EP3271115A1

EP3271115A1 - Hand-held power tool and mechanical percussion mechanism

Info

Publication number: EP3271115A1
Application number: EP16707048.1A
Authority: EP
Inventors: Cheu Chyong Teh
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2015-03-17
Filing date: 2016-02-24
Publication date: 2018-01-24
Anticipated expiration: 2036-02-24
Also published as: EP3271115B1; US20180029206A1; CN107405759A; WO2016146354A1; DE102015204807A1; US11185963B2; CN107405759B

Abstract

The invention relates to a hand-held power tool (100) with a mechanical percussion mechanism (200), comprising an input shaft (120) for rotationally driving a percussion element (300) associated with the mechanical percussion mechanism (200). According to the invention, at least one V-shaped guide groove is provided on the outer circumference of the input shaft (120), the base lines thereof converging in a connection section being at least partially concave-polygonal.

Description

description

title

Hand tool and mechanical percussion state of the art

The present invention relates to a portable power tool with a mechanical percussion mechanism, which has a drive shaft for the rotary drive of the impact mechanism associated with the mechanical striking mechanism. In addition, the invention has a mechanical percussion to the object, which has a provided with at least one drive cams impactor and provided with at least one output cam output shaft, wherein the at least one drive cam for the striking drive of the output cam is formed in a percussion mode of the mechanical percussion and the impactor cooperates with a drive shaft.

From EP 2 168 725 A1 a rotary impact tool is known in which a drive shaft is rotationally driven by a rotary drive power source, the drive shaft having an outer peripheral surface and a cam groove formed on the outer circumferential surface. A hammer is disposed coaxially with the drive shaft, the hammer having an inner peripheral surface and a cam groove formed on the inner peripheral surface. Furthermore, the rotary impact tool has an anvil engageable with the hammer along a rotational direction and a compression spring for axially biasing the hammer in the direction of the anvil or a corresponding one

Tool holder. For mechanical coupling between the drive shaft and the hammer a ball is provided, which engages in the cam groove of the drive shaft and in the cam groove of the hammer. The hammer is designed in such a way that it can rotate along a rotational location line defined by the cam groove of the drive shaft and the cam groove of the hammer. A

The shape of a rotary locus of the hammer is in the direction of advancement or downforce. formed as a curve in which a pitch angle of the rotational location line changes continuously with the change of the hammer rotation angle.

A disadvantage of this prior art, inter alia, that due to the geometry of the cam grooves, a wear-increasing frontal or edge-side collision between the hammer cam and the anvil cam is possible. This means that the hammer and the anvil are more often not synchronized with each other depending on the operating condition of the rotary impact tool in its operation, i. out of engagement.

Disclosure of the invention

An object of the present invention is therefore to provide a hand tool with a hammer mechanism, in which the synchronization between a striker and a drive shaft is at least largely ensured in all operating conditions and requires a reduced drive torque.

This problem is solved by a hand-held power tool having a mechanical percussion mechanism which has a drive shaft for rotationally driving a striking body associated with the mechanical impact mechanism. At least one V-shaped guide groove is provided on an outer circumference of the drive shaft, the baselines of which converge in a connecting section being configured concave-polygonal in the output direction at least in sections.

The invention thus allows improved synchronization between drive and driven cams of the mechanical percussion mechanism due to an improved progression geometry of the V-shaped guide grooves, so that in particular the risk of wear-increasing, frontal or peripheral collisions between them is considerably reduced. In addition, reduces a necessary for the operation of the impact mechanism, mechanical drive torque. The co-operating with the impactor drive shaft is preferably driven via a transmission for speed and torque adjustment of a mains or battery-powered electric motor. Preferably, in the at least one guide groove of the drive shaft, a driving ball is arranged, which in a on an inner circumference of a

Through opening of the impactor trained driving recess engages.

Thus, a reliable mechanical coupling between the drive shaft and the striker while maintaining a necessary relative mobility for generating required in operation, pulsating rotational shocks is given.

In the case of an advantageous embodiment, the connecting portion between the baselines of the V-shaped guide groove is curved at least substantially semicircular.

Due to the increased radius of the connecting portion, the axial velocity of the impactor is reduced.

According to a development, the connecting portion has an enlarged radius.

Due to the comparatively large radius results in an improved time course of the movement speed of the impactor.

Preferably, the baselines on both sides of the connecting portion each have a substantially rectilinear central portion with a first predetermined pitch angle, which is preferably greater than 45 °.

This results in a high axial acceleration of the impactor and, consequently, a high impact energy.

Preferably, a substantially rectilinear end section adjoins the two middle sections in each case with a second predetermined pitch angle, which is preferably less than 45 °.

As a result, the probability that the drive cam and the output cam collide with each other frontally or peripherally, significantly reduced. In an advantageous embodiment, the first predetermined pitch angle is greater than the second predetermined pitch angle.

This results in optimum operating characteristics of the hammer mechanism in impact mode.

According to a favorable embodiment, two parallel spaced apart to each baseline of the V-shaped guide groove arranged contour lines converge at an acute point in a connection point.

As a result, there is a reduced friction of the Mitnehmerkugeln within the guide when passing the connection point.

Preferably, the at least one V-shaped guide groove has a substantially semicircular cross-sectional geometry.

This results in a linear, i. a maximum large-area contact between the driving ball and the associated guide groove or Mitnehmer recess.

In accordance with an advantageous further development, the at least one driving recess is formed in the shape of a hollow-ridge with a base line substantially corresponding to the baseline.

As a result, a reliable guidance of the driving balls between the drive shaft and the impactor is ensured in cooperation with the V-shaped guide groove.

The problem mentioned at the outset is also solved by a mechanical percussion mechanism which has a striker provided with at least one drive cam and an output shaft provided with at least one output cam, wherein the at least one drive cam for the striking drive of the output cam is formed in a percussion mode of the mechanical impact mechanism and the Impact body cooperates with a drive shaft, wherein at least one V-shaped guide groove is provided on an outer circumference of the drive shaft, whose in a connecting portion to Commencing baselines are formed in the output direction at least partially concave-polygonal.

Because of the polygonal-concave guide grooves according to the invention, the drive torque to be applied by a drive motor for operating the percussion mechanism can be reduced along with other positive effects and, consequently, significantly increase the service life of a particularly impact-fed impact wrench. In addition, there is an improved synchronization between the drive and the output cam of the impact mechanism, which among other things leads to a reduction in wear and an increase in the life.

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:

1 is a schematic representation of a hand tool, which is equipped with a tool holder and a mechanical impact mechanism according to the invention,

2 is a partial perspective view of a drive shaft with two V-shaped guide grooves,

3 is a plan view of a V-shaped guide groove of the drive shaft of Fig. 2,

4 is a perspective view of a striking body with a through hole,

5 is a partial perspective view of the impactor of FIG. 4 with a driving recess,

6 shows a measuring diagram in which an axial displacement of the striking body of FIGS. 4 and 5 resulting from the guide groove geometry according to the invention is determined in each case as a function of a rotation angle between the drive shaft of FIGS. 2 and 3 and the impact body a common, linear guide groove and a concave-polygonal guide groove according to the invention is applied, and

7 shows a measuring diagram in which the axial velocity of the impact body of FIGS. 4 and 5 resulting from the guide groove geometry according to the invention is illustrated as a function of time t for the conventional linear guide groove and the concave-polygonal guide groove according to the invention.

Description of the embodiments

1 shows a handheld power tool 100, which is equipped with a tool holder 450 and with a mechanical striking mechanism 200 according to the invention. The hand tool 100 has a housing 1 10 with a handle 126 and is mechanically and electrically connected to a preferably replaceable battery pack 130 according to an embodiment for off-grid power supply.

The hand tool 100 is exemplified as a cordless rotary impact wrench. It should be noted, however, that the present invention is not limited to cordless impact wrenches, but rather may be applied to various power tools in which a tool is rotated and an impact mechanism according to the invention is used, e.g. in a percussion drill, etc., regardless of whether the power tool is independent of the mains with a battery pack or network-dependent operable. In addition, it should be understood that the present invention is not limited to power tool hand tools.

In the housing 1 10 are powered by the battery pack 130 with power, electric drive motor 1 14, a gear 1 18 and the hammer mechanism 200 are arranged. The drive motor 1 14 is eg via a manual switch 128 actuated, that is switched on and off, and may be any type of motor, such as an electronically commutated motor or a DC motor. Preferably, the drive motor 1 14 is so electronically controlled or controlled that both a re versierbetrieb, as well as specifications with respect to a desired rotational speed can be realized. The functioning and the structure of a suitable Drive motor are well known in the art and therefore will not be further described here for the sake of brevity of the description.

The drive motor 1 14 is preferably connected via an associated motor shaft 1 16 with the transmission 1 18, which converts a rotation of the motor shaft 1 16 in a rotation of a provided between the transmission 1 18 and striking mechanism 200 drive shaft 120. This conversion is preferably such that the drive shaft 120 rotates relative to the motor shaft 116 with increased torque but reduced rotational speed. The drive motor 1 14 is illustratively arranged in a motor housing 1 15 and the transmission 1 18 in a transmission housing 1 19, wherein the transmission housing 1 19 and the motor housing 1 15 are arranged for example in the housing 1 10.

The coupled with the drive shaft 120, mechanical percussion 200 is an example arranged in an optional striking mechanism housing 220 Drehbzw. A rotary impactor comprising a striking body 300 which effects high intensity, abrupt turning pulses and via an output cam assembly 410 to an output shaft 400, e.g. an output spindle, transmits. It should be understood, however, that the use of optional percussion gear housing 220 is merely exemplary in nature and is not intended to limit the invention. On the contrary, it can also be applied to striking mechanisms without separate percussion mechanism housings, which are e.g. are arranged directly in the housing 1 10 of the power tool 100. In addition, the operation and construction of a suitable impact mechanism of the prior art, e.g. from DE 20 2006 014 850 U1, are well known and will therefore not be described in more detail here for the purpose of brevity of the description, with the exception of the elements shown and described below in FIGS. 2 to 7. However, reference should be made at this point explicitly to DE 20 2006 014 850 111, the disclosure of which is regarded as an inherent part of the present description and from which an embodiment of an exemplary percussion mechanism can be derived.

On the output shaft 400, the tool holder 450 is preferably provided, which is preferably designed for receiving insert tools and according to one embodiment, at least with an insert tool 140 with outer polygon coupling 142, but preferably also with an insert tool with polygon socket coupling, eg a socket, connectable. The Insert tool 140 is exemplified as a screwdriver bit with the external polygon coupling 142, illustratively a hexagonal coupling formed, which is arranged in a suitable internal receptacle of the tool holder 450. Such a screwdriver bit and a suitable socket wrench are sufficiently known from the prior art, so that is omitted here for the purpose of scarcity of the description to a detailed description.

The impactor 300 is preferably axially biased in the direction of the tool holder 450 and the output shaft 400 by means of a compression spring, not shown. The output shaft 400 with the tool holder 450, and the

Impact mechanism 200, the drive shaft 120, the gear 1 18, the motor shaft 1 16 and the drive motor 1 14 are illustratively arranged along a longitudinal central axis 150 in the housing 1 10 of the power tool 100. FIG. 2 shows the drive shaft 120 of FIG. 1, which, according to one embodiment, has two at least substantially V-shaped guide grooves 162, 164. These V-shaped guide grooves 162, 164 are preferably formed in a preferably cylindrical outer circumference 160 of the at least partially hollow cylindrical running according to an embodiment and coaxial with the longitudinal central axis 150 of FIG. 1 extending drive shaft 120. The hollow cylindrical

Portion of the drive shaft 120 serves e.g. for receiving a guide element or guide pin of the output shaft 400 of FIG. 1.

The V-shaped guide grooves 162, 164 preferably each have a substantially C-shaped and preferably semicircular cross-sectional geometry. In each guide groove 162, 164 each a driver ball 166, 168 is added. The two driver balls 166, 168 are preferably each to preferably maximally to their respective Equatorialumfängen in the V-shaped guide grooves 162, 164th

FIG. 3 shows the drive shaft 120 of FIG. 2 to illustrate the V-shaped guide groove 162 of FIG. 2 formed according to one embodiment. The V-shaped guide groove 162 preferably has two baselines 170, 172 which are preferably in an arcuate, preferably converge at least approximately semicircular connecting portion 174, which points in an output direction 176 of the drive shaft 120. The connecting portion 174 illustratively has a radius Ri. The base lines 170, 172 extending symmetrically with respect to the longitudinal central axis 150 of FIG. 1 each have a center section 180, 182 adjoining the connecting section 174 on both sides, preferably at least approximately rectilinear. At these preferably each in turn preferably at least approximately rectilinear end portion 184, 186 closes at a deviating from 180 °, obtuse or elongated angle γι. The baselines 170, 172 thus have, according to the invention, an at least sectionally concave-polygonal course, ie, the baselines 170, 172 represent two polygonal pulls which are respectively "curved" toward one another in the direction of the longitudinal center axis 150 or run towards one another. Parallel to each of the two baselines 170, 172 of the V-shaped guide groove 162 extends in each case a contour line 190, 192 which converge at an acute angle in a connection point Pi opposite the connecting section 174.

FIG. 4 shows the preferably cylindrical, solid impact body 300 of FIG. 1, which according to one embodiment has a preferably cylindrical passage opening 302. This preferably encloses the longitudinal center axis 150 of FIG. 1 coaxially. In an inner circumference 304 of the through hole 302 are preferably two driving recesses 306, 308 embedded, preferably each having an approximately C- or L-shaped, preferably semi-circular cross-sectional geometry for receiving a respective Mitnehmerkugel 166.168 of FIG. 2 to preferably at most equatorial circumferences.

On an illustratively annular end face 310 of the striking body 300, preferably two drive cams 312, 314 designed in the manner of axial projections are preferably integrally formed, which according to one embodiment are positioned on both sides of the passage opening 302 and diametrically opposite one another. The drive cams 312, 314 cooperate in a suitable manner with two output cams, not shown, of the impact mechanism to create the output cam arrangement 410 of FIG. 1.

4 shows the striking body 300 of FIG. 4 to illustrate the driving recess 306 of FIG. 4 formed according to an embodiment. This is preferably arranged in the inner circumference 304 of preferably centrally to the longitudinal center. axis 150 extending through hole 302 formed in the impactor 300.

The driving recess 306 is preferably formed corresponding to the cooperating with them V-shaped guide groove 162 and 164 of Fig. 2 and has an arcuate, preferably at least approximately semicircular connecting portion 320 with a radius R2, to both sides in each case a baseline 322, 324 connects. The latter in each case has a rectilinear middle section 326, 328, which in each case preferably merges into a likewise rectilinear end section 330, 332 at a blunt or extended angle Y2, which differs from 180.degree. In parallel to the base lines 322, 324, an approximately S-shaped curved contour line 334, 336 preferably runs together, which converge at an acute angle in a point P2 located opposite the connecting section 320.

The same applies to the geometric course of the here concealed second, preferably diametrically arranged to MitnahmeEussparung 306 MitnahmeEussparung 308 of Figure 4. The radii R 1 of the V-shaped guide grooves (see Fig. 2 and Fig. 3) and the radii R2 of Mitnahmeaussparungen 306, 308 are preferably the same size.

6 shows a measuring diagram in which an axial displacement S (9) of the striking body 300 of FIG. 4 and FIG. 5 resulting from the guide groove geometry according to the invention is determined as a function of a rotational angle Θ between the drive shaft 120 of FIG. 2 and FIG. 3 and the impactor 300 are each plotted for a conventional linear guide groove and the concave polygonal guide groove 162 or 164 according to the invention from FIGS. 2 and 3. It can be seen that, in the case of the conventional linear guide groove - as indicated by a dotted graph 500 - compared to the inventive at least partially concave polygonal guide groove 162 and 164 of Fig. 2 and Fig. 3 - as with a indicated by dashed curve 600 - depending on the plotted on a horizontal coordinate axis rotation angle Θ each lower and only in two (buckling) - points Ki, 2 of the graph 500 results in an approximately equal axial displacement of the impactor 300. The two graphs 500, 600 each extend in mirror symmetry to the vertical coordinate axis at which the axial displacement S (9) is plotted. The course of the graph 600 results from the above-described guide groove geometry of the concave-polygonal guide grooves 162 and 164 of FIGS. 2 and 3, respectively, and accordingly also has an arcuate connection portion 602 with a radius Rβ corresponding to the connection portion 174 of FIG 3 corresponds to and on each of which an at least approximately rectilinear middle section 604, 606 adjoins, these middle sections 604, 606 corresponding to the central sections 180, 182 of FIG. An angle CM between an illustrative horizontal axis 612, or a first parallel line drawn illustratively to the horizontal coordinate axis, and both middle sections 604, 606 is preferably greater than 45 ° and is illustratively approximately 55 ° in each case. This angle CM is preferably greater than an angle O 2 between a corresponding horizontal axis 614, or a second parallel line drawn illustratively to the horizontal coordinate axis, and two end sections 608, 610 corresponding to the end sections 184, 186 of FIG. 3, which are preferably smaller than 45 ° and illustratively is about 43 °. It also follows that the two end portions 608, 610 in two (buckling) points Ki, 2 each at an angle of 180 ° different angle Y3 to the central portions 604, 606 connect. This obtuse angle Y3 is preferably about 165 °. The radius R3 preferably corresponds to the radii Ri, 2 of

V-shaped and concave-polygonal guide grooves 162 and 164 of Fig. 2 and Fig. 3 of the drive shaft 120 of FIG. 2 and the driving recesses

The same applies to the three angles γι, 2, 3 (see in particular Fig. 3 and Fig. 5).

7 illustrates a further measuring diagram in which an axial velocity v (t) of the striking body 300 of FIG. 4 and FIG. 5 resulting from the guide groove geometry according to the invention is dependent on the time t for a common linear guide groove and the concave-polygonal guide groove 162 and 164 of Fig. 2 and Fig. 3 is plotted. It can be seen that in the conventional, linear guide groove - as indicated by a dotted graph 700 - compared to the present invention at least partially concave polygonal guide groove 162 and 164 of Fig. 2 and Fig. 3 - as with a dashed curve 800 indicates that, depending on the time t applied to a horizontal coordinate axis, a lower axial velocity v (t) of the impactor 300 of FIG. 4 and FIG. 5 is always set. The section 802, the sections 804, 806 and the sections 808, 810 of the Graphs 800 correspond to the connection section 602, the middle sections 604, 606 and the end sections 608, 610 of the graph 600 of FIG. 6.

In particular, a lesser increase in the axial velocity v (t) of the impactor 300 of FIGS. 4 and 5 over time t, which results in the at least partially polygonal-concave guide grooves 162 and 164 of FIG. 2 and FIG Among other things result leads to a small number and hardness of collision situations between the drive and the output cam of the hammer mechanism 200 of FIG. This results in a softer and, at the same time, lower-wear running behavior of the percussion mechanism 200 of FIG. 1 and, associated therewith, a significant increase in the operating comfort of the handheld power tool 100 of FIG. 1. In addition, the percussion mechanism 200 of the handheld power tool 100 of FIG. 1 equipped with the at least partially concave-polygonal guide grooves 162 or 164 of FIG. 2 requires lower drive torques, so that in the case of a hand-held power tool fed independently of the mains, a longer operating time of the electric drive motor 1 14 of Fig. 1 without interim battery pack change or interim charging of the battery pack 130 of FIG. 1 is possible.

Claims

claims

1 . A hand tool (100) comprising a mechanical percussion mechanism (200) which has a drive shaft (120) for rotationally driving a striking body (300) associated with the mechanical striking mechanism (200), characterized in that on an outer periphery (160) of the drive shaft (120). at least one V-shaped guide groove (162, 164) is provided, whose converging in a connecting portion (174) baselines (170, 172) in the output direction (176) are formed at least partially concave polygonal.

2. Hand tool according to Claim 1, characterized in that in the at least one guide groove (162, 164) of the drive shaft (120) a Mitnehmerkugel (166, 168) is arranged, which in a on an inner periphery (304) of a through hole (302). the driving body (300) formed driving recess (306, 308) engages.

3. Hand tool according to Claim 1 or 2, characterized in that the connecting portion (174) between the baselines (170, 172) of the V-shaped guide groove (162, 164) is curved at least substantially semicircular.

4. Hand tool according to one of the preceding claims,

characterized in that the connecting portion (174) has an increased radius (Ri).

5. Hand tool according to one of the preceding claims,

characterized in that the baselines (170, 172) on both sides of the connecting portion (174) each have a substantially rectilinear central portion (180, 182) with a first predetermined pitch angle (α-ι), which is preferably greater than 45 °.

6. Hand tool according to Claim 5, characterized in that in each case a substantially rectilinear end section (184, 186) adjoins the two middle sections (180, 182) with a second predetermined pitch angle (0: 2), which is preferably less than 45 °.

7. Hand tool according to Claim 6, characterized in that the first predetermined pitch angle (α-ι) is greater than the second predetermined pitch angle (02).

8. Hand tool according to one of the preceding claims,

characterized in that two are spaced parallel to each baseline

(170, 172) of the V-shaped guide groove (162, 164) arranged contour lines (190, 192) converge at an acute angle in a connection point (P1).

Powered hand tool according to claim 8, characterized in that the at least one V-shaped guide groove (162, 164) has a substantially semicircular cross-sectional geometry.

0. Hand tool according to one of claims 2 to 9, characterized in that the at least one driving recess (306, 308) is formed with a groove-shaped substantially corresponding to the baseline base line (322, 324).

1 . Mechanical percussion mechanism (200), which has a striker (300) provided with at least one drive cam (312, 314) and an output shaft (400) provided with at least one output cam (312, 314), wherein the at least one drive cam (312, 314) for the striking drive of the output cam in a percussion mode of the mechanical percussion mechanism (200) is formed and the striking body (300) cooperates with a drive shaft (120), characterized in that on an outer periphery (160) of the drive shaft (120) at least one V-shaped Guide groove (162, 164) is provided, in a connecting portion (174) converging baselines (170, 172) in the output direction (176) are formed at least partially concave-polygonal.