DE102009027688A1 - Hand held power tool - Google Patents

Abstract

The invention relates to a hand-held power tool (10) comprising - a housing (20) with a grip area (40), - a tool area (50) for a linearly and / or oscillating drivable tool (60), - a housing-side operating portion (30 ) for the user-side activation of the tool (60) and / or the power tool (10), - in the housing (20) arranged drive unit (80) for generating a working movement of the tool (60), - in the housing (20) arranged electronic unit ( 200) for applying at least control and / or regulating signals to the drive unit (80), - an operating voltage unit (90) for providing a direct electrical voltage, the drive unit (80) comprising at least one excitation actuator (100) with a volume of excitation-active material - Is electrically powered during operation of the operating voltage unit (90), - is controlled or regulated by the electronic unit (200). It is proposed that the electronic unit (200) is designed to operate the at least one excitation actuator (100) at a resonance frequency (f_res).

Description

State of the art

The Invention is based on a hand-held power tool comprising a housing with a grip area, a tool area for a linearly and / or rotationally drivable oscillating Tool, a housing-side control panel to the 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, one arranged in the housing Electronic unit for acting on the drive unit with 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 exciter character with a Volume of excitation active material, which in the operation of the operating voltage unit is electrically supplied, controlled by the electronic unit or regulated.

hand-held Power tools are characterized by the fact that they are portable are held in hand and by a server in operation and be guided. You can wirelessly over battery packs or be operated with mains power. In particular, these exist usually only one housing, which 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 is based on a hand-held power tool, comprising a housing with a grip area, a tool area for a linearly and / or rotationally drivable oscillating Tool, a housing-side control panel to the 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, one arranged in the housing Electronic unit for acting on the drive unit with 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 has at least one excitation actuator with a Volume of excitation active material, which in the operation of the operating voltage unit is electrically supplied, controlled by the electronic unit or regulated.

It it is proposed that the electronic unit is designed around the at least one excitation actuator in a resonant frequency to operate.

Becomes the excitation actuator operated at its resonant frequency, so can at sufficiently high quality of the vibration system accordingly an electrical input power a high mechanical output power be delivered. The excitation actuator may be an ultrasonic excitation actuator, in particular a piezoelectric actuator in the construction of a Langevin oscillator. The piezoelectric actuator has piezoelectric as excitation-active material Material on. Typically, the quality of the undamped oscillatory system at values over 100, typically over 500. The Resonance system of the excitation actuator, which has the resonance frequency, includes the Langevin transducer with piezoelectrically active material and components coupled to the vibrator, in particular components, which amplify the ultrasound and / or transferred to a processing location. Such components are for. B. known as a booster or sonotrode. This allows a size reduction and providing a compact device. Advantageous becomes a compact power tool of high performance created, which is handy at the same time.

It can also be several excitation factors, eg. B. with the same or with different resonant frequency, may be provided 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 connection can z. B. cohesive or non-positive. The power tool is in particular a processing machine, with the objects or Machined or modified surfaces such as drills, rotary hammers, cutting tools, grinding machines, milling, sawing, welding equipment and the like.

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

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 one favorable development of at least one excitation factor at the tool tip a vibration amplitude of at least 3 microns, preferably at least 8 μm, in particular at least 12 μm exhibit. A correspondingly high oscillation amplitude is advantageous for a good power transfer to the workpiece and thus for a high work progress through the Power tool.

According to one favorable development of the invention can input side the electronic unit an electric power for applying of the at least one excitation factor amount to at least 20 watts. Advantageously, thus a sufficient power for a Electric power tool can be ensured. usual Services are in the DIY sector, for small cutting systems approximately between 20 watts and 250 watts, preferably 50 watts to 150 Watt. For more powerful applications, eg. B. Drilling, powers are from 50 W to 1000 W, preferably 200 watts needed up to 500 watts. In the professional artisan area the power requirement for small systems is around 50 and 400 watts, preferably 100 to 250 watts. For big ones Systems will power from 200 W to 2000 watts, preferably 400 watts to 1000 watts used. Nevertheless, a power tool can be created with handy dimensions, on the one hand of the hand of the editor can be included or held and for provides enough power for processing.

According to one favorable development of the invention can be a maximum electrical excitation field strength of the at least one excitation actuator in the range below 300 V / mm (in terms of thickness, in particular slice thickness, of the piezoelectrically active material), preferably in the range between 50 V / mm and 220 V / mm. At 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 are the electrical voltages below 1000 volts. this makes possible advantageous use of the excitation in the hand-held Electric machine tool with sufficient mechanical output power at advantageously small dimensions.

According to one favorable development of the invention can be an electrical Output voltage of the operating voltage unit when supplied with electrochemical Storage within 3 volts to 100 volts DC is preferred in the range of 3.5V to 40V, especially at 36V, 24V, 18 volts, 14.4 volts, 12 volts, 10.6 volts, 7.2 volts, and 3.6 volts. Advantageous can use battery packs or rechargeable battery packs Be that small and light enough to be easy to handle the power tool to ensure 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 z. B. using a bridge rectifier with smoothing capacitor at 1.4 U _network . In a further embodiment, the mains voltage by means of an input side Transformers are converted to a suitable voltage for the operating voltage unit.

According to one favorable development of the invention, the operating frequency the at least one excitation factor in the range between 10 kHz and 1000 kHz, preferably between 30 kHz and 50 kHz, in particular between 35 kHz and 45 kHz, more preferably around 40 kHz. With increasing frequency, the size of the Components and increases the mechanical load of the vibration system, wherein advantageous in the selected frequency range Size ratios with high output power and favorable weight of the electric machine tool.

According to one favorable development of the invention, the operating voltage unit comprise an electrochemical storage, preferably a rechargeable electrochemical storage. The operating voltage unit has a only small space requirement, what for the compactness and the weight the power tool is advantageous. Are cheap Systems based on z. As lithium ions (Li-ion) or else Nickel-metal hydride (NiMeH), nickel cadmium (NiCd) or lead and the same. These can be fixed in the housing be integrated and recharged via a charging port. Alternatively, the operating voltage unit can be designed as a change system be, with exchangeable electrochemical storage, if necessary also be rechargeable externally, and in one intended inclusion in or on the housing can be inserted. The rated voltage of the operating voltage unit depending on the power requirement z. B. between 3 volts dc and 48 Volts dc lie, z. B. at 12 volts dc.

According to one favorable development of the invention, the operating voltage unit an AC / DC conversion unit. In this case can also be a Power supply for the power tool provided be, and in the operating voltage unit, the rectification and smoothing the mains voltage. Although needed the preparation of the mains voltage more space than an energy storage, the more space-saving and compact construction in a single Housing, however, still allows a simplified Operation and handling of the power tool.

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

According to one favorable development of the invention can 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, the at least one excitation actuator with electrical Power applied, be provided. It can be a space saving Structure of the power inductors in a single coil core will be realized. The favorable with excitation actuators signal filtering and inductive compensation of the piezoelectric actuator can directly over a specifically set leakage inductance of a transmission transformer that is required anyway provided or by a wound on the same spool core Inductance can be given. An additional one Coil core with a further inductance in the power circuit can be omitted.

According to one favorable development of the invention can at least drive unit, Electronic unit and operating voltage unit so in the housing be distributed that a center of gravity in the area of the grip part lies. The operator can make the power tool safe and secure easy to handle. The safety and ease of use are increased.

According to one favorable development of the invention, the drive unit at least one further next to the at least one excitation actuator Drive component include. Advantageously, the working movement a driven by the at least one further drive component tool one superimposed by the at least one excitation actuator movement which greatly improves work progress and the processing can be facilitated.

According to one favorable development of the invention, the at least an excitation actuator a main energy consumer of the power tool form, for preferably at least 50% electrical Input power can be provided. In a cheap Training can be at least 75% for the excitation factor, preferably at least 80% of the electrical input power provided be. The work progress of the electric machine tool in use Ultrasound is particularly large, so another one Energy consumers, in particular a further drive component, such as a drill, a chisel, a knife or the like, smaller can be designed. This can also drive and the associated Electronic components and the power supply are smaller, which in turn improved the ease of use and improved Handling of the hand-held power tool allowed.

According to a favorable development of the invention, one or more operating indications for an activated state of the at least one Excitation actuator be provided. 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 one favorable development of the invention, the drive unit, which imparts a working movement to the tool, the tool overlay vibrations impress. The drive unit can be used as a further drive component For example, have an electric drive motor in the housing of the power tool is added. The motor shaft is usually via a gear unit coupled with a tool shaft, the carrier of the tool is and executes the labor movement. The tool is usually replaceable to attach to the tool shaft.

The Power tool can, for. B. for machining of Workpieces are used, to reduce the Spangröße advantageous the excitation in the Power tool is arranged, which overlay vibrations can generate in the tool. These superposition vibrations are superimposed on the working movement of the tool.

The superposition oscillations, which not from the drive motor but from the excitation actuator can go out, depending on the type of power tool and depending on the tool used and the to be machined workpiece material with a frequency can be generated, resulting in a significant reduction in chip size leads. Because smaller chips also have a smaller heat capacity can show the chips in a shorter Cool down period, reducing the risk of fire. In addition, the smaller chips lead to a reduced risk of injury, since the outgoing of them Impulse is lower.

The Frequency of the superposition oscillations is expediently in the ultrasonic range and thus can, for example, at least 20 kHz. This relatively high Frequency has the advantage that vibrations of this magnitude no longer to be heard for man, so that no noise is generated. To change It has been shown that vibrations of this magnitude are particularly effective to the size of the chips, which arise when machining a workpiece, significantly to reduce.

It may be appropriate, overlay vibrations to generate that in even greater magnitude lie. Basically there are vibrations all the way to the Megahertz range is considered. In addition, it is also possible overlay vibrations to generate at lower frequency.

On Reason of superposition to the working movement of the tool on the one hand, and the usually much higher frequency the generation of overlay vibrations remains without Influence on the work movement and thus on the result of the work Workpiece machining. In addition, the overlay vibrations usually only a very small amplitude, allowing the machining of the workpiece is not affected.

The advantageous generation of superposition oscillations in the tool can be used in both rotary and translatory or mixed rotationally translational working movements of the Tool are used. According to a favorable Execution is the power tool as a grinder, For example, designed as an angle grinder, as a tool a mounted on a tool shaft grinding wheel, wherein in this case, the tool movement is an exclusive one Rotation movement is. But also translational Movements, for example in lifting saws, the oscillating lifting movement To run.

The overlay vibrations can according to an advantageous embodiment be excited orthogonal to the plane of movement of the tool, in the work movement takes place. For example, you can for grinding wheels, the superposition vibrations in the direction the grinding wheel carrying tool shaft are applied. In a translatory working movement, however, the superimposition oscillation takes place perpendicular to the translation movement.

According to one further expedient embodiment but it is also possible that the overlay vibrations excite the tool in the plane of movement. Im Fal le a grinding wheel means this is that the grinding wheel is excited perpendicular to the tool shaft so that the vector of excitation in the plane of motion of the Grinding wheel is located.

Of Further, it may be appropriate, the of the Excitation actuator outgoing superposition oscillations on a bearing of the tool to act, the vibrations spread over the bearing on the tool. In the event of of several camps, this is preferably done via the Tool-near bearing to load the gear unit as well of the drive motor by the superposition oscillations to avoid.

When Excitation actuator can perform differently, active actuators are used by supplying energy can be excited to generate vibration. According to one advantageous embodiment may be provided that the excitation actuator designed as a Langevin oscillator with clamped piezo elements is that changes its extent by applying a voltage. By a correspondingly high-frequency voltage application may occur the piezoelectric element in the desired frequency of the superposition oscillations expand and contract, the excitation with a Component in the power transmission chain between the drive unit or drive motor and tool is coupled, so that the Vibrations of the excitation actuator spread into the tool can. As already described above, the excitation takes place preferably via a bearing of the tool shaft, which is the Tool carries. According to another Embodiment is provided that the excitation actuator as magnetorestrictive excitation actuator is formed, which is in particular suitable for generating ultrasonic vibrations.

drawing

Further Advantages are shown in the following description of the drawing. In the drawing, embodiments of the invention shown. The drawing, the description and the claims contain numerous features in combination. The specialist will expediently also consider the features individually and summarize to meaningful further combinations.

It show by way of example:

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

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

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 ( 3a ) and a favorable timing for reducing the size of a filter unit ( 3b );

4 a course of an ultrasonic amplitude along a sonotrode;

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

6 an equivalent circuit diagram of an ideal transformer;

7 a designed as angle grinder electric power tool in section;

8th in an individual view, arranged on a tool shaft grinding wheel of the angle grinder 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;

9 the grinding wheel off 8th with bearing and excitation actuator in a plan view; and

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 the invention

In the figures are the same or similar components with the same Numbered.

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

The hand-held power tool 10 includes a housing 20 with a grip area 40 , An operator holds the power tool 10 at the grip area 40 and can the power tool 10 to lead. The grip area 40 may optionally be decoupled with a damping element, not shown, with respect to other housing areas. The power tool 10 further includes a tool area 50 for a linear and / or oscillating drivable tool 60 , about a knife ( 1 ) or a drill ( 2 ) or another tool according to another device type.

A housing-side control panel 30 serves for the user-side activation of the tool 60 and / or the power tool 10 , The control panel 30 can z. B. be a switch or a controller or include several controls, of which z. B. one for turning on the power tool 10 and one for turning on and / or controlling the tool 60 can be provided.

In the case 20 is a drive unit 80 arranged in the examples according to 1 and 2 includes only one drive component that is driven by an excitation actuator 100 is formed. This can be designed as a piezo-excited Langevin oscillator (also called a piezoactuator), which is a volume of piezoelectrically active material 102 includes, for. B. piezoceramic discs that are pressed together and perform a change in length when exposed to electrical voltage. When Beauschlagung with high-frequency electrical voltage ultrasound is generated in a conventional manner, via a coupling element 106 to a tool 60 is directed. The coupling element 106 may be a known sonotrode. The length and shape as well as the material of the coupling element 106 determine a resonant frequency of the excitation actuator 100 , Also the tool 60 can affect the resonant frequency. In the embodiments in 1 and 2 is the excitation factor 100 designed so that Langevin oscillator and coupling element 106 are combined in one unit, and their entire length corresponds to approximately half the wavelength λ / 2 of the ultrasonic vibration. Other embodiments may provide that the excitation factor 100 composed of several components with the length λ / 2. These can be: Vibration generator, known as a converter, in particular z. A Langevin transducer, amplitude transformation pieces 104 known as a booster, possibly extension pieces, as well as the coupling element 106 known as sonotrode.

One in the case 20 arranged electronic unit 200 serves to pressurize the drive unit 80 with at least control and / or regulating signals, as well as the voltage supply of the excitation actuator 100 , An operating voltage unit 90 , here as a battery or battery pack with batteries or rechargeable batteries 92 designed, serves to provide a DC electrical 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 electronics unit 200 is formed around the at least one excitation actuator 100 to operate at a resonant frequency f_res. In this case, the electronic unit includes 200 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 that controls the excitation factor 100 can excite in the resonant frequency, wherein a phase shift between the current fed and the voltage fed to 0 ° is set. 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 be done by a maximum of the in the excitation 100 fed electricity is regulated.

Is the excitation factor 100 a piezoactuator, is the volume of the piezoelectrically active material 102 , z. B. stacked piezoelectric discs, conveniently at least 0.2 cm ³ , preferably 0.5 cm ³ , in particular at least 1 cm ³ . The excitation factor 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 exhibit. The power density allows use in a hand-held power tool 10 with sufficient power output of the tool 60 ,

The activation of the tool 60 through the activation factor 30 can with a signal means 122 ( 2 ) are displayed.

In 1 is the electronics unit 200 particularly space-saving on a single board 210 integrated. In 2 is the electronics unit on two boards 212 . 214 split, one in the main part and a protruding transversely from the main part grip part of the T-shaped housing 20 is arranged. Advantageously, drive unit 80 , Electronic unit 200 and operating voltage unit 90 so in the case 20 that distributes a center of gravity in the area of the grip part 40 lies.

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 utility grid or a DC power supply with a battery pack.

With mains supply of the electronic unit 200 , z. B. with 220 volts ac, is an assembly 94 provided, which rectifies and smooths the AC voltage. The electronics unit 200 includes a power generation unit 222 into which the DC voltage is fed and the via a corresponding filter unit 226 to the excitation actuator 100 is coupled. A control unit 224 provides the control signals for the excitation actuator 100 ready. 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.

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

The maximum electrical excitation field strength of the at least one excitation actuator preferably lies 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. At 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 an embodiment variant, the power generation unit 222 be executed by 4 MOSFET semiconductors in a known full-bridge topology. In a further variant, the generation of the operating signal by a half-bridge (also known) with z. B. a midpoint capacitor for filtering the DC share done.

3b illustrates one way the size of the filter unit 226 to be as small as possible. This can be done by the power unit 222 from the control unit 224 also be controlled so that this means z. B. a sine-wave modulation instead of simple square-wave signals generates a sine-like rectangular voltage. 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 leads. For this purpose, the number of square pulses per period of the sine 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 from the control unit 224 z. B. are changed during load changes during operation.

4 , shows a course of an ultrasonic amplitude along a designed as a piezoelectric actuator excitation 100 , The coupling element 106 is designed as a sonotrode. The to the piezoelectric material 102 adjacent area of the excitation actuator 100 gets along with the piezo disks 102 referred to as a converter. The piezoelectric material 102 is excited by the fed high-frequency AC voltage to vibrations, via the converter in the coupling element 102 be transmitted. At a like in 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 of the excited oscillation. Changes in the resonant frequency f_res of the oscillation system of the excitation actuator 100 (optionally with coupled tool) in operation are preferably balanced, z. B. with an already mentioned above phase locked loop, with the phase shift between the excitation of the excitation 100 is regulated to zero in these fed-in electrical voltage and the supplied electric current (phase zero control), or with a maximum regulation of the in the excitation actuator 100 fed electric current.

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 resonant frequency and from -90 ° below the resonance frequency f_res to + 90 ° above the resonance frequency f_res changes. When passing through the parallel resonance f_res2 changes the phase shift is + 90 ° below the resonance frequency at -90 ° above the resonance frequency.

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

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 7 presented as an angle grinder illustrated power tool 10 includes a housing 20 , which consists of a motor housing 22 and a handle housing 24 exists, being between motor housing 22 and handle housing 24 a damping element 26 is arranged. The power tool 10 gets on the handle housing 24 which holds the grip area 40 forms. In the motor housing 22 is a drive unit 80 with one as an electric drive motor 82 trained drive component, which has a gear unit 62 with a tool shaft 64 is coupled and this drives. The tool shaft 64 is a carrier designed as a grinding wheel tool 60 , which are interchangeable with the tool shaft 64 is attached.

In 8th is the tool shaft 64 and attached thereto, designed as a grinding wheel tool 60 shown in single representation. The tool shaft 64 having the longitudinal axis L is in bearings 70 and 72 rotatably mounted, which are spaced apart in the housing 20 are arranged. On the opposite side of the grinding wheel is located on the tool shaft 64 a bevel gear 74 , about which the tool shaft 64 from the electric drive motor 82 is driven.

To reduce the size of the chips that are used when machining a workpiece with the tool designed as a grinding wheel 60 incurred, is designed as a grinding wheel tool 60 offset in addition to their rotary working movement in high-frequency oscillations. These are overlapping vibrations, that of the working movement of the tool designed as a grinding wheel 60 be superimposed. These beat oscillations are using the excitation 100 generated as the further drive component of the drive unit 80 also in the housing 10 the hand-held power tool 10 is arranged and directly or indirectly designed as a grinding wheel tool 60 to the superposition vibrations. In the embodiment according to 8th acts on the excitation actuator 100 the tool-side bearing 70 the tool shaft 64 and generates overlay vibrations orthogonal to the longitudinal axis L of the tool shaft 64 are directed. These superposition vibrations directed orthogonally to the longitudinal axis L are transmitted via the tool shaft 64 also on the designed as a grinding wheel tool 60 , which likewise exercises orthogonal to the longitudinal axis L and thus in its plane of motion superposition oscillations.

In principle, it is also possible to use the excitation factor 100 to be positioned 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 designed as a grinding wheel 60 to directly apply this to superposition oscillations.

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

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

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

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• - EP 1598171 B1 [0003]

Claims (28)

Hand-held power tool ( 10 ) - a housing ( 20 ) with a grip area ( 40 ), - a tool area ( 50 ) for a linear and / or oscillating drivable tool ( 60 ), - a housing-side control panel ( 30 ) for the user-side activation of the tool ( 60 ) and / or the power tool ( 10 ), - one in the housing ( 20 ) arranged drive unit ( 80 ) for generating a working movement of the tool ( 60 ), - one in the housing ( 20 ) arranged electronic unit ( 200 ) for charging 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 ) at least one excitation factor ( 100 ) comprising a volume of excitation-active material which - in operation from the operating voltage unit ( 90 ) is electrically supplied, - from the electronic unit ( 200 ) is controlled or regulated, characterized in that the electronic unit ( 200 ) is formed around the at least one excitation actuator ( 100 ) in a resonant frequency (f_res) to operate. Hand-held power tool according to claim 1, characterized in that the electronic unit ( 200 ) a control unit ( 224 ) with frequency adaptation for tracking the resonance frequency (f_res) of the at least one excitation actuator ( 100 ). Hand held power tool after a of the preceding claims, characterized in that the exciting active material is piezoelectric. Hand-held power tool according to claim 3, characterized in that the volume of the piezoelectric material is at least 0.2 cm ³ , preferably 0.5 cm ³ , in particular at least 1 cm ³ . Claims, characterized in that the at least one excitation factor ( 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 at least one excitation actuator ( 100 ) having. Hand held power tool after a 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 μm, preferably at least 8 μm, 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 ) an electrical power for acting on the at least one excitation actuator ( 100 ) is at least 20 watts. Hand held power tool after a of the preceding claims, characterized in that a slice thickness of the excitation actuator 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, based on a thickness, in particular a slice thickness, of the piezoelectrically active material, preferably in the range between 50 V / mm and 220 V / mm. Hand-held power tool according to one of the preceding claims, characterized in that an input voltage of the at least one excitation actuator ( 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 10, 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 ) an electrochemical storage ( 92 ), preferably a rechargeable electrochemical store ( 92 ). Hand-held power tool according to one of the preceding claims, characterized in that the operating voltage unit ( 90 ) a rectifier ( 94 ). Hand-held power tool according to one of the preceding claims, characterized in that the electronic unit ( 200 ) on a board ( 210 ) is concentrated. Hand-held power tool according to one of the preceding claims, characterized in that for signal filtering and / or for inductive compensation of the at least one excitation actuator ( 100 ) at least one inductance in a power circuit of the electronics unit ( 200 ) containing the at least one excitation factor ( 100 ) is supplied with electric power, is provided. Hand-held power tool according to one of the preceding claims, characterized in that at least drive unit ( 80 ), Electronic unit ( 200 ) and operating voltage unit ( 90 ) so in the housing ( 20 ) are distributed that a center of gravity in the region of the handle part ( 40 ) lies. Hand-held power tool according to one of the preceding claims, characterized in that the drive unit ( 80 ) next to the at least one excitation factor ( 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 ) a main energy consumer of the power tool ( 10 ), for which at least 50% electrical input power is preferably provided. Hand-held power tool according to one of the preceding claims, characterized in that one or more optical and / or audible and / or haptic operation ( 120 . 122 ) for an activated state of the at least one excitation actuator ( 100 ) are provided. Hand held power tool after a of the preceding claims, characterized in that a workfield lighting is provided. Hand-held power tool according to one of the preceding claims, characterized in that the excitation actuator ( 100 ) for generating superposition oscillations in the tool ( 60 ) provided for a working movement of the tool ( 60 ) are superimposed. Hand-held power tool according to 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 19, characterized. that the tool ( 60 ) is a grinding wheel. Hand-held power tool according to one of claims 18 to 20, characterized in that the superimposed oscillations of 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 tool shaft ( 64 ); - in the plane of movement where 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 ) to a warehouse ( 70 . 72 ) of the tool ( 60 ) acts. 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.