Method for operating a hand-held power tool

Abstract

The invention relates to a method (100) for operating a hand-held power tool (10) comprising an electric motor (11), the method comprising the following method steps. A model signal of an operating variable of the electric motor (11) is used. A signal of the operating variable of the electric motor (11) is detected. The detected signal is compared with the model signal by determining a comparison parameter on the basis of the detected signal and the model signal. The comparison parameter is compared with a first specifiable threshold value. An amplitude of the signal of the operating variable is determined. The determined amplitude is compared with a second specifiable threshold value. The work progress of the hand-held power tool (10) is ascertained on the basis of the comparison of the determined comparison parameter with the first threshold value and the comparison of the determined amplitude with the second threshold value.

Description

[0001] Description

[0002] Method for operating a hand-held power tool

[0003] It is known from the prior art to determine the condition of a rotary impact mechanism of a handheld power tool during use of a rotary impact wrench. However, this method only distinguishes between the rotary impact mechanism's operating modes. In some applications, simply knowing whether a rotary impact mechanism is operating or not is insufficient. For example, when screwing in a wood screw, the rotary impact mechanism begins to operate even though the wood screw is not yet fully screwed into the material, as the required torque already exceeds the so-called disengagement torque of the rotary impact mechanism at this point.

[0004] A reaction based solely on the status of the rotary impact mechanism is therefore not conducive to correct automatic system function, such as shutting down a handheld power tool. Despite known options for detecting the activation of the rotary impact mechanism, some applications pose a challenge when it comes to detecting work progress during screwing, particularly screw joints in inhomogeneous materials, such as concrete screw joints or screw joints in a reinforced concrete wall containing concrete, stone, and iron.

[0005] An object of the present invention is to specify an improved method for operating a handheld power tool and to provide an improved handheld power tool. This object is achieved by a method for operating a handheld power tool and a handheld power tool having the features of the respective independent claims. Advantageous further developments are specified in the dependent claims. A method for operating a handheld power tool with an electric motor comprises the following method steps: A model signal of an operating variable of the electric motor is used. A signal of the operating variable of the electric motor is detected. The detected signal is compared with the model signal by determining a comparison parameter based on the detected signal and the model signal. The comparison parameter is compared with a first predefinable threshold value. An amplitude of the signal of the operating variable is determined.The determined amplitude is compared with a second predefined threshold. The work progress of the handheld power tool is determined based on the comparison of the determined comparison parameter with the first threshold and the comparison of the determined amplitude with the second threshold.

[0006] The first threshold and the second threshold refer to different variables. The first threshold is defined such that it can be compared with the reference parameter. The second threshold is defined such that it can be compared with the amplitude of the signal of the operating variable.

[0007] Advantageously, the method enables the work progress when operating the hand-held power tool, for example a work progress when screwing a screw using the hand-held power tool, to be reliably detected even for a screw connection in an inhomogeneous material.

[0008] In one embodiment, an operating state of the electric motor is adjusted depending on the work progress. The handheld power tool is thus operated by determining the work progress and adjusting the operating state of the electric motor depending on the work progress. Advantageously, a suitable response to the work progress can occur, particularly when screwing in inhomogeneous materials (e.g., concrete). This means that even with inhomogeneous materials, an application-specific response of the handheld tool to the work progress is possible. A suitable and application-specific response can, for example, prevent damage to a screw or the material into which it is to be screwed. Furthermore, work with the handheld power tool can be carried out more quickly, which leads to higher user productivity.

[0009] In one embodiment, the operating state of the electric motor is adjusted if the determined comparison parameter is smaller than the first threshold and the determined amplitude of the signal of the operating variable is greater than the second threshold. This advantageously allows the detection of a screw head contacting a material to be screwed together during a screw connection.

[0010] In one embodiment, the amplitude of the signal of the operating variable is determined on the basis of the comparison parameter or on the basis of a comparison parameter estimate.

[0011] In one embodiment, adjusting the operating state of the electric motor comprises adjusting the operating variable or an operating variable profile of the electric motor.

[0012] In one embodiment, the operating variable is a speed of the electric motor or an operating variable correlated with the speed. In one embodiment, the model signal has an oscillating profile. Advantageously, such a model signal represents the impact operation of an impact wrench or rotary impact wrench, so that the impact operation can be reliably detected. In one embodiment, a mean square deviation or a cross-correlation is determined as the comparison parameter.

[0013] A handheld power tool comprises an electric motor with a sensor and a control device. The sensor is designed to detect a signal of an operating variable of the electric motor. The control device is designed to carry out a method according to one of the aforementioned embodiments. The method for operating a handheld power tool is explained below in conjunction with schematic drawings. They show:

[0014] Fig. 1 : Method steps of a method 1 for operating a hand-held power tool;

[0015] Fig. 2: a sequence of different work progresses when screwing a screw into an inhomogeneous material in a cross-sectional view; and

[0016] Fig. 3: a hand-held power tool.

[0017] Fig. 1 schematically shows method steps of a method 100 for operating a handheld power tool. The handheld power tool comprises an electric motor. The handheld power tool can be designed, for example, as an impact wrench, in particular as a rotary impact wrench. However, the handheld power tool can be designed as any handheld power tool with an electric motor, in particular as a handheld power tool for which detection of work progress is relevant. For example, the handheld power tool can be designed as a percussion drill.

[0018] In a first method step 101, a model signal of an operating variable of the electric motor is provided and used. The operating variable of the electric motor is, for example, a speed of the electric motor. However, the operating variable can also be an operating variable correlated with the speed. The model signal can, for example, be provided in a memory of the handheld power tool. However, the model signal can also be provided externally, for example via a terminal device that is connected to the handheld power tool via a wireless connection. In an optional second method step 102, the model signal can be segmented if appropriate. However, segmenting the model signal is not absolutely necessary.

[0019] The model signal of the operating variable can, for example, have an oscillating profile. An oscillating model signal of the operating variable can, for example, be represented by a trigonometric signal profile. The oscillating model signal represents, for example, the impact operation of an impact wrench or rotary impact wrench.

[0020] The following explains an example and typical model signal of an operating variable of an electric motor in an impact wrench. The model signal can, for example, be selected such that the operating variable is plotted as a function of time. Alternatively, a different variable, such as the rotation angle of the electric motor, can be selected as the reference variable instead of time.

[0021] The exemplary model signal comprises a first range characterized by a monotonic increase in the operating variable, as well as a section in which the operating variable remains approximately constant. In the first range, the impact wrench operates without impact.

[0022] In a second mode, the impact wrench operates in rotary impact mode. Rotary impact mode is characterized by an oscillating operating variable, whereby the shape of the oscillation can be trigonometric, sinusoidal, or otherwise oscillating. This characteristic operating variable shape in impact wrench mode is created by the winding and free-running of an impact mechanism striker and a system chain located between the impact mechanism and the electric motor, including the gearbox.

[0023] In a third method step 103, a signal representing the operating variable of the electric motor is detected. For this purpose, the electric motor has a sensor for detecting the signal representing the operating variable of the electric motor. The speed of the electric motor can be detected, for example, using a Hall sensor.

[0024] In a fourth method step 104, the recorded signal of the operating variable is compared with the model signal of the operating variable. This is done by determining a comparison parameter based on the recorded signal and the model signal. For example, a mean square deviation or a cross-correlation based on the model signal of the operating variable and the recorded signal of the operating variable can be determined as a comparison parameter. However, another comparison parameter can also be determined.

[0025] In a fifth method step 105, the comparison parameter is compared with a first predeterminable threshold value. The first predeterminable threshold value can be set, for example, by a user of the handheld power tool within the scope of an optional sixth method step 106. The user can set the first threshold value, for example, via a terminal device of the handheld power tool or via a control panel of the handheld power tool. The first threshold value can, for example, be stored in the memory of the handheld power tool.

[0026] In a seventh method step 107, an amplitude of the operating variable signal is determined. The amplitude of the operating variable signal can be determined, for example, based on the comparison parameter or on an estimate of the comparison parameter, i.e., based on the calculation of the comparison parameter. However, the amplitude can be determined in any desired way based on the operating variable signal. The model signal can be taken into account, although this is not mandatory.

[0027] In an eighth method step 108, the determined amplitude is compared with a second predeterminable threshold value. The second threshold value can be stored in the memory of the handheld power tool or, in an optional ninth method step 109, set on the handheld power tool or via a terminal device. In a tenth method step 110, a work progress of the handheld power tool is determined based on the comparison of the determined comparison parameter with the first threshold value and the comparison of the determined amplitude with the second threshold value. Determining the work progress includes checking whether the comparison parameter is smaller or larger than the first threshold value and whether the amplitude is smaller or larger than the second threshold value.For example, a head contact of a screw head on the material to be screwed can be detected if the comparison parameter is smaller than the first threshold value and the amplitude is larger than the second threshold value.

[0028] In an eleventh method step 111, an operating state of the electric motor is adapted depending on the work progress, ie a reaction takes place to the work progress, for example a work progress of a screw connection.

[0029] Adapting the operating state of the electric motor can, for example, comprise adapting the operating variable or an operating variable profile of the electric motor. This can, for example, comprise changing the speed, i.e., increasing the speed, reducing the speed, or stopping the electric motor. For example, a reversal of the direction of the electric motor can also be initiated in response to work progress. The operating variable profile can, for example, be adapted such that it represents, for example, at least in sections, a constant increase in the operating variable or, for example, an oscillating operating variable with a predeterminable impact frequency for impact operation of the handheld power tool.

[0030] If a desired work progress is achieved, this can be signaled to the user. For example, a lamp on the handheld power tool can be configured to illuminate when a certain work progress has been reached. For example, within the scope of method 100, it can be determined with regard to work progress that a head contact has been reached during a screw connection, i.e., that a screw has been screwed into a material until a screw head rests on the material into which the screw is being screwed.

[0031] Such a head contact can be detected, for example, if the determined comparison parameter is smaller than the first threshold and the determined amplitude of the operating variable signal is greater than the second threshold. The operating state of the electric motor can then be adjusted. If the determined comparison parameter is smaller than the first threshold, this means that the detected signal matches the model signal with sufficient accuracy. This can, for example, indicate proper impact operation of the handheld power tool. If the amplitude of the operating variable is also greater than the second threshold, this can, for example, signal a head contact.

[0032] Fig. 2 schematically shows an exemplary sequence 200 of different work progresses when screwing a screw 206 into an inhomogeneous material 207 in a cross-sectional view. In the exemplary representation of Fig.

[0033] In Fig. 2, the inhomogeneous material 207 is, for example, concrete or reinforced concrete. A blind hole 208 drilled before screwing in the screw 206 is not shown in Fig. 2, but merely indicated.

[0034] At a first time 201, the screw 206 is applied. The handheld power tool is not yet in impact mode. At the first time 201, the comparison parameter is greater than the first threshold. The amplitude is less than the second threshold.

[0035] At a subsequent second time 202, the screw 206 has already been partially screwed into the inhomogeneous material 207. The handheld power tool begins impact operation. At this time, the comparison parameter is smaller than the first threshold value. The amplitude of the operating variable is smaller than the second threshold value at the second time 202. Head contact has not yet been reached. At a subsequent third time 203, the screw 206 has been screwed further into the inhomogeneous material 207. In this area, the inhomogeneous material 207 comprises, for example, flint or steel. The comparison value is smaller than the first threshold value. The handheld power tool is in impact operation. The amplitude is higher than at the second time 202, but not greater than the second threshold value. For this reason, head contact has not yet been detected.

[0036] At a subsequent fourth time point 204, the screw 206 has been screwed further into the inhomogeneous material 207. The comparison parameter is smaller than the first threshold. The amplitude at the fourth time point 204 is smaller than the second threshold because the screw head 210 has not yet made contact with the inhomogeneous material 207.

[0037] At a subsequent fifth time point 205, the screw 206 has been fully tightened. The screw head 210 rests against a surface 211 of the inhomogeneous material 207. In this case, the comparison parameter is smaller than the first threshold. Furthermore, the amplitude is greater than the second threshold. The head contact has been reached and is correctly detected. Based on this progress, a reaction can now be made and the operating state of the electric motor can be adjusted.

[0038] Fig. 3 shows a schematic diagram of a hand-held power tool 10.

[0039] In addition to the electric motor 11 with the sensor 12 for detecting the signal of the operating variable and the memory 13, the hand-held power tool 10 has a control device 14. The control device 14 is designed to determine the comparison parameter and to compare the comparison parameter with the first threshold value. The control device 14 is further designed to determine the amplitude of the signal of the operating variable and to compare the determined amplitude of the signal of the operating variable with the second threshold value. The control device 14 is further designed to determine a work progress depending on the comparisons and to signal the work progress, for example by activating a lamp of the hand-held power tool 10 and indicating the work progress by lighting up or flashing. The control device 14 can also be designed to initiate a reaction, i.e.to adapt the operating variable of the electric motor 11 if the comparison parameter is smaller than the first threshold value and the determined amplitude is greater than the second threshold value.

Claims

Claims 1. Method (100) for operating a hand-held power tool (10), wherein the hand-held power tool (10) has an electric motor (11), the method comprising the following process steps: - Using a model signal of an operating parameter of the electric motor (11), - Acquiring a signal of the operating parameters of the electric motor (11), - Comparing the acquired signal with the model signal by determining a comparison parameter based on the acquired signal and the model signal, - Comparing the comparison parameter with a first predefinable threshold value, - Determining the amplitude of the signal of the operating quantity, - Comparing the determined amplitude with a second predefinable threshold value, - Determining the work progress of the hand-held machine tool (10) based on comparing the determined comparison parameter with the first threshold and comparing the determined amplitude with the second threshold.

2. The method according to claim 1 with the following additional method step: - Adjusting the operating state of the electric motor (11) depending on the progress of the work.

3. Method according to one of the preceding claims, wherein the operating state of the electric motor (11) is adjusted when the determined comparison parameter is smaller than the first threshold and the determined amplitude of the operating variable signal is larger than the second threshold.

4. Method according to any one of the preceding claims, where the amplitude of the signal of the operating variable is determined based on the comparison parameter or on the basis of a comparison parameter estimate.

5. Method according to one of the preceding claims, wherein adjusting the operating state of the electric motor (11) comprises adjusting the operating size or an operating size profile of the electric motor (11).

6. Method according to one of the preceding claims, wherein the operating parameter is a rotational speed of the electric motor (11) or an operating parameter correlated with the rotational speed.

7. Method according to one of the preceding claims, wherein the model signal has an oscillating profile.

8. Method according to one of the preceding claims, wherein a mean squared deviation or a cross-correlation is determined as a comparison parameter.

9. Hand-held power tool (10) comprising an electric motor (11) with a sensor (12) and a control device, wherein the sensor (12) is configured to detect a signal of an operating parameter of the electric motor (11), wherein the control device is configured to perform a method according to one of the preceding claims.

10. Hand-held power tool (10) according to claim 9, wherein the hand-held power tool (10) is an impact wrench, in particular a rotary impact wrench.

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