EP2644320A1 - Handheld electric power tool - Google Patents

Abstract

The hand-held electric machine tool (10) has a housing (20) with a gripping area (40), and a tool area (50) for a linear and oscillatory driven tool (60). An operating voltage unit (90) is arranged for providing an electrical direct current voltage. An electronics unit (200) is formed to operate an excitation actuator (100) in a resonance frequency.

Description

State of the art

The invention relates to a hand-held power tool comprising a housing with a handle portion, a tool area for a linearly and / or rotationally oscillating drivable tool, a housing-side control panel for user-side activation of the tool and / or the power tool, a housing arranged in the drive unit for generating a Working movement of the tool, an electronic unit arranged in the housing for applying the required processing power consisting of at least control and / or control signals, an operating voltage unit for providing a DC electrical voltage to the electronic unit, wherein the drive unit comprises at least one excitation actuator with a volume of excitation active material which is electrically powered by the operating voltage unit in operation, is controlled or regulated by the electronic unit.

Hand-held power tools are characterized by being portable and held and guided by an operator in the hand during operation. They can be operated wirelessly via battery packs or with mains power. In particular, these usually consist of only one housing, which is completely held by the user.

In the EP 1598171 B1 describes a mechanical construction of a welding head of a portable welding gun, in which an ultrasonic actuator applied to the welding head with mechanical power.

Disclosure of the invention

The invention relates to a hand-held power tool, comprising a housing with a handle portion, a tool area for a linearly and / or rotationally oscillating drivable tool, a housing-side control unit for user-side activation of the tool and / or the power tool, a housing arranged in the drive unit for generating a working movement of the tool, an electronics unit arranged in the housing for applying the required processing power consisting of at least control and / or control signals, an operating voltage unit for providing a DC electrical voltage to the electronics unit, wherein the drive unit at least one excitation actuator with a volume excitation active material includes, which is electrically powered by the operating voltage unit in operation, is controlled or regulated by the electronic unit.

It is proposed that the electronics unit is designed to operate the at least one excitation actuator at a resonant frequency.

If the excitation actuator is operated at its resonant frequency, a high mechanical output power can be delivered if the quality of the oscillatory system is sufficiently high in accordance with an electrical input power. The excitation actuator may be an ultrasonic excitation actuator, in particular a piezoelectric actuator in the construction of a Langevin transducer. The piezoelectric actuator has piezoelectric material as excitation-active material. Typically, the quality of the undamped oscillatory system is typically greater than 500 at values greater than 100. The resonant system of the excitation actuator, which has the resonant frequency, comprises the Langevin transducer with piezoelectric active material and components coupled to the vibrator, particularly components that amplify the ultrasound and / or or transferred to a processing location. Such components are known, for example as a booster or sonotrode. This enables a size reduction and the provision of a compact device. Advantageously, a compact power tool of high performance is thus created, which is at the same time handy.

Several excitation factors, e.g. be provided with the same or with different resonant frequency, as a drive component. Alternatively, one or more further drive components, such as an electric motor, may be provided. The various drive components may be operated alternatively or in combination. If the at least one excitation actuator is operated in resonance, the power output is particularly high, so that for a given output power of the power tool, the construction can be particularly compact, which is convenient handling of the hand-held power tool. The proposed power tool is a one-piece device, can be dispensed with disturbing connection cable between separate housing parts. The electric machine tool can be operated cordlessly with batteries or rechargeable batteries or also - additionally or alternatively - be operated with mains power via a mains cable. The tool may be an insert tool detachably connected to the excitation actuator, or it may be fixedly connected to the excitation actuator. The compound can e.g. be cohesive or non-positive. In particular, the electric machine tool is a machine tool used to machine or modify objects or surfaces, such as drills, rotary hammers, cutting tools, grinders, milling machines, saws, welders and the like.

According to a favorable development of the invention, the electronic unit may comprise a control unit with frequency adaptation for tracking the resonance frequency of the at least one excitation actuator. Advantageously, during operation of the electric machine tool, the resonance frequency can be continuously adjusted if the resonant frequency of the excitation actuator changes due to, for example, temperature change, change of the tool coupled to the excitation actuator or load on the tool. Thus, an optimal power yield is always possible during operation. Advantageously, the electronic unit may comprise a phase locked loop, with which the resonance frequency can be excited with high accuracy. Thus, a phase shift between electric current and electrical voltage, which are supplied to the piezoelectric active material for exciting the ultrasonic vibrations, to a fixed value, in particular 0 ° phase difference between the current and voltage signal, adjusted and maintained, whereby an optimal power output can be achieved can.

According to a favorable development of the invention, the volume of the piezoelectrically active material may be at least 0.2 cm ³ , preferably 0.5 cm ³ , in particular at least 1 cm ³ . Advantageously, a sufficient ultrasound power can be achieved with a small size of the excitation actuator.

According to a favorable development of the invention, the at least one excitation actuator may have a power density of at least 5 watts / cm ³ , preferably of at least 20 watts / cm ³ , based on the volume of the piezoelectrically active material of the at least one excitation actuator. A correspondingly high power density is advantageous for a hand-held compact power tool with the smallest possible dimensions and low production costs.

According to a favorable development, the at least one excitation actuator on the tool tip can have a vibration amplitude of at least 3 μm, preferably at least 8 μm, in particular at least 12 μm. A correspondingly high vibration amplitude is advantageous for a good power transmission to the workpiece and thus for a high work progress through the power tool.

According to a favorable development of the invention, on the input side of the electronic unit, an electrical power for acting on the at least one excitation actuator can amount to at least 20 watts. Advantageously, a sufficient power for a power tool can be ensured. Usual benefits are in the home improvement sector, for small cutting systems about between 20 watts and 250 watts, preferably 50 watts to 150 watts. For more powerful applications, eg drilling, powers from 50W to 1000W, preferably 200W to 500W are needed. In the professional craftsman sector, the power requirement for small systems is approximately between 50 and 400 watts, preferably 100 to 250 watts. For large systems, powers of 200 W to 2000 watts, preferably 400 watts to 1000 watts are used. Nevertheless, a power tool with handy dimensions can be created, which can be included or held by the hand of the operator on the one hand and on the other hand provides sufficient power for processing.

According to a favorable development of the invention, a maximum electrical excitation field strength of the at least one excitation actuator can be in the range below 300 V / mm (based on the thickness, in particular slice thickness, of the piezoelectrically active material), preferably in the range between 50 V / mm and 220 V. / mm. With a slice thickness of the excitation actuator of typically 1 mm to 10 mm, preferably 2 mm to 6 mm, in particular by 5 mm, the electrical voltages are less than 1000 volts. This advantageously makes it possible to use the excitation actuator in the hand-held power tool with sufficient mechanical output power and advantageously small dimensions.

According to a favorable development of the invention, an electrical output voltage of the operating voltage unit when supplied with electrochemical storage can be within 3 volts to 100 volts DC, preferably in the range of 3.5V to 40V, in particular at 36 volts, 24 volts, 18 volts, 14.4 Volts, 12 volts, 10.6 volts, 7.2 volts, and 3.6 volts. Advantageously, battery packs or rechargeable battery packs can be used, which are small and light enough to ensure good handling of the power tool with high output power yet.

According to a favorable development of the invention, a DC voltage component of the electrical output voltage of the operating voltage unit can be at supply with mains voltage within 0.5 U _network (rms value of the mains voltage) to 2 U _network . Preferably, for example, using a bridge rectifier with smoothing capacitor at 1.4 U _network . In a further embodiment, the mains voltage can be converted by means of an input-side transformer to a voltage suitable for the operating voltage unit.

According to a favorable development of the invention, the operating frequency of the at least one excitation actuator can be in the range between 10 kHz and 1000 kHz, preferably between 30 kHz and 50 kHz, in particular between 35 kHz and 45 kHz, particularly preferably around 40 kHz. As the frequency increases, the size of the components decreases and the mechanical load of the oscillating system increases, with advantageous size ratios in the selected frequency range result in high output and low weight of the power tool.

According to a favorable development of the invention, the operating voltage unit can comprise an electrochemical store, preferably a rechargeable electrochemical store. The operating voltage unit has only a small footprint, which is advantageous for the compactness and weight of the power tool. Conveniently, systems based on e.g. Lithium-ion (Li-ion) or nickel-metal hydride (NiMeH), nickel-cadmium (NiCd) or lead and the like. These can be firmly integrated in the housing and recharged via a charging port. Alternatively, the operating voltage unit may be formed as a change system, with exchangeable electrochemical storage, which may optionally be externally rechargeable, and which can be plugged into a receptacle provided in or on the housing. The rated voltage of the operating voltage unit may, depending on the power requirement, e.g. between 3 volts dc and 48 volts dc, e.g. at 12 volts dc.

According to a favorable development of the invention, the operating voltage unit may comprise an AC / DC conversion unit. In this case, a mains connection for the electric machine tool can be provided, and in the operating voltage unit, the rectification and smoothing of the mains voltage can take place. Although the preparation of the mains voltage requires more space than an energy store, the further space-saving and compact design in a single housing still allows a simplified operation and handling of the power tool.

According to a favorable development of the invention, the electronic unit can be concentrated on a circuit board. This allows a particularly space-saving arrangement in the housing. The electronic control of the excitation actuator is particularly compact.

According to a favorable development of the invention, for signal filtering and for inductive compensation of the at least one excitation actuator, at least one inductance in a power circuit of the electronic unit, which supplies the at least one excitation actuator with electrical power, is provided be. It can be a space-saving structure of the power inductors realized in a single bobbin. The favorable in excitation actuators signal filtering and inductive compensation of the piezoelectric actuator can be provided directly via a specifically set leakage inductance of a transmission transformer anyway required or be given by a wound on the same coil core inductance. An additional coil core with a further inductance in the power circuit can thereby be omitted.

According to a favorable development of the invention, at least the drive unit, the electronic unit and the operating voltage unit can be distributed in the housing such that a center of mass lies in the area of the handle part. The operator can handle the power tool safely and conveniently. The safety and ease of use are increased.

According to a favorable development of the invention, the drive unit can comprise, in addition to the at least one excitation actuator, at least one further drive component. Advantageously, the working movement of a tool driven by the at least one further drive component can be superimposed by the at least one excitation actuator movement, whereby the work progress can be significantly improved and the processing can be facilitated.

According to a favorable development of the invention, the at least one excitation actuator can form a main energy consumer of the electric machine tool, for which preferably at least 50% electrical input power can be provided. In a favorable development, at least 75%, preferably at least 80%, of the electrical input power can be provided for the excitation actuator. The progress of the electric machine tool when using ultrasound is particularly large, so that a further energy consumer, in particular a further drive component, such as a drill, a Meisel, a knife or the like, can be made smaller. Thus, the drive and the associated electronic components and the power supply can be smaller, which in turn allows improved ease of use and improved handling of the hand-held power tool.

According to a favorable development of the invention, one or more operating displays can be provided for an activated state of the at least one excitation actuator. The display can be made optically and / or acoustically and / or haptically. The reliability of the power tool is increased because it is clearly visible when the excitation is activated and can deliver mechanical power.

According to a favorable development of the invention, the drive unit, which imparts a working movement to the tool, can impress the tool on superposition oscillations. The drive unit can have as an additional drive component, for example, an electric drive motor, which is accommodated in the housing of the power tool. The motor shaft is usually coupled via a gear unit with a tool shaft, which is the carrier of the tool and performs the working movement. The tool is usually replaceable to attach to the tool shaft.

The power tool may e.g. be used for machining of workpieces, to reduce the chip size advantageously the excitation is arranged in the power tool, which can generate overlay oscillations in the tool. These superimposed vibrations are superimposed on the working movement of the tool.

The superposition oscillations, which do not originate from the drive motor, but from the excitation actuator, depending on the type of power tool and depending on the tool used and the workpiece material to be machined at a frequency can be generated, which leads to a significant reduction of the chip size. Since smaller chips also have a smaller heat capacity, the chips can cool down in a shorter period of time, whereby the risk of fire is reduced. In addition, the smaller chips per se lead to a reduced risk of injury, since the pulse emanating from them is lower.

The frequency of the superposition oscillations is expediently in the ultrasound range and can thus amount to at least 20 kHz, for example. This relatively high frequency on the one hand has the advantage that vibrations of this magnitude are no longer audible to humans, so no noise pollution arises. On the other hand, it has been found that vibrations of this magnitude are particularly effective in order to significantly reduce the size of the chips that arise during the machining of a workpiece.

It may be appropriate to generate overlay oscillations that are in much larger orders of magnitude. In principle, vibrations up to the megahertz range come into consideration. In addition, it is also possible to generate heterodyne oscillations at a lower frequency.

Due to the superposition of the working movement of the tool on the one hand and the usually much higher frequency remains generating the overlay vibrations without effect on the working movement and thus on the result of workpiece machining. In addition, the overlay vibrations usually have only a very small amplitude, so that the machining of the workpiece is not impaired.

The advantageous generation of superposition oscillations in the tool can be used both in rotational and in translational or mixed rotationally translatory working movements of the tool. According to a favorable embodiment, the electric machine tool is designed as a grinding device, for example as an angle grinder, which has a tool mounted on a tool shaft grinding wheel as a tool, in which case the tool movement is an exclusive rotational movement. But also translational movements come, for example in lifting saws that perform an oscillating stroke movement.

The superposition vibrations can be excited according to an advantageous embodiment orthogonal to the plane of movement of the tool in which the working movement takes place. For example, in the case of grinding wheels, the superposition vibrations can be applied in the direction of the tool shaft carrying the grinding wheel. In contrast, in the case of a translatory working movement, the superimposition oscillation takes place perpendicularly to the translational movement.

However, according to a further expedient embodiment, it is also possible that the superposition oscillations excite the tool in the plane of motion. In the event of For a grinding wheel this means that the grinding wheel is excited perpendicular to the tool shaft, so that the vector of the excitation lies in the plane of movement of the grinding wheel.

Furthermore, it may be expedient to let the overlay oscillations emanating from the excitation actuator act on a bearing of the tool, the oscillations also propagating to the tool via the bearing. In the case of several bearings, this is preferably done via the tool-near bearing to avoid loading of the gear unit and the drive motor by the superposition oscillations.

As an excitation actuator, different active actuators can be used, which can be excited by supplying energy for vibration generation. According to an advantageous embodiment, it may be provided that the excitation actuator is designed as a Langevin oscillator with clamped piezo elements which changes its extent by applying a voltage. By a correspondingly high-frequency voltage application, the piezoelectric element can expand and contract in the desired frequency of the superposition oscillations, wherein the excitation is coupled to a component in the power transmission chain between the drive unit or drive motor and tool, so that the vibrations of the excitation actuator spread into the tool can. As already described above, the excitation preferably takes place via a bearing of the tool shaft which carries the tool. According to a further embodiment, it is provided that the excitation actuator is designed as a magnetostrictive excitation actuator, which is particularly suitable for generating ultrasonic vibrations.

drawing

Further advantages emerge from the following description of the drawing. In the drawings, embodiments of the invention are shown. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations.

They show by way of example:

Fig. 1

an embodiment of a hand-held power tool in an embodiment as a cutting device;

Fig. 2

another embodiment of a hand-held power tool in an embodiment as a drill;

Fig. 3a, 3b

a schematic diagram of a drive with an AC power supply with AC power or a DC power supply with a battery pack ( Fig. 3a ) and a favorable timing for reducing the size of a filter unit ( Fig. 3b );

Fig. 4

a course of an ultrasonic amplitude along a sonotrode;

Fig. 5

an impedance characteristic for detecting a resonance frequency of an excitation actuator;

Fig. 6

an equivalent circuit diagram of an ideal transformer;

Fig. 7

a designed as angle grinder electric power tool in section;

Fig. 8

in an individual view, arranged on a tool shaft grinding wheel of the angle grinder Fig. 7 wherein the tool shaft is received in bearings and the tool-near bearing is acted upon by a Anreungsaktor transverse to the shaft axis with high-frequency oscillations;

Fig. 9

the grinding wheel off Fig. 8 with bearing and excitation actuator in a plan view; and

Fig. 10

a further embodiment in which the excitation actuator acts on the grinding wheel supporting tool shaft in the axial direction with high-frequency oscillations.

Embodiments of the invention

In the figures, the same or similar components are numbered with the same reference numerals.

To illustrate the invention show the FIGS. 1 and 2 Various examples of hand-held power tools 10. Fig. 1 shows a cutting device with elongated housing shape; Fig. 2 shows a drill with T-shaped housing.

The handheld power tool 10 includes a housing 20 having a handle portion 40. An operator holds the power tool 10 on the handle portion 40 and may guide the power tool 10. The grip area 40 may optionally be decoupled with a damping element, not shown, with respect to other housing areas. The electric machine tool 10 further comprises a tool region 50 for a linearly and / or oscillatory drivable tool 60, such as a knife ( Fig. 1 ) or a drill ( Fig. 2 ) or another tool according to another device type.

A housing-side operating part 30 serves for the user-side activation of the tool 60 and / or of the power tool 10. The operating part 30 may e.g. be a switch or a controller or also comprise a plurality of controls, of which e.g. one for turning on the power tool 10 and one for turning on and / or controlling the tool 60 may be provided.

In the housing 20, a drive unit 80 is arranged, which in the examples according to Fig. 1 and Fig. 2 includes only one drive component formed by an excitation actuator 100. This can be designed as a piezo-excited Langevin oscillator (also called a piezoactuator) which comprises a volume of piezoelectrically active material 102, eg piezoceramic disks which are pressed together and which undergo a change in length when subjected to electrical voltage. When Beauschlagung with high-frequency electrical voltage ultrasound is generated in a conventional manner, which is passed via a coupling element 106 to a tool 60. The coupling element 106 may be a per se known sonotrode. The length and the shape as well as the material of the coupling element 106 determine a resonance frequency of the excitation actuator 100. The tool 60 can also influence the resonance frequency. In the embodiments in Fig.1 and Fig.2 the excitation actuator 100 is designed so that Langevin oscillator and coupling element 106 are combined in one unit, and whose entire length corresponds to approximately half the wavelength λ / 2 of the ultrasonic vibration. Other embodiments may provide that the excitation actuator 100 is composed of several components of length λ / 2. These can be: Vibration generator, known as a converter, in particular, for example, a Langevin oscillator, amplitude transformation pieces 104 known as boosters, possibly extension pieces, as well as the coupling element 106 known as a sonotrode.

An electronic unit 200 arranged in the housing 20 serves to apply at least control and / or regulating signals to the drive unit 80 as well as to the voltage supply of the excitation actuator 100. An operating voltage unit 90, here designed as a battery pack with batteries or rechargeable batteries 92, serves to provide it an electrical DC voltage for the electronic unit 90, which converts the operating voltage into a high-frequency voltage signal with which the excitation actuator 100 is excited to vibrate in the desired manner.

The electronic unit 200 is configured to operate the at least one excitation actuator 100 at a resonant frequency f_res. In this case, the electronic unit 200 comprises a control unit 224 for tracking the resonance frequency f_res of the excitation actuator 100. The control unit 224 may comprise a phase locked loop which can excite the excitation actuator 100 at its resonant frequency, with a phase shift between the injected current and the injected voltage being set to 0 ° becomes. The resonance frequency f_res is preferably readjusted when the resonant frequency changes due to heating or load changes on the tool. Alternatively, a frequency tracking can also take place by regulating to a maximum of the current fed into the excitation actuator 100.

If the excitation actuator 100 is a piezoactuator, the volume of the piezoelectrically active material 102, for example stacked piezoelectric disks, is favorably at least 0.2 cm ³ , preferably 0.5 cm ³ , in particular at least 1 cm ³ . The excitation actuator 100 may have a power density of at least 5 watts / cm ³ , preferably at least 20 watts / cm ³ , based on the volume of the piezoelectric active material 102 of the excitation actuator 100. The power density allows use in a hand-held Power tool 10 with sufficient power output of the tool 60th

The activation of the tool 60 by the activation actuator 30 can be performed with a signal means 122 (FIG. Fig. 2 ) are displayed.

In Fig. 1 the electronic unit 200 is particularly space-saving integrated on a single board 210. In Fig. 2 the electronic unit is divided into two boards 212, 214, wherein one in the main part and a projecting in the transverse part of the main body grip portion of the T-shaped housing 20 is arranged. Drive unit 80, electronic unit 200 and operating voltage unit 90 are advantageously distributed in housing 20 in such a way that a center of mass lies in the area of handle part 40.

Fig. 3a shows a schematic diagram of a control of the excitation actuator 100, for example in the form of a piezoelectric actuator 100, with an AC power supply from a supply network or a DC power supply with a battery pack.

With mains supply of the electronics unit 200, e.g. with 220 volts ac, an assembly 94 is provided which rectifies and smooths the AC voltage. The electronic unit 200 comprises a power generation unit 222 into which the DC voltage is fed and which is coupled to the excitation actuator 100 via a corresponding filter unit 226. A control unit 224 provides the control signals for the excitation actuator 100. The operating frequency of the excitation actuator 100 is in the range between 10 kHz and 1000 kHz, preferably between 30 kHz and 50 kHz, in particular between 35 kHz and 45 kHz, particularly preferably around 40 kHz.

If the supply by the operating voltage unit 90 by means of batteries or rechargeable batteries 92, the space required can be reduced, since the assembly 94 for rectification and smoothing can be omitted. The electrical output voltage of the operating voltage unit 90 is preferably below 100 volts, at about 36 volts or 10.8 volts.

The maximum electrical excitation field strength of the at least one excitation actuator is preferably in the range below 300 V / mm (based on the thickness, in particular slice thickness, of the piezoelectrically active material), preferably in the range between 50 V / mm and 220 V / mm. With a slice thickness of the excitation actuator 100 of typically 1 mm to 10 mm, preferably 2 mm to 6 mm, in particular by 5 mm, the electrical voltages are less than 1000 volts

In one embodiment, the power generation unit 222 may be implemented by means of 4 MOSFET semiconductors in a full-bridge topology known per se. In a further variant, the generation of the operating signal may also be effected by a half-bridge (also known) with e.g. a mid-point capacitor for filtering the DC component.

Fig. 3b illustrates a way to make the size of the filter unit 226 as small as possible. For this purpose, the power unit 222 can also be controlled by the control unit 224 in such a way that it generates a sine-wave-like square-wave voltage by means of, for example, a sine-wave modulation instead of simple square-wave signals. Depending on the amount of timing, ie the number of individual pulses, which together form a sine, the content of unwanted harmonic harmonic frequencies can be significantly reduced, resulting in a smaller design of the filter unit 226. For this purpose, the number of square pulses per period of the sinusoidal signal is greater than 6, preferably in a range between 6 and 100, in particular in a range between 10 and 26. In one embodiment, the number and width of the rectangular pulses of the control unit 224, for example, during load changes during of the operation are changed.

Fig. 4 , shows a profile of an ultrasonic amplitude along an excitation actuator 100 designed as a piezoelectric actuator. The coupling element 106 is designed as a sonotrode. The region of the excitation actuator 100 which adjoins the piezoelectric material 102 is designated together with the piezoelectric disks 102 as a converter. The piezoelectric material 102 is excited by the fed high-frequency AC voltage to vibrations, which are transmitted via the converter in the coupling element 102. At a like in Fig. 4 shown three-stage structure of the excitation actuator 100, this additionally consists of a booster 104 for amplitude adjustment. Along the longitudinal extent M of the excitation actuator 100 takes on average the amplitude Amp excited vibration too. Changes in the resonant frequency f_res of the oscillation system of the excitation actuator 100 (possibly with coupled tool) during operation are preferably compensated, for example with a phase-locked loop already mentioned above, with which the phase shift between the voltage applied to excite the excitation actuator 100 and the supplied electrical current is regulated to zero (phase zero control), or with a maximum control of the fed into the excitation actuator 100 electrical current.

Fig. 5 shows an impedance characteristic of a piezoactively executed excitation actuator with the resonance frequencies f_res and f_res2. Characteristic A shows a profile of the impedance Imp as a function of the frequency f, which passes through an impedance minimum at the resonance frequency f_res and an impedance maximum at f_res2. The frequency f_res is referred to as a series resonance, f_res2 as a parallel resonance.

Curve B shows the course of the phase shift between current and voltage, which has a zero crossing at the resonance frequency and changes from -90 ° below the resonance frequency f_res to + 90 ° above the resonance frequency f_res. When passing through the parallel resonance f_res2, the phase shift of + 90 ° below the resonance frequency changes to -90 ° above the resonance frequency.

For signal filtering and for inductive compensation of the at least one excitation actuator 100, at least one inductance in a power circuit of the electronics unit, which supplies the at least one excitation actuator 100 with electrical power, may be provided. It can be a space-saving structure of the power inductors realized together with the transmission transformer in a single bobbin. The favorable with excitation actuators 100 signal filtering and inductive compensation of the piezoelectric actuator can be provided directly via a deliberately set leakage inductance of a transmission transformer anyway required or be given by a wound on the same coil core inductance. An additional coil core with a further inductance in the power circuit can thereby be omitted.

Fig. 6 shows for explanation an equivalent circuit diagram with an ideal transformer. The inductance M serves the actual transmission from primary side to secondary side. The stray inductances arise because the windings can never be ideally coupled. L1 and L2 represent the part of the magnetic field that can not be "captured" by the secondary coil. L1 and L2 are to be considered as an air coil.

In the Fig. 7 shown as an angle grinder electric power tool 10 includes a housing 20 which consists of a motor housing 22 and a handle housing 24, wherein between the motor housing 22 and handle housing 24, a damping element 26 is arranged. The power tool 10 is held on the handle housing 24, which forms the grip portion 40. In the motor housing 22, a drive unit 80 is received with a formed as an electric drive motor 82 drive component, which is coupled via a gear unit 62 with a tool shaft 64 and drives them. The tool shaft 64 carries a tool 60 designed as a grinding wheel which is interchangeably fixed to the tool shaft 64.

In Fig. 8 is the tool shaft 64 and attached thereto, designed as a grinding wheel tool 60 shown in detail. The tool shaft 64, which has the longitudinal axis L, is rotatably mounted in bearings 70 and 72 which are spaced apart in the housing 20 are arranged. On the end face opposite the grinding wheel there is a bevel gear 74 on the tool shaft 64, via which the tool shaft 64 is driven by the electric drive motor 82.

In order to reduce the size of the chips produced during the machining of a workpiece with the tool 60 designed as a grinding wheel, the tool 60 designed as a grinding wheel is set in high-frequency oscillations in addition to its rotary working movement. These are overlapping vibrations that are superimposed on the working movement of the tool 60 designed as a grinding wheel. These superposition vibrations are generated by means of the excitation actuator 100, which is also arranged as a further drive component of the drive unit 80 in the housing 10 of the hand-held power tool 10 and directly or indirectly excites the designed as a grinding wheel tool 60 to the superposition oscillations. In the embodiment according to Fig. 8 the excitation actuator 100 acts on the tool-side bearing 70 of the tool shaft 64 and generates superposition oscillations that are orthogonal to the longitudinal axis L of the tool shaft 64 are addressed. These superposition vibrations directed orthogonally to the longitudinal axis L are also transmitted via the tool shaft 64 to the tool 60 designed as a grinding wheel, which likewise exercises orthogonal to the longitudinal axis L and thus overlapping vibrations in its movement plane.

In principle, it is also possible to position the excitation actuator 100 at a different location, for example at the tool-distant bearing 72 or directly at a position on the tool shaft 64 or on the tool 60 designed as a grinding wheel, in order to apply this directly to superposition oscillations.

As excitation actuator 100, various active actuators can be used. Preferably, actuators are used. generate the high-frequency vibrations in the ultrasonic range, in particular in a frequency range of at least 20 kHz, possibly also frequencies in higher orders of magnitude come into consideration, especially into the megahertz range, or even smaller frequencies.

As excitation actuator 100, a piezoelectric element is used by way of example. whose length changes by applying an electrical voltage. Since piezoelectric elements react very quickly to changes in voltage, a correspondingly rapid change in length in the excitation actuator can be generated by the application of a high-frequency voltage, which has an effect on the tool 60 embodied here by way of example as a grinding wheel.

The excitation actuator 100 can also be designed as a magnetoresistive actuator in which the electrical resistance can be changed by applying an external magnetic field.

In the embodiment according to Fig. 8 and 9 the superposition vibrations in the direction of arrow 110 are generated orthogonal to the longitudinal axis L of the tool shaft 64 and the tool 60 designed as a grinding wheel. In the embodiment according to Fig. 10 on the other hand, the excitation with the superposition oscillations according to arrow direction 110 takes place in the direction of the longitudinal axis L of tool shaft 64 and tool 60 and thus perpendicular to the plane of movement of the tool 60 designed as a grinding wheel. The excitation actuator 100, via which the superposition oscillations are generated, acts either directly on the tool shaft 64 or one or both bearings 70 and 72 or directly the tool 60 with the superposition vibrations in the axial direction.

Claims (26)

Hand-held power tool (10) comprising a housing (20) with a grip area (40), a tool region (50) for a linearly and / or oscillatory drivable tool (60), a housing-side operating part (30) for the user-side activation of the tool (60) and / or the power tool (10), a drive unit (80) arranged in the housing (20) for producing a working movement of the tool (60), an electronics unit (200) arranged in the housing (20) for acting on the drive unit (80) with at least control and / or regulating signals, an operating voltage unit (90) for providing a direct electrical voltage,
wherein the drive unit (80) comprises at least one excitation actuator (100) having a volume of excitation-active material which is electrically supplied in operation by the operating voltage unit (90), is controlled or regulated by the electronic unit (200),
characterized in that the electronic unit (200) is adapted to operate the at least one excitation actuator (100) at a resonant frequency (f_res), the electronic unit (200) comprising a frequency matching control unit (224) for tracking the resonant frequency (f_res) of the at least one excitation actuator (100). Hand-held power tool according to one of the preceding claims, characterized in that the excitation-active material is piezoelectric. Hand-held power tool according to claim 2, characterized in that the volume of the piezoelectric material is at least 0.2 cm ^3, preferably 0.5 cm ^3, especially at least 1 cm ^3. Claims, characterized in that the at least one excitation actuator (100) has a power density of at least 5 watts / cm ³ , preferably at least 20 watts / cm ³ , based on the volume of the piezoelectrically active material (102) of the at least one excitation actuator (100). having. Hand-held power tool according to one of the preceding claims, characterized in that the at least one excitation actuator on the tool tip has a vibration amplitude of at least 3 microns, preferably at least 8 microns, in particular at least 12 microns. Hand-held power tool according to one of the preceding claims, characterized in that the input side of the electronic unit (200) is an electric power for acting on the at least one excitation actuator (100) at least 20 watts. Hand-held power tool according to one of the preceding claims, characterized in that a slice thickness of the excitation is typically 1 mm to 10 mm, preferably 2 mm to 6 mm, in particular by 5 mm. Hand-held power tool according to one of the preceding claims, characterized in that an input field strength of the at least one excitation actuator (100) in the range of 300 V / mm are based on a thickness, in particular a slice thickness of the piezoelectric active material, preferably in the range between 50 V / mm and 220 V / mm. Hand-held power tool according to any one of the preceding claims, characterized in that an input voltage of at least one Anregungsaktors (100) is in the range below 1000 volts, preferably in the range between 300 volts and 700 volts. Hand-held power tool according to one of the preceding claims, characterized in that an electrical output voltage of the operating voltage unit (90) is below 100 volts. Hand-held power tool according to one of claims 1 to 9, characterized in that an electrical output voltage of the operating voltage unit (90) is above 100 volts. Hand-held power tool according to one of the preceding claims, characterized in that the operating frequency of the at least one excitation actuator (100) in the range between 10 kHz and 1000 kHz, preferably between 30 kHz and 50 kHz, in particular between 35 kHz and 45 kHz. Hand-held power tool according to one of the preceding claims, characterized in that the operating voltage unit (90) comprises an electrochemical storage (92), preferably a rechargeable electrochemical storage (92). Hand-held power tool according to one of the preceding claims, characterized in that the operating voltage unit (90) comprises a rectifier (94). Hand-held power tool according to one of the preceding claims, characterized in that the electronic unit (200) is concentrated on a circuit board (210). Hand-held power tool according to one of the preceding claims, characterized in that for signal filtering and / or inductive compensation of the at least one excitation actuator (100) at least one inductance in a power circuit of the electronics unit (200), the at least one excitation actuator (100) with electrical power is provided for. Hand-held power tool according to one of the preceding claims, characterized in that at least the drive unit (80), electronics unit (200) and operating voltage unit (90) are distributed in the housing (20) that a center of mass in the region of the handle portion (40). Hand-held power tool according to one of the preceding claims, characterized in that the drive unit (80) in addition to the at least one excitation actuator (100) comprises at least one further drive component. Hand-held power tool according to one of the preceding claims, characterized in that the at least one excitation actuator (100) forms a main energy consumer of the power tool (10), for which preferably at least 50% electrical input power is provided. Hand-held power tool according to one of the preceding claims, characterized in that one or more optical and / or acoustic and / or haptic Betriebsabzeigen (120, 122) for an activated state of the at least one excitation actuator (100) are provided. Hand-held power tool according to one of the preceding claims, characterized in that the excitation actuator (100) for generating overlapping vibrations in the tool (60) is provided, which are superimposed on a working movement of the tool (60). Hand-held power tool according to any one of the preceding claims, characterized in that the tool (60) is rotatably mounted and the working movement of the tool (60) is a rotational movement. Hand-held power tool according to claim 22, characterized in that the tool (60) is a grinding wheel. Hand-held power tool according to one of claims 21 to 23, characterized in that the superposition oscillations excite the tool (60) in at least one of the following directions orthogonal to the plane of movement of the tool (60) in which the working movement of the tool (60) takes place; - in the direction of the longitudinal axis (L) of a tool (60) carrying the tool shaft (64); in the plane of movement in which the working movement of the tool (60) takes place; and or - perpendicular to the tool shaft (64). Hand-held power tool according to one of the preceding claims, characterized in that the excitation actuator (100) acts on a bearing (70, 72) of the tool (60). Hand-held power tool according to one of the preceding claims, characterized in that the excitation-active material (104) of the excitation actuator (100) is magnetostrictive.

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