EP4017685A1

EP4017685A1 - Hand-held power tool

Info

Publication number: EP4017685A1
Application number: EP20753360.5A
Authority: EP
Inventors: Maximilian Knyrim; Michael UNSÖLD
Original assignee: Hilti AG
Current assignee: Hilti AG
Priority date: 2019-08-19
Filing date: 2020-08-10
Publication date: 2022-06-29
Also published as: CN113924189A; WO2021032515A1; EP3782766A1; US11969867B2; US20220288758A1

Abstract

Hand-held power tool having a tool fitting for holding a striking and rotating tool on a working axis, an electric motor, an impact mechanism which has a striker that is moved periodically along the working axis, and having a rotary drive, which drives a spindle carrying the tool fitting in rotation about the working axis, wherein the rotary drive has a step-down eccentric transmission connected to the electric motor and the spindle is coupled to the eccentric transmission.

Description

Hand machine tool

The present invention relates to a hand machine tool with a tool holder for holding a percussive and rotating tool on a working axis. The hand machine tool is equipped with an electric motor, a hammer mechanism that has a hammer periodically moved along the working axis, and with a rotary drive that drives a spindle carrying the tool holder to rotate about the working axis.

Such a handheld power tool, which can be designed as a hammer drill, for example, is known from EP 3 181 301 A1.

The object of the present invention is to provide a handheld power tool, in particular a rotary hammer or combination hammer, with a comparatively compact and robust rotary drive.

The object is achieved in that the rotary drive has a step-down eccentric gear connected to the electric motor and the spindle is coupled to the eccentric gear. The invention includes the knowledge that when the drilling tool (striking and rotating tool) is varied, other drill diameters or types of drill sometimes require a slower speed of the tool holder for the best possible drilling behavior. This makes a comparatively more step-down gear necessary, which - at least in the case of the hand-held power tools of the prior art - disadvantageously increases the space requirement, the costs, the number of components, the complexity and the weight of these machines.

In the hand power tool according to the invention, which can be designed as a hammer drill or combination hammer, an eccentric gear (also cycloid gear or circular thrust gear) is used. This instead of spur gears and / or bevel gears, which are used exclusively or at least predominantly in hand machine tools of the prior art.

As a result, a comparatively compact and robust rotary drive can be provided.

It has been found to be advantageous if the eccentric gear has an internally toothed ring gear and an externally toothed inner gear. The ring gear can with respect to the Electric motor placedest be arranged. In a particularly preferred embodiment, the inner wheel is driven via a rotatably mounted eccentric. It has been found to be advantageous if the eccentric gear has a reduction of at least 1:40, preferably 1:50. In a particularly preferred embodiment, the eccentric gear has a torsionally rigid coupling which is designed to compensate for a radial offset of the inner wheel caused by the eccentric. The coupling is preferably designed as a parallel crank coupling or as a cross slide coupling.

It has been found to be advantageous if the hammer mechanism has a gear component for converting the rotary movement of the electric motor into a periodic translational movement parallel to the working axis. The gear component is preferably integrated with the eccentric gear.

The gear component can have an impact mechanism eccentric wheel or a swash plate, which is arranged coaxially to the eccentric gear and / or is designed in one piece with a drive eccentric of the circular thrust gear. The striking mechanism eccentric wheel and the drive eccentric of the circular thrust gear can be one and the same component. Both the eccentric and an impact mechanism eccentric wheel can be driven by one and the same eccentric shaft. The eccentric shaft and a crankshaft of the electric motor can be arranged coaxially to one another or offset parallel to one another. In a further preferred embodiment, the rotary drive is synchronized with the hammer mechanism. The percussion mechanism can have an exciter connected to the gear component and a pneumatic chamber, with the hammer preferably being coupled to the exciter via the pneumatic chamber.

Preferably, no couplings are provided in the rotary drive which could interrupt a transmission of a torque from the electric motor to the spindle.

Further advantages emerge from the following description of the figures. Various exemplary embodiments of the present invention are shown in the figures. The figures, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into useful further combinations.

In the figures, the same and similar components are numbered with the same reference symbols. Show it:

1 shows a first preferred exemplary embodiment of a handheld power tool according to the invention; 2 shows a first preferred embodiment of a rotary drive; 3 shows a second preferred embodiment of a rotary drive; 4 shows a third preferred embodiment of a rotary drive; and FIG. 5 shows a plan view of an eccentric gear of FIGS. 2 to 5.

Execution for board:

A preferred exemplary embodiment of a handheld power tool 100 according to the invention is shown in FIG. 1. 1 shows a hammer drill 101 as an example of a percussive hand-held power tool 100. The hammer drill 101 has a tool holder 2 in which a drill, chisel or other percussive tool 4 can be inserted and locked coaxially to a working axis 3. The hammer drill 101 has a pneumatic hammer mechanism 50 which can periodically exert blows in an impact direction 6 on the tool 4. A rotary drive 70 can rotate the tool holder 2 continuously about the working axis 3. The pneumatic hammer mechanism 50 and the rotary drive are driven by an electric motor 8, which is fed with electrical current from a battery 9 or a power line.

The striking mechanism 50 and the rotary drive 70 are arranged in a machine housing 10. A handle 11 is typically arranged on a side of the machine housing 10 facing away from the tool holder 2. The user can hold the hammer drill 101 by means of the handle 11 and guide it in operation. An additional auxiliary handle can be attached near the tool holder 2. An operating button 12 is arranged on or in the vicinity of the handle 11, which the user can actuate preferably with the holding hand. The electric motor 8 is switched on by pressing the operating button 12. The electric motor 8 typically rotates for as long as the operating button 12 is held down.

The tool 4 can be moved in the tool holder 2 along the working axis 3. For example, the tool 4 has an elongated groove into which a ball 5 or another locking body of the tool holder 2 engages. The user holds the tool 4 in a working position in that the user presses the tool 4 indirectly against a substrate using the hammer drill 101.

The tool holder 2 is attached to a spindle 13 of the rotary drive 70. The tool holder 2 can rotate about the working axis 3 with respect to the machine housing 10. At least one claw 1 or other suitable means in the tool holder 2 transmit a torque from the tool holder 2 to the tool 4.

According to the invention, the rotary drive 70 has a step-down eccentric gear 20 connected to the electric motor 8, the spindle 13 being coupled to the eccentric gear 20. The eccentric gear 20 is only indicated schematically in FIG. 1 and is explained in detail with reference to the other figures. The pneumatic hammer mechanism 50 has an exciter 14, a hammer 15 and an anvil 16 along the impact direction 6. The exciter 14 is forced to periodically move along the working axis 3 by means of the electric motor 8. The exciter 14 is connected via a gear component 17 for converting the rotary movement of the electric motor 8 into a periodic, translational movement along the working axis 3. An exemplary gear component 17 includes an impact mechanism eccentric wheel 21 or a swash plate. A period of the translational movement of the exciter 14 is specified by the speed of the electric motor 8 and possibly a reduction ratio in the transmission component 17.

The striker 15 couples to the movement of the exciter 14 via an air spring. The air spring is formed by a pneumatic chamber 18 closed between the exciter 14 and the striker 15. The striker 15 moves in the striking direction 6 until the striker 15 strikes the striker 16. The striker 16 rests against the tool 4 in the striking direction 6 and transmits the impact to the tool 4. The period of the movement of the striker 15 is identical to the period of the movement of the exciter 14. The striker 15 thus strikes with a number of strikes is equal to the inverse of the period. The optimum number of strokes is predetermined by the mass of the club 15 and the geometric dimensions of the pneumatic chamber 18. An optimal number of beats can be in the range between 25 Hz and 100 Hz.

The exemplary hammer mechanism 50 has a piston-shaped exciter 14 and a piston-shaped hammer 15, which are guided by a guide tube 19 along the working axis 3. The outer surfaces of the exciter 14 and the striker 15 rest on the inner surface of the guide tube 19. The pneumatic chamber 18 is closed off by the exciter 14 and the hammer 15 along the working axis 3 and by the guide tube 19 in the radial direction. Sealing rings in the outer surfaces of exciter 14 and hammer 15 can improve the airtight seal of pneumatic chamber 18.

The rotary drive 70 contains the spindle 13, which is arranged coaxially to the working axis 3. The spindle 13 is hollow, for example, and the hammer mechanism 50 is arranged inside the spindle. The tool holder 2 is placed on the spindle 13. The tool holder 2 can be detachably or permanently connected to the spindle 13 via a locking mechanism. The spindle 13 is connected to the electric motor 8, more precisely via its crankshaft 25, via the reducing eccentric gear 20. The speed of the spindle 13 is lower than the speed of the electric motor 8. The spindle 13 preferably rotates periodically. For example, the spindle 13 can be rotated continuously via the reducing eccentric gear 20 at a speed of less than 50 revolutions per minute (rpm). The spindle 13 is preferably rotated continuously via the reducing eccentric gear 20 via a bevel gearing 23 provided on the spindle 13. The rotary drive 70 is synchronized with the striking mechanism 50.

The spindle 13 can be rigidly coupled to the electric motor 8. A rotary movement of the electric motor 8 forces a rotary movement of the spindle 13. Preferably, no couplings are provided in the rotary drive 70 which could interrupt a transmission of a torque from the electric motor 8 to the spindle 13.

FIG. 2 now shows a first preferred exemplary embodiment of a rotary drive 70, which in FIG. 1 is only indicated schematically within the handheld power tool 100.

The rotary drive 70 has a step-down eccentric gear 20 which is connected to the electric motor 8 via the crankshaft 25. For this purpose, the crankshaft 25 is coupled to an eccentric shaft 34 via a shaft gear 26. A transmission ratio of 1: 6 between the crankshaft 25 and the eccentric shaft 34 is exemplified here via the shaft gear 26. On the output side, the eccentric gear 20 is coupled to the spindle 13 via a bevel gearing 23.

The eccentric gear 20 has an internally toothed ring gear 30 and an externally toothed inner gear 31. The ring gear 30 is arranged so as to be positioned in relation to the electric motor 8. The inner wheel 31 can be driven via a rotatably mounted eccentric 33. The eccentric 33 is rotationally connected to the crankshaft 25. The eccentric 33 and the crankshaft 25 can be formed integrally with one another.

The eccentric gear 20 has a torsionally rigid coupling 35 which is designed to compensate for a radial offset (radial direction R) of the inner wheel 31 caused by the eccentric 33. In the exemplary embodiments of FIGS. 2 to 5, the coupling 35 is designed as a parallel crank coupling. The torsionally rigid coupling 35 is coupled, on the one hand, to the internal gear 31 and, on the other hand, to an output body 37. The output body 37 is in turn coupled to the spindle 13 via the bevel gearing 23 (see also FIG. 1). A transmission ratio of 1: 4 between the output body 37 and the spindle 13 is realized here by way of example via the bevel gearing 23.

In the exemplary embodiment in FIG. 2, the eccentric gear 20 itself has a transmission ratio of 1:16 between the internal gear 31 and the ring gear 30. As can already be seen from FIG. 1, the hammer mechanism 50, which is only partially shown here in FIG. 2, has a gear component 17 for converting the rotary movement of the electric motor 8 into a periodic translational movement parallel to the working axis 3. For this purpose, the transmission component 17 contains an impact mechanism eccentric wheel 21. The impact mechanism eccentric wheel 21 is rotationally coupled to the crankshaft 25 via a further shaft gear 26 ′. As an example, a transmission ratio of 1: 6 between crankshaft 25 and striking mechanism eccentric gear 21 is implemented here.

A second preferred exemplary embodiment of a rotary drive 70 is shown in FIG. 3. In this exemplary embodiment, the gear component 17 together with the striking mechanism eccentric wheel 21 is integrated or at least partially integrated with the eccentric gear 20. For this, the striking mechanism eccentric wheel 21 is arranged coaxially to the eccentric shaft 34. Both the eccentric 33 and the striking mechanism eccentric wheel 21 are driven by one and the same eccentric shaft 34.

It can be clearly seen that the eccentric shaft 34, which drives the eccentric 33, and the crankshaft 25 of the electric motor (not shown here) are arranged offset parallel to one another. Here, as an example, a gear ratio of 1: 6 between crankshaft 25 and eccentric shaft 34 is implemented using a shaft gear 26 ″.

A transmission ratio of 1: 1.25 between the output body 37 and the spindle 13 is realized here by way of example via the bevel gearing 23. In the exemplary embodiment in FIG. 3, the eccentric gear 20 itself has a transmission ratio of 1:50 between the inner gear 31 and the ring gear 30. Here, the eccentric 33 drives the internal gear 31, which rolls in the most positioned ring gear 30. The different number of teeth between ring gear 30 and inner gear 31 results in a rotary movement. For the greatest possible gear ratio, a difference in number of teeth of 1 is aimed for here as an example. Here, the internal gear 31 rotates relative to the most positioned ring gear 30 by one tooth per eccentric rotation. The inner wheel 31 thus performs two superimposed movements: the eccentric wobbling movement (in the radial direction R) and a comparatively slow rotary movement.

A third preferred exemplary embodiment of a rotary drive 70 is shown in FIG. 4. In this exemplary embodiment, the gear component 17 together with the striking mechanism eccentric wheel 21 is further spatially integrated with the eccentric gear 20 - in comparison with the exemplary embodiment in FIG. 3. This was achieved in that the eccentric shaft 34 is designed or arranged identically or at least coaxially to the crankshaft 25. As in the exemplary embodiment in FIG. 3, the striking mechanism eccentric wheel 21 is also arranged here coaxially to the eccentric shaft 34. Both the eccentric 33 and the striking mechanism eccentric wheel 21 are driven by one and the same eccentric shaft 34. In contrast to the Exemplary embodiments of FIGS. 2 and 3 are the one bevel gearing 23, via which a movement takes place from the output body 37 to the spindle 13, arranged on the end of the spindle 13. In the exemplary embodiment in FIG. 4, too, transmission to an exciter, not shown here, is carried out via the transmission component 16, which contains the striking mechanism eccentric wheel 21.

Finally, FIG. 5 shows a top view of the eccentric gear 20 which is used in the exemplary embodiments of FIGS. 2 to 5. The eccentric 33, which is arranged in the center and is supported via a ball bearing 36 within the inner wheel 31, can be clearly seen. The eccentric is driven via the eccentric shaft 34 (in one piece with the crankshaft 25 in FIG. 4), whereby the inner wheel 31 performs two superimposed movements, namely an eccentric wobbling movement (in the radial direction R) and a comparatively slow rotary movement (in the circumferential direction U). The ring gear 30 is arranged fixedly in relation to the machine housing 10 (cf. FIG. 1) of the handheld power tool. The eccentric shaft 34 (apart from the eccentric 33) is arranged coaxially to the ring gear 30. The torsionally rigid coupling 35, which in the present case is designed as a parallel crank coupling, can also be clearly seen.

Reference list

1 claw

2 tool holder

3 working axis

4 hitting tool

5 bullet

6 Direction of lay

8 electric motor

9 battery

10 machine housings

11 handle

12 operating buttons

13 spindle

14 pathogens

15 rackets

16 anvil

17 Transmission component

18 pneumatic chamber

19 guide tube

20 eccentric gears

21 Impact mechanism eccentric wheel

23 bevel teeth

25 crankshaft

26, 26 ‘, 26" shaft gear

30 ring gear

31 internal gear

33 eccentric

34 eccentric shaft

35 torsionally rigid coupling

36 ball bearings

37 output body

50 striking mechanism 70 rotary drive

100 hand machine tool

101 Rotary hammer R radial direction

U circumferential direction

Claims

1. Hand machine tool (100), in particular rotary hammer (101), with a tool holder (2) for holding a striking and rotating tool (4) on a working axis (3), an electric motor (8), an impact mechanism (50), one has hammer (15) periodically moved along the working axis (3), and with a rotary drive (70) which drives a spindle (13) carrying the tool holder (2) to rotate about the working axis (3), characterized in that the rotary drive ( 70) has a step-down eccentric gear (20) connected to the electric motor (8) and the spindle (13) is coupled to the eccentric gear (20).

2. Hand machine tool (100) according to claim 1, characterized in that the eccentric gear (20) has an internally toothed ring gear (30) and an externally toothed inner gear (31), the ring gear (30) being arranged in a fixed position with respect to the electric motor (8), and the inner wheel (31) is driven via a rotatably mounted eccentric (33).

3. Hand machine tool (100) according to claim 2, characterized in that the eccentric gear (20) has a torsionally rigid coupling (35) which is designed to compensate for a radial offset of the inner wheel (31) caused by the eccentric (33).

4. Hand machine tool (100) according to claim 2, characterized in that the coupling (35) is designed as a parallel crank coupling or as a cross slide coupling.

5. Hand machine tool (100) according to claim 1, characterized in that the hammer mechanism (50) has a gear component (17) for converting the rotary movement of the electric motor (8) into a periodic translational movement parallel to the working axis (3).

6. Hand machine tool (100) according to one of the preceding claims, characterized in that the gear component (17) is integrated with the eccentric gear (20).

7. Hand machine tool (100) according to claim 5 or 6, characterized in that the gear component (17) is an impact mechanism

Eccentric wheel (21) or a swash plate, which is arranged coaxially to the eccentric gear (20) and / or is formed in one piece with an eccentric (33) of the eccentric gear (20).

8. Hand machine tool (100) according to one of the preceding claims, characterized in that the rotary drive (70) is synchronized with the hammer mechanism (50).

9. Hand machine tool (100) according to one of the preceding claims, characterized in that the eccentric gear (20) has a reduction of at least 1:40, preferably 1:50.

10. Hand machine tool (100) according to one of claims 7 to 9, characterized in that an eccentric shaft (34) carrying the eccentric (33) is formed or arranged identically or at least coaxially to a crankshaft 25 of the electric motor (8).

11. Hand machine tool (100) according to one of the preceding claims, characterized in that the hammer mechanism (50) has an exciter (14) connected to the gear component and a pneumatic chamber (18), the hammer (15) via the pneumatic chamber (18) is coupled to the exciter (14).