EP3861170B1 - Method for controlling a ground compaction machine and ground compaction machine - Google Patents

Description

The invention relates to a method for controlling a soil compaction machine, in particular for avoiding compaction errors. In addition, the invention relates to a soil compacting machine with a control unit that is designed to carry out the method and/or carries it out.

Generic soil compaction machines are designed, for example, as road rollers, in particular tandem rollers or compactors. They are used in road and path construction to compact the subsoil, for example hot layers of asphalt or soil. For this purpose, the soil compaction machines typically have compaction drums, which are designed, for example, as roller drums with a hollow-cylindrical base body. The compression drums can either have smooth, round surfaces, or they can also be polygonal or designed as crusher drums with projections projecting beyond the circumference of the hollow-cylindrical base body. One or more compaction drums can be provided on a soil compaction machine. It is also possible that a compaction drum is used in combination with wheels or other chassis. The generic soil compacting machines are in particular designed to be self-propelled and include a drive motor, which is typically a diesel internal combustion engine. This drives, among other things, the compaction drum, so that during operation of the soil compaction machine, the soil compaction machine is moved over a soil to be compacted at a driving speed.

In order to increase the compaction performance of the generic soil compaction machine, a vibration with a vibration frequency is typically excited in at least one compaction drum by means of an excitation device. The exciter device is also referred to as a vibration exciter and comprises, for example, one or more circular exciters and can be designed in particular as a directional vibrator. By exciting a vibration on the compaction drum, the compaction performance can be increased many times over compared to a simple passage of the soil compaction machine over the soil to be compacted. A generic excitation device is, for example, from EP 2 172 279 A1 the applicant, from which WO 97/15726 A1 or from the WO 2018/174853 A1 known.

During operation of the soil compaction machines, there is often a change in the driving speed and/or the vibration frequency. This can lead to undesired effects including compression errors. A monitoring of the vibration impacts per route, such as from the WO 97/15726 A1 or the WO 2018/174853 A1 known, can therefore be useful in this context. If, for example, the driving speed is reduced while the vibration frequency remains the same, the compaction drum performs an increased number of oscillations over a shorter distance due to the vibrations. In this way, more compaction is achieved over this shorter distance than if the roller were to run faster with the same vibration frequency. This goes so far that if the speed is too slow, the roller will actually press dents into the soil to be compacted and/or particles in the subsurface material to be compacted will be significantly destroyed and thereby reduced in size. On the other hand, if the soil compacting machine travels too fast at a given vibration frequency, relatively too few vibration vibrations are carried out over a large distance, which means that the individual vibration vibrations or impacts are too far apart. This can lead to the formation of waves in the ground. The problem here is that it is hardly possible to even out these bumps once they have arisen. Even if you drive over the affected areas several times, it cannot always be guaranteed that the compaction errors have been rectified. This is made even more difficult by the fact that excessive compaction is also disadvantageous, so that the affected area cannot be driven over as often as desired. During the compaction work, the operator of the soil compaction machine must therefore pay a large part of his attention to ensuring that no compaction errors occur. This distracts him from the actual compaction work.

This problem occurs in particular with hybrid systems, which are being used more and more frequently due to ever more stringent environmental regulations. soil compaction machines, which are designed, for example, as hydraulic or electric hybrids, typically have a drive motor designed for lower power, which is supported during work when power peaks occur with energy from an intermediate storage device, for example a hydraulic pressure storage device or an electrical storage device. However, if the energy contained in the intermediate store is not sufficient to bridge a power peak, either because the power peak is too large or lasts too long, the required power exceeds the maximum power made available by the drive motor. In this case, the driving speed and/or the vibration frequency of the soil compaction machine typically has to be reduced. In this way, in hybrid systems the above-described problem arises that the vehicle is driving too fast or too slow for a given vibration frequency or that the vibration frequency is too high or too low for a given driving speed.

It is therefore the object of the present invention to specify a method for controlling a soil compacting machine and a soil compacting machine in which the occurrence of unevenness in the soil to be compacted, including compaction errors, is reliably avoided. At the same time, this should be possible with as little effort as possible for the operator of the soil compaction machine and, in particular, should improve the use of hybrid systems.

The object is achieved with a method and a soil compacting machine according to the independent claims. Preferred developments are specified in the dependent claims.

In concrete terms, the solution is achieved with a method mentioned at the outset by determining and monitoring the number of vibration impacts per route covered from the driving speed and the vibration frequency, comparing the determined number of vibration impacts per route covered with specified limit values and reducing the vertical vibration amplitude of the compaction drum if the or falling below at least one of the limit values. In the present case, a period of those oscillations into which the compaction drum is set by the excitation device is referred to as a vibration impact. A vibratory impact therefore includes, for example, in the case of a vibration in the vertical direction, the compaction drum falling downwards from a neutral position, then lifting the compaction drum back to the neutral position and upwards beyond this, with a subsequent lowering of the compaction drum again to the neutral position . The number of such vibration impacts per distance traveled is then specified, for example, as vibration impacts per meter or per foot and referred to as the IPF value (from English: " impacts per foot "). The designation IPF value is used here independently of the unit of length used, so that the unit used in each case must be specified for specific values. A value that specifies the vibration impacts per meter is therefore also referred to as the IPF value.

A basic idea of the invention is therefore based on determining and monitoring the IPF value. As a result, the IPF value can be used as a control variable in the process. The number of vibration impacts per distance traveled is calculated from the known parameters of the driving speed and the vibration frequency. Specifically, the IPF value is equal to dividing the vibration frequency by the vehicle speed. Since the driving speed and the vibration frequency are also typically measured continuously, the IPF value can also be determined and monitored continuously. Knowing the IPF value makes it possible to compare the current value with a target value, a target value range or limit values. For example, limit values can be specified, such as a maximum IPF value and a minimum IPF value, between which the IPF value currently measured and therefore present on the soil compaction machine should ideally be during working operation. In this range, the number of vibration impacts per traveled distance is adjusted in such a way that the vibration impacts applied to the soil to be compacted are both far enough apart not to carry out excessive compaction at one point and close enough to one another so that the soil is compacted uniformly , without creating waves.

On the other hand, if this range of the permissible IPF value is left because the current IPF value either exceeds the maximum limit value or falls below the minimum limit value, the vertical vibration amplitude of the compaction drum is reduced in the method according to the invention. The vertical vibration amplitude corresponds to that vibration component of the compaction drum that vibrates or is aligned in the vertical direction. As used herein, "vertical" means perpendicular to a substantially level ground surface. In particular, this vertical vibration or vertical vibration amplitude brings a lot of compaction power into the soil, so that there is a risk of compaction errors if the IPF value is outside the optimal range. In the case of a circular vibrator that vibrates equally in all directions, the vertical vibration amplitude therefore corresponds to the current total amplitude. In the case of a directional vibrator, for example, the direction of the vibration can be freely adjusted, so that the vibration can be adjusted, for example, between full vertical alignment and full horizontal alignment. An oscillation of a directional oscillator can always be viewed as a superimposition of a horizontal and a vertical oscillation. With such a directional oscillator the vertical vibration amplitude always corresponds to that part of the vibration that is aligned in the vertical direction. By reducing the vertical vibration amplitude, it is achieved according to the invention that a lower compaction power is applied to the ground. This prevents compaction errors, since excessive local compaction is ruled out both with an IPF value that is too high or too low. In the case of a directional vibrator in particular, this also means that it can continue to be operated at a constant frequency, which means that there is no need to reduce the vibration frequency with the excitation device then having to be started up again. This has advantages both with regard to the drive motor, which can be operated more precisely in the optimal power range, and with regard to the comfort for an operator.

The method according to the invention is carried out, for example, by a control unit of the soil compacting machine. The control unit can either be designed as a separate control unit or, for example, be integrated into an on-board computer of the soil compacting machine. In particular, the method is carried out automatically by the control unit, without an operator having to enter further control commands for this purpose. However, the control unit can be designed, for example, to switch the method according to the invention on and off. Either the control unit itself or the on-board computer of the soil compaction machine therefore has a control element via which the method can be switched on or off. This control element can be either a switch or just part of a digital or virtual user interface. The control unit can also comprise a display device which, for example, shows an operator the current IPF value and/or steps currently taken by the control unit as part of the method. This display device can also be implemented, for example, via a screen of the on-board computer.

In principle, the vertical vibration amplitude can be reduced with any exciter device capable of doing this. For example, excitation devices can be used that have different discrete stages of different vibration frequencies. These levels can then be used if the corresponding limit values are not reached or exceeded. However, it is particularly advantageous and therefore preferred that the vertical vibration amplitude is reduced steplessly. This is the case, for example, with an excitation device such as is used by the applicant's “BOMAG Asphalt Manager”. The present invention can be used particularly flexibly with such an excitation device. For example, an optimal range between a maximum IPF value and a minimum IPF value can be set as limit values for the IPF value here, in which the method does not yet reduce the vertical Vibration amplitude performs. If these limit values are exceeded or fallen below, then the vertical vibration amplitude does not have to be abruptly reduced sharply, but the vertical vibration amplitude can be reduced, for example, with the amount by which the vibration amplitude is reduced being proportional to the exceeding or falling below of the limit value is divided by the current, measured IPF value. In this way, the process adapts the compaction performance to the respective operating situation of the soil compaction machine in a particularly flexible manner by vibrating the compaction drum.

It has been found that optimal compaction, which does not require reducing the vertical vibration amplitude, is for example in a range of 30-55 vibration impacts per meter, preferably 35-50 vibration impacts per meter and most preferably 40-45 vibration impacts per meter can be done. Another preferred range is also 30-42 beats per meter. These values are therefore preferably used, in particular also in pairs, as stated, for the minimum and the maximum limit value of the IPF value. Preferred values for the minimum limit are therefore 25, 30, 35 or 40 vibrations per meter and for the maximum limit 55, 50, 45 or 40 vibrations per meter. According to the invention, if the maximum limit value is exceeded or if the minimum limit value is not reached, the vertical vibration amplitude is reduced. In the present application, the maximum limit value is referred to as IPF _max and the minimum limit value as IPF _min .

In extreme cases, the vertical vibration amplitude can be reduced until the vertical vibration amplitude has completely disappeared. In particular, it is preferred that the vertical vibration amplitude is reduced to zero when the number of vibration impacts per route traveled exceeds or falls below a critical limit value. In the present case, the critical limit value is also referred to as IPF _end . Since the invention provides that the vertical vibration amplitude is reduced both when the current IPF value is too low and when the current IPF value is too high, there is both a low critical limit value below which the vertical vibration amplitude is reduced to zero also has a high critical limit above which the vertical vibration amplitude is reduced to zero. The low critical limit value is, for example, 30, preferably 25, particularly preferably 20 vibration impacts per meter. The high critical limit value is, for example, 55, preferably 60, particularly preferably 65 vibration impacts per meter. A particularly preferred embodiment of the present invention provides that reducing the vertical vibration amplitude between the maximum limit IPF _max and the high critical limit and/or between the minimum limit IPF _min and the low critical limit occurs linearly between the maximum possible vertical vibration amplitude that can be set on the exciter device and a vertical vibration amplitude of zero. Another advantage of reducing the vertical vibration amplitude to zero is that the invention then implements an automatic switch-off in which, for example, when the machine stops and comes to a standstill, the vertical vibration amplitude is automatically adjusted to zero, i.e. completely switched off. In this way, an operator can simply stop the machine on the move without having to remember to turn off the vibration to avoid compacting a dent in the ground. This effect also occurs in the case of reversing travel, which frequently occurs during operation of the soil compacting machine, and in which the operator does not have to constantly switch the excitation device on and off thanks to the invention. This increases the ease of use of the soil compaction machine.

When the soil compaction machine is in operation, power peaks may occur, for example when the machine is started up and when, for example, slopes or embankments are being driven up. If, due to such an operating situation, more power is suddenly required from the soil compaction machine, the driving speed and/or the vibration frequency often has to be changed, in particular reduced, in the short term in order to meet the power requirement. In these situations, the method according to the invention can simplify the control of the soil compacting machine considerably. It is therefore preferred for the driving speed and/or the vibration frequency to be changed on the basis of an increased power requirement of the soil compacting machine. Especially with these changes, which are sometimes difficult for the operator to foresee, it is particularly practical if, in case of doubt, the method automatically reduces the vertical vibration amplitude without the operator having to do anything. In this way, compaction errors can be efficiently avoided.

As already explained at the outset, the problem of power peaks occurring and the resulting temporary overloading of the drive motor is particularly problematic in hybrid systems. It is precisely these systems that benefit particularly greatly from the present invention, which ensures that no compaction errors occur even when power peaks occur and the associated reactions of the machine in relation to a change in driving speed and/or vibration frequency. In a preferred embodiment, the soil compaction machine is designed as a hybrid, in particular an electric or hydraulic hybrid, educated. In particular, the soil compacting machine includes an intermediate store and, before the driving speed and/or the vibration frequency is changed, additional power is released by the intermediate store when the required power of the soil compacting machine is increased. The temporary store can, for example, be an electrical store, such as a rechargeable battery, or a hydraulic store, for example a pressure store. Additional power is therefore released either by releasing additional electrical energy or, for example, by releasing pressurized hydraulic fluid held in the intermediate store. In this way, power peaks that typically occur in hybrid systems are to be bridged.

However, the energy stored in the intermediate storage is often not sufficient to completely bridge the power peak. For example, driving uphill lasts longer than can be maintained under the current operating parameters of the drive motor and the buffer. In order to fully exploit the full potential of the hybrid system, it is preferable in this case for the driving speed and/or the vibration frequency to be changed only after the energy stored in the buffer store has been completely consumed, if there is still an increased required power of the soil compaction machine. In this way, the vertical vibration amplitude is only then reduced by the method, as a result of which it is possible to work longer with a high vertical vibration amplitude and thus a high compaction performance. In this way, the method according to the invention is particularly efficient, particularly in conjunction with a hybrid system.

In a preferred embodiment of the invention, it is also provided that the charging state of the buffer store is also used to control the method. The state of charge of the buffer store is thus detected by means of a suitable sensor. Based on the state of charge, a decision is then made, for example by the control unit, whether a power peak can be bridged by using the energy stored in the buffer store or whether the vertical vibration amplitude must be reduced immediately. In particular, the transition from releasing additional power or energy from the buffer store to reducing the vertical vibration amplitude can be controlled by the control unit based on the measured state of charge of the buffer store. Irrespective of the charge status of the intermediate store, the necessary measures are always taken to avoid compaction errors.

In principle, the method can be used in such a way that only and exclusively a reduction in the vertical vibration amplitude is carried out. In other words, the vertical vibration amplitude can only be increased by the operator himself, for example via a control command. This can serve as an additional safety measure, so that the compaction does not suddenly start again without the operator's will. However, in order to further relieve the operator, it is preferably provided as an alternative to this that the vertical vibration amplitude is increased if the at least one limit value is again exceeded or fallen below. For example, if the currently measured IPF value is again above the minimum critical limit value or below the maximum critical limit value, the vertical vibration amplitude can be increased again from zero. The continuous adjustment of the vertical vibration amplitude between the critical limit values and the maximum or minimum limit value can essentially take place the other way round to the reduction already described above. In this way, the compaction power currently applied to the soil is always adapted to the current operating situation without the operator having to intervene.

In particular, the potential of the machine is best exploited when maximum compaction takes place in the optimum range between the maximum and minimum limit values. This means in particular that the vertical vibration amplitude is adjusted to its maximum value when the number of vibration impacts per distance traveled is in a predetermined optimum range, in particular between the limit values IPF _max and IPF _min . If the soil compaction machine is in this desired optimal range, this state is also used for maximum compaction performance.

The method according to the invention reduces the vertical vibration amplitude caused by the exciter device on the compaction drum. This reduction typically also causes the power consumption of the excitation device to drop. For example, if only horizontal vibrations are excited by a directional oscillator, then the power consumption of the excitation device can be reduced by half compared to the case where only vertical vibrations are excited. In this way, additional power is released in the drive train of the soil compaction machine, which can then be used for other purposes. In a preferred embodiment, it is provided, for example, that the power saved by reducing the vertical vibration amplitude is used to increase the driving speed and/or the vibration frequency. In this way, a slowing down of the soil compaction machine and/or a reduction in the vibration frequency can be at least partially counteracted. Overall, the speed of the soil compaction machine is reduced less as a result, which in turn makes working more efficient.

However, the particular efficiency of the invention when used with a hybrid system is also shown here again. A particularly preferred embodiment provides that the power saved by reducing the vertical vibration amplitude is used to charge the buffer store. In particular, in the case of a long-lasting power peak, in which the energy stored in the buffer store has already been consumed, the buffer store is correspondingly empty. If the vertical vibration amplitude then has to be reduced as a result of a change in the driving speed and/or the vibration frequency based on the current IPF value measured then, the released power can at least be used to charge the buffer store. In this way, a charged buffer store is available again at the next power peak, so that the efficiency of the hybrid system increases.

Starting up and braking the excitation device in particular can be disruptive when the soil compaction machine is in operation. It is therefore preferred that the vibration frequency of the vibration of the at least one compaction drum is kept essentially constant. In particular, this is kept constant. In the present context, essentially means that there may be operational fluctuations, but no externally induced or controlled changes are made to the vibration frequency. In this way, the excitation device can always be driven in the same way and it does not have to be coupled when reversing, for example. Of course, this also means that when peak loads occur, the driving speed is reduced in order to bridge them. In the method according to the invention, therefore, preferably only the driving speed is changed and the vibration frequency is kept constant. Alternatively, it is also possible to change the vibration frequency and in particular the vibration frequency and the driving speed. The vibration frequency can also be reduced in order to bridge a power peak. However, it must be ensured that the vibration frequency is not reduced to the resonance frequency of the drum, so that the machine is not damaged. Even when there is a change in the vibration frequency, it is therefore preferred that this is only changed in such a way that the excitation device is operated supercritically during working operation. In particular, it is preferred to reduce the vibration frequency when the vertical vibration amplitude is essentially zero, ie the vibration is only aligned horizontally, for example. In this case, reducing the vibration frequency can also reduce wear. In this case, the damage to the work result that would otherwise be feared is also lower. By changing the vibration frequency and/or driving speed the control unit can regulate or control compliance with the optimum IPF value particularly flexibly.

In addition, the present invention also makes it possible to always operate the drive motor as close as possible to its optimum power point, since a possibility is specified of overcoming load peaks without changing the power output by the drive motor. It is therefore preferred that a power output or the speed of a drive motor of the soil compacting machine is kept essentially constant. In particular, the power output or the speed is kept constant. Here, too, essentially means that operational fluctuations are possible, but, for example, no externally induced or controlled changes in the power output or the speed are made. Such optimal operation of the drive motor extends its service life and at the same time reduces fuel consumption.

The object mentioned at the outset is also achieved by a soil compacting machine with a control unit which is designed to carry out the method according to the invention and/or carries it out. The method according to the invention is therefore used to control the ground milling machine, which is designed for this use and includes at least one control unit that is able to carry out the method. All the features, effects and advantages described above for the method also apply in a figurative sense to the soil compacting machine according to the invention. At the same time, all the features, effects and advantages described for the soil compacting machine also apply to the method according to the invention. Reference is therefore made to the respective other versions only to avoid repetition.

The soil compaction machine includes in particular a machine frame, a drive motor, at least one compaction drum, an exciter device for exciting a vibration on the compaction drum with a vibration frequency, and a frequency sensor for measuring the vibration frequency and a distance sensor for measuring the distance covered. The frequency sensor and the distance traveled sensor are connected to the control unit and supply it, in particular continuously, with corresponding measured values of the vibration frequency and the distance traveled. These are used by the control unit when carrying out the method.

As has also already been explained above, the soil compacting machine is very particularly preferably designed as a hybrid, in particular a hydraulic hybrid, with an intermediate store. The present invention is particularly advantageous precisely in the case of such a hybrid system.

Figur 1:

eine Seitenansicht einer Tandemwalze;

Figur 2:

eine Seitenansicht eines Walzenzuges;

Figur 3:

ein Schema des Antriebs und der Steuereinheit einer Bodenverdichtungsmaschine;

Figur 4:

den zeitlichen Ablauf des Verfahrens bei stufenweiser Erhöhung der Fahrgeschwindigkeit;

Figur 5:

den zeitlichen Ablauf des Verfahrens bei stufenweiser Verringerung der Fahrgeschwindigkeit;

Figur 6:

den zeitlichen Ablauf des Verfahrens beim Einsatz eines Hybridsystems; und

Figur 7:

ein Ablaufdiagramm des Verfahrens.

The invention is explained in more detail below with reference to the exemplary embodiments shown in the figures. They show schematically:

Figure 1:

a side view of a tandem roller;

Figure 2:

a side view of a compactor;

Figure 3:

a scheme of the drive and control unit of a soil compaction machine;

Figure 4:

the timing of the procedure when the driving speed is gradually increased;

Figure 5:

the timing of the procedure when driving speed is gradually reduced;

Figure 6:

the timing of the process when using a hybrid system; and

Figure 7:

a flowchart of the process.

Components that are the same or have the same effect are denoted by the same reference symbols in the figures. Repeating components are not separately identified in each figure.

the Figures 1 and 2 show generic and inventive soil compaction machines 1. The soil compaction machine 1 of figure 1 is as a tandem roller, the one of figure 2 designed as a roller train. The soil compaction machines 1 comprise a driver's cab 2 and a machine frame 3, as well as a drive motor 4, which is typically a diesel internal combustion engine. The drive motor 4 drives, among other things, a chassis which comprises at least one compaction drum 5 fastened to the machine frame 3 via a drum holder 6 . In the case of the tandem roller figure 1 this has a compression bandage 5 both at the front and at the rear. The roller according to figure 2 has a front compaction drum 5 and has two wheels 7 on its rear chassis axle. During operation of the soil compaction machine 1, it is driven over the soil 8 to be compacted, for example in the forward direction a. Of course, however, it is also possible to compress against the forward direction a, ie backwards will. In at least one of the compaction drums 5 of the soil compaction machine 1, an excitation device is arranged, which causes the respective compaction drum 5 to oscillate, in particular to vibrate. This increases compaction performance. In order to measure the respective vibration frequency of the compaction drum 5, the soil compaction machines 1 have frequency sensors 33, in particular one frequency sensor 33 per compaction drum 5. In addition, the soil compaction machines 1 are able to detect the distance they have covered. They have a distance sensor 34 for this purpose. This can either determine the distance traveled from the driving speed or be designed, for example, as a rotation sensor on the wheels 7 or the compaction drums 5 . In addition, the soil compacting machines 1 include a control unit 15 which is connected to the frequency sensor 33 and the distance sensor 34 . The control unit 15 is designed to carry out the method according to the invention or executes it. In particular, the method according to the invention is carried out individually for each compaction drum 5 or alternatively for all compaction drums 5 of a soil compaction machine 1 together.

figure 3 shows schematically the drive of the soil compacting machine 1 and its interconnection with the control unit 15. A drive pump 9 and a vibration pump 10 are arranged on the drive motor 4. Both are driven by the drive motor 4. The drive pump 9 is connected to the drive motor 11 by a hydraulic line 19 , which drives at least one wheel 7 or at least one compaction drum 5 of the soil compaction machine 1 . The vibration pump 10 is also connected via a hydraulic line 19 to a vibration motor 12, which supplies the excitation device 13 with energy via a mechanical coupling 20, so that the excitation device 13 causes the compaction drum 5 to vibrate during operation. An amplitude control 14 is also provided on the excitation device 13 via a mechanical coupling 20, via which the vibration amplitude, in particular the vertical vibration amplitude of the compaction drum 5, which is caused by the excitation device 13, can be adjusted. According to a particularly preferred embodiment, the soil compacting machine 1 is designed as a hybrid system. For this purpose, it is provided that a pump/motor unit 16 is also arranged on the drive motor 4, which is connected via hydraulic lines 19 to a charging/discharging valve 17 and via this to an intermediate store 18, for example a hydraulic pressure store. If excess power is available in the drive train of the soil compaction machine 1, the pump/motor unit 16 acts as a pump and loads the buffer store 18 via the charging/discharge valve 17. In the event of power peaks that exceed the power output of the drive motor 4, however, the buffer store 18 can stored energy over that Charge / discharge valve 17 are released, so that the pump / motor unit 16 works as a motor and additional power, for example in the form of torque, initiates in the drive train. Power peaks can be bridged in this way as long as the energy stored in the buffer store 18 is sufficient.

figure 3 also shows the control unit 15 and its connection to the frequency sensor 33 and to the distance sensor 34. In addition, however, the control unit 15 is also connected with control lines 21 to other components of the drive. In the present case, the control lines 21 are, for example, electrical lines via which both control commands and recorded measured values can be transported. The control unit 15 is designed, for example, in particular to measure the vibration frequency of the excitation unit 13, for example via the frequency sensor 33, and the distance traveled, for example via the distance sensor 34. In addition, the control unit 15 is designed to control the amplitude controller 14 in such a way that, according to the method, it reduces or increases the vertical vibration amplitude depending on the measured or calculated current IPF value.

figure 4 shows the system and its reaction over time with a gradual increase in driving speed v. The abscissa of all given diagrams denoted the time t. The diagrams are arranged in such a way that the individual marked points in time along the abscissa correspond in all diagrams. This also applies to the figures 5 and 6 . At the beginning of the figure 4 In the course of the illustrated sequence, to the left of time t ₁ in the diagram, the soil compaction machine 1 is in normal working mode and travels at a constant driving speed v over the soil 8 to be compacted remains essentially constant over time. In the exemplary embodiments shown, the power peak is therefore compensated for by adapting the driving speed v, as will be described below. Alternatively, however, the vibration frequency f could also be changed, either alone or together with the driving speed v. At time t ₁ the operator of the soil compacting machine 1 accelerates. The driving speed v increases until a constant, increased driving speed v has been reached again. Because the vibration frequency f remains constant and the driving speed v increases, the number of vibration impacts per distance traveled, i.e. the IPF value, decreases (see diagram below). However, the IPF value is still above a minimum limit value IPF _min , so that, as shown in the upper diagram, the vertical vibration amplitude A also remains constant, for example at its maximum at the Excitation device 13 adjustable value. At time t ₂ the operator accelerates the soil compacting machine 1 further. This time, the driving speed v increases in such a way that, due to the constant vibration frequency f, the IPF value drops below the specified minimum limit value IPF _min . This happens at time t ₃ . The control unit, which calculates the IPF value from the driving speed v and the vibration frequency f, notices that the IPF value has fallen below the minimum limit value IPF _min and therefore initiates a reduction in the vertical vibration amplitude A at time t ₃ , as in the top one diagram is shown. The vertical vibration amplitude A is therefore changed (in all the exemplary embodiments shown in the figures) as a function of the IPF value by the control unit. The change in the vertical vibration amplitude A is therefore slightly offset in time from the change in the IPF value and takes place later, since the vertical vibration amplitude A is regulated or controlled as a function of the IPF value. The soil compacting machine 1 is further accelerated by the operator up to time t ₄ , until a constant driving speed v is reached again. The reduction of the vertical vibration amplitude A by the control unit 15 is therefore also continued up to the point in time t ₄ , at which point the IPF value no longer changes either. The soil sealing machine 1 or the excitation device 13 is therefore operated with a reduced vertical vibration amplitude A between the times t ₄ and t ₅ . This remains essentially constant between these two points in time. However, at time t ₅ the soil compacting machine 1 is accelerated again. This time the acceleration goes so far that at time t ₆ the IPF value falls below the critical limit value IPF _end . Up to this point, the control unit 15 has continuously reduced the vertical vibration amplitude A in proportion to the decrease in the IPF value. The method according to the invention is now either designed in such a way that the vertical vibration amplitude of A is just zero when the critical limit value IPF _end is reached, or the method according to the invention is designed in such a way that the control unit 15 increases the vertical vibration amplitude A via the amplitude control for 10 reaches the critical limit IPF _end to zero, no matter what the previous value of the vertical vibration amplitude A was. In the exemplary embodiment shown, the vertical vibration amplitude A reaches zero just when the IPF value falls below the critical limit value, in this case the low critical limit value IPF _end . Only at time t ₇ is the driving speed v of the soil compacting machine 1 reduced again by the operator, so that the IPF value again rises above the critical limit value IPF _end at time t ₈ . From this point in time, the vertical vibration amplitude A is increased again, starting from zero in the exemplary embodiment shown. Between the times t ₆ and t ₈ the excitation device 13 is therefore operated with a constant vibration frequency f but with a vertical vibration amplitude A equal to zero. For example, the excitation device 13 generates during this time only horizontal vibrations. The increase in the vertical vibration amplitude A corresponds proportionally to the increase in the IPF value, until the time t ₉ the soil compacting machine 1 was braked in such a way that the IPF value rises above the minimum limit value IPF _min again. From this point in time, the vertical vibration amplitude A is increased until it returns to its maximum value from the start of the sequence shown. The soil compaction machine 1 is in the optimal operating state and applies the maximum compaction power to the soil 8 to be compacted.

figure 5 shows the flow of a similar situation as figure 4 , where in figure 5 the case of a gradual reduction in the driving speed v is shown. Such a reduction in the driving ability v can occur, for example, in order to bridge power peaks of the soil compacting machine 1 that occur during working operation, for example when it has to drive up a slope. In a figurative sense, the above statements apply to figure 4 also for them figure 5 , which is why only the differences are discussed. At time t ₁ , the soil compaction machine 1 according to figure 5 braked. However, the driving speed v remains so high that the IPF value increases, but remains below the maximum limit value IPF _max . For this reason, the slowed-down soil compacting machine 1 is still in the optimum range, so that the vertical vibration amplitude A remains constant. The maximum limit value IPF _max of the IPF value is then only exceeded at time t ₃ as a result of the further slowdown occurring at time t ₂ , so that a reduction in the vertical vibration amplitude A is initiated by the control unit 15 here as well. Here too, between times t ₄ and t ₅ , soil compaction machine 1 is operated with a constant, reduced vertical vibration amplitude A, since the currently calculated IPF value is between the maximum limit value IPF _max and the critical limit value IPF _end , in particular the high critical value limit, located. As a result of the further reduction in the driving speed v from time t ₅ , the IPF value then finally rises above the critical limit value IPF _end at time t ₆ , as a result of which the vertical vibration amplitude A is set to zero. Here, too, compaction errors are avoided. From time t ₇ the soil compaction machine 1 is accelerated again, so that at time t ₈ the value falls below the critical limit value IPF _end and from time tg it also falls below the maximum limit value IPF _max . Once the critical limit value IPF _end has been undercut, the vertical vibration amplitude A is again increased in proportion to the increase in the IPF value. Once the maximum limit value IPF _max has been undercut, the control unit 15 then sets the maximum vertical vibration amplitude A again. The compaction in the optimal operating state of the soil compaction machine 1 can then be continued.

In figure 6 the particularly advantageous integration of the method according to the invention in a hybrid system is illustrated. The top four diagrams correspond to those of figures 4 and 5 , and show the vertical vibration amplitude A, vibration frequency f, running speed v, and IPF value. In particular, the sequence shown corresponds to the case with a reduction in driving speed v according to figure 5 , although the procedure is simplified. At the beginning of the figure 6 In the sequence shown, the soil compaction machine 1 is in normal working mode, it drives at a constant driving speed v and compacts the soil 8 with a constant vibration frequency f. As shown in the bottom diagram, the drive motor 4 is operated with a constant power output E or with a constant speed. At this point in time, the power required for the entire operation of the soil compacting machine 1, ie the required power L, is below the power output E achieved by the drive motor 4. At the point in time t ₁ , the required power L of the soil compacting machine 1 increases. The reason for this can be, for example, that the soil compacting machine 1 has to compact uphill. As long as the required power L remains below the power output E generated by the drive motor, nothing happens for the time being. At time t ₂ , however, the required power L exceeds the power output E of the drive motor 4. At this point in time, the hybrid system of the soil compacting machine 1 makes itself felt. Specifically, the buffer store 18 releases additional energy or power and feeds this into the drive train of the soil compacting machine 1 . The power output H of the buffer 18 increases. The increased power requirement of the soil compacting machine 1 can be covered by the additional power output H from the intermediate store 18 . For this reason, the soil compacting machine 1 can continue its work operation unimpaired. However, at time t ₃ the energy reserves of the buffer store 18 are approaching their end and the power output H from the buffer store 18 decreases. From this point in time, the power required by the soil compaction machine 1 can no longer be covered by the combination of the drive motor E and the intermediate store 18 . In order to keep work going, the required power has to be reduced elsewhere. According to the invention, this preferably takes place at the driving speed v, which is reduced from time t ₃ in order to absorb the increased power requirement. Since the vibration frequency f remains constant, the IPF value also increases as the driving speed v decreases. As previously in connection with figure 5 explained, the IPF value at time t ₄ exceeds the maximum limit value IPF _max , so that from this point in time the control unit 15 reduces the vertical vibration amplitude A, which was kept constant up to time t ₄ . The driving speed v is reduced until the power available is sufficient for the operation of the soil compacting machine 1 . At time t ₅ this is achieved, so that the driving speed v can be kept constant from here. The increase in the IPF value therefore also ends at time t ₅ , so that the reduction in the vertical vibration amplitude A also stops at time t ₅ . The vertical vibration amplitude A can now remain constant. The increased power requirement decreases again later, for example because the ground exposure machine 1 moves from an embankment onto a level area, so that at the time t ₆ the required power L falls below the power E output by the drive motor 4 again. At this point in time, the driving speed v can then be increased again, which leads to a drop in the IPF value and an associated increase in the vertical vibration amplitude A, as already described above.

figure 6 shows another advantage of the method. As already explained above, the excitation device 13 consumes less power when the vertical vibration amplitude A is reduced. The power that is available as a result can be used elsewhere on the soil compaction machine 1 . So are in figure 6 two different options are shown as an example. On the one hand, the power that is released can be used to reduce the driving speed v of the soil compacting machine 1 less. This is represented by the broken line in the diagram of the driving speed v. The dashed curve shows the course of the driving speed v when the power released by reducing the vertical vibration amplitude A is used to maintain a higher driving speed v. The solid line, on the other hand, shows the case in which the additional power is not invested in the driving speed v. By using the power released by reducing the vertical vibration amplitude A, a higher driving speed v can be set, so that the compaction process becomes more efficient overall. However, as an alternative to this, it is also possible to use the power released by reducing the vertical vibration amplitude A to charge the buffer store 18 . This is also indicated by the dashed line in the diagram of the power output H from the intermediate store 18 . The dashed line illustrates a charging process of the intermediate store 18, since the dashed line runs under the zero line of the power output H, which runs parallel to the time axis. The negative power output shown corresponds to one charging process. The charging process of the intermediate store 18 takes place over the entire period in which the vertical vibration amplitude A is reduced, since less power is required from the excitation device 13 over this entire period and the excess power is therefore available for charging the intermediate store 18 . In this way, the buffer 18 can be at least partially recharged directly after the energy stored in it has been completely consumed, so that when the next power peak, an at least partially charged buffer store 18 is already available again.

figure 7 shows an exemplary flowchart of the method 22 according to the invention. The method 22 comprises the excitation 23 of a vibration on a compaction drum 5 by the excitation device 13 and the moving 24 of the soil compaction machine 1 over the soil 8. If the soil compaction machine 1 is designed as a hybrid system, it can be used to bridge a power peak in step 22 power or energy from a buffer 18 are released. For various reasons, the driving speed v and/or the vibration frequency f can change during working operation, for example if the energy in the intermediate store 18 is not sufficient to completely bridge the increased power requirement of the soil compaction machine 1 . Due to a change 28 in the driving speed v and/or the vibration frequency f, the current IPF value of the soil compacting machine 1, which is determined and monitored in step 25, also changes. The determined IPF value is then compared in step 26 with predefined limit values IPF _max , IPF _min , IPF _end . If the measured IPF value is in an optimal range between the minimum limit value IPF _min and the maximum limit value IPF _max , nothing happens and work continues undisturbed. If, on the other hand, the measured IPF value is below the minimum limit value IPF _min or above the maximum limit value IPF _max , the vertical vibration amplitude A is reduced 27 in the first case and the vertical vibration amplitude A is increased 29 in the second case vertical vibration amplitude A, the method 22 starts again from the beginning. If, on the other hand, the vertical vibration amplitude A is reduced in step 27, the power consumption of the excitation device 13 decreases and, due to the reduced power requirement, excess energy is available, which can be used in step 30, for example, to increase the driving speed v and/or the vibration frequency f increase or at least buffer their reduction. As an alternative to this, it is also possible to use the energy saved in step 31 to charge the buffer store 18 . All in all, the present invention makes it possible to efficiently prevent compaction errors from occurring during operation of the soil compacting machine 1 . At the same time, this requires almost no attention from the operator, which increases the ease of use of the soil compacting machine 1 . These advantages are particularly evident when used with a hybrid system.

Claims (15)

1. A method (22) for controlling a ground compaction machine (1), in particular for avoiding compaction errors, comprising the steps of:

   a) exciting (23) a vibration with a vibration frequency (f) in at least one compaction drum (5) by means of an excitation device (13),

   b) advancing (24) the ground compaction machine (1) at a travel speed (v) over a ground (8) to be compacted,

   c) varying (28) the travel speed (v) and/or the vibration frequency (f),

   d) determining and monitoring (25) the number of vibration impacts per traveled distance (IPF) from the travel speed (v) and the vibration frequency (f), and

   e) comparing (26) the determined number of vibration impacts per traveled distance (IPF) with predetermined limit values (IPF_max, IPF_min, IPF_end),

   characterized by
   f) reducing (27) the vertical vibration amplitude (A) of the compaction drum (5) if exceeding and/or falling below at least one of the limit values (IPF_max, IPF_min, IPF_end).
2. The method (22) according to claim 1,
   characterized in that
   said reducing (27) of the vertical vibration amplitude (A) is performed in a continuous manner.
3. The method (22) according to any one of the preceding claims,
   characterized in that
   the vertical vibration amplitude (A) is reduced to zero if the number of vibration impacts per traveled distance (IPF) exceeds or falls below a critical limit value (IPF_end).
4. The method (22) according to any one of the preceding claims,
   characterized in that
   the travel speed (v) and/or the vibration frequency (f) are varied (28) due to an increased demanded power (L) of the ground compaction machine (1).
5. The method (22) according to any one of the preceding claims,
   characterized in that
   the ground compaction machine (1) comprises an intermediate store (18), and that upon an increased demanded power (L) of the ground compaction machine (1) additional power is released (18) by the intermediate store (18) prior to varying (28) the travel speed (v) and/or the vibration frequency (f).
6. The method (22) according to claim 5,
   characterized in that
   the travel speed (v) and/or the vibration frequency (f) are varied (28) only after the energy stored in the intermediate store (18) has been completely consumed if an increased demanded power (L) of the ground compaction machine (1) still exists.
7. The method (22) according to any one of the preceding claims,
   characterized in that
   the vertical vibration amplitude (A) is increased when the at least one limit value (IPF_max, IPF_min, IPF_end) is again exceeded or fallen below.
8. The method (22) according to any one of the preceding claims,
   characterized in that
   the vertical vibration amplitude (A) is adjusted to its maximum value when the number of vibration impacts per traveled distance (IPF) is in a predetermined optimum range, in particular between the limit values (IPF_max, IPF_min).
9. The method (22) according to any one of the preceding claims,
   characterized in that
   the power saved by reducing (27) the vertical vibration amplitude (A) is used to increase (30) the travel speed (v) and/or the vibration frequency (f).
10. The method (22) according to any one of the preceding claims,
    characterized in that
    the power saved by reducing (27) the vertical vibration amplitude (A) is used to charge (31) the intermediate store (18).
11. The method (22) according to any one of the preceding claims,
    characterized in that
    the vibration frequency (f) of the vibration of the at least one compaction drum (5) is kept essentially constant.
12. The method (22) according to any one of the preceding claims,
    characterized in that
    a power output (E) of a drive motor (4) of the ground compaction machine (1) is kept essentially constant.
13. A ground compaction machine (1) having a control unit (15) which is configured for performing, and/or performs, the method (22) according to any one of the preceding claims.
14. The ground compaction machine (1) according to claim 13, having a machine frame (3), a drive motor (4), at least one compaction drum (5), an excitation device (13) for exciting a vibration at the compaction drum (5) at a vibration frequency (f), a frequency sensor (33) for measuring the vibration frequency (f), and a distance sensor (34) for measuring the traveled distance.
15. The ground compaction machine (1) according to any one of claims 13 or 14, which is configured as a hybrid, in particular a hydraulic hybrid, having an intermediate store (18).

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