EP1736284B1 - Hand-held power tool with a damping device - Google Patents

Description

The invention relates to a power-driven hand tool, in particular a power tool with a housing in which a motor is accommodated for driving a tool, and with a damping device for actively influencing the vibration behavior, which has at least one damping element with a sensor which upon deformation, an electrical sensor signal which is supplied to one of the electrical circuit, which generates a control signal derived therefrom, which is supplied with an actuator with a certain phase shift to the sensor signal.

Such a hand tool is from the JP 01 274973 A known, and is also the US 2004/0206521 refer to.

In the known hand tool vibration of a screwdriver bit is synchronized with the vibration of a vibration generating unit and superimposed so as to give a phase difference of 180 °, whereby the vibration generated by the bit should be canceled and thus not transferred to a handle.

With such an active vibration damping, a certain reduction of the vibrations generated by a hand tool can be achieved, but a stronger vibration damping is strongly dependent on the particular design, so that an effective vibration reduction is rarely achievable.

The invention is therefore based on the object to provide a power tool, which is provided with an effective damping device for damping vibrations.

This object is achieved by a power tool according to claim 1.

According to the invention, an effective transmission of the vibrations to the damping element is ensured in this way by a cohesive connection of the damping element with the housing, thereby achieving an improvement in the vibration behavior.

In this case, the damping behavior can be adapted within wide limits to the respective field of application.

For example, the damping behavior can be designed such that at least one selected frequency spectrum is damped by vibrations.

In this case, unpleasant or physiologically disadvantageous vibrations can be reduced for a user of the power tool.

The damping device preferably has at least one sensor and at least one actuator independent thereof.

However, the sensor and actuator can also be combined into a single component.

According to a further embodiment of the invention, the damping device has at least one piezoelectric transducer element, a piezomagnetic transducer element, an antiferroelectric transducer element, an electrostatic transducer element, a magnetostrictive transducer element, or a strain-memory transducer element.

In principle, all known types of sensor elements and actuator elements are conceivable that convert mechanical energy into electrical energy or electrical energy into mechanical energy.

In addition, strain gauges, micro-pressure sensors, polymeric sensors or composite sensors, such as composite fiber sensors, may also be used as sensor elements.

According to a further embodiment of the invention, the damping device has at least one nanotube element, preferably a carbon nanotube element.

When using nanotubes, in particular carbon nanotubes, it is possible to produce significantly greater forces in the actuator than is the case with conventional polymer and piezoactuators. Carbon nanotubes can also be operated with a very low supply voltage, while polymer actuators and piezo actuators require supply voltages of up to several hundred volts. Also, carbon nanotubes show no overshoot behavior.

Here, nanotube elements with at least one layer with single or multiwall carbon nanotubes or nanotubes from other organic components, such as BN, MoS ₂ or V ₂ O ₅ , can be used.

Overall, the use of nanotube actuators allows a significantly improved response and a more effective damping than is possible with the usual known in the art actuators.

According to a further embodiment of the invention, the electrical circuit has means for forming from the sensor signal a characteristic of the vibrations of the power tool value which can be fed to a memory.

In this way, a detection of the vibration and storage is enabled to objectively record the vibration values that occur when working with such a hand tool and so make it available for a control. In this way, a "vibration dosimeter" can be realized. In this case, a weighting can be carried out as a function of the respective frequencies and of the amplitudes, as far as this is desired for the respective application.

Stored characteristic values for the vibration behavior of the hand tool can also be used to set maintenance intervals, ie, for example, when a replacement or overhaul of a bearing or of the coals should take place in an electric motor.

According to a further embodiment of the invention, the electrical circuit has a microprocessor.

With such an embodiment, a particularly effective reduction of vibrations can be achieved and at the same time a simple structure, which corresponds to the particular application can be adapted by software. Since many power tools already microprocessors are already used, an existing microprocessor control for the tool can be adjusted accordingly and also use for this purpose.

Depending on the particular application, the phase-shifted control signal can be designed in such a way that the vibration is virtually completely suppressed or reduced to a tolerable level for the respective operation.

It is also possible to generate a phase-shifted control signal that leads the sensor signal.

Furthermore, the electrical damping device may be constructed such that a control signal is generated from the sensor signal according to a self-learning algorithm, which is preferably optimized for the reduction of vibrations or optimized in another way.

According to a further embodiment of the invention, at least one damping element is flat, in particular strip-shaped, formed.

In this way, attachment to any housing parts in a particularly simple manner can be realized.

The term "damping element" is here to be understood as meaning any mechanical / electrical or electrical / mechanical transducer element, which may be a single component acting as sensor and actuator or two separate elements for sensor and actuator which are in close proximity to one another are arranged or spatially interconnected.

According to a further embodiment of the invention, the hand tool has at least two functional elements which are selected from the group formed by a motor part, a gear part and a handle part, and in which at least one damping element is arranged in the region of a connection point between two functional elements.

Regardless of how the hand tool is designed in detail, in this way a particularly effective damping of vibrations is made possible. Particularly in the area of the connection points between different functional elements that transmit mechanical energy, a particularly effective damping is thus made possible.

It has been shown that, in particular in the connection region between the various functional elements of a hand tool, the critical points lie, through which a development can be particularly influenced by vibrations and a gain or reduction. For this reason, the arrangement of damping elements is particularly effective in these areas, for example between the engine part and transmission part or between the handle part and transmission part or between the motor part and handle part to reduce vibrations.

According to a further embodiment of the invention, at least one damping element is arranged in the region of a bearing point of the motor.

Thus, the propagation of possibly occurring vibrations, which are caused by the electric motor itself, can be counteracted particularly effectively.

According to a further embodiment of the invention, at least one damping element is accommodated on an inner side or an outer side of the housing.

In this case, damping elements, e.g. be applied by gluing or by casting directly on a housing surface.

According to a further embodiment of the invention, at least one damping element is received on a protruding from the housing handle, in particular on a handle handle. In this case, the damping element is preferably arranged in particular in the connection region between the handle and the rest of the housing.

According to a further embodiment of the invention, the electrical energy necessary for the operation of the electrical circuit is obtained from vibration energy, which is exposed to the damping element.

Such a configuration is particularly advantageous when the damping element is arranged in a detachable from the housing part, such as in a handle in the form of a handle handle, which is removably attached to the housing. This is also advantageous for battery-operated machines and machines with compressed-air drive.

According to a further embodiment of the invention, an external power source for operating the electrical circuit is provided.

With such an embodiment, a significantly more effective damping behavior and a particularly targeted adaptation of the damping behavior to a wide variety of requirements can be ensured.

According to a further embodiment of the invention, the housing is designed as a pistol housing with an elongated housing part, in which the motor is accommodated, and with a pistol handle, wherein at least one damping element is provided in the transition region between the pistol grip and the elongate housing part.

In this way, the vibration behavior of the housing can be influenced in a particularly effective manner.

According to a further embodiment of the invention, the housing is designed as a pistol housing with an elongate housing part, in which the engine and a transmission are accommodated, and with a pistol grip, wherein at least one damping region is provided in the transition region between the engine and transmission.

If the hand tool also has a gearbox in addition to the motor, a particularly effective influencing of the vibration behavior is likewise made possible in this way.

According to a further embodiment of the invention, the hand tool in rod form, for example, as an angle grinder formed with an elongated housing part in which the engine is received, and with a gear head in which a gear is received, wherein at least one damping element in the region of a connection between the gear head and elongated housing part is provided.

According to another variant of the invention, in which the hand tool is also in rod form, e.g. is designed as an angle grinder, at least one damping element is provided on the elongate housing part in the region of an end of the motor facing away from the gear head.

With such an embodiment, a particularly effective influencing of vibrations in an embodiment of the hand tool as an angle grinder can be achieved.

According to a further embodiment of the invention, the housing has a main housing part, which via webs with a Handle is connected, wherein at least one damping element is provided in the region of the webs.

Even with such a design of a hand tool can thus achieve a particularly effective influencing the vibration behavior.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Fig. 1

eine perspektivische Ansicht einer ersten Ausführung eines kraftgetriebenen Handwerkzeuges in Form eines Winkelschleifers;

Fig. 2

eine schematische Darstellung einer möglichen Überlagerung zwischen Sensorsignal und Steuersignal;

Fig. 3

eine vereinfachte Darstellung einer möglichen Ausführung einer erfindungsgemäßen Dämpfungseinrichtung unter Verwendung eines Mikroprozessors;

Fig. 4

eine schematische Darstellung einer weiteren Ausführung einer erfindungsgemäßen Dämpfungseinrichtung, die ohne externe Energiezufuhr auskommt;

Fig. 5

eine schematische Darstellung einer weiteren Ausführung einer erfindungsgemäßen Dämpfungseinrichtung mit externer Energiezufuhr;

Fig. 6

eine schematische Ansicht einer weiteren Ausführung eines erfindungsgemäßen Handwerkzeuges;

Fig. 7

eine schematische Seitenansicht einer weiteren Ausführung eines erfindungsgemäßen Handwerkzeuges;

Fig. 8

eine vereinfachte Schnittdarstellung durch das Handwerkzeug gemäß Fig. 7 längs der Linie VIII-VIII und

Fig. 9

eine gegenüber der Ausführung gemäß Fig. 8 abgewandelte Ausführungsform eines erfindungsgemäßen Handwerkzeuges mit abgewandelter Anordnung der Dämpfungselemente.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments with reference to the drawings. Show it:

Fig. 1

a perspective view of a first embodiment of a power tool in the form of an angle grinder;

Fig. 2

a schematic representation of a possible superposition between sensor signal and control signal;

Fig. 3

a simplified illustration of a possible embodiment of a damping device according to the invention using a microprocessor;

Fig. 4

a schematic representation of another embodiment of a damping device according to the invention, which requires no external power supply;

Fig. 5

a schematic representation of another embodiment of a damping device according to the invention with external power supply;

Fig. 6

a schematic view of another embodiment of a hand tool according to the invention;

Fig. 7

a schematic side view of another embodiment of a hand tool according to the invention;

Fig. 8

a simplified sectional view of the hand tool according to Fig. 7 along the line VIII-VIII and

Fig. 9

one compared to the embodiment according to Fig. 8 modified embodiment of a hand tool according to the invention with a modified arrangement of the damping elements.

In Fig. 1 is an inventive hand tool 10, which is designed as an angle grinder, shown in a perspective side view. The hand tool 10 has a housing 12, which is connected at its front end with a gear housing 14 and at the rear end of a handle part 16 is provided. Within the housing 12, a motor 24 is received in the form of a universal motor, which is coupled in the connecting region to the transmission housing 14 with an angular gear (not shown), from the output shaft 27, a tool 20 can be driven in the form of a grinding wheel. The tool 20 is partially enclosed in a known manner by a protective hood 22. Laterally on the gear housing 14, a handle handle 18 is additionally screwed.

Such an angle grinder, which is basically known in construction, is designed as a two-hand angle grinder and can be held on the handle handle 18 with a first hand and on the handle part 16 with a second hand. According to the invention, at least one damping device is now provided, by means of which vibrations occurring during operation can be effectively damped.

For this purpose, two damping elements 30, 31 are added in the transition region between the motor 24 and the gearbox 26 accommodated within the gearbox 14. Further, two further damping elements 32, 33 are provided in the transition region between the motor 24 and the adjoining handle part 16 or in the transition region between the motor 24 and an adjoining electronic module 28.

These damping elements 30 to 33 are used for active damping of vibrations in conjunction with a suitable electrical circuit, as will be described below.

By means of the damping elements 30 to 33, a sensor signal is generated which is approximately proportional to a mechanical disturbance (for example oscillation) exerted on the damping element in question.

In Fig. 2 is such a signal as an approximately sinusoidal signal U _s for a certain period of time during a machining operation occurring vibration shown schematically.

From this sensor signal U _s , a phase-shifted control signal is generated with the aid of a suitable electrical circuit, which is supplied to the damping element 30 to 33 again. Such a phase-shifted signal is schematically shown in FIG Fig. 2 represented as U _w . In the case of a periodic signal, complete cancellation can be achieved with a signal of the same amplitude phase-shifted by 180 °.

Depending on the phase relationship between the sensor signal U _s and the control signal U _w , depending on the amplitude ratio between the two signals, mechanical coupling between the damping elements 30 to 33 and the relevant housing parts and other influencing variables, a targeted influencing of mechanical vibrations can be achieved, which the Housing is exposed.

It is conceivable to achieve a substantially complete extinguishment of a vibration. In many cases, however, only a certain damping of vibration will be achieved.

An example of a suitable control circuit is shown schematically in FIG Fig. 3 shown damping device 34 can be seen.

Here, a mechanical vibration (vibration) is detected by a sensor 36, the signal is first amplified analogously by an amplifier 37 and then converted by means of an A / D converter 38 into a digital signal. The digitized sensor signal is supplied to a microprocessor 40. The microprocessor 40 now generates, according to a suitable control algorithm, a phase-shifted signal therefrom via a D / A converter 42 in turn converted into an analog signal and an actuator 44 is supplied.

The sensor 36 and the actuator 44 may be separate components, but are preferably located in close proximity, such as to allow effective damping of vibration. Sensor 36 and actuator 44 are in Fig. 1 shown together as "damping elements", which are usually immediately adjacent or spatially combined components. However, it is not excluded that in special cases, the respective sensor and the respective actuator are arranged spatially distant from each other. A combination of sensor and actuator to a single component is possible.

In Fig. 4 a possible embodiment of a damping device according to the invention is designated overall by the numeral 54.

The respective damping device 54 operates without external power supply, which is particularly advantageous if the respective damping device is to be integrated in a removable part, such as a removable handle.

In the damping device 54, electrical energy is obtained by means of an actuator 58, which reacts to a mechanical deformation. The electrical energy is coupled into a bidirectional amplifier 60, which may be, for example, a switching amplifier. The amplifier 60 is connected to a control electronics 62 and to a storage element 63, for example a capacitor. The amplifier 60 serves to amplify electrical signals, which are supplied by the actuator 58, and for storing the energy obtained in the memory element 63. Similarly, the amplifier 60 serves to amplify signals of the control electronics 62 and for re-coupling to the actuator 58. In this embodiment, a sensor 56 in the immediate vicinity of the actuator 58th arranged and connected to an input of the control electronics 62.

Mechanical noise (vibrations) detected by the sensor 56 produce a sensor signal from which is derived in the control electronics 62 a phase-shifted control signal which is supplied to the actuator 58, such as to achieve a damping of the mechanical disturbance.

With suitable dimensioning, an attenuation of the mechanical output signal to about 30% of its initial value can be achieved without external energy supply.

The actuator 58 may be, for example, a piezoelectric transducer element, a piezomagnetic transducer element, an antiferroelectric transducer element, an electrostatic transducer element, a magnetostrictive transducer element, a strain-memory transducer element, a piezoceramic transducer element, or a nanotube element, preferably a carbon nanotube element. Nanotube element, act.

In principle, all types of known transducer elements are conceivable, which convert electrical energy into mechanical energy, and vice versa.

Particularly preferred are nanotube elements having at least one layer with single or multiwall carbon nanotubes or nanotubes of other organic components, such as BN, MoS ₂ or V ₂ O ₅ .

With carbon nanotubes, significantly higher sensitivities at lower voltages (e.g., compared to piezoelectric elements) can be produced compared to other known actuators.

The sensor 56 may be constructed identically to the actuator 58. However, it may also be a differently constructed sensor, such as a strain gauge, a micro-pressure sensor, a polymeric sensor, an acceleration sensor or other suitable sensor.

Fig. 5 shows a further embodiment of a damping device 64 according to the invention with external power supply.

On a housing part 67, a sensor 66 and an actuator 68 are added in the immediate vicinity. The output signal of the sensor 66 is coupled to an amplifier 70 whose output is connected to an electronic control unit 72. The control electronics 72 generates a phase-shifted control signal which is supplied to an amplifier 73, which outputs an amplified signal to the actuator 68. The control signal has some phase shift to the sensor signal to provide damping of vibration to the housing part 67. The electronic components 70, 72, 73 are powered by an external power supply 65, which may be part of a power supply of an already existing controller. The use of an active power supply usually offers advantages over autonomous execution according to Fig. 4 , as a more effective damping of vibrations is possible, as in a circuit according to Fig. 4 can be achieved.

In order to achieve an effective damping of vibrations in a power-driven hand tool, such as a power tool, it is essential on which points of the housing the respective damping elements are arranged, which are either combinations of sensor and actuator in the immediate vicinity or can be a combined element.

The damping elements are preferably arranged such that they are arranged either in the immediate vicinity of a possible source for the generation of vibrations (for example in the region immediately adjacent to an electric motor, for example in the region of the armature bearing) or in the connection region between individual functional elements of the hand tool. The functional elements include motor, gearbox and handle.

Thus, the damping elements are preferably arranged in the connecting region between the engine and transmission, between the engine and the grip part or between the transmission and the grip part, depending on how the relevant hand tool is constructed. As far as additional handles are provided on the relevant hand tool, the damping elements are preferably provided in the transition region between the respective handle and the housing.

With such arrangements, vibrations that occur when working with the hand tool can be reduced particularly effectively.

A first such arrangement has already been described with reference to Fig. 1 explained.

Fig. 6 shows a further inventive tool 90 in the form of a hammer drill.

The hand tool 90 has an elongate housing 92, are received in the engine and transmission.

At the front end, a receptacle 98 is shown in the form of a chuck, in which a tool, such as a drill 100, may be included. In the front lower portion of the housing 92, a handle handle 94 is provided which protrudes downward and is connected via a damping element 101 to the housing part 92. At the end facing away from the receptacle 98 of the housing 92, this is followed by a handle 96, which is connected via webs 104, 105 with the housing part 92. In the webs, ie in the transition region between the handle part 96 and the housing part 92, again damping elements 102, 103 are provided.

Fig. 7 shows a possible arrangement of damping elements in a power tool gun-shaped tool 110, which may be about a drill or screwdriver.

The hand tool 110 has an elongate housing part 112 and a pistol grip 114, which is connected to the elongate housing part 112 is connected. Within the elongated housing part 112, a motor 124 is received, from which a gear 126 is driven, which is finally connected in a manner not shown with a receptacle 118 in the form of a chuck to drive a tool received therein. The motor 124 has at its end remote from the receptacle 118 an armature bearing 125 and is coupled to an electronic module 128, which may be received, for example, within the gun handle 114.

In order to achieve an effective damping of vibrations in such a constructed hand tool, damping elements 129, 130 are provided in the transition region between the engine 124 and gear 126.

In addition, in the transition region between the elongated housing part 112 and the gun handle 114 further damping elements 133, 134 are arranged.

Furthermore, further damping elements 131, 132 may be provided on the motor 124, in particular in the region of its armature bearing 125, in order to damp vibrations that may be generated in the region of the armature bearing 125.

The damping elements themselves may be accommodated, for example, in correspondingly shaped recesses on housing sections or may be applied flat on the inside or outside of the housing. To bond with the relevant housing part is a bond or other cohesive connection, which is achieved for example during an injection process of a plastic housing. In each Case has an intimate cohesive connection with the relevant housing part has the advantage of ensuring effective transmission of mechanical energy between the respective damping element and the housing part.

Fig. 8 shows by way of example how the respective damping elements 129, 130 are embedded in openings in the side wall of the housing.

Fig. 9 shows as an example as an alternative, a planar application of damping elements 146, 147 on webs 142, 144, which are provided on the inside of the housing.

It is understood that this represents only one of many conceivable possible attachment forms of the damping elements.

Claims (18)

1. A hand-held power tool, in particular electric tool, having a housing (12; 92; 112) in which a motor (24; 124) is received for driving a tool (20; 100), and a damping system (34; 54; 64) for actively influencing the vibration behavior, which comprises at least one damping element (30, 31, 32, 33; 101, 102, 103; 129, 130, 131, 132, 133,134; 146, 147) with a sensor (36; 56; 66) that emits an electric sensor signal when deformation occurs, which signal is supplied to an electric circuit (37; 62; 70) that generates therefrom a control signal which is supplied to an actor (44; 58; 68) at a given phase angle relative to the sensor signal, characterized in that the damping element (30, 31, 32, 33; 101, 102, 103; 129, 130, 131, 132, 133, 134; 146, 147) is connected to the housing (12; 92; 112) by a material connection.
2. The hand-held tool as defined in claim 1, characterized in that the damping system (34; 54; 64) comprises at least one piezoelectric transducer element, one piezo-magnetic transducer element, one antiferroelectric transducer element, one electrostatic transducer element, one magnetostrictive transducer element or one deformation memory transducer element.
3. The hand-held tool as defined in any of the preceding claims, characterized in that the damping system (34; 54; 64) comprises at least one nanotube element, preferably a carbon nanotube element.
4. The hand-held tool as defined in any of the preceding claims, characterized in that the damping system (34; 54; 64) comprises a nanotube element which has at least one layer with single or multi-wall carbon nanotubes or with nanotubes made from other organic components, such as BN, MoS₂ or V₂O₅.
5. The hand-held tool as defined in any of the preceding claims, characterized in that the electric circuit (40) comprises means for deriving from the sensor signal a value characteristic of the vibrations of the hand tool that can be supplied to a memory (46).
6. The hand-held tool as defined in any of the preceding claims, characterized in that the electric circuit derives from the sensor signal (U_s) a phase-shifted control signal (U_w) that is timed ahead of the sensor signal (U_s).
7. The hand-held tool as defined in any of the preceding claims, characterized in that the electric circuit (40) comprises means for deriving from the sensor signal (U_s), based on a self-learning algorithm, a control signal (U_w) that is optimized for the reduction of vibrations.
8. The hand-held tool as defined in any of the preceding claims, characterized in that at least one actor and/or sensor (30, 31, 32, 33; 101, 102, 103; 129 , 130, 131, 132, 133, 134; 146, 147) is configured two-dimensional, in particular in strip-like shape.
9. The hand-held tool as defined in any of the preceding claims, characterized in that at least two functional elements selected from the group formed by a motor unit (24; 124), a gear unit (26; 126) and a grip unit (16, 96; 114), with at least one actor and/or sensor (30, 31, 32, 33; 102, 103; 129, 130, 133, 134; 146, 147) being arranged in the area of a joint between two functional elements.
10. The hand-held tool as defined in any of the preceding claims, characterized in that at least one actor and/or sensor (131, 132) is arranged in the area of an armature bearing (125) of the motor (124).
11. The hand-held tool as defined in any of the preceding claims, characterized in that at least one actor and/or sensor (30, 31, 32, 33; 101, 102, 103; 129 130, 131, 132, 133, 134; 146, 147) is received on an inside or an outside of the housing (12; 92; 112).
12. The hand-held tool as defined in any of the preceding claims, characterized in that at least one actor and/or sensor (146, 147) is received on a web (142, 144) inside the housing (12; 92; 112).
13. The hand-held tool as defined in any of the preceding claims, characterized in that the electric energy necessary for operation of the electric circuit (60, 62) is derived from vibration energy to which the hand-held tool is exposed.
14. The hand-held tool as defined in any of the preceding claims, characterized in that the housing is configured as a pistol housing having an elongated housing element (112), in which the motor (124) is received, and a pistol grip (114), with at least one actor and/or sensor (133, 134) being provided in the transition area between the pistol grip (114) and the elongated housing element (112).
15. The hand-held tool as defined in any of the preceding claims, characterized in that the housing is designed as a pistol housing having an elongated housing element (112), in which the motor (124) and a gearbox (126) are received, and a pistol grip (114), with at least one actor and/or sensor (129, 130) being arranged in the transition area between the motor (124) and the gearbox (126).
16. The hand-held tool as defined in any of claims 1 to 13, which is configured in bar shape, having an elongated housing element (12), in which the motor (24) is received, and a gearhead (14), in which a gearbox (26) is received, with at least one actor and/or sensor (30, 31) being provided in the area of the joint between the gearhead (14) and the elongated housing element (12).
17. The hand-held tool as defined in any of claims 1 to 13 or 16, which is designed in bar shape, having an elongated housing element (12), in which the motor (24) is received, and a gearhead (14), in which a gearbox (26) is received, with at least one actor and/or sensor (32, 33) being provided on the elongated housing element in the area of an end of the motor (24) opposite the gearhead.
18. The hand-held tool as defined in any of claims 1 to 13, 16 or 17, wherein the housing comprises a main housing element (92), which is connected with a grip (96) via webs, with at least one damping element (102, 103) being provided in the area of the webs (104, 105).

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