DE102020110468A1 - Method for regulating the damping of the movement of a press roll of a high pressure roller press and corresponding high pressure roller press - Google Patents

Abstract

The invention relates to a method for regulating the damping of the movement of a loose roller (3) of a high-pressure roller press (1), the high-pressure roller press (1) having a hydraulic system (8) which presses the loose roller (3) against a fixed roller (2) and so on maintains a predetermined nip pressure in the nip (7) between the loose roll (3) and the fixed roll (2) when grinding material passes the nip (7) between the loose roll (3) and the fixed roll (2), according to the invention is characterized by the use an adaptive damping control which controls the damping of a mechanical oscillatory movement of the loose roll. The invention further relates to a high-pressure roller press having such an adaptive damping control.

Description

The invention relates to a method for regulating the damping of the movement of a loose roll of a high-pressure roller press, the high-pressure roller press having a hydraulic system which presses the loose roller against a fixed roller and thus maintains a predetermined nip pressure in the nip between the loose roller and the fixed roller when the material to be ground is between the nip the loose roller and the fixed roller happened. The invention also relates to a high pressure roller press having such a control.

To comminute or compact granular material, high-pressure roller presses are often used, which consist of two counter-rotating, usually equally large, rotatably mounted press rollers that rotate at the same peripheral speed and form a narrow roller gap between them. The ground material to be comminuted or compacted is drawn through this roller gap, the ground material being crushed or compacted under the high pressure that prevails in the roller gap. The result of this treatment, namely comminution or compression, is largely dependent on the material properties of the ground material to be comminuted. The crushing in the roller gap described here was first used by Schönert et al. in the German Offenlegungsschrift DE 27 08 053 A1 described as high-pressure comminution and since then it has been regarded as a genus of types of comminution in addition to grinding by shearing and breaking.

High-pressure roller presses differ fundamentally from other presses that are used for size reduction. In particular, high-pressure roller presses, which are intended for crushing rock, cannot be compared with roller presses, for example for crushing grain. Grain is ground in grain rollers. Grain rollers have weights in the range of a maximum of 100 kg. The entire apparatus structure of a grain roller is very different from high pressure roller presses. Grain rollers also work with shear. In contrast, high pressure roller presses work without shear.

High pressure roller presses also differ significantly from belt rollers for rolling steel. Steel belt rollers are characterized by their smooth running. The steel between the belt rolls is either very ductile, because the steel to be rolled is hot-deformed, or the steel is cold-deformable. As a result, the smoothness of running a steel roll is quite good due to the nature of the rolling process. It is thus possible to operate a belt roller with two rollers arranged horizontally one above the other, the nip pressure being generated by the rollers' own weight and also by hydraulic aids. Problems with vibration are not to be expected due to the ductility of the steel to be rolled. Belt rolls reach a nip speed of up to 200 km / h, depending on the steel to be rolled. Steel belt rollers can be compared to a cake dough roller that rolls over a raw pizza dough and spreads the pizza dough in the process, although the forces acting in a steel belt roller are many orders of magnitude greater. High-pressure roller presses for crushing ores and rock reach roller gap speeds at best in the lower double-digit km / h range. Due to the high speed of rotation, belt rollers work with a rotational frequency in a desirable manner far away from the natural frequencies of their own structure. In the case of high pressure roller presses that work at a much lower speed, the desirable state of a natural frequency far beyond the number of roller revolutions is not possible.

The present invention is concerned with high-pressure roller presses for comminuting brittle ground material such as rock and ores, the brittleness of the ground material being an essential prerequisite for the suitability of this grinding process for the respective ground material. Belt rollers for steel work in a different operational extreme than high-pressure roller presses, namely with ductile steel, which deforms under the roller and does not break up spontaneously due to brittleness and thus evades the pressure in the roller gap. In high-pressure roller presses, the rollers lie horizontally next to each other and form a roller gap through which the ground material runs vertically. High pressure roller presses have a nip pressure of 50 MPa and more. Due to the horizontal mounting of the rollers and the operation with brittle material, the overall mechanical behavior of the high pressure roller press cannot be compared with the mechanical behavior of vertically stacked belt rollers, which also run smoothly and smoothly due to the ductility of the steel to be rolled. In high-pressure roller presses, the grinding material, which is not always uniform, passes through the roller gap and due to the high pressure generated by hydraulic presses that move the rollers in a horizontal direction, a high-pressure roller press can tend to vibrate. The vibration can develop as a result of a slight change in the properties of the material to be ground. It can happen that dry, brittle regrind draws air with it when it is crushed in the roller gap. If there is a no longer negligible proportion of heavily comminuted material in the nip, the air trapped in the millbase can also escape spontaneously when the millbase is compressed before it is broken up spontaneously by brittle cracks, thus giving way to the nip pressure. The vibration behavior of the The high pressure roller press can therefore be influenced by non-linear forces, the description of which cannot be considered in the classical analysis of a damped vibration. The natural frequencies of high-pressure roller presses are undesirably in the range of external excitation frequencies, such as the sudden yield in the event of a brittle fracture, the spontaneous escape of air from the highly compressed grist, the rotation of the grinding rollers and the loading with a bucket elevator.

In addition to the pressure in the roller gap, high-pressure crushing depends on a number of parameters to be observed in the high-pressure roller press used for optimum, low-energy and low-wear crushing. For example, it is important that the rollers of the high-pressure roller press used rotate without relative slippage, so that the rollers do not grind by shearing movement of the material to be ground, but instead exclusively press. Furthermore, it has been found that the correct amount of fresh material fed into the nip of the high-pressure roller press used per unit of time also plays a significant role for the optimal functioning of the high-pressure roller press used. If the roller gap is filled with too little fresh material per unit of time, the high-pressure roller press works as a crusher, especially when using rollers equipped with hard reinforcement bodies, the granular material to be crushed being broken as fresh material by point loads. This type of comminution is less energy-efficient than high-pressure comminution and it does not lead to the desired fine product. If, on the other hand, the roller gap is filled with too much granular material as fresh material per unit of time, the regrind of fresh material and circulating material in the roller gap is compressed too much, trapped air can no longer escape and the roller gap of the high-pressure roller press used tends to become clogged. In this case, the resiliently mounted rollers give way, the excess fresh material falls through the roller gap without being crushed and the high-pressure roller press then works again in the previous state until it has to repeatedly give way in order to let the excess fresh material pass through the roller gap. The roller press thus gets into a first type of oscillatory movement alongside other oscillatory movements and it begins to vibrate mechanically.

In addition to this type of mechanical vibration, which arises from the fact that the rollers move back and forth in their flexible bearing at a high frequency compared to the moving masses, there is another vibration movement within the high-pressure roller press in the form of a vibration movement of the rollers, which is caused by the repetitive, braking effect of the overfilled roller gap on the rotating rollers occurs. As a result of this rhythmic deceleration due to an overfilled roller gap and renewed acceleration by the drive, the rollers start to vibrate in rotation in which the moment and the angular speed of the rollers fluctuate evenly. This is particularly the case with the driven rolls when a high pressure roll press has only one driven roll with one roll running along with it.

Special types of vibratory movements can arise if the overload with too much fresh material occurs only in part of the roller gap. The rollers can then show a combined oscillation, which consists of a back and forth movement of the rollers in the horizontal direction perpendicular to the extension of the nip and a rotational oscillation. The rollers can also undergo a slight, oscillating change in position during which the respective roller rotates by very small angular amounts about a vertical axis. During this movement, the roller is not shifted evenly with the two bearing blocks carrying it, but the two bearing blocks at each end of a roller change their position alternately.

Mechanical vibratory movements of very short duration and high frequency and amplitude in the form of a blow also occur when large pieces of the fresh material are passed or when components that cannot be crushed by high pressure treatment in the roller gap, such as pieces of metal, i.e. hammer heads unwanted in the fresh material, large steel rivets or bolts, excavator teeth or other undesirable pieces of metal that can get into the fresh material when the raw material is broken down.

Furthermore, mechanical oscillatory movements can arise within a high-pressure roller press when the high-pressure roller press is started if the material to be ground is not yet in equilibrium in circulation or if the material in circulation has a composition that is not yet in equilibrium. Mechanical vibratory movements also arise when using fresh food that is wet and fine-grained.

If the frequency of a mechanical vibratory movement mentioned above happens to reach the frequency of a natural vibration of the high pressure roller press, more energy is transferred to the entire system of the high pressure roller press with each individual vibration movement, causing severe damage to the bearings, the roller surfaces and other components of the The high-pressure roller press can be created as a whole, not least because the rollers can weigh more than 50 t, larger rollers can even weigh 100 t, and a vibrating mass of this magnitude also poses very great challenges to very stable machine frames.

Of course, the entire system of the high pressure roller press is mechanically damped due to its structure. On the one hand, the damping is provided by the hydraulic system, in which the hydraulic fluid flows back and forth at high speed through the lines, which are fine in comparison with the diameters of the hydraulic rams or cylinders. The viscosity of the hydraulic fluid causes strong and rather linear damping when flowing through the lines at high speed. A linear damping can be described by the classic description of a damped oscillation. In addition, the movement of the bearing blocks on the slide rails of the loose rollers also absorbs a high level of mechanical energy in the form of friction, as a result of which an oscillating movement is damped. The movement of the bearing blocks follows less of a linear damping, since the transition from static friction (no movement with slight surface deformation in the elastic range) to sliding friction occurs suddenly. The sliding friction is also not linear. The resistance to sliding friction decreases with speed. Due to the large number of possible vibrations, i.e. bending vibrations, torsional vibrations, vibrations whose damping obeys static / sliding friction, vibrations that are damped by the viscosity of the hydraulic fluid, and the large number of external vibration excitations, such as periodic loading of ground material through a bucket elevator, are in a high pressure roller press to observe a large number of different natural vibrations, i.e. different resonance frequencies. The operating speed can also lead to a vibratory movement in the event of a beating bearing or in the event of a vertical runout of the rollers.

If the high pressure roller press gets into an unwanted oscillation mode, it turns out that the high pressure roller press is no longer working in an energy-efficient manner and, moreover, is also subject to high mechanical loads.

In order to avoid or even prevent the formation of mechanical vibratory movements in the high-pressure roller press, which occurs when the roller gap is overloaded with fresh material, the amount of fresh material fed in per unit of time can be regulated by, for example, when an undesired vibration movement is detected in the high-pressure roller press, less fresh material per Unit of time is given to the nip by the feed device. However, this has the disadvantage that a comparatively long follow-up time of the controlled system from the controlled feeding device to the detected oscillatory movements has to be accepted. It takes a certain amount of time until the changed loading of the roller gap with fresh material takes effect and the vibratory movement is ultimately reduced as a result. By then, considerable damage to the high-pressure roller press can already have occurred or accumulate if this type of control intervention is required more frequently.

• In der Druckschrift US2010/0102152A1 werden Kegelbrecher beschrieben, die mit Näherungssensoren wie beispielweise Ultraschall- oder Lasersensoren ausgestattet sind. Durch Messung der Breite des Austrittsspalts kann die Breite des Spaltes durch Heben oder Senken des Kegels den Prozessbedingungen angepasst werden, wodurch ungleichmäßige Rotationen, die den Kegel beschädigen können, vermieden werden.

The following measures are known from the prior art for monitoring the function of shredding devices:

• In the pamphlet US2010 / 0102152A1 describes cone crushers that are equipped with proximity sensors such as ultrasonic or laser sensors. By measuring the width of the exit gap, the width of the gap can be adapted to the process conditions by raising or lowering the cone, thereby avoiding uneven rotations that can damage the cone.

In US2004 / 0255679A1 describes a drum mill for crushing minerals, which has an acoustic sensor in the drum, with the aid of which excessive loads on the drum, for example from rocky rock, can be detected.

DE10132067A1 discloses a method for acoustic monitoring of threatening operating conditions, for example slip, in roller mills. For this purpose, the noises occurring in the roller mill or the sound level are recorded with a microphone and the frequency spectrum is evaluated.

In the DE102011018705A1 discloses a method for regulating the nip pressure as a function of an observed vibration of the high pressure roller press. Depending on the operating status, the pressure in the hydraulic system is varied so that the high-pressure roller press can always be operated close to the maximum pressure.

Also in the German Offenlegungsschrift DE 44 14 366 A1 is taught to reduce the pressure of the hydraulic system when measured vibration amplitudes exceed a predetermined value over a certain period of time and, conversely, to increase the pressure when predetermined vibration amplitudes are not exceeded.

In the German patent DE 196 47 483 B4 a high pressure roller press is disclosed which is disclosed in US Pat its hydraulic system has a variable bladder accumulator that absorbs pressure peaks in the hydraulic system. Pressure peaks are generated during the passage of material that cannot be comminuted by brittle fracture when the heavy roller presses are forced to make sudden and very rapid evasive movements while opening the nip when this material is passed. When the gas volume of the bladder accumulator changes, the spring constant of the buffer system is changed and thus the pressure increase when the volume in the hydraulic system changes. By changing the gas volume in the bladder accumulator, the hardness of the spring system is changed.

In the German Offenlegungsschrift DE 10 2007 059 072 A1 a high pressure roller press with two loose rollers is taught. In this high pressure roller press, the nip pressure is also maintained via a hydraulic system that acts on the roller position. At the specified location is also taught, in order to keep the viscosity-related resistance of the pressure medium when flowing through the lines as low as possible, it is necessary to keep the flexible lines of the hydraulic system short. Since the nip position has to be checked when using two loose rolls, it is necessary that the entire system works with as little damping as possible in order to be able to regulate the nip position quickly.

None of the publications discloses how these undesirable operating conditions, which are associated with press roll vibration, can be avoided or eliminated in advance, i.e. already in the development stage.It would therefore be desirable if a high pressure roll press could be operated in a controlled manner so that the mechanical vibratory movements do not take place. The object of the invention is therefore to operate a generic high-pressure roller press in such a way that a mechanical oscillatory movement does not occur.

The object according to the invention is achieved in that the high-pressure roller press has adaptive damping in the hydraulic system. A specific method for adaptive damping is in the claims 2 until 7th specified. A high-pressure roller having adaptive damping, consisting of a throttle in the hydraulic system and a control device corresponding thereto, is defined in the subclaims 8th until 13th specified.

The special feature of this control is that the high pressure roller press can be operated with constant hydraulic pressure despite the vibration control. This protects the hydraulic pump, which is not subjected to constant load changes and enables the high-pressure roller press to work more time in the ideal state and thus become more efficient.

mit x gleich der Ortskoordinate, t gleich der Zeit, m gleich der bewegten Masse, c gleich dem Dämpfungskoeffizienten und k gleich der Rückstellkraft.The equation of motion of an oscillating system can be described by assuming a harmonic oscillation behavior $$\text{m}*\frac{d^{2}x}{dt}+\text{C.}*\frac{dx}{dt}+\text{k}*x=0$$

with x equal to the position coordinate, t equal to time, m equal to the moving mass, c equal to the damping coefficient and k equal to the restoring force.

All of the high-pressure roller presses described so far act in the control or regulation of the vibration behavior on the linear link. The linear term is the restoring force k in the aforementioned equation. In order to adaptively avoid the tendency to oscillate when an oscillation occurs, the restoring force is changed. So k is changed in the equation of motion.

Assuming that the moving mass of a press roll is and will remain unchanged, an alternative to intervening in the system that obeys the aforementioned equation of motion, but at least can be described by it to a good approximation, is to intervene in the damping constant c.

In order to avoid vibrations during operation of a high pressure roller press, the idea of the invention provides for the damping to be adjusted by means of a control loop so that when a vibration is detected, the oscillation behavior of the loose roller of a high pressure roller press is such that the oscillation behavior corresponds to the aperiodic limit case of a damped oscillator as much as possible is equivalent to. A settling time or relaxation time is specified as a guide element, within which the system has returned to a non-oscillating state after the occurrence of a forced oscillation, for example when a regrind component that cannot be crushed by brittle fracture is passed or when the regrind composition changes and / or the regrind moisture content changes. The forced vibration, which is calculated by means of a vibration analysis, enters the system as a disturbance variable, and an attenuator enters the control loop as a manipulated variable. The coupling path of the control loop is the path of the forced oscillation of the loose roller, which is to be avoided, and the damping of the movement of the loose roller, both of which interact with one another. Since the loose roller can also be overdamped and, if the damping is too strong, can change into the so-called and undesired "creep case", the regulation is necessary on the one hand avoids the creep case detectable by vibration analysis, but also avoids the vibrations occurring if the damping is too low. Since the observable and undesirable natural frequency of the loose roll in a high pressure roller press is close to its operating frequency of rotation or in the vicinity of its harmonics, a high pressure roller press can easily excite itself to oscillating states during operation. The adaptive damping via the control enables the high pressure roller press to run smoothly, which works outside of the ideal operating parameter range of the roller gap in the shortest possible time. The ideal operating parameters are the rotational speed of the press rollers, the roller gap width, the roller gap pressure and the grinding stock flow as the quotient of the grinding stock feed quantity per time.

In the previously known control system for avoiding vibrations in a high-pressure roller press, intervention is made in the ideal operating parameters, namely in the roller nip pressure, which can be set via the hydraulic pressure and is proportionally related to it, and via the roller nip width, which inevitably increases when the pressure drops. The mean rotational frequency of the press roll can be assumed to be almost constant due to the large mass and the associated moment of inertia. The flow of regrind can also be assumed to be reasonably constant with appropriate control by a feed device. However, the grinding stock behavior is not sufficiently constant, in particular with regard to the tendency of the grinding stock to trap air, and the homogeneity of the grinding stock. The largest mean disturbance variables are therefore the variation in the properties of the regrind, followed by the uniformity of the regrind flow. These two disturbance variables cause the loose roll of a high-pressure roll press to set itself vibrating as a result of the rotation. In order to operate the nip pressure and the nip geometry outside of the ideal state in the shortest possible time, the adaptive damping control is more suitable than previously known methods.

The method described here for regulating the damping of the movement of a loose roller of a high-pressure roller press, the high-pressure roller press having a hydraulic system which presses the loose roller against a fixed roller and thus maintains a predetermined nip pressure in the roller gap between the loose roller and the fixed roller when grinding material passes the roller gap between the loose roller and the fixed roller passes, can have the following steps in a specific embodiment of the method: measuring mechanical vibrations on the machine frame at at least one point and / or measuring pressure fluctuations in the hydraulic system at at least one point, and / or measuring electrical current fluctuations in the electrical power consumption at least a drive motor as the first step, the at least one mechanical oscillation and / or the pressure fluctuation and / or the current fluctuation entering a control loop of the control as at least one disturbance variable. After the measurement, a vibration analysis is carried out as a mathematical operation in a process computer. Such vibration analyzes can include: low-pass filtering, high-pass filtering or band-pass filtering. A Fourier transformation can be carried out, in particular a fast Fourier transformation. Statistical smoothing methods for the data can be carried out, such as, for example, a singular value decomposition. Mathematical Gaussian convolution and noise suppression systems can also be used. Finally, mathematical lock-in amplifier simulations can also be used, in which the signals to be filtered are modulated with a periodic signal in order to filter signals. The person skilled in the art is free here to choose an ideal vibration analysis. After the vibration has been determined by vibration analysis, the next step follows, namely determining at least one damping constant from the result of the vibration analysis. The damping constant is the constant in front of the first order differential element in an equation of motion for a harmonic, damped oscillator. Given a known vibration behavior, this damping constant allows conclusions to be drawn about the expected leveling behavior of the entire system. If the damping constant is too large, the loose roll of the high pressure roller press to be controlled would tend to creep, in which the high pressure roller press works outside of the ideal state and thus works inefficiently, but still consumes energy. If the damping is too low, the loose roll of the high-pressure roller press would tend to mechanical vibrations, which cause severe damage to the high-pressure roller press, the foundation and, in the worst case, to the environment, such as cracks in buildings due to vibrations transmitted via the ground to the foundation of a company building . The next control step is followed by a comparison of the at least one damping constant with a predetermined damping constant in each case, with each predetermined damping constant entering the control loop as a reference variable. The damping constant indirectly describes the settling time or the relaxation time of the loose roller. The result of the comparison is followed by the next step of the regulation, namely setting at least one adjustable throttle in the hydraulic system, the throttle position of the respective adjustable throttle being included in the control loop as a manipulated variable, and the respective adjustable throttle in the hydraulic system has a damping effect on the movement of the loose roller and thus the control loop is closed. The step of comparing the determined damping constant with the target damping constant can also be done via a known PID control, a PI control, a PD control or an ID control where P stands for “proportional”, I for “integral” and d for "differential". This control strategy is well known to the measurement and control technician and reference is made to the relevant specialist literature.

The specification described above is particularly suitable for regulating a system of a high-pressure roller press in which a large number of forced oscillation states can be measured. In contrast to belt rolls, which, due to the nature of the rolling process with ductile steel, have a rather calm, i.e. low-vibration operating state, high-pressure roll presses show vibrations that come from the following sources, for example: higher-frequency vibrations through the use of so-called "stud lining", i.e. the Equipment of the surface of a press roll with a large number of hard bodies, inhomogeneous grist quality, sudden brittle breakage of the grist to be shredded, frequency converter with industry-typical 400 Hz alternating current with very high current consumption in the vicinity of the system (so-called mains hum), the same with 50 Hz or 60 Hz , depending on the existing mains frequency. Further vibrations may generate beating bearings, the rotation of the press roll itself, if it is washed out and possibly no longer ideally cylindrical or shows first surface damage as a sign of wear. After all, the machine frame shows all kinds of natural frequencies, be it bending vibrations from steel belts, torsional vibrations or longitudinal vibrations. With the very high loads, these vibrations can also occur as torsional vibrations of the shaft for driving the loose roller. Finally, undesirable bearing vibrations caused by the meshing of gears can also be found in an overall vibration pattern of a high pressure roller press.

In order to filter out precisely the vibration that is necessary for control from the complex vibration spectrum and to ignore the vibrations that are unavoidable, for example high-frequency mains humming, bearing damage, rhythmic loading of the high-pressure roller press with grist by a bucket elevator or by an undesirably rhythmic conveying of an overloaded conveyor belt, it is suitable to carry out a Fourier transformation (frequency transformation) for the vibration analysis and to only carry out the control based on selected peaks in the frequency-transformed spectrum. A sequence of the following steps is suitable as a configuration of the vibration analysis: Fourier transformation of the measured vibrations and / or pressure fluctuations and / or electrical current fluctuations, selection of predetermined linear combinations of individual frequency components from the Fourier-transformed vibrations, determination of a damping constant for the individual Fourier-transformed vibrations from a time series of the frequency components, feeding back the damping constants to a controller. The damping constant can be determined by regression, the regression calculation being based on a linearized exponential function. So an exponential coefficient of a decay curve is calculated by statistical methods. Here, too, reference is made to the relevant literature on statistical data evaluation.

For data processing, it is suitable to process the data from a measured vibration diagram with a mathematical low-pass filter before the Fourier transformation.

Today's microcontrollers are used in measurement. and control units are used, able to process very complex and large amounts of data. In order to simplify the data analysis, it can be advantageous if, during the control, a linear combination of certain oscillation states (“oscillation 1 with frequency 1 is only relevant if there is also vibration 2 with frequency 2 occurs at the same time ”) weights the determined damping constants and combines them into a weighted damping constant. For this purpose, it is advisable to weight the various damping constants and combine the weighted damping constants into one value if more than one damping constant is determined.

A very special type of damping is achieved through the use of an adjustable one-way flow control valve in the hydraulic system. A throttle check valve is characterized by a fluid flow that is throttled evenly in both directions, whereby the strength of the throttling effect can be adjusted with an actuator. However, there is a check valve parallel to the throttle. The check valve opens to the flow in a first direction and closes to the flow in an opposite, second direction. The use of a one-way flow control valve, which is built into the hydraulic system in such a way that the loose roller can move freely away from the fixed roller with almost no additional throttle damping and only against the restoring force of a bladder accumulator in the hydraulic system (undamped), however, it can only move back towards the fixed roller in a damped manner can move, enables the settling time (relaxation time) of the loose roller to be significantly shortened, which means the damping effect is further improved. The throttle check valve introduces a strong non-linear element into the equation of motion, which describes the motion of the idler roller. The non-linear element makes the analytical description and calculation of the settling time almost impossible. For a control system, however, the underlying mathematical model is irrelevant if only the relaxation time, which is based on the number of zero crossings of the movement and the time required for this, as a measure of the damping constant.

By regulating the high pressure roller press with constant pressure, it is necessary that the hydraulic system has a switch and / or the loose roller has a stop in order to prevent the loose roller from reaching directly to the fixed roller when idling. If the rollers touch each other under pressure, it is easier for the reinforcement of the surface with hard bodies to be damaged. In order to make the high-pressure roller insensitive to undesired idling, it can be provided that the hydraulic system has an automatic pressure switch-off, which is triggered when the loose roller comes closer than a predetermined value to the fixed roller, with a mechanical switch on the machine frame indicating the approximation of the Detected loose roller on the fixed roller. A mechanical stop can also achieve a similar result.

• 1 eine Hochdruckwalzenpresse mit Orten von beispielhaft angeordneten Dehnungsmesstreifen,
• 2 ein beispielhaftes, unbearbeitetes Schwingungsdiagramm eines Schwingungsdetektors,
• 3 dass Schwingungsdiagramm aus 2 nach Verarbeitung durch einen Tiefpassfilter,
• 4 das bearbeitete Schwingungsdiagramm aus 3 nach Fouriertransformation,
• 5 Auswahl eines Fourierkoeffizienten aus 4 als Darstellung über die Zeit,
• 6 Darstellung einer Fourierreihe aus 4, die über einen Schwellwert ausgewählt wird,
• 7 eine Rücktransformation der ausgewählten Fourierreihen aus 6,
• 8 Darstellung der Wirkung einer unzureichenden (zu geringen) Dämpfung auf das Schwingungsverhalten der Loswalze,
• 9 Darstellung der Wirkung einer idealen (optimalen) Dämpfung auf das Schwingungsverhalten der Loswalze,
• 10 Darstellung der Wirkung einer zu starken Dämpfung auf das Schwingungsverhalten der Loswalze,
• 11 eine Hochdruckwalzenpresse mit Hydrauliksystem aus dem STAND DER TECHNIK
• 12 eine Ausgestaltung der erfindungsgemäßen Hochdruckrollenpresse mit maximaler Anzahl von Schwingungssensoren und einem optionalen Drosselrückschlagventil,
• 13 Wiederholung der Figuren 8, 9 und 10, die bei Einsatz einer einstellbaren Drossel entstehen, zum Vergleich mit vergleichbaren Diagrammen, bei Einsatz eines Drosselrückschlagventils in 14,
• 14 Diagramme aus Figuren 8, 9 und 10, jedoch bei Einsatz eines Drosselrückschlagventils.

The invention is explained in more detail with reference to the following figures. It shows:

• 1 a high-pressure roller press with locations of strain gauges arranged by way of example,
• 2 an exemplary, unprocessed vibration diagram of a vibration detector,
• 3 that vibration diagram from 2 after processing through a low-pass filter,
• 4th the edited vibration diagram 3 after Fourier transformation,
• 5 Selection of a Fourier coefficient 4th as a representation over time,
• 6th Representation of a Fourier series 4th , which is selected via a threshold value,
• 7th an inverse transformation of the selected Fourier series 6th ,
• 8th Representation of the effect of insufficient (insufficient) damping on the vibration behavior of the loose roller,
• 9 Representation of the effect of ideal (optimal) damping on the vibration behavior of the loose roller,
• 10 Representation of the effect of excessive damping on the vibration behavior of the loose roller,
• 11 a PRIOR ART high pressure roller press with hydraulic system
• 12th an embodiment of the high-pressure roller press according to the invention with a maximum number of vibration sensors and an optional one-way flow control valve,
• 13th Repetition of the figures 8th , 9 and 10 that arise when using an adjustable throttle, for comparison with comparable diagrams, when using a one-way flow control valve in 14th ,
• 14th Diagrams from figures 8th , 9 and 10 , but when using a one-way flow control valve.

In 1 is a generic high pressure roller press 1 shown, which two counter-rotating press rollers as a fixed roller 2 and loose roller 3 having that in a machine frame 4th are recorded, which in turn at different positions with sensors 20th is equipped for the detection of vibratory movements. The two press rolls, fixed roll 2 and loose roller 3 the high pressure roller press 1 , are via hydraulic rams 17th and 18th pressed together without touching each other. By means of a feeding device, not shown here, the ground material to be comminuted is transferred to the roller gap 7th the high pressure roller press 1 between the fixed roller 2 and the loose roller 3 abandoned and thereby by the between the two rotating press rollers, fixed roller 2 and the loose roller 3 crushed, prevailing pressure. The comminution takes place by brittle fracture while avoiding shearing stress. At various points on the machine frame 4th the high pressure roller press 1 are strain gauges 20th attached as sensors for the detection of vibratory movements. The ones from the strain gauges 20th Measured vibrations are forwarded to an evaluation device, not shown here, where the amplitude and / or the frequency of the measured vibrational movement is compared with a previously determined setpoint. If the amplitude exceeds a critical value at a predetermined frequency, which is determined by a Fourier transformation or more generally by frequency filtering, the position of a throttle valve, not shown in this drawing, is changed, whereby the damping of the movement is increased. When the intensity of the oscillation movement again falls below the previously determined critical range due to the increase in the damping effect of the throttle valve, the damping is controlled by a control strategy, preferably according to PID- Procedure, slowly decreased again, so that the roller press 1 always works in a damping range that brings the mechanical vibratory movement of the loose roller into the aperiodic limit of the damped vibration as far as possible. As the whole system of the high pressure roller press 1 with the not necessarily linear damping of the movement of the bearing blocks in the machine frame 4th cannot be fully described by an equation of motion of a damped harmonic oscillation, the control strategy pursues a damping that corresponds as closely as possible to the movement pattern of the aperiodic limit case with an initial deflection in a first direction, a return with slight overshoot and slowly approaching the zero position.

In 2 is an example of an oscillation diagram as F ₁ (t) (function 1 after the time t ), which could have been detected by almost any motion sensor. The mechanical deflection is on the abscissa D. (Eng. Displacement) and on the ordinate is the time t (engl. time) shown. Particularly suitable sensors for vibration measurement are: strain gauges 20th at various points on the machine frame 4th . Strain gauges 20th longitudinal vibrations of a metal belt of the machine frame 4th measure and also torsional vibrations of a drive shaft. Accelerometers at just as many points on the machine frame 4th can measure bending vibrations of the corresponding metal belt when it vibrates like a guitar string. In terms of the locally resolved amplitude, this oscillation is only very small, usually in the range of a few µm, but sufficient to measure characteristic oscillations. Accelerometers can also measure if the entire high pressure roller press 1 due to the loose roller swinging back and forth 3 carries out a corresponding countermovement in space. The pressure recording in the hydraulic system is suitable as a further measurement source 8th and also the measurement of the power consumption of the drive motors. Each vibration source has its own and typical superimpositions of negligible vibrations, such as the very high line frequency or converter frequency when measuring the power consumption, the rotation frequency and its harmonics when measuring accelerations by acceleration sensors, and again the line frequency when measuring longitudinal vibrations and the frequency that is caused by the brittle breaking of the grist rather than gray noise, i.e. not Gaussian noise with hard signal peaks. An acceleration sensor directly on a bearing block will receive an actual vibration from the loose roller as the dominant vibration. The aim of the invention is to regulate the damping state with detected vibrations before the high-amplitude back and forth movements of the loose roller 3 appear.

To prepare the signal for the first time, it can be subjected to low-pass filtering, which suppresses gray noise and the line frequency. The result of the low-pass filtering is in 3 the low-pass filtered signal of the deflection-time diagram 2 as F ₂ (t) (function 2 after the time t ) shown. Essentially, two oscillations of different frequencies can still be seen here, namely a dominant fundamental oscillation and a harmonic and traces of higher harmonics.

In 4th is the Fourier transform, which is a frequency filtering of a signal in parallel channels a) ... b) ... n) can be understood. The Fourier transform converts the signal 3 in a frequency-time diagram, with the frequency from channel a) as a function F _a (f, t) (function a) according to the frequency f and according to the time t ), Channel b) as a function F _b (f, t) (function b) according to the frequency f and according to the time t ) and channel n) as a function F _n (f, t) (function n) according to the frequency f and according to the time t ) is shown.

The dominant vibration in the channel a) is selected here and is in 5 as an illustration of a) over time t shown. The coefficient x (a) of the damping part e ^{- (x (a) * 1) of} the vibration is suitable for regression analysis to determine a damping coefficient with which the damping control can be carried out. A regression analysis of the time course of the coefficient F _a (f, t) allows a value x (a) to be determined, assuming a negative-exponential course. It is an observation with the invention that the rocking of the loose roller 3 that it is important to prevent, shows the typical frequency patterns that can be found in the natural oscillation frequencies of the machine frame of the high-pressure press. Even very strong, massive steel belts of a machine frame of a high pressure roller press already show very strong machine frame-specific vibration patterns clearly before the loose roller begins to rock 3 entry. All that is needed to see this pattern is a high pressure roller press 1 with a sensitive vibration analysis and to identify the vibration pattern shortly before the occurrence of the loose roller vibration to be avoided. This can be done with common statistical means, namely a temporal correlation analysis, but it is also possible for a person skilled in the art to recognize the pattern with the naked eye. Once the pattern has been recognized, it can be programmed into the control device as a typical machine frame-specific pattern.

Depending on the observed vibration pattern, it is possible to select different coefficients after the Fourier transformation. In the simplest case, it is also possible to define a threshold value and identify all coefficients that exceed the threshold value as the dominant vibration component. This approach is in 6th shown in which the coefficient a) and b) exceed a threshold value in C (Eng. Coefficient). An inverse transformation of these Fourier coefficients shows that there is a dominant and a higher harmonic oscillation with different phase positions in this example according to the distance from the natural frequency. The two back-transformed oscillations are in 7th shown.

In 7th is the upper oscillation as the deflection D. (Eng. Displacement) of the frequency with the coefficient a) over time t ) shown. The deflection is in the lower oscillation diagram D. (Eng. Displacement) of the frequency with the coefficient b) over time t ) shown.

The control strategy now determines from the decay of the oscillation in, for example in 7th via a continuous signal ( 5 ) a coefficient x (a) for damping the equation of motion for a tell-tale vibration in the machine frame 4th a high pressure roller press 1 . This signal is the feedback signal into the control loop. If the damping is too strong, thus the coefficient x (a) is too large, then the damping of the movement of the loose roller is reduced 3 by partially opening a throttle slide of a throttle in the hydraulic system 8th a high pressure roller press 1 decreased and vice versa. The different control states are shown in the figures 8th (Attenuation too low), 9 (Attenuation ideal) and 10 (Damping too strong) shown. If the damping is too low, the loose roller can move 3 in the event of an externally imposed oscillation, for example due to the rotation of the loose roller 3 with a specified number of revolutions, for this number of revolutions certain nip pressure, which is proportional to the hydraulic pressure of the hydraulic ram 17th and 18th and a material property of the ground material that does not match, level off only after a few oscillation cycles. If a 100-ton roller vibrates back and forth at a frequency significantly greater than 1 Hz, the impacts transmitted to the ground can cause damage in the immediate vicinity. It has already been observed that an improperly operated and unsupervised high-pressure roller press caused cracks in the foundation of a nearby company building. This state of affairs must be avoided as a matter of urgency. If the damping is too great, the high pressure roller press runs 1 although quiet. The occurring creep case ( 10 ), in which after deflection of the loose roller 3 if it only slowly finds its way back to the ideal working point at D = 0, this means that the high pressure roller press is working inefficiently for this time. The roller gap is too large and the material that passes through is not crushed, but rather broken into large pieces. The hatched area under the curve in 10 shows the deflection over time. The greater the deflection D. (Eng. Displacement), the more inefficiently the high pressure roller press works 1 . In 9 is shown how the loose role 3 after a deflection, for example due to the passage of an excavator tooth or passage of an excessively large grist, after a short period of one-time overshooting t _max is back in equilibrium and thus in the ideal working point.

In 11 A PRIOR ART high pressure roll press is shown having a fixed roll 2 and a loose roller 3 . The roll 3 is via hydraulic ram 17th and 18th against the fixed roller 2 pressed. Hydraulic fluid from a reservoir 23 is used to exert force by means of a hydraulic pump 19th into the pistons of the hydraulic rams 17th and 18th pumped. A bladder accumulator is used to compensate for sudden load peaks (passage of an excavator tooth, a piece of metal, too large a piece of regrind) 14th provided, which has a pressurized air cushion against which the hydraulic fluid can expand when this is caused by a jerky movement of the loose roller 3 intermittently from the piston of the hydraulic ram 17th and 18th is pushed back into the line system of the hydraulic system.

In 12th an embodiment of the high pressure roller press according to the invention is shown. The essential element here is an adjustable throttle 15th or an adjustable one-way flow control valve 16 between the hydraulic system 8th and the bladder accumulator 14th . Through the throttle 15th or the one-way flow control valve 16 can the movement of the loose roller 3 with constant working pressure in the roll gap 7th be dampened. Is it a one-way flow control valve? 16 , so can hydraulic fluid in the event of an abrupt displacement of the idler roller 3 fast and undamped by the bypass 16.2 in the direction of the bladder accumulator flow 14th and expand there. The reflux from the pressurized bladder accumulator 14th however, is through the throttle 16.1 damped because the free cross-section for the flow of hydraulic fluid through the throttle 16.1 is limited. The viscosity of the hydraulic fluid thus generates a counterforce that is opposite to the flow velocity of the hydraulic fluid. The high pressure roller press 1 has different vibration sensors, each with an individual vibration diagram as a disturbance variable 13th produce. They are strain gauges 20th at various points on the machine frame 4th to put acceleration sensors in these very places, to put a digital manometer 21 in the Hydraulic system 8th for the detection of pressure fluctuations and a digital ammeter 22nd for the detection of vibrations in the power consumption of the electric drive motors. All of these sensors provide a vibration diagram that can be processed as described above. From a determined damping coefficient, which is representative of the vibration behavior of the loose roller 3 the control device determines a control value for the throttle, for example according to the PID control strategy 16.1 . The thrush 16.1 acts on the vibration behavior of the loose roller 3 and thus the control loop is closed. In this example a high pressure roller press 1 is a position switch 24 present, which prevents the loose roll 3 the fixed roller 2 touched under pressure. Come the roll 3 the fixed roller 2 too close, the position switch switches 24 the hydraulic pump 19th to avoid damage to the rigid reinforcement (pattern on the press rolls loose roll 3 and fixed roller 2 from rectangles).

In the figures 13th and 14th are the different effects of a throttle 15th and a one-way flow control valve 16 on the settling time (relaxation time) of the loose roller 3 shown. 13th is just a repetition of the figures 8th , 9 and 10 . In 14th the middle example shows that a one-way flow control valve 16 to a significant shortening of the settling time (relaxation time) t _max to t _{max, new} leads. In the event of an evasive movement, the loose roller can move 3 with little or no damping with opening of the nip 7th withdraw what is in the middle diagram of 14th is shown with a rightmost arrow in bold type on the far left. The arrow in bold stands for a fast and unrestrained or undamped movement. The check valve is during this return movement 16.2 open and hydraulic fluid flows through the bypass, the check valve 16.2 at the throttle 16.1 past. During the forward movement of the loose roller 3 in the direction of the fixed roller 2 is the check valve 16.2 closed and the hydraulic fluid from the bladder accumulator 14th must find the way through the throttle 16.1 to take. Through the throttle 16.1 the return movement of the loose roller happens 3 due to the pressure in the bladder accumulator 14th slower and with damping, represented by an arrow pointing to the left, not in bold, which represents a slower movement due to stronger damping. Considerable kinetic energy is consumed in the process. The overshoot amplitude behaves for the period of return almost as in the case with only one throttle 15th without bypass / check valve 16.2 . As soon as the turning point is reached when overshooting, the loose roller moves 3 again undamped (right, bold arrow to the right) by the force of the compressed grist back into the ideal position. This is the return when a one-way flow control valve is used 16 faster than in the case of damping in both directions with a throttle that acts equally in both flow directions 15th . Due to the rapid movement in one direction, the settling time (relaxation time) t _{max is now} significantly shorter, so that the high-pressure roller press 1 is only operated outside of its optimal operating point for a very short period of time. It should be pointed out at this point that the introduction of a one-way flow control valve creates a strong anharmonic component in the movement system of the loose roller 3 is introduced, which can lead to stronger harmonics of the equation of motion, thus stronger jerk moments (third derivative of the location according to time in an equation of motion) can occur, which can travel as shock waves through the soil and can develop their effect at an undesired location. However, it is a great advantage of the invention that the adaptive damping is regulated by the vibration analysis in such a way that the impacts only occur to a greatly reduced extent. The inevitable impact that occurs, for example, when an excavator tooth passes through the roller gap, is caused by the unbraked or undamped evasive movement of the loose roller 3 associated with significantly lower shock wave transmission to the ground than with a movement that is damped in both directions. In this way, the strong impacts in the ground or in the machine frame are weakened, but the rhythmic anharmonic vibration components that are avoided are amplified. Since the stronger vibration components are corrected from the outset, the damping method has an advantage over the entire bandwidth of the application.

List of reference symbols

1

High pressure roller press

2

Fixed roller

3

Loose roll

4th

Machine frame

7th

Nip

8th

Hydraulic system

10

Regulator

11

Reference variable

12th

Manipulated variable

13th

Disturbance

14th

Bladder accumulators

15th

Throttle, adjustable

16

One-way flow control valve, adjustable

16.1

Throttle, adjustable

16.2

Bypass, check valve

17th

Hydraulic ram

18th

Hydraulic ram

19th

hydraulic pump

20th

Strain gauges

21

digital manometer

22nd

digital ammeter

23

Storage

24

Position switch

30th

Vibration diagram

31

Fourier transform

a)

Time series

b)

Time series

D.

Deflection

C.

coefficient

e

Base of the natural logarithm

p

pressure

t

Time

tmax

Leveling off time (relaxation time)

tmax, new

shortened settling time, shortened relaxation time

f

frequency

F.

Function of

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 2708053 A1 [0002]
• US 2010/0102152 A1 [0015]
• US 2004/0255679 A1 [0016]
• DE 10132067 A1 [0017]
• DE 102011018705 A1 [0018]
• DE 4414366 A1 [0019]
• DE 19647483 B4 [0020]
• DE 102007059072 A1 [0021]

Claims (13)

Method for regulating the damping of the movement of a loose roller (3) of a high-pressure roller press (1), the high-pressure roller press (1) having a hydraulic system (8) which presses the loose roller (3) against a fixed roller (2) and thus a predetermined nip pressure in the The roller gap (7) between the loose roller (3) and the fixed roller (2) is maintained when the material to be ground passes the roller gap (7) between the loose roller (3) and the fixed roller (2), characterized by the use of an adaptive damping control which regulates the damping controlled by a mechanical oscillating movement of the loose roller. Method for regulating the damping of the movement of a loose roller (3) of a high-pressure roller press (1) Claim 1 , wherein the adaptive damping control performs the following control steps - measuring mechanical vibrations on the machine frame (4) at at least one point and / or - measuring pressure fluctuations in the hydraulic system (8) at at least one point and / or - measuring electrical current fluctuations in the electrical power consumption at least of a drive motor, the at least one mechanical vibration and / or the pressure fluctuation and / or the current fluctuation entering a control loop of the control as at least one disturbance variable (13), - Carrying out a vibration analysis as a mathematical operation in a process computer, - Determining at least one damping constant the result of the vibration analysis, - comparison of the at least one damping constant with a predetermined damping constant each, with each predetermined damping constant entering the control loop as a reference variable (11), - positions of at least one adjustable throttle (15, 16) i m hydraulic system (8), the throttle position of the respective adjustable throttle (15, 16) entering the control loop as a manipulated variable (12), the respective adjustable throttle (15, 16) in the hydraulic system (8) having a damping effect on the movement of the loose roller (3) and thus the control loop is closed. Procedure according to Claim 2 , characterized by the use of a throttle check valve (16) which is connected to the hydraulic system in such a way that - a movement of the loose roller (3) with opening of the roller gap (7) hydraulic fluid the throttle (16.1) through a bypass (16.2) in the throttle check valve ( 16) lets pass and - a movement of the loose roller (3) with narrowing of the roller gap (7) allows hydraulic fluid to only pass through the throttle (16.1). Method according to one of the Claims 2 until 3 , characterized by a sequence of the following steps in the vibration analysis - Fourier transforming of the measured vibrations and / or pressure fluctuations and / or the electrical current fluctuations, - Selecting predetermined linear combinations of individual frequency components from the Fourier-transformed vibrations, - Determining a damping constant for the individual Fourier-transformed vibrations a time series of the frequency components, - feeding back the damping constants to a controller (10). Method according to one of the Claims 2 until 4th , characterized by low-pass filtering of the measured vibrations and / or pressure fluctuations and / or electrical current fluctuations before the Fourier transforming step. Method according to one of the Claims 2 until 4th , characterized by - weighting of the various damping constants, - combining the weighted damping constants into one value if more than one damping constant is determined. High-pressure roller press (1), comprising - at least one fixed roller (2), and - at least one loose roller (3), the high-pressure roller press (1) having a hydraulic system (8) which counteracts a loose roller (3) assigned to a fixed roller (2) the assigned fixed roller (2) presses and thus maintains a predetermined roller gap pressure in the roller gap (7) between the loose roller (3) and the fixed roller (2) when the grinding material enters the roller gap (7) between the loose roller (3) and the fixed roller (2) happens, characterized in that an adaptive damping control controls the mechanical oscillatory movement of the loose roller. High pressure roller press after Claim 7 , having characterized in that an adjustable throttle (15, 16) is present in the hydraulic system (8), which can be adjusted via a controller (10) to regulate the damping of the fluid flow in the hydraulic system (8). High pressure roller press according to one of the Claims 7 or 8th , characterized in that the hydraulic system (8) maintains a constant pressure (p). High pressure roller press according to one of the Claims 7 until 9 , characterized in that the hydraulic system (8) has an automatic pressure switch-off which is triggered when the loose roller (3) comes closer than a predetermined value to the fixed roller (2), a mechanical switch (24) on the machine frame (4) the approach of the loose roller (3) to the fixed roller (2) is detected and / or that the high-pressure roller press has a mechanical stop for the loose roller, which prevents the loose roller from touching the fixed roller under pressure. High pressure roller press according to one of the Claims 7 until 10 , characterized in that the controller (10) according to the Claims 1 until 5 is working. High pressure roller press according to one of the Claims 7 until 11 , characterized in that the hydraulic system (8) is buffered by a bladder accumulator (14) which is connected to the hydraulic system (8) via the adjustable throttle (15, 16). High pressure roller press according to one of the Claims 8 until 12th , characterized in that the adjustable throttle (16) is a throttle check valve.

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