EP1464611B1 - Process for stilling the motion of a link chain of a chain hoist, in particular for preventing the emergence of a resonant vibration of the link chain, and chain hoist therefor - Google Patents

Abstract

The method for running moderation of a link chain of a haulage chain, in which the link chain is guided over an electric motor driven polygonal chain wheel with unequal pitch, has a periodic and/or random and damping control value superimposed on the speed of the chain wheel (4), and the control value effects a change of the chain speed in a way that a forming of a resonance oscillation is prevented. The electric motor (2) is controlled via an electronic damper (8). An independent claim is included for a haulage chain for carrying out the proposed method of running moderation.

Description

The invention relates to a method for smoothing a link chain of a chain hoist, in particular for preventing the formation of a resonant vibration of the link chain, in which a link chain is passed over a polygonal sprocket with non-uniform pitch, which is driven by an electric motor. The invention also relates to a chain hoist with a guided over a polygonal chain and a chain acting on the sprocket electric motor.

German Patent Application DE 1 531 307 A1 discloses a chain hoist with an electromotive drive. The chain hoist consists essentially of a driven by the electric motor sprocket over which the chain, in particular a round steel chain, is guided with a load receiving means. The sprocket is in this case designed as a so-called pocket wheel, whose pockets receive the chain links of the chain for transmitting the lifting forces in a form-fitting manner. In this case, a lying and a stationary chain link change in the process of the sprocket. According to the curvature of the chain, the sprocket has an uneven polygonal circumference. This polygonal circumference of the sprocket causes, that at the end of the chain of the sprocket effective radius of the sprocket changes depending on the angle and thus the speed of the chain varies periodically. The periodic fluctuations thus occur even at constant speed of the electric motor. This is associated with a restless running of the chain, a constant threshold load of the chain hoist and possibly occurring disturbing resonance effects.

In order to reduce the fluctuations in the running speed of the chain from the sprocket, it is known that the output gear arranged on the electric motor and the drive gear of the sprocket meshing therewith thus run out of contour in a shape deviating from the circular shape, thus counteracting the above-described polygonal effect Swing sprocket.

This mechanically acting compensation system can only lead to a limited homogenization of the running speed of a chain of a chain hoist, since it takes into account only the low-order mathematical elements in the polygon effect. In addition, these mechanically acting compensation systems require increased design effort.

Furthermore, German Patent Application DE 199 58 709 A1 discloses a method and a device for reducing the polygon effect in the deflection region of passenger conveyor systems, in particular escalators or moving walkways. The passenger conveyor systems have an endless revolving link chain or so-called Gallsche chain, which rotates between two pulleys and is removed at least rolling in the area of their upper run. The link chain or Gallsche chain and the deflection wheels are characterized by a uniform division. One of the two deflection wheels is driven by an electric drive. In order to reduce the polygon effect occurring during the rotation of the plate-link chain around the deflection wheels, the rotational speed of the deflection wheel is superimposed on a different type of rotational speed. As a result, the electric drive is controlled by a frequency converter in such a way that it rotates at a non-constant speed. A control device associated with the frequency converter processes as inputs the phase angle of the deflection wheel and / or the speed of the chain.

A further development of the above-described device for reducing the Polygon effect in the deflection of passenger transport systems, especially escalators or moving walkways, is known from German Patent DE 101 20 767 C2. There, a position-dependent control of the speed of the chain is brought about to the effect that the speed fluctuations are determined, which arise at the chain strand in the drive with a substantially constant rotational frequency. A compensation of the determined speed fluctuations should then be achieved in that the deflection wheel is operated with non-uniform rotational frequency and for this purpose a mathematical function is determined, which is synchronized in the operating state only with the angular position of the deflection wheel.

The above-described methods and devices for reducing the polygon effect in the deflection region of passenger conveyor systems relate to an endless circumferential link chain. This link chain has in the usual way a fixed length, has an equal pitch and is supported at least in the region of the upper strand. The occurring polygon effect is thus dependent on the uniform pitch of the sprocket. The fact that the link chain rests at least in the region of the link chain, this experiences a strong damping. In addition, the occurring and to be reduced polygon effect is easier to control by the fixed length of the link chain.

Based on this prior art, the present invention, the object of the invention is based on a method for running calm a link chain of a chain hoist, in particular to prevent the formation of a resonant vibration of the link chain, and to optimize a chain hoist hereby.

This object is achieved by a method for reducing the polygon effect in a chain drive, in particular in a hoist, with the features of claim 1 and by a chain drive, in particular for a hoist, by the features specified in claim 7. Due to the characterizing features of the subclaims 2 to 6 and 8 to 11, the invention is further configured in an advantageous manner.

According to the invention, in a method for smoothing a link chain of a chain hoist, in particular to prevent the formation of a chain Resonant vibration of the link chain, in which a link chain is guided over a polygonal sprocket with non-uniform pitch, which is driven by an electric motor, avoiding resonance vibrations, characterized in that the speed of the sprocket a periodic and / or stochastic and damping control variable is superimposed and the damping control quantity causes a change in the chain speed in the manner that formation of a resonance vibration is prevented. This method prevents self resonant excitation in the area of the stroke with changing effective chain length and for different loads.

To simulate a damped kinetic model of the electric motor is controlled by an electronic damper.

In a preferred embodiment it is provided that the electronic damper as a first input quantity, a target rotational speed of the sprocket and a second input quantity, an actual angle of the sprocket are supplied and in the electronic damper from the two input variables, a damping control variable is calculated in the form of a Subdued speed is passed to the electric motor.

Preferably, a damping force in the electronic damper, which is proportional to the velocity fluctuation amplitude of the load and is calculated from the sensed actual angle, is calculated as the damping control variable.

The method monitors itself in an advantageous manner in which the effect of an uplifting resonance oscillation is detected by sensors and, if necessary, the damping control variable is changed.

The driving of the electric motor can be simplified if a constant load of the chain hoist is to be handled. Then, in a speed feedforward control, the chain speed is superimposed with a programmable speed pattern to avoid the formation of a resonant vibration of the link chain.

Also, in a chain hoist with a via a polygonal sprocket guided chain and with an electric motor acting on the sprocket, a reduction of the effects of the polygon effect achieved in that the electric motor is preceded by an electronic damper which causes a control of the electric motor in such a way that formation of a resonant vibration of the link chain is prevented.

Advantageously, a smooth running of the chain, a lower threshold load of the chain hoist and hardly occurring disturbing resonance effects are achieved by the electronic damper. The electronic damper can be adapted particularly advantageously to a change in the damping parameters.

It is particularly advantageous that the electronic damper as the first input variable is assigned a target rotational speed of the sprocket and the second input an actual angle of the sprocket. Preferably, a sensor in the form of a pulse generator for impulse-wise determination of the actual angle is arranged on the sprocket, of which at least one angle-synchronous pulse is generated per sprocket rotation. The instantaneous angular position is then determined by interpolation between two successive pulses.

The electronic damper is preferably designed as a pilot control member, which is part of an open loop. This solution is less expensive compared to a possible closed loop with a state controller.

In a preferred embodiment, an empirical optimization of the damping control variable is achieved in that at least sensor detects the effect of a building resonant vibration and, if necessary, the damping control variable is changed.

Figur 1

ein Blockschaltbild eines erfindungsgemäß ausgebildeten Kettenzug mit einem elektronischem Dämpfer und

Figur 2

ein Kraft-Zeit-Diagramm der polygonerregten Kettenschwingung eines Kettenzugs nach dem Stand der Technik und

Figur 3

ein Kraft-Zeit-Diagramm der polygonerregten Kettenschwingung eines erfindungsgemäßen Kettenzugs.

The invention will be described below with reference to a drawing. Show it:

FIG. 1

a block diagram of an inventively designed chain hoist with an electronic damper and

FIG. 2

a force-time diagram of the polygon excited chain vibration of a chain hoist according to the prior art and

FIG. 3

a force-time diagram of the polygon excited chain vibration of a chain hoist according to the invention.

1 shows a block diagram of a chain drive according to the invention in application for a chain hoist 1 for lifting and lowering of loads 6, of which schematically an electric motor 2, a connected to the output shaft, not shown, gearbox 3 and connected to its again not shown output shaft Sprocket 4 can be seen. The sprocket 4 is formed in a conventional manner as a pocket wheel with a polygonal circumference and with a non-uniform pitch for receiving the relatively pivotable chain links of the link chain 5. According to the non-uniform pitch of the sprocket 4, the chain 5 is guided with its chain links in the manner to the sprocket 4, that the individual members alternately standing behind one another and lying with the sprocket 4 engage. The link chain 5 is designed as a round steel chain and is used in a conventional manner as a support member for the load to be lifted or lowered 6, which depends on the lower end of the chain 5.

The chain 5 which is suspended freely as a supporting element is not guided mechanically and is almost undamped with respect to lateral deflections. The effective length of the chain 5 varies depending on the vertical position of the load 6. Also, in operation, the load 6 to be handled by the chain hoist 1 may change. The natural frequency of the chain hoist 1 is a function of the spring constant of the chain 5, in which also the variable effective length of the chain 5 is received, and the mass of load 6 and chain 5. By the variable masses of the loads 6 and the changing effective lengths of the chain With the change of the mass and the effective length of the chain 5, the natural frequencies of the chain hoist and the position of the resonance points along the chain 5 change. The chain hoist 1 thus represents an oscillatory structure with pronounced Resonance points. The associated mechanical model corresponds to an undamped oscillator.

It is known that excitation of a chain hoist 1 in the range of its natural frequencies leads to resonance effects. Such resonance effects have the undesirable consequence that, starting from the low damping of the chain 5, there are considerable predominantly lateral deflections of the chain 5.

The exciter frequencies that are suitable for the excitation of the chain hoist 1 result from the geometry and the speed of the sprocket 4. Since, as described above, the sprocket 4 has a non-uniform pitch, at least two excitation frequencies are generated by the relative to the axis of rotation the sprocket 4 different geometrically arranged engagement points for the vertical and horizontal links of the chain 5 are conditional. These two excitation frequencies are superimposed additively.

The associated path fluctuation amplitude y _pol is: $$y_{\mathrm{pole}}={\mathrm{<figure-callout\; id="1"\; label="s"\; filenames="imgf0001.png"\; state="\{\{state\}\}">s</figure-callout>}}_1\sin \left(\mathrm{e}{\mathrm{\Psi }}_{\mathrm{wheel}}\right)+{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="imgf0001.png"\; state="\{\{state\}\}">s</figure-callout>}}_2\sin \left(2\mathrm{e}{\mathrm{\Psi }}_{\mathrm{wheel}}\right)$$

e

Anzahl der Ecken des Kettenrades

s₁

Fourier-Koeffizient

s₂

Fourier-Koeffizient

Ψ_rad

Ist-Winkel im Bogenmaß

Where:

e

Number of corners of the sprocket

s ₁

Fourier coefficient

s ₂

Fourier coefficient

Ψ _rad

Actual angle in radians

The associated velocity fluctuation amplitude ẏ _pol is: $${\dot{y}}_{\mathrm{pole}}={\dot{\psi }}_{\mathrm{wheel}}\left[\mathrm{e}{\mathrm{s}}_1\cos \left(\mathrm{e}{\mathrm{\Psi }}_{\mathrm{wheel}}\right)+2\mathrm{e}{\mathrm{s}}_2\cos \left(2\mathrm{e}{\mathrm{\Psi }}_{\mathrm{wheel}}\right)\right]$$

In addition to the vertical speed fluctuations of the unguided link chain 5, horizontal speed fluctuations also occur on a smaller scale. In the case of link chains, on the other hand, only one exciter frequency is generated by the uniform sprocket 4. These excitation frequencies cause the chain drive 1 at least two positions of the usable stroke of the chain 5 gets into the unwanted self-resonance. When driving through the resonance points along the stroke of the load 6, the load 6 gets into violent vibrations. The oscillation amplitude of the speed variation of the chain 5 and the resulting chain force fluctuation is many times greater than the caused by the polygon effect speed and chain force variations. In contrast to the oscillations caused by the natural resonance, the polygon effect hardly leads to a disturbance of the operation of the chain hoist 1.

The non-uniform pitch of the sprocket 4 causes the well-known as a polygon effect variation of the running speed of the chain 5 of the sprocket 4, which also leads to a rough running of the chain hoist 1, but are lower compared to the above-described resonance effects

Based on the knowledge that in the system considered in kinetic terms of the chain hoist 1 virtually no damping, the present invention is based on the core idea to realize this lack of damping electronically. For this purpose, the electric motor 2, which is supplied with power via a power output stage 7, is preceded by an electronic damper 8. The task of the electronic damper 8 is to control or regulate the electric motor 2 via the power output stage 7 in such a way that the polygon effect caused by the chain 5 running over the sprocket 4 is changed to such an extent that the excitation of the natural resonances in the region of the Stroke with changing effective chain length and for different loads is prevented. A smooth run of the chain 5 and thus the load 6 is the direct result.

A suitable control variable for the electronic damper 8 can be determined on the basis of the following kinetic principles.

The equation of motion for the virtually undamped chain hoist 1 is: $$\mathrm{m}{\ddot{\mathrm{y}}}_{\mathrm{m}}+\mathrm{k}{\mathrm{y}}_{\mathrm{m}}=\mathrm{k}{\mathrm{y}}_{\mathrm{pole}}$$

m

Masse der Kette 5 und der Last 6

k

Federkonstante der Kette 5

y_m

Wegschwankungsamplitude bezogen auf die Masse m

Where:

m

Mass of the chain 5 and the load 6

k

Spring constant of the chain 5

y _m

Path fluctuation amplitude with respect to the mass m

Compared to a desired for the operation of a chain hoist 1 dampened system lacks the usual in muted systems Term c ẏ _m . In the present invention, this term is realized by the electronic damping force F _D. The required damping force F _D is determined in the electronic damper 8 via a continuous sensory detection of the respective current angular position ψ _rad from the Wegschwankungsamplitude y _pol .

The equation of motion for the damped with the electronic damper 8 chain 1 is: $$\mathrm{m}{\ddot{\mathrm{y}}}_{\mathrm{m}}+\mathrm{k}{\mathrm{y}}_{\mathrm{m}}=\mathrm{k}{\mathrm{y}}_{\mathrm{pole}}+{\mathrm{F}}_{\mathrm{D}}$$

m

Masse der Kette 5 und der Last 6

k

Federkonstante der Kette 5

y_m

Wegschwankungsamplitude bezogen auf die Masse m

Where:

m

Mass of the chain 5 and the load 6

k

Spring constant of the chain 5

y _m

Path fluctuation amplitude with respect to the mass m

From the solution of the differential equation _m , the velocity fluctuation amplitude ẏ _m relative to the mass m can be determined: $${\dot{y}}_{\mathrm{m}}={\dot{\psi }}_{\mathrm{k}}\left[{\mathrm{V}}_1\mathrm{e}{\mathrm{s}}_1\cos \left(\mathrm{e}{\mathrm{\Psi }}_{\mathrm{wheel}}-{\mathrm{\phi }}_1\right)+{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="imgf0001.png"\; state="\{\{state\}\}">V</figure-callout>}}_{2}2\mathrm{e}{\mathrm{s}}_2\cos \left(2\mathrm{e}{\mathrm{\Psi }}_{\mathrm{wheel}}-{\phi }_2\right)\right]$$

und $$\varphi =\frac{2D\eta }{1-{\eta }^2}$$

mit D als Dämpfungsmaß nach Lehr und η als Frequenzverhältnis.Where: $$V=\sqrt{\frac{1}{{\left(1-{\eta }^2\right)}^2+4{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="imgf0001.png"\; state="\{\{state\}\}">D</figure-callout>}}^2{\eta }^2}}$$

and $$\phi =\frac{2D\eta }{1-{\mathrm{<figure-callout\; id="2"\; label="\eta "\; filenames="imgf0001.png"\; state="\{\{state\}\}">\eta </figure-callout>}}^2}$$

with D as attenuation measure according to Lehr and η as frequency ratio.

From a comparison of the equation of the velocity amplitude ẏ _pol in the region of the sprocket 4 with the equation for the velocity amplitude ẏ _m in the region of the mass m, it follows that the damping control variable is amplified by V ₁ , V ₂ and by φ ₁ , φ _{2 out of} phase Correction signal is. The variables V ₁ , V ₂ and φ ₁ , φ ₂ are determined by solving the differential equation. The variables V ₁ , V ₂ and φ ₁ , φ ₂ can be easily changed and thereby an adaptation for the consideration of dead times, which are caused by inertias or play in the chain drive, easily possible. Thus, a simple optimization of the electronic damper 8 to perform the actual state of the chain drive 1.

A suboptimal adjustment of the damping control variable means that the resonance vibration is not sufficiently damped, in the worst case even fanned.

The so determined damping control magnitude is supplied to the electric damper and causes the polygonal effect counteracting swelling speed change of the sprocket 4. For this purpose, the electronic damper 8 is supplied with the target speed n _target as the first input variable. As a further input serves the actual angle ψ _{wheel of} the sprocket 4, which is tapped in the present embodiment on the sprocket 4 or optionally on the electric motor 2 or the transmission 3 via a sensor in the form of a pulse generator 9. The pulse generator 9 may be optical, magnetic or inductive, of which at least one angle-synchronous pulse is generated per revolution of the sprocket 4. The instantaneous angular position ψ _rad is then determined by interpolation between 2 consecutive pulses. In principle, it is also possible to determine the polygon effect via other variables which are preferably easier to detect, such as, for example, the current of the motor 2, the chain speed or the chain force.

The electronic damper 8 is formed in the present embodiment as a pilot control element, in which the second input variable of the actual angle Ψ _rad over a mathematical function y _m (Ψ _rad ) higher order in a correction value for the first input variable, the target speed n _{Soll is} converted and in the summation point with the target speed n _{Soll is} superimposed. As an output, the electronic damper 8 thus again delivers a desired value n * _desired as an input variable for the power output stage 7.

In principle, it would also be possible to design the electronic damper 8 as a state controller and thus to form a closed control loop in contrast to the control loop with the above-described pilot control element.

In addition, an optimization of the damping control variable by returning the motor current, the chain speed or the chain force in the electronic damper 8 is achieved. These measurable variables experience a corresponding, superimposed oscillation due to an incipient resonance oscillation, which inferences that there is still a resonance oscillation or allow residual resonance oscillation. On this basis, the damping control variable ẏ _m in the electronic damper 8 can then be optimized.

In a simplified embodiment of the electronic damper 8, the chain speed can simply be modulated so that the critical frequency excitation is prevented by the change in speed. It is thus counteracted targeted setting of an excitation of the chain hoist 1 by the exciter frequency is changed continuously. It is also possible in the case of a constant load 6 by means of a speed feedforward path-dependent to superimpose the chain speed with a programmable speed pattern so that thus resonance vibrations are prevented.

Also, the resonance points can be determined by the above-described feedback of the motor current, the chain speed or the chain force in the electronic damper 8 or speed-dependent with known load 6 from the system sizes of the chain drive 1 determinable, so that a position detection on the chain drive is sufficient to approximate to determine a resonance point.

FIG. 2 shows a force-time diagram of the polygon-excited chain oscillation of a chain hoist according to the prior art. In comparison, a force-time diagram of the polygon-excited chain oscillation of a chain hoist according to the invention is shown in FIG. It can be seen that over the time shown in the x-axis from 0 to about 11 seconds, in which a trial load lifting operation is carried out, the fluctuation width of the y-axis applied chain force amplitude of up to about ± 700N by the present invention electronic damper 8 can be reduced to about ± 70N. As a result, a smooth running of the chain and a lower threshold load of the chain hoist is achieved.

LIST OF REFERENCE NUMBERS

1

chain

2

electric motor

3

transmission

4

Sprocket

5

link chain

6

load

7

Power output stage

8th

electronic damper

9

pulse

Ψ _rad

Actual angle

n _target

Target speed

n * _Soll

Damping control variable

Claims (11)

1. Method of stabilising the running of a link articulated chain of a chain hoist, in particular in order to prevent the formation of a resonant vibration of the link chain, in which a link chain is guided over a polygonal chain wheel with irregular pitch which is driven by an electric motor, characterised in that a periodic and/or stochastic as well as damping control variable is superimposed on the speed of the chain wheel (4) and the damping control variable produces a change in the chain speed in such a way that formation of a resonant vibration is prevented.
2. Method as claimed in Claim 1, characterised in that the electric motor (2) is controlled by an electronic damper (8).
3. Method as claimed in Claim 2, characterised in that a desired rotational speed (n_Soll) of the chain wheel (5) is supplied to the electronic damper (8) as a first input variable and an actual angle (Ψ_rad) of the chain wheel (5) is supplied as a second input variable, and the damping control variable is calculated in the electronic damper (8) from the two input variables and is transferred to the electric motor (2) in the form of a damped rotational speed (n*_Soll).
4. Method as claimed in any one of Claims 1 to 3, characterised in that a damping force (F_D) is calculated as the damping control variable in the electronic damper (8), is proportional to the amplitude of speed fluctuation (ẏ _m) of the load (6) and is calculated from the sensor-detected actual angle (Ψ_rad).
5. Method as claimed in any one of Claims 1 to 4, characterised in that the effect of a resonant vibration building up is detected by sensor means and if required the damping control variable is changed.
6. Method as claimed in any one of claims 1 to 5, characterised in that in the case of a constant load to be lifted and/or lowered, by means of a speed pilot control a programmable speed pattern is superimposed on the chain speed as a function of distance in order to prevent the formation of a resonant vibration of the link chain (5).
7. Chain hoist with a chain guided over a polygonal chain wheel and with an electric motor acting on the chain wheel with irregular pitch, in particular for carrying out the method as claimed in any one of Claims 1 to 6, characterised in that an electronic damper (8) is connected in front of the electric motor (2) and effects control of the electric motor (2) in such a way that formation of a resonant vibration of the link chain (5) is prevented
8. Chain hoist as claimed in Claim 7, characterised in that a desired rotational speed (n_Soll) of the chain wheel (4) as a first input variable and an actual angle (Ψ_rad) of the chain wheel (4) as a second input variable are provided to the electronic damper (8).
9. Chain hoist as claimed in any one of Claims 7 or 8, characterised in that a sensor in the form of a pulse generator (9) is disposed on the chain wheel (4) for determination of the actual angle (Ψ_rad) in pulsed form.
10. Chain hoist as claimed in any one of Claims 7 to 9, characterised in that the electronic damper is constructed as a pilot control element.
11. Chain hoist as claimed in any one of Claims 7 to 10, characterised in that at least one sensor detects the effect of a resonant vibration building up and if required the damping control variable is changed.

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