EP2480380A1

EP2480380A1 - Power tool comprising a percussion assembly and a counterweight for compensating vibrations of the power tool

Info

Publication number: EP2480380A1
Application number: EP10740197A
Authority: EP
Inventors: Willy Braun
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2009-09-24
Filing date: 2010-07-27
Publication date: 2012-08-01
Also published as: CN102510791B; DE102009044938A1; WO2011035955A1; CN102510791A

Abstract

The invention relates to a power tool (7) comprising a percussion assembly (8), an eccentric shaft (32) for driving the percussion assembly, and a counterweight (2) for compensating vibrations of the power tool caused in particular by the percussion assembly. The counterweight (2) at least partly surrounds the eccentric shaft (32).

Description

description

title

Power tool with a striking mechanism assembly and a balancing mass to compensate for vibrations of the power tool

State of the art

The present invention relates to a power tool with a percussion assembly, an eccentric shaft for driving the percussion unit, and a compensating mass for the compensation of vibrations of the power tool.

With the entry into force of the legal requirement to couple the daily allowable workload with the use of power tools to the physical load acting on the operator, this applies to power tools, especially in the case of drilling and drilling

Schlaghämmern, the subject of vibration is becoming increasingly important.

When hammering and chiselling a hammer, the greatest physical strain on the operator comes from the housing vibration generated by the hammer mechanism. Especially with large drills and impact hammers, the vibrations are very pronounced due to the high impact energy. For operators of such machines, the permitted working time is reduced considerably without further measures. As a result, in the development of increasingly worked solutions in which vibrations of power tools are reduced. This ensures that you can continue to work with these devices without restrictions.

FIG. 1 shows a typical housing vibration 100 resulting from vibrations of the housing of drilling and striking hammers 7, which is caused by a percussion unit 8, in which the club 81 is driven by an eccentric piston drive 12. The horizontal axis 101 shows the angle of rotation [in °]. represents, on the vertical axis 102, the deflection [in mm] of the housing. The vibration-generating housing vibration 100 is composed of a plurality of frequency components. The main frequency is derived from the periodic acceleration of the carrier 81. However, FIG. 1 shows that the deflection, which is caused by the periodic acceleration of the racket 81, is superimposed on further frequency components from other sources of vibration, eg from the impact and recoil processes of the impact chain and unbalanced mass forces of the drive , Because the housing oscillation 100 does not substantially sinusoidally with the main frequency, but the sinusoidal waveform with main frequency are superimposed on other frequency components.

Since nonlinear systems work with only partially harmonic motion sequences, the individual vibration components are superimposed in a complex manner. By playing between the individual components, by nonlinear elasticity gradients, by the non-linear impact processes and by only approximately harmonious reaction forces from the percussion result inharmonious housing vibrations of complex order.

In practice, the generation of counter-forces, which counteract the housing vibrations, with the help of absorbers or counter-oscillators.

A damper is a spring-mass system with a fixed resonant frequency that can achieve significant vibration reduction only in a small region near the resonant frequency.

In the case of the counteroscillator, a balancing mass is coupled to the drive of the electric tool and is driven in such a way that it is driven out of the drive of the electric tool

Gegenschwingers resulting reaction force of the vibration source counteracts as well as possible.

Known drive concepts for the balancing mass of a counter-oscillator can be divided into two classes: In the first case, the balancing mass is forcibly driven by means of an eccentric crank or cross-grinding drive. In the second case, the balancing mass is driven by cams, wherein the required contact contact is made by means of a spring loading of the balancing mass. In this case, the balancing mass is not forced.

Examples of a positively driven leveling compound are shown in EP 1 475 190 A2 and EP 1 439 038 A1. In EP 1 475 190 A2 the balancing mass is arranged around the hammer tube and is driven by an additional connecting rod linked to the striking mechanism eccentric. In the case of EP 1 439 038 A1, a parallelepiped compensating mass provided with a transverse slot is arranged above the eccentric. In the transverse slot runs to the axis of rotation eccentric bolt of Schlagwerksexzenters so that the balancing mass is driven by a cross-loop. An example of a spring-loaded balancing mass shows the document

WO 2004/082897 A1. In order for the balancing mass of the cam geometry to follow this mimic, considerable pressure forces must be applied to the balancing mass via the elastic spring elements. This not only requires additional effort, space and costs. But the additional spring pressure increases frictional and wear effects, and much of the energy needed to compress the spring is lost as well, so the overall efficiency is degraded and more engine power is required. The hitherto known embodiments have in common that the balancing mass is arranged relatively far away from the source of vibration causing source. As a result, the power flow path is very long and reduces the efficiency of the achievable by the balancing mass damping.

Disclosure of the invention

The object of the invention is therefore to provide a power tool with a leveling compound for damping vibrations of the power tool, which in hard to reach areas of the power tool with little construction Share is very compact and very inexpensive to install, which is very precisely positioned, and with the improved damping is achievable.

The object is achieved with a power tool with a percussion unit, an eccentric shaft for driving the percussion unit, and a compensating mass for the compensation of vibrations of the power tool, which are caused by the percussion unit, wherein the balancing mass surrounds the eccentric shaft at least partially. In such an arrangement of the compensating mass, at least partially provided around the eccentric shaft used to drive the percussion mechanism, the power flow path for compensating the percussion drive causing the vibrations is minimal. As a result, the achievable damping is optimal.

Preferably, the balancing mass has a recess through which the eccentric shaft is guided. In this embodiment, the balancing mass surrounds the eccentric shaft on all sides. The balancing mass is therefore arranged in a hard to reach area of the power tool, but does not hinder the drive of the eccentric shaft.

The striking mechanism assembly preferably comprises a connecting rod with a racket, wherein the connecting rod spaced from the eccentric shaft and is driven eccentrically thereabove, wherein a harmonious rotational movement of the eccentric shaft in a cyclic, substantially harmonious movement of the racket in a

Turning direction is changed. A harmonic rotary motion within the meaning of the invention is a rotary movement with a substantially constant fundamental frequency. In the case of a harmonic pushing movement in the sense of the invention, the change of location with time has a substantially unifrequent sinusoidal course. The term "essentially" refers to effects caused by friction

According to the invention, the change of location with time a multifrequent course.

In a preferred embodiment, a drive means for driving the balancing mass is non-rotatably arranged on the eccentric shaft. Therefore, when driving the percussion mechanism assembly, the drive means, and thus also the Equal mass driven. The drive of the balancing mass is therefore integrated in the eccentric drive.

Preferably, the drive means is made in one piece with the eccentric shaft. Compared to a multi-part solution, for example, with pressed-on the eccentric shaft drive means, the one-piece embodiment has the advantage that it occupies less space with the same eccentricity, since no minimum wall thicknesses must be maintained. By rotation of the drive means about the eccentric shaft, the balancing mass is in a preferred embodiment, starting from a starting point substantially in a direction of movement back and forth and returns to the starting point. In this embodiment, the balancing mass is moved by the drive means substantially axially cyclically back and forth. In this case, the direction of movement preferably extends transversely to the drive axis, in this case the eccentric axis, particularly preferably substantially in and against the direction of impact of the striker of the striking mechanism assembly.

Preferably, the balancing mass is driven so that it performs a substantially anti-cyclical to Schlagwerksbaugruppe occurring vibration. In this case, it is preferred that the oscillation taking place in an anticyclical manner to the percussion unit takes place in phase displacement with respect to the oscillation of the percussion unit in order to compensate for only approximately harmonious reaction forces. The skilled person understands that the anticyclical oscillation of the balancing mass can be superimposed on other oscillations for compensation of frequency components of the vibrations from other vibration sources, so that the movement of the balancing mass is inharmonious. Such vibration sources are, for example, impact and recoil operations of the impact chain as well as further unbalanced mass forces of the drive, inharmonious motion sequences, play between the individual components and non-linear elasticity courses.

Particularly preferably, the drive means is at least partially disposed in the recess of the balancing mass. Therefore, it cooperates with the recess defining surface of the balancing mass. Preferably, the

Balancing mass positive and / or non-positive with the drive means coupled, so that no additional component costs for the drive of the balancing mass arises. In addition, the dimensions of the drive means are preferably adapted to the dimensions of the balancing mass.

Preferably, the balancing mass is forcibly driven in driving the drive means, so that the motion transmission between the drive means and the balancing mass is unique even at high reaction forces and high operating frequency. In addition, in such an embodiment, no additional drive energy, no additional space and no additional costs for other pressure means such as springs needed. Such a drive allows a very large dynamics. Furthermore, no lifting of the contact partners is possible.

Further preferably, the leveling compound extends substantially flat, so that the leveling compound is made very compact, in particular from a metal sheet or a metal alloy and occupies little space in the power tool. Preferably, the balancing mass is punched from the metal sheet. Alternatively, the balancing mass may also be sintered. Such a balancing weight is very inexpensive to produce.

Advantageously, depending on the required weight and the material used, the dimension of the balancing mass in the direction of the eccentric axis can be very small and / or the dimensions in the transverse direction to the eccentric shaft can be very small, so that the balancing mass can be adapted to the spatial installation conditions. The balancing mass can therefore also be integrated into an existing power tool, since almost no additional space is needed. Also preferably, the mass distribution of the balancing mass is adaptable to the mass distribution of the power tool, so that by a suitably selected mass distribution vibration components are compensated, which are caused in particular by an uneven mass distribution in the power tool.

In a further preferred embodiment, the power tool has an eccentric disk, in particular for driving the striking mechanism assembly, in particular for driving the connecting rod, which rotatably attached to the eccentric shaft. is arranged, wherein the eccentric shaft is rotatably mounted with a first bearing in a bearing block, and wherein the balancing mass between the eccentric disc and the bearing block is arranged. Preferably, the balancing mass is stored in the bearing block. The arrangement of the balancing mass between the eccentric disc and the bearing block has the advantage that the friction conditions are very favorable, especially in the case of hardened steel bearing block, since the arrangement is arranged in the lubricant chamber of the power tool. The balancing weight is therefore always in the fully lubricated area of the power tool, without any additional effort. The introduction of the forces by the balancing mass is therefore very close to the vibration source, namely directly to the eccentric disc and very close to the striking axis. Another advantage is the very compact, simple and inexpensive overall structure of the arrangement. Furthermore, the balancing mass in this arrangement allows a good balance of air cushioning forces and unbalanced masses, causing a reduction in the Exzenterlagerbelastung is effected.

Preferably, the eccentric shaft is also rotatably mounted with a second bearing in a percussion mechanism housing of the percussion mechanism, wherein the bearing block is arranged in the percussion mechanism housing.

In a further preferred embodiment, the drive means is manufactured in one piece with the eccentric disc. Or in a further preferred embodiment, the eccentric shaft, the eccentric disc and the drive means are made in one piece.

Further preferably, the bearing block limits the direction of movement of the balancing mass, in particular on its sides, for example by a slotted guide. Also preferably, the bearing block limits the direction of movement of the balancing mass to its side facing away from the eccentric disc. Also preferably, the eccentric limited the direction of movement of the balancing mass. This arrangement results in a very small tolerance chain.

In an alternative embodiment, the direction of movement of the compensating mass is limited by holding elements which are in the bearing block and / or on Housing are arranged. Such holding elements are for example U-shaped plastic elements which receive the balancing mass and through which it is guided.

The drive means preferably comprises a cam, wherein the cam cooperates with the recess for driving the balancing mass. The balancing mass with the recess and the cam used for the drive can be produced very inexpensively by known means.

In a preferred embodiment, the cam is curved, so that with this arrangement inharmonic movements of the balancing mass can be achieved, and therefore caused not only by the vibrations caused by the percussion mechanism vibrations caused by other sources of vibration of the power tool are at least partially compensated. The cam-shaped contour of the cam substantially determines the amount and direction of deflection of the balance cup. Therefore, by adjusting the contour, in particular its slope, both a multiple back and forth oscillating balancing mass and one or more rest points of the balancing mass can be achieved within a drive cycle of the drive means. The contour therefore makes it possible to accelerate the movement of the balancing mass and to perform shock processes with the balancing mass. Likewise, the contour allows a temporal extension of forward and backward movements of the balancing mass. Therefore, both phase-shifted vibration processes as well as acceleration and shock processes, such as the striking mechanism, can be very well balanced. By adjusting the contour, the movement of the balancing mass can be very easily adapted to the vibration conditions of the power tool, so that a very good vibration control is possible.

In a further preferred embodiment, the drive means comprises at least one coupling means, wherein the balancing mass comprises at least one counter-coupling means, wherein the coupling means cooperates with the counter-coupling means for driving the balancing mass. The provision of a coupling means, which cooperates with a negative feedback means, allows a variety of other positive and / or non-positively acting together drive options for the balancing mass.

The drive means is preferably the eccentric disc. Therefore, in addition to the eccentric, which is also used to drive the percussion unit, no further drive means required, so that the component cost, installation costs and the required space is minimal.

In order to optimize the sliding and rolling conditions of the coupling means with the counter coupling means, the coupling means and / or the counter coupling means can be provided with a rotating means, for example a sleeve, a wheel or a rotatable bearing.

Further preferably, the coupling means is a groove and the negative feedback means a bolt which engages in the groove, or vice versa. Also preferably, the coupling means is a web and the counter-coupling means a groove which engages around the web, or vice versa. These embodiments make it possible, by the interaction of a coupling or counter coupling means raised with respect to a surface against a surface, to engage the submerged into the countersunk or grasp the submerged around the raised means so as to ensure a defined course of movement is. By the groove or the web are curved, a nearly arbitrary course of movement of the balancing mass can be achieved. The amount of deflection of the balancing mass is thereby determined essentially by the curved contour. Therefore, by virtue of the curved contour of the cyclic movement of the percussion mechanism assembly, additional movement components can be superimposed on the compensating mass, so that inharmonic vibration components of the power tool can be compensated.

In a further preferred embodiment, the drive means comprises at least two driving bolts as coupling means, wherein the compensating mass comprises at least two driving webs as negative feedback means. In this case, a coupling means which is raised in relation to a surface cooperates with a counter-coupling means which is also raised in relation to a surface. Here, too, a defined movement is ensured by the driving bolts take each take a driving bar alternately. This drive of the balancing mass acts similar to a step transmission, so that inharmonic vibration components can be compensated with the balancing mass. The deflection of the balancing mass is determined by the position of the driving pin on the drive means and by the length and contour of the driving webs.

In a further preferred embodiment, the driving bolts are arranged on a cam of the drive means, which engages in a recess of the balancing mass, wherein the cam has a curved contour. In this embodiment, the deflection of the balancing mass is determined both by the cooperating driving pin and driving webs, as well as by the contour of the cam.

The skilled person understands that even by adapting the contour of the recess of the balancing mass a change in the deflection of the balancing mass can be achieved, and therefore an inharmonic pushing movement of the balancing mass can be achieved.

In the power tool according to the invention, the balancing weight for the compensation of vibrations of the power tool in a very difficult to reach area is very efficient, very space-saving and yet inexpensive to integrate. By adjusting the contour of the drive means and / or the balancing mass vibrations caused by other sources of vibration can be compensated in addition to the caused by the cyclic substantially harmonic thrust movement of the racket vibrations.

In the following the invention will be described with reference to figures. The figures are merely exemplary and do not limit the general idea of the invention. shows a typical housing vibration caused by vibrations of the housing of drilling and hammering, FIGS. 2 to 4 each show a detail of a power tool with percussion mechanism, wherein the power tool is here a hammer drill, and wherein in FIG. 2 a longitudinal section through the power tool 7 is shown, in Fig. 3 is a plan view of an eccentric disc of the power tool. 7 4 shows a horizontal section through a balancing mass arranged in the electric tool 7,

Figs. 5-9 show various embodiments of balancing masses and drive means, and

10 shows the deflection of the balancing mass of FIGS. 4-7 and 9

depending on the angle of rotation of the eccentric shaft.

Fig. 1 shows, as already described in the introductory part of this patent application, a typical housing vibration, which results from vibrations of the housing of drilling and hammering.

2 to 4 each show a detail of a power tool 7 with impact mechanism assembly 8, wherein the power tool 7 is here a hammer drill, and wherein in FIG. 2 a longitudinal section through the power tool 7 is shown, in FIG. 3 is a plan view of an eccentric 10 of the power tool 7, and FIG. 4 shows a horizontal section through a balancing mass 2 arranged in the power tool 7.

The electric tool 7 is driven by means of an electric motor (not shown here), wherein the electric motor 7 drives a motor shaft 9 with a drive pinion 91, and wherein the drive pinion 91 drives the eccentric disk 10. The eccentric 10 is rotatably disposed on an eccentric shaft 32 which is rotatably supported about an eccentric axis 33 by means of a first eccentric bearing 61 and a second eccentric bearing 62. The first eccentric bearing 61 is arranged in a housing 14 of the striking mechanism assembly 8 and the second eccentric bearing 62 in the bearing block 13, wherein the bearing block 13 itself is also arranged in the housing 14 of the striking mechanism assembly 8. On the eccentric shaft 32, a spur gear 17 is further arranged rotatably, which drives a clutch spur gear 16 and a bevel gear 15. The bevel gear 15 drives a driven gear 18, which is arranged around a hammer tube 19 of the striking mechanism assembly 8 so that it is driven.

On the eccentric 10 a connecting rod 12 is eccentrically arranged eccentrically about the eccentric axis 33 by means of an eccentric pin 1 1. About the connecting rod 12, the rotational movement of the eccentric disk 10 is converted into a linear movement. The connecting rod 12 therefore drives a racket 81 of the striking mechanism assembly 8 cyclically in a substantially harmonic pushing movement.

To compensate for the vibrations of the power tool 7, this has a balancing mass 2. The balancing mass 2 is driven by means of a drive means 3, which is rotatably mounted about the eccentric axis 33, wherein a rotational movement of the drive means 3 is converted to the eccentric axis 33 in a pushing movement of the balancing mass 2.

In the power tool 7 shown here, the leveling compound 2 is arranged between the eccentric disk 10 and the bearing block 13. The drive means 3 is a cam 31, which is arranged in a recess 21 of the balancing mass 2 in order to ensure a safe transmission of movement. The cam is rotatably disposed about the eccentric shaft 32, so that the eccentric axis 33 is the drive axis of the drive means 3. The drive means 3 and the balancing mass 2 are thereby coupled so that the balancing mass 2 is forcibly driven by the latter when the drive means 3 is rotated.

As FIG. 4 shows, the cam 31 has a circular contour 35. The cam 31 rotates eccentrically on rotation of the drive means 3 about the eccentric axis 33. FIG. 4 shows the eccentricity 331 of the cam 31 during a partial revolution of the drive means 3 about the eccentric axis 33. The recess 21 and the cam 31 are so dimensioned in that when the cam 31 is rotated in a direction of rotation 4 there is always a contact contact between the cam 31 and the recess 21. When the cam 31 rotates eccentrically in the direction of rotation 4 about the eccentric axis 33, it therefore moves the balancing mass 2 axially. The balancing mass 2 is thus in a direction of movement 5 and moves, which extends transversely to the eccentric axis 33. Thus, the balancing mass 2 in the power tool 7 in the direction of movement 5 can move freely back and forth, recesses 22 are provided on her.

In this contour 25 of the balancing mass 2 performs a harmonic rotation of the drive means 3 due to the circular contour 35 of the drive means 3 and the existing during rotation of the drive means 3 contact between the drive means 3 and the balancing mass 2 to a substantially harmonic thrust movement of the balancing mass 2. Der The course of the oscillation 100 of the balancing mass 2 with time is therefore essentially uni-sinusoidal.

10 a) shows the course of the movement 100 of the balancing mass 2 during a 360 ° rotation of the drive means 3 about the eccentric axis 33. The horizontal axis 101 shows the angle of rotation [in °], the vertical axis 102 shows the deflection [ in mm] of the balancing mass 2. The amplitude of the curve of the vibration 100 of the balancing mass 2 corresponds to the eccentricity 331. In the present case, the drive means 3 and the balancing mass 2 are provided so that there is a phase shift to the harmonic oscillatory movement of the racket 81 of the striking mechanism assembly 8. However, with this embodiment, only a substantially harmonic countermovement can be effected. An attenuation of vibrations, which are caused in addition to a cyclically moving vibration cause, for example, the acceleration of the racket 81, by still further sources of vibration is thus not satisfactorily possible.

FIGS. 5-9 show embodiments of balancing masses 2 and drive means 3 of different embodiments. With the embodiments listed here are inharmonic pushing movements of the balancing mass 2 executable, so that with them an attenuation of vibrations of the power tool 7, in particular of the housing, which are caused by a variety of vibration sources are possible.

In Fig. 5, the drive means 3 is formed as a cam 31 which is arranged on the eccentric shaft 32 and rotatable about the eccentric axis 33. At the cam 31 is a means for coupling 31 1 arranged eccentrically. The means for coupling 31 1 is here a pin. The balancing mass 2 has, as an antidote to the coupling 21 1, a symmetrical groove into which the pin 31 1 engages. For the Fig. 5, the terms pen and means for coupling 31 1, and the terms groove and means for negative feedback 21 1 are used synonymously.

The groove 21 1 has a symmetrical V-shaped contour 25 with an angle of attack 251. Upon rotation of the drive means 3 in a direction of rotation 4, the pin 31 1 is eccentrically rotated about the eccentric axis 33. Since the groove 21 1 is not circular but V-shaped, and therefore the pin 31 1 can not move freely along the groove 21 1, pushes the pin 31 1 in its eccentric movement about the eccentric axis 33 against the balancing mass 2 and moves it axially.

Fig. 5 a) shows the balancing mass 2 at a starting point 20 at a rotational angle of 0 ° of the drive means 3. FIG. 5 b) shows the balancing mass 2 after a partial revolution of the drive means 3, through which the balancing mass 2 with respect to the starting point 20 has moved axially by a deflection amount 201 in a direction of movement 5.

Fig. 10 c) shows the course of movement 100 of the balancing mass 2 of Fig. 5 at a 360 ° - rotation of the drive means 3 about the eccentric axis 33. Again, on the horizontal axis 101 of the rotation angle [in °] and on the vertical Axis 102, the deflection [in mm] of the balancing mass 2 shown.

In this embodiment, the movement can be changed over the angle of attack 251 of the groove 21 and the eccentricity 331 of the pin 31. This embodiment allows, as shown in Fig. 10 c), compared to that of FIGS. 2-4 steeper movement respectively acceleration amplitudes and resting phases.

To allow a free back and forth movement of the balancing mass 2 in the power tool 7, this balancing mass has 2 recesses 22. As drive means 3, for example, the eccentric 10 of the Elec- rowerkzeugs 7, wherein the pin 31 1 is arranged eccentrically on the eccentric disc 10.

In Fig. 6, a further embodiment of balancing mass 2 and drive means 3 is shown. Fig. 6 a) shows a plan view, while Fig. 6 b) shows a section through the line A-A. The drive means 3 is designed as a circular cam 31. On the drive means 3, a first driving pin 31 1 and a second driving pin 312 are arranged as a means for coupling 31 1, 312. The balancing mass 2 has as means for negative feedback 21 1, 212 a first driving rib 21 1 and a second driving rib 212, which protrude here into a recess 21 of the balancing mass 2. The recess 21 itself is dimensioned so that it does not affect the movement of the balancing mass 2.

The first driving pin 31 1 is arranged so that when turning the drive means 3 in the direction of rotation 4 in touching contact with the first driving web 21 1 and the balance mass 2 entrains and axially displaces in the direction of movement 5 until it is out of touch with the first driving web 21 1 device. The second driving pin 312 is arranged so that when turning the drive means 3 in the direction of rotation 4 comes in touching contact with the second driving bar 212 and the balance mass 2 entrains and axially displaces in the opposite direction of movement 5 until it out of touch with the second driving bar 212th device. The driving webs 21 1, 212 and driving pins 31 1, 312 are also arranged so that they come successively in touch contact and out of touch. In a 360 ° rotation of the drive means 3, therefore, the leveling compound 2 is once again moved back and forth.

The course of the movement 100 of the leveling compound 2 of FIG. 6 during a 360 ° rotation of the drive means 3 about the eccentric axis 33 is shown in FIG. 10 e). On the horizontal axis 101, in turn, the rotation angle [in °] and on the vertical axis 102, the deflection [in mm] of the balancing mass 2 is shown. In this embodiment can be on the number and position of the driving pin 31 1, 312 and driving webs 21 1, 212 and the contour 25 of the driving webs 21 1, 212 change the movement.

Analogous to that of FIGS. 2-4, the drive means of FIG. 7 has a cam 31, which is arranged non-rotatably on the eccentric shaft 32 and is rotatable about the eccentric shaft 33. To drive the balancing mass 2 of the cam 31 cooperates with the recess 21 of the balancing mass 2 by engaging in the recess 21 of the balancing mass 2, so that the drive means 3 and the balancing mass 2 are positively and / or non-positively coupled, and the balancing mass 2 is forcibly driven by the latter when rotating the drive means 3 and is moved axially back and forth.

Compared with the drive means 3 of FIGS. 2 to 4, however, the cam 31 of FIG. 7 has a curved contour 35, namely the contour 35 of a dagger.

Analogous to Fig. 5, Fig. 7 shows a) the balancing mass 2 at a starting point 20 at a rotational angle of 0 ° of the drive means 3. FIG. 7 b) shows the balancing mass 2 after a partial revolution of the drive means 3, through which the Compensation mass 2 relative to the starting point 20 has moved axially by a deflection amount 201 in a direction of movement 5.

In the embodiment of FIG. 7, a harmonic rotation of the drive means 3 leads to an inharmonic pushing movement of the balancing mass 2. The course of the oscillation 100 of the balancing mass 2 over time is multifrequent. Fig. 10 b) shows the course of the movement 100 of the balancing mass 2 in a 360 ° rotation of the drive means 3 about the eccentric axis 33. On the horizontal axis 101 of the rotation angle [in °] and on the vertical axis 102, the deflection [in mm] of the balancing mass 2 shown.

The course of the movement 100 of the balancing mass 2 in a 360 ° rotation of the drive means 3 about the eccentric axis 33 shows a steeper rise and rest periods. The cam 31 is preferably arranged on the eccentric shaft 32 of the power tool 7.

FIG. 8 shows, analogously to FIG. 7, a drive means 3 with a cam 31, wherein the compensating mass 2 has a recess 21 into which the cam 31 engages.

However, the cam 31 of FIG. 8 has a different curved contour 35, and furthermore the recess 21 has a contour 25 which influences the course of the movement 100 of the leveling compound 2. Even with this embodiment, therefore, almost any course of motion 100 of the balancing mass 2 can be made possible. Within a 360 ° rotation of the drive means 3 in the direction of rotation 4 about the eccentric axis 33, therefore, both returning movements as well as modes with multiple frequency components can be realized.

FIG. 9 shows an embodiment whose drive means 3 has a groove with a curved contour 35 as means for coupling 31 1. As an antidote to the coupling 21 1, the balancing mass 2 on a pin. The terms groove and means for coupling 31 1 and the terms pen and means for negative feedback 21 1 are therefore used synonymously for Fig. 9.

The distance of the contour 35 of the groove 31 1 of the drive means 3 of FIG. 9 to the eccentric axis 33 varies. Therefore, in this embodiment, an almost arbitrary course of movement 100 of the balancing mass 2 can be generated. Within a 360 ° rotation of the drive means 3 in the direction of rotation 4 about the eccentric axis 33 can by the curved contour 35 of the groove 31 1 both a returning movement as well a waveform with multiple frequency components can be realized.

The groove 31 1 is preferably arranged in the eccentric disk 10 of the power tool 7, for example milled. As a result, the drive means 3 can be integrated very cost-effectively in the power tool 7 in a very space-saving manner and with minimal expenditure on components. To the sliding and Abwälzverhältnisse of the pin 21 1 in the groove 31 1 to improve, the pin 21 1 can be provided for example with a sleeve or a rotatable bearing.

As an alternative to the embodiment with a groove as a means for coupling 31 1, in which a pin engages as an antidote to the coupling 21 1, an embodiment is conceivable in which a gripping element, for example with a U-shaped form, engages around a web.

Claims

claims

Power tool (7) with a striking mechanism assembly (8), an eccentric shaft (32) for driving the striking mechanism assembly (8), and a balancing mass (2) for compensation of vibrations of the power tool (7), in particular of housing vibrations, in particular by the striking mechanism assembly ( 8) are caused,

characterized in that

the balancing mass (2) at least partially surrounds the eccentric shaft (32).

Power tool (18) according to claim 1, characterized in that the balancing mass (2) has a recess (21) through which the eccentric shaft (32) is guided.

Power tool (18) according to one of the preceding claims, characterized in that for driving the balancing mass (2) a drive means (3) is non-rotatably mounted on the eccentric shaft (32).

Power tool (18) according to one of the preceding claims, characterized in that the drive means (3) is arranged at least partially in the recess (21) of the balancing mass (2).

Power tool (18) according to one of the preceding claims, characterized in that the compensating mass (2) extends substantially flat.

Power tool (18) according to one of the preceding claims, characterized in that an eccentric disc (10), in particular for driving the striking mechanism assembly (8), non-rotatably on the eccentric shaft (32) is arranged, and that the eccentric shaft (32) with a first bearing (61) is rotatably mounted in a bearing block (13), wherein the balancing mass (2) between the eccentric disc (10) and the bearing block (13) is arranged.

Power tool (18) according to one of the preceding claims, characterized in that the eccentric shaft (32) with a second bearing (62) in a striking mechanism housing (14) of the striking mechanism assembly (8) is rotatably mounted, wherein the bearing block (13) in the striking mechanism housing (14) is arranged.

8. Power tool (18) according to any one of the preceding claims, characterized in that the drive means (3) comprises a cam (31), wherein the cam (31) for driving the balancing mass (2) with the recess (21) cooperates.

9. Power tool (18) according to any one of claims 1-7, characterized in that the drive means (3) at least one coupling means (31 1, 312), and that the balancing mass (2) comprises at least one counter-coupling means (21 1, 212) , wherein the coupling means (31 1, 312) for driving the balancing mass (2) with the counter-coupling means (21 1, 212) cooperates.

10. Power tool (18) according to claim 9, characterized in that the drive means (3) is the eccentric disc (10).

1 1. Power tool (18) according to any one of claims 9-10, characterized in that the coupling means (31 1) is a groove and the counter-coupling means (21 1) is a bolt which engages in the groove, or vice versa.

12. Power tool (18) according to any one of claims 9 - 10, characterized in that the coupling means (31 1) is a web and the counter-coupling means (21 1) is a groove which engages around the web, or vice versa.

13. Power tool (18) according to any one of claims 9 - 10, characterized in that the drive means (3) at least two driving pins (31 1, 312) as a coupling means, and that the balancing mass (2) at least two driving webs (21 1, 212 ) as negative feedback means.