WO2016055254A1

WO2016055254A1 - Handheld power tool with an excitation actuator which can vibrate

Info

Publication number: WO2016055254A1
Application number: PCT/EP2015/071561
Authority: WO
Inventors: Jochen Roser; Georg Hejtmann; Michael Guenther
Original assignee: Robert Bosch Gmbh
Priority date: 2014-10-07
Filing date: 2015-09-21
Publication date: 2016-04-14
Also published as: DE102014220227A1; EP3204196A1

Abstract

The invention relates to a handheld power tool (100) with a drive unit (103) for vibrating an insert tool (130), said drive unit having at least one excitation actuator (105) which can vibrate and which is coupled to a coupling element (110) in order to transmit vibrations to the insert tool (130). The vibrations are generated by the excitation actuator (105) during the operation of the drive unit (103) when a specified actuation voltage is applied to the excitation actuator (105), said excitation actuator (105) having at least one excitation element (132, 134) which is made of a piezoelectric material. According to the invention, a temperature sensor (199) is paired with the excitation actuator (105) in order to detect the respective current operating temperature of the excitation actuator in order to allow an adaptation of the specified actuation voltage dependent on the respective current operating temperature.

Description

Description title

Hand-held power tool with a vibratory excitation actuator prior art

The present invention relates to a hand-held power tool having a drive unit for oscillating drive of an insert tool having at least one oscillatory excitation actuator which is coupled to a coupling element for transmitting vibrations to the insert tool, the excitation actuator during operation of the drive unit upon application of a predetermined drive voltage the excitation actuator are generated, wherein the excitation actuator has at least one excitation element, which is formed of a piezoelectric material.

Such a hand-held power tool is known from the prior art, with a drive unit for oscillating drive a

Insert tool is provided. The drive unit, which has an excitation actuator which is provided with an excitation element formed of a piezoelectric material, is assigned a cooling system for preventing an uncontrolled increase in a respective operating temperature of the excitation actuator during operation of the power tool. This cooling system is preferably arranged in a tool housing of the hand-held power tool and designed in the manner of a connection for a compressed air cooling.

A disadvantage of this prior art is that the cooling system or the connection for the compressed air cooling in the tool housing of the hand-held power tool is arranged and thus leads to the increase of a space required for the tool housing space.

Disclosure of the invention An object of the invention is therefore to provide a new hand-held

To provide a power tool with reduced dimensions, in which an uncontrolled increase in a respective operating temperature of an associated excitation actuator during operation of the power tool can be at least largely prevented.

This problem is solved by a hand-held power tool with a drive unit for oscillating drive an insert tool having at least one oscillatory excitation actuator, which is coupled to a coupling element for transmitting vibrations to the insert tool, the excitation actuator during operation of the drive unit when applying a predetermined drive voltage be generated to the excitation actuator. The excitation actuator has at least one excitation element, which is formed from a piezoelectric material, wherein the excitation actuator for detecting its respective current operating temperature, a temperature sensor is assigned to allow depending on the current operating temperature adjustment of the predetermined drive voltage.

The invention thus makes it possible to provide a new hand-held power tool with at least one excitation actuator which has comparatively small dimensions and in which an uncontrolled increase in a respective operating temperature of the excitation actuator during operation of the

Power tool can be safely and reliably prevented.

Preferably, the temperature sensor is arranged in the region of the drive unit.

Thus, in a simple manner, the operating temperature of the

Drive unit and thus of this associated Anreungsaktors be determined.

Preferably, the temperature sensor is attached to the coupling element.

Thus, a reliable and unadulterated detection of a

Operating temperature of the drive unit characterizing temperature of the coupling element allows. The drive unit is preferably associated with a control for adapting the predetermined drive voltage. Thus, the drive voltage can be quickly and easily adapted to the current operating temperature of the drive unit and the excitation actuator.

According to one embodiment, the control element is designed to control the predetermined drive voltage as a function of the respective current one

Adjust operating temperature such that a temperature-related

Damage or thermal destruction of the excitation is at least largely prevented. Thus, a safe and reliable operation of the hand-held

Power tool will be enabled.

Preferably, the control is designed to the predetermined

Adjusting drive voltage as a function of the respective current operating temperature such that the excitation actuator associated

Oscillation amplitude during operation is at least approximately constant.

Thus, a generation of a vibration amplitude independent of the respective operating temperature of the excitation actuator can be made possible in a simple manner, whereby a self-destruction of the excitation actuator due to an uncontrolled increase in its operating temperature is at least largely prevented.

Preferably, the control element is adapted to the adaptation of the predetermined drive voltage on the basis of a relationship determined between the respective current operating temperature, the associated oscillation amplitude and the predetermined one for the excitation actuator

To execute drive voltage.

Thus, a secure and reliable adaptation of the associated

Vibration amplitude can be enabled. According to one embodiment, the drive unit is assigned a data store in which at least the determined relationship is retrievably stored in the manner of a lookup table.

Thus, the determined relationship can be retrieved quickly and easily and a time-consuming determination of the relationship, for. when restarting the hand-held power tool can be prevented.

The control element is preferably designed to carry out the adaptation of the predetermined drive voltage in such a way that when the actual operating temperature rises, the preset drive voltage is lowered.

Thus, simply and safely a further increase in the respective current operating temperature of the excitation in the operation of the hand-held

Power tools are at least largely prevented.

According to one embodiment, the hand-held power tool is designed in the manner of an ultrasonic cutter.

Thus, the present invention can be easily incorporated

Ultrasonic cutters find application.

Brief description of the drawings

The invention is explained in more detail in the following description with reference to exemplary embodiments illustrated in the drawings. Show it:

1a is a perspective view of a longitudinally opened, hand-held power tool with a drive unit and a temperature sensor according to the invention,

1 b shows an enlarged, perspective view of the drive unit of FIG. 1 a with the temperature sensor,

2a shows a schematic temperature diagram for the drive unit of FIG. 1a and FIG. 1b, before an adaptation of a corresponding drive voltage, FIG. 2b is a schematic Ansteuerspannungsdiagramm for the drive unit of Fig. 1 a and Fig. 1 b, before an adaptation of a corresponding drive voltage,

2c shows a schematic vibration amplitude

/ Oscillation speed diagram for the drive unit of FIG. 1 a and FIG. 1 b, before adaptation of a corresponding drive voltage,

3 shows an exemplary reference diagram for determining a tool-specific relationship between the drive voltage and the operating temperature of the drive unit of FIG. 1 a and FIG. 1 b, FIG.

4a shows a schematic temperature diagram for the drive unit of Fig. 1a and Fig. 1 b, after an adjustment of the drive voltage by means of the context of Fig. 3,

4b is a schematic Ansteuerspannungsdiagramm for the drive unit of Fig. 1a and Fig. 1 b, after an adjustment of the drive voltage by means of the relationship of Fig. 3, and

4c shows a schematic vibration amplitude

/ Oscillation speed diagram for the drive unit of FIG. 1 a and FIG. 1 b, after an adaptation of the drive voltage by means of the relationship of FIG. 3.

Description of the embodiments

1 a shows a hand-held power tool 100 according to the present invention, which is designed, for example, in the manner of an ultrasonic cutter, preferably a miniaturized ultrasonic cutter and is therefore also referred to below as the "ultrasonic cutter 100" for simplifying the description In the manner of a cutting blade trained insert tool 130, which is hereinafter also referred to as "cutting blade 130" to simplify the description, and a tool housing 180. This illustratively forms an interior 185, in which at least partially one for oscillating drive of the cutting blade 130 provided drive unit 103 and an operating element 150 for switching on and off of the drive unit 103 are arranged.

According to one embodiment, the ultrasonic cutter 100 for mains-independent power supply is mechanically and electrically connected to a battery pack 190 illustratively formed from two battery cells. It is noted, however, that the present invention is not limited to battery powered ultrasonic cutters, but rather may be applied to a variety of handheld power tools that utilize a vibratory excitation actuator for vibratory driving an associated insert tool, regardless of whether the power tool is power dependent or independently of the mains with the battery pack 190 is operable. For example, the present invention can also be applied to hand-held drilling and / or sawing tools in which a vibratory excitation actuator or the drive unit 103 is used for the oscillating drive of an associated insertion tool.

The drive unit 103 preferably has at least one oscillatable excitation actuator 105, which is coupled to a coupling element 110 for transmitting vibrations to the insertion tool 130. The vibrations are generated by the excitation actuator 105 during operation of the drive unit 103

Applying a predetermined drive voltage (Ui in Fig. 2b) to the

Excitation actuator 105 generated. For this purpose, the excitation actuator 105 at least one and illustratively two at least partially planar or plan and exemplary disc or annular trained excitation elements 132, 134. These preferably have a piezoelectric material at least in some areas and are therefore also referred to below as "piezor rings"

Excitation actuator 105 is also referred to below as a "piezoactuator." An exemplary piezoactuator and exemplary piezor rings are shown in WO

2010/076230 A1, whose disclosure is explicitly in the present

Registration is included, so that can be dispensed with a detailed description of the piezoelectric actuator 105 and the piezo rings 132, 134 and their functionality.

The piezoring 134 is illustratively at least partially planar against a tendon 140 and / or the piezo ring 132 at. The piezo ring 132 is also illustratively at least partially flat against the coupling element 1 10th at. As a result of the preferably direct attachment of the tensioning element 140 to the coupling element 10, the piezo rings 132, 134 are clamped between these two components as described above.

According to one embodiment, a temperature sensor 199 is assigned to the piezoelectric actuator 105 for detecting its respective current operating temperature (T ₂ in FIG. _{4 a} ). This is preferably arranged at least in the region of the drive unit 103 and preferably attached to the coupling element 1 10.

The detection of the respective current operating temperature (T ₂ in Fig. 4a) of the piezoelectric actuator 105 is used for temperature-dependent adaptation of the respective predetermined driving voltage (U ₂ in Fig. 4b). For this purpose, the drive unit 103 is preferably associated with a control element 125 for adapting this particular predetermined drive voltage (U ₂ in FIG. 4b), which is designed to supply the respective predetermined drive voltage (U ₂ in FIG. ₄ b) as a function of the respective current operating temperature (FIG. T ₂ in Fig. 4a) to be adapted such that a temperature-induced damage or thermal destruction of the piezoelectric actuator 105 is at least largely prevented. In order to make this possible, the control element 125 adapts the respective predetermined one

Activation voltage (U ₂ in Fig. 4b) in response to the respective current operating temperature (T ₂ in Fig. 4a) such that a piezoelectric actuator 105 associated vibration amplitude (s ₂ in Fig. 4c) during operation of the hand-held power tool 100 at least approximately is constant and thus independent of the current operating temperature (T ₂ in Fig. 4a).

Preferably, the control 125 fits the respective predetermined

Drive voltage (U ₂ in Fig. 4b) on the basis of a determined for the piezoelectric actuator 105 relationship (310 in Fig. 3) between the respective current operating temperature (T ₂ in Fig. 4a), the associated oscillation amplitude (s ₂ in Fig. 4c ) and the respective predetermined drive voltage (U ₂ in Fig. 4b), where preferably (at a slope of the respective current operating temperature T _2, a lowering of the respective predetermined drive voltage (U ₂ in Fig. 4b) is performed in Fig. 4a). Preferably, this relationship (310 in FIG. 3) is stored in a data memory 170 assigned to the drive unit 103, preferably in the manner of a look-up table, and at least retrievable by the control element 125. During operation of the ultrasonic cutter 100, a user actuates, for example, by pressing the operating element 150, as a result of which the control element 125 is activated and supplied with power by the battery pack 190. The powered control 125 then controls the piezoelectric actuator 105 so that this as described in WO 2010/076230 A1 describes vibrations generated on the coupling element

1 10 and transferred from this to the cutting blade 130. In this case, the coupling element 110 formed as an interface to the cutting blade 130 preferably serves to reinforce a signal generated by the piezoelectric actuator 105

Oscillation amplitude. During operation of the ultrasonic cutter 100, the control element 125 now executes a control method according to the invention as follows: The temperature sensor 199 measures continuously, but at least at predetermined time intervals, the respective operating temperature (T ₂ in FIG. _{4 a} ) of the piezoactuator 105, which then controls the control element 125 evaluated with the help of the determined relationship (310 in Fig. 3), to then a respective

predetermined drive voltage (U ₂ in Fig. 4b) to control such that an at least approximately constant oscillation amplitude (s ₂ in Fig. 4c) of the

Piezoactuator 105 is generated.

Fig. 1 b shows the drive unit 103 of Fig. 1 a with the piezoelectric actuator 105, which illustratively has the two piezo rings 132, 134, wherein the arrangement of the

Temperature sensor 199 of FIG. 1 a in the region of the drive unit 103, or its attachment to the coupling element 1 10, is illustrated.

The temperature sensor 199 is preferably clamped to the drive unit 103 or the coupling element 110 by means of a clamping connection, but it could also be clamped by means of any other connection, e.g. one

Screw and / or welded connection, on the drive unit 103 or the

Coupling element 1 10 be attached.

FIGS. 2 a to 2 c show exemplary measurement diagrams 210, 220, 230 that can be measured during operation of the drive unit 103 or the piezoactuator 105 of FIGS. 1 a and 1 b. These measurement diagrams 210, 220, 230 are preferably determined once, for example, for a respective tool type in a trial operation of the ultrasound cutter 100 of FIG. 1a, or once during the production of the ultrasound cutter 100 or at recurring time intervals only for this ultrasound cutter 100. In such a trial operation 1 a is initially operated without the control method according to the invention in order to obtain the relationship described above (310 in FIG. 3) for a subsequent one Working operation of the ultrasonic cutter 100 of Fig. 1 a to determine.

FIG. 2 a shows the measurement diagram 210, which illustratively has an operating temperature operating time curve 206 which represents an operating temperature Ti of the piezoactuator 105 measured by the temperature sensor 199 of FIGS. 1 a and 1 b as a function of an operating time t. The operating time t is illustratively plotted on an abscissa 202 and the operating temperature ΤΊ on an ordinate 204 of the measurement diagram 210. The operating temperature operating time curve 206 has an at least approximately linear course with increasing operating temperature ΤΊ with increasing operating time t.

FIG. 2 b shows the measurement diagram 220, which illustratively has a drive voltage operating time curve 216, which is an at least substantially constant one applied to the piezoactuator 105 of FIG. 1 a and FIG. 1 b during operation

Drive voltage Ui over the operating time t of Fig. 2a represents. Analogous to

2a, the operating time t is plotted on an abscissa 212 and the drive voltage Ui is plotted on an ordinate 214 of the measurement diagram 220. From a synopsis of Fig. 2a and Fig. 2b shows that the

Operating temperature Ti of the piezoelectric actuator 105 at constant drive voltage Ui over the operating time t increases.

Fig. 2c shows the measurement diagram 230, which illustratively a

Vibration amplitude / vibration velocity-time curve 226, one of the operating temperature Ti of Fig. 2a and the

Drive voltage Ui of Fig. 2b resulting oscillation amplitude or

Vibration speed v-ι of the piezoelectric actuator 105 as a function of the operating time t of Fig. 2a and Fig. 2b. In this case, analogously to FIGS. 2 a and 2b, the operating time t is illustrative of an abscissa 222 and FIG

Oscillation amplitude Si or vibration velocity v-ι applied to an ordinate 224 of the measurement diagram 230.

The oscillation amplitude / oscillation velocity-time curve 226 illustratively has a gradient that increases at least approximately linearly over the operating time t. From a combination of FIGS. 2a to 2c, it is thus clear that the oscillation amplitude Si or oscillation speed v-1 increases over the operating time t with a constant drive voltage Ui and an increasing operating temperature Ti. This can lead to temperature-related damage or even a thermal destruction of the piezoelectric actuator 105 lead.

FIG. 3 shows an exemplary reference diagram 305 that shows a relationship 310 between a reference to a reference drive voltage U _RE F

Drive voltage U of the piezoelectric actuator 105 of Fig. 1 a and Fig. 1 b and its

Operating temperature T at a constant oscillation amplitude or

Vibration velocity represents. In this case, the operating temperature T is plotted on an abscissa 312 of the reference diagram 305, and the ratio of the drive voltage U to the ordinate 314 is plotted

Referenzansteuerspannung U _RE F- from a plurality of measuring points 317,

318, 319 derived approximate curve 316 illustratively has a linearly decreasing profile.

According to one embodiment, the relationship 310 illustrates a relationship between a respective current operating temperature T, a predetermined drive voltage U and an associated one

Oscillation amplitude or oscillation speed. In this context, the relationship 310 shows, in particular, that the preset drive voltage U must be reduced when the respective current operating temperature T increases, in order to achieve a constant oscillation amplitude or oscillation speed of the oscillator

Piezoactors 105 of Fig. 1 a and Fig. 1 b to produce in operation.

Accordingly, the context 310 according to the invention from

Control element 125 of FIG. 1 a is used, which now controls the predetermined drive voltage (U ₂ in FIG. ₄ b) of the piezoelectric actuator 105 in the operating mode of the ultrasonic cutter 100 of FIG.

adjusts that with increasing operating temperature (T ₂ in Fig. 4a) of the piezoelectric actuator 105, a constant operating temperature independent oscillation amplitude (s ₂ in Fig. 4c) is formed. By the use according to the invention of the determined relationship 310, the operating temperature (T ₂ in FIG. _{4 a} ) increases

Drive voltage (U ₂ in Figure 4b) lowered and a temperature-induced damage or even a thermal destruction of the piezoelectric actuator 105 of the ultrasonic cutter 100 can thus be prevented. The determined

Relation 310 is preferably stored in the data memory 170 of FIG. 1 a and can therefore be called up at any time during operation of the ultrasound cutter 100. FIGS. 4 a to 4c show exemplary measurement diagrams 410, 420, 430 that are measurable during operation of the drive unit 103 or of the piezoactuator 105 of FIGS. 1 a and 1 b, respectively, when the control element 125 of FIG 1 a with the control method according to the invention as described above

be controlled. The control method is based on an evaluation of the relationship 310 of FIG. 3 as described above.

4 a shows the measurement diagram 410, which illustratively has an operating temperature operating time curve 406 which represents an operating temperature T _{2 of} the piezoactuator 105 measured by the temperature sensor 199 of FIGS. 1 a and 1 b as a function of an operating time t. The operating time t is illustratively plotted on an abscissa 402 and the operating temperature T ₂ on an ordinate 404 of the measurement diagram 410. The operating temperature operating time curve 406 has an at least approximately linear course with increasing operating temperature T ₂ as the operating time t increases.

4b shows the measurement diagram 420, which illustratively has a drive voltage operating time curve 416, which represents a drive voltage U ₂ applied during operation to the piezoactuator 105 of FIG. 1 a and FIG. 1 b over the operating time t of FIG. 4 a , Analogously to FIG. 4 a, the operating time t is plotted on an abscissa 412 and the drive voltage U _{2 is} plotted on an ordinate 414 of the measurement diagram 420. From a combination of FIGS. 4 a and 4 b, it follows that the drive voltage U ₂ according to the invention

Control method with over the operating time t increasing operating temperature

T _{2 of} the piezoelectric actuator 105 is lowered.

FIG. 4c shows the measurement diagram 430, which illustratively shows a

Vibration amplitude / vibration velocity-time curve 426, one of the operating temperature T ₂ of Fig. 4a and the

Triggering voltage U ₂ of Fig. 4b resulting, at least approximately constant oscillation amplitude s ₂ or vibration velocity v _{2 of} the piezoelectric actuator 105 as a function of the operating time t of Fig. 4a and Fig. 4b. Analogous to FIGS. 4 a and 4b, the operating time t is illustrative on an abscissa 422 and the oscillation amplitude s ₂ or

Vibration velocity v ₂ plotted on an ordinate 424 of the measurement diagram 430. From a combination of FIGS. 4a to 4c, it follows that the oscillation amplitude s ₂ or oscillation speed v ₂ remains at least approximately constant when the drive voltage U _{2 is} lowered over the operating time t when the operating temperature T ₂ increases. Thus, a temperature-induced damage or even a thermal destruction of the piezoelectric actuator 105 with the control method according to the invention can be reliably and reliably prevented.

Claims

claims

1 . Hand-held power tool (100) with a drive unit (103) for oscillating drive of an insert tool (130), which has at least one oscillatory excitation actuator (105), which with a

Coupling element (1 10) for transmitting vibrations to the

Insertion tool (130) is coupled to the excitation actuator (105) during operation of the drive unit (103) when applying a predetermined

Drive voltage (U ₂ ) to the excitation actuator (105) are generated, wherein the excitation actuator (105) at least one excitation element (132,134), which is formed of a piezoelectric material, characterized in that the excitation actuator (105) for detecting its respective current Operating temperature (T ₂ ) is associated with a temperature sensor (199) to allow depending on the current operating temperature (T ₂ ) adjustment of the predetermined drive voltage (U ₂ ).

2. Hand-held power tool according to claim 1, characterized in that the temperature sensor (199) in the region of the drive unit (103) is arranged.

3. Hand-held power tool according to claim 1 or 2, characterized

characterized in that the temperature sensor (199) on the coupling element (1 10) is attached.

4. Hand-held power tool according to one of the preceding

Claims, characterized in that the drive unit (103) is associated with a control element (125) for adaptation of the predetermined drive voltage (U ₂ ).

5. Hand-held power tool according to claim 4, characterized in that the control element (125) is adapted to the predetermined drive voltage (U ₂ ) as a function of the respective current Adjust operating temperature (T ₂ ) such that a temperature-induced damage or thermal destruction of the excitation (105) is at least largely prevented.

Hand-held power tool according to claim 4 or 5, characterized in that the control element (125) is adapted to adjust the predetermined drive voltage (U ₂ ) in dependence on the respective current operating temperature (T ₂ ) such that a the

Excitation actuator (105) associated vibration amplitude (s ₂ ) is at least approximately constant in operation.

7. hand-held power tool according to claim 6, characterized in that the control element (125) is adapted to the adaptation of the predetermined drive voltage (U ₂ ) on the basis of a for the

Excitation actuator (105) determined relationship (310) between the current operating temperature (T ₂ ), the associated

Oscillation amplitude (s ₂ ) and the predetermined drive voltage (U ₂ ) to perform.

Hand-held power tool according to claim 7, characterized in that the drive unit (103) is associated with a data memory (170), in which at least the determined relationship (310) in the manner of a

Lookup table is retrievable stored. 9. Hand-held power tool according to one of claims 6 to 8, characterized in that the control element (125) is adapted to carry out the adaptation of the predetermined drive voltage (U ₂ ) such that at a slope of the respective current operating temperature (T ₂ ) a Lowering of the predetermined drive voltage (U ₂ ) takes place.

10. Hand-held power tool according to one of the preceding

Claims, which is designed in the manner of an ultrasonic cutter.