EP2558645B1 - Method for operating a milling machine with a vertically adjustable milling drum - Google Patents

Description

The invention relates to a method for operating a ground milling machine having at least one height-adjustable milling drum. The invention further relates to a control device for carrying out this method, as well as a ground milling machine.

Ground milling machines with height-adjustable milling drums or milling rotors are known from the prior art, wherein the depth of cut in the soil material to be processed (for example a road surface slab) can be changed or adapted to the situation, for example with regard to unevenness, via the height adjustment. The height adjustment of a milling drum is accomplished by one or more actuators. The prior art is on the DE 25 40 047 A1 and the DE 10 2006 020 293 A1 directed.

The problem with the operation of a ground milling machine with a height-adjustable milling drum is in particular the lowering of the milling drum in order to immerse the milling drum in the soil material (eg an asphalt bed) or to increase the milling depth of the milling drum already in engagement with the soil material. In an abrupt or too fast lowering of the milling drum, the drive motor of the ground milling machine can be claimed beyond its performance limit, resulting in engine stall or worse still to damage. In addition, the cutting tools on the milling drum can be damaged.

An object of the invention is to provide measures to avoid or reduce the problems associated with the prior art.

This object is achieved by a method for operating a ground milling machine with the features of claim 1. Preferred and advantageous developments and refinements of this method are specified in the dependent claims. The solution of the problem further extends to a control device for a ground milling machine, which controls the inventive method and / or regulates. Such a control device is in particular a control device. Preferably, the control and / or regulation is software-based.

The solution of the problem also extends to a ground milling machine having at least one such control device and thus capable of carrying out the method according to the invention. This ground milling machine is a construction machine with a control station (large milling machine) or a hand-held construction machine (small milling machine). Such a ground milling machine is in particular a road milling machine or a trench cutter.

The method according to the invention for operating a ground milling machine, which has at least one height-adjustable milling drum, provides that the milling drum executes an automatically controlled and / or controlled wobbling movement during lowering during operation.

Under a wobbling motion is understood that the milling drum is not rigidly rigid or rigidly lowered horizontally, but that the downward movement is a rocking motion of the Fräswalzenachse superimposed, resulting in a rocking or staggering lowering movement. Compared to a rigid straight lowering of the milling drum, the increase of the braking torque acting on the milling drum during lowering with a superimposed wobbling motion is smaller. In addition, the chisel and milling chisel holder are spared. It is preferably provided that the wobbling movement is guided so that a maximum of only 50% of the cutting tools are on an engagement line in engagement with the soil material. This allows a faster immersion of the milling rotor in, in particular hard, soil material.

Under a control is understood that the tumbling movement of the milling drum is carried out in a predetermined manner. On the other hand, a regulation is understood as an automated process in which the tumbling movement is changed in a control loop and adapted to the situation required.

It is preferably provided that the tumbling movement is a 3-dimensional (spatial) Storkelbewegung the Fräswalzenachse. Under a 3-dimensional Storkelbewegung is understood in particular that at least one end and preferably both ends of the Fräswalzenachse perform a rolling motion. This will be related to the following FIG. 3 explained in more detail. The three-dimensional Torkelbewegung succeeds, for example, concretely by the simultaneous down or start up of the rotor in the vertical direction and the forward or reverse drive of the machine.

Likewise, it can be provided that the tumbling motion is a 2-dimensional tilting movement of the milling drum axis. Such a 2-dimensional tilting movement of the milling drum axis can, for. B. be accomplished by an automated alternating actuation of the axially opposite actuators for height adjustment of the milling drum, resulting in an alternating oscillating movement of the Fräswalzenachse when lowering. This will be related to the following FIG. 2 explained in more detail. For this purpose, however, it is necessary that the actuators are actuated separately. In particular, it is provided that, when the actuating drives are alternately actuated, the tilting angle of the milling drum axis which is set and / or the tilting frequency is controlled and / or regulated. The relevant actuation of the actuators is preferably carried out by a control device.

The method according to the invention has many advantages. Due to the method according to the invention it comes z. B. in milling to less interference, whereby the ease of use increases and the reliability of the Bodenfräsmaschine is improved. In addition, the chisel and Fräsmeißelhalter be spared on the milling drum, whereby the service life can be extended.

The drive motor of a ground milling machine provides both the drive energy required for driving the ground milling machine and the drive energy required for the rotary drive of the milling drum. Furthermore, the drive motor also provides the drive power for ancillaries such. B. for the actuators for height adjustment of the milling drum, ready. The drive motor is typically a diesel engine that originally has high torque. However, if the milling drum is lowered too fast, the drive motor can be "strangled". Particularly affected are z. B. Small milling. Furthermore, components of the powertrain can be damaged.

A preferred development of the method according to the invention therefore provides that when lowering the milling drum, the instantaneous speed or power of the drive motor of the ground milling machine is detected and that the lowering of the milling drum is automatically reduced when the current speed or power reaches or falls below a critical level. Thus it follows that lowering speed over the Absenkweg (lowering distance) is not constant but variable. It is envisaged that the lowering speed of the milling drum is automatically increased again when the current speed or power of the drive motor again exceeds the critical level.

By automatically lowering the lowering speed, at least the increase of the braking torque acting on the milling drum, which is generated by the engagement of the milling cutter arranged in the milling drum in the soil material is reduced, so that the drive motor is not abruptly loaded to its performance limit or beyond , The reduction in the lowering speed is controlled in this case, z. B. by a predetermined amount (eg. By a defined percentage). Alternatively, a regulation of the lowering speed is possible, as below explained in more detail. In the context of the invention, instead of the instantaneous speed or the instantaneous power of the drive motor, a corresponding thereto operating parameters, such. B. the instantaneous speed of the milling drum (especially at a rigid gear ratio), detected and compared to a defined critical level. Furthermore, z. B. in hydraulically driven milling drums and the oil pressure and / or the pump volume can be used.

Alternatively or possibly also in addition to a control of the lowering speed can be provided that the current speed or power of the drive motor of the Bodenfräsmaschine is detected when lowering the milling drum and that the lowering of the milling drum as a function of this detected speed or power automatically in a control process by means of a Control loop regulated and thereby changed. As a result, a maximum possible lowering speed of the milling drum can be realized in an advantageous manner at each operating time.

Controlling the lowering speed is understood to mean an automated process in which a situation-required change in the lowering speed takes place via the lowering path in a control loop. On the other hand, control of the lowering speed is understood to mean an automated process in which, if necessary, the lowering speed is defined above the lowering distance, ie. H. done in a predetermined manner. In the prior art, a milling drum is lowered without particular attention to the lowering speed and, in particular, without control and / or regulating operations associated with the lowering speed.

If the construction machine has several height-adjustable milling drums, the lowering can be controlled and / or regulated separately or jointly. If several actuators are provided for the height adjustment of a milling drum, then the lowering speed can preferably be controlled and / or regulated for each individual actuator (in a separate or in a common control loop). Despite the wobbling movement, it is thus possible to control and / or regulate the lowering speed of the milling drum. It is also possible, via the separate control of the actuators and the respective control and / or regulation of Absenkgeschwindigkeiten realize a tumbling motion of the milling drum to. The control and / or regulation of the lowering speed can in this case z. B. be accomplished via a separate adjustment of the hydraulic pressure in the actuators and / or the flow rate (a hydraulic oil or the like) to the respective actuators.

Furthermore, it is preferably provided that the control process takes place only as long as the instantaneous speed or power of the drive motor reaches or falls below a critical level and that the control process is automatically (re) terminated when the current speed or power of the drive motor again exceeds the critical level.

In addition, it may alternatively and / or additionally be provided that the lowering speed of the milling drum is regulated and / or controlled as a function of the instantaneous driving speed of the ground milling machine. This makes it possible to take into account that the driving speed of the ground milling machine also has an influence on the braking torque acting on the milling drum.

To avoid stalling of the drive motor can also be provided that the current speed of the ground milling machine is controlled and / or controlled in dependence on the current lowering speed of the milling drum and thus changed. This can be done alternatively and / or in addition to other control and / or control operations. The idea here is to find when lowering the milling drum for the Bodenfräsmaschine an operating point at which the power provided by the drive motor to the individual consumers (drive, rotary drive, actuator) is best distributed without the drive motor is claimed beyond its optimal power point ,

Fig. 1

den Eingriff einer höhenverstellbaren Fräswalze in ein Bodenmaterial, in einer Seitenansicht;

Fig. 2

das Absenken der Fräswalze aus der Fig. 1 mit einer 2-dimensionalen Taumelbewegung, in einer Vorderansicht;

Fig. 3

eine 3-dimensionale Taumelbewegung der Fräswalze beim Absenken, in einer perspektivischen Ansicht; und

Fig. 4

einen Regelkreis zur Regelung der Absenkgeschwindigkeit der Fräswalze aus der Fig. 1.

The invention will be further described by way of example with reference to the figures. They show schematically:

Fig. 1

the engagement of a height-adjustable milling drum in a soil material, in a side view;

Fig. 2

the lowering of the milling drum from the Fig. 1 with a 2-dimensional wobble, in a front view;

Fig. 3

a 3-dimensional wobbling movement of the milling drum when lowering, in a perspective view; and

Fig. 4

a control loop for controlling the lowering speed of the milling drum from the Fig. 1 ,

Fig. 1 shows a milling drum 10 in a schematic side view. The milling drum 10 is arranged height-adjustable via two actuators 20a / 20b on a ground milling machine, not shown. The actuators 20a / 20b are located at the axial ends of the milling drum 10, as in the front view of Fig. 2 shown. On the milling drum 10 a plurality of not shown in detail milling bits are arranged, which upon rotation of the milling drum 10 in the specified direction of rotation R (optionally also in the opposite direction of rotation) loosen and remove a soil material S with a defined height H (cutting depth).

The milling depth H can be changed by means of the height adjustment by means of the actuators 20a / 20b, which are in particular hydraulically actuated actuators (so-called lifting columns), in the milling operation. Furthermore, the rotary milling drum 10 can be lowered into the soil material S via the actuators 20a / 20b at the beginning of the milling operation. The lowering movement is indicated by the arrow A.

In an abrupt or too fast lowering of the milling drum 10, the drive motor of the ground milling machine can be overloaded. To avoid this, it is provided that the milling drum 10 performs an automatically controlled and / or controlled tumbling motion during lowering A during operation. This will be related to the following Fig. 2 explained in more detail.

Fig. 2 schematically shows the lowering of the milling drum 10 with a 2-dimensional wobbling (tilting) T, the increase of the force acting on the milling drum 10 braking torque less than the straight or horizontal lowering of the milling drum 10 fails. The rocking wobble T is generated by initially only the left actuator 20a is actuated, whereupon the left axle bearing of the milling drum 10 is lowered by the Absenkbetrag x down, causing an inclination of the Fräswalzenachse L of the milling drum 10 by the angle d. Subsequently, only the right actuator 20b is actuated, whereupon the right axle bearing of the milling drum 10 is lowered by the same or a higher lowering amount y down. This is repeated continuously until the milling drum 10 has taken its new position, wherein the Fräswalzenachse L is tilted alternately (see reference L '). The tilting positions of the milling drum 10 that occur during lowering with such a tumbling motion T are shown in dotted lines and denoted by 10 'and 10 ".

In order to realize the tilting movement T, it is not necessary that only one of the actuators 20a and 20b is actuated in each case. It is also possible that both actuators 20a and 20b are operated simultaneously, but with an alternately different lowering speed.

Fig. 3 schematically shows a 3-dimensional wobbling (Torkelbewegung) T ', in which the axis ends of the Fräswalzenachse L of the milling drum 10 describe a rolling motion on a circular path (possibly also on another trajectory) and so a staggering wobble T' of the milling drum 10 is brought about. The actuators 20a and 20b are designed to perform such a spatial wobbling movement T 'accordingly. It can be provided that only one of the Actuators 20a or 20b for performing such a 3-dimensional wobbling movement T 'is formed.

Fig. 4 schematically shows a control loop for controlling the lowering speed of the milling drum 10. The control circuit is activated only when lowering the milling drum 10 and separately controls the two actuators 20a and 20b.

Box I represents a momentary, d. H. at a certain time of operation, acting on the milling drum 10 braking torque, which is caused by the engagement of the milling drum 10 arranged on the milling cutter in the soil material S. The montane braking torque depends on the soil material S or the soil condition (strength, composition, porosity, etc.). The instantaneous braking torque is also dependent on the current speed of the milling drum 10, the depth of cut H and the current ground speed of the ground milling machine (no exhaustive list).

For a given drive power of the drive motor of the ground milling machine, an increasing braking torque on the milling drum 10 leads to a reduction in the speed D of the drive motor. Since a lowering of the milling drum 10 causes an additional increase in the braking torque acting on the milling drum 10, this can lead to a critical speed level being reached or undershot. Box II represents the permanent detection of the instantaneous speed D of the drive motor.

The detected instantaneous speed D is compared for the purpose of monitoring with a predetermined critical speed K (box III). If the detected instantaneous rotational speed D reaches or falls below the critical rotational speed K, a control process is started in which the lowering speed of the milling drum 10 realized by the actuators 20a and 20b is reduced (box IV) until the detected instantaneous rotational speed D of the Drive motor exceeds the critical speed K again. Reducing the lowering speed can, for. B. caused by appropriate control of the control valves for the actuators 20a and 20b (change the hydraulic pressure in the actuators and / or the flow to the actuators concerned), the lowering speed are also reduced to the value 0 (stop the lowering movement) can. It is also conceivable to slightly raise the milling drum 10 in the opposite direction (-A). Preferably, a PID controller (box III) is used for control.

Likewise, in the previously explained control circuit z. B. also detects the pressure level of the hydraulic drive of the milling drum 10 and are set for the purpose of monitoring and / or control a critical pressure level against.

Claims (14)

1. A method for operating a ground milling machine which comprises at least one height-adjustable milling drum (10),
   characterized in that
   the milling drum (10) performs a tumbling movement (T, T') which is controlled by way of automatic open-loop and/or closed-loop control during lowering (A) in operation.
2. The method according to claim 1,
   characterized in that
   said tumbling movement is a three-dimensional staggering movement (T') of the milling drum axis (L).
3. The method according to claim 1,
   characterized in that
   said tumbling movement is a two-dimensional tilting movement (T) of the milling drum axis (L).
4. The method according to claim 3,
   characterized in that
   said two-dimensional tilting movement (T) of the milling drum axis (L) is produced by an automatically alternating actuation of the axially opposite actuators (20a, 20b) for the height adjustment of the milling drum (10).
5. The method according to claim 4,
   characterized in that
   during the alternating actuation of the actuators (20a, 20b) the tilting angle (d) of the milling drum axis (L) and/or the tilting frequency will be controlled by means of open-loop and/or closed-loop control.
6. The method according to any one of the preceding claims,
   characterized in that
   during the lowering (A) of the milling drum (10) the current speed (D) or power of the drive motor of the ground milling machine will be detected and that the lowering speed of the milling drum (10) will be reduced automatically when the current speed (D) or power reaches or falls beneath a critical level (K).
7. The method according to claim 6,
   characterized in that
   the lowering speed of the milling drum (10) will automatically be increased again when the current speed (D) or power of the drive motor exceeds the critical level (K) again.
8. The method according to any one of the preceding claims,
   characterized in that
   during the lowering (A) of the milling drum (10) the current speed (D) or power of the drive motor of the ground milling machine will be detected and that the lowering speed of the milling drum (10) will be changed depending on said detected speed (D) or power in a closed-loop control process by means of a control loop.
9. The method according to claim 8,
   characterized in that
   the closed-loop control of the lowering speed is produced by a separate adjustment of the hydraulic pressure in the actuators (20a, 20b) for the height adjustment of the milling drum (10) and/or the volume flow of a hydraulic medium to said actuators (20a, 20b).
10. The method according to claim 8 or 9,
    characterized in that
    the closed-loop control process will only occur as long as the current speed (D) or power of the drive motor reaches or falls beneath a critical level (K), and that the closed-loop control process will be terminated automatically when the current speed (D) or power of the drive motor exceeds the critical level (K) again.
11. The method according to any one of claims 8 to 10,
    characterized in that
    the lowering speed of the milling drum (10) will further be controlled by means of closed-loop and/or open-loop control depending on the current travelling speed of the ground milling machine.
12. The method according to any one of claims 8 to 11,
    characterized in that
    further the current travelling speed of the ground milling machine will be controlled by means of closed-loop and/or open-loop control depending on the current lowering speed of the milling drum (10).
13. A control device for a ground milling machine which controls the method according to any one of the preceding claims by means of closed-loop and/or open-loop control.
14. A ground milling machine, especially a road milling machine or a trench cutting machine, comprising a control device according to claim 13.

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