Drive unit for a mobile machine tool, and mobile machine tool

Abstract

The invention relates to a drive unit for a mobile machine tool, comprising a battery unit for providing an output-side DC voltage, an electric motor, a motor inverter circuit which is connected between the battery unit and the electric motor and by means of which the DC voltage provided by the battery unit can be clocked in order to drive the electric motor, an intermediate circuit capacitor which is connected between the battery unit and the motor inverter circuit and by means of which an intermediate circuit voltage is defined, and a circuit breaker device having a circuit breaker, the circuit breaker device being designed to detect a voltage gradient of the intermediate circuit voltage and to switch the circuit breaker using the voltage gradient in order to disconnect the battery unit from the motor inverter circuit.

Description

[0001] 2023ID00112

[0002] Hilti Aktiengesellschaft in Schaan

[0003] Principality of Liechtenstein

[0004] Drive unit for a mobile machine tool

[0005] and mobile machine tool

[0006] AREA OF INVENTION

[0007] The present invention relates to a drive unit for a mobile machine tool and a mobile machine tool with such a drive unit.

[0008] Common mobile machine tools comprise a drive unit consisting of a battery pack, an intermediate circuit, a motor inverter circuit, and an electric motor. These drive units often incorporate circuit breakers. Such a circuit breaker allows the battery pack to be decoupled from the drive unit's intermediate circuit, for example, during power-up or in the event of a short circuit. This protects the battery pack and / or other drive unit components from high incoming currents. These high currents or current spikes can occur, for instance, when switching on or inserting the battery pack, leading to arcing and causing significant wear on the battery pack's contacts.

[0009] The circuit breaker can typically be arranged in a supply line to a positive electrode of the battery unit or between the battery unit and the DC link of the drive unit. Alternatively, topologies are also known in which the circuit breaker is arranged in a downstream line to a negative electrode of the battery unit or between the battery unit and the DC link of the drive unit.

[0010] Since the circuit breaker often performs safety-critical functions, it is important that it does not fail or become damaged in the event of a short circuit. Furthermore, the circuit breaker must open in case of a fault to decouple the battery unit from the DC link. To open the circuit breaker, it is triggered by a switching signal, which is generated beforehand based on measurements within the drive unit. Known methods in the art measure a current across a measuring resistor and compare this current with a predetermined reference current value, which corresponds to the maximum permissible current within the drive unit. If the measured current exceeds the predetermined reference current value, the switching signal is generated, and the circuit breaker opens.

[0011] opened, so that no current can flow from the battery unit into the intermediate circuit and thus into the motor inverter circuit and vice versa.

[0012] Measuring via the resistor is not power-free. Several watts of power loss can occur during measurement, potentially creating a hotspot and causing thermal problems within the drive unit. With typical battery currents of approximately 100 A, a 1 mΩ resistor can dissipate up to 10 watts. Cooling this resistor requires a heat sink and a cooling airflow. Therefore, there is still room for improvement.

[0013] One object of the present invention is therefore to provide an improved drive unit for a mobile machine tool and / or an improved mobile machine tool, and in particular to provide an improved protection circuit for the drive unit.

[0014] REVELATION OF THE INVENTION

[0015] Accordingly, a drive unit for a mobile machine tool is proposed. The drive unit comprises a battery unit for providing an output DC voltage, an electric motor, a motor inverter circuit connected between the battery unit and the electric motor, through which the DC voltage provided by the battery unit can be switched to drive the electric motor, a DC link capacitor connected between the battery unit and the motor inverter circuit, through which a DC link voltage is defined, and a protective switching device with a circuit breaker. The protective switching device is configured to detect a voltage gradient of the DC link voltage and, using this voltage gradient, to switch the circuit breaker to disconnect the battery unit from the motor inverter circuit, particularly in the event of a short circuit in the DC link of the drive unit.

[0016] Alternatively, a drive unit for a mobile machine tool is proposed. The drive unit comprises a battery unit for providing an output DC voltage, an electric motor, a motor inverter circuit connected between the battery unit and the electric motor, through which the DC voltage provided by the battery unit can be switched to drive the electric motor, a DC link capacitor connected between the battery unit and the motor inverter circuit, through which a DC link voltage is defined, and a measuring device designed to detect a voltage gradient of the DC link voltage, and under the use of - 3 - 2023ID00112

[0017] The motor inverter circuit can be switched off based on the voltage gradient. Alternatively, instead of using the protective switching device, the motor inverter circuit can also be switched off directly based on the voltage gradient to prevent a short circuit. For this purpose, a measuring device for measuring the voltage gradient can be provided. All descriptions relating to measuring the voltage gradient, and subsequently provided for the protective switching device, also apply analogously to the measuring device.

[0018] The battery unit is preferably designed to supply a direct current (DC) voltage. The battery unit is preferably used to power the electric motor. The battery unit preferably has at least two or more contacts or contact points. These contacts are preferably connection points through which electrical energy is transferred from the battery unit to the drive unit. The battery unit is preferably a rechargeable energy storage device or a rechargeable battery that can store electrical energy and release it as needed.

[0019] The motor inverter circuit preferably forms a motor inverter bridge that can function as a voltage-source inverter (VSI). The DC voltage supplied by the battery unit is preferably converted into AC voltage using pulse-width modulation. This pulsed AC voltage enables the electric motor to be driven. The pulse-width modulation ensures precise control of the output voltage and frequency, thereby allowing efficient regulation of the electric motor's power output.

[0020] The DC link capacitance defines the DC link of the drive unit. The DC link capacitance preferably includes a DC link capacitor. The DC link capacitor can be a ceramic capacitor. A ceramic capacitor is a type of electrical capacitor that uses ceramic as the dielectric material. These capacitors preferably comprise thin ceramic layers alternately stacked with metal foils as electrodes. Ceramic capacitors are used in a compact format due to their high stability, temperature resistance, and capacitance. MLCC stands for Multilayer Ceramic Capacitor. MLCCs are a special type of ceramic capacitor consisting of several layers of ceramic material and metal, stacked alternately on top of each other and then compressed into a small, compact package.This design enables high capacity values ​​in a small installation space. - 4 - 2023ID00112.

[0021] The DC link voltage is preferably defined by the voltage drop across the DC link capacitor. The DC link capacitor is used in a drive train with a battery unit and switching device connected in parallel to smooth voltage fluctuations and ensure stable operating conditions. For example, the battery unit cannot always compensate directly and quickly for sudden load changes; therefore, the DC link capacitor buffers energy and supplies the motor-inverter circuit (e.g., the inverter) with additional energy when needed. This reduces voltage spikes and protects the components from damage caused by high currents. At the same time, the DC link capacitor supports pulse-width modulation by dampening rapid current fluctuations, which increases the efficiency and lifespan of the entire system.

[0022] The protective switching device is designed to disconnect the connection between the battery unit and the DC link or motor inverter circuit in the event of an emergency or short circuit, thus protecting the battery unit from sudden overload due to current spikes during a short circuit. For this purpose, the protective switching device includes a circuit breaker that can be opened in the event of a short circuit, for example, based on a switching signal.

[0023] The present drive unit enables low-loss and rapid measurement due to the circuit breaker's operation based on the voltage gradient rather than a measuring current. This, in turn, allows for rapid switching of the circuit breaker, for example, within a few microseconds, thus protecting the drive unit in the event of a short circuit, a fault, or during power-up. The voltage gradient can also be referred to as the voltage drop. This approach offers a way to detect a short circuit based on the voltage gradient and, upon detection, to open the circuit breaker or thereby disconnect the drive unit. Because of the method used to detect the short circuit, which triggers the circuit breaker's opening, no power loss or heat is generated.This also eliminates the need for cooling, which would otherwise be necessary for a measuring resistor to measure a (short-circuit) current.

[0024] According to another aspect, a mobile machine tool with such a drive unit is proposed.

[0025] The mobile machine tool can be a hand-held power tool or hand-held power tool, for example a drill, a screwdriver, a chisel, a grinder, a saw, or the like. (Conceivable - 5 - 2023ID00112)

[0026] The mobile machine tool may also be a construction robot or include a construction robot. The mobile machine tool may have a manipulator, in particular a multi-axis manipulator. The mobile machine tool may have a drive device for driving a tool, for example a drill, a chisel, a suction cup, or the like.

[0027] The mobile machine tool can be set up, for example, for processing stone, such as concrete, and / or metal and / or wood. It can be designed for tasks such as drilling, chiseling, sawing and / or grinding.

[0028] Generally, the mobile machine tool can be set up for carrying out work in building construction and / or civil engineering. It is conceivable that it is not set up for use in mining.

[0029] The mobile machine tool can be portable; for example, it can weigh less than 50 kg, and in particular less than 25 kg.

[0030] In one embodiment, it is proposed that the protection switch includes a transistor, in particular a MOSFET.

[0031] The circuit breaker can be designed as a gate-terminal transistor, in particular as a metal-oxide-semiconductor field-effect transistor, and / or as a 3-terminal transistor, in particular as a high-electron-mobility transistor. Other semiconductor-based transistor types, such as gate-insulated bipolar transistors (IGBTs), can also be used.

[0032] In one embodiment, it is proposed that the protective switching device includes a voltage divider for dividing the DC link voltage and a differentiator circuit for detecting the voltage gradient using the divided DC link voltage.

[0033] To detect this (steep) voltage gradient or voltage drop, an op-amp P circuit is preferably used as the differentiator circuit, which can differentiate the DC link voltage, especially after voltage division. The voltage division can, for example, be performed with a division factor of 10, so that a DC link voltage of 22 volts is divided to 2.2 volts for the differentiator circuit. Other division factors are, of course, also conceivable. The voltage gradient is preferably not changed by the voltage divider. - 6 - 2023ID00112

[0034] A differentiator circuit is an electronic circuit that determines the rate of change of an input signal, i.e., calculates its derivative. In an op-amp P circuit (operational amplifier circuit), an operational amplifier is configured to function as a differentiator. This is achieved by using a capacitor at the input and a resistor in the feedback loop of the op-amp. This arrangement ensures that the output voltage is proportional to the rate of change of the input voltage.

[0035] In one embodiment, it is proposed that the differentiator circuit is configured to generate an output voltage signal that corresponds to the voltage gradient of the intermediate circuit voltage.

[0036] The output of the differentiator circuit preferably contains a voltage, the output voltage signal, which corresponds to the voltage gradient or the derivative of the input voltage of the DC link (after voltage division). This output voltage signal, which corresponds to the DC link voltage gradient, is preferably compared by means of a comparator with a threshold value or level that corresponds to the permissible voltage gradient, or is directly fed to the protective switching device as a switching signal for switching the circuit breaker.

[0037] In one embodiment, it is proposed that the protective switching device has a comparator by which a threshold for switching the protective switch can be set, and which is configured to compare the output voltage signal with the threshold and to output a comparator signal based on the comparison.

[0038] A comparator is an electronic circuit or component that compares two voltages and outputs a specific voltage based on the result. Typically, a comparator provides a digital output signal. If the input voltage at one input is higher than at the other, a high level (e.g., 1 or High) is output; otherwise, a low level (e.g., 0 or Low) is output. Thus, if the voltage gradient is high enough, a comparator signal with a sufficiently high level is generated to directly trigger a protective circuit. Alternatively, the comparator signal can be generated as a binary signal, from which a switching signal can then be generated. The comparator signal can, for example, be generated as a short signal pulse caused by the (sudden) voltage drop during a short circuit. - 7 - 2023ID00112

[0039] In one embodiment, it is proposed that the protective switching device comprises a flip-flop memory or a microcontroller, wherein the flip-flop memory or the microcontroller is configured to switch the protective switch using the comparator signal, in particular by generating a switching signal, in order to disconnect the battery unit from the motor inverter circuit, particularly in the event of a short circuit.

[0040] The comparator signal, which serves, for example, as a switching signal for switching the circuit breaker, is fed into a flip-flop memory, for example, to store the comparator signal in the event of a short circuit or fault and to protect the protective switching device from unintentional re-energizing.

[0041] A flip-flop memory is preferably a digital circuit that has two stable states and can therefore store a single bit (0 or 1). The flip-flop memory stores the information of the (last) comparator signal until it is modified by an input signal (e.g., a clock pulse of the comparator signal).

[0042] A microcontroller is preferably an integrated circuit (IC) that functions as a small, self-contained computer. The microcontroller typically includes a processor (CPU), memory (RAM and ROM), and various input and output interfaces on a single chip.

[0043] In one embodiment, it is proposed that the differentiator circuit includes a capacitor for interference suppression, which is arranged in parallel.

[0044] A differentiator circuit with a capacitor for interference suppression in parallel is preferably designed to form the derivative of the input signal and is therefore particularly sensitive to rapid signal changes. A capacitor is preferably integrated into the circuit to suppress high-frequency interference, which can arise, for example, from noise or external influences. This capacitor is preferably arranged in parallel with the resistor of the differentiator circuit. This parallel connection preferably limits high frequencies and stabilizes the output signal, making the circuit more resistant to interference.

[0045] In one embodiment, it is proposed that the circuit breaker has a bypass path comprising a diode and a resistor, wherein the bypass path is configured to charge the DC link capacitance when the circuit breaker is open. - 8 - 2023ID00112

[0046] The bypass path is used to charge the DC link capacitor in a controlled manner. The diode ensures that the current flows only in a specific direction, thus controlling the charging process. The resistor limits the current flow, so the DC link capacitor charges slowly instead of charging to full power immediately. This creates a delay or a gradual increase in the voltage across the DC link capacitor. Once the DC link capacitor reaches the required voltage, the circuit breaker can be closed.

[0047] In one embodiment, it is proposed that the flip-flop memory is configured to at least temporarily store the comparator signal.

[0048] A flip-flop memory, designed to at least temporarily store the comparator signal, serves to retain the comparator's output state for a certain period. The comparator preferably outputs a signal that is either high (1) or low (0), depending on the voltage comparison. This signal can be volatile, meaning it changes rapidly depending on the input conditions. The flip-flop memory stores this signal so that it remains available even when the comparator signal itself is no longer present. This storage makes it possible to retain the comparator result and subsequently process or utilize it further in the circuit, even if the comparator's input voltages change.

[0049] In another aspect, a method for switching a circuit breaker of a drive unit for a mobile machine tool is proposed, wherein the drive unit comprises a battery unit for providing an output DC voltage, an electric motor, a motor inverter circuit connected between the battery unit and the electric motor, by which the DC voltage provided by the battery unit can be switched to drive the electric motor, an intermediate circuit capacitor connected between the battery unit and the motor inverter circuit, by which an intermediate circuit voltage is defined; and a protective switching device with a circuit breaker, wherein the method comprises the steps:

[0050] a) Detecting a voltage gradient of the intermediate circuit voltage; and

[0051] b) Switching the circuit breaker to disconnect the battery unit from the motor inverter circuit using the voltage gradient.

[0052] Furthermore, a computer program product is proposed which includes instructions that, when executed by a computer, cause it to perform the procedure described above. - 9 - 2023ID00112

[0053] A computer program product, such as a computer program tool, can be provided or delivered from a server on a network, for example, as a storage medium such as a memory card, USB stick, CD-ROM, DVD, or as a downloadable file. This can be done, for example, in a wireless communication network by transmitting the corresponding file containing the computer program product or tool.

[0054] The embodiments and features described for the proposed method apply accordingly to the proposed machine tool.

[0055] Other possible implementations of the invention also include combinations of features or embodiments described previously or subsequently with regard to the exemplary embodiments, even if not explicitly mentioned. In such cases, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

[0056] Further advantageous embodiments and aspects of the invention are the subject of the dependent claims and the exemplary embodiments of the invention described below. The invention is further explained below with reference to preferred embodiments and the accompanying figures. - 10 - 2023ID00112

[0057] BRIEF DESCRIPTION OF THE FIGURES

[0058] The following description explains the invention with reference to exemplary embodiments and figures. The figures show:

[0059] Fig. 1 shows a schematic view of a battery-powered mobile machine tool;

[0060] Fig. 2 shows a schematic view of a drive unit;

[0061] Fig. 3 shows another schematic view of a drive unit;

[0062] Fig. 4 shows another schematic view of a drive unit.

[0063] Fig. 5 shows a current or voltage time diagram of a short circuit;

[0064] Fig. 6 shows a schematic view of a differentiator circuit; and

[0065] Fig. 7 shows a schematic flowchart of a given process.

[0066] Identical or functionally equivalent elements are indicated by the same reference symbols in the figures, unless otherwise specified. - 11 - 2023ID00112

[0067] FORMS OF EXECUTION OF THE INVENTION

[0068] Figure 1 shows a mobile machine tool 100. The machine tool 100 is, by way of example, a hand-held machine tool, more precisely a drill. Other preferred embodiments include a chiseling machine, a grinding machine, or a sawing machine. The machine tool 100 has a housing 101 for protecting and storing other components. The machine tool 100 is designed as a portable device. It has, for example, a weight between 0.5 and 15 kg and generally less than 25 kg or 50 kg.

[0069] The machine tool 100 has an electric motor 102, which has a stator 103 and a rotor 104. The rotor 104 is, for example, rotationally coupled to a spindle 106 of a tool holder 107 via a gearbox 105. The gearbox 105 is, for example, a reduction gearbox. The gearbox 105 may be switchable between several gear ratios. The machine tool 100 may contain a percussion mechanism, which is designed as part of the gearbox 105 or the tool holder 107 and / or is connected between the gearbox 105 and the tool holder 107.

[0070] The tool holder 107 is preferably configured to receive an interchangeable tool 108. For example, a chuck (not shown) of the tool holder 107 can be opened and / or closed by rotating a handle 109 of the tool holder 107 relative to the spindle 106. This chuck could be, for example, a quick-release drill chuck, an SDS drill chuck, and / or a TE-C drill chuck. The tool 108 can be driven, for example, by rotating, impact, and / or hammering action via the tool holder 107.

[0071] The electric motor 102 is, for example, a brushless DC motor. The electric motor 102 can be operated to generate torque between the stator 103 and the rotor 104. A control device 111 is configured to switch an electric current flow from a battery unit 112 to the stator 103 upon actuation of an actuating element 110. The battery unit 112 is preferably a single accumulator or a circuit of several accumulators.

[0072] For example, the control device 111 is configured to detect the rotational position (rotational angle and / or angular velocity) of the rotor 104 relative to the housing 101 by means of a Hall sensor circuit 113 or another angle sensor device. For example, AMR sensors and / or resolvers can also be used. Fer- - 12 - 2023ID00112

[0073] Angle estimation using sensorless algorithms is also conceivable. Furthermore, angle measurement is not necessary in the case of brushless DC motors. For example, the control device 111 is also configured to supply (not shown in Fig. 1) windings of the stator 103 with electric current. The control device 111 has, for example, an evaluation logic for this purpose, and it can, for example, be configured to execute a computer program whose commands cause the control device 111 to execute a method for operating the mobile machine tool 100.

[0074] Fig. 2 shows a drive unit 200 of the tool tractor 100 in one embodiment. The drive unit 200 comprises the battery unit 112 for providing an output DC voltage, the electric motor 102, and a motor inverter circuit 202, which is connected between the battery unit 112 and the electric motor 102 and by which the DC voltage provided by the battery unit 112 can be pulsed to drive the electric motor 108. The motor inverter circuit 202 comprises six transistors 203, in particular MOSFETs, for pulsing the provided DC voltage.

[0075] The drive unit 200 further comprises an intermediate circuit capacitor 204, which is connected between the battery unit 112 and the motor inverter circuit 202 and defines an intermediate circuit voltage. The intermediate circuit capacitor 204 includes an intermediate circuit capacitor 205. The intermediate circuit capacitor 205 can be a ceramic capacitor.

[0076] The drive unit 200 also includes a protective switching device 206 with a circuit breaker 207. The circuit breaker 207 comprises a transistor, in particular a MOSFET. The protective switching device 206 is configured to detect a voltage gradient G (see Fig. 6) of the DC link voltage applied to the DC link capacitor 205 and, using the voltage gradient G, to switch the circuit breaker 207 to disconnect the battery unit 112 from the motor inverter circuit 202. The circuit breaker 207 is arranged in a supply line 208 to a positive electrode of the battery unit 112 or between the battery unit 112 and the DC link capacitor 204. Alternatively, the circuit breaker 207 can be arranged in a downstream line 209 to a negative electrode of the battery unit 112 or between the battery unit 112 and the DC link capacitor 204.

[0077] The protective switching device 206 is connected to the control device 111, which can perform the switching of the protective switch 207 using the voltage gradient G. The control device 111 can also be configured to control the voltage gradient. - 13 - 2023ID00112

[0078] to detect gradient G. Alternatively, the protective switching device 206 can also have a further control device that can detect the voltage gradient G and / or switch the protective switch 207 using the voltage gradient G.

[0079] The protective switching device 206 can also include a microcontroller 210 which is configured to switch the protective switch 207 using the comparator signal in order to disconnect the battery unit 112 from the motor inverter circuit 202, particularly in the event of a short circuit.

[0080] Figures 3 and 4 show further embodiments of the drive unit 200. The protective switching device 206 has a voltage divider 300 for dividing the DC link voltage U1 and a differential circuit 302 for detecting the voltage gradient G using the divided DC link voltage U1T. The differential circuit 302 is also shown schematically in another embodiment in Figure 6.

[0081] The differentiator circuit 302 is designed to generate an output voltage signal U2 that corresponds to the voltage gradient G of the intermediate circuit voltage U1.

[0082] Furthermore, the protective switching device 206 includes a comparator 304, which, firstly, allows a threshold value U3 for switching the protective switch 207 to be set, and secondly, is configured to compare the output voltage signal U2 with the threshold value U3 and, based on the comparison, output a comparator signal U4. The threshold value U3 is preferably generated by means of a voltage divider.

[0083] In other embodiments, the drive unit can also have a measuring device instead of a protective switch 206. This measuring device is configured to detect a voltage gradient G of the DC link voltage U1 and to switch off the motor inverter circuit 202 using the voltage gradient G. The measuring device can include the voltage divider 300 for dividing the DC link voltage U1 and the differentiator circuit 302 for detecting the voltage gradient G using the divided DC link voltage U1T.

[0084] According to the embodiment shown in Fig. 4, the protective switching device 206 has a flip-flop memory 306 which is configured to switch the protective switch 207 using a switching signal U5, based on the comparator signal U4, in order to disconnect the battery unit 112 from the motor inverter circuit 202, particularly in the event of a short circuit. - 14 - 2023ID00112

[0085] The flip-flop memory 306 is designed to at least temporarily store the comparator signal U4. This also applies analogously to the measuring device.

[0086] By way of example only, the differentiator circuit 302 according to Fig. 4 also has a capacitor 308 for interference suppression, which is arranged in parallel with a resistor 309 of the differentiator circuit 302.

[0087] By way of example, the circuit breaker 207 according to Fig. 4 also has a bypass path 310. The bypass path 310 comprises a diode 312 and a resistor 314. The bypass path 310 is designed to charge the DC link capacitance 204 when the circuit breaker 207 is (initially) open, i.e., when the mobile machine tool 100 is switched on.

[0088] Fig. 5 shows a current and voltage-time diagram of a short circuit. The current I and the voltage U within the drive unit 200 are plotted over time t. In the event of a short circuit K, for example in the intermediate circuit of the drive unit 200, the voltage U drops rapidly, resulting in a high voltage gradient G. A short circuit event can be detected here based on the voltage gradient G (and not, as is usually the case, by measuring the current through a measuring resistor).

[0089] Fig. 6 shows an embodiment of the differentiator circuit 302. It depicts a circuit of an operational amplifier differentiator. The intermediate circuit voltage U1 serves as the input signal and is applied to a capacitor C, one terminal of which is connected to the reference potential (ground) and the other terminal to junction X. Junction X is in turn connected to the inverting input of an operational amplifier A. The non-inverting input of the operational amplifier A is connected to ground potential.

[0090] Resistor 309 is connected between node X and the output of operational amplifier A. The current through the resistor is denoted If, while the current flowing into node X is denoted lin. The output voltage signal -U2 of the circuit is also connected to ground.

[0091] Fig. 7 shows a schematic flowchart of an existing method M10 for switching a circuit breaker 200. Method M10 includes, in step S11, the detection of a voltage gradient G of the intermediate circuit voltage. Furthermore, the - 15 - 2023ID00112

[0092] Method M10, in step S12, switches the circuit breaker 207 to disconnect the battery unit 112 from the motor inverter circuit 202 using the voltage gradient G. Steps S11 and S12 can each have several substeps.

[0093] This may include a computer program product containing instructions that, when executed by a computer, cause the computer to perform procedure M10 in order to switch the circuit breaker 207. Procedure M10 may, for example, be executable on the control unit 111 or on the microcontroller 210.

[0094] Although the present invention has been described using exemplary embodiments, it can be modified in many ways. The descriptions also apply to the measuring device. - 16 - 2023ID00112

[0095] REFERENCE MARK LIST

[0096] 100 mobile machine tools

[0097] 101 cases

[0098] 102 Electric motor

[0099] 103 Stator

[0100] 104 Rotor

[0101] 105 gearbox

[0102] 106 Spindle

[0103] 107 Tool holder

[0104] 108 tools

[0105] 109 Handle

[0106] 110 Actuating element

[0107] 111 Control device

[0108] 112 battery unit

[0109] 113 Hall sensor circuit

[0110] 200 drive unit

[0111] 202 Motor inverter circuit

[0112] 203 Transistor

[0113] 204 DC link capacity

[0114] 205 Intermediate circuit capacitor

[0115] 206 Protective switching device

[0116] 207 circuit breakers

[0117] 208 Lead to the positive electrode

[0118] 209 Negative electrode lead 210 Microcontroller

[0119] 300 voltage dividers

[0120] 302 Differentiator Circuit

[0121] 304 Comparator

[0122] 306 flip-flop memories

[0123] 308 Capacitor

[0124] 309 Differentiator circuit resistance 310 Bypass path

[0125] 312 Diode of the bypass path

[0126] 314 Resistance of the bypass path - 17 - 2023ID00112

[0127] A Operational amplifier

[0128] I Electricity

[0129] I in electricity

[0130] If electricity

[0131] C capacitor

[0132] II Tension

[0133] U1 DC link voltage

[0134] U1T shared intermediate circuit voltage

[0135] U2 output voltage signal

[0136] U3 threshold

[0137] U4 comparator signal

[0138] U5 switching signal

[0139] t time

[0140] G voltage gradient

[0141] K Short circuit

[0142] X Junction

[0143] M10 Method for switching a circuit breaker

[0144] 511 Detecting a voltage gradient of the intermediate circuit voltage 512 Switching the circuit breaker

Claims

- 18 - 2023ID00112 PATENT CLAIMS 1. Drive unit (200) for a mobile machine tool (100), comprising: a battery unit (112) for providing an output DC voltage; an electric motor (102); a motor inverter circuit (202) connected between the battery unit (112) and the electric motor (102), through which the DC voltage provided by the battery unit (112) can be switched to drive the electric motor (108); an intermediate circuit capacitor (204) connected between the battery unit (112) and the motor inverter circuit (202), through which an intermediate circuit voltage (U1) is defined; and a protective switching device (206) with a circuit breaker (207), characterized by the fact that the protective switching device (206) is designed to detect a voltage gradient (G) of the intermediate circuit voltage (U1) and to switch the protective switch (207) to disconnect the battery unit (112) from the motor inverter circuit (202) using the voltage gradient (G).

2. Drive unit (200) according to claim 1, wherein the protective switch (207) comprises a transistor, in particular a MOSFET.

3. Drive unit (200) according to claim 1 or 2, wherein the protective switching device (206) comprises a voltage divider (300) for dividing the DC link voltage (U1) and a differential circuit (302) for detecting the voltage gradient (G) using the divided DC link voltage (U1T).

4. Drive unit (200) according to claim 3, wherein the differentiator circuit (302) is configured to generate an output voltage signal (U2) corresponding to the voltage gradient (G) of the intermediate circuit voltage (U1).

5. Drive unit (200) according to claim 4, wherein the protective switching device (206) has a comparator (304) by which a threshold value (U3) for switching the protective switch (207) can be set, and which is configured to compare the output voltage signal (U2) with the threshold value (U3) and to output a comparator signal (U4) on the basis of the comparison. - 19 - 2023ID00112 6. Drive unit (200) according to claim 5, wherein the protective switching device (206) comprises a flip-flop memory (306) or a microcontroller (210), wherein the flip-flop memory (306) or the microcontroller (210) is configured to switch the protective switch (207) using the comparator signal (U4) in order to disconnect the battery unit (112) from the motor inverter circuit (202), particularly in the event of a short circuit.

7. Drive unit (200) according to one of claims 3 to 6, wherein the differential circuit (302) has a capacitor (308) for interference suppression, which is arranged in parallel.

8. Drive unit (200) according to one of the preceding claims, wherein the circuit breaker (207) has a bypass path (310) comprising a diode (312) and a resistor (314), wherein the bypass path (310) is configured to charge the intermediate circuit capacitance (204) when the circuit breaker (207) is open.

9. Drive unit (200) according to claim 6, wherein the flip-flop memory (306) is configured to at least temporarily store the comparator signal (U4).

10. Mobile machine tool (100) comprising a drive unit (200) according to any one of claims 1 to 9.

11. Method (M10) for switching a protective switch (207) of a drive unit (200) for a mobile machine tool (100), wherein the drive unit (200) comprises a battery unit (112) for providing an output DC voltage, an electric motor (102), a motor inverter circuit (202) connected between the battery unit (112) and the electric motor (102), and by which the DC voltage provided by the battery unit (112) can be pulsed to drive the electric motor (108), an intermediate circuit capacitor (204) connected between the battery unit (112) and the motor inverter circuit (202), and by which an intermediate circuit voltage (U1) is defined; and a protective switching device (206) with a protective switch (207), wherein the method (M10) comprises the steps: Detection (S11) of a voltage gradient (G) of the intermediate circuit voltage (U1); and - 20 - 2023ID00112 Switching (S12) of the circuit breaker (207) to disconnect the battery unit (112) from the motor inverter circuit (202) using the voltage gradient (G).

12. Computer program product comprising instructions which, when the program is executed by a computer, cause it to execute the method (M10) according to claim 11.

13. Drive unit (200) for a mobile machine tool (100), comprising: a battery unit (112) for providing an output DC voltage; an electric motor (102); a motor inverter circuit (202) connected between the battery unit (112) and the electric motor (102), through which the DC voltage provided by the battery unit (112) can be switched to drive the electric motor (108); an intermediate circuit capacitor (204) connected between the battery unit (112) and the motor inverter circuit (202), through which an intermediate circuit voltage (U1) is defined; and a measuring device designed to detect a voltage gradient (G) of the intermediate circuit voltage (U1) and to switch off the motor inverter circuit (202) using the voltage gradient (G).

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