Method for controlling a road milling machine and road milling machine

1 . A method for controlling a road milling machine for milling a ground comprising a milling drum and a rear blade, the method comprising, when there is an obstacle located in the ground to be milled, the steps of:

a) milling the ground at a predetermined milling depth (FT) along a working direction (a);

b) advancing the road milling machine in the working direction (a) towards the obstacle located in the ground;

c) raising the milling drum and the rear blade out of the ground in the working direction (a) in front of the obstacle;

d) moving over the obstacle in such a way that the milling drum remains out of contact with the obstacle; and

e) lowering the milling drum and the rear blade to the predetermined milling depth (FT) in the working direction (a) behind the obstacle and continuing the milling of the ground,

wherein the road milling machine is controlled in such a way that in step c) the raising of the milling drum is carried out before the raising of the rear blade out of the ground, wherein the road milling machine continues to move in the working direction (a) between the raising of the milling drum and the raising of the rear blade, and

wherein, when raising the milling drum, the height of the rear blade is adjusted to below a lower apex of the milling drum by at least 10% of a diameter of the milling drum.

2 . The method according to claim 1 ,

wherein the raising of the milling drum leaves an excavation area (AB) in which the milling depth (FT) of the milled track begins to decrease in the working direction (a) as a result of the raising of the milling drum, wherein the excavation area (AB) has a front edge (VK) at its deepest point,

wherein the raising of the rear blade takes place at a displacement point (V 2 ) along the working direction (a) which is at a distance (y) from the front edge (VK) of the excavation area (AB) which is smaller than a distance (x) of the rear blade from an axis of rotation of the milling drum, or

the raising of the rear blade takes place at a displacement point (V 3 ) along the working direction (a) which is on the front edge (VK).

3 . The method according to claim 1 ,

wherein the raising of the rear blade is controlled in such a way that a lower edge of the rear blade facing the ground follows a predetermined trajectory (T) during the raising, taking into account the advancement speed and the acceleration of the road milling machine.

4 . The method according to claim 3 ,

wherein the trajectory (T) has at least one of the following features:

the trajectory (T) comprises exclusively one movement transverse to the working direction (a) vertically upwards, which is not superimposed with a traveling movement of the road milling machine in the working direction (a), and a subsequent movement horizontally in the working direction (a);

the trajectory (T) comprises a plurality of step-wise movements transverse to the working direction (a) vertically upwards, wherein the lower edge is moved horizontally in the working direction (a) between the steps, and wherein the step-wise vertical movements are not superimposed with a traveling movement of the road milling machine in the working direction (a);

the trajectory (T) comprises at least one tilted movement, simultaneously transverse to the working direction (a) vertically upwards and horizontally in the working direction (a); and

the trajectory (T) follows a ramp (R) in the excavation area (AB) created by the raising of the milling drum in such a way that the lower edge substantially abuts the surface of the ramp (R) over the entire excavation area (AB).

5 . The method according to claim 3 ,

wherein the lowering of the rear blade to the predetermined milling depth (FT) in the working direction (a) behind the obstacle is controlled in such a way that the lower edge of the rear blade follows the same trajectory (T) as followed during the lowering as during the raising, in the opposite direction.

6 . The method according to claim 1 ,

wherein at least one sensor device is arranged in front of the milling drum in the working direction (a), which sensor device is designed to detect obstacles in the ground to be milled, wherein the at least one sensor device comprises an inductive, capacitive, or magnetic sensor, an optical sensor, or a sound sensor.

7 . The method according to claim 6 ,

wherein the operator is shown a representation of the obstacle on a display device produced from data obtained from a sensor device, and in that the operator can specify on the display device the front and rear edges of the obstacle in the working direction (a), wherein steps c), d), and e), are then carried out in such a way that the milling drum remains out of contact with the edges of the obstacle specified by the operator.

8 . The method according to claim 6 ,

wherein a position in the working direction (a) at which the raising of the milling drum is carried out is determined taking into account a position of the obstacle, the milling depth (FT) and also the geometry of the milling drum in order to keep the milling drum out of contact with the obstacle.

9 . The method according to claim 6 ,

wherein the magnetic sensor comprises a metal detector.

10 . The method according to claim 6 ,

wherein the optical sensor comprises a camera or a thermal imaging camera.

11 . The method according to claim 6 ,

wherein the sound sensor comprises an ultrasonic sensor.

12 . The method according to claim 1 ,

wherein in order to carry out steps c), d), and e), an extension (E) of the obstacle in the working direction (a) is input in advance by the operator, or in that the extension (E) of the obstacle in the working direction (a) is determined by a sensor device.

13 . The method according to claim 1 ,

wherein steps c), d), and e), are carried out automatically, triggered by a single control command from an operator or by the detection of an obstacle by a sensor device.

14 . The method according to claim 1 ,

wherein during steps c) and d), a conveyor device of the road milling machine is put out of operation automatically.

15 . The method according to claim 1 ,

wherein to continue the milling of the ground according to step e), machine settings with regard to milling depth (FT) and/or advancement speed and/or operation of the conveyor device are automatically set as machine settings set in step a).

16 . A road milling machine for milling a ground in a working direction (a), comprising:

a machine frame supported by travel devices;

a milling drum case mounted on the machine frame having a front blade, two side blades and a rear blade which is height-adjustable relative to the machine frame;

a milling drum mounted rotatably about an axis of rotation in the milling drum case; and

a control device,

wherein the control device is designed to carry out the method according to claim 1 , and

wherein the road milling machine has an adjusting device for adjusting the height of the rear blade, which is designed in such a way that the rear blade is adjustable to below a lower apex of the milling drum by at least 10% of the diameter of the milling drum.

17 . The road milling machine according to claim 16 , wherein the road milling machine has an adjusting device for adjusting the height of the rear blade, which is designed in such a way that the rear blade is adjustable to below a lower apex of the milling drum by at least 20% of the diameter of the milling drum.

18 . The road milling machine according to claim 16 , wherein the road milling machine has an adjusting device for adjusting the height of the rear blade, which is designed in such a way that the rear blade is adjustable to below a lower apex of the milling drum by at least 30% of the diameter of the milling drum.