EP1607186A1 - Electro-pneumatic hammer drill / chisel hammer with modifiable impact energy - Google Patents

Abstract

The hammer has a sensor device (10, 11) which captures a parameter correlated to the individual impact energy transferred to the substrate being broken down. A regulator (9) compares this parameter with an ideal value and generates a setting value. An actuator (7) impinged by the setting value tracks the individual impact energy to the ideal value. The sensor device can detect the momentary position and/or speed of the piston (4) in the forward direction to the impact tool and in the reverse direction whereby the kinetic energy difference is determined in a micro controller from the differential speed as a measure for the individual impact energy.

Description

The invention relates to a rotary and / or chisel hammer with electropneumatic Schlagwerk, whose impact energy is changeable.

Known are three basic ways to the impact energy of electropneumatic To set impact mechanisms for mining equipment of the type mentioned.

(a) Speed setting

A first possibility is the impact energy of the percussion over the Set the speed of the drive motor. This is the case with combi-hammers, for example in chisel mode increases the engine speed to in this mode a to be able to pull maximum power out of the mining equipment. In hammer drill mode In contrast, the power of the engine is divided into about two equal shares.

Half of the torque of the motor for the rotary drive on the one hand and for the percussion on the other hand used. In chisel mode, the rotary drive not needed, so that the rotary drive power additionally fed to the hammer mechanism can be. For this purpose, the speed is increased, so that the pressure peaks and thus the kinetic energy of, for example, one acting on a percussion piston Air piston is increased. The result is a higher single impact energy. in principle it is also known, the speed and thus the impact performance by active Reduce switching of the device user to realize a Feinschlag.

(b) Changeable air openings in the impact mechanism

Another way to change the impact energy is in the Air piston acting upon pneumatic spring of the electro-pneumatic impact mechanism defined leakage or a defined air exchange with a closed produce larger external volume. This usually happens by enlarging or Reduction of defined snort openings. One achieves thereby with constant Working frequency a reduction in impact energy. Thus, DE 34 23 493 recommends C2 for adjusting the impact energy of rotary hammers that on the flying mass acting impact pads by switching on / off of the circumference of a guide cylinder for the flying and percussion piston in a plane perpendicular to the cylinder axis Manually change distributed equalization holes using a control knob. Another possibility is described in DE 39 23 134 A1, in which for a pneumatic Schlagwerk proposed the way of the flying piston by setting to change the length of action of an acting on this air spring. To the guide cylinder in the region of the air spring openings, which through a axially displaceable, provided with openings sleeve, which at the same time as a spring-loaded Support for the percussion piston (striker) is used, are changeable. By a knob allows the breakthroughs more or less on the openings Align to adjust the impact strength.

(c) Changing the connecting rod stroke of a compression piston

The third possibility is the stroke of the connecting rod of the compression piston for the air spring acting on the air piston via a cycloidal or planetary gear to adjust (see EP 0 063 725 A2). At reduced stroke of the connecting rod is the air piston accelerates less strongly. This leads to a lower one Impact energy. The adjustment of the Pleuelhubs takes place mechanically by a from the Device user to be operated control handle.

These three basically known ways to change the Impact energy have the following limitations or disadvantages:

With option (a) (speed setting), the impact energy is at the beat frequency coupled. A change in the impact energy always brings a change the beat frequency. At the highest frequencies one achieves the highest impact energy. For many applications, however, this is exactly the wrong one Direction. For a good degradation efficiency with high life of the tools needed high frequency at low impact energies and vice versa, to achieve optimal degradation performance

The possibilities (b) (changeable air openings in the impact mechanism) and (c) (change of the Pleuelhubs) Although allow a partial decoupling of impact energy and beat frequency. In the method (b) can, however, usually only select or set two beat energies. By a sliding sleeve individual snaps open or closed. The method (c) is mechanically relatively complex.

All three possibilities known in the prior art have in common that the Impact energy of the percussion is adjusted only and after changing the Setting with a certain spread to an operating value. This Operating value, however, is not only the temperature and the respective lubrication state depending on the percussion mechanism, but also strongly on its age. ever If the gaskets become leaky in the percussion mechanism, the single impact energy decreases. The higher the temperature, the higher the single impact energy becomes.

The invention is therefore based on the object, an electropneumatic impact mechanism for rotary hammers whose single impact energy is in choose a wide frequency range independent of the beat frequency, regulate or can be adjusted so as to achieve an optimal degradation for each substrate.

This task is performed on a rotary / chisel hammer with electropneumatic Schlagwerk solved in that to change the impact energy according to the invention a sensor device which correlates the single impact energy or a thereto Size recorded and a control device are present, in which the single impact energy corresponding size compared to a target value and a Control value is generated, which is an adjusting device for tracking the single impact energy acted upon the setpoint.

The electropneumatic hammer mechanism preferably comprises in a guide tube or guide cylinder via a motor-driven connecting rod by a compressor piston, also called exciter piston, compressed air shock pad, here referred to as "air spring", which is a displaceable flying piston acted upon, and at the output side end of the guide tube through this guided percussion piston or striker, the z. B. via an air pressure cushion ("Pressure pad" below) or directly on a percussion tool acts.

The sensor device and the regulation of the single impact energy and the Adjusting device for tracking the single impact energy can - as in dependent Claims defined and explained in more detail below - in different Implementation variants be realized.

The inventive control is an exact compliance with a desired single impact energy regardless of the temperature or the respective Condition of the percussion enabled. The single impact energy can in one wide frequency range, regardless of the beat frequency chosen become. Thus, for example, for the processing of tiles a low Select impact energy at high beat frequency of, for example, 100 Hz while you often use the maximum for chiselling or hammering concrete Impact energy at a relatively low impact frequency of, for example, 30 to 60 Hz wishes.

The defined in claim 1 invention thus relates to a electro-pneumatic rotary or chisel hammer with electronic single-stroke control, where the single impact energy or (a) correlated to the single impact energy Size (s) detected by a sensor, in a digital or analogue control be processed and compared with a target size to a manipulated variable for to generate an actuator that controls the single impact energy to the setpoint. Preferably, the controller is a PI controller.

The dependent claims define advantageous embodiments of the Invention.

The sensor may be, for example, a speed sensor, which the Speed of the flying piston detected in the forward and reverse direction. To For this purpose, for example, the flying piston with circumferential grooves or contrasting, be provided axially successive rings whose temporal Sequence when passing the piston by a on or in the guide tube held Hall sensor, in particular a differential Hall sensor or also an optical sensor can be detected. The difference of the kinetic energy in forward and return flight of the flying piston is a measure of the single impact energy.

Another advantageous way to determine the single impact energy exists in the use of a magneto-elastic sensor, the shock wave in the striker or in the Flying piston detected by the magneto-elastic effect.

It is advantageous for tracking the single impact energy, the beat frequency, d. H. the engine speed, to provide as the output of the controller. Another possibility the single impact energy control consists in fixed and in one of Practice corresponding operating range freely selectable beat frequency by a controllable valve to change the pressure or a leakage of the air spring or to regulate. This valve can be an electromagnetically or piezoelectrically actuated Be a valve. In chisel hammers or rotary hammers, in which the rotational movement that is not transmitted directly through the guide tube Valve attached directly to or in the guide tube to the dead volume to keep small. In rotary hammers on the other hand, in which the rotary drive over the guide tube takes place, is a rotatory decoupling between the guide tube and the surrounding housing necessary. This can z. B. a sealed Sleeve around rotationally or axially adjustable air outlet openings in the guide tube be provided.

Fig. 1

die schematische Darstellung eines Bohr-/Meisselhammers, dessen elektropneumatisches Schlagwerk erfindungsgemäß geregelt ist;

Fig. 2

eine Funktions-Blockbilddarstellung zur Veranschaulichung der erfindungsgemäßen Regelung der Einzelschlagenergie über unterschiedliche Ventilsteuerungen;

Fig. 3

eine Funktionsbilddarstellung für die Einzelschlag-Energieregelung über Ventile;

Fig. 4

eine Ausführungsvariante der Erfindung, bei der die Flugkolbengeschwindigkeit mittels zweier durch Permanentmagneten vorgespannter digitaler Hall-Schalter oder differenzieller Hall-Sensoren bestimmt wird;

Fig. 5

zwei zeitkorrelierte Signaldiagramme zur Veranschaulichung der Bestimmung der Flugkolbengeschwindigkeit aus den Sensorsignalen zweier digitaler Hall-Schalter;

Fig. 6

die zeitkorrelierte Darstellung der Signale zweier differenzieller Hall-Sensoren zur Messung der Fluggeschwindigkeit (oben), den Signalverlauf nach Durchlaufen einer Komparatorschaltung mit Schwelle (Mitte) und des Signalverlaufs am Ausgang einer nachgeschalteten Flip-Flop-Triggerschaltung (unten);

Fig. 7

die schematische Darstellung eines elektropneumatischen Schlagwerks, bei dem die Position und Geschwindigkeit eines Flugkolbens mittels eines Hall-Arrays bestimmt werden;

Fig. 8

mit Teilfiguren 8A und 8B die schematische Darstellung eines elektropneumatischen Schlagwerks, bei dem die Flugkolbengeschwindigkeit nach dem Prinzip der Induktion bestimmt wird;

Fig. 9

die schematische Darstellung eines elektropneumatischen Schlagwerks, bei dem die Flugkolbenposition mittels eines LVD-Transformators bestimmt wird;

Fig. 10

die schematische Darstellung eines elektropneumatischen Schlagwerks, bei dem die Flugkolbenposition und die -geschwindigkeit mittels eines Abstandssensors bestimmt werden, der senkrecht zur Bewegungsrichtung des Flugkolbens angebracht ist;

Fig. 11

eine Funktions-Block-Übersichtdarstellung zur Veranschaulichung der Variation der Einzelschlagenergie eines elektropneumatischen Schlagwerks über eine Drehzahlregelung;

Fig. 12

eine der Übersichtdarstellung nach Fig. 10 entsprechende Blockschaltbild-Anordnung zur Änderung der Einzelschlagenergie eines elektropneumatischen Schlagwerks über eine Drehzahlregelung;

Fig. 13

eine Blockschaltbild-Anordnung für eine Schlagenergieregelung eines elektropnematischen Schlagwerks über eine veränderbare Leckage, wobei sich ein Drehzahlregler und ein Energieregler gegenseitig beeinflussen (können);

Fig. 14

eine Detailansicht einer veränderbaren Leckagebohrung im Führungsrohr eines elektropneumatischen Schlagwerks, das entsprechend der Anordnung von Fig. 12 geregelt wird;

Fig. 15

eine abgewandelte Ausführungsvariante eines elektropneumatischen Schlagwerks, bei dem die Einzelschlagenergie bei konstanter Schlagfrequenz über eine veränderbare Leckage am Schlagwerk durch tangentiale (rotatorische) Verschiebung einer Hülse bewirkt wird;

Fig. 16

die Prinzipdarstellung eines elektropneumatischen Schlagwerks, bei dem die Einzelschlagenergie durch Messung einer Stoßwelle in einem Döpper mittels des magneto-elastischen Effekts (ME-Effekt) erfolgt; und

Fig. 17

eine vereinfachte Signalpfadanordnung zur Berechnung der Einzelschlagenergie E_S aus dem bei Messung der Stoßwelle im Döpper nach Fig. 15 erhaltenen Sensorsignal.

The invention and advantageous embodiments and additions are explained below with reference to the drawings. Show it:

Fig. 1

the schematic representation of a drill / chisel hammer whose electropneumatic impact mechanism is regulated according to the invention;

Fig. 2

a functional block diagram illustrating the regulation of the single impact energy according to the invention via different valve controls;

Fig. 3

a functional image representation of the single-stroke energy regulation via valves;

Fig. 4

an embodiment of the invention, in which the flying piston velocity is determined by means of two biased by permanent magnets digital Hall switch or differential Hall sensors;

Fig. 5

two time-correlated signal diagrams for illustrating the determination of the air piston velocity from the sensor signals of two digital Hall switches;

Fig. 6

the time-correlated representation of the signals of two differential Hall sensors for measuring the airspeed (above), the waveform after passing through a comparator circuit with threshold (center) and the waveform at the output of a downstream flip-flop trigger circuit (bottom);

Fig. 7

the schematic representation of an electro-pneumatic percussion, in which the position and speed of a flying piston are determined by means of a Hall array;

Fig. 8

with sub-figures 8A and 8B, the schematic representation of an electro-pneumatic percussion, in which the air piston velocity is determined according to the principle of induction;

Fig. 9

the schematic representation of an electro-pneumatic percussion, in which the flying-piston position is determined by means of an LVD transformer;

Fig. 10

the schematic representation of an electro-pneumatic percussion, in which the flying-piston position and -speed are determined by means of a distance sensor which is mounted perpendicular to the direction of movement of the flying piston;

Fig. 11

a functional block overview representation to illustrate the variation of the single impact energy of an electro-pneumatic impact mechanism via a speed control;

Fig. 12

a block diagram arrangement corresponding to the overview representation of Figure 10 for changing the single impact energy of an electropneumatic impact mechanism via a speed control.

Fig. 13

a block diagram arrangement for Schliegergieregelung an electropnematic percussion via a variable leakage, with a speed controller and a power controller mutually influence (can);

Fig. 14

a detailed view of a variable leakage bore in the guide tube of an electro-pneumatic percussion mechanism, which is controlled according to the arrangement of Figure 12;

Fig. 15

a modified embodiment of an electropneumatic percussion mechanism, in which the single impact energy is effected at a constant impact frequency via a variable leakage on percussion by tangential (rotational) displacement of a sleeve;

Fig. 16

the schematic diagram of an electro-pneumatic impact mechanism, in which the single impact energy is measured by measuring a shock wave in an anvil by means of the magneto-elastic effect (ME effect); and

Fig. 17

a simplified signal path arrangement for calculating the single impact energy E _S from the obtained when measuring the shock wave in the striker of FIG. 15 sensor signal.

The schematic representation of Fig. 1 illustrates an electropneumatic Drill and / or chisel hammer 1, on the opposite of a drive and handle area protruding tool-side end of a tool holder 6 (without inserted Tool shown) is present. Laterally on the outside of only in outline shown device housing 7 is a user to be actuated Mode selector switch 2, via which the hammer drill operation on the one hand or the Chisel operation on the other hand, and optionally other operating modes such as Feinmeisseln and Schweebeleisseln are preselected. The selection position of the selector switch 2 is a usually realized in a microcontroller 9 electronic Control and regulation communicated when pressing a manual push button 12 switched by an ON / OFF switch 13 in standby mode or from a symbolized only as a connecting cable 14 power supply is disconnected. The term "microcontroller" includes both a fully integrated digital or hybrid, e.g. B. as ASIC realized circuit as well as the alternative a built in discrete components circuit arrangement. One in his Structure principle known electropneumatic impact mechanism 15 is in the front Part of the device housing 7 installed. This percussion includes one in one only indicated guide tube 16 in the rear region guided exciter pistons 3, via a connecting rod drive 17 when selecting the chisel forward, d. H. in the direction of the tool holder 6, and is driven backwards. One with a plurality of axially spaced regions of different magnetic permeability, in particular with axially successive equally spaced circumferential grooves 10 (of which only two are shown) provided with the free piston 4 is Feed of the excitation piston 3 at the back by an air-shock pad (air spring) 20th acted upon, which in turn acts on a striker 5 via a pressure pad 21, the above the tool holder 6, for example, a chisel (not shown) drives.

According to the invention, in the embodiment shown in Fig. 1, the single impact energy of the electro-pneumatic percussion over a through a Actuator, z. B. a motorized leakage 18 from the microcontroller (microprocessor) 9 regulated to change the pressure in the air spring 20. These changeable leakage 18 may be due to one or more radial openings, so-called Schnauflöcher 19, on the guide tube 16 in the region of the air spring 20th be realized, by one of an actuator 31, for example a Stepper motor, rotatable punching sleeve 32 can be varied with one of the number the Schanuflöscher 19 corresponding number of oblique windows 33 is provided. To determine the actual kinetic energy of a single beat, measures a sensor 11, for example a differential Hall sensor, the speed of the flying lance 4 by scanning the passage of the circumferential grooves 10 in the forward direction and so in the recoil in the reverse direction. The differential speed is a measure of the energy transferred to the striker 5 of a single strike. This speed difference signal is fed to the microcontroller 9, the value of the calculated single impact energy as PI control against an energy setpoint value and a control value signal to the actuator 31 supplies, which rotates the hole sleeve 32 accordingly and thereby the or on Circumference of the guide tube 16 formed puff holes 19 releases or closes, So a leakage at the air-shock pad 20 varies.

The functional block diagram representation of FIG. 2 illustrates the different possibilities for default values of the single impact energy, speed, etc., for the PI controller 34 in the microcontroller 9, which influences, for example, the actuator 31 as an actuator and thus the air spring 20 in the impact mechanism 15. The mode selector 2 can - as mentioned - set basic operating instructions, such as hammer drilling, chiselling, Feinmeisseln, Schwebeleisseln, which together with the values of a setpoint generator 25 and optionally with signals from other input sources 26 for speed, current and voltage the default value E _{should determine} for the single impact energy.

The sensor device 11 supplies to the controller 34 in the microcontroller 9 an actual value of the differential speed, from which the actual value of the kinetic energy E _{kin of} a single stroke is determined, which is against the default value E _{should be} compared. The controller 34 supplies a control value G (s) to the valve device 35, which can be realized as a pressure reducing valve or as a passage control valve.

With the control arrangement according to FIG. 3, pressure peaks can be achieved by means of the pressure reducing valve restrict. Any excess pressure will be in the front Pressure pad 21 diverted, creating an additional damping of the flying piston. 4 is reached. The air piston 4 accelerating force then results from the Difference between the pressures at the two ends of the free piston issue. About the pressure reducing valve, the pressure peaks between the exciter piston 3 and the flying piston 4 reduced. The excess pressure is used to increase the static pressure in the front pressure pad 21. In doing so may However, the pressure peaks are only reduced to the extent that it is guaranteed that the excitation piston 3 and the flying piston 4 do not touch. The pressure peaks arise from the impulse that is necessary to the direction of movement of the Fly piston 4, as well as the rigidity of the overall system. Unless the Valve device 35 is realized as a passage control valve, the latter is more advantageous connected to an outer chamber.

In the context of the invention and for the determination of the single impact energy comes at preferred embodiments of the invention, the measurement of the air piston velocity an important meaning too. Tried and tested in experimental setups are presented below.

An incremental magnetic measuring method has already been described in DE 102 19 950 C1. By attaching the circumferential grooves 10 on the lateral surface of the cylindrical Flying piston 4, the magnetic field of a permanent magnet is periodic modulated. This magnetic flux modulation can be achieved by a semiconductor magnetic field sensor be measured. The period of this oscillation thus measured is a measure of the speed of the flying piston 4.

If Δx denotes the mutual axial distance (structure width or period) of the circumferential grooves 10, then the flying-piston velocity v is calculated according to: v = Ax .delta.t = f · Δx

During the forward movement of the flying piston 4 in the direction of the anvil 5, an oscillation frequency approximately three times higher is measured, depending on the number of impacts k, than in the case of the backward movement. Assuming the flying piston velocity amounts to about 10 m / s in the forward movement and the period of the circumferential grooves 10 amounts to 3 mm, the result is a period of 300 μs or a frequency of about 3 kHz. This frequency can be easily measured, for example, via the counter input of the microcontroller 9. For this purpose, for example, only the positive signal component is formed via a diode and then converted via a comparator into a square-wave signal and fed directly into the counter input of the microcontroller 9. From the thus sampled frequencies or pulse widths, the single impact energy E _s can be calculated as follows: e S = m FK 2 · (V 2 in front -v 2 reset )

In it m _FK denotes the mass of the flying piston. The ratio of the return flight _velocity v _back to the forward _velocity v _{before is} called the collision number k. It indicates how much impulse has been absorbed by the processed surface and therefore also says something about the nature of the ground. k = v reset v in front ≈ 0.1 ... 0.3

An embodiment for measuring the time of flight or flying piston velocity The principle representation is illustrated by means of Hall switches and an XOR circuit 4, to which the signal waveform representation of FIG. 5 belongs.

The air piston velocity is biased by means of two with permanent magnets digital Hall switch 11a and 11b in the sensor 11, d. H. a kind of "magnetic Photocell "measured.

A Hall switch is a Hall element whose output is set to logical 1 (or analog at logical 0) as soon as the local field strength exceeds a certain minimum threshold. If you clamp such a Hall switch with a permanent magnet before and sets the threshold accordingly, z. B. at a programmable Hall switch, so this reacts with a logical 1, once a ferromagnetic Body is brought in the vicinity of this sensor, in the case of the invention of the flying pistons 4th

The digital Hall switches 11a and 11b are arranged at a defined distance .DELTA.s from each other in the front half of the percussion mechanism on the guide tube 16 so that the flying lance 4 in the foremost position of the working position, ie at the time of impact on the backwardly pressed striker. 5 , both Hall switches 11a, 11b covered so that both switch through. With this arrangement of the sensor 11, the flying piston velocity can be determined simply by first guiding both sensor outputs to an XOR gate whose output acts on the counter input of the microcontroller 9. This measures the pulse width of the two rectangular pulses, which are denoted by t ₁ and t ₂ ; see. Fig. 5.

From these two times t ₁ and t _2, the aviation piston speeds in forward and reverse flight leave on every shot calculated as follows: v in front = .DELTA.s t 1 v reset = .DELTA.s t 2

A variant provides the measurement of the air piston velocity by means of differential Hall sensors. The simplest construction consists of two identical Hall elements, approximately as illustrated in FIG. 4 by references 11a and 11b, which stand next to each other at a small distance and whose outputs are fed to a differential amplifier. In this case, analog signals are measured, the course of which is qualitatively illustrated in FIG. 6 (top) for the Hall element 11a by the solid curve A and by the dashed curve B for the Hall element 11b. Each time the leading edge of the flying mass 4 passes by the Hall elements 11a, 11b, a flux change and thus a voltage signal is detected at the location of these sensors. This analog signal is converted by means of a comparator (not shown) with a threshold into a digital signal, the qualitative course of which is shown in the center of the diagram of FIG. This signal triggers a flip-flop. The first pulse sets the flip-flop, the second clears it again. As a result, rectangular pulses are generated whose width corresponds to the forward speed t ₁ and the return speed t _{2 of} the flying piston 4.

It should be noted that it is already sufficient in principle, only one to use differential sensor. The width of the peak of the analogue then obtained Signal is a measure of the time that the Aero-piston 4 needs to take this Sensor to move past and thus a measure of the airspeed.

A somewhat more sophisticated but advantageous method of operation reliability is the use of a Hall sensor array 70 consisting of 2 ⁿ digital Hall switches as illustrated in FIG. 7. This makes it possible to determine the position and the speed of the flying piston 4 over the length of the entire sensor. The determination of the air piston velocity corresponds to that already described. If, for the purpose of determining a position of the flying piston 4, the 2 ^n- Hall switches are converted by an n-fold multiplexer from a 2 ⁿ -times parallel signal directly into an n-bit serial signal, then this signal describes the instantaneous position of the flying piston 4.

Another way to measure the free piston velocity in the Figures 8A and 8B is based on the principle of induction. there the magnetic field of the guide tube 16 surrounding or arranged outside and a coil 93 coupled to the guide tube 16 via a yoke 94 modulated by the passing ferromagnetic flight piston 4 and thus induces a voltage in the coil 93. The flying mass 4 can be part of a magnetic Circle are understood, consisting of river guidance, if necessary Permanent magnet and coil winding. By the river change it comes to a Stress induction in the coil, especially if the edge of the Flying piston 4 past the coil. The amount of induced voltage as well the width of the voltage peak is a measure of the aircraft piston velocity. ever faster the air piston 4 passes, the higher the induced voltage and the shorter the voltage pulse.

A further embodiment variant of the invention for determining the single impact energy shown in FIG. 9 is based on a measurement according to the LVDT principle. In order to determine the exact position of the flying piston 4 or its velocity, a differential linear transformer 80 is used, a so-called LVDT (Linear Variable Differential Transformer) transformer, in which the flying mass 4 is a longitudinally displaceable magnetic core acts and thus the coupling between a field winding 81 and sensor windings 82a, 82b changed complementarily. Both the drive circuit for the field winding 81 and the sensor windings (not shown) for the sensor windings 82a, 82b supply an analog voltage signal that is proportional to the position of the magnetic core, here realized by the flying mass 4. It is important that the voltages in the sensor windings 82a, 82b are demodulated in synchronism with the excitation signal. At the same time the excitation voltage is measured as a reference. As a result, drift (amplitude, phase) are compensated away. The reader will find a detailed description of such a circuit in data sheets from manufacturers (eg Analog Devices, Philips) or at the Internet addresses
http://www.analog.com/Uploaded Files / Data_Sheets / 34397787AD698_b.pdf
http://www.analog.com/Uploaded Files / Data_Sheets / 82602395AD598_a.pdf
http://www.semiconductors.philips.com/acrobat/datasheets/NE552_SA5521_3.pdf

Another advantageous proven possibility for measuring the position and velocity of the flying piston 4 by means of a distance sensor 90 mounted perpendicular to its direction of movement is illustrated in FIG. To determine the impact energy, this solution is based on a travel measurement of the flying piston 4. For this purpose, the flying mass 4 between a rear annular seal 91, usually an O-ring or lip seal, and a front leading edge 92 is formed conically decreasing. With an eddy current sensor or Hall element as a distance sensor 90, which is mounted laterally on the guide tube 16, the distance to the over a substantial portion of its axial length conical lateral surface of the flying piston 4 is measured. If the distance sensor 90 delivers a distance-proportional signal in the case of an eddy-current sensor, for example, the flying-piston position x _FK (t) can be calculated from this signal. If the distance sensor 90 does not supply a distance-proportional signal, for example in the case of a Hall sensor, then the lateral surface of the flying piston 4 can be designed such that the non-linearity is compensated. In this case too, its position can be determined while the flying piston 4 passes by. By differentiation of the position value, it is thus also possible to measure the flying-piston velocity at the location of the distance sensor 90. The particular advantage of this embodiment is that the sign of the speed is maintained. For a simple separation of the signals during forward and backward movement of the flying piston 4 is possible.

The relationship between the measuring voltage of the Hall or eddy current sensor and the flying piston velocity can be represented as follows:

The measuring voltage U (t) is proportional to the position x (t) of the flying piston 4: u ( t ) = H [ x ( t )] = Δ H Δ s · x ( t ) = m · x ( t ) m = Δ h / Δ s : slope of the wedge or cone on the flying mass 4
u ( t ): measured voltage

The aircraft piston velocity results from the derivation of the measured sensor voltage u (t): ν FK ( t ) = ∂ ∂ t x ( t ) = 1 m · ∂ u ( t ) ∂ t

11 and 12 serve to explain the tracking of the single impact energy via a speed control 27. The explained with reference to FIGS. 1 to 10 assemblies are provided with the corresponding reference numerals and will not be described again. The determination of the instantaneous single impact energy E _S takes place, for example, according to Eq. (2). The manipulated variable G (s) generated by the controller 34 in the microcontroller 9 in relation to a default value E _{soll is} applied in this case to the speed control 27, which may likewise be implemented in the microcontroller 9. This specifies the rotational speed ω _red for a drive motor 41, which can be realized, for example, as a universal motor, SR motor or PLDC motor.

The set value G (s) for the setpoint speed ω _soll provided by the (energy) controller 34 can also be preset by actuation of a changeover switch 51 by means of a pontentiometer 52 which can be actuated via the manual pushbutton 12, if the electropneumatic drill / chisel hammer passes through the Users should be set individually for certain work processes. _To ω of the engine speed target value is ω in a comparator 53 against a tapped at the motor shaft, for example a tacho generator 54 actual rotation set value _is compared, and the difference Δω reaches the engine controller 50. These in FIGS. 11 and 12 shown simplest way of controlling the Impact energy is evidently via the regulation of the rotational speed of the drive motor 41. The single impact energy E depends roughly quadratically on the impact frequency f and thus on the engine speed ω _red . By determining the forward and backward speed of the flying mass 4, the instantaneous impact energy is measured and compared with the target value. The control difference is the input of the regulator 34 delivered via the sensor 11, also referred to as a beat energy regulator, symbolized by G (s) in FIG. 11: G (s) = Δω should AE

This controller 34 calculates the new setpoint ω _soll for the speed controller H (s), which may be in simple PI controllers with anti-windup. The following applies: H (s) = .DELTA.U Δω

ΔU denotes the effective voltage across the motor terminals. It is called Pass the setpoint to block PE (= Power Electronics). This block PE can for Universal motors a simple phase control by means of a triac But it can also be a more complex control for electronically commutated Engines such as brushless DC motors or switched reluctance motors.

Fig. 13 with the detail of Fig. 14 illustrate one in one Functional design studied variant of the invention for control the single impact energy, preferably at a constant beat frequency, over a controllable leakage in percussion 15 by axial displacement of a sleeve 36th This leakage is provided for example by two or four radial openings or bores 71 in the guide tube 16 in the region of the air spring 20. Wie 14 reveals the cross sections of the bores 71 behind, so in the direction of the exciter piston 3, gradually from. This can be added axial displacement of the sleeve 36 a continuous cross-sectional change realize the way of the sleeve 36. Fig. 13 illustrates a partial Cover of the holes 71.

In a modification of the control arrangement according to FIG. 12, the arrangement of FIG. 13 recognize that in this embodiment for Schlagenergieregelung the Speed controller H (s) in the motor control 50 and the (energy) controller G (s) in the Regulation 34 depend on each other and influence each other, so that a Parameter change is possible. The controller constants for the energy regulator hang from the operating point of the percussion and thus the beat frequency, so the Speed off. These parameters can be stored in the form of look-up tables and depending on the speed used. With heavy energy lowering (i.e. large leakage) the impact mechanism is sensitive to minor disturbances and Changes, and it is the more sensitive, the higher the beat rate. This is taken into account in the controller with adapted controller constants. Out For this reason, there is a bidirectional connection 55 between G (s) and H (s). An actuator 56, realized for example as a linear motor, linear stepping motor or Voice coil actuator, shifts the sleeve 36 in the axial direction to change the Leakage 18 via the bore 71 as specified by the energy regulator G (s).

Another way to control the single impact energy at a constant Impact frequency over a leak 18 on percussion 15, which in principle the reader is already known from the description of FIG. 1, FIG. 15. In this case, the perforated sleeve 32 is rotatable, wherein as an actuator 56 a Stepper motor, a torque motor, a DC motor with worm gear or a Helical gear 37 as shown in FIG. 1 in question. The rotatable hole sleeve 32nd has the mentioned in connection with Fig. 1 inclined window 33 (with bevelled Frame), resulting in a continuous cross-sectional change of as Schnauflöcher 19 serving holes 71 via the tangential Verdrehweg the Perforated sleeve 32 can be realized. In the position shown in Fig. 15 are the Quersschnitte the holes 71 partially open, which is a reduction of the single impact energy equivalent. When fully open holes 71 is the Schlagwerk deactivated.

Another advantageous variant for measuring the energy of a single beat and for Schlierenergieregelung will be described below with reference to Figs. 16 and 17.

The measuring principle for the determination of the single impact energy is based on the measurement the shock wave in the striker 5 upon impact of the flying piston 4. An axial preferably Coil 83 wound around the lower portion of the striker 5 magnetizes the Beater 5 in the axial direction at a certain operating point. Depending on use source 84 - voltage source or power source - will either be the Voltage or current change caused by momentary magnetic flux changes in the made of a magneto-elastic steel (Ni-containing) made anvil 5 measured due to the magneto-elastic effect. In the example shown this voltage U2 is tapped via a shunt 85; it is proportional to Change of the mechanical stress in the material of the beatpiece 5.

In the collision of flying piston 4 and striker 5 an elastic shock wave is generated in both bodies, which propagates with the wave propagation velocity γ in the elastic material of the striker 5, which is defined by the elasticity E * and the density ρ: ρ = e * ρ ≈ 5300 ms -1

For steel applies: E * ≈ 2 x 10 11 N m 2 ρ ≈ 7850 kg m 2

The shock wave reaches the tip of the tool and generates a high mechanical compressive and tensile stress, which leads to a failure of the substrate lead to the mining of the subsoil.

The speed of the displacements in the material is related to the mechanical stresses via Hook's law. ν = ∂ u ∂ t = ∂ u ∂ x ∂ x ∂ t = ε · ∂ x ∂ t = ε · γ = σ e * γ

From the mechanical stresses in one of the shock body, in particular the striker 5, the elastic energy of the pulse and thus the single impact energy can be calculated. It is given by the integral of the square of the mechanical stresses.

A: Querschnittsfläche, über welcher gemessen wird

Z: mechanische Wellenimpedanz des Materials

τ: Impulsdauer (typischerweise 100 bis 200 µs)

Where:

A: cross-sectional area over which is measured

Z: mechanical wave impedance of the material

τ: pulse duration (typically 100 to 200 μs)

If the shockwave wanders through the striker 5, its magnetic properties change. This happens within a time of about 50 to 100 μs. During this time, a common constant current source acts as a constant voltage source due to inertia. During this time, a short current change, which is proportional to the change in the mechanical stresses in the striker 5, is measured across the shunt 85. The voltage or current source 84 is advantageously supported by a large capacitor (not shown) which is not capable of doing so is to compensate for rapid power fluctuations. The current change, as illustrated in FIG. 17, is AC-coupled, amplified via an operational amplifier (not shown), first bandpass filtered in 86 and digitized via an AD converter 87, and then in a computing unit 88 (microcontroller) with one sufficient sampled high cycle time. As illustrated by functional blocks, the digitized signal is first numerically integrated in the arithmetic unit 88, then squared and then numerically integrated again over the pulse duration τ (eg 500 μs) to obtain the single beat energy E _S at the output. It is important to ensure a clean triggering and separation of the pulse bursts, in order to separate the first shock pulse clearly from the signals resulting from multiple reflections. As a trigger signal can be used on the striker 5, the tapped ME signal itself or an additional signal, eg. B. the flying-piston position or recorded on the device housing 7 acceleration (not shown). In the simplified block diagram of Fig. 17, the factor A indicates a gain which depends on the type of ME sensor. The pulse duration τ is about 100 to 200 μs.

In general, the demands on the dynamics of the Schlierenergiereglers The following applies: The dynamics of the controller is not determined by the beat frequency certainly. It is not essential to the energy of the individual Single stroke to regulate. Rather, the controller is designed so that, for example within 0.3 to 0.5 seconds the single impact energy to a desired Setpoint adjusted. A higher dynamics is not required in practice. It is important that, for example, the wear-related decrease of the single impact energy can be compensated for without drilling on delicate surfaces, such as marble or granite slabs, a given single impact energy is exceeded, otherwise there is a risk that in To form the material to be machined too long cracks. That's the requirements to the actuators of the controller is not extremely high, so that z. B. for the above-described Leakage change through an adjustable sleeve used a stepper motor can be, for example, a spindle stepping motor.

Claims (20)

Drilling and / or chipping hammer with electropneumatic hammer mechanism whose impact energy is changeable,
marked by a sensor device (10, 11, 11a, 11b) which detects a quantity correlated to the single impact energy transmitted to a surface to be degraded; a control device (9, 34), in which the size corresponding to the single impact energy _is compared with a desired value (E setpoint) and a control value (G (s)) is generated, and an acted upon by the manipulated variable actuator (7) for tracking the single impact energy to the target value. Drill and / or chisel hammer according to claim 1, whose electropneumatic percussion mechanism comprises a fly piston (4) which is displaceable in a guide tube (16) by an electromotive driven exciter piston (3) via a drive-side air spring (20) and an end face of the guide tube (16). having an anvil (5) which acts on an impact tool via an air pressure cushion (21) driven by the air piston (4),
characterized in that the sensor device (11) detects the instantaneous position and / or the velocity of the flying mass (4) in the forward direction to the impact tool and in the backward direction, and that in a microcontroller (9) from the differential speed, the kinetic energy difference is determined as a measure of the single impact energy. Drill and / or chisel hammer according to claim 1, whose electropneumatic percussion mechanism comprises a fly piston (4) which is displaceable in a guide tube (16) by an electromotive driven exciter piston (3) via a drive-side air spring (20) and an end face of the guide tube (16). having an anvil (5) acting on an impact tool via an air pressure pad (21) driven by the air piston (4),
characterized in that the striker (5) contains a magneto-elastic, ferromagnetic material or consists of this material, the sensor device has a magneto-elastic sensor associated with the striker (5), which detects the striker with magnetic flux and detects magnetic permeability changes and thus magnetic flux changes in the striker due to shock waves generated in the striker (5) as a sensor signal due to the impact of the flying plunger (4), and a device (86) for calculating the single impact energy (E _S ) from the sensor signal. Drill and / or chisel hammer according to claim 2, characterized in that the control device has a PI controller (34). Drill and / or chisel hammer according to claim 2, characterized in that the actuator of the control device by the control value (G (s)) actuated a controllable valve means (35) which controls the pressure in the air spring (20) for tracking the impact energy changed. Drill and / or chisel hammer according to claim 5, characterized in that the valve means (35) and the pressure in a pressure pad (21) between the flying piston (4) and the Dopper (5) changed. Drill and / or chisel hammer according to claim 2, characterized in that the sensor device (11) has two biased with permanent magnets digital Hall switch (11a, 11b) on the guide tube (16) in the displacement of the flying piston (4) at a predetermined distance (Δs) are arranged from each other. Drill and / or chisel hammer according to claim 2, characterized in that the sensor device (11) has two differential Hall sensors, which are arranged on the guide tube (16) in the displacement path of the flying piston (4) with a predetermined distance next to each other. Drill and / or chisel hammer according to claim 2, characterized in that the sensor device (11) has a differential Hall sensor, which is arranged on the guide tube (16) in the displacement path of the flying piston (4). Drill and / or chisel hammer according to claim 2, characterized in that the sensor device (11) a Hall Sehalter array (70) having a plurality of at a predetermined mutual distance (Δs) along the guide tube (16) in the displacement of the flying piston ( 4) arranged successive Hall switch. Drill and / or chisel hammer according to claim 2, characterized in that the sensor arrangement (11) has a guide tube (16) in the displacement of the flying piston (4) surrounding the LVD transformer (80), wherein the flying mass (4) as longitudinally slidable magnetic core acts, the longitudinal displacement between the coupling between a field winding (81) and at least one sensor winding (82a, 82b) changed. Drill and / or chisel hammer according to claim 2, characterized in that the sensor arrangement (11) on the guide tube (16) perpendicular to the direction of movement of the flying piston (4) arranged in its displacement distance sensor (90), wherein the flying piston at least one Part of its axial length conical shell portion has. Drill and / or chisel hammer according to claim 2 to 12, characterized in that the control device controls the speed of the drive motor for the excitation piston (3). Drill and / or chisel hammer according to claim 5, characterized by a motor speed detecting tachogenerator (54) whose actual speed value (ω _is ) against a presettable by the user speed setpoint (ω _soll ) in a comparator (53) is comparable , wherein the determined speed deviation (Δω) acts as an additional influencing variable on the impact energy regulator (G (s)) on the actuator (56). Drill and / or chisel hammer according to claim 5, characterized in that the controllable valve device is a variable leakage (18) on the air spring (20). Drill and / or chisel hammer according to claim 15, characterized in that the changeable leakage by at least one guide tube (16) passing through Schnaufloch (19) and an axially or tangentially by an actuator axially displaceable relative to the guide tube perforated sleeve (32) is formed. Drill and / or chisel hammer according to claim 16, characterized in that the perforated sleeve (32) has a with an obliquely to the axis of the guide tube (16) extending edge formed window (oblique window) (33) which is movable over the Schnauföffnung. Drill and / or chisel hammer according to claim 15, characterized in that the changeable leakage (18) by at least one of the guide tube (16) passing through bore (71) and an axially by the actuator (56) adjustable sleeve (36) is formed. Drill and / or chisel hammer according to claim 18, characterized in that the bore (71) has chamfered wall sections. Drill and / or chisel hammer according to claim 2, characterized in that the sensor device comprises an induction sensor (87, 88).

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