EP4108831B1 - Road miller and method for controlling a road miller - Google Patents

Description

The invention relates to a method for controlling a road milling machine comprising a milling drum and a rear blade when there is an obstacle in the ground to be milled. In addition, the invention relates to a road milling machine for carrying out the method.

Generic road milling machines are used in road and path construction, for repairing and renewing roadways, squares and runways. Specifically, these are, for example, road milling machines, especially cold milling machines, for example of the tail rotor or center rotor type. They typically include a machine frame supported by driving devices, such as track drives or wheels. The primary working tool of generic road milling machines is a milling drum mounted in a milling drum box so that it can rotate about an axis of rotation. The milling drum is typically equipped with a hollow cylindrical jacket, on the outer peripheral surface of which a large number of milling tools, for example milling cutters, are arranged. During operation, the milling drum is rotated around the axis of rotation so that the milling tools are driven into the ground and mill it away. How far the milling drum dips into the ground is determined by the milling depth specified by the operator, for example. The milling depth can be achieved, for example, by a relative adjustment of the milling drum or the milling drum box relative to the machine frame. For this purpose, it is known to store the milling drum box on the machine frame via a lifting device that is at least partially adjustable in the vertical direction relative to the machine frame. Additionally or alternatively, the machine frame including the milling device can be adjustable in the vertical direction to the ground. For this purpose, it is known to connect the machine frame to the driving devices via suitable lifting devices, for example lifting columns. Around the milled material thrown around To contain the milling drum, the milling drum is usually surrounded by the milling drum box, which is mounted, for example, on the machine frame and which can have a front shield, two side shields and a rear shield that is height-adjustable relative to the machine frame. A so-called hold-down device can also be provided. The hold-down device, like the front shield, is arranged transversely to the working direction in front of the milling drum and the rear shield is arranged transversely to the working direction behind the milling drum, while the side shields house the milling drum laterally parallel to the working direction. The height adjustment of the machine frame and/or the milling drum box and/or parts thereof can be controlled using a control device. The milling drum box also serves to guide the milled material onto a conveyor device, for example a conveyor belt, from which the milled material is transferred to a transport vehicle, for example a truck, for transport. This can be done, for example, in the milling direction forwards or backwards.

When the road milling machine is in operation, the hold-down device is typically pressed from above onto the ground to be milled in the working direction in front of the milling drum, guided floating over it or held just above the ground. It serves to prevent large clods from breaking out of the ground to be milled and to ensure that the milling drum mills off sufficiently small pieces of milled material. The front shield can have a transfer opening through which the milled material can emerge from the interior of the milling drum box onto the transport device. Such a transfer opening can also be provided in the rear shield. The side shields close the milling drum box laterally, are typically guided gliding over the ground and prevent milled material from escaping to the side. The rear shield, in turn, similar to the hold-down device, is pressed from above onto the milled surface, also called the milling bed, in the working direction behind the milling drum, guided floating above it or held just above the milling bed. In this position, known as the working position, the rear blade shears off any protruding soil components remaining in the milling bed. On the other hand, the rear shield also strips off milled material remaining in the milling bed and carries it with the road milling machine inside the milling drum box until it reaches the conveyor device during further operation.

During milling work, it often happens that there are obstacles in the ground to be milled. These can be, for example, installations, such as shafts, manhole covers, metal plates or similar. These internals should not be damaged by milling work. In addition, damage to the milling drum and the milling tools themselves, which could occur in the event of a collision with the obstacles, should also be avoided. It is therefore necessary that the operator of the road milling machine stops it in front of every obstacle and raises the milling drum including the milling drum box until it is in a vertical position above the obstacle was adjusted, for example with approx. 2 cm of ground clearance, and then the obstacle is driven over with the milling drum out of contact with the ground. Behind the obstacle, the operator must stop the road milling machine again, lower the milling drum again to the desired milling depth and continue the milling process. Overall, this process requires a large number of steps that the operator must carry out as precisely as possible during the workflow. An additional problem is that by lifting the milling drum and the milling drum box in front of the obstacle, a not inconsiderable amount of milled material remains on the milled ground in the milling bed. This remaining milled material must then be removed by hand or by machine, which is a laborious process, which increases the time required to complete the construction site and thus also the costs. Soil that is not milled away by the milling drum in the working direction in front of and behind the obstacle may also have to be removed by hand or by machine in a post-processing step. The effort required for this post-processing varies greatly, depending on how precisely the operator raises the milling drum before the obstacle and lowers it again after the obstacle. However, this creates a tension because, on the one hand, the operator wants to prevent a collision between the obstacle and the milling drum, and on the other hand, the manual post-processing effort should be kept as low as possible. As a result, the operator often tries to mill as close to the obstacle as possible and to let the milling drum sink back into the ground behind the obstacle as close to the obstacle as possible. Misjudgments by the operator can therefore lead to damage to the obstacle and the milling drum or to increased post-processing effort. The DE 10 2016 015499 A1 discloses a method for controlling a road milling machine, which includes a conveyor device with a primary conveyor belt and a secondary conveyor belt. The road milling machine also has a milling drum cat, which includes height-adjustable side plates on the sides. During milling operation, the milling drum cat is lowered until a milling drum arranged within the milling drum cat engages with a desired milling depth in the ground to be processed, with the road milling machine moving in the working direction for milling the ground. In front of a milling surface obstacle, the milling drum is raised together with the milling drum box from the milling position into a transport position and then lowered back into the milling position. The US 10 2010 014695 A1 discloses a road milling machine for milling a soil in one working direction, the road milling machine having a machine frame on which a milling drum box with a front shield, two side shields and a height-adjustable rear shield is mounted. Furthermore, the road milling machine also includes a control device, via which the milling drum and the rear shield can be lifted when surface obstacles are encountered in the direction of travel.

Against this background, the object of the present invention is to increase the economic efficiency of the milling process when there are obstacles in the ground to be milled. In particular, the operator of the road milling machine should be relieved and the workload of the necessary post-processing should be reduced.

This problem is solved with a method and a road milling machine according to the independent claims. Preferred further developments are specified in the dependent claims.

1. a) Abfräsen des Bodens in einer vorgegebenen Frästiefe entlang einer Arbeitsrichtung,
2. b) Annähern der Straßenfräsmaschine in Arbeitsrichtung an das im Boden befindliche Hindernis,
3. c) Ausheben der Fräswalze und des Heckschildes aus dem Boden in Arbeitsrichtung vor dem Hindernis,
4. d) Überfahren des Hindernisses derart, dass die Fräswalze außer Kontakt mit dem Hindernis bleibt, und
5. e) Absenken der Fräswalze und des Heckschildes bis zur vorgegebenen Frästiefe in Arbeitsrichtung hinter dem Hindernis und Fortsetzen des Abfräsens des Bodens.

Ein Kerngedanke der vorliegenden Erfindung liegt nun darin, dass die Straßenfräsmaschine derart gesteuert wird, dass in Schritt c) das Ausheben der Fräswalze zeitlich vor dem Ausheben des Heckschildes aus dem Boden durchgeführt wird, wobei sich die Straßenfräsmaschine zwischen dem Ausheben der Fräswalze und dem Ausheben des Heckschildes weiter in Arbeitsrichtung bewegt. Mit anderen Worten erfolgt das Ausheben des Heckschildes und das Ausheben der Fräswalze im laufenden Fräsprozess nacheinander, und die Straßenfräsmaschine fährt zwischen dem Ausheben des Heckschildes und dem Ausheben der Fräswalze zumindest ein Stück weit weiter in Arbeitsrichtung. Der Heckschild wird also nicht gleichzeitig mit der Fräswalze aus dem Fräsbett angehoben, sondern verbleibt während und/oder nach dem Anheben der Fräswalze noch in der Arbeitsstellung. Dadurch wird der Heckschild in seiner Arbeitsstellung in Arbeitsrichtung näher an das Hindernis herangeführt als wenn der Heckschild zusammen mit der Fräswalze angehoben werden würde, wie dies im Stand der Technik der Fall ist. Der Heckschild wird in Horizontalrichtung auf die Wegstrecke bezogen somit erst an einer Stelle ausgehoben, in der er in Fräsrichtung gesehen auf Höhe desjenigen Bereiches ist, in dem vorher die Fräswalze ausgehoben worden ist. Damit werden der Heckschild und die Fräswalze somit beim Annähern an ein zu überfahrendes Bodenhindernis relativ zueinander verstellt, derart, dass die Fräswalze in Vertikalrichtung gegenüber dem Heckschild angehoben wird, gefolgt von einer Phase, in der der Heckschild relativ zur Fräswalze angehoben wird. In Bezug auf die Wegstrecke vollziehen die Fräswalze und der Heckschild somit sukzessive zueinander die Hubbewegung und nicht gleichzeitig. Auf diese Weise kann der Heckschild seine Funktion, das abgefräste Fräsgut auf dem Fräsbett abzustreifen und mit dem Fräswalzenkasten mitzuführen, länger ausführen, als wenn er von vorneherein zusammen mit der Fräswalze ausgehoben worden wäre, denn er wird der Hubbewegung der Fräswalze zeitlich nachlaufend dem Hindernis in seiner abgesenkten Position näher angenähert. Insgesamt wird durch diese Maßnahme also weniger Fräsgut auf dem Fräsbett zurückgelassen, wenn der Heckschild dann schließlich vor dem Hindernis aus dem Fräsbett angehoben wird.Specifically, the solution is achieved with a method for controlling a road milling machine comprising a milling drum and a rear shield in the event of an obstacle in the ground to be milled, comprising the steps:

1. a) milling the ground at a predetermined milling depth along a working direction,
2. b) approaching the road milling machine in the working direction to the obstacle in the ground,
3. c) lifting the milling drum and the rear blade out of the ground in the working direction in front of the obstacle,
4. d) driving over the obstacle in such a way that the milling drum remains out of contact with the obstacle, and
5. e) Lower the milling drum and the rear blade to the specified milling depth in the working direction behind the obstacle and continue milling the ground.

A core idea of the present invention is that the road milling machine is controlled in such a way that in step c) the lifting of the milling drum is carried out before the rear shield is lifted out of the ground, with the road milling machine between the lifting of the milling drum and the lifting of the Rear shield moved further in the working direction. In other words, the lifting of the rear shield and the lifting of the milling drum take place one after the other during the ongoing milling process, and the road milling machine moves at least a little further in the working direction between the lifting of the rear shield and the lifting of the milling drum. The rear shield is therefore not lifted out of the milling bed at the same time as the milling drum, but remains in the working position during and/or after the milling drum is raised. As a result, the rear shield is brought closer to the obstacle in its working position in the working direction than if the rear shield were to be raised together with the milling drum, as is the case in the prior art. The rear shield is therefore only excavated in the horizontal direction relative to the distance at a point in which, viewed in the milling direction, it is at the level of the area in which the milling drum was previously excavated. This will make the rear shield and the Milling drum thus adjusted relative to each other when approaching a ground obstacle to be driven over, such that the milling drum is raised in the vertical direction relative to the rear shield, followed by a phase in which the rear shield is raised relative to the milling drum. In relation to the distance traveled, the milling drum and the rear shield therefore carry out the lifting movement successively relative to each other and not at the same time. In this way, the rear shield can carry out its function of stripping the milled material on the milling bed and carrying it along with the milling drum box for longer than if it had been lifted out together with the milling drum from the outset, because it will move towards the obstacle in time after the lifting movement of the milling drum closer to its lowered position. Overall, this measure means that less milled material is left behind on the milling bed when the rear shield is finally lifted out of the milling bed in front of the obstacle.

The lifting of the milling drum and the lifting of the rear shield each refer to a relative movement of the milling drum or the rear shield in the vertical direction relative to the ground or a virtual ground reference plane. The milling drum can, for example, be designed to be height-adjustable within the milling drum box relative to the milling drum box. In this case, the milling drum can be raised independently of the rear blade and the rear blade can remain in the working position without having to be adjusted. However, it is also possible for the milling drum to be designed to be height-adjustable together with the entire milling drum box. In this case, when the milling drum is raised, the entire milling drum box including the rear shield is also raised. It may therefore be necessary for the rear shield to be extended downwards relative to the rest of the milling drum box during the lifting of the milling drum in order to remain in the working position in order to compensate for a vertical adjustment of the entire milling drum box. In other words: Ideally, the extension movement of the rear shield takes place during the lifting of the remaining milling drum box in such a way that the lifting movement of the remaining milling drum box is compensated for in the vertical direction. Approximately, the stroke adjustment of the rear shield is preferably controlled in such a way that it maintains its vertical position in relation to the ground surface while the rest of the milling drum box is being lifted. Here, the rear shield is adjusted relative to the milling drum and relative to the machine frame, but ideally it remains in the same relative position relative to the ground, specifically the working position. It is therefore not a case of “lifting out” the rear shield according to the invention.

Due to the rotation of the milling drum during operation, cutting circles are defined by the milling tools, in particular by the chisel tips. The cutting circles describe those Paths on which, for example, the chisel tips move together with the milling drum around the axis of rotation. The cutting circles determine how much soil is removed by the milling drum at a certain vertical height or how great the milling depth ultimately is. If we are talking about a diameter of the milling drum, this means in particular the diameter of the largest cutting circle. During operation, soil is removed along this cutting circle by the milling drum. Lifting the milling drum out of the ground therefore leaves an excavation area in which the milling depth of the milled track begins to decrease due to the lifting of the milling drum in the working direction. In the excavation area there is typically a ramp or a transition area from the milling bed lying in the predetermined milling depth to the unmilled ground, whereby the transition area can essentially represent a negative of the milling drum circumferential section or of cutting circle segments of the milling drum when the milling drum is excavated, for example when the machine is stationary. The creation of this ramp is due to the geometry of the milling drum and the cutting circles. At the lowest point of the excavation or milling area, it has a front edge. The deepest point of the excavation area is the point immediately vertically below the axis of rotation of the milling drum at the position at which the milling drum is excavated. This front edge has the distance corresponding to the previous milling depth to the height of the unmilled ground surface. The front edge of the excavation area is created at the position where the milling drum mills the ground to the full, specified milling depth before it is excavated. It therefore describes the transition from the ground milled to the full, specified milling depth or the milling bed floor to the ramp of the excavation area.

According to the invention, the rear shield should be excavated closer to the front edge of the excavation area in the working direction than in the prior art. The later the rear shield is lifted out, the more milled material is carried along in the working direction and the less milled material is left on the milling bed after lifting. It is therefore preferred that the rear shield is excavated as close as possible and in particular directly to the front edge of the excavation area. The position in the working direction at which the rear blade is moved vertically upwards from its working position or away from the milling bed floor and is thus lifted is referred to as the displacement point. According to a preferred embodiment of the invention, it is therefore provided that the rear shield is lifted at a displacement point along the working direction, which has a distance to the front edge of the excavation area that is smaller than a distance of the rear shield to the axis of rotation of the milling drum. In the prior art, however, the milling drum and the rear shield are typically excavated at the same time, so that the distance of the displacement point of the prior art to the front edge of the excavation area is equal to the distance of the rear shield to the axis of rotation of the milling drum. The distances mentioned always refer to the working direction. The distance according to the invention between the said displacement point and the front edge of the excavation area corresponds in particular to a maximum of 75%, preferably a maximum of 50% and particularly preferably a maximum of 25%, of the distance of the rear shield to the axis of rotation of the milling drum in the working direction. A particularly preferred alternative of the invention provides that the rear shield is lifted out at a displacement point along the working direction, which is located on, in particular directly on, the front edge. The rear shield is therefore preferably lifted out of the milling track at the same position in the working direction as the milling drum. As already explained, the ramp begins in the working direction behind the front edge of the excavation area, i.e. the depth of the milled track decreases. At this point at the latest, the rear shield must be raised, otherwise it could collide with the ramp and be damaged. At the same time, by carrying the rear blade in the working position up to the front edge of the excavation area, as little milled material as possible is left on the milling bed up to the front edge.

In principle, the longer carrying of the rear shield in the working position compared to the prior art is already advantageous in relation to the smaller amount of milled material left behind in the milling bed. However, in a further development, the invention advantageously also provides for controlling the manner in which the rear shield is raised, so that the rear shield traverses a predetermined path of movement, also referred to below as a trajectory. The lower edge of the rear shield facing the ground is used as a reference point for the movement path. The movement path or trajectory of the rear shield is created by superimposing all the movements that the rear shield performs, for example a height adjustment in the vertical direction of the rear shield itself and the travel movement of the road milling machine in the working direction. It can also happen that the road milling machine accelerates or brakes. Both the driving speed and in particular an acceleration of the road milling machine are preferably detected by sensors on the machine, so that these are available and also used for the control of the rear shield along the trajectory according to the invention. Overall, it is therefore preferably provided that the lifting of the rear shield is controlled in such a way that a lower edge of the rear shield facing the ground follows a predetermined trajectory during the lifting, taking into account the feed speed and in particular the acceleration of the road milling machine. The trajectory begins when the tail blade is in the working position at the displacement point. she begins i.e. directly on or slightly above the milling bed at the displacement point where the lifting of the rear shield begins. The trajectory ends in a raised position of the rear shield, in which the rear shield has been raised at least by the specified milling depth. In this raised position, the rear shield can be guided over the obstacle in the working direction without damaging it or being damaged yourself. The trajectory preferably also includes a movement of the rear shield in the working direction and therefore preferably ends in the working direction behind the excavation area, i.e. in the area of the unmilled ground or the obstacle. The rear shield can either be guided floating over the obstacle, in particular without pressure, i.e. without being subjected to a tracking force in the vertical direction downwards towards the obstacle. The rear shield is in contact with the obstacle, but slides along it without any damage. Alternatively, the rear shield can be adjusted beyond the obstacle with a vertical safety distance, for example 2 cm, so that the rear shield can be guided over the obstacle without contact or floating.

Between the start and end points of the trajectory described above, it can take different forms. For example, the trajectory exclusively includes a vertically upward movement transverse to the working direction and a subsequent horizontal movement in the working direction. In this embodiment it is therefore provided that the rear shield is adjusted in a single vertical movement between the working position and the raised position. In particular, it can be provided that the movement vertically upward transverse to the working direction is not superimposed on a travel movement of the road milling machine in the working direction. The road milling machine is stopped for the adjustment of the rear blade and does not move in the working direction while the rear blade is adjusted vertically upwards from the working position to the raised position. Only then does the road milling machine and thus also the rear shield move again in the working direction. In other words, the trajectory has the form of a single, particularly rectangular, step. However, the trajectory can also have the shape of several, especially rectangular, steps. For example, the trajectory includes several stepwise movements vertically upwards transversely to the working direction, with the lower edge of the rear shield being moved horizontally in the working direction between the steps. The horizontal movement in the working direction is achieved by the advance of the road milling machine. As already described for the single-stage trajectory, it can also be provided here that the gradual vertical movements are not superimposed on a travel movement of the road milling machine in the working direction. This also means that the road milling machine is stopped during the vertical adjustment of the rear blade and does not move in the working direction. Due to the multi-stage design of the trajectory, the rear shield and in particular the lower edge of the rear shield is held closer to the ramp of the excavation area than, for example, by the single-stage trajectory. This works better the more stages are provided. It is therefore preferred that the trajectory comprises at least two, preferably at least three, particularly preferably at least four and very particularly preferably at least five stages. This makes it possible to at least partially carry the milled material carried by the rear shield further up the ramp in the excavation area and not leave it completely behind in the milling bed, where it requires complex post-processing.

In order to make the movement sequence during the excavation of the rear shield more fluid and at the same time to keep the rear shield or the lower edge of the rear shield even closer to the surface of the ramp of the excavation area, it is particularly preferably provided that the trajectory has at least one oblique movement, at the same time transverse to the working direction vertically upwards and horizontally in the working direction. In other words, the adjustment of the rear shield in the vertical direction is superimposed on the forward movement of the road milling machine in the working direction. Overall, this results in an at least partially oblique trajectory, in particular directed obliquely forward and upward. It is particularly preferred that the road milling machine moves in the working direction during the entire lifting of the rear shield. The road milling machine is not stopped during excavation and continues to move in the working direction, creating a particularly fluid workflow. The oblique movement can be used in both single-stage and multi-stage trajectories. As a result, the steps of the trajectory are no longer rectangular, but rather have an obtuse angle. In the case of the multi-stage design of the trajectory, in which the lifting of the rear shield from the working position to the lifted position is divided into several, separate movements, it is preferred that all of these separate movements are designed obliquely. In other words, it is preferred that every movement of the rear blade in the vertical direction away from the milling bed floor is superimposed on a forward movement of the road milling machine.

According to a particularly preferred embodiment, it is provided that the trajectory follows a ramp created by lifting the milling drum in the excavation area in such a way that the lower edge of the rear shield essentially rests on the surface of the ramp over the entire excavation area. This embodiment requires particularly precise control of the vertical position of the rear shield and the feed speed of the road milling machine, in particular including its acceleration. These values for the movement of the rear shield and the road milling machine are therefore recorded by a control device. In addition, it is advantageous to to know the geometry of the milling drum and in particular its diameter or the diameter of the cutting circles, as this determines the shape of the ramp. The geometry of the milling drum is known in advance and is stored in the control device and/or can be entered into the control device. All parameters are therefore known and are used by the control device to adjust the rear shield or are taken into account during the adjustment so that the rear shield follows the trajectory. The lower edge of the rear shield can, for example, be subjected to a force directed vertically downwards onto the ground, as is usual in work operations, so that the lower edge of the rear shield scrapes the surface of the ramp. At the same time, the height position of the rear shield must be adjusted according to the ramp geometry so that the rear shield can actually follow the shape of the ramp and does not get stuck on it. Alternatively, it can be provided that the rear shield is guided up the ramp in a sliding or floating manner without being pressed onto the ground. The rear shield is in contact with the surface of the ramp, but is not actively subjected to a force directed towards the ground. The trajectory follows the surface of the ramp. Finally, it is also possible to control the lower edge of the rear shield along a trajectory that corresponds to the shape of the ramp, but to space the lower edge from the ramp by a safety distance, for example 2 cm. The lower edge of the rear shield is guided floating along the ramp. The embodiments mentioned all describe options in which the lower edge of the rear shield essentially rests on the surface of the ramp over the entire excavation area. In particular, the lower edge of the rear shield and thus the rear shield itself is adjusted particularly close along the ramp between the working position and the raised position. In this way, a large part of the loose material to be milled in the milling drum box is transported up the ramp by the rear blade and does not remain in the milling bed. This results in significant time savings as there is no need for rework.

In principle, the method according to the invention can be carried out manually step by step by an operator by controlling the road milling machine accordingly. However, in order to relieve the operator's burden as much as possible, it is preferably provided that at least step c), and in particular also steps d) and e), are carried out automatically, in particular triggered by a single control command from an operator. The milling of the ground in normal operation according to step a) and the approach of the road milling machine to the obstacle according to step b) are carried out or controlled by the operator as usual. In order to use the method according to the invention, the operator then positions the road milling machine as close as possible to the obstacle. Instead of then controlling the lifting of the milling drum, the operator simply enters a control command on the control device of the road milling machine, for example via a control element such as a switch or a touchscreen. The lifting of the milling drum according to step c) is then carried out automatically by the control device of the road milling machine, with the rear shield and in particular the lower edge of the rear shield being guided in particular along the predetermined trajectory. Once the excavation has been completed, the operator can control driving over the obstacle again according to step d) and position the road milling machine behind the obstacle. By means of a further control command from the operator, the lowering according to step e) is then preferably carried out automatically again by the control device, in particular the working parameters which were already present before the lifting according to c) are set here again. In this way, work can continue quickly and easily.

The operator can also enter the extent of the obstacle in the working direction in advance, for example on the control device. If the extent of the obstacle in the working direction is entered in advance by the operator, all steps c), d) and e) can be carried out automatically by a single control command from the operator, in particular by the control device. As already explained, the operator positions the road milling machine as close as possible to the obstacle. Then the operator simply issues the control command to the control device, whereupon it automatically lifts the milling drum according to step c), drives over the obstacle according to step d) and lowers the milling drum and the rear shield according to step e), without the The operator must continue to work for this. The operator simply carries out normal milling work up to just in front of the obstacle, then issues the control command, whereupon the road milling machine automatically mills around the obstacle, and can then continue the milling work in the working direction behind the obstacle as normal. In this way, not only is rework minimized, but the workload on the operator of the road milling machine is also relieved during work.

As described above, the method according to the invention can be carried out by the operator of the road milling machine recognizing the obstacle in the ground to be milled and determining or specifying its extent in the working direction as the basis for automatic control. However, the detection of the obstacle itself and also its dimensions, in particular the extent in the working direction, can alternatively also be carried out by a sensor device. For this purpose, it is preferably provided that at least one sensor device is arranged in front of the milling drum in the working direction and is designed to detect obstacles in the soil to be milled. For this purpose, the sensor device can include, for example, an inductive, capacitive or magnetic sensor, for example a metal detector. Additionally or alternatively, the sensor device can also include an optical sensor, for example a camera or a thermal imaging camera, or a sound sensor, for example an ultrasonic sensor. It is important that the sensor device is able to detect obstacles that lie within the milling width of the road milling machine or the milling drum. The detection range of the sensor device must therefore cover the entire milling width of the milling drum so that even laterally offset obstacles can be reliably detected. In order to achieve this, the sensor device can, for example, also have several sensors, for example also several sensors of different types, for example distributed transversely to the working direction.

If the road milling machine has a sensor device which can detect an obstacle located in the ground to be milled, it is particularly preferably provided that step c), and in particular also steps d) and e), are carried out automatically, triggered by the detection an obstacle through the sensor device. To carry out steps c), d) and e), the extent of the obstacle in the working direction is particularly preferably determined by the sensor device. The sensor device therefore automatically detects a front edge of the obstacle in the working direction and a rear edge in the working direction and determines the extent of the obstacle in the working direction between these two edges. The lifting of the milling drum according to step c), the driving over the obstacle according to step d) and the lowering of the milling drum and the rear shield according to step e) are then carried out automatically, without the operator having to take any further action. In particular, it is no longer even necessary for the operator to issue a control command that triggers these steps. This is also preferably carried out automatically by the control device based on the detection of the obstacle.

In order to increase the flexibility and, if necessary, the safety of the method according to the invention, it can also be provided that the sensor device detects the presence and in particular the dimensions of the obstacle, but the operator still has specific specifications for controlling, in particular, the lifting according to step c) and driving over according to step d) and/or lowering according to step e). In particular, the operator should be given the opportunity to determine how much unmilled ground should remain around the obstacle. For this purpose, it is preferably provided that the operator is shown a representation of the obstacle created from data obtained by the sensor device on a display device, and that the operator can specify the front and rear edges of the obstacle in the working direction on the display device, with 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. For example, the image from a camera can be displayed to the operator on the display device, with the obstacle being visible in the image. The operator can then use input elements, for example a touchscreen, to determine the front and rear edges of the obstacle in the working direction based on the image. These dimensions of the obstacle in the working direction determined by the operator are then used as the basis for further control. The control is carried out in such a way that the milling drum is lifted out of the ground in front of the front edge of the obstacle in the working direction and is only lowered back into the ground behind the rear edge of the obstacle in the working direction. This avoids potentially damaging contact between the milling drum and the obstacle.

According to a particularly preferred embodiment, the approach of the road milling machine in the working direction to the obstacle in the ground according to step b) is also carried out automatically by the control device. It can be provided here that the control device positions the road milling machine as close as possible to the obstacle. On the one hand, the milling drum should be lifted as close as possible in front of the obstacle in order to keep as little as possible any protruding residues of the soil to be milled, which subsequently have to be removed manually or mechanically. On the other hand, it should be ensured that neither the obstacle nor the milling drum are damaged by a collision. Due to the geometry of the milling drum, it should be noted that the road milling machine can approach obstacles at varying degrees depending on the milling depth. Due to the circular diameter of the milling drum, it must be excavated earlier at high milling depths and later at lower milling depths to keep it out of contact with the obstacle. It is therefore preferably provided that the position in the working direction at which the milling drum is lifted out is determined taking into account the position of the obstacle, the milling depth and in particular the geometry of the milling drum in order to keep it out of contact with the obstacle. In particular, this position is determined automatically by the control device, so that step b) of approaching the road milling machine in the working direction to the obstacle in the ground is also carried out automatically by the control device and without intervention by the operator. In this case, the operator can concentrate completely on milling the ground according to step a). All further steps b) to e), which deal with the avoidance due to the obstacle, are preferably carried out automatically by the control device.

Since the road milling machine removes less or no milled material from the ground during steps c) and d), it is preferably provided that a conveyor device is installed while these steps are being carried out the road milling machine is put out of operation, especially automatically. This can also be carried out by the control device. In this way, while these steps are being carried out, additional attention does not have to be paid to the error-free and low-loss transfer of the milled material to a transport vehicle. Corresponding sources of error are thereby reduced and occupational safety is increased. In addition, the conveyor device is preferably automatically reactivated in step e) in order to continue the milling process smoothly.

In order to ensure a simple, quick and seamless transition of the milling work before the obstacle and after the obstacle, it is preferably provided that the same machine settings are automatically used to continue milling the soil according to step e), in particular with regard to milling depth and / or feed speed and / or Operation of the conveyor device can be set, in particular as they were in step a). The milling work should continue in the working direction behind the obstacle with the same machine settings that were set in front of the obstacle. Accordingly, the respective settings are saved by the control device and automatically restored in step e).

In order to leave as little milled material as possible on the obstacle, it is preferably provided that the rear shield is in the excavated position either resting against the unmilled ground and the obstacle or with a safety distance, for example 2 cm, while driving over the obstacle according to step d). this is kept floating. In this way, a large part of the material to be milled is transported out of the milling bed in front of the obstacle in the working direction, then transported over the obstacle by the rear blade and kept in the milling drum box until the milling drum is repositioned. As soon as the milling work begins again in the working direction behind the obstacle, the milled material can then be transported to the conveyor and disposed of as normal. The repositioning of the milling drum in the working direction behind the obstacle can basically proceed in the same way as at the start of a new milling track. In order to leave the cleanest possible milling bed behind the obstacle at the beginning of the new milling track in the working direction, it can preferably be provided that the lowering of the rear shield is controlled to the predetermined milling depth in the working direction behind the obstacle in such a way that the lower edge of the rear shield is during the lowering of one of the trajectories described here follows in the opposite direction. In principle, this can be any of the trajectories described above. In particular, it is the same trajectory as during excavation. The lowering of the rear shield and the feed speed of the road milling machine are controlled in such a way that the corresponding trajectory is carried out exactly the other way around. This way you stay both in front of and behind The obstacle leaves behind as little milled material as possible, which has to be removed in complex rework.

The process can be further improved if obstacle widths are saved during the process. In this case, the obstacle width refers to the extent of the obstacle in the travel or milling direction of the road milling machine. This can be useful, for example, for obstacles that have to be driven over several times and/or obstacles with standard widths, such as manhole covers, etc. In this case, the operator can signal, for example, by manual triggering that such an obstacle with a saved width has been reached. This determines the distance over which the milling drum and the rear shield should be lifted according to the above information. In particular, there is no longer any need for the driver to trigger the lowering. Additionally or alternatively, an offset can also be provided. This denotes a distance, in particular also manually definable, in the milling direction in front of and behind the obstacle. This can be set individually for each obstacle by the operator or can also be stored as a defined size in a memory device.

The task mentioned at the beginning can also be solved with a road milling machine for milling a floor in one working direction. The road milling machine according to the invention comprises a milling drum box which is height-adjustable relative to the ground. This height adjustment can be achieved via an adjusting device which is designed in such a way that the milling drum box is completely or partially height-adjustable relative to the machine frame. Additionally or alternatively, the machine frame can be connected to the driving devices running on the ground via vertically adjustable lifting devices. In this case, the milling drum box is adjusted in the vertical direction together with the machine frame. The milling drum box has a front shield, two side shields (one on the front of the milling drum) and a rear shield that is height-adjustable relative to the machine frame and can have a hold-down device. In addition, it comprises a milling drum rotatably mounted in the milling drum box about a rotation axis, in particular horizontal and transverse to the working direction, and a control device. The road milling machine according to the invention is characterized in that the control device is designed to carry out the method described above, with at least step c) being carried out automatically by the control device in such a way that the milling drum is lifted out before the rear shield is lifted out of the ground , whereby the road milling machine continues to move in the working direction between lifting the milling drum and lifting the rear shield. All of the features, effects and advantages mentioned above for the method therefore also apply in a figurative sense to the method according to the invention road milling machine and vice versa. Reference is only made to the other statements to avoid repetition.

As already mentioned at the beginning, the milling drum can either be designed to be height-adjustable within the milling drum box and relative to it, or the milling drum is designed to be height-adjustable together with the milling drum box. Depending on how the height of the milling drum of the road milling machine is adjusted, it can be advantageous for the rear shield and in particular the lower edge of the rear shield to be designed to be lowerable lower than the milling drum and in particular its lower apex. The lower apex of the milling drum is related to the largest cutting circles of the milling drum. In other words, it is preferably provided that the road milling machine has an adjusting device for adjusting the height of the rear shield, which is designed such that the rear shield can be adjusted below the lower apex of the milling drum, in particular by at least 10%, preferably by at least 20%, in particular preferably by at least 30% of the diameter of the milling drum. This ensures in particular that the rear shield can still be in the working position while the milling drum is or has already been lifted, even if the height of the milling drum is basically adjusted together with the entire milling drum box. In this case, the rear shield carries out a countermovement for compensation, in which the rear shield is adjusted vertically below the milling drum and in particular below its lower apex.

Figur 1:

eine Seitenansicht einer Straßenfräsmaschine;

Figur 2:

eine Draufsicht auf einen Fräswalzenkasten und eine Fräswalze;

Figuren 3-9:

einen zeitlichen Ablauf von Fräsarbeiten bei einem im zu fräsenden Boden befindlichen Hindernis;

Figur 10:

eine Detailansicht gemäß Ausschnitt X aus Figur 5;

Figur 11:

eine Detailansicht gemäß Figur 10 mit angehobener Fräswalze;

Figur 12:

eine einstufige Trajektorie;

Figur 13:

eine weitere einstufige Trajektorie mit in Richtung der Vorderkante des Aushubbereiches verschobener Verlagerungsstelle;

Figur 14:

eine weitere einstufige Trajektorie mit einer Verlagerungsstelle, die der Vorderkante des Aushubbereiches entspricht;

Figur 15:

eine mehrstufige Trajektorie;

Figur 16:

eine mehrstufige Trajektorie mit schrägen Abschnitten;

Figur 17:

eine einstufige, schräge Trajektorie;

Figur 18:

eine Trajektorie, bei der die Unterkante des Heckschildes im Wesentlichen an der Oberfläche der Rampe im Aushubbereich anliegt;

Figur 19:

eine Sensoreinrichtung mit einem Sensor;

Figur 20:

eine Sensoreinrichtung mit mehreren Sensoren;

Figur 21:

den Einfluss der Frästiefe auf die Position des Aushebens der Fräswalze; und

Figur 22:

ein Ablaufdiagramm des Verfahrens.

The invention is explained in more detail below using the exemplary embodiments shown in the figures. It shows schematically:

Figure 1:

a side view of a road milling machine;

Figure 2:

a top view of a milling drum box and a milling drum;

Figures 3-9:

a time sequence of milling work in the event of an obstacle in the ground to be milled;

Figure 10:

a detailed view according to section X Figure 5 ;

Figure 11:

a detailed view according to Figure 10 with raised milling drum;

Figure 12:

a single-stage trajectory;

Figure 13:

a further single-stage trajectory with the displacement point shifted towards the front edge of the excavation area;

Figure 14:

another single-stage trajectory with a displacement point corresponding to the leading edge of the excavation area;

Figure 15:

a multi-stage trajectory;

Figure 16:

a multi-stage trajectory with oblique sections;

Figure 17:

a single-stage, oblique trajectory;

Figure 18:

a trajectory in which the lower edge of the rear shield essentially rests on the surface of the ramp in the excavation area;

Figure 19:

a sensor device with a sensor;

Figure 20:

a sensor device with several sensors;

Figure 21:

the influence of the milling depth on the position of lifting the milling drum; and

Figure 22:

a flowchart of the procedure.

Identical or identically acting components are designated with the same reference numbers. Repetitive components are not designated separately in each figure.

Figure 1 shows a road milling machine 1, here a road milling machine or cold milling machine of the center rotor type, for milling a floor 8 in working direction a. The road milling machine 1 has a machine frame 3 and an operator's cab 2. The machine frame 3 is carried via lifting columns 15, which connect the machine frame 3 to the driving devices 6, which in the exemplary embodiment shown are designed as chain drives, which, however, can also be wheels. The machine frame 3 can be adjusted in height relative to the floor 8 or adjusted in the vertical direction via the lifting columns 15. The road milling machine 1 also includes a drive motor 4, which is typically a diesel internal combustion engine, but can also be an electric motor, for example. A hybrid drive is also possible. As the primary working unit, the road milling machine 1 has a milling drum 9, which is mounted in a milling drum box 7 so that it can rotate about an axis of rotation 10. When the road milling machine 1 is in operation, the milling drum 9 rotates about the axis of rotation 10 and thereby mills ground material from the ground 8. This detached milled material is transferred from the milling roller box 7 to a conveyor device 5, which typically comprises a conveyor belt and which is designed to load the milled material onto a transport vehicle (not shown) for removal. The milling drum box 7 can be arranged stationary on the machine frame 7 in the vertical direction. Alternatively, an adjusting device can also be provided, which is designed such that the milling drum box can be adjusted in the vertical direction relative to the machine frame. In this case, the lifting devices 15 could also be dispensed with. In the exemplary embodiment shown, there is a control device 18 in the driver's cab 2, which is, for example, part of the on-board computer of the road milling machine 1. In particular, the control device 18 is equipped with input means via which an operator can input control commands to the control device 18 for controlling the road milling machine 1. In addition, the control device 18 has a display device 26 connected, for example a display. The display device 26 can also be designed as an input means, for example as a touchscreen.

In Figure 2 a top view of the milling drum 9 arranged in the milling drum box 7 is shown. A closure in the vertical direction upwards or a lid is in Fig. 2 not shown for clarity reasons. The milling drum 9 has a large number of milling tools 11, for example milling cutters. The milling tools 11 are arranged distributed over the outer jacket of the hollow cylindrical milling drum 9, for example in spirals. Overall, the milling drum box 7 surrounds the milling drum 9 in a hood-like manner and is essentially designed to be open only in the direction of the base 8, i.e. downwards (in addition, a material passage opening can also be provided in the front and/or rear shield). In the working direction a at the front, the milling drum box 7 is closed by a front plate 13. The front shield 13 can include a hold-down device. The hold-down device can also be arranged as a separate element in the working direction a in front of the front plate 13. In particular, when the milling drum 9 rotates in the opposite direction of rotation with respect to the driving devices 6, the hold-down device pressing on the ground 8 in front of the milling drum 9 prevents larger clods from breaking out of the ground 8. The milling drum box 7 is delimited on the side by side plates 12, which are on the ground 8 can be slid along next to the milling drum 9 and prevent milled material from escaping laterally from the milling drum box 7. In the working direction a, the milling drum box 7 is closed off by a rear shield 14. The rear shield 14 wipes off the milled material lying on the floor 8 and ensures that it is transported with the milling drum box 7 and channeled away from it. In this way, the cleanest possible milling bed is left behind. In principle, the front shield 13, the side shields 12 and the rear shield 14 can each be designed to be height-adjustable. For reasons of clarity, only one adjusting device 28 for adjusting the height of the rear shield 14 is shown. This includes, for example, one or more, in particular double-acting, hydraulic cylinders. The rear shield 14 is height-adjustable via the adjusting device 28, in particular relative to the machine frame 3 and/or to the milling drum 9 and/or to the floor 8.

The Figures 3-9 illustrate the timing of milling work and an obstacle 16 located in the ground 8 to be milled. The obstacle 16 can be, for example, a manhole cover, a shaft or another installation in the ground 8. In particular, the obstacle 16 should not be damaged or destroyed by the milling work. At the same time, the milling drum 9 or its milling tools 11 should also be protected from damage caused by a collision with the obstacle 16. Figure 3 shows the situation before the milling work began. The milling drum 9 is arranged in a raised position above the ground 8. she will then rotatingly lowered into the ground 8 while the road milling machine 1 moves over the ground 8 in the working direction a. The milling drum 9 thereby removes the soil 8 and a milling track is created. This situation is in Figure 4 shown. The road milling machine 1 is moved up to just in front of the obstacle 16 in the working direction a. Figure 5 shows the situation in which the road milling machine 1 was positioned and stopped in front of the obstacle 16. In order to prevent a collision between the milling drum 9 and the obstacle 16, the milling drum 9 is then raised vertically upwards by at least the predetermined milling depth of the milling track, as shown in Figure 6 is shown. According to the invention, the rear shield 14 initially remains in its working position and is therefore not adjusted vertically upwards from the ground 8 at the same time as the milling drum 9. Compared to the milling drum 9, the rear shield 14 can, if necessary, be adjusted vertically downwards. Next, the road milling machine 1 moves over the obstacle 16 with the milling drum 9 in such a way that the milling drum 9 does not touch the obstacle 16. How exactly the rear shield 14 can be lifted out of the milling track will be explained in more detail below. The situation of driving over the obstacle 16 with the milling drum 9 raised and the rear plate 14 raised is in Figure 7 shown. Figure 8 in turn shows the next work step, in which the milling drum 9 is lowered back into the ground 8 behind the obstacle 16 in the working direction a and mills a new milling track behind the obstacle 16 in the working direction a. This milling work behind the obstacle 16 can then be carried out accordingly Figure 9 continue as usual. The invention makes it possible for only minimal rework to be necessary both in the working direction a in front of and behind the obstacle 16, for example in order to remove unmilled ground material or milled material that has been left lying around.

In Figure 10 is the section X Figure 5 shown enlarged. During the milling work, the road milling machine 1 or the milling drum 9 was positioned just in front of the obstacle 16. Up to the obstacle 16, the milling drum 9 has removed a milling track at a milling depth FT. As in Figure 11 shown, the milling drum 9 is now raised vertically from the milling track by at least the milling depth FT. In addition to the milling depth FT, the milling drum 9 can be raised by a safety distance, for example 2 cm. In this way it is ensured that the milling tools 11 of the milling drum 9 do not come into contact with the obstacle 16. As also in Figure 11 shown, the rear shield 14 is still in its working position. In particular, the lower edge 19 of the rear shield 14 is still in contact with the milling bed base 27. From the situation in Figure 11 starting, the lifting of the rear shield 14 is controlled in such a way that the lower edge 19 of the rear shield 14 is one of those described in more detail below Figures 12-18 shown trajectories T follows.

In Figure 12 A case is shown in which the rear shield 14 is lifted out at the same time as the milling drum 19. By lifting the milling drum 9, an excavation area AB is created in the working direction a in front of the obstacle 16, the shape of which essentially corresponds to the circumference of the milling drum 9 or its cutting circles, and which runs from the milling bed floor 27 to the unmilled floor 8. The line transverse to the working direction a, where the milling depth FT is still maximum, but then begins to decrease in the working direction a, is referred to as the front edge VK of the excavation area AB. As from a comparison of the Figures 11 and 12 As can be seen, the front edge VK of the excavation area AB lies directly vertically below the axis of rotation 10 of the milling drum 9 at the position at which the milling drum 9 is lifted out of the milling track. The distance between the axis of rotation 10 of the milling drum 9 and the rear shield 14 in the working direction a is referred to as x. Figure 12 now shows the case that the rear shield 14 is lifted out at the same time as the milling drum 9, i.e. the displacement point V ₁ at which the rear shield 14 is lifted out of the milling track is removed by the distance x from the front edge VK of the excavation area AB. In addition, the lower edge 19 of the rear shield 14 is guided along a single-stage, rectangular trajectory T.

Figure 13 shows a case in which the lower edges 19 of the rear shield 14 are excavated at a displacement point V ₂ , the displacement point V ₂ being a distance y from the front edge VK of the excavation area AB, the distance y being smaller than the distance x. For this it is necessary that the rear shield 14 remains in the working position after the milling drum 9 has been lifted and the road milling machine 1 continues to move in the working direction a between the lifting of the milling drum 9 and the lifting of the rear shield 14, specifically by the difference in the distance x minus the Distance y. Only after the road milling machine 1 has moved further in working direction a by this difference is the rear shield 14 lifted at the displacement point V ₂ . This has the advantage that the rear shield 14 still fulfills its function up to the displacement point V ₂ and transports the loose milled material collected in the milling drum box 17 with the milling drum box 7. In this way, after the rear shield 14 has been raised, less milled material remains on the milling bed base 27. Also in the Figure 13 the lower edges 19 of the rear shield 14 are guided along a single-stage, rectangular trajectory T.

In Figure 14 a case is shown in which the rear shield 14 is excavated from the milling track at a displacement point V ₃ , the displacement point V ₃ corresponding to the front edge VK of the excavation area AB. In other words, the distance is y in the case of Figure 14 equals zero. The rear shield 14 is therefore maintained in the working position after the milling drum 9 has been lifted out of the milling track up to the front edge VK of the excavation area AB and only at the front edge VK as well excavated from the milling track. The rear shield 14 is therefore lifted out of the milling track at the same position in the working direction a as the milling drum 9. Since the milling depth FT in the working direction a begins to decrease behind the front edge VK, it is necessary to lift the rear shield 14 at the front edge VK at the latest. The trajectory T, along which the lower edge 19 of the rear shield 14 is guided, can be adapted in different ways to the geometry of the ramp R in the excavation area AB. In the Figure 14 Trajectory T shown is again single-stage and rectangular.

Further examples of differently shaped trajectories T can be found in the Figures 15-18 out. Although there are in the Figures 15-18 only cases are shown in which the rear shield 14 is lifted at the displacement point V ₃ corresponding to the front edge VK. However, according to the invention, cases are also included in which the shapes of the trajectories T der Figures 15-18 starting from a displacement point V ₂ at a distance y from the front edge VK of the excavation area AB, and in which the distance y is in particular not zero. For example, shows Figure 15 a multi-stage trajectory T, in the present case a two-stage trajectory T. Of course, the trajectory T can optionally also include a higher number of stages. In addition, the example shown is the Figure 15 about rectangular steps, which come about because the vertical height adjustment of the rear shield 14 is carried out without interference with the feed movement of the road milling machine 1. In other words, the height adjustment of the rear shield 14 is always carried out when the road milling machine 1 is stationary and does not move in working direction a. In Figure 16 A case is shown in which there is also a multi-stage trajectory T, although the individual stages have an obtuse angle. For this purpose, the height adjustment of the rear shield 14 in the vertical direction is superimposed on a movement of the road milling machine 1 in the working direction a, so that overall an obliquely forward and upward trajectory T is created. Here too, as in the other exemplary embodiments with a multi-stage trajectory T, the height adjustment of the rear shield 14 in the vertical direction is not adjusted in a single movement from the working position to the raised position, but rather at intervals. In particular, there are further sections between vertical movement sections of the rear shield 14, in which the lower edge 19 of the rear shield 14 is only moved in the working direction a with the road milling machine 1 by its feed, which creates the horizontal parts of the trajectory T. Figure 17 again shows a single-stage trajectory T, although this is oblique. The trajectory T according to Figure 17 So includes a single continuous movement of the rear shield 14 in the vertical direction from the working position to the raised position. The vertical adjustment of the rear shield 14 is continuously superimposed by the movement of the road milling machine 1 in the working direction a, so that the overall oblique movement path results. The angle of the oblique trajectory T relative to a horizontal, in particular the milling bed base 27, is selected such that the trajectory T runs from the front edge of the excavation area AB to the end of the excavation area AB opposite the front edge VK in the working direction a. In particular, the angle is chosen such that the lower edge 19 of the rear shield 14 rests on the front edge VK and on the end of the excavation area AB opposite the front edge VK in the working direction a or hovers above it with a predetermined safety distance. In other words, the trajectory T runs from the front end of the ramp R in the working direction a to the rear end of the ramp R in the working direction a. In Figure 18 Finally, a trajectory T is shown, the course of which is adapted to the excavation area AB or the ramp R. Taking into account the geometry of the milling drum 9 and the feed speed of the road milling machine 1 and in particular its acceleration, the lower edge 19 of the rear shield 14 is guided along the trajectory T in such a way that the lower edge 19 follows the surface of the ramp R and either touches it or in it hovers above it at a predetermined safety distance.

Figure 19 shows a top view of the milling drum box 7 based on Figure 2 . When the milling drum 9 is in operation, it mills the ground 8 in the working direction a, whereby the milling track 29 is created. The milling track 29 is created over the entire milling width FB of the milling drum 9. The milling width FB essentially corresponds to the extent of the milling drum 9 along the axis of rotation 10. In the working direction a in front of the milling drum 9 and also in front of the milling drum box 7 there is a sensor device in the exemplary embodiment shown 17 arranged, which is designed to detect obstacles 16 in the ground 8 and in particular within the milling width FB. For this purpose, the sensor device 17 is designed such that it has a detection area EB that covers the entire milling width FB. In Figure 20 is shown in an exemplary embodiment in which the sensor device 17 comprises several individual sensors. Each of the sensors has a detection area EB that is smaller than the milling width FB. Overall, however, the sensor device 17 is again designed in such a way that the entirety of the detection areas EB of all sensors of the sensor device 17 cover the entire milling width FB. The sensor device 17 can additionally be designed to detect or determine the extent E of the obstacle 16 in the working direction a. This is in Figure 19 for example shown using a round obstacle 16, for example a manhole cover. In Figure 20 This is shown in the case of non-round, for example rectangular obstacles 16, for example installation shafts. The extent E of the obstacles 16 is how in particular Figure 20 emerges, always related to the working direction a. It runs from the front edge of the obstacle 16 in the working direction a to the rear edge of the obstacle 16 in the working direction a. If this extension E and thus the edges of the obstacle 16 are taken into account when controlling the road milling machine 1 as described above, it can be efficiently prevented that the milling drum 9 comes into contact with the obstacle 16.

In Figure 21 It is shown what influence the milling depth has on the position at which the milling drum 9 has to be lifted out of the milling track 29 in order to avoid contact between the obstacle 16 and the milling drum 9. In particular, two different positions of milling drums 9 are shown in dashed lines, which are located at different milling depths FT ₁ and FT ₂ , the milling depth FT ₁ being greater than the milling depth FT ₂ . The different milling depths FT ₁ , FT ₂ result in different distances A ₁ , A ₂ between the respective axis of rotation 10 of the milling rollers 9 and the obstacle 16, in which the milling roller 9 must be lifted out of the milling track 29. In particular, the milling drum 9 can be lifted out of the milling track 29 at a smaller milling depth FT ₂ at a smaller distance A ₂ in front of the obstacle 16 than at a higher milling depth FT ₁ . The road milling machine 1 can therefore move closer to the obstacle 16 at a lower milling depth FT than at a higher milling depth FT. This parameter, together with the geometry of the milling drum 9, is therefore taken into account by the control device 18 when it automatically determines the position of the lifting of the milling drum 9.

In Figure 22 a flowchart of the method 20 for controlling the road milling machine 1 is shown in the event of an obstacle 16 located in the ground 8 to be milled. The method 20 begins with the milling 21 of the ground 8 at a predetermined milling depth FT in the working direction a during the normal operation of the road milling machine 1. This is followed by an approach 22 of the road milling machine 1 to the obstacle 16 located in the ground 8. This can be done either by the operator be carried out, or for example also automatically by the control device 18, in particular if a sensor device 17 is present which can detect the obstacle 16 located in the floor 8. The road milling machine 1 is positioned in front of the obstacle 16. Next, the milling drum 9 and the rear shield 14 are lifted out of the ground 8 in front of the obstacle 16. Here, it is provided according to the invention that the milling drum 9 is lifted out 23 'before the rear shield 14 is lifted out of the ground 8 , and that the road milling machine 1 moves further in working direction a between the lifting 23 of the milling drum 9 and the lifting 23 'of the rear shield 14. This causes the distance y between the front edge VK of the excavation area AB and the displacement point V _2/3 of the rear shield 14 shortened. This is then followed by driving over 24 of the obstacle 16, with the milling drum 9 remaining out of contact with the obstacle 16. Finally, the milling drum 9 and the rear shield 14 are lowered 25 to the predetermined milling depth FT in the working direction a behind the obstacle 16, so that the milling process can be continued. Both the lifting 23, 23 ', the driving over 24 and the lowering 25 can be carried out automatically by the control device 18. This can be triggered, for example, by a single control command from the operator or, alternatively, also by the detection of the obstacle 16 by the sensor device 17. The method 20 described herein relieves the operator of the road milling machine of constantly repeating control processes on obstacles 16 during work. At the same time, less milled material is left behind in the milling bed, so that necessary rework is reduced by the method 20 according to the invention. Overall, the milling process of the road milling machine 1 can therefore be made more economical and efficient.

Claims (14)

1. Method (20) for controlling a road milling machine (1) comprising a milling drum (9) and a rear blade (14) when there is an obstacle (16) located in the ground (8) to be milled, comprising the following steps:

   a) milling (21) the ground (8) at a predetermined milling depth (FT) along a working direction (a);

   b) advancing (22) the road milling machine (1) in the working direction (a) towards the obstacle (16) located in the ground (8);

   c) raising (23, 23') the milling drum (9) and the rear blade (14) out of the ground (8) in the working direction (a) in front of the obstacle (16);

   d) moving over (24) the obstacle (16) in such a way that the milling drum (9) remains out of contact with the obstacle (16); and

   e) lowering (25) the milling drum (9) and the rear blade (14) to the predetermined milling depth (FT) in the working direction (a) behind the obstacle (16) and continuing the milling (21) of the ground (8),

   characterized in that
   the road milling machine (1) is controlled in such a way that in step c) the raising (23) of the milling drum (9) is carried out before the raising (23) of the rear blade (14) out of the ground (8), wherein the road milling machine (1) continues to move in the working direction (a) between the raising (23) of the milling drum (9) and the raising (23) of the rear blade (14).
2. Method (20) according to claim 1,

   wherein the raising (23) of the milling drum (9) 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 (23) of the milling drum (9), wherein the excavation area (AB) has a front edge (VK) at its deepest point,

   characterized in that

   the raising (23') of the rear blade (14) takes place at a displacement point (V₂) 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 (14) from an axis of rotation (10) of the milling drum (9), or

   the raising (23') of the rear blade (14) takes place at a displacement point (V₃) along the working direction (a) which is on the front edge (VK).
3. Method (20) according to any one of the preceding claims,
   characterized in that
   the raising (23') of the rear blade (14) is controlled in such a way that a lower edge (19) of the rear blade (14) facing the ground (8) follows a predetermined trajectory (T) during the raising (23'), taking into account the advancement speed and in particular the acceleration of the road milling machine (1).
4. Method (20) according to the preceding claim,
   characterized in that
   the trajectory (T) has at least one of the following features:

   - it comprises exclusively one movement transverse to the working direction (a) vertically upwards, which in particular is not superimposed with a traveling movement of the road milling machine (1) in the working direction (a), and a subsequent movement horizontally in the working direction (a);

   - it comprises a plurality of step-wise movements transverse to the working direction (a) vertically upwards, wherein the lower edge (19) is moved horizontally in the working direction (a) between the steps, and wherein the step-wise vertical movements are in particular not superimposed with a traveling movement of the road milling machine (1) in the working direction (a);

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

   - it follows a ramp (R) in the excavation area (AB) created by the raising (23) of the milling drum (9) in such a way that the lower edge (19) substantially abuts the surface of the ramp (R) over the entire excavation area (AB).
5. Method (20) according to any one of the preceding claims,
   characterized in that
   at least one sensor device (17) is arranged in front of the milling drum (9) in the working direction (a), which detects obstacles (16) in the ground (8) to be milled, wherein the at least one sensor device (17) comprises in particular an inductive, capacitive or magnetic sensor; for example, a metal detector, an optical sensor, for example a camera or a thermal imaging camera, or a sound sensor, for example an ultrasonic sensor.
6. Method (20) according to any one of the preceding claims,
   characterized in that
   in order to carry out steps c), d) and e), an extension (E) of the obstacle (16) in the working direction (a) is input in advance by the operator, or in that the extension (E) of the obstacle (16) in the working direction (a) is determined by the sensor device (17).
7. Method (20) according to any one of the preceding claims,
   characterized in that
   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 (16) by the sensor device (17).
8. Method (20) according to any one of claims 5 - 7,
   characterized in that
   the operator is shown a representation of the obstacle (16) on a display device (26) produced from data obtained from the sensor device (17), and in that the operator can specify on the display device (26) the front and rear edges of the obstacle (16) in the working direction (a), wherein steps c), d) and e) are then carried out in such a way that the milling drum (9) remains out of contact with the edges of the obstacle (16) specified by the operator.
9. Method (20) according to any one of claims 5-8,
   characterized in that
   the position in the working direction (a) at which the raising (23) of the milling drum (9) is carried out is determined taking into account the position of the obstacle (16), the milling depth (FT) and in particular also the geometry of the milling drum (9) in order to keep it out of contact with the obstacle (16).
10. Method (20) according to any one of the preceding claims,
    characterized in that
    during steps c) and d) a conveyor device (5) of the road milling machine (1) is put out of operation, in particular automatically.
11. Method (20) according to any one of the preceding claims,
    characterized in that
    to continue the milling (21) of the ground (8) according to step e), the same machine settings, in particular with regard to milling depth (FT) and/or advancement speed and/or operation of the conveyor device (5), are automatically set as in step a).
12. Method (20) according to any one of claims 3 - 11,
    characterized in that
    the lowering (25) of the rear blade (14) to the predetermined milling depth (FT) in the working direction (a) behind the obstacle (16) is controlled in such a way that the lower edge (19) of the rear blade (14) follows a trajectory (T), in particular the same trajectory (T) is following during the lowering (25) as during the raising (23), in the opposite direction.
13. Road milling machine (1) for milling a ground (8) in a working direction (a), having

    - a machine frame (3) supported by travel devices (6),

    - a milling drum case (7) mounted on the machine frame (3) having a front blade (13), two side blades (12) and a rear blade (14) which is height-adjustable relative to the machine frame (3),

    - a milling drum (9) mounted rotatably about an axis of rotation (10) in the milling drum case (7), and

    - a control device (18),

    characterized in that
    the control device (18) is designed to carry out the method (20) according to any one of the preceding claims, wherein step c) is carried out automatically by the control device (18) in such a way that the raising (23) of the milling drum (9) is carried out before the raising (23) of the rear blade out of the ground (8), wherein the road milling machine (1) continues to move in the working direction (a) between the raising(23) of the milling drum (9) and the raising (23) of the rear blade (14).
14. Road milling machine (1) according to claim 13,
    characterized in that
    it has an adjusting device (28) for adjusting the height of the rear blade (14), which is designed in such a way that the rear blade (14) can be adjusted to below the lower apex of the milling drum (9), in particular by at least 10%, preferably by at least 20%, particularly preferably by at least 30%, of the diameter of the milling drum (9).

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