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

Abstract

A hand-held power tool includes a tool holder, a motor for rotational and/or percussive driving of the tool holder, and a magnetic field sensor disposed in a vicinity of the motor, where a magnetic field of the motor that is created by driving the tool holder by the motor is detectable by the magnetic field sensor. The hand-held power tool further includes a control device where the control device determines a load state of the motor in dependence on a detected magnetic field of the motor and differentiates between an idle mode of the hand-held power tool and a load mode of the hand-held power tool based on the determined load state of the motor.

Claims

1. A hand-held power tool, comprising: a tool holder; a motor for rotational and/or percussive driving of the tool holder; a magnetic field sensor disposed in a vicinity of the motor, wherein a magnetic field of the motor that is created by driving the tool holder by the motor is detectable by the magnetic field sensor, wherein the magnetic field sensor detects as the magnetic field of the motor a magnetic field of a current that is consumed by the motor when the tool holder is driven by the motor; a control device, wherein the control device determines a load state of the motor in dependence on a detected magnetic field of the motor and differentiates between an idle mode, a purely drilling mode, and a drilling and impacting mode of the hand-held power tool based on the determined load state of the motor and wherein the control device reduces a speed of the motor when the hand-held power tool is differentiated to be in the idle mode by the control device and increases the speed of the motor when the hand-held power tool is differentiated to be in the drilling and impacting mode by the control device; and an operating time counter, wherein an operating time of the motor in dependence on the determined load state by the control device is detectable by the operating time counter.

2. A method for operating a hand-held power tool which has a tool holder and a motor for rotational and/or percussive driving of the tool holder, comprising the steps of: detecting a magnetic field of the motor that is created by driving of the tool holder by the motor; determining a load state of the motor in dependence on the detected magnetic field by a control device; differentiating between an idle mode, a purely drilling mode, and a drilling and impacting mode of the hand-held power tool by the control device based on the determined load state of the motor; reducing a speed of the motor by the control device when the hand-held power tool is differentiated to be in the idle mode by the control device; increasing the speed of the motor by the control device when the hand-held power tool is differentiated to be in the drilling and impacting mode by the control device; and determining an operating time of the motor by an operating time counter in dependence on the load state of the motor determined by the control device.

3. The method as claimed in claim 2, wherein the detecting the magnetic field of the motor comprises detecting a magnetic field of a current that is consumed by the motor when the tool holder is driven by the motor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic view of a hand-held power tool; and

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

DETAILED DESCRIPTION OF THE DRAWINGS

(3) 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.

(4) 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, 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 via a power line 17. In the example shown in FIG. 1, the rechargeable battery 7 supplies the motor 4 with current and for this purpose is connected to the motor 4 by the power line 17.

(5) A user can hold and guide the hammer drill 1 by a handle 8. The handle 8 is part of a housing 9 of the hammer drill 1. The hammer drill 1 can be put into operation by means of a main button 10. By actuating the main button 10, the motor 4 is supplied with current from the rechargeable battery 7 via the power line 17. Supplying power to the motor 4 makes it drive the drive shaft 6. The drive shaft 6 coupled to the tool holder 2 sets the tool holder 2 in a rotary motion about a working axis 11. As a result, the tool 3 is rotated about the working axis 11. During operation, in addition to the rotation about the working axis 11, the hammer drill 1 can strike the tool 3 into a base material in a direction of impact 12 along the working axis 11. For example, the hammer drill 1 is set up in such a way that the impacting motion of the tool 3 only begins when an object is being machined. For example, by pressing the switched-on hammer drill 1 against the object to be machined, the tool holder 2 is driven by the striking mechanism 5. Because the striking mechanism 5 drives the tool holder 2, in addition to the rotary motion about the working axis 11, the tool 3 performs impacting motions in the direction of impact 12. In an exemplary embodiment, the hammer drill 1 has a mode selector switch 13, 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.

(6) FIG. 2 shows a schematic view of a method for operating the hammer drill 1 from FIG. 1.

(7) In a first step S1 of the method, a magnetic field of the motor 4 that is created by the driving of the tool holder 2 is detected.

(8) For this purpose, the hammer drill 1 has, adjacent to the motor 4, in particular adjacent to the power line 17, a magnetic field sensor 14 for load detection of the motor 4, as can be seen in FIG. 1. The current required for the rotational and/or percussive driving of the tool holder 2 flows through the power line 17 to the motor 4 and generates a magnetic field around the power line 17. The magnetic field sensor 14 detects the magnetic field of the motor 4, in particular the power line 17.

(9) In a second step S2 of the method, a load state of the motor 4 is determined in dependence on the detected magnetic field.

(10) The intensity of the current flowing through the power line 17 depends on the then-applicable power consumption of the motor 4 of the hammer drill 1. Thus, the strength of the magnetic field generated by the current flowing through the power line 17 is also dependent on the then-applicable power consumption of the motor 4 of the hammer drill 1.

(11) By actuating the main button 10, the motor 4 is set in a rotary motion. As long as the tool 3 is not yet machining the workpiece, that is to say that the hammer drill 1 is in an idle mode, the load on the motor 4 is low and the power consumption of the motor 4 is correspondingly low. In this state, a current with a low current intensity flows through the current conductor 17, which generates a weak magnetic field around the current conductor 17. If a workpiece is then machined with the tool 3, the load on the motor 4 and the power consumed by the motor 4 increase in comparison with the idle mode. If the workpiece is machined with the tool 3 in a purely drilling mode of the hammer drill 1, the current intensity of the current flowing through the current conductor 17 and the strength of the magnetic field generated by the current around the current conductor 17 increase. If, in addition to the drilling mode, an impacting mode begins, the load on the motor 4 increases even further. In such a drilling and impacting mode of the hammer drill 1, the load absorption of the motor is correspondingly great and a current with a great current intensity flows through the current conductor 17. This generates a strong magnetic field around the current conductor 17.

(12) By detecting the magnetic field around the current conductor 17 in the first step S1 of the method, these different load states can be determined and differentiated by a control device 15 of the hammer drill 1 in the second step S2 of the method. In particular, the magnetic field sensor 14 transmits the detected magnetic field to the control device 15 as a signal. The control device 15 compares the detected magnetic field with specific limit values and thus determines whether the tool is in an idle mode, a purely drilling mode or a drilling and impacting mode. The specific limit values are specific values for the magnetic field strength. For example, the control device 15 determines that the tool is in an idle mode if the detected magnetic field is less than a first limit value. For example, the control device 15 determines that it is in a purely drilling mode if the detected magnetic field is greater than or equal to the first limit value and less than a second limit value. For example, the control device 15 determines that it is in a drilling and impacting mode if the detected magnetic field is greater than or equal to the second limit value.

(13) In a third step S3 of the method, an operating time of the motor 4 is determined in dependence on the determined load state.

(14) For this purpose, the hammer drill 1, in particular the control device 15, can have for example an operating time counter 16 for recording the operating time of the motor 4 in dependence on the determined load state, as can be seen in FIG. 1. The control device 15 and/or the operating time counter 16 have for example a memory unit (not shown) for storing the recorded operating time in dependence on the determined load state. The operating time counter 16 records the operating time of the motor 4 continuously or at frequent time intervals, for example from actuation of the main button 10, and assigns it to the load state determined by the control device 15. For example, after switching on the hammer drill 1 via the main button 10, the operating time counter 16 first records an operating time in the idle mode, followed by an operating time in the drilling and impacting mode.

(15) In a fourth step S4 of the method, the hammer drill 1 is set, in particular controlled, in dependence on the determined load state. For example, the motor speed of the motor 4 is changed in dependence on the determined load state. For example, the motor speed is reduced in the idle mode and the motor speed is increased in the impacting and drilling mode. By adapting the motor speed to the load state of the hammer drill 1, the energy consumption of the hammer drill 1 can be reduced.

LIST OF REFERENCE CHARACTERS

(16) 1 Hand-held power tool (hammer drill) 2 Tool holder 3 Tool 4 Motor 5 Striking mechanism 6 Drive shaft 7 Rechargeable battery 8 Handle 9 Housing 10 Main button 11 Working axis 12 Direction of impact 13 Mode selector switch 14 Magnetic field sensor 15 Control device 16 Operating time counter 17 Power line S1 Method step S2 Method step S3 Method step S4 Method step