Power tool for testing a monitoring temperature change, method, computer program product, computer-readable medium and control device

Abstract

A power tool (10) comprising an electric motor (1) for driving a tool (2), an operating element (3) for actuation by a user to carry out a user input, a temperature sensor (4) for measuring a monitoring temperature of the power tool (10), and a control device (5) for controlling the electric motor (1), wherein the control device (5) is designed to energize the electric motor (1) in response to the user input in order to put the electric motor (1) into a drive state in which the electric motor (1) drives the tool (2), and wherein the control device (5) is further designed to check whether a positive monitoring temperature change of the detected monitoring temperature that occurred in the drive state reaches or exceeds a predetermined maximum temperature change (ΔTmax), and in response thereto,that the monitoring temperature change reaches or exceeds the predetermined maximum temperature change (ΔTmax), to reduce and / or terminate the current supply to the electric motor in order to put the electric motor (1) into a cooling state in which the electric motor (1) does not drive the tool (2) and in which the electric motor (1) cools down, wherein the control device (5) is designed to detect a starting temperature value of the monitoring temperature with the temperature sensor (4) at the beginning of the drive state, to calculate a temperature threshold value based on the starting temperature value and the maximum temperature change (ΔTmax), and to compare the monitoring temperature measured with the temperature sensor (4) with the temperature threshold value in the drive state in order to determine whether the monitoring temperature change reaches or exceeds the predetermined maximum temperature change (ΔTmax),wherein the starting temperature value is a first starting temperature value (ST1) and the temperature threshold value is a first temperature threshold value (SW1), and the control device is designed to assume a further driving state in response to a user input made after the end of the driving state, to detect a second starting temperature value (ST2) of the monitoring temperature at the beginning of the further driving state, to calculate a second temperature threshold value (SW2) based on the second starting temperature value (ST2) and the maximum temperature change (ΔTmax), and to put the electric motor (1) into the cooling state in response to the measured monitoring temperature reaching or exceeding the second temperature threshold value (SW2) in the further driving state.

Description

[0001] The invention relates to a power tool for testing a monitoring temperature change, comprising an electric motor for driving a tool, an operating element for actuation by a user to carry out a user input, a temperature sensor for measuring a monitoring temperature of the power tool and a control device for controlling the electric motor, wherein the control device is designed to energize the electric motor in response to the user input in order to put the electric motor into a drive state in which the electric motor drives the tool.

[0002] EP 2 484 494 B1 describes a hand-held machine tool with a control device which is designed to correct a temperature switch-off limit value as a function of a course of actual temperature values.

[0003] US 2010 / 0 117 580 A1 describes a rechargeable power tool in which a microcomputer, upon switching a trigger switch, determines the magnitude relationship between the detected temperature output by the first thermistor and the first temperature threshold, the second temperature threshold and the third temperature threshold, as well as the magnitude relationship between the first calculated temperature rise rate and the first preset temperature rise rate.If the detected temperature is determined to be greater than the first temperature threshold, or if the first calculated temperature rise rate is determined to be greater than the first preset temperature rise rate after the detected temperature is determined to be greater than the second temperature threshold, the microcomputer is put into a limited operation mode in which the speed of the motor is limited to a predetermined value or less.

[0004] DE 10 2007 000 524 A1 discloses an electric hand-held power tool with a manageable outer housing, an electric motor with a fan for generating a cooling air flow and with an electronic module connected to a temperature sensor with an electronic motor control and a computing means for motor temperature control, which includes a motor temperature model, wherein the temperature sensor is arranged directly on the electronic module.

[0005] An object of the invention is to reduce the risk of damage to the power tool.

[0006] The object is achieved by a power tool according to claim 1. The control device of the power tool is designed to check whether a positive monitoring temperature change of the detected monitoring temperature that occurred in the drive state reaches or exceeds a predetermined maximum temperature change, and in response to the monitoring temperature change reaching or exceeding the predetermined maximum temperature change, to reduce and / or terminate the current supply to the electric motor in order to put the electric motor into a cooling state in which the electric motor does not drive the tool and in which the electric motor cools down, wherein the control device is designed to detect a starting temperature value of the monitoring temperature with the temperature sensor at the beginning of the drive state, to calculate a temperature threshold value based on the starting temperature value and the maximum temperature change,and in the drive state, to compare the monitoring temperature measured with the temperature sensor with the temperature threshold value to determine whether the monitoring temperature change reaches or exceeds the predetermined maximum temperature change, wherein the start temperature value is a first start temperature value and the temperature threshold value is a first temperature threshold value, and the control device is designed to assume a further drive state in response to a user input made after the end of the drive state, to detect a second start temperature value of the monitoring temperature at the beginning of the further drive state, to calculate a second temperature threshold value based on the second start temperature value and the maximum temperature change, and in response to the measured monitoring temperature reaching or exceeding the second temperature threshold value in the further drive state,to put the electric motor into the cooling state.,

[0007] The electric motor expediently comprises a winding arrangement with windings that are energized in the drive state and thus heat up. Excessive heating of the windings can lead to damage to the windings and thus to damage to the power tool. Preferably, no temperature sensor is present for directly and / or immediately measuring a winding temperature of the winding arrangement. In particular, each temperature detected in the power tool, in particular the monitoring temperature, follows the winding temperature with a delay, so that the winding temperature can already assume a critical value that potentially damages the winding arrangement before a currently detected actual value of the monitoring temperature indicates that the critical value of the winding temperature has been reached - i.e., in particular, before the currently detected actual value also assumes the critical value.Therefore, an approach in which the electric motor is put into the cooling state based on the (absolute) currently recorded actual value of the monitoring temperature carries the risk that the winding temperature has already reached the critical value before or when the electric motor is put into the cooling state and that the winding arrangement has already been damaged.

[0008] The present invention is based in particular on the approach of placing the electric motor into the cooling state based on the change in the monitoring temperature occurring in the drive state. The monitoring temperature change is in particular the total change in the monitoring temperature in the drive state. For example, the monitoring temperature change is a difference present in the drive state between a starting temperature value of the monitoring temperature detected at the beginning of the drive state and the current actual value of the monitoring temperature subsequently detected, in particular continuously, in the drive state. The maximum temperature change defines a maximum temperature difference for the drive state, in particular for each drive state, by which the monitoring temperature may increase in the respective drive state before (or without) the control device placing the electric motor into the cooling state.The maximum temperature change therefore represents a temperature budget for the drive state, specifically for each drive state. If the temperature budget for a drive state is exhausted, the control unit puts the electric motor into the cooling state. This can reduce the risk of damage to the electric motor.

[0009] For example, a monitoring temperature change that is greater than the maximum temperature change could lead to a critical winding temperature, without this critical winding temperature being detectable solely from the absolute, currently recorded actual value of the monitoring temperature. By taking the monitoring temperature change into account—that is, by considering the temperature delta of the monitoring temperature—this scenario in particular can be prevented, thus preventing the risk of damage to the electric motor.This applies in particular to a case in which the electric motor is operated at a speed (in particular significantly) below the maximum speed (for example when the control element is partially pressed) and is therefore less well cooled and / or in a case in which there is misuse - i.e. improper use - of the power tool, for example if the electric motor is loaded beyond its intended load.

[0010] Advantageous further training is the subject of the subclaims.

[0011] The invention further relates to a method for operating a power tool, comprising the steps of: actuating an operating element of the power tool to energize an electric motor of the power tool, so that the electric motor is placed in a drive state in which the electric motor drives a tool of the power tool; checking whether a positive monitoring temperature change occurring in the drive state reaches or exceeds a predetermined maximum temperature change ΔTmax in response to the monitoring temperature change reaching or exceeding the predetermined maximum temperature change; reducing and / or terminating the energization of the electric motor to place the electric motor in a cooling state in which the electric motor does not drive the tool and in which the electric motor cools down, wherein a starting temperature value of the monitoring temperature is detected at the beginning of the drive state;a temperature threshold is calculated based on the start temperature value and the maximum temperature change ΔTmax, and in the drive state, a measured monitoring temperature is compared with the temperature threshold to determine whether the monitoring temperature change reaches or exceeds the predetermined maximum temperature change ΔTmax, wherein the start temperature value is a first start temperature value and the temperature threshold is a first temperature threshold, and in response to a user input made after the end of the drive state, a further drive state is assumed, at the beginning of the further drive state, a second start temperature value of the monitoring temperature is detected, a second temperature threshold is calculated based on the second start temperature value and the maximum temperature change ΔTmax, and in response thereto,that in the further drive state the measured monitoring temperature reaches or exceeds the second temperature threshold, the electric motor is put into the cooling state.,

[0012] Preferably, the method is carried out using the power tool explained above and / or below. In particular, the method is further developed in accordance with the power tool explained above and / or below.

[0013] The invention further relates to a computer program product comprising instructions for causing the power tool to carry out the method.

[0014] The invention further relates to a computer-readable medium on which the computer program product is stored.

[0015] The invention further relates to a method for operating a control device of a power tool, comprising the step of installing the computer program product on the control device.

[0016] The invention further relates to a control device for a power tool, wherein the control device is configured to energize an electric motor of the power tool in response to a user input in order to place the electric motor into a drive state in which the electric motor drives a tool of the power tool, and wherein the control device is further configured to check whether a positive monitoring temperature change of a detected monitoring temperature that occurred in the drive state reaches or exceeds a predetermined maximum temperature change, and in response to the monitoring temperature change reaching or exceeding the predetermined maximum temperature change, to reduce and / or terminate the energization of the electric motor in order to place the electric motor into a cooling state in which the electric motor does not drive the tool and in which the electric motor cools down,wherein the control device is designed to calculate a respective temperature threshold value each time the electric motor is put into the drive state, wherein the temperature threshold value is calculated as the sum of a start temperature value, the monitoring temperature, and the maximum temperature change, wherein the control device is designed to detect the start temperature value with a temperature sensor of the power tool at the beginning of the drive state, wherein the control device is designed to compare the monitoring temperature detected by the temperature sensor with the temperature threshold value in the drive state in order to determine whether the monitoring temperature change reaches or exceeds the maximum temperature change, wherein the start temperature value is a first start temperature value and the temperature threshold value is a first temperature threshold value, wherein the control device is designed,in response to a user input after the end of the drive state, to enter a further drive state, to record a second starting temperature value of the monitoring temperature at the beginning of the further drive state, to calculate a second temperature threshold based on the second starting temperature value and the maximum temperature change, and in response to the measured monitoring temperature reaching or exceeding the second temperature threshold in the further drive state, to put the electric motor into the cooling state.

[0017] Further exemplary details and exemplary embodiments are explained below with reference to the figures. Fig. 1 a schematic representation of a power tool, Fig. 2 a temporal progression of a monitoring temperature over several drive phases and cooling phases, and Fig. 3 a flowchart of a method for operating a power tool.

[0018] The Fig. Figure 1 shows a schematic representation of a power tool 10, which is embodied in particular as a hand-held power tool. By way of example, the power tool 10 is embodied as a screwdriver, in particular as a hand-held screwdriver. For example, the power tool 10 is a cordless screwdriver. Alternatively, the power tool can be embodied as a circular saw, milling machine, or grinder.

[0019] The power tool 10 comprises an electric motor 1, which expediently serves to drive a tool 2. By way of example, the power tool 10 comprises the tool 2. The tool 2 is designed, for example, as a screwdriver blade. Alternatively, the tool can be a saw blade (for example, when the power tool is designed as a circular saw), a milling tool (for example, when the power tool is designed as a milling cutter), or a grinding element (for example, when the power tool is designed as a grinder).

[0020] The power tool has an operating element 3, which is embodied, for example, as a button, in particular as a trigger button. In particular, the operating element 3 is embodied as a pistol trigger. The operating element 3 can be actuated by a user of the power tool 10 to execute a user input.

[0021] The power tool 10 further comprises a temperature sensor 4 for measuring a monitoring temperature of the power tool 10. The monitoring temperature shall be referred to as the temperature detected by the temperature sensor 4.

[0022] The power tool 10 further comprises a control device 5 for controlling the electric motor 1. The control device 5 is configured to energize the electric motor 1 in response to the user input in order to place the electric motor 1 into a drive state in which the electric motor 1 drives the tool 2. The drive state is a state in which the electric motor 1 is energized by the control device 5, in particular continuously, and / or in which the electric motor 1 drives the tool 2, in particular continuously. In the drive state, the energization of the electric motor 1 heats the electric motor 1 and / or increases the monitoring temperature.

[0023] The control device 5 is further configured to check whether a positive monitoring temperature change of the detected monitoring temperature occurring in the drive state reaches or exceeds a predetermined maximum temperature change ΔTmax. The positive monitoring temperature change is, in particular, a temperature increase during the drive state, preferably a temperature increase from a starting temperature value of the monitoring temperature present at the beginning of the drive state, in particular to a current actual value of the monitoring temperature detected in the drive state. The starting temperature value is, in particular, the value of the monitoring temperature at a starting time of the drive state.The control device 5 expediently first records the starting temperature value and then, in the drive state, repeatedly, in particular continuously, records the current actual value of the monitoring temperature in order to check whether the positive monitoring temperature change reaches or exceeds the predetermined maximum temperature change ΔTmax. The positive monitoring temperature change is expediently the difference between the current actual value of the monitoring temperature and the starting temperature value of the monitoring temperature. The maximum temperature change ΔTmax can also be referred to as a temperature budget. The maximum temperature change ΔTmax is the maximum temperature change (permitted by the control device 5) of the monitoring temperature within a (in particular continuous) operating state. The maximum temperature change ΔTmax is preferably stored in the control device 5 and / or is calculated by the control device 5.The maximum temperature change ΔTmax is in particular a predetermined temperature difference value.

[0024] The predetermined maximum temperature change ΔTmax is expediently large enough so that in a single drive state a work process, for example a complete screwing in of a screw, can be completely completed with the power tool 10 without the (in particular total) positive monitoring temperature change occurring in this drive state exceeding the predetermined maximum temperature change ΔTmax.

[0025] The control device 5 is further configured, in response to the monitoring temperature change reaching or exceeding the predetermined maximum temperature change ΔTmax, to reduce and / or terminate the current supply to the electric motor in order to place the electric motor 1 into a cooling state in which the electric motor 1 does not drive the tool 2 and in which the electric motor 1 cools down. The cooling state is expediently a state in which the current supply to the electric motor 1 is lower than in the drive state and / or in which no current is supplied to the electric motor 1. By placing the electric motor 1 into the cooling state, the control device 5 terminates the drive state.

[0026] Putting the electric motor 1 into drive mode can also be referred to as switching on the electric motor 1.

[0027] When the electric motor 1 is switched on, the control device 5 measures the starting temperature value of the monitoring temperature. The monitoring temperature is, for example, the temperature of the control device 5. The control device 5 is expediently designed to calculate a respective temperature threshold value each time the electric motor 1 is switched to the drive state—that is, each time the electric motor 1 is switched on—specifically as the sum of the starting temperature value and the maximum temperature change ΔTmax.

[0028] Preferably, the temperature sensor 4 is arranged at a distance from the electric motor 1 and / or at a distance from a winding arrangement 6 of the electric motor 1.

[0029] By way of example, the control device 5 comprises power electronics 7. The control device 5 is particularly designed to provide the current supply to the electric motor 1 via the power electronics 7. In particular, the power electronics 7 supplies current to the electric motor 1. The temperature sensor 4 is preferably assigned to the power electronics 7. For example, the temperature sensor 4 is part of the power electronics 7 or is arranged in the region of the power electronics 7, for example next to the power electronics 7, in particular such that the temperature sensor 4 measures a temperature of the power electronics 7 as the monitoring temperature. The temperature sensor 4 assigned to the power electronics 7 can also be referred to as a power electronics temperature sensor 4A.

[0030] Furthermore, the temperature sensor 4 can be assigned to the electric motor 1. For example, the temperature sensor can be part of the electric motor 1 or arranged in the region of the electric motor 1, in particular such that the temperature sensor 4 measures a temperature of the electric motor 1 as the monitoring temperature. The temperature sensor 4 assigned to the electric motor 1 can also be referred to as the electric motor temperature sensor 4B.

[0031] Preferably, both the power electronics temperature sensor 4A and the electric motor temperature sensor can be present. The power electronics temperature sensor 4A is expediently spaced further from the winding arrangement 6 than the electric motor temperature sensor 4B.

[0032] Optionally, the electric motor temperature sensor 4B can be omitted - i.e. not present.

[0033] For example, the temperature detected by the power electronics temperature sensor increases faster in the drive state than the temperature detected by the electric motor temperature sensor.

[0034] The power tool 10 preferably comprises a drive section 8 in which the electric motor 1 is arranged, and / or a handle section 9 in which the temperature sensor 4 is arranged.

[0035] For example, the temperature sensor 4 is arranged in the z-direction below the control element 3 and / or the electric motor 1 is arranged in the z-direction above the control element 3.

[0036] The temperature sensor 4 is arranged in particular outside the electric motor 1 and / or at a distance from the electric motor 1, in particular such that the monitoring temperature detected by the temperature sensor 4 (in particular during intended use) is not determined by the heat emitted by the electric motor 1, in particular not by the heat emitted by the winding arrangement 6, but is determined in particular by the heat emitted by the power electronics 7.

[0037] In the following, with reference to the Fig. 1, further exemplary details of the structure of the power tool 10 will be discussed. Reference is made to the horizontally oriented x-direction and the orthogonal to the x-direction and vertically oriented z-direction.

[0038] By way of example, the power tool 10 is T-shaped and / or pistol-shaped. The power tool 10 has the handle section 9, which the user can grip with his hand in order to carry and guide the power tool 10. The handle section 9 is expediently aligned vertically with its longitudinal axis. The power tool 10 further has the drive section 8. The tool 2 is arranged at the front end of the drive section 8. A shaft arrangement 14, via which the tool 2 is driven by the electric motor 1, expediently runs through the drive section 8. The drive section 8 is exemplarily aligned horizontally with its longitudinal axis, in particular parallel to the x-direction. The power tool 10 further comprises an energy storage section 15, which is exemplarily arranged at the bottom of the handle section 9.The energy storage section 15 comprises an energy storage device 16, for example a battery, from which the control device 5, in particular the power electronics 7, and / or the electric motor 1 is fed, in particular in the drive state.

[0039] By way of example, the power tool has a gear mechanism 17. The shaft arrangement 14 comprises, by way of example, a drive shaft 14A (in particular aligned parallel to the x-direction) and an output shaft 14B (in particular aligned parallel to the x-direction), which are coupled to one another via the gear mechanism 17. The drive shaft 14A runs, by way of example, from the electric motor 1 to the gear mechanism 17. The output shaft 14B runs, by way of example, from the gear mechanism 17 to the tool 2.

[0040] Using the control element 3, the user can control the drive of the tool 2 provided by the electric motor 1, in particular starting, stopping, and / or varying its strength (in particular the speed and / or force). The control element 3 is preferably arranged on the handle section 9.

[0041] The control device 5 preferably comprises a control unit 18, which is embodied, for example, as a microcontroller, and serves in particular to control the power electronics 7 in order to adjust the current supply to the electric motor 1, in particular according to an actuation of the operating element 3 detected by the control unit 18. The control unit 18 is expediently designed to read the temperature sensor 4 in order to detect the monitoring temperature. The control unit 18 is also expediently designed to check whether the monitoring temperature change reaches or exceeds the predetermined maximum temperature change ΔTmax.

[0042] The power tool 10 expediently comprises an outer housing 19, in which the control device 5, the electric motor 1, and / or the temperature sensor 4 are arranged. The handle portion 9 is, for example, part of the outer housing 19.

[0043] The power tool 10 comprises, by way of example, a control device circuit board 21 on which the control device 5, in particular the control unit 18 and / or the power electronics 7, and / or the temperature sensor 4, in particular the power electronics temperature sensor 4A, is arranged. The control device circuit board 21 is arranged, by way of example, in the handle section 9. The power tool 10 comprises, by way of example, a cable arrangement 22 that runs from the control device circuit board 21, in particular from the power electronics 7, to the electric motor 1 and via which the electric motor 1 is supplied with current. The cable arrangement 22 comprises, by way of example, three cables.

[0044] The electric motor 1 comprises, for example, a rotor 23, which can be set into a rotary motion by energizing the winding arrangement 6 in order to drive the tool 2. The rotor 23 is coupled to the shaft arrangement 14, in particular the drive shaft 14A.

[0045] Optionally, the power tool 10 has an electric motor circuit board 24, which is arranged, for example, in the area of ​​the electric motor 1, in particular in the area of ​​the rotor 23. For example, the electric motor circuit board 24 is arranged in front of the rotor 23 in the x-direction. A magnetic sensor 25, in particular a Hall sensor, is preferably arranged on the electric motor circuit board 24. The control device 5 is expediently designed to detect a position of the rotor 23 using the magnetic sensor 25. Optionally, the temperature sensor 4, in particular the electric motor temperature sensor 4B, is arranged on the electric motor circuit board 24.

[0046] The temperature sensor 4, in particular the power electronics temperature sensor 4A and / or the electric motor temperature sensor 4B, is designed, for example, as an NTC sensor, PTC sensor, P100 sensor, P1000 sensor or infrared sensor.

[0047] In the following, with reference to the Fig. 2 will explain in more detail how the control device 5 switches the electric motor 1 from the drive state to the cooling state based on the monitoring temperature change.

[0048] The Fig. Figure 2 shows a time course of the monitoring temperature. Time t is plotted on the horizontal axis, and temperature T is plotted on the vertical axis.

[0049] The one in the Fig. The temporal progression of the monitoring temperature shown in Figure 2 shows a number of consecutive drive states and cooling states, with each drive state followed by a cooling state. In each drive state, the monitoring temperature rises, and in each cooling state, the monitoring temperature decreases.

[0050] Each time period during which a driving state lasts shall be referred to as a driving phase, and each time period during which a cooling state lasts shall be referred to as a cooling phase. For example, the driving phases and the cooling phases occur alternately.

[0051] Conveniently, each drive phase—i.e., each drive state—continues only as long as the user operates the control element 3. By stopping the operation of the control element 3, the user can stop the drive state and put the electric motor 1 into the cooling state.

[0052] The control device 5 is expediently designed to successively place the electric motor 1 into several drive states. Preferably, the control device 5 places the electric motor 1 into a cooling state after each drive state. Preferably, the control device 5 is designed to provide a maximum current supply in each of the drive states, in particular the same maximum current supply to the electric motor 1, and thus, in particular, to provide the same maximum power for driving the tool 2 in each drive state, in particular independently of a respective starting temperature value of the monitoring temperature present at the beginning of each drive state (in particular under the condition that the respective starting temperature value is less than a maximum temperature threshold value MT).In particular, the control device 5 is designed to allow either the same maximum current supply or no current supply at all in each drive state. The control device 5 is expediently designed to provide no drive state (in particular, no drive of the tool 2) with a (particularly temperature-dependent) throttling of the current supply.

[0053] Preferably, the control device 5 is designed to detect a starting temperature value of the monitoring temperature at the beginning of the drive state with the temperature sensor 4. For example, the control device 5 detects the starting temperature value in response to the actuation of the operating element 3. In the Fig. 2, the control device 5 detects a first start temperature value ST1 of the monitoring temperature at the beginning of a first drive state assumed in a first drive phase AP1.

[0054] The control device 5 is designed in particular to calculate a temperature threshold value based on the starting temperature value and the maximum temperature change ΔTmax, in particular by adding the maximum temperature change ΔTmax to the starting temperature value. In the example shown, the Fig. 2, the control device 5 calculates a first temperature threshold value SW1 by adding the maximum temperature change ΔTmax to the first start temperature value ST1.

[0055] The control device 5 is expediently designed to compare the monitoring temperature measured by the temperature sensor 4 with the temperature threshold value in the drive state in order to determine whether the monitoring temperature change reaches or exceeds the predetermined maximum temperature change ΔTmax. In particular, after detecting the start temperature value, the control device 5 continuously detects the monitoring temperature - i.e., the current actual value of the monitoring temperature - and continuously compares the current actual value of the monitoring temperature with the temperature threshold value. The control device 5 is designed, in response to the current actual value of the monitoring temperature reaching or exceeding the temperature threshold value, to end the drive state and to switch to the cooling state, in particular by reducing or terminating the current supply to the electric motor 1. In the example of the Fig. 2, the control device 5 compares the current actual value of the monitoring temperature with the first temperature threshold value ST1 in the first drive phase AP1 to check whether the monitoring temperature change in the first drive phase AP1 reaches or exceeds the predetermined maximum temperature change ΔTmax. In the example of Fig. 2, the current actual value of the monitoring temperature in the first drive phase AP1 does not reach the first temperature threshold SW1. For example, the first drive phase AP1—and thus the first drive state—is terminated by the user using control element 3, for example, by the user ceasing to operate control element 3.

[0056] The electric motor 1 is put into the first cooling state (present in the first cooling phase KP1) by the termination of the first drive state.

[0057] Preferably, the control device 5 is configured to calculate a separate, individual temperature threshold value for each drive state, based on the starting temperature value detected at the beginning of the respective drive state. This expediently results in different temperature threshold values ​​for different starting temperature values. Preferably, the control device 5 uses the same predetermined maximum temperature change ΔTmax in each drive state to calculate the respective temperature threshold value.

[0058] Preferably, the control device 5 is designed to assume a further drive state in response to a user input made after the end of the (first) drive state. The further drive state shall be referred to as the second drive state. The control device 5 is designed to detect a second starting temperature value ST2 of the monitoring temperature at the beginning of the second drive state, to calculate a second temperature threshold value SW2 based on the second starting temperature value ST2 and the maximum temperature change ΔTmax, and to put the electric motor 1 into the cooling state in response to the measured monitoring temperature (in particular the current actual value of the monitoring temperature) reaching or exceeding the second temperature threshold value SW2 in the further drive state.

[0059] The control device 5 is expediently designed to calculate the second temperature threshold value SW2 as a threshold value that differs from the first temperature threshold value SW1 when the second temperature start value ST2 differs from the first temperature start value ST1.

[0060] In the example of Fig. 2, during the first cooling phase KP1, the user actuates the control element 3 at a time when the monitoring temperature is greater than the first starting temperature value ST1, so that a temperature value greater than the first starting temperature value ST1 is detected as the second starting temperature value ST2. The control device 5 calculates a second temperature threshold value SW2 by adding the predetermined maximum temperature change ΔTmax to the second starting temperature value ST2, which, for example, is greater than the first temperature threshold value SW1.

[0061] In the example of Fig. 2, the control device 5 compares the current actual value of the monitoring temperature with the second temperature threshold value ST2 in the second drive phase AP2 to check whether the monitoring temperature change in the second drive phase AP2 reaches or exceeds the predetermined maximum temperature change ΔTmax. In the example of Fig. 2, the current actual value of the monitoring temperature in the second drive phase AP2 does not reach the second temperature threshold SW2. Purely by way of example, the current actual value of the monitoring temperature in the second drive phase AP2 exceeds the first temperature threshold SW1, which, however, is irrelevant at this point in time and therefore exceeding this first temperature threshold SW1 does not result in the electric motor being put into the cooling state. By way of example, the second drive phase AP2 - and thus the second drive state - is ended by the user using the control element 3, for example by the user ceasing to operate the control element 3. The electric motor 1 is put into the second cooling state (given in the second cooling phase KP2) by ending the second drive state.

[0062] Preferably, the control device 5 forcibly puts the electric motor 1 into the cooling state when the positive monitoring temperature change of the detected monitoring temperature that occurred in the drive state reaches or exceeds the predetermined maximum temperature change ΔTmax (for example, when the current actual value of the monitoring temperature reaches or exceeds the applicable temperature threshold value), even if the user continues to operate the operating element 3.

[0063] In the example of Fig. 2, the user actuates the control element 3 in the second cooling phase KP2, so that the control device detects a third starting temperature value ST3 and places the electric motor 1 into a third drive state (in a third drive phase AP3). The control device 5 calculates a third temperature threshold value SW3 by adding the predetermined maximum temperature change ΔTmax to the third starting temperature value ST3, which is, for example, greater than the second temperature threshold value SW2. In the example of Fig. 2, the control device 5 compares the current actual value of the monitoring temperature with the third temperature threshold value ST3 in the third drive phase AP3 to check whether the monitoring temperature change in the third drive phase AP3 reaches or exceeds the predetermined maximum temperature change ΔTmax. In the example of Fig. 2, the current actual value of the monitoring temperature in the third drive phase AP3 reaches the third temperature threshold value SW3, causing the control device 5 to forcibly place the electric motor 1 into the third cooling state (in the third cooling phase AP3), even if the user continues to operate the control element 3.

[0064] Preferably, the control device 5 is configured to activate a cooling criterion in response to the monitoring temperature change (in particular in the drive state) reaching or exceeding the predetermined maximum temperature change ΔTmax (i.e., for example, when the current actual value of the monitoring temperature reaches or exceeds the applicable temperature threshold), which must be met before the electric motor 1 can be placed into a / the further drive state. The cooling criterion preferably comprises a predetermined negative minimum temperature change ΔTmin for the monitoring temperature. In particular, the control device 5 is configured to block the drive state—i.e., to prevent the assumption of a further drive state—until the cooling criterion is met, for example, until the monitoring temperature has decreased by the predetermined minimum temperature change ΔTmin.For example, the control device 5 is configured to calculate a temperature release threshold based on the temperature threshold and the predetermined negative minimum temperature change ΔTmin, in particular by subtracting the (magnitude) of the predetermined negative minimum temperature change ΔTmin from the temperature threshold. The control device 5 is expediently configured to release—i.e., to allow—the drive state in response to the current actual value of the monitoring temperature falling below the temperature release threshold.

[0065] In particular, the control device 5 is configured to calculate a separate, individual temperature release threshold for each of several drive states, based on the respective temperature threshold. This expediently results in different temperature release thresholds for different temperature thresholds. The control device 5 preferably uses the same predetermined negative minimum temperature change ΔTmin to calculate each temperature release threshold.

[0066] Purely as an example, the negative minimum temperature change ΔTmin (in terms of magnitude) is smaller than the predetermined maximum temperature change ΔTmax.

[0067] In the example of Fig. 2, the control device 5 calculates a third temperature release threshold FW3 based on the third temperature threshold SW3 and the negative minimum temperature change ΔTmin. The temperature release threshold FW3 is referred to here as the third temperature release threshold FW3 because it is calculated based on the third temperature threshold SW3.

[0068] Purely by way of example, the third temperature release threshold FW3 is greater than the first temperature threshold SW1. It is therefore possible, for example, for a temperature release threshold to be greater than a temperature threshold.

[0069] Optionally, the control device 5 is configured to determine the cooling criterion, in particular the negative minimum temperature change ΔTmin, based on the detected monitoring temperature. For example, the control device 5 can be configured to set a greater negative minimum temperature change ΔTmin for a higher detected monitoring temperature (e.g., for a higher starting temperature value and / or a higher temperature threshold value) than for a lower monitoring temperature.

[0070] In the example of Fig. 2, the monitoring temperature decreases in the third cooling phase KP3 to below the third temperature release threshold value FW3, so that the control device 5 permits the drive state again. By (in particular continued or repeated) actuation of the control element 3, the user can return the electric motor to the drive state after the cooling criterion has been met - in the Fig. 2, for example, into the fourth drive state in the fourth drive phase AP4. The control device 5 calculates a fourth temperature threshold value SW4 for the fourth drive state based on a fourth start temperature value ST4, which is, for example, greater than the third temperature threshold value SW3.

[0071] Preferably, the control device 5 is designed not to activate the cooling criterion in response to the drive state being terminated without the monitoring temperature change reaching or exceeding the predetermined maximum temperature change ΔTmax. In the example of Fig. 2, the cooling criterion is not activated in the first drive phase AP1, second drive phase AP2 and / or fourth drive phase AP4 because the monitoring temperature does not reach or exceed the respective temperature threshold value SW1, SW2, SW4.

[0072] Preferably, the control device 5 is configured to compare the calculated temperature threshold value with a maximum temperature threshold value MT, and, if the maximum temperature threshold value MT is smaller than the temperature threshold value, to use the maximum temperature threshold value MT as the temperature threshold value. In the example of Fig. 5, the control device 5 calculates a fifth temperature threshold ST5 for a fifth drive state (in a fifth drive phase AP5) based on a fifth starting temperature value of the monitoring temperature, which is greater than the maximum temperature threshold MT, so that the control device 5 uses the maximum temperature threshold MT as the fifth temperature threshold. The control device 5 thus limits the calculated temperature threshold to the maximum temperature threshold MT. The maximum temperature threshold MT is determined, for example, in advance—that is, in particular, at the development stage—for example, according to the electronic components of the power tool.

[0073] In the example of Fig. 2, the user actuates the control element 3 in the fourth cooling phase KP4, so that the control device detects a fifth starting temperature value ST5 and places the electric motor 1 into a fifth drive state (in a fifth drive phase AP5). The control device 5 calculates a fifth temperature threshold value by adding the predetermined maximum temperature change ΔTmax to the fifth starting temperature value ST5, which, for example, is greater than the maximum temperature threshold value MT and is therefore limited by the control device 5 to the maximum temperature threshold value. In the example of Fig. 2, the control device 5 compares the current actual value of the monitoring temperature with the fifth temperature threshold (which is equal to the maximum temperature threshold MT) in the fifth drive phase AP5 to check whether the monitoring temperature change in the fifth drive phase AP5 reaches or exceeds the predetermined maximum temperature change ΔTmax. In the example of Fig. 2, the current actual value of the monitoring temperature in the fifth drive phase AP5 reaches the fifth temperature threshold (which is equal to the maximum temperature threshold MT), causing the control device 5 to forcibly place the electric motor 1 into the fifth cooling state (in the fifth cooling phase KP5), even if the user continues to operate the control element 3.

[0074] In the example of Fig. 2, the control device 5 calculates a fifth temperature release threshold value FW5 on the basis of the fifth temperature threshold value (which is exemplarily limited to the maximum temperature threshold value MT) and the negative minimum temperature change ΔTmin.

[0075] In the example of Fig. 2, the monitoring temperature decreases in the fifth cooling phase to below the fifth temperature release threshold value FW5, so that the control device 5 permits the drive state again. By (in particular, continued or repeated) actuation of the control element 3, the user can return the electric motor to the drive state after the cooling criterion has been met.

[0076] The numbers “first”, “second” etc. used above are intended in particular to Fig. 2 and explained above. A scenario expediently comprises at least one drive phase and / or at least one cooling phase. In the Fig. 2, these scenarios occur one after the other in the order shown, purely for illustrative purposes. For convenience, each scenario can also occur on its own (i.e., without the other scenarios), or the scenarios can occur in a different order. The numbers used do not necessarily require that the feature designated by the number be present in a specific number. For example, the term "fifth drive state" does not require that there are five drive states, but is merely intended to facilitate orientation in the drawing and text.

[0077] Purely optionally, the control device 5 is configured to determine the maximum temperature change ΔTmax based on the detected monitoring temperature. For example, the control device 5 can be configured to set a smaller maximum temperature change ΔTmax for a higher detected monitoring temperature (e.g., for a higher starting temperature value) than for a lower monitoring temperature.

[0078] A method for operating the power tool 10 will be described below. Fig. 3 shows a flowchart of an exemplary embodiment of such a method.

[0079] The method comprises actuating the operating element 3 to energize the electric motor 1 so that the electric motor 1 is put into the drive state in which the electric motor 1 drives the tool 2.

[0080] In the example of Fig. 3, the operating element 3 is actuated in the first step S1. Actuating the operating element 3 can also be referred to as switching on the power tool 10.

[0081] The first step S1 is preferably followed by a second step S2, in which the control device 5 checks whether the electric motor 1 is cool enough to be in the drive state. For example, the control device 5 checks whether a currently detected actual value of the monitoring temperature is below a previously set temperature release threshold and / or below a threshold value, for example, a switch-on threshold. If this is not the case, the drive state is immediately terminated by the control device 5 or not started at all, and the method continues with a sixth step S6, in which the power tool 10 is placed in the cooling state. For example, the electric motor 1 is switched off in the sixth step S6.

[0082] In the example of Fig. 3, the method continues with the third step S3 if the test performed in the second step S2 is passed. In the third step S3, the control device 5 calculates the temperature threshold. For example, in the third step S3, the control device 5 detects the starting temperature value and calculates the temperature threshold based on the starting temperature value.

[0083] The method then continues with the fourth step S4, in which the electric motor 1 is energized so that it is in the drive state, and the user expediently performs a work process, for example a screwdriving process, with the power tool 10. In the drive state, the fifth step S5 is continuously performed, in which the control device 5 checks whether the current actual value of the monitoring temperature is lower than the temperature threshold value calculated (based on the start temperature value). If the current actual value is lower than the temperature threshold value, the control device 5 leaves the electric motor 1 in the drive state. Otherwise, the control device 5 continues with the sixth step S6 and puts the electric motor 1 into the cooling state.

[0084] Preferably, the method therefore comprises checking whether a positive monitoring temperature change occurring in the drive state reaches or exceeds a predetermined maximum temperature change ΔTmax, and, in response to the monitoring temperature change reaching or exceeding the predetermined maximum temperature change ΔTmax, reducing and / or terminating the current supply to the electric motor 1 in order to put the electric motor 1 into a cooling state in which the electric motor 1 does not drive the tool 2 and in which the electric motor 1 cools down.

[0085] Optionally, the control device 5 can be designed to perform a cyclic recalculation of the temperature threshold value, for example based on one or more gradients, for example the monitoring temperature. This is described in the Fig. 3 indicated by the arrow from step S5 to step S3.

Claims

[1] Power tool (10), comprising an electric motor (1) for driving a tool (2), an operating element (3) for actuation by a user to carry out a user input, a temperature sensor (4) for measuring a monitoring temperature of the power tool (10) and a control device (5) for controlling the electric motor (1), wherein the control device (5) is designed to energize the electric motor (1) in response to the user input in order to put the electric motor (1) into a drive state in which the electric motor (1) drives the tool (2), and wherein the control device (5) is further designed to check whether a positive monitoring temperature change of the detected monitoring temperature that occurred in the drive state reaches or exceeds a predetermined maximum temperature change (ΔTmax), and in response thereto,that the monitoring temperature change reaches or exceeds the predetermined maximum temperature change (ΔTmax), to reduce and / or terminate the current supply to the electric motor in order to put the electric motor (1) into a cooling state in which the electric motor (1) does not drive the tool (2) and in which the electric motor (1) cools down, wherein the control device (5) is designed to detect a starting temperature value of the monitoring temperature with the temperature sensor (4) at the beginning of the drive state, to calculate a temperature threshold value based on the starting temperature value and the maximum temperature change (ΔTmax), and to compare the monitoring temperature measured with the temperature sensor (4) with the temperature threshold value in the drive state in order to determine whether the monitoring temperature change reaches or exceeds the predetermined maximum temperature change (ΔTmax),wherein the starting temperature value is a first starting temperature value (ST1) and the temperature threshold value is a first temperature threshold value (SW1), and the control device is designed to assume a further driving state in response to a user input made after the end of the driving state, to detect a second starting temperature value (ST2) of the monitoring temperature at the beginning of the further driving state, to calculate a second temperature threshold value (SW2) based on the second starting temperature value (ST2) and the maximum temperature change (ΔTmax), and to put the electric motor (1) into the cooling state in response to the measured monitoring temperature reaching or exceeding the second temperature threshold value (SW2) in the further driving state. [2] Power tool (10) according to claim 1, wherein the temperature sensor (4) is arranged at a distance from the electric motor (1) and / or at a distance from a winding arrangement (6) of the electric motor (1). [3] Power tool (10) according to claim 1 or 2, wherein the control device (5) comprises power electronics (7) and is designed to provide the current supply to the electric motor (1) via the power electronics (7), and wherein the temperature sensor (4) is assigned to the power electronics (7). [4] Power tool (10) according to any preceding claim, comprising a drive section (8) in which the electric motor (1) is arranged, and a handle section (9) in which the temperature sensor (4) is arranged. [5] Power tool (10) according to any preceding claim, wherein the control device (5) is designed to compare the calculated temperature threshold value with a maximum temperature threshold value (MT) and, if the maximum temperature threshold value (MT) is smaller than the temperature threshold value, to use the maximum temperature threshold value (MT) as the temperature threshold value. [6] Power tool (10) according to any preceding claim, wherein the control device (5) is configured to calculate the second temperature threshold value (SW2) as a threshold value that differs from the first temperature threshold value (SW1) when the second temperature start value (ST2) differs from the first temperature start value (ST1). [7] Power tool (10) according to any preceding claim, wherein the control device (5) is designed, in response to the monitoring temperature change reaching or exceeding the predetermined maximum temperature change (ΔTmax), to activate a cooling criterion which must be met before the electric motor (1) can be put into a / the further drive state. [8] Power tool (10) according to claim 7, wherein the control device (5) is designed not to activate the cooling criterion in response to the drive state being terminated without the monitoring temperature change reaching or exceeding the predetermined maximum temperature change (ΔTmax). [9] Power tool (10) according to claim 7 or 8, wherein the cooling criterion comprises a predetermined negative minimum temperature change (ΔTmin) for the monitoring temperature. [10] Power tool (10) according to one of claims 7 to 9, wherein the control device (5) is designed to determine the cooling criterion on the basis of the detected monitoring temperature. [11] Method for operating a power tool (10), comprising the steps: - actuating an operating element (3) of the power tool (10) to energise an electric motor (1) of the power tool (10) so that the electric motor (1) is placed in a drive state in which the electric motor (1) drives a tool (2) of the power tool, - Check whether a positive monitoring temperature change occurring in the drive state reaches or exceeds a predetermined maximum temperature change (ΔTmax), - in response to the monitoring temperature change reaching or exceeding the predetermined maximum temperature change (ΔTmax), reducing and / or terminating the current supply to the electric motor (1) in order to put the electric motor (1) into a cooling state in which the electric motor (1) does not drive the tool (2) and in which the electric motor (1) cools down, wherein at the beginning of the drive state, a starting temperature value of the monitoring temperature is detected, a temperature threshold value is calculated on the basis of the starting temperature value and the maximum temperature change (ΔTmax), and in the drive state, a measured monitoring temperature is compared with the temperature threshold value in order to determine whether the monitoring temperature change reaches or exceeds the predetermined maximum temperature change (ΔTmax), wherein the starting temperature value is a first starting temperature value (ST1) and the temperature threshold is a first temperature threshold (SW1),and in response to a user input made after the end of the drive state, a further drive state is assumed, at the beginning of the further drive state, a second start temperature value (ST2) of the monitoring temperature is recorded, a second temperature threshold value (SW2) is calculated based on the second start temperature value (ST2) and the maximum temperature change (ΔTmax), and in response to the measured monitoring temperature reaching or exceeding the second temperature threshold value (SW2) in the further drive state, the electric motor (1) is put into the cooling state. [12] Method according to claim 11, wherein the monitoring temperature change is detected with a temperature sensor (4) which is arranged at a distance from the electric motor (1) and / or at a distance from a winding arrangement (6) of the electric motor (1). [13] Method according to claim 11 or 12, wherein the current supply to the electric motor (1) is provided via power electronics (7), and wherein the temperature sensor (4) is assigned to the power electronics (7). [14] Method according to one of claims 11 to 13, wherein the power tool (10) comprises a drive section (8) in which the electric motor (1) is arranged, and a handle section (9) in which the temperature sensor (4) is arranged. [15] Method according to one of claims 11 to 14, wherein the calculated temperature threshold is compared with a maximum temperature threshold (MT), and, if the maximum temperature threshold (MT) is less than the temperature threshold, the maximum temperature threshold (MT) is used as the temperature threshold. [16] The method according to any one of claims 11 to 15, wherein, when the second temperature start value (ST2) is different from the first temperature start value (ST1), the second temperature threshold value (SW2) is calculated as a threshold value different from the first temperature threshold value (SW1). [17] Method according to one of claims 11 to 15, wherein in response to the monitoring temperature change reaching or exceeding the predetermined maximum temperature change (ΔTmax), a cooling criterion is activated which must be met before the electric motor (1) can be put into a / the further drive state. [18] The method of claim 17, wherein in response to the drive state being terminated without the monitoring temperature change reaching or exceeding the predetermined maximum temperature change (ΔTmax), the cooling criterion is not activated. [19] A method according to claim 17 or 18, wherein the cooling criterion comprises a predetermined negative minimum temperature change (ΔTmin) for the monitoring temperature. [20] Method according to one of claims 17 to 19, wherein the cooling criterion is determined on the basis of the detected monitoring temperature. [21] A computer program product (11) comprising instructions for causing the power tool (10) of claim 1 to perform the method of any one of claims 11 to 20. [22] A computer-readable medium (12) on which the computer program product (11) according to claim 21 is stored. [23] Method for operating a control device (5) of a power tool (10), comprising the step of: installing the computer program product (11) according to claim 21 on the control device (5). [24] Control device (5) for a power tool (10), wherein the control device (5) is designed, in response to a user input, to energize an electric motor (1) of the power tool (10) in order to put the electric motor (1) into a drive state in which the electric motor (1) drives a tool (2) of the power tool (10), and wherein the control device (5) is further designed to check whether a positive monitoring temperature change of a detected monitoring temperature that occurred in the drive state reaches or exceeds a predetermined maximum temperature change (ΔTmax), and in response to the monitoring temperature change reaching or exceeding the predetermined maximum temperature change (ΔTmax), to reduce and / or terminate the energization of the electric motor (1) in order to put the electric motor (1) into a cooling state,in which the electric motor (1) does not drive the tool (2) and in which the electric motor (1) is cooling down, wherein the control device (5) is designed to calculate a respective temperature threshold value each time the electric motor (1) is put into the drive state, wherein the temperature threshold value is calculated as the sum of a starting temperature value, the monitoring temperature, and the maximum temperature change (ΔTmax), wherein the control device (5) is designed to detect the starting temperature value with a temperature sensor (4) of the power tool (10) at the beginning of the drive state, wherein the control device (5) is designed to compare the monitoring temperature detected by the temperature sensor (4) with the temperature threshold value in the drive state in order to determine whether the monitoring temperature change reaches or exceeds the maximum temperature change (ΔTmax),wherein the starting temperature value is a first starting temperature value (ST1) and the temperature threshold value is a first temperature threshold value (SW1), wherein the control device (5) is designed to assume a further driving state in response to a user input made after the end of the driving state, to detect a second starting temperature value (ST2) of the monitoring temperature at the beginning of the further driving state, to calculate a second temperature threshold value (SW2) based on the second starting temperature value (ST2) and the maximum temperature change (ΔTmax), and to put the electric motor (1) into the cooling state in response to the measured monitoring temperature reaching or exceeding the second temperature threshold value (SW2) in the further driving state.

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