Drive unit for a hand-held power tool, and hand-held power tool

Abstract

The invention relates to a drive unit for a hand-held power tool, comprising: a voltage source; a DC / DC converter (304) which is connected to the voltage source (300) and is designed to convert an input-side DC voltage (U1) provided by the voltage source (300) into an output-side DC voltage (U2), in particular a smoothed DC voltage; power electronics (2) which are connected to the DC / DC converter (304) and can be operated using the output-side DC voltage (U2); and an electric motor (8) which is connected to the power electronics (2), the power electronics (2) being designed to control and / or drive the electric motor (8) on the basis of the output-side DC voltage (U2).

Description

[0001] 2023ID00184

[0002] Hilti Aktiengesellschaft in Schaan

[0003] Principality of Liechtenstein

[0004] Drive unit for a hand-held power tool and hand-held power tool

[0005] AREA OF INVENTION

[0006] The present invention relates to a drive unit for a hand-held power tool and a hand-held power tool with such a drive unit.

[0007] Power electronics for controlling an electric motor in a hand-held power tool are supplied with a direct current (DC) voltage, often provided by a battery or rectifier. The control of the electric motor by the power electronics functions most reliably when this DC voltage is constant and stable over time.

[0008] However, voltage dips or fluctuations can occur during operation between the power source and the power electronics. In conventional power electronic designs, a capacitor is installed in a DC link to compensate for these fluctuations, especially near an active part of the power electronics, in order to stabilize the supply voltage.

[0009] This DC link capacitance typically comprises one or more capacitors, which take up installation space and incur significant costs due to the capacitor material used. Even with a typical amount of DC link capacitance, disturbances on the DC power supply side can still cause fluctuating voltage at the input of the power electronics, negatively affecting the operation of the power tool.

[0010] To improve the quality of the motor control provided by the power electronics, it is therefore desirable to achieve a constant, stable voltage level at the input of the power electronics. Furthermore, to save costs and space, it is desirable to reduce the required DC link capacitance to the minimum necessary level. Therefore, a technical solution is desired that improves the power supply without requiring additional DC link capacitance, or at least reduces it.

[0011] Against this background, the object of the present invention is to create an improved drive unit for a hand-held power tool and / or an improved hand-held power tool.

[0012] REVELATION OF THE INVENTION

[0013] According to a first aspect, a drive unit for a hand-held power tool is proposed. The drive unit comprises a voltage source (also called the main power supply of the drive unit) and a DC / DC converter (also called a DC-DC converter) connected in parallel to the voltage source. The DC-DC converter is configured to convert an input DC voltage (also called input voltage) provided by the voltage source into an output DC voltage (also called output voltage), in particular a smoothed or constant DC voltage. The drive unit further comprises power electronics connected in parallel to the voltage source and the DC / DC converter, which can be operated by the output DC voltage; and an electric motor connected to the power electronics. The power electronics are configured to control and / or drive the electric motor based on the output DC voltage.The output DC voltage preferably supplies the power electronics and thus the electric motor with electrical drive power.

[0014] By introducing a DC / DC converter in parallel between the voltage source and the power electronics, a stable, constant voltage can be provided to the power electronics with less or even no DC link capacitance. The DC / DC converter preferably regulates an input voltage provided by the voltage source to a constant DC output voltage, which is supplied to the input of the power electronics. The DC / DC converter preferably converts the input voltage to a constant, stable voltage value suitable for operating the motor control provided by the power electronics. A constant voltage level can thus be achieved even without DC link capacitance or at least with reduced capacitance. This results in savings in materials and costs.

[0015] According to a second aspect, a hand-held power tool with such a drive unit is proposed. - 3 - 2023ID00184

[0016] The hand-held power tool is preferably designed as a drill, impact drill, rotary hammer, circular saw, jigsaw, reciprocating saw, angle grinder, mixer, or the like. Preferably, the hand-held power tool or power tool can be battery-operated and have one or more batteries, particularly interchangeable ones, for example, a lithium-ion battery.

[0017] The specifications for the drive unit apply accordingly to the hand-held power tool and vice versa.

[0018] In one embodiment, it is proposed that the DC / DC converter comprises a buck converter and / or a boost converter and / or a buck-boost converter and / or a cuk converter and / or a SEPIC converter and / or a flyback converter and / or a push-pull converter and / or a DC / DC converter comprising an active H-bridge.

[0019] A DC / DC converter is preferably an electronic circuit that converts a direct current (DC) voltage from one voltage level to another. There are various types of DC / DC converters that differ in their construction and operation. A buck converter (step-down converter) has at least one switch (transistor), one diode, one inductor (coil), and one capacitor, and is preferably configured to step down an input voltage to a lower output voltage. The switch is preferably turned on and off at a specific frequency, thereby storing energy in the inductor and then releasing it to the output. A boost converter (step-up converter) has at least one switch, one diode, one inductor, and one capacitor, and is preferably configured to step up an input voltage to a higher output voltage.When the switch is closed, energy is preferably stored in the inductor. When the switch opens, the stored energy is preferably released to the output via the diode. A buck-boost converter preferably comprises a combination of buck and boost converter components. This can include at least one switch, one diode, one inductor, and one capacitor. The buck-boost converter is preferably configured to either increase or decrease the input voltage, depending on the load requirements. The output voltage can be higher or lower than the input voltage. A cuk converter comprises at least two inductors, two capacitors, one switch, and one diode, and is preferably configured to either increase or decrease the input voltage. It has the advantage of a continuous input and output current, which means less ripple. (A - 4 - 2023ID00184.)

[0020] A SEPIC converter (Single-Ended Primary Inductor Converter) has at least two inductors, a switch, two capacitors, and a diode, and is preferably designed similarly to a Cuk converter to increase or decrease the input voltage and provides galvanic isolation between input and output. A flyback converter has at least one switch, a diode, a multi-winding inductor (transformer), and a capacitor, provides galvanic isolation, and can convert one input voltage into multiple output voltages. A push-pull converter has a center-tapped transformer, two switches, and two diodes, and preferably offers high efficiency. The transformer provides galvanic isolation and can supply multiple output voltages. A DC / DC converter with an active H-bridge is a circuit that converts DC voltage from one voltage level to another.The active H-bridge is preferably a special circuit arrangement consisting of four or more switches (e.g., MOSFETs and / or IGBTs) that can reverse the direction of the current through the load. This enables efficient voltage conversion and is often used in applications requiring precise control and high efficiency. In this case, the DC / DC converter can also be configured with a half-H-bridge, which has at least two switches (e.g., MOSFETs and / or IGBTs).

[0021] In one embodiment, it is proposed that the drive unit has a DC capacitor which is arranged between the DC / DC converter and the power electronics and is connected in parallel with the DC / DC converter and the power electronics.

[0022] The drive unit can also include several DC capacitors, each connected in parallel to the DC / DC converter and the power electronics. The additional DC capacitor, designed as an intermediate circuit capacitor, further stabilizes the output voltage of the DC / DC converter, thus preferably eliminating any existing voltage ripple from the already stabilized, constant output voltage. Voltage ripple, also known simply as ripple, refers to undesirable fluctuations or ripples in the output voltage of a DC / DC converter circuit. These fluctuations result from the superimposed AC component and can be a consequence of switching operations within the DC / DC converter.

[0023] In one embodiment, it is proposed that the voltage source is provided by at least two contacts that can be connected to at least one battery unit. - 5 - 2023ID00184

[0024] The voltage source is preferably designed to supply a direct current (DC) voltage. The voltage source preferably forms an integral part of the drive unit and is used to supply power to the electric motor. The voltage source 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 contacts of the voltage source are preferably designed so that they can be connected to at least one battery unit. The battery unit is preferably a rechargeable energy storage device that can store electrical energy and release it as needed. The arrangement or design ensures that the voltage source, through the aforementioned contacts and their connection options with the battery unit, functions reliably and efficiently.

[0025] In one embodiment, it is proposed that the voltage source has a terminal that includes an AC / DC converter configured to convert a mains AC voltage into a DC voltage.

[0026] The connection terminal is preferably a connection or terminal point on the voltage source, through which the voltage source can be connected to other components or an external power source. The AC / DC converter is an electrical component or circuit designed to convert an alternating current (AC) voltage into a direct current (DC) voltage. The converter is preferably integrated into or connected to the connection terminal. A mains-side AC voltage is preferably an AC voltage supplied by an external power grid, typically with standardized voltage and frequency values ​​(e.g., 230V, 50Hz in Europe).

[0027] In one embodiment, it is proposed that the DC / DC converter has a control bandwidth of at least 80 kHz, preferably at least 100 kHz.

[0028] The DC / DC converter preferably has the capability to regulate the output voltage over a specific frequency range. The minimum requirement is 80 kHz. The preferred requirement is 100 kHz. This allows the DC / DC converter to respond quickly and precisely to changes in input conditions or load requirements, which is determined by the control bandwidth. A high control bandwidth ensures better performance and stability of the converter, as the DC / DC converter can react more quickly to disturbances. The DC / DC converter should be able to maintain a stable output voltage even during rapid changes in operating conditions. This - 6 - 2023ID00184

[0029] These features are particularly advantageous in applications with high demands on control and stability, such as in power electronics.

[0030] For example, the DC / DC converter can have a control bandwidth that is at least five times greater than the pulse-width modulation frequency used to switch the power electronics. In particular, the power electronics can be an inverter comprising several transistor bridges, each switchable via pulse-width modulation. Furthermore, a high control bandwidth can allow for a reduction in the capacitance of a capacitor in the intermediate circuit.

[0031] In one embodiment, it is proposed that the DC / DC converter has at least one semiconductor-based switch comprising a semiconductor material having a band gap of at least two electron volts (2 eV).

[0032] Preferably, the DC / DC converter has at least two switches. The band gap (also called bandgap) is preferably the energy required to promote an electron from the valence band to the conduction band of a semiconductor material. Examples of semiconductor materials used include beta-gallium oxide (β-Ga₂O₃), gallium nitride (GaN), or silicon carbide (SiC). Beta-gallium oxide (β-Ga₂O₃) has a band gap of approximately 4.8 to 4.9 eV. Beta-gallium oxide is an ultra-wideband semiconductor used in high-voltage and high-power electronics. Gallium nitride (GaN) has a band gap of approximately 3.4 eV. Gallium nitride is a semiconductor used in high-frequency and high-power electronics. Silicon carbide (SiC) has a band gap of approximately 2.3 to 3.3 eV, depending on the polytype structure (e.g. 4H-SiC, 6H-SiC).Silicon carbide is known for its excellent thermal and electrical performance and is frequently used in power electronics and high-temperature applications. These materials offer high efficiency and stability under extreme conditions.

[0033] In one embodiment, it is proposed that the DC / DC converter is configured to provide the output DC voltage to the power electronics at a constant, in particular (pre-)adjustable or selectable, voltage level.

[0034] The DC / DC converter is therefore preferably designed to provide a constant DC output voltage, which is particularly adjustable to meet the specific requirements of the power electronics. This means that the output voltage remains stable even with fluctuations in the input voltage or load conditions, which ensures reliable and consistent operation. - 7 - 2023ID00184

[0035] This ensures performance. Additionally, the power electronics are not tied to a fixed input voltage. During operation, this allows, for example, a turbo mode to be implemented, in which the power electronics receive a higher DC voltage, particularly temporarily, from the DC / DC converter. If the drive unit includes a battery serving as the voltage source, the DC / DC converter can also compensate for voltage fluctuations in the battery caused by discharge, so that the output voltage can be supplied to the power electronics at a constant level, regardless of the current input voltage. Thus, the power electronics no longer need to be designed for the lowest battery voltage, but can also be designed for a voltage at which the power electronics and the electric drive operate as efficiently as possible.The use of the DC / DC converter thus makes it possible to select and maintain the optimal operating point of the power electronics and the electric drive, thereby enabling the power electronics or the electric drive to operate more efficiently and with lower losses, even if the input voltage drops during operation due to gradual battery discharge. The output voltage can preferably be adjusted as a function of the input voltage, in particular by factoring.

[0036] - 8 - 2023ID00184

[0037] BRIEF DESCRIPTION OF THE FIGURES

[0038] The following description explains the invention with reference to exemplary embodiments and figures. The figures show:

[0039] Fig. 1 shows a schematic view of a battery-powered hand tool;

[0040] Fig. 2 shows a schematic view of a mains-powered hand-held power tool;

[0041] Fig. 3 shows a schematic view of a drive unit; and

[0042] Fig. 4 shows a schematic stress-time diagram.

[0043] Identical or functionally equivalent elements are indicated by the same reference symbols in the figures, unless otherwise specified.

[0044] - 9 - 2023ID00184

[0045] FORMS OF EXECUTION OF THE INVENTION

[0046] Fig. 1 shows a schematic view of a battery-powered hand tool 1, which here is configured as an impact drill. The hand tool 1 has a mounting bay 4, which in this example has two contacts K1 and K4. The mounting bay 4 is designed to receive a battery unit 30. In each case, the two contacts K1 and K4 of the mounting bay 4 are brought into contact with two corresponding contacts KT and K4' of the battery unit 30.

[0047] A consumer of the hand-held power tool 1, in particular an electric motor (without reference numerals in Fig. 1), is connected between contacts K1 and K4 of the receiving bay 4. In the illustrated example, contacts K1 and K4 are connected to a power electronics unit 2, which switches the drive current for the electric motor. The power electronics unit 2 and the electric motor form part of an electric drive unit 100, which is shown in detail in Fig. 3 according to an exemplary embodiment.

[0048] The dashed box in Fig. 1 is purely an example of a system 1000 comprising a battery-powered hand tool 1 and a battery unit 30 with several cell arrangements 31 , 32.

[0049] Fig. 2 shows a schematic view of another example of an electric hand-held power tool 1, which is designed as a drilling machine. The hand-held power tool 1 has a tool holder 6 in which a drill bit is inserted as a drilling tool 7. The hand-held power tool 1 is driven by an electric motor 8. An operator can guide the hand-held power tool 1 by means of a handle 11 and start it up by means of a push button 12. During operation, the hand-held power tool 1 rotates the drilling tool 7, in particular continuously, about a working axis 13 and can thereby drill the drilling tool 7 into a substrate along the working axis 13.

[0050] The hand-held power tool 1 shows an embodiment of the electric drive unit 100 in Fig. 2. The electric drive unit 100 (see embodiment in Fig. 3) comprises an electric motor 8 and the power electronics 2 for controlling the electric motor 8. The electric drive unit 100 is, by way of example, coupled to a connection terminal 15 via an electrical cable arrangement 14, which can be connected to a power supply (not shown) by means of a plug 16. Alternatively, the hand-held power tool 1 can also be powered by a battery (as shown in Fig. 1). A drive train of the hand-held power tool 1 also includes, for example, a drive shaft and a gearbox between the electric motor 8 and the drive shaft (not shown). The gearbox (not shown) can, for example, adjust the speed of the electric motor 8 to a desired speed of the drill bit 7.

[0051] Fig. 3 shows a detailed embodiment of the drive unit 100 of the hand-held power tool 1. The drive unit 100 comprises a voltage source 300. In the example of Fig. 1, the voltage source 300 can be the voltage supplied between contacts K1 and K4. Alternatively, in the example of Fig. 2, the voltage source 300 can be the connection terminal 15, in which case the connection terminal 15 may preferably include an AC / DC converter (not shown) to convert an AC voltage supplied via the plug 16 into a DC voltage Ui.

[0052] To provide a stable, and in particular fluctuation-free, constant DC voltage U2 at an input side 302 of the power electronics 2, the drive unit 100 comprises a DC / DC converter 304, which is arranged in parallel between the voltage source 300 and the power electronics 2. Alternatively, the DC / DC converter 304 can also be connected in series with the voltage source 300.

[0053] The DC / DC converter 304 can comprise a buck converter and / or a boost converter and / or a buck-boost converter and / or a cuk converter and / or a SEPIC converter and / or a flyback converter and / or a push-pull converter. The DC / DC converter 304 preferably comprises at least one semiconductor-based switch comprising a semiconductor material having a bandgap of at least 2 electron volts (eV). The DC / DC converter 304 further comprises a control bandwidth of at least 80 kHz, preferably at least 100 kHz, to enable such fast switching intervals as to provide the constant or smoothed DC voltage U2.

[0054] In particular, the DC / DC converter 304 has a control bandwidth that is at least five times greater than a pulse-width modulation frequency with which the power electronics 2 can be switched. Specifically, the power electronics 2 can be an inverter comprising several transistor bridges, each of which can be switched via pulse-width modulation.

[0055] Preferably, the DC / DC converter 304 has at least two switches (not shown). The DC / DC converter 304 is connected in parallel to the voltage source 300 and in parallel to the power electronics 2. The voltage provided by the voltage source 300 is - 11 - 2023ID00184

[0056] The DC voltage Ui can vary under certain circumstances (see Fig. 4), so a constant voltage value is not always supplied. The DC / DC converter 304 can convert the DC voltage Ui into the constant DC voltage U2, which has a stable and constant voltage value over time (see Fig. 4). The DC voltage Ui serves as the input voltage for the DC / DC converter 304 and is converted into the constant DC voltage U2 within the DC / DC converter 304. The DC / DC converter 304 thus provides the constant DC voltage U2 at an output 306. Optionally, at least one DC capacitor 308 can be arranged in parallel between the DC / DC converter 304 and the power electronics 2. The DC capacitor 308 may be preferred to further stabilize the constant DC voltage U2.

[0057] Fig. 4 schematically shows a voltage-time diagram. The DC voltages Ui and U2 are plotted against time t. It can be seen that the DC voltage Ui, which is provided on the output side of the voltage source 300, varies or oscillates around an average DC voltage value UM over time t. This variation can be "smoothed out" by the DC / DC converter 304, so that a constant DC voltage U2 can be provided at one output side of the DC / DC converter 304.

[0058] Figure 4 further shows that the DC / DC converter 304 can be configured to supply the output DC voltage U2 to the power electronics 2 at a constant, and in particular, (pre-)adjustable or selectable, voltage level. Figure 4 schematically illustrates that the output DC voltage U2 can, for example, be designed to be at the average DC voltage value UM of the DC voltage Ui. However, it is also possible to set the output DC voltage U2 to a level that is above or below such an average DC voltage value UM. An output DC voltage U2 above such an average DC voltage value UM is labelled U2,high. An output DC voltage U2 below such an average DC voltage value UM is labelled U2,low. - 12 - 2023ID00184

[0059] REFERENCE MARK LIST

[0060] 1 hand-held power tool

[0061] 2 Power Electronics

[0062] 4 Receiving bay

[0063] 5 main switches

[0064] 6 Tool holder

[0065] 7 Drilling tool

[0066] 8 Electric motor

[0067] 11 Handle

[0068] 12 buttons

[0069] 13 working axis

[0070] 14. Line arrangement

[0071] 15 connection terminals

[0072] 16 plugs

[0073] 19 battery units

[0074] 20 battery units

[0075] 30 battery units

[0076] 31 cell arrangement

[0077] 32 cell arrangement

[0078] 33 Cell

[0079] 100 drive units

[0080] 300 voltage source

[0081] 302 Entrance page

[0082] 304 DC / DC converter

[0083] 306 Home page

[0084] 308 DC capacitor

[0085] 1000 System

[0086] K1 Contact

[0087] K1 ' Contact

[0088] K4 Contact

[0089] K4' Contact

[0090] Ui DC voltage or input voltage

[0091] U2 DC voltage or output voltage

[0092] U2, low DC voltage

[0093] U2, high DC voltage - 13 - 2023ID00184

[0094] UM average DC voltage value t time

Claims

1. - 14 - 2023ID00184 PATENT CLAIMS 1. Drive unit (100) for a hand-held power tool (1), comprising: a voltage source (300); a DC / DC converter (304) connected to the voltage source (300) and configured to convert an input DC voltage (Ui) provided by the voltage source (300) into an output DC voltage (U2), in particular a smoothed DC voltage; power electronics (2) connected to the DC / DC converter (304) and operable by the output DC voltage (U2); and an electric motor (8) connected to the power electronics (2), wherein the power electronics (2) are configured to control and / or drive the electric motor (8) on the basis of the output DC voltage (U2).

2. Drive unit (100) according to claim 1, wherein the DC / DC converter (304) comprises a buck converter and / or a boost converter and / or a buck-boost converter and / or a cuk converter and / or a SEPIC converter and / or a flyback converter and / or a push-pull converter and / or a DC / DC converter comprising an active H-bridge.

3. Drive unit (100) according to claim 1 or 2, wherein the drive unit (100) has at least one DC capacitor (308) arranged between the DC / DC converter (304) and the power electronics (2), and connected in parallel with the DC / DC converter (304) and the power electronics (2).

4. Drive unit (100) according to one of claims 1 to 3, wherein the voltage source (300) is provided by at least two contacts (K1-K4) which can be connected to at least one battery unit (19, 20, 30).

5. Drive unit (100) according to one of claims 1 to 3, wherein the voltage source (300) has a connection terminal (15) comprising an AC / DC converter configured to convert a mains AC voltage into a DC voltage (Ui).

6. Drive unit (100) according to one of claims 1 to 5, wherein the DC / DC converter (304) has a control bandwidth that is at least five times greater than a pulse width modulation frequency with which the power electronics (2) can be switched. - 15 - 2023ID00184 7. Drive unit (100) according to one of claims 1 to 6, wherein the DC / DC converter (304) has a control bandwidth of at least 80 kHz, preferably at least 100 kHz.

8. Drive unit (100) according to any one of claims 1 to 7, wherein the DC / DC converter (304) has at least one semiconductor-based switch comprising a semiconductor material having a band gap of at least 2 electron volts.

9. Drive unit (100) according to one of claims 1 to 8, wherein the DC / DC converter (304) is configured to provide the output DC voltage (U2) to the power electronics (2) at a constant, in particular adjustable, voltage level.

10. Hand-held power tool (1) with a drive unit (100) according to one of claims 1 to 9.

11. System (1000) comprising a hand-held power tool (1) according to claim 10, a battery unit (19, 20, 30) and a charging device for charging the battery unit (19, 20, 30).

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