The invention relates to a ground milling machine, in particular a stabiliser or recycler, having a machine frame which is supported by running gears and on which is arranged a milling/mixing roller arranged in a roller housing which is open at the bottom and has a roller flap at the rear in the working direction which can be pivoted about a pivot axis extending transversely to the longitudinal direction of the ground milling machine. In addition, the invention relates to a method for operating such a ground milling machine.
For stabilising ground with insufficient load-bearing capacity, stabilisers are known by which a powdered or liquid binding agent is introduced into the ground in order to increase its load-bearing capacity. Self-propelled and non-self-propelled stabilisers are known which are attached to or towed by a towing vehicle. The known recyclers differ from the stabilisers in that the recyclers are used not only for improvement or solidification of ground, but also for remediation of damaged surface layers of roads or paths.
Stabilisers or recyclers have a machine frame on which a milling/mixing roller is arranged for milling the ground to be stabilised or the road surface layer to be remediated, which is located in a roller housing which is open at the bottom. The roller housing has a roller flap at the front in the working direction and a roller flap at the rear in the working direction, and these flaps can be pivoted about a pivot axis running transversely to the longitudinal direction of the machine frame. The roller housing is closed at the sides by side parts extending in the longitudinal direction.
The volume enclosed by the roller housing forms a mixing chamber for the milled material and the binding agent. One or more dosing devices are located on the roller housing, which provide a predetermined amount of possibly different binding agents or water for the volume of the mixing chamber.
To pivot the front and rear roller flap, a roller flap adjustment device is provided which has at least one actuator for pivoting the front or rear roller flap and a control device for actuating the at least one actuator, so that the lower edge of the front or rear roller flap is adjustable in height relative to the ground. The control device of the rear roller flap is designed in such a way that the at least one actuator is controlled during milling operation in such a way that the rear roller flap lies in a floating position with a predetermined contact force on the ground.
In addition, the known stabilisers or recyclers have a milling/mixing roller adjustment device which is designed in such a way that the height of the milling/mixing roller relative to the machine frame can be adjusted, so that the milling depth can be changed.
When the milling/mixing roller is applied and the milling operation is started, and also when the milling depth is increased during the milling operation, the rear roller flap, even in the floating position, exerts considerable counter-pressure on the material in the roller housing. Practice has shown that this counter-pressure can lead to an accumulation of material in the mixing chamber. If there is an accumulation of material, the mixing ratio of material and binding agent can no longer meet the specifications. Another disadvantage is that higher power is required to operate the milling/mixing roller or the milling process can only be carried out at a lower working speed.
Raising the lower edge of the rear roller flap after the application of the milling/mixing roller or after the increase in the milling depth can facilitate the outflow of accumulated material from the roller housing as the ground milling machine advances. However, if the rear roller flap is opened too far, there is a risk that material will be thrown backwards out of the roller housing.
The object of the invention is to improve the operation of a ground milling machine or its working result, in particular when applying the milling/mixing roller to start milling or when increasing the milling depth during milling. One object of the invention is, in particular, to avoid an accumulation of material when applying the milling/mixing roller or when increasing the milling depth, or to ensure an optimal mixing ratio of milled material and binding agent. A further object of the invention is to avoid an increase in the power required to operate the milling/mixing roller or a reduction in the working speed when applying the milling/mixing roller or when increasing the milling depth
Another object of the invention is to provide a method with which a ground milling machine can be operated, in particular when applying the milling/mixing roller to start milling or when increasing the milling depth during milling to avoid an accumulation of material.
According to the invention, these objects are achieved by the features of the independent claims. The dependent claims relate to advantageous embodiments of the invention.
The ground milling machine according to the invention, in particular a stabiliser or recycler, and the method according to the invention are characterised by a roller flap position correction mode, which can be activated manually after the milling/mixing roller has been applied and the ground milling machine has started up or during the actual milling operation after the milling depth has been increased or activated automatically. The roller flap position correction mode comprises at least one roller flap position correction cycle to optimise the position of the rear roller flap so that an accumulation of material and the problems resulting therefrom are largely avoided. The roller flap position correction mode can be activated manually by the machine operator or can be started fully automatically, so that manual intervention is not necessary. Manual intervention is not required while operating the ground milling machine in the roller flap position correction mode. After the roller flap position has been corrected, the roller flap position correction mode can be deactivated again automatically.
The control device of the roller flap adjustment device is designed in such a way that in the at least one roller flap correction cycle, the floating position of the rear roller flap is cancelled in a first step and the rear roller flap is pivoted upwards from a first pivoted position into a second pivoted position, so that the lower edge of the rear roller flap is raised. Consequently, the material accumulated in the roller housing can flow out. The pivot angle by which the roller flap is pivoted upwards can be specified by the control device. The roller housing should be opened wide enough so that accumulated material can flow out of the roller housing unhindered, on the one hand, but not so wide that there is a greater risk of material being thrown out, on the other hand. In a second step, after the rear roller flap has assumed the second pivoted position, the floating position is set again so that the rear roller flap assumes a third pivoted position in which the lower edge of the rear roller flap rests on the ground.
A preferred embodiment provides that the at least one roller flap position correction cycle includes a checking routine.
The basic principle of the checking routine is to monitor the movement of the roller flap after the floating position has been restored.
The checking routine provides for comparing a variable correlating with the third pivoted position with a threshold value or comparing a variable correlating with the third pivoted position with the value of a variable correlating with the first pivoted position, wherein the roller flap position correction mode is deactivated on the basis of a comparison of the value of a variable correlating with the third pivoted position with a threshold value or on the basis of a comparison of the value of a variable correlating with the third pivoted position with the value of a variable correlating with the first pivoted position.
If the raised roller flap falls back into a lower position after the floating position has been reset, i.e. it does not remain in the raised position, it is assumed that a continuous flow of material has been established, in which the milled material that accumulates in the mixing chamber and the material flowing out of the mixing chamber under the roller flap is in a state of equilibrium, so that an accumulation of material does not occur. In particular, it can be checked whether the roller flap drops back into the position from which it was raised. In this case, the roller flap position correction mode can be deactivated.
A threshold value can be defined for the movement of the roller flap. If the roller flap movement after resetting of the floating position is less than or equal to the threshold, i.e. the roller flap has not fallen back by a predetermined amount, another roller flap position correction cycle is carried out. If, on the other hand, the movement of the roller flap is greater than the threshold value, i.e. the roller flap has fallen back by a predetermined amount, the roller flap position correction mode is deactivated.
The variable correlating with the pivoted positions can be a variable that can be easily detected with little technical effort. The evaluation of the values of this variable depends on whether the variable increases or decreases as the roller flap is raised. For example, if the variable is a pivot angle, the evaluation depends on which angle is defined as the pivot angle. Different mathematical methods can be used to compare the variables correlating with the pivoted positions before and after the milling flap is raised.
A preferred embodiment provides that the variable correlating with the first and third pivoted position is a variable correlating with the height of the lower edge of the rear roller flap. The value of this variable increases when the roller flap is opened. In this embodiment, the roller flap position correction cycles are carried out until it is determined at least once that the height of the lower edge of the rear roller flap in the third pivoted position is equal to or less than the height of the lower edge of the rear roller flap in the first pivoted position. On the other hand, a further roller flap position correction cycle is carried out if the height of the lower edge of the rear roller flap in the third pivoted position is greater than the height of the lower edge of the rear roller flap in the first pivoted position. Consequently, the roller flap position correction mode can be terminated after only one or more roller flap position correction cycles. The roller flap position correction mode can therefore only include one roller flap position correction cycle if it is to be checked only once that the lower edge of the rear roller flap in the third pivoted position is equal to or less than the height of the lower edge of the rear roller flap in the first pivoted position, and this is also the case. However, the repeated determination of these conditions has the advantage that the roller flap position correction mode is only deactivated when a state of equilibrium has been set permanently.
The height of the lower edge of the roller flap is a variable related to a reference plane, which may be the unmilled ground. If the height of the ground in relation to the machine frame or to the roller housing is known, the height of the lower edge of the roller flap can be determined from the height of the roller flap in relation to the machine frame or the roller housing.
The at least one actuator of the roller flap adjustment device can be a piston-cylinder arrangement that acts on the roller flap and, for detection of the variable correlating with the first and/or third pivoted position, a measuring unit, in particular a distance sensor, can be provided that detects the position of the piston of the piston-cylinder arrangement. For example, the piston of the piston-cylinder arrangement can be pivotally attached to the machine frame and the cylinder can be pivotally attached to the roller flap, or vice versa. This embodiment can be easily implemented without major technical effort. In this embodiment, the pivoted positions can be compared simply by comparing the stroke of the piston when lifting with the stroke of the piston when lowering. If the piston is extended during lowering by a smaller distance than the piston was retracted when raising the roller flap, i.e. the roller flap maintains its upper position or is raised even further by the material flow, another roller flap position correction cycle is carried out. If, on the other hand, the roller flap falls back into a lower position after being raised due to the absence of a material flow, the checking is terminated.
The control device of the roller flap adjustment device is preferably designed in such a way that the floating position is set again in the second step after a predetermined time interval has elapsed or after a predetermined distance has been covered after the floating position has been cancelled or the roller flap has been pivoted into the third pivoted position. The time interval or the distance can be measured taking into account the dynamic conditions in relation to the material flow during milling.
The pivot angle by which the roller flap is pivoted upwards depends on the volume of the milled material. A further preferred embodiment provides a memory in which a pivot angle or a variable correlating with the pivot angle by which the rear roller flap is pivoted from the first into the second pivoted position is stored for different milling depths, the control device of the roller flap adjustment device being designed in such a way that, depending on the set milling depth, the pivot angle or a variable correlating with the pivot angle is read from the memory.
For manual activation of the roller flap position correction mode, the control device of the roller flap adjustment device can have an operating element, for example a knob or switch or a button on a touch-sensitive screen (touch screen), the control device being designed in such a way that the roller flap position correction mode is activated by actuation of the operating element.
The control device of the roller flap adjustment device can also be designed in such a way that the roller flap position correction mode is activated fully automatically when, after the ground milling machine has started up milling operation, a predetermined time interval has elapsed or the ground milling machine has covered a predetermined distance. The point in time at which the ground milling machine starts up can be determined by monitoring control signals that can be made available by the central control and computing device of the ground milling machine, or by acquiring measured values from suitable sensors, for example distance sensors.
Since a ground milling machine generally has a milling/mixing roller adjustment device that is designed in such a way that the height of the milling/mixing roller relative to the machine frame can be adjusted so that the milling depth can be changed, the control device for the roller flap adjustment device can be designed in such a way that the roller flap position correction mode is activated when the milling/mixing roller adjustment device has increased the milling depth by a predetermined value during the milling operation and after the increase in the milling depth a predetermined time interval has elapsed or the milling/mixing roller adjustment device has increased the milling depth by a predetermined value during the milling operation and after the increase in the milling depth the ground milling machine has covered a predetermined distance. The time interval or the distance can be measured taking the dynamic conditions during the milling operation into account. The milling/mixing roller can be adjusted in height relative to the machine frame, the machine frame being supported by lifting columns which are fastened to running gears, so that the height of the machine frame can be adjusted relative to the ground.
Embodiments of the invention are described in detail below with reference to the drawings.
In the drawings:
To adjust the height of the milling/mixing roller 9, the ground milling machine has a milling/mixing roller adjustment device 16, which in the present embodiment comprises a piston-cylinder arrangement 17 with a piston 17A and a cylinder 17B. The piston-cylinder arrangement 17 may also be referred to as a roller adjustment actuator 17 for adjusting the height of the milling/mixing roller 9 relative to the machine frame 5. By actuation of the piston 17A of the piston-cylinder arrangement 17, the height of the milling/mixing roller 9 can be adjusted relative to the machine frame 5 or the ground 6, with the axis of the milling/mixing roller moving on a circular path. A height adjustment of the milling/mixing roller 9 relative to the ground 6 is also possible by retracting or extending the lifting columns 4. To control the piston-cylinder arrangement 17 of the milling/mixing roller adjustment device 16, a control device 18 (not shown in
A front and rear roller flap adjustment device 19 is provided to adjust the position of the roller flaps 12, 13 at the front and rear in the working direction. In the embodiments described below, only the rear roller flap is considered.
The roller flap adjustment device 19 of the rear roller flap 13 has at least one actuator 20 acting on the roller flap. In the present embodiment, the actuator is a piston-cylinder arrangement 20, of which the piston 20A is pivotally attached to the machine frame 5 and of which the cylinder 20B is pivotally attached to the rear roller flap 13.
By moving the piston 20A of the piston-cylinder arrangement 20 to a specific position, which is hereinafter designated as a, or by retracting or extending the piston 20A from an initial position by a predetermined distance, which is hereinafter designated as Δa, the rear roller flap 13 can be pivoted upwards or downwards about the pivot axis 14 running transversely to the working direction into a predetermined pivoted position α or by a predetermined pivot angle Δα, which correlates with the distance Δa, so that the lower edge 13A of the roller flap 13 can be raised or lowered relative to the ground 6 (
To control the actuator 20, the roller flap adjustment device 19 has a control device 21 (not shown in
The control and computing unit 21A of the control device 21 of the roller flap adjustment device 19 can have, for example, a general processor, a digital signal processor (DSP) for continuously processing digital signals, a microprocessor, an application-specific integrated circuit (ASIC), an integrated circuit consisting of logic elements (FPGA) or other integrated circuits (IC) or hardware components, in order to control the actuators. A data processing program (software) can run on the hardware components. A combination of the different components is also possible.
The roller flap adjustment device 19 also includes other components known to a person skilled in the art, in particular hydraulic components, for example hydraulic pumps, hydraulic valves, hydraulic lines.
In addition, the ground milling machine has a drive device (not shown) for hydraulic components, for example hydraulic pumps or hydraulic motors, for example for driving the running gears.
The control of the rear roller flap 13 by the control device 21 of the roller flap adjustment device 19 is described in detail below with reference to
For application of the milling/mixing roller 9, the machine operator moves the ground milling machine to the desired position with the milling/mixing roller 9 raised. In this position, the lifting columns 4 are largely extended and the milling/mixing roller 9 is moved into an upper position (
The milling/mixing roller 9 is now lowered to the desired milling depth so that the milling process begins (
The roller flap adjustment device 19 can also be designed in such a way that the roller flap 13 does not rest on the ground under its own weight, but is loaded or relieved of load with an additional contact force. If in the floating position both chambers are subjected to a pressure which preferably does not correspond to the system pressure, the movement of the roller flap downwards can be supported by a corresponding design of the effective contact surfaces of the cylinder, for example with the same pressure in both cylinder chambers.
In principle, the invention can also be implemented by a roller flap adjustment device 19 with a single-acting piston-cylinder arrangement. A single-acting piston-cylinder arrangement is characterised in that it can only be actuated in one direction. The roller flap adjustment device 19 only needs to be able to raise the roller flap. The floating position is achieved in that when no hydraulic pressure is applied to the piston-cylinder arrangement, the roller flap sinks in the direction of gravity under its own weight.
When the ground milling machine is started and moves in the working direction 11, the mixing chamber of the roller housing 8 fills with the milled material, which is deposited behind the milling/mixing roller 9 in the working direction.
In practice, however, it has been shown that after the milling/mixing roller 9 has been applied, material can accumulate in the roller housing 8 while the ground milling machine is being advanced, since the milling/mixing roller in the floating position exerts a not inconsiderable counter-pressure on the milled material. In the event of an accumulation of material, the mixing ratio of material and binding agent can no longer meet the specifications and the drive power required to drive the milling/mixing roller can increase. In the worst case, accumulated material can impede the movement of the milling/mixing roller to such an extent that the combustion engine of the drive device stalls. The problem described above can also occur when the milling depth is increased during the milling operation.
The control device 21 of the roller flap adjustment device 19 or the central control and computing device of the ground milling machine, which can comprise the control and computing unit of the control device of the roller flap adjustment device, is configured in such a way that the following method steps are carried out. The roller flap adjustment device 19 provides a roller flap position correction mode that can be activated manually or automatically and comprises at least one roller flap position correction cycle.
For manual activation of the roller flap position correction mode, the control device 21 of the roller flap adjustment device 19 has an operating element 26 (
After the control signal is received, the roller flap position correction mode is switched on, so that a first roller flap position correction cycle is carried out. In the roller flap position correction cycle, the control device switches off the floating position of the rear roller flap 13 and controls the piston-cylinder arrangement 20 of the roller flap adjustment device in such a way that the rear roller flap 13 is pivoted with a first pivot angle α1 (
The automatic activation of the roller flap position correction mode is described below. When the ground milling machine is started and the milling depth is greater than zero, the drive device generates a control signal which is received by the control and computing unit 21A of the control device 21 of the roller flap adjustment device 19. After the control signal is received, a timer 21AA or an odometer 21AB is started. The timer and/or the odometer can be a component of the roller flap adjustment device 19, in particular the control and computing unit 21A thereof, or can be other components of the ground milling machine. When the predetermined time interval has expired or the ground milling machine has covered the predetermined distance, the control device 21 switches off the floating position in a first step and pivots the rear roller flap 13 from the first pivoted position (
The roller flap position correction mode is also activated automatically when the milling/mixing roller adjustment device 16 generates a control signal which signals to the control and computing unit 21A of the control device 21 of the roller flap adjustment device 19 that the milling/mixing roller adjustment device during the milling operation has increased the milling depth by a predetermined value.
If the state of equilibrium shown in
To carry out the checking routine, in one embodiment the control device 21 of the roller flap adjustment device 19 is configured in such a way that, on the basis of a comparison of the value of the variable correlating with the third pivoted position, which in the present embodiment is the distance Δa, with a threshold value, a state of equilibrium is inferred. Taking the dynamic conditions into account, different threshold values can be defined, which can be stored in the memory 27 and can be read out by the control and computing unit 21A of the control device 21 of the roller flap adjustment device 19.
For this check, the control device detects the distance Δa3 that the piston 20A of the piston-cylinder arrangement 20 of the roller flap adjustment device 19 has travelled when pivoting from the second into the third pivoted position (
If the distance Δa3 is less than the threshold value or equal to the threshold value, i.e. the roller flap 13, as shown in
The control device again detects the distance Δa that the piston 20A of the piston-cylinder arrangement 20 of the roller flap adjustment device 19 has retracted during pivoting from the second into the third pivoted position. The checking routine described above is then carried out again.
If the distance Δa is less than or equal to the threshold, i.e. the roller flap 13, as shown in
In a particularly preferred embodiment, a state of equilibrium is inferred on the basis of a comparison of the value of the variable correlating with the third pivoted position (
The control device 21 of the roller flap adjustment device 19 can also be configured in such a way that the roller flap position correction mode can only be automatically activated again when the milling/mixing roller has been brought back into the zero position. This prevents the roller flap position correction mode from being activated automatically after the ground milling machine has only been at a temporary standstill.
Number | Date | Country | Kind |
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102021131906.4 | Dec 2021 | DE | national |