running gear on the left side in the working direction is retracted if the second distance value is less than the prespecified distance value.

8. The road milling machine of claim 1, wherein the controller is configured to retract or extend the respective lifting devices such that the deviation of the first distance value or the second distance value from the prespecified distance value is minimized.

9. The road milling machine of claim 1, wherein the lateral distance of the reference point of the second distance measuring device from the reference point of the first distance measuring device in the first levelling mode corresponds to the lateral distance of the reference point of the second distance measuring device from the reference point of the first distance measuring device in the second levelling mode.

10. The road milling machine of claim 1, wherein one or more of the first and second distance measuring device comprises at least one distance sensor which is a tactile distance sensor or a contactless distance sensor.

11. The road milling machine of claim 1, wherein: one or more of the first and second distance measuring device comprises a row of distance sensors arranged with an offset in the longitudinal direction of the road milling machine, and one or more of the first and second distance measuring device is configured to determine the respective distance value from the distances measured by the distance sensors.

12. A method for controlling a road milling machine comprising a machine frame on which a milling drum is arranged, at least one running gear on a left side of the road milling machine in the working direction, at least one running gear on a right side of the road milling machine in the working direction, and lifting devices respectively corresponding to each of said running gears and upon which the machine frame is supported, the method comprising: measuring a first distance between at least one first reference point and a driving surface; measuring a second distance between at least one second reference point and the driving surface; and in a first levelling mode for a track section on an outer side of the driving surface, wherein the first and second reference points are each located on a first side of the milling drum closest to a centre of the driving surface, and the second reference point lies at a lateral distance extending from the first reference point and away from the milling drum: comparing a first distance value corresponding to the first measured distance to a first prespecified distance value, and actuating the at least one lifting device corresponding to the first side of the milling drum according to a deviation therefrom; and comparing a second distance value corresponding to the second measured distance to a second prespecified distance value, and actuating the at least one lifting device corresponding to a second and opposing side of the milling drum according to a deviation therefrom.

13. The method of claim 12, wherein the lifting devices are retracted and extended to minimize the deviation of the first distance value determined by the first distance measurement or the second distance value determined by the second distance measurement from the prespecified distance value.

14. The method of claim 12, wherein the lateral distance of the second reference point from the first reference point in the first levelling mode corresponds to the lateral distance of the second reference point from the first reference point in the second levelling mode.

15. The method of claim 12, wherein the distance measurement is a tactile or contactless distance measurement.

16. The method of claim 12, wherein the distance from the driving surface is measured at a series of reference points offset in the longitudinal direction of the road milling machine.

17. The method of claim 12, wherein: the first and second reference points lie on the left side of the milling drum in the working direction, and the second reference point lies at a lateral distance from and on the left side of the first reference point, according to the deviation of the first distance value from the prespecified distance value, the at least one lifting device corresponding to the at least one running gear on the left in the working direction is actuated, and according to the deviation of the second distance value from the prespecified distance value, the at least one lifting device corresponding to the at least one running gear on the right in the working direction is actuated.

18. The method of claim 17, wherein during the movement of the construction machine in a track section on the outer side of the driving surface: the at least one lifting device corresponding to the at least one running gear on the left side in the working direction is retracted if the first distance value is greater than the prespecified distance value, the at least one lifting device corresponding to the at least one running gear on the left side in the working direction is extended if the first distance value is less than the prespecified distance value, the at least one lifting device corresponding to the at least one running gear on the right side in the working direction is extended if the second distance value is greater than the prespecified distance value, and the at least one lifting device corresponding to the at least one running gear on the right side in the working direction is retracted if the second distance value is less than the prespecified distance value.

19. The method of claim 12, wherein: the first and second reference points lie in the working direction on the right side of the milling drum, and the second reference point lies at a lateral distance from the first reference point on the right side of the first reference point, according to the deviation of the first distance value from the prespecified distance value, the at least one lifting device corresponding to the at least one running gear on the right side in the working direction is actuated, and according to the deviation of the second distance value from the prespecified distance value, the at least one lifting device corresponding to the at least one running gear on the left side in the working direction is actuated.

20. The method of claim 19, wherein: the at least one lifting device corresponding to the at least one running gear on the right side in the working direction is retracted if the first distance value is greater than the prespecified distance value, the at least one lifting device corresponding to the at least one running gear on the right side in the working direction is extended if the first distance value is less than the prespecified distance value, the at least one lifting device corresponding to the at least one running gear on the left side in the working direction is extended if the second distance value is greater than the prespecified distance value, and the at least one lifting device corresponding to the at least one running gear on the left side in the working direction is retracted if the second distance value is less than the prespecified distance value.

21. The method of claim 12, wherein in a second levelling mode for a track section on an inner side of the driving surface: the first reference point lies on the left side of the milling drum in the working direction, the second reference point lies on the right side of the milling drum in the working direction and at a prespecified lateral distance to the right of the first reference point.

22. The method of claim 21, wherein during movement of the construction machine in a track section on the inner side of the driving surface: the at least one lifting device corresponding to the at least one running gear on the left side in the working direction is retracted if the first distance value is greater than the prespecified distance value, the at least one lifting device corresponding to the at least one running gear on the left side in the working direction is extended if the first distance value is less than the prespecified distance value, the at least one lifting device corresponding to the at least one running gear on the right side in the working direction is retracted if the second distance value is greater than the prespecified distance value, and the at least one lifting device corresponding to the at least one running gear on the right side in the working direction is extended if the second distance value is less than the prespecified distance value.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) An embodiment of the invention is explained in more detail below with reference to the drawings, in which:

(2) FIG. 1 shows a side view of an embodiment of a road milling machine,

(3) FIG. 2 shows the levelling device of the road milling machine in a highly simplified schematic representation,

(4) FIG. 3 shows a plan view of a driving surface that is being machined by the road milling machine, in which the road milling machine is machining a track section on the outside of the driving surface,

(5) FIG. 4 shows a plan view of a driving surface that is being machined by the road milling machine, in which the road milling machine is machining a track section on the inside of the driving surface, and

(6) FIG. 5 shows a simplified schematic representation of the road milling machine machining the track section on the outside of the driving surface.

DETAILED DESCRIPTION

(7) FIG. 1 shows a side view of a self-propelled road milling machine 1 for milling road surfaces. The road milling machine 1 has a chassis 2 and a machine frame 3. The chassis 1 has, in the working direction A, a front left running gear 4 and a front right running gear 5, as well as a left rear running gear 6 and a right rear running gear 7. Chain tracks or wheels can be used as the running gear.

(8) To adjust the height and/or inclination of the machine frame 3 relative to the surface of the ground (traffic surface), the road milling machine has lifting devices 4A, 5A, 6A, 7A on which the machine frame 3 is supported, and which are functionally assigned to the individual running gear mechanisms 4, 5, 6, 7. The lifting devices 4A, 5A, 6A, 7A each have a piston/cylinder arrangement 9.

(9) The road milling machine 1 further has a milling drum 10 equipped with milling tools, which is arranged on the machine frame 3 between the front and rear running gear mechanisms 4, 5, 6, 7 in a milling drum housing 11, which is closed on the longitudinal sides by a left and a right edge protector 12, 13.

(10) By retracting and extending the piston/cylinder assemblies 9 of the lifting devices 4A, 5A, 6A, 7A, the height and/or inclination of the machine frame 3, and the milling drum 10 arranged on the machine frame, can be adjusted relative to the traffic surface 8.

(11) A conveyor device 14 with a conveyor belt is provided to carry away the milled surface pavement.

(12) The road milling machine according to the invention has a levelling device 15 (shown only schematically in FIG. 1) for driving the lifting devices 4A, 5A, 6A, 7A. FIG. 2 shows a highly simplified schematic representation of the levelling device. The levelling device 15 will be described below.

(13) The levelling device 15 has a first distance measuring device 16 and a second distance measuring device 17, which in the present embodiment each have a distance sensor 16A, 17A. However, instead of distance measuring devices with only one sensor, distance measuring devices with a plurality of distance sensors arranged in a row—as known in the prior art—can also be used. As a result, further description of these distance measuring systems is not necessary here.

(14) The levelling device 15 described below is intended for a road milling machine which is particularly suitable for right-hand traffic.

(15) The first distance measuring device 16 has a distance sensor 16A which is arranged on the left side of the machine frame 3 in the working direction A between the front and rear running gear mechanisms 4, 5, 6, 7, preferably laterally adjacent to the milling drum 10 (FIG. 5). This distance sensor 16A is in the present embodiment a tactile distance sensor that makes use of the left edge protector 12, to which a draw-wire sensor 12A is attached. If the edge protector is attached via two height-adjustable hydraulic cylinders that are offset in the direction of travel, the height of the edge protector can also be detected by means of a displacement measuring system integrated into the hydraulic cylinders, rather than by means of a draw-wire sensor. The edge protector 12 rests on the traffic surface 8. The draw-wire sensor 12A measures the distance by which the edge protector 12 moves up and down. Consequently, the distance a can be measured between a first reference point R1, which is related to the road milling machine, and the traffic surface 8 on which the edge protector 12 rests.

(16) In the present embodiment, the second distance measuring device 17 has an optical distance sensor 17A which is arranged on the left side of the machine frame 3 in the working direction between the front and rear running gear mechanisms 4, 5, 6, 7, preferably at the height of the milling drum 10. Preferably, the reference points R1 and R2 of the first and/or second distance sensors 16, 17 lie in a vertical plane which is intersected substantially orthogonally by the longitudinal axis of the machine frame, and in which the axis of the milling drum preferably also substantially lies. The reference point R2 of the second distance sensor 17A lies at a prespecified lateral distance c from the reference point R1 of the first distance sensor 16A, on the left side of the reference point R1 of the first distance sensor 16A in the working direction A. The second distance sensor 17A is attached to a holder 19—for example, to a laterally projecting rod—which in turn is attached to the machine frame 3.

(17) The measurement on the inner side of the driving surface 20B is preferably carried out in the region of the driving surface centre 20C, particularly preferably on the driving surface centre 20C, since the driving surface 20 has the least damage at this position. Consequently, a measurement is not carried out on the shoulder 20D of the driving surface 20 (berm). In the present embodiment, the driving surface 20 is about twice as wide as the width of the milling drum 10 (milling track). The prespecified distance c between the two distance sensors 16A, 17A should therefore correspond to approximately half the driving surface width, or to the width of the road milling machine, or the width of the milling drum, or the spacing of the running gear (track width). Other distances can in an analogous manner result from the given lane width or the width of the milling track.

(18) Moreover, the levelling device 15 has a control and computation unit 21 configured to perform the following steps.

(19) In the levelling mode for a track section on the outside of the driving surface 20A, the control and computing unit 21 activates the first and/or second distance measuring devices 16, 17. The first distance sensor 16A measures the distance a, and the second distance sensor 17A measures the distance b. If a plurality of distances a.sub.1, a.sub.2, a.sub.3 and b.sub.1, b.sub.2, b.sub.3 is measured with a plurality of distance sensors, the control and computing unit 21 of the levelling device 15 calculates, by way of example, the average of the distances a.sub.1, a.sub.2, a.sub.3 and b.sub.1, b.sub.2, b.sub.3 as the distance value a.sub.actual or b.sub.actual. From the distance values, the milling depth can be determined after an adjustment of the distance measuring device—which will be described in more detail below.

(20) At the beginning of the milling work, the levelling device 15 is adjusted—and in particular the zero point is set. To set the zero point, the lifting devices 4, 5, 6, 7 are adjusted in such a manner that the milling drum 10 contacts the traffic surface 8 with the cylindrical surface inscribed by the tips of the milling tools. For this purpose, the lifting devices 4A, 5A, 6A, 7A are retracted until the milling tools of the rotating milling drum 10 begin to scratch the road surface. This process initiates first contact. When the milling bits contact the traffic surface 8, the distance measuring devices 16, 17 are set to zero. When the lifting devices 4A, 5A, 6A, 7A are further retracted and the milling drum 10 penetrates into the road surface, negative distance values are captured. The amount of the distance values corresponds to the milling depth. The determined distance values can be displayed as positive values—e.g., 5 cm milling depth.

(21) The determined distance values a.sub.actual and b.sub.actual are each compared to prespecified distance values a.sub.target and b.sub.target.

(22) FIGS. 3 and 5 show the case in which the road milling machine 1 will machine the right track section on the outside of the driving surface 20A, wherein this track section is inclined toward the outside of the driving surface. During its alignment, the road milling machine 1 therefore assumes an inclination with respect to the horizontal. The set milling depth corresponds to the thickness of the cover to be removed from the road surface.

(23) As the road milling machine 1 advances, the determined distance values a.sub.actual and b.sub.actual, which correspond to the actual milling depth, are compared with the prespecified distance values a.sub.target and b.sub.target which correspond to the desired milling depth (Δ a=a.sub.actual−a.sub.target or Δb=b.sub.actual−b.sub.target). According to the deviation of the actual distance value from the target distance value of the first distance sensor 16A (Δ a=a.sub.actual−a.sub.target), control signals are generated for the lifting device(s) 4A, 6A which is/are functionally assigned to the left—in the working direction—front and/or rear running gear 4, 6, and, according to the deviation of the actual distance value from the target distance value of the second distance sensor 17 (Δb=b.sub.actual−b.sub.target), control signals are generated for the lifting device(s) 5A, 7A which is/are functionally assigned to the right—in the working direction—front and/or rear running gear 5, 7. The control signals are received by the lifting devices 4A, 5A, 6A, 7A, and the lifting devices are moved in such a manner that the difference between the actual values and the target values is minimal.

(24) The lifting devices 4A, 6A which are functionally assigned to the left—in the working direction A—front and/or the rear running gear 4, 6 are retracted if the first distance value a.sub.actual determined by the first distance measuring device 16 is greater than the prespecified distance value a.sub.target, and the lifting devices 4A, 6A which are functionally assigned to the left—in the working direction A—front and/or rear running gear 4, 6 are extended if the first distance value a.sub.actual determined by the first distance measuring device 16 is less than the prespecified distance value a.sub.target. In an analogous manner, the lifting devices 5A, 7A which are functionally assigned to the right—in the working direction A—front and/or the rear running gear 5, 7 are extended if the second distance value b.sub.actual determined by the second distance measuring device 17 is greater than the prespecified distance value b.sub.target, and the lifting devices 5A, 7A which are functionally assigned to the right—in the working direction A—front and/or rear running gear 5, 7 are retracted if the second distance value b.sub.actual determined by the second distance measuring device 17 is less than the prespecified distance value b.sub.target. The front and/or rear lifting devices 4A, 5A, 6A, 7A can be retracted and/or extended, respectively, by the same distance if the distance sensors are positioned at the height of the longitudinal axis 18 of the milling drum 9 arranged in the centre between the front and rear running gear mechanisms 4, 5, 6, 7.

(25) With the adjustment described above, the desired milling depth is maintained over the width of the driving surface section being machined. Since the driving surface 20 is wider than the milling track—in the present embodiment, about twice as wide as the milling track—the track section 20B on the inner side of the road must also still be machined. To machine this section, the levelling device 15 provides a different levelling mode. This levelling mode corresponds to the known levelling, in which a distance measurement is carried out on the end faces of the milling drum 10 on both sides of the road milling machine. Consequently, the first distance measuring device 16 can be utilized, the same being designed in such a manner that its reference point R1 lies on the left side of the milling drum 10 in the working direction A. The levelling device 15 again generates the control signals for the lifting devices 4A, 6A of the left front and/or rear running gear 4, 6. However, the levelling device 15 in the present embodiment cannot make use of the second distance measuring device 17. Therefore, this distance measuring device 17 can be deactivated or need not be present (installed).

(26) The control signals for the left and right, front and/or rear lifting devices 4, 5, 6, 7 are then generated by a levelling device 15, which will be described below. Since the levelling mode for the inside of the driving surface again provides for two distance measuring devices 16, 17, these distance measuring devices are again referred to as the first and/or the second distance measuring devices 16, 17. The levelling device 15 for the inner side 20B of the driving surface can be provided as the above-described levelling device for the outer side 20A of the driving surface if the distance sensor 17A of the second distance measuring device 17 is arranged on the right side of the machine frame 3 in the working direction A at a prespecified distance c from the distance sensor 16A of the first distance measuring device 16.

(27) The distance sensors 16A, 17A can be designed as interchangeable units that can be attached to suitable brackets, such that the road milling machine can be equipped with suitable distance sensors for each of the levelling modes. However, it is also possible to even provide three distance measuring devices, or at least three distance sensors, on the road milling machine 1, of which only two distance measuring devices or distance sensors are activated for each given levelling mode.

(28) In the present embodiment, the distance measurement is performed on the right side of the machine with an optical distance sensor 17A′ (FIGS. 4 and 5). The distance measurement on the right side of the machine can also be done with the right edge protector and a draw-wire sensor, which is already present on the left and right sides in the known road milling machines.

(29) The control and computation unit 21 is configured for the levelling mode in the left track section on the inner side 20B of the driving surface in such a manner that the lifting devices 4A, 6A of the left front and/or rear running gear 4, 6 are retracted if the first distance value determined by the first distance measuring device 16 is greater than the prespecified distance value, and the lifting devices 4A, 6A of the left front and/or rear running gear 4, 6 are extended if the first distance value determined by the first distance measuring device 16 is less than the prespecified distance value. In an analogous manner, the lifting devices 5A, 7A of the rights front and/or rear running gear 5, 7 are retracted if the second distance value determined by the second distance measuring device 17′ is greater than the prespecified distance value, and the lifting devices 5A, 7A of the right front and/or rear running gear 5, 7 are extended if the second distance value determined by the second distance measuring device 17′ is less than the prespecified distance value. With this adjustment, the inner side 20A of the driving surface can be machined.