EP3610990B1 - Control method for a hand-held machine tool, handheld machine tool and system including the handheld machine tool and a stand - Google Patents

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.

Handheld power tools, such as drills, can have a protective function which protects a user of the handheld power tool from excessive torque acting back on the housing, in particular the handle. The protective function reduces a torque output of a motor of the handheld power tool when the retroactive torque exceeds a certain limit value. However, if the hand-held power tool is not held in the hand by a user during operation, but held by a stand, it is desirable to switch off the protective function.

A hand machine tool with a protective function is from the EP 1 008 422 A2 and the EP 1 186 383 B1 known. Furthermore, from the EP 3 221 090 A1 ( EP 3 023 203 A1 ) a control method for a handheld power tool for recognizing a purely chiseling operation of a hammer drill and for suppressing a protective function of the handheld power tool in purely chiseling operation is known. The 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 create 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 driving the tool holder in rotation about a working axis. The control method has a step of detecting a rotary movement of a housing of the handheld power tool about the working axis. The control method furthermore has a step of triggering a protective function for reducing a torque output of 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 variable of a frequency spectrum of a detected rotary movement about the working axis.

The handheld power tool controlled with the control method is, for example, a rotary hammer, a combination hammer, a core drill or a screwdriver. The tool holder of the hand machine tool is used to insert a rotatable tool, for. B. a drill. The motor of the hand machine tool is used in particular to set the tool in rotation about the working axis by driving the tool holder in a rotating manner about the working axis. By rotating the tool, an object, such as a subsurface 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 handheld power tool detects the rotary motion of the housing. Such a rotary movement of the housing can in particular be caused 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 can cause a rotational movement of the housing about the working axis through a retroactive torque. Particularly when machining an inhomogeneous object and / or a non-yielding object with the handheld power tool, a rotary movement of the housing can occur. The inhomogeneity and / or the non-yielding of the object can in particular lead to a temporally variable rotational movement of the tool, which in turn causes a temporally variable rotational movement of the housing due to the retroactive torque.

The rotary movements can include vibrations of the handle about 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 change in the rotational movement over time is recorded by detecting the rotary movement. For example, the detected rotary movement has an angular velocity that varies over time, a rotational speed that changes over time, a torque that changes over time and / or an angular deflection that changes over time. For example, the detected rotational movement has a braking and acceleration of the 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 rotary movement around 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 rotational 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 rotary movement exceeds the specific limit value, a user holding the hand-held power tool can be protected from dangerous rotary movements of the housing. In particular, a user can thus be protected from rotary movements of the housing which he cannot compensate for by applying force when holding the handheld power tool.

These rotary movements of the housing, which are dangerous for the user, can result from high retroactive torques due to severe inhomogeneity and / or non-yielding of the object to be processed. For example, a reinforcement iron hit while 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 that can otherwise lead 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 variable of a frequency spectrum of a detected rotary movement about the working axis.

In the case of 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 rotary movement of the housing. In the case of an object to be machined that yields normally, that is to say in particular when no tool blockage occurs, the force of the user is sufficient to counteract the retroactive torque. The user then perceives the remaining rotary movement of the housing, for example, as a shaking of the handheld power tool.

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

In the third step of the control method, the frequency spectrum of the detected rotary movement of the housing is provided. The frequency spectrum is provided, for example, by the control device, which determines the temporal change in the detected rotational movement, e.g. B. as a signal from the rotary motion sensor receives. 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 rotational movement from the time domain into the frequency domain. The transformation into the frequency domain takes place, 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 specific frequency range can be filtered, for example, by frequency filtering the frequency spectrum made available and / or by frequency filtering the detected rotary movement before the frequency spectrum is made available.

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 from the frequency spectrum, for example, in that it is read therefrom, calculated with the aid of an algorithm and / or generated with the aid of electronic signal processing. The characteristic variable of the frequency spectrum is determined, for example, by the control device. The generation of the characteristic variable with the help of electronic signal processing takes place, for example, with the help of electronic components and / or electronic circuits, e.g. B. a band pass filter, low pass filter and / or integrator. The characteristic variable of the frequency spectrum is a frequency-dependent function or a constant, in particular frequency-independent, value. The characteristic variable 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 a transformation of the detected rotational movement from the time period into the frequency space. For example, the frequency spectrum can be made available from the detected rotational movement by frequency filtering 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 variable of the frequency spectrum can be a strength and / or amplitude of the detected rotational movement. In this case, the characteristic variable of the frequency spectrum can be a time-dependent function or a constant value which, in particular, is time-independent.

By providing the frequency spectrum of the detected rotary movement and determining the characteristic variable 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 rotary movement of the housing, Frequency ranges and / or frequency components are determined and used in a further evaluation.

Because the strength and / or amplitude of frequencies, frequency ranges and / or frequency components contained in the detected rotary movement of the housing is determined, 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 depending on the characteristic size of the frequency spectrum, the protective function can be switched off in stator-held operation. As a result, no protective function that interferes with the machining process, which is associated with a reduction in the torque output of the motor, is triggered in the stator-held operation.

The control method is carried out, for example, with the aid of 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 a plurality of algorithms which is / 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 variable 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 ensures that the handheld power tool is used every time it is used, e.g. B. every new drilling attempt, starts in safe mode with the protective function switched on. The determination that takes place in the second step as to whether the detected rotational movement exceeds the specific limit value and the determination of the characteristic variable in the third step are carried out at the same time, for example.

The respective unit, for example the processor, can be implemented in terms of hardware and / or also in terms of software. In the case of a hardware implementation, the unit can be used as a device or as part of a device, for example as 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, can be provided or delivered as a storage medium such as a memory card, USB stick, CD-ROM, DVD, or also 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 variable of the frequency spectrum of the rotary movement about the working axis falls below a certain threshold value.

The specific threshold value is, for example, a specific speed, a specific angular speed, 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 rotary movement of the housing, for which the characteristic value is below the specific threshold value, is a rotary movement which can only occur in stand-held operation, but not in hand-held operation. This makes it possible to distinguish even better between handheld operation of the handheld power tool and stand-held operation of the handheld power tool.

As a result, the fact that the protective function is switched off when the characteristic size of the frequency spectrum of the rotary movement around the working axis falls below the specific threshold value can be used to ensure that the protective function is only switched off in stand-held mode and that hand-held operation is in safe mode with the protective function switched on.

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

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

In particular, determining the characteristic variable from the frequency spectrum includes filtering 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 filtering of the frequency spectrum can also be done by one or more electronic components and / or circuits, such as, for example, 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 can be carried out 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 hand-held operation and stand-held operation is particularly great in the mentioned frequency ranges. This allows the stand-held operation to be distinguished even better from the hand-held operation.

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

In particular, the determination of the characteristic variable includes 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 rotational movement has negative components, e.g. B. by braking the angular velocity, and positive components, z. B. by accelerating the angular velocity. For determining the strength of the rotary movement of the housing, only the strength of the negative and positive components is essential, but not their sign. As a result, the characteristic variable can be determined more easily by forming the absolute value, e.g. B. calculated. In particular, a Averaging out negative and positive components can be avoided when averaging.

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

In particular, determining the characteristic variable includes calculating a rectification value of the detected rotary movement.

Because the characteristic variable is based on a rectification value of the detected rotary movement, a time average value of the amount of the detected rotary movement can be used to differentiate between stand-held and hand-held operation and the stand-held operation can thus be better recognized.

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

In particular, the determination of the characteristic variable includes 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 integration over time can also be carried out by an electronic component and / or circuit, such as an integrator or low-pass filter.

Due to the integration over time, high frequencies of the detected rotary movement can (partially) be attenuated, while low frequencies are retained and / or allowed to pass. Since the stand-held operation at low frequencies of the rotary movement of the housing can be better distinguished from the hand-held operation, the characteristic variable based on the time integration allows better recognition of the stand-held operation.

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 variable starts again each time the main switch of the handheld power tool is actuated, the determination of the characteristic variable is restarted for each individual use of the handheld power tool, for example each drilling attempt. This is the basis of the characteristic The size of a specific individual use of the handheld power tool is only based on the time integration of the detected rotary movement for this

Hand machine tool use. In particular, it can be ensured that the handheld power tool starts with each new use in the safe mode with the protective function switched on.

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

The size of the constant value can be selected so that the characteristic variable by subtracting the constant value in the case of stand-held operation has a value and / or value range less than zero, in particular a negative value, and in the case of hand-held operation one Has value and / or value range 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 rotational movement comprises a detection of an angular velocity.

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

According to a further embodiment, the change in the rotational movement over time includes an acceleration and deceleration of the angular velocity.

According to a further embodiment, the rotational movement is detected by means of a rotational movement sensor, in particular a gyro sensor.

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

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

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

Because the protective function activates the brake of the motor, the torque output in hand-held operation can be reduced quickly if a very high retroactive torque suddenly occurs.

According to a second aspect, a handheld power tool is proposed. The handheld power tool has a tool holder and a motor for driving the tool holder in rotation about a working axis. The handheld power tool also has a rotational movement sensor for detecting a rotational movement of a housing of the handheld power tool about the working axis. The hand-held 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 temporal change in the detected rotary movement about the working axis.

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

According to an embodiment of the second aspect, the rotational movement 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 fixedly attached to and / or in the stand in stand-held operation, but is releasably attached again. In particular, the hand-held power tool can be detached from the stand in order to switch to hand-held operation.

In particular, the stand has a strength and robustness that is suitable for counteracting 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 the tool jamming.

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 on the basis of exemplary embodiments and figures. In the figures shows:

Fig. 1

a schematic view of a hand machine tool;

Fig. 2

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

Fig. 3

a diagram of a frequency spectrum of a change over time of a detected rotary movement of the handheld power tool according to FIG Fig. 1 .

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

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 a rotary hammer as an exemplary embodiment of the handheld power tool 1 for which the control method is used. The hammer drill 1 has a tool holder 2, in which a shank end of a tool 3, for. B. a drill can be used. A primary drive of the hammer drill 1 is formed by a motor 4, which has an impact mechanism 5 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 the hammer drill 1 by a handle 8 and guide it. The handle 8 is part of a housing 9 of the hammer drill 1. The user can put the hammer drill 1 into operation 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 rotary 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 rotating about the working axis 11 in a striking direction 12 along the working axis 11 into a substrate. In one embodiment, the hammer drill 1 has an operation 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 for chiselling. Instead of being held in the hand by the user, the hammer drill 1 can also be held by a stand (not shown). In particular, the hammer drill 1 can be operated while held by the stand.

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

As long as the workpiece and / or the substrate give way during drilling, the retroactive torque is low. In hand-held operation, the user can adequately counteract this small retroactive torque. The user only perceives the remaining rotary movement of the housing 9 about the working axis 11 as a shaking of the housing 9. In stand-held operation, the stand can counteract such a small 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 mode is even less than in the hand-held mode.

If the tool 3 jams in the workpiece, the sudden braking of the rotating tool 3 results in a high retroactive torque. In the stator-held operation, the stator can still adequately counteract this high retroactive torque. However, in hand-held operation, the user can no longer adequately handle this high retroactive torque counteract this, 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 hammer drill 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 hammer drill 1, so that the protective device 13 can be switched off in the stand-held operation.

Fig. 2 FIG. 11 shows a schematic view of the control method for the hammer drill 1 from FIG Fig. 1 .

In a first step S1 of the control method, the rotary movement of the housing 9, in particular of the handle 8, of the hammer drill 1 about the working axis 11 is recorded. For this purpose, the hammer drill 1 has a rotary motion sensor 14. An exemplary rotary motion sensor 14 is a gyro sensor which directly determines the angular velocity about the working axis 11. The gyro sensor 14 has a small plate suspended in an oscillating manner, the oscillation frequency of which is influenced by the Coriolis force. The gyro sensor scans the oscillation frequency, determines the associated angular speed around the working axis 11 and outputs the detected angular speed as a measurement signal. The angular velocity is continuously detected by the gyro sensor 14 from the actuation of the main button 10 during the operation of the hammer drill 1. The gyro sensor 14 can be arranged close to the working axis 11 or offset to 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 hammer drill 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 retroactive torque is too high or in the stand- to switch off stopped 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 specific 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 from rotary movements of the housing 9 in hand-held operation, 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 variable of a frequency spectrum of a temporal change in the detected rotary movement about the working axis 11.

To detect the operation of the hammer drill 1 with a stand, 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 operation with the stand. To this end, 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 are shown in the stand-held mode. Furthermore shows Fig. 3 three examples of frequency spectra 18 in hand-held operation. As in Fig. 3 As can 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 the stand-held mode, in particular on average, is significantly smaller than the amplitude of the frequency spectra 18 in the hand-held mode.

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 variable of the frequency spectrum is a mean value of the amplitude of one of the frequency spectra 17 in FIG Fig. 3 in the frequency range 1.4 to 1.8 Hz.

The control device 15 compares the mean value, calculated for the frequency range 1.4 to 1.8 Hz, of the amplitude of one of the frequency spectra 17 with the determined threshold value in order to distinguish a hand-held operation of the hammer drill 1 from a stand-held operation. In Fig. 3 a constant value is provided with the reference numeral 19 as an example for the specific threshold value. When the control device 15 determines that the calculated mean value falls below the specific threshold value 19, and thus determines that the hammer drill 1 is in stand-alone operation, it transmits a switch-off 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 interference from 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 provided without a transformation of the detected angular velocity from the time period into the frequency space. In the modification, the temporal change in the angular velocity of the housing 9 detected by the gyro sensor 14 is processed in such a way that it passes through a plurality of frequency filters in particular. For this purpose, the detected angular speed 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 band-pass filter, low-pass filter and integrator.

The following describes the determination of the characteristic variable in the case of modification. First, 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 therefrom, both of which are referred to below as “signal” for short. For this purpose, the signal passes an (electronic or computer-aided) 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, which is particularly suitable for recognizing the stator-held operation. Further a differential input voltage (DC voltage 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 (braking) values, the positive and negative values can be rectified by forming the amount of the filtered signal. The filtered and rectified signal passes an (electronic or computer-aided) low-pass filter of 0.5 Hz, which allows low frequencies below 0.5 Hz to pass and attenuates higher frequencies. A constant value is then subtracted from the rectified and filtered signal. A temporal integration then follows with the aid of the algorithm of the control device 15 or an electronic integrator. The temporal integration acts like another low-pass filter by allowing low frequencies to pass and attenuating high frequencies. The subtracted constant value is selected such that the characteristic variable generated by the repeated frequency filtering, rectification, integration and subtraction described has a negative value in the case of stand-held operation and a positive value in the case of hand-held operation. This makes it easy to distinguish between these two operating modes.

REFERENCE LIST

1

Hand machine tool (hammer drill)

2

Tool holder

3

Tool

4th

engine

5

Percussion

6th

drive shaft

7th

accumulator

8th

Handle

9

casing

10

Main button

11

Working axis

12th

Direction of impact

13th

Protective device

14th

Rotary motion sensor (gyro sensor)

15th

Control device

16

brake

17th

Frequency spectrum

18th

Frequency spectrum

19th

certain threshold

S1

Process step

S2

Process step

S3

Process step

Claims (13)

1. Control method for a hand-held power tool (1), which has a tool fitting (2) and a motor (4) for driving the tool fitting (2) in a rotating manner about a working axis (11), comprising the steps of:

   detecting (S1) a rotating movement of a housing (9) of the hand-held power tool (1) about the working axis (11),

   triggering (S2) a protective function for reducing a torque output of the motor (4) if the detected rotating movement about the working axis (11) exceeds a specific limit value, and

   switching off (S3) the protective function on the basis of a characteristic variable of a frequency spectrum of a detected rotating movement about the working axis (11).
2. Control method according to Claim 1, characterized in that the protective function is switched off (S3) if the characteristic variable of the frequency spectrum of the rotating movement about the working axis (11) is below a specific threshold value.
3. Control method according to Claim 1 or 2, characterized in that the characteristic variable of the frequency spectrum comprises an amplitude of the frequency spectrum.
4. Control method according to one of Claims 1 to 3, characterized in that the characteristic variable of the frequency spectrum comprises a characteristic variable of the frequency spectrum in a frequency range below 20 Hz, preferably below 10 Hz, particularly preferably below 2 Hz.
5. Control method according to one of Claims 1 to 4, characterized in that the characteristic variable of the frequency spectrum is based on a temporal integration of the rotating movement.
6. Control method according to Claim 5, characterized in that the temporal integration is re-started every time a main switch (10) is actuated.
7. Control method according to one of Claims 1 to 6, characterized in that the detection (S1) of the rotating movement comprises detecting an angular velocity.
8. Control method according to Claim 7, characterized in that the change over time of the rotating movement comprises an acceleration and deceleration of the angular velocity.
9. Control method according to one of Claims 1 to 8, characterized in that the detection (S1) of the rotating movement is carried out by means of a rotating movement sensor (14), in particular a gyro sensor.
10. Control method according to one of Claims 1 to 9, characterized in that the protective function activates a brake (16) of the motor (4).
11. Hand-held power tool (1) comprising
    a tool fitting (2),
    a motor (4) for driving the tool fitting (2) in a rotating manner about a working axis (11), a rotating movement sensor (14) for detecting a rotating movement of a housing (9) of the hand-held power tool (1) about the working axis (11),
    a protective device (13), which is designed to trigger a protective function for reducing a torque output of the motor (4) if the detected rotating movement about the working axis (11) exceeds a specific limit value, and
    a control device (15), which is designed to switch off the protective function on the basis of a characteristic variable of a frequency spectrum of a detected rotating movement about the working axis (11).
12. Hand-held power tool (1) according to Claim 11, characterized in that the rotating movement sensor (14) is a gyro sensor.
13. System comprising a hand-held power tool (1) according to Claim 11 or 12 and a stand for holding the hand-held power tool (1).

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