Hand-held power tool and method for operating a hand-held power tool

Abstract

The hand-held power tool (1) includes a housing (8), which has a first housing element (9) and a second housing element (10), wherein the first housing element (9) and the second housing element (10) are decoupled from one another and are movable relative to one another. The hand-held power tool (1) furthermore includes a tool holder (2) and a motor (4) for rotational and/or percussive driving of the tool holder (2). Furthermore, the hand-held power tool (1) has a magnetic field sensor (16) for detecting a spacing (L) between the first housing element (9) and the second housing element (10). Moreover, the hand-held power tool (1) includes a control device (18) for setting a motor speed of the motor (4) in accordance with the detected spacing (L).

Claims

1-14. (canceled)

15. A hand-held power tool comprising: a housing having a first housing element and a second housing element, the first housing element and the second housing element being decoupled from one another and movable relative to one another; a tool holder; a motor for rotational or percussive driving of the tool holder; a magnetic field sensor for detecting a spacing between the first housing element and the second housing element; and a controller for setting a motor speed of the motor in accordance with the detected spacing.

16. The hand-held power tool as recited in claim 14 wherein the controller is designed to determine a pressing force from the detected spacing and to set the motor speed of the motor in accordance with the pressing force determined.

17. The hand-held power tool as recited in claim 16 wherein the controller is designed to increase the motor speed of the motor in accordance with the pressing force determined if the pressing force determined is greater than a first particular threshold value.

18. The hand-held power tool as recited in claim 17 wherein the controller is designed to set the motor speed of the motor to a maximum motor speed if the pressing force determined is greater than a second particular threshold value, wherein the second particular threshold value is greater than the first particular threshold value.

19. The hand-held power tool as recited in claim 15 further comprising a magnet arranged on the first housing element, the magnetic field sensor being arranged on the second housing element, the magnetic field sensor being designed to detect a spacing between the magnetic field sensor and the magnet as the spacing between the first housing element and the second housing element.

20. The hand-held power tool as recited in claim 15 wherein the magnetic field sensor is a 3D magnetic field sensor.

21. The hand-held power tool as recited in claim 15 wherein the tool holder is arranged on the first housing element, and the second housing element has a handle of the hand-held power tool.

22. The hand-held power tool as recited in claim 15 wherein the first housing element is arranged at least partially within the second housing element.

23. The hand-held power tool as recited in claim 15 wherein the controller is designed to set the motor speed of the motor in accordance with the detected spacing by closed-loop control of the motor speed in accordance with the detected spacing.

24. The hand-held power tool as recited in claim 15 wherein the controller is designed to set the motor speed of the motor in accordance with the detected spacing by open-loop control of the motor speed in accordance with the detected spacing.

25. A method for operating a hand-held power tool having a motor for rotational or percussive driving of a tool holder, a magnetic field sensor and a housing having a first housing element and a second housing element, wherein the first housing element and the second housing element are decoupled from one another and are movable relative to one another, the method comprising the following steps: detecting a spacing between the first housing element and the second housing element via the magnetic field sensor; and setting a motor speed of the motor in accordance with the detected spacing.

26. The method as recited in claim 25 further comprising determining a pressing force from the detected spacing.

27. The method as recited in claim 25 wherein the setting of the motor speed of the motor in accordance with the detected spacing includes open-loop control of the motor speed in accordance with the detected spacing.

28. The method as recited in claim 25 wherein the setting of the motor speed of the motor in accordance with the detected spacing includes closed-loop control of the motor speed in accordance with the detected spacing.

29. The method as recited in claim 26 wherein the setting of the motor speed of the motor includes increasing the motor speed in accordance with the pressing force determined if the pressing force determined is greater than a first particular threshold value.

30. The method as recited in claim 29 wherein the setting of the motor speed of the motor includes setting the motor speed to a maximum motor speed if the pressing force determined is greater than a second particular threshold value, wherein the second particular threshold value is greater than the first particular threshold value.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0057] The following description explains the invention with reference to exemplary embodiments and figures. In the figures:

[0058] FIG. 1 shows a schematic view of a hand-held power tool; and

[0059] FIG. 2 shows a schematic view of a method for operating the hand-held power tool according to FIG. 1.

DETAILED DESCRIPTION

[0060] An embodiment of hand-held power tool 1 and a method for operating the hand-held power tool 1 are described below with reference to FIGS. 1 and 2.

[0061] FIG. 1 shows a hammer drill as an exemplary embodiment of the hand-held power tool 1. The hammer drill 1 has a tool holder 2, in which a shaft end of a tool 3, for example a drill bit or a chiseling tool, can be inserted. A motor 4, which drives a striking mechanism 5 and a drive shaft 6, forms a primary drive of the hammer drill 1. A rechargeable battery 7 or a power cord (not shown) supplies the motor 4 with power.

[0062] The hammer drill 1 has a housing 8, which comprises a first housing element 9 and a second housing element 10. The second housing element 10 has a handle 11, by which a user can hold and guide the hammer drill 1. The user can put the hammer drill 1 into operation by means of a main button 12. Owing to the actuation of the main button 12, the motor 4 rotates at an adjustable motor speed, the motor 4 drives the drive shaft 6, and the drive shaft 6 imparts a rotary motion to the tool holder 2 about a working axis 13. As a result, the tool 3 is rotated about the working axis 13. During operation, in addition to the rotation about the working axis 13, the hammer drill 1 can strike the tool 3 into a base material in a direction of impact 14 along the working axis 13. Because the striking mechanism 5 drives the tool holder 2, in addition to the rotary motion about the working axis 13, the tool 3 performs striking motions in the direction of impact 14. In an exemplary embodiment, the hammer drill 1 has a mode selector switch (not shown), by means of which the tool holder 2 can be decoupled from the drive shaft 6, so that a purely chiseling mode of the hammer drill 1 is possible.

[0063] The first housing element 9 and the second housing element 10 of the hammer drill 1 are decoupled mechanically from one another by decoupling means 15. The tool holder 2, the motor 4, the striking mechanism 5, the drive shaft 6 and the rechargeable battery 7 are arranged on the first housing element 9. The second housing element 10 comprises the handle 11. In the case of a drilling and/or percussive mode of the hammer drill 1, reaction forces of the tool 3 and of the tool holder 2 can lead to vibration of the first housing element 9. By virtue of the decoupling of the first housing element 9 from the second housing element 10 by means of the decoupling means 15, this vibration of the first housing element 9 is not transmitted, or transmitted only in attenuated form, to the handle 11. In the embodiment shown in FIG. 1, the decoupling is achieved by arrangement of the first housing element 9 within the second housing element 10. In another embodiment (not shown), the decoupling of the first housing element 9 from the second housing element 10 can instead be achieved by arrangement of the second housing element 10 with the handle 11 adjacent to the first housing element 9.

[0064] There is a variable spacing L between the first housing element 9 and the second housing element 10. In the state of rest, i.e. without the user pressing the hammer drill 1 against a workpiece, the spacing L is predetermined by the decoupling means 15.

[0065] The user who wishes to work on a workpiece with the hammer drill 1 holds the hammer drill 1 by the decoupled handle 11 and puts the hammer drill 1 into operation by actuating the main button 12. By actuation of the main button 12, the motor 4 is first of all set in a rotary motion at a low motor speed. The tool 3 is furthermore set in a rotary motion about the working axis 13. The user applies the tool 3 of the hammer drill 1 to the workpiece. To work on the workpiece and start the percussive mode, the user exerts a pressing force F on the handle 11. This pressing force F is aligned substantially in the direction of the workpiece, i.e. along the working axis 13.

[0066] The variable spacing L between the first housing element 9 and the second housing element 10 is reduced by the pressing force F of the user. In particular, the pressing force F compresses the decoupling means 15. The harder the user presses against the handle 11, the smaller the spacing L between the first housing element 9 and the second housing element 10 becomes.

[0067] FIG. 2 shows a schematic view of a method for operating the hammer drill 1 from FIG. 1.

[0068] In a first step S1 of the method, the spacing L between the first housing element 9 and the second housing element 10 is detected by means of the magnetic field sensor 16.

[0069] To detect the spacing L between the first housing element 9 and the second housing element 10, the hammer drill 1 has the magnet 17 in addition to the magnetic field sensor 16. The magnetic field sensor 16 is arranged on the second housing element 10. The magnet 17 is arranged on the first housing element 9. The magnetic field sensor 16 detects the magnetic field of the magnet 17, in particular the magnetic flux density of the magnet 17. The greater the pressing force F of the user against the handle 11, the smaller is the spacing L between the first housing element 9 and the second housing element 10, in particular between the magnetic field sensor 16 and the magnet 17. The smaller the spacing L between the magnetic field sensor 16 and the magnet 17, the greater is the magnetic field detected by the magnetic field sensor 16. Consequently, the magnetic field sensor 16 can detect the spacing L by detecting the magnetic field of the magnet 17. The magnetic field sensor 16 transmits the spacing L as a signal to a control device 18 of the hammer drill 1.

[0070] In a second step S2 of the method, the pressing force F is determined from the detected spacing L. In particular, the control device 18 determines the pressing force F from the detected spacing L by a calculation with the aid of an algorithm in the control device 18.

[0071] In a third step S3 of the method, the motor speed of the motor 4 is set in accordance with the detected spacing L, in particular in accordance with the pressing force F determined.

[0072] In particular, the control device 18 is designed to increase the motor speed of the motor 4 in accordance with the pressing force F determined if the pressing force F determined is greater than a first particular threshold value. For this purpose, the control device 18 compares the pressing force F determined in the second step S2 of the method with the first particular threshold value. The first particular threshold value is a particular pressing force which indicates reliable application of the tool 3 to the workpiece.

[0073] If the control device 18 determines that the pressing force F determined is greater than the first particular threshold value and, consequently, the tool 3 has been reliably applied to the workpiece, the control device 18 sends a signal to the motor 4 to increase the motor speed. In particular, the control device 18 sends a signal to the motor 4 to increase the motor speed of the motor 4 continuously and in direct proportion to the pressing force F determined as the pressing force rises. Owing to the increase in the motor speed, the percussive mode of the tool holder 2 starts. By the further increase in the motor speed, an impact frequency, impact amplitude and/or impact force are continuously increased. By virtue of the fact that the motor speed is first of all increased and the percussive mode starts only when the first particular threshold value is exceeded, the tool can be applied more easily to the workpiece.

[0074] Moreover, the control device 18 is designed to set the motor speed of the motor 4 to a maximum motor speed if the pressing force F determined is greater than a second particular threshold value, wherein the second particular threshold value is greater than the first particular threshold value. For this purpose, the control device 18 compares the pressing force F determined with the second particular threshold value. The second particular threshold value corresponds to a particular pressing force which, in particular, indicates that the tool 3 is reliably engaging on the workpiece.

[0075] If the control device 18 determines that the pressing force F determined is greater than the second particular threshold value, that is to say as soon as the tool reliably engages on the workpiece, the control device 18 sets the motor speed to the maximum motor speed for which the motor 4 is designed. The maximum power of the hammer drill 1 is thus available.

[0076] With the hammer drill 1 described and the method described for operating the hammer drill 1, the user can work safely and in an intuitive manner on a workpiece with the tool 3 of the hammer drill 1 by means of a pressing-force-controlled gentle run-up of the hammer drill 1 and a subsequent pressing-force-controlled maximum power output of the hammer drill 1.

LIST OF REFERENCE SIGNS

[0077] 1 Hand-held power tool (hammer drill)
2 Tool holder

3 Tool

4 Motor

[0078] 5 Striking mechanism
6 Drive shaft
7 Rechargeable battery

8 Housing

[0079] 9 First housing element
10 Second housing element

11 Handle

[0080] 12 Main button
13 Working axis
14 Direction of impact
15 Decoupling means
16 Magnetic field sensor

17 Magnet

[0081] 18 Control device
S1 Method step
S2 Method step
S3 Method step