Method for operating an electric hand-held power tool

Abstract

A method (100) for operating an electric hand-held power tool (1) comprises the following method steps. It is checked whether the electric hand-held power tool (1) is being operated in a percussive mode (S2). To do this, an operating current (14) of a drive motor (2) of the electric hand-held power tool (1) is compared with a specifiable first threshold value (IT). The electric hand-held power tool (1) is being operated in the percussive mode (S2) if the operating current (14) is greater than the specifiable first threshold value (IT). If the electric hand-held power tool (1) is being operated in the percussive mode (S2), it is checked whether consecutive speed values (ISj) of the drive motor (2) correspond to a specifiable speed (IS). To do this, speed values (ISJ) for operating current maximums (PJ) of the drive motor (2) are determined and are compared with the specifiable speed (IS). If the consecutive speed values (ISJ) correspond to the specifiable speed (IS), the percussive mode (S2) is continued for a specifiable duration and with a specifiable percussion frequency.

Description

[0001] Description

[0002] Method for operating an electric hand-held power tool

[0003] The present invention relates to a method for operating an electric hand-held power tool, in particular a rotary impact wrench.

[0004] Methods for operating impact wrenches are known from the prior art. One problem that arises when operating an impact wrench is that a user has no way to consistently determine the tightening torque when tightening or loosening screws and nuts. This is especially true when an impact wrench is used over an extended period of time, as battery voltage decreases over time, thus only allowing a reduced tightening torque to be applied.

[0005] In addition, a user will notice a significant change in the applied torque when using the same impact wrench, for example, to switch from a hard joint, such as a direct metal-to-metal joint, to a medium or soft joint, which, for example, comprises a metal and a fastener with lower rigidity, such as plastic, rubber, or wood. The torque applied to a hard joint is typically higher than for a soft joint. Furthermore, the accuracy of determining the tightening torque is lower at low drive motor speeds than at higher speeds. In addition, the fluctuation in the torque output is higher for soft joints than for hard joints and therefore impairs the quality of the joint. If the impact wrench is additionally only controlled in an open loop, i.e.Without a control loop providing feedback to a sensor signal, large fluctuations in torque output occur. Changes to tool settings typically require calibration of the output and consistency, which is time-consuming.

[0006] An object of the present invention is to provide an improved method for operating an electric handheld power tool, as well as a computer program product for implementing the method, a machine-readable storage medium on which the computer program product is stored, and an improved electric handheld power tool. This object is achieved by a method for operating an electric handheld power tool, a computer program product for implementing the method, a machine-readable storage medium on which the computer program product is stored, and an electric handheld power tool having the features of the respective independent claims. Advantageous further developments are specified in the dependent claims.

[0007] A method for operating an electric hand-held power tool, in particular an impact wrench, comprises the following method steps. A check is carried out to determine whether the electric hand-held power tool is being operated in impact mode. In this case, an operating current of a drive motor of the electric hand-held power tool is compared with a predeterminable first threshold value. The electric hand-held power tool is being operated in impact mode if the operating current is greater than the predeterminable first threshold value. A check is carried out to determine whether successive speed values ​​of the drive motor correspond to a predeterminable speed when the electric hand-held power tool is being operated in impact mode. In this case, speed values ​​for operating current maxima of the drive motor are determined and compared with the predeterminable speed.The impact operation is continued for a preset period of time and at a preset impact frequency if the successive speed values ​​correspond to the preset speed.

[0008] The electric hand-held power tool can be designed as a rotary impact wrench or as another electrical device. The electric hand-held power tool is designed to rotate a tool holder in order to perform a task, such as tightening or loosening screws and nuts or performing another task that requires the generation of torque. Furthermore, the electric hand-held power tool is designed to apply rotary impacts to the tool holder. For this purpose, the electric hand-held power tool has a rotary impact hammer mechanism arranged on a shaft that is coupled to the drive motor and the tool holder via an anvil.

[0009] Advantageously, the method enables a reliable and stable connection to be established with a specified tightening torque. This is ensured by the impact operation occurring at speed values ​​that correspond to the preset speed, the preset duration, and the preset impact frequency, whereby the tightening torque can be reproduced consistently and, for example, independently of the battery voltage of the electric hand-held power tool. In comparison, known impact wrenches cannot provide a constant tightening torque as the battery voltage decreases. To determine the speed of the drive motor, a Hall sensor, for example, can be used, which provides a relationship between a rotation angle and the speed for connections of varying hardness.

[0010] Impact operation is initially detected when the operating current exceeds the preset first threshold value. However, impact operation is only continued for the preset period of time when the speed values ​​correspond to the preset speed. For example, it may be sufficient for three consecutive speed values ​​to assume the value of the preset speed. For example, a speed corresponds to the preset speed precisely when it has a value that deviates from the preset speed by a maximum of five percent. Within the scope of such a fluctuation in the speed of the drive motor, this can be assumed to be constant. However, a different limit value can also be assumed within which a speed fluctuation is considered constant.If several speed values ​​match the specified speed, this is interpreted as consistent impact operation.

[0011] Impact mode is only terminated once the specified time has elapsed, since, taking into account the specified speed, a certain period of time is required for the electric hand-held power tool to operate in impact mode to achieve the desired tightening torque. A specified frequency of rotary impacts during impact mode of the electric hand-held power tool, and thus a frequency at which speed values ​​occur, in combination with the specified time, determines the number of rotary impacts that occur during impact mode.

[0012] In one embodiment, it is checked whether further speed values ​​correspond to the predeterminable speed as long as the impact operation continues. The operation of the electric hand-held power tool is terminated prematurely if the further speed values ​​do not assume the value of the predeterminable speed. Alternatively, the impact operation is continued until the predeterminable time period is exceeded if the further speed values ​​correspond to the predeterminable speed. Advantageously, the speed of the drive motor is monitored in the area of ​​its local maxima, and the impact operation is only terminated prematurely if a deviation occurs. This can, for example, prevent a connection from being established with a torque that deviates from a required tightening torque.

[0013] In one embodiment, before checking the speed values, it is checked whether the operating current in impact mode has a first operating current maximum. If the operating current in impact mode does not have a first operating current maximum, it is checked whether a lead time of the electric hand-held power tool has elapsed. In one embodiment, it is checked whether a lead time of the electric hand-held power tool has elapsed if the speed values ​​do not correspond to the predeterminable speed. Advantageously, it can be examined whether the operating current assumes unusual values ​​within the lead time for the lead time. This could potentially damage a connection to be produced.

[0014] In one embodiment, a check is carried out to determine whether the increase in the operating current within the lead time is greater than a predefinable second threshold value if the lead time has not elapsed. Operation of the electric hand-held power tool is terminated prematurely if the increase in the operating current is greater than the second threshold value. If the operating current has a increase within the lead time that is greater than the second threshold value, this is assessed as an attempt to repeat work that has already been carried out. For example, a screw connection that has already been tightened to the desired tightening torque may be incorrectly tightened again. This may damage the screw connection and / or components to be connected to one another. This can advantageously be prevented by detecting such a process in good time by monitoring the increase in the operating current within the lead time.For example, an unusual increase in the operating current is interpreted as a trigger for retightening a screw connection. In this case, operation is terminated prematurely. If the gradient does not exceed the second threshold, a check is performed again to determine whether the lead time has elapsed before the second threshold is exceeded.

[0015] In one embodiment, a check is performed to determine whether a user of the electric hand-held power tool actuates an activation switch of the electric hand-held power tool when the operating current is less than the predeterminable first threshold. Operation of the electric hand-held power tool is terminated prematurely if the user no longer actuates the activation switch. A check is performed again to determine whether the operating current is greater than the predeterminable first threshold when the user actuates the activation switch.

[0016] In one embodiment, it is indicated that the preset time period has been exceeded or that the operation of the electric hand-held power tool has ended prematurely. Advantageously, this indicates, for example, a screwing status to the user. If the preset time period has been exceeded, the tightening torque has been reached and a reliable screw connection has been established. The operation of the electric hand-held power tool is ended prematurely if the further speed values ​​do not correspond to the preset speed, the gradient of the operating current is greater than the second threshold value, or the user no longer presses the activation switch. This information can be displayed, for example, using LEDs on the electric hand-held power tool.Alternatively or additionally, different acoustic signals can indicate whether the specified time period has been exceeded or whether the operation of the electric hand tool has been terminated prematurely.

[0017] In one embodiment, the method comprises the following further method step. A further phase of impact operation is initiated after the predeterminable time period has elapsed. Within the further phase of impact operation, the electric hand-held power tool is operated for a predeterminable additional time period and at a predeterminable additional impact frequency such that additional speed values ​​correspond to a predeterminable additional speed. The additional speed values ​​are determined for additional operating current maxima of the drive motor and compared with the predeterminable additional speed. In this case, the electric hand-held power tool is advantageously operated in dual impact operation with different drive motor speeds. This allows the tightening torque to be controlled even more precisely.

[0018] In one embodiment, the predeterminable additional speed is greater than the predeterminable speed. For example, the predeterminable speed can be reduced by ten to seventy percent compared to the predeterminable additional speed. This allows, for example, hard connections that require a comparatively high tightening torque to be reliably produced by gradually building up the torque using two maximum values ​​for the drive motor speed in different impact phases. In a further embodiment, more than two impact phases can also occur or be carried out, with different speeds being predeterminable for the speed values ​​and durations in each case.In one embodiment, the predeterminable speed, the predeterminable time duration and the predeterminable impact frequency are specified as a function of the hardness of the components to be joined using the hand-held electric power tool. This allows the tightening torque to be advantageously adapted to a hard, soft or intermediate connection to be produced. In the case of a hard connection, the impact operation can be continued for 0.1 to 0.3 seconds, for example. In the case of an intermediate connection, it may be necessary to continue the impact operation for 0.1 to 1 second, for example. In the case of a soft connection, the impact operation can be continued for 0.5 to 1.5 seconds, for example. The values ​​stated are merely examples and are not restrictive. Other time periods can also be selected for different connections.This advantageously ensures that the tightening torque can be applied precisely and reproducibly, even for different connections. Accordingly, the further speed, the further duration, and the further impact frequency in the further phase of the impact operation can also be specified depending on the degree of hardness. The components to be connected are understood to be components of a screw connection and / or materials to be screwed together, for example, a screw and a nut as components of the screw connection, and metal and wood as materials to be joined together by means of the screw connection.

[0019] In one embodiment, the presettable speed is specified as a function of the battery voltage of the electric handheld power tool. For example, the presettable speed can increase linearly below a presettable battery voltage and remain constant above the presettable battery voltage. The presettable additional speed can also be specified as a function of the battery voltage.

[0020] In one embodiment, the drive motor is controlled using pulse-width modulation. Advantageously, the speed of the drive motor can be precisely controlled during impact operation and optionally during the subsequent phase of impact operation. This allows the speed to be kept particularly constant during impact operation.

[0021] A computer program product comprises instructions that, when executed by a processor, cause the processor to perform a method according to one of the embodiments. The computer program product is stored on a machine-readable storage medium.

[0022] An electric hand-held power tool comprises a drive motor for driving a tool holder, a current sensor for detecting an operating current of the drive motor, a speed sensor for detecting a speed of the drive motor, and a controller for controlling the drive motor and for receiving and evaluating sensor signals from the current sensor and the speed sensor.The controller is designed to check whether the electric hand-held power tool is operated in impact mode, wherein an operating current of the drive motor of the electric hand-held power tool is compared with a predeterminable first threshold value, wherein the electric hand-held power tool is operated in impact mode if the operating current is greater than the first threshold value, and whether successive speed values ​​of the drive motor correspond to a predeterminable speed when the electric hand-held power tool is operated in impact mode, and to continue the impact mode for a predeterminable period of time and with a predeterminable impact frequency if the successive speed values ​​correspond to the predeterminable speed.

[0023] The electric hand-held power tool and the method for operating the electric hand-held power tool are explained in detail below in conjunction with schematic drawings. They show:

[0024] Fig. 1 : Components of an electric hand tool;

[0025] Fig. 2: an exemplary speed and operating current profile of a drive motor of the electric hand-held power tool within the scope of a method for operating the electric hand-held power tool; Fig. 3: another exemplary speed and operating current profile of the drive motor within the scope of the method for operating the electric hand-held power tool;

[0026] Fig. 4: different speeds of the drive motor for different applications;

[0027] Fig. 5: different speeds of the drive motor depending on the battery voltage;

[0028] Fig. 6: an exemplary sequence of a method for operating the electric hand-held power tool; and

[0029] Fig. 7: an exemplary statistic regarding the quality of results achieved using the electric hand tool.

[0030] Fig. 1 schematically shows an electric handheld power tool 1. The electric handheld power tool 1 has a drive motor 2 for driving a tool holder 3. The tool holder 3 can be designed, for example, to accommodate a socket or a screw bit. In this case, the electric handheld power tool 1 is designed, for example, as an impact wrench 1.

[0031] The drive motor 2 is designed to rotate the tool holder 3 about a longitudinal axis of the tool holder 3. The tool holder 3 is connected to an anvil 4 or has an anvil 4, i.e. the anvil 4 is monolithically connected to a tool holder element of the tool holder 3. The anvil 4 is connected to a rotary impact hammer mechanism 5, which has a rotary impact hammer. During impact operation, the anvil 4 rotates with the rotary impact hammer. This allows the tool holder 3 to be driven in a pulsed manner in order to exert torque impacts on the tool holder 3. This allows a tightening torque to be built up. The rotary impact hammer mechanism 5 is connected to a gear 6 via an intermediate shaft. The gear 6 is connected to the drive motor 2 via a shaft.

[0032] To control the drive motor 2, the electric hand-held power tool 1 has a controller 7 and a battery 8 connected to the controller 7. The controller 7 is designed to set the drive motor 2 in rotation by applying an electrical voltage to the drive motor 2. The drive motor 2 can, for example, be an electronically commutated motor (EC motor for short). The controller 7 can be designed to control the drive motor 2 using pulse width modulation (PWM). In pulse width modulation, an input voltage is typically modulated using a periodic sawtooth or square wave voltage, whereby a speed of the drive motor 2 can be controlled in a targeted manner. For example, this can generate a modulated input signal that is sinusoidal.

[0033] The electric handheld power tool 1 further comprises a current sensor 9 for detecting an operating current of the drive motor 2 and a speed sensor 10 for detecting a speed of the drive motor 2. The current sensor 9 and the speed sensor 10 are connected to the controller 7. The controller 7 is configured to receive and evaluate sensor signals from the current sensor 9 and the speed sensor 10. The speed sensor 10 can be configured, for example, as a Hall sensor. The speed sensor 10 is configured to determine the rotational speed of the drive motor 2 by measuring a rotation angle.

[0034] The electric hand-held power tool 1 also has a user interface 11 connected to the controller 7. The user interface 11 is provided, for example, to allow a user to select settings of the electric hand-held power tool 1. For example, it is possible for an impact mode of the electric hand-held power tool 1 to be set via the user interface 11. The impact mode can be selected depending on the task to be performed. For example, different impact modes can be provided for different degrees of hardness of connections, such as for soft and hard screw connections and / or materials to be joined together.

[0035] An activation switch 12 is connected to the controller 7 and is provided to activate operation of the drive motor 2 or the electric handheld power tool 1. In addition, the electric handheld power tool 1 has a display device 13. The display device 13 can, for example, comprise a plurality of light-emitting diodes designed to emit different signal colors. This can, for example, indicate a screw connection status. A successfully completed work process, in which, for example, a predeterminable tightening torque was applied to a screw connection, can be indicated, for example, by means of a green light-emitting diode. A premature termination of the operation of the electric handheld power tool 1 can, for example, be indicated by means of a red light-emitting diode.In addition, different categories can be indicated by arranging the LEDs to emit continuous or pulsed light depending on the cause of the premature termination of operation of the electric hand-held power tool 1. The display device 13 can also be omitted. Alternatively, acoustic devices can be provided that are designed to generate different signal tones depending on the condition of a screw connection.

[0036] Fig. 2 schematically shows an exemplary operating current profile 14 and an associated speed profile 15 of the drive motor 2 of the electric hand-held power tool 1 in the context of a method for operating the electric hand-held power tool 1. By way of example, a scenario is shown in which a metal screw connection was produced, wherein an operating current 14 and a speed 15 are plotted against time.

[0037] The operating current profile 14 and the speed profile 15 can each be divided into two zones S1, S2. In one zone S2, impact operation takes place, while in a preceding zone S1, no impact operation takes place. In the following, impact operation is also provided with the reference symbol S2. In impact operation S2, the tool holder 3 is driven in a pulsed manner. In a first method step, it is checked whether the electric hand-held power tool 1 is being operated in impact operation S2. At a time ts, the operating current 14 exceeds a predefinable threshold value IT. This defines the start of impact operation S2 of the electric hand-held power tool 1, i.e. that zone S2 starts at time ts. The operating current 14 increases in this area due to a resistance, for example a resistance of a screw connection. In the first method step, the operating current 14 is compared with the predefinable first threshold value IT.The electric hand-held power tool 1 is operated in impact mode S2 when the operating current 14 is greater than the predefinable first threshold value IT.

[0038] In a second method step, it is checked whether successive speed values ​​ISj of the drive motor 2 correspond to a predefinable speed IS when the electric hand-held power tool 1 is operated in impact mode. The operating current I3 increases between ts and a subsequent time t2 and has a first local operating current maximum Pi at time t2. Since rotary impacts are exerted periodically in impact mode, the operating current 14 is periodic and has a plurality of local operating current maxima Pj with a predefinable impact frequency. In impact mode S2, the operating current 14 is therefore sinusoidal. In comparison, the speed 15 in impact mode S2 is constant and ideally has the value IS, which can be specified, for example, via the user interface 11.

[0039] A local operating current maximum Pj is defined as an operating current value that occurs periodically with the rotation of the drive motor 2, but which may, however, be subject to fluctuations in amplitude. Such an operating current maximum Pj can also be referred to as an operating current peak Pj. An operating current peak Pj represents a rotary impact during impact operation. The temporal interval between the operating current peaks Pj is determined by the predeterminable impact frequency.

[0040] Each operating current maximum Pj can be assigned a speed ISj, where j = 0, 1, 2, 3, ..., n and the ISj ideally assume the same values, but can actually be subject to fluctuations. The speeds ISj can be considered identical and the speed IS thus constant if the speeds ISj assigned to the operating current maxima Pj assume values ​​within a predeterminable speed interval [ISLOW, ISHI]. In the further process step, speed values ​​ISj are determined at the time of operating current maxima Pj of the drive motor 2 and compared with the predeterminable speed IS.

[0041] Impact operation S2 is terminated at a time t4 following time t2. A time t3 lying between times t2 and t4 defines a predeterminable period of time t4 - ts, within which impact operation S2 is continued, for example, to achieve a predeterminable tightening torque. Time t3 is given, for example, by three consecutive operating current maxima Pi, P2, P3 occurring, for which the speeds IS1, IS2, IS3 of drive motor 2 each assume the value IS of the predeterminable speed. In this case, consistent impact operation S2 can be assumed. Impact operation S2 is then continued for the predeterminable period of time t4 - t3 at the predeterminable impact frequency.

[0042] If the speed values ​​ISj do not correspond to the predefinable speed, a check can be made as to whether a lead time t0 of the electric hand-held power tool 1 has elapsed before time t2. Zone S1 comprises the lead time t0 of the electric hand-held power tool 1, within which the drive motor 2 is started up, the operating current 14 and the speed 15 of the drive motor 2 increasing over time until a local maximum is reached at time t0. From time t0 to a subsequent time t1 preceding time t2, the speed 15 remains constant and at a maximum, while the operating current 14 initially decreases, then remains essentially constant and then exceeds the predefinable first threshold value IT. Between time h and time t2, the speed 15 decreases to the predefinable value IS.

[0043] If the lead time to has not elapsed, it can be checked whether a gradient S of the operating current 14 within the lead time to is greater than a predeterminable second threshold value. As an example, Fig. 2 shows that the gradient S can be determined based on the initially maximum operating current ax present at time to by determining a gradient of a straight line that connects the origin with l ma x. However, the gradient S can also be determined differently. Operation of the electric hand-held power tool 1 can be terminated prematurely if the gradient S of the operating current 14 is greater than the second threshold value, since this is interpreted as a repeated tightening of an already tightened screw connection.

[0044] The control of the drive motor 2 within the scope of the method is carried out by the controller 7 based on sensor signals from the current sensor 9 and the speed sensor 10. The controller 7 is thus designed to check whether the electric hand-held power tool 1 is operated in impact mode S2, wherein the operating current 14 of the drive motor 2 is compared with a predeterminable first threshold value IT. In addition, the controller 7 is designed to check whether successive speed values ​​ISj of the drive motor 2 correspond to the predeterminable speed IS when the electric hand-held power tool 1 is operated in impact mode S2, and to continue the impact mode S2 for the predeterminable time period t4 - t3 and at the predeterminable impact frequency if the successive speed values ​​ISj correspond to the predeterminable speed IS.

[0045] The controller 7 thus comprises an algorithm, which can also be referred to as a computer program product. The algorithm comprises instructions that, when executed by the controller 7, cause it to perform the method. The algorithm is stored in a memory of the controller 7 or in an external memory.

[0046] Fig. 3 schematically shows another exemplary operating current profile 14 and another associated speed profile 15 of the drive motor 2 of the electric handheld power tool 1 within the scope of the method for operating the electric handheld power tool 1. Once again, an operating current 14 and a speed 15 are plotted against time. The diagrams in Fig. 2 and Fig. 3 have similarities. The essential differences are explained below. Merely by way of example, the time ts corresponds to the time ti, in contrast to Fig. 2. Previously used reference numerals are retained for similar and identical elements.

[0047] 3, as part of a further method step, a further phase Z2 of the impact operation S2 is initiated by the controller 7 after the predeterminable time period t4 - ts has elapsed. The impact operation S2 therefore has two impact phases Z1, Z2. A first impact phase Z1 covers the time range between ts and t4. A second impact phase Z2 covers a time range between t4 and a subsequent time te. The electric hand-held power tool 1 is operated within the second phase Z2 of the impact operation S2 for a predeterminable further time period te - ts and with a predeterminable further impact frequency. The fact that the predeterminable further time period is given by te - ts and not by te - 14 results from the fact that a time period ts - 14 is required to switch the drive motor 2 from the first impact phase Z1 to the second impact phase Z2.In the second impact phase Z2, the drive motor 2 is driven such that additional speed values ​​ISj correspond to the predeterminable additional speed ISo, which is, for example, greater than the predeterminable speed IS of the first phase Z1. Fig. 3 shows, as an example, a tolerance interval [Low, IHI] only for the predeterminable speed IS. The predeterminable speeds IS, ISo can also be referred to as pulse speeds. The additional speed values ​​ISj are determined for the additional operating current maxima Pj of the drive motor 2 and compared with the predeterminable additional speed ISo.

[0048] In comparison to Fig. 2, Fig. 3 shows a dual impact mode S2, which can be used in particular for hard connections in order to achieve a high tightening torque. The predeterminable speed IS, the predeterminable first time period t4 - ts and the predeterminable impact frequency can be specified, for example, depending on the degree of hardness of components to be joined by means of the electric hand-held power tool 1. This also applies to the predeterminable further speed IS0, the predeterminable second time period te - ts and the predeterminable further impact frequency. Fig. 4 schematically shows various speeds 15 of the drive motor 2 as a function of time, which can be used for different applications. By way of example, Fig. 4 shows three scenarios with different speeds 15 in impact mode S2, wherein, for example, no dual impact mode S2 is present, i.e.that in impact mode S2, only one specified speed ISA, ISB, ISC is used, where ISA < ISB < ISc. These pulse speeds ISA, ISB, ISC can be used, for example, in impact mode S2 for soft, intermediate, and hard connections or screw joints.

[0049] Fig. 5 schematically shows various speeds 15 of the drive motor 2 as a function of a battery voltage 16. The speed 15 is specified as a percentage of a maximum speed of the drive motor 2. The battery voltage 16 has a minimum VMIN and a maximum VMAX. In general, the battery voltage 16 can be referred to as the supply voltage 16 if the electric hand-held power tool 1 has a power source 8 other than a battery 8.

[0050] The pulse speeds ISA and ISB correspond, for example, to less than 80% of the maximum speed. The pulse speed ISc, on the other hand, has a value that is, for example, greater than 80% of the maximum speed of the drive motor 2. Below a critical battery voltage V1, the speed ISc cannot be maintained, so that the speed 15 of the drive motor increases, for example, linearly from approximately 70% to ISc for battery voltages in the range between VMIN and V1. This can be achieved, for example, by pulse-width modulation of the drive motor 2. The profile of the speed 15 in the range between VMIN and V1 can also be designed differently than that shown in Fig. 5.

[0051] The predeterminable speed IS can therefore be specified as a function of the battery voltage 16. For example, the predeterminable speed IS can be selected as a function of the battery voltage 16 up to a critical battery voltage V1. From the critical battery voltage V1, the speed IS can be specified independently of the battery voltage 16. This is particularly useful for high speeds IS. Fig. 6 schematically shows a flowchart of an exemplary method 101 for operating the electric handheld power tool 1.

[0052] At the beginning 101 of the method 100, a user can specify a speed IS, a time duration, and an impact frequency for the impact operation S2 in a step 102. In this case, a further speed IS0, a further time duration, and a further impact frequency can also be specified if a dual impact operation S2 is to be carried out. The selection of the speed IS can be set on the user interface 11. The selection of the aforementioned parameters can be made, for example, based on a required tightening torque, for example based on a degree of hardness of a connection to be made. This selection can also be made from a third device via a wireless connection such as Wi-Fi or Bluetooth. The second step 102 can also be omitted if a setting is retained.

[0053] In a second step 102, the activation switch 12 of the electric hand-held power tool is actuated. In a fourth step 104, information stored in a memory of the electric hand-held power tool 1 about the results of activities already carried out using the electric hand-held power tool 1 can be deleted. The fourth step 104 can also be omitted. In a fifth step 105, the supply or battery voltage is read out and, in an optional sixth step 106, modulated, for example by means of PWM, in order to generate a desired input signal for the drive motor 2. In a seventh step 107, the drive motor 2 is driven on the basis of the input signal from the controller 7. For example, the input signal can be generated as a function of the supply or battery voltage, with parameters being determined on the basis of the supply or battery voltage within the framework of pulse width modulation.Battery voltage can be selected in order to achieve the predeterminable speed IS and thus a required tightening torque. Optionally, a check can now be carried out to determine whether a torque is being exerted again on a connection that has already been made. This can damage connections that have already been made. To avoid this, a check can be carried out in an eighth step 108 to determine whether the lead time t has elapsed. If this is not the case, the operating current 14 of the drive motor 2 is read out using the current sensor 9 in a ninth step 109. In a tenth step 110, a maximum value of the operating current 14 within the lead time t can be stored in the memory of the electric hand-held power tool 1. In this case, a check can be carried out again in an eleventh step 111 to determine whether the lead time t has elapsed.If this is the case, in a twelfth step 112 the gradient S is determined on the basis of the operating current, for example on the basis of the maximum operating current 14 within the lead time t0. In a thirteenth step 113 it is checked whether the determined gradient S is greater than the predefinable second threshold value. If this is the case, the drive motor 2 is switched off in a fourteenth step 114, i.e. operation is terminated prematurely, since this is interpreted as a renewed attempt to exert a torque on a connection that has already been tightened. In a fifteenth step 115, information NG1 about the fact that operation was terminated prematurely because renewed tightening was detected can be stored in the memory.Alternatively, after the eleventh step 111, the eighth step 108 can be carried out again if the check in the eleventh step 111 shows that the lead time to has not yet elapsed, whereby this check is carried out again in the eighth step 108 until the lead time to has elapsed, or the drive motor 2 is switched off prematurely in the fourteenth step 114.

[0054] If the lead time t has elapsed and no gradient S has been determined that exceeds the second threshold value, the operating current 14 is read out in a sixteenth step and compared with the predefinable first threshold value IT in a seventeenth step 117 to determine whether the electrical hand-held power tool 1 is being operated in impact mode S2. If this is not the case, a check can be made in an eighteenth step 118 as to whether the user is still actuating the activation switch 12. If this is the case, the sixteenth and seventeenth steps 116, 117 are repeated. If the user no longer actuates the activation switch 12, the drive motor 2 is switched off prematurely in a nineteenth step 119. In a twentieth step 115, information NG3 stating that operation was ended prematurely because the user is no longer actuating the activation switch 12 can be stored in the memory.

[0055] If the operating current I4 is greater than the predefinable first threshold value IT, a twenty-first step 121 can be used to check whether the operating current I4 has a first operating current peak Pj. If this is the case, the associated speed ISj can be read out and stored in the memory in a twenty-second step 122. The speed ISj is thus determined for the time at which the operating current I4 has the operating current peak Pj. If the operating current I4 does not have an operating current peak Pj, the eighth step 108 is carried out, i.e., a check is carried out to determine whether the lead time t0 has elapsed in order to rule out premature pickup.

[0056] In a twenty-third step 123, a check is made to determine whether successive speed values ​​ISj for a corresponding number of operating current peaks Pj each correspond to the predeterminable speed IS. If this is the case, the impact operation S2 is continued for the predeterminable period of time. For this purpose, a timer can be activated in a twenty-fourth step 124, and a check can be made in a twenty-fifth step 125 to determine whether the predeterminable period of time has been exceeded. If the predeterminable period of time has been exceeded, the drive motor 2 is switched off in a twenty-sixth step 126. In this case, operation is terminated because a desired tightening torque has been reached. In a twenty-seventh step 127, information OK indicating that operation has been terminated because a work target has been reached can be stored in the memory.

[0057] If it emerges during the twenty-fifth step 125 that the presettable time period has not yet been exceeded, the speed of drive motor 2 can be read out in a twenty-eighth step 128 in order to check in a twenty-ninth step 129 whether further speed values ​​ISj correspond to the presettable speed IS. If this is not the case, drive motor 2 is shut down prematurely in a thirtieth step 130. In a thirty-first step 131, information NG2 can be stored in the memory indicating that operation has been terminated because the further speed values ​​ISj do not correspond to the presettable speed IS.If, however, the further speeds ISj correspond to the predeterminable speed IS, the twenty-fifth step 125 is repeated until either the predeterminable time period has elapsed or the further speed values ​​ISj do not correspond to the predeterminable speed IS and the drive motor 2 is switched off.

[0058] Alternatively, after the twenty-fourth step 124, the first phase Z1 of the impact operation S2 can be initiated in a thirty-second step 132 by specifying the speed IS. In a thirty-third step 133, a check is then made to determine whether the predeterminable time period has been exceeded. If this is the case, the second phase Z2 of the impact operation Z2 is initiated in a thirty-fourth step 134 by selecting the further predeterminable speed IS0. These speeds can alternatively also be selected in the second step 102, so that a selection in the thirty-second step 132 and the thirty-fourth step 134 can be omitted, and the phases Z1, Z2 are initiated by the controller 7. In a thirty-fifth step 135, a timer is activated, and in a thirty-sixth step 136, a check is made to determine whether the further predeterminable time period has been exceeded.If this is the case, the drive motor 2 is switched off according to the twenty-sixth step 126. According to the twenty-seventh step 127, information OK indicating that operation has ended because a work target has been reached can be stored in the memory. Even in dual impact mode S2, the speed of the drive motor 2 can be monitored according to the twenty-eighth and twenty-ninth steps 128, 129, as long as the predeterminable time period or the further predeterminable time period has not elapsed, in order to interrupt the drive motor 2 if necessary, if the speed, or more precisely the further speed values ​​ISj, do not match the predeterminable speed IS or the further speed ISo. In a thirty-seventh step 137, the method 100 can be terminated after the drive motor 2 has been switched off in the fifteenth, twentieth, twenty-seventh, or thirty-first step 115, 120, 127, 131.Depending on the scenario, the information OK; NG1, NG2, NG3 can be displayed to the user immediately. If the predeterminable time period is exceeded, it is assumed that the required tightening torque has been reached. This is therefore interpreted as the successful completion of a task and can be displayed, for example, by means of an LED on the electric hand-held power tool 1, which is designed, for example, to emit a green light continuously, which represents the information OK and confirms to the user that a goal has been achieved. If operation was ended prematurely, this can be displayed, for example, by a further LED that is designed to emit a red light. For example, the further LED can be designed to emit a red light continuously if at least one speed value ISj does not correspond to the predeterminable speed IS orISO, or if it has been detected that repeated tightening has occurred and operation has been terminated prematurely. The continuous illumination of the additional LED thus represents the information NG1 and NG2. The additional LED can also be configured to emit pulsed red light, thereby representing and displaying the information NG3.

[0059] Since the information OK; NG1, NG2, NG3 can be stored in the memory, statistics can be created from which the quality of work performed with the electric handheld power tool 1 can be determined. Fig. 7 schematically shows an example of statistics regarding the quality of results achieved using the electric handheld power tool. A frequency N of the scenarios represented by the information OK; NG1, NG2, NG3 stored in the memory is plotted in a bar chart. This allows a user to analyze and, if necessary, optimize work processes. The information and statistics can be transferred to external devices via an interface of the electric handheld power tool 1, for example via an I / O port, or a wireless connection such as Wi-Fi or Bluetooth.

Claims

Claims 1. Method (100) for operating an electric hand-held power tool (1), in particular a rotary impact wrench (1), comprising the following method steps: - Checking whether the electric hand-held power tool (1) is operated in impact mode (S2), wherein an operating current (14) of a drive motor (2) of the electric hand-held power tool (1) is compared with a predeterminable first threshold value (IT), wherein the electric hand-held power tool (1) is operated in impact mode (S2) if the operating current (14) is greater than the predeterminable first threshold value (IT), - Checking whether successive speed values ​​(ISj) of the drive motor (2) correspond to a predeterminable speed (IS) when the electric hand-held power tool (1) is operated in impact mode (S2), whereby speed values ​​(ISj) for operating current maxima (Pj) of the drive motor (2) are determined and compared with the predeterminable speed (IS), - Continuing the impact operation (S2) for a preset period of time and with a preset impact frequency if the successive speed values ​​(ISj) correspond to the preset speed (IS).

2. Method (100) according to claim 1, wherein it is checked whether further speed values ​​(ISj) correspond to the predeterminable speed (IS) as long as the impact operation (S2) is continued, wherein the operation of the electric hand-held power tool (1) is terminated prematurely if the further speed values ​​(ISj) do not correspond to the predeterminable speed (IS) or, wherein the impact operation (S2) is continued until the predeterminable time period is exceeded if the further speed values ​​(ISj) correspond to the predeterminable speed (IS).

3. Method (100) according to claim 1 or 2, wherein, before checking the speed value values ​​(ISj), it is checked whether the operating current (14) in impact mode (S2) has a first operating current maximum (Pi), wherein, if the operating current (14) in impact mode (S2) does not have a first operating current maximum (Pi), it is checked whether a lead time (to) of the electrical hand-held power tool (1) has elapsed.

4. Method (100) according to claim 1 or 2, wherein, if the speed values ​​(ISj) do not correspond to the predeterminable speed (IS), it is checked whether a lead time (to) of the electric hand-held power tool (1) has elapsed.

5. Method according to claim 3 or 4, wherein it is checked whether a gradient (S) of the operating current (14) within the lead time (to) is greater than a predeterminable second threshold value if the lead time (to) has not elapsed, wherein the operation of the electrical hand-held power tool (1) is terminated prematurely if the gradient (S) of the operating current (14) is greater than the second threshold value.

6. Method (100) according to one of the preceding claims, wherein it is checked whether a user of the electric hand-held power tool (1) actuates an activation switch (12) of the electric hand-held power tool (1) when the operating current (14) is less than the predeterminable first threshold value (IT), wherein the operation of the electric hand-held power tool (1) is terminated prematurely when the user no longer actuates the activation switch (12), wherein it is checked again whether the operating current (14) is greater than the predeterminable first threshold value (IT) when the user actuates the activation switch (12).

7. Method (100) according to one of claims 2, 5 and 6 with the following further method steps: - Indication that the preset time period has been exceeded or that the operation of the electrical hand tool (1) has been terminated prematurely.

8. Method (100) according to claim 1, comprising the following further method step: - initiating a further phase (Z2) of the impact operation (S2) after the predeterminable time period has elapsed, wherein the electric hand-held power tool (1) is operated within the further phase (Z2) of the impact operation (S2) for a predeterminable further time period and with a predeterminable further impact frequency such that additional speed values ​​(ISj) correspond to a predeterminable further speed I So, wherein the additional speed values ​​(ISj) for additional operating current maxima (Pj) of the drive motor (2) are determined and compared with the predeterminable further speed (I So).

9. The method (100) according to claim 8, wherein the predeterminable further speed (ISo) is greater than the predeterminable speed (IS).

10. Method (100) according to one of the preceding claims, wherein the predeterminable speed (IS), the predeterminable first time duration and the predeterminable impact frequency are predetermined depending on a degree of hardness of components to be connected by means of the electric hand-held power tool (1).

11. Method (100) according to one of the preceding claims, wherein the predeterminable speed (IS) is specified as a function of a battery voltage (16) of a battery (8) of the electric hand-held power tool.

12. Method (100) according to one of the preceding claims, wherein the drive motor (2) is controlled in a pulse-width modulated manner.

13. A computer program product comprising instructions which, when executed by a processor, cause the processor to perform a method (100) according to any one of the preceding claims.

14. A machine-readable storage medium, wherein the computer program product according to claim 13 is stored on the machine-readable storage product.

15. An electric hand-held power tool (1) comprising a drive motor (2) for driving a tool holder (3), a current sensor (9) for detecting an operating current (14) of the drive motor (2), a speed sensor (10) for detecting a speed (15) of the drive motor (2), and a controller (7) for controlling the drive motor (2) and for receiving and evaluating sensor signals from the current sensor (9) and the speed sensor (10), wherein the controller (7) is designed to check whether the electric hand-held power tool (1) is operated in impact mode (S2), wherein an operating current (14) of the drive motor (2) of the electric hand-held power tool (1) is compared with a predeterminable first threshold value (IT), wherein the electric hand-held power tool (1) is operated in impact mode (S2) if the operating current (14) is greater than the first threshold value (IT), and,whether successive speed values ​​(ISj) of the drive motor (2) correspond to a predeterminable speed (IS) when the electric hand-held power tool (1) is operated in impact mode (S2), and to continue the impact mode (S2) for a predeterminable period of time and with a predeterminable impact frequency if the successive speed values ​​(ISj) correspond to the predeterminable speed (IS).

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