METHOD FOR SETTING THE LIFT POSITION OF A MACHINE FRAME OF A GROUND MILLING MACHINE, WHICH MACHINE FRAME IS CONNECTED VIA LIFTING MEANS TO MOVEMENT MEANS, AND GROUND MILLING MACHINE

Abstract

A method for setting the lifting position of a machine frame of a ground milling machine, which machine frame is connected via lifting means to movement means, and to a ground milling machine.

Claims

1-10. (canceled)

11. A method to set a lift position of a machine frame of a ground milling machine, which machine frame is connected via lifting means to movement means, the method comprising the steps of: a) detecting and monitoring an actual longitudinal inclination of the machine frame relative to a plumb-line direction with at least one longitudinal inclination sensor and transmitting the actual longitudinal inclination of the machine frame to a control unit; b) defining a target longitudinal inclination of the machine frame; c) then, if the actual longitudinal inclination deviates from the target longitudinal inclination, updating a lifting position of the lifting means in a controlled manner by the control unit, such that the actual longitudinal inclination is approximated to the target longitudinal inclination of the machine frame.

12. The method according to claim 11, wherein step c) is carried out depending on a limit value, such that a controlled updating is only performed: if a difference limit value between the target longitudinal inclination and the actual longitudinal inclination is exceeded; and/or time-dependently after a fixed time interval.

13. The method according to claim 12, wherein the time interval is dynamically adapted by the control unit such that a length of the time interval decreases as the difference limit values increase, and vice versa.

14. The method according to claim 11, wherein the movement means comprise front and rear movement means and the lifting means comprise front and rear lifting means, and the front and rear movement means are each connected to the machine frame via the front and rear lifting means, respectively, and wherein the controlled updating of the lift position by the control unit is carried out exclusively in respect of the front or rear lifting means of the front or rear movement means.

15. The method according to claim 14, wherein the front or rear lifting means, which are updated in a controlled manner by the control unit in step c), are coupled to one another in an oscillating manner with respect to their individual lift position.

16. The method according to claim 11, wherein the controlled updating in step c) is performed: exclusively on a basis of a longitudinal inclination detection of the machine frame in relation to the plumb-line direction; reference-free in relation to a ground surface; and/or exclusively gravity-dependently.

17. The method according to claim 11, wherein the target longitudinal inclination of the machine frame is predefined manually in step b), in particular within a predefined permissible target longitudinal inclination range.

18. A ground milling machine, comprising: a machine frame, a ground milling means, front movement means and rear movement means, wherein at least the front movement means or the rear movement means are connected to the machine frame in a height-adjustable manner via vertically adjustable lifting means each with an actuator; a drive device for driving the actuators of the lifting means; and a control device configured to control lift adjustment of the lifting means by the actuators, wherein the control device comprises at least one longitudinal inclination sensor to determine a longitudinal inclination of the machine frame with respect to a plumb-line direction, and in that a control unit is present which is configured such that the control unit controls a lift adjustment of the lifting means as a function of a longitudinal inclination change of the machine frame.

19. The ground milling machine according to claim 18, wherein the longitudinal inclination sensor is at least one of: a capacitive, magnetostrictive, electronic, inductive and/or optical inclination sensor or a gyroscope sensor; mounted on the machine frame in a vibration-damped manner; arranged at a level of a driver's cab and/or at a level of the ground milling unit, as seen in a horizontal plane.

20. The ground milling machine according to claim 18, wherein the ground milling machine is operable to operate as follows: a) detecting and monitoring an actual longitudinal inclination of the machine frame relative to the plumb-line direction with the at least one longitudinal inclination sensor and transmitting the actual longitudinal inclination of the machine frame to the control unit; b) defining a target longitudinal inclination of the machine frame; c) then, if the actual longitudinal inclination deviates from the target longitudinal inclination, updating a lifting position of the lifting means in a controlled manner by the control unit, such that the actual longitudinal inclination is approximated to the target longitudinal inclination of the machine frame.

21. The ground milling machine according to claim 18, wherein the ground milling machine is a road milling machine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The invention will be described in more detail below with reference to the exemplary embodiments shown in the figures, which show schematically:

[0029] FIG. 1 a side view of a ground milling machine;

[0030] FIG. 2 a plan view of the ground milling machine according to FIG. 1;

[0031] FIG. 3 a schematic representation of the structure of a control system;

[0032] FIG. 4 a schematic sectional view of a lifting means with movement means;

[0033] FIG. 5 a side view of a ground milling machine on a horizontal surface;

[0034] FIG. 6 a side view of a ground milling machine on a slope; and

[0035] FIG. 7 a flow chart of a method according to the invention.

DETAILED DESCRIPTION

[0036] Like components are denoted in the figures with like reference signs, wherein not every repeating component is marked separately in the figures.

[0037] FIG. 1 illustrates a construction machine of the type in question, specifically a cold road milling machine 1. Essential elements of the road milling machine 1 are a machine frame 2, which defines the rigid, basic supporting structure of the road milling machine 1, a milling drum 4 (indicated by a dashed line) arranged in a milling drum box 3, movement means 5, specifically for example crawler tracks, which are connected to the machine frame 2 via lifting means, in the present case for example in the form of vertically adjustable lifting columns 6, and which carry the ground milling machine 1, a drive device 9, in particular an internal combustion engine, and a driver's cab 7. The lifting means are adjustable in the height direction H, i.e. in the direction of their longitudinal axis. Furthermore, one or more conveying devices can be provided, for example a front loading conveyor belt 8. In working operation, the ground milling machine 1 travels in the working direction a under its own drive in the forward direction over the ground surface to be milled up, wherein the milling drum 4 rotates about an axis of rotation R running horizontally and transversely to the working direction and plunges into the ground surface and mills up the ground surface using milling tools, not specified in more detail, in a manner known per se in the prior art.

[0038] FIG. 2 illustrates the basic structure of the ground milling machine 1 in a schematic plan view. Accordingly, the ground milling machine 1 as a whole comprises a pair of front movement means 5.sub.VR and 5.sub.VL, which are connected to the machine frame 2 via one each of the lifting columns 6.sub.VR and 6.sub.VL There is also a pair of rear movement means 5.sub.HR and 5.sub.HL connected to the machine frame via the lifting columns 6.sub.HR and 6.sub.HL. Here, “H” and “V” denote the arrangement in the forward direction a of the ground milling machine 1 and designate the “rear” and “front” respectively, “R” and “L” denote the side of the ground milling machine 1 as seen in the forward direction and designate the “right” and “left” respectively.

[0039] FIGS. 1 and 2 also show the longitudinal axis L of the ground milling machine 1. This corresponds to the longitudinal extension of the ground milling machine 1 in the forward direction and parallel to the ground surface.

[0040] During working operation of the ground milling machine 1, two fundamental challenges arise for the machine operator with regard to the positional stability of the ground milling machine 1. On the one hand, it is desired to mill up the ground surface at a predefined and controlled milling depth (“levelling”), for example, in order to ensure sufficient surface removal and to avoid damaging deeper layers of the roadbed as applicable. On the other hand, due to their high center of gravity, such ground milling machines tend to tip over comparatively quickly, especially when driving over ground obstacles, such as milling edges. In order to increase the tipping stability of these ground milling machines 1, a so-called “oscillation” is therefore provided which, in the sense of a pendulum axis, provides for the counter-rotating height compensation of the pair of front movement means 5.sub.VR and 5.sub.VL and rear movement means 5.sub.HR and 5.sub.HL and left movement means 5.sub.VL and 5.sub.HL and right movement means 5.sub.VR and 5.sub.HR and thus at least partially compensates for unevenness of the ground towards the machine frame 2. The lifting means 6 are designed to be height-adjustable for this purpose. To this end, each lifting means 6 can, for example, have an actuator 10 in the form of a double-acting hydraulic cylinder, the design and mode of operation of which is shown in more detail in FIG. 4 as a matter of precaution, but is also known in the prior art. The two rear lifting means can be/become coupled to each other, for example hydraulically or electronically, in a temporarily oscillating manner, in order to realize a 3-fold pendulum movement. For this purpose, the tilting lines KL are shown in FIG. 2.

[0041] As will be described further below, the present system makes it possible to control the lift adjustment of the front or rear lifting means depending on an actual longitudinal inclination value of the machine frame 2 with respect to a plumb-line direction V. For determining an actual longitudinal inclination value, the ground milling machine 1 has a longitudinal inclination sensor 13. This is for determining the current inclination of the longitudinal inclination sensor 13 present direction of gravity acceleration. The longitudinal inclination W is thus determined in a virtual reference plane, which is defined by the longitudinal extension L of the ground milling machine 1 in the forward or working direction A and by the plumb-line direction V. The determination of the position of the machine frame 2 in this virtual reference plane relative to the plumb-line direction V and the change in this position are relevant for the system. In the present case, it is not necessarily a matter of determining an absolute angle, but rather a change in the actual longitudinal inclination relative to a target longitudinal inclination. For this purpose, the actual inclination angle can be determined along a reference beam which extends in the virtual reference plane and runs, for example, parallel to the longitudinal extension of the machine frame or perpendicularly thereto. The longitudinal inclination sensor 13 can be mounted directly on the machine frame 2 or also positioned in the driver's cab 7, for example.

[0042] FIG. 3 illustrates a possible overall structure of the lifting system by which the machine frame is connected to the movement means 5. The machine frame 2 is shown here by dashed lines in a machine frame plane ME, which runs parallel to the longitudinal extension and which in the present example runs parallel to the horizontal ground surface. The drive device 9 is provided to drive the height adjustment and may be, for example, an internal combustion engine that drives a hydraulic pump of a corresponding hydraulic supply system. For this purpose, the drive device 9 can be fluidically connected to each of the actuators 10 of the lifting means 6, which are designed as hydraulic cylinders, via corresponding hydraulic lines 17 (dot-and-dash lines). The coordination of the actuating movement of the actuators 10 and thus of the lifting columns 6 is achieved via a control unit 18, which is connected to the longitudinal inclination sensor 13 arranged in a stationary manner relative to the machine frame. Furthermore, displacement and/or pressure and/or weight sensors 19 can be provided on the individual lifting means 19.

[0043] The basic construction of possible lifting means is shown as an example in FIG. 4. FIG. 4 is a longitudinal sectional view through a lifting column 6 in the vertical direction along its central longitudinal axis. The essential element of each lifting column 6 is in particular an actuator 10, via which the adjustment force is applied. In the specific exemplary embodiment, the actuator 10 is a hydraulic cylinder-piston unit with a hydraulic cylinder 11 and a piston 12. For linear guidance, a pair of outer sleeves 16a, 16b is provided in a manner known per se, which shields the cylinder-piston unit from the outside.

[0044] In the present case, the control unit 18 is designed to control in particular the lift position of the rear lifting means as a function of the actual longitudinal inclination towards a defined target longitudinal inclination. FIG. 5 shows an initial position of the ground milling machine 1, in which it stands on a horizontal ground surface and is in contact with the ground at a milling depth FT. In this case, the standing plane of the ground milling machine 1 is thus perpendicular to the plumb-line direction V. If the ground milling machine 1 moves out of the position in FIG. 5 into an incline, as indicated in FIG. 6, this is detected by the longitudinal inclination sensor 13 by a change in the actual longitudinal inclination of the machine frame 2. This results in a deviation of the actual longitudinal inclination from the target longitudinal inclination and the control unit 18 initiates a readjustment process in which the rear lifting means in the present case are extended and the machine frame thus resumes a horizontal position. The longitudinal axis of the machine frame is then no longer parallel to the ground, but still perpendicular to the plumb-line direction V.

[0045] FIGS. 5 and 6 first show the angle W, which indicates the longitudinal angle of inclination between the plumb-line direction V and an angle leg running perpendicularly thereto in the horizontal plane in the direction of the working direction A. The angle W is a 90° angle in the present case. In FIG. 6, AW indicates the deviation of a parallel line P, running parallel to the ground in the virtual reference plane defined by the plumb-line direction V and machine longitudinal direction L, from the longitudinal direction L the machine frame 2 in this plane.

[0046] A comparison of FIGS. 5 and 6 shows here that if only the lift adjustment of the lifting means is controlled, for example only at the rear, the milling depth varies with changing inclines in the terrain. In order to counteract this, it can be provided that the driver, for example manually, readjusts the milling depth and/or a levelling system monitors and adjusts the desired milling depth. For this purpose, it can be provided, for example, that such a levelling system then uses stroke path sensors that are located on side plates of the milling drum box or are implemented in corresponding lifting means for the side plates in a manner known per se. However, it is preferred that such a levelling system is temporarily switched off if the aforementioned adaptation of the longitudinal inclination of the machine frame towards the actual longitudinal inclination is carried out by the control unit 13.

[0047] Lastly, FIG. 7 illustrates the basic sequence of a possible control method. In step 21, the actual longitudinal inclination of the machine frame is first determined and monitored. In parallel, beforehand or subsequently, a target longitudinal inclination can be defined in step 22. If driving operation is now started, for example, the determination and monitoring of the actual longitudinal inclination according to step 1 continues to run in the background, wherein if the actual longitudinal inclination deviates from the target longitudinal inclination, it is provided in step 23 that a controlled updating of the lift position of the lifting means, in this case for example the rear lifting means, is carried out by the control unit. The readjustment is performed in such a way that the actual longitudinal inclination is approximated to the target longitudinal inclination of the machine frame by the lift adjustment of the rear lifting means. It can be provided that, during these phases of adjustment of the actual longitudinal inclination, interventions of a levelling system for setting the milling depth are prevented.

[0048] A functionally upstream step 24 can be provided as a trigger threshold for step 23 and monitors whether the deviation of the actual longitudinal inclination from the target longitudinal inclination exceeds a defined limit value and/or a time interval. Only when the limit value is exceeded is a readjustment carried out.