EP3610990A1 - Control method for a hand-held machine tool, handheld machine tool and system including the handheld machine tool and a stand - Google Patents

Abstract

The control method according to the invention for a hand tool (1), which has a tool holder (2) and a motor (4) for rotatingly driving the tool holder (2) about a working axis (11), comprises the steps: detecting (S1) a rotary movement of a housing (9) the handheld power tool (1) around the working axis (11), triggering (S2) a protective function to reduce the torque output of the motor (4) when the detected rotational movement about the working axis (11) exceeds a certain limit value, and switching off (S3 ) the protective function as a function of a characteristic size of a frequency spectrum of a detected rotary movement about the working axis (11).

Description

FIELD OF THE INVENTION

The present invention relates to a control method for a handheld power tool, a handheld power tool and a system with the handheld power tool and a stand.

Hand-held machine tools, such as, for example, drilling machines, can have a protective function which protects a user of the hand-held machine tool against excessive torque which acts on the housing, in particular the handle. The protective function reduces the torque output of a motor of the hand machine tool if the retroactive torque exceeds a certain limit. However, if the handheld power tool is not held in the hand of a user during operation, but is held by a stand, it is desirable to switch off the protective function.

A hand tool with a protective function is out of the EP 1 008 422 A2 and the EP 1 186 383 B1 known. Furthermore, from the EP 3 221 090 A1 a control method for a hand tool for detecting a purely chiseling operation of a rotary hammer and for suppressing a protective function of the hand tool in a purely chiseling operation is known. Purely chiseling operation is recognized by means of rotating and swiveling movements about a transverse axis running transversely to a working axis.

Against this background, the object of the present invention is to improve a control method for a handheld power tool, to provide an improved handheld power tool and a system with such an improved handheld power tool and a stand.

DISCLOSURE OF THE INVENTION

According to a first aspect, a control method for a handheld power tool is proposed. The handheld power tool has a tool holder and a motor for rotatingly driving the tool holder about a working axis. The control method has a step of detecting a rotary movement of a housing of the handheld power tool around the working axis. The control method further includes a step of triggering a protective function to reduce a torque output from the motor if the detected rotational movement about the working axis exceeds a specific limit value. The control method also has a step of switching off the protective function as a function of a characteristic size of a frequency spectrum of a detected rotary movement about the working axis.

The handheld machine tool controlled by the control method is, for example, a hammer drill, a combination hammer, a core drill or a screwdriver. The tool holder of the hand tool is used to insert a rotatable tool, e.g. B. a drill. The motor of the hand-held power tool is used in particular to set the tool in rotation about the working axis by rotating the tool holder around the working axis. By rotating the tool, an object, such as a surface and / or a wall, can be processed.

In a first step of the control method, the rotary movement of the housing, in particular the handle, of the handheld power tool about the working axis is recorded. For example, a rotary motion sensor of the hand machine tool detects the rotary motion of the housing. Such a rotary movement of the housing can be caused in particular by a retroactive torque of the tool and / or the tool holder if the tool and / or the tool holder are not completely decoupled from the housing. For example, an interaction of the tool with the object to be machined by a retroactive torque can cause the housing to rotate about the working axis. Especially when processing an inhomogeneous object and / or a non-yielding object with the handheld power tool, the housing can rotate. The inhomogeneity and / or the non-yielding of the object can, in particular, lead to a rotational movement of the tool that changes over time, which in turn causes a rotational movement of the housing that changes over time due to the retroactive torque.

The rotary movements can include vibrations of the handle around a central position. The detected rotational movement of the housing about the working axis is in particular a rotational movement that changes over time. In particular, the temporal change in the rotary movement is recorded by the detection of the rotary movement. For example, the detected rotary movement has a temporally variable angular velocity, a temporally variable speed, a temporally variable torque and / or a temporally variable angular deflection. For example, the detected rotary movement has a braking and accelerating angular velocity.

In a second step of the control method, the protective function for reducing the torque output of the motor is triggered when the detected rotational movement about the working axis exceeds the specific limit value.

For example, a protective device and / or a control device of the handheld power tool determines whether the detected rotational movement of the housing about the working axis exceeds the specific limit value. For example, the protective device and / or the control device triggers the protective function when the specific limit value is exceeded.

The specific limit value is, for example, a specific angular velocity, a specific speed, a specific torque and / or a specific angular deflection. Because the protective function for reducing the torque output of the motor is triggered when the detected rotational movement exceeds the specific limit value, a user holding the hand power tool can be protected against dangerous rotational movements of the housing. In particular, a user can thus be protected against rotational movements of the housing which he cannot compensate for by exerting force when holding the handheld power tool.

These rotational movements of the housing, which are dangerous for the user, can result from high retroactive torques due to strong inhomogeneity and / or non-yielding of the object to be processed. For example, a reinforcement iron hit when drilling in concrete can cause a sudden tool blockage and thus a high retroactive torque. By triggering the protective function, the user can be protected from such a high retroactive torque, which can otherwise lead, for example, to injuries in the area of the wrist or arm or to a fall from a ladder, scaffolding, etc.

In a third step of the control method, the protective function is switched off as a function of a characteristic size of a frequency spectrum of a detected rotary movement about the working axis.

In a hand-held operation of the hand-held power tool, by holding the hand-held power tool, the user counteracts the retroactive torque that leads to the rotational movement of the housing. In the case of a normally yielding object to be processed, that is to say in particular when there is no tool blockage, the force of the user is sufficient to counteract the retroactive torque. The user then perceives the remaining rotational movement of the housing, for example, as shaking the handheld power tool.

In the case of a hand-held power tool with a stand, which is operated by the stand, the stand can counteract the retroactive torque to a greater extent than is possible for the user in hand-held operation. In particular, due to the stiffness and robustness of the stator, the retroactive torque can be counteracted to a greater extent in stator-held operation and thus the rotational movement of the housing can be suppressed more than is possible in hand-held operation. Consequently, the rotational movement of the housing in stand-held operation differs from the rotational movement in hand-held operation in that the rotational movement of the housing in stand-held operation is less than in hand-held operation. For example, the rotational movement of the housing in the stand-held operation has a smaller amplitude of the angular velocity than the rotational movement in the hand-held operation. This difference particularly affects certain frequency ranges of the rotary movement.

In the third step of the control method, the frequency spectrum of the detected rotational movement of the housing is provided. The frequency spectrum is provided, for example, by the control device, which monitors the change over time of the detected rotary movement, e.g. B. received as a signal from the rotary motion sensor. The frequency spectrum provided has in particular a strength and / or amplitude of frequency components of the detected rotary movement as a function of the frequency. The frequency spectrum is calculated, for example, by transforming the detected rotary movement from the time domain to the frequency domain. The transformation into the frequency domain is carried out, for example, by a Fourier transformation of the detected rotary movement.

The frequency spectrum can, for example, also be a strength and / or amplitude of the frequency components of the detected rotary movement for a specific frequency range. The determined frequency range can be filtered, for example, by frequency filtering the provided frequency spectrum and / or before providing the frequency spectrum by frequency filtering the detected rotary movement.

The characteristic size of the frequency spectrum is a property of the frequency spectrum that is determined from the frequency spectrum. The characteristic variable is determined, for example, from the frequency spectrum by reading it off, calculating it using an algorithm and / or generating it using electronic signal processing. The characteristic size of the frequency spectrum is determined, for example, by the control device. The characteristic quantity is generated with the aid of electronic signal processing, for example with the aid of electronic components and / or electronic circuits, for. B. a bandpass filter, lowpass filter and / or integrator. The characteristic size of the frequency spectrum is a frequency-dependent function or a constant, in particular frequency-independent, value. The characteristic size of the frequency spectrum is, for example, the strength and / or amplitude of the frequency spectrum of the detected rotary movement.

In embodiments, the frequency spectrum can also be provided without transforming the detected rotary movement from the period into the frequency space. For example, the frequency spectrum from the detected rotary movement can be provided by frequency filters of certain frequencies and / or frequency ranges without a transformation into the frequency space. In this case, the frequency spectrum provided can in particular be a function of time and not of frequency. In this case, the characteristic size of the frequency spectrum can be a strength and / or amplitude of the detected rotary movement. In this case, the characteristic size of the frequency spectrum can be a time-dependent function or a constant value, which is in particular time-independent.

By providing the frequency spectrum of the detected rotary movement and determining the characteristic size of the frequency spectrum, an analysis, in particular a frequency-dependent analysis, of the detected rotary movement of the housing of the handheld power tool can be carried out. In particular, the strength and / or amplitude of frequencies contained in the detected rotational movement of the housing, Frequency ranges and / or frequency components are determined and used in a further evaluation.

By determining the strength and / or amplitude of frequencies, frequency ranges and / or frequency components contained in the detected rotational movement of the housing, a hand-held operation of the hand-held power tool can be distinguished from a stand-held operation of the hand-held power tool.

Because the protective function is switched off as a function of the characteristic size of the frequency spectrum, the protective function can be switched off in stand-held operation. As a result, no protective function which interferes with the machining process and is associated with a reduction in the torque output of the motor is triggered in stator-held operation.

The control method is carried out, for example, using the control device of the handheld power tool. The control device has, for example, a processor and a computer program executed with the aid of the processor. The control device, for example the computer program, comprises in particular an algorithm or several algorithms which are / are set up to determine whether the detected rotational movement exceeds the specific limit value, to trigger the protective function, to provide the frequency spectrum, to determine the characteristic variable and / or switch off the protective function depending on the characteristic size of the frequency spectrum.

The detection of the rotary movement of the housing and / or the determination of the characteristic size of the detected rotary movement starts again, for example, each time a main switch and / or main button of the handheld power tool is actuated. This can ensure that the handheld power tool with each new use, e.g. B. every new drilling attempt starts in safe mode with the protective function switched on. The determination, carried out in the second step, as to whether the detected rotational movement exceeds the determined limit value, and the determination of the characteristic variable, which is carried out in the third step, are carried out simultaneously, for example.

The respective unit, for example the processor, can be implemented in terms of hardware and / or also in terms of software. In a hardware implementation, the unit can be a device or part of a device, for example a computer or be designed as a microprocessor. In the case of a software implementation, the unit can be designed as a computer program product, as a function, as a routine, as part of a program code or as an executable object.

A computer program product, such as a computer program means, for example as a storage medium, such as Memory card, USB stick, CD-ROM, DVD, or in the form of a downloadable file from a server in a network. This can be done, for example, in a wireless communication network by transmitting a corresponding file with the computer program product or the computer program means.

According to one embodiment, the protective function is switched off when the characteristic size of the frequency spectrum of the rotary movement around the working axis falls below a certain threshold value.

The specific threshold value is, for example, a specific speed, a specific angular velocity, a specific torque and / or a specific angular deflection. The specific threshold value is in particular smaller than the specific limit value. In particular, a detected rotational movement of the housing, for which the characteristic value is below the specific threshold value, is a rotational movement that can only occur in a stand-held operation, but not in a hand-held operation. This makes it possible to distinguish even better a hand-held operation of the hand-held power tool from a stand-held operation of the hand-held power tool.

Consequently, by switching off the protective function when the characteristic size of the frequency spectrum of the rotary movement around the working axis falls below the certain threshold value, it can be ensured that the protective function is only switched off in the stand-held operation and that the hand-held operation in the safe mode with the protective function switched on.

According to a further embodiment, the characteristic size of the frequency spectrum comprises an amplitude of the frequency spectrum.

According to a further embodiment, the characteristic size of the frequency spectrum comprises a characteristic size of the frequency spectrum in one Frequency range below 20 Hz, preferably below 10 Hz, particularly preferably below 2 Hz.

In particular, the determination of the characteristic variable from the frequency spectrum has a filtering of the frequency spectrum in such a way that only the frequency range below 20 Hz, preferably below 10 Hz, particularly preferably below 2 Hz, is used for determining the characteristic variable. For example, the characteristic variable is determined for a frequency range from 1 to 10 Hz, preferably for a frequency range from 1.4 to 1.8 Hz.

The frequency spectrum is filtered, for example, by the control device, in particular an algorithm of the control device. The frequency spectrum can also be filtered by one or more electronic components and / or circuits, such as a bandpass filter, a lowpass filter and / or an integrator.

Because the characteristic size of the frequency spectrum has a characteristic size of the frequency spectrum in a frequency range below 20 Hz, preferably below 10 Hz, particularly preferably below 2 Hz, the stator-held operation in a frequency range in which the rotary movement of the housing is particularly small in stand-held operation. In other words, the difference in the rotational movement of the housing between the hand-held operation and the stand-held operation is particularly large in the frequency ranges mentioned. As a result, the stand-held operation can be distinguished even better from the hand-held operation.

According to a further embodiment, the characteristic size of the frequency spectrum comprises an absolute value.

In particular, the determination of the characteristic variable shows that the absolute value, that is to say the mathematical amount, of the detected rotary movement is formed. For example, the temporal change in the detected rotary movement has negative components, e.g. B. by braking the angular velocity, and positive components, e.g. B. by accelerating the angular velocity. Only the strength of the negative and positive components is essential for determining the strength of the rotary movement of the housing, but not their sign. Consequently, the characteristic variable can be determined more easily by forming the absolute value, e.g. B. calculated. In particular, a Averaging out of negative and positive parts when averaging is avoided.

According to a further embodiment, the characteristic size of the frequency spectrum comprises a rectification value.

In particular, the determination of the characteristic variable has a calculation of a rectification value of the detected rotary movement.

Because the characteristic quantity is based on a rectification value of the detected rotary movement, a temporal mean value of the amount of the detected rotary movement can be used for the differentiation between stand-held and hand-held operation and the stand-held operation can thus be better recognized.

According to a further embodiment, the characteristic size of the frequency spectrum is based on a temporal integration of the change over time.

In particular, the determination of the characteristic variable has the temporal integration of the detected rotary movement. The time integration takes place, for example, by the control device, in particular by an algorithm of the control device. The time integration can also be carried out by an electronic component and / or circuit, such as an integrator or low-pass filter.

The temporal integration can (partially) attenuate high frequencies of the detected rotary movement, while low frequencies are retained and / or let through. Since the stator-held operation can be better distinguished from the hand-held operation at low frequencies of the rotary movement of the housing, the characteristic variable based on the time integration allows the stator-held operation to be better recognized.

According to a further embodiment, the time integration is restarted each time a main switch is actuated.

Because the time integration for determining the characteristic size starts again each time the main switch of the hand-held power tool is actuated, the determination of the characteristic size is restarted for each individual use of the hand-held power tool, for example every drilling attempt. This is based on the characteristic Size of a certain individual use of the hand tool only on the temporal integration of the detected rotary movement for this hand tool use. In particular, it can be ensured that the handheld power tool starts in safe mode with the protective function switched on each time it is used.

According to a further embodiment, the characteristic size of the frequency spectrum comprises a subtraction of a constant value.

The size of the constant value can be chosen so that the characteristic size by subtracting the constant value has a value and / or value range less than zero in the case of a stand-held operation, in particular a negative value, and one in the case of a hand-held operation Value and / or range of values greater than zero, in particular is a positive variable. This makes it easier to distinguish between hand-held and stand-held operation.

According to a further embodiment, the detection of the rotary movement comprises detection of an angular velocity.

Because the detected rotational movement is the angular velocity of the housing, the change in the rotational movement over time can be precisely recorded and thus the stator-held operation can be recognized well.

According to a further embodiment, the change in the rotational movement over time includes accelerating and decelerating the angular velocity.

According to a further embodiment, the detection of the rotary movement is carried out by means of a rotary movement sensor, in particular a gyro sensor.

Because the rotary movement is detected by means of a gyro sensor, the angular velocity of the rotary movement can be recorded directly.

In embodiments of the control method, however, any other known measurement method for acceleration, angular velocity or angle of rotation can also be used, such as, for example, linear acceleration sensors based on piezoelectric measurement methods, pulse wheel and magnetic angle step sensors, micromechanical acceleration sensors, optical measurement methods, magnetohydrodynamic ones Measuring methods, rotational acceleration measuring methods based on the Ferraris principle, capacitive measuring methods or strain gauge accelerometers.

According to a further embodiment, the protective function activates a brake of the motor.

The fact that the protective function activates the brake of the motor means that the torque output in hand-held operation can be quickly reduced in the event of a sudden occurrence of a very high retroactive torque.

According to a second aspect, a handheld power tool is proposed. The handheld power tool has a tool holder and a motor for rotatingly driving the tool holder about a working axis. The handheld power tool also has a rotary motion sensor for detecting a rotary motion of a housing of the handheld power tool about the working axis. The handheld power tool also has a protective device which is set up to trigger a protective function for reducing a torque output of the motor when the detected rotational movement about the working axis exceeds a specific limit value. The handheld power tool also has a control device which is set up to switch off the protective function as a function of a characteristic variable of a frequency spectrum of a change over time of the detected rotary movement about the working axis.

This creates a hand-held power tool that can be operated both in a hand-held operation with the protective function switched on and in a stand-held operation with the protective function switched off automatically. Further properties and advantages that have been described for the control method apply accordingly to the proposed hand machine tool.

According to an embodiment of the second aspect, the rotary motion sensor is a gyro sensor.

According to a third aspect, a system with a handheld power tool according to the second aspect or an embodiment of the second aspect and with a stand for holding the handheld power tool is proposed.

In particular, the hand-held power tool is fixed on and / or in the stand in the stand-held operation, but can be detached again. In particular, the handheld power tool can be released from the stand in order to switch to hand-held operation.

The stand has, in particular, a strength and robustness which is suitable for opposing a retroactive torque with a greater force than is possible for a user. The stand is particularly suitable for counteracting a high retroactive torque due to a blocking of the tool.

The embodiments and features described for the control method apply accordingly to the handheld power tool and the system and vice versa.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1

eine schematische Ansicht einer Handwerkzeugmaschine;

Fig. 2

eine schematische Ansicht eines Steuerungsverfahrens für die Handwerkzeugmaschine gemäß Fig. 1; und

Fig. 3

ein Diagramm eines Frequenzspektrums einer zeitlichen Veränderung einer erfassten Drehbewegung der Handwerkzeugmaschine gemäß Fig. 1.

The following description explains the invention using exemplary embodiments and figures. The figures show:

Fig. 1

a schematic view of a hand machine tool;

Fig. 2

a schematic view of a control method for the hand tool according to Fig. 1 ; and

Fig. 3

a diagram of a frequency spectrum of a change over time of a detected rotational movement of the hand tool according to Fig. 1 ,

Identical or functionally identical elements are indicated by the same reference symbols in the figures, unless stated otherwise.

EMBODIMENTS OF THE INVENTION

The following is based on the Figures 1 to 3 An embodiment of a control method for a handheld power tool 1 is described. Fig. 1 shows as an embodiment of the hand tool 1, for which the control method is used, a hammer drill. The hammer drill 1 has a tool holder 2, in which a shaft end of a tool 3, for. B. a drill can be used. A motor 4, which has a striking mechanism 5, forms a primary drive of the rotary hammer 1 and drives a drive shaft 6. An accumulator 7 or a power line (not shown) supplies the motor 4 with current. A user can hold and guide the hammer drill 1 by a handle 8. The handle 8 is part of a housing 9 of the hammer drill 1. The user can start the hammer drill 1 by means of a main button 10. By actuating the main button 10, the drive shaft 6 coupled to the tool holder 2 sets the tool holder 2 in a rotational movement about a working axis 11. As a result, the tool 3 is rotated about the working axis 11. During operation, the hammer drill 1 can strike the tool 3 in addition to the rotation about the working axis 11 in a striking direction 12 along the working axis 11 in a subsurface. In one exemplary embodiment, the hammer drill 1 has an operating selector switch (not shown), by means of which the tool holder 2 can be decoupled from the drive shaft 6, so that the hammer drill 1 can be operated purely by chiseling. The hammer drill 1 can also be held by a stand (not shown) instead of being held in the hand of the user. In particular, the hammer drill 1 can be operated held by the stand.

During a drilling operation, the hammer drill 1 exerts a retroactive torque on the user or the stand, which results in response to a torque transmitted from the tool 3 to a workpiece. This retroactive torque is exerted on the user in hand-held operation and on the stand in stand-held operation.

As long as the workpiece and / or the surface yields during drilling, the retroactive torque is low. In hand-held operation, the user can counteract this low retroactive torque sufficiently. The user only perceives the remaining rotational movement of the housing 9 about the working axis 11 as a shaking of the housing 9. In stator-held operation, the stator can counteract such a low retroactive torque even more than the user could. Consequently, the remaining rotational movement of the housing 9 about the working axis 11 in the stand-held operation is even less than in the hand-held operation.

If the tool 3 is blocked in the workpiece, a high retroactive torque results due to the sudden braking of the rotating tool 3. In stator-held operation, the stator can still sufficiently counteract this high retroactive torque. However, the user can no longer adequately handle this high retroactive torque in hand-held operation counteract, which is why the entire hammer drill 1 including the housing 9 and the handle 8 begins to rotate about the axis of rotation 11 of the tool 3.

The hammer drill 1 has a protective device 13 for reducing a torque output of the motor 4, which protects the user from excessive retroactive torque of the tool 3 in hand-held operation. In the stand-held operation of the rotary hammer 1, however, it is desirable to switch off the protective device 13.

In the control method, the stand-held operation can be distinguished from the hand-held operation of the rotary hammer 1, so that the protective device 13 can be switched off in the stand-held operation.

Fig. 2 shows a schematic view of the control method for the hammer drill 1 Fig. 1 ,

In a first step S1 of the control method, the rotational movement of the housing 9, in particular the handle 8, of the rotary hammer 1 about the working axis 11 is recorded. For this purpose, the rotary hammer 1 has a rotary motion sensor 14. An exemplary rotary motion sensor 14 is a gyro sensor which directly determines the angular velocity around the working axis 11. The gyro sensor 14 has a swinging, suspended plate, the oscillation frequency of which is influenced by the Coriolis force. The gyro sensor scans the oscillation frequency, determines the associated angular velocity about the working axis 11 and outputs the detected angular velocity as a measurement signal. The angular velocity is continuously recorded by the gyro sensor 14 from the actuation of the main button 10 during the operation of the rotary hammer 1. The gyro sensor 14 can be arranged near the working axis 11 or offset from the working axis 11 in the housing 9, in particular in the handle 8. The gyro sensor 14 transmits the detected angular speed to a control device 15 of the rotary hammer 1. The control device 15 processes the detected angular speed, in particular a change in the detected angular speed over time, in order to trigger the protective function in hand-held operation when the torque is too high or in the stator mode. stop operation completely.

In a second step S2 of the control method, the protective function of the protective device 13 for reducing a torque output of the motor 4 is triggered, when the angular velocity of the rotation of the housing 9 about the working axis 11 detected by the gyro sensor 14 exceeds a certain limit value. The specific limit value is a specific angular velocity, which indicates that the tool 4 is blocked. In step S2, the control device 15 compares the detected angular velocity with the determined limit value. If the control device 15 determines that the detected angular velocity exceeds the determined limit value, the control device 15 sends a corresponding signal to the protective device 13. The protective device 13 then triggers the protective function. For example, the protective device 13 sends a brake signal to a brake 16 of the motor 4 as a protective function. The motor 4 is then preferably braked to a standstill. As a result, the user can be protected in the hand-held operation from rotational movements of the housing 9 which he could not compensate for by exerting force.

In a third step S3 of the control method, the protective function is switched off as a function of a characteristic size of a frequency spectrum and a change over time of the detected rotary movement about the working axis 11.

In order to recognize the stator-held operation of the rotary hammer 1, the control device 15 determines whether the angular velocity detected by the gyro sensor 14 over time suggests such a low retroactive torque that can only occur in a stator-held operation. For this purpose, the control device 15 calculates a frequency spectrum of the detected angular velocity. The frequency spectrum is provided, for example, by a Fourier transformation of the angular velocity detected by the gyro sensor 14 into the frequency space.

Fig. 3 shows a diagram of the calculated frequency spectrum of the detected angular velocity. The Y axis in Fig. 3 indicates the amplitude of the frequency components of the detected angular velocity of the housing 9 in arbitrary units. The X axis in Fig. 3 specifies the frequency in Hertz (Hz) for a frequency range from 0 to 10 Hz. In Fig. 3 four examples of frequency spectra 17 in stator-held operation are shown. Furthermore shows Fig. 3 three examples of frequency spectra 18 in hand-held operation. As in Fig. 3 To be seen, in the frequency range from 1 to 10 Hz, in particular in the frequency range from 1 to 5 Hz, the amplitude of the frequency spectra 17 in stand-held operation, in particular on average, is significantly smaller than the amplitude of the frequency spectra 18 in hand-held operation.

In order to distinguish the stand-held operation from the hand-held operation, a characteristic variable of the frequency spectrum is determined by the control device 15 in the third step S3 of the method. For example, the characteristic size of the frequency spectrum is an average of the amplitude of one of the frequency spectra 17 in Fig. 3 in the frequency range 1.4 to 1.8 Hz.

The control device 15 compares the mean value of the amplitude of one of the frequency spectra 17 calculated for the frequency range 1.4 to 1.8 Hz with the determined threshold value in order to distinguish a hand-held operation of the rotary hammer 1 from a stand-held operation. In Fig. 3 a constant value is provided with the reference symbol 19 as an example of the determined threshold value. If the control device 15 determines that the calculated mean value falls below the determined threshold value 19 and thus determines that the hammer drill 1 is operating in a stator position, it transmits a shutdown signal to the protective device 13. The protective device 13 then switches off the protective function. The stand-held operation of the hammer drill 1 can thus take place without a disturbance due to the protective function.

The following is a modification of the Figures 1 to 3 described embodiment shown. In the modification, in the third step of the method, the frequency spectrum is made available from the time period into the frequency space without transforming the detected angular velocity. In the modification, the temporal change in the angular velocity of the housing 9 detected by the gyro sensor 14 is processed such that it in particular passes through a number of frequency filters. For this purpose, the detected angular velocity z. B. processed by an algorithm of the control device 15. The detected angular velocity can, however, also be converted into a voltage signal and the further processing of the voltage signal can take place by means of electronic components such as an electronic bandpass filter, low-pass filter and integrator.

The determination of the characteristic variable in the case of the modification is described below. First of all, a frequency filter is applied to the temporal change in the angular velocity detected by the gyro sensor 14 or to the voltage signal based thereon, both of which are briefly referred to below as "signals". For this purpose, the signal passes an (electronic or computer-assisted) bandpass filter with a filter range of 1.4 to 1.8 Hz in order to pass a frequency range of 1.4 to 1.8 Hz that is particularly suitable for recognizing the stand-held operation. Furthermore a differential input voltage (DC offset, DC offset) can be subtracted from the signal.

Since the detected temporal change in the angular velocity of the housing 9 - and thus also the voltage signal - has positive (accelerating) and negative (decelerating) values, the positive and negative values can be rectified by forming the amount of the filtered signal. The filtered and rectified signal passes through an (electronic or computer-based) low-pass filter of 0.5 Hz, which allows low frequencies of below 0.5 Hz to pass and attenuates higher frequencies. A subtraction of a constant value follows from the rectified and filtered signal. Then there is a time integration using the algorithm of the control device 15 or an electronic integrator. The temporal integration acts like another low-pass filter in that it allows low frequencies to pass through and attenuates high frequencies. The subtracted constant value is chosen so that the characteristic variable produced by the repeated frequency filtering, rectification, integration and subtraction described has a negative value in the case of a stand-held operation and has a positive value in the case of a hand-held operation. This makes it easy to distinguish between these two operating modes.

LIST OF REFERENCE NUMBERS

1

Hand tool (hammer drill)

2

tool holder

3

Tool

4

engine

5

striking mechanism

6

drive shaft

7

accumulator

8th

handle

9

casing

10

main switch

11

working axis

12

impact direction

13

guard

14

Rotary motion sensor (gyro sensor)

15

control device

16

brake

17

frequency spectrum

18

frequency spectrum

19

certain threshold

S1

step

S2

step

S3

step

Claims (13)

Control method for a hand tool (1), which has a tool holder (2) and a motor (4) for rotatingly driving the tool holder (2) about a working axis (11), with the steps: Detecting (S1) a rotary movement of a housing (9) of the handheld power tool (1) about the working axis (11), Triggering (S2) a protective function for reducing a torque output of the motor (4) when the detected rotational movement about the working axis (11) exceeds a certain limit value, and Switching off (S3) the protective function as a function of a characteristic size of a frequency spectrum of a detected rotary movement about the working axis (11). Control method according to claim 1, characterized in that the protective function is switched off (S3) when the characteristic size of the frequency spectrum of the rotary movement about the working axis (11) falls below a certain threshold value. Control method according to claim 1 or 2, characterized in that the characteristic size of the frequency spectrum has an amplitude of the frequency spectrum. Control method according to one of claims 1 to 3, characterized in that the characteristic size of the frequency spectrum has a characteristic size of the frequency spectrum in a frequency range below 20 Hz, preferably below 10 Hz, particularly preferably below 2 Hz. Control method according to one of claims 1 to 4, characterized in that the characteristic size of the frequency spectrum is based on a temporal integration of the rotary movement. Control method according to Claim 5, characterized in that the time integration starts again each time a main switch (10) is actuated. Control method according to one of claims 1 to 6, characterized in that the detection (S1) of the rotary movement comprises detection of an angular velocity. Control method according to claim 7, characterized in that the temporal change in the rotary movement comprises an acceleration and deceleration of the angular velocity. Control method according to one of claims 1 to 8, characterized in that the detection (S1) of the rotary movement is carried out by means of a rotary motion sensor (14), in particular a gyro sensor. Control method according to one of claims 1 to 9, characterized in that the protective function activates a brake (16) of the motor (4). Hand tool (1) with
a tool holder (2),
a motor (4) for rotatingly driving the tool holder (2) about a working axis (11),
a rotary motion sensor (14) for detecting a rotary motion of a housing
(9) the hand tool (1) about the working axis (11),
a protective device (13) which is set up to trigger a protective function for reducing a torque output of the motor (4) when the detected rotational movement about the working axis (11) exceeds a specific limit value, and
a control device (15) which is set up to switch off the protective function as a function of a characteristic variable of a frequency spectrum of a detected rotary movement about the working axis (11). Hand tool (1) according to claim 11, characterized in that the rotary motion sensor (14) is a gyro sensor. System with a hand tool (1) according to claim 11 or 12 and a stand for holding the hand tool (1).

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